JPS61172604A - Cold rolling method of chromium stainless steel sheet - Google Patents

Abstract

PURPOSE:To perform the cold rolling of a chromium stainless steel excellent in finished gloss by using the emulsion of a soluble oil, prepared by using a mineral oil as a base oil, as a rolling oil and keeping the concentration of iron impurities of the rolling oil at low level. CONSTITUTION:In cold rolling a chromium stainless steel sheet, the emulsion of a soluble oil, prepared by using a mineral oil as a base oil, is used as a rolling oil. Further, the concentration of iron impurities of the rolling oil is kept to be <=200ppm during rolling. Therefore, the concentration of iron impurities is controlled during rolling, by removing scums and a rolling oil, having highly concentrated iron impurities, located at the upper part beneath the liquid level, in a dirty tank for instance, and removing further the residual iron impurities by providing a magnetic separator to a clean tank, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to the use of an emulsion in which mineral oil is suspended in water as a rolling oil during cold rolling of Cr-based stainless steel sheets or copper strips (collectively referred to as stainless steel sheets). The present invention relates to a method for obtaining products with good surface gloss.

Conventional Technology Stainless steel sheets are required to have a good surface gloss, so neat oil (mineral oil is not emulsified and is supplied straight to the mill) is generally used as the rolling oil in cold rolling.

However, when high-speed rolling under high pressure is carried out, there are problems such as a seizure phenomenon called heat streaks occurring on the surface of the steel sheet, and seizure of intermediate paper. Oil emulsions (soluble oil suspended in fine particles in water and fed to the mill) are also used (Stainless Steel Handbook, published August 30, 1972, p. 821).

When stainless steel sheets are cold-rolled using emulsion as rolling oil, products with good surface gloss cannot be obtained due to the heavy contamination of the rolling oil. At that time, it was only possible to perform cold rolling to produce products with a polished finish.

Ferritic steel types such as 5O5430 or 5O84
2B finished products of martensitic steel grades such as 10.

Although it is widely used because it has excellent surface gloss and is relatively inexpensive, it has not been possible to produce it by cold rolling at high pressure and high speed using a soluble oil emulsion as the rolling oil.

Problems to be Solved by the Invention The present invention is capable of producing 2B finished products of ferritic or martensitic stainless steel sheets with high efficiency by cold rolling a soluble oil emulsion using mineral oil as a base oil and rolling oil. The purpose is to manufacture.

Means for Solving the Problems The present invention provides a method for cold rolling Cr-based stainless steel sheets.
This is a method for cold rolling a Cr-based stainless steel sheet, using an emulsion based on mineral oil as the rolling oil, and maintaining the concentration of iron impurities in the rolling oil at 200 PPII or less.

In the present invention, Cr-based stainless steel plate refers to 5OS4
The rolling oil used in cold rolling of ferritic stainless steel plates such as 30 or martensitic stainless steels such as 5US410 is mineral oil base oil such as spindle oil or machine oil, and emulsifiers are added to this. An emulsion is used, which is prepared by suspending the emulsion in water.

Means for maintaining the concentration of iron contaminants in the rolling oil at 200 pP- or less is not particularly limited, but examples include removing scum in the dirty tank and further installing a magnetic separator in the clean tank to prevent iron contaminants. It is effective to remove the impurities and to understand and control the concentration of the impurities by measuring the length of the column chromatography.

Using an emulsion based on working mineral oil as a rolling oil,
When a stainless steel sheet is cold-rolled, the surface gloss of the cold-rolled sheet is good when fresh oil is used, but as the amount of rolling increases and the rolling oil becomes dirty, the surface gloss of the cold-rolled sheet deteriorates. Rolling oil is used in circulation, and the amount of iron contaminants in the rolling oil increases during rolling operations. The surface gloss of cold-rolled Cr-based stainless steel sheets deteriorates as the concentration of iron impurities in the rolling oil increases, and this relationship is shown in Figure 1, when the concentration of iron impurities exceeds 200 ppm. The gloss of the rolled sheet deteriorates rapidly. If the concentration of iron impurities is 200PP# or less, the cold-rolled sheet will have good gloss even in Cr-based stainless steel sheets, and it will be heat treated, pickled, and temper rolled to produce 2B.
Finished products can be manufactured. In addition, iron contaminants are 5
Since the lubricity during cold rolling is better when the concentration is 0 ppm or more, the lower limit of the concentration is preferably 50 ppm.

Rolling oil is used by being circulated through a filter as shown in Figure 2, but since the particle size of the oil droplets in the rolling oil emulsion is usually around 5 mm, it is necessary to use a filter with a coarser mesh than this. It is used. On the other hand, iron contaminants in the rolling oil when Cr stainless steel is cold rolled are mostly fine particles with a particle size of 1 ILs or less, and therefore cannot be removed by a filter.

The concentration of iron impurities exceeds 200 ppm when approximately 1,500 tons of new oil is rolled, but the relationship between the amount of rolling and the increase in concentration is not necessarily constant, and increasing the frequency of replacing new oil is preferable from a cost standpoint. do not have.

Therefore, in order to maintain the concentration of iron impurities below +200 ppm, for example, the scum and rolling oil with a high concentration of iron impurities in the upper layer below the liquid level should be removed in the dirty tank shown in Figure 2, and then transferred to a clean tank. It is effective to install a magnetic separator to remove residual iron impurities and to monitor and manage the concentration in the rolling oil.

The removal of scum in a dirty tank will be explained with reference to FIG. The rolling oil discharged from the rolling mill is introduced into the inlet l.
The liquid falls into the dirty tank, forming scum 2 on the liquid surface. The scum 2 contains impurities such as iron impurities, grease, bearing oil, and waste oil, which are removed by suction by the vacuum pump 3.

However, iron contaminants also exist below the liquid surface, and their concentration is particularly high in the region 10 to 15 inches below the liquid surface, so the float pump 4 is used to remove them.

Place the lower end of the suction port 5 of the float pump 4 below the liquid level.
The iron contaminants 6 concentrated on the surface layer of the rolling oil are removed by suction together with the rolling oil. At this time, the remaining scum that could not be removed by the vacuum pump 3 is also removed at the same time.

Even if such treatment is carried out in a dirty tank, the concentration of iron impurities in the rolling oil will only decrease to about 350 PP.
In order to make it 200 pP- or less, another means is required, and the magnetic separator system in a clean tank will be explained with reference to FIGS. 4 and 5.

The rolling oil sent from the dirty tank through the filter is introduced deep into the clean tank through the introduction pipe 11 and led out toward the magnetic separator 13. The magnetic separator 13 is of an automatic scraping conveyor type, and iron contaminants in the rolling oil are captured and removed.

A suction pump 12 is attached to the clean tank, and purified rolling oil is supplied to the rolling mill again. Therefore, the flow of rolling oil in the clean tank is controlled by the inlet pipe 11.
Due to the blowing out of the rolling oil from the tank and the suction action of the spool pump 12, there is no stagnation in the tank as shown by the arrow in FIG.

How to understand the concentration of iron contaminants in rolling oil.

For example, it is effective to measure the column chromatography length of rolling oil. What is column chromatography length and iron contaminant concentration?
There is a good correlation as shown in FIG. Note that the column chromatography length is an index representing the cleanliness of rolling oil, and indicates the degree of contamination of the adsorbent when rolling oil is poured into the adsorbent. In other words, the longer the column chromatography length, the more severe the rolling oil stains.

Example 2 Using a 0-high Sendzimir rolling mill, an emulsion prepared by suspending refined mineral oil with emulsifiers, rust preventives, and oiliness improvers in 7.5% water was used as rolling oil.

5US430 stainless steel plate thickness 3.8cm to 0.8mm
■Table 1 shows the change in reflectance of the cold-rolled sheet when it was cold-rolled to the intestine.

The rolling oil circulation system is as shown in Fig. 2, and in the method of the present invention, a vacuum pump 3 and a float pump 4 as shown in Fig. 3 are provided in the dirty tank, and a vacuum pump 3 and a float pump 4 as shown in Fig. 5 are provided in the clean tank. magnetic separator 1
3 was installed, and the operating status of each pump and magnetic separator was adjusted by measuring the column chromatography length of the rolling oil on the outlet side of the clean tank. In the conventional method, only a vacuum pump as shown in FIG. 3 is provided in the dirty tank.

Table 1 In the conventional method, the concentration of iron impurities exceeded 200 ppm when the cumulative rolling amount was 2,000 mm, and the gloss of the cold-rolled sheet deteriorated, making it impossible to use 2B finished products. In the method of the present invention, in which the concentration is maintained at 200 ppm or less, 1
Even after rolling at 800G), the cold-rolled sheet had good gloss and a 2B finished product could be used.

Effects of the Invention In conventional rolling using neat oil, the surface temperature of the steel plate increases due to the insufficient cooling performance of the neat oil, resulting in heat streaks and seizure of intermediate paper on the surface of the steel plate, making it difficult to roll at high speed and under high pressure. has been hindered.

However, with the method of the present invention, Cr-based 2B finished products with good gloss can be rolled using soluble oil with excellent cooling properties, and high-speed, high-reduction rolling with higher efficiency than with neat oil can be carried out, improving productivity and reducing costs. There was a devaluation.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the concentration of iron impurities in rolling oil and the reflectance of a cold rolled sheet, Figure 2 is a diagram showing the circulation system of rolling oil in a cold rolling mill, and Figures 3 to 3 5 is a diagram showing an example of a means for cleaning rolling oil, FIG. 3.4 is an elevational view, and FIG. 5 is a plan view. FIG. 6 is a diagram showing the relationship between the concentration of iron impurities in rolling oil and the column chromatography length. l...Inlet port, 2...Scum, 3...Vacuum pump, 4...Float pump, 5.Fist/suction port, 6
・O・Iron contaminants, 8・・φ dirty tank, 1O・・
・Clean tank, 11@Φ・Introduction pipe, 12 Keyaki...Suction pump, 13...Magnetic separator.

Claims (1)

[Claims] In the cold rolling of Cr stainless steel sheets, an emulsion based on mineral oil is used as the rolling oil, and the concentration of iron impurities in the rolling oil is maintained at 200 ppm or less. Inter-rolling method.