JPS5813408A - Descaling method for hot rolled steel sheet - Google Patents

Abstract

PURPOSE:To reduce a time of pickling and to improve a consumption unit of pickling liquid, by pickling a hot rolled sheet of low carbon steel after cold- rolling the sheet in a range of a specified draft while jetting a specified quantity of water for cooling and lubricating. CONSTITUTION:A hot rolled sheet of low carbon steel is cold-rolled in 5- 30% draft while jetting water for cooling and lubricating at the rate of 0.3- 3l/min./mm. of the sheet width. The draft is regulated in the above-mentioned range, because an exfoliative effect is insufficient when rolled in a <=5% draft and the effect becomes saturated in a >=30% draft. The jetting flow rate of water for cooling and lubricating is regulated in the above-mentioned range, because of an insufficient cooling which causes heat scratchs when he water is jetted at the flow rate of <=0.1l/min./mm. sheet width, and the occurrence of the heat scratch is prevented when the water is jetted at the rate of <=3l/min./ mm. sheet width, even if the cold rolling speed is made faster. Next, the pickling is performed, and also the running speed of the sheet in the pickling bath is made faster.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing scale from hot rolled steel sheets.

Conventionally, in order to remove scale from low carbon hot rolled steel sheets, the hot rolled steel sheets are cold rolled in advance and then pickled.

This is because if the hot rolled steel sheet is cold rolled in advance, cracks will occur in the scale of the hot rolled steel sheet and the pickling time will be shortened.

By the way, rolling oil is used in cold rolling, but if the rolling oil adheres to the steel plate, the oil film will prevent the scale from coming into contact with the pickling solution, deteriorating the pickling properties, and causing problems in the pickling solution. Rolling oil accumulates on the steel plate, contaminating the pickling solution, so it is necessary to pickle the cold-rolled steel plate after degreasing and cleaning, and the overall processing time required for descaling increases by the amount of degreasing and cleaning equipment required. However, when degreasing and cleaning equipment and its operating costs are included, productivity declines.

Therefore, in order to omit the degreasing and cleaning process, hot-rolled steel sheets are cold-rolled without using rolling oil, and a small amount of water is used, or hot-rolled steel sheets are cold-rolled without lubrication. However, in this case, since the rolling reduction is less than 5%, the scale cracking rate of the hot rolled steel sheet due to cold rolling is small, so it is necessary to either lengthen the pickling bath or slow down the threading speed. This increases the overall processing time required for school removal, resulting in a decrease in productivity.

The present invention was developed to solve the various problems in conventional scale removal from hot rolled steel sheets, and an example of its implementation will be described below.

That is, a low carbon steel hot rolled steel plate is rolled at a rolling reduction rate of 5 to 30 yen, and water for cooling and lubrication is supplied at a rate of 90.1 liters per 1 mm of steel sheet width.
After cold rolling at a jet speed of ~3e/min, pickling is performed.

Here, the reason why the rolling reduction rate was set to 5 to 30% is that if the rolling reduction rate is 5 or less, the scale peeling effect is small, and the rolling reduction rate is 30% or less.
% or more, the scale peeling effect is saturated.

In addition, the reason why the cooling and lubricating water was set at 0.11/min to 3e/min per 1 am of steel sheet width is that the injection amount of cooling and lubricating water is insufficient in order to perform cold rolling with a rolling reduction of 5% or more. ,
Heat scratches occur due to the lack of cooling water, and if the amount of water sprayed is extremely insufficient, peeled scales will adhere to the rolling rolls.To prevent this, the amount of water sprayed for cooling and lubrication must be at least as low as possible for the steel plate. 0.1 (1
/minute or more is required.

Moreover, when the cold rolling speed of hot-rolled steel sheets is set to 500 mPm or less, the injection amount of cooling and lubricating water should be reduced to 1/1 per width of the steel sheet.
For example, if amide is used as a lubricant at a concentration of less than 1%, it will cause a heat scratch of 1° or harm the pickling with tap water or industrial water. Care must be taken if a large amount of the agent accumulates in the washing solution, as this may impede long-term continuous operation.

As mentioned above, water for cooling and lubrication is applied at a rate of 0.0 mm per 1 mm of steel plate width.
11/min~37! Although spraying for 1/min has the effect of blowing off the peeled scale, it is preferable to remove the peeled scale on the surface of the cold-rolled steel plate with a roll-shaped brush before pickling.

As mentioned above, the present invention is capable of rolling low carbon steel hot rolled steel sheets at a rolling reduction rate of 5 to 5.
30%, and cooling and lubricating water is injected at 0.111/min to 31/min per mm of steel sheet width, and after cold rolling, pickling is performed, so the scale in the cold rolling process of hot rolled steel sheet is reduced. The peeling effect and the effect of blowing off the peeled schools are large, and therefore the pickling tank can be shortened or the threading speed can be increased, so the pickling time can be greatly shortened, and the pickling tank can be shortened. Since the scale accumulated in the pickling solution is reduced, the unit consumption of the pickling solution can be improved.

Generally, when cooling and lubricating water is used during cold rolling, the steel plate rusts and the product value decreases, but in the case of the method of the present invention, the steel plate is pickled immediately after cold rolling.
There is no side pipe problem.

Claims (1)

[Claims] Low carbon steel hot rolled steel plate at a reduction rate of 5 to 30% and cooling and lubricating water @ 1m71! This 0νノト31;/9
A method for removing scale from a hot-rolled steel sheet, which comprises cold rolling without jetting, and then pickling.