JPH07115060B2 - Descaling method for steel - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for descaling secondary scale produced on the surface of steel in a hot rolling process.

[0002]

2. Description of the Related Art Steel scales include a primary scale formed during heating of the material and a secondary scale formed during rolling after removing the material, both of which cause surface defects after rolling. Therefore, it is necessary to remove the steel material before rolling. As a conventional removing means for the secondary scale, for example, there is a technique introduced in Japanese Patent Publication No. 51-5821.

The feature of this technique is that, in the descaling method of the secondary scale produced on the steel surface during hot rolling of the steel material, the low pressure spray zone by the low pressure water jet group of 10 kg / cm ² or less and the low pressure spray zone. 30 to 50 kg / cm ² of water jet injection device installed at a position immediately after passage of, the scale is levitated in the low pressure spray zone, and the scale pieces levitated by the water jet ejection device are scattered. It is configured as follows.

[0004]

The above-mentioned conventional method is intended to enable de-secondary scale easily by using a low-pressure water jet which is simple in terms of equipment without requiring a high-pressure water jet. Has not clarified the relationship between the water jet condition on the steel surface and the steel surface properties, etc., and it is almost impossible to obtain a quantitatively stable de-secondary scale effect only with the two-stage configuration of the low-pressure water jet. could not.
The present invention provides a quantitatively stable descaling method for steel products by a two-stage low-pressure water jet system.

[0005]

[Means for Solving the Problems] A feature of the present invention is that in a descaling method of a secondary scale produced on the surface of a high temperature steel material, a material unit area is applied to the surface of the steel material at an injection pressure of 25 to 80 kgf / cm ^2. 18 l / l / m ² per unit area of the material at an injection pressure of 135-170 kgf / cm ² by injecting a water amount of 4 l / m ² or more per unit, removing water on the surface of the steel product to recover heat on the downstream side. It is a method for descaling steel materials by injecting a water amount of m ² .

[0006]

The technical significance of the reason for limitation in the present invention will be described in detail below. First, the inventors calculated the sum of the calculated temperature changes on the surface of the steel material to be injected at the water injection collision part as an index of the degree of secondary scale cracking on the surface of the steel material due to water injection, and used as an index of the degree of peeling and scale scattering. As a result, the total sum of water jet collision forces was calculated, the relationship between these two variables and the surface properties of the steel material was observed in detail, and the de-secondary scale effect index condition was extracted from the result. De-secondary scale effect index = ΣΔT ² × ΣP ^0.5 ΣΔT: Sum of calculated temperature change amount at Desuke collision part ΣP: Sum of Desuke collision force Even if the water injection collision force is made smaller than this condition, temperature at Desuke collision part Descaling can be ensured by increasing the amount of change, so considering the feasibility, the first stage descaling (hereinafter referred to as Desuke) will be converted to a low-pressure water jet, and water on the steel surface will be removed downstream of this. Then, the temperature of the steel material surface is changed by an injection pressure of 135 to 170 kgf / cm ^{2 on} the surface of the steel material to cause proper cracking, and peeling and scale are scattered to form a scale pattern. We have completed the Desuke method that eliminates all occurrences. Next, a low-pressure water jet jet scale was installed on the first stage Desuke of the rolling line, and the relationship between the water jet conditions and the surface properties of the steel material was investigated. As a result, the low-pressure water jet jet of the first stage has an injection pressure of at least 25 kgf.
/ Cm ² and flow rate per unit area of material is 4 l /
By securing m ² or more, the number of scale patterns generated can be reduced as shown in FIG. The recuperation before the water injection in the second stage requires the material passage time of the first stage and the second stage descaling by 5
It is necessary to secure a drainage band of 2.5 to 5 seconds at the same time as securing ~ 15 seconds. In the second stage, the injection pressure may be the lower limit of the general usage range, but by securing a flow rate per material unit area of 18 l / m ² or more, the number of scale patterns generated can be reduced as shown in FIG. If the above matters are found and all these conditions are satisfied,
As shown in, the number of scale patterns generated can be reduced as in the case of using a high-pressure water jet, and a quantitatively stable de-secondary scale effect can be obtained with relatively simple equipment.

[0007]

EXAMPLE A rough bar 10 was used in the hot rolling apparatus shown in FIG.
Descale 1 by the first Desuke 11 and the second Desuke 12
A ~ 7-high rolling stand was hot-rolled and wound on the coiler 14.

The rolling conditions (Table 1) and the descaling conditions (Table 2) were as follows.

[Table 1]

[Table 2]

[0009]

According to the present invention, the number of scale patterns generated can be reduced as in the case of using a high-pressure water jet, and a quantitatively stable de-secondary scale can be obtained with simple equipment.

[Brief description of drawings]

FIG. 1 is a chart showing the number of scale patterns generated and a flow rate per unit area in the first descaling.

FIG. 2 is a chart of the number of generated scale patterns and the flow rate per unit area in the second descaling.

FIG. 3 is an explanatory diagram of an example of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidetaka Ageo No. 1 Nishinosu, Oita City, Oita Prefecture Nippon Steel Co., Ltd. Oita Works (56) Reference JP-A-60-61114 (JP, A) Sho 48-38242 (JP, A)

Claims (1)

[Claims] 1. A method for descaling a secondary scale produced on the surface of a high temperature steel material, wherein the surface of the steel material is 25-80 kgf.
Water of 4 l / m ² or more per unit area of material is injected with an injection pressure of / cm ² , and water on the surface of the steel material is removed downstream to reheat it, and then 135 to 170 kgf / cm on the surface of the steel material.
Per material unit area ² injection pressure 18~50l / m ²
A method for descaling a steel material, which comprises injecting a specified amount of water.