EP0378925A1 - Powdered steel for cold processing tool - Google Patents

Powdered steel for cold processing tool Download PDF

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Publication number
EP0378925A1
EP0378925A1 EP89313419A EP89313419A EP0378925A1 EP 0378925 A1 EP0378925 A1 EP 0378925A1 EP 89313419 A EP89313419 A EP 89313419A EP 89313419 A EP89313419 A EP 89313419A EP 0378925 A1 EP0378925 A1 EP 0378925A1
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Prior art keywords
steel
wear resistance
high speed
cold processing
speed tool
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EP89313419A
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German (de)
French (fr)
Inventor
Yoshitomo Hitachi
Yukinori Matsuda
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Daido Steel Co Ltd
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Daido Steel Co Ltd
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    • 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
    • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
    • C22C33/0292—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5% with more than 5% preformed carbides, nitrides or borides
    • 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
    • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
    • C22C33/0285—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5% with Cr, Co, or Ni having a minimum content higher than 5%

Definitions

  • the present invention concerns improvement in powdered steel for producing cold processing tools used under severe conditions.
  • the tools made with this powdered steel have high wear resistance and of good hardenability, and further, of high hardness and high toughness.
  • SKD 11 As the material for producing tools for cold processing of metals, there has been used, in the field of melted materials, various steels for cold tools represented by SKD 11. SKD 11 is a steel of a good wear resistance and relatively high toughness, and therefore, is a material easy to use.
  • vacuum heat treatment has come to be use more and more because it causes less distortion during the heat treatment.
  • the wear resistance of SKD 11 is given mainly by the carbides of M7C3 type and M23C6 type, which are eutectic. If the quantities of the carbides are increased for the purpose of hightening the wear resistance, then the toughness decreases to shorten the life of the presision dies.
  • high speed tool steels such as SKH 51 are better than the usual alloyed tool steels.
  • carbides are mainly of M6C type and MC type, and the steels may not exhibit the wear resistance which is inherant in the high speed tool steels.
  • the object of the present invention is to improve the present status of the art and provide a steel for cold processing tools of good wear resistance, high toughness, and having such a high hardenability that the steel is hardenable by conventional heat treatment apparatus and under the usual conditions, thus being suitable as the material of the tools for precise cold processing used under sever conditions, particularly, of various dies.
  • the conventional heat treatment apparatus and usual conditions mean the apparatus, heating temperature and cooling means which have been used for hardening the conventional materials such as the above mentioned SKD 11. These are chosen because of the economical demand to carry out the treatment with existing facilities and the operational convenience that, at the hardening operation various kinds of mterials are treated together in one furnace, and therefore, it is desired to get the hardening effect at the same heting temperture. Thus, these are important factors for industrial practice.
  • the steel may contain, in addition to the above components, up to 10.0 % of W in such a range that W + 2Mo is 8.0 or less.
  • the hatched demain is the range of the alloy composition according to the present invention.
  • hardenability increase is realized by the fact that those of M7C3 type and M23C6 type, which are easy to dissolve in the matrix and useful for improving the hardenability, share 29 volume % or more of the carbide particles.
  • high carbon - high chromium is one of the characteristic features, and this gives the high wear resistance and hardenability. Inclusive of this effect, the significance of the alloy components and the reasons for chosing the alloy composition are explained below:
  • the carbon content of this steel is so high as at least 1.5 %, which is the typical carbon content in SKD 11.
  • M7C3 (M is mainly Cr) type carbide which gives the same wear resistance as that of the high alloy tool steel to the present powdered steel and hightens the hardenability thereof.
  • the upper limit 5.0 %, the effect of increasing the hardness saturates and the toughness decrases.
  • Si up to 3.0 %
  • Mn up to 3.0 %
  • Chromium forms carbides with a large amount of carbon and brings about improved wear resistance and hardenability.
  • the lower limit of 10.0 % is necessary for this, and addition exceeding 30.0 % causes formation of too much carbides.
  • Molibdenum cuases precipitaion of fine particles of the carbide, MoC, which contributes to the wear resistance. As the amount of Mo becomes too large, percentage of Mo2C in the carbides increases, and is not useful for hightening the hardenability, and further, undesirable for the toughness.
  • V 0.1 - 10.0 %
  • Vanadium forms, like Mo, fine carbide, VC, which hightens the wear resistance. Too much additon lowers the toughness.
  • the powdered high speed tool steel according to the present invention has a high hardenability, and therefore, even if it is processed to a large sized tool, sufficient hardness of the tool can be obtained even by vacuum heat treatment. Because of precipitation of large amount of the carbides in the form of fine particles the abresion resistance is high and the toughness is at a satisfactory level.
  • the tool steel is suitable as the material for large sized and precise cold processing tools used under severe conditions such as forging molds and rolling rollers. Further, it is useful for various machine parts to which wear resistance is required.
  • the hardening was carried out by vacuum heating and gas quenching.
  • the temperature of the heating is in the ordinary range for SKD 11 steel, which is lowere than the hardening temperature for high speed tool steels, and the quenching rate is about 0.5 o C/sec.
  • the tempering was practiced as high temperature tempering by subjection the sintered bodies to the temperatures to which tools may reach when used.
  • Test pieces were prepared from the samples, and tested to determine the bend fracture strength, which is a parameter of the toughness, and the wear resistance.
  • the wear resistance was measured by Ohgoshi-type rapid abrasion tester under the following conditions.
  • Mating material SCM 415 (annealed) Circulating distance: 200 m Circulating speed: 2.93 m/sec Load: 6.3 kgf

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Powder Metallurgy (AREA)

Abstract

Disclosed is a powdered high speed tool having good wear resistance used for producing cold processing tools such as forging molds and rolling rollers.
The powdered high speed tool steel essentially consists of 1.5 - 5.0 % of C, up to 3.0 % of Si, up to 3.0 % of Mn 10 - 30 % of Cr, 0.5 - 4.0 % of Mo, 0.1 - 10 % of V and the balance substantially of Fe, provided that the followings are met:
F(C) = Cr + 15.5C ≧ 40, and
F(H) = 3.8C - 0.62Cr ≧ -5.
The steel may optionally further contain up to 10 % of Mo in the range that W + 2Mo is up to 8.0 %.

Description

    BACKGROUND OF THE INVENTION Field of the Invention
  • The present invention concerns improvement in powdered steel for producing cold processing tools used under severe conditions. The tools made with this powdered steel have high wear resistance and of good hardenability, and further, of high hardness and high toughness.
    • State of the Art
  • As the material for producing tools for cold processing of metals, there has been used, in the field of melted materials, various steels for cold tools represented by SKD 11. SKD 11 is a steel of a good wear resistance and relatively high toughness, and therefore, is a material easy to use.
  • Because of the recent trend of larger-size and more precision in cold processing tools, such as increased demand for large cold forging molds and desire to minimize clearance of punching dies, vacuum heat treatment has come to be use more and more because it causes less distortion during the heat treatment.
  • In the vacuum heat treatment, cooling is carried out by gas cooling, and therefore, it is difficult to increase the cooling rate. Further, due to the mass effect imposed by the larger objects to be treated, wear resistant and high toughness materials of good hardenability have been demanded.
  • The wear resistance of SKD 11 is given mainly by the carbides of M₇C₃ type and M₂₃C₆ type, which are eutectic. If the quantities of the carbides are increased for the purpose of hightening the wear resistance, then the toughness decreases to shorten the life of the presision dies.
  • On the other hand, from the view point of high wear resistance and toughness with good balance there­between, high speed tool steels such as SKH 51 are better than the usual alloyed tool steels. However, it is difficult to increase the hardenability thereof,because the carbides are mainly of M₆C type and MC type, and the steels may not exhibit the wear resistance which is inherant in the high speed tool steels. Thus, it has been difficult to lengthen the tool life.
    • SUMMARY OF THE INVENTION
  • The object of the present invention is to improve the present status of the art and provide a steel for cold processing tools of good wear resistance, high toughness, and having such a high hardenability that the steel is hardenable by conventional heat treatment apparatus and under the usual conditions, thus being suitable as the material of the tools for precise cold processing used under sever conditions, particularly, of various dies.
  • The conventional heat treatment apparatus and usual conditions mean the apparatus, heating temperature and cooling means which have been used for hardening the conventional materials such as the above mentioned SKD 11. These are chosen because of the economical demand to carry out the treatment with existing facilities and the operational convenience that, at the hardening operation various kinds of mterials are treated together in one furnace, and therefore, it is desired to get the hardening effect at the same heting temperture. Thus, these are important factors for industrial practice.
  • The powdered steel for cold processing tools according to the presnt invention has the alloy ompositon consisting of 1.5 - 5.0 % of C, up to 3.0 % of Si, 3.0 % of Mn, 10.0 - 30.0 % of Cr, 0.5 - 4.0 % of Mo and 0.1 - 10.0 % of V, provided that
    F(C) = Cr + 15.5 C ≧ 40 and
    F(H) = 3.8 C - 0.62 Cr ≧ -5,
    and the balance substantially of Fe, and has a high wear resistance and high toughness.
  • The steel may contain, in addition to the above components, up to 10.0 % of W in such a range that W + 2Mo is 8.0 or less.
  • In both the alloy compositions, with respect to the types of the carbides in the steel, where MC, M₇C₃ and M₂₃C₆ are considered, it is preferable that they exist in such a relation that fulfils, in volume ratio,
    (M₇C₃ + M₂₃C₆)/MC = 0.5 - 4.
    • DRAWING
    • The attached single drawing is a graph showing the status of the present powdered steel for cold processing tools in the high-C, high-Cr tool steels.
  • The hatched demain is the range of the alloy composition according to the present invention.
    • DETAILED EXPLANATION OF THE PREFERRED EMBODIMENTS
  • For the purpose of realizing the wear resistance of the cold processing tool steel higher than that of SKD 11, it is necessary to increase the amount of the carbides. However, increase in the amount of carbides generally causes decrease of toughness. In order to avoid this, powder metallurgy is chosen in the present invention. This is because the carbides precipitates in the form of fine particles, and formation of the huge carbide particles, which gives undesirable influence on the toughness, is prevented even though the material is heat-treated during the processing.
  • On the other hand, hardenability increase is realized by the fact that those of M₇C₃ type and M₂₃C₆ type, which are easy to dissolve in the matrix and useful for improving the hardenability, share 29 volume % or more of the carbide particles. These types of the carbides are those of Cr, and by satisfying the above noted conditions,
    F(C) = Cr + 15.5 C ≧ 40, and
    F(H) = 3.8 C - 0.62 C ≧ -5
    the above mentioned carbide profile can be realized.
  • In the alloy composition of the powdered steel for cold processing tools according to the present invention, as described above, high carbon - high chromium is one of the characteristic features, and this gives the high wear resistance and hardenability. Inclusive of this effect, the significance of the alloy components and the reasons for chosing the alloy composition are explained below:
    • C : 1.5 - 5.0 %
  • In order to form a large quantity of the carbides, the carbon content of this steel is so high as at least 1.5 %, which is the typical carbon content in SKD 11. This ensures formation of the M₇C₃ (M is mainly Cr) type carbide, which gives the same wear resistance as that of the high alloy tool steel to the present powdered steel and hightens the hardenability thereof. At or more of the upper limit, 5.0 %, the effect of increasing the hardness saturates and the toughness decrases.
    • Si: up to 3.0 %, Mn: up to 3.0 %
  • These elements are added to the steel as the deoxidation agent. Si is further expected to cause secondary hardening during the high temperature tempering. Both the elements, if added in too much quantities, decrease the toughness.
    • Cr: 10.0 - 30.0 %
  • Chromium forms carbides with a large amount of carbon and brings about improved wear resistance and hardenability. The lower limit of 10.0 % is necessary for this, and addition exceeding 30.0 % causes formation of too much carbides.
    • Mo: 0.5 - 4.0 %
  • Molibdenum cuases precipitaion of fine particles of the carbide, MoC, which contributes to the wear resistance. As the amount of Mo becomes too large, percentage of Mo₂C in the carbides increases, and is not useful for hightening the hardenability, and further, undesirable for the toughness.
    • W: up to 10.0 % (provided that in + 2Mo: up to 8.0 %)
  • As noted above, a portion of Molybdenum can be replaced by tungsten. The influence of added W is about twice of Mo, and the carbides thereof, WC and W₂C are not favorable for the heat treatment. Thus, the above limitation is given.
    • V: 0.1 - 10.0 %
  • Vanadium forms, like Mo, fine carbide, VC, which hightens the wear resistance. Too much additon lowers the toughness.
  • The powdered high speed tool steel according to the present invention has a high hardenability, and therefore, even if it is processed to a large sized tool, sufficient hardness of the tool can be obtained even by vacuum heat treatment. Because of precipitation of large amount of the carbides in the form of fine particles the abresion resistance is high and the toughness is at a satisfactory level.
  • Consequently, the tool steel is suitable as the material for large sized and precise cold processing tools used under severe conditions such as forging molds and rolling rollers. Further, it is useful for various machine parts to which wear resistance is required.
    • EXAMPLES
  • Steels of the alloy compositions shown in Table 1 were prepared and the molten steels were atomized by gas spraying. The obtained powderes were subjected to HIP treatment to sinter, and the sintered bodies were annealed, forged and heat treated.
  • The hardening was carried out by vacuum heating and gas quenching. The temperature of the heating is in the ordinary range for SKD 11 steel, which is lowere than the hardening temperature for high speed tool steels, and the quenching rate is about 0.5oC/sec. On the other hand, the tempering was practiced as high temperature tempering by subjection the sintered bodies to the temperatures to which tools may reach when used.
  • Test pieces were prepared from the samples, and tested to determine the bend fracture strength, which is a parameter of the toughness, and the wear resistance. The wear resistance was measured by Ohgoshi-type rapid abrasion tester under the following conditions.
    Mating material: SCM 415 (annealed)
    Circulating distance: 200 m
    Circulating speed: 2.93 m/sec
    Load: 6.3 kgf
  • The results of the above tests are shown in Table 2 with the heat treating conditions.
    Figure imgb0001
    Figure imgb0002

Claims (4)

1. A powdered high speed tool steel having good wear resistance and toughness, characterized in that the steel essentially consists of 1.5 - 5.0 % of C, up to 3.0 % of Si, up to 3.0 % of Mn, 10.0 - 30.0 % of Cr, 0.5 - 4.0 % of Mo, 0.1 - 10.0 % of V and the balance substan­tially of Fe, provided that the followings are met:
F(C) = Cr + 15.5C ≧ 40, and
F(H) = 3.8C - 0.62Cr ≧ -5.
2. A powdered high speed tool steel according to claim 1, characterized in that the steel contains, further to the above alloy components, up to 10.0 % of W in the range that W + 2Mo is up to 8.0 %.
3. A powdered high speed tool steel according to claim 1, characterized in that the metal carbides are contained therein in the range which satisfy the following relation:
(M₇C₃ + M₂₃C₆)/MC = 0.5 - 4.0 (volume ratio)
4. A powdered high speed tool steel according to claim 2, characterized in that the metal carbides are contained therein in the range which satisfy the following relation:
(M₇C₃ + M₂₃C₆)/MC = 0.5 - 4.0 (volume ratio)
EP89313419A 1988-12-27 1989-12-21 Powdered steel for cold processing tool Withdrawn EP0378925A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP63330078A JP2684736B2 (en) 1988-12-27 1988-12-27 Powder cold work tool steel
JP330078/88 1988-12-27

Publications (1)

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EP0378925A1 true EP0378925A1 (en) 1990-07-25

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4445154A1 (en) * 1994-12-17 1996-06-20 Fischer Artur Werke Gmbh Process for producing an expansion anchor made of corrosion-resistant steel
JP2013221606A (en) * 2012-04-19 2013-10-28 Nsk Ltd Linear guide device
US9890435B2 (en) * 2014-09-26 2018-02-13 Hitachi Metals, Ltd. Cold work tool material and method of manufacturing cold work tool

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3217427B2 (en) * 1992-01-31 2001-10-09 株式会社フジコー Lump-resistant mineral wear material
KR101551453B1 (en) * 2007-09-28 2015-09-08 회가내스 아베 (피유비엘) Metallurgical powder composition and method of production
US9162285B2 (en) 2008-04-08 2015-10-20 Federal-Mogul Corporation Powder metal compositions for wear and temperature resistance applications and method of producing same
EP2969327A1 (en) * 2013-03-15 2016-01-20 Federal-Mogul Corporation Powder metal compositions for wear and temperature resistance applications and method of producing same

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4615734A (en) * 1984-03-12 1986-10-07 General Electric Company Solid particle erosion resistant coating utilizing titanium carbide, process for applying and article coated therewith
DE3736350A1 (en) * 1986-10-31 1988-05-19 Mitsubishi Metal Corp FE-BASED SINTER ALLOY WITH CARBIDES DISPERSED IN IT
EP0271238A2 (en) * 1986-12-11 1988-06-15 Crucible Materials Corporation Wear and corrosion resistant alloy articles
EP0348380A1 (en) * 1988-06-21 1989-12-27 BÖHLER Gesellschaft m.b.H. Use of an iron-base alloy in the manufacture of sintered parts with a high corrosion resistance, a high wear resistance as well as a high toughness and compression strength, especially for use in the processing of synthetic materials

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4615734A (en) * 1984-03-12 1986-10-07 General Electric Company Solid particle erosion resistant coating utilizing titanium carbide, process for applying and article coated therewith
DE3736350A1 (en) * 1986-10-31 1988-05-19 Mitsubishi Metal Corp FE-BASED SINTER ALLOY WITH CARBIDES DISPERSED IN IT
EP0271238A2 (en) * 1986-12-11 1988-06-15 Crucible Materials Corporation Wear and corrosion resistant alloy articles
EP0348380A1 (en) * 1988-06-21 1989-12-27 BÖHLER Gesellschaft m.b.H. Use of an iron-base alloy in the manufacture of sintered parts with a high corrosion resistance, a high wear resistance as well as a high toughness and compression strength, especially for use in the processing of synthetic materials

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, vol. 10, no. 230 (C-365), 9th August 1986; & JP-A-61 064 854 (NISSAN MOTOR CO.) 03-04-1986 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4445154A1 (en) * 1994-12-17 1996-06-20 Fischer Artur Werke Gmbh Process for producing an expansion anchor made of corrosion-resistant steel
US5637158A (en) * 1994-12-17 1997-06-10 Fischerwerke Artur Fischer Gmbh & Co. Kg Method for the manufacture of an expansible anchor consisting of corrosion-resistant steel
JP2013221606A (en) * 2012-04-19 2013-10-28 Nsk Ltd Linear guide device
US9890435B2 (en) * 2014-09-26 2018-02-13 Hitachi Metals, Ltd. Cold work tool material and method of manufacturing cold work tool

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JP2684736B2 (en) 1997-12-03

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