JP2606473B2 - Hot cutting of 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 hot-cutting steel material having a skid mark portion, and more particularly, to a method of cutting a bloom or slab having a skid mark by being heated by a walking beam type heating furnace or the like. When hot cutting after rolling or after heating furnace extraction, by changing the cutting pressure of the skid mark part and the non-skid mark part,
The present invention relates to a hot cutting method for a steel material that enables uniform cutting with good yield.

[0002]

2. Description of the Related Art As is well known, hot scarfing is a well-known method of removing surface defects of steel by mainly utilizing the heat of reaction between cutting oxygen and iron. Technology, and its cutting conditions are the surface temperature of the material to be cut,
It is set depending on the moving speed (table speed) of the material to be cut, the cutting pressure (oxygen), and the type of steel. After rolling or heating a bloom or slab with a skid mark generated by heating in a walking beam heating furnace, etc. When hot cutting after furnace extraction, the occurrence of uncut parts due to insufficient molten slag,
The problem of reduced yield due to over-machining occurs.

FIG. 3 shows an example of the relationship between the temperature of a workpiece and the amount of abrasion when the abrasion pressure is changed. The abrasion conditions are shown in Table 1. As shown in FIG. 3, when the workpiece temperature is low (900
℃), even if the cutting pressure is set to a high value, the generation of molten slag is not sufficiently obtained, and uncut portions are generated. On the other hand, even when the temperature of the material to be cut is high (950 ° C. or higher), Abrasion amount 1.4
It can be understood that when the target is 0.7 mm (one side 0.7 mm), the molten slag is interrupted at the skid mark portion and an uncut portion is generated.

[0004]

[Table 1]

FIG. 4 illustrates 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 constant. When the table speed is increased for the purpose of light cutting, It can be seen that the generation of molten slag is insufficient at the skid mark portion of the material, an uncut portion is generated, and even when the table speed is controlled, the cut amount of 1.4 mm is the stable cutting limit.

[0006]

As described 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 cut off by skid marks generated in the material. There is a problem that is. As a countermeasure, the skid mark part (temperature drop of about 50 ° C)
As a method to prevent cutting of the molten slag in the above, the table speed and the cutting pressure are determined so that the skid mark part can be cut, but in this method the surface other than the skid mark part is over-cut and the yield It is the actual situation that is causing the decline.

[0007] In view of such circumstances, the present invention aims at improving the yield in hot cutting and stably performing light cutting.
An object of the present invention is to propose a hot-cutting method for a steel material, which prevents a cut of a molten slag at a skid mark portion and enables uniform light-cutting in a longitudinal direction of the steel material.

[0008]

SUMMARY OF THE INVENTION According to the present invention, the cutting pressure of a skid mark portion and a non-skid mark portion is changed to prevent the molten slag from being cut off at the skid mark portion and to reduce the uniform lightness in the longitudinal direction of the steel material. It is a method that enables fusing, the gist of which is to detect the skid mark part from the temperature distribution of the material to be cut, and to make the amount of skidding of the skid mark part and non-skid mark part uniform. This is a hot cutting method for controlling the cutting pressure on the portion higher than that of the non-skid mark portion.

[0009]

According to the present invention, in hot cutting of a steel material having a skid mark portion, a cutting pressure control means according to a temperature of a material to be cut is provided as a means for preventing the uncut portion from remaining and improving the yield. As described above, the surface other than the skid mark portion is over-melted in the table speed control, but according to the cutting pressure control in accordance with the temperature of the workpiece at a constant table speed, the skid mark portion is This is because it is possible to appropriately set the amount of abrasion of the non-skid mark portion and to obtain uniform molten slag in the longitudinal direction of the steel material.

[0010] When hot-cutting a steel material heated by a heating furnace such as a walking beam furnace or the like and having a skid mark after rolling or after extracting the heating furnace, a thermometer is installed in front of the cutting device. The surface temperature of the steel material is measured by the thermometer. The skid mark portion and the non-skid mark portion are discriminated from the indicated value of the thermometer, and the timing at which the skid mark portion is positioned in the welding device is calculated from the table speed to change the welding pressure. Make the cutting pressure higher than the non-skid mark part. By doing so, there is no breakage of the molten slag at the skid mark portion, and no uncut portion is generated. In addition, since the non-skid mark portion is switched to a low cutting pressure and is cut, there is no over-cutting. Therefore, the unskid mark portion and the skid mark portion are uniformly melted.

[0011]

FIG. 1 is a schematic view showing an example of an apparatus configuration for carrying out the method of the present invention. 1 is a material to be cut, 2 is a transfer table, 3 is a hot scarfer unit, 4 is an operating valve,
Is a thermometer, 6 is a table speedometer, 7 is a skid mark position calculator, and 8 is a cutting pressure control panel.

The work material 1 is conveyed on the transfer table 2 at a constant speed and is cut by the hot scarfer unit 3. In the present invention, a thermometer is provided on the work material transfer line. 5 is installed, the surface temperature of the workpiece is measured, the indicated value is input to the skid mark position calculator 7, the skid mark portion and the non-skid mark portion are determined, and the input is input from the table speedometer 6. From the table speed, the position at which the skid mark section 1-1 reaches the hot scarfer unit 3 is calculated. When the skid mark position is calculated, a pressure change command 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 control the skid mark portion. The cutting pressure for is increased.
When the cutting of the skid mark portion is completed, a pressure change command is issued from the cutting pressure control panel 8, and the cutting pressure is switched to the original low pressure. Hereinafter, the cutting pressure is alternately switched between low pressure and high pressure in accordance with the temperature distribution of the workpiece 1 to perform cutting.

FIG. 2 exemplifies a temperature pattern and a cutting pressure pattern of the material to be cut. The portion corresponding to the skid mark portion has a lower temperature than the other portions. The cutting pressure is switched from low pressure to high pressure. On the other hand, since the other parts of the material to be cut except for the skid mark portion are at a high temperature, the cutting pressure is set to a low pressure. Here, as an example, the cutting pressure is set to 1.8 kg / cm.
^{When 2} (low pressure) is changed to 2.3 Kg / cm ² (high pressure), the amount of ablation changes from 1.5 mm to 2.3 mm. In addition, as a result of investigating the response at the time of cutting pressure switching,
In both cases, it takes 1.5 seconds from the switching of the solenoid valve to the reaching of the set pressure, and the cutting pressure control corresponding to the temperature of the material to be cut is sufficiently possible.

[0014]

As described above, according to the method of the present invention, the cutting of the molten slag at the skid mark portion can be prevented,
Since uniform light cutting in the longitudinal direction of the material to be cut is possible, it is possible to prevent unremoved portions from remaining and improve the yield, which is a great effect for cutting steel materials with skid marks. is there.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of the configuration of an apparatus for carrying out 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 a relationship between a workpiece material temperature and a cutting amount when a cutting pressure of a hot scarfer is changed.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cutting material 2 Transport 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)

(57) [Claims] In a method for hot-cutting a work material having a skid mark portion, a skid mark portion is detected from a temperature distribution of the work material to be cut, and a cutting amount of the skid mark portion and a non-skid mark portion is detected. A hot cutting method for a steel material, characterized in that the cutting pressure on the skid mark portion is controlled to be higher than that of the non-skid mark portion so that the temperature is uniform.