JPH04294864A - Method for hot-scarfing steel material - Google Patents

Abstract

PURPOSE:To provide means uniformly scarfing a steel material having skid mark at good yield. CONSTITUTION:The material 1 to be scarfed is conveyed on conveying table 2 at the constant velocity and scarfed with a hot scarfer unit 3. Surface temp. of the material to be scarfed is measured with a thermometer 5 set on the conveying line for material to be scarfed and this detected value is inputted in a skid mark position calculator 7. Based on table velocity inputted from a table velocity meter 6, time, when the skid mark part reaches to the hot scarfer unit 3, is calculated. Pressure changing command is outputted to a scarfing pressure control panel 8, and a working valve 4 in scarfing oxygen supply system is controlled, and scarfing pressure to the skid mark part is changed from low pressure to high pressure. Cut-off of the molten slag at the skid mark is eliminated and unscarfing part is not developed. Surface except the skid mark is not excessively scarfed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for hot cutting a steel material having skid marks, and more specifically, a method for hot cutting a steel material having skid marks. , by changing the cutting pressure of the skid mark part and the non-skid mark part when hot cutting after rolling or heating furnace extraction,
This invention relates to a hot cutting method for steel materials that enables uniform cutting with high yield.

0002

[Prior Art] As is well-known, hot scarfer cutting is a means of removing surface defects from steel, in which the heat of reaction between cutting oxygen and iron is mainly used to remove a certain amount of the surface of the steel. The cutting conditions are the surface temperature of the material to be cut,
It is set depending on the moving speed of the workpiece (table speed), cutting pressure (oxygen), steel type, etc., but after rolling or heating blooms or slabs that have been heated with a walking beam heating furnace and have skid marks. When hot-melting is performed after furnace extraction, problems arise, such as the generation of uncut parts due to insufficient molten slag, and a decrease in yield due to over-cutting.

FIG. 3 shows an example of the relationship between the temperature of the material to be cut and the amount of cutting when the cutting pressure is changed, and the cutting conditions are shown in Table 1. From Fig. 3, when the temperature of the material to be cut is low (900
℃), even if the cutting pressure is set high, molten slag cannot be sufficiently generated and uncut areas are generated. Cutting amount 1.4
It can be seen that when the target is 0.7 mm on one side, the molten slag is interrupted at the skid mark part and an uncut part is generated.

0004

[Table 1]

FIG. 4 shows an example of the relationship between the table speed and the cutting amount when the temperature of the workpiece and the cutting pressure are kept constant. When the table speed is increased for the purpose of light cutting, It can be seen that molten slag is insufficiently generated at the skid mark portion of the material, resulting in uncut areas, and even if the table speed is controlled, a cutting amount of 1.4 mm is the limit for stable cutting.

[0006]

[Problems to be Solved by the Invention] As mentioned above, when the temperature of the material to be cut is low, the generation of molten slag is insufficient in the current hot cutting, and the molten slag is shredded by skid marks that occur on the material. There is a problem of being exposed. As a countermeasure against this, conventionally the skid mark area (temperature drop of about 50℃)
As a method to prevent the molten slag from being shredded, the table speed and cutting pressure are determined so that the skid marks can be machined, but with this method, surfaces other than the skid marks are over-cut and the yield is reduced. The reality is that this is causing a decline.

[0007] In view of the current situation, the present invention aims to improve the yield in hot cutting and to achieve stable light cutting.
This paper attempts to propose a method for hot cutting of steel that prevents the molten slag from being shredded at skid mark areas and enables uniform light cutting in the longitudinal direction of the steel.

[0008]

[Means for Solving the Problems] This invention prevents molten slag from fragmenting at the skid mark part and uniformly lightens the steel material in the longitudinal direction by changing the cutting pressure on the skid mark part and the non-skid mark part. This is a method that enables melt cutting, and its gist is to detect skid mark areas from the temperature distribution of the material to be cut, and to cut the skid marks so that the amount of melt cutting in the skid mark areas and non-skid mark areas is uniform. This is a hot cutting method that controls the cutting pressure for the non-skid mark part to be higher than that for the non-skid mark part.

[0009]

[Operation] In the present invention, in hot cutting of steel materials having skid marks, a cutting pressure control means according to the temperature of the material to be cut is used as a means for preventing uncut areas from remaining and improving yield. The reason for this is that table speed control results in over-cutting of surfaces other than the skid mark area, but if the table speed is kept constant and the cutting pressure is controlled according to the temperature of the workpiece, the skid mark area and This is because it is possible to appropriately set the amount of melting in the non-skid mark portion, and to obtain uniform generation of molten slag in the longitudinal direction of the steel material.

[0010] When hot-cutting a steel material that has been heated in a heating furnace such as a walking beam furnace and has skid marks after rolling or extraction in a heating furnace, a thermometer should be installed in front of the cutting equipment. , Measure the surface temperature of the steel material using the thermometer. The skid mark part and the non-skid mark part are distinguished from the reading of this thermometer, and the timing at which the skid mark part is positioned in the cutting machine is calculated from the table speed, and the cutting pressure is changed. Make the cutting force higher than the non-skid mark area. By doing so, fragmentation of the molten slag at the skid mark portion is eliminated, and no unmelted portion is generated. Furthermore, since the non-skid mark portions are cut by switching to a low cutting pressure, they are not over-cut. Therefore, the non-skid mark portion and the skid mark portion are uniformly machined.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing an example of the configuration of an apparatus for carrying out the method of the present invention, in which 1 is a material to be cut, 2 is a conveyance table, 3 is a hot scarfer unit, 4 is an operating valve, and 5 is a A thermometer, 6 a table speed meter, 7 a skid mark position calculator, and 8 a cutting pressure control panel.

The material to be cut 1 is conveyed at a constant speed on a conveyance table 2 and is cut by a hot scarfer unit 3. However, in this invention, a thermometer is installed in the conveyance line of the material to be cut. 5 is installed, the surface temperature of the material to be welded is measured, and the indicated value is input to the skid mark position calculator 7 to determine the skid mark part and the non-skid mark part, and the temperature is input from the table speed meter 6. The position where the skid mark portion 1-1 reaches the hot scarfer unit 3 is calculated from the table speed determined by the table speed. When the skid mark position is calculated, a command to change the pressure for the skid mark position, that is, a command to increase the cutting pressure, is sent to the cutting pressure control panel 8, and the operating valve 4 of the cutting oxygen supply system is controlled to remove the skid mark. The cutting pressure is increased. When the skid mark part is finished being cut, a pressure change command is issued from the cutter pressure control panel 8, and the cutter pressure is switched to the original low pressure. Thereafter, the cutting pressure is alternately switched between low pressure and high pressure according to the temperature distribution of the material 1 to be cut, and cutting is performed.

FIG. 2 shows an example of the temperature pattern and cutting pressure pattern of the material to be cut.The part corresponding to the skid mark part is lower in temperature than other parts. The cutting pressure is switched from low pressure to high pressure. On the other hand, since the other parts of the material to be melted except for the skid mark portion are at a high temperature, the melting pressure is set to a low pressure. Here, as an example, the cutting pressure is 1.8Kg/cm.
When changing from 2 (low pressure) to 2.3 Kg/cm2 (high pressure), the cutting amount changes from 1.5 mm to 2.3 mm. In addition, as a result of investigating the response when switching the cutting pressure, it was found that
It takes 1.5 seconds from switching the electromagnetic valve to reaching the set pressure for both falling and falling pressures, making it possible to control the cutting pressure in accordance with the temperature of the material to be cut.

[0014]

[Effects of the Invention] As explained above, according to the method of the present invention, molten slag can be prevented from being shredded at the skid mark portion, and
Since uniform light cutting is possible in the longitudinal direction of the workpiece, it prevents uncut areas from remaining and improves yield, and is highly effective in cutting steel materials with skid marks. be.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus configuration for implementing the method of the present invention.

FIG. 2 is a diagram illustrating a temperature pattern and a cutting pressure pattern of a material to be cut in the present invention.

FIG. 3 is a diagram showing the relationship between the temperature of the material to be cut and the amount of cutting when the cutting pressure of the hot scarfer is changed.

FIG. 4 is a diagram showing the relationship between the table speed and the amount of cutting when the temperature of the material to be cut and the cutting pressure are kept constant.

[Explanation of symbols]

1 Material to be cut 2 Transfer table 3 Hot scarfer unit 4 Operating valve 5 Thermometer 6 Table speed meter 7 Skid mark position calculator 8 Cutting pressure control panel

Claims (1)

[Claims] Claim 1: In a method for hot cutting a workpiece having a skid mark part, the skid mark part is detected from the temperature distribution of the workpiece, and the amount of melting of the skid mark part and the non-skid mark part is determined. 1. A method for hot cutting a steel material, the method comprising controlling the cutting pressure on the skid mark part to be higher than on the non-skid mark part so that the cutting pressure is uniform.