Classifications

• • 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

Definitions

• ABSTRACT A tool steel for hot working containing, in weight percent, from 0.25 to 0.60% carbon, not more than 0.6% silicon, from 0.50 to 1.50% manganese, from 0.50 to 1.50% nickel, from 1.50 to 3.50% chromium, from 2.00 to 4.50% molybdenum, from 1.20 to 3.00 vanadium, from 0.50 to 5.00% cobalt, balance essentially iron and impurities, or containing, in weight percent, from 0.25 to 0.60% carbon, not more than 0.60% silicon, from 0.50 to 1.50% manganese, from 0.50 to 1.50% nickel, from 1.50 to 3.50% chromium, from 0.50 to 3.50% tungsten, from 1.50 to 3.00% molybdenum, from 1.20 to 3.00% vanadium, from 0.50 to 5.00% cobalt, balance essentially iron and impurities.
• This tool steel affords excellent high temperature mechanical strength, toughness, high temperature wear resistance, and heat check resistance.
• AISI H19 base steels of a high W-V-Co alloy system find a wide application as materials having the highest high temperature mechanical strength for meeting a demand arising from hot working which requires excellent mechanical strength and wear resistance at high temperature.
• a tool steel for hot working containing, in weight 2 mium, from 0.50 to 3.50% tungsten, from 1.50 to 3.00% molybdenum, from 1.20 to 3.00% vanadium, from 0.50 to 5.00% cobalt, balance essentially iron and impurities.
• This tool steel affords excellent high temperature mechanical strength, toughness, high temperature wear resistance, and heat check resistance.
• the tool steel according to the present invention has a composition being added suitable amounts of carbide forming elements such as W, Mo and V to a low Crlow SiMnNi-Co alloy system which is the fundamental components of this steel.
• the invention of this tool steel is: to improve resistance to the temper softening as well as high-temperature strength due to precipitation hardening by adding a small amount of chrominum, a suitable amount of tungsten and molybdenum and a great amount of vanadium; to present a suitable degree of oxidative characteristic due to the addition of small amounts of chrominum and silicon, suitable amounts of molybdenum and manganese to thereby facilitate the formation of oxide films on the surface of a die due to the temperature rise in service; and to provide the aforesaid oxide film which is intimate and adhesive, due to the addition of cobalt, nickel or tungsten, .in an attempt to improve high-temperature wear resistance, corrosion resistance, roughsurface condition and heat check resistance due to the resulting good lubricity and good heat insulating property; and to provide high resistance to the development or propagation of cracks by addition nickel to the composition of the steel.
• Table 2 illustrates the heat treatment condition (target hardenss of HRC) and the high-temperature strengths, proving that the steels according to the present invention afford high-temperature strengths superior or equivalent to those of the conventional steels iron and impurities; and a tool steel containing, in (AISI H19).
• the amount of manganese is between 0.50 and F cture t h k /mm m Dug g mm 1.50%.
• Manganese should be present for improving the l' l Sm] A characteristic to form a heat-insulating-oxidized film, Present invention, Steel B 262 Present invention, Steel (3 9 that IS, one of the prominent features of the present Present invenfim" Steel D 267 invention.
• lf manganese is excessive in amounts, then Prior art, Steel E 237 there results lowered A transformatlon point and higher tempered hardness as well as lowered machin-
• the heat treatment conditions used are the same as i the upper 1mm of the amolint of manganese those given in Table 2.
• the amount of nickel is too low, then there results no Table 5 desired effect of nickel added.
• the amount of Number Average depth Maximum depth nickel should be not less than 0.50%.
• Chromlnum should be present within the range of prcseminvemion from 1 50 to 3.50%, preferably, from 2.00 to 3.50%.
• Steel A I 12 0.14 M 1 chrominum is necessary for improving the high temper- H4 (H4 057 ature strength and temper softening resistance as well
• Prior art steel E 120 0.18 0.65 as for affording a suitable characteristic of an oxidized film plus improved wear resistance due to the formation of carbides in combination with carbon.
• Chromi- The results shown above are attributable to the excelnum is further necessary for improving A, transformalent high temperature strength, and high resistance tion point effect and hardenability. In this sense, against the development or propagation of cracks plus chrominum is of supreme importance as an element for the steels of the present invention. If the amount of chrominum is too low, then there resultsinsufficient oxidation resistance, with theresulting rough surface, lowered hardenability, .lowered A, transformation point and lowered wear resistance. Thus, the lower limit of the amount of chrominum should be 1.50%.
• chrominum of an excessive amount promotes precipitation and cohesion of car bides, thus lowering the temper softening resistance and high temperature strength.
• the upper limits of chrominum is set to 3.50%.
• Tungsten is present within the range of from 0.50% to 3.50%, preferably, from 1.00 to 3.50%.
• Tungsten is necessary because of its unique effect to improve the wear resistance due to the formation of carbides which hardly forms solid solutions upon heating for hardening as well as to increase the high temperature yield strength due to the precipitation of fine carbides in tempering, in addition to an attempt to provide an intimate oxidized film on the surface of a die due to a temperature rise in service.
• the effect of tungsten on the characteristics of an oxide film depends on the amounts of Cr, Mo, Si, Mn, Ni, Co. Thus, optimum combination of those elements can present excellent characteristics as shown in Table 3.
• Tungsten of an excessive amount tends to form large size carbides, thus causing lowered toughness. Thus, the amount of tungsten is limited to not more than 3.50%. On the other hand, tungsten of a too small amount, there results the failure to obtain the intended effect of tungsten. Thus, tungsten should be present in amounts of not less than 0.50%.
• Molybdenum is present in the range of from 2.00 to 4.50%. Molybdenum is necessary for forming carbides to increase wear resistance and for improving the hardenability due to the formation of solid solution thereof into a matrix. In addition, molybdenum precipitates fine carbides at the time of tempering to increase the temper softening resistance as well as high temperature strength, in addition to its feasibility to form a protec tive oxidized film. If the amount of molybdenum is excessive, then there results lowered toughness. Thus, the upper limit of molybdenum is set to 4.50%. On the other hand, if molybdenum is too low in amounts, then there results no intended effect due to the addition of molybdenum.
• the upper limit of molybdenum is set to 3.00%, and the lower limit thereof is set to 0.50%.
• the range of the molybdenum level is between 2.50 to 350% while in the case of combined addition of molybdenum with tungsten, the amount of molybdenum should range from 1.00 to 3.00%.
• Vanadium is present within the range of from 1.20 to 3.00%, preferably, from 1.20 to 2.50%.
• Vanadium is necessary-for forming a great amount of carbides which hardly form solid solutions to thereby improve the wear resistance and thermal stick resistance.
• vanadium fonns solid solutions in a matrix at the time of heating for hardening, thus precipitating fine carbides which are hardly cohesive in tempering. This increases the softening resistance at elevated temperatures thus affording excellent high-temperature yield strength, which is one of the outstanding features of the present invention.
• vanadium should be present in a great amount for the steels of the present invention.
• the addition of vanadium presents a fine grain size ofcrystals to improve toughness as well as to raise the A, transformation temperature, thus improving high-temperature yield strength at elevated temperatures as well as heat check resistance.
• the upper limit of vanadium is set to 3.00%. If the amount of vanadium is too low, then there results no intended effect due to the addition of vanadium. Thus, the lower limit of vanadium is set to 1.20%.
• Cobalt is present within the range of from 0.50 to 5.00%, preferably, from 0.70 to 4.00%. Cobalt is necessary for affording excellent wear resistance at elevated temperatures. This is because of the formation of a protective oxide film which is intimate and adhesive, at the time of the temperature rise in a die in service. This prevents its metallic contact with work pieces, preventing the temperature rise in a die as well as presenting high wear resistance. In addition, cobalt presents a heat insulating property due to the formation of an oxide film, improvement in heat check resistance due to the protective action of the film, and suppression of formation of crack developing nucleuses. The aforesaid effect of cobalt differs by the added amount of nickel, tungsten, molybdenum and the like.
• cobalt should not be added in a great amount. If the amount of cobalt is excessive, then there results lowered toughness. Thus, cobalt should be present in amounts of no more than 5.00%. On the other hand, if the amount of cobalt is too low, then there may not attain the intended effect due to the addition of cobalt. Thus, cobalt should be present in amounts of no less than 0.50%.
• the steels for hot working according to the present invention present high resistance against the development or propagation of cracks, excellent high wear resistance and seizing resistance due to the formation of a dense and adhesive oxide film by temperature rise at hot working.
• the steels of the present invention suppress the formation of the initial cracks or crack developing nucleuses as well as insure a long service life with consistent high performances.
• a tool steel for hot working consisting essentially of, in weight percent, from 0.25 to 0.60% carbon, not more than 0.6% silicon, from 0.50 to 1.50% manganese, from 0.50 to 1.50% nickel, from 1.50 to 3.50% chromium, from 2.00 to 4.50% molybdenum, from 1.20 to 3.00% vanadium, from 0.50 to 5.00% cobalt, balance essentially iron and impurities.
• a tool steel for hot working consisting essentially of, in weight percent, from 0.03 to 0.50% carbon, no more than 0.60% silicon, from 0.50 to 1.00% manganese from 0.70 to 1.40% nickel, from 2.00 to 3.50% chromium, from 2.5 to 3.50% molybdenum, from 1.20 to 2.50% vanadium, from 0.70 to 4.00% cobalt, balance essentially iron and impurities.
• a tool steel for hot working consisting essentially of, in weight percent, from 0.25 to 0.60% carbon, not more than 0.60% silicon, from 0.50 to 1.50% manganese, from 0.50 to 1.50% nickel, from 1.50 to 3.50% chromium, from 0.50 to 3.50% tungsten, from 1.50 to 3.00% molybdenum, from 1.20 to 3.00% vanadium,
• a tool steel for hot working consisting essentially of, in weight percent, from 0.30 to 0.50% carbon, no more than 0.60% silicon, from 0.50 to 1.00% manga

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Steel (AREA)

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• 1973
  • 1973-11-28 JP JP13273773A patent/JPS5436893B2/ja not_active Expired
• 1974
  • 1974-11-27 US US527740A patent/US3928025A/en not_active Expired - Lifetime

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