EP2742165A1 - Steel for manufacturing carburized steel parts, carburized steel parts produced with said steel, and method for manufacturing same - Google Patents

Steel for manufacturing carburized steel parts, carburized steel parts produced with said steel, and method for manufacturing same

Info

Publication number
EP2742165A1
EP2742165A1 EP12750727.5A EP12750727A EP2742165A1 EP 2742165 A1 EP2742165 A1 EP 2742165A1 EP 12750727 A EP12750727 A EP 12750727A EP 2742165 A1 EP2742165 A1 EP 2742165A1
Authority
EP
European Patent Office
Prior art keywords
steel
temperature
traces
content
hours
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP12750727.5A
Other languages
German (de)
French (fr)
Other versions
EP2742165B1 (en
Inventor
Christophe MENDIBIDE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ascometal France Holding Sas
Original Assignee
Ascometal SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ascometal SA filed Critical Ascometal SA
Publication of EP2742165A1 publication Critical patent/EP2742165A1/en
Application granted granted Critical
Publication of EP2742165B1 publication Critical patent/EP2742165B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/60Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using solids, e.g. powders, pastes
    • C23C8/62Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using solids, e.g. powders, pastes only one element being applied
    • C23C8/64Carburising
    • C23C8/66Carburising of ferrous surfaces
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/06Surface hardening
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00Heat treatment of ferrous alloys
    • C21D6/002Heat treatment of ferrous alloys containing Cr
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/001Ferrous alloys, e.g. steel alloys containing N
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/002Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/06Ferrous alloys, e.g. steel alloys containing aluminium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/60Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/02Pretreatment of the material to be coated
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/04Treatment of selected surface areas, e.g. using masks
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/20Carburising
    • C23C8/22Carburising of ferrous surfaces
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/80After-treatment
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00Drill bits
    • E21B10/46Drill bits characterised by wear resisting parts, e.g. diamond inserts
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2241/00Treatments in a special environment

Definitions

  • the invention relates to iron and steel, and more particularly to the grades of case hardening steels with a high degree of resilience.
  • Such a drill bit is a forged tool consisting of three rotating steel cones "entangled" in one another and making it possible to crush the geological formations during oil or gas exploration operations. These three cones are rotated, via one or more bearings, on three welded steel arms.
  • the machining tracks machined on the arms and inside the cones are generally, in conventional production processes, treated superficially by atmospheric carburization to reach a conventional depth, where the Vickers hardness is 550 HV, included on average between 1 and 1.5 mm.
  • the present invention relates to a new steel grade that can be used for making cones and arms.
  • trephines There are several kinds of such trephines.
  • One of them is the bit with "inserted tooth", that is to say in which spikes, most often made of tungsten carbide obtained by powder metallurgy, are crimped into each of the cones.
  • the steel subject of the present invention is not limited, in its use, to this type of drill bit, and could also be used for the production of "machined tooth” bits.
  • the reference grades used for the manufacture of the cones and arms constituting the drill bits are steels strongly alloyed with nickel at levels of up to 3.5% by weight (especially the grade of 15NiCrMo13).
  • This alloying element is usually considered necessary to give the product the level of ductility essential to withstand the severity of the mechanical stresses in service.
  • This ductility must be associated with tensile characteristics and high quenchability.
  • the properties typically sought for these shades are, in fact:
  • this characteristic can be evaluated by the coefficient ⁇ corresponding to the difference in hardness between Jominy points J 5 and J 3 .
  • the Jominy curve should satisfy ⁇ ⁇ 3.5 HRC and Ji> 40 HRC; it is recalled that the Jominy curve is a curve which reflects the hardenability of a steel; it is obtained at by means of a standardized test (in particular by the NF EN ISO 642 standard) by measuring the hardness along a generatrix of a cylindrical specimen soaked by a jet of water watering one of its ends; the hardness measured at a depth of x mm from said end is designated J x ;
  • An austenitic grain size such that the grain index is greater than ASTM 5;
  • US-A-6 146 472 provides an example.
  • the increase in resilience is obtained by controlling the magnification resistance of the austenitic grain via the use of an Nb-Al-N microalloy, combined with an optimized heat treatment.
  • the resilience values indicated in this document are at best close to 60J, and the examples presented are castings which do not make it possible to check the quenchability criterion ⁇ ⁇ 3.5 HRC.
  • US-A-2005/0081962 discloses a carburizing steel not using Ni, but whose resilience does not exceed 51 J, which is not sufficient.
  • the object of the invention is to provide a carburizing steel used in particular for the manufacture of drill bits, not requiring addition of Ni and nevertheless meeting all the criteria of ductility, hardenability, Re, Rm and Kv cited above.
  • the subject of the invention is a steel for the manufacture of cemented parts, characterized in that its composition, in percentages by weight, is: - 0.1% ⁇ C ⁇ 0.15%;
  • traces ⁇ 0 ⁇ 30 ppm Preferably, traces ⁇ 0 ⁇ 30 ppm.
  • the subject of the invention is also a case-hardened steel piece, characterized in that it is made of a steel having the preceding composition and in that it has undergone a cementation.
  • the invention also relates to a method for manufacturing a cemented part, characterized in that:
  • a blank of said workpiece is made of a steel having the preceding composition.
  • This shaping can be performed by any method (forging, machining, rolling ...);
  • said pressure may be from 5 to 20 mbar, and the succession of steps of the cementation may be the following:
  • the invention is based on a careful adjustment of the composition of the steel, to meet all the criteria mentioned above.
  • the steel that is the subject of the present invention is also different from that described in US Pat. No. 6,146,472 in that the accessible resilience is significantly greater, and in that the improvement of the resilience is not generated at least mainly, by a control of the grain size.
  • This has the advantage of not modifying the ability of the grade to thermomechanical treatment and limit the risk of abnormal magnification of the austenitic grain during cementation.
  • the segregating effect of niobium which may lead to a heterogeneous austenitic grain size is, in particular, avoided.
  • the level of resilience accessible by the present invention is also significantly higher.
  • the type of carburizing used with the steel described in the present invention is not limited to the atmospheric carburization process which could be replaced by other surface hardening processes, for example low pressure carburizing.
  • the present invention is based on a steel whose composition is defined below. All grades are given in percentages by weight. By using a composition defined as described below, it is possible to develop, without the voluntary addition of nickel and without using large quantities of other expensive elements, a steel having a hardenability, mechanical characteristics after quenching followed by and a carburizing ability (carbon uptake, resilience to the core, carburizing depth, residual austenite content, etc.) similar to those of the reference grades of 3.5% Ni usually used for the manufacture of carbon fiber drill bits. drilling. The content of C is between 0.10% and 0.15%, a carbon content limited to a relatively narrow range, and which is low, compared with those generally encountered in case-hardening steels.
  • the Mn content is between 0.8% and 2%.
  • Manganese is used with chromium and molybdenum to compensate for the loss of hardenability associated with decreased carbon content. For its effect to be sufficient, a content greater than or equal to 0.8% is required. Since this alloying element can pose problems of segregation, it is preferable that its concentration does not exceed 2%.
  • the Cr content is between 1% and 2.5%.
  • chromium is used to ensure a sufficient degree of quenchability to the grade.
  • the minimum content of 1% is chosen so that the effect of this alloying element on quenchability is sufficient.
  • the maximum content of 2.5% is defined in order to avoid a detrimental effect on the use properties, in particular by formation of coarse chromium carbides.
  • Mo content is between 0.2% and 0.6%.
  • Molybdenum is a third element used to adjust the quenchability of the grade. It is also an alloying element that can be used judiciously to increase resilience, especially at low temperatures. Molybdenum also exacerbates the effect of boron on hardenability, and can therefore be used for this purpose in the case of boron alloyed grades. For a content of less than 0.2% the increase in hardenability is too low and this value is therefore chosen as the minimum level. For high concentrations, molybdenum tends to decrease the ability of forging steels. In addition, because it is an expensive alloying element, its use at an excessive content would lead to a loss of economic benefit brought about by the non-use of nickel. For these reasons, a maximum content of 0.6% is preferred.
  • the Si content is less than 0.35%.
  • silicon can be used as a deoxidizing element.
  • the residual content of this element does not in any case generally exceed 0.35%. It should also not exceed a content of 0.35% in the steels of the invention, because silicon is an alloying element that can limit, by barrier effect, the carbon uptake during cementation.
  • the Ni content is less than or equal to 0.7%, preferably 0.3%.
  • one of the objects of the present invention is to make it possible to do without an addition voluntary of this element. However, it is still present in the residual state in the raw materials used to make steel, especially in scrap metal.
  • the 0.3% content corresponds to the maximum level most commonly encountered when no voluntary addition of nickel is made during the elaboration.
  • the B content is less than 0.005%.
  • Boron is an optional element. It can be used to optimally adjust the quenchability of the grade if the levels of Mn, Cr and Mo are not quite sufficient for this purpose. But for this alloy element to actually act on the quenchability, it must be maintained in solid solution. For that, the precipitation of nitrides or oxides of boron must be avoided. This result can be obtained by adding a higher affinity alloy element with nitrogen, for example titanium, and controlling the production process to limit the dissolution of nitrogen and oxygen in the steel.
  • the Ti content is less than 0.1% and preferably less than 0.04%. Titanium is optionally added to allow the boron to be maintained in solid solution by precipitation of titanium nitrides which reduce the amount of nitrogen that may be combined with boron. Its content should optimally be chosen according to the amount of nitrogen in the grade. To be completely effective, a stoichiometric amount of titanium must be added to ensure precipitation of all of the nitrogen contained in the steel as TiN, and thus maintain the boron in solid solution. This is verified if the Ti / N ratio is greater than 3.4. In the case of substoichiometric titanium addition, the effect of boron on quenchability can still be expressed but is less pronounced. Beyond the prescribed limit, there is a risk of formation of TiN too coarse during solidification, and moreover the addition of Ti becomes excessively expensive.
  • the N content is less than 0.02%, preferably less than 0.01%.
  • boron addition from 5 to 50 ppm
  • a nitrogen content of less than 0.01% is therefore recommended. If the boron is not used (B ⁇ 5ppm), it is not absolutely essential to strictly control the nitrogen content, which can then go up to 0.02% without detrimental effect on the properties of the elaborated steel. .
  • the Al content must be at most 0.1%: Aluminum is an optional element. It can be used as a deoxidizer for steel to replace silicon, and to optimize the behavior of the austenitic grain during cementation.
  • the V content is at most 0.3%.
  • Vanadium is an optional element. It can be used as a micro-alloy element for better control of grain size during carburizing, providing further improvement in resilience.
  • the P content is at most 0.025%. This limit is recommended to avoid risk of weakening the steel. At an excessively high content, this element tends to segregate at the austenitic grain boundaries, which can lead to an increase in the ductile-brittle transition temperature and a decrease in the resilience at room temperature.
  • the Cu content is at most 1%, preferably at most 0.6%.
  • a maximum content of 1% is recommended because it is an expensive element that provides no benefit of quenchability or resilience.
  • the preferred maximum value of 0.6% is a content usually recognized as being below which copper has no significant effect on the mechanical properties of steel. Nevertheless, use at a higher level is possible without modifying the ability of the grade to be used for the manufacture of drill bits.
  • the S content is not strictly imposed in the definition of steel according to the most general invention, but it must be controlled according to the intended application.
  • a low content will be sought if it is desired to improve the inclusion cleanliness by not forming sulphides (typically ⁇ 0.01%) and a higher content may be chosen (typically from 0.03% to 0.1%) if a gain in machinability is sought and provided that the inclusion cleanliness remains consistent with the requirements of the intended application for steel.
  • the O content is most often at most 0.003% (30 ppm), so as to optimize the inclusion cleanliness. This limit may possibly be exceeded if the future application of the steel does not require a very good inclusion cleanliness, and in any case a specific O content does not constitute an intrinsic property of the steel according to the invention.
  • the control of the oxygen content is ensured by inerting systems during casting and by a control of the content of deoxidizing elements such as Si and Al.
  • deoxidizing elements such as Si and Al.
  • the composition of which is controlled so that this chemical equilibrium leads to the establishment of a low dissolved oxygen content in the liquid metal, and then avoiding the reoxidation of the liquid metal until casting by an effective protection against atmospheric oxygen, for example the inerting of the surface of the metal with argon, and the confinement of the pouring jets in refractory tubes themselves filled with argon;
  • the dissolved oxygen content is limited by the carbon present in the liquid steel, which causes the departure of the excess dissolved oxygen under form of CO; then, as in the previous case, the low dissolved oxygen content must be preserved until casting by an effective protection of the liquid steel against atmospheric reoxidation.
  • enrichment stage at a temperature of 900 to 980 ° C and a carbon potential of between 0.8 and 1.2 for a period of 3 to 20 hours; these conditions may vary depending on the exact composition of the steel being treated, and especially on the carburizing depth involved; typically for a temperature of 960 ° C a treatment of 3 to 6h makes it possible to temper the part to a depth of 1 to 1, 5 mm;
  • the criteria for choosing the diffusion temperature are mainly, and conventionally for the person skilled in the art, related to the situation of the phase transformation points of the treated grade, and to the fact that this temperature must not be too high to minimize the deformations of the part during the quenching which follows;
  • This type of carburizing is just one example, and other methods can be used.
  • the succession of steps may be as follows, to aim at a surface C content typically of 0.5 to 0. , 8%:
  • enrichment stage at a temperature of 900 to 980 ° C. and at a carbon potential of between 0.8 and 1.2 for a period of 3 to 20 hours; these conditions may vary depending on the exact composition of the steel being treated, and especially on the carburizing depth involved; typically for a temperature of 960 ' ⁇ a treatment of 3 to 6h allows to temper the part to a depth of 1 to 1, 5 mm avoiding the surface oxidation problems that may be encountered during an air cementation.
  • the criteria for choosing the diffusion temperature are mainly, and conventionally for the person skilled in the art, related to the situation of the phase transformation points of the treated grade, and to the fact that this temperature must not be too high to minimize the deformations of the part during the quenching which follows;
  • quenching for example with oil or gas (quenching pressure of between 3 and 10 bar), at a temperature of less than or equal to 1 ° C.;
  • the mechanical properties obtained on the final product depend not only on the composition of the steel, but also the thermal and thermomechanical treatments it undergoes until the product is obtained. It may however be noted that in the case where the final product must be cemented, the conditions of its hot shaping by forging, rolling or otherwise, are of little importance. Indeed, the Cementation is accompanied by a quenching and tempering operation which gives the product a new structure and erases the consequences of hot shaping. It is then this treatment which confers on the product the essential of its mechanical properties, if it is not itself followed by any other treatment which could modify them.
  • the steel Before forging, the steel is in the form of ingots of square section 100x100 mm and 200 mm high. After forging, the 40x40 mm section bars are cooled in still air and then normalized for 2 hours at a temperature of 875, 900 or 925 ⁇ , chosen according to the transformation point Ac3 of the grade. This standardization is intended to homogenize the carbon content and initial microstructure throughout the product.
  • Castings Nos. 1 to 4 are those whose composition is in accordance with the present invention.
  • Castings Nos. 5 to 10 are those in which at least one of the alloying elements is outside the claimed ranges. All concentrations are given in% by weight, except nitrogen, oxygen and boron, which are given in ppm by weight.
  • the table also shows the temperature of the transformation point Ac3 (in ° C) of each of the grades.
  • the quenchability of the different samples was evaluated by means of Jominy tests.
  • the austenitization temperature was chosen, according to the transformation point of the steel in question, among the temperatures 875, 900 and 925 ° C.
  • This heat treatment cycle makes it possible to estimate the resilience expected at the core of the parts treated by cementation.
  • a cylinder 1 1NiCrMo13 has therefore been placed in the carburization charge to serve as a reference and determine the reference characteristics that must achieve, for the sample format considered, shades developed in accordance with the present invention.
  • the composition of the casting used as a reference is given in Table 3.
  • the carbon potential in the diffusion phase was adapted to the treated grade so as to control the residual austenite surface content.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Mining & Mineral Resources (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Abstract

The invention relates to steel for manufacturing carburized steel parts, characterized in that the composition thereof is: 0.1 wt % ≤ C ≤ 0.15 wt %; 0.8 wt % ≤ Mn ≤ 2 wt %; 1 wt % ≤ Cr ≤ 2.5 wt %; 0.2 wt % ≤ Mo ≤ 0.6 wt %; trace elements ≤ Si ≤ 0.35 wt %; trace elements ≤ Ni ≤ 0.7 wt %; trace elements ≤ B ≤ 0.005 wt %; trace elements ≤ Ti ≤ 0.1 wt %; trace elements ≤ N ≤ 0.01 wt % if 0.0005 wt % (5ppm) ≤ B ≤ 0.005 wt %, and trace elements ≤ N ≤ 0.02 wt % if trace elements ≤ B ≤ 0.0005 wt % (5ppm); - traces ≤ Al ≤ 0.1 wt %; trace elements ≤ V ≤ 0.3 wt %; trace elements ≤ P ≤ 0.025 wt %; trace elements ≤ Cu ≤ 1 wt %, preferably < 0.6 wt %; and trace elements ≤ S ≤ 0.1 wt %, the remainder being iron and impurities resulting from production. The invention also relates to a carburized steel part produced with said steel, and to the method for manufacturing same.

Description

Acier pour la fabrication de pièces cémentées, pièce cémentée réalisée avec cet acier et son procédé de fabrication  Steel for the manufacture of case-hardened parts, case-hardened part made of this steel and its method of manufacture
L'invention concerne la sidérurgie, et plus particulièrement les nuances d'aciers de cémentation présentant une résilience élevée.  The invention relates to iron and steel, and more particularly to the grades of case hardening steels with a high degree of resilience.
Une des principales applications de tels aciers est la fabrication de pièces mécaniques de gros format et plus particulièrement la fabrication de trépans de forage (« drill bits »).  One of the main applications of such steels is the manufacture of large format mechanical parts and more particularly the manufacture of drill bits.
Un tel trépan est un outil forgé constitué de trois cônes rotatifs en acier "enchevêtrés" les uns dans les autres et permettant de broyer les formations géologiques lors des opérations d'exploration pétrolière ou gazière. Ces trois cônes sont en rotation, par l'intermédiaire d'un ou plusieurs roulements, sur trois bras en acier assemblés par soudage. Les pistes de roulement usinées sur les bras et à l'intérieur des cônes sont généralement, dans les procédés classiques de production, traitées superficiellement par cémentation atmosphérique pour atteindre une profondeur conventionnelle, où la dureté Vickers est de 550 HV, comprise en moyenne entre 1 et 1 ,5 mm.  Such a drill bit is a forged tool consisting of three rotating steel cones "entangled" in one another and making it possible to crush the geological formations during oil or gas exploration operations. These three cones are rotated, via one or more bearings, on three welded steel arms. The machining tracks machined on the arms and inside the cones are generally, in conventional production processes, treated superficially by atmospheric carburization to reach a conventional depth, where the Vickers hardness is 550 HV, included on average between 1 and 1.5 mm.
La présente invention concerne une nouvelle nuance d'acier pouvant être utilisée pour la fabrication des cônes et des bras. Il existe plusieurs sortes de tels trépans. L'une d'elles est le trépan à "dent insérées" c'est à dire dans lequel des picots, le plus souvent en carbure de tungstène obtenu par métallurgie des poudres, sont sertis dans chacun des cônes. L'acier faisant l'objet de la présente invention ne se limite pas, dans son utilisation, à ce type de trépans, et pourrait également être utilisé pour la production de trépans à "dents usinées".  The present invention relates to a new steel grade that can be used for making cones and arms. There are several kinds of such trephines. One of them is the bit with "inserted tooth", that is to say in which spikes, most often made of tungsten carbide obtained by powder metallurgy, are crimped into each of the cones. The steel subject of the present invention is not limited, in its use, to this type of drill bit, and could also be used for the production of "machined tooth" bits.
Actuellement, les nuances de référence utilisées pour la fabrication des cônes et des bras constituant les trépans sont des aciers fortement alliés au nickel à des teneurs pouvant atteindre 3,5% en poids (notamment la nuance de type 15NiCrMo13). Cet élément d'alliage est considéré habituellement comme nécessaire pour conférer au produit le niveau de ductilité indispensable pour résister à la sévérité des sollicitations mécaniques subies en service. Cette ductilité doit être associée à des caractéristiques de traction et à une trempabilité élevée. Les propriétés typiquement recherchées pour ces nuances sont, en effet :  Currently, the reference grades used for the manufacture of the cones and arms constituting the drill bits are steels strongly alloyed with nickel at levels of up to 3.5% by weight (especially the grade of 15NiCrMo13). This alloying element is usually considered necessary to give the product the level of ductility essential to withstand the severity of the mechanical stresses in service. This ductility must be associated with tensile characteristics and high quenchability. The properties typically sought for these shades are, in fact:
- une trempabilité telle que la courbe Jominy soit horizontale, typiquement au moins sur une profondeur de 20mm ; tel que décrit dans le document FR-A-2 765 890, cette caractéristique peut être évaluée par le coefficient β correspondant à la différence de dureté entre les points Jominy J 5 et J3. Pour que la trempabilité soit suffisante, il convient que la courbe Jominy vérifie β < 3.5 HRC et Ji > 40 HRC ; on rappelle que la courbe Jominy est une courbe qui traduit la trempabilité d'un acier ; elle est obtenue au moyen d'un essai normalisé (notamment par la norme NF EN ISO 642) en mesurant la dureté le long d'une génératrice d'une éprouvette cylindrique trempée par un jet d'eau arrosant l'une de ses extrémités ; la dureté mesurée à une profondeur de x mm à partir de ladite extrémité est désignée par Jx ; a hardenability such that the Jominy curve is horizontal, typically at least over a depth of 20 mm; as described in document FR-A-2 765 890, this characteristic can be evaluated by the coefficient β corresponding to the difference in hardness between Jominy points J 5 and J 3 . For quenchability to be sufficient, the Jominy curve should satisfy β <3.5 HRC and Ji> 40 HRC; it is recalled that the Jominy curve is a curve which reflects the hardenability of a steel; it is obtained at by means of a standardized test (in particular by the NF EN ISO 642 standard) by measuring the hardness along a generatrix of a cylindrical specimen soaked by a jet of water watering one of its ends; the hardness measured at a depth of x mm from said end is designated J x ;
- une limite d'élasticité Re supérieure à 900 MPa ;  a yield strength Re greater than 900 MPa;
- une résistance à la traction Rm supérieure à 1200 MPa, ;  a tensile strength Rm greater than 1200 MPa;
- une résilience Kv mesurée à 20 °C supérieure à 75 J ;  a resilience Kv measured at 20 ° C. of greater than 75 J;
- une bonne aptitude à la cémentation atmosphérique ; elle se traduit, notamment par la possibilité de trouver des conditions de cémentation atmosphérique permettant d'atteindre les caractéristiques suivantes :  a good aptitude for atmospheric carburizing; it results, in particular by the possibility of finding conditions of atmospheric cementation making it possible to reach the following characteristics:
• une profondeur de cémentation à 550 HV comprise entre 1 .2 et 1 .5 mm; • a carburising depth at 550 HV between 1 .2 and 1 .5 mm;
• une dureté superficielle supérieure à 670 HV ; • superficial hardness greater than 670 HV;
• une taille de grain austénitique telle que l'indice de grain est supérieur à ASTM 5 ;  An austenitic grain size such that the grain index is greater than ASTM 5;
· une teneur volumique superficielle maximale en austénite résiduelle (à 20 μηι sous la peau du métal) dans la couche cémentée inférieure à une teneur de l'ordre de 40 %, telle que ce qui est typiquement recherché après traitement des nuances de cémentation de type 15NiCrMo13.  A maximum superficial content in residual austenite (at 20 μηι under the skin of the metal) in the lower case-hardened layer at a content of about 40%, such as that which is typically sought after treatment of cementation type shades. 15NiCrMo13.
Cependant, les aciers habituellement utilisés dans ce contexte ont, comme on l'a dit, une teneur en Ni nécessitant un ajout significatif de cet élément onéreux et dont le prix d'achat est très variable dans le temps. On a donc essayé de remplacer ces aciers par des aciers de cémentation sans Ni ayant une résilience améliorée.  However, the steels usually used in this context have, as has been said, a Ni content requiring a significant addition of this expensive element and whose purchase price is very variable over time. It has therefore been attempted to replace these steels with Ni-free carburizing steels having improved resilience.
Le document US-A-6 146 472 en présente un exemple. L'augmentation de la résilience y est obtenue par un contrôle de la résistance au grossissement du grain austénitique via l'utilisation d'un microalliage Nb-AI-N, associé à un traitement thermique optimisé. Cependant, les valeurs de résiliences indiquées dans ce document sont au mieux voisines de 60J, et les exemples présentés sont des coulées qui ne permettent pas de vérifier le critère de trempabilité β < 3.5 HRC.  US-A-6 146 472 provides an example. The increase in resilience is obtained by controlling the magnification resistance of the austenitic grain via the use of an Nb-Al-N microalloy, combined with an optimized heat treatment. However, the resilience values indicated in this document are at best close to 60J, and the examples presented are castings which do not make it possible to check the quenchability criterion β <3.5 HRC.
De même, le document US-A-2005/0081962 décrit un acier pour cémentation n'utilisant pas de Ni, mais dont la résilience n'excède pas 51 J, ce qui n'est pas suffisant.  Similarly, US-A-2005/0081962 discloses a carburizing steel not using Ni, but whose resilience does not exceed 51 J, which is not sufficient.
Le but de l'invention est de proposer un acier de cémentation utilisable notamment pour la fabrication de trépans, ne nécessitant pas d'addition de Ni et répondant néanmoins à tous les critères de ductilité, trempabilité, Re, Rm et Kv cités plus haut.  The object of the invention is to provide a carburizing steel used in particular for the manufacture of drill bits, not requiring addition of Ni and nevertheless meeting all the criteria of ductility, hardenability, Re, Rm and Kv cited above.
A cet effet, l'invention a pour objet un acier pour la fabrication de pièces cémentées, caractérisé en ce que sa composition, en pourcentages pondéraux est : - 0,1 %≤C≤ 0,15% ; For this purpose, the subject of the invention is a steel for the manufacture of cemented parts, characterized in that its composition, in percentages by weight, is: - 0.1% ≤C≤ 0.15%;
- 0,8% < Mn < 2% ;  - 0.8% <Mn <2%;
- 1 % < Cr < 2,5% ;  - 1% <Cr <2.5%;
- 0,2% < Mo < 0,6% ;  - 0.2% <Mo <0.6%;
- traces < Si < 0,35% ;  - traces <If <0.35%;
- traces < Ni < 0,7%, de préférence traces < Ni < 0,3% ;  traces <Ni <0.7%, preferably traces <Ni <0.3%;
- traces < B < 0,005% ;  - traces <B <0.005%;
- traces < Ti < 0,1 %, de préférence traces < Ti < 0,04% ;  traces <Ti <0.1%, preferably traces <Ti <0.04%;
- traces < N < 0,01 % si 0.0005 % < B < 0,005%, et traces < N < 0.02 % si traces < B < 0.0005 % ;  - traces <N <0.01% if 0.0005% <B <0.005%, and traces <N <0.02% if traces <B <0.0005%;
- traces < Al < 0,1 % ;  - traces <Al <0.1%;
- traces < V < 0,3% ;  - traces <V <0.3%;
- traces < P < 0,025% ;  - traces <P <0.025%;
- traces < S < 0,1% ;  - traces <S <0.1%;
- traces < Cu < 1 %, de préférence < 0,6% ;  traces <Cu <1%, preferably <0.6%;
le reste étant du fer et des impuretés résultant de l'élaboration. the rest being iron and impurities resulting from the elaboration.
De préférence, traces < O < 30 ppm.  Preferably, traces <0 <30 ppm.
L'invention a également pour objet une pièce cémentée en acier, caractérisée en ce qu'elle est en un acier ayant la composition précédente et en ce qu'elle a subi une cémentation.  The subject of the invention is also a case-hardened steel piece, characterized in that it is made of a steel having the preceding composition and in that it has undergone a cementation.
Il peut s'agir d'un trépan de forage.  It can be a drill bit.
L'invention a également pour objet un procédé de fabrication d'une pièce cémentée, caractérisé en ce que :  The invention also relates to a method for manufacturing a cemented part, characterized in that:
- on prépare une ébauche de ladite pièce en un acier ayant la composition précédente. Cette mise en forme peut être réalisée par un procédé quelconque (forgeage, usinage, laminage...) ;  a blank of said workpiece is made of a steel having the preceding composition. This shaping can be performed by any method (forging, machining, rolling ...);
- et on pratique une cémentation sur ladite ébauche.  and a cementation is carried out on said blank.
Dans le cas d'un procédé de cémentation atmosphérique, la succession d'étapes peut être la suivante :  In the case of an atmospheric cementation process, the succession of steps may be as follows:
- chauffage jusqu'à la température du palier d'enrichissement.  - heating up to the temperature of the enrichment stage.
- palier d'enrichissement à une température de 900 à 980 °C pendant 3 à 20 h et à un potentiel carbone compris entre 0.8 et 1 .2% ;  enrichment stage at a temperature of 900 to 980 ° C. for 3 to 20 hours and at a carbon potential of between 0.8 and 1.2%;
- diffusion à une température de 820 à 880 °C à un potentiel carbone compris entre 0.6 et 0.8%, avec un temps de traitement de 1 à 4 h ;  diffusion at a temperature of 820 to 880 ° C. at a carbon potential of between 0.6 and 0.8%, with a treatment time of 1 to 4 hours;
- trempe à l'huile à une température inférieure ou égale à l ôO'C - revenu à une température comprise entre 150 et 250^ et pendant une durée comprise entre 1 et 4h. oil quenching at a temperature of less than or equal to 1 ° C - Income at a temperature between 150 and 250 ^ and for a period of between 1 and 4 hours.
Dans le cas où la cémentation est effectuée à basse pression, ladite pression peut être de 5 à 20 mbar, et la succession d'étapes de la cémentation peut être la suivante :  In the case where the cementation is carried out at low pressure, said pressure may be from 5 to 20 mbar, and the succession of steps of the cementation may be the following:
- chauffage jusqu'à la température du palier d'enrichissement.  - heating up to the temperature of the enrichment stage.
- palier d'enrichissement à une température de 900 à 980 °C pendant 3 à 20 h et à un potentiel carbone compris entre 0.8 et 1 .2% ;  enrichment stage at a temperature of 900 to 980 ° C. for 3 to 20 hours and at a carbon potential of between 0.8 and 1.2%;
- diffusion à une température de 890 à 950 °C à un potentiel carbone compris entre 0.6 et 0.8%, avec un temps de traitement de 1 à 4 h ;  diffusion at a temperature of 890 to 950 ° C. at a carbon potential of between 0.6 and 0.8%, with a treatment time of 1 to 4 hours;
- trempe à une température inférieure ou égale à l ôO 'C  quenching at a temperature of less than or equal to 100.degree.
- revenu à une température comprise entre 150 et 250 °C et pendant une durée comprise entre 1 et 4h.  - Income at a temperature between 150 and 250 ° C and for a period of between 1 and 4 hours.
Comme on l'aura compris, l'invention repose sur un ajustement soigné de la composition de l'acier, permettant de satisfaire tous les critères cités plus haut.  As will be understood, the invention is based on a careful adjustment of the composition of the steel, to meet all the criteria mentioned above.
En outre l'acier objet la présente invention se différencie également de celui décrit dans US-A-6 146 472 en ce que les résiliences accessibles sont significativement supérieures, et en ce que l'amélioration de la résilience n'est pas générée, au moins principalement, par un contrôle de la taille de grain. Ceci présente l'avantage de ne pas modifier l'aptitude de la nuance au traitement thermomécanique et de limiter le risque de grossissement anormal du grain austénitique lors de la cémentation. L'effet ségrégeant du niobium risquant de conduire à une taille de grain austénitique hétérogène est, notamment, évité. Le niveau de résilience accessible par la présente invention est également significativement plus élevé.  In addition, the steel that is the subject of the present invention is also different from that described in US Pat. No. 6,146,472 in that the accessible resilience is significantly greater, and in that the improvement of the resilience is not generated at least mainly, by a control of the grain size. This has the advantage of not modifying the ability of the grade to thermomechanical treatment and limit the risk of abnormal magnification of the austenitic grain during cementation. The segregating effect of niobium which may lead to a heterogeneous austenitic grain size is, in particular, avoided. The level of resilience accessible by the present invention is also significantly higher.
Le type de cémentation utilisable avec l'acier décrit dans la présente invention ne se limite pas au procédé de cémentation atmosphérique qui pourrait être remplacé par d'autres procédés de durcissement superficiel, par exemple la cémentation basse pression.  The type of carburizing used with the steel described in the present invention is not limited to the atmospheric carburization process which could be replaced by other surface hardening processes, for example low pressure carburizing.
La présente invention repose sur un acier dont la composition est définie ci- dessous. Toutes les teneurs sont données en pourcentages pondéraux. En utilisant une composition définie comme décrit ci-après, il est possible d'élaborer, sans addition volontaire de nickel et sans utiliser de quantités importantes d'autres éléments coûteux, un acier ayant une trempabilité, des caractéristiques mécaniques après trempe suivie d'un revenu et une aptitude à la cémentation (prise de carbone, résilience à cœur, profondeur de cémentation, teneur en austénite résiduelle...) voisines de celles des nuances de référence à 3,5% de Ni utilisées habituellement pour la fabrication des trépans de forage. La teneur en C est comprise entre 0,10% et 0,15%, soit une teneur en carbone limitée à une gamme relativement étroite, et qui est faible, comparativement à celles généralement rencontrées dans les aciers de cémentation. Cette faible teneur en carbone permet d'atteindre des résiliences très élevées dans le cœur des pièces cémentées. La perte de trempabilité et la diminution de la dureté à cœur des produits après cémentation, qui résulteraient normalement de cet abaissement de la teneur en C, sont compensées par un ajustement optimisé de la concentration des autres éléments d'alliage. The present invention is based on a steel whose composition is defined below. All grades are given in percentages by weight. By using a composition defined as described below, it is possible to develop, without the voluntary addition of nickel and without using large quantities of other expensive elements, a steel having a hardenability, mechanical characteristics after quenching followed by and a carburizing ability (carbon uptake, resilience to the core, carburizing depth, residual austenite content, etc.) similar to those of the reference grades of 3.5% Ni usually used for the manufacture of carbon fiber drill bits. drilling. The content of C is between 0.10% and 0.15%, a carbon content limited to a relatively narrow range, and which is low, compared with those generally encountered in case-hardening steels. This low carbon content makes it possible to achieve very high resilience in the core of the cemented parts. The loss of quenchability and the decrease in the hardness of the after-carburized products, which would normally result from this lowering of the C content, are compensated by an optimized adjustment of the concentration of the other alloying elements.
La teneur en Mn est comprise entre 0,8% et 2%. Le manganèse est utilisé avec le chrome et le molybdène pour compenser la perte de trempabilité associée à la diminution de la teneur en carbone. Pour que son effet soit suffisant, une teneur supérieure ou égale à 0,8% est requise. Cet élément d'alliage pouvant poser des problèmes de ségrégation, il est préférable que sa concentration n'excède pas 2%.  The Mn content is between 0.8% and 2%. Manganese is used with chromium and molybdenum to compensate for the loss of hardenability associated with decreased carbon content. For its effect to be sufficient, a content greater than or equal to 0.8% is required. Since this alloying element can pose problems of segregation, it is preferable that its concentration does not exceed 2%.
La teneur en Cr est comprise entre 1 % et 2,5%. Comme le manganèse, le chrome est utilisé pour assurer un niveau de trempabilité suffisant à la nuance. La teneur minimale de 1 % est choisie pour que l'effet de cet élément d'alliage sur la trempabilité soit suffisant. La teneur maximale de 2,5 % est définie de manière à éviter un effet néfaste sur les propriétés d'emploi, notamment par formation de carbures de chrome grossiers.  The Cr content is between 1% and 2.5%. Like manganese, chromium is used to ensure a sufficient degree of quenchability to the grade. The minimum content of 1% is chosen so that the effect of this alloying element on quenchability is sufficient. The maximum content of 2.5% is defined in order to avoid a detrimental effect on the use properties, in particular by formation of coarse chromium carbides.
La teneur en Mo est comprise entre 0,2% et 0,6 %. Le molybdène est un troisième élément utilisé pour ajuster la trempabilité de la nuance. Il s'agit également d'un élément d'alliage qui peut être judicieusement utilisé pour augmenter la résilience, notamment à basse température. Le molybdène permet aussi d'exacerber l'effet du bore sur la trempabilité, et peut donc être utilisé à cet effet dans le cas de nuance alliées au bore. Pour une teneur inférieure à 0,2% l'augmentation de la trempabilité est trop faible et cette valeur est donc choisie comme niveau minimum. Pour de fortes concentrations, le molybdène tend à diminuer l'aptitude des aciers au forgeage. En outre, comme il s'agit d'un élément d'alliage onéreux, son utilisation à une teneur excessive conduirait à une perte du bénéfice économique apporté par la non-utilisation de nickel. Pour ces raisons, une teneur maximale de 0,6% est préférée.  The Mo content is between 0.2% and 0.6%. Molybdenum is a third element used to adjust the quenchability of the grade. It is also an alloying element that can be used judiciously to increase resilience, especially at low temperatures. Molybdenum also exacerbates the effect of boron on hardenability, and can therefore be used for this purpose in the case of boron alloyed grades. For a content of less than 0.2% the increase in hardenability is too low and this value is therefore chosen as the minimum level. For high concentrations, molybdenum tends to decrease the ability of forging steels. In addition, because it is an expensive alloying element, its use at an excessive content would lead to a loss of economic benefit brought about by the non-use of nickel. For these reasons, a maximum content of 0.6% is preferred.
La teneur en Si est inférieure à 0,35 %. Tout comme l'aluminium, le silicium peut être utilisé comme élément de désoxydation. Pour un acier qui a été désoxydé par ajout de silicium, la teneur résiduelle de cet élément n'excède de toute façon généralement pas 0,35%. Il convient également de ne pas dépasser une teneur de 0,35% dans les aciers de l'invention, car le silicium est un élément d'alliage qui peut limiter, par effet barrière, la prise de carbone lors de la cémentation.  The Si content is less than 0.35%. Like aluminum, silicon can be used as a deoxidizing element. For a steel which has been deoxidized by addition of silicon, the residual content of this element does not in any case generally exceed 0.35%. It should also not exceed a content of 0.35% in the steels of the invention, because silicon is an alloying element that can limit, by barrier effect, the carbon uptake during cementation.
La teneur en Ni est inférieure ou égale à 0,7%, de préférence 0,3%. Comme on l'a dit, l'un des objets de la présente invention est de permettre de se passer d'un ajout volontaire de cet élément. Il est néanmoins toujours présent à l'état résiduel dans les matières premières utilisées pour élaborer l'acier, notamment dans les ferrailles. La teneur de 0,3% correspond à la teneur maximale la plus généralement rencontrée lorsqu'aucun ajout volontaire de nickel n'est effectué en cours d'élaboration. The Ni content is less than or equal to 0.7%, preferably 0.3%. As has been said, one of the objects of the present invention is to make it possible to do without an addition voluntary of this element. However, it is still present in the residual state in the raw materials used to make steel, especially in scrap metal. The 0.3% content corresponds to the maximum level most commonly encountered when no voluntary addition of nickel is made during the elaboration.
La teneur en B est inférieure à 0,005%. Le bore est un élément optionnel. Il peut être utilisé pour ajuster optimalement la trempabilité de la nuance si les teneurs en Mn, Cr et Mo ne sont pas tout à fait suffisantes à cet effet. Mais pour que cet élément d'alliage agisse effectivement sur la trempabilité, il doit être maintenu en solution solide. Pour cela, la précipitation de nitrures ou d'oxydes de bore doit être évitée. Ce résultat peut être obtenu en ajoutant un élément d'alliage à plus forte affinité avec l'azote, par exemple du titane, et en contrôlant le procédé d'élaboration pour limiter la dissolution d'azote et d'oxygène dans l'acier.  The B content is less than 0.005%. Boron is an optional element. It can be used to optimally adjust the quenchability of the grade if the levels of Mn, Cr and Mo are not quite sufficient for this purpose. But for this alloy element to actually act on the quenchability, it must be maintained in solid solution. For that, the precipitation of nitrides or oxides of boron must be avoided. This result can be obtained by adding a higher affinity alloy element with nitrogen, for example titanium, and controlling the production process to limit the dissolution of nitrogen and oxygen in the steel.
La teneur en Ti est inférieure à 0.1 % et préférablement inférieure à 0,04%. Le titane est optionnellement ajouté pour permettre au bore d'être maintenu en solution solide par précipitation de nitrures de titane qui diminuent la quantité d'azote qui serait susceptible de se combiner au bore. Sa teneur doit optimalement être choisie en fonction de la quantité d'azote de la nuance. Pour être totalement efficace, une quantité stœchiométrique de titane doit être ajoutée pour assurer une précipitation de la totalité de l'azote contenu dans l'acier sous forme de TiN, et ainsi maintenir le bore en solution solide. Ceci est vérifié si le rapport Ti/N est supérieur à 3,4. En cas d'ajout sous- stœchiométrique de titane, l'effet du bore sur la trempabilité peut quand même s'exprimer mais est moins marqué. Au-delà de la limite prescrite, il y a un risque de formation de TiN trop grossiers lors de la solidification, et de plus l'addition de Ti devient excessivement onéreuse.  The Ti content is less than 0.1% and preferably less than 0.04%. Titanium is optionally added to allow the boron to be maintained in solid solution by precipitation of titanium nitrides which reduce the amount of nitrogen that may be combined with boron. Its content should optimally be chosen according to the amount of nitrogen in the grade. To be completely effective, a stoichiometric amount of titanium must be added to ensure precipitation of all of the nitrogen contained in the steel as TiN, and thus maintain the boron in solid solution. This is verified if the Ti / N ratio is greater than 3.4. In the case of substoichiometric titanium addition, the effect of boron on quenchability can still be expressed but is less pronounced. Beyond the prescribed limit, there is a risk of formation of TiN too coarse during solidification, and moreover the addition of Ti becomes excessively expensive.
La teneur en N est inférieure à 0.02%, de préférence inférieure à 0,01 %. Dans le cas d'une élaboration avec ajout de bore et de titane, il est nécessaire de contrôler la teneur en azote de l'acier pour limiter le risque de formation de nitrures de titane TiN grossiers, qui peuvent détériorer les propriétés d'emploi du produit. Dans le cas d'un ajout de bore (de 5 à 50 ppm), une teneur en azote inférieure à 0,01 % est donc recommandée. Si le bore n'est pas utilisé (B < 5ppm), il n'est pas absolument indispensable de contrôler strictement la teneur en azote qui peut alors aller jusqu'à 0,02% sans effet néfaste sur les propriétés de l'acier élaboré.  The N content is less than 0.02%, preferably less than 0.01%. In the case of elaboration with addition of boron and titanium, it is necessary to control the nitrogen content of the steel to limit the risk of formation of coarse titanium nitride TiN, which can deteriorate the properties of use of the product. In the case of boron addition (from 5 to 50 ppm), a nitrogen content of less than 0.01% is therefore recommended. If the boron is not used (B <5ppm), it is not absolutely essential to strictly control the nitrogen content, which can then go up to 0.02% without detrimental effect on the properties of the elaborated steel. .
La teneur en Al doit être au maximum de 0,1 % : L'aluminium est un élément optionnel. Il peut être utilisé comme désoxydant de l'acier en remplacement du silicium, et pour optimiser la tenue du grain austénitique lors de la cémentation. La teneur en V est au maximum de 0,3%. Le vanadium est un élément optionnel. Il peut être utilisé comme élément de micro-alliage pour un meilleur contrôle de la taille de grain lors de la cémentation, apportant une amélioration supplémentaire de la résilience. The Al content must be at most 0.1%: Aluminum is an optional element. It can be used as a deoxidizer for steel to replace silicon, and to optimize the behavior of the austenitic grain during cementation. The V content is at most 0.3%. Vanadium is an optional element. It can be used as a micro-alloy element for better control of grain size during carburizing, providing further improvement in resilience.
La teneur en P est au maximum de 0.025%. Cette limite est recommandée pour ne pas risquer de fragiliser l'acier. A une teneur trop importante, cet élément a, en effet, tendance à ségréger aux joints de grain austénitiques, ce qui peut conduire à une augmentation de la température de transition ductile-fragile et à une baisse de la résilience à température ambiante.  The P content is at most 0.025%. This limit is recommended to avoid risk of weakening the steel. At an excessively high content, this element tends to segregate at the austenitic grain boundaries, which can lead to an increase in the ductile-brittle transition temperature and a decrease in the resilience at room temperature.
La teneur en Cu est au maximum de 1 %, de préférence au maximum de 0.6%. Une teneur maximale de 1 % est recommandée car il s'agit d'un élément onéreux qui n'apporte aucun bénéfice de trempabilité ou de résilience. La valeur maximale préférée de 0.6% est une teneur usuellement reconnue comme étant celle en dessous de laquelle le cuivre n'a pas d'effet notable sur les propriétés mécaniques de l'acier. Néanmoins sont utilisation à une teneur plus élevée est envisageable sans modifier l'aptitude de la nuance à être utilisée pour la fabrication de trépans de forage.  The Cu content is at most 1%, preferably at most 0.6%. A maximum content of 1% is recommended because it is an expensive element that provides no benefit of quenchability or resilience. The preferred maximum value of 0.6% is a content usually recognized as being below which copper has no significant effect on the mechanical properties of steel. Nevertheless, use at a higher level is possible without modifying the ability of the grade to be used for the manufacture of drill bits.
Les effets négatifs du cuivre à des teneurs plus élevées sont en particulier le risque d'apparition de défauts de surface lors du laminage (faïençage). Des additions de Ni et/ou Si peuvent permettre d'y remédier, mais l'invention exigeant des teneurs relativement basses en ces éléments, on ne peut pas beaucoup compter sur eux pour limiter les effets néfastes du cuivre, d'où les limites de 1 %, mieux 0,6%, pour la teneur en cuivre des aciers de l'invention.  The negative effects of copper at higher levels are in particular the risk of appearance of surface defects during rolling (crazing). Additions of Ni and / or Si may make it possible to remedy this, but since the invention requires relatively low levels of these elements, we can not rely heavily on them to limit the harmful effects of copper, hence the limits of 1%, better 0.6%, for the copper content of the steels of the invention.
La teneur en S n'est pas strictement imposée dans la définition de l'acier selon l'invention la plus générale, mais elle doit être contrôlée en fonction de l'application envisagée. Une basse teneur sera recherchée si l'on souhaite améliorer la propreté inclusionnaire en ne formant pas de sulfures (typiquement < 0.01 %) et une teneur plus élevée pourra être choisie (typiquement de 0.03% à 0,1 %) si un gain en usinabilité est recherché et sous réserves que la propreté inclusionnaire demeure conforme aux exigences requises par l'application envisagée pour l'acier.  The S content is not strictly imposed in the definition of steel according to the most general invention, but it must be controlled according to the intended application. A low content will be sought if it is desired to improve the inclusion cleanliness by not forming sulphides (typically <0.01%) and a higher content may be chosen (typically from 0.03% to 0.1%) if a gain in machinability is sought and provided that the inclusion cleanliness remains consistent with the requirements of the intended application for steel.
La teneur en O est le plus souvent au maximum de 0.003% (30 ppm), de manière à optimiser la propreté inclusionnaire. Cette limite peut éventuellement être dépassée si l'application future de l'acier ne nécessite pas une très bonne propreté inclusionnaire, et en tout cas une teneur en O déterminée ne constitue pas une propriété intrinsèque de l'acier selon l'invention.  The O content is most often at most 0.003% (30 ppm), so as to optimize the inclusion cleanliness. This limit may possibly be exceeded if the future application of the steel does not require a very good inclusion cleanliness, and in any case a specific O content does not constitute an intrinsic property of the steel according to the invention.
Le contrôle de la teneur en oxygène est assuré par des systèmes d'inertage lors de la coulée et par un contrôle de la teneur en éléments désoxydants tels que Si et Al. Lorsque ces éléments désoxydants sont présents à de faibles teneurs, on peut néanmoins assurer une faible teneur en oxygène dans le métal liquide : The control of the oxygen content is ensured by inerting systems during casting and by a control of the content of deoxidizing elements such as Si and Al. When these deoxidizing elements are present at low levels, it is nevertheless possible to ensure a low oxygen content in the liquid metal:
- soit en agitant le métal liquide de façon à le placer en équilibre chimique avec le laitier, dont on maîtrise la composition de sorte que cette équilibre chimique conduise à l'établissement d'une faible teneur en oxygène dissous dans le métal liquide, et en évitant ensuite les réoxydations du métal liquide jusqu'à la coulée par une protection efficace contre l'oxygène atmosphérique, par exemple l'inertage de la surface du métal par de l'argon, et le confinement des jets de coulée dans des tubes en réfractaire eux-mêmes remplis d'argon ;  or by agitating the liquid metal so as to place it in chemical equilibrium with the slag, the composition of which is controlled so that this chemical equilibrium leads to the establishment of a low dissolved oxygen content in the liquid metal, and then avoiding the reoxidation of the liquid metal until casting by an effective protection against atmospheric oxygen, for example the inerting of the surface of the metal with argon, and the confinement of the pouring jets in refractory tubes themselves filled with argon;
- soit en conduisant l'élaboration du métal liquide au moins en partie sous pression réduite, de sorte que la teneur en oxygène dissous soit limitée par le carbone présent dans l'acier liquide, ce qui entraîne le départ de l'oxygène dissous excédentaire sous forme de CO ; ensuite, comme dans le cas précédent, la basse teneur en oxygène dissous doit être conservée jusqu'à la coulée par une protection efficace de l'acier liquide contre les réoxydations atmosphériques.  or by driving the elaboration of the liquid metal at least partially under reduced pressure, so that the dissolved oxygen content is limited by the carbon present in the liquid steel, which causes the departure of the excess dissolved oxygen under form of CO; then, as in the previous case, the low dissolved oxygen content must be preserved until casting by an effective protection of the liquid steel against atmospheric reoxidation.
Pour les autres éléments, ils peuvent être présents à l'état de simples impuretés résultant de l'élaboration.  For the other elements, they can be present in the state of simple impurities resulting from the elaboration.
Dans le cas d'un procédé de cémentation atmosphérique visant à obtenir une teneur en carbone superficielle typiquement de 0,5 à 0,8%, la succession d'étapes peut être la suivante :  In the case of an atmospheric cementation process intended to obtain a surface carbon content typically of 0.5 to 0.8%, the succession of steps may be as follows:
- chauffage jusqu'à la température du palier d'enrichissement ; une vitesse de l'ordre de l O Omin pour ce chauffage est conseillée pour procurer un bon contrôle de l'évolution de la taille des grains ;  heating up to the temperature of the enrichment stage; a speed of the order of 10 mm for this heating is advisable to provide a good control of the evolution of the grain size;
- palier d'enrichissement à une température inférieure de 900 à 980 'Ό et à un potentiel carbone compris entre 0.8 et 1 .2, pendant une durée de 3 à 20 h ; ces conditions peuvent varier en fonction de la composition exacte de l'acier traité, et surtout de la profondeur de cémentation visée ; typiquement pour une température de 960 °C un traitement de 3 à 6h permet de cémenter la pièce sur une profondeur de 1 à 1 ,5 mm ;  enrichment stage at a temperature of 900 to 980 ° C and a carbon potential of between 0.8 and 1.2 for a period of 3 to 20 hours; these conditions may vary depending on the exact composition of the steel being treated, and especially on the carburizing depth involved; typically for a temperature of 960 ° C a treatment of 3 to 6h makes it possible to temper the part to a depth of 1 to 1, 5 mm;
- diffusion à une température de 820 à 880 °C à un potentiel carbone compris entre 0.6 et 0.8%, avec un temps de traitement de 1 à 4 h, typiquement de l'ordre de 2h ; les critères de choix de la température de diffusion sont principalement, et classiquement pour l'homme du métier, liés à la situation des points de transformation de phase de la nuance traitée, et au fait que cette température ne doit pas être trop élevée pour minimiser les déformations de la pièce lors de la trempe qui suit ;  diffusion at a temperature of 820 to 880 ° C. at a carbon potential of between 0.6 and 0.8%, with a treatment time of 1 to 4 hours, typically of the order of 2 hours; the criteria for choosing the diffusion temperature are mainly, and conventionally for the person skilled in the art, related to the situation of the phase transformation points of the treated grade, and to the fact that this temperature must not be too high to minimize the deformations of the part during the quenching which follows;
- trempe à l'huile à une température inférieure ou égale à l ôO'O ; - revenu à une température comprise entre 150 et 250^ et pendant une durée classiquement de l'ordre de 2h, en tout cas comprise entre 1 et 4h. oil quenching at a temperature of less than or equal to 100%; - Income at a temperature between 150 and 250 ^ and for a period typically of the order of 2h, in any case between 1 and 4h.
Ce type de cémentation n'est qu'un exemple, et d'autres procédés peuvent être utilisés. En particulier, on peut avoir recours à une cémentation basse pression pour éviter d'éventuels problèmes d'oxydation superficielle et/ou intergranulaire lors du traitement, et aussi pour accéder à des profondeurs de cémentation plus importantes que les 1 à 2 mm habituellement accessibles par une cémentation atmosphérique et/ou réduire la durée de cémentation grâce à la température élevée à laquelle la cémentation basse pression est pratiquée.  This type of carburizing is just one example, and other methods can be used. In particular, it is possible to use a low-pressure carburizing to avoid possible surface oxidation and / or intergranular problems during the treatment, and also to reach carburizing depths greater than the 1 to 2 mm usually accessible by atmospheric carburizing and / or reducing the cementation time due to the high temperature at which low pressure carburizing is practiced.
Dans le cas d'un procédé de cémentation basse pression conduite à une pression de quelques millibars (de 5 à 20 mbars), la succession d'étapes peut être la suivante, pour viser une teneur en C superficielle typiquement de 0,5 à 0,8% :  In the case of a low pressure carburizing process conducted at a pressure of a few millibars (5 to 20 mbar), the succession of steps may be as follows, to aim at a surface C content typically of 0.5 to 0. , 8%:
- chauffage jusqu'à la température du palier d'enrichissement ; une vitesse de l'ordre de l O Omin pour ce chauffage est conseillée pour procurer un bon contrôle de l'évolution de la taille des grains ;  heating up to the temperature of the enrichment stage; a speed of the order of 10 mm for this heating is advisable to provide a good control of the evolution of the grain size;
- palier d'enrichissement à une température de 900 à 980 'Ό et à un potentiel carbone compris entre 0.8 et 1 .2, pendant une durée de 3 à 20 h ; ces conditions peuvent varier en fonction de la composition exacte de l'acier traité, et surtout de la profondeur de cémentation visée ; typiquement pour une température de 960 'Ό un traitement de 3 à 6h permet de cémenter la pièce sur une profondeur de 1 à 1 ,5 mm en évitant les problèmes d'oxydation de surface qui peuvent être rencontrés lors d'une cémentation atmosphérique.  enrichment stage at a temperature of 900 to 980 ° C. and at a carbon potential of between 0.8 and 1.2 for a period of 3 to 20 hours; these conditions may vary depending on the exact composition of the steel being treated, and especially on the carburizing depth involved; typically for a temperature of 960 'Ό a treatment of 3 to 6h allows to temper the part to a depth of 1 to 1, 5 mm avoiding the surface oxidation problems that may be encountered during an air cementation.
- diffusion à une température de 890-950 'Ό à un potentiel carbone compris entre 0.6 et 0.8%, avec un temps de traitement de 1 à 4 h, typiquement de l'ordre de 2h ; les critères de choix de la température de diffusion sont principalement, et classiquement pour l'homme du métier, liés à la situation des points de transformation de phase de la nuance traitée, et au fait que cette température ne doit pas être trop élevée pour minimiser les déformations de la pièce lors de la trempe qui suit ;  diffusion at a temperature of 890-950 ° at a carbon potential of between 0.6 and 0.8%, with a treatment time of 1 to 4 hours, typically of the order of 2 hours; the criteria for choosing the diffusion temperature are mainly, and conventionally for the person skilled in the art, related to the situation of the phase transformation points of the treated grade, and to the fact that this temperature must not be too high to minimize the deformations of the part during the quenching which follows;
- trempe, par exemple à l'huile ou au gaz (pression de trempe comprise entre 3 et 10 bars), à une température inférieure ou égale à l ôO 'C ;  quenching, for example with oil or gas (quenching pressure of between 3 and 10 bar), at a temperature of less than or equal to 1 ° C.;
- revenu à une température comprise entre 150 et 250 ^ et pendant une durée classiquement de l'ordre de 2h, en tout cas comprise entre 1 et 4h.  - Income at a temperature between 150 and 250 ^ and for a period typically of the order of 2h, in any case between 1 and 4h.
Bien entendu, les propriétés mécaniques obtenues sur le produit final dépendent non seulement de la composition de l'acier, mais aussi des traitements thermiques et thermomécaniques qu'il subit jusqu'à l'obtention du produit. On peut cependant remarquer que dans le cas où le produit final doit être cémenté, les conditions de sa mise en forme à chaud par forgeage, laminage ou autre, n'ont que peu d'importance. En effet, la cémentation est accompagnée par une opération de trempe et revenu qui confère au produit une nouvelle structure et efface les conséquences de la mise en forme à chaud. C'est alors ce traitement qui confère au produit l'essentiel de ses propriétés mécaniques, s'il n'est lui-même suivi par aucun autre traitement qui pourrait les modifier. Of course, the mechanical properties obtained on the final product depend not only on the composition of the steel, but also the thermal and thermomechanical treatments it undergoes until the product is obtained. It may however be noted that in the case where the final product must be cemented, the conditions of its hot shaping by forging, rolling or otherwise, are of little importance. Indeed, the Cementation is accompanied by a quenching and tempering operation which gives the product a new structure and erases the consequences of hot shaping. It is then this treatment which confers on the product the essential of its mechanical properties, if it is not itself followed by any other treatment which could modify them.
On va à présent décrire les résultats d'essais effectués sur des aciers selon l'invention et des aciers de référence. Tous les résultats présentés ont été obtenus sur des coulées de laboratoire forgées à 1200 ^ en barres de section carrée de 40 mm de côté.  The results of tests carried out on steels according to the invention and reference steels will now be described. All the results presented were obtained on laboratory castings forged at 1200 square-section bars of 40 mm side.
Avant forgeage, l'acier se présente sous forme de lingotins de section carrée 100x100 mm et de 200 mm de hauteur. Après forgeage, les barres de section 40x40 mm sont refroidies à l'air calme puis normalisées pendant 2h à une température de 875, 900 ou 925^, choisie en fonction du point de transformation Ac3 de la nuance. Cette normalisation est destinée à homogénéiser la teneur en carbone et la microstructure initiale dans tout le produit.  Before forging, the steel is in the form of ingots of square section 100x100 mm and 200 mm high. After forging, the 40x40 mm section bars are cooled in still air and then normalized for 2 hours at a temperature of 875, 900 or 925 ^, chosen according to the transformation point Ac3 of the grade. This standardization is intended to homogenize the carbon content and initial microstructure throughout the product.
La composition des différentes nuances testées est donnée au Tableau 1 . Les coulées n °1 à 4 sont celles dont la composition est conforme à la présente invention. Les coulées n ° 5 à 10 sont celles dont au moins un des éléments d'alliage est en dehors des intervalles revendiqués. Toutes les concentrations sont données en % pondéraux, sauf l'azote, l'oxygène et le bore qui sont donnés en ppm pondéraux. Le tableau indique également la température du point de transformation Ac3 (en °C) de chacune des nuances.  The composition of the different shades tested is given in Table 1. Castings Nos. 1 to 4 are those whose composition is in accordance with the present invention. Castings Nos. 5 to 10 are those in which at least one of the alloying elements is outside the claimed ranges. All concentrations are given in% by weight, except nitrogen, oxygen and boron, which are given in ppm by weight. The table also shows the temperature of the transformation point Ac3 (in ° C) of each of the grades.
Ech C Si Mn Ni Cr Mo S P O Al N Cu B Ti V Ac3Ech C If Mn Ni Cr Mo S P O Al N Cu B Ti V Ac3
% % % % % % % % PP % PP % PP % % °C m m m %%%%%%%% PP% PP% PP%% ° C m m m
Inv. 1 0,1 0,2 1 ,4 0,0 2,1 0,4 0.0 0.0 7 0,0 115 0,0 3 0,0 0,0 857  Inv. 1 0.1 0.2 1, 4 0.0 2.1 0.4 0.0 0.0 7 0.0 115 0.0 3 0.0 0.0 857
07 74 84 67 07 43 08 09 22 7 09 1 07 74 84 67 07 43 08 09 22 7 09 1
Inv. 2 0,1 0.2 1 ,5 0,0 2,0 0,4 0.0 0.0 21 0,0 120 0,0 3 0,0 0,0 845 Inv. 2 0.1 0.2 1, 5 0.0 2.0 0.4 0.0 0.0 21 0.0 120 0.0 3 0.0 0.0 845
37 39 36 72 58 01 08 08 02 8 06 1 37 39 36 72 58 01 08 08 02 8 06 1
Inv. 3 0,1 0.2 0,8 0,0 1 ,4 0,4 0.0 0.0 10 0,0 67 0,0 31 0,0 0,0 874 Inv. 3 0.1 0.2 0.8 0.0 1, 4 0.4 0.0 0.0 0.0 67 0.0 0.0 0.0 0.0 874
14 35 93 59 28 06 05 07 30 6 23 1 14 35 93 59 28 06 05 07 30 6 23 1
Inv. 4 0,1 0.2 1 ,0 0,0 1 ,5 0,3 0.0 0.0 13 0,0 78 0,0 29 0,0 0,2 861 Inv. 4 0.1 0.2 1, 0 0.0 1, 5 0.3 0.0 0.0 13 0.0 78 0.0 29 0.0 0.2 861
46 43 17 56 19 76 06 07 18 5 19 1 46 43 17 56 19 76 06 07 18 5 19 1
Réf. 5 0,1 0.0 1 ,2 0,1 1 ,3 0,0 0.0 0.0 18 0,0 148 0,2 1 0,0 0,0 826 Ref. 5 0.1 0.0 1, 2 0.1 1, 3 0.0 0.0 0.0 18 0.0 148 0.2 1 0.0 0.0 826
60 40 40 80 80 90 31 8 20 1 02 0 60 40 40 80 80 90 31 8 20 1 02 0
Réf. 6 0,0 0.3 1 ,2 0,2 0,9 0,0 0.0 0.0 12 0,0 100 0,2 36 0,0 0,0 881 Ref. 6 0.0 0.3 1, 2 0.2 0.9 0.0 0.0 0.0 0.0 0.0 0.2 0.2 0.0 0.0 0.0 881
70 80 50 60 40 80 04 12 30 1 22 1 Réf. 7 0,1 0.2 1 ,3 0,0 1 ,6 0,1 0.0 0.0 9 0,0 175 0,0 25 0,0 0,0 84870 80 50 60 40 80 04 12 30 1 22 1 Ref. 7 0.1 0.2 1, 3 0.0 1, 6 0.1 0.0 0.0 9 0.0 175 0.0 25 0.0 0.0 848
30 60 50 50 60 00 08 08 20 5 06 130 60 50 50 60 00 08 08 20 5 06 1
Réf. 8 0,1 0,9 1 ,4 0,0 1 ,4 0,2 0.0 0.0 10 0,0 141 0,0 2 0,0 0,0 882 Ref. 8 0.1 0.9 1, 4 0.0 1, 4 0.2 0.0 0.0 10 0.0 141 0.0 2 0.0 0.0 882
20 30 70 50 40 10 07 08 20 4 05 1 20 30 70 50 40 10 07 08 20 4 05 1
Réf. 9 0,1 0,2 1 ,1 0,0 1 ,9 0,1 0.0 0.0 14 0,0 155 0,0 10 0,0 0,0 851 Ref. 9 0.1 0.2 1, 1 0.0 1, 9 0.1 0.0 0.0 14 0.0 155 0.0 10 0.0 0.0 851
20 50 10 60 20 60 06 08 20 6 06 1 20 50 10 60 20 60 06 08 20 6 06 1
Réf. 10 0,1 0.8 0,5 0,0 1 ,5 0,8 0.0 0.0 12 0,0 143 0,0 4 0,0 0,0 916 Ref. 10 0.1 0.8 0.5 0.0 1, 5 0.8 0.0 0.0 12 0.0 143 0.0 4 0.0 0.0 916
30 80 30 50 10 60 08 07 20 4 06 1  30 80 30 50 10 60 08 07 20 4 06 1
Tableau 1 : compositions et températures Ac3 des échantillons testés Table 1: Ac3 compositions and temperatures of the tested samples
Du fait de la présence significative d'AI à des teneurs assez comparables, les teneurs en O des différents échantillons sont toutes comprises entre 7 et 21 ppm et n'influent pas sensiblement sur les propriétés obtenues. Due to the significant presence of AI at fairly comparable levels, the O contents of the various samples are all between 7 and 21 ppm and do not significantly affect the properties obtained.
La trempabilité des différents échantillons a été évaluée au moyen d'essais Jominy. La température d'austénitisation a été choisie, en fonction du point de transformation de l'acier considéré, parmi les températures 875, 900 et 925 °C.  The quenchability of the different samples was evaluated by means of Jominy tests. The austenitization temperature was chosen, according to the transformation point of the steel in question, among the temperatures 875, 900 and 925 ° C.
Pour évaluer les caractéristiques mécaniques, des pièces de section carrée de To evaluate the mechanical characteristics, pieces of square section of
20 mm de côté ont été prélevées dans chacune des barres forgées puis traitées par le cycle thermique suivant : 20 mm of side were taken in each of the bars forged then treated by the following thermal cycle:
- chauffage jusqu'à la température d'austénitisation ;  heating up to the austenitization temperature;
- austénitisation à 930 ^ pendant 30 minutes ;  austenitization at 930 ° C for 30 minutes;
- trempe à l'huile à 30 <€ ; oil quenching at 30 ° C . ;
- revenu à Ι ΘΟ 'Ό pendant 2h ;  - income at Ι ΘΟ 'Ό for 2 hours;
- refroidissement à l'air.  - air cooling.
Ce cycle de traitement thermique permet d'estimer la résilience attendue à cœur des pièces traitées par cémentation.  This heat treatment cycle makes it possible to estimate the resilience expected at the core of the parts treated by cementation.
Des éprouvettes de traction et de résilience (type Charpy avec entaille en V) ont ensuite été usinées dans les pièces ainsi traitées. Le Tableau 2 présente les résultats obtenus et on va les comparer aux propriétés requises pour la production de trépans. Les données soulignées indiquent les résultats qui ne sont pas conformes au critère Ji > 40, ou au critère de trempabilité β < 3,5 HRC, ou dont les caractéristiques d'élasticité, de traction et de résilience sont insuffisantes. Ech T Jominy (°C) Ji β Re (MPa) Rm (MPa) Kv 20°C (J)Traction and resilience test pieces (Charpy type with V notch) were then machined in the parts thus treated. Table 2 presents the results obtained and will be compared to the properties required for the production of drill bits. The underlined data indicate results that do not meet criterion Ji> 40, or quenchability criterion β <3.5 HRC, or whose elasticity, tensile and resilience characteristics are insufficient. Echo T Jominy (° C) Ji β Re (MPa) Rm (MPa) Kv 20 ° C (J)
Inv. 1 875 40,9 1 ,9 995 1280 121 Inv. 1 875 40.9 1, 9 995 1280 121
Inv. 2 875 43,5 2,9 967 1291 108  Inv. 2,875 43.5 2.9 967 1291 108
Inv. 3 900 40,2 3 907 1204 160  Inv. 3 900 40.2 3 907 1204 160
Inv. 4 900 43,6 2 949 1212 89  Inv. 4,900 43.6 2,949 1212 89
Ref. 5 875 44,4 10,1 1016 1319 46  Ref. 5,875 44.4 10.1 1016 1319 46
Ref. 6 900 35,4 10,7 746 850 - Ref. 6,900 35.4 10.7 746 850 -
Ref. 7 875 41 10,1 821 1 106 123 Ref. 7,875 41 10,1 821 1,106,123
Ref. 8 925 43 L3 982 1298 12,  Ref. 8 925 43 L 3 982 1298 12,
Ref. 9 875 41 ,1 887 1 184 109  Ref. 9,875 41, 1,887 1,184,109
Ref. 10 925 41 ,2 10,4 820 1 1 14 142  Ref. 10 925 41, 2 10.4 820 1 1 14 142
Tableau 2 : propriétés mécaniques des échantillons testés Table 2: Mechanical properties of the tested samples
On note que toutes les nuances dont la composition est conforme à la présente invention sont caractérisées par des caractéristiques mécaniques supérieures aux minima requis pour la production de trépans, soit Re supérieure à 900 MPa, Rm supérieure à 1200 MPa, Kv à 20 °C supérieure à 75 J, et par une trempabilité satisfaisant les critères β < 3,5 HRC et Ji > 40 HRC. Inversement, toutes les nuances dont la composition est hors de la présente invention ont une trempabilité insuffisante et/ou des caractéristiques mécaniques trop faibles. C'est, en particulier, le cas de l'échantillon 6 pour lequel les caractéristiques mécaniques Re et Rm sont de toute façon franchement trop faibles pour que l'acier soit utilisable pour fabriquer des trépans, et pour lequel il n'a pas été jugé utile de mesurer la résilience. It is noted that all grades whose composition is in accordance with the present invention are characterized by mechanical characteristics greater than the minimum required for the production of drill bits, ie Re greater than 900 MPa, Rm greater than 1200 MPa, Kv at 20 ° C higher at 75 J, and by a hardenability satisfying the criteria β <3.5 HRC and Ji> 40 HRC. Conversely, all the shades whose composition is outside the present invention have insufficient quenchability and / or mechanical characteristics too low. It is, in particular, the case of the sample 6 for which the mechanical characteristics Re and Rm are in any case frankly too low for the steel to be usable to manufacture drill bits, and for which it has not been considered useful to measure resilience.
On a également testé l'aptitude à la cémentation des aciers selon l'invention. Des essais de cémentation ont été réalisés dans les conditions suivantes.  The ability to cement the steels according to the invention was also tested. Carburizing tests were carried out under the following conditions.
Ces essais ont été menés sur des cylindres de diamètre 25 mm et de longueur 120 mm placés dans des charges industrielles de l'ordre de 150 à 200 kg. Après cémentation, les cylindres cémentés sont caractérisés de la manière suivante :  These tests were carried out on cylinders of diameter 25 mm and length 120 mm placed in industrial loads of the order of 150 to 200 kg. After carburising, the cemented cylinders are characterized in the following manner:
- détermination, selon la norme NF EN ISO 2639, de la profondeur conventionnelle de cémentation à 550 HV et de la dureté superficielle par des essais de microdureté sous une charge de 0,1 Kg (dite « profondeur à 550 HV0,1 ») ;  - determination, according to standard NF EN ISO 2639, of the conventional 550 HV HVAC and the surface hardness by microhardness tests under a load of 0.1 kg (called "depth at 550 HV0.1");
- détermination de la taille de grain austénitique en couche et à cœur après attaque Béchet-Beaujard ; cette évaluation a été réalisée conformément à la norme NF EN ISO 643 ; - dosage, par diffractométrie des rayons X, de la teneur en austénite résiduelle à 20 μηι sous la surface des pièces. - determination of the size of austenitic grain layer and heart after attack Béchet-Beaujard; this evaluation was carried out in accordance with standard NF EN ISO 643; - X-ray diffractometry determination of the residual austenite content at 20 μηι below the surface of the parts.
Les essais de cémentation ont été effectués sur les nuances n °1 et n °3 placées dans une charge de cémentation industrielle et traitées à pression atmosphérique dans les conditions suivantes :  The cementation tests were carried out on grades No. 1 and No. 3 placed in an industrial cementation charge and treated at atmospheric pressure under the following conditions:
- chauffage à 9 <C/min jusqu'à 950 °C ; heating at 9 < C / min up to 950 ° C;
- maintien isotherme à 950 ^ pendant 5h avec un potentiel carbone (dit « potentiel carbone d'enrichissement ») de 1 .2% ; on rappelle qu'une atmosphère de cémentation gazeuse est caractérisée par son potentiel carbone qui est la teneur en carbone d'un échantillon de l'acier en équilibre à l'état austénitique avec l'atmosphère de cémentation, à la température et à la pression d'utilisation ;  - isothermal maintenance at 950 ° for 5h with a carbon potential (called "carbon enrichment potential") of 1 .2%; it is recalled that a gaseous carburizing atmosphere is characterized by its carbon potential, which is the carbon content of a sample of the equilibrium steel in the austenitic state with the carburizing atmosphere, at temperature and pressure. of use;
- refroidissement à 870 ^ et maintien à cette température pendant 2h avec un potentiel carbone (dit « potentiel carbone de diffusion ») compris entre 0.6 et 0.7% ;  cooling to 870 ° C. and keeping at this temperature for 2 hours with a carbon potential (called "diffusion carbon potential") of between 0.6 and 0.7%;
- trempe à l'huile à 30 °C ;  oil quenching at 30 ° C .;
- revenu à 190 °C pendant 2h.  - income at 190 ° C for 2 hours.
Ces conditions sont celles d'un cycle de cémentation standard utilisé pour traiter les nuances 1 3NiCrMo13 actuellement utilisées pour la fabrication de cônes de forage.  These conditions are those of a standard carburization cycle used to treat the grades 1 3NiCrMo13 currently used for the manufacture of drill cones.
Un cylindre en 1 3NiCrMo13 a donc été placé dans la charge de cémentation pour servir de référence et déterminer les caractéristiques de référence que doivent atteindre, pour le format d'échantillon considéré, les nuances élaborées conformément à la présente invention. La composition de la coulée utilisée comme référence est donnée au Tableau 3.  A cylinder 1 1NiCrMo13 has therefore been placed in the carburization charge to serve as a reference and determine the reference characteristics that must achieve, for the sample format considered, shades developed in accordance with the present invention. The composition of the casting used as a reference is given in Table 3.
Tableau 3 : composition de l'échantillon de référence en acier 13NiCrMo1 3 Table 3: Composition of the reference sample in 13NiCrMo1 steel 3
Le potentiel carbone dans la phase de diffusion (potentiel carbone diff.) a été adapté à la nuance traitée de manière à maîtriser la teneur superficielle en austénite résiduelle. The carbon potential in the diffusion phase (diff carbon potential) was adapted to the treated grade so as to control the residual austenite surface content.
Les résultats de caractérisation de la nuance de référence sont donnés au The characterization results of the reference grade are given in
Tableau 4. Ceux des deux nuances élaborées conformément à la présente invention sont donnés au Tableau 5. On note que les caractéristiques des nuances conformes à la présente invention sont identiques ou quasiment identiques à celles de la nuance de référence, et respectent donc en tous points les minimas requis pour la fabrication de trépans de forage à savoir : Table 4. Those of the two grades elaborated according to the present invention are given in Table 5. It is noted that the characteristics of the shades according to the present invention are identical or almost identical to those of the grade of reference, and thus respect in all points the minima required for the manufacture of drill bits namely:
profondeur de cémentation comprise entre 1 et 1 .5 mm ;  carburizing depth of between 1 and 1.5 mm;
- dureté superficielle supérieure à 670 HV ;  - superficial hardness greater than 670 HV;
- teneur en austénite résiduelle inférieure à 40 ;  - residual austenite content of less than 40;
- indice de grain ASTM supérieur à 5  - ASTM grain index greater than 5
Tableau 4 : résultats des essais de cémentation (Référence) Table 4: Cementation Test Results (Reference)
Tableau 5 : résultats des essais de cémentation (Invention) Table 5: Results of the cementation tests (Invention)

Claims

REVENDICATIONS
1 .- Acier pour la fabrication de pièces cémentées, caractérisé en ce que sa composition, en pourcentages pondéraux est :  1 .- Steel for the manufacture of cemented parts, characterized in that its composition, in percentages by weight is:
- 0,1 %≤C≤ 0,15% ;  - 0.1% ≤C≤ 0.15%;
- 0,8% < Mn < 2% ;  - 0.8% <Mn <2%;
- 1 % < Cr < 2,5% ;  - 1% <Cr <2.5%;
- 0,2% < Mo < 0,6% ;  - 0.2% <Mo <0.6%;
- traces < Si < 0,35% ;  - traces <If <0.35%;
- traces < Ni < 0,7% ;  - traces <Ni <0.7%;
- traces < B < 0,005% ;  - traces <B <0.005%;
- traces < Ti < 0,1 % ;  - traces <Ti <0.1%;
- traces < N < 0,01 % si 0.0005 % < B < 0,005%, et traces < N < 0.02 % si traces < B < 0.0005 % ;  - traces <N <0.01% if 0.0005% <B <0.005%, and traces <N <0.02% if traces <B <0.0005%;
- traces < Al < 0,1 % ;  - traces <Al <0.1%;
- traces < V < 0,3% ;  - traces <V <0.3%;
- traces < P < 0,025% ;  - traces <P <0.025%;
- traces < Cu < 1 %, de préférence < 0.6 % ;  traces <Cu <1%, preferably <0.6%;
- traces < S < 0,1 %  - traces <S <0.1%
le reste étant du fer et des impuretés résultant de l'élaboration. the rest being iron and impurities resulting from the elaboration.
2.- Acier selon la revendication 1 , caractérisé en ce que sa teneur en O est inférieure ou égale à 30 ppm.  2. Steel according to claim 1, characterized in that its O content is less than or equal to 30 ppm.
3. - Pièce cémentée en acier, caractérisée en ce qu'elle est en un acier ayant la composition selon la revendication 1 ou 2, et en ce qu'elle a subi une cémentation.  3. - Hardened steel piece, characterized in that it is a steel having the composition according to claim 1 or 2, and in that it has undergone a cementation.
4. - Pièce cémentée selon la revendication 3, caractérisée en ce qu'il s'agit d'un trépan de forage.  4. - Cemented part according to claim 3, characterized in that it is a drill bit.
5. - Procédé de fabrication d'une pièce cémentée, caractérisé en ce que :  5. - Process for manufacturing a cemented part, characterized in that:
- on prépare une ébauche de ladite pièce en un acier selon la revendication 1 , et on la met en forme par forgeage ;  - Preparing a blank of said piece of a steel according to claim 1, and is shaped by forging;
- et on pratique une cémentation sur ladite ébauche.  and a cementation is carried out on said blank.
6.- Procédé selon la revendication 5, caractérisé en ce que la cémentation est effectuée à pression atmosphérique, et en ce que la succession d'étapes de la cémentation est la suivante:  6. A process according to claim 5, characterized in that the carburizing is carried out at atmospheric pressure, and in that the succession of steps of the carburizing is the following:
- chauffage jusqu'à la température du palier d'enrichissement.  - heating up to the temperature of the enrichment stage.
- palier d'enrichissement à une température de 900 à 980 °C pendant 3 à 20 h et à un potentiel carbone compris entre 0.8 et 1 .2% ; - diffusion à une température de 820 à 880 °C à un potentiel carbone compris entre 0.6 et 0.8%, avec un temps de traitement de 1 à 3 h ; enrichment stage at a temperature of 900 to 980 ° C. for 3 to 20 hours and at a carbon potential of between 0.8 and 1.2%; diffusion at a temperature of 820 to 880 ° C. at a carbon potential of between 0.6 and 0.8%, with a treatment time of 1 to 3 hours;
- trempe à l'huile à une température inférieure ou égale à l ôO'O  - oil quenching at a temperature of less than or equal to
- revenu à une température comprise entre 150 et 250^ et pendant une durée comprise entre 1 et 4h.  - Income at a temperature between 150 and 250 ^ and for a period of between 1 and 4 hours.
7.- Procédé selon la revendication 5, caractérisé en ce que la cémentation est effectuée à basse pression, en ce que ladite pression est de 5 à 20 mbar, et en ce que la succession d'étapes de la cémentation est la suivante :  7.- Method according to claim 5, characterized in that the carburizing is carried out at low pressure, in that said pressure is 5 to 20 mbar, and in that the succession of steps of the cementation is as follows:
- chauffage jusqu'à la température du palier d'enrichissement.  - heating up to the temperature of the enrichment stage.
- palier d'enrichissement à une température de 900 à 980 °C pendant 3 à 20 h et à un potentiel carbone compris entre 0.8 et 1 .2% ;  enrichment stage at a temperature of 900 to 980 ° C. for 3 to 20 hours and at a carbon potential of between 0.8 and 1.2%;
- diffusion à une température de 890 à 950 °C à un potentiel carbone compris entre 0.6 et 0.8%, avec un temps de traitement de 1 à 4 h ;  diffusion at a temperature of 890 to 950 ° C. at a carbon potential of between 0.6 and 0.8%, with a treatment time of 1 to 4 hours;
- trempe à une température inférieure ou égale à l ôO 'O  quenching at a temperature of less than or equal to
- revenu à une température comprise entre 150 et 250^ et pendant une durée comprise entre 1 et 4h.  - Income at a temperature between 150 and 250 ^ and for a period of between 1 and 4 hours.
EP12750727.5A 2011-08-09 2012-08-08 Steel for manufacturing carburized steel parts, carburized steel parts produced with said steel, and method for manufacturing same Active EP2742165B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR1157254A FR2978969B1 (en) 2011-08-09 2011-08-09 STEEL FOR THE PRODUCTION OF CEMENTED PARTS, CEMENTED PART PRODUCED WITH THIS STEEL AND METHOD FOR MANUFACTURING THE SAME
PCT/EP2012/065523 WO2013021009A1 (en) 2011-08-09 2012-08-08 Steel for manufacturing carburized steel parts, carburized steel parts produced with said steel, and method for manufacturing same

Publications (2)

Publication Number Publication Date
EP2742165A1 true EP2742165A1 (en) 2014-06-18
EP2742165B1 EP2742165B1 (en) 2020-03-11

Family

ID=46727184

Family Applications (1)

Application Number Title Priority Date Filing Date
EP12750727.5A Active EP2742165B1 (en) 2011-08-09 2012-08-08 Steel for manufacturing carburized steel parts, carburized steel parts produced with said steel, and method for manufacturing same

Country Status (6)

Country Link
US (1) US9587301B2 (en)
EP (1) EP2742165B1 (en)
CA (1) CA2843360C (en)
ES (1) ES2787260T3 (en)
FR (1) FR2978969B1 (en)
WO (1) WO2013021009A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6414385B2 (en) * 2014-02-27 2018-10-31 新日鐵住金株式会社 Carburized parts
CN109439877A (en) * 2018-08-22 2019-03-08 重庆银雁科技有限公司 A kind of motorcycle rear axle hardening and tempering process

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2765890B1 (en) 1997-07-10 1999-08-20 Ascometal Sa PROCESS FOR MANUFACTURING A MECHANICAL PART IN CEMENTED OR CARBONITRIDE STEEL AND STEEL FOR THE MANUFACTURE OF SUCH A PART
JP3894635B2 (en) * 1997-08-11 2007-03-22 株式会社小松製作所 Carburized member, manufacturing method thereof, and carburizing system
US6146472A (en) 1998-05-28 2000-11-14 The Timken Company Method of making case-carburized steel components with improved core toughness
JP3932102B2 (en) * 2001-07-17 2007-06-20 大同特殊鋼株式会社 Case-hardened steel and carburized parts using the same
SE525378C2 (en) * 2002-01-21 2005-02-08 Sandvik Ab Elements for striking rock drilling and method for its preparation
EP1342800A1 (en) * 2002-03-04 2003-09-10 Hiroshi Onoe Steel for high-strength screws and high-strength screw
JP4313983B2 (en) 2002-04-18 2009-08-12 Jfeスチール株式会社 Steel for case hardening bearings with excellent toughness and rolling fatigue life in sub-high temperature range
JP2003328079A (en) * 2002-05-14 2003-11-19 Nippon Steel Corp Steel pipe superior in workability for cold forging, and manufacturing method therefor
DE10243179A1 (en) * 2002-09-18 2004-04-08 Edelstahlwerke Buderus Ag Case hardening steel used in the manufacture of workpieces e.g. for the construction of vehicles contains alloying additions of chromium, niobium and titanium
JP5333074B2 (en) * 2009-09-04 2013-11-06 新日鐵住金株式会社 Steel pipe manufacturing method for steel tower

Also Published As

Publication number Publication date
FR2978969A1 (en) 2013-02-15
CA2843360C (en) 2019-11-19
ES2787260T3 (en) 2020-10-15
US20140224383A1 (en) 2014-08-14
CA2843360A1 (en) 2013-02-14
WO2013021009A1 (en) 2013-02-14
US9587301B2 (en) 2017-03-07
EP2742165B1 (en) 2020-03-11
FR2978969B1 (en) 2013-09-13

Similar Documents

Publication Publication Date Title
EP1896624B1 (en) Martensitic stainless steel composition, method for making a mechanical part from said steel and resulting part
EP2038445B1 (en) Duplex stainless steel
EP2164998B1 (en) Hardened martensitic steel having a low or zero content of cobalt, process for manufacturing a part from this steel, and part thus obtained
WO2011124851A2 (en) Mechanical part made of steel having high properties and process for manufacturing same
WO2015075262A1 (en) Martensitic stainless steel, part made of said steel and method for manufacturing same
EP3286349A1 (en) Steel, product made of said steel, and manufacturing method thereof
CA3065036A1 (en) Method for producing high-strength steel parts with improved ductility, and parts obtained by said method
WO2017064684A1 (en) Steel, product created from said steel, and manufacturing method thereof
CA2718848C (en) Steel with high properties for solid parts
EP0209437B1 (en) Lightly alloyed, forged steel cylinder for cold rolling
CA2843360C (en) Steel for manufacturing carburized steel parts, carburized steel parts produced with said steel, and method for manufacturing same
EP3274483B1 (en) Parts with a bainitic structure having high strength properties and manufacturing process
EP2134882A2 (en) Microalloyed steel with good resistance to hydrogen for the cold-forming of machine parts having high properties
WO2006125899A1 (en) Steel for submarine hulls with improved weldability
JP2009102733A (en) Method for producing rolling member
WO2020115531A1 (en) Stainless steel, products made of this steel and methods of manufacturing same
WO2022253912A1 (en) Hot-formed steel part and manufacturing method
WO1985004906A1 (en) Method for producing steel bars or rod wire and corresponding products
EP1042524A1 (en) Case hardening structural steel, method for obtaining same and parts formed with same
BE402523A (en)

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20140129

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

DAX Request for extension of the european patent (deleted)
RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: ASCO INDUSTRIES

17Q First examination report despatched

Effective date: 20151023

19U Interruption of proceedings before grant

Effective date: 20180228

19W Proceedings resumed before grant after interruption of proceedings

Effective date: 20190102

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: ASCOMETAL FRANCE HOLDING SAS

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: GRANT OF PATENT IS INTENDED

INTG Intention to grant announced

Effective date: 20191023

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE PATENT HAS BEEN GRANTED

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

Free format text: NOT ENGLISH

REG Reference to a national code

Ref country code: CH

Ref legal event code: EP

REG Reference to a national code

Ref country code: AT

Ref legal event code: REF

Ref document number: 1243220

Country of ref document: AT

Kind code of ref document: T

Effective date: 20200315

REG Reference to a national code

Ref country code: DE

Ref legal event code: R096

Ref document number: 602012068401

Country of ref document: DE

REG Reference to a national code

Ref country code: IE

Ref legal event code: FG4D

Free format text: LANGUAGE OF EP DOCUMENT: FRENCH

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NO

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200611

Ref country code: FI

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: RS

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

REG Reference to a national code

Ref country code: NL

Ref legal event code: MP

Effective date: 20200311

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: HR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: SE

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: GR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200612

Ref country code: LV

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: BG

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200611

REG Reference to a national code

Ref country code: LT

Ref legal event code: MG4D

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

REG Reference to a national code

Ref country code: ES

Ref legal event code: FG2A

Ref document number: 2787260

Country of ref document: ES

Kind code of ref document: T3

Effective date: 20201015

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: CZ

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: IS

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200711

Ref country code: PT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200805

Ref country code: RO

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: LT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: SM

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: EE

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: SK

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

REG Reference to a national code

Ref country code: AT

Ref legal event code: MK05

Ref document number: 1243220

Country of ref document: AT

Kind code of ref document: T

Effective date: 20200311

REG Reference to a national code

Ref country code: DE

Ref legal event code: R097

Ref document number: 602012068401

Country of ref document: DE

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DK

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: AT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

26N No opposition filed

Effective date: 20201214

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SI

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: PL

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: MC

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20200808

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20200808

Ref country code: LI

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20200831

Ref country code: CH

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20200831

REG Reference to a national code

Ref country code: BE

Ref legal event code: MM

Effective date: 20200831

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20200808

Ref country code: IE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20200808

Ref country code: BE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20200831

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: TR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: MT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: CY

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: MK

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

Ref country code: AL

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20200311

P01 Opt-out of the competence of the unified patent court (upc) registered

Effective date: 20230502

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: IT

Payment date: 20230822

Year of fee payment: 12

Ref country code: ES

Payment date: 20230914

Year of fee payment: 12

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20230829

Year of fee payment: 12

Ref country code: DE

Payment date: 20230911

Year of fee payment: 12