JPS61210194A - Method for washing special steel sheet - Google Patents

Abstract

PURPOSE:To prevent the formation of an oil stain, rust or other stain on the surfaces of a special steel sheet by spraying a cooling liq. to cool the steel sheet to a specified temp. or below as well as to remove deposits such as rolling oil on the steel sheet and by applying a rust preventive when the steel sheet is coiled immediately after cold rolling. CONSTITUTION:A special steel sheet is sent into a washing zone 5 placed at the outlet side of the final stand of a tandem rolling mill. In the zone 5, cooling water is sprayed from upper and lower cooling water headers 6, 7 to cool the steel sheet 1 to <=90 deg.C as well as to remove deposits such as rolling oil on the surfaces of the steel sheet 1 by washing. Cooling water remaining on the steel sheet 1 is removed with wringer roll 8, a rust preventive is applied, and the steel sheet 1 is coiled around a coiler 9. The formation of an oil stain, rust or other stain on the surfaces of the steel sheet can be prevented.

Description

Detailed Description of the Invention (Industrial Field of Application) In a cold rolling mill, a material to be rolled is wound into a coil while droplets due to dew condensation of rolling oil or its vapor are attached to the surface of the material to be rolled. If left after that, it can cause plate surface stains and rust called oil stain, but studies have revealed that such plate surface stains are affected by the type of gli and also by the winding temperature. Based on this understanding, this specification describes how to eliminate the problem of plate surface contamination during winding immediately after cold rolling of a special gI4gi plate, such as a laminated M plate, which generally has high deformation resistance. The results of the development research will be described.

By the way, when rolling general cold-rolled steel sheets as well as special [4+ sheets] such as silicon steel sheets and stainless steel sheets, rolling oil is sprayed between the rolled material and the rolls in a cold rolling mill to serve as lubrication as well. This prevents the plate temperature from rising due to processing heat.

After the material to be rolled is rolled to a predetermined thickness, it is wound up on a winding machine called a tension reel, and then sent to the next process.

The drop-like adhering residue of the rolling oil during winding results in the occurrence of plate surface stains during the coil processing time.

(Prior art) When a material to be rolled is wound up by a winder, a draining device is installed on the exit side of the final stand in a continuous rolling mill, and on the exit side of the final rolling pass in a rolling mill with a jingle stand. In order to remove droplets caused by condensation of rolling oil or its vapor on the surface of the rolled material, in particular, in continuous rolling mills, a cleaning liquid called detergent is used to simultaneously lightly reduce and clean the rolled material at the final stand. In addition, Japanese Patent Application Laid-Open No. 52-95561 discloses that a cleaning device is installed between the tandem mill and the take-up reel to clean the strip. In many cases, it is impossible to completely prevent splashes and dew droplets of rolling oil vapor from adhering to the surface of the rolled material. The dirt on the top of the product was deemed to be non-defective and it took time and effort to discard that part, which also caused a decrease in yield.

Incidentally, oil staining or rust can be avoided by sending the steel to a degreasing line or annealing equipment immediately after winding after cold rolling, but these subsequent lines are also used for manufacturing processes other than steel sheets. As an example, it is not practical in terms of logistics efficiency.

(Problems to be Solved by the Invention) After the special steel scrap plate is rolled up immediately after cold rolling, it occurs due to rolling treatment residues while waiting for the process to be subjected to the next process. The purpose of this invention is to establish a reliable method for preventing plate surface stains such as oil stain and rust.

(Means for Solving the Problems) The present invention provides a method for cleaning deposits such as rolling oil adhering to the steel plate when winding the special diwi plate with a winding machine immediately after cold rolling. This is a method for cleaning special scrap steel plates, which comprises cooling the steel plate to a temperature of 90'C or less by spraying a cleaning liquid or a cooling liquid, and applying a rust preventive agent to the surface of the steel plate.

Now, the inventors investigated the trends that lead to the formation of oil stain and rust after a period of time when splashes of rolling oil or droplets due to dew condensation of the oil vapor adhere to the surface of a rolled material.
It has been found that there is a causal relationship shown in Figure 1 between the winding temperature and the winding temperature. In the figure, the plot marked with ○ is an example of silicon steel, and the plot marked with ◇ is an example of a general cold-worked steel plate.

The score has the following contents.

L The board surface is almost free of dirt λ There is some dirt on the board surface, but it can be used as a product if cleaned in the next process & 4 Black rust can be seen in some places on the board surface 4 Black rust on the board surface is The trend in the phase diagram, where rust is starting to grow and rust can be seen all over the board surface, is that the higher the temperature, the faster the reaction rate, and that the coil wound around the boiling point of water is exposed to oil stains. Although this is almost consistent with the empirical tradition that says that it is easy to wind, the winding temperature of 90°
While the problem of sheet surface staining is virtually eliminated at temperatures below 90°C, sheet surface staining reaches its maximum at temperatures above 90°C, especially at 100°C.In contrast, with ordinary cold-rolled steel sheets, the sheet surface stains when rolled at high temperatures of 150°C or higher. The situation is different from that where surface stains occur frequently.

Special steel sheets with high deformation resistance easily rise in temperature to over 100"C due to the processing heat of cold rolling, so coils wound immediately after rolling are placed in the temperature range where sheet surface contamination frequently occurs. There are many opportunities for roughness, and the occurrence of plate surface stains is much more of a problem than with general cold-rolled conditioned plates.

In the present invention, the temperature of the steel plate is particularly cooled to 90"C or less by cleaning during winding of the special steel scrap plate immediately after cold rolling, thereby attempting to isolate the steel plate from the temperature range where plate surface contamination frequently occurs.

For this cleaning, hot water washing or water washing is preferred, but other cleaning liquids may be used. Further, by mixing a rust preventive agent in this case, the rust preventive agent can be advantageously applied to the surface of the steel sheet. The rust preventive agent may be applied after the steel plate reaches the squeezing roller after cleaning.

Now, Fig. 2 illustrates a specific example of the case where silicon shaving strip 1 is cooled in a cleaning zone and then wound up at the exit side of a cold rolling mill, particularly at the exit side of a finishing stand of a tandem rolling mill in this example. ,
In the figure, 2 is the work roll drainer, 3 is the thickness gauge, 4 is the tension roll meter, 5 is the cleaning zone, 6 is the water-cooled upper header, 7 is the water-cooled lower header, 8 is the drainer roll, and 9 is the winder. be.

(Function) As already mentioned with reference to Fig. 1, in the case of materials with high deformation resistance, the winding temperature increases to around 150°C due to the accumulation of processing heat during the process leading to the final stand, and the entire surface of the rolled material is heated. Due to the occurrence of oil stains on the plate surface, there was no choice but to reduce the rolling reduction ratio, but still
It is generally difficult to lower the winding temperature to below 0°Cζ, and in order to prevent sheet surface stains, it is necessary to roll the sheet in a rolling mill, then roll it up and then immediately send it to the degreasing line for the next process. However, with this invention, the surface of the steel sheet that exits the rolling mill is cleaned by cooling it to 90°C or less, and a rust preventive agent is applied to the surface of the steel sheet. Even under high-efficiency rolling operations such as a rolling reduction of about 30% and a rolling speed of 1200 mpm, it is possible to reliably prevent plate surface staining due to the influence of the winding temperature, and of course there is no need to worry about oil stain or rust. This made it possible to retain the material for about 10 days before sending it to the next process.

(Example) According to FIG. 2, after measuring the thickness of the silicon steel strip 1 that has come out of the final stand of a continuous cold rolling mill using an X-ray or R-ray thickness meter 3, the silicon steel strip 1 is passed through a cleaning sheath 75. The water-cooled upper header 6 and the lower header head spray cooling water containing a rust preventive agent to clean the board surface, and then the surface water is drained off by the squeezing roll 8 and the board is wound into the winder 9.

The temperature of the silicon steel strip 1 at the exit from the final stand was 16°C, but due to cooling during passing through the cleaning zone 5, the temperature at the time of winding decreased to 82°C. Even after leaving the coil for 10 days, no staining was observed on the plate surface.

(Effects of the invention) Coupled with the application of the rust preventive agent after cooling, oil stains and rust that often occur on the board surface when the coil is unwound after the waiting time for the process are removed. It is possible to advantageously avoid the occurrence of sheet surface contamination, which eliminates the disadvantages of conventional technology, which required the sheet to be sent to the next process such as a degreasing line without delay immediately after rolling, and to maintain steady-state appropriateness across each steel type. The benefits of being able to design processes that take into account physical distribution are significant.

[Brief explanation of the drawing]

Figure 1 is a graph showing the influence of the winding temperature on sheet surface staining after 24 hours or more has elapsed after winding, by comparing silicon steel sheet with general cold-rolled steel sheet. Figure 2 is a specific example of equipment. FIG. 1... Steel plate 2... Drainer 5...
Washing zone 6...Water cooling upper header 7...
Water cooling lower header 8... Draining roll 9... Winding machine Fig. 1 50 60 7080QO100ffO/20 Super 0 prayer f60 strip γ orange removal ζ agricultural return

Claims (1)

[Scope of Claims] 1. When winding up a special steel plate with a winding machine immediately after cold rolling, when cleaning deposits such as rolling oil adhering to the steel plate, spraying a cleaning liquid or a cooling liquid. 1. A method for cleaning a special steel plate, comprising: cooling the steel plate to a temperature of 90° C. or lower, and applying a rust preventive agent to the surface of the steel plate.