JPS5946297B2 - Sendzimir rolling roll - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to Sendzimir rolling rolls, and more particularly to the material of the rolls.

Traditionally, as materials for Sendzimir rolling rolls, in weight percent,
C1, 4~1.6%, SiO, 6% or less, Mn0, 3~
0.6%, Cr11-13%, Mo0.8-1.2%,
Steel consisting of V 0.7 to 0.9% and the remainder Fe has been used.

As for the heat treatment method, after oil quenching from 1030 to 1050°C, tempering is performed at 500 to 520°C to achieve Hs80.
We have adopted a method to obtain a hardness of ~85.

However, recently, heat treatment methods have been developed to reduce residual stress to O or compressive stress in order to improve accident resistance.
Surface hardening methods using slow cooling below a point or induction heating hardening are now being adopted.

Furthermore, due to the recent economic situation, there is an urgent need to reduce roll manufacturing costs, and chemical components are being reviewed.

Roll materials for Sendzimir rolling mills are generally made of cold die steel (SKDII equivalent material).

In addition, from the viewpoint of accident resistance, i.e., damage caused by seizure accidents to the rolled material during rolling, a high-temperature tempering method of 500 to 520°C is adopted after quenching to minimize the amount of quenched residual austenite, and to reduce the amount of quenched martensite. Generally, it is annealed in a so-called secondary hardening temperature range to improve toughness.

Secondary hardening during tempering is caused by the decomposition of residual austenite and the precipitation of fine carbides from martensite, and for this purpose, the addition of Mo and V has been considered essential.

For this reason, the cost of the rolls had to be high.

An object of the present invention is to provide a Sendzimir roll that has sufficient wear resistance even after heat treatment without producing residual stress or induction heating quenching, and does not contain V.

In the present invention, the composition of the roll is C1.4 to C1.6 in weight%.
%, SiO, 6% or less, Mn0, 8-1.2%, Cr1
It is characterized by consisting of 1 to 13% Mo, 0.8 to 1.2% Mo, and the remainder Fe and impurities.

In the present invention, the amount of C and Cr is necessary to maintain the wear resistance inherent in cold die steel and maintain the hardness of Hs80 or higher, and 1.4 to 1.6% of C and 11 to 13% of Cr are both components. This is important in terms of balance, and if the amount is less than this, the required hardness will not be obtained and the wear resistance will also decrease.

Further, if the amount is increased more than this, forgeability will be impaired, but it is not necessary to increase the amount more than this in order to maintain the current wear resistance.

Further, Mo is essential for increasing resistance to temper softening, and Mo has a greater effect than V.

If the amount of Mo is less than 0.8%, the hardness decreases with each increase in the number of times of tempering at 500 to 520° C. after quenching, and the required hardness and wear resistance cannot be obtained.

The present invention does not include V in order to reduce roll cost.

However, if ■ is not included, bainite transformation is likely to occur when slow cooling is performed to below the Ms point (below 300'C) during quenching in order to improve the accident resistance of the sesidimia roll. In some cases, the hardenability deteriorates and the required hardness cannot be obtained.

To compensate for this, the amount of Mn added was increased to prevent a decrease in hardenability.

'The optimal amount of Mn added is 0.8 to 1.2%, and if it is less than 0.8%, an improved heat treatment method, that is, a quenching method that gradually cools the area below the Ms point, or a surface quenching method using induction heating quenching, is recommended. There is some precipitation of paynite, and on the other hand, if it exceeds 1.2%, the amount of residual austenite after quenching increases, making the heat treatment conditions complicated.

Figure 1 shows conventional steel type 42 (C1,42%, Si0.42
%, Mn 0.41%, Cr12.02%, M.

0.98%, vo, si%) and the invention alloy A61 (C1
,46%, Si0.50%, Mn1.09%, Cr11
．． 36%, Mo1.01%, Vo, 06%) to 1050
quenching temperature at 400°C, then soaked in salt at 30°C.
Transfer to a 0°C electric furnace and cool to room temperature at 5°C/Hr.
This shows the change in hardness when tempered three times under the tempering conditions of 20'CX1.5Hr, and the hardness after tempering three times is almost the same for both.

Next, in Figure 2, the same steel type as in Figure 1 is heat treated to Hs83, 80# emery paper is placed on a 170 mmφ flat disk, rotated at 700 RPM, and the test piece is pressed onto it with a load of 1 kg. Comparing the amount of wear when reciprocating to the center twice, there is almost no difference between the two steel types.

When a work roll of 92mm diameter x 1114mmJ was prototyped using the alloy of the present invention and an electrical steel plate was rolled using a Sendzimir rolling mill, the amount of wear was comparable to conventional steel types (proving that it can withstand practical use).

According to the present invention, although it does not contain V, it has the same wear resistance as conventional rolls and also has excellent accident resistance.

[Brief explanation of drawings]

FIG. 1 is a curve diagram showing a comparison of heat treatment hardness between a conventional steel type and an alloy of the present invention, and FIG. 2 is a graph showing a comparison of wear resistance between a conventional steel type and an alloy of the present invention.

Claims (1)

[Claims] 1% by weight, C1.4-1.6%, Si 0.6% or less, Mn 0.8-1.2%, Cr 11-13%, Mo
A Sendzimir rolling roll characterized in that it is made of steel consisting of 0.8 to 1.2% Fe with the remainder being Fe.