JP6587204B2 - Cemented carbide composite roll and manufacturing method thereof - Google Patents

Description

  The present invention comprises an outer layer excellent in wear resistance, rough skin resistance and the like and an inner layer excellent in toughness, and is a highly durable cemented carbide composite roll suitable for rolling steel materials such as plate materials, wire rods, bar materials, And a manufacturing method thereof.

  Made of tungsten carbide (WC) cemented carbide with excellent wear resistance, rough skin resistance, etc., to meet the demands for higher quality of rolled materials, such as improved dimensional accuracy, and improved productivity by reducing the number of roll change man-hours. Rolls for rolling are used, and cemented carbide rolling rolls having various structures have been proposed.

For example, as shown in FIG. 8, Japanese Patent Laid-Open No. 3-281007 (Patent Document 1) discloses a roll main body 105 provided with a fastening flange portion 103 fixed at both ends and a detachable fastening flange portion 104, as shown in FIG. Fitted to the roll body 105 via metal ring spacers 111 and 111 and a cylindrical spacer 114 having an expansion coefficient of 15 × 10 ^-6 / ° C or higher and a thermal conductivity of 0.4 cal / cm · sec · ° C or higher. A cemented carbide rolling roll comprising a cemented carbide cylinder 110 is proposed. The tightening force of the tightening flange portions 103 and 104 is improved by utilizing the thermal expansion of the ring spacers 111 and 111. However, even with the ring-shaped spacers 111 and 111 and the cylindrical spacer 114, the adhesion between the cemented carbide cylinder 110 and the roll body 105 is not sufficient with the tightening force by the tightening flange portions 103 and 104. In addition, the cemented carbide cylindrical body 110 may slip with respect to the roll body 105 during rolling.

  In order to solve the problems of the cemented carbide roll of such an assembly type structure, a cemented carbide composite roll in which a cemented carbide outer layer and a metal inner layer are diffusion-bonded has been proposed. For example, Japanese Patent Laid-Open No. 2001-47111 (Patent Document 2) discloses a cemented carbide composite roll in which an outer layer member made of a WC-based cemented carbide is metal-bonded to the outer periphery of an inner layer member made of a material having excellent toughness. A cemented carbide composite roll has been proposed in which a WC cemented carbide intermediate layer having a smaller content of WC particles than the outer layer is provided on the inner side, and the inner layer member and the intermediate layer are joined via a metal layer. In Patent Document 2, the intermediate layer has an inclined WC composition from the outer layer member to the inner layer member, thereby changing the physical property values such as the coefficient of thermal expansion and the elastic coefficient continuously from the outer layer member to the inner layer member. It describes that the strength of the joint is improved.

  However, the cemented carbide composite roll described in Patent Document 2, in which a cemented carbide outer layer excellent in wear resistance and an iron-based alloy inner layer are joined via an intermediate layer, has an outer diameter of 300 mm or more and a roll length. It has been found that the bonding reliability of the outer layer and the inner layer may not be sufficient for increasing the size of a hot sheet rolling roll of 500 mm or more. Further, when used in more severe rolling conditions, higher bonding strength between the outer layer and the inner layer is required. Further, in the production, a process for forming an intermediate layer is required, which takes time and increases the production cost.

JP-A-3-281007 JP 2001-47111 A

  Accordingly, the object of the present invention is to provide a super-hard alloy outer layer excellent in wear resistance, rough skin resistance, etc. and an iron-based alloy inner layer excellent in toughness, which are directly joined without an intermediate layer difficult to construct. It is a hard alloy composite roll, which is to provide a cemented carbide composite roll having a very high bonding strength between them and an efficient manufacturing method thereof.

  As a result of diligent research in view of the above-mentioned purpose, as a result of diligent research on the composition of the iron-based alloy inner layer that is directly diffusion-bonded to the cemented carbide outer layer, it was found that a cemented carbide composite roll with extremely high bonding strength was obtained I came up with the invention.

  That is, the cemented carbide composite roll of the present invention is obtained by diffusion bonding a cemented carbide outer layer and an iron-based alloy inner layer, the inner layer is 0.65-1.2 mass% C, 1.8-7.5 mass% Ni, It is made of an iron-based alloy containing 0.01 to 3% by mass of Cr and 0.01 to 1.5% by mass of Mo.

  The inner layer preferably further contains 0.1 to 2.0% by mass of Si and 0.1 to 0.9% by mass of Mn.

  The tensile strength at the boundary between the outer layer and the inner layer is preferably 600 MPa or more. The fatigue strength at the boundary between the outer layer and the inner layer is preferably 200 MPa or more.

  The cemented carbide outer layer preferably contains 70 to 88% by mass of WC particles.

  The method of the present invention for producing a cemented carbide composite roll in which a cylindrical outer layer member made of cemented carbide and an inner layer member made of an iron-based alloy are diffusion-bonded comprises 0.65 to 1.2% by mass of C and 1.8 to 7.5% by mass. The inner surface of the outer layer member is diffusion-bonded to the outer surface of the inner layer member containing Ni, 0.01 to 3% by mass of Cr, and 0.01 to 1.5% by mass of Mo.

The method for producing the cemented carbide composite roll of the present invention comprises:
After the cylindrical outer layer member is disposed so as to surround the inner layer member, a cylindrical restraining member having a thermal expansion coefficient smaller than that of the outer layer member is disposed so as to surround the outer layer member. A step of diffusion bonding the outer layer member;
In the step, the outer surface of the inner layer member having the largest coefficient of thermal expansion presses the inner surface of the outer layer member, and the inner surface of the restraining member having the smallest coefficient of thermal expansion presses the outer surface of the outer layer member. A gap between each of the inner layer member, the outer layer member, and the restraining member is set.

  It is preferable that both axial ends of the restraining member protrude from both axial end surfaces of the outer layer member.

  The constraining member is preferably thicker than the outer layer member.

  The restraining member is preferably made of graphite or ceramics.

  The restraining member is preferably formed by coaxially stacking a plurality of ring members.

  It is preferable to interpose a reaction preventing material between the restraining member and the outer layer member.

  In the cemented carbide composite roll of the present invention, the cemented carbide outer layer comprises 0.65 to 1.2 mass% C, 1.8 to 7.5 mass% Ni, 0.01 to 3 mass% Cr, and 0.01 to 1.5 mass% Mo. Since it is directly diffusion-bonded without an intermediate layer and an iron-based alloy inner layer made of an iron-based alloy contained, the fragile η phase described later is not generated in the cemented carbide of the bonding boundary, and the outer layer and The inner layer has high bonding strength. Therefore, even a large rolling roll having an outer diameter of 300 mm or more and a roll length of 500 mm or more can be used for long-term rolling. Further, the process of forming the intermediate layer is unnecessary, and the manufacturing cost can be reduced accordingly.

It is a fragmentary sectional front view which shows the cemented carbide composite roll of this invention. It is sectional drawing which shows the example which manufactures the cemented carbide composite roll of this invention by the diffusion bonding method. FIG. 3 is an enlarged view of a portion A in FIG. It is sectional drawing which shows the diffusion bonding method using the constraining member comprised by the some ring member piled up coaxially. It is sectional drawing which shows the example which manufactures the cemented carbide composite roll of this invention by HIP method. 3 is a cross-sectional view showing a joining experiment in Examples 1 and 2. FIG. 3 is a front view showing a tensile test piece of Example 2. FIG. FIG. 3 is a partial cross-sectional view showing a cemented carbide rolling roll disclosed in Japanese Patent Laid-Open No. 3-281007.

  The present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to these, and can be appropriately changed or improved without departing from the technical idea of the present invention. The description relating to one embodiment of the present invention also applies to other embodiments unless otherwise specified.

[1] Cemented carbide composite roll A cemented carbide composite roll 10 of the present invention that can be used for rolling a rolled material such as steel is composed of a cemented carbide outer layer 1 and a ferrous alloy as shown in FIG. The alloy inner layer 2 is joined. The outer layer 1 whose surface is in contact with the material to be rolled is required to have excellent wear resistance, rough skin resistance and mechanical strength, and the inner layer 2 constituting the roll shaft whose both ends are supported by bearings (not shown) is a high machine. Strength and toughness are required.

(1) Outer layerThe cemented carbide outer layer 1 of the cemented carbide composite roll of the present invention is a sintered alloy in which hard WC particles are bonded with a metal such as Co, Ni, Cr, Fe, etc. Carbides such as Ta and Nb may be contained. In order for the outer layer 1 to have high wear resistance, rough skin resistance and mechanical strength, the average particle size of WC particles is preferably 3 to 10 μm, and the content of WC particles is preferably 70 to 88% by mass, and 72 to 85%. The mass% is more preferable. The thickness of the outer layer 1 is preferably set in the range of 5 to 50 mm in consideration of gradual wear due to rolling.

(2) Inner layer The inner layer 2 to be joined with the cemented carbide outer layer 1 contains 0.65 to 1.2% by mass of C, 1.8 to 7.5% by mass of Ni, 0.01 to 3% by mass of Cr, and 0.01 to 1.5% by mass of Mo. Formed of an iron-based alloy. When joining the outer layer 1 made of cemented carbide and the inner layer 2 made of iron alloy, carbon diffuses from the outer layer 1 made of cemented carbide to the inner layer 2 at the joining interface due to the difference in carbon activity between the two layers. It is known that the carbon in 1 falls. As a result, a η phase, which is a carbide having a low carbon composition, is generated in the cemented carbide and the mechanical strength of the cemented carbide is deteriorated.

  As a result of the joining experiment between the outer layer 1 made of cemented carbide and the inner layer 2 made of iron alloy, if the carbon content of the inner layer 2 is 0.65% by mass or more, the diffusion of C from the outer layer 1 made of cemented carbide to the inner layer 2 is substantially reduced. It has been found that it is possible to suppress the occurrence of the η phase. On the other hand, if the carbon content of the inner layer 2 exceeds 1.2% by mass, graphite is generated at the boundary between the outer layer 1 and the inner layer 2 and the bonding strength is reduced. The lower limit of the carbon content of the inner layer 2 is preferably 0.7% by mass, and more preferably 0.75% by mass. Further, the upper limit of the carbon content of the inner layer 2 is more preferably 1.0% by mass.

  It was found that when the inner layer 2 contains 1.8 to 7.5% by mass of Ni, the internal stress remaining in the inner layer 2 after bonding can be controlled, and the strength of the inner layer 2 itself can be secured. If the Ni content is less than 1.8% by mass, the residual stress of the inner layer 2 may be too high. On the other hand, if the Ni content exceeds 7.5% by mass, the strength of the inner layer 2 becomes too low, and the tensile strength at the joint boundary between the outer layer 1 and the inner layer 2 cannot be made 600 MPa or more. The lower limit of the Ni content of the inner layer 2 is preferably 1.9% by mass, more preferably 2% by mass. Further, the upper limit of the Ni content of the inner layer 2 is preferably 6% by mass, and more preferably 5% by mass.

  The inner layer 2 contains 0.01 to 3% by mass of Cr and 0.01 to 1.5% by mass of Mo. Cr has the effect of increasing strength without impairing toughness. If Cr is less than 0.01% by mass, the effect is small. If the Cr content exceeds 3% by mass, the hardness of the inner layer 2 may become too high and become brittle. The lower limit of the Cr content is preferably 0.03% by mass. The upper limit of the Cr content is more preferably 2% by mass, and most preferably 1.2% by mass. Mo also has the effect of increasing strength without impairing toughness. If Mo is less than 0.01% by mass, the effect is small. If it contains more than 1.5% by mass of Mo, the hardness of the inner layer 2 may become too high and become brittle like Cr. The lower limit of the Mo content is preferably 0.03% by mass. The upper limit of the Mo content is more preferably 1% by mass.

  As described above, by using the inner layer 2 made of an iron-based alloy containing 0.65 to 1.2 mass% C, 1.8 to 7.5 mass% Ni, 0.01 to 3 mass% Cr and 0.01 to 1.5 mass% Mo, The cemented carbide outer layer and inner layer can be directly joined without an intermediate layer, and the outer diameter is 300 mm or more and the overall length is 500 mm or more. Can have.

  The inner layer 2 preferably further contains 0.1 to 2% by mass of Si and 0.1 to 0.9% by mass of Mn. Since Si has a deoxidizing effect and enhances quenching curability, it is preferably 0.1% by mass or more, but if it exceeds 2% by mass, the toughness may be deteriorated. Similarly, Mn also has a deoxidizing effect and increases quenching curability, so 0.1% by mass or more is preferable, but if it exceeds 0.9% by mass, the toughness may be deteriorated. The inner layer 2 may contain V, Nb, Co, W, Cu, etc. as inevitable impurities.

  The tensile strength at the boundary between the outer layer 1 and the inner layer 2 is preferably 600 MPa or more, and more preferably 700 MPa or more so that the outer layer 1 and the inner layer 2 do not peel even when used for a long time for rolling. The tensile strength at the boundary between the outer layer 1 and the inner layer 2 can be measured by a tensile test of a test piece including the boundary between the outer layer 1 and the inner layer 2. Further, in order to prevent the outer layer 1 and the inner layer 2 from peeling after bonding, the fatigue strength (attraction fatigue strength) at the boundary between the outer layer 1 and the inner layer 2 is preferably 200 MPa or more, more preferably 250 MPa or more. .

[2] Manufacturing method of cemented carbide composite roll The cemented carbide roll of the present invention has a structure in which the outer layer 1 and the inner layer 2 are joined, so that the interface between the outer layer 1 and the inner layer 2 is joined without a gap. good. A diffusion bonding method or a hot isostatic pressure (HIP) method can be used for such bonding.

(1) Diffusion Bonding Method As shown in FIG. 2, the inner layer member 12 is placed on the base 8. After the cylindrical cradle 9 is placed on the base 8 so as to surround the inner layer member 12, the cylindrical outer layer member 11 is placed on the cylindrical cradle 9. Next, the cylindrical restraining member 16 having a smaller coefficient of thermal expansion than the outer layer member 11 is placed on the base 8 so as to surround the outer layer member 11.

The outer layer member 11, the inner layer member 12, and the restraining member 16 arranged in this way are heated in an inert atmosphere, and diffusion bonding of the outer layer member 11 and the inner layer member 12 is performed. The diffusion bonding temperature is preferably 1000 to 1320 ° C. If the diffusion bonding temperature is less than 1000 ° C, the surface pressure between the outer layer member 11 and the inner layer member 12 may be insufficient and sufficient bonding strength may not be obtained, and if the diffusion bonding temperature exceeds 1320 ° C, The cemented carbide outer layer member 11 may melt. The diffusion bonding temperature is more preferably 1100 to 1300 ° C, and most preferably 1200 to 1260 ° C. The time for maintaining the diffusion bonding temperature may be about 1 to 120 minutes. As the inert atmosphere, an inert gas such as N ₂ or Ar, a reducing gas such as H ₂ , or a vacuum can be used.

In the temperature range from room temperature to the diffusion bonding temperature of 1000 to 1320 ° C., the coefficient of thermal expansion must satisfy the relationship of inner layer member 12> outer layer member 11> restraining member 16. The thermal expansion coefficient of the iron-based alloy inner layer member 12 in the range from room temperature to a temperature of 1000 to 1320 ° C. is about 11 to 15 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the cemented carbide outer layer member 11 is 6 ˜10 × 10 ⁻⁶ / ° C., and the coefficient of thermal expansion of the restraining member 16 is sufficiently smaller than these. The material satisfying such a thermal expansion coefficient is preferably graphite or ceramic having a thermal expansion coefficient of about 4 to 9 × 10 ⁻⁶ / ° C. Graphite or ceramics has high strength and rigidity at a diffusion bonding temperature of 1000 to 1320 ° C., and does not bond with cemented carbide. Among them, isotropic graphite having a thermal expansion coefficient of 6 × 10 ⁻⁶ / ° C. or less and a bending strength at 1000 ° C. of 30 MPa or more is particularly preferable.

In consideration of such a difference in coefficient of thermal expansion, the outer surface of the inner layer member 12 that is most thermally expanded by heating sufficiently presses the inner surface of the outer layer member 11, and the inner surface of the restraining member 16 that is least thermally expanded is the outer layer member 11. the outer surface so as to sufficiently push the, it is necessary to set the gap G ₂ between the outer member 11 and the restraining member 16 [see FIG. 3]. For example, a steel inner layer member 12 (thermal expansion coefficient: 13 × 10 ⁻⁶ / ° C.), a cemented carbide outer layer member 11 (thermal expansion coefficient: 7.5 × 10 ⁻⁶ / ° C.), a graphite constraining member 16 (heat In the case of manufacturing a roll having an inner diameter of the cemented carbide outer layer member 11 of 300 mm and an outer diameter of about 350 mm using an expansion coefficient of 5 × 10 ⁻⁶ / ° C., the outer layer member 11 and the inner layer member 12 is preferably a gap G ₁ is 1.0 to 2.0 mm, the gap G ₂ between the outer member 11 and the restraining member 16 is preferably 1.3 to 2.0 mm.

  As described above, the restraint member 16 having a smaller coefficient of thermal expansion than the outer layer member 11 is disposed outside the outer layer member 11, and the thermal expansion of the outer layer member 11 and the inner layer member 12 is restrained by the restraint member 16, so that the inner layer that is most thermally expanded. The outer surface of the member 12 is in close contact with the inner surface of the outer layer member 11 with a surface pressure (bonding surface pressure) necessary for diffusion bonding. As a result, a cemented carbide composite roll having good bonding reliability can be obtained even when the outer diameter is 300 mm or more and the roll length is 500 mm or more.

As shown in FIG. 2, the total length L ₃ is preferably longer than the total length L ₁ of the outer member 11, also the axial end surfaces 1a of the axial end surfaces 6a, 6b is the outer layer member 11 of the restraining member 16 of the restraining member 16 , It preferably projects by a length D from 1b. As a result, the outer layer member 11 can be uniformly restrained between both ends in the axial direction, so that the outer layer member 11 is uniformly diffusion bonded to the inner layer member 12 over the entire length L ₁ of the outer layer member 11. For example, the full length L ₂ of the inner layer member 12 is 600 mm, if the overall length L ₁ of the outer member 11 is 500 mm, D is preferably 10 to 100 mm.

Since the restraining member 16 must sufficiently restrain the outer layer member 11 at the diffusion bonding temperature, the restraining member 16 is preferably thicker than the outer layer member 11. For example, a diameter T ₂ of the inner layer member 12 is 320 mm, when the thickness T ₁ of the outer member 11 is 27 mm, the thickness T ₃ of the restraining member 16 is preferably 100 to 150 mm.

  As shown in FIG. 4, the restraining member 16 can be configured by stacking a plurality (six in the illustrated example) of relatively short ring members 61 to 66 coaxially in the axial direction. Since the thermal expansion restraining force of the restraining member 16 acts in the radial direction, even if the ring members 61 to 66 separated in the axial direction are used, the thermal expansion restraining effect is the same. Of course, each of the ring members 61 to 66 is preferably made of graphite or ceramics. When manufacturing a cemented carbide composite roll having a length of 500 mm or more, it is preferable to use the ring members 61 to 66 from the viewpoint of ease of manufacturing.

  It is preferable to interpose a reaction preventing material between the restraining member 16 and the outer layer member 11 so that the reaction does not occur even when contacting the outer layer member 11 at the diffusion bonding temperature. As the reaction preventing material, ceramics such as alumina having low reactivity with the outer layer member 11 is preferable. The reaction inhibitor may be in the form of powder or woven fabric. In the case of powder, the slurry may be applied to the outer surface of the outer layer member 11 or the inner surface of the restraining member 16. In the case of a woven fabric shape, the outer layer member 11 may be wound around the outer periphery.

  When the outer layer member 11 and the inner layer member 12 are diffusion bonded, the outer layer member 11 becomes the outer layer 1 and the inner layer member 12 becomes the inner layer 2. Thereafter, the restraining member 16 is removed to obtain a cemented carbide composite roll 10 in which the outer layer 1 and the inner layer 2 are integrated. If necessary, a desired portion of the cemented carbide composite roll 10 is machined to obtain a dimension and shape suitable for hot sheet rolling.

(2) Hot isostatic pressure (HIP) method As shown in FIG. 5, after the cylindrical outer layer member 11 is placed in the cylindrical HIP can portion 20a, the inner layer member 12 made of an iron-based alloy is placed inside the cylindrical outer layer member 11. A cup-shaped HIP can portion that covers the end surface of the outer layer member 11 and welds the doughnut-shaped HIP can portions 20b, 20b to the cylindrical HIP can portion 20a, and further covers the inner layer member 12 on the donut-shaped HIP can portions 20b, 20b. Weld 20c and 20c and depressurize the resulting HIP can. Then, the HIP can is put into the HIP device and the HIP process is performed. The HIP temperature is preferably 1100 to 1300 ° C, and the HIP pressure is preferably 100 to 140 MPa.

  The outer layer member 11 and the inner layer member 12 are firmly joined by HIP, the outer layer member 11 becomes the outer layer 1, and the inner layer member 12 becomes the inner layer 2. After cooling, the HIP can 20 is removed by machining to obtain a cemented carbide composite roll 10 in which the outer layer 1 and the inner layer 2 are integrated. Also in this case, a desired portion of the cemented carbide composite roll 10 may be machined as necessary.

  The following examples of the present invention will be described in more detail, but the present invention is not limited thereto.

Example 1
Using a cemented carbide having the composition shown in Table 1, a cylindrical outer layer test piece 31 having an outer diameter of 20 mm and a thickness of 20 mm was produced. Also, five types of cylindrical inner layer test pieces 32 (inner layers 1 to 5) having an outer diameter of 20 mm and a length of 20 mm were prepared using an iron-based alloy having the composition shown in Table 2. After stacking the outer layer test piece 31 and the inner layer test piece 32 as shown in FIG. 6 and placing them in a graphite jig 34, the jig 34 is pressed from above in vacuum, and diffusion bonding is performed under the conditions shown in Table 3. It performed and produced the joining test pieces 1-5.

  As a result of observing the bonding boundary between each of the bonding test pieces 1 to 5, in the bonding test pieces 1 and 4, since the generation of η phase and graphite was suppressed at the bonding boundary between the inner layer test piece 32 and the outer layer material test piece 31, The strength is sufficiently high and the bonding reliability is high. In the joint test piece 3, graphite was generated at the joint boundary between the inner layer test piece 32 and the outer layer test piece 31. Further, in the bonding test piece 2 and the bonding test piece 5, the η phase was observed at the bonding boundary between the inner layer test piece 32 and the outer layer test piece 31. Accordingly, it is assumed that the bonding strength of the bonding test pieces 2, 3 and 5 is low.

Example 2
25 mm diameter x 75 mm long outer layer test piece 31 having the composition shown in Table 1, and 25 mm diameter x 75 mm long iron-based alloy inner layer test piece having the composition of joining test piece 1 shown in Table 2. 32 was produced. After placing the outer layer test piece 31 and the inner layer test piece 32 in a graphite jig 34 as shown in FIG. 6, pressurizing the jig 34 from above in vacuum, and performing diffusion bonding under the conditions shown in Table 4, A joining test piece 6 was prepared.

  A tensile test piece 45 having the shape shown in FIG. The tensile test piece 45 was composed of an outer layer test piece part 41 and an inner layer test piece part 42, and had a diameter of 6.3 mm and a gauge distance of 19 mm. The boundary part 43 of both test piece parts was located in the center between the gauge points. The tensile test piece 45 was subjected to a tensile strength test and a fatigue strength (pulling pressure) test. The results are shown in Table 4. The tensile test piece 45 (joint test piece 6) having an inner layer within the composition range of the present invention had a tensile strength of 600 MPa or more and a fatigue strength of 200 MPa or more.

Example 3
Using an iron-based alloy (thermal expansion coefficient: 13 × 10 ⁻⁶ / ° C.) having the composition shown in Table 5, a roll shaft-shaped inner layer member 12 having an outer diameter of 316 mm and a total length of 1000 mm was produced. Further, a graphite hollow cylindrical restraining member 16 (thermal expansion coefficient: 5 × 10 ⁻⁶ / ° C.) having an outer diameter of 600 mm, an inner diameter of 359.7 mm, and a total length of 1200 mm was produced.

Also, a hollow cylindrical outer layer member 11 having an outer diameter of 359 mm, an inner diameter of 317.5 mm, and a total length of 520 mm is manufactured using a cemented carbide (thermal expansion coefficient: 7.5 × 10 ⁻⁶ / ° C.) having the composition shown in Table 1. did. As shown in FIG. 2, the outer layer member 11 is disposed on the outer periphery of the inner layer member 12 placed on the base 8, and the restraining member 16 is disposed on the outer periphery of the outer layer member 11. In this state, it was placed in a vacuum furnace and held at 1290 ° C. for 60 minutes for diffusion bonding to produce a cemented carbide composite roll 10.

  The ends of the outer layer 1 and the inner layer 2 of the cemented carbide composite roll 10 were visually inspected, and the entire bonding surface was inspected by penetrant flaw detection. As a result, no boundary defect was observed over the entire bonding surface. Further, no peeling between the outer layer 1 and the inner layer 2 was observed.

1: outer layer, 2: inner layer, 8: base, 9: cradle, 10: cemented carbide composite roll,
11: Outer layer member, 12: Inner layer member, 16: Restraint member, 20: HIP can, 31: Outer layer test piece,
32: Inner layer specimen, 34: Graphite jig, 45: Bond specimen, 46: Tensile specimen,
61-66: Ring member for restraining member, L ₁ : Length of outer layer member, L ₂ : Length of inner layer member,
L ₃ : Length of restraining member, D: Length of restraining member extending from each end of outer layer member, T ₁ : Thickness of outer layer member,
T ₂ : Diameter of inner layer member, T ₃ : Thickness of restraint member, G ₂ : Gap between outer layer member and restraint member

Claims (9)

In a composite roll for rolling made of cemented carbide in which a cemented carbide outer layer containing 70 to 88% by mass of WC particles and an iron-based alloy inner layer constituting a roll axis are diffusion-bonded, the inner layer is 0.65 to 1.2% by mass From an iron-based alloy consisting of C, 1.8-7.5 mass% Ni, 0.01-3 mass% Cr , 0.01-1.5 mass% Mo , 0.1-2.0 mass% Si, and 0.1-0.9 mass% Mn Do Ri, cemented carbide composite roll of tensile strength of the boundary portion of the inner layer and the outer layer, characterized in der Rukoto least 600 MPa. 2. The cemented carbide composite roll according to claim 1 , wherein fatigue strength at a boundary portion between the outer layer and the inner layer is 200 MPa or more. In a method of manufacturing a cemented carbide composite roll in which a cylindrical outer layer member made of a cemented carbide containing 70 to 88% by mass of WC particles and an inner layer member made of an iron-based alloy are diffusion bonded, 0.65 to 1.2% by mass of C, 1.8-7.5 mass% of Ni, 0.01 to 3 wt% of Cr, 0 .01~1.5 mass% of Mo, the outer surface of the inner layer consisting of 0.1-2.0 wt% of Si and 0.1-0.9 mass% of Mn A method comprising diffusion bonding the inner surface of the outer layer member at a diffusion bonding temperature of 1000 to 1320 ° C. in an inert atmosphere . 4. The method for manufacturing a cemented carbide composite roll according to claim 3 , wherein after the cylindrical outer layer member is disposed so as to surround the inner layer member, the outer layer member has a coefficient of thermal expansion so as to surround the outer layer member. A step of disposing a small cylindrical restraint member and diffusion bonding the inner layer member and the outer layer member by heating;
In the step, the outer surface of the inner layer member having the largest coefficient of thermal expansion presses the inner surface of the outer layer member, and the inner surface of the restraining member having the smallest coefficient of thermal expansion presses the outer surface of the outer layer member. A method of setting a gap between each of an inner layer member, the outer layer member, and the restraining member. 5. The method for producing a cemented carbide composite roll according to claim 4 , wherein both end portions in the axial direction of the restraining member protrude from both end surfaces in the axial direction of the outer layer member. The method of manufacturing a cemented carbide composite roll according to claim 4 or 5, wherein said restraining member is equal to or thicker than the outer layer member. The method of manufacturing a cemented carbide composite roll according to any one of claims 4-6, wherein said restraining member is made of graphite or ceramics. The method of manufacturing a cemented carbide composite roll according to any one of claims 4-7, wherein the forming by stacking said restraining member a plurality of ring members coaxially. The method of manufacturing a cemented carbide composite roll according to any one of claims 4-8, wherein the interposing a reaction preventing material between said outer member and said restraining member.