JPH05287435A - Roll material for rolling - Google Patents

Abstract

PURPOSE:To obtain a highly efficient roll material for rolling reduced in rolling force and combining superior wear resistance with cracking resistance by preparing a roll material for rolling having a composition which contains specific percentages of C, V, Co, Mo, and W and has the balance iron and where chromium equivalent is regulated to a specific value or below. CONSTITUTION:The roll material for rolling having a composition which consists of, by weight, 1.0-2.5% C, 3.0-10.0% V, 5.0-10.0% Co, further <=3% of either or both of Mo and W, and the balance iron and where the chromium equivalent represented by equation (chromium equivalent %) =Cr%+0.75(Mo%+W%) is regulated to <=12% is prepared. By this method, the highly efficient roll remarkably improved in wear resistance and cracking resistance can be stably provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling roll material which is applied to steel rolling rolls such as hot strip mills and which particularly reduces rolling load and has both abrasion resistance and crack resistance. It is a thing.

[0002]

2. Description of the Related Art Conventionally, as a roll material of this type, C: 2 to 3.2%, C, which has appropriate wear resistance and crack resistance.
r: 12 to 18%, high chromium cast iron containing Ni and Mo at 2% or less, or C: 3 to 3.4%, Cr: 0.4 to
High alloy grain cast iron containing 1.5%, Ni: 2 to 5%, Mo: 1% or less was widely used (see Iron and Steel Foundation Joint Research Group “Abrasion of Steel Materials” P16).

In JP-A-58-87249, C: 2.4 to 3.5%, V: 6.1 to 14% Cr,
Roll materials containing alloy elements of Mo, W, and Co have been tried to improve wear resistance.

[0004]

Abrasion resistance and crack resistance are the most important properties required for rolling rolls.
If the wear of the roll is small, the plate thickness accuracy of the rolled steel product is improved, the frequency of roll replacement is reduced, and the work efficiency is improved. On the other hand, if the crack resistance is insufficient, cracks occur due to heat and mechanical load during use, which causes a great trouble, interrupts the rolling operation, and eventually damages the rolling equipment. Therefore, it is strongly desired to combine both of the above characteristics.

In this respect, as compared with high chromium cast iron materials and high alloy grain cast iron materials, JP-A-58-87249 (Japanese Patent Publication No. 2-19)
In the roll material disclosed in Japanese Patent No. 181), the carbide that crystallizes is hard and the hardness after quenching is also high, so that the wear resistance is extremely good. However, it cannot be said that the crack resistance is good.

Further, there is a problem that the rolling load is increased when it is subjected to rolling. Needless to say, if the rolling load increases, productivity is impaired due to equipment restrictions, and power consumption also increases, resulting in higher costs and worse economic efficiency.

Therefore, the present invention particularly reduces the rolling load,
In addition, it is intended to provide a high-performance rolling material for rolling having both good wear resistance and good crack resistance.

[0008]

In order to solve the above-mentioned problems, the rolling material for rolling of the present invention is C: 1.0 to 2.5% V: 3.0 to 10.0% Co: 5 0.0 to 10.0% Further, at least one kind of Mo and W is contained in an amount of 3% or more, and the chromium equivalent calculated by the chromium equivalent% = Cr% + 0.75 (Mo% + W%) is 12% or less, and the balance. Is characterized by consisting essentially of iron.

[0009]

The reason for limiting the C content to the above range of 1.0 to 2.5% is as follows. That is, C is the lower limit of 1.0%
If the amount is less than the above, hard carbide is hardly crystallized and wear resistance is significantly deteriorated, and improvement in performance cannot be expected. On the other hand, the upper limit value is 2.5%
If it exceeds, the abrasion resistance is improved, but brittle carbides are increased, and the improvement in the crack resistance that the rolling roll must have cannot be achieved.

MC with V content is extremely hard among carbides
It is selected in balance with C to crystallize the type VC carbide. Particularly in the case of the material of the present invention, this VC carbide is used to improve the wear resistance, but this carbide is important because it directly crystallizes from the molten metal as a primary crystal and controls the structure. That is, in the range of C: 1.0 to 2.5%, when V is less than the lower limit of 3%, hard VC carbides are not crystallized and solid solution occurs in the matrix structure. On the other hand, when it exceeds 10% of the upper limit, carbides increase and the crack resistance is impaired.

The reason why Co is limited to 5 to 10% will be described. Most of Co dissolves in the matrix to improve its strength,
Especially, it has a remarkable effect at high temperature. Now, when each carbide has VC carbide that is crystallized free, the wear resistance of the carbide itself is extremely high, but if the wear resistance of the surrounding base is not, the surrounding wears and only the carbide remains and the protrusions A file was formed, and a phenomenon occurred in which the friction coefficient in the roll bite (the rolling contact portion between the roll and the plate) was increased and the rolling load was increased. Therefore, Co was added to improve the hardness and strength of the matrix to improve wear resistance and eliminate this phenomenon.

The effect is shown in FIG. 1. The rolling load has a strong correlation with the Co content, and the reduction effect is remarkable especially at 5% or more. Even when contacting the reinforcing roll, the abrasion of the reinforcing roll was similarly increased, but this was eliminated. On the other hand, since Co is extremely expensive, the upper limit value at which it is possible to find a practically remarkable effect by adding it in relation to the cost is limited to 10% or less.

Further, Cr and M are used as main alloying elements.
o and W are also useful for improving roll performance. All of them are easily bonded to C, and some of them form MC carbide with V to improve wear resistance and form a solid solution in the matrix to improve matrix hardness and strength, but in the roll material of the present invention, It forms a hard M ₆ C eutectic carbide.

However, when Cr is added alone, M ₇ C ₃ type brittle mesh-like carbides crystallize out, so M
It is M ₆ C that contains 3% or more of either o or W.
It is essential for the formation of carbides. Further, it is necessary to limit the amount of carbides in order to secure crack resistance and not hinder the rolling load reducing effect in the Co range, and the chromium equivalent having a strong correlation with the amount of carbides was set to 12% or less.

In addition, due to the deoxidation of the molten metal and the like,
Useful elements Si and Mn are 0.5% each
The content of impurities, such as P and S, may be about 0.03% or less contained in ordinary castings, and they may be contained, and these do not impair the effects of the present invention.

[0016]

EXAMPLE As a working example of the present invention, a work roll for a hot strip finishing mill was manufactured. The melting is performed in a high frequency induction furnace, the casting is performed by the continuous casting method disclosed in Japanese Patent Publication No. 44903/44, and the core material is forged steel (SCM44).
0) was adopted as a composite roll. As for the heat treatment, after casting, annealing, quenching and tempering were performed.

Table 1 shows concrete manufacturing qualities of the conventional example and the examples of the present invention and the qualities of use in actual rolling. In the examples of the present invention, roll cracks caused by troubles during use are shown. It is obvious that the rolling load was low and the rolling performance was remarkably improved.

[0018]

[Table 1]

[0019]

EFFECTS OF THE INVENTION By applying the present invention to a steel rolling roll, it becomes possible to stably supply a high-performance roll having significantly improved wear resistance and crack resistance, and reduce the rolling load. As a result, the quality of rolled products and the productivity and economic efficiency in rolling operations have been improved.

[Brief description of drawings]

FIG. 1 is a drawing showing rolling load when the roll material disclosed in the present invention is used.

Claims (1)

[Claims] 1. C: 1.0 to 2.5% V: 3.0 to 10.0% Co: 5.0 to 10.0% Further, at least one kind of Mo and W is contained in an amount of 3% or more, and Rolling material for rolling characterized in that the chromium equivalent represented by the formula is 12% or less, and the balance substantially consists of iron. Chrome equivalent% = Cr% + 0.75 (Mo% + W%)