JP5692126B2 - Electric heating device and electric heating method - Google Patents

Description

  The present invention relates to an electric heating device and an electric heating method.

  Patent Document 1 discloses a first heating process in which a block heater is pressed against a high strength portion and partially heated with respect to press working, and both ends in the longitudinal direction of the workpiece are sandwiched between a pair of electrode blocks. A work heating process is disclosed that includes a second heating process in which the entire work is heated by energizing between the blocks, and only the portion to be made high in strength is heated to a quenching temperature or higher. The workpiece heated in the heating process is press-molded into a desired shape by a press die, and a portion having high strength is quenched.

JP 2009-95869 A

It is known that a workpiece heated to a high temperature undergoes deformation (such as undulation and swell) due to thermal expansion. When such deformation occurs in the contact portion with the electrode, the contact state between the electrode and the workpiece is not uniform, and the resistance value between the electrode and the workpiece may vary, resulting in uneven heating.
In consideration of deformation due to thermal expansion of a workpiece, the present invention provides a technique for suppressing uneven heating due to current heating by causing the electrode and the workpiece to contact with each other at a uniform surface pressure during current heating.

  The current heating device of the present invention comprises electrodes disposed at both ends of the workpiece, and electrode holders disposed so as to face the electrodes, and sandwiches both ends of the workpiece by the electrodes and electrode holders, In the energization heating apparatus that heats by energizing between the electrodes, the contact surface of the electrode and the electrode presser with the work is formed in a curved shape that swells toward the electrode.

  It is preferable that the energization heating device further includes a work presser having the same shape as the curved shape deformed by the electrode and the electrode presser of the work, and supporting a central portion in the current supply direction of the work from both sides in the thickness direction. .

  In a preferred embodiment of the electric heating device of the present invention, the workpiece is processed in advance into a shape corresponding to the curved shape of the electrode and electrode presser.

  The current heating method of the present invention uses the electrodes disposed at both ends of the work and the electrode retainers disposed so as to face the electrodes, and sandwiches both ends of the work by the electrodes and the electrode retainers. An electric heating method for heating by energizing between the electrodes, wherein the contact surface of the electrode and the electrode retainer with the workpiece is formed in a curved shape that swells toward the electrode side, and the workpiece is connected to the electrode and the electrode. Electric current is heated in a state of being deformed along the curved shape of the presser.

  In the energization heating method, the energization direction center of the work is disposed on both sides in the thickness direction during energization heating of the work using the work presser having the same shape as the curved shape deformed by the electrode and the electrode presser of the work. It is preferable to support from.

  In a preferred embodiment of the current heating method of the present invention, the workpiece is processed in advance into a shape corresponding to the curved shape of the electrode and electrode presser.

  According to the present invention, the contact state between the workpiece and the electrode during energization heating can be made uniform and the heating unevenness can be reduced by the electrode shape considering the direction of thermal expansion of the workpiece during energization heating.

It is a figure which shows an electricity heating apparatus. It is a figure which shows the thermal expansion of the workpiece | work in electrical heating. It is a figure which shows the work holding | suppressing of an electricity heating apparatus. It is a figure which shows one Embodiment of the workpiece | work thrown into an electric heating apparatus.

As shown in FIG. 1, the energization heating device 1 heats by energizing while sandwiching both ends of the work 2. The workpiece 2 is a rectangular flat plate made of a hardenable steel material.
The electric heating device 1 includes a pair of electrodes 10 and an electrode presser 20 disposed so as to face the electrode 10 with the workpiece 2 interposed therebetween. The electrode 10 and the electrode retainer 20 are each arranged at the end of the work 2. The both ends of the work 2 are sandwiched and supported by the electrode 10 and the electrode presser 20 from the thickness direction. An appropriate power supply device is connected to the electrode 10, and a current is passed between the electrodes 10 in a state where the work 2 is sandwiched, thereby generating Joule heat in the work 2 and heating it.
The workpiece 2 heated to a temperature equal to or higher than the quenching temperature by the electric heating device 1 is transferred to a press molding device and press-molded into a desired product shape. At this time, the workpiece 2 is quenched by holding the workpiece 2 in the press molding apparatus for a predetermined time.

As shown in FIGS. 1 and 2, the pressing surface of the workpiece 2 of the electrode 10 and the electrode pressing member 20, that is, the contact surface with the workpiece 2 is formed in a curved shape that swells toward the electrode 10 side. In other words, the workpiece contact surface of the electrode 10 is curved in a concave shape with a depressed central portion in a direction orthogonal to the energization direction of the workpiece 2, and the workpiece contact surface of the electrode presser 20 is a direction orthogonal to the energization direction of the workpiece 2. It is formed so that it may curve in the convex shape which the center part protruded.
Thus, since the electrode 10 and the electrode presser 20 are formed in a curved shape, the workpiece 2 is sandwiched in a deformed state along the curved shape that swells toward the electrode 10 side. At this time, by sandwiching both ends of the work 2 by the electrode 10 and the electrode presser 20, the entire work 2 is held in the same curved shape.

The workpiece 2 is heated to a high temperature (higher than the quenching temperature) by energization heating. For this reason, thermal expansion occurs in the work 2 being energized and heated and deforms.
As shown in FIG. 2, the workpiece 2 is in the radial direction of the curved shape (the radial direction from the R center of the curved shape, and the direction indicated by the arrow in the figure) at the portion sandwiched between the electrode 10 and the electrode holder 20. Expands and deforms along the circumferential direction. At this time, since the pressing surfaces of the electrode 10 and the electrode holder 20 are curved toward the electrode 10, the workpiece contact surface of the electrode 10 exists in the expansion direction of the workpiece 2, and the workpiece 2 and the electrode 10 are uniform. The state of being in close contact with is maintained.

  As described above, the electrode 10 and the electrode presser 20 have a shape that curves toward the electrode 10, whereby the direction of thermal expansion of the workpiece 2 can be regulated toward the electrode 10. Thereby, even if expansion | swelling by the heating of the workpiece | work 2 arises, a change in the adhesion degree of the workpiece | work 2 and the electrode 10 is lose | eliminated, and a uniform surface pressure is maintained. Therefore, there is no change in the resistance value between the workpiece 2 and the electrode 10, and the workpiece 2 can be uniformly energized and heated using the energization heating device 1, and temperature unevenness in the workpiece 2 can be reduced.

Further, both the electrode 10 and the electrode holder 20 that sandwich the workpiece 2 may be used as electrodes.
For example, when the thickness of the workpiece 2 is large, efficient energization heating can be performed by energizing from both sides in the thickness direction.

As shown in FIG. 3, the electric heating device 1 further includes a work presser 30. The work retainer 30 is a pair of thin plates that sandwich the work 2 from both sides in the thickness direction. The contact surface of the work retainer 30 with the work 2 is formed in the same curved shape as the curved shapes of the electrode 10 and the electrode retainer 20, and at least the contact portion with the work 2 is made of a heat insulating material. The work presser 30 is disposed at the center between the electrodes 10, that is, at the center of the work 2 in the energizing direction.
The work presser 30 supports the central portion of the work 2 during the electric heating by the electric heating apparatus 1. Thereby, the deflection | deviation by the thermal expansion of the whole material can be suppressed physically, and the deformation | transformation to the thickness direction of the workpiece | work 2 can be suppressed.

The workpiece 2 is shown in the embodiment in which a curved shape is given by the electrode 10 and the electrode presser 20 when sandwiched by the current heating device 1, but as shown in FIG. 2 can be processed in advance into a shape corresponding to the curved shape of the electrode 10 and the electrode presser 20.
In this case, it is not always necessary to provide a curved shape having the same curvature R (curvature radius), and an R (radius) larger than the curvature R of the electrode 10 and the electrode presser 20, that is, a gentle curved shape is previously set. It is good also as pre-processing positioning of the deformation | transformation by the clamp of the electrode 10 and the electrode holding | suppressing 20.
For example, when using a large workpiece 2 having a large length in the energization direction or a large thickness, the electrode 10 is formed in a curved shape along the shape of the electrode 10 and the electrode presser 20 in advance. And the amount of deformation due to the sandwiching of the electrode holder 20 is reduced, and natural clamping becomes possible.

About the magnitude | size of the curve of the electrode 10, the electrode holder 20, and the workpiece | work holder 30, ie, the curved shape of the workpiece | work 2, what is necessary is just the range which does not affect the press process by the press molding apparatus of a post process. In particular, in a range that does not affect the pressing step, it is preferable that the curvature R is small, and the deformed shape of the workpiece 2 has a reasonable inclination, so that unevenness in surface pressure is reduced.
For example, when the width of the workpiece 2 is set to 300 [mm], it is preferable to provide a curved shape of R = 300 [mm], and it is preferable to provide a curvature R that is approximately the same as the width of the workpiece 2.

  1: Electric heating device, 2: Work, 10: Electrode, 20: Electrode holding, 30: Work holding

Claims (6)

An electrode disposed at both ends of the workpiece, and an electrode holder disposed so as to face the electrode; by sandwiching both ends of the workpiece by the electrode and the electrode holder and energizing between the electrodes; An electric heating device for heating,
A contact heating surface of the electrode and the electrode retainer with the work is formed in a curved shape that swells toward the electrode side.   The energization heating apparatus according to claim 1, further comprising a work retainer that has the same shape as the curved shape deformed by the electrode and the electrode retainer of the work, and that supports a central portion in the energization direction of the work from both sides in the thickness direction. .   The energization heating apparatus according to claim 1, wherein the workpiece is processed into a shape corresponding to a curved shape of the electrode and the electrode presser in advance. By using the electrodes arranged at both ends of the workpiece and the electrode holders arranged so as to face the electrodes, the both ends of the workpiece are clamped by the electrodes and the electrode holders, and energized between the electrodes An electric heating method for heating,
The contact surface of the electrode and the electrode holder with the work is formed in a curved shape that swells toward the electrode, and the work is heated while being deformed along the curved shape of the electrode and the electrode holder. A characteristic heating method.   5. The central portion in the energization direction of the workpiece is supported from both sides in the thickness direction during energization heating of the workpiece by using the workpiece presser having the same shape as the curved shape deformed by the electrode and the electrode presser of the workpiece. The energization heating method according to 1.   The energization heating method according to claim 4 or 5, wherein the workpiece is processed in advance into a shape corresponding to a curved shape of the electrode and the electrode presser.

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