JPS5924888B2 - Cold rolling method of steel strip - Google Patents

Description

[Detailed description of the invention] This invention relates to a method for cold rolling copper strips.

As is well known, in cold rolling of steel strip, rolling oil is used to reduce friction between the copper strip and the rolls.

Mineral oil, esters, etc., which are easily emulsifiable, are generally used as this rolling oil, and this is mixed at an oil concentration of around 4% for roll cooling and lubrication, and the coolant is sprayed into the work roll bite. do.

However, it cannot be denied that the lubricity is inferior when compared to the case where palm oil, beef tallow, etc., which are difficult to emulsify, are directly supplied to the roll.

Particularly when rolling a thin material (Q, 5mm mm or less) at high speed, there is insufficient lubrication in the roll bite, causing metal contact between the steel strip and the roll, causing a so-called heat scratch, which damages the surface of the steel strip. In addition to impairing the aesthetic appearance, these scratches are printed on the roll and reduce the roll unit consumption.

Therefore, in the conventional cold rolling using a rolling oil spray method using a coolant, the rolling speed cannot be increased, and there is a limit to the rolling speed.

That is, in the case of conventional spray application of rolling oil using a coolant, the upper limit of the rolling speed at which scratches do not occur is about 700 mpm at maximum for a sheet with a thickness of 0.3 mm;
For a 5 urn plate thickness, the maximum speed is about 1200 mpm.

The purpose of the present invention is to prevent metal contact between the roll and the steel strip due to lack of oil film of rolling oil (lubricating oil) during cold rolling.
Suppresses the occurrence of so-called heat scratches,
Another object of the present invention is to provide a rolling method that increases the rolling speed of thin materials and improves productivity.

As mentioned above, the cause of heat scratch defects on copper strips during cold rolling is insufficient lubrication due to lack of oil film of rolling oil in the rolling machine roll bite of copper strips during cold rolling. It is thought that the situation of insufficient lubrication is different between the upper and lower surfaces of the steel strip, and as a result of investigating the lubrication conditions on the upper and lower surfaces of the copper strip, heat scratch flaws (hereinafter simply referred to as scratch flaws) were found. It was found that the cause of this was mainly due to the small amount of rolling oil adhering to the lower surface of the steel strip.

The present invention has been made based on the above knowledge, and in addition to the conventional coolant A that injects rolling oil for roll cooling and lubrication, a high concentration rolling oil B with an oil concentration of 10% or more is applied to the roll of the work roll. Cold rolling is performed by spraying the underside of the copper strip between the rolling mill stands before it is bitten.

The timing and position of injecting this highly concentrated rolling oil B are determined at steel strip 3.
In order to ensure that the rolling oil B sprayed onto the lower surface works effectively during rolling, it is preferable to do so immediately before the steel strip is rolled. As a result of the investigation, it was confirmed that #3 and #4 stands where the rolling speed is high and the reduction ratio is large are more likely to cause this.

From this result, injection of high-concentration rolling oil can be omitted in #1 and #2 stands where the rolling speed is relatively slow, and injection of high-concentration rolling oil can be omitted in the #5 stand because the rolling reduction is relatively small; When using a roll, it is preferable to perform spraying, and when using a dull roll, it may be omitted.

In other words, the final stand in cold rolling plays an important role in controlling the roughness of the product surface. On the other hand, when a blind finish is required, a bride roll is used, and in this case the rolling method for both is slightly different. Even if the speed is increased, there is little risk of oil film breakage, and therefore, the spray injection of high-concentration rolling oil B between stands #4 and #5 will worsen in terms of basic unit, and will cause oil to adhere to the steel strip after rolling. This is not necessary in the case of a dull roll because the amount of the roll becomes a dog and has an adverse effect, but in the case of a flight roll, although the rolling reduction rate at the #5 stand is slightly lower, a considerable rolling reduction rate is still required, and therefore, the rolling reduction rate is still high. It is more effective to inject concentrated rolling oil B.

Further, it is preferable that the nozzle device for injecting this high concentration rolling oil be installed behind the tension roll 4 between the stands, with care taken so that the injected rolling oil B is not squeezed by the tension roll.

In the method of the present invention, the oil concentration of the rolling oil B is set to 103 or more because when the rolling oil B is injected, the oil content adhering to the copper strip, which is effective for lubrication, increases rapidly at a concentration of 10% or more. This is based on test results showing that the effect is remarkable; if the amount is less than 10%, a sufficient lubricating effect as a lubricating oil cannot be obtained and it is difficult to prevent scratches.

Further, the upper limit is not particularly limited, but it is preferably up to 50% in consideration of economical efficiency and the like.

The oil used for rolling oil B may be the same as that for coolant A, and mineral oils, esters, etc., which are easily emulsified and are used for coolants, are suitable.

The injection amount of rolling oil B is 100 to 200. g/min/per header is preferred.

Further, the amount of oil attached may be about 300 to 400 mg/m.

The injection pressure of rolling oil is 1kg/ffl~4ky/
d is preferable; if the pressure is too low, the amount of oil deposited will be small and the effect will be reduced.

On the other hand, if the pressure is too high, the amount of rolling oil floating in the air will increase, which is not preferable.

Therefore, the injection pressure is preferably about 1 kg/i to 4 ky/cyrt.

Further, as the spray nozzle 6 for injecting the rolling oil B, a full cone type which has good plate-out properties of the rolling oil is suitable.

Fig. 2 shows an example of this rolling oil injection nozzle device, but this injection nozzle needs to adjust the injection amount of rolling oil depending on the width of the rolled material, so it can be used for both wide and narrow widths. In this way, the spray header is divided into 5a and 5b, and the rolling oil supply pipes are also branched into 7a for wide width and γb for narrow width, and on-off valves 8a and 8b such as electromagnetic valves are provided at the starting end of each supply pipe, respectively. , when the rolled material is narrow, open the on-off valve 8a.
b is closed, and rolling oil is injected from a nozzle provided in the header 5a via the oil supply pipe 7a, and in the case of rolling a wide material, the on-off valves 8a and 8b are opened, and the oil supply pipe 7a + 7b is closed.
Rolling oil B is passed through the nozzles provided in the headers 5a and 5b.
is injected onto the lower surface of the steel strip.

Next, one embodiment of the present invention will be described.

Using a 5-stand tandem mill, 2.4 vrm thickness, 1
When a steel strip having a width of 1000i was cold rolled to a thickness of Q, 3 vrm, high concentration rolling oil according to the method of the present invention was injected under the conditions shown in Table 1, and cold rolling was performed.

Note that the conditions for coolant are also shown for comparison.

As a result of cold rolling performed under the conditions shown in Table 1, the rolling speed was 700 mpm when only the conventional rolling oil for coolant was applied, but according to the method of the present invention, #3 and #4 If high-concentration rolling oil is sprayed on the copper strip before it is inserted into the stand, high-speed rolling of 1200 mpm can be performed, and there are no scratches on the surface of the steel strip, which improves rolling efficiency. I was able to improve my RLJ.

As explained above, the present invention provides sufficient rolling performance by injecting high-concentration rolling oil into a stand with a high reduction ratio and high speed rolling that is prone to lack of lubrication, and also prevents the occurrence of scratches. It has the effect of improving quality, preventing roll damage and improving roll consumption, and is also effective in improving production efficiency through high-speed rolling, which has a great industrial effect. be.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram for implementing the method of the present invention, and FIG. 2 is a diagram showing the configuration of a rolling oil injection nozzle. In the diagram, 1: Work role, 2: Backup role, 3
: Steel strip, 4: Tension roll, 5a. 5b: Rolling oil injection header, 6: Rolling oil injection nozzle,
7a, 7b: Rolling oil supply pipe, 8a, sb:
Open/close valve.

Claims (1)

[Claims] 1 In cold rolling performed by spraying less than 10% rolling oil on the front and back surfaces of the steel strip, apart from the rolling oil spray injection system, the copper strip is heated immediately before the copper strip is bitten by the rolls of the rolling mill. A method for cold rolling a copper strip, characterized in that rolling is carried out by directly injecting rolling oil with an oil concentration of 10% or more onto the lower surface of the strip.