JP6992680B2 - 3D hot bending quenching device and quenching method - Google Patents

Description

The present invention relates to a three-dimensional hot bending quenching apparatus and a quenching method.

_In recent years, in order to reduce the weight of automobiles by improving fuel efficiency for the purpose of preventing global warming and to improve the safety in the event of a collision of automobiles, the strength and wall thickness of automobile components have been increased. It is being promoted. Three-dimensional hot bending quenching (hereinafter, also referred to as "3DQ") is known as one of the technologies for realizing high strength and thinning of automobile components.

Patent Document 1 discloses 3DQ. In short, 3DQ is a push for manufacturing a bent steel pipe by performing bending or shearing on the downstream side of the support means while extruding the steel pipe, which is a material held so as to be able to be fed in the axial direction by the support means, from the upstream side. It is a through processing method.

The tip of the steel pipe is gripped by an industrial robot provided on the downstream side of the support means. An annular and copper high-frequency induction heating coil arranged around the outer circumference of the steel pipe on the exit side of the support means heats the steel pipe sent in the axial direction to _three or more points of Ac.

A water cooling device located on the downstream side of the high-frequency induction heating coil rapidly cools the heated steel pipe. As a result, a heating region having _three or more Ac points is formed in a part of the steel pipe in the axial direction. Then, the bent steel pipe is manufactured by applying a bending moment or a shearing force to the heating region by the supporting means and the industrial robot by controlling the gripping position of the steel pipe by the industrial robot.

When bending or shearing a steel pipe, which is a work material, as in 3DQ, heating the steel pipe uniformly within the cross section, that is, suppressing the temperature from becoming non-uniform in the circumferential direction of the cross section of the steel pipe. Is required to do.

For example, when the number of turns of the high-frequency induction heating coil is one (one turn), the temperature tends to be non-uniform in the circumferential direction of the cross section of the steel pipe, as described below. FIG. 3 is a diagram showing a one-turn high-frequency induction heating coil. As shown in FIG. 3, in the one-turn high-frequency induction heating coil 100, when an insulating material (not shown) is sandwiched between the start portion 100a and the end portion 100b of one turn in the gap portion 100c or the gap portion 100c. Is provided with its insulating material). When the steel pipe is heated by using such a one-turn high-frequency induction heating coil 100, the portion of the steel pipe facing the insulating portion is not heated or the heating efficiency is lower than that of the other portions. Therefore, the temperature in the circumferential direction of the cross section of the steel pipe becomes non-uniform.

Therefore, in general, by increasing the number of turns of the high-frequency induction heating coil to 2 or more, the influence of the insulating portion of the high-frequency induction heating coil is alleviated, and the non-uniformity of the temperature in the cross-sectional circumferential direction of the steel pipe is suppressed.

On the other hand, in 3DQ, the steel pipe is deformed only in the heating region while preventing out-of-plane deformation by the low temperature regions existing on both sides in the axial direction of the heating region. Therefore, in order to suppress the occurrence of molding defects such as wrinkles on the inner peripheral side of the bent portion, the length of the heated region, which is the deformed region, in the steel pipe feed direction (also referred to as “heating width” in the present specification) is made as short as possible. It is desirable to do.

For that purpose, it is desirable to shorten the length of the high-frequency induction heating coil in the steel tube feed direction (also referred to as “coil width” in the present specification), and further, the number of turns of the high-frequency induction heating coil should be as small as possible, that is, winding. It is desirable to use a high frequency induction heating coil (also referred to as "1 turn coil" in the present specification) having a number of 1.

However, in the one-turn coil, as described above, the non-uniformity of the temperature in the circumferential direction of the cross section of the steel pipe occurs due to the insulating portion of the high frequency induction heating coil. This non-uniformity can be suppressed to some extent by heat conduction by reducing the processing speed. However, since the one-turn coil is used, the heating output is insufficient, the machining speed cannot be increased in the straight portion or the low curvature portion where the bending is loose, and the productivity is lowered.

That is, regarding the coil width of the high-frequency induction heating coil used in 3DQ, the condition for suppressing the non-uniformity of the temperature in the circumferential direction of the cross section of the steel pipe and the condition for suppressing the wrinkle of the bent portion are in a trade-off relationship.

Patent Document 2 discloses a high frequency induction heating coil used for 3DQ. In this high frequency induction heating coil, two high frequency induction heating coils of one turn are arranged side by side in series in the feed direction of the steel pipe, and the ratio of the ineffective coil length Ln of the two high frequency induction heating coils to the inner circumference coil length L0. By setting (Ln / L0) to 0.05 or less, the steel pipe can be heated uniformly in the circumferential direction and in a narrow range in the feed direction of the steel pipe.

Further, when a bending member having a high curvature portion (small bending radius portion) is manufactured by performing bending with a small bending radius in 3DQ, that is, bending with a high curvature, if the processing speed of the bending portion is high, the steel pipe is formed. The speed change of the manipulator of the industrial robot to be gripped becomes excessive, the manipulator vibrates, and the machining accuracy decreases. This phenomenon occurs remarkably especially in the latter half of machining due to the relationship of speed = turning radius (∝ machined part length) x angular velocity of the manipulator of an industrial robot.

Patent Document 3 discloses a method of narrowing the heating width of a steel pipe and suppressing the occurrence of wrinkles by reducing the processing speed and the heating output at a high curvature portion of the steel pipe. INDUSTRIAL APPLICABILITY According to the present invention, when machining a straight portion and a low curvature portion of a bent steel pipe, the heating output and the machining speed are increased to ensure productivity, and when machining a high curvature portion of the bent steel pipe, the heating output and the machining speed are lowered. , Prevents deterioration of machining accuracy.

Japanese Unexamined Patent Publication No. 2007-83304 International Publication No. 2011/088817 International Publication No. 2016/031970

Since the invention disclosed in Patent Document 1 uses a one-turn coil, it is possible to suppress non-uniformity of the temperature in the circumferential direction of the cross section of the steel pipe by slowing down the processing speed, but it is undeniable that the productivity is lowered due to the use of the one-turn coil. do not have.

In the invention disclosed in Patent Document 1, it is necessary to move the high frequency induction heating coil with respect to the feeding direction of the steel pipe, and the structure of the high frequency induction heating coil becomes complicated. In addition, the steel pipe and the high-frequency induction heating coil may interfere with each other depending on the cross-sectional shape of the steel pipe.

The invention disclosed in Patent Documents 2 and 3 uses two electrically connected 1-turn high-frequency induction heating coils. Therefore, it is not easy to narrow the heating width, and it is not possible to prevent the occurrence of wrinkles on the bending inner peripheral side of the high curvature portion.

INDUSTRIAL APPLICABILITY According to the present invention, a high-strength bent steel pipe provided with a straight portion or a low-curvature portion and a high-curvature portion in the axial direction can be manufactured with high accuracy and productivity without causing uneven quenching and wrinkles. It is to provide a three-dimensional hot bending quenching apparatus and a quenching method.

The present inventors use 3DQ to prevent the occurrence of wrinkles on the inner peripheral side of bending when processing a high-curvature portion on a steel pipe, and to prevent a decrease in productivity, in order to manufacture a bent steel pipe. On the premise that the machining speed is reduced when machining curved parts and the machining speed is increased in other parts, intensive studies were conducted. As a result, the present invention was completed by obtaining the findings A to C listed below.

As the steel pipe, it is preferable for industrial production to target a steel pipe having a diameter of 17.3 mm to 100.0 mm and a wall thickness of 0.8 mm to 6.5 mm and having a tensile strength of 1470 MPa or more after quenching. When the stability of production is more important, the steel pipes have a diameter of 17.3 mm to 80.0 mm and a wall thickness of 0.8 mm to 3.2 mm and a tensile strength of 1470 MPa or more after quenching. Is desirable.

(A) Two 1-turn high-frequency induction heating coils that are electrically cut off from each other and can independently control their respective heating outputs are arranged side by side in series in the feed direction of the steel pipe. Of these two high-frequency induction heating coils, the downstream-side high-frequency induction heating coil is referred to as a one-turn coil having a small coil width (also referred to as a "narrow-width one-turn coil" in the present specification).

(B) In the processing of the high curvature portion, in order to make the heating width of the steel pipe as narrow as possible, heating is performed using only a narrow width 1-turn coil. In the machining of parts other than the high curvature portion, in order to increase the machining speed and improve productivity, both the narrow width 1-turn coil and the upstream coil are used to increase the heating output for heating.

(C) (The total heating output of the narrow 1-turn coil and the upstream coil) / By setting the machining speed within a specific range according to the cross-sectional line length and wall thickness of the steel pipe, in the feed direction of the steel pipe. Keep the heating temperature within the specified temperature range.

The present invention is as listed below.
(1) A three-dimensional hot bending quenching device provided with a high-frequency induction heating coil, which can heat the steel pipe while moving relative to the steel pipe in the axial direction of the steel pipe as a material. ,
The high frequency induction heating coil is a one-turn coil, and is a first high frequency induction heating coil having a first insulating portion provided between a start portion and an end portion of one turn of the one turn coil, and the first high frequency induction heating coil. A second high-frequency induction heating coil having a second insulating portion provided between a start portion and an end portion of one turn of the one-turn coil, which is a one-turn coil independent of the high-frequency induction heating coil of the above steel pipe. Have side by side in the relative feed direction of
The first high-frequency induction heating coil is arranged on the downstream side of the second high-frequency induction heating coil in the feed direction, and has a coil width of 4 to 10 mm, which is the length in the steel tube feed direction.
In the cross section orthogonal to the feeding direction of the steel pipe, the first insulating portion and the second insulating portion are connected to each other in the circumferential direction of the first high frequency induction heating coil and the second high frequency induction heating coil. Positioned off,
The first high-frequency induction heating coil and the second high-frequency induction heating coil are electrically insulated, and their respective heating outputs can be controlled independently.
The first high-frequency induction heating coil and the second high-frequency induction heating coil are three-dimensional hot bending quenching devices characterized in that the steel pipe can be heated to 900 to 1050 ° C.

(2) The three-dimensional hot bending quenching apparatus according to item (1), comprising an insulating member arranged between the first high frequency induction heating coil and the second high frequency induction heating coil.

(3) A first high-frequency power supply device and a second high-frequency power supply device independent of the first high-frequency power supply device are provided.
The first high frequency power supply device supplies high frequency power to the first high frequency induction heating coil.
The three-dimensional hot bending quenching device according to item (1) or (2), wherein the second high frequency power supply device supplies high frequency power to the second high frequency induction heating coil.

(4) A three-dimensional hot bending quenching method using the three-dimensional hot bending quenching apparatus according to any one of (1) to (3).
When a bent portion having a curvature of {0.1 + 50 (t / D) ² } / D or more is formed on the steel pipe, the relative feed rate of the steel pipe is set to 20 mm / sec or less and the first high frequency induction heating is performed. The steel pipe is heated only by the coil,
When a portion other than the bent portion (for example, a straight portion or a low curvature portion) is formed on the steel pipe, the relative feed rate of the steel pipe is set to 60 mm / sec or more, and the first high frequency induction heating coil and the first high frequency induction heating coil are formed. The steel pipe is heated by the high frequency induction heating coil of 2.
When the curvature changes in the longitudinal direction of the steel pipe, the curvature becomes {0.1 + 50 (t / D) ² } / D, and when the relative feed rate is changed, the absolute value is 10 mm / A three-dimensional hot bending and quenching method comprising changing the relative feed rate at an acceleration of sec / sec or more and starting or stopping the heating of the second high-frequency induction heating coil.
However, D is the diameter of the steel pipe, and t is the wall thickness of the steel pipe.

According to the present invention, the high-curvature portion is processed at a low processing speed, a low heating output, and a narrow heating width, so that wrinkles are suppressed and the portion other than the high-curvature portion such as a straight portion or a low curvature portion is suppressed. In the part, by machining at a high machining speed and high heating output, while suppressing the non-uniformity of the temperature in the circumferential direction of the cross section of the steel pipe, the high productivity of the entire part and the high curvature on the inner circumference side of the bend. Wrinkles can be suppressed.

FIG. 1 is an explanatory diagram schematically illustrating a three-dimensional hot bending quenching apparatus according to the present invention. FIG. 2 is a graph showing an example of the heating output pattern of the high frequency induction heating coil. FIG. 3 is a diagram showing a one-turn coil.

The present invention will be described with reference to the accompanying drawings.
1. 1. Three-dimensional hot bending quenching apparatus 1 according to the present invention
FIG. 1 is an explanatory diagram schematically illustrating a three-dimensional hot bending quenching apparatus 1 according to the present invention.

The three-dimensional hot bending and quenching device 1 (hereinafter referred to as “3DQ device 1”) is an upstream of a steel pipe 3 held so as to be feedable in the axial direction by a support means 2 by a feed means 4 such as an industrial robot or a ball screw. While continuously extruding from the side, bending or shearing is performed on the downstream side of the support means 2 to manufacture a bent steel tube.

The tip of the steel pipe 3 is gripped by the effector 6 attached to the tip of the manipulator of the industrial robot 5 provided on the downstream side of the support means 2. An annular and copper high-frequency induction heating coil 7 arranged around the outer circumference of the steel pipe 3 on the exit side of the support means 2 heats the steel pipe 3 sent in the axial direction to _three or more points of Ac. As a result, a heating region 3a having _three or more Ac points is formed in a part of the steel pipe 3 in the axial direction. In the present embodiment, the heated steel pipe 3 is rapidly cooled by the water cooling device 10 arranged on the downstream side of the high frequency induction heating coil 7.

In the present embodiment, by controlling the gripping position of the steel pipe 3 by the industrial robot 5, the supporting means 2 and the industrial robot 5 apply a bending moment or a shearing force to the heating region 3a to manufacture the bent steel pipe. ..

The high frequency induction heating coil 7 heats the steel pipe 3 while moving relative to the steel pipe 3 in the axial direction of the steel pipe 3. That is, the steel pipe 3 may pass through the inside of the fixed and installed high frequency induction heating coil 7, or the high frequency induction heating coil 7 may be moved in the axial direction of the fixed and supported steel pipe 3.

The high frequency induction heating coil 7 has a first high frequency induction heating coil 8 and a second high frequency induction heating coil 9 arranged side by side in the relative feed direction of the steel tube 3. As described above, in the present invention, the two-turn coil used as the high-frequency induction heating coil in the conventional 3DQ apparatus is replaced with the electrically independent first high-frequency induction heating coil 8 and the second high-frequency induction heating coil 9. Divide into.

The first high frequency induction heating coil 8 is arranged on the downstream side of the second high frequency induction heating coil 9 in the feed direction of the steel pipe 3. The first high frequency induction heating coil 8 and the second high frequency induction heating coil 9 are 1-turn coils, respectively. Similar to the 1-turn coil 100 described above, the first high frequency induction heating coil 8 has a first insulating portion (not shown), and the second high frequency induction heating coil 9 has a second insulating portion (not shown). have.

Of the first high-frequency induction heating coil 8 and the second high-frequency induction heating coil 9, the first high-frequency induction heating coil 8 used for processing a high curvature portion has a narrower coil width to narrow the heating width of the steel pipe 3. Since it is effective for this purpose, a one-turn coil is used, and the coil width is 4 to 10 mm.

In the machining of straight parts and low curvature parts of bent steel pipes, both the heating output and the machining speed are increased to increase productivity. In this case, there is no problem even if the heating width of the steel pipe 3 (the length in the axial direction of the steel pipe of the heating region 3a) is wide, so that both the first high frequency induction heating coil 8 and the second high frequency induction heating coil 9 are used and cooled. Since there is no problem even if the distance to the coil is a little long, the second high frequency induction heating coil 9 is arranged on the upstream side.

On the other hand, in the machining of the high curvature portion of the bent steel pipe, both the heating output and the machining speed should be suppressed to a low level, and the heating width of the steel pipe 3 should be narrowed. Therefore, only the first high frequency induction heating coil 8 is used from heating to cooling. Shorten the distance.

The first insulating portion (not shown) of the first high frequency induction heating coil 8 arranged in series in the feed direction of the steel tube 3 and the second insulating portion (not shown) of the second high frequency induction heating coil 9 are For example, as disclosed in Patent Document 2, in order to suppress non-uniformity of the temperature in the circumferential direction of the cross section, the first high frequency induction heating coil 8 and the second high frequency induction heating coil 9 are positioned so as to be offset in the circumferential direction. In other words, the first insulating portion and the second insulating portion are arranged so as to be offset from each other in the circumferential direction of the steel pipe 3 (heating region 3a) when viewed from the feeding direction of the steel pipe 3.

The degree of this deviation between the first insulating portion and the second insulating portion may be such that the non-uniformity of the temperature in the circumferential direction of the cross section of the steel pipe 3 is suppressed, but in reality, two high frequency inductions are performed. It is desirable that the central angles of the first high-frequency induction heating coil 8 and the second high-frequency induction heating coil 9 are deviated by 30 ° or more from the relationship of the installation locations of the bus bars 11 and 12 of the heating coils 8 and 9, respectively.

The first high-frequency induction heating coil 8 and the second high-frequency induction heating coil 9 are electrically insulated, and their respective heating outputs can be controlled independently.

Specifically, an insulating member 13 is provided between the first high-frequency induction heating coil 8 and the second high-frequency induction heating coil 9 in the feed direction of the steel pipe 3. It is desirable to provide an insulating member 14 between the first high frequency induction heating coil 8 and the water cooling device 10.

Further, the 3DQ device 1 includes a first high frequency power supply device 15 and a second high frequency power supply device 16 independent of the first high frequency power supply device 15. The first high frequency power supply device 15 supplies high frequency power to the first high frequency induction heating coil 8 via the bus bar 11, and the second high frequency power supply device 16 supplies the second high frequency induction heating coil via the bus bar 12. High frequency power is supplied to 9.

The first high-frequency induction heating coil 8 and the second high-frequency induction heating coil 9 are heated so that the heating temperature of the steel tube 3 is 900 to 1050 ° C. Table 1 summarizes an example of the processing conditions in the 3DQ apparatus 1 according to the present embodiment. In the above-described embodiment, the case where the 3DQ device 1 includes the first high-frequency induction heating coil 8 and the second high-frequency induction heating coil 9 has been described, but the 3DQ device 1 further includes a third high-frequency induction heating coil. Other high frequency induction heating coils such as a heating coil may be provided. That is, the 3DQ device 1 may include three or more high frequency induction heating coils. In this case, among the plurality of high-frequency induction heating coils, the high-frequency induction heating coil arranged on the most downstream side in the feed direction of the steel tube 3 is set as the first high-frequency induction heating coil, and electricity is generated from the other high-frequency induction heating coil. Is insulated.

In Table 1, high curvature and low curvature can be classified according to the presence or absence of wrinkles under normal machining conditions when a two-turn coil is used. From the experimental data shown in the document "Plasticity and Machining" (Vol. 57, No. 668, pp. 49-55), the presence or absence of wrinkles in the round tube can be estimated by the following equation (1).

Wrinkle limit bending R = D / {0.1 + 50 (t / D) ² } ・ ・ ・ ・ ・ (1)
In the equation (1), D is the diameter of the steel pipe 3 and t is the wall thickness of the steel pipe 3.

From the equation (1), the “high curvature portion” in Table 1 means a bent portion having a curvature of 1 / R = {0.1 + 50 (t / D) ² } / D or more.

The heating output in Table 1 is determined according to the processing speed and the cross-sectional shape of the steel pipe 3, and the bent steel pipe manufactured by 3DQ obtains the desired high strength (TS: 1470 MPa or more) by quenching. The heating temperature of the steel pipe 3 is adjusted to 900 to 1050 ° C.

In order to perform such heating, cooling and bending in a series of steps, it is possible to use the high frequency induction heating coil properly in the high curvature part, the straight part other than the high curvature part and the low curvature part, but the processing equipment is large. Therefore, it becomes difficult to secure the processing accuracy.

2. 2. Three-dimensional hot bending and quenching method according to the present invention A three-dimensional hot bending and quenching method using the above-mentioned three-dimensional hot bending and quenching apparatus according to the present invention will be described.

FIG. 2 is a graph showing an example of the processing speed of the steel pipe 3 and the heating output pattern of the high frequency induction heating coil 7. More specifically, FIG. 2A shows an example of the heating output pattern of the first high frequency induction heating coil 8, and FIG. 2B shows the heating output pattern of the second high frequency induction heating coil 9. An example is shown.

As shown in the graph of FIG. 2, when a high curvature portion having a curvature of {0.1 + 50 (t / D) ² } / D or more is formed in the steel pipe 3, for example, the first high frequency induction heating coil 8 is used. The heating output is set to 20 kW, the relative feed rate of the steel pipe 3 is set to 20 mm / sec or less, and the steel pipe 3 is heated only by the first high frequency induction heating coil 8. Even when the 3DQ device 1 is provided with three or more high-frequency induction heating coils, when forming a high-curvature portion on the steel pipe 3, the steel pipe 3 is heated only by the first high-frequency induction heating coil 8. ..

Further, when forming a low curvature portion or a straight portion other than the high curvature portion on the steel pipe 3, for example, the heating output of the first high frequency induction heating coil 8 and the second high frequency induction heating coil 9 is set to 40 kW. The steel tube 3 is heated by the first high frequency induction heating coil 8 and the second high frequency induction heating coil 9 with the relative feed rate of the steel tube 3 being 60 mm / sec or more. When the 3DQ device 1 is provided with three or more high-frequency induction heating coils, for example, when forming a low-curvature portion or a straight portion other than the high-curvature portion on the steel pipe 3, all the high-frequency induction heating coils are used. Heats the steel tube 3 with. It is industrially impossible to change the relative feed rate to 60 mm / sec or more or 20 mm / sec or less at the moment when the curvature becomes {0.1 + 50 (t / D) ² } / D. Is. Therefore, when the curvature changes in the longitudinal direction of the steel pipe, the curvature becomes {0.1 + 50 (t / D) ² } / D, and when the relative feed rate is changed, the relative feed rate is changed. The relative feed rate is changed at an industrially possible acceleration with an absolute value of 10 mm / sec / sec or more so that the feed rate is 60 mm / sec or more or 20 mm / sec or less, and the second feed rate is changed. The heating of the high frequency induction heating coil may be started or stopped.

As a result, in the high curvature portion, machining can be performed in a narrow heating width due to the low machining speed and low heating output, so that the occurrence of wrinkles on the bending inner peripheral side of the high curvature portion is suppressed, and the generation other than the high curvature portion is suppressed. In the low-curvature portion and the straight portion of the above, processing can be performed at a high processing speed and a high heating output, so that a decrease in productivity is suppressed. Therefore, it is possible to achieve both high productivity of the entire component and suppression of wrinkles in the high curvature portion.

The first straight part (length 500 mm, diameter 50.8 mm, wall thickness 1.0 mm), the high curvature part (bending radius 350 mm, bending angle 90 °, curvature 1/325 mm ^-1 ), and the second straight part (bending radius 350 mm, curvature 1/325 mm -1) A bent steel tube having a length (length of 500 mm) in the axial direction was manufactured by heating the steel tube as a material to 950 ° C. using the 3DQ device 1 shown in FIG. 1 and the conventional 3DQ device.

In Examples 1 and 2 of the present invention in Table 3 below, as shown in FIG. 1, a first high-frequency induction heating coil 8 and a second high-frequency induction heating coil 9 having a coil width of 6 mm are arranged. On the other hand, in Comparative Example 1 of Table 3, two 1-turn coils were arranged with the degree of deviation (phase difference) between the first insulating portion and the second insulating portion being 0. In Examples 1 and 2 of the present invention and Comparative Example 1, when forming the first and second straight portions, the steel pipe is heated by using two high frequency induction heating coils, and when forming the high curvature portion, the steel pipe is heated. The steel pipe was heated using only the high frequency induction heating coil on the downstream side. In Comparative Examples 2 to 4, one 1-turn coil was arranged, and in Comparative Examples 5 to 7, one 2-turn coil was arranged.

Table 2 summarizes the heating width (mm), heating output (kW), and wrinkle limit R (mm) for each processing speed (mm / sec) of the used 1-turn coil and 2-turn coil. The "heating width" in Table 2 was determined as the width of the heating region (maximum ultimate temperature-200 ° C.) based on "Plasticity and Machining" Vol. 56, No. 658, pp. 49-54.

The results are summarized in Table 3. In Table 3, wrinkles were marked with ◯ (pass) when the inner surface of the bent steel pipe was smooth, and × (failed) when unevenness was observed inside the bent steel pipe. In the evaluation, if all the items were ○, the evaluation was passed, and if any item was ×, the evaluation was × (failed).

In Example 1 of the present invention, using the 3DQ device 1, the coil width of the first high-frequency induction heating coil 8 is 6 mm, the phase difference between the first insulating portion and the second insulating portion is 180 °, and the steel pipe. Was produced by heating to 950 ° C. Further, in Example 2 of the present invention, using the 3DQ device 1, the coil width of the first high frequency induction heating coil 8 is 6 mm, and the phase difference between the first insulating portion and the second insulating portion is 90 °. , Manufactured by heating a steel pipe to 950 ° C. Therefore, in Examples 1 and 2 of the present invention, high productivity of the entire component and suppression of wrinkles in the high curvature portion could be achieved.

On the other hand, in Comparative Example 1, although the coil width of the first high frequency induction heating coil 8 was 6 mm and the steel pipe was heated to 950 ° C. using the 3DQ device 1, the first insulating portion and the first insulating portion and the steel pipe were manufactured. Since the phase difference of the second insulating portion was 0 °, uneven baking occurred.

In Comparative Example 2, since one 1-turn coil was arranged, uneven baking occurred.

In Comparative Example 3, since one one-turn coil was arranged and the processing speed in the high curvature portion was not reduced, uneven baking and wrinkles on the inner peripheral side of the high curvature portion occurred.

In Comparative Example 4, the processing speed at the first and second straight portions was not increased, so that the productivity was lowered. In Comparative Example 5, since one 2-turn coil was arranged and the machining speed in the first and second straight lines was not increased, wrinkles were generated on the inner peripheral side of the high curvature portion, and the productivity was also lowered.

In Comparative Example 6, since one 2-turn coil was arranged, wrinkles were generated on the inner peripheral side of the high curvature portion.

Further, in Comparative Example 7, since one 2-turn coil was arranged and the processing speed in the high curvature portion was not reduced, wrinkles occurred on the inner peripheral side of the high curvature portion.

1 3D hot bending quenching device (3DQ device)
2 Support means 3 Steel pipe 3a Heating region 4 Feeding means 5 Industrial robot 6 Effector 7 High frequency induction heating coil 8 First high frequency induction heating coil 9 Second high frequency induction heating coil 10 Water cooling device 11, 12 Bus bar 13 Insulation member 14 Insulation member 15 First high-frequency power supply device (The power supply line from the outside to the high-frequency power supply device is omitted.)
16 Second high-frequency power supply device (The power supply line from the outside to the high-frequency power supply device is omitted.)

Claims (4)

A three-dimensional hot bending quenching device provided with a high-frequency induction heating coil, which can heat the steel pipe while moving relative to the steel pipe in the axial direction of the steel pipe as a material.
The high frequency induction heating coil is a one-turn coil, and is a first high frequency induction heating coil having a first insulating portion provided between a start portion and an end portion of one turn of the one turn coil, and the first high frequency induction heating coil. A second high-frequency induction heating coil having a second insulating portion provided between a start portion and an end portion of one turn of the one-turn coil, which is a one-turn coil independent of the high-frequency induction heating coil of the above steel pipe. Have side by side in the relative feed direction of
The first high-frequency induction heating coil is arranged on the downstream side of the second high-frequency induction heating coil in the feed direction, and has a coil width of 4 to 10 mm, which is the length in the steel tube feed direction.
In the cross section orthogonal to the feeding direction of the steel pipe, the first insulating portion and the second insulating portion are connected to each other in the circumferential direction of the first high frequency induction heating coil and the second high frequency induction heating coil. Positioned off,
The first high-frequency induction heating coil and the second high-frequency induction heating coil are electrically insulated, and their respective heating outputs can be controlled independently.
The first high-frequency induction heating coil and the second high-frequency induction heating coil are three-dimensional hot bending quenching devices characterized in that the steel pipe can be heated to 900 to 1050 ° C. The three-dimensional hot bending quenching apparatus according to claim 1, further comprising an insulating member arranged between the first high frequency induction heating coil and the second high frequency induction heating coil. A first high frequency power supply device and a second high frequency power supply device independent of the first high frequency power supply device are provided.
The first high frequency power supply device supplies high frequency power to the first high frequency induction heating coil.
The three-dimensional hot bending quenching device according to claim 1 or 2, wherein the second high-frequency power supply device supplies high-frequency power to the second high-frequency induction heating coil. A three-dimensional hot bending and quenching method using the three-dimensional hot bending and quenching apparatus according to any one of claims 1 to 3.
When a bent portion having a curvature of {0.1 + 50 (t / D) ² } / D or more is formed on the steel pipe, the relative feed rate of the steel pipe is set to 20 mm / sec or less and the first high frequency induction heating is performed. The steel pipe is heated only by the coil,
When forming a portion other than the bent portion in the steel pipe, the steel pipe is used with the first high-frequency induction heating coil and the second high-frequency induction heating coil with the relative feed rate of the steel pipe set to 60 mm / sec or more. Heat and
When the curvature changes in the longitudinal direction of the steel pipe, the curvature becomes {0.1 + 50 (t / D) ² } / D, and when the relative feed rate is changed, the absolute value is 10 mm / A three-dimensional hot bending and quenching method comprising changing the relative feed rate at an acceleration of sec / sec or more and starting or stopping the heating of the second high-frequency induction heating coil.
However, D is the diameter of the steel pipe, and t is the wall thickness of the steel pipe.

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