JP7092020B2 - Induction heating method for steel sheet members - Google Patents

Description

The present invention relates to an induction heating method for a steel sheet member.

In recent years, for example, as a structural member for an automobile, a steel plate member having a hard region that withstands an impact and a soft region that absorbs an impact has been developed in order to improve impact resistance. Patent Document 1 discloses a method of forming a hard region and a soft region on one steel sheet member by heating and baking only a part of the region of the steel sheet member to a temperature higher than the austenite transformation completion temperature A3. Has been done.

On the other hand, after the entire steel sheet member is made into a hard region by quenching, only a part of the region may be heated and tempered to form a hard region and a soft region on one steel sheet member.

Japanese Unexamined Patent Publication No. 2012-144773

The inventors have studied a method of inducing heating by arranging a steel plate member between a pair of plate-shaped coils arranged facing each other and electrically connected as a method of heating the steel plate member, and have solved the following problems. I found it.

During induction heating, the resistance of the plate-shaped coil changes between the non-arranged region (for example, a notch) where the steel plate member is not arranged between the pair of plate-shaped coils and the arranged region where the steel plate member is arranged. do. Specifically, in the plate-shaped coil arrangement region, the resistance is increased by the demagnetizing field from the steel plate member, whereas in the non-arranged region of the plate-shaped coil, the influence of the demagnetizing field from the steel plate member is small. Therefore, in the plate-shaped coil, the resistance becomes smaller in the non-arranged region than in the arranged region, and the current concentrates in the non-arranged region. As a result, there is a problem that the steel sheet member cannot be heated uniformly.

The present invention has been made in view of such circumstances, and provides an induction heating method for a steel sheet member capable of uniformly heating the steel sheet member.

The induction heating method for a steel sheet member according to one aspect of the present invention is
It is an induction heating method for a steel plate member, in which a steel plate member is arranged between a pair of plate-shaped coils that are arranged facing each other and electrically connected to each other for induction heating.
When the steel plate member is placed between the pair of plate-shaped coils and induced and heated,
A dummy plate made of an induction heating material is inserted into a non-arranged region where the steel plate member is not arranged between the pair of plate-shaped coils.

In the method for inducing heating a steel plate member according to one aspect of the present invention, when the steel plate member is arranged between a pair of plate-shaped coils and induced to be heated, the steel plate member is not arranged between the pair of plate-shaped coils. A dummy plate made of a material capable of induction heating is inserted in the arrangement region. Therefore, in the flat plate coil, the resistance difference between the arranged region where the steel plate member is arranged and the non-arranged region where the steel plate member is not arranged becomes small, and the steel plate member can be heated uniformly.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an induction heating method for a steel sheet member capable of uniformly heating the steel sheet member.

It is a perspective view which shows the induction heating method of the steel plate member which concerns on 1st Embodiment. It is a top view which shows the positional relationship of the steel plate member 10, the dummy steel plate 20, and the plate coil 31. FIG. 2 is a cross-sectional view taken along the line III-III of FIG. It is a top view which shows the positional relationship of the steel plate member 10 and the plate-shaped coil 31 in the induction heating method of the steel plate member which concerns on a comparative example. FIG. 6 is a sectional view taken along line VV of FIG. It is a perspective view of an example of a steel plate member. It is a figure which shows the simulation result in the induction heating method of the steel plate member which concerns on Example and the comparative example.

Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Further, in order to clarify the explanation, the following description and drawings are appropriately simplified.

(First Embodiment)
<Induction heating method for steel sheet members>
First, with reference to FIG. 1, the induction heating method for the steel sheet member according to the first embodiment will be described. FIG. 1 is a perspective view showing an induction heating method for a steel plate member according to the first embodiment.
As a matter of course, the right-handed xyz orthogonal coordinates shown in FIG. 1 and other drawings are for convenience to explain the positional relationship of the components. Normally, the z-axis positive direction is vertically upward, and the xy plane is the horizontal plane.

The induction heating method for a steel sheet member according to the present embodiment is suitable as an induction heating method for a steel sheet member for an automobile, which is required to have both high strength and excellent shock absorption characteristics. The induction heating method for the steel sheet member according to the present embodiment can be used for both quenching and tempering applications. The following description describes the use for tempering.

For the sake of simplicity, the steel plate member 10 shown in FIG. 1 has a simple flat plate shape, but the use and shape of the steel plate member to which the induction heating method for the steel plate member according to the present embodiment is applied. Is not limited in any way. The steel plate member 10 shown in FIG. 1 is, for example, a floor member for a vehicle. As another example of the steel plate member, a vehicle member having a hat-shaped cross section perpendicular to the longitudinal direction such as a side member (for example, a front side member and a rear floor side member) and a pillar can be mentioned.

As shown in FIG. 1, the steel plate member 10 is induced and heated by the induction heating device 30. The induction heating device 30 includes a pair of plate-shaped coils 31 (upper plate-shaped coil 31a, lower plate-shaped coil 31b), a tubular coil 32, and a high-frequency power supply 33.
The steel plate member 10 is not particularly limited, but is, for example, a steel plate for hot stamping made of manganese / boron steel having a thickness of about 1 to 4 mm. The steel plate member 10 before induction heating is, for example, a hard material having a microstructure whose entire surface is made of martensite.

In the present embodiment, the upper plate-shaped coil 31a and the lower plate-shaped coil 31b are xy-planar rectangular copper plates having the y-axis direction as the longitudinal direction, and overlap each other in the xy-planar view. The upper plate-shaped coil 31a and the lower plate-shaped coil 31b are arranged to face each other and are electrically connected by a tubular coil 32. Then, the steel plate member 10 is arranged between the upper plate-shaped coils 31a and the lower plate-shaped coils 31b arranged so as to face each other, and induction heating is performed.

As shown in FIG. 1, the tubular coil 32 is a copper tube that is joined to a pair of plate-shaped coils 31 and is provided so as to go around the outside of the pair of plate-shaped coils 31. That is, the tubular coil 32 constitutes a one-turn coil together with the pair of plate-shaped coils 31. Both ends of the tubular coil 32 are connected to the high frequency power supply 33, forming a closed circuit as a whole. Cooling water for cooling the pair of plate-shaped coils 31 flows inside the tubular coil 32.

As shown in FIG. 1, in the present embodiment, the tubular coil 32 is branched into two on the upper surface of the upper plate coil 31a and the lower surface of the lower plate coil 31b, and extends in the y-axis direction. The tubular coil 32 extends in the z-axis direction on one end side in the y-axis direction of the pair of plate-shaped coils 31 and connects them in series. Further, the tubular coil 32 is connected to the high frequency power supply 33 on the other end side of the pair of plate coils 31 in the y-axis direction.

Here, FIG. 2 is a plan view showing the positional relationship between the steel plate member 10, the dummy steel plate 20, and the plate-shaped coil 31. FIG. 3 is a sectional view taken along line III-III of FIG. In FIG. 2, the tubular coil 32 is omitted. As shown in FIG. 3, in the present embodiment, the tubular coil 32 is a square pipe and is joined to the upper surface of the upper plate-shaped coil 31a and the lower surface of the lower plate-shaped coil 31b. Further, as described above, the tubular coil 32 is branched into two on the upper surface of the upper plate-shaped coil 31a and the lower surface of the lower plate-shaped coil 31b. The tubular coil 32 is not limited to a square pipe, and may be, for example, a round pipe.

As shown in FIGS. 2 and 3, the steel plate member 10 has a notch portion 11. The cutout portion 11 constitutes a non-arranged region in which the steel plate member 10 is not arranged between the pair of plate-shaped coils 31. If the notch portion 11 is arranged between the pair of plate-shaped coils 31, the position and shape of the notch portion 11 are not limited in any way. Further, if a non-arranged region in which the steel plate member 10 is not arranged is formed between the pair of plate-shaped coils 31, the region is not limited to the notch portion 11. In the present embodiment, when the steel plate member 10 is induced and heated, the dummy steel plate 20 is inserted into the non-arranged region (notch portion 11 of the steel plate member 10) between the pair of plate-shaped coils 31.

The dummy steel plate 20 is made of, for example, a steel plate of the same type as the steel plate member 10, but may be made of a steel plate of a different type from the steel plate member 10. Further, instead of the dummy steel plate 20, a dummy plate made of a material other than steel that can be induced and heated may be used. For example, a dummy plate made of a metal material other than steel, carbon, or the like can be used.

Here, the induction heating method of the steel plate member according to the comparative example will be described with reference to FIGS. 4 and 5. FIG. 4 is a plan view showing the positional relationship between the steel plate member 10 and the plate-shaped coil 31 in the induction heating method for the steel plate member according to the comparative example, and is a view corresponding to FIG. 2. 5 is a VV cross-sectional view of FIG. 4, which corresponds to FIG.

The configuration of the induction heating device 30 in the comparative example is the same as that shown in FIG. The steel plate member 10 shown in FIGS. 4 and 5 is the same as the steel plate member 10 shown in FIGS. 1 to 3, and has a notch portion 11. As shown in FIGS. 4 and 5, in the method of inducing heating of a steel plate member according to a comparative example, when the steel plate member 10 is induced to be heated, a non-arranged region (notch of the steel plate member 10) between a pair of plate-shaped coils 31 is used. Do not insert the dummy steel plate 20 into the portion 11).

In the comparative example, when the steel plate member 10 is induced and heated, the non-arranged region (notch portion 11 of the steel plate member 10) between the pair of plate-shaped coils 31 and the arranged region in which the steel plate member 10 is arranged are paired. The resistance of the plate-shaped coil 31 of the above changes.

More specifically, as shown in FIG. 5, in the arrangement region of the pair of plate-shaped coils 31, the resistance is increased by the demagnetizing field from the steel plate member 10. On the other hand, in the non-arranged region of the pair of plate-shaped coils 31, the influence of the demagnetic field from the steel plate member 10 is small. Therefore, in the pair of plate-shaped coils 31, the resistance is relatively smaller in the non-arranged region than in the arranged region, and the current is concentrated in the non-arranged region. As a result, the steel plate member 10 could not be heated uniformly. Specifically, the heating temperature in the vicinity of the non-arranged region of the steel plate member 10 (the cutout portion 11 of the steel plate member 10) is lowered.

On the other hand, as shown in FIG. 3, in the induction heating method for the steel plate member according to the present embodiment, when the steel plate member 10 is induced and heated, a non-arranged region (the steel plate member 10) between the pair of plate-shaped coils 31 is used. A dummy steel plate 20 is inserted into the notch portion 11). Therefore, the resistance in the arranged region and the non-arranged region of the pair of plate-shaped coils 31 becomes the same, and the current also becomes the same. As a result, in the induction heating method for the steel sheet member according to the present embodiment, the steel sheet member 10 can be uniformly heated.

<Specific examples of steel plate members>
Next, with reference to FIG. 6, the configuration of a specific example of the steel sheet member to be heated by using the induction heating method of the steel sheet member according to the first embodiment will be described. FIG. 6 is a perspective view of an example of a steel plate member. The steel plate member 50 shown in FIG. 6 is a steel plate member for pillars, which is a member for vehicles, and more specifically, a center pillar reinforcement. The arrows shown in FIG. 6 indicate each direction in the vehicle.

As shown in FIG. 6, the steel plate member 50 includes a main body portion 51, an upper flange portion 52, and a lower flange portion 53.
The use and shape of the steel plate member 50 shown in FIG. 6 is merely an example, and the use and shape of the steel plate member to which the induction heating method for the steel plate member according to the present embodiment is applied may be limited. do not have.

As shown in FIG. 6, the main body portion 51 is a portion having a hat-shaped cross section including a top plate 51a, a side wall 51b, and a flange portion 51c extending in the vertical direction. More specifically, a pair of side walls 51b are formed inward from the widthwise end of the top plate 51a extending in the vertical direction. Further, the flange portion 51c projects outward from the end portion of each side wall 51b.

Further, the main body 51 is slightly curved so as to project outward as a whole. Further, the upper end portion and the lower end portion of the main body portion 51 extend in the width direction (front-back direction) and are formed in a T-shape in a plan view. Here, the lower end portion is wider in the width direction (front-back direction) than the upper end portion.

The upper flange portion 52 includes a plate surface that rises outward from the upper end portion of the main body portion 51, and a plate surface that projects upward from the outer end portion of the surface (outside in the longitudinal direction of the main body portion 51). That is, the upper flange portion 52 is a portion having an L-shaped cross section extending in the width direction (front-back direction).

The lower flange portion 53 is a flat plate-shaped portion extending downward (outside in the longitudinal direction) from the lower end portion of the top plate 51a and extending in the width direction (front-back direction). A notch 53a is provided on the lower side of the lower flange portion 53.

In FIG. 6, a pair of plate-shaped coils 310 (upper plate-shaped coil 310a, lower plate-shaped coil 310b) used for tempering the steel plate member 50 are shown by a two-dot chain line. In the steel plate member 50, the lower portion of the lower flange portion 53 and the main body portion 51 located between the pair of plate-shaped coils 310 is a soft region. The other region is a hard region. The cutout portion 53a of the lower flange portion 53 constitutes a non-arranged region in which the steel plate member 50 is not arranged between the pair of plate-shaped coils 310.

<Simulation result>
Next, with reference to FIG. 7, the thermal analysis simulation result in which the steel plate member 50 shown in FIG. 6 is induced and heated will be described. FIG. 7 is a diagram showing simulation results in the induction heating method for steel sheet members according to Examples and Comparative Examples. A configuration diagram is shown in the upper part of FIG. 7. The thermal analysis results of Comparative Examples and Examples are shown in the middle and lower rows, respectively.

As shown in the upper part of FIG. 7, in the thermal analysis simulation, the upper plate-shaped coil 310a shown in FIG. 6 is composed of four upper plate-shaped coils 311a, 312a, 313a, 314a extending in the y-axis direction. ing. Although not shown in FIG. 7, the lower plate-shaped coil 310b shown in FIG. 6 is also composed of four upper plate-shaped coils 311b, 312b, 313b, and 314b extending in the y-axis direction. ..

The tubular coil 320 includes four pairs of plate coils, an upper plate coil 311a, a lower plate coil 311b, an upper plate coil 312a, a lower plate coil 312b, an upper plate coil 313a, a lower plate coil 313b, and an upper plate coil 320. It is a copper tube connecting the side plate-shaped coil 314a and the lower plate-shaped coil 314b in this order. That is, the tubular coil 320 is provided so as to make four turns around the outside of these four pairs of plate-shaped coils (that is, the outside of the steel plate member 50 arranged between the plate-shaped coils 310). That is, the tubular coil 320 constitutes a 4-turn coil together with a pair of plate-shaped coils 310 divided into four. Both ends of the tubular coil 320 are connected to the high frequency power supply 33, forming a closed circuit as a whole.

As shown in the lower part of FIG. 7, in the embodiment, when the steel plate member 10 is induced and heated, the dummy steel plates 20a, 20b, and 20c are inserted into the non-arranged region between the pair of plate-shaped coils 310. On the other hand, as shown in the lower part of FIG. 7, in the comparative example, when the steel plate member 10 was induced and heated, the dummy steel plate was not inserted into the non-arranged region between the pair of plate-shaped coils 310.

As shown in the middle part of FIG. 7, in the comparative example, the heating temperature in the vicinity of the cutout portion 53a of the steel plate member 50 was particularly low, and the steel plate member 50 could not be heated uniformly. On the other hand, as shown in the lower part of FIG. 7, in the embodiment, the dummy steel plate 20a was inserted into the cutout portion 53a of the steel plate member 50 of the steel plate member 50. As a result, the temperature in the vicinity of the notch 53a increased, and the steel plate member 50 could be heated more uniformly than in the comparative example.
As described above, the effect of the induction heating method for the steel sheet member according to the present embodiment was confirmed by the thermal analysis simulation.

The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the spirit.

10 Steel plate member 11 Notch 20, 20a, 20b, 20c Dummy steel plate 30 Induction heating device 31, 310 Plate coil 31a, 310a-314a Upper plate coil 31b, 310b-314b Lower plate coil 32 Tubular coil 33 High frequency power supply 50 Steel plate member 51 Main body 51a Top plate 51b Side wall 51c Flange 52 Upper flange 53 Lower flange 53a Notch 320 Tubular coil

Claims (1)

It is an induction heating method for a steel plate member, in which a steel plate member is arranged between a pair of plate-shaped coils that are arranged facing each other and electrically connected to each other for induction heating.
When the steel plate member is placed between the pair of plate-shaped coils and induced and heated,
A dummy plate made of an induction heating material is inserted into the notch portion of the steel plate member formed at the end of the steel plate member between the pair of plate-shaped coils.
Induction heating method for steel sheet members.

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