JP2001105009A - Cold-rolling method excellent in dimensional accuracy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cold-rolling method excellent in dimensional accuracy in heavy-duty cold-rolling in which the dimensional accuracy of a material to be rolled is strict and for which tool size is large. SOLUTION: This is the cold-rolling method excellent in the dimensional accuracy by which rolling rolls preliminarily heated up to a temperature not lower than a stationary temperature at the time of cold-rolling using a low frequency induction heater are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold rolling method which has strict dimensional accuracy of a workpiece and has excellent dimensional accuracy in cold heavy rolling with a large tool size.

[0002]

2. Description of the Related Art In general, when a temperature of a tool during cold rolling gradually increases due to processing heat of a workpiece, a cooling device may be required to prevent the temperature. As an example, an oil coolant or the like can be cited. However, in the case of cold rolling or the like having a large processing amount per unit time, it is difficult to prevent the temperature of the tool from rising. Therefore, the dimensions of the workpiece gradually change due to the thermal expansion of the tool. Therefore, especially when dimensional adjustment is possible, the dimensional adjustment is repeated many times until the tool reaches the steady temperature, or when dimensional adjustment is not possible, the workpiece processed until the tool reaches the steady temperature. In some cases, the workpiece must be scrapped.

[0003] When the above-mentioned dimensional adjustment is repeated, machining is interrupted during that time, so that the temperature of the tool, which has risen to near the steady temperature, decreases, and the time for rising to the steady temperature is delayed. On the other hand, a batch furnace or a heating method using a heating element has been proposed as a conventional technique, but it is difficult to heat only a roll in a batch furnace, and in the case of a heating element, heating is performed from a roll outer peripheral surface. There is a problem that the entire temperature becomes non-uniform and it takes a long time to make it uniform. Furthermore, in order to heat a roll having a complicated caliber shape, it is necessary to prepare a large number of heating elements for each dimension.

[0004] In order to solve these problems, Japanese Patent Laid-Open Publication No. Hei 2 (1994) discloses a method in which a heating tool is used as a cold tool in cold working and heating is controlled to a required temperature during operation by in-line heating. No. 303647 is known. This is an extrusion molding device for forging parts used in a sizing process performed to enhance the processing accuracy of the outer peripheral surface of a rough member formed by hot forging or warm forging,
This is a device for extruding a forged part capable of maintaining a predetermined amount of dimensional accuracy of a molded product by finely adjusting the external dimensions of the die itself used for sizing. The die is heated by a heater, and the die is heated by a heater driving means. Since the die can be maintained at the required temperature, the die thermally expands and contracts by the amount corresponding to the temperature to increase or decrease its external dimensions, and the rough member ground by the cutting edge of the center processing hole has the desired dimensional accuracy. It is molded into a molded article.

[0005]

As described above, a method for heating a cold tool to a required temperature during operation by in-line heating by a heating element is known. However, in cold rolling or the like in which a rolling roll rotates or moves at a high speed, it is difficult to control heating to a required temperature during in-line operation as disclosed in JP-A-2-303647. Further, there is a problem that it is very difficult to uniformly heat a pillar roll die having a complicated caliber shape, for example, and the heating method is also difficult.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have intensively developed and as a result, the roll incorporated in the roll shaft is set to a constant temperature during cold working. Predicts the temperature of natural cooling from in-line installation to the start of rolling, and preheats and rolls off-line in advance to a steady temperature or higher, so there is no dimensional change in the dies, no dimensional change in the material to be rolled, and the shaft is incorporated A low-frequency induction heater enables the entire roll to be heated uniformly so that only the roll that is heated can be heated, and a cold rolling method with excellent dimensional accuracy has been developed. The gist of the invention lies in a cold rolling method excellent in dimensional accuracy, characterized in that a rolling roll heated using a low-frequency induction heater in advance to a steady temperature during cold rolling is used. .

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing a heated state of a rolling roll according to the present invention. As shown in FIG. 1, the rolling roll 3 incorporated in the shaft 1 and the roll chock 2 is heated by a low-frequency induction heater 4 in advance to a stationary temperature of 80 to 120 ° C., which is a steady temperature during cold working, in an offline manner. It is to be offered to. As described above, since the temperature of the rolling roll 3 is preliminarily heated to 80 to 120 ° C., which is a steady temperature during processing, there is no dimensional change of the roll due to thermal expansion, and the dimensional change of the workpiece is reduced.

[0008] The heating method is a low frequency 50 to 8 so that only the rolling roll 3 incorporated in the shaft 1 can be heated.
A 0 Hz induction heater 4 was employed. In other words, when the frequency becomes high, only the roll surface is heated, and the temperature difference between the outer and inner circumferences increases, and the overall temperature is not stable and the dimensional change of the workpiece is large. Low frequency.

FIG. 2 is a diagram showing the temperature condition of the inner and outer circumferences of the rolling roll after heating the induction heater. This figure 2
As shown in, when comparing the high frequency induction heater and the low frequency induction heater, the rolling roll temperature by the high frequency induction heater is higher on the outer circumference,
While the inner circumference is extremely low and the temperature difference between the inside and outside is large, according to the low frequency induction heater, the inside and outside temperature of the rolling roll can be almost uniformly uniform at both the inside and outside temperature of about 118 ° C., and the inside and outside temperature difference is extremely small. Heating became possible.

[0010]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples. Roll dies in a 100 VMR cold pilger mill were heated with a horizontal induction heater.
After heating to 18 ° C, it was incorporated into a cold pilger mill and the roll die temperature immediately before the start of processing was set to a steady temperature of 87 ° C
To 93 ° C, and from the φ92 × 13t mother pipe to φ57
The cold rolling of the product of x6.65t was performed. Table 1 shows the results. As shown in Table 1, in the present invention, the outer diameter change amount of the material to be rolled is almost 0 mm and the product dimensional change amount is small as compared with the comparative example, so that the number of dimensional adjustments can be greatly reduced. As a result, the productivity was improved, and the amount of debris due to deviation from dimensions was reduced. In addition, the roll target dimensions can be set to the center of tolerance, and the roll dies are further heated, so that the die caliber dimensions are increased by about 0.2 mm. It has become possible.

[0011]

[Table 1]

[0012]

As described above, according to the present invention, the number of times of dimensional adjustment can be greatly reduced, and since the dimensional change is small, the amount of scrap can be reduced, and the target rolling dimension can be set at the center of tolerance. Furthermore, since the roll die is heated, the size of the die caliber becomes large, so that the die scratches due to the die do not occur. Therefore, they increase productivity,
In addition, it has an extremely excellent effect of improving the yield.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a heated state of a rolling roll according to the present invention.

FIG. 2 is a diagram showing a temperature condition of the inner and outer circumferences of a rolling roll after heating an induction heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shaft 2 Roll chock 3 Roll roll 4 Low frequency induction heater

Claims (1)

[Claims] 1. A cold rolling method with excellent dimensional accuracy, characterized by using a rolling roll preheated to a steady temperature during cold rolling using a low-frequency induction heater.