JP2003311305A - Composite roll for hot rolling excellent in crack resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite roll for hot rolling excellent in crack resistance by reducing tensile residual stress in the radial direction of an end face of a roll barrel part and simultaneously preventing the oxidation corrosion on the end face of a roll. <P>SOLUTION: This roll is the composite roll in which the outer layer consisting of a high-speed steel base alloy and an inner layer consisting of a steel base material are bonded by building-up method by tinkering, caliber grooves are formed on the roll barrel part and a chamfer is formed so that the boundary between the outer layer and the inner layer is present on a face chamfering the corner part at the roll barrel end part. The tilt angle of the chamfer is taken as within the range of 5-30° to the radial direction of the roll and substance for preventing the oxidation corrosion is adhered or coated on the surface of the boundary between the outer layer and the inner layer on the chamfered face. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a roll
Composite Roll for Hot Rolling Made of Cast Overlay with Bar Groove
It is about. [0002] 2. Description of the Related Art Rolling rolls have a body surface to be used.
In addition, that there is little wear, that the skin is hard to occur,
It is required that cracks and chips do not occur. these
For the purpose, casting molds with a hard outer layer
Forging rolls with hardened body by heat treatment
Rolls of these various materials and manufacturing methods depending on the application
Is generally used. Such various composite rolls
Among them, the outer layer made of high-speed alloy (high-speed outer layer)
The inner layer made of steel material was joined by casting and overlaying
Composite rolls have excellent wear resistance and other properties.
Have been used. [0003] SUMMARY OF THE INVENTION Conventional high-speed steel outer layer and steel
Composite roll for hot rolling with an inner layer made of
Therefore, the outer layer of high-speed steel is
Inherent in the roll, despite its poor breakage resistance
Rolling stress such as rolling pressure and thermal stress in addition to residual stress
However, most of the load is applied to the outer layer.
There is a problem that breakage is likely to occur in the vicinity. In order to prevent the breakage near the roll body end face,
For example, Japanese Patent Application Laid-Open No. 6-182409 discloses
An outer layer of an alloy and an inner layer of a steel material, wherein the outer layer and the inner layer
The boundary with the layer exists on the chamfered surface of the roll body corner
HIP made by chamfering
Are described. This
The residual tensile stress in the radial direction at the end of the roll
Can be reduced. [0005] The casting method is different from the HIP method.
This technology is applied to composite rolls with
The boundary between the outer layer of high-speed steel and the inner layer made of steel
Carbon in the base near the outer layer of the part
Is more likely to occur. Troostite is oxidized and corroded
Low due to the cooling water used during rolling.
The boundary between the outer layer and the inner layer on the end face of the
Cracks are generated at each position, and stress concentrates microscopically
However, the problem of breakage occurred. Accordingly, the present invention solves the above-mentioned problems,
Reduces the tensile residual stress in the radial direction at the end of the roll body.
At the same time, by preventing oxidation corrosion of the roll end face.
To provide a composite roll for hot rolling with excellent splitting resistance.
aimed to. [0007] SUMMARY OF THE INVENTION That is, the hot rolling of the present invention
The composite roll consists of an outer layer made of a high-speed alloy and a steel-based material.
The inner layer consisting of
A caliber groove in the outer shell and the inner and outer layers
Boundary exists in the chamfered surface of the roll body corner
A composite roll having a chamfer as described above,
Angle of inclination of 5 ° to 30 ° with respect to the roll radial direction.
Boundary between outer layer and inner layer within the chamfered plane
Attach or apply a substance that prevents oxidative corrosion on the surface of
It is characterized by having. [0008] [Function] The inclination angle of the chamfer applied to the roll body end corner is low.
Cast roll-up composite roll with a caliber groove
If the residual stress in the radial direction of the roll end face is kept small,
Both of them affect the caliber, so special consideration is required.
Must. That is, the inclination angle of the chamfer is set to the roll radius
Must be within the range of 5-30 ° to the direction.
You. The stress control by the roll body end surface shape
The angle of inclination of the chamfer applied to the corners is
If less than 5 °, there is substantially no effect. More than 30 °
In this case, the actual body length is shortened and the number of calipers may be reduced.
It is not preferable because of its potential. More preferable roll body end
The angle of inclination of the chamfer applied to the corner is 10 to 30 °. In the present invention, the high-speed steel for forming the outer layer is used.
The chemical composition of the alloy is as follows: C is 1.0 to 3.5% by weight;
i is 2.0% or less, Mn is 2.0% or less, and Cr is 10.
0% or less, W is 3.0 to 15.0%, Mo is 2.0 to 1
0.0%, Fe group containing 1.0 to 15.0% V
Gold is preferred. The reasons for limiting each chemical component range are detailed below.
I do. C: 1.0 to 3.5% C combines with simultaneously contained Cr, W, Mo and V to form
It forms hard carbides and contributes to improvement of wear resistance. However
However, if it becomes excessive, the amount of carbide becomes excessive, and the material becomes
Embrittles. Further, C forms a solid solution in the matrix and hardens the base by tempering.
Has the effect of reducing the toughness of the base if excessive
Let it. Therefore, the content of C is 1.0 to 3.5%.
preferable. A more preferable C content is 1.5 to 2.7%.
It is. Si: 2.0% or less Si has the effect of increasing the hardness of the matrix in addition to the deoxidizing effect, oxidation resistance
It has the effect of enhancing the properties and corrosion resistance. Therefore, 2.0% or less
It is contained below. Further preferred Si content is 0.2 to
1.0%. Mn: 2.0% or less Mn also has a deoxidizing effect and further enhances the hardenability.
Therefore, the content is 2.0% or less. More preferred M
The n content is 0.2 to 1.0%. Cr: 10.0% or less Cr combines with C to form carbides and impart wear resistance
As well as a solid solution in the base to enhance hardenability,
It has the effect of increasing temper hardenability. However, excess
If contained in the steel, the toughness of the matrix will be reduced.
The content is as follows. A more preferred Cr content is 3.
0 to 5.0%. W: 3.0-15.0%, Mo: 2.0
~ 10.0% W and Mo combine with C to form an M6C-type carbide.
To improve wear resistance,
Has the effect of increasing the secondary curability. However, excess
In addition to making the material expensive, the toughness
Therefore, as the content in the present invention, W is
3.0 to 15.0%, Mo is preferably 2.0 to 10.0%.
New More preferably, the W content is 3.0 to 10.0.
% And Mo are 4.0 to 10.0%. V: 1.0-15.0% V, like W and Mo, is carbonized
The material is an MC type carbide, and the MC type carbide is Hv2
500-3000, M₆Hardness of C-type carbide (Hv
1500 to 1800). For this reason, wear resistance is essential.
If an alloy with a high V content is used for the required roll,
Life is improved. However, even if it is contained excessively, the toughness is poor.
And the machinability deteriorates. Low V content
If the amount is too large, the effect cannot be achieved. Therefore, V is 1.
0 to 15.0%. Further preferred V content is
4.0 to 10.0%. Co: 15% or less Co may be contained in the above chemical components. Co has heat resistance
It is effective to provide
Can be However, when it is excessive, the toughness is low.
Therefore, the content is set to 15% or less. Even better
The preferred Co content is 10% or less. Further, the inner layer of the present invention withstands a rolling load.
Cast steel, forged steel, rolled steel, etc., as long as they have sufficient strength
Any steel-based material can be used. [0018] BEST MODE FOR CARRYING OUT THE INVENTIONExample As the outer layer, C: 1.9%, Si: 0.8 by weight ratio
%, Mn: 0.5%, Cr: 4.6%, W: 4.3%,
An Fe-based alloy containing Mo: 2.2% and V: 4.8%,
Casting overlay method using SCM440 core material as inner layer
For angle of body diameter φ690mm, body length 1250mm
Rolls were manufactured. Figure 1 shows a schematic cross-sectional view of the roll drum end face.
Show. In FIG. 1, 1 is a roll body, 2 is an inner layer, 3 is
The outer layers, 4 and 4a, are the shapes of the corners of the roll body end, and 7 is
2 shows a bar groove. In manufacturing, the distance from the surface of this roll is
By the finite element method at a pitch of 10 mm,
The radial residual stress (σr) was calculated. Figure 2 shows this total
The change of σr obtained from the calculation is shown. In FIG. 2, the curve
Curve 6 is outside when 5 is not chamfered at the corner of the roll body.
The boundary between the layer and the inner layer is within the chamfered surface of the roll body corner.
Shown is the result of chamfering to be present. In addition, the curve
6 is to set the chamfering inclination angle θ at the barrel end corner to 20 °
This is shown. These values should agree well with the measured values
I also checked. As shown in FIG.
The highest tensile residual stress is found on the layer side
Was. When a chamfer is formed as in curve 6, curve 5
Compared to the case without chamfering
It can be seen that the force is about half the value. As an embodiment of the present invention, reference numeral 4a in FIG.
The beveling angle θ at the barrel end is 20 °.
Then, a composite roll for angles was manufactured. Row in this case
The residual stress in the radial direction at the end face is shown by the curve 6 in FIG.
The residual tensile strength near the boundary between the outer and inner layers at the end of the trunk
The stress was kept small. Also, the body end corner of this composite roll
Liquid as a substance to prevent oxidative corrosion on chamfered surfaces
Epoxy resin paint was applied with a brush. For angle rolling
As a result, even if used for a long time,
With the outer layer of the chamfered surface of the roll barrel edge
The inner layer boundary is not corroded,
No cracks were seen and the condition remained healthy. [0021]Comparative Example 1 As Comparative Example 1, the same components and dimensions
Do not chamfer the corner of the barrel end as shown by the straight line 4 in FIG.
An angle composite roll was manufactured in the shape. In addition, the trunk end
The surface is coated with a substance that prevents oxidative corrosion as in the previous embodiment.
Clothed. When this roll was subjected to actual rolling,
Cracking occurred. According to the survey results, the breakage was
Generated from the outer layer near the boundary of the outer layer,
To the surface. The position of this starting point is shown in FIG.
Almost coincides with the peak position of the maximum tensile stress in the curve 5
Was. [0022]Comparative Example 2 As Comparative Example 2, the same components and dimensions
The chamfer of the body end corner is taken along the straight line 4a in FIG.
The boundary between the outer layer and the inner layer is
Chamfer so that it lies within the chamfered surface
Processing was performed to produce a composite roll for angles. this
At the time, prevent oxidation corrosion on the chamfered surface of the roll barrel end corner.
Material was not applied or applied. Angle rolling fruit
As a result of being subjected to mill rolling,
But several months after use, similar to Comparative Example 1
A part breakage accident occurred. When this roll was observed for fracture surface, Comparative Example 1 was obtained.
Similarly to the above, the breakage occurs from the outer layer near the boundary between the outer and inner layers,
To the surface of the tool. Further details of the breakage generation part
Observation shows that decay along the boundary from the outer layer side near the outer inner layer
The food was progressing and some cracks were occurring. Again
When observing the interface structure, the corroded part is mainly
Precipitate is deposited and the part is selectively corroded.
It turned out to be the starting point of the crack. [0024] The composite roll for hot rolling of the present invention has a body
At the same time as reducing the radial tensile residual stress on the end face
In addition, by preventing oxidative corrosion of the end face, it has excellent breakage resistance.
It has excellent accident resistance, long life, and high quality.
Products can be produced stably.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view of a body end portion of a composite roll body for hot rolling in Examples and Comparative Examples. FIG. 2 shows the relationship between the distance from the roll surface and the residual stress in the radial direction of the end face of the roll in Examples and Comparative Examples. [Description of Signs] 1 Roll, 2 Inner layer, 3 Outer layer, 4, 4a Shape of body end corner, 5 Curve of end face residual stress without chamfering, 6 Change of end face residual stress with chamfering Curve, 7 caliber groove

Claims (1)

Claims: 1. An outer layer made of a high-speed alloy and an inner layer made of a steel material are joined by a cast overlaying method to form a caliber groove in a roll body, and an outer layer and an inner layer are formed. A composite roll formed with a chamfer such that a boundary between the chamfer and the roll body end corner is present in a chamfered surface, wherein an inclination angle of the chamfer is in a range of 5 ° to 30 ° with respect to a roll radial direction. A composite roll for hot rolling excellent in cracking resistance, characterized in that a substance for preventing oxidative corrosion is adhered or applied to the surface of the boundary between the outer layer and the inner layer in the chamfered surface.