JP3051259B2 - Electric rolling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric rolling method for a rolled material, and more particularly to an energizing rolling method in which a rolling mill itself is used as an electrode to energize the rolled material and roll while heating the material.

[0002]

2. Description of the Related Art In a conventional rolling mill, rolling is performed after heating a material to be rolled to a predetermined rolling temperature in a heating furnace or the like. In the heating furnace, a so-called skid mark or the like is applied to a rolled steel material by a water-cooled skid or the like. Various attempts have been made to eliminate the temperature distribution due to the occurrence of a temperature distribution, such as arranging skids in a staggered manner or performing non-water cooling. However, even with these methods, the temperature distribution of the material to be rolled is not eliminated, and when the material to be rolled is rolled by a rolling mill while maintaining this temperature distribution, the rolled material can be sufficiently reduced by the rolling resistance corresponding to the temperature distribution. It is difficult to obtain rolling dimensional accuracy. With respect to such a rolling method, there has been proposed a method of providing a current-carrying heating electrode between a rough rolling mill and a finishing mill and heating a rolled material as disclosed in JP-A-61-245911.

[0003]

However, in such an electrode, sparks usually occur when a large current is passed through a rolled material, and such electrodes are not practical unless there is a means for preventing the occurrence of sparks. Also, in this method, the stray current to the rough rolling mill is reduced by grounding the rough rolling mill, but the rolling mill behind the electrode provided behind the rough rolling mill, the roll, etc. Since the potentials are almost the same, it is not a means for cutting the stray current in this direction. Therefore, if the stray current cannot be reliably shut off, the input electric power does not effectively enter the rolled material, and the efficiency is deteriorated. The present invention solves the above-mentioned problems, and provides an energization rolling method that enables energization without generating a spark, improves rolling dimensional accuracy, and easily cuts stray current to a line. is there.

[0004]

According to the present invention, in order to solve the above-mentioned problems, a mill for determining the final rolling dimension after energizing rolling while preventing sparks by energizing with rolling rolls is provided. The purpose of this method is to increase the rolling accuracy and reduce the stray current to the line, and to achieve a stable energizing rolling method.The feature of this method is that the rolled material is passed through a primary ring transformer provided between rolling mills. A secondary voltage is induced directly in the rolled material by applying a 1-hour voltage to the transformer, and a closed circuit is formed by short-circuiting a current-carrying rolling mill provided before and after the transformer with a conductor having a very small resistance. , Flowing through this closed circuit 2
This is an energization rolling method in which a rolled material is heated to a predetermined temperature by a next current, and is rolled while being energized by a rolling mill as it is.

[0005]

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a rolling process in a case where a current is directly applied to a rolled material 3 to perform direct heating and rolling, and shows an example of energization and heating of a steel sheet by a transformer effect type energization heating device provided with a transformer between rolling mills. ing. That is, in this electric heating device, the rolled material comes into contact with the rolling mill and electric current roll arranged before and after the transformer, and the rolled material 3 is passed through and rolled. At this time,
When a primary voltage 2 is applied to the transformer 8, a secondary voltage is induced in the rolled material 3, and a current flowing in a closed circuit including the rolls 1 and 6 and the rolled material 3 short-circuited by the conductive material 4 causes a rolled material to be generated. The steel sheet is heated by a specific resistance of the steel sheet and heated to a predetermined temperature for rolling. At this time, if the rolled material had a temperature distribution before rolling, the resistance of the rolled material would be distributed according to the temperature. In this case, the current selectively flows through a portion having a low resistance to generate heat, so that heat generation in this portion increases, and the temperature distribution of the rolled material is made uniform. As a result, even if rolling is performed, the reduction in rolling dimensional accuracy due to temperature does not occur.

[0006] The electric power supplied at this time may be the minimum electric power required for rolling, and the heating can be completed in a short time, so that the work efficiency is greatly improved. This method is also extremely effective in preventing spark generation, which is a problem when conducting electric heating. That is, when energizing, the material to be rolled and the roll are brought into close contact with each other so as to cause plastic deformation, so that energization can be performed in a stable contact state, so that spark does not occur. Further, by providing a power supply transformer between the rolls, the voltage induced in the rolled material sandwiched between the energizing rolls 7 as shown in FIG. As shown in FIG. 3, with respect to the potential at the time of energizing the transformer effect type, the roll voltage can be made extremely low, and the stray current to the line can be made small. Even by using a relatively small choke coil, most stray currents can be cut and safe operation is possible.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A transformer-type current-carrying heating device as shown in FIG.
Two pairs of upper and lower cast iron rolls with an outer shape of 200 mm and a body length of 500 mm are used.
m, using a mild steel plate (0.06% C) with a thickness of 0.5 mm, a passing speed of 6 to 60 mpm, and a rolling force of max4 to
An electric heating experiment was performed up to n. The rolling temperature is 7
A maximum of 10,000 currents in the range of 00 to 900 ° C
[A] was energized. As a result, the current value at which sparks are generated in the rolls at the time of energization was about 10 [A] per 1 mm of the sheet width at the time of the pressing force within the elastic deformation, but by applying pressure until plastic deformation occurs. It was possible to energize up to the maximum power supply capacity of the experimental facility of 50 [A]. At this time, a voltage of 400 V at the maximum was applied to the transformer, but the voltage generated at the roll was extremely small at 4 V at the maximum, and safe energization was possible. Furthermore, in an experiment in which the steel sheet was heated by a burner on the entrance side of the energizing roll and electricity was applied to the steel sheet having a non-uniform temperature distribution to increase the temperature, the steel sheet having a temperature distribution of about ± 50 ° C. before heating was heated immediately before pressing. The temperature was controlled to be equal to or less than ± 5, and the purpose of rolling at a uniform temperature could also be achieved.

[0008]

As described above, in the electric heating method according to the present method, the rolled material can be made to have a uniform temperature distribution with a minimum necessary input energy. Enables uniform rolling. Furthermore, since the roll voltage can be lowered even when a large amount of electric power is applied, not only safe operation can be performed, but also hot rolling can be performed in a short time, and work efficiency can be drastically increased. Further, even during the energization, no spark is generated, so that a high-quality rolled material with stable quality can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration in which a rolled material is heated and rolled by applying current;

FIG. 2 is a rolling process diagram when a power supply transformer is provided between the rolls according to the present invention;

FIG. 3 is a diagram showing a relationship with a potential at the time of energization of a transformer effect type.

[Explanation of symbols]

 1, 6 Roll roll 2 Primary voltage 3 Rolled material 4 Conductive material 5 Backup roll 7 Electricity roll 8 Transformer

Claims (1)

(57) [Claims] The method according to claim 1] ring-shaped transformer material to be rolled is provided with a strip passing opening can pass, is provided between the rolling roll stand short-circuit conductive material, heating the material to be rolled by the current induced in the material to be rolled by the transformer An electric rolling method that rolls while rolling.