Cemented carbide and its production method, and rolling roll

Abstract

A cemented carbide comprising 55-90 parts by mass of WC particles, and 10-45 parts by mass of an Fe-based binder phase, the binder phase having a composition comprising 2.5-10% by mass of Ni, 0.2-1.2% by mass of C, 0.5-5% by mass of Cr, 0.2-2.0% by mass of Si, 0.1-3% by mass of W, 0-5% by mass of Co, and 0-1% by mass of Mn, the balance being substantially Fe and inevitable impurities, and the cemented carbide being substantially free from composite carbides having major axes of 5 m or more. This cemented carbide is produced by cooling at a cooling rate of 60 C./hour or more between 900 C. and 600 C., after vacuum sintering.

Claims

1. A cemented carbide comprising 55-90 parts by mass of WC particles, and 10-45 parts by mass of a binder phase containing Fe as a main component, said binder phase having a composition comprising 2.5-10% by mass of Ni, 0.2-1.2% by mass of C, 0.5-5% by mass of Cr, 0.2-2.0% by mass of Si, 0.1-3% by mass of W, 0-5% by mass of Co, and 0-1% by mass of Mn, the balance being substantially Fe and inevitable impurities; and said cemented carbide being substantially free from composite carbides having major axes of 5 m or more.

2. The cemented carbide according to claim 1, wherein said WC particles have a median diameter D50 of 2-10 m.

3. The cemented carbide according to claim 1, said inevitable impurities in said binder phase are at least one selected from the group consisting of Mo, V, Nb, Ti, Al, Cu, N and O.

4. The cemented carbide according to claim 1, wherein at least one selected from the group consisting of Mo, V and Nb in said inevitable impurities is 2% or less by mass in total.

5. The cemented carbide according to claim 4, wherein at least one selected from the group consisting of Ti, Al, Cu, N and O in said inevitable impurities is 0.5% or less by mass each and 1% or less by mass in total.

6. The cemented carbide according to claim 4, wherein a bainite phase and/or a martensite phase in said binder phase is 50% or more by area in total.

7. The cemented carbide according to claim 1, wherein said cemented carbide has compressive yield strength of 1200 MPa or more.

8. A rolling composite roll comprising an outer layer made of the cemented carbide recited in claim 1, said outer layer being metallurgically bonded to a peripheral surface of a steel sleeve or shaft.

9. A method for producing the cemented carbide recited in claim 1, comprising press-molding a mixture comprising 55-90 parts by mass of WC powder, and 10-45 parts by mass of metal powder comprising 2.5-10% by mass of Ni, 0.3-1.7% by mass of C, 0.5-5% by mass of Cr, 0.2-2.0% by mass of Si, 0-5% by mass of Co, and 0-2% by mass of Mn, the balance being Fe and inevitable impurities; vacuum-sintering the resultant green body at a temperature from its liquid phase generation start temperature to said liquid phase generation start temperature+100 C.; and then cooling the resultant sintered body at a cooling rate of 60 C./hour or more between 900 C. and 600 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a SEM photograph showing a cross section structure of the cemented carbide of Sample 2.

(2) FIG. 2 is a graph showing stress-strain curves of Samples 2 and 8 measured by a uniaxial compression test.

(3) FIG. 3 is a schematic view showing a test piece used in the uniaxial compression test.

(4) FIG. 4 is a graph showing an example of the measurements of a liquid phase generation start temperature by a differential thermal analyzer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) The embodiments of the present invention will be described in detail below, and it should be noted that explanations of one embodiment are applicable to other embodiments unless otherwise mentioned, and that the following explanations are not restrictive but may be modified within the scope of the present invention.

(6) [1] Cemented Carbide

(7) (A) Composition

(8) The cemented carbide of the present invention comprises 55-90 parts by mass of WC particles, and 10-45 parts by mass of an Fe-based binder phase.

(9) (1) WC Particles

(10) The cemented carbide of the present invention contains 55-90 parts by mass of WC particles. When the WC particles are less than 55 parts by mass, the cemented carbide exhibits too low a Young's modulus because of a relatively low percentage of hard WC particles. On the other hand, when the WC particles exceed 90 parts by mass, the cemented carbide does not have enough strength because of a relatively low percentage of the binder phase. The lower limit of the amount of WC particles is preferably 60 parts by mass, more preferably 65 parts by mass. The upper limit of the amount of WC particles is preferably 85 parts by mass.

(11) WC particles preferably have a median diameter D50 (corresponding to a particle size at a cumulative volume of 50%) of 2-10 m. When the median particle size is less than 2 m, composite carbides are likely formed because of increased boundaries between WC particles and the binder phase. On the other hand, when the median particle size is more than 10 m, the cemented carbide has low strength. The lower limit of the median diameter D50 of WC particles is preferably 4 m, more preferably 5 m, most preferably 6 m. The upper limit of the median diameter D50 of WC particles is preferably 9 m, more preferably 8 m, most preferably 7 m.

(12) Because WC particles are clustered in the cemented carbide, it is difficult to measure the particle sizes of WC particles on a photomicrograph. In the case of the cemented carbide of the present invention, a green body is sintered in vacuum at a temperature from (liquid phase generation start temperature) to (liquid phase generation start temperature+100 C.) as described below, resulting in substantially no difference in particle size between WC powder in the raw material and WC particles in the cemented carbide. Accordingly, the particle size of WC particles dispersed in the cemented carbide is expressed by the particle size of WC powder in the raw material.

(13) WC particles preferably have relatively uniform particle sizes. To this end, in a cumulative particle size distribution curve determined by a laser diffraction and scattering method, the particle size distribution of WC particles has preferably D10 (particle size at a cumulative volume of 10%) of 1-5 m, a median diameter D50 of 5-8 m, and D90 (particle size at a cumulative volume of 90%) of 8-12 m, more preferably D10 of 3-5 m, D50 of 6-7 m, and D90 of 9-10 m.

(14) (2) Binder Phase

(15) In the cemented carbide of the present invention, the binder phase has a composition comprising

(16) 2.5-10% by mass of Ni,

(17) 0.2-1.2% by mass of C,

(18) 0.5-5% by mass of Cr,

(19) 0.2-2.0% by mass of Si,

(20) 0.1-3% by mass of W,

(21) 0-5% by mass of Co, and

(22) 0-1% by mass of Mn,

(23) the balance being substantially Fe and inevitable impurities.

(24) (i) Indispensable Elements

(25) (a) Ni: 2.5-10% by Mass

(26) Ni is an element necessary for securing the hardenability of the binder phase. When Ni is less than 2.5% by mass, the binder phase has insufficient hardenability, failing to provide the cemented carbide with sufficient compressive yield strength. On the other hand, when Ni is more than 10% by mass, the binder phase is austenized, resulting in low hardenability, also failing to provide the cemented carbide with sufficient compressive yield strength. The lower limit of the Ni content is preferably 3% by mass, more preferably 4% by mass. Also, the upper limit of the Ni content is preferably 8% by mass, more preferably 7% by mass.

(27) (b) C: 0.2-1.2% by Mass

(28) C is an element necessary for securing the hardenability of the binder phase, and for preventing the formation of coarse composite carbides. When C is less than 0.2% by mass, the binder phase has too low hardenability. On the other hand, when C is more than 1.2% by mass, coarse composite carbides are formed, providing the cemented carbide with low strength. The lower limit of the C content is preferably 0.3% by mass, more preferably 0.5% by mass. Also, the upper limit of the C content is preferably 1.1% by mass, more preferably 1.0% by mass.

(29) (c) Cr: 0.5-5% by Mass

(30) Cr is an element necessary for securing the hardenability of the binder phase. When Cr is less than 0.5% by mass, the binder phase has too low hardenability, failing to provide sufficient compressive yield strength. On the other hand, when Cr is more than 5% by mass, coarse composite carbides are formed, providing the cemented carbide with low strength. Cr is preferably 4% or less by mass, more preferably 3% or less by mass.

(31) (d) Si: 0.2-2.0% by Mass

(32) Si is an element necessary for strengthening the binder phase. When Si is less than 0.2% by mass, the binder phase is not sufficiently strengthened. On the other hand, when Si, a graphitizing element, is more than 2.0% by mass, graphite is likely precipitated, lowering the strength of the cemented carbide. The lower limit of the Si content is preferably 0.3% by mass, more preferably 0.5% by mass. Also, the upper limit of the Si content is preferably 1.9% by mass.

(33) (e) W: 0.1-3% by Mass

(34) W dissolved from WC particles into the binder phase by sintering is contained at a percentage of 0.1-3% by mass in the binder phase. When the W content in the binder phase is more than 3% by mass, coarse composite carbides are formed, providing the cemented carbide with low strength. The lower limit of the W content is preferably 0.8% by mass, more preferably 1.2% by mass.

(35) Also, the upper limit of the W content is preferably 2.5% by mass.

(36) (ii) Optional Elements

(37) (a) Co: 0-5% by Mass

(38) Co has a function of improving sinterability, but it is not indispensable for the cemented carbide of the present invention. The Co content is preferably substantially 0% by mass, but 5% or less by mass of Co would not adversely affect the structure and strength of the cemented carbide of the present invention. The upper limit of the Co content is more preferably 2% by mass, most preferably 1% by mass.

(39) (b) Mn: 0-1% by Mass

(40) Mn has a function of improving hardenability, but it is not indispensable for the cemented carbide of the present invention. The Mn content is preferably substantially 0% by mass, but 1% or less by mass of Mn would not adversely affect the structure and strength of the cemented carbide of the present invention. The upper limit of the Mn content is more preferably 0.5% by mass, most preferably 0.3% by mass.

(41) (iii) Inevitable Impurities

(42) Inevitable impurities include Mo, V, Nb, Ti, Al, Cu, N, 0, etc.

(43) Among them, at least one selected from the group consisting of Mo, V and Nb is preferably 2% or less by mass in total. The amount of at least one selected from the group consisting of Mo, V and Nb is more preferably 1% or less by mass, most preferably 0.5% or less by mass in total. Also, the amount of at least one selected from the group consisting of Ti, Al, Cu, N and O is preferably 0.5% or less by mass each and 1% or less by mass in total. Particularly, each of N and O is preferably less than 1000 ppm. As long as the amounts of inevitable impurities are within the above ranges, the structure and strength of the cemented carbide of the present invention are not substantially affected.

(44) (B) Structure

(45) (1) Composite Carbides

(46) The cemented carbide of the present invention has a structure substantially free from composite carbides having major axes of 5 m or more.

(47) The composite carbides are those composed of W and metal elements, for example, (W, Fe, Cr).sub.23C.sub.6, (W, Fe, Cr).sub.3C, (W, Fe, Cr).sub.2C, (W, Fe, Cr).sub.7C.sub.3, (W, Fe, Cr).sub.6C, etc. The cemented carbide of the present invention is preferably substantially free from composite carbides having major axes of 5 m or more. The major axis of each composite carbide is the maximum length (length of the longest straight line among those connecting two points on a periphery) of each composite carbide on a photomicrograph (magnification: 1000) of a polished cross section of the cemented carbide. The cemented carbide free from composite carbides having major axes of 5 m or more in the binder phase has bending strength of 1700 MPa or more. The term substantially free from composite carbides means that composite carbides having major axes of 5 m or more are not observed on a SEM photograph (magnification: 1000). Less than about 5% by area of composite carbides having major axes of less than 5 m may exist in the cemented carbide of the present invention, when analyzed by EPMA.

(48) (2) Bainite Phase and/or Martensite Phase

(49) The binder phase in the cemented carbide of the present invention preferably has a structure comprising 50% or more by area in total of a bainite phase and/or a martensite phase. The term bainite phase and/or martensite phase is used because the bainite phase and the martensite phase have substantially the same function, and are difficult to be distinguished from each other on a photomicrograph. With such structure, the cemented carbide of the present invention has high compressive yield strength and mechanical strength.

(50) Because the binder phase contains 50% or more by area in total of a bainite phase and/or a martensite phase, the cemented carbide of the present invention has compressive yield strength of 1200 MPa or more. The total amount of a bainite phase and/or a martensite phase is preferably 70% or more by area, more preferably 80% or more by area, most preferably substantially 100% by area. Other phases than the bainite phase and the martensite phase are a pearlite phase, an austenite phase, etc.

(51) (3) Diffusion of Fe into WC Particles

(52) EPMA analysis has revealed that in the sintered cemented carbide, 0.3-0.7% by mass of Fe exists in WC particles.

(53) (C) Properties

(54) Because the cemented carbide of the present invention having the above composition and structure has compressive yield strength of 1200 MPa or more and bending strength of 1700 MPa or more, a rolling roll having an outer layer made of the cemented carbide of the present invention does not suffer dents by compressive yield on the rolling surface, when used in the cold rolling of a metal strip (steel strip). Accordingly, the high-quality rolling of a metal strip can be continuously conducted, with a long life of the rolling roll. Of course, the cemented carbide of the present invention can be used for rolls for hot-rolling a metal strip.

(55) The compressive yield strength is a yield stress in a uniaxial compression test, in which a test piece shown in FIG. 3 receives an axial load. Namely, in a stress-strain curve of the uniaxial compression test as shown in FIG. 2, a stress at a point at which stress and strain deviate from a straight-line relation is defined as the compressive yield strength.

(56) In the cemented carbide of the present invention, the compressive yield strength is more preferably 1500 MPa or more, most preferably 1600 MPa or more, and the bending strength is more preferably 2000 MPa or more, most preferably 2300 MPa or more.

(57) The cemented carbide of the present invention further has a Young's modulus of 385 GPa or more and Rockwell hardness of 80 HRA or more. The Young's modulus is preferably 400 GPa or more, more preferably 450 GPa or more, and the Rockwell hardness is preferably 82 HRA or more.

(58) [2] Production Method of Cemented Carbide

(59) (A) Raw Material Powder

(60) 55-90 parts by mass of WC powder was wet-mixed with 10-45 parts by mass of metal powder comprising 2.5-10% by mass of Ni, 0.3-1.7% by mass of C, 0.5-5% by mass of Cr, 0.2-2.0% by mass of Si, 0-5% by mass of Co, and 0-2% by mass of Mn, the balance being Fe and inevitable impurities, in a ball mill, etc., to prepare a raw material powder. Because W is diffused from WC powder into the binder phase during sintering, W need not be contained in the raw material powder. The WC powder content is preferably 60-90 parts by mass, more preferably 65-90 parts by mass. The upper limit of the WC powder content is preferably 85 parts by mass. To prevent the formation of composite carbides, the C content in the raw material powder is 0.3-1.7% by mass, preferably 0.5-1.5% by mass.

(61) The metal powder for forming the binder phase may be a mixture of constituent element powders, or an alloyed powder of all constituent elements. Carbon may be in a powder form such as graphite, carbon black, etc., or may be added to powder of each metal or alloy. Cr may be added in the form of an alloy with Si (for example, CrSi.sub.2). The median diameter D50 of powder of each metal or alloy, for example, Fe powder, Ni powder, Co powder, Mn powder, and CrSi.sub.2 powder, is preferably 1-10 m.

(62) (B) Press-Molding

(63) The raw material powder is dried, and then press-molded to a green body having a desired shape by a method such as die press molding, cold-isostatic pressing (CIP), etc.

(64) (C) Sintering

(65) The green body is sintered at a temperature from (liquid phase generation start temperature) to (liquid phase generation start temperature+100 C.) in vacuum. The liquid phase generation start temperature of the green body is a temperature at which a liquid phase starts to be generated during temperature elevation in the sintering step, measured by a differential thermal analyzer. FIG. 4 shows an example of the measurement results. As shown by the arrow in FIG. 4, the liquid phase generation start temperature of the green body is a temperature at which an endothermic reaction starts. Sintering at a temperature exceeding the liquid phase generation start temperature+100 C. generates coarse composite carbides, providing the resultant cemented carbide with low strength. On the other hand, sintering at a temperature lower than the liquid phase generation start temperature leads to insufficient densification, providing the resultant cemented carbide with low strength. The lower limit of the sintering temperature is preferably the liquid phase generation start temperature+10 C., and the upper limit of the sintering temperature is preferably the liquid phase generation start temperature+90 C., more preferably the liquid phase generation start temperature+80 C. The resultant sintered body is preferably subjected to HIP.

(66) (D) Cooling

(67) The sintered body is cooled at an average cooling rate of 60 C./hour or more between 900 C. and 600 C. Cooling at an average cooling rate of less than 60 C./hour increases the percentage of a pearlite phase in the binder phase of the cemented carbide, failing to obtain 50% or more in total by area of a bainite phase and/or a martensite phase, thereby providing the cemented carbide with low compressive yield strength. The sintered body can be cooled at an average cooling rate of 60 C./hour or more in the sintering furnace; or cooled in the sintering furnace, heated again to 900 C. or higher, and then cooled at an average cooling rate of 60 C./hour or more. In the case of conducting HIP, the above cooling may be conducted in a cooling step in the HIP furnace.

(68) [3] Applications

(69) The cemented carbide of the present invention is preferably used for an outer layer metallurgically bonded to a tough steel sleeve or shaft of a rolling composite roll. Because this outer layer of the rolling composite roll has high compressive yield strength, bending strength, Young's modulus and hardness, it is particularly suitable for the cold rolling of a metal strip (steel strip). The rolling composite roll of the present invention is preferably used as a work roll, in (a) a 6-high rolling mill comprising a pair of upper and lower work rolls for rolling a metal strip, a pair of upper and lower intermediate rolls for supporting the work rolls, and a pair of upper and lower backup rolls for supporting the intermediate rolls, or (b) a 4-high rolling mill comprising a pair of upper and lower work rolls for rolling a metal strip, and a pair of upper and lower backup rolls for supporting the work rolls. At least one stand of the above mill is preferably used in a tandem rolling mill comprising pluralities of rolling mill stands.

(70) In addition, the cemented carbide of the present invention is widely used for wear-resistant tools, corrosion-resistant, wear-resistant parts, dies, etc., in which conventional cemented carbides are used.

(71) The present invention will be explained in further detail by Examples below, without intention of restriction.

Example 1

(72) WC powder having purity of 99.9%, and a median diameter D50 of 6.4 m, D10 of 4.3 m, D50 of 6.4 m, and D90 of 9.0 m measured by a laser diffraction particle size analyzer (SALD-2200 available from Shimadzu Corporation) was mixed with a binder phase powder formulated to the composition shown in Table 1 at a ratio shown in Table 2, to prepare mixture powders (Samples 1-10). Each binder phase powder had a median diameter D50 of 1-10 m, containing trace amounts of inevitable impurities.

(73) Each mixture powder was wet-mixed for 20 hours in a ball mill, dried, and press-molded at pressure of 98 MPa to obtain cylindrical green bodies (Samples 1-10) of 60 mm in diameter and 40 mm in height. A sample of 1 mm1 mm2 mm was cut out of each green body, to measure its liquid phase generation start temperature by a differential thermal analyzer. The results are shown in Table 3.

(74) TABLE-US-00001 TABLE 1 Sample Composition of Binder Phase Powder (% by mass) No. Si Mn Ni Cr Mo V C Co Fe.sup.(1) 1 0.80 5.02 1.21 1.29 Bal. 2 0.80 5.02 1.21 1.29 Bal. 3 0.81 5.05 1.21 0.79 Bal. 4 1.61 5.02 2.41 1.27 Bal. 5 0.80 5.02 4.02 1.26 Bal. 6 0.80 2.61 3.52 1.29 Bal. 7* 0.92 0.45 0.17 5.13 1.31 0.88 0.71 Bal. 8* 5.43 1.30 Bal. 9* 0.80 5.00 2.40 1.77 Bal. 10* 31.13 6.67 Bal. Note: *Comparative Example. .sup.(1)Bal. includes inevitable impurities.

(75) TABLE-US-00002 TABLE 2 WC Powder Binder Phase Powder Sample No. (parts by mass) (parts by mass) 1 80 20 2 70 30 3 70 30 4 70 30 5 70 30 6 70 30 7* 70 30 8* 70 30 9* 70 30 10* 85 15 Note: *Comparative Example.

(76) TABLE-US-00003 TABLE 3 Liquid Phase Generation Start Sample No. Temperature 1 1210 C. 2 1210 C. 3 1230 C. 4 1210 C. 5 1210 C. 6 1210 C. 7* 1160 C. 8* 1220 C. 9* 1200 C. 10* 1310 C. Note: *Comparative Example.

(77) The green bodies were vacuum-sintered under the conditions shown in Table 4, and subjected to HIP under the conditions shown in Table 4 to produce cemented carbides [Samples 1-6 (the present invention), and Samples 7-10 (Comparative Examples)]. Each cemented carbide was elevated by the following method.

(78) TABLE-US-00004 TABLE 4 Cooling Vacuum Sintering HIP Average Sintering Holding Holding Cooling Sample Temperature Time Temperature Time Rate.sup.(1) No. ( C.) (hour) ( C.) (hour) ( C./hour) 1 1260 2 1230 2 100 2 1260 2 1230 2 100 3 1280 2 1230 2 100 4 1260 2 1230 2 100 5 1260 2 1230 2 100 6 1260 2 1230 2 100 7* 1350 2 1230 2 100 8* 1330 2 1230 2 100 9* 1260 2 1230 2 100 10* 1400 2 1350 2 100 Note: *Comparative Example. .sup.(1)Average cooling rate between 900 C. and 600 C.

(79) (1) Compressive Yield Strength

(80) With a strain gauge attached to a surface of a center portion of each compression test piece shown in FIG. 3, which was cut out of each cemented carbide, an axial load was applied to the test piece to generate a stress-strain curve. In the stress-strain curve, stress at a point at which stress and strain deviated from a straight-line relation was regarded as compressive yield strength. The results are shown in Table 5.

(81) (2) Bending Strength

(82) A test piece of 4 mm3 mm40 mm was cut out of each cemented carbide, and measured with respect to bending strength under a four-point bending test conditions with a fulcrum distance of 30 mm. The results are shown in Table 5.

(83) (3) Young's Modulus

(84) A test piece of 10 mm in width, 60 mm in length and 1.5 mm in thickness was cut out of each cemented carbide, and measured by a free-resonance, intrinsic vibration method (JIS Z2280). The results are shown in Table 5.

(85) (4) Hardness

(86) Each cemented carbide was measured with respect to Rockwell hardness (A scale). The results are shown in Table 5.

(87) TABLE-US-00005 TABLE 5 Compressive Bending Young's Yield Strength Strength Modulus Hardness Sample No. (MPa) (MPa) (GPa) (HRA) 1 1780 2574 534 86.1 2 1800 2714 496 84.4 3 1550 2490 496 84.2 4 1720 2126 496 84.3 5 1700 1766 496 82.6 6 2000 2019 496 85.1 7* 2200 1470 494 85.1 8* 300 1786 496 79.4 9* 1680 1430 496 84.2 10* 400 2580 535 84.2 Note: *Comparative Example.

(88) (5) Observation of Structure

(89) Each sample was mirror-polished, and then observed by SEM to determine the presence or absence of composite carbides, and the total area ratio of a bainite phase and a martensite phase in the binder phase. The results are shown in Table 6. FIG. 1 is a SEM photograph of the cemented carbide of Sample 2. White particles are WC particles, and gray portions are a binder phase.

(90) TABLE-US-00006 TABLE 6 Bainite Phase and/or Composite Sample No. Martensite Phase.sup.(1) Carbides.sup.(2) 1 50% or more by area No 2 50% or more by area No 3 50% or more by area No 4 50% or more by area No 5 50% or more by area No 6 50% or more by area No 7* 50% or more by area Yes 8* Less than 50% by area No 9* 50% or more by area Yes 10* Note Evaluated No Note: *Comparative Example. .sup.(1)The total area ratio (%) of a bainite phase and a martensite phase in the binder phase. .sup.(2)The presence or absence of composite carbides having diameters of 5 m or more in the binder phase.

(91) (6) Composition of Binder Phase

(92) The composition of the binder phase of each sample was measured by a field-emission electron probe microanalyzer (FE-EPMA). Point analysis with a beam diameter of 1 m was conducted at 10 arbitrary points in other portions than WC particles, and the measured values were averaged to determine the composition of the binder phase. When composite carbides having diameters of 5 m or more existed, other portions than the WC particles and the composite carbides were measured. The results are shown in Table 7.

(93) TABLE-US-00007 TABLE 7 Sample Composition of Binder Phase (% by mass).sup.(1) No. Si Mn Ni Cr W Mo V C Co Fe.sup.(2) 1 0.91 4.92 0.89 1.60 0.81 Bal. 2 0.93 4.89 0.94 1.63 0.83 Bal. 3 0.84 4.82 0.94 2.29 0.69 Bal. 4 1.84 4.84 1.75 1.47 0.74 Bal. 5 0.90 4.92 3.39 1.65 0.88 Bal. 6 0.84 2.60 2.82 1.70 0.88 Bal. 7* 0.70 0.24 0.19 4.03 1.48 0.17 0.14 0.70 Bal. 8* 4.83 1.15 0.31 Bal. 9* 0.97 5.10 0.70 1.11 0.88 Bal. 10* 31.27 6.53 Bal. Note: *Comparative Example. .sup.(1)Analyzed value. .sup.(2)Bal. includes inevitable impurities.

Example 2

(94) Using a raw material powder having the same composition as that of Sample 1 in Example 1, a cylindrical green body was produced by the same method as in Example 1. Each green body was sintered in the same manner as in Example 1, to produce an integral roll of 44 mm in outer diameter and 620 mm in length. When this roll was used for the cold rolling of a 0.6-mm-thick, pure-Ni strip, defects due to dents on the rolling surface were not generated on the pure-Ni strip.

(95) Using a raw material powder having the same composition as that of Sample 10 (Comparative Example) in Example 1, an integral roll of 44 mm in outer diameter and 620 mm in length was similarly produced. When this roll was used for the rolling of a 0.6-mm-thick, pure-Ni strip, defects due to dents on the rolling surface were generated on the pure-Ni strip.