EP4281591A1 - Procédé de fabrication d'un acier à outils comme support pour revêtements pvd et acier à outils - Google Patents

Procédé de fabrication d'un acier à outils comme support pour revêtements pvd et acier à outils

Info

Publication number
EP4281591A1
EP4281591A1 EP22702639.0A EP22702639A EP4281591A1 EP 4281591 A1 EP4281591 A1 EP 4281591A1 EP 22702639 A EP22702639 A EP 22702639A EP 4281591 A1 EP4281591 A1 EP 4281591A1
Authority
EP
European Patent Office
Prior art keywords
weight
steel
steel material
temperature
carbides
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.)
Pending
Application number
EP22702639.0A
Other languages
German (de)
English (en)
Inventor
Alfred HACKL
Harald Leitner
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.)
Voestalpine Boehler Edelstahl GmbH and Co KG
Original Assignee
Voestalpine Boehler Edelstahl GmbH and Co KG
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 Voestalpine Boehler Edelstahl GmbH and Co KG filed Critical Voestalpine Boehler Edelstahl GmbH and Co KG
Publication of EP4281591A1 publication Critical patent/EP4281591A1/fr
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/14—Both compacting and sintering simultaneously
    • B22F3/15—Hot isostatic pressing
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D6/001—Heat treatment of ferrous alloys containing Ni
    • 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
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D6/007—Heat treatment of ferrous alloys containing Co
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/02—Hardening by precipitation
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • C22C33/0264—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 5%
    • 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
    • C22C38/18—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
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • 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
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • 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
    • C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt
    • 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
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
    • B22F2005/001—Cutting tools, earth boring or grinding tool other than table ware
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

  • the invention relates to a method for producing a steel material as a carrier for PVD coatings, a method for producing a high-pressure-resistant tool, such as a stamping tool, which is coated with a PVD coating.
  • the invention also relates to a steel material as a base for PVD coatings, a high-strength tool, such as a stamping tool, which is coated with a PVD coating, and the use of the steel material as a base for PVD coatings.
  • High-speed steels and modern cold-work steels are used in many areas and often have a very high level of hardness and sufficient toughness. Such steels are used, for example, for tools that remove by drilling, milling or cutting.
  • a high level of hot hardness is required, especially for high-speed work applications, since these areas of application not only lead to strong heating of the workpiece, but also to very strong heating of the tool. In this respect, it is important that these steels retain their mechanical characteristics even at higher working temperatures that may be achievable.
  • such steels are also exposed to high pressures in many cold work applications, so that high compressive strength is also required. This applies, for example, to fine blanking and stamping, so that the compressive strength is required here in order to avoid early chipping.
  • such steels are used as active elements in the field of stamping and precision blanking, which, in addition to high pressure loads, are also intended to withstand wear and tear.
  • the level of hardness and fatigue strength of the tool can also be increased with a suitable coating.
  • the surface of the tool is coated with a high-strength hard material. This increases the wear resistance and the service life of the tool and thus reduces the demands on tool steels in many areas of application.
  • a carrier material which has a high compressive strength, otherwise Hertzian pressure, for example, can lead to the "eggshell effect". This occurs when there is a large difference in hardness between the carrier material and hard material coating Hard material coating together because the soft surface gives in. When used, such tools have to withstand high pressures.
  • a pressure-resistant carrier material supports the effect of the hard material coating and thus leads to an overall improved performance of the tool.
  • high-strength tool steels it is also desirable for high-strength tool steels to have sufficient toughness to achieve long service lives and, in particular, to avoid brittleness that can lead to premature tool damage.
  • Known cold work steels are characterized by a high carbide content, which gives the steel a high degree of hardness. A high proportion of carbide also leads to high abrasive and adhesive wear resistance.
  • Known high-strength, high-performance tool steels for high-speed and cold-work applications include alloys which, in addition to iron, contain, for example, 0.8-2.4% carbon, 4-8% chromium, 2-5% molybdenum, 2-9% vanadium, 1-15% tungsten and up to contain up to 12% cobalt.
  • the essential proportion of these elements is intended to ensure high hardness, which is ensured on the one hand by the carbon, which allows the formation of carbides, these carbides being formed with the alloying elements chromium, molybdenum, tungsten and vanadium.
  • the primary carbides are precipitated from the liquid phase during cooling.
  • the nucleation in the liquid phase is fast, the growth of the carbides is accelerated and accordingly leads to large carbide particles with a size of about 15 pm.
  • the primary carbides occur more frequently in the segregation zones because the concentration of the carbide-forming elements is higher there. During a subsequent heat treatment, the segregation zones are partially broken down and the primary carbides are dissolved.
  • Secondary carbides are precipitated from the solid phase below the solidus temperature. They are usually smaller than the primary carbides and have a size of 1-2 pm.
  • the secondary carbides are formed, for example, from the alloying elements tungsten, molybdenum and vanadium and can be present as MC or MeC carbides, among other things.
  • Secondary hardening carbides are formed during heat treatment, especially during tempering at approx. 500 °C, when carbide-forming elements that are still dissolved in the matrix combine with carbon.
  • the secondary hardening carbides are very small and have a size of approx. 100 nm.
  • the hardness and toughness parameters cannot both be increased at will at the same time. As is known to those skilled in the art, very high hardness often means low toughness. The steels The low toughness observed with high proportions of carbide leads to premature tool failure in certain applications.
  • a high proportion of carbides is the main factor in achieving the desired high hardness of a cold work steel.
  • the associated reduction in toughness is accepted.
  • Another way to increase the hardness of the steel is to strengthen the steel matrix.
  • These are the so-called matrix steels, which by definition contain no carbides.
  • the known matrix steels show good fracture toughness and improved fatigue behavior.
  • the hardness level of such carbide-free steels is limited to max. 56-58 HRC.
  • Carbides distributed in the steel are necessary for higher hardness levels.
  • Matrix steels are also characterized by a comparatively low wear resistance.
  • Powder-metallurgical production has become established for these types of steel, in which liquid steel is broken down into a powder in a gas stream (atomization) and this powder is then compacted and shaped, in particular by hot isostatic pressing.
  • a high-speed steel is known from EP 1 469 094 B1, which has a hardness of 57 HRC, which is achieved by a high proportion of carbide-forming elements such as vanadium, molybdenum and tungsten.
  • the carbide particles have an average diameter of 0.5 ⁇ m and a density of more than 80 to 10 3 particles/mm 2 .
  • the carbide particles are formed during diffusion annealing at 1300 °C for 10 to 20 h and rapid cooling to 900 °C with a cooling rate of at least 3 °C/min and subsequent heating to 1100 °C for no longer than 10 h.
  • a high-speed steel is known from EP 3 050 986 B1, which has a relatively high hardness of 45-60 HRC, which is caused by a high carbide concentration.
  • the carbide precipitates are particles with a maximum size of 1 ⁇ m and an average diameter of 0.5 ⁇ m.
  • the heat treatment corresponds to that of heat treatment known from EP 1 469 094 B1.
  • the nitrogen content in the alloy composition has been greatly reduced and is at most 0.018% in order to reduce the formation of carbonitrides and thereby increase toughness.
  • a high-speed steel is known from EP 3 315 617 A1 which has a maximum hardness of 69 HRC and the following alloy layer in % by weight: 0.5-2.2 C, 0.1-1.0 Si, 0. 1-1.0 Mn, ⁇ 0.025 P, ⁇ 0.0040 S, 3.0-7.0 Cr, 5.0-30.0 W + 2Mo, 0.6-5.0 V, ⁇ 10 Co, ⁇ 0.3 AI, ⁇ 0.015 Ca, ⁇ 0.0100 N, ⁇ 0.0040 O (oxygen).
  • the steel matrix contains MC and MeC carbides of at least 0.4 ⁇ m, which have a surface area of at least 3.8% and 6.8% respectively.
  • the high proportion of large carbide particles serves to increase the wear resistance, which is 0.370x l0 -7 mm 3 /kg for the alloy layer mentioned.
  • the object of the invention is to create a method for producing a tool steel as a carrier for PVD coatings, which has a high level of hardness of at least 62 HRC and also has a high compressive strength in the form of the compression limit Rp0.2 of at least 2700 MPa.
  • the object is achieved with the steel material having the features of claim 7.
  • Advantageous developments are characterized in the subclaims dependent thereon.
  • a hybrid steel was developed which has a high level of hardness compared to known carbide-containing cold work steels and at the same time has a high level of toughness compared to known matrix steels.
  • the steel material according to the invention is characterized by a high compression limit Rp0.2. This creates a steel material that is exceptionally suitable as a carrier for subsequent PVD coatings and consequently for the production of a stamping tool in particular.
  • the carbide content is reduced compared to known types of steel with a comparable level of hardness. They are secondary carbides precipitated from the solid phase and have a small carbide size. The carbides contained are round and homogeneously distributed.
  • the steel material according to the invention does not contain any primary carbides. Surprisingly, a high level of hardness and high compressive strength (compression limit) are nevertheless achieved, with toughness being significantly increased. This is achieved with a powder-metallurgical production route, a balanced alloy composition and a heat treatment tailored to this.
  • the alloy according to the invention consists of the following elements:
  • V Vanadium
  • W Tungsten
  • Co Co
  • N Nitrogen
  • Titanium (Ti) ⁇ 1.5 ⁇ 0.3
  • the remainder is iron and alloy-related impurities.
  • alloying elements in such steels act as follows:
  • Carbon essentially serves to set the desired level of hardness.
  • the carbon content should not be too high, as this can lead to a high proportion of precipitations in the form of carbides, which could have a negative effect on toughness and fatigue strength.
  • the upper limit according to the invention is therefore 0.75% by weight, preferably 0.68% by weight, particularly preferably 0.63% by weight.
  • the lower limit according to the invention is 0.55% by weight, preferably 0.58% by weight.
  • the desired level of hardness is not achieved below 0.55% by weight. Above 0.75 wt%, primary carbides may form, thereby reducing toughness.
  • Si is a solid solution hardener and is not a carbide-forming element in steel, but influences the carbide precipitation kinetics in the steel. It stabilizes the carbon so that it is only available for the formation of carbides at higher temperatures. Silicon serves as a deoxidizing agent and is therefore present in low concentrations in almost all steels due to the manufacturing process. It increases scale resistance, yield strength and tensile strength without significantly reducing elongation. On the other hand, a decrease in the silicon content leads to a reduction in the anisotropy of the mechanical properties. A low silicon content allows for initial formation of metastable M3C carbides. These act as a C reservoir for the subsequent precipitation of the desired MC carbides.
  • the upper limit according to the invention is therefore 1.00% by weight, preferably 0.94% by weight, particularly preferably 0.88% by weight.
  • the lower limit according to the invention is 0.70% by weight. Below 0.70% by weight, the desired hardness cannot be reliably achieved.
  • the upper limit according to the invention is therefore 0.60% by weight, preferably 0.50% by weight, more preferably 0.40% by weight, particularly preferably 0.27% by weight.
  • the lower limit according to the invention is 0.20% by weight, preferably 0.22% by weight.
  • chromium With a proportion of more than 4.00% by weight, chromium leads to the desired solid solution strengthening. In general, chromium reduces the critical cooling rate and thus increases hardenability. The addition of chromium is important for through hardening, so that tools with larger dimensions can also be hardened. Furthermore, increased chromium content can lead to carbide precipitation of type M7C3 and thus increase hardness. Thus, too high a chromium content can also lead to negative effects in terms of toughness. In addition, too high a chromium content of more than 5.00% by weight can have negative effects on the retained austenite content during hardening.
  • the upper limit according to the invention is therefore 5.00% by weight, preferably 4.70% by weight, particularly preferably 4.23% by weight.
  • the lower limit according to the invention is 4.00% by weight, preferably 4.10% by weight.
  • Molybdenum forms special carbides and mixed carbides with iron. These are of the M2C, MeC and MC types.
  • the addition of molybdenum increases the activation energy for C diffusion in austenite and thus the diffusion coefficient for C or C diffusion humiliated. This results in the lower bainite start temperature (Bs) and reduced bainite formation.
  • Bs bainite start temperature
  • Mo leads to a refinement of the microstructure, ie a fine structure is predominant regardless of the cooling rate (1 °C/s to 60 °C/s). Grain coarsening remains low because of the low dissolution rate and the high dissolution temperature of the carbides (carbides counteract grain coarsening).
  • Austenitizing (solution annealing) at higher hardening temperatures can thus achieve improved tempering resistance, since more carbide-forming elements can be precipitated and more carbides are formed as a result.
  • the hard carbides also increase the high-temperature yield point and wear resistance.
  • Mo improves the scaling resistance of the steel. Contents that are too high impair the machinability and, if it remains dissolved in the matrix, the thermal conductivity. It could also happen that embrittlement occurs during tempering due to the occupation of the former austenite grain boundaries with carbides.
  • the upper limit according to the invention is therefore 3.50% by weight, preferably 3.20% by weight, particularly preferably 2.74% by weight.
  • the lower limit according to the invention is 1.80% by weight, preferably 2.00% by weight.
  • vanadium is one of the strongest carbide-forming elements because of its high affinity for C. During tempering, it forms fine and evenly distributed MC-type precipitates. These are preferred because of the higher thermal resistance compared to other carbide types. This leads to an increase in high-temperature strength, an increase in yield point and wear resistance and an improvement in tempering resistance. However, at higher concentrations, a higher hardening temperature is required to dissolve the thermally stable MC primary carbides.
  • the upper limit according to the invention is therefore 1.50% by weight, preferably 1.25% by weight, particularly preferably 1.12% by weight.
  • the lower limit according to the invention is 0.80% by weight, preferably 0.90% by weight.
  • Cobalt is an austenite stabilizing element. It does not form carbides but remains dissolved in the matrix and thus influences carbon diffusion. This leads to an increase in hot hardness, improved hot brittleness and the high matrix hardness according to the invention, which manifests itself in a high compression limit Rp0.2. Too high levels can Limit toughness, which is why the upper limit according to the invention is 5.00% by weight, preferably 4.30% by weight, particularly preferably 3.70% by weight. According to the invention, the lower limit is 3.00% by weight, preferably 3.50% by weight.
  • the nitride and carbonitride particles are relatively large because they are formed in the melt. Too much nitrogen can therefore reduce toughness and promote intergranular stress corrosion. More than 0.10% by weight of nitrogen can lead to a deterioration in toughness.
  • the steel material is usually atomized into powder with N2, it contains small traces of nitrogen due to the manufacturing process. Since few nitride formers (Al, Ti, Nb) are alloyed, no nitrides are formed, but N remains interstitially dissolved and increases the hardness of the matrix, which consists of martensite.
  • the upper limit according to the invention is therefore 0.10% by weight, preferably 0.80% by weight, particularly preferably 0.5% by weight.
  • the lower limit is 0.02% by weight, preferably 0.03% by weight, particularly preferably 0.04% by weight.
  • the upper limit according to the invention is 3.00% by weight, preferably 2.70% by weight, particularly preferably 2.40% by weight. According to the invention, the lower limit is 1.80% by weight, preferably 2.00% by weight.
  • the tungsten equivalent W eq which is defined as W+2Mo, shows the hot hardness and tempering resistance as well as a measure of the microstructure.
  • the W eq should be less than 10.0% by weight, preferably less than 9.1% by weight, since otherwise the toughness is reduced and the tendency to brittle fracture increases. This value is preferably between 7.5 and 8.2% by weight, particularly preferably 7.9% by weight, since this is advantageous for machinability as well as the hot hardness.
  • the Weq should not be less than 5.4% by weight.
  • this W eq setting can also have a positive effect on the structure, since the carbide content is high enough to achieve a high level of hardness and excellent wear resistance and at the same time is not unnecessarily high, which would have a negative impact on toughness.
  • Nickel is one of the alloying elements that promote solidification according to the stable iron-carbon system. By reducing the critical cooling rate, nickel increases through hardening and through aging. Nickel also increases toughness, especially in the low-temperature range, has a grain-refining effect and reduces sensitivity to overheating. High nickel contents result in small or sometimes negative coefficients of thermal expansion.
  • the upper limit according to the invention is 1.50% by weight.
  • the upper limit of the nickel content can preferably also be selected at 1.00, particularly preferably at 0.35 or 0.30 or 0.27 or 0.25% by weight. Nickel can also only be present as a production-related impurity, i.e. without intentional alloying.
  • the lower limit can be 0.04% by weight.
  • Niobium acts similarly to vanadium and forms MC-type carbides. However, niobium leads to a more angular shape of MC carbides, which is why the maximum addition is limited to 1.5% by weight, preferably to 0.5% by weight. Since Nb forms nitrides, which can impair atomization by "clogging", the upper limit can particularly preferably be 0.21% by weight, particularly preferably 0.11% by weight. The lower limit can be 0.002% by weight. Preferably no niobium is added.
  • Copper is an optional element that can contribute to increased hardness. If used, the preferred range is up to 1.00% by weight, more preferably up to 0.1% by weight. However, it is difficult to recycle Cu-bearing steel, so copper is not usually added intentionally. A technically feasible lower limit can be 0.006% by weight.
  • the preferred range is 0.02-1.50% by weight.
  • a particularly preferred upper limit is 0.3% by weight. However, typically none of these items are added.
  • the lower limit can be 0.005% by weight. Since Ti can also form nitrides, which can impair atomization by "clogging", the Ti upper limit can particularly preferably be 0.18% by weight, particularly preferably 0.09% by weight.
  • Aluminum is used as a deoxidizer.
  • the upper limit can be 1.5% by weight, preferably 0.3% by weight. Since Al forms nitrides, which can impair atomization by "clogging", the upper limit can particularly preferably be 0.18% by weight, particularly preferably 0.09% by weight. A technically feasible lower limit can be 0.005% by weight .
  • Boron can increase the hardness of the steel material.
  • the boron content is limited to 0.8% by weight, preferably ⁇ 0.006% by weight.
  • the lower limit can be 0.0002% by weight.
  • Phosphorus tends to diffuse to grain boundaries and weaken grain cohesion. Phosphorus is therefore limited to ⁇ 0.35% by weight, preferably to ⁇ 0.05% by weight. A technically feasible lower limit can be 0.001% by weight.
  • Sulfur contributes to better machinability. However, high S levels can have a negative effect on toughness. Therefore, sulfur is limited to ⁇ 0.35% by weight, preferably to ⁇ 0.05% by weight. A technically feasible lower limit can be 0.001% by weight.
  • the tool steel satisfies the following formula (1): 0.005 ⁇ 0.8[Nb] + [Ti] + [Al] ⁇ 0.18 where [Nb], [Ti], and [Al] represent the contents of represent Nb, Ti and Al in % by weight. Too much of these elements can cause clogging during atomization and degrade powder properties, so the upper limit may be 0.18 wt%.
  • the tool steel satisfies the following formula ( 2): 2.7 ⁇ 1/2 [ Mo] + [W] ⁇ 4.5 where [Mo] and [W] are the contents of Mo and W by weight. % represent. This results in particularly advantageously uniformly finely distributed carbides, since no primary carbides are formed, but rather the carbides are formed from the solid phase as secondary carbides.
  • the tool steel satisfies the following relation (3): 0.5 ⁇ [C]/[V] ⁇ 0.6 where [C] and [V] represent the contents of C and V in % by weight. Outside this ratio, primary MC-type carbides can form, reducing toughness.
  • This ratio can be achieved with the heat treatment according to the invention of the alloy according to the invention.
  • the toughness can be reduced. If this ratio is exceeded, i.e. too few carbides are formed, the grains can become coarser during hardening, i.e. excessive grain growth.
  • the hardness in HV is determined according to DIN EN ISO 6507-1.
  • the steel material is preferably processed by powder metallurgy.
  • a steel melt is generally atomized into powder. This powder is filled into a capsule, sealed airtight and then hot isostatically pressed (HIP process).
  • HIP process hot isostatically pressed
  • This already dense and homogeneous material is formed, for example by rolling or forging, and then annealed. Annealing is used for further processing of the steel material, such as subsequent surface treatment or the like. Heat treatment is then carried out. This can also be done at the customer's site, for example after the tool has been manufactured.
  • the steel material or tool is brought to a temperature range of 1100-1180 °C, with the holding time being selected depending on the temperature. The holding period begins when the steel material has been heated through, i.e. the desired temperature has also been reached in the core. After the intended holding time, the steel material is subjected to rapid cooling, in particular with an X value ⁇ 3, in particular between 0.08 and 3.
  • the carbide content is lowered to a range in which the person skilled in the art would expect a significantly reduced level of hardness and reduced compressive strength.
  • the nitrogen content is increased and is now significantly higher than in the known steel grades.
  • One skilled in the art would expect a reduced level of toughness in this area. According to the invention, however, it was found that, despite the reduction in the carbide content and the increase in the nitrogen content, the effects mentioned surprisingly do not occur and thus a high degree of hardness in combination with a high level of toughness is achieved.
  • the alloy according to the invention achieves a hardness of at least 62 HRC, preferably at least 63 HRC measured according to ASTM E18-17 with a high toughness of at least 73 J impact bending work at room temperature measured according to SEP 1314.
  • the alloy according to the invention has a high compressive strength, specified as the compression limit Rp0.2 of at least 2700 MPa, preferably >2800 MPa, more preferably >2900 MPa, particularly preferably >2950 MPa, determined by means of a uniaxial compression test in accordance with ASTM E606.
  • the compressive strength was not determined using standard cylinder compression tests, but using a uniaxial compression test as part of an LCF test (Low Cycle Fatigue) according to ASTM E606, with the test being carried out with the following parameters: Testing machine: servo-hydraulic Instron 8854, 250 kN load cell , Extensometer is a laser extensometer from Fiedler; Specimen type LCF specimen with shortened shaft; Sample size: 12 mm initial length Lo, 9 mm diameter; Test speed 0.00025 1/s, strain controlled; Test at room temperature. This is the strain-controlled loading of the first cycle of the LCF test.
  • the range around 1150° C. represents the optimal hardening temperature for the alloy according to the invention.
  • the matrix is enriched with the appropriate alloying elements, resulting in a high-strength matrix.
  • This is called the "Matrix" or "Steel Matrix”. denotes the material surrounding the carbides.
  • the high hardness and compressive strength is based not only on the carbides but also on the hard matrix.
  • the balanced alloy composition means that the carbide content is significantly lower at the hardening temperature according to the invention than in the known steel grades.
  • the subsequent tempering treatment is matched to the alloy composition according to the invention in such a way that the secondary hardening carbides that arise from the solid phase during tempering are significantly smaller.
  • the invention thus relates to a method for producing a tool steel for cold and high-speed work applications, with a steel material consisting of the following alloying elements: (all figures in % by weight):
  • V 0.80 to 1.50
  • N 0.020 to 0.10 and optionally one or more of
  • Phosphorus (P) ⁇ 0.35 remainder iron and unavoidable impurities resulting from the smelting process is melted and processed into a powder by atomization and the powder is then hot isostatically pressed and the hot isostatically pressed powder is then optionally hot-formed and further processed, with a heat treatment following, with the heat treatment being carried out in such a way that that the steel material and/or the tool made from it is first heated to a hardening temperature of 1100 °C - 1180 °C, then held at this hardening temperature for a maximum of 2 to 20 minutes and then at a cooling rate of ⁇ 3 to a temperature of ⁇ 60 °C C, preferably ⁇ 30 °C for the purpose of hardening and then tempered, the tempering treatment comprising at least two cycles in which the steel material is heated to a temperature of 530 °C to 560 °C and at least two hours at this temperature of 530 °C to 560 °C and to a temperature ⁇ 60
  • three starting cycles are run.
  • the steel material which has at least one or more or all element(s) with the following concentration value(s): (all data in % by weight):
  • V 0.90 to 1.25
  • the steel material is heated at a hardening temperature selected from the group of 1180° C., 1160° C. or 1100° C. and for a duration selected from the group of a maximum of 2 minutes, a maximum of 3 minutes or a maximum of 20 minutes and then to a temperature ⁇ 60 °C for the purpose of hardening.
  • a hardening temperature selected from the group of 1180° C., 1160° C. or 1100° C. and for a duration selected from the group of a maximum of 2 minutes, a maximum of 3 minutes or a maximum of 20 minutes and then to a temperature ⁇ 60 °C for the purpose of hardening.
  • the steel material is tempered, the tempering treatment being at a temperature selected from the group of 530°C, 550°C or 560°C for a duration selected from the group of at least 1.5, 2, 2.5, 3, 3.5 hours is carried out whereby at least two tempering cycles are run and the steel material is preferably cooled to a temperature of ⁇ 60 °C after each tempering cycle.
  • the steel material is cooled to a temperature of ⁇ 30° C. after heating at the hardening temperature and/or after each tempering step.
  • the steel material and/or the tool made from it is heated at a hardening temperature of 1180° C. for a maximum of 2 minutes, then at a cooling rate of X ⁇ 3 to a temperature ⁇ 60° C., preferably ⁇ 30° C is cooled for the purpose of hardening and then tempered, the tempering treatment being carried out at a temperature of 560 °C for at least 2 hours, with at least two tempering cycles being run and the steel material and/or the tool made from it preferably heated to one temperature after each tempering cycle of ⁇ 60°C, preferred
  • the steel material and/or the tool made from it is heated at a hardening temperature of 1160° C. for a maximum of 3 minutes, then at a cooling rate of X ⁇ 3 to a temperature ⁇ 60° C., preferably ⁇ 30° C is cooled for the purpose of hardening and then tempered, the tempering treatment being carried out at a temperature of 530 °C for at least 2 hours, with at least two tempering cycles being run and the steel material and/or the tool made from it being preferably heated to one temperature after each tempering cycle of ⁇ 60°C, preferred
  • the steel material and/or the tool made from it is heated at a hardening temperature of 1150° C. for a maximum of 3 minutes, after which it is cooled at a rate of X ⁇ 3 to a temperature ⁇ 60° C., preferably ⁇ 30° C cooled for the purpose of hardening and then tempered, the tempering treatment being carried out at a temperature of 530 °C for at least 2 hours, with at least two tempering cycles being run and the steel material and/or the tool made from it preferably heated to one temperature after each tempering cycle of ⁇ 60 °C, preferably ⁇ 30 °C.
  • the steel material and/or the tool made from it is heated at a hardening temperature of 1140° C. for a maximum of 3 minutes. it is then cooled at a cooling rate of X ⁇ 3 to a temperature of ⁇ 60° C., preferably ⁇ 30° C., for the purpose of hardening and then tempered, with the tempering treatment being carried out at a temperature of 530° C. for at least 2 hours at least two tempering cycles are run and the steel material and/or the tool made from it is preferably cooled to a temperature of ⁇ 60° C., preferably ⁇ 30° C., after each tempering cycle.
  • the steel material and/or the tool made from it is heated at a hardening temperature of 1100° C. for a maximum of 20 minutes, then at a cooling rate of X ⁇ 3 to a temperature ⁇ 60° C., preferably ⁇ 30° C is cooled for the purpose of hardening and then tempered, the tempering treatment being carried out at a temperature of 530 °C for at least 2 hours, with at least two tempering cycles being run and the steel material and/or the tool made from it being preferably heated to one temperature after each tempering cycle of ⁇ 60 °C, preferably ⁇ 30 °C.
  • a steel matrix is advantageously created which comprises MC and MeC carbides to increase the hardness and compressive strength, the MC carbides having an average diameter of 0.6 ⁇ m and the MeC carbides having an average diameter of 0.9 ⁇ m.
  • a steel matrix is adjusted, with the carbide density in the matrix at a maximum of 27538 particles/mm 2 and a minimum of 12688 particles/mm 2 for MeC - and at a maximum of 39845 particles/mm 2 and a minimum of 21093 particles/mm 2 for MC carbides lies.
  • the particle density was determined by REM investigations of a cross-section finely polished with 0.05 pm Al2O3 OPS using 20 different measuring points, each with: image section 43.1 pm x 32.3 pm, image resolution 1024 x 768 pixels, 15 keV electron beam energy, InA sample current, 100 ps dwell time per pixel.
  • a steel matrix is set, with the average area proportion of the MeC carbides being at most 1.9% and the MC carbides being at most 1.3%.
  • the surface area was measured in the same way as the particle density and determined using EDX element distribution.
  • a steel material is advantageously formed which has a hardness of at least 62 HRC, preferably at least 63 HRC, measured according to ASTM E18-17.
  • a steel material is formed which has a toughness, measured as impact bending work at room temperature according to SEP 1314, of at least 73 J.
  • a steel material is formed that has a compressive strength, measured as compression limit Rp0.2, of >2700 MPa, preferably >2800 MPa, more preferably >2900 MPa, particularly preferably >2950 MPa.
  • the invention also relates to a tool steel for cold and high-speed applications, which is produced in particular according to the above-mentioned method, the steel material consisting of the following alloying elements (all figures in % by weight):
  • V 0.80 to 1.50
  • N 0.02 to 0.10 and optionally one or more of
  • Phosphorus (P) ⁇ 0.35 The remainder is iron and unavoidable impurities resulting from the smelting process.
  • the carbon content in the steel alloy has an upper limit of 0.75% by weight, preferably 0.68% by weight, particularly preferably 0.63% by weight and a lower limit of 0.55% by weight, preferably at 0.58% by weight. Less than 0.55% by weight.
  • the vanadium content in the steel alloy has an upper limit of 1.50% by weight, preferably 1.25% by weight, particularly preferably 1.12% by weight and a lower limit of 0.80% by weight, preferably 0.90% by weight.
  • the cobalt content in the steel alloy has an upper limit of 5.00% by weight, preferably 4.30% by weight, particularly preferably 3.70% by weight and a lower limit of 3.00% by weight. %, preferably 3.50% by weight.
  • the steel material and/or the tool made from it is hardened at 1100-1180° C. for a maximum of 2 to 20 minutes and cooled at a cooling rate of ⁇ 3 to a temperature of ⁇ 60° C., preferably ⁇ 30° C.
  • the steel material and/or the tool made from it is tempered at 530-560° C. for at least 2 hours with at least two tempering cycles.
  • the tool steel can be used as a carrier for a PVD coating.
  • the tool steel can be used for a stamping or fine blanking tool.
  • FIG. 1 the possible steel compositions according to the invention
  • Figure 2 is a comparison table showing two known steel materials and the material of the present invention.
  • FIG. 3 a highly schematized production route, the powder-metallurgical PM route is according to the invention
  • Figure 4 a thermodynamic stability calculation for various
  • FIG. 5 SEM images of an inventive hardened at 1150°C
  • FIG. 6 another SEM image of a cross section showing the MeC
  • FIG. 7 a heat treatment according to the invention.
  • FIG. 9 the carbide proportions at a hardening temperature of 1150° C.
  • FIG. 10 the size distribution of the MeC carbides
  • FIG. 11 the size distribution of the MC carbides
  • Figure 12 for hardening temperature 1030 °C: hardness and impact bending work (SB) in
  • Figure 13 for hardening temperature 1070 °C: hardness and impact bending work (SB) in
  • Figure 14 for hardening temperature 1150 °C: hardness and impact bending work (SB) in
  • FIG. 15 Compressive strength results
  • FIG. 16 examples of steel compositions according to the invention.
  • FIG. 17 examples of steel compositions not according to the invention.
  • Figure 18 exemplary heat treatment consisting of hardening and tempering.
  • FIG. 1 shows the analysis range within which the invention can be carried out and the effects according to the invention can be achieved.
  • FIG. 2 shows the composition of the steel material according to the invention, which is in the range of the composition according to FIG. 1 and represents an embodiment of the steel material.
  • This steel material is compared with two other embodiments, namely REF 1 (EP3050986) and REF 2 (EP1469094), which compared to the known embodiments the silicon, molybdenum and cobalt content are significantly increased and in particular the nickel content differs greatly and in particular is reduced .
  • FIG. 3 shows a conventional melt-metallurgical production route (not according to the invention), the possible powder-metallurgical production route for producing the powder (according to the invention), and corresponding objects therefrom.
  • a corresponding molten steel is atomized into a powder, in particular with nitrogen or other inert gases. If necessary, this powder is classified by sifting or sieving, and the classified powder is then combined into a desired particle size range, filled into a corresponding capsule, which is welded and then compacted by hot isostatic pressing. Accordingly, a material converted in this way can then be subjected to hot forming.
  • the dense and homogeneous material obtained by hot isostatic pressing can be rolled or forged to the required dimensions in a forming process.
  • the thickness after hot rolling can be example 60 mm, which corresponds to a degree of deformation of V times the diameter reduction.
  • Segregation occurs in steel materials that contain segregation-active elements and are manufactured using the conventional casting process. In the segregation zones there is often an imbalance in the element concentrations. This can lead to the formation of primary carbides, although primary carbide formation would not be expected due to the alloy position in thermodynamic equilibrium.
  • the powder metallurgical manufacturing route has the advantage that the occurrence of segregation zones and thus the formation of primary carbides are prevented.
  • the production parameters when atomizing the molten steel have a significant influence on the powder grain size and thus on the carbide grain size. Fine adjustment of the setting parameters for temperature and pressure is also necessary in the HIP process so that there is no carbide growth or carbide cluster formation. Particularly in the case of such high-alloy steels as in the subject matter according to the invention, high carbide proportions are often present. Carbides have a positive effect on compressive strength and hardness in general. Nevertheless, in terms of toughness, compressive strength and fatigue strength, carbides represent "defects" that limit these properties. In this regard, it is particularly important that the carbides are small, round and homogeneously distributed over the cross-section. Due to the high number of carbides, such In high-alloy steels, it is often the case that the carbides conglomerate during the conventional casting process, which can severely limit the toughness and fatigue strength and consequently also the service life of the tool made from them.
  • these are the so-called secondary hardening carbides of the MC and MeC types, which are formed from the solid phase during a tempering treatment.
  • the secondary carbides usually have a smaller particle size compared to the primary carbides separated from the melt.
  • FIG. 1 A thermodynamic stability calculation using ThermoCalc for different carbide phases is shown in FIG. The calculation shows which carbide phases are in equilibrium or thermodynamically stable at a certain temperature. This is necessary for setting the curing temperature at which there is sufficient solubility of the carbide phases is given.
  • Carbides of the M23C6 and M7C3 type completely dissolve in the matrix during hardening, carbides of the MC and M6C type largely, but not completely, dissolve. However, complete solubility of the carbides is not desired, which is why the maximum hardening temperature is limited to 1180 °C.
  • a certain proportion of carbides should remain in the structure during hardening in order to prevent the grains from becoming coarser. This can be explained by the fact that carbides act as growth brakes and slow down unwanted grain growth.
  • the maximum hardening temperature at which the effects according to the invention can still be achieved is 1180.degree. If the temperature is exceeded, more carbon and carbide formers are dissolved in the matrix. This increases the hardness of the steel material, but leads to a significant reduction in toughness. It is particularly important to adhere to the holding time, which must not be more than 2 minutes in the temperature range around 1180 °C. Longer holding times increase carbide growth at the stated temperature.
  • the optimal holding time here is a maximum of 3 minutes.
  • the lower limit according to the invention for the hardening temperature is therefore 1100.degree. C., in particular 1150.degree.
  • the upper temperature limit at which the effects according to the invention can also be achieved is 1180.degree.
  • FIG. A steel surface hardened at 1150° C. and then heat-treated according to the invention has fine, singular, finely distributed carbides. There are no segregations, carbide agglomerates or inhomogeneities in the structure.
  • the carbide phase distribution is particularly homogeneous (FIG. 6).
  • the carbides especially of type MC and MeC, are round and evenly distributed in the steel matrix. There are no carbide conglomerates. In addition, no large primary carbides are present.
  • a finely tuned heat treatment has a significant influence on the size, homogeneous distribution and finally the area percentage of the carbides. Since the secondary carbides are precipitated from the solid phase, a fine adjustment of the holding time matched to the respective hardening temperature and the subsequent tempering treatment is necessary.
  • the temperature range between 530° C. and 560° C. has turned out to be particularly advantageous for a tempering treatment in the case of the alloy layer according to the invention.
  • the temperature of 560 °C is exceeded, the level of hardness is reduced too much. If the temperature falls below 530 °C, the toughness is significantly reduced. In addition, this leads to an increased proportion of retained austenite, which cannot be completely eliminated even after a three-stage tempering treatment. Therefore, the upper limit for the tempering treatment is 560°C and the lower limit is 530°C.
  • Hardening and tempering treatments according to the invention are shown in FIG.
  • the steel material and/or the tool made from it is hardened at a temperature of 1180° C. for a maximum of 2 minutes and then rapidly cooled to ⁇ 30° C. with X ⁇ 3 (FIG. 7).
  • X values are used to define cooling rates and describe the time required to cool a steel from 800 °C to 500 °C in hectoseconds.
  • the temperature falls below the 30 °C limit, since the retained austenite is broken down here.
  • a residual austenite can severely affect the mechanical characteristics. It can also lead to tool failure. This can be explained by a structural transformation during operation, which is accompanied by a change in volume and dimensions.
  • the steel is heated two or three times at 560 °C for 120 minutes each time tempered. After each tempering cycle, the steel material is preferably cooled to ⁇ 30 °C.
  • the proportion of retained austenite is significantly reduced after each hardening and tempering cycle consisting of heating, holding and cooling. Depending on the desired minimum retained austenite content, up to three tempering cycles can be provided, since with each additional tempering cycle a further portion of the retained austenite turns into the desired martensite.
  • the lowest possible proportion of retained austenite is so advantageous because it transforms under load and the corresponding part, e.g. a punch, can then tend to brittle fracture.
  • cooling to ⁇ 60° C., preferably ⁇ 30° C. must take place after each hardening cycle and advantageously after each tempering cycle.
  • the steel material and/or the tool made from it is hardened at 1160° C. for a maximum of 3 minutes. It is then cooled to ⁇ 30 °C, with the values ⁇ 3 being observed. After cooling, the steel material is tempered two or three times at 560°C for 120°C each. After each tempering cycle, the steel material is preferably cooled to ⁇ 30 °C.
  • the steel and/or the tool made from it is hardened at a temperature of 1150° C. for a maximum of 3 minutes and then cooled to ⁇ 30° C.
  • the steel is then tempered two or three times at 530 °C for 120 minutes each. After each tempering cycle, the steel material is preferably cooled to ⁇ 30 °C.
  • the steel and/or the tool made from it is hardened at 1140° C. for a maximum of 3 minutes. It is then cooled to ⁇ 30 °C and tempered two or three times at 530 °C for 120 min each time. After each tempering cycle, the steel is preferably cooled to ⁇ 30 °C.
  • the steel material and/or the tool made from it is hardened at 1100° C. for a maximum of 20 minutes and then cooled to ⁇ 30° C. Subsequently, the steel material is subjected to a tempering treatment of two or three cycles of tempering at 530 °C for 120 min each. After each tempering cycle, the steel is preferably cooled to ⁇ 30 °C.
  • the tempering treatment according to the invention provides for tempering to be carried out immediately after hardening for at least 2 hours for each tempering cycle, with the furnace being set to the tempering temperature as a target value. Direct heating to this setpoint is carried out, this being done in a nitrogen atmosphere. In each cycle, the set temperature is heated for 2 hours and then the heating is switched off while the nitrogen atmosphere is present. The end temperature is below 30 °C and when it is reached the next cycle is started. Two or three cranking cycles are carried out. It is of course possible to carry out each tempering cycle differently with regard to the tempering temperature or heating and cooling rates, but it can certainly be advantageous to carry out each tempering cycle identically.
  • the resulting carbide content varies depending on the heat treatment and in particular on the hardening temperature used, as this dissolves elements that are required for the formation of the later secondary hardening carbides. However, it is advantageous if a certain proportion of secondary carbides is retained in the structure. This slows grain growth and thus prevents the grains from becoming coarse.
  • the sample hardened at 1070 °C contains 1.59% and 2.62% MeC carbides. Hardening at 1030 °C gives 1.51% MC and 3.43% MeC carbides. The lowest carbide content is determined in the sample hardened at 1150 °C and is accordingly 1.33% for MC and 2.45% for MeC carbides. The results show that the desired low carbide content can only be achieved in the narrow temperature window according to the invention. The carbide content is given as an area fraction.
  • the vanadium-rich MC carbides have a maximum size of 1.5 ⁇ m and the tungsten and molybdenum-rich MeC carbides have a maximum size of 2.1 ⁇ m.
  • the average diameter of the small MC carbides is 0.6 ⁇ m, while the average diameter of the larger MeC carbides is 0.9 ⁇ m (FIG. 9).
  • the size distribution of the MC and MeC carbides is shown in Figures 10 and 11. Carbide size is given as ECD (Equivalent Circle Diameter).
  • the carbide density in the matrix is a maximum of 27538 particles/mm 2 for MeC and a maximum of 39845 particles/mm 2 for MC carbides. Accordingly, it is advantageous if the average area proportion of the large MeC carbides is at most 1.9% and the small MC carbides is at most 1.3%.
  • FIG. 15 shows the results of the uniaxial compression test with modulus of elasticity (E), 0.05% compression limit at 0.05% deformation (Rp0.05), 0.01% compression limit at 0.1% deformation (Rp0.1 ) and compression limit at 0.2% deformation (Rp0.2). The samples are measured at room temperature with a test speed of 0.00025 1/s.
  • the specimens are of the LCF type with a shortened shank and have a diameter of 9 mm and an initial gauge length (Lo) of 12 mm (measured with an Instron 8854 servo-hydraulic testing machine, load cell 250 kN).
  • FIG. 16 shows various powder-metallurgically produced steels according to the invention, heat treatments and the resulting hardness in HRC, toughness in the form of impact bending work (SB) in Joule and compression limit Rp0.2 in MPa.
  • FIG. 17 shows various steel compositions not according to the invention, which were tempered with a heat treatment consisting of hardening and tempering and the resulting hardness, toughness and compression limit.
  • FIG. 18 shows an exemplary heat treatment consisting of hardening and 3 tempering cycles.
  • the hardening temperature of 1150°C two breakpoints are introduced, the first at 690°C, the second at 850°C. These ensure the heating of the steel material.
  • the alloy composition and heat treatment according to the invention it is possible to create a steel material with an excellent combination of hardness and toughness.
  • the material according to the invention has an exceptionally good toughness with a very high degree of hardness, so that it has been possible to reconcile two conflicting mechanical properties.
  • the advantage of the invention is that the advantage in terms of hardness and toughness, in particular at the specified hardening temperature of around 1150° C., can be achieved if the specified heat treatment cycle is observed. At the specified hardening temperature, a hardness of 65 HRC and toughness of 73 J can be achieved. Even small downward or upward deviations in the hardening temperature cannot be ruled out, but the significant hardness-toughness advantages over the prior art are no longer guaranteed to the same extent. At temperatures above 1180 °C there is a risk that the material will begin to melt, which is also undesirable.
  • the advantage of the invention is that the method according to the invention makes it possible to achieve very reliable mechanical properties that were previously incompatible with one another in this form.
  • very high hardness values of over 62 HRC are achieved with toughness of 70-90 J or more (measured as impact bending work at room temperature according to SEP 1314), which previously could not be reliably achieved with these materials in this form in this area. To do this, it is necessary to adhere to this narrow selection.
  • a high compressive strength, measured as the compression limit Rp0.2, of over 2700 MPa is achieved with a hardness level of 62-65 HRC.
  • Such a steel material is excellently suited as a carrier material for PVD coatings, in particular hard material coatings, and for the production of high-strength tools, in particular stamping and fine-blanking tools.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Powder Metallurgy (AREA)
  • Laminated Bodies (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Physical Vapour Deposition (AREA)

Abstract

L'invention concerne un acier à outils ainsi qu'un procédé de fabrication d'un acier à outils pour applications de travail à froid et/ou de coupe rapide, en particulier comme produit intermédiaire pour la fabrication d'outils de travail à froid et/ou de coupe rapide munis d'un revêtement PVD composé des éléments d'alliage suivants : (tous les chiffres indiqués sont des pourcentages en poids) : C = 0,55 à 0,75, Si = 0,70 à 1,00, Mn = 0,20 à 0,5015, Cr = 4,00 à 5,00, Mo = 1,80 à 3,50, V = 0,80 à 1,50, W = 1,80 à 3,00, Co = 3,00 à 5,0020, N = 0,02 à 0,10, ainsi qu'éventuellement un ou plusieurs éléments parmi Ni ≤ 1,525, Cu ≤ 1,0, Ti ≤ 1,5, Nb ≤ 1,5, Ta ≤ 1,5, Hf ≤ 1,530, Zr ≤ 1,5, Al ≤ 1,5, B ≤ 0,8, S ≤ 0,35, P ≤ 0,3535, le reste étant du fer et des impuretés inévitables issues de la fusion.
EP22702639.0A 2021-01-20 2022-01-20 Procédé de fabrication d'un acier à outils comme support pour revêtements pvd et acier à outils Pending EP4281591A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102021101105.1A DE102021101105A1 (de) 2021-01-20 2021-01-20 Verfahren zur Herstellung eines Werkzeugstahls als Träger für PVD-Beschichtungen und ein Werkzeugstahl
PCT/EP2022/051195 WO2022157227A1 (fr) 2021-01-20 2022-01-20 Procédé de fabrication d'un acier à outils comme support pour revêtements pvd et acier à outils

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EP4281591A1 true EP4281591A1 (fr) 2023-11-29

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EP (1) EP4281591A1 (fr)
CA (1) CA3207645A1 (fr)
DE (1) DE102021101105A1 (fr)
MX (1) MX2023008530A (fr)
WO (1) WO2022157227A1 (fr)

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0599910B1 (fr) * 1991-08-07 1997-03-05 Erasteel Kloster Aktiebolag Acier rapide produit selon des techniques de la metallurgie des poudres
JP4179024B2 (ja) 2003-04-09 2008-11-12 日立金属株式会社 高速度工具鋼及びその製造方法
AT412000B (de) * 2003-04-24 2004-08-26 Boehler Edelstahl Gmbh & Co Kg Kaltarbeitsstahl-gegenstand
JP2005206913A (ja) * 2004-01-26 2005-08-04 Daido Steel Co Ltd 合金工具鋼
BRPI0603856A (pt) 2006-08-28 2008-04-15 Villares Metals Sa ligas duras de composição enxuta
SE533988C2 (sv) 2008-10-16 2011-03-22 Uddeholms Ab Stålmaterial och förfarande för framställning därav
EP3050986B1 (fr) 2013-09-27 2019-07-31 Hitachi Metals, Ltd. Acier pour outil à vitesse élevée et procédé de production de ce dernier
JP6529234B2 (ja) * 2014-09-22 2019-06-12 山陽特殊製鋼株式会社 高い靭性と軟化抵抗性を有する高速度工具鋼
CN114086063A (zh) 2015-06-22 2022-02-25 日立金属株式会社 高速工具钢钢材的制造方法、高速工具钢制品的制造方法及高速工具钢制品

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WO2022157227A1 (fr) 2022-07-28
MX2023008530A (es) 2023-09-15
DE102021101105A1 (de) 2022-07-21
CA3207645A1 (fr) 2022-07-28

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