JPS6045001B2 - Cold rolling method of stainless steel strip in Sendzimer rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cold rolling stainless steel strip using a 20-high Sendzimer rolling mill.

As shown in Fig. 1, the work roll 1 of the Sendzimer rolling mill
The stainless steel strip S is rolled at a rolling reduction rate of 5 to 25 per bath depending on the
%, rolling blade 50-500 tons, forward tension 15-40 kg
During rolling with a rear tension of 10 to 35 to 9/1, a phenomenon in which the steel strip S broke due to front and rear tension fluctuations was often experienced. As a result of various investigations conducted by the present inventors, it has been confirmed that this tension fluctuation occurs due to slip occurring between the first intermediate drive roll 2 and the second intermediate drive roll 3.

That is, during rolling of the steel strip S, the rolling speed is controlled by the rotational speed and circumferential speed of the work roll 1, while the tension is controlled independently by the driving torque of the reel for both the front and rear sides. There is.

However, when a slip occurs between the first intermediate drive roll 2 and the second intermediate drive roll 3, the rotation of the second intermediate drive roll 3 instantaneously increases, resulting in an apparently accelerated state.

In such a situation, acceleration/deceleration compensation (
Forging) causes tension fluctuations, and at the same time, slippage makes it impossible to independently control the front and rear tensions.
The steel strip s is pulled with the same tension on both the front and rear sides, and if this phenomenon occurs instantaneously or recovers, the tension fluctuation becomes an impact and the steel strip s breaks.

The slip phenomenon between the first intermediate drive roll 2 and the second intermediate drive roll 3 occurs without any electrical or mechanical signs being observed immediately before, and the steel strip s slips instantly. It is impossible to prevent this by operation because the steel strip S breaks, and it is impossible to prevent the steel strip S from being damaged due to the time loss, damage to the rolls, and reduction in the yield of the steel strip. Therefore, it is extremely important to prevent the slip phenomenon. On the other hand, since stainless steel strips are required to have surface gloss, the surface roughness of the rolls used for cold rolling is generally fine.
The initial surface roughness of the intermediate drive roll 3 is 0.4μ (R
a), and when the throughput of the material to be rolled is 30 tons or more, the Ra is less than 0.1μ (Ra), and in particular, the second intermediate drive roll 3 continuously rolls 2000 tons or more.

Therefore, the surface roughness of the first intermediate drive roll 2 and the second intermediate drive opening/5 step 3 becomes finer due to the rolling history, the contact ratio between both rolls 2 and 3 decreases, and the frictional force decreases at both ends. roll 2
, 3 slips. In addition, in FIG. 1, 4 is a second intermediate idler roll, and 5 is a bucking bearing. Based on the above-mentioned knowledge, the present invention prevents the slip phenomenon between the first intermediate drive roll 2 and the second intermediate drive roll 3, and also prevents the second intermediate drive roll 3 from impairing the surface quality of the rolled material. The control range for surface roughness was established to prevent problems from occurring in the past.

That is, the surface finish roughness of the second intermediate drive roll 3 is set to 0.
．． ? (Ra) or more 0. It was set to less than the radius (Ra).

Figure 2 shows a conventional second intermediate drive roll 3 with a surface finish roughness of 0.4μ (Ra) and a surface finish roughness of 1.0μ.
FIG. 4 shows the change in surface roughness of the material to be rolled with the second intermediate drive roll 3 (Ra) according to the rolling tonnage of the present invention.

In both cases, the surface roughness decreases by about 0.2 to 0.3 p (Ra), and in the case of 1.0 p (Ra) finish, it decreases by 0.7 to 0.3 p (Ra).
0. ? It becomes almost constant at (Ra).

Next, Table 1 below shows the relationship between the surface roughness of the second intermediate drive roll 3 during rolling and the presence or absence of rolling abnormalities.

As is clear from Table 1 above, the surface roughness is 0.6p (
If the end is less than Ra), slipping may occur.
On the other hand, when it is 1.6p (Ra) or more, the surface roughness is transferred to the steel strip S via the work roll 1, a fine pattern is generated on the surface of the steel strip S, and the surface gloss is inhibited, which is undesirable. .

Therefore, the surface roughness of the second intermediate drive roll 3 is 0.6p (Ra
) or more and less than 1.6 p (Ra) is most preferable, and the reduction in surface roughness due to the above-mentioned rolling is 0.2 to 0.3 p7 (Ra)
Considering this, the appropriate initial surface roughness control range for preventing roll slip during rolling and not impeding the surface gloss of the steel strip S is 0.8p (Ra) or more and 1.6p (R
a) Must be less than

In this way, the surface roughness of the second intermediate drive roll 3 is set to 0.8p.
(Ra) or more and less than 1.6μ (Ra) and even when the rolling throughput was 3000 tons, no roll slip occurred at all. Table 2 below shows the conventional second intermediate drive roll 3 and the second intermediate drive roll 3 according to the present invention.
This shows a comparison of the number of roll slip accidents over a three-month period. As described above, according to the present invention, roll slip does not occur during rolling, and smooth rolling is possible. Therefore, there is no risk of steel strip breakage or damage to the work roll, first intermediate drive roll, second intermediate drive roll, second intermediate idler roll, backing bearing, etc. due to steel strip breakage, which improves productivity. Can make a significant contribution.

[Brief explanation of the drawing]

Figure 1 shows the arrangement of rolls in the Sendzimer rolling mill, and Figure 2 shows the initial surface roughness of the second intermediate drive roll at 0.4p (
It is a graph showing the change in surface roughness with respect to the rolling tonnage of the rolled material when Ra) and 1.0 μ (Ra) are set.

Claims (1)

[Claims] 1. When rolling a stainless steel strip using a 20-high Sendzimer rolling mill, the initial surface roughness should be 0.8μ (Ra) or more1.
．． A method of cold rolling stainless steel strip in a Sendzimer rolling mill, characterized by using a second intermediate drive roll maintained at less than 6μ (Ra).