[go: up one dir, main page]
More Web Proxy on the site http://driver.im/

EP0510598B1 - Wear-resistant compound roll - Google Patents

Wear-resistant compound roll Download PDF

Info

Publication number
EP0510598B1
EP0510598B1 EP19920106860 EP92106860A EP0510598B1 EP 0510598 B1 EP0510598 B1 EP 0510598B1 EP 19920106860 EP19920106860 EP 19920106860 EP 92106860 A EP92106860 A EP 92106860A EP 0510598 B1 EP0510598 B1 EP 0510598B1
Authority
EP
European Patent Office
Prior art keywords
roll
carbide particles
wear
compound
compound roll
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.)
Expired - Lifetime
Application number
EP19920106860
Other languages
German (de)
French (fr)
Other versions
EP0510598A3 (en
EP0510598A2 (en
Inventor
Takuya Ohsue
Akira Noda
Hiroshi Fukuzawa
Itsuo Korenaga
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.)
Proterial Ltd
Original Assignee
Hitachi Metals Ltd
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 Hitachi Metals Ltd filed Critical Hitachi Metals Ltd
Publication of EP0510598A2 publication Critical patent/EP0510598A2/en
Publication of EP0510598A3 publication Critical patent/EP0510598A3/en
Application granted granted Critical
Publication of EP0510598B1 publication Critical patent/EP0510598B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C33/00Making ferrous alloys
    • C22C33/02Making ferrous alloys by powder metallurgy
    • C22C33/0257Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • C22C33/0278Making 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%
    • C22C33/0292Making 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
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21BROLLING OF METAL
    • B21B27/00Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F7/00Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
    • B22F7/06Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools
    • B22F7/08Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools with one or more parts not made from powder
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C33/00Making ferrous alloys
    • C22C33/02Making ferrous alloys by powder metallurgy
    • C22C33/0257Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/36Ferrous alloys, e.g. steel alloys containing chromium with more than 1.7% by weight of carbon

Definitions

  • the present invention relates to a wear-resistant compound roll, and more particularly to a wear-resistant compound roll having a shell portion formed around a core portion, the shell portion being made of a sintered alloy material showing excellent wear resistance.
  • the rolls are required to have roll surfaces suffering from little wear, little surface roughening, little sticking with materials being rolled, less cracks and fractures, etc.
  • cast compound rolls having hard outer surfaces and forged steel rolls having roll body portions hardened by heat treatment, etc. are conventionally used.
  • various materials and production methods are used for preparing these rolls.
  • JP-A-62-7802 discloses a compound roll constituted by a shell portion and a roll core, the shell portion being made from powder of a high-speed steel, a high-Mo cast iron, a high-Cr cast iron, a Ni-Cr alloy, etc., and diffusion-bonded to the roll core by a HIP treatment.
  • JP-A-58-128525 discloses a cemented carbide roll and a compound ring roll whose ring portion is made of a cemented carbide.
  • JP-A-58-87249 discloses a wear-resistant cast roll having a composition consisting essentially of 2.4-3.5% of C, 0.5-1.3% of Si, 0.3-0.8% of Mn, 0-3% of Ni, 2-7% of Cr, 2-9% of Mo, 0-10% of W, 6-14% of V, and balance Fe and inevitable impurities.
  • W, Mo and V form metal carbides, contributing to providing the roll with excellent wear resistance.
  • this roll material is produced by casting, it still suffers from the problems that the particle sizes of metal carbides are as large as 50-200 ⁇ m, and that the distribution of the metal carbides is microscopically not uniform.
  • JP-A-1252704 discloses a wear-resistant compound roll produced by a HIP process.
  • JP-A-2-270944 discloses a wear-resistant and surface-roughening resistant one-piece roll produced by subjecting an alloy powder consisting of, by weight, 1.2 - 3.5 % of C, 3 - 6 % of Cr, 4 - 10 % of Mo, 2 - 15 % of W, 2 - 10 % of V 1 - 15 % of Co and balance of inevitable impurities and Fe to hot isostatic press, said roll containing 5 - 40 % by area of carbides of 25 - 100 ⁇ m particle size and having no powdery areas of alloy in the matrix.
  • An object of the present invention is, accordingly, to provide a wear-resistant compound roll having a shell portion made of a sintered alloy showing excellent wear resistance.
  • the wear-resistant compound roll according to the present invention has a shell portion produced by sintering an alloy powder comprising, by weight, 1.0-3.5% of C, 0,2-1% of Si, 0,2-1% of Mn, 10% or less of Cr, 3-15% of W, 2-10% of Mo, 1-15% of V, optionally 3-15% of Co, and balance Fe and inevitable impurities, the shell portion containing carbide particles having particle sizes within the range of 3-50 ⁇ m in a martensite or bainite matrix, and an area ratio of the carbide particles in the metal structure of the sintered shell portion being 15% or more, wherein among the carbide particles having particle sizes of 0.5 ⁇ m or more, the number of the carbide particles having particle sizes of 3 ⁇ m or more is 10% or more.
  • the alloy powder used for producing the shell portion of the compound loll in the present invention has a composition comprising, by weight, 1.0-3.5% of C, 0,2-1% of Si, 0,2-1% of Mn, 10% or less of Cr, 3-15% of W, 2-10% of Mo, 1-15% of V, optionally 3-15% of Co, and balance Fe and inevitable impurities.
  • C is combined with Cr, W, Mo and V to form hard carbides, contributing to the increase in wear resistance.
  • carbon content is excessive, too much carbides are formed, making the alloy brittle.
  • C is dissolved in the matrix to show the function of secondary hardening by tempering.
  • the toughness of the matrix is decreased.
  • the C content is 1.0-3.5 weight %.
  • the preferred C content is 1.5-3.0 weight %.
  • Si has a function of deoxidation, hardening of the alloy matrix, increasing oxidation resistance and corrosion resistance, and improving the atomizability of the alloy. To achieve these effects, the amount of Si is 0.2-1 weight %.
  • Mn is contained in an amount of 0,2-1 weight %, because it has a function of deoxidation and increasing the hardenability of the alloy.
  • the Cr not only contributes to the improvement of wear resistance by forming carbides with C but also enhances the hardenability of the alloy by dissolving into the matrix, and increasing the secondary hardening by tempering. However, when Cr is in an excess amount, the toughness of the matrix is lowered. Accordingly, the Cr content is 10 weight % or less. The preferred Cr content is 3-6 weight %.
  • W and Mo not only increase wear resistance by combining with C to form M 6 C-type carbides, but also are dissolved in the matrix, thereby increasing the hardness of the matrix when heat-treated. However, when they are in excess amounts, the toughness of the alloy decreases, and the material becomes expensive. Accordingly, W is 3-15 weight %, and Mo is 2-10 weight %. The preferred W content is 3-10 weight %, and the preferred Mo content is 4-10 weight %.
  • V is combined with C like W and Mo. It forms MC-type carbides which have a hardness Hv of 2500-3000, extremely larger than the hardness Hv of 1500-1800 of the M 6 C-type carbides. Accordingly, V is an element contributing to the improvement of wear resistance.
  • V content is lower than 1 weight %, its effect is too small.
  • the V content exceeds 15 weight %, the atomizability and workability of the alloy become poor. Accordingly, the V content is 1-15 weight %.
  • the preferred V content is 4-15 weight %.
  • Co is an element effective for providing the alloy with heat resistance, it may be added to the alloy powder. However, when it is in an excess amount, it lowers the toughness of the alloy. Accordingly, Co is preferably 3-15 weight %. The more preferred Co content is 5-10 weight %.
  • an alloy having the above composition is melted and formed into powder by a gas atomization method, etc.
  • the alloy powder obtained by such a method desirably has an average particle size of 30-300 ⁇ m.
  • the shell portion of the compound roll according to the present invention has a martensite or bainite matrix. Because of this matrix structure, the shell portion shows excellent mechanical strength.
  • the core portion of the compound roll may be made of any iron-base alloy materials such as cast iron, cast steel, forged steel, etc.
  • the alloy powder "P" obtained by atomization, etc. is charged into a metal capsule 2 disposed around a roll core portion 1.
  • the metal capsule 2 is evacuated through a vent 3 provided in an upper portion thereof and sealed, to keep the inside of the metal capsule 2 in a vacuum state. It is then subjected to a HIP treatment.
  • the metal capsule 2 may be made of steel or stainless steel plate having a thickness of about 3-10 mm.
  • the HIP treatment is usually conducted at a temperature equal to or higher than the temperature from which the alloy powder starts to be melted (hereinafter referred to as "melting-start temperature"). Specifically, the HIP treatment is conducted at a temperature of 1100-1300°C and a pressure of 9.81 - 14.715 ⁇ 10 3 N/cm 2 (1000-1500 atm) in an inert gas atmosphere such as argon, etc. for 1-8 hours, preferably 2-5 hours.
  • the most important feature of the present invention is that by conducting the HIP treatment at a temperature not lower than the melting-start temperature of the alloy powder, the sizes and distribution of carbides in the alloy matrix of the shell portion of the compound roll are controlled, thereby improving the wear resistance of the compound roll.
  • Figs. 1 and 9 which are photomicrographs showing the metal structures of Example 1 and Comparative Example 1, the sizes and distribution of carbides in the alloy matrix vary remarkably depending on the HIP treatment temperature even for the same alloy composition.
  • Fig. 9 which is a photomicrograph of the metal structure of Comparative Example 1, appears to indicate that fine carbide particles uniformly distributed in the alloy matrix are better than those having larger sizes.
  • the compound roll whose shell portion has such a metal structure shows poor wear resistance when the compound roll is used for rolling.
  • Fig. 1 verifies that the larger the sizes of the carbide particles in the matrix the higher wear resistance can be obtained.
  • the carbide particles contributing to improving the wear resistance of the compound roll have particle sizes of 3 ⁇ m or more, as shown in Fig. 1.
  • the carbide particles distributed in the alloy matrix have particle sizes less than 3 ⁇ m as shown in Fig. 9, it is considered that by the wearing mechanism shown in Fig. 3(b) the carbide particles do not substantially contribute to the improvement of the wear resistance of the compound roll.
  • the overall metal structure of the roll is deformed because the carbide particles 11 in the matrix 10 have small particle sizes. Accordingly, wearing of the roll takes place easily.
  • the carbide particles having particle sizes of 3 ⁇ m or more Even though there are carbide particles having particle sizes of 3 ⁇ m or more, the improvement of the wear resistance cannot be expected as long as the amount of the carbide particles is too small. Accordingly, the carbide particles having particle sizes within the range of 3 ⁇ m to 50 ⁇ m should occupy 15 % or more of the matrix by an area ratio.
  • the preferred area ratio of the carbide particles in the alloy matrix is 20-40 %.
  • the percentage of the number of the carbide particles having particle sizes of 3 ⁇ m or more to the number of the carbide particles having particle sizes of 0.5 ⁇ m or more should be 10 % or more. When the above percentage is less than 10 %, the wear resistance of the shell portion is deteriorated.
  • the preferred percentage of the number of the carbide particles having particle sizes of 3 ⁇ m or more to the number of the carbide particles having particle sizes of 0.5 ⁇ m or more is 10-40 %.
  • the compound roll having the metal structure meeting the above requirements shows improved wear resistance due to the mechanism shown in Fig. 3 (a). Specifically, even when the wearing particle 9 is brought into contact with the roll surface, the particle 9 is sustained by the large carbide particles 11, preventing the particle 9 from damaging the overall metal structure. By this mechanism, the roll is well protected from wearing.
  • the metal capsule 2 is removed by a lath. It is then subjected to a heat treatment in the pattern such as shown in Fig. 4. The desired compound roll is obtained after finish working.
  • Alloy powder having a composition shown in Table 1 was charged into a cylindrical metal capsule 2 disposed around a roll core portion 1 as shown in Fig. 2.
  • the metal capsule 2 was evacuated through a vent 3 in an upper portion thereof while heating the overall metal capsule 2 at about 500°C, and the vent 3 was sealed to keep the inside of the metal capsule 2 at about 1.333 ⁇ 10 -3 hPa (1 x 10 -3 torr).
  • this metal capsule 2 was placed in an argon gas atmosphere and subjected to a HIP treatment at a temperature of 1250 °C and at a pressure of 9.81 ⁇ 10 3 N/cm 2 (1000 atm) for 2 hours.
  • the temperature at which the alloy powder started to melt was 1195 °C.
  • Table 1 Chemical Components of Alloy Powder (weight %) C Si Mn Cr Mo W V Co Fe 2.5 0.4 0.4 4.0 5.3 8.8 6.9 8.4 Bal.
  • the outside metal capsule 2 was removed by lathing, and the resulting sample was subject to a heat treatment in the pattern shown in Fig. 4. Thereafter, the compound roll was subjected to finish work to provide a hollow compound roll consisting of a shell portion 4 made of a sintered alloy having an outer diameter of 350 mm and a thickness of 20 mm and a roll core portion 5 having an inner diameter of 250 mm and a length of 400 mm as shown in Fig. 5.
  • This compound roll had a shell portion 4 having a metal structure shown in Fig. 1.
  • Example 1 For comparison, a HIP treatment was conducted on the same compound roll as in Example 1 at a temperature of 1170 °C, lower than the above melting-start temperature of 1195°C, for the same period of time, and the same working as above was then conducted to provide a compound roll of Comparative Example 1.
  • the metal structure of the shell portion of the compound roll of Comparative Example 1 is shown in Fig. 9.
  • the compound rolls produced by the above method were subjected to an abrasive wear test method.
  • a test piece of 10 mm x 10 mm x 15 mm was machined from the shell portion of each compound roll, and subjected to a tempering treatment so that the test pieces 8 had various levels of hardness.
  • an emery paper 7 was attached to a test table 6, and the test table 6 was rotated.
  • Each test piece 8 was pushed onto the emery paper 7 under pressure of 598.6 N/mm 2 (60 kg mm 2 ) for 3 minutes to conduct the wear test.
  • the weight of the test piece was measured to evaluate a weight loss by wearing.
  • the results are shown in Fig. 7.
  • the straight line A denotes Example 1 and the straight line B denotes Comparative Example 1.
  • the weight loss of the compound roll of the present invention is about one-third that of the compound roll of Comparative Example 1 on the same hardness level. This means that the compound roll of the present invention (Example 1) is about three times as wear-resistant as the compound roll of Comparative Example 1.
  • Each compound roll consisted of a shell portion 4 made of a sintered alloy having the same composition as in Example 1 and having an outer diameter of 400 mm and a thickness of 30 mm, and a roll core portion 5 having an inner diameter of 280 mm and a length of 500 mm.
  • Each compound roll was formed with four round calibers each having a semi-circular cross section having a radius of 11 mm.
  • each compound roll was used as a finish roll for rolling a steel rod.
  • 690 tons of steel per each caliber was rolled by the compound roll of Example 2, while only 210 tons of steel per each caliber was rolled by the compound roll of Comparative Example 2.
  • the compound roll of the present invention is more than three times as wear-resistant as the compound roll of Comparative Example 2 which was subjected to a HIP treatment at a temperature lower than the melting-start temperature of the alloy powder for the shell portion.
  • the shell portion of the compound roll of the present invention is prepared by a HIP treatment at a temperature equal to or higher than the melting-start temperature of the alloy powder, the shell portion has carbide particles having large particle sizes. Therefore, the wear resistance of the compound roll of the present invention is as high as three times or more that of the conventional compound roll.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Composite Materials (AREA)
  • Manufacturing & Machinery (AREA)
  • Powder Metallurgy (AREA)
  • Reduction Rolling/Reduction Stand/Operation Of Reduction Machine (AREA)

Description

    BACKGROUND OF THE INVENTION
  • The present invention relates to a wear-resistant compound roll, and more particularly to a wear-resistant compound roll having a shell portion formed around a core portion, the shell portion being made of a sintered alloy material showing excellent wear resistance.
  • The rolls are required to have roll surfaces suffering from little wear, little surface roughening, little sticking with materials being rolled, less cracks and fractures, etc. For this purpose, cast compound rolls having hard outer surfaces and forged steel rolls having roll body portions hardened by heat treatment, etc. are conventionally used. Depending on applications, various materials and production methods are used for preparing these rolls.
  • Further, a higher wear resistance is increasingly demanded for rolls, and compound rolls provided with shell portions made of sintered alloys were recently proposed. For instance, JP-A-62-7802 discloses a compound roll constituted by a shell portion and a roll core, the shell portion being made from powder of a high-speed steel, a high-Mo cast iron, a high-Cr cast iron, a Ni-Cr alloy, etc., and diffusion-bonded to the roll core by a HIP treatment. JP-A-58-128525 discloses a cemented carbide roll and a compound ring roll whose ring portion is made of a cemented carbide.
  • JP-A-58-87249 discloses a wear-resistant cast roll having a composition consisting essentially of 2.4-3.5% of C, 0.5-1.3% of Si, 0.3-0.8% of Mn, 0-3% of Ni, 2-7% of Cr, 2-9% of Mo, 0-10% of W, 6-14% of V, and balance Fe and inevitable impurities. Among the above alloy components, W, Mo and V form metal carbides, contributing to providing the roll with excellent wear resistance. However, since this roll material is produced by casting, it still suffers from the problems that the particle sizes of metal carbides are as large as 50-200 µm, and that the distribution of the metal carbides is microscopically not uniform.
  • Recently, research has been conducted to provide a compound roll having metal carbide particles whose sizes are extremely small and uniform, by using a HIP method instead of a casting method.
  • These rolls show improved wear resistance as compared with the conventional cast iron rolls and forged rolls. However, in view of the demand level of wear resistance which is becoming higher recently, these rolls are still insufficient.
  • To further improve the wear resistance, large amounts of carbide-forming elements are added to roll materials, thereby forming large amounts of high-hardness metal carbides in the roll matrix. Particularly, since vanadium carbide (VC) shows extremely higher hardness than the other metal carbides, the wear resistance of the roll can be remarkably improved by forming VC in the roll matrix.
  • When the alloy powder containing a large amount of a carbide-forming element (particularly V) is used and subjected to a HIP treatment, fine carbides are precipitated. However, the wearing of the roll is relatively large despite the large amount of VC. Accordingly, such cast rolls are not satisfactory from the aspect of wear resistance and resistance to surface roughening.
  • JP-A-1252704 discloses a wear-resistant compound roll produced by a HIP process.
  • JP-A-2-270944 discloses a wear-resistant and surface-roughening resistant one-piece roll produced by subjecting an alloy powder consisting of, by weight, 1.2 - 3.5 % of C, 3 - 6 % of Cr, 4 - 10 % of Mo, 2 - 15 % of W, 2 - 10 % of V 1 - 15 % of Co and balance of inevitable impurities and Fe to hot isostatic press, said roll containing 5 - 40 % by area of carbides of 25 - 100 µm particle size and having no powdery areas of alloy in the matrix.
  • OBJECT AND SUMMARY OF THE INVENTION
  • An object of the present invention is, accordingly, to provide a wear-resistant compound roll having a shell portion made of a sintered alloy showing excellent wear resistance.
  • The wear-resistant compound roll according to the present invention has a shell portion produced by sintering an alloy powder comprising, by weight, 1.0-3.5% of C, 0,2-1% of Si, 0,2-1% of Mn, 10% or less of Cr, 3-15% of W, 2-10% of Mo, 1-15% of V, optionally 3-15% of Co, and balance Fe and inevitable impurities, the shell portion containing carbide particles having particle sizes within the range of 3-50 µm in a martensite or bainite matrix, and an area ratio of the carbide particles in the metal structure of the sintered shell portion being 15% or more, wherein among the carbide particles having particle sizes of 0.5 µm or more, the number of the carbide particles having particle sizes of 3 µm or more is 10% or more.
  • BRIEF DESCRIPTION OF THE DRAWINGS
    • Fig. 1 is a microphotograph showing the metal structure of a test piece cut out from the shell portion of the compound roll according to the present invention;
    • Fig. 2 is a cross-sectional view showing an apparatus for producing a wear-resistant compound roll according to the present invention;
    • Fig. 3 (a) is a schematic view showing the wearing mechanism of the compound roll of the present invention;
    • Fig. 3. (b) is a schematic view showing the wearing mechanism of the conventional roll;
    • Fig. 4 is a schematic view showing a heat treatment pattern as one example of heat treatment conditions used in the production of the wear-resistant compound roll of the present invention;
    • Fig. 5 is a cross-sectional view showing the compound roll;
    • Fig. 6 is a schematic view for explaining an abrasive wear test method;
    • Fig. 7 is a graph showing the relation between weight loss by wear and hardness;
    • Fig. 8 is a cross-sectional view showing another example of a compound roll; and
    • Figs. 9 is a microphotograph showing the metal structure of the conventional roll.
    DETAILED DESCRIPTION OF THE INVENTION
  • The alloy powder used for producing the shell portion of the compound loll in the present invention has a composition comprising, by weight, 1.0-3.5% of C, 0,2-1% of Si, 0,2-1% of Mn, 10% or less of Cr, 3-15% of W, 2-10% of Mo, 1-15% of V, optionally 3-15% of Co, and balance Fe and inevitable impurities.
  • In this alloy, C is combined with Cr, W, Mo and V to form hard carbides, contributing to the increase in wear resistance. However, when the carbon content is excessive, too much carbides are formed, making the alloy brittle. Further, C is dissolved in the matrix to show the function of secondary hardening by tempering. However, if C is in an excess amount, the toughness of the matrix is decreased. For these reasons, the C content is 1.0-3.5 weight %. The preferred C content is 1.5-3.0 weight %.
  • Si has a function of deoxidation, hardening of the alloy matrix, increasing oxidation resistance and corrosion resistance, and improving the atomizability of the alloy. To achieve these effects, the amount of Si is 0.2-1 weight %.
  • Mn is contained in an amount of 0,2-1 weight %, because it has a function of deoxidation and increasing the hardenability of the alloy.
  • Cr not only contributes to the improvement of wear resistance by forming carbides with C but also enhances the hardenability of the alloy by dissolving into the matrix, and increasing the secondary hardening by tempering. However, when Cr is in an excess amount, the toughness of the matrix is lowered. Accordingly, the Cr content is 10 weight % or less. The preferred Cr content is 3-6 weight %.
  • W and Mo not only increase wear resistance by combining with C to form M6C-type carbides, but also are dissolved in the matrix, thereby increasing the hardness of the matrix when heat-treated. However, when they are in excess amounts, the toughness of the alloy decreases, and the material becomes expensive. Accordingly, W is 3-15 weight %, and Mo is 2-10 weight %. The preferred W content is 3-10 weight %, and the preferred Mo content is 4-10 weight %.
  • V is combined with C like W and Mo. It forms MC-type carbides which have a hardness Hv of 2500-3000, extremely larger than the hardness Hv of 1500-1800 of the M6C-type carbides. Accordingly, V is an element contributing to the improvement of wear resistance. When the V content is lower than 1 weight %, its effect is too small. On the other hand, when the V content exceeds 15 weight %, the atomizability and workability of the alloy become poor. Accordingly, the V content is 1-15 weight %. The preferred V content is 4-15 weight %.
  • Since Co is an element effective for providing the alloy with heat resistance, it may be added to the alloy powder. However, when it is in an excess amount, it lowers the toughness of the alloy. Accordingly, Co is preferably 3-15 weight %. The more preferred Co content is 5-10 weight %.
  • In the production of the alloy powder, an alloy having the above composition is melted and formed into powder by a gas atomization method, etc. The alloy powder obtained by such a method desirably has an average particle size of 30-300 µm.
  • By using the above alloy powder, it is possible to produce a compound roll having a shell portion with excellent wear resistance, the shell portion being diffusion-bonded to the roll core portion.
  • The shell portion of the compound roll according to the present invention has a martensite or bainite matrix. Because of this matrix structure, the shell portion shows excellent mechanical strength.
  • With respect to the core portion of the compound roll, it may be made of any iron-base alloy materials such as cast iron, cast steel, forged steel, etc.
  • Next, the method of producing the wear-resistant compound roll according to the present invention will be described.
  • As shown in Fig. 2, the alloy powder "P" obtained by atomization, etc. is charged into a metal capsule 2 disposed around a roll core portion 1. The metal capsule 2 is evacuated through a vent 3 provided in an upper portion thereof and sealed, to keep the inside of the metal capsule 2 in a vacuum state. It is then subjected to a HIP treatment. Incidentally, the metal capsule 2 may be made of steel or stainless steel plate having a thickness of about 3-10 mm.
  • The HIP treatment is usually conducted at a temperature equal to or higher than the temperature from which the alloy powder starts to be melted (hereinafter referred to as "melting-start temperature"). Specifically, the HIP treatment is conducted at a temperature of 1100-1300°C and a pressure of 9.81 - 14.715·103 N/cm2 (1000-1500 atm) in an inert gas atmosphere such as argon, etc. for 1-8 hours, preferably 2-5 hours.
  • The most important feature of the present invention is that by conducting the HIP treatment at a temperature not lower than the melting-start temperature of the alloy powder, the sizes and distribution of carbides in the alloy matrix of the shell portion of the compound roll are controlled, thereby improving the wear resistance of the compound roll. As is clear from Figs. 1 and 9, which are photomicrographs showing the metal structures of Example 1 and Comparative Example 1, the sizes and distribution of carbides in the alloy matrix vary remarkably depending on the HIP treatment temperature even for the same alloy composition.
  • At a first glance, Fig. 9, which is a photomicrograph of the metal structure of Comparative Example 1, appears to indicate that fine carbide particles uniformly distributed in the alloy matrix are better than those having larger sizes. However, it has been found that the compound roll whose shell portion has such a metal structure shows poor wear resistance when the compound roll is used for rolling. Fig. 1 verifies that the larger the sizes of the carbide particles in the matrix the higher wear resistance can be obtained.
  • In this case, the carbide particles contributing to improving the wear resistance of the compound roll have particle sizes of 3 µm or more, as shown in Fig. 1. When the carbide particles distributed in the alloy matrix have particle sizes less than 3 µm as shown in Fig. 9, it is considered that by the wearing mechanism shown in Fig. 3(b) the carbide particles do not substantially contribute to the improvement of the wear resistance of the compound roll. Specifically, when there is a wearing particle 9 in contact with the roll surface, the overall metal structure of the roll is deformed because the carbide particles 11 in the matrix 10 have small particle sizes. Accordingly, wearing of the roll takes place easily. On the other hand, as shown in Fig. 3(a), when the carbide particles 11 dispersed in the roll matrix 10 have particle sizes of 3 µm or more, good wear resistance can be achieved. However, if the particle sizes of the carbide particles exceed 50 µm, severe wearing takes place unevenly at microscopic level from site to site depending on whether there are carbide particles or not.
  • Even though there are carbide particles having particle sizes of 3 µm or more, the improvement of the wear resistance cannot be expected as long as the amount of the carbide particles is too small. Accordingly, the carbide particles having particle sizes within the range of 3 µm to 50 µm should occupy 15 % or more of the matrix by an area ratio. The preferred area ratio of the carbide particles in the alloy matrix is 20-40 %.
  • With respect to the particle sizes of the carbide particles, the percentage of the number of the carbide particles having particle sizes of 3 µm or more to the number of the carbide particles having particle sizes of 0.5 µm or more should be 10 % or more. When the above percentage is less than 10 %, the wear resistance of the shell portion is deteriorated. The preferred percentage of the number of the carbide particles having particle sizes of 3 µm or more to the number of the carbide particles having particle sizes of 0.5 µm or more is 10-40 %.
  • The compound roll having the metal structure meeting the above requirements shows improved wear resistance due to the mechanism shown in Fig. 3 (a). Specifically, even when the wearing particle 9 is brought into contact with the roll surface, the particle 9 is sustained by the large carbide particles 11, preventing the particle 9 from damaging the overall metal structure. By this mechanism, the roll is well protected from wearing.
  • After the HIP treatment, the metal capsule 2 is removed by a lath. It is then subjected to a heat treatment in the pattern such as shown in Fig. 4. The desired compound roll is obtained after finish working.
  • The present invention will be described in further detail by means of the following Examples, without any intention of restricting the scope of the present invention.
  • Example 1, Comparative Example 1
  • Alloy powder having a composition shown in Table 1 was charged into a cylindrical metal capsule 2 disposed around a roll core portion 1 as shown in Fig. 2. The metal capsule 2 was evacuated through a vent 3 in an upper portion thereof while heating the overall metal capsule 2 at about 500°C, and the vent 3 was sealed to keep the inside of the metal capsule 2 at about 1.333 · 10-3 hPa (1 x 10-3 torr). After that, this metal capsule 2 was placed in an argon gas atmosphere and subjected to a HIP treatment at a temperature of 1250 °C and at a pressure of 9.81 · 103 N/cm2 (1000 atm) for 2 hours. Incidentally, the temperature at which the alloy powder started to melt was 1195 °C. Table 1
    Chemical Components of Alloy Powder (weight %)
    C Si Mn Cr Mo W V Co Fe
    2.5 0.4 0.4 4.0 5.3 8.8 6.9 8.4 Bal.
  • After the HIP treatment, the outside metal capsule 2 was removed by lathing, and the resulting sample was subject to a heat treatment in the pattern shown in Fig. 4. Thereafter, the compound roll was subjected to finish work to provide a hollow compound roll consisting of a shell portion 4 made of a sintered alloy having an outer diameter of 350 mm and a thickness of 20 mm and a roll core portion 5 having an inner diameter of 250 mm and a length of 400 mm as shown in Fig. 5. This compound roll had a shell portion 4 having a metal structure shown in Fig. 1.
  • For comparison, a HIP treatment was conducted on the same compound roll as in Example 1 at a temperature of 1170 °C, lower than the above melting-start temperature of 1195°C, for the same period of time, and the same working as above was then conducted to provide a compound roll of Comparative Example 1. The metal structure of the shell portion of the compound roll of Comparative Example 1 is shown in Fig. 9.
  • In both compound rolls, the shell portion 4 and the core portion 5 were diffusion-bonded to each other by the HIP treatment. In Figs. 1 and 9, white granular portions are carbide particles. Big differences are appreciated between the carbide particles in Fig. 1 and those in Fig. 9 in the particle size and distribution. The particle sizes and distribution of carbide particles are shown in Table 2. Table 2
    Particle Size of Carbides (µm) Area Ratio of Carbides (%)
    Av.(1) Min.(2) Max.(3) Total Amount of Carbides(4) Carbides of 3-50 µm Carbides of 3 µm or More (%)
    Example 1 5.2 0.3 18.7 30 22 32
    Comparative Example 1 1.0 0.2 2.5 30 0 0
    Note:
    (1) Average particle size.
    (2) Minimum particle size.
    (3) Maximum particle size.
    (4) Carbide particles having particle sizes of 0.5 µm or more were counted.
  • Next, the compound rolls produced by the above method were subjected to an abrasive wear test method. For this purpose, a test piece of 10 mm x 10 mm x 15 mm was machined from the shell portion of each compound roll, and subjected to a tempering treatment so that the test pieces 8 had various levels of hardness. As shown in Fig. 6, an emery paper 7 was attached to a test table 6, and the test table 6 was rotated. Each test piece 8 was pushed onto the emery paper 7 under pressure of 598.6 N/mm2 (60 kg mm2) for 3 minutes to conduct the wear test. Before and after the wear test, the weight of the test piece was measured to evaluate a weight loss by wearing. The results are shown in Fig. 7. In the figure, the straight line A denotes Example 1 and the straight line B denotes Comparative Example 1.
  • As is clear from the comparison of the straight line A with the straight line B, the weight loss of the compound roll of the present invention (Example 1) is about one-third that of the compound roll of Comparative Example 1 on the same hardness level. This means that the the compound roll of the present invention (Example 1) is about three times as wear-resistant as the compound roll of Comparative Example 1.
  • Example 2, Comparative Example 2
  • Two hollow compound rolls each having a shape as shown in Fig. 8 were produced under the same conditions as in Example 1. Each compound roll consisted of a shell portion 4 made of a sintered alloy having the same composition as in Example 1 and having an outer diameter of 400 mm and a thickness of 30 mm, and a roll core portion 5 having an inner diameter of 280 mm and a length of 500 mm. Each compound roll was formed with four round calibers each having a semi-circular cross section having a radius of 11 mm.
  • Each compound roll was used as a finish roll for rolling a steel rod. As a result, 690 tons of steel per each caliber was rolled by the compound roll of Example 2, while only 210 tons of steel per each caliber was rolled by the compound roll of Comparative Example 2. This means that the compound roll of the present invention is more than three times as wear-resistant as the compound roll of Comparative Example 2 which was subjected to a HIP treatment at a temperature lower than the melting-start temperature of the alloy powder for the shell portion.
  • As described above in detail, since the shell portion of the compound roll of the present invention is prepared by a HIP treatment at a temperature equal to or higher than the melting-start temperature of the alloy powder, the shell portion has carbide particles having large particle sizes. Therefore, the wear resistance of the compound roll of the present invention is as high as three times or more that of the conventional compound roll.

Claims (2)

  1. A wear-resistant compound roll having a shell portion produced by sintering an alloy powder comprising, by weight, 1.0 - 3.5 % of C, 0.2 - 1 % of Si, 0.2 - 1 % of Mn, 10 % or less of Cr, 3 - 15 % of W, 2 - 10 % of Mo, 1 - 15 % of V, optionally 3 - 15 % of Co, and balance Fe and inevitable impurities, said shell portion containing carbide particles having particle sizes within the range of 3 - 50 µm in a martensite or bainite matrix, and an area ratio of said carbide particles in said matrix of the sintered shell portion being 15 % or more, wherein among said carbide particles having particle sizes of 0.5 µm or more, the number of carbide particles having particle sizes of 3 µm or more is 10 % or more.
  2. A wear-resistant compound roll according to claim 1, wherein said number of carbide particles having particle sizes of 3 µm or more is 10 - 40 %.
EP19920106860 1991-04-22 1992-04-22 Wear-resistant compound roll Expired - Lifetime EP0510598B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP90280/91 1991-04-22
JP9028091 1991-04-22

Publications (3)

Publication Number Publication Date
EP0510598A2 EP0510598A2 (en) 1992-10-28
EP0510598A3 EP0510598A3 (en) 1993-07-14
EP0510598B1 true EP0510598B1 (en) 1996-07-10

Family

ID=13994109

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19920106860 Expired - Lifetime EP0510598B1 (en) 1991-04-22 1992-04-22 Wear-resistant compound roll

Country Status (2)

Country Link
EP (1) EP0510598B1 (en)
DE (1) DE69212054T2 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06182409A (en) * 1992-12-21 1994-07-05 Hitachi Metals Ltd Combined sleeve roll and its production
FR2833195B1 (en) * 2001-12-07 2004-01-30 Giat Ind Sa PROCESS FOR FITTING A PROTECTIVE COATING ON THE INTERNAL WALL OF A TUBE, TUBE AND IN PARTICULAR WEAPON TUBE PRODUCED BY THIS PROCESS
GB2492425B (en) * 2011-10-10 2013-05-15 Messier Dowty Ltd A method of forming a composite metal item
CN112547224B (en) * 2020-11-27 2022-10-11 湖北秦鸿新材料股份有限公司 Wear-resistant grinding roller

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63195250A (en) * 1987-02-10 1988-08-12 Daido Steel Co Ltd Roll for rolling mill
JPH01252704A (en) * 1988-03-31 1989-10-09 Kubota Ltd Complex member and its manufacture
US5053284A (en) * 1989-02-02 1991-10-01 Hitachi Metals, Ltd. Wear-resistant compound roll
JPH02270944A (en) * 1989-04-13 1990-11-06 Hitachi Metals Ltd Roll stock having wear resistance and resistance to surface roughness and its production

Also Published As

Publication number Publication date
DE69212054D1 (en) 1996-08-14
DE69212054T2 (en) 1996-11-07
EP0510598A3 (en) 1993-07-14
EP0510598A2 (en) 1992-10-28

Similar Documents

Publication Publication Date Title
US5106576A (en) Method of producing a wear-resistant compound roll
JP4346780B2 (en) Heat-resistant and wear-resistant composite structural member and manufacturing method thereof
JP2857724B2 (en) High speed steel based sintered alloy
EP0510598B1 (en) Wear-resistant compound roll
US5403670A (en) Compound sleeve roll and method for producing same comprising chamfered axial ends
EP3748025A1 (en) Cemented carbide and cemented carbide composite roll for rolling
JPH07179997A (en) High speed steel type powder alloy
JPH07166300A (en) High speed steel type powder alloy
JPH075934B2 (en) Composite member having excellent wear resistance, seizure resistance, and rough skin resistance, and method for manufacturing the same
JP2791445B2 (en) High speed steel based sintered alloy
JPH05148510A (en) Wear resistant composite roll and manufacture thereof
JPH1161349A (en) Roll and its manufacture
JP2796893B2 (en) High speed steel based sintered alloy
JPH07268569A (en) Wear resistant sintered alloy and rolling roll constituted thereof
JPH01252704A (en) Complex member and its manufacture
JP3032995B2 (en) High-speed steel-based sintered alloy for steel roll, roll body and manufacturing method
JP2796894B2 (en) High speed steel based sintered alloy
JPH01252703A (en) Roll for rolling shaped steel and manufacture thereof
JP2775614B2 (en) High speed steel based sintered alloy
JP3032996B2 (en) High-speed steel-based sintered alloy for steel roll, roll body and manufacturing method
JPH10280101A (en) Heat resisting and wear resisting member and its production
JP2796897B2 (en) High speed steel based sintered alloy
JP2972031B2 (en) High-speed steel-based sintered alloy for steel roll, roll body and manufacturing method
JP2964197B2 (en) High-speed steel-based sintered alloy for steel roll, roll body and manufacturing method
JPH11172364A (en) Production of sintered tool steel

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): DE FR

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): DE FR

17P Request for examination filed

Effective date: 19940110

17Q First examination report despatched

Effective date: 19940211

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE FR

REF Corresponds to:

Ref document number: 69212054

Country of ref document: DE

Date of ref document: 19960814

ET Fr: translation filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20100521

Year of fee payment: 19

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20100430

Year of fee payment: 19

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

Effective date: 20111230

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20110502

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20111101

REG Reference to a national code

Ref country code: DE

Ref legal event code: R119

Ref document number: 69212054

Country of ref document: DE

Effective date: 20111101