JPS6147603B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for cold rolling steel strip using a Sendzimir rolling mill. In the cold rolling of stainless steel strips, a Sendzimir rolling mill with winding and unwinding means on the entry and exit sides and small-diameter work rolls is usually used to perform reversible rolling and apply rolling oil during rolling. ing. FIG. 1 is a schematic diagram showing a Sendzimir rolling mill. Since the Sendzimir rolling mill is vertically symmetrical, only the upper part is shown. In the figure, 1 is a rack for rolling down, 2a~
2d is bucking bearing shaft, 3 is 2 intermediate drive rolls, 4 is 2 intermediate idle rolls, 5 is 1
An intermediate roll, 6 is a work roll, 7 is a wiper, 8 is a sprayer, and 9 is a stainless steel strip. When the rolling down rack 1 is moved upward by a rolling cylinder (not shown), the bucking bearing shafts 2b and 2c are biased. Rolling down is carried out by moving the work roll 6 downwards. Also, the rolling oil is spray 8
The liquid is sprayed from there toward the work roll 6. moreover,
In order to prevent rolling oil from adhering to the steel strip 9 and spilling out of the rolling mill, the rolling oil is wiped off by wipers 7 provided on the inlet and outlet sides of the rolling mill. By the way, the gloss of the steel strip 9 and the surface roughness Ra of the work roll 6 have a relationship as shown in FIG.
The smaller the surface roughness Ra of the work roll 6, the higher the gloss of the steel strip 9. Therefore, in order to improve the gloss of the steel strip 9, it is necessary to use a work roll 6 with a small surface roughness Ra to reduce the surface roughness of the steel strip 9. However, when a work roll 6 with a small surface roughness Ra is used, the surface of the steel strip 9 becomes smooth, and most of the rolling oil is wiped away by the wiper 7 on the exit side of the rolling mill. Almost no rolling oil is contained in between.
On the other hand, in normal rolling operations, the unwinding tension of the next pass is smaller than the winding tension of the previous pass, so this tension difference ΔT causes loosening of the steel strip 9 when unwinding it, and the steel strip 9 is rolled loosely. Slippage occurs between the strips 9, and this slippage causes misalignment flaws on the surface of the steel strips 9. In order to prevent this misalignment from occurring, a slip sheet is usually inserted between the steel plates 9.
In this case, interleaving sheets are used, which increases costs, and the work of inserting interleaving sheets is complicated, resulting in poor workability and reduced productivity. This invention was made in order to solve the above-mentioned problems, and provides a cold rolling method for steel strips that is inexpensive, has good workability, and does not cause any misalignment defects on the surface of the steel strip. The purpose is to provide. In order to achieve this object, the present invention provides a method of cold rolling a steel strip by performing reversible rolling using a Sendzimir rolling mill having winding and unwinding means on the entry side and the exit side, and applying rolling oil during rolling. In the rolling process before the finishing pass, when the tension difference ΔT between winding and unwinding is 1.5 Kg/mm ² or less, a work roll with a surface roughness Ra of 0.1μ<Ra<1.0μ is used, and the above tension is When the difference ΔT is more than 1.5Kg/ ^mm2 and less than 10Kg/ ^mm2 , the surface roughness Ra is (9
ΔT/85−1/17) Use a work roll with μ<Ra<1.0μ. That is, in the past, the work roll 6 with the same surface roughness Ra = 0.1μ as the finishing pass was used for rolling before the finishing pass, but in this invention, the work roll 6 with the same surface roughness Ra = 0.1μ as the finishing pass By using the work roll 6 with a large Ra, the steel strip 9
An oil pit corresponding to the tension difference ΔT is formed on the surface of the steel strip 9, and an oil film is formed between the wound steel strips 9 by the oil pit, and the slippage of the steel strip 9 due to the tension difference ΔT between winding and unwinding is prevented by this oil film. Prevents the occurrence of co-slip defects caused by. Therefore, there is no need to insert interleaving paper between the steel strips 9. Then, in the finishing pass, a work roll 6 with a surface roughness of Ra = 0.1 μ or less is used, and rolling is performed at a reduction rate of 18 to 25%.
Insert a slip sheet only for this finishing pass. in this way,
The reason why the work roll 6 with a small surface roughness Ra is used in the finishing pass is to ensure the same level of surface quality (gloss, luster) as before. FIG. 3 is a graph showing the relationship between the surface roughness Ra of the work roll 6 and the tension difference ΔT between winding and unwinding. By the way, in order to form oil pits in the steel strip 9, it is desirable to use a work roll 6 with a large surface roughness Ra, but it is not recommended to use a work roll 6 with a surface roughness Ra = 1.0μ or more during rolling before the finishing pass. Then, in the finishing pass, the surface roughness Ra = 0.1
Using a work roll 6 with a diameter of less than μ, the rolling reduction rate is 18 to 25%.
Even when rolled, the effects of rolling before the finishing pass, that is, the scratch marks of the roll grinder remain, and the level of surface quality deteriorates. In addition, in order to eliminate this effect, it is possible to increase the reduction rate in the finishing pass, but if the reduction rate is 25% or more, the oil pit will not be able to be held, resulting in heat scratches or poor shape. (ear elongation). Therefore, in rolling before the finishing pass, regardless of the tension difference ΔT, the surface roughness of the work roll 6
It is necessary to keep Ra below 1.0μ, that is, below line a in FIG. In addition, the surface roughness of the work roll 6
When Ra is 0.1 μ or less, oil pits are not formed on the surface of the steel strip 9 as described above, and most of the rolling oil is wiped away by the wiper 7, so there is almost no oil film between the rolled steel strips 9. Therefore, even if the tension difference ΔT is 1.5 Kg/mm ² or less, co-slip defects will occur due to the slippage of the steel strip 9 due to the tension difference ΔT. Therefore, in rolling before the finishing pass, the tension difference ΔT is 1.5 When it is less than Kg/mm ¹ , the surface roughness Ra needs to be more than 0.1μ, that is, more than line b in Fig. 3. Furthermore, when the tension difference ΔT exceeds 1.5Kg/mm ² , the tension difference ΔT
Unless the oil film formed between the wound steel strips 9 is made thicker by increasing the surface roughness Ra according to the size of Therefore, when the tension difference ΔT exceeds 1.5 Kg/mm ² during rolling before the finishing pass, the surface roughness Ra should be reduced to (9ΔT/85-1/
17) It is necessary to make it a value exceeding μ, that is, the value should be greater than line c in Fig. 3. In other words, if rolling is carried out using work rolls 6 with surface roughness Ra within the range surrounded by lines a to c in FIG. No defects will occur. As explained above, in the steel strip cold rolling method according to the present invention, in the rolling before the finishing pass,
Since there is no need to insert a slip sheet between the steel strips, costs can be reduced, and since there is no need to insert a slip sheet during rolling before the finishing pass, the rolling speed can be increased. Since idle time can be reduced, workability is improved and productivity is increased. Tables 1 and 2 compare the rolling speed and throughput of the conventional method and the method of this invention, respectively.

【table】

[Table] Furthermore, even without inserting interleaving paper between the steel strips, no misalignment defects occur, and the surface properties of the steel strips are the same as with conventional methods, making it possible to produce high-grade steel strips that do not impair marketability. can be manufactured. As described above, the effects of this invention are remarkable.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the Sendzimir rolling mill, Figure 2
The figure is a graph showing the relationship between the gloss of the steel strip and the surface roughness Ra of the work roll, and Figure 3 is a graph showing the relationship between the surface roughness Ra of the work roll and the tension difference ΔT between winding and unwinding. . 6... Work roll, 7... Wiper, 8... Spray, 9... Stainless steel strip.

Claims (1)

[Claims] 1. In a method of cold-rolling a steel strip by performing reversible rolling and applying rolling oil during rolling using a Sendzimir rolling mill having winding and unwinding means on the entry and exit sides, the rolling process is performed before the finishing pulse. When the tension difference ΔT between and unwinding is 1.5Kg/ ^mm2 or less, use a work roll with a surface roughness Ra of 0.1μ<Ra<1.0μ, and the tension difference ΔT is 1.5Kg/mm2 ^.
A cold rolling method for steel strip, characterized in that when the surface roughness Ra exceeds 10 Kg/mm ² and is less than or equal to 10 Kg/mm 2 , a work roll with a surface roughness Ra of (9ΔT/85−1/17)μ<Ra<1.0μ is used.