US20190256943A1 - Method for producing a cold-rolled steel strip having trip-characteristics made of a high-strength mangan-containing steel - Google Patents

Method for producing a cold-rolled steel strip having trip-characteristics made of a high-strength mangan-containing steel Download PDF

Info

Publication number
US20190256943A1
US20190256943A1 US16/308,319 US201716308319A US2019256943A1 US 20190256943 A1 US20190256943 A1 US 20190256943A1 US 201716308319 A US201716308319 A US 201716308319A US 2019256943 A1 US2019256943 A1 US 2019256943A1
Authority
US
United States
Prior art keywords
strip
content
rolling
steel
hot
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.)
Abandoned
Application number
US16/308,319
Other languages
English (en)
Inventor
Peter Palzer
Thomas Evertz
Martin Schubert
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.)
Salzgitter Flachstahl GmbH
Original Assignee
Salzgitter Flachstahl GmbH
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 Salzgitter Flachstahl GmbH filed Critical Salzgitter Flachstahl GmbH
Assigned to SALZGITTER FLACHSTAHL GMBH reassignment SALZGITTER FLACHSTAHL GMBH ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: EVERTZ, THOMAS, PALZER, Peter, SCHUBERT, MARTIN
Publication of US20190256943A1 publication Critical patent/US20190256943A1/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0278—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D2201/00—Treatment for obtaining particular effects
    • C21D2201/02—Superplasticity
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys

Definitions

  • the invention relates to a method for producing a cold-rolled steel strip made of a high-strength, manganese-containing steel.
  • Steel strip is understood to mean hereinunder in particular steel strips but also steel sheets.
  • Typical tensile strengths Rm in these steels are about 800 MPa to 2000 MPa.
  • Elongations at fracture A80 have values of about 3% to 40%.
  • European patent application EP 2 383 353 A2 discloses a high-strength, manganese-containing steel, a steel strip made from this steel and a method for producing this steel strip.
  • the steel consists of the elements (contents are in % by weight and relate to the steel melt): C: to 0.5; Mn: 4 to 12.0; Si: up to 1.0; Al: up to 3.0; Cr: 0.1 to 4.0; Cu: up to 4.0; Ni: up to 2.0; N: up to 0.05; P: up to 0.05; S: up to 0.01, with the remainder being iron and unavoidable impurities.
  • one or more elements from the group “V, Nb, Ti” are provided, wherein the sum of the contents of these elements is at most equal to 0.5.
  • the steel is said to be characterised in that it can be produced in a more cost-effective manner than steels with a high content of manganese and at the same time has high elongation at fracture values and, associated therewith, a considerably improved deformability.
  • a method for producing a steel strip from the high-strength, manganese-containing steel described above has the following working steps:
  • this steel can have a metastable austenite with the capacity for stress-induced martensite formation (TRIP effect).
  • the international patent application WO 2005/061152 A1 also describes a method for producing hot strips from a deformable lightweight steel, which can be successfully cold-deep-drawn, with a Mn content of 9 to 30 wt. %. In addition to a high level of tensile strength, the hot strip has TRIP properties.
  • the German laid-open document DE 197 27 759 A1 discloses an ultra-high-strength austenitic lightweight steel which can be successfully deep-drawn with a tensile strength of up to 1100 MPa, which likewise has TRIP and TWIP properties.
  • the German laid-open document DE 10 2012 111 959 A1 describes a high manganese-content steel material with TRIP and TWIP properties, which undergoes an increase in harness and deformability by virtue of cold-forming below ambient temperature preferably in the range of +25° C. to ⁇ 200° C.
  • the German laid-open document DE 10 2009 030 324 A1 describes a high manganese-content steel with a low tendency towards hydrogen embrittlement and with high tensile strengths while at the same time having high elongation at fracture values.
  • the patent application US 2012/0059196 A1 discloses a method for producing a hot strip with a horizontal strip casting installation.
  • the hot strip consists of the main components, Fe, Mn, Si and Al, has TRIP and/or TWIP properties and is suitable for deep-drawing.
  • the patent U.S. Pat. No. 6,358,338 B1 also relates to a method for producing a steel strip from a high manganese-content steel. In order to increase the tensile strength and extensibility, the steel strip is subjected to recrystallisation annealing after cold-rolling.
  • US 2009/0074605 A1 a high manganese-content steel strip with excellent crash behaviour and with high tensile strength and elongation values is produced in that the steel strip is cold-rolled after hot-rolling and then annealed at 600° C.
  • German laid-open document DE 10 2012 013 113 A1 describes TRIP steels which have a predominantly ferritic basic microstructure having incorporated residual austenite. Owing to its intense cold-hardening, the TRIP steel achieves high values for uniform elongation and tensile strength.
  • a disadvantage with these manganese-containing steels with a TRIP effect is that, during production of a cold-rolled steel strip, the achievable degree of deformation is limited owing to the intense cold-hardening of the material during cold-rolling and the high loading on the roll stand associated therewith.
  • a plurality of cold-rolling steps with correspondingly low degrees of deformation are often required, wherein prior to a renewed cold-rolling step, in each case recrystallisation annealing must be carried out in order to loosen the material and therefore render it capable of being cold-rolled.
  • This procedure with a plurality of cold-rolling steps with intermediate recrystallising annealing is very time-consuming and expensive and associated with additional CO 2 emissions.
  • the object of the present invention is to provide a method for producing a cold-rolled steel strip made of a high-strength, manganese-containing steel with TRIP properties, with which the cold-rolling to the required end thickness can be effected in a more economical and ecologically-friendly manner.
  • a production route from the melting of the steel to the steel strip cold-rolled to the required end thickness is to be provided.
  • Mn more than 3.0 to 12 with the remainder being iron including unavoidable steel-associated elements, with optional addition by alloying of one or more of the following elements (contents in wt. % and in relation to the steel melt):
  • high-strength steels are understood to be steels with a tensile strength of 800 MPa to 2000 MPa.
  • the cause of the intense cold-hardening of these high-strength, manganese-containing steels with a TRIP effect is the proportion of residual austenite contained in the microstructure in addition to martensite and/or ferrite and/or bainite and/or perlite.
  • This residual austenite can be converted at appropriate ambient temperatures into martensite (TRIP effect both ⁇ as well as ⁇ ′ martensite), wherein at ambient temperature up to about 50° C. a substantial proportion of martensite formation always takes place owing to the TRIP effect.
  • TRIP effect both ⁇ as well as ⁇ ′ martensite
  • the cold-rolled strip then has a high level of strength and low residual deformation capability.
  • the influence of mechanical stresses can cause deformation twins (TWIP effect).
  • the TRIP conversion mechanism from austenite to martensite is now wholly or partly suppressed and so substantially higher degrees of deformation are possible during rolling in only one rolling pass.
  • cold-rolling is conventionally frequently related to cold-rolling at ambient temperature.
  • cold-rolling is also used for cold-rolling at raised temperature.
  • this raised temperature in the case of cold-rolling in accordance with the invention is clearly below the AC1 conversion temperature associated with a microstructure conversion.
  • the cold-rolling in accordance with the invention also preferably takes place below a homologous temperature, at precisely which creeping processes still do not occur in the steel sheet.
  • FIG. 1 the influence of the deformation temperature during rolling on the hardening behaviour of the material is illustrated with the aid of the characteristic values of tensile tests.
  • deformation temperatures 100° C. or 200° C.
  • clearly greater elongation values are achieved while having a clearly lower increase in tensile strength.
  • “Being at a temperature” is understood to mean that the temperature is the result of a preceding process step or this temperature has been maintained.
  • the preceding process step can mean a reheating step, a continuous or discontinuous processing step using the available heat in the hot strip or pre-strip, in particular a hot-rolling process, or maintenance of the temperature in a furnace.
  • the conversion of austenite into martensite by increasing the stacking fault energy in the first rolling pass is substantially reduced or avoided and so the strip hardens less intensely during the cold-rolling process and more deformation twins (TWIP effect) are formed in the austenite.
  • TWIP effect deformation twins
  • the steel strip comprises a considerably residual deformation capability since the deformation twins formed in the austenite and residual austenite which may be present can wholly or partially convert into martensite at ambient temperature owing to the TRIP effect, this is associated with an increase in the maximum elongation and therefore an improvement in the deformation capability for the production of components from the flat product even without additional annealing associated with the cold-rolling process.
  • deformation twins brings about improved behaviour during subsequent deformations with respect to hydrogen-induced delayed crack formation and hydrogen embrittlement compared with cold-rolling without prior heating with an optionally associated annealing process.
  • the steel used for the method in accordance with the invention has a multi-phase microstructure, including ferrite and/or martensite and/or bainite and/or perlite and residual austenite/austenite.
  • the proportion of residual austenite/austenite can be 5% to 80%.
  • the residual austenite/austenite can partially or completely convert into martensite owing to the TRIP effect when mechanical stresses are present.
  • the alloy forming the basis of the invention has a TRIP and/or TWIP effect when subjected to the relevant mechanical stress. Owing to the intense hardening (similar to cold-hardening) at ambient temperature, induced by the TRIP and/or TWIP effect and by the increase in the dislocation density, the steel achieves very high values in terms of elongation at fracture, in particular uniform elongation, and tensile strength. In an advantageous manner, this property is achieved owing to the residual austenite present, only in the case of manganese contents of over 3 wt. %.
  • the steel in accordance with the invention is suitable in particular for producing a high-strength steel strip which can be provided with a metallic or non-metallic coating, e.g. a zinc-based coating. It may feasibly be used inter alia in the automotive industry, shipbuilding, plant design, infrastructure, the aerospace industry and in household appliances.
  • the high proportion of austenite means that the steel produced in accordance with the invention is suitable for low-temperature stresses.
  • the steel has a tensile strength Rm of >800 to 2000 MPa and an elongation at fracture A80 of 3 to 40%, preferably >8 to 40%.
  • Alloy elements are generally added to the steel in order to influence specific properties in a targeted manner.
  • An alloy element can thereby influence different properties in different steels.
  • the effect and interaction generally depend greatly upon the quantity, presence of further alloy elements and the solution state in the material. The correlations are varied and complex.
  • the effect of the alloy elements in the alloy in accordance with the invention will be discussed in greater detail hereinafter.
  • the positive effects of the alloy elements used in accordance with the invention will be described hereinafter:
  • Carbon C is required to form carbides, stabilises the austenite and increases the strength. Higher contents of C impair the welding properties and result in the impairment of the elongation and toughness properties, for which reason a maximum content of 0.9 wt. % is set. The minimum content is set at 0.0005 wt. %. A content of 0.05 to 0.42 wt. % is preferred because in this range the ratio of residual austenite to other phase proportions can be set in a particularly advantageous manner.
  • Manganese Mn stabilises the austenite, increases the strength and the toughness and renders possible a deformation-induced martensite formation and/or twinning in the alloy in accordance with the invention. Contents ⁇ 3 wt. % are not sufficient to stabilise the austenite and therefore impair the elongation properties whereas with contents of over 12 wt. % the austenite is stabilised too much and as a result the strength properties, in particular the yield strength, are reduced.
  • a range of over 5 to ⁇ 10 wt. % is preferred because in this range the ratio of the phase proportions to each other and the conversion mechanisms can be advantageously influenced during rolling to the end thickness.
  • Aluminium Al improves the strength and elongation properties, decreases the relative density and influences the conversion behaviour of the alloy in accordance with the invention.
  • Al contents of more than 10 wt. % impair the elongation properties and cause predominantly brittle fracture behaviour.
  • an Al content of 0.1 to 5 wt. % is preferred in order to increase the strength while having a good degree of elongation.
  • contents of >0.5 to 3 wt. % render possible a particularly high level of strength and elongation at fracture.
  • Silicon Si impedes the diffusion of carbon, reduces the relative density and increases the strength and elongation properties and toughness properties. Contents of more than 6 wt. % prevent further processing by cold-rolling by reason of embrittlement of the material. Thus, a maximum content of 6 wt. % is set. Optionally, a content of 0.05 to 3 wt. % is set because contents in this range positively influence the deformation properties. Si contents of >0.1 to 1.5 wt. % have proved to be particularly advantageous for the deformation and conversion properties.
  • Chromium Cr improves the strength and reduces the rate of corrosion, delays the formation of ferrite and perlite and forms carbides.
  • the maximum content is set to 6 wt. % since higher contents result in an impairment of the elongation properties and substantially higher costs.
  • a Cr content of 0.1 to 4 wt. % is preferred in order to reduce the precipitation of coarse Cr carbides.
  • contents of >0.5 to 2.5 wt. % have proved to be advantageous for stabilising the austenite and precipitating fine Cr carbides.
  • the total content of Al+Si+Cr should be more than 1.2 wt. %.
  • Molybdenum Mo acts as a carbide-forming agent, increases the strength and increases the resistance to delayed crack formation and hydrogen embrittlement. Mo contents of more than 3 wt. % impair the elongation properties, for which reason a maximum content of 3 wt. % is set. For the manganese steel in accordance with the invention having average manganese contents, a Mo content of 0.005 to 1.5 wt. % is preferred in order to avoid the precipitation of excessively large Mo carbides. In particular, contents of 0.01 wt. % to 0.6 wt. % bring about the precipitation of desired Mo carbides while incurring reduced alloy costs.
  • Phosphorus P is a trace element from iron ore and is dissolved in the iron lattice as a substitution atom. Phosphorous increases the hardness by means of solid solution hardening and improves the hardenability. However, attempts are generally made to lower the phosphorous content as much as possible because inter alia it exhibits a strong tendency towards segregation owing to its low diffusion rate and greatly reduces the level of toughness. The attachment of phosphorous to the grain boundaries can cause cracks along the grain boundaries during hot-rolling. Moreover, phosphorous increases the transition temperature from tough to brittle behaviour by up to 300° C. For the aforementioned reasons, the phosphorous content is limited to a maximum of 0.1 wt. %, wherein contents ⁇ 0.04 wt. % are advantageously sought for the aforementioned reasons.
  • Sulphur S like phosphorous, is bound as a trace element in the iron ore. It is generally not desirable in steel because it exhibits a strong tendency towards segregation and has a greatly embrittling effect, whereby the elongation and toughness properties are impaired. An attempt is therefore made to achieve amounts of sulphur in the melt which are as low as possible (e.g. by deep vacuum treatment). For the aforementioned reasons, the sulphur content is limited to a maximum of 0.1 wt. %. In a particularly advantageous manner the limit is ⁇ 0.2 wt. % in order to reduce the precipitation of MnS.
  • Nitrogen N is likewise an associated element from steel production. In the dissolved state, it improves the strength and toughness properties in steels with a high manganese content of greater than or equal to 4 wt. % Mn. Lower Mn-alloyed steels with ⁇ 4 wt. % Mn, which contain free nitrogen, tend to have a strong aging effect. The nitrogen diffuses even at low temperatures to dislocations and blocks the same. It thus produces an increase in strength associated with a rapid loss of toughness. Binding of the nitrogen in the form of nitrides is possible e.g. by alloying aluminium, vanadium, niobium or titanium. For the aforementioned reasons, the nitrogen content is limited to a maximum of 0.1 wt. %, wherein contents ⁇ 0.05 wt. % are preferably sought to substantially avoid the formation of AlN.
  • Microalloy elements are generally added only in very small amounts ( ⁇ 0.1 wt. % per element). In contrast to the alloy elements, they mainly act by precipitate formation but can also influence the properties in the dissolved state. Despite the small amounts added, microalloy elements greatly influence the production conditions and the processing properties and final properties.
  • Typical microalloy elements are vanadium, niobium and titanium. These elements can be dissolved in the iron lattice and form carbides, nitrides and carbonitrides with carbon and nitrogen.
  • Vanadium V and niobium Nb act in a grain-refining manner in particular by forming carbides, whereby at the same time the strength, toughness and elongation properties are improved. Contents of more than 1.5 wt. % do not provide any further advantages.
  • a minimum content of greater than or equal to 0.005 wt. % and a maximum content of 0.6 (V) or 0.4 (Nb) wt. % is preferably provided, with which the alloy elements advantageously provide grain refinement.
  • the contents of V can continue to be restricted to 0.01 wt. % to 0.3 wt. % and the contents of Nb to 0.01 to 0.1 wt. %.
  • Tantalum Ta tantalum acts in a similar manner to niobium as a carbide-forming agent in a grain-refining manner and thereby improves the strength, toughness and elongation properties at the same time. Contents over 0.5 wt. % do not provide any further improvement in the properties. Thus, a maximum content of 0.5 wt. % is optionally set. A minimum content of 0.005 wt. % and a maximum content of 0.3 wt. % are preferred, with which the grain refinement can advantageously be produced. In order to improve economic feasibility and to optimise grain refinement, a content of 0.01 wt. % to 0.1 wt. % is particularly preferably sought.
  • Titanium Ti acts in a grain-refining manner as a carbide-forming agent, whereby at the same time the strength, toughness and elongation properties are improved, and reduces the inter-crystalline corrosion.
  • Ti contents of more than 1.5 wt. % impair the elongation properties, for which reason a maximum Ti content of 1.5 wt. % is set.
  • a minimum content of 0.005 and a maximum content of 0.6 wt. % are set, with which Ti is advantageously precipitated.
  • a minimum content of 0.01 wt. % and a maximum content of 0.3 wt. % are provided, which ensures optimum precipitation behaviour with low alloy costs.
  • Tin Sn increases the strength but, similarly to copper, accumulates beneath the scale layer and at the grain boundaries at higher temperatures. Owing to the penetration into the grain boundaries it leads to the formation of low melting point phases and, associated therewith, to cracks in the microstructure and to solder brittleness, for which reason a maximum content of ⁇ 0.5 wt. % is optionally provided. For the aforementioned reasons, contents of ⁇ 0.2 wt. % are preferably set. Contents of ⁇ 0.05 wt. % are particularly advantageously preferred in order to avoid low melting point phases and cracks in the microstructure.
  • Copper Cu reduces the rate of corrosion and increases the strength. Contents of over 3 wt. % impair producibility by forming low melting point phases during casting and hot-rolling, for which reason a maximum content of 3 wt. % is set. Optionally, a maximum content of ⁇ 0.5 wt. % is provided, with which the occurrence of cracks during casting and hot-rolling can be advantageously prevented. Cu contents of ⁇ 0.1 wt. % have proved to be particularly advantageous in avoiding low melting point phases and in avoiding cracks.
  • Tungsten W acts as a carbide-forming agent and increases the strength and heat resistance. W contents of more than 5 wt. % impair the elongation properties, for which reason a maximum content of 5 wt. % is set. Optionally, a maximum content of 3 wt. % and a minimum content of 0.01 wt. % is set, with which the precipitation of carbides advantageously takes place. In particular, a minimum content of 0.2 wt. % and a maximum content of 1.5 wt. % are preferred, which renders possible optimum precipitation behaviour with low alloy costs.
  • Cobalt Co increases the strength of the steel, stabilises the austenite and improves the heat resistance. Contents of more than 8 wt. % impair the elongation properties, for which reason a maximum content of 8 wt. % is set. Optionally, a maximum content of ⁇ 5 wt. % and a minimum content of 0.01 wt. % is set which advantageously improve the strength and heat resistance. Preferably, a minimum content of 0.3 wt. % and a maximum content of 2 wt. % are provided which advantageously influences the austenite stability along with the strength properties.
  • Zirconium Zr acts as a carbide-forming agent and improves the strength. Zr contents of more than 0.5 wt. % impair the elongation properties, for which reason a maximum content of 0.5 wt. % is set. Optionally, a maximum content of 0.3 wt. % and a minimum content of 0.005 wt. % is set, since in this range carbides are advantageously precipitated. Preferably, a minimum content of 0.01 wt. % and a maximum content of 0.2 wt. % is provided which advantageously render possible optimum carbide precipitation with low alloy costs.
  • Boron B delays the austenite conversion, improves the hot-forming properties of steels and increases the strength at ambient temperature. It achieves its effect even with very low alloy contents. Contents above 0.15 wt. % greatly impair the elongation and toughness properties, for which reason the maximum content is set to 0.15 wt. %. Optionally, a minimum content of 0.001 wt. % and a maximum content of 0.08 wt. % are set, with which the strength-increasing effect of boron is advantageously used. A minimum content of 0.002 wt. % and a maximum content of 0.01 wt. % are preferred which render possible optimum use for increasing strength whilst at the same time improving the conversion behaviour.
  • Tellurium Te improves the corrosion-resistance and the mechanical properties and machinability. Furthermore, Te increases the solidity of MnS which, as a result, is lengthened to a lesser extent in the rolling direction during hot-rolling and cold-rolling. Contents above 0.5 wt. % impair the elongation and toughness properties, for which reason a maximum content of 0.5 wt. % is set. Optionally, a minimum content of 0.005 wt. % and a maximum content of 0.3 wt. % are set, which advantageously improve the mechanical properties and increase the solidity of MnS present. Furthermore, a minimum content of 0.01 wt. % and a maximum content of 0.1 wt. % are preferred which render possible optimisation of the mechanical properties whilst at the same time reducing alloy costs.
  • Calcium Ca is used for modifying non-metallic oxidic inclusions which could otherwise result in the undesired failure of the alloy as a result of inclusions in the microstructure which act as stress concentration points and weaken the metal composite. Furthermore, Ca improves the homogeneity of the alloy in accordance with the invention. In order to achieve a corresponding effect, a minimum content of 0.0005 wt. % may be necessary. Contents above 0.1 wt. % do not provide any further advantage in the modification of inclusions, impair producibility and should be avoided by reason of the high vapour pressure of Ca in steel melts. Therefore, a maximum content of 0.1 wt. % is provided.
  • a production route in accordance with the invention from the melting of the steel to the finished steel strip with a required end thickness of less than 10 mm, preferably less than 4 mm, from a high-strength, manganese-containing steel comprises the following steps:
  • Mn more than 3.0 to 12 with the remainder being iron including unavoidable steel-associated elements, with optional addition by alloying of one or more of the following elements (in wt. %):
  • annealing temperature 580 to 820° C.
  • annealing duration 1 minute to 48 hours
  • annealing temperature 580 to 820° C.
  • annealing duration 1 minute to 48 hours.
  • the steel strip optionally coating the steel strip with a corrosion protection coating.
  • Typical thickness ranges for the pre-strip are 1 mm to 35 mm and for slabs and thin slabs they are 35 mm to 450 mm. Provision is preferably made that the slab or thin slab is hot-rolled to form a hot strip having a thickness of 20 mm to 1.5 mm or the pre-strip, cast to approximately the final dimensions, is hot-rolled to form a hot strip having a thickness of 8 mm to 1 mm.
  • the cold-rolled steel strip produced in accordance with the invention has a thickness of e.g. >0.15 mm to 10 mm.
  • Re-heating temperatures in the range of 720° C. to 1200° C. are provided for hot-rolling of the pre-strip from the casting heat to form a hot strip with optional intermediate heating between the individual rolling passes of the hot-rolling process. If only a few rolling passes are then necessary, the re-heating temperature can be selected at the lower end of the range.
  • the hot strip can optionally be subjected to a heat treatment in the temperature range between 580° C. and 820° C. for 1 minute to 48 hours, wherein higher temperatures are associated with shorter treatment times and vice versa.
  • Annealing can take place both in a batch-type annealing process (longer annealing times) and e.g. in a continuous annealing process (shorter annealing times).
  • the optional annealing serves to reduce the strength and/or to increase the residual austenite proportion of the hot strip prior to the cold-rolling process, whereby the deformation properties are advantageously improved for the subsequent process.
  • cold-rolling takes place with the hot strip at a temperature raised in accordance with the invention with the aim of setting the thicknesses of ⁇ 0.15 mm to 10 mm for the steel strip as required for the end use.
  • a further annealing process can optionally be performed, if need be coupled with a coating process and finally a skin-pass rolling process, by means of which the surface structure required for the end use is set.
  • the steel strip is galvanised by hot-dipping or electrolytically or is coated metallically, inorganically or organically.
  • a steel strip produced by the method in accordance with the invention has a tensile strength Rm >800 to 2000 MPa and an elongation at fracture A80 of 3 to 40%, preferably >8 to 40%. In this case, high levels of strength tend to be associated with lower elongations at fracture and vice versa.
  • the cold-rolled steel strip produced in accordance with the invention can then be processed e.g. as a sheet metal portion, coil or panel by cold-forming at ambient temperature or by warm-forming at temperatures of 60° C. to below the AC3, preferably ⁇ 450° C., to form a component wherein by means of the considerable residual deformation capability it is possible to dispense with intermediate annealing depending on usage.
  • the cold-rolled steel strip produced in accordance with the invention can be processed to form pipes with longitudinal or spiral weld seams, wherein in this case also, by means of the considerable residual deformation capability of the steel strip, it is possible to dispense with intermediate annealing depending on usage.
  • the pipe can thus comprise an outer and/or inner metallic, organic or inorganic coating.
  • the pipe produced in this way can then be deformed further, e.g. drawn or expanded or deformed using internal high pressure and processed further to form a component.
  • Ballistic steels are used in order to protect vehicles and buildings against shelling and explosions, and have a high level of hardness and toughness.
  • alloys 1 to 4 contain the following elements in the stated quantities in wt. %:
  • Cumulative rolling force is understood to be the adding up of the rolling forces of the individual passes in order to obtain a comparable measure for the expenditure of force.
  • the rolling force was standardised to a band width of 1000 mm.
  • the degree of deformation e is defined as the quotient of the change in thickness ⁇ d of the steel strip under investigation and the initial thickness d0 of the steel strip under investigation.
  • the reduction in rolling force is the calculated decrease in the rolling force at 250° C. compared with the rolling force during cold-rolling.
  • the elongation characteristic values represent the elongation in the rolling direction.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
US16/308,319 2016-06-09 2017-06-08 Method for producing a cold-rolled steel strip having trip-characteristics made of a high-strength mangan-containing steel Abandoned US20190256943A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE102016110661.5 2016-06-09
DE102016110661.5A DE102016110661A1 (de) 2016-06-09 2016-06-09 Verfahren zur Herstellung eines kaltgewalzten Stahlbandes aus einem hochfesten, manganhaltigen Stahl
PCT/EP2017/063958 WO2017211952A1 (fr) 2016-06-09 2017-06-08 Procédé de fabrication d'une bande d'acier laminée à froid présentant des propriétés trip à partir d'un acier à résistance élevée contenant du manganèse

Publications (1)

Publication Number Publication Date
US20190256943A1 true US20190256943A1 (en) 2019-08-22

Family

ID=59061988

Family Applications (1)

Application Number Title Priority Date Filing Date
US16/308,319 Abandoned US20190256943A1 (en) 2016-06-09 2017-06-08 Method for producing a cold-rolled steel strip having trip-characteristics made of a high-strength mangan-containing steel

Country Status (6)

Country Link
US (1) US20190256943A1 (fr)
EP (1) EP3469108B1 (fr)
KR (1) KR20190020694A (fr)
DE (1) DE102016110661A1 (fr)
RU (1) RU2711696C1 (fr)
WO (1) WO2017211952A1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019209933A1 (fr) * 2018-04-24 2019-10-31 Nucor Corporation Alliages d'acier exempts d'aluminium et leurs procédés de fabrication
CN109440010B (zh) * 2018-12-20 2021-08-13 唐山钢铁集团高强汽车板有限公司 一种1100MPa级高强捆带钢及其生产方法

Family Cites Families (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4533391A (en) * 1983-11-07 1985-08-06 Allegheny Ludlum Steel Corporation Work-hardenable substantially austenitic stainless steel and method
DE19727759C2 (de) * 1997-07-01 2000-05-18 Max Planck Inst Eisenforschung Verwendung eines Leichtbaustahls
FR2796083B1 (fr) * 1999-07-07 2001-08-31 Usinor Procede de fabrication de bandes en alliage fer-carbone-manganese, et bandes ainsi produites
DE102004061284A1 (de) * 2003-12-23 2005-07-28 Salzgitter Flachstahl Gmbh Verfahren zum Erzeugen von Warmbändern aus Leichtbaustahl
WO2005061152A1 (fr) * 2003-12-23 2005-07-07 Salzgitter Flachstahl Gmbh Procede pour produire des feuillards a chaud a partir d'un acier leger
DE102005052774A1 (de) * 2004-12-21 2006-06-29 Salzgitter Flachstahl Gmbh Verfahren zum Erzeugen von Warmbändern aus Leichtbaustahl
KR100723180B1 (ko) * 2005-05-03 2007-05-30 주식회사 포스코 가공성이 우수한 냉연강판과 그 제조방법
KR100851158B1 (ko) * 2006-12-27 2008-08-08 주식회사 포스코 충돌특성이 우수한 고망간형 고강도 강판 및 그 제조방법
FR2944789B1 (fr) 2009-04-22 2011-05-20 Rhodia Operations Procede de preparation d'un terpenylcyclohexanol
DE102009030324A1 (de) * 2009-06-24 2011-01-05 Voestalpine Stahl Gmbh Manganstahl und Verfahren zur Herstellung desselben
EP2383353B1 (fr) 2010-04-30 2019-11-06 ThyssenKrupp Steel Europe AG Acier à résistance élevée comprenant du Mn, produit plat en acier composé d'un tel acier et son procédé de fabrication
DE112013001144A5 (de) * 2012-02-25 2014-10-30 Technische Universität Bergakademie Freiberg Verfahren zur Herstellung hochfester Formteile aus hochkohlenstoff- und hochmanganhaltigem austenitischem Stahlguss mit TRIP/TWIP-Eigenschaften
JP5793459B2 (ja) * 2012-03-30 2015-10-14 新日鐵住金ステンレス株式会社 加工性に優れた耐熱フェライト系ステンレス冷延鋼板、冷延素材用フェライト系ステンレス熱延鋼板及びそれらの製造方法
DE102012013113A1 (de) 2012-06-22 2013-12-24 Salzgitter Flachstahl Gmbh Hochfester Mehrphasenstahl und Verfahren zur Herstellung eines Bandes aus diesem Stahl mit einer Mindestzugfestigkleit von 580MPa
CN102912219A (zh) * 2012-10-23 2013-02-06 鞍钢股份有限公司 一种高强塑积trip钢板及其制备方法
DE102012111959A1 (de) * 2012-12-07 2014-06-12 Benteler Automobiltechnik Gmbh Verfahren zur Herstellung eines Kraftfahrzeugbauteils sowie Kraftfahrzeugbauteil
RU2631219C2 (ru) * 2013-05-06 2017-09-19 Зальцгиттер Флахшталь Гмбх Способ изготовления деталей из легкой конструкционной стали и детали из легкой конструкционной стали
FI126798B (en) * 2013-07-05 2017-05-31 Outokumpu Oy Stainless steel with strength against delayed cracking and process for its manufacture
WO2015086903A1 (fr) * 2013-12-13 2015-06-18 Outokumpu Oyj Procédé pour la production d'acier inoxydable duplex à haute resistance
WO2015195062A1 (fr) * 2014-06-16 2015-12-23 Hayat Fatih Acier présentant une ductilité supérieure et une haute résistance et son procédé de fabrication
DE102015112886A1 (de) * 2015-08-05 2017-02-09 Salzgitter Flachstahl Gmbh Hochfester aluminiumhaltiger Manganstahl, ein Verfahren zur Herstellung eines Stahlflachprodukts aus diesem Stahl und hiernach hergestelltes Stahlflachprodukt

Also Published As

Publication number Publication date
EP3469108B1 (fr) 2024-07-31
RU2711696C1 (ru) 2020-01-21
DE102016110661A1 (de) 2017-12-14
WO2017211952A1 (fr) 2017-12-14
EP3469108A1 (fr) 2019-04-17
KR20190020694A (ko) 2019-03-04

Similar Documents

Publication Publication Date Title
US11352679B2 (en) Medium-manganese steel product for low-temperature use and method for the production thereof
US9732404B2 (en) Method of producing high-strength steel plates with excellent ductility and plates thus produced
JP4956998B2 (ja) 成形性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法
US20230141152A1 (en) Cold rolled heat treated steel sheet and a method of manufacturing thereof
US20210301376A1 (en) High-tensile steel containing manganese, use of said steel for flexibly-rolled sheet-products, and production method and associated steel sheet-product
US20120018058A1 (en) Process for manufacturing a cold rolled trip steel product
US20160208352A1 (en) A high-hardness hot-rolled steel product, and a method of manufacturing the same
CN109642263B (zh) 一种用于制造在进一步加工过程中具有改进性能的高强度钢带的方法以及这种钢带
US11261503B2 (en) Method for producing a flat steel product made of a manganese-containing steel, and such a flat steel product
US11519050B2 (en) Method for producing a re-shaped component from a manganese-containing flat steel product and such a component
US20180230579A1 (en) High-tensile manganese steel containing aluminium, method for producing a sheet-steel product from said steel and sheet-steel product produced according to this method
JP4772431B2 (ja) 伸びと穴拡げ性に優れた溶融亜鉛めっき高強度鋼板の製造方法
KR20230016218A (ko) 열처리 냉연 강판 및 그 제조 방법
US11214846B2 (en) Method for producing a shaped component from a medium-manganese flat steel product and such a component
US20210140008A1 (en) Method for producing a hot or cold strip and/or a flexibly rolled flat steel product made of a high-strength manganese steel and flat steel product produced by said method
US20190256943A1 (en) Method for producing a cold-rolled steel strip having trip-characteristics made of a high-strength mangan-containing steel
JPH04325657A (ja) 伸びフランジ性の優れた高強度熱延鋼板及びその製造方法
US20190085434A1 (en) Method for producing a hot-formed steel component, and hot formed steel component
KR20210014055A (ko) 고강도 강판 및 이의 제조방법
JP4848722B2 (ja) 加工性に優れた超高強度冷延鋼板の製造方法
KR101489243B1 (ko) 가공성 및 도금밀착성이 우수한 고강도 합금화 용융 아연도금강판 및 그 제조방법
JP7440605B2 (ja) 高強度鋼板及びこの製造方法
JP2003239040A (ja) 成形性に優れた溶融亜鉛メッキ高強度鋼板およびその製造方法
KR950007784B1 (ko) 점용접성 및 프레스 가공성이 우수한 초고강도 냉연강판의 제조방법
KR20120110538A (ko) 고강도 강판 및 그 제조 방법

Legal Events

Date Code Title Description
AS Assignment

Owner name: SALZGITTER FLACHSTAHL GMBH, GERMANY

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:PALZER, PETER;EVERTZ, THOMAS;SCHUBERT, MARTIN;REEL/FRAME:047782/0873

Effective date: 20181212

STPP Information on status: patent application and granting procedure in general

Free format text: APPLICATION DISPATCHED FROM PREEXAM, NOT YET DOCKETED

STPP Information on status: patent application and granting procedure in general

Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION

STPP Information on status: patent application and granting procedure in general

Free format text: NON FINAL ACTION MAILED

STPP Information on status: patent application and granting procedure in general

Free format text: FINAL REJECTION MAILED

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION