EP2535430B1 - Tool steel for high-performance thermoforming tools and production process for same - Google Patents

Tool steel for high-performance thermoforming tools and production process for same Download PDF

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EP2535430B1
EP2535430B1 EP11008259.1A EP11008259A EP2535430B1 EP 2535430 B1 EP2535430 B1 EP 2535430B1 EP 11008259 A EP11008259 A EP 11008259A EP 2535430 B1 EP2535430 B1 EP 2535430B1
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mass
steel
tool steel
hot
tool
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German (de)
French (fr)
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EP2535430A3 (en
EP2535430A2 (en
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Frank Dr. Hippenstiel
Peter Vetter
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Buderus Edelstahl GmbH
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Buderus Edelstahl GmbH
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Priority to PL11008259T priority patent/PL2535430T3/en
Priority to SI201131649T priority patent/SI2535430T1/en
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    • 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
    • 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
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
    • 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
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • 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
    • C21D2211/004—Dispersions; Precipitations

Definitions

  • the invention relates to a tool steel for more highly stressed hot forming tools and a method for its production.
  • Hot working steels are alloyed steels for applications in which the surface temperature of the tools is generally above 200 ° C.
  • the steel group is alloyed to set the required hot hardness and tempering resistance with correspondingly high levels of alloying elements, preferably chromium, molybdenum and vanadium (CrMoV steels).
  • alloying elements preferably chromium, molybdenum and vanadium (CrMoV steels).
  • Certain types of steel contain nickel as the preferred alloying element.
  • the carbon contents of the hot-working steels are between 0.30 and 0.55 mass%.
  • Hot work tool steels are used for all tools of non-cutting forming of metals and other materials at elevated temperatures.
  • Ur- and forming processes at elevated temperatures include die casting, forging and extrusion.
  • glass processing, rolling, hot extrusion and the so-called press hardening of high-strength body components are also to be mentioned.
  • the hot working steels used today are standardized in DIN EN ISO 4 957 and can be seen in Table 1 .
  • Table 1 secondary hardening chromium-molybdenum-vanadium steels are commonly used.
  • the nickel-chromium-molybdenum and nickel-chromium-molybdenum-vanadium steels as well as the tungsten-chromium-cobalt-vanadium steels form two further groups.
  • Table 2 provides an overview of the common hot-work steel grades according to the steel-iron list.
  • the secondary hardening chromium-molybdenum-vanadium steels are preferably used in the die-casting and extrusion of light metal as well as for heavy-duty forging press tools for the drop forging of steel. Due to the required tempering and wear resistance, a corresponding alloy is used, as a rule with chromium contents of 5.0% by mass and about 1.0% by mass of molybdenum and 0.5 to 1.0% by mass of vanadium. Since these elements tend to carbide, precipitates are formed in the compensation structure, which ensure the required properties, but reduce the toughness of the material.
  • One approach to increase the toughness of these materials has heretofore been to improve carbide formation in size and distribution in the steel matrix. For this purpose, corresponding changes in the manufacturing process were made.
  • the group of nickel-chromium-molybdenum and nickel-chromium-molybdenum-vanadium steels are preferably used for dynamically stressed, crack-sensitive forging tools for drop forging.
  • the reason is mainly the relatively good toughness, which is mainly due to the nickel content.
  • a tempering resistance in the temperature range between 350 and 600 ° C is missing, here the hardness drops significantly. Therefore, it is to be expected during use with a correspondingly higher wear, which causes higher tooling costs.
  • the tungsten-chromium-cobalt-vanadium steels are rarely used for standard applications due to the very high production costs. Therefore, the use is limited only to applications where a much higher thermal stability compared to the chromium-molybdenum-vanadium hot working steels is required. When using this steel group, it should be noted that in some cases the toughness behavior is lower than with the chromium-molybdenum-vanadium hot-work steels.
  • EP 1 887 096 A1 Also, a hot work tool steel is described wherein an alloy composition has been developed which substantially provides for the reduction of chromium and the other carbide forming elements (such as molybdenum, tungsten or vanadium) are alloyed according to the application requirements according to wear requirements.
  • chromium and the other carbide forming elements such as molybdenum, tungsten or vanadium
  • the carbon content is adjusted in conjunction with the manganese content, the nickel content, the chromium content, the molybdenum content, with an additional relationship between boron, aluminum, titanium, cykon and nitrogen.
  • a hot-work steel wherein the hot-working steel is to be used for press forging and contains carbon in addition to relatively high levels of silicon and manganese and also tungsten and molybdenum, as well as banadium and niobium.
  • the chemical composition is intended to ensure that the number of carbides remaining at a tempering temperature higher than that of conventional steels is reduced in order to prevent crystallization of the carbides and to ensure high temperature resistance. For grain refinement niobium is added.
  • FIG. 4 shows the development task with regard to tempering resistance, which is regarded as a measure of the heat resistance.
  • the required resource efficiency essentially relates to the alloying costs.
  • the indispensable material properties should be set with as few noble alloying elements as possible.
  • the manufacturing process is to be coordinated so that the material by a high metallurgical purity, Seigerungsarmut and the ability to later surface refinement -by z. As welding and / or thermal coating -austician.
  • the tool steel according to the invention for higher-strain forming tools has the following composition: Carbon: 0.28 to 0.40 mass%, Silicon: 0.03 to 0.50 mass%, Manganese: 0.03 to 0.70 mass%, Chrome: 2.00 to 3.5 mass%, Nickel: 0.30 to 1.00 mass%, Molybdenum: 0.60 to 1.60 mass%, vanadium: 0.15 to 0.35 mass%, Tungsten: 0.001 to 1.00 mass%, Niobium: 0.01 to 0.10 mass% as well a residue of iron and common impurities, the steel having a fine-grained tough structure, the composition satisfying the following condition: 9.5 ⁇ % C ⁇ 10 + % V ⁇ 5 + % Not a word ⁇ 3 + % W ⁇ 2 + % CR + % Nb ⁇ 3 ⁇ 16
  • niobium and / or titanium can be added.
  • the proposed alloy composition results in an excellent combination of high heat resistance and toughness in the tempered state.
  • With the intended carbon content of 0.28 to 0.40 mass% it is possible to achieve tempering strengths in the strength range of 1400 to 1600 MPa, which is usual for chromium-molybdenum-vanadium hot-work steels.
  • the other alloying elements were chosen to ensure very good hot strength.
  • To improve the toughness compared with the known hot-work steels the chromium content and also the vanadium content were markedly lowered. As a result, the number of carbides in the charge structure has been somewhat reduced.
  • the toughness potential of the invention-appropriate Composition can be increased.
  • the marginal reduction in wear resistance was compensated for by the targeted addition of niobium.
  • niobium has the advantage that during the quenching or heat treatment necessary for dissolving possible grain boundary carbides, possible grain growth is prevented. Therefore, correspondingly higher Austenitizing temperatures can be used, as is the case with comparable steels.
  • the hot-working steel according to the invention is clearly superior to the known hot-work steels with the same strength situation.
  • ISO-V specimens yield about 20 percent higher impact energy than conventional CrMoV and NiCrMoV hot work steels.
  • the very good material properties could be proven in laboratory tests, which are to determine the wear of hot working tools under operating conditions, by unusually high lifetime statistics.
  • the inventive method for producing a tool steel provides that the crude steel is produced in an electric arc furnace or LD converter with subsequent secondary metallurgical treatment of the melt in the ladle furnace and / or degassing, wherein as a deoxidation Si, Al, carbon and / or Diffusiondeoxididation is selected, wherein after the secondary metallurgical treatment of the tool steel in the strand or block casting process to a slab (or billets), a billet or ingot is poured, wherein the solidification cross section is matched to the later dimension of the tool steel block and the molded Tool steel is subjected to a homogenization treatment at about 1250 to 1300 ° C for a period of at least 24 hours.
  • the crude steel is produced in an electric arc furnace or LD converter with subsequent secondary metallurgical treatment of the melt in the ladle furnace and / or degassing.
  • deoxidation process either a Si and / or Al and a diffusion or carbon deoxidation can be selected.
  • the use of secondary metallurgical measures for the formation of inclusions such.
  • introduction of calcium or the use of premelted top slags can be used to adjust the required level of purity.
  • the casting of the steel in the strand or block casting process to a slab (or billet) or billet or an ingot, the solidification cross section to be used is matched to the later dimension of the tool steel block and the selected hot forming process.
  • homogenizing treatment or diffusion annealing takes place at about 1250 to 1300 ° C. The duration depends on the size of the ingot, but is at least about 24 hours. Diffusion annealing is used to homogenize the chemical composition and minimize possible crystal segregation.
  • the subsequent hot forming takes place preferably by forging at temperatures of about 1200 to 850 ° C and with at least three times the degree of deformation.
  • the formed workpiece is austenitized after the subsequent cooling of the material at about 850 to 900 ° C and then about 50 to 100 hours at a temperature in the range of 680 to 710 ° C isothermal purpose Conversion held in the perlite. Subsequently, a fine structure treatment for setting a fine-grained structure with uniform carbide distribution.
  • the blanks for the hot working tools to be produced are machined out of the forging, if necessary machined according to the respective production drawings and then tempered.
  • the workpieces are preferably cooled to room temperature in air and then tempered to the desired endurance according to the tempering diagram.
  • at least two tempering takes place on a service hardness, usually a maximum of 4 6 HRc. After tempering, slow cooling to room temperature occurs to set a low stress material condition.
  • the new CrMoNiV steel is particularly suitable as hot-work steel due to its fine-grained, tough microstructure and the significantly higher thermal conductivity compared to the known CrMoV steels for all types of metal forming tools such as forging dies or hot sheet metal forming, but also for tools of light metal processing in the heated state such as B. die casting.
  • Figure 3 compares the main results of the material investigations of the steel according to the invention with the known hot working steels. It can be seen from the illustration that the steel according to the invention by no means resists the known CrMoV-alloyed hot-work steels, but in particular has better strength and toughness values in the temperature range between 500 and 600 ° C.
  • the higher toughness potential is particularly useful in the drop forging industry to avoid early die bridge, which makes it difficult to calculate forging processes or tool life in the case of fracture-prone, deep die engraving or even uneven mold temperatures. Calculable forging processes are, however, necessary for a reliable cost calculation as well as for an economical production of hot formed parts.
  • the steel according to the invention is characterized by a significantly better thermal conductivity, in particular compared to the known CrMoV steels, which is likewise reflected positively in the service properties.

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  • Crystallography & Structural Chemistry (AREA)
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Description

Die Erfindung betrifft einen Werkzeugstahl für höher beanspruchte Warmumformwerkzeuge sowie ein Verfahren zu dessen Herstellung.The invention relates to a tool steel for more highly stressed hot forming tools and a method for its production.

Warmarbeitsstähle sind legierte Stähle für Anwendungszwecke, bei denen die Oberflächentemperatur der Werkzeuge im Allgemeinen über 200 °C liegt. Die Stahlgruppe ist zur Einstellung der erforderlichen Warmhärte und Anlassbeständigkeit mit entsprechend hohen Gehalten an Legierungselementen, vorzugsweise Chrom, Molybdän und Vanadium (CrMoV-Stähle) legiert. Bestimmte Stahlsorten enthalten als bevorzugtes Legierungselement Nickel. In der Regel liegen die Kohlenstoffgehalte der Warmarbeitsstähle zwischen 0,30 bis 0,55 Massen-%.Hot working steels are alloyed steels for applications in which the surface temperature of the tools is generally above 200 ° C. The steel group is alloyed to set the required hot hardness and tempering resistance with correspondingly high levels of alloying elements, preferably chromium, molybdenum and vanadium (CrMoV steels). Certain types of steel contain nickel as the preferred alloying element. As a rule, the carbon contents of the hot-working steels are between 0.30 and 0.55 mass%.

Warmarbeitsstähle werden für sämtliche Werkzeuge der spanlosen Umformung von Metallen und anderen Werkstoffen bei erhöhten Temperaturen verwendet. Ur- und Umformverfahren bei erhöhten Temperaturen sind u.a. das Druckgießen, das Schmieden und das Strangpressen. Weiter sind die Glasverarbeitung, das Walzen, das Warmfließpressen sowie das so genannte Presshärten von hochfesten Karosseriebauteilen zu nennen.Hot work tool steels are used for all tools of non-cutting forming of metals and other materials at elevated temperatures. Ur- and forming processes at elevated temperatures include die casting, forging and extrusion. Also to be mentioned are glass processing, rolling, hot extrusion and the so-called press hardening of high-strength body components.

Die heute zur Anwendung kommenden Warmarbeitsstähle sind in der DIN EN ISO 4 957 genormt und in der Tafel 1 ersichtlich. Derzeit werden üblicherweise die sekundärhärtenden Chrom-Molybdän-Vanadiumstähle am häufigsten genutzt. Neben dieser Gruppe bilden die Nickel-Chrom-Molybdän- und die Nickel-Chrom-Molybdän-Vanadium-Stähle sowie die Wolfram-Chrom-Cobalt-Vanadium-Stähle zwei weitere Gruppen. Tafel 2 bietet eine Übersicht der gebräuchlichen Warmarbeitsstähle gemäß Stahl-Eisen-Liste.The hot working steels used today are standardized in DIN EN ISO 4 957 and can be seen in Table 1 . Currently, secondary hardening chromium-molybdenum-vanadium steels are commonly used. In addition to this group, the nickel-chromium-molybdenum and nickel-chromium-molybdenum-vanadium steels as well as the tungsten-chromium-cobalt-vanadium steels form two further groups. Table 2 provides an overview of the common hot-work steel grades according to the steel-iron list.

Die sekundärhärtenden Chrom-Molybdän-Vanadiumstähle finden vorzugsweise Verwendung beim Druckgießen und Strangpressen von Leichtmetall sowie für hoch beanspruchte Schmiedepressenwerkzeuge für das Gesenkschmieden von Stahl. Aufgrund der geforderten Anlass- und Verschleißbeständigkeit erfolgt ein entsprechender Legierungseinsatz, in der Regel mit Chromgehalten von 5,0 Massen-% sowie etwa 1,0 Massen-% Molybdän sowie 0,5 bis 1,0 Massen-% Vanadin. Da diese Elemente zur Carbidbildung neigen, werden Ausscheidungen im Vergütungsgefüge gebildet, die die geforderten Eigenschaften gewährleisten, aber die Zähigkeit des Werkstoffes herabsetzen. Ein Ansatz die Zähigkeit dieser Werkstoffe zu erhöhen, war bislang die Verbesserung der Carbidausbildung hinsichtlich Größe und Verteilung in der Stahlmatrix. Hierzu wurden entsprechende Änderungen im Herstellungsprozess vorgenommen. Dies ist zum Beispiel das Herstellen solcher Güten mittels sondermetallurgischen Verfahren wie (Druck-)Elektro-Schlacke-Umschmelzen oder Vakuum-Induktions-Schmelzen bzw. Umschmelzen im Vakuum-Elektrolichtbogenofen, dem Homogenisieren bzw. Diffusionsglühen von Rohblöcken oder von geeigneten Zwischenabmessungen während der Warmumformung des Stahles, spezielle Schmiedetechnologien, die in der Lage sein sollen, einen quasi-isotropen Werkstoffzustand einzustellen, sowie besondere Feinstruktur-Glühverfahren. Mit diesen Maßnahmen, in der Regel sogar Kombinationen von einzelnen Maßnahmen, ist es gelungen, die Lebensdauer der Chrom-Molybdän-Vanadium Warmarbeitsstähle zu verbessern. Dies wird im Wesentlichen auf den Zähigkeitszuwachs in Folge einer homogeneren Verteilung der Carbide im Vergütungsgefüge zurückgeführt.The secondary hardening chromium-molybdenum-vanadium steels are preferably used in the die-casting and extrusion of light metal as well as for heavy-duty forging press tools for the drop forging of steel. Due to the required tempering and wear resistance, a corresponding alloy is used, as a rule with chromium contents of 5.0% by mass and about 1.0% by mass of molybdenum and 0.5 to 1.0% by mass of vanadium. Since these elements tend to carbide, precipitates are formed in the compensation structure, which ensure the required properties, but reduce the toughness of the material. One approach to increase the toughness of these materials has heretofore been to improve carbide formation in size and distribution in the steel matrix. For this purpose, corresponding changes in the manufacturing process were made. This is, for example, the production of such grades by means of special metallurgical processes such as (pressure) electro-slag remelting or vacuum induction melting or remelting in a vacuum electric arc furnace, the homogenization or diffusion annealing of ingots or of suitable intermediate dimensions during hot working of the Steel, special forging technologies that are capable be set to set a quasi-isotropic material state, and special fine-structure annealing. With these measures, usually even combinations of individual measures, it has been possible to improve the service life of the chrome-molybdenum-vanadium hot-work tool steels. This is essentially attributed to the increase in toughness as a result of a more homogeneous distribution of the carbides in the charge structure.

Die Gruppe der Nickel-Chrom-Molybdän- und die Nickel-Chrom-Molybdän-Vanadium-Stähle finden in der Regel für dynamisch beanspruchte, rissempfindliche Schmiedewerkzeuge für das Gesenkschmieden vorzugsweise Verwendung. Der Grund liegt vor allem in der relativ guten Zähigkeit, die im Wesentlichen auf den Nickelgehalt zurückzuführen ist. Allerdings fehlt bei dieser Stahlgruppe eine Anlassbeständigkeit im Temperaturbereich zwischen 350 bis 600 °C, hier fällt die Härte signifikant ab. Daher ist beim Gebrauch mit einem entsprechend höheren Verschleiß zu rechnen, der höhere Werkzeugkosten verursacht.The group of nickel-chromium-molybdenum and nickel-chromium-molybdenum-vanadium steels are preferably used for dynamically stressed, crack-sensitive forging tools for drop forging. The reason is mainly the relatively good toughness, which is mainly due to the nickel content. However, in this steel group a tempering resistance in the temperature range between 350 and 600 ° C is missing, here the hardness drops significantly. Therefore, it is to be expected during use with a correspondingly higher wear, which causes higher tooling costs.

Die Wolfram-Chrom-Cobalt-Vanadium-Stähle werden aufgrund der sehr hohen Herstellungskosten nur selten für Standardanwendungen eingesetzt. Daher ist die Verwendung nur auf Anwendungen begrenzt, bei denen eine deutlich höhere Warmfestigkeit im Vergleich zu den Chrom-Molybdän-Vanadium Warmarbeitsstählen erforderlich ist. Beim Einsatz dieser Stahlgruppe ist zu beachten, dass zum Teil das Zähigkeitsverhalten geringer ist als bei den Chrom-Molybdän-Vanadium Warmarbeitsstählen.The tungsten-chromium-cobalt-vanadium steels are rarely used for standard applications due to the very high production costs. Therefore, the use is limited only to applications where a much higher thermal stability compared to the chromium-molybdenum-vanadium hot working steels is required. When using this steel group, it should be noted that in some cases the toughness behavior is lower than with the chromium-molybdenum-vanadium hot-work steels.

Zusammenfassend kann festgehalten werden, dass es abgestimmt auf die jeweiligen Anforderungen im Bereich der Urformung sowie der spanlosen Umformung Warmarbeitsstähle gibt. Allerdings besteht zum Teil eine ungeklärte Fragestellung in der Werkstoffentwicklung, nämlich in wie weit sich die Warmfestigkeit und die Zähigkeit bei neuen Stahlgüten erhöhen lassen. Hierzu gab es in der jüngsten Zeit einige Bemühungen, so wird in DE 195 31 260 C5 ein Verfahren zur Herstellung eines Warmarbeitsstahles beschrieben. Auf Basis eines Nickel-Chrom-Molybdän-Vanadium Stahles ist es gelungen, eine Stahllegierung einschließlich eines Herstellungsprozesses zu entwickeln, die sowohl eine höhere Festigkeit als auch eine höhere Zähigkeit bei vergleichbarer Verschleißbeständigkeit gegenüber den herkömmlichen Warmarbeitsstählen aufweist.In summary, it can be stated that there are hot-work tool steels tailored to the respective requirements in the field of primary forming as well as non-cutting forming. However, there is sometimes an unresolved issue in materials development, namely how far the hot strength and toughness of new steel grades can be increased. There have been some efforts in recent times DE 195 31 260 C5 a method for producing a hot work tooling described. Based on a nickel-chromium-molybdenum-vanadium steel, it has been possible to develop a steel alloy, including a manufacturing process, which has both a higher strength and a higher toughness with comparable wear resistance compared to conventional hot-work steels.

In EP 1 887 096 A1 wird ebenfalls ein Warmarbeitsstahl beschrieben, wobei eine Legierungszusammensetzung entwickelt wurde, die im Wesentlichen die Reduzierung von Chrom vorsieht und die anderen Carbid bildenden Elemente (wie Molybdän, Wolfram oder Vanadium) je nach Anwendungsgebiet entsprechend den Verschleißanforderungen zu legiert werden.In EP 1 887 096 A1 Also, a hot work tool steel is described wherein an alloy composition has been developed which substantially provides for the reduction of chromium and the other carbide forming elements (such as molybdenum, tungsten or vanadium) are alloyed according to the application requirements according to wear requirements.

Aus der US 2005/0115644 A1 ist ein Stahl für Einspritzformen für Plastikmaterial oder für die Produktion von Bauteilen für die Bearbeitung von Metallen bekannt. Hierbei wird der Kohlenstoffgehalt in Verbindung mit dem Mangangehalt, dem Nickelgehalt, dem Chromgehalt, dem Molybdängehalt eingestellt, wobei zusätzlich ein Zusammenhang zwischen Bor, Aluminium, Titan, Zykon und Stickstoff besteht.From the US 2005/0115644 A1 is a steel known for injection molds for plastic material or for the production of components for the machining of metals. In this case, the carbon content is adjusted in conjunction with the manganese content, the nickel content, the chromium content, the molybdenum content, with an additional relationship between boron, aluminum, titanium, cykon and nitrogen.

Aus der JP 05044655 ist ein Warmarbeitsstahl bekannt, bei dem die Gefahr von großen Rissen dadurch verhindert wird, dass die Zähigkeit auf das Niveau eines gehärteten und angelassenen Stahls angehoben wird, während die geleistete Härte und Hochtemperaturfestigkeit erhalten bleibt, wobei der Stahl als Legierungselemente Mangan, Nickel, Chrom, Banadium, Niob und Molybdän oder Wolfram enthält.From the JP 05044655 A hot working steel is known in which the risk of large cracks is prevented by the toughness is raised to the level of a hardened and tempered steel, while maintaining the hardness and high temperature resistance, the steel being used as alloying elements manganese, nickel, chromium, Banadium, niobium and molybdenum or tungsten contains.

Aus der JP 11368181 ist ebenfalls ein Warmarbeitsstahl bekannt, der sehr gute Schweißeigenschaften besitzen soll und neben 0,1 - 0,3 % Kohlenstoff, Silizium, Mangan, Chrom, Banadium und Molybdän und/oder Wolfram, während noch eine weitere Reihe Nebenmetalle eingeführt wird.From the JP 11368181 A hot working steel is also known which is said to have very good welding properties and besides 0.1-0.3% carbon, silicon, manganese, chromium, banadium and molybdenum and / or tungsten, while still another series of minor metals is introduced.

Aus der JP 01270917 ist ebenfalls ein Warmarbeitsstahl bekannt, wobei der Warmarbeitsstahl zum Pressschmieden verwendet werden soll und neben Kohlenstoff relativ hohe Gehalte an Silizium und Mangan sowie ebenfalls Wolfram und Molybdän, sowie Banadium und Niob enthält. Durch die chemische Zusammensetzung soll sichergestellt werden, dass die Zahl der zurückbleibenden Karbide bei einer Anlasstemperatur die über der konventioneller Stähle liegt, reduziert wird, um die Auskristallisierung der Karbide zu unterbinden und die hochtemperaturfestigkeit zu sichern. Zur Kornfeinerung wird Niob zugegeben.From the JP 01270917 is also known a hot-work steel, wherein the hot-working steel is to be used for press forging and contains carbon in addition to relatively high levels of silicon and manganese and also tungsten and molybdenum, as well as banadium and niobium. The chemical composition is intended to ensure that the number of carbides remaining at a tempering temperature higher than that of conventional steels is reduced in order to prevent crystallization of the carbides and to ensure high temperature resistance. For grain refinement niobium is added.

Die Aufgaben der vorliegenden Erfindung besteht darin, einen Stahl für höher beanspruchte Warmumformwerkzeuge zu entwickeln, der folgende, wesentliche Gebrauchseigenschaften besitzt:

  • ▪ feinkörniger, zäher Gefügezustand
  • ▪ gute Zerspanbarkeit bei hoher Verschleißbeständigkeit
  • ▪ ausreichende Warmfestigkeit bei sehr guten Zähigkeitseigenschaften
  • ▪ hohe Wärmeleitfähigkeit
  • ▪ ressourceneffizienter Einsatz von Legierungselementen
The objects of the present invention is to develop a steel for higher stressed hot forming tools which has the following essential performance characteristics:
  • ▪ fine-grained, tough microstructure
  • ▪ good machinability with high wear resistance
  • ▪ sufficient heat resistance with very good toughness properties
  • ▪ high thermal conductivity
  • ▪ Resource-efficient use of alloying elements

Im Vergleich zu den Nickel-Chrom-Molybdän-Vanadium-Stählen sollte die Anlassbeständigkeit deutlich höher sein, so dass ein möglichst breites Anwendungsspektrum im Werkzeugbau abgedeckt wird. In Bild 4 ist die Entwicklungsaufgabe hinsichtlich der Anlassbeständigkeit, die als Maß für die Warmfestigkeit gilt, dargestellt.In comparison to the nickel-chromium-molybdenum-vanadium steels, the tempering resistance should be significantly higher, so that the widest possible range of applications is covered in toolmaking. Figure 4 shows the development task with regard to tempering resistance, which is regarded as a measure of the heat resistance.

Die geforderte Ressourceneffizienz bezieht sich im Wesentlichen auf die Legierungskosten. Die unabdingbaren Werkstoffeigenschaften sollen mit möglichst wenig edlen Legierungselementen eingestellt werden. Des Weiteren ist der Herstellungsprozess so abzustimmen, dass sich der Werkstoff durch eine hohe metallurgische Reinheit, Seigerungsarmut sowie die Fähigkeit zu einer späteren Oberflächenveredelung -durch z. B. Schweißen und / oder thermisches Beschichten -auszeichnet.The required resource efficiency essentially relates to the alloying costs. The indispensable material properties should be set with as few noble alloying elements as possible. Furthermore, the manufacturing process is to be coordinated so that the material by a high metallurgical purity, Seigerungsarmut and the ability to later surface refinement -by z. As welding and / or thermal coating -auszeichnet.

Die Aufgabe wird mit einem Werkzeugstahl für höher beanspruchte Warmumformwerkzeuge mit den Merkmalen des Anspruch 1 gelöst.The object is achieved with a tool steel for more highly stressed hot forming tools having the features of claim 1.

Es ist eine weitere Aufgabe ein Verfahren zur Herstellung des Werkzeugstahles zu schaffen.It is another object to provide a method of making the tool steel.

Die Aufgabe wird mit einem Verfahren mit den Merkmalen des Anspruchs 2 gelöst.The object is achieved by a method having the features of claim 2.

Weiterbildungen sind in den hiervon abhängigen Unteransprüchen gekennzeichnet.Further developments are characterized in the dependent claims.

Der erfindungsgemäße Werkzeugstahl für höher beanspruchte Umformwerkzeuge besitzt die folgende Zusammensetzung: Kohlenstoff: 0,28 bis 0,40 Massen-%, Silizium: 0,03 bis 0,50 Massen-%, Mangan: 0,03 bis 0,70 Massen-%, Chrom: 2,00 bis 3,5 Massen-%, Nickel: 0,30 bis 1,00 Massen-%, Molybdän: 0,60 bis 1,60 Massen-%, Vanadium: 0,15 bis 0,35 Massen-%, Wolfram: 0,001 bis 1,00 Massen-%, Niob: 0,01 bis 0,10 Massen-% sowie einem Rest aus Eisen und üblichen Verunreinigungen, wobei der Stahl ein feinkörniges zähes Gefüge aufweist, wobei die Zusammensetzung folgende Bedingung einhält: 9,5 ≤ % C × 10 + % V × 5 + % Mo × 3 + % W × 2 + % CR + % Nb × 3 ≤ 16

Figure imgb0001
The tool steel according to the invention for higher-strain forming tools has the following composition: Carbon: 0.28 to 0.40 mass%, Silicon: 0.03 to 0.50 mass%, Manganese: 0.03 to 0.70 mass%, Chrome: 2.00 to 3.5 mass%, Nickel: 0.30 to 1.00 mass%, Molybdenum: 0.60 to 1.60 mass%, vanadium: 0.15 to 0.35 mass%, Tungsten: 0.001 to 1.00 mass%, Niobium: 0.01 to 0.10 mass% as well a residue of iron and common impurities, the steel having a fine-grained tough structure, the composition satisfying the following condition: 9.5 ≤ % C × 10 + % V × 5 + % Not a word × 3 + % W × 2 + % CR + % Nb × 3 ≤ 16
Figure imgb0001

Im Gegensatz zu den üblichen Stählen für Warmumformwerkzeuge (auch Warmarbeitsstähle genannt) werden bei der patentgemäßen Erfindung die Gebrauchseigenschaften Warmfestigkeit und Zähigkeit derart kombiniert, dass ein sehr wirtschaftlicher Einsatz dieses Stahles bei Temperaturen zwischen 200 bis 600 °C in Frage kommt. Im Vergleich zu konventionellen, bekannten Warmarbeitsstählen werden geringere Gehalte an Legierungselementen benötigt.In contrast to the usual steels for hot forming tools (also called hot work tool steels) in the patent invention, the use properties of heat resistance and toughness combined in such a way that a very economical use of this steel at temperatures between 200 to 600 ° C in question. Lower levels of alloying elements are required compared to conventional, known hot-work steels.

Alternativ zu dem Gehalt an Vanadium kann ein Gehalt von 0,15 bis 0,35% an Niob und / oder Titan zulegiert werden.As an alternative to the content of vanadium, a content of 0.15 to 0.35% of niobium and / or titanium can be added.

Die vorgeschlagene Legierungszusammensetzung führt zu einer hervorragenden Kombination von hoher Warmfestigkeit und Zähigkeit im vergüteten Zustand. Mit dem vorgesehenen Kohlenstoffgehalt von 0,28 bis 0,40 Massen-% lassen sich Vergütungsfestigkeiten in dem für Chrom-Molybdän-Vanadium Warmarbeitsstählen üblichen Festigkeitsbereich von 1400 bis 1600 MPa erzielen. Die anderen Legierungselemente wurden so gewählt, dass eine sehr gute Warmfestigkeit sichergestellt wird. Zur Verbesserung der Zähigkeit gegenüber den bekannten Warmarbeitsstählen wurde der Chrom- und auch der Vanadiumgehalt deutlich abgesenkt. Dies führt dazu, dass die Anzahl an Carbiden im Vergütungsgefüge etwas reduziert wurde. Damit kann das Zähigkeitspotenzial der erfindungsgerechten Zusammensetzung erhöht werden. Die marginale Absenkung der Verschleißbeständigkeit wurde durch die gezielte Zugabe von Niob ausgeglichen. Niob hat zusätzlich den Vorteil, dass während der zur Auflösung von möglichen Korngrenzencarbiden erforderlichen Austenitisierung beim Vergüten bzw. bei der Wärmebehandlung, ein mögliches Kornwachstum verhindert wird. Daher können entsprechend höhere Austenitisierungs-temperaturen genutzt werden, als dies bei vergleichbaren Stählen den Fall ist. Zur Einstellung der erforderlichen Anlasstemperaturen von über 550 °C, die alleine schon zum Abbau der wärmebehandlungsbedingten Eigenspannungen zweckmäßig sind, sind Kohlenstoffgehalte von mindestens 0,28 Massen-%, Chromgehalte von mindestens 2,00 Massen-%, Molybdängehalte von mindestens 0,60 Massen-% und Vanadiumgehalte von mindestens 0,15 Massen-% notwendig. Werden diese Elemente, die die Warmfestigkeit von Stählen steigern, in ihren Mindestgehalten zu legiert, so kann eine Warmstreckgrenze von über 800 MPa bei Temperaturen bis 550 °C erwartet werden.The proposed alloy composition results in an excellent combination of high heat resistance and toughness in the tempered state. With the intended carbon content of 0.28 to 0.40 mass%, it is possible to achieve tempering strengths in the strength range of 1400 to 1600 MPa, which is usual for chromium-molybdenum-vanadium hot-work steels. The other alloying elements were chosen to ensure very good hot strength. To improve the toughness compared with the known hot-work steels, the chromium content and also the vanadium content were markedly lowered. As a result, the number of carbides in the charge structure has been somewhat reduced. Thus, the toughness potential of the invention-appropriate Composition can be increased. The marginal reduction in wear resistance was compensated for by the targeted addition of niobium. In addition, niobium has the advantage that during the quenching or heat treatment necessary for dissolving possible grain boundary carbides, possible grain growth is prevented. Therefore, correspondingly higher Austenitizing temperatures can be used, as is the case with comparable steels. To set the required tempering temperatures of over 550 ° C, which alone are expedient to reduce the heat treatment-related residual stresses, carbon contents of at least 0.28 mass%, chromium contents of at least 2.00 mass%, molybdenum contents of at least 0.60 mass -% and vanadium contents of at least 0.15 mass% necessary. If these elements, which increase the heat resistance of steels, are alloyed in their minimum contents, then a hot yield strength of more than 800 MPa at temperatures up to 550 ° C can be expected.

Bei den Zähigkeitseigenschaften ist der erfindungsgemäße Warmarbeitsstahl den bekannten Warmarbeitsstählen bei gleicher Festigkeitslage deutlich überlegen. Im Kerbschlagbiegeversuch lassen sich an ISO-V-Proben etwa 20 Prozent höhere Schlagenergiewerte als bei den herkömmlichen CrMoV- und NiCrMoV-Warmarbeitsstählen ermitteln. Die sehr guten Werkstoffeigenschaften konnten in Labortests, die den Verschleiß von Warmarbeitswerkzeugen unter Betriebsbedingungen ermitteln sollen, durch ungewöhnlich hohe Lebensdauerkennzahlen belegt werden.In the case of the toughness properties, the hot-working steel according to the invention is clearly superior to the known hot-work steels with the same strength situation. In the notched-bar impact test, ISO-V specimens yield about 20 percent higher impact energy than conventional CrMoV and NiCrMoV hot work steels. The very good material properties could be proven in laboratory tests, which are to determine the wear of hot working tools under operating conditions, by unusually high lifetime statistics.

Das erfindungsgemäße Verfahren zum Herstellen eines Werkzeugstahles sieht vor, dass die Rohstahlerzeugung in einem Elektrolichtbogenofen oder LD-Konverter mit anschließender sekundärmetallurgischer Behandlung der Schmelze im Pfannenofen und/oder Entgasungsanlagen erfolgt, wobei als Desoxidationsprozess eine Si-, Al-, Kohlenstoff- und/oder Diffusionsdesoxididation gewählt wird, wobei nach der sekundärmetallurgischen Behandlung der Werkzeugstahl im Strang- oder Blockgussverfahren zu einer Bramme (oder Knüppel), einem Vorblock oder einem Rohblock vergossen wird, wobei der Erstarrungsquerschnitt auf die spätere Abmessung des Werkzeugstahlblockes abgestimmt ist und der vergossene
Werkzeugstahl einer Homogenisierungsbehandlung bei etwa 1250 bis 1300 °C für eine Zeitdauer von wenigstens 24 Stunden unterzogen wird.The inventive method for producing a tool steel provides that the crude steel is produced in an electric arc furnace or LD converter with subsequent secondary metallurgical treatment of the melt in the ladle furnace and / or degassing, wherein as a deoxidation Si, Al, carbon and / or Diffusiondeoxididation is selected, wherein after the secondary metallurgical treatment of the tool steel in the strand or block casting process to a slab (or billets), a billet or ingot is poured, wherein the solidification cross section is matched to the later dimension of the tool steel block and the molded
Tool steel is subjected to a homogenization treatment at about 1250 to 1300 ° C for a period of at least 24 hours.

Die Rohstahlerzeugung erfolgt in einem Elektrolichtbogenofen oder LD-Konverter mit anschließender sekundärmetallurgischen Behandlung der Schmelze im Pfannenofen und / oder Entgasungsanlagen. Als Desoxidationsprozess kann entweder eine Si- und / oder AI- sowie eine Diffusions- oder Kohlenstoffdesoxidation gewählt werden. Die Nutzung von sekundärmetallurgischen Maßnahmen zur Einformung von Einschlüssen wie z. B. das Einspulen von Calcium oder die Verwendung von vorgeschmolzenen Top-Schlacken kann zur Einstellung des geforderten Reinheitsgradniveaus genutzt werden. Anschließend erfolgt das Vergießen des Stahles im Strang- oder Blockgussverfahren zu einer Bramme (oder Knüppel) bzw. Vorblock oder einem Rohblock, der zu verwendende Erstarrungsquerschnitt ist auf die spätere Abmessung der Werkzeugstahlblockes und den gewählten Warmumformprozess abzustimmen.The crude steel is produced in an electric arc furnace or LD converter with subsequent secondary metallurgical treatment of the melt in the ladle furnace and / or degassing. As deoxidation process either a Si and / or Al and a diffusion or carbon deoxidation can be selected. The use of secondary metallurgical measures for the formation of inclusions such. As the introduction of calcium or the use of premelted top slags can be used to adjust the required level of purity. Subsequently, the casting of the steel in the strand or block casting process to a slab (or billet) or billet or an ingot, the solidification cross section to be used is matched to the later dimension of the tool steel block and the selected hot forming process.

Vor der Warmumformung des Vorblocks bzw. Rohblocks findet eine Homogenisierungsbehandlung bzw. ein Diffusionsglühen bei etwa 1250 bis 1300 °C statt. Die Dauer richtet sich nach der Größe des Gussblockes, beträgt aber mindestens etwa 24 Stunden. Das Diffusionsglühen dient der Homogenisierung der chemischen Zusammensetzung und minimiert mögliche Kristallseigerungen.Before hot-forming the billet or ingot, homogenizing treatment or diffusion annealing takes place at about 1250 to 1300 ° C. The duration depends on the size of the ingot, but is at least about 24 hours. Diffusion annealing is used to homogenize the chemical composition and minimize possible crystal segregation.

Die im Anschluss daran stattfindende Warmumformung findet vorzugsweise durch Schmieden bei Temperaturen von etwa 1200 bis 850 °C und mit einem mindestens dreifachen Verformungsgrad statt. Das umgeformte Werkstück wird nach der anschließenden Abkühlung des Werkstoffes bei ca. 850 bis 900 °C austenitisiert und dann etwa 50 bis 100 Stunden bei einer Temperatur im Bereich von 680 bis 710 °C isotherm zwecks
Umwandlung in der Perlitstufe gehalten. Anschließend erfolgt eine Feinstrukturbehandlung zur Einstellung eines feinkörnigen Gefüges bei gleichmäßiger Carbidverteilung.The subsequent hot forming takes place preferably by forging at temperatures of about 1200 to 850 ° C and with at least three times the degree of deformation. The formed workpiece is austenitized after the subsequent cooling of the material at about 850 to 900 ° C and then about 50 to 100 hours at a temperature in the range of 680 to 710 ° C isothermal purpose
Conversion held in the perlite. Subsequently, a fine structure treatment for setting a fine-grained structure with uniform carbide distribution.

Nach dieser Behandlung werden die Rohlinge für die herzustellenden Warmarbeitswerkzeuge mechanisch aus dem Schmiedestück herausgearbeitet, ggf. entsprechend den jeweiligen Fertigungszeichnungen bearbeitet und dann vergütet. Dabei werden die bei etwas 850 bis 950 °C austenitisierten Werkstücke in einem Medium, was Öl, Polymer oder Wasser sein kann, vergütet. Es können auch (vor-) bearbeitete Werkstücke in einem Blei- oder Salzbad oder alternativ beispielsweise mit einer Warmbadsimulation im Vakuum gehärtet werden. In jedem Fall werden die Werkstücke nach dem Abschrecken vorzugsweise an Luft auf Raumtemperatur abgekühlt und dann entsprechend dem Anlassdiagramm auf die gewünschte Einsatzfestigkeit angelassen. Üblicherweise erfolgt nach dem Vergüten ein mindestens zweimaliges Anlassen auf eine Gebrauchshärte, in der Regel maximal 4 6 HRc. Nach dem Anlassen erfolgt ein langsames Abkühlen auf Raumtemperatur, um einen spannungsarmen Werkstoffzustand einzustellen.After this treatment, the blanks for the hot working tools to be produced are machined out of the forging, if necessary machined according to the respective production drawings and then tempered. The austenitized at some 850 to 950 ° C workpieces in a medium, which may be oil, polymer or water, tempered. It is also possible to cure (pre) machined workpieces in a lead or salt bath or, alternatively, for example with a hot bath simulation in a vacuum. In any case, after quenching, the workpieces are preferably cooled to room temperature in air and then tempered to the desired endurance according to the tempering diagram. Usually, after tempering, at least two tempering takes place on a service hardness, usually a maximum of 4 6 HRc. After tempering, slow cooling to room temperature occurs to set a low stress material condition.

Der neue CrMoNiV-Stahl eignet sich besonders als Warmarbeitsstahl durch seinen feinkörnigen, zähen Gefügezustand und der im Vergleich zu den bekannten CrMoV-Stählen deutlich höheren Wärmeleitfähigkeit für alle Werkzeugarten der Metallumformung wie beispielsweise Schmiedegesenke oder aber Warmblechumformung, aber auch für Werkzeuge der Leichtmetallverarbeitung im erwärmten Zustand wie z. B. dem Druckgießen.The new CrMoNiV steel is particularly suitable as hot-work steel due to its fine-grained, tough microstructure and the significantly higher thermal conductivity compared to the known CrMoV steels for all types of metal forming tools such as forging dies or hot sheet metal forming, but also for tools of light metal processing in the heated state such as B. die casting.

Das Bild 3 stellt die wesentlichen Ergebnisse der Werkstoffuntersuchungen des erfindungsgemäßen Stahles den bekannten Warmarbeitsstählen gegenüber. Aus der Darstellung ist zu entnehmen, dass der erfindungsgemäße Stahl den bekannten CrMoV-legierten Warmarbeitsstählen keinesfalls nachsteht, sondern insbesondere im Temperaturbereich zwischen 500 und 600 °C bessere Festigkeits- und Zähigkeitswerte aufweist. Das höhere Zähigkeitspotenzial dient besonders in der Gesenkschmiedeindustrie der Vermeidung frühzeitiger Gesenkbrücke, die bei bruchgefährdeten, tiefen Gesenkgravuren, oder auch ungleichmäßigen Werkzeugtemperaturen die Kalkulierbarkeit von Schmiedeprozessen bzw. Werkzeugstandzeiten erschwert. Berechenbare Schmiedeprozesse sind aber für eine verlässliche Kostenkalkulation sowie für eine wirtschaftliche Produktion von Warmumformteilen notwendig. Ferner wird mit der Erhöhung des Zähigkeitspotenzials auch der Betriebssicherheit der Schmiedewerkzeuge Rechnung getragen. Des Weiteren zeichnet sich der erfindungsgemäße Stahl durch eine insbesondere gegenüber den bekannten CrMoV-Stählen deutlich besser Wärmeleitfähigkeit aus, was sich ebenfalls positiv in den Gebrauchseigenschaften widerspiegelt. Figure 3 compares the main results of the material investigations of the steel according to the invention with the known hot working steels. It can be seen from the illustration that the steel according to the invention by no means resists the known CrMoV-alloyed hot-work steels, but in particular has better strength and toughness values in the temperature range between 500 and 600 ° C. The higher toughness potential is particularly useful in the drop forging industry to avoid early die bridge, which makes it difficult to calculate forging processes or tool life in the case of fracture-prone, deep die engraving or even uneven mold temperatures. Calculable forging processes are, however, necessary for a reliable cost calculation as well as for an economical production of hot formed parts. Furthermore, with the increase of the toughness potential also the operational safety of the forging tools is taken into account. Furthermore, the steel according to the invention is characterized by a significantly better thermal conductivity, in particular compared to the known CrMoV steels, which is likewise reflected positively in the service properties.

Claims (9)

  1. Tool steel for more highly stressed hot forming tools having the following composition: carbon: 0.28 to 0.40 mass%, silicon: 0.03 to 0.50 mass%, manganese: 0.03 to 0.70 mass%, chromium: 2.00 to 3.5 mass%, nickel: 0.30 to 1.00 mass%, molybdenum: 0.60 to 1.60 mass%, vanadium: 0.15 to 0.35 mass%, Tungsten: 0.001 to 1.00% by mass, niobium: 0.01 to 0.10% by mass and
    a balance of iron and common impurities, wherein the steel has a fine-grained tough structure; wherein the composition satisfies the following condition: 9, 5 ≤ % C x 10 + % V x 5 + % Mo x 3 + % W x 2 + % CR + % Nb x 3 ≤ 16.
  2. Method for the manufacture of a tool steel according to claim 1, characterized in that the crude steel is produced in an electric arc furnace or LD converter with subsequent secondary metallurgical treatment of the melt in the ladle furnace and / or degassing systems, wherein as deoxidation process a Si-, AI-, carbon and / or diffusion-deoxidation is chosen, wherein after the secondary metallurgical treatment of the tool steel in the strand or ingot casting method to a slab (or billets), a billet or ingot is poured, wherein the solidification cross section is matched to the later dimension of the tool steel block and the poured tool steel is subjected to a homogenization treatment at about 1250 to 1300 °C for a period of at least 24 hours.
  3. Method according to claim 2, characterized in that the tool steel is subjected to hot working by forging at temperatures of about 850 to 1200 °C with an at least three-fold degree of deformation.
  4. Method according to claim 3, characterized in that the formed workpiece is austenitized after the subsequent cooling of the material at about 850 to 900 °C and is then held about 50 to 100 hours at a temperature in the range of 680 to 710 °C isothermally for the purpose of conversion in the Perlite.
  5. Manufacturing process for blanks for hot work tools to be produced from a tool steel according to one of claims 2 to 4 with a composition according to claim 1, characterized in that the blanks are annealed after mechanical machining, wherein the workpieces austenitized at about 850 to 950 °C in a medium of oil, polymer or water or the tempered workpieces are hardened in a lead or salt bath or alternatively in a warm bath simulation in a vacuum, wherein the workpieces are cooled after quenching in air to room temperature and then tempered according to the tempering diagram to the desired operational strength.
  6. Method according to claim 5, characterized in that the cast steel is subjected to a remelting process by means of ESU before or between steps of hot working.
  7. Method according to claim 6, characterized in that the homogenization / diffusion annealing treatment of the cast steel is saved by the remelting.
  8. Use of a tool steel according to claim 1 for the production of hot working tools.
  9. Use of a tool steel according to claim 1 for the production of a plastic molding tool.
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ES2716421T3 (en) 2019-06-12
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EP2535430A3 (en) 2014-03-05
EP2535430A2 (en) 2012-12-19

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