JPH101749A - Roll material for cold rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a roll material for cold rolling excellent in indentation resistance, long in a service life and furthermore excellent in cost performance. SOLUTION: This roll material has a compsn. contg., by weight, 0.7 to 1.3% C, 0.3 to 1.5% Si, 0.15 to 1.5% Mn, 0.15 to 1.5% Ni, 1.0 to 6.0% Cr, 0.2 to 0.8% Mo and 0.01 to 0.2% V, furthermore contg. one or more kinds among Ti, Nb, Zr and Re by 0.02 to 0.12% in total, and the balance substantial Fe with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roll material for cold rolling which exhibits extremely excellent dent resistance without impairing mechanical properties.

[0002]

2. Description of the Related Art Conventional roll materials for cold rolling include, by weight, C: 0.70 to 1.20% and Si: 0.15 to 0.15%.
1.00%, Mn: 0.15 to 1.00%, Cr: 1.
3 to 6.00%, Mo: 0.20 to 0.50%, V:
Steel comprising less than 0.40% is used. In recent years,
For further improvement of wear resistance and high hardening depth, high Cr
There is a tendency for high alloying such as formation of steel and high speed steel. However, at present, the production cost increases due to high alloying, and sufficient cost performance has not been obtained. On the other hand, dent resistance has not been solved as an important issue of the roll material for cold rolling.

[0003]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is a component system of the above-mentioned conventional roll material for cold rolling, which exhibits an excellent effect particularly on dent resistance. An object of the present invention is to provide a roll material for cold rolling excellent in cost performance.

[0004]

Means for Solving the Problems To solve the above problems, the roll material for cold rolling of the present invention comprises C:
0.7-1.3%, Si: 0.3-1.5%, Mn:
0.15 to 1.5%, Ni: 0.15 to 1.5%, C
r: 1.0 to 6.0%, Mo: 0.2 to 0.8%, V:
0.01 to 0.2%, and one or more of Ti, Nb, Zr and Re in a total of 0.02 to 0.12%
And the balance is Fe and inevitable impurities.

The reasons for limiting the content of each component in the present invention are described below. C: 0.7 to 1.3% C is an important component for determining the hardness as a roll for cold rolling. If it is less than 0.7%, sufficient hardness cannot be obtained, and if it exceeds 1.3%, eutectic carbides (Fe, Cr,
(Eutectoid of metal such as Mo and V and carbon) is likely to be formed, and mechanical strength is likely to be reduced, so C: 0.7 to 1.3.
%.

Si: 0.3 to 1.5% Mn: 0.15 to 1.5% Ni: 0.15 to 1.5% Si is generally used as a deoxidizing agent, but is quenched together with Mn and Ni. It is a component that has a significant effect on sex. Si
Particularly, in the continuous cooling transformation curve of the roll material according to the present invention, the effect of shifting the pearlite nose to the longer time side and the effect of shifting the Ms point to the higher temperature side are obtained. However, excessive addition lowers toughness, so that S
i: 0.3 to 1.5%. On the other hand, Mn and Ni are elements that greatly contribute to hardenability, but increase the amount of retained austenite because the Ms point is shifted to a lower temperature side.
Therefore, Mn: 0.15 to 1.5%, Ni: 0.15 to
1.5%.

[0007] Cr: 1.0 to 6.0% Cr improves the quenchability and the wear resistance. Generally, the amount of Cr and the depth of cure are in a substantially proportional relationship. However, on the other hand, if the addition exceeds 6%, eutectic carbides appear, which significantly impairs grindability and lowers accident resistance.
6.0%.

Mo: 0.2-0.8% Mo significantly improves tempering resistance and wear resistance, but excessive addition causes the appearance of eutectic carbides.
0.2 to 0.8%.

V: 0.01 to 0.2% V can be expected to have the same effect as Mo, but if it is 0.01%, it has no effect. If it exceeds 0.2%, it combines with carbon to reduce the hardness of the roll. Therefore, the content is set to 0.01 to 0.2%.

One or more of Ti, Nb, Zr and Re: 0.02 to 0.12% in total A small amount of these elements can increase the austenite crystal grain coarsening temperature. Thereby, when obtaining a high hardening depth in a low alloy steel, even if the quenching temperature is set higher, it is possible to maintain the accident resistance without impairing the mechanical properties. If the total amount is less than 0.02%, there is no effect, and if it exceeds 0.12%, the effect is saturated and the roll grindability is rather deteriorated.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a roll material for cold rolling according to the present invention will be described with reference to the drawings. FIG. 1 shows the effect of each trace element of Ti, Nb, Zr, and Re on austenite crystal grain coarsening with respect to the quenching temperature. In order to investigate the effect of each trace element, Ti, Nb, Z were added to conventional steel Nos. 12 to 16 shown in Table 1 below.
Steel to which r or Re was added was used. By containing Ti, Nb, Zr or Re as in the steel of the present invention,
Even if the quenching temperature is increased, growth of austenite crystal grains can be suppressed. For comparison, the effects of other trace elements are also shown, but no significant effect is obtained with Y, Hf, and Ta. That is, as shown in FIG. 1, when the quenching temperature is 900 ° C., 0.05% of Ti, Nb, Zr,
No matter which of Re, Y, Hf, and Ta is added, the austenite grain size (the relative value is 1) is almost the same. However, when the quenching temperature was raised to 950 ° C., 0.05% of Ti,
The grain size is suppressed to about 1.2 in the four types of steels containing any of Nb, Zr, and Re, while 0.05% of Y, H
The grain size of the steel to which f or Ta is added is 1.3 to 1.
4 and larger.

FIG. 2 shows the relationship between the quenching temperature and the Charpy impact value of the above four types of steel. The specimen is
□ 3.5 × 55 (mm) without notch, commonly used for high hardness materials. It was confirmed that the addition of Ti, Nb, Zr and Re did not impair the Charpy impact value so much even when the quenching temperature was increased. That is,
Four kinds of steels containing Ti, Nb, Zr or Re have a Charpy impact value at room temperature of about 25 J / cm ² at a quenching temperature of 900 ° C., whereas the Charpy impact value at a quenching temperature of 950 ° C. The impact value drops by 2-3 J / cm ² . On the other hand, Ti,
Steel containing no Nb, Zr or Re element has a quenching temperature of 900
In the case of ℃, the impact value is also about 25 J / cm ² , whereas at a quenching temperature of 950 ° C., the impact value is reduced by 10 J / cm ² .

FIG. 3 shows the relationship between the amounts of Ti, Nb, Zr, and Re added and the austenite grain size. The crystal grain size (crystal grain size) becomes finer as the addition amount of each element increases to 0.05%, the crystal grain size increases when the addition exceeds 0.05%, and the grain refinement effect exceeds 0.15%. Became constant, and rather, the grinding property tended to deteriorate. If the content is 0.02% or less, the effect is small, and there is a high possibility that it will be inevitable. Ti, Nb, Zr, Re
Austenitic particle size ratio when 0.02% is added,
Since the particle size ratio when 0.12% is added is about the same, the range is set to 0.02 to 0.12%.

Next, the roll material of the present invention was applied to an actual roll. Table 1 shows the components of the roll material according to the present invention and those of the conventional steel as a comparative material, which were used in an actual machine.

[0015]

[Table 1]

Sample Nos. 1 to 8 were made of Ti, Nb, Zr, R
e, the steels of the present invention containing e.
This is a conventional steel containing no Nb, Zr, or Re. In addition, the roll manufactured with these components has a body diameter of 440 mm and a body length of 14 mm.
This is a work roll for a cold single lever mill having a length of 20 mm and a total length of 4100 mm.

FIG. 4 shows the measurement results of the hardness of each roll.
Shore hardness is representative of rebound hardness, Vickers hardness is representative of indentation hardness, and it is well known that each is affected by the residual stress of the roll itself. In particular, Shore hardness has a large effect. It is considered that the Vickers hardness has a correlation with the dent. According to the measurement results, the Vickers hardness of the roll made of the steel of the present invention is remarkably improved as compared with the roll made of the conventional steel at the same Shore hardness.

FIG. 5 shows the evaluation results of the dent resistance of the roll. The dent resistance represents the resistance of the roll surface to being damaged by the material to be rolled. Here, the dent resistance of the roll was evaluated by the roll life based on the frequency of roll replacement performed due to the dent of the roll generated during rolling. The material to be rolled is ordinary steel and the final finish thickness is 0.2-0.3
mm. The basis for the roll change is when a dent having a depth of 5 μm or more is formed on the roll surface. Each time, the roll is polished to remove the dent. The life ratio in the figure indicates, so to speak, the amount of material that can be rolled by a roll once polished. Assuming that the life of 16 rolls until they are used for rolling and replaced is 1,
The life of the other rolls is indicated by a relative comparison value. As a result, Invention Steel No. The life of the roll composed of the conventional steel No. 2 to 2.3 as compared with those consisting of 9 to 16
A dramatic effect was seen.

[0019]

According to the present invention, a roll material is obtained by adding at least one of Ti, Nb, Zr and Re to a conventional roll material in a total amount of 0.02 to 0.12%. It is possible to provide a roll material for cold rolling that is excellent in dent resistance, has a long roll life, and is excellent in cost performance.

[Brief description of the drawings]

FIG. 1 shows the quenching temperature and Ti,
It is a figure which shows the relationship with austenite crystal grain size ratio at the time of adding Nb, Zr, and Re.

FIG. 2 is a diagram showing a relationship between a quenching temperature and a Charpy impact value in the roll material of the present invention.

FIG. 3 shows Ti, Nb, Zr,
It is a figure which shows the relationship between the addition amount of Re and the austenite crystal grain size ratio.

FIG. 4 shows the hardness H of each of the roll material of the present invention and a comparative material.
It is a figure which shows v, Hs.

FIG. 5 is a view showing a life ratio indicating dent resistance of a cold rolling roll made of the roll material of the present invention and a comparative material.

Claims (1)

[Claims] 1. The chemical composition in terms of weight ratio, C: 0.7-1.
3%, Si: 0.3-1.5%, Mn: 0.15-1.
5%, Ni: 0.15 to 1.5%, Cr: 1.0 to 6.
0%, Mo: 0.2 to 0.8%, V: 0.01 to 0.2
%, And further contains at least one of Ti, Nb, Zr and Re in a total amount of 0.02 to 0.12%, with the balance being Fe and an unavoidable impurity alloy. Excellent roll material for cold rolling.