WO2016092867A1

WO2016092867A1 - Work roll for scale breaker

Info

Publication number: WO2016092867A1
Application number: PCT/JP2015/053729
Authority: WO
Inventors: 山崎　浩; 伸公高崎; 隆行小林
Original assignee: 第一高周波工業株式会社
Priority date: 2014-12-08
Filing date: 2015-02-12
Publication date: 2016-06-16
Also published as: TW201625366A

Abstract

The objective of the present invention is to provide a highly reliable work roll for scale breakers that includes a body part having high wear resistance and also a shaft part which is less likely to break, and that is capable of ensuring stable life. The present invention achieves said objective by a scale breaker work roll in which a body part 2 is made of a high-speed steel or a semi-high-speed steel, wherein: a shaft insertion part 31 is constituted by fitting a portion of a shaft member 3 made of a material having greater toughness than the high-speed steel or semi-high-speed steel of the body part 2 into a fitting hole 22 opened in each surface 21 on opposite ends of the body part 2; and the body part 2 and each shaft insertion part 31 are integrated.

Description

Work roll for scale breaker

The present invention relates to a work roll for a scale breaker, and more particularly, a scale breaker work whose reliability and life are greatly improved by using materials having respective necessary characteristics for a body part and a shaft part. It relates to a role (hereinafter sometimes simply referred to as “work role”).

When rolling a steel sheet, an iron oxide film (scale) is formed on the steel sheet surface by air oxidation. Such a coating (scale) is removed by causing a crack by repeatedly bending the steel sheet (scale breaking). In scale braking, a tension leveler type scale breaker is often used for removing the scale and at the same time improving the flatness of the plate.

The tension leveler type scale breaker is composed of a number of rolls. When the plate is threaded, it comes into contact with the steel plate to physically remove the scale and to prevent the work roll from being bent and to flatten the steel plate. It consists of a backup roll and so on. In a tension leveler type scale breaker, as for a roll such as a work roll and a backup roll, a set of a plurality of roll groups are alternately arranged in the vertical direction, and a steel sheet is bent and stretched when traveling between the rolls.

Work rolls are likely to be worn due to contact with the traveling steel plate or large tensile stress in the traveling direction of the steel plate, leading to reduced scale removal and flattening performance. For this reason, it is sometimes necessary to restore the performance by polishing the surface of the contact part (body part) with the steel plate, or to replace the roll itself with a new one. The reduction in productivity and the cost required for roll replacement are problems.

A technique that uses high-speed steel (high-speed tool steel) with high wear resistance as a material for a roll that is resistant to wear and can reduce the frequency of polishing and replacement has been proposed (for example, Patent Document 1).
Patent Document 2 discloses only a roll having a wear-resistant material layer formed by liquid phase sintering of high-speed material powder on the outer periphery of a steel shaft, that is, only a contact portion (body) with a steel plate. A roll made of high-speed material has been proposed.

On the other hand, a work roll consists of a shaft part with a thin diameter of the trunk | drum of a center part and both front-end | tip parts. The body portion is a portion for contacting the steel plate to remove the scale and flattening, and the shaft portion is a portion in which a bearing for controlling the rotational movement of the roll is incorporated.
Usually, the work roll is strongly pulled in the direction of travel of the plate material during operation, and the central portion is bent in the direction of travel, so that a very large load is applied to the shaft portion of the work roll.

The above-mentioned high-speed steel and semi-high-speed steel have high wear resistance, and can reduce wear due to contact with the traveling steel plate. By using high-speed steel or the like on the surface of the body, It is possible to reduce the frequency of the grinding of the body and the replacement of the roll.
However, because high-speed steel and semi-high-speed steel have the disadvantage that the toughness is not sufficient, in a roll formed entirely of high-speed steel, such as the roll of Patent Document 1, the load is concentrated on the shaft portion with a small diameter. Therefore, depending on the operating conditions, there are cases where the roll cannot be used because the shaft portion breaks before the roll becomes unusable due to wear of the body portion.
Moreover, even if it is a roll like patent document 2, since sintering of high-speed material powder is performed at about 1300 degreeC high temperature, a shaft part will also be heated at the time of sintering, and a shaft will be influenced by this heating. There was a case where the part was damaged.

When the shaft portion of the work roll breaks due to operation (operation), the shaft portion cannot be repaired and reused, and the roll having the broken shaft portion is always discarded.
At that time, high-speed steel has a high steel material cost, and it is necessary to dispose a roll made of high-speed steel due to breakage of the shaft part before it becomes a scrap diameter that cannot be polished due to wear of the body part from the viewpoint of material cost It is wasteful and costly.

Also, normally, the work roll status is periodically checked by stopping the equipment once every two weeks. When the wear of the barrel is severe, the performance is restored by polishing or the work roll is replaced. The shaft breakage may occur before two weeks have passed since the start of the use of a new work roll, and the shaft breakage occurs unexpectedly and suddenly, so the device must be stopped. The damage caused by the decline in sex is also enormous.

For this reason, even though the high-speed steel can be used as a material for the body part, the problem of wear of the body part can be solved, causing breakage of the shaft part, which causes problems such as reduced productivity and increased cost. There was room for further improvement in work roll materials.

JP-A-5-169216 JP 2004-250731 A

The present invention has been made in view of the above-mentioned background art, the problem is not only high wear resistance of the body portion that contacts the steel plate, it is difficult to break the shaft portion, can ensure a stable life, The object is to provide a scale breaker work roll that is highly reliable and capable of reducing costs.

As a result of intensive studies to solve the above-mentioned problems, the present inventor has solved the above-mentioned problems by using a hybrid work roll using steel materials having necessary characteristics for the trunk and the shaft. I found that it can be solved.
Specifically, by using a work roll that is formed of a high-speed steel or semi-high-speed steel with high wear resistance and formed with a shaft portion made of a material with high toughness, not only problems due to wear of the body, The present invention has been completed by finding that the problem caused by breakage of the shaft portion can be solved, the life is long, the reliability can be improved, and the cost can be reduced.

That is, the present invention provides a work roll for a scale breaker having a body portion made of high-speed steel or semi-high speed steel, and the body portion is made of high-speed steel or semi-high speed steel in a fitting hole formed in both end side planes of the body portion. A scale breaker work roll comprising: a shaft insertion portion configured by fitting a part of a shaft member made of a material having higher toughness than steel; and the body portion and the shaft insertion portion are integrated. It is to provide.

ADVANTAGE OF THE INVENTION According to this invention, the said problem and the said subject can be solved, and there can be provided the work roll for scale breakers which has few failures by the abrasion of a trunk | drum or a shaft part, has a long life, and was excellent in stability. .

If the shaft part of the work roll breaks, the work roll must be discarded even if the body part can be used. The technology has not been able to take full advantage of the high-speed steel, which has high wear resistance.
The work roll of the present invention employs high-speed steel or semi-high-speed steel that is resistant to wear as a material of the body portion, and makes the shaft portion difficult to break.
For this reason, unlike the prior art, it is no longer necessary to dispose of the work roll due to breakage of the shaft part before the diameter of the body part is abandoned due to wear of the body part, and carbon steel, low alloy steel, SUJ2 ( Compared with high carbon chrome bearing steel, etc., the cost of the steel material is several times higher, but the advantage of high-speed steel or semi-high-speed steel that it is excellent as a material of the body part with high friction can be fully utilized.
In other words, since the shaft portion is not broken, it is possible to use the work roll by repeating the polishing many times until the wear of the barrel progresses to the scrap diameter, and the work roll can be replaced. Productivity is also greatly improved by decreasing the frequency.

Ordinary steel can be increased in toughness (tempering treatment) by lowering the hardness to some extent by tempering after the hardness is increased and the toughness is decreased by quenching. Rolls such as carbon steel, low alloy steel, SUJ2 and the like that were used before high-speed steel was adopted as a raw material for rolls could improve the strength and toughness of the shaft portion by tempering treatment.
However, high-speed steel and semi-high-speed steel such as high-speed steel and semi-high-speed steel have the property of maintaining high hardness and difficult toughness (secondary hardening phenomenon) even at high temperature tempering temperatures during tempering treatment. When is adopted as the material of the shaft part, the toughness of the shaft part can be improved by the tempering treatment and cannot be easily broken.
For this reason, when the steel sheet is strongly pulled in the traveling direction, the load is concentrated particularly on the shaft portion into which the bearing (bearing) is incorporated, and the shaft portion is broken.

In the present invention, the barrel is formed of high-speed steel or semi-high-speed steel, the shaft member is formed of a material having higher toughness than high-speed steel or semi-high-speed steel, and the both are integrated, so that the shaft is resistant to breakage, The portion can provide a hybrid work roll having excellent wear resistance.

Particularly, in the present invention, as a method of integrating the body portion and the shaft member, shrink fitting performed by setting the surface of the body portion to about 150 to 400 ° C. is suitable. Since this shrink-fit temperature is lower than the tempering temperature (500 to 600 ° C.) of the high-speed steel or semi-high-speed steel forming the body portion, the influence of heating due to shrink-fit does not reach the body portion.
That is, because the temperature at the time of tempering the body and the temperature at the time of integration of the body and the shaft member happen to match in terms of the temperature difference between them, It is possible to provide a work roll having both necessary performances.

As described above, in the present invention, since the shaft portion is hardly broken while maintaining the wear resistance of the high-speed steel or semi-high-speed steel of the body portion of the work roll, the wear resistance is high, and the frequency of polishing and replacement is high. The advantages of high-speed steel or semi-high-speed steel, which can be reduced, can be fully utilized. There is little waste. In addition, sudden equipment stoppage due to shaft breakage can be prevented, greatly improving productivity and reliability.

It is a schematic diagram which shows the state before integrating a trunk | drum and a shaft member (The difference of the diameter 31D of a fitting part and the diameter 32D of a protrusion part is exaggerated and drawn). FIG. 3 is a schematic view showing a roll for a scale breaker of the present invention formed integrally with a body portion and a shaft member (the difference between the diameter of the fitting portion and the diameter of the protruding portion is exaggerated).

Hereinafter, the present invention will be described, but the present invention is not limited to the following embodiments, and can be implemented with arbitrary modifications.

The scale breaker work roll 1 of the present invention is a hybrid work roll formed by integrating a body 2 and a shaft member 3 formed of different materials.

FIG. 1 schematically shows a state before the body 2 and the shaft member 3 are integrated. An annular recess or an annular protrusion may be present on the peripheral wall of the body portion 2, but these are omitted in the drawing.
The body portion 2 is formed of high-speed steel or semi-high speed steel, and cylindrical fitting holes 22 are formed in the center portions of the both-end side planes 21 of the body portion 2.
The shaft member 3 is made of a material having higher toughness than the high-speed steel or semi-high-speed steel forming the body, and includes a fitting portion 31 and a protruding portion 32. The fitting portion 31 is a portion that is fitted into the fitting hole 22 of the trunk portion 2 and functions as the shaft insertion portion 31. The protruding portion 32 is a portion that is not fitted into the fitting hole 22 and remains exposed. When the work roll 1 is used, the protruding portion 32 functions as a shaft portion 32 in which a bearing (bearing) is incorporated. is there.

As schematically shown in FIG. 2, by performing an operation such as shrink fitting in a state where the fitting portion (shaft insertion portion) 31 of the shaft member 3 is fitted in the fitting hole 22 of the trunk portion 2, the trunk portion 2 is obtained. And the shaft insertion part 31 is integrated, and the work roll 1 for scale breakers of this invention is completed.

<Body>
The trunk | drum 2 in the work roll of this invention is formed with high-speed steel or semi-high-speed steel. High-speed steel and semi-high-speed steel are characterized in that a large amount of special metal components such as chromium (Cr), tungsten (W), molybdenum (Mo), and vanadium (V) are added. Due to the presence of carbides of these special metal components, high-speed steel and semi-high-speed steel are hardened by quenching, and are excellent in wear resistance and corrosion resistance. For this reason, high-speed steel or semi-high-speed steel is suitable as a material for the body portion where wear occurs when it comes into direct contact with the steel plate.

High-speed steel is a high-speed tool steel of the symbol SKH, which is standardized in JIS G4403 of Japanese Industrial Standard (JIS).

Among them, high-speed steel containing, by weight, C: 0.8 to 1.3%, Cr: 3 to 5%, Mo: 4 to 7%, W: 4 to 11%, V: 1 to 5% Is particularly suitable for the present invention.
In addition to these metal components, the high-speed steel used in the present invention may contain cobalt (Co).

Specific examples of high-speed steel suitable for the present invention include SKH51, SKH52, SKH53, SKH55, and SKH56 according to JIS G4403.

Semi-high-speed steel (matrix high-speed steel) has a lower carbon (C) content than high-speed steel, and other alloy components are the same as high-speed steel. Semi-high-speed steel is characterized by higher toughness than high-speed steel.

The dimension of the trunk | drum 2 is suitably determined according to the kind of scale breaker apparatus with which a work roll is used.
The length of the body 2 is not limited, but is usually 100 cm to 400 cm, preferably 150 cm to 195 cm.
The diameter of the body 2 is not limited, but is usually 60 mm to 100 mm, preferably 70 mm to 90 mm.

A cylindrical fitting hole 22 into which a part of the shaft member 3 (fitting portion 31) is fitted is formed in the center portion of the both end side planes 21 existing on both sides of the body portion 2.

The depth 22L of the fitting hole is preferably 40 mm or more and 150 mm or less, more preferably 50 mm or more and 100 mm or less, and particularly preferably 55 mm or more and 70 mm or less.
If it is too shallow, the joint strength between the body part 2 and the shaft insertion part 31 is weak, and a crack may occur at the boundary of the joint part.
If the depth is too deep, the entire length of the shaft member 3 is increased, and only the labor for cutting is increased, and the bonding strength between the body portion 2 and the shaft insertion portion 31 is not increased.

In particular, when the body portion 2 and the shaft member 3 are integrated by shrink fitting, it is necessary to precisely create the fitting hole 22 in consideration of deformation at the time of contraction, but the depth 22L of the fitting hole is deep. If it is too high, precise processing becomes more difficult, and it is not preferable to make it deeper than necessary.
Furthermore, when the depth 22L of the fitting hole is too deep, it is difficult to uniformly heat the periphery of the fitting hole 22, and the diameter is reduced during the insertion of the shaft insertion portion 31 and may be inserted only halfway. Also grows.
The above-described problem also applies when the depth 22L of the fitting hole is too deep and the fitting holes from both ends penetrate.

The diameter 22D of the fitting hole is appropriately determined according to the diameter 31D of the fitting portion of the corresponding shaft member 3, but is preferably 15 mm or more and 40 mm or less, and more preferably 20 mm or more and 30 mm or less.

There is no particular limitation on the method for producing the fitting hole 22, and a known method can be used. The fitting hole 22 is preferably produced after the body 2 is quenched and tempered.

胴 The barrel formed of high-speed steel or semi-high-speed steel is quenched and then tempered.

At the time of quenching, at least the surface 20 of the barrel portion 2 is quenched, and after quenching, the barrel portion 2 is tempered at 500 ° C. or more and 600 ° C. or less, and then the shaft member 3 is fitted into the fitting hole 22. It is preferable that the shaft insertion portion 31 is configured so that the body portion 2 and the shaft insertion portion 31 are integrated, and it is particularly preferable that only the surface of the body portion is quenched by induction hardening.

When the trunk | drum 2 is high-speed steel, 1000 degreeC or more and 1350 degrees C or less are preferable, and 1150 degreeC or more and 1250 degrees C or less are especially preferable.
When the trunk | drum 2 is a semi-high-speed steel, 1000 degreeC or more and 1350 degrees C or less are preferable, and 1050 degreeC or more and 1150 degrees C or less are especially preferable.
High-speed steel and semi-high-speed steel are extremely hardened by quenching in the above temperature range, and wear resistance is improved.

The method for quenching the body 2 is not particularly limited, but it is preferable to quench only the surface 20 of the body by induction quenching.
Induction hardening is a method of hardening that causes electromagnetic induction by high-frequency electromagnetic waves and heats the surface, and only the surface of the steel material is hardened, and the inside can be kept in a state of maintaining toughness to some extent. It is a quenching technique.
Since the surface of the trunk | drum 2 contacts with the steel plate which is a to-be-processed object, it is preferable that hardness is as high as possible.

On the other hand, when the fitting hole 22 is manufactured after quenching, it is easier to perforate (manufacture) if the internal hardness remains low. Further, in order to reduce the influence of deformation when integrating the body 2 and the shaft member 31 by shrink fitting or the like, and to suppress the risk of cracking, it is better to maintain toughness to some extent inside the body.
For the reasons described above, the induction hardening is a method in which the hardness of the surface is increased (toughness is decreased) and the hardness is not significantly increased (the toughness is not significantly decreased). This is a suitable method.

After quenching the barrel 2, tempering is performed. The tempering temperature is preferably 500 ° C. or higher and 600 ° C. or lower, and more preferably 530 ° C. or higher and 570 ° C. or lower.

The method of tempering the body 2 is not particularly limited, and tempering is performed in a commonly used heating furnace.

Tempering of the body portion 2 formed of high-speed steel or semi-high-speed steel is performed at a high temperature as described above. In general steel materials, when tempering, the hardness decreases instead of recovering toughness reduced by quenching to some extent, but high-speed steel and semi-high-speed steel contain a large amount of Cr, W, Mo, V, so By tempering at such a high temperature, a stable carbide is formed and the hardness is increased (secondary curing phenomenon).
However, on the other hand, high-speed steel and semi-high-speed steel do not improve toughness by high-temperature tempering. Therefore, when high-speed steel or semi-high-speed steel is used as the material for the shaft, the shaft cannot be reinforced to prevent breakage. . According to the present invention, it is possible to eliminate the disadvantages of such high-speed steel and semi-high-speed steel.

<Shaft member>
The shaft member 3 in the work roll of the present invention is formed of a material having higher toughness than the high-speed steel or semi-high-speed steel of the body portion 2.
The shaft member 3 includes a fitting portion 31 and a protruding portion 32. The fitting portion 31 is a portion that is fitted into the fitting hole 22 of the trunk portion 2, functions as the shaft insertion portion 31, and is integrated with the trunk portion 2. The protruding portion 32 is a portion that does not fit into the body portion 2 and constitutes a shaft portion, that is, a portion into which a bearing is incorporated when using a work roll.

During the operation of the scale breaker device, the work roll is pulled strongly in the traveling direction of the traveling steel plate, so the load is concentrated on the shaft portion with a small diameter. May break.
In the work roll of the present invention, in order to prevent breakage of the shaft portion, the shaft member 3 (particularly, the protruding portion 32 that functions as the shaft portion after being integrated with the body portion) is made from the high-speed steel or semi-high speed steel of the body portion 2. It is made of a material with high toughness.

The material of the shaft member 3 must be a material having higher toughness than the high-speed steel or semi-high-speed steel of the body 2. Higher toughness is preferable as the material of the shaft member 3, and the material of the shaft member 3 is selected in consideration of the steel material cost, availability, and the like.

Specific examples of the shaft member 3 are preferably chromium molybdenum steel, carbon steel, SUJ2 (high carbon chromium bearing steel), nickel chromium molybdenum steel, and the like.
Moreover, the thing to which the tempering process which makes toughening, such as hardening and tempering, was given is more preferable.

Chromium molybdenum steel is a carbon steel material for machine structure of the symbol SCM standardized in JIS G4053.
Chromium molybdenum steel is excellent in hardenability and is difficult to reduce toughness during tempering, so it is often used for parts with a high risk of brittle fracture, such as crankshafts. It is suitable as a material used for the roll shaft.

In order to obtain a sufficient quenching effect, steel materials having a high carbon content such as SCM435, SCM440, and SCM445 are preferable among chromium molybdenum steels.

Carbon steel is a steel material whose amount of elements other than C is not classified as alloy steel. In order to obtain a sufficient quenching effect, a material having a weight% and C of 0.4% or more is suitable as the material of the shaft member 3.
Specific examples of such carbon steel include S45C, S50C, and the like among carbon steel materials for machine structure standardized in JIS G4051.

Nickel-chromium-molybdenum steel is a carbon steel material for mechanical structure of the symbol SNCM standardized in JIS G4053, and expensive nickel (Ni) is added to further increase the toughness of chromium-molybdenum steel.

In order to obtain a sufficient quenching effect, a steel material having a large carbon content such as SNCM240, SNCM439, and SNCM447 is preferable among nickel chromium molybdenum steels.

SUJ2 (high carbon chrome bearing steel) is a material often used for bearings and the like, and is inexpensive. SUJ2 (high carbon chrome bearing steel) is one of steel materials used as a material for rolls before high-speed steel is adopted.

The diameter 31D of the fitting portion of the shaft member 3 and the diameter 32D of the protruding portion may be the same or different. That is, before integration with the trunk portion 2, the boundary 33 between the fitting portion 31 and the protruding portion 32 may or may not be visible.
FIG. 1 illustrates a case where the diameter 31D of the fitting portion is larger than the diameter 32D of the protruding portion. In this way, after integrating the body portion 2 and the shaft insertion portion 31, it becomes difficult for a step to occur at the boundary portion between the shaft insertion portion 31 and the protruding portion 32, and the stress is broken at the boundary portion due to stress concentration. Less likely to occur.
FIG. 1 shows exaggeratedly the difference between the diameter 31D of the fitting portion and the diameter 32D of the protruding portion. Specifically, the difference between the two (32D−31D) is preferably from 0.3 mm to 5 mm, and more preferably from 0.5 mm to 2 mm.

Furthermore, when the diameter 31D of the fitting portion is different from the diameter 32D of the protruding portion (when the presence of the boundary 33 can be clearly confirmed), the boundary 33 is integrated into a smooth taper shape or an arc shape having a large diameter. Steps are less likely to occur after conversion.

The diameter 31D of the fitting portion is substantially the same as the diameter 22D of the fitting hole, preferably 15 mm or more and 40 mm or less, and more preferably 20 mm or more and 30 mm or less.
The length 31L of the fitting portion is substantially the same as the depth 22L of the fitting hole, preferably 40 mm or more and 150 mm or less, more preferably 50 mm or more and 100 mm or less, and particularly preferably 55 mm or more and 70 mm or less.
In addition, it is preferable to perform chamfering processing, and particularly preferable to perform R chamfering processing, in order to reduce stress concentration, at the rear end of the fitting hole.

The diameter 32D of the protruding portion is substantially the same as the diameter 31D of the fitting portion, preferably 15 mm or more and 40 mm or less, and more preferably 20 mm or more and 30 mm or less.
The length 32L of the protruding portion is preferably 30 mm or more and 100 mm or less, more preferably 40 mm or more and 80 mm or less, and particularly preferably 50 mm or more and 60 mm or less.

The ratio 31L: 32L of the length 31L of the fitting portion and the length 32L of the protruding portion is preferably 4: 1 to 1: 2, and more preferably 2: 1 to 1: 1.

<Integration of body and shaft member>
Examples of the operation for fitting a part of the shaft member 3 into the fitting hole 22 and integrating the body portion 2 and the shaft member 3 (the shaft insertion portion 31 thereof) include shrink fitting, welding, brazing, and screwing.
However, in a method such as screwing, the thread may be broken or the shaft may be broken near the boundary 33 due to stress concentration. In addition, in methods such as welding and brazing, the shaft portion may become high temperature, the toughness may be reduced, and the shaft portion may be broken, or the joint strength may be low.

For this reason, an operation for fitting a part of the shaft member 3 into the fitting hole 22 and integrating the body portion 2 and the shaft insertion portion 3 (the shaft insertion portion 31 thereof) is shrink fitting, and the temperature around the fitting hole 22 is adjusted. It is preferable to integrate the body portion 2 and the shaft insertion portion 3 (the shaft insertion portion 31 thereof) by shrink fitting at 150 ° C. or more and 400 ° C. or less.
The temperature around the fitting hole 22 is more preferably 200 ° C. or higher and 350 ° C. or lower, and particularly preferably 250 ° C. or higher and 300 ° C. or lower. By setting it as such a temperature range, the trunk | drum 2 and the shaft insertion part 3 can fully be integrated.
Since shrink fitting can be performed at a relatively low temperature as described above, the shaft portion is not exposed to a high temperature during heating, and a locally weak portion such as a screw thread is not formed. It is hard to break.

In addition, since the above temperature range is lower than the tempering temperature (500 to 600 ° C.) of high-speed steel or semi-high-speed steel, the influence of heating by shrink fitting does not reach the body 2 and the friction resistance of the body 2 is reduced. do not do.
As described above, when the body 2 and the shaft member 3 are integrated by shrink fitting, they can be integrated at a temperature lower than the tempering temperature of high-speed steel or semi-high-speed steel. That is, when shrink fitting is adopted as an integration method, the temperature at the time of tempering of the body portion coincides with the temperature at the time of integration of the body portion and the shaft member. The effect of the present invention to provide a work roll in which the performance required for each of the trunk and the shaft is maintained is exhibited without affecting the properties.

When the body 2 and the shaft insertion portion 31 are integrated by shrink fitting, it is defined by a value obtained by dividing the shrinkage allowance (the difference between the diameter 31D of the fitting portion and the diameter 22D of the fitting hole) by the diameter 31D of the fitting portion. The shrink fit rate is preferably 0.5 / 1000 or more and 2/1000 or less, more preferably 0.6 / 1000 or more and 1.8 / 1000 or less, and particularly preferably 0.7 / 1000 or more and 1.5 / 1000 or less.
When the lower limit of the shrinkage fit rate is equal to or higher than the above, tightening is sufficient, and the portion constituting the shaft member 3 does not fall off.
When the upper limit of the shrinkage fit is not more than the above, distortion due to excessive tightening does not occur, and there is no possibility of breakage. In addition, shrink fitting is inevitably performed by heating to a certain temperature, but if the upper limit of the shrink fitting rate is not more than the above, the shrink fitting temperature is the tempering temperature of high-speed steel or semi-high-speed steel (500 to 600.degree. C.), and the effect of the present invention is exhibited because the influence of heating during integration does not reach the body.

In the case of shrink fitting, after designing the shape of the fitting hole 22 and the shaft insertion portion 31 in consideration of the volume change at the time of expansion / contraction, the body portion 2 and the shaft insertion portion 31 are integrated, It is easy to make a structure in which a step such as a step at the boundary portion between the shaft insertion portion 31 and the protruding portion 32 is unlikely to be deformed, and it is possible to have a shape in which breakage is unlikely to occur.
Specifically, as shown in FIG. 1, a chamfered portion 31 a is provided at the tip of the fitting portion (shaft insertion portion) 31, or a chamfered portion 22 a is provided at the entrance of the fitting hole 22, during heating (during expansion). ), The deformation at the time of contraction can be suppressed.

The work roll for a scale breaker of the present invention has high wear resistance of the body and high toughness of the shaft, and therefore has a long life and can prevent a decrease in productivity due to line stoppage. This is because the body and the shaft member are formed of different materials, and the above operation is adopted as an operation for integrating the body and the shaft member.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples and comparative examples as long as the gist thereof is not exceeded.

[Comparative Example 1]
Two work rolls (Daiichi High-Frequency Industrial Co., Ltd., DHH-511) with a barrel portion formed entirely of high-speed steel, including the barrel portion and the shaft portion, are attached to a tension leveler type scale breaker device, and a steel plate The scale braking process was performed in continuous operation.

[Example 1]
A cylindrical member having the same composition as the high-speed steel used in Comparative Example 1 was quenched at 1200 ° C. and then tempered at 550 ° C. A hole having a diameter of 26 mm and a depth of 80 mm was formed in the flat surfaces on both ends of the cylindrical member to form a body portion.
A shaft member was made of chromium molybdenum steel (SCM440). The fitting part of the shaft member had a diameter of 26.05 mm and a length of 80 mm, and the protruding part had a diameter of 25 mm and a length of 55 mm. The boundary between the fitting portion and the protruding portion is a smooth taper.

The temperature around the body fitting hole is set to 300 ° C., the shaft insertion portion of the shaft member is shrink-fitted into the body fitting hole, and the body portion and the shaft member are integrated to separate the body portion and the shaft portion. The work roll formed with the material of this was produced. The shrinkage fit rate was 1.9 / 1000, and it was visually confirmed that there was no step at the boundary between the body part and the shaft part.

The overall shape of the produced work roll was almost the same as the work roll used in Comparative Example 1.
The produced work roll was attached to a tension leveler type scale breaker device in the same manner as in Comparative Example 1, and the steel sheet scale breaking treatment was performed in a continuous operation under the same conditions as in Comparative Example 1.

[Example 2]
Except that the chromium molybdenum steel (SCM440) is changed to the carbon steel (S45C), a work roll having a body portion and a shaft portion formed of different materials is produced in the same manner as in Example 1, and scale braking of the steel plate is performed. The treatment was performed continuously.

<Results of Examples and Comparative Examples>
In Comparative Example 1, after 85 hours from the start of operation, one shaft portion of the work roll was broken at the root, and the operation was stopped. Although the work roll body was visually confirmed for some scratches, it was still usable at least after polishing. However, the shaft part was broken, so it had to be replaced with a new work roll.

On the other hand, in Example 1 and Example 2, the shaft portion was not broken, and the scale braking process was performed smoothly. Two weeks after the start of operation, as a periodic inspection, the state of the work roll was confirmed, and no abnormality was found in the shaft. The torso was confirmed to have some scratches but was usable. For this reason, operation was started again.

In Example 1 and Example 2, the state of the work roll was confirmed by regular inspection every two weeks thereafter, but no abnormality was found in the shaft portion.
When traces of spalling and peeling were confirmed on the barrel, the same work roll could be used again by polishing the surface of the barrel. The barrel was repeatedly polished and used for about one year until the barrel diameter reached 70 mm, which was the scrap diameter, but no breakage of the shaft occurred.

Since the work roll for scale breaker of the present invention has a long life and excellent productivity, it is widely used for rolling steel sheets in steelworks, coil centers, and the like.

DESCRIPTION OF SYMBOLS 1 Work roll for scale breakers 2 Trunk part 20 Trunk part surface 21 Both-ends side plane 22 of the trunk part Fitting hole 22a Chamfering part 22L of fitting hole Depth of fitting hole 22D Diameter of fitting hole 3 Shaft member 31 Fitting part (axial fitting part )
31a Chamfered part 31L of the fitting part Length 31D of the fitting part Diameter 32 of the fitting part Projecting part (shaft part)
32L Length of protruding part 32D Diameter of protruding part 33 Boundary between fitting part and protruding part

Claims

A scale breaker work roll whose body is made of high-speed steel or semi-high-speed steel, and a material having higher toughness than the high-speed steel or semi-high speed steel of the body in the fitting holes formed in the both end side planes of the body A scale breaker work roll comprising: a shaft insertion portion configured by fitting a part of the shaft member formed in step 1; and the body portion and the shaft insertion portion are integrated.
The operation of fitting a part of the shaft member into the fitting hole and integrating the body portion and the shaft insertion portion is shrink fitting. The work roll for scale breakers according to claim 1, wherein the body portion and the shaft insertion portion are integrated with each other.
The work roll for a scale breaker according to claim 1 or 2, wherein the shaft member is formed of chromium molybdenum steel, carbon steel, SUJ2 (high carbon chromium bearing steel) or nickel chromium molybdenum steel.
The scale breaker work roll according to any one of claims 1 to 3, wherein a depth of the fitting hole into which a part of the shaft member is fitted is 40 mm or more.
After quenching at least the surface of the barrel part and tempering the barrel part at 500 ° C. or more and 600 ° C. or less after the quenching, the shaft member is fitted into the fitting hole to form a shaft insertion part, The work roll for a scale breaker according to any one of claims 1 to 4, wherein the body portion and the shaft insertion portion are integrated.
The work roll for a scale breaker according to claim 5, wherein only the surface of the body is quenched by induction quenching.
Of the shaft members, the diameter of the fitting portion that is fitted into the fitting hole is larger than the diameter of the protruding portion that constitutes the shaft portion without being fitted into the fitting hole, and after the trunk portion and the shaft insertion portion are integrated The work roll for a scale breaker according to any one of claims 1 to 6, wherein a step is hardly generated at a boundary between the fitting portion and the protruding portion of the shaft member.