JP2015096275A - Cemented-carbide-made composite roll and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cemented-carbide-made composite roll composed of an outer layer made of a cemented carbide having excellent abrasion resistance, roughening resistance and the like and an inner layer made of iron alloy having excellent toughness and a manufacturing method for the same.SOLUTION: A cemented-carbide-made composite roll for rolling, made by diffusion-welding an outer layer made of cemented carbide to an inner layer made of iron alloy through an intermediate layer made of iron alloy containing 0.65-1.2 mass% C and 1.8-7.5 mass% Ni, can be manufactured by welding an inner surface of a cylindrical intermediate layer member to an outer surface of an inner layer member and then diffusion-welding the inner surface of the outer layer member to the outer surface of the intermediate layer member.

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.

  JP-A-2004-167501 (Patent Document 3) is a cemented carbide composite roll in which a cemented carbide outer layer member is joined to the outer periphery of a steel or iron alloy inner layer member, and includes an inner layer member and an outer layer member. A composite roll for rolling made of cemented carbide characterized by providing an intermediate layer having a Young's modulus of 190 GPa or less in between is proposed. In Patent Document 3, by setting the Young's modulus of the intermediate layer to 190 GPa or less, the strain between the outer layer and the inner layer is absorbed, and even if the difference in thermal expansion coefficient between the outer layer and the inner layer is large, excessive residual stress inside the roll Does not occur, and it is described that it is possible to avoid the problem of separation of the boundary joining portion during roll production. Patent Document 3 exemplifies Invar alloy and SUS304 as the material of the intermediate layer.

  However, the cemented carbide composite roll described in Patent Documents 2 and 3 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. It has been found that the bonding reliability of the outer layer and the inner layer may not be sufficient to increase the size of a roll for hot sheet rolling with a length 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.

JP-A-3-281007 JP 2001-47111 A JP 2004-167501 A

  Accordingly, an object of the present invention is a cemented carbide composite roll comprising a cemented carbide outer layer excellent in wear resistance, rough skin resistance, and the like and an iron-based alloy inner layer excellent in toughness, both of which have extremely high joint strength. And an efficient manufacturing method thereof.

  As a result of earnest research in view of the above-mentioned purpose, an outer layer made of cemented carbide and an inner layer made of iron-based alloy are formed through an intermediate layer made of an iron-based alloy containing 0.65-1.2% by mass of C and 1.8-7.5% by mass of Ni. It was discovered that when heated in a pressure contact state, the outer layer and the inner layer were strongly diffusion bonded, and the present invention was conceived.

  That is, the cemented carbide composite roll of the present invention is obtained by diffusion bonding a cemented carbide outer layer and an iron alloy inner layer through an intermediate layer, and the intermediate layer is 0.65 to 1.2 mass% C and 1.8 to It is characterized by comprising an iron-based alloy containing 7.5% by mass of Ni.

  The intermediate layer preferably further contains 3% by mass or less of Cr and 1.5% by mass or less of Mo.

  The thickness of the intermediate layer is preferably 0.5 to 50 mm.

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

  The cemented carbide outer layer preferably contains 70 to 88% by mass of WC particles. The iron-based alloy inner layer preferably contains 1.0% by mass or more in total of at least one selected from the group consisting of Cr, Ni, Mo, V, W, Ti and Nb.

  The method of the present invention for producing a cemented carbide composite roll in which a cylindrical outer layer member made of a cemented carbide and an inner layer member made of an iron-based alloy are diffusion-bonded has an outer surface of the inner layer member of 0.65 to 1.2% by mass of C. And after joining the inner surface of the cylindrical intermediate | middle layer member containing 1.8 to 7.5 mass% Ni, the inner surface of the said outer layer member is diffusion-bonded to the outer surface of the said intermediate | middle layer member, It is characterized by the above-mentioned.

The first manufacturing method of the cemented carbide composite roll of the present invention,
A cylindrical first restraining member having a thermal expansion coefficient smaller than that of the inner layer member is arranged on the outer periphery of the inner layer member fitted with the cylindrical intermediate layer member so as to surround the inner layer member. A first step of diffusion bonding the intermediate layer member to produce an intermediate member having an intermediate layer diffusion bonded to the outer periphery of the inner layer member;
After disposing the cylindrical outer layer member so as to surround the intermediate member, a cylindrical second restraining member having a smaller coefficient of thermal expansion than that of the outer layer member is disposed so as to surround the outer layer member. A second step of diffusion bonding the intermediate layer and the outer layer member,
In the first step, the outer surface of the inner layer member having a large coefficient of thermal expansion presses the inner surface of the intermediate layer member, and the inner surface of the first restraining member having a small coefficient of thermal expansion presses the outer surface of the intermediate layer member. To set the respective gaps of the inner layer member, the intermediate layer member and the first restraining member,
In the second step, the outer surface of the intermediate layer formed on 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 second restraining member having the smallest coefficient of thermal expansion. The gaps of the intermediate member, the outer layer member, and the second restraining member are set so that the inner surface presses the outer surface of the outer layer member.

  In the first manufacturing method, the second restraining member is preferably thicker than the outer layer member.

The second manufacturing method of the cemented carbide composite roll of the present invention,
Disposing a cylindrical outer layer member having a smaller coefficient of thermal expansion than the inner layer member so as to surround the outer periphery of the inner layer member fitted with the cylindrical intermediate layer member;
Arranging a restraining member having a smaller coefficient of thermal expansion than the outer layer member so as to surround the outer layer member;
A step of diffusion bonding the inner layer member and the outer layer member through the intermediate layer member by heating,
The inner layer member such that the outer surface of the inner layer member having the largest thermal expansion coefficient presses the inner surface of the intermediate 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 intermediate layer member and the restraining member is set.

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

  In the second manufacturing method, it is preferable that the restraining member is thicker than the outer layer member.

  In the first and second manufacturing methods, it is preferable that both of the restraining members are made of graphite or ceramics.

  In the first and second manufacturing methods, each of the restraining members is preferably formed by coaxially stacking a plurality of ring members.

  In the first and second manufacturing methods, it is preferable that a reaction preventing material is interposed between the restraining member and the outer layer member.

  In the cemented carbide composite roll of the present invention, the cemented carbide outer layer and the iron alloy inner layer are intermediate layers made of an iron alloy containing 0.65 to 1.2% by mass of C and 1.8 to 7.5% by mass of Ni. Therefore, a fragile η phase is not generated in the cemented carbide at the joining boundary, and the joining strength between the outer layer and the inner layer is high. 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.

It is a fragmentary sectional front view which shows the cemented carbide composite roll of this invention. It is sectional drawing which shows the method of joining an intermediate | middle layer to an inner layer member by the diffusion bonding method. It is sectional drawing which shows the example which manufactures the cemented carbide composite roll of this invention by the diffusion bonding method. FIG. 4 is an enlarged view of a portion A in FIG. 3 (a). 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 below in detail 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 via the intermediate layer 3. 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 iron-based alloy of the inner layer 2 is preferably steel or cast iron. In order for the inner layer 2 to have sufficient toughness, a steel containing 1.0% by mass or more in total of at least one selected from the group consisting of Cr, Ni, Mo, V, W, Ti and Nb is preferable. In particular, the Cr content is preferably 0.5 to 1.5 mass%, the Mo content is preferably 0.1 to 0.5 mass%, and the Ni content is preferably 1.5 to 2.5 mass%.

(3) Intermediate layer Intermediate layer 3 essential for joining cemented carbide outer layer 1 and iron-based alloy inner layer 2 having different physical properties contains 0.65 to 1.2% by mass of C and 1.8 to 7.5% by mass of Ni. 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, the diffusion of C from the outer layer 1 made of cemented carbide to the inner layer 2 is prevented if the carbon content of the intermediate layer 3 is 0.65 mass% or more. It has been found that it is possible to substantially suppress the occurrence of the η phase. On the other hand, if the carbon content of the intermediate layer 3 exceeds 1.2% by mass, graphite is generated at the boundary between the outer layer 1 and the intermediate layer 3, and the bonding strength is reduced. The lower limit of the carbon content of the intermediate layer 3 is preferably 0.7% by mass, and more preferably 0.75% by mass. Further, the upper limit of the carbon content of the intermediate layer 3 is more preferably 1.0% by mass.

  It was found that when the intermediate layer 3 contains 1.8 to 7.5% by mass of Ni, the internal stress remaining in the intermediate layer 3 after bonding can be controlled, and the strength of the intermediate layer 3 itself can be secured. If the Ni content is less than 1.8% by mass, the residual stress of the intermediate layer 3 becomes too high and the intermediate layer 3 may be destroyed. On the other hand, if the Ni content exceeds 7.5% by mass, the strength of the intermediate layer 3 becomes too low, and the tensile strength at the joint boundary between the outer layer 1 and the intermediate layer 3 cannot be made 600 MPa or more. The lower limit of the Ni content of the intermediate layer 3 is preferably 1.9% by mass, more preferably 2% by mass. Further, the upper limit of the Ni content of the intermediate layer 3 is preferably 6% by mass, and more preferably 5% by mass.

  When the C content of the intermediate layer 3 is 0.65% by mass or more, the hardenability is lowered. Therefore, a hardenability equivalent to or higher than that of the inner layer 2 is required for controlling the residual stress of the composite roll. Therefore, the Ni content of the intermediate layer 3 is preferably larger than the Ni content of the inner layer 2.

  As described above, the intermediate layer 3 made of an iron-based alloy containing 0.65 to 1.2% by mass of C and 1.8 to 7.5% by mass of Ni is a large outer layer 1 having an outer diameter of 300 mm or more and a total length of 500 mm or more. However, it can have sufficient bonding strength to the inner layer 1.

  The intermediate layer 3 preferably contains 3% by mass or less of Cr and 1.5% by mass or less of Mo. If it contains more than 3% by mass of Cr and / or more than 1.5% by mass of Mo, the hardness of the intermediate layer 3 becomes so high that it becomes brittle and may be destroyed. The lower limit of the Cr content is preferably 0.01% by mass, more 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. Further, the lower limit of the Mo content is preferably 0.01% by mass, more preferably 0.03% by mass. The upper limit of the Mo content is more preferably 1% by mass.

  The intermediate layer 3 preferably further contains 0.5 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 0.5% 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 intermediate layer 3 may contain V, Nb, Co, W, Cu, etc. as inevitable impurities.

  The thickness of the intermediate layer 3 is preferably 0.5 to 50 mm. If the thickness of the intermediate layer 3 is less than 0.5 mm, the effect of suppressing the η phase is insufficient, and if the thickness of the intermediate layer 3 exceeds 50 mm, the tensile residual stress of the intermediate layer 3 or the inner layer 2 becomes excessive. There is a risk of breaking at the bonding interface. The thickness of the intermediate layer 3 is more preferably 10 to 30 mm, and most preferably 15 to 25 mm.

  The tensile residual stress of the mid layer 3 is preferably less than 100 MPa, and more preferably less than 50 MPa.

  The tensile strength at the boundary between the outer layer 1 and the intermediate layer 3 is preferably 600 MPa or more, and more preferably 700 MPa or more so that the outer layer 1 and the intermediate layer 3 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 intermediate layer 3 can be measured by a tensile test of a test piece including the boundary between the outer layer 1 and the intermediate layer 3. In addition, in order to prevent the outer layer 1 and the inner layer 2 from peeling after joining, the fatigue strength (attraction fatigue strength) at the boundary between the outer layer 1 and the intermediate layer 3 is preferably 200 MPa or more, more preferably 250 MPa or more. preferable.

[2] Cemented carbide composite roll manufacturing method Since the cemented carbide roll of the present invention has a structure in which the outer layer 1 and the inner layer 2 are joined via the intermediate layer 3, the interface between the outer layer 1 and the intermediate layer 3, In addition, the interface between the intermediate layer 3 and the inner layer 2 may be joined without a gap. A diffusion bonding method or a hot isostatic pressure (HIP) method can be used for such bonding.

(A) Diffusion bonding method
(1) First diffusion bonding method In the first diffusion bonding method, the hollow cylindrical intermediate layer member 13 is diffusion bonded to the inner layer member 12, and the intermediate member 14 in which the intermediate layer 3 is bonded to the inner layer member 12 is produced. A first diffusion bonding step is performed, and then a cemented carbide outer layer member 11 is diffusion bonded to the intermediate layer 3 of the intermediate member 14 to form a cemented carbide composite roll.

(a) First diffusion bonding step As shown in FIG. 2, after the inner layer member 12 corresponding to the roll shaft is disposed on the base 8, the first diffusion bonding step is performed on the base 8 so as to surround the inner layer member 12. A cylindrical cradle 9a is placed. Next, the hollow cylindrical intermediate layer member 13 is placed on the first cylindrical receiving base 9a so as to surround the inner layer member 12. Finally, the first cylindrical restraining member 16a is placed on the base 8 so as to surround the inner layer member 12.

The inner layer member 12 and the intermediate layer member 13 arranged as described above are heated in an inert atmosphere, and diffusion bonding of the inner layer member 12 and the intermediate layer member 13 is performed. The diffusion bonding temperature is preferably 1000 to 1300 ° C, more preferably 1100 to 1250 ° C. If the diffusion bonding temperature is less than 1000 ° C., sufficient bonding strength cannot be obtained. If the diffusion bonding temperature exceeds 1300 ° C., the iron-based alloy intermediate layer member 13 containing 0.65 to 1.2% by mass of C is obtained. There is a risk of melting. 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 1300 ° C., the coefficient of thermal expansion must satisfy the relationship of inner layer member 12> first constraining member 16a. 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 1300 ° C. is about 11 to 15 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the first restraining member 16a is Must be small enough. The material satisfying such a thermal expansion coefficient is graphite or ceramics having a thermal expansion coefficient of about 4 to 9 × 10 ⁻⁶ / ° C. Since the first restraining member 16a must sufficiently withstand the diffusion bonding temperature and the diffusion bonding stress, it must have high strength and high rigidity at the diffusion bonding temperature. Accordingly, isotropic graphite having a coefficient of thermal expansion of 6 × 10 ⁻⁶ / ° C. or less and a bending strength at 1000 ° C. of 30 MPa or more is particularly preferable.

The outer layer surface of the inner layer member 12 is connected between the inner layer member 12 that is largely thermally expanded by heating and the first restraining member 16a that is slightly thermally expanded so that the intermediate layer member 13 is sufficiently closely bonded to the inner layer member 12. The gap G ₁ with the inner surface of the first restraining member 16a is such that G ₁ −T ₃ (where T ₃ is the thickness of the intermediate layer member 13) is in the range from room temperature to a temperature of 1000 to 1300 ° C. And the first constraining member 16a must be set to be sufficiently smaller than the difference in thermal expansion. For example, when the diameter T _{2 of} the steel inner layer member 12 (thermal expansion coefficient: 14 × 10 ⁻⁶ / ° C.) is 300 mm and the thickness T ₃ of the intermediate layer member 13 is 10 mm, the first graphite The inner diameter of the restraining member 16 (thermal expansion coefficient: 8 × 10 ⁻⁶ / ° C.) is preferably T ₂ + T ₃ +2.5 mm.

  In the first diffusion bonding, a hollow constraining member 6 having a smaller coefficient of thermal expansion than the inner layer member 2 is fitted to the outer surface of the intermediate layer member 3, and the intermediate layer member and the inner layer member that are to be expanded by heating are constrained. Constrained by the member, the outer diameter side of the inner layer member is in close contact with the inner diameter side of the intermediate layer member due to the thermal expansion of the inner layer member, and the surface pressure (bonding surface pressure) required for diffusion bonding to the bonding surface of the intermediate layer member 3 and the inner layer member 2 ) Can be secured.

(b) Second diffusion bonding step After the outer peripheral surface of the intermediate layer 3 of the intermediate member 14 is machined to a predetermined dimension, the intermediate member 14 is placed on the base 8 as shown in FIG. Place. After the second cylindrical cradle 9b is placed on the base 8 so as to surround the intermediate member 14, the cylindrical outer layer member 11 is placed on the second cylindrical cradle 9b. Next, the second cylindrical restraining member 16b 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 intermediate member 14, and the restraining member 16 arranged in this manner are heated in an inert atmosphere, and diffusion bonding of the outer layer member 11 and the intermediate layer 3 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 intermediate layer 3 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> second constraining member 16b. 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 It is about ˜10 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the second restraining member 16b must be sufficiently smaller than these. The material satisfying such a thermal expansion coefficient is preferably graphite or ceramics having a thermal expansion coefficient of about 4 to 9 × 10 ⁻⁶ / ° C., like the first restraining member 16a. 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 second restraining member 16b that is least thermally expanded is as fully press the outer surface of the outer layer member 11, it is necessary to set the gap G ₂ of the gap G ₁ between the outer member 11 and the intermediate layer 3, and an outer layer member 11 and the second constraining member 16b [FIG See 3 (b)]. For example, the diameter T _{2 of} the steel inner layer member 12 (thermal expansion coefficient: 14 × 10 ⁻⁶ / ° C.) is 300 mm, the thickness T ₃ of the intermediate layer ₃ is 10 mm, and the outer layer member made of cemented carbide. 11 (thermal expansion coefficient: 7.5 × 10 ⁻⁶ / ° C.) having an inner diameter of 304.5 mm, an outer diameter of 358 mm, and a second restraining member 16b made of graphite (thermal expansion coefficient: 5 × 10 ⁻⁶ / )) Is 359.7 mm, the gap G ₁ between the outer layer member 11 and the inner layer member 12 is preferably 1.0 to 2.0 mm, and the gap G ₂ between the outer layer member 11 and the second restraining member 16b is It is preferably 1.3 to 2.0 mm.

  As described above, the second restraining member 16b 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 second restraining member 16b. The outer surface of the intermediate layer 3 formed on the outer periphery of the inner layer member 12 that thermally expands most closely contacts 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. 3 (a), the second constraining the total length L ₃ is long of preferably than the total length L ₁ of the outer member 11 of the member 16b, also a second axial end surfaces 6a of the restraining member 16b, 6b is It is preferable that the outer layer member 11 protrudes by a length D from both axial end surfaces 1a and 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 second restraining member 16b must sufficiently restrain the outer layer member 11 without being deformed or damaged at the diffusion bonding temperature, the second restraining member 16b 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 second constraining member 16b is preferably 100 to 150 mm.

  As shown in FIG. 4, the second restraining member 16b 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 second restraining member 16b 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. Of course, the first restraining member 16a can also be configured by stacking a plurality of relatively short ring members coaxially in the axial direction.

  It is preferable to interpose a reaction preventing material between the second restraining member 16b 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 through the intermediate layer 3, the outer layer member 11 becomes the outer layer 1, and the inner layer member 12 becomes the inner layer 2. Thereafter, the second restraining member 16b is removed, and the cemented carbide composite roll 10 in which the outer layer 1 and the inner layer 2 are integrated via the intermediate layer 3 is obtained. 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) Second Diffusion Bonding Method The cylindrical intermediate layer member 13 and the cylindrical outer layer member 11 can be integrated with the inner layer member 12 by one diffusion bonding. In this case, the intermediate layer member 13 is joined to the inner layer member 12 by a method such as shrink fitting or cold fitting. Thereafter, diffusion bonding is performed under the same conditions as in the second diffusion bonding step of the first diffusion bonding method. Therefore, diffusion bonding between the inner layer member 12 and the intermediate layer member 13 and diffusion bonding between the intermediate layer member 13 and the outer layer member 11 are simultaneously performed at a diffusion bonding temperature of 1000 to 1320 ° C.

(2) Hot Isostatic Pressure (HIP) Method As shown in FIG. 5, after inserting the cylindrical outer layer member 11 into the cylindrical HIP can portion 20a, the iron in which the intermediate layer 3 is formed inside the cylindrical outer layer member 11 An iron alloy inner layer member 12 joined with a base alloy inner layer member 12 or an intermediate layer member 13 is disposed, and the donut-shaped HIP can portions 20b, 20b covering the end surface of the outer layer member 11 are welded to the cylindrical HIP can portion 20a. Further, the cup-shaped HIP can portions 20c, 20c covering the inner layer member 12 are welded to the donut-shaped HIP can portions 20b, 20b, and the pressure inside the obtained HIP can is reduced. 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.

  By HIP, the outer layer member 11 and the inner layer member 12 are firmly joined via the intermediate layer 3 (intermediate layer member 13), the outer layer member 11 becomes the outer layer 1, and the inner layer member 12 becomes the inner layer 2. Further, the intermediate layer member 13 becomes the intermediate layer 3. 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 via the intermediate layer 3. 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 shown in FIG. 6 was produced. Further, using an iron-based alloy having the composition shown in Table 2, a cylindrical inner layer test piece 32 having an outer diameter of 20 mm and a length of 20 mm shown in FIG. 6 was produced. Further, five types of disk-shaped intermediate layer test pieces 33 (intermediate layers 1 to 5) having an outer diameter of 30 mm and a thickness of 5 mm were prepared using an iron-based alloy having the composition shown in Table 3. After stacking the outer layer test piece 31, the intermediate layer test piece 33 and the inner layer test piece 32 as shown in FIG. 6 and placing them in a graphite jig 34, the jig 34 was pressed from above in vacuum, and the results are shown in Table 3. Diffusion bonding was performed under the conditions shown, and bonding test pieces 1 to 5 were produced.

  As a result of observing the bonding boundary of 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 of the intermediate layer test piece 33 and the outer layer material test piece 31, The bonding strength was sufficiently high and the bonding reliability was high. However, in the joining test piece 3, graphite was generated at the joining boundary between the intermediate layer test piece 33 and the outer layer test piece 31. In the joining test pieces 2 and 5, an η phase was observed at the joining boundary between the intermediate layer test piece 33 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.

注：(1) WC粒子の平均粒径は5μmであった。

Notes: (1) The average particle size of the WC particles was 5 μm.

Example 2
An outer layer test piece 31 having a composition shown in Table 1 having a diameter of 25 mm × 75 mm in length and an iron-based alloy inner test piece 32 having a composition shown in Table 2 having a diameter of 25 mm × length of 75 mm were prepared. Further, two types of iron alloy intermediate layer test pieces 33 having a diameter of 25 mm and a thickness of 10 mm having the compositions of the joining test pieces 1 and 2 shown in Table 3 were prepared. After placing the outer layer test piece 31, the intermediate layer test piece 32 and the inner layer test piece 33 in the graphite jig 34 as shown in FIG. Then, diffusion bonding was performed to prepare bonding test pieces 6 and 7.

  Tensile test pieces 45 and 46 having the shape shown in FIG. Each of the tensile test pieces 45 and 46 was composed of an outer layer test piece part 41, an intermediate layer test piece part 43 and an inner layer test piece part 42, and had a diameter of 6.3 mm and a gauge distance of 19 mm. The intermediate layer test piece 43 was located at the center between the gauge points. Each tensile test piece 45, 46 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 intermediate 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. In contrast, the tensile test piece 46 (joint test piece 7) having an intermediate layer outside the composition range of the present invention had a tensile strength of less than 600 MPa and a fatigue strength of less than 200 MPa.

Example 3
Using a ferrous alloy having the composition shown in Table 2, a roll shaft-shaped inner layer member 12 having an outer diameter of 270 mm and a total length of 1000 mm was produced. Further, an intermediate layer member 13 having an outer diameter of 335 mm, an inner diameter of 270 mm, and a total length of 600 mm was produced using an iron-based alloy having the composition shown in Table 5. Further, a first graphite hollow cylindrical restraining member 16a having an outer diameter of 600 mm, an inner diameter of 336.5 mm, and a total length of 1100 mm was produced. As shown in FIG. 2, with each member placed on the graphite base 8, it was put in a vacuum furnace and held at a temperature of 1290 ° C. for 60 minutes to perform diffusion bonding, thereby producing an intermediate member 14.

  The outer peripheral surface of the intermediate layer 3 of the intermediate member 14 was machined to an outer diameter of 316 mm, and then placed on the graphite base 8. In addition, a hollow cylindrical outer layer member 11 having an outer diameter of 358 mm, an inner diameter of 317.5 mm, and a total length of 520 mm was produced using a cemented carbide having the composition shown in Table 1. Further, a second graphite restraining member 16b having an outer diameter of 600 mm, an inner diameter of 359.7 mm, and a total length of 1200 mm was produced. As shown in FIG. 3A, the outer layer member 11 is disposed on the outer periphery of the intermediate member 14 placed on the base 8, and the second restraining member 16b 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, the intermediate layer 3 and the inner layer 2 of the cemented carbide composite roll 10 were visually inspected, and the entire joint surface was inspected by penetrant flaw detection. As a result, no boundary defect was observed over the entire bonding surface. Further, peeling of the outer layer 1 and the intermediate layer 3 and peeling of the intermediate layer 3 and the inner layer 2 were not observed.

  As a result of the same tensile test as in Example 2, the tensile strength was 780 MPa or more and the fatigue strength was 258 MPa or more. Further, the tensile residual stress of the intermediate layer 3 was less than 100 MPa.

1: Outer layer
2: Inner layer
3: Middle layer
8: Base
9a, 9b: First and second cradle
10: Cemented carbide composite roll
11: Outer layer member
12: Inner layer member
13: Middle layer member
14: Intermediate member
16a, 16b: first and second restraining members
20: HIP can
31: Outer layer specimen
32: Inner layer specimen
34: Graphite jig
45: Joining specimen
46: Tensile test piece
61-66: Ring member for restraint member
L ₁ : Length of outer layer member
L ₂ : Length of inner layer member
L ₃ : Length of the second restraining member
D: Length of the second restraining member extending from each end of the outer layer member
T ₁ : Thickness of outer layer member
T ₂ : Diameter of inner layer member
T ₃ : thickness of the second restraining member
G ₁ : Gap between the outer layer member and the intermediate layer
G ₂ : The gap between the outer layer member and the second restraining member

Claims (17)

In a composite roll for rolling made of cemented carbide, in which a cemented carbide outer layer and an iron-based alloy inner layer are diffusion-bonded via an intermediate layer, the intermediate layer is 0.65 to 1.2% by mass of C and 1.8 to 7.5% by mass of Ni. A cemented carbide composite roll comprising an iron-based alloy containing 2. The cemented carbide composite roll according to claim 1, wherein the intermediate layer further contains 3% by mass or less of Cr and 1.5% by mass or less of Mo. 3. The cemented carbide composite roll according to claim 1, wherein the intermediate layer has a thickness of 0.5 to 50 mm. The cemented carbide composite roll according to any one of claims 1 to 3, wherein a tensile strength at a boundary portion between the outer layer and the intermediate layer is 600 MPa or more. The cemented carbide composite roll according to any one of claims 1 to 4, wherein a fatigue strength at a boundary portion between the outer layer and the intermediate layer is 200 MPa or more. The cemented carbide composite roll according to any one of claims 1 to 5, wherein the cemented carbide outer layer contains 70 to 88% by mass of WC particles. The cemented carbide composite roll according to any one of claims 1 to 6, wherein the iron-based alloy inner layer includes at least one selected from the group consisting of Cr, Ni, Mo, V, W, Ti and Nb in a total of 1.0. A cemented carbide composite roll containing at least mass%. In the method of manufacturing 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, 0.65 to 1.2% by mass of C and 1.8 to 1.2% on the outer surface of the inner layer member A method comprising joining the inner surface of a cylindrical intermediate layer member containing 7.5% by mass of Ni and then diffusion-bonding the inner surface of the outer layer member to the outer surface of the intermediate layer member. In the method for producing a cemented carbide composite roll according to claim 8,
A cylindrical first restraining member having a thermal expansion coefficient smaller than that of the inner layer member is arranged on the outer periphery of the inner layer member fitted with the cylindrical intermediate layer member so as to surround the inner layer member. A first step of diffusion bonding the intermediate layer member to produce an intermediate member having an intermediate layer diffusion bonded to the outer periphery of the inner layer member;
After disposing the cylindrical outer layer member so as to surround the intermediate member, a cylindrical second restraining member having a smaller coefficient of thermal expansion than that of the outer layer member is disposed so as to surround the outer layer member. A second step of diffusion bonding the intermediate layer and the outer layer member,
In the first step, the outer surface of the inner layer member having a large coefficient of thermal expansion presses the inner surface of the intermediate layer member, and the inner surface of the first restraining member having a small coefficient of thermal expansion presses the outer surface of the intermediate layer member. To set the respective gaps of the inner layer member, the intermediate layer member and the first restraining member,
In the second step, the outer surface of the intermediate layer formed on 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 second restraining member having the smallest coefficient of thermal expansion. A method of setting a gap between each of the intermediate member, the outer layer member, and the second restraining member so that an inner surface presses the outer surface of the outer layer member. 10. The method of manufacturing a cemented carbide composite roll according to claim 9, wherein both axial end portions of the first and second restraining members protrude from both axial end surfaces of the intermediate layer member and the outer layer member. Feature method. 11. The method for producing a cemented carbide composite roll according to claim 9, wherein the second restraining member is thicker than the outer layer member. In the method for producing a cemented carbide composite roll according to claim 8,
Disposing a cylindrical outer layer member having a smaller coefficient of thermal expansion than the inner layer member so as to surround the outer periphery of the inner layer member fitted with the cylindrical intermediate layer member;
Arranging a restraining member having a smaller coefficient of thermal expansion than the outer layer member so as to surround the outer layer member;
A step of diffusion bonding the inner layer member and the outer layer member through the intermediate layer member by heating,
The inner layer member such that the outer surface of the inner layer member having the largest thermal expansion coefficient presses the inner surface of the intermediate 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 the intermediate layer member and the restraining member. 13. The method for producing a cemented carbide composite roll according to claim 12, wherein both axial end portions of the restraining member protrude from both axial end surfaces of the intermediate layer member and the outer layer member. 14. The method for producing a cemented carbide composite roll according to claim 12 or 13, wherein the restraining member is thicker than the outer layer member. 15. The method for producing a cemented carbide composite roll according to claim 8, wherein the restraining member is made of graphite or ceramics. 16. The method for manufacturing a cemented carbide composite roll according to claim 8, wherein the constraining member is formed by coaxially stacking a plurality of ring members. 17. The method for producing a cemented carbide composite roll according to claim 8, wherein a reaction preventing material is interposed between the restraining member and the outer layer member.

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