JP2004167501A - Composite roll made of cemented carbide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite roll made of cemented carbide for rolling which prevents the breaking of roll such as the boundary joint is separated when the roll is manufactured without causing excessive residual stress in the interior of the roll even in the case difference between thermal expansion coefficients of the outer layer and the inner layer is large. <P>SOLUTION: This composite roll made of cemented carbide, in which the outer layer consisting of the cemented carbide is joined to the outer periphery of the inner layer consisting of a steel base or an iron base material, has one or more intermediate layers between the inner layer and the outer layer and the Young's modulus of at least one intermediated layer ( intermediate layer A ) is ≤ 190 GPa. The intermediate layer A is an alloy containing one kind of Fe, Ni and Co of ≥ 30 wt.%. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention is used for rolling of steel materials such as a strip, a plate, a wire, and a bar, and an outer layer made of a tungsten carbide (WC) cemented carbide is joined to an outer periphery of an inner layer made of a material having excellent toughness. The present invention relates to a composite roll for cemented carbide rolling.
[0002]
[Prior art]
Tungsten carbide (WC) cemented carbide with excellent abrasion resistance, rough surface resistance, etc. is used for wire rods in order to respond to demands for higher quality of rolled materials such as improvement of dimensional accuracy and productivity improvement by reducing man-hours for roll change. It is applied to rolls for rolling bars, flat bars, and strips. As is well known, a WC-based cemented carbide is a sintered alloy in which WC is bonded with a metal element such as Co, Ni, Cr, and Fe, and often contains carbides such as Ti, Ta, and Nb in addition to WC. is there.
[0003]
Conventionally, various techniques have been proposed as composite rolls for cemented carbide rolling in which an outer layer made of a WC-based cemented carbide is joined to the outer periphery of an inner layer made of a material having excellent toughness.
[0004]
Patent Document 1 discloses that in a cemented carbide composite roll in which an outer layer made of a hard metal is metal-bonded to the outer periphery of an inner layer made of a material having excellent toughness, the content of WC particles inside the outer layer is larger than that of the outer layer. There is described a cemented carbide composite roll having a small number of at least one intermediate layer of a cemented carbide, wherein the inner layer and the intermediate layer are joined via a metal layer.
[0005]
In Patent Document 2, the roll barrel is composed of three or more concentric layers, the outermost layer has a Young's modulus of 35,000 kgf / mm ² or more, and the thickness of the layer is 3% or more of the roll radius. A composite roll for cold rolling of stainless steel is described in which the intermediate layer located between the shaft core and the outer layer has a Young's modulus smaller than that of the outermost layer and larger than that of the shaft core.
[0006]
[Patent Document 1]
JP 2001-47111 A [Patent Document 2]
Japanese Patent No. 3,188,643
[Problems to be solved by the invention]
In the case of a composite roll in which the outer layer is made of a cemented carbide and the inner layer is made of an iron-based or steel-based material as in the prior art, the inner layer has a larger coefficient of thermal expansion than the outer layer. for ~12 × ¹⁰ -6 / K, the thermal expansion coefficient of the outer layer is 5~8 × ^{10 -6} / K, a roll temperature rise during rolling, the tensile stress acts on the surface of the outer layer.
[0008]
When rolling is performed in a state where an excessive tensile stress acts on the outer layer surface of the roll, cracks are easily generated on the surface due to thermal shock during rolling, and the roll advances. Since the cemented carbide forming the outer layer has relatively low toughness, when a crack is generated on the surface, the cemented carbide easily develops and the roll may be broken.
[0009]
Therefore, in a cemented carbide composite roll, it is necessary to apply an appropriate compressive residual stress to the outer layer surface of the roll in advance so that excessive tensile stress does not act on the outer layer surface of the roll.
[0010]
However, the higher the WC content in the outer layer, the lower the coefficient of thermal expansion with respect to the inner layer, so that the residual stress generated inside the roll increases. This stress acts on the inner layer as a tensile stress in the axial direction and the circumferential direction, and acts on the inner layer as a tensile stress in any position of the outer layer and the inner layer. Therefore, if such residual stress becomes excessive, there is a possibility that peeling of the roll boundary joint portion or breakage of the roll from the inner layer may occur at the time of manufacturing or rolling use.
[0011]
Accordingly, an object of the present invention is to prevent a roll from breaking, such as a boundary joining portion being peeled off during roll manufacturing, without generating excessive residual stress inside the roll even when the difference in thermal expansion coefficient between the outer layer and the inner layer is large. To provide a composite roll for cemented carbide rolling.
[0012]
[Means for Solving the Problems]
The cemented carbide rolling composite roll of the present invention is a cemented carbide composite roll in which an outer layer made of a cemented carbide is joined to the outer periphery of an inner layer made of a steel or iron-based material, wherein the inner layer and the outer layer And at least one intermediate layer, wherein the Young's modulus of at least one intermediate layer (hereinafter referred to as an intermediate layer A) is 190 GPa or less.
[0013]
Further, the present invention is a cemented carbide composite roll in which an outer layer made of a cemented carbide is joined to the outer periphery of an inner layer made of a steel or iron-based material, wherein two or more layers are provided between the inner layer and the outer layer. It is characterized by having an intermediate layer and having a Young's modulus of 190 GPa or less of an intermediate layer bonded to the inner layer, that is, the intermediate layer closest to the inner layer (hereinafter referred to as an intermediate layer A).
[0014]
In the present invention, the intermediate layer A is formed of an alloy containing any one of Fe, Ni, and Co in an amount of 30% by weight or more. The thickness of the intermediate layer A in a cross section perpendicular to the roll axis direction is desirably 500 μm or more.
[0015]
Further, in the bending roll according to JIS R1601, the bending strength of the bending test piece including the boundary joining portion between the inner layer, the intermediate layer, and the outer layer is 600 MPa or more. It is desirable that
[0016]
Further, it is preferable that a circumferential compressive residual stress of 100 to 800 MPa is applied to the outer layer surface at the center of the roll body.
[0017]
[Action]
When joining the outer and inner layers in a composite roll with an outer layer made of cemented carbide and an inner layer made of an iron-based or steel-based material, the difference in heat shrinkage during cooling after joining at a high temperature causes a difference between the two. Strain and the resulting internal stress are generated. That is, the cemented carbide has a small coefficient of linear thermal expansion of 5 to 8 × 10 ⁻⁶ / K, while the inner layer has a high coefficient of thermal expansion of 10 to 12 × 10 ⁻⁶ / K. This causes internal stress.
[0018]
This internal stress is proportional to the Young's modulus and strain of the material. The Young's modulus of the cemented carbide forming the outer layer is 450 to 650 GPa depending on the amount of WC contained in the alloy, and the iron-based or steel-based material forming the inner layer is about 205 GPa.
[0019]
Therefore, one or more intermediate layers are interposed between the inner layer and the outer layer, and the Young's modulus of at least one of the intermediate layers is set to 190 GPa or less, thereby absorbing the distortion between the inner layer and the outer layer and generating the inner layer. Stress can be reduced.
[0020]
When metal bonding the outer layer and the inner layer, C diffuses from the outer layer to the inner layer. As a result, the WC of the cemented carbide near the joint between the outer layer and the inner layer is changed to double carbide (W, Co) 3C. This double carbide is brittle as compared with WC and causes a reduction in the strength of the boundary joint. By forming the intermediate layer A with an alloy based on any one of Fe, Ni, and Co, the diffusion of C can be suppressed, and the affinity with the outer layer is good and the bonding strength can be increased. it can.
[0021]
When the intermediate layer absorbs the strain, it must be elastically deformed. Therefore, if the intermediate layer has a certain thickness, the distortion becomes excessive and the intermediate layer itself may be broken. In order to prevent this, the intermediate layer A needs to have a thickness of 500 μm or more.
[0022]
In the composite roll for cemented carbide rolling according to the present invention, in a bending test based on JIS R1601, the bending strength of the bending test piece including the boundary joint between the inner layer, the intermediate layer, and the outer layer is set to 600 MPa or more. Further, by applying a compressive residual stress in the circumferential direction of 100 to 800 MPa to the outer layer surface at the center of the roll body, the safety factor against peeling from the boundary joint at the time of rolling use can be increased.
[0023]
The cemented carbide rolling composite roll of the present invention, particularly when the inner layer is solid, suppresses excessive residual stress inside the roll and exerts an effect of imparting an appropriate compressive residual stress to the outer layer surface. preferable. Further, as the intermediate layer A, an invar-based alloy is preferable.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
(Example 1)
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view illustrating the HIP method used to manufacture the composite roll for rolling of Example 1. In FIG. 1, the right half is omitted because it is symmetrical. In FIG. 1, a hollow cylindrical SCM440 having an outer diameter of 242 mm, an inner diameter of 180 mm, and a length of 600 mm was disposed as an inner layer 1 in the center of a HIP can 2 having an inner diameter of 300 mm and a length of 650 mm. The Young's modulus of the inner layer 1 is 206 MPa.
[0025]
Further, as the intermediate layer 4 showing the intermediate layer A, which is a feature of the present invention, an outer layer composed of an invar alloy of C: 0.5%, Ni: 30%, Co: 16%, and the balance substantially Fe. A hollow cylindrical sleeve having a diameter of 249 mm, an inner diameter of 243 mm, and a length of 600 mm was prepared and placed on the outer periphery of the inner layer 1. The Young's modulus of the mid layer 4 is 135 GPa. In Example 1, the intermediate layer is a single layer composed of only the intermediate layer A.
[0026]
Then, in the gap formed between the outer surface of the intermediate layer 4 and the inner surface of the HIP can 2, as the outer layer 3, an outer diameter φ298 mm of a calcined body of WC: 88%, Co: 12% by weight, A sleeve made of cemented carbide having an inner diameter of 250 mm and a length of 600 mm was arranged. The Young's modulus of the cemented carbide sleeve forming the outer layer 3 is 500 GPa.
[0027]
Thereafter, the HIP can was welded and sealed with a steel lid, deaerated with a vacuum pump, and then HIPed at 1300 ° C. and 1000 atm with a HIP device. After cooling, the HIP can was machined and removed to obtain a cemented carbide composite sleeve roll in which an outer layer made of a cemented carbide was joined to the outer periphery of the inner layer. A color check confirmed that there was no crack on the roll end face. In addition, it was confirmed that the outer layer, the intermediate layer, and the inner layer were soundly joined by an ultrasonic flaw detector.
[0028]
Further, in order to measure the strength of the boundary joining portion of the roll, a sample was machined and cut from the center of the roll, and a bending test in accordance with JIS R1601 was performed. A transverse rupture test piece at the boundary junction including the inner layer, the intermediate layer, and the outer layer was cut out in the roll diameter direction and subjected to a test. The transverse rupture strength was 900 MPa on average. Also, a strain gauge was attached to the outer layer surface at the center of the roll body, and the residual stress at this position was measured. As a result, it was confirmed that the compressive residual stress in the circumferential direction was 350 MPa, which was within an appropriate range.
[0029]
(Example 2)
FIG. 2 is a schematic sectional view illustrating the HIP method used to manufacture the composite roll for rolling of Example 2. In FIG. 2, the right half is omitted because it is symmetrical. In FIG. 2, a solid SNCM439 having an outer diameter of 70 mm and a length of 1700 mm was disposed as an inner layer 1 in the center of a HIP can 2 having an inner diameter of 100 mm and a length of 1800 mm. The Young's modulus of the inner layer 1 is 206 MPa.
[0030]
In addition, as the first intermediate layer 4 showing the intermediate layer A which is a feature of the present invention, a hollow cylindrical sleeve made of SUS304 material having an outer diameter of 73 mm, an inner diameter of 71 mm, and a length of 1700 mm is prepared. It was arranged on the outer circumference. The Young's modulus of the first intermediate layer 4 is 135 GPa.
[0031]
Then, in the gap formed between the outer surface of the first intermediate layer 4 and the inner surface of the HIP can 2, as the outer layer 3, it is composed of a sinter having a weight ratio of WC: 87% and Co: 13%. A sleeve made of cemented carbide having an outer diameter of 98 mm, an inner diameter of 78 mm, and a length of 1700 mm was arranged. The Young's modulus of the cemented carbide sleeve forming the outer layer 3 is 500 GPa.
[0032]
Further, in the gap formed between the outer surface of the first intermediate layer 4 and the inner surface of the outer layer 3, as the second intermediate layer 7, a cemented carbide having a weight ratio of WC: 40% and Co: 60% is used. Was mixed. After the HIP processing described later, the second intermediate layer 7 is sintered. The Young's modulus of the second intermediate layer 7 is 300 GPa. In Example 2, the intermediate layer is a multilayer composed of the first intermediate layer 4 and the second intermediate layer 7.
[0033]
Thereafter, the HIP can was welded and sealed with a steel lid, deaerated with a vacuum pump, and then HIPed at 1300 ° C. and 1000 atm with a HIP device. After cooling, the HIP can was machined and removed to obtain a cemented carbide composite roll in which an outer layer made of a cemented carbide was joined to the outer periphery of the inner layer. A color check confirmed that there was no crack on the roll end face. Further, it was confirmed that each of the outer layer, the second intermediate layer, the first intermediate layer, and the inner layer was soundly bonded by the ultrasonic flaw detector.
[0034]
Further, in order to measure the strength of the boundary joining portion of the roll, a sample was machined and cut from the center of the roll, and a bending test in accordance with JIS R1601 was performed. A transverse rupture test piece at the boundary junction including the inner layer, the intermediate layer, and the outer layer was cut out in the roll diameter direction and subjected to a test. The transverse strength was 1000 MPa on average. Further, a strain gauge was attached to the outer layer surface at the center of the roll body, and the residual stress at this position was measured. As a result, it was confirmed that the compressive residual stress in the circumferential direction was 330 MPa, which was within an appropriate range.
[0035]
(Comparative Example 1)
A rolling composite roll of Comparative Example 1 was manufactured by the method of FIG. 1 in the same manner as in Example 1 except that the material of the intermediate layer 4 was different. In FIG. 1, a hollow cylindrical SCM440 having an outer diameter of 242 mm, an inner diameter of 180 mm, and a length of 600 mm was disposed as the inner layer 1 as the inner layer 1 in the center of the HIP can 2 having an inner diameter of 300 mm and a length of 650 mm. The Young's modulus of the inner layer 1 is 206 MPa.
[0036]
Further, as the intermediate layer 4, a hollow cylindrical cemented carbide sleeve having an outer diameter of 249 mm, an inner diameter of 243 mm, and a length of 600 mm made of a temporary sintered body of WC: 40% and Co: 60% by weight is prepared. This was arranged on the outer periphery of the inner layer 1. The mid layer 4 has a Young's modulus of 300 GPa. In Comparative Example 1, the intermediate layer is a single layer composed of only the intermediate layer 4.
[0037]
Then, as the outer layer 3, a cemented carbide sleeve having an outer diameter of 298 mm, an inner diameter of 250 mm, and a length of 600 mm made of a temporary sintered body of WC: 88% and Co: 12% by weight is disposed on the outer periphery of the inner layer 1. The Young's modulus of the cemented carbide sleeve forming the outer layer 3 is 500 GPa.
[0038]
Thereafter, the HIP can was sealed by welding with a steel lid, deaerated by a vacuum pump, and then subjected to HIP at 1300 ° C. and 1000 atm by a HIP device. After cooling, the HIP can was machined and removed to obtain a cemented carbide composite sleeve roll in which an outer layer of a cemented carbide was joined to the outer periphery of the inner layer. When a color check was performed, cracks were confirmed on the roll end face. Further, it was confirmed by an ultrasonic flaw detector that the outer layer and the inner layer were peeled over the entire peripheral surface.
[0039]
【The invention's effect】
According to the present invention, even when the difference between the thermal expansion coefficients of the outer layer and the inner layer is large, excessive residual stress does not occur inside the roll, and the roll can be prevented from being broken such as the boundary joint peeling off during roll production.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view illustrating a HIP method used to manufacture a composite roll for rolling.
FIG. 2 is a schematic cross-sectional view illustrating a HIP method used for producing another composite roll for rolling.
[Explanation of symbols]
1 inner layer, 2 HIP can, 3 outer layer,
4 Intermediate layer, 5 Heater, 6 HIP furnace, 7 Second intermediate layer

Claims (6)

A cemented carbide composite roll in which an outer layer made of a cemented carbide is joined to the outer periphery of an inner layer made of a steel or iron-based material, and having one or more intermediate layers between the inner layer and the outer layer. A cemented carbide rolling composite roll, wherein at least one intermediate layer (intermediate layer A) has a Young's modulus of 190 GPa or less. A cemented carbide composite roll in which an outer layer made of a cemented carbide is joined to an outer periphery of an inner layer made of a steel or iron-based material, having two or more intermediate layers between the inner layer and the outer layer. A cemented carbide rolling composite roll, wherein the intermediate layer (intermediate layer A) bonded to the inner layer has a Young's modulus of 190 GPa or less. The composite roll for cemented carbide rolling according to claim 1 or 2, wherein the intermediate layer (A) is an alloy containing at least 30% by weight of any one of Fe, Ni and Co. 4. The composite roll for cemented carbide rolling according to claim 1, wherein the intermediate layer A has a thickness of 500 μm or more. 5. 5. A bending test according to JIS R1601, wherein a bending test specimen including a boundary joint between the inner layer, the intermediate layer and the outer layer has a bending strength of 600 MPa or more. The composite roll for cemented carbide rolling described in the above item. The cemented carbide rolling composite according to any one of claims 1 to 5, wherein a circumferential compressive residual stress of 100 to 800 MPa is applied to an outer layer surface at a central portion of the roll body. roll.

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