JP2018176220A - Method of welding hot press molded articles - Google Patents

Abstract

The present invention provides a method for welding a hot-press molded product that can stabilize the quality of a welded portion when spot welding is performed. A hot press molded product P1 is obtained by hot press molding from a steel sheet S1 having a galvanized layer G1 on the surface. The laser beam L1 is irradiated to the welding planned area A1 by using the fiber laser oscillator 51a to the welding planned area A1 that encloses a plurality of spot welding scheduled execution parts X1 on the surface of the hot press molded product P1 in a rectangular shape. The deposited oxide film W1 is vaporized and removed. Thereafter, the press plate P2 is overlaid on the hot press-formed product P1, and spot welding is performed on the spotting scheduled execution portion X1 in each welding scheduled area A1. [Selection] Figure 3

Description

  The present invention relates to a method of welding a hot press-formed product obtained by hot pressing.

  It is generally known that when a hot press-formed product is obtained by hot press forming from a steel plate having a galvanized layer or an alloyed galvanized layer on the surface, an oxide film is formed on the surface. The oxide film attached to the surface of the hot press molded product may reduce the adhesion of the coating film. For example, in Patent Document 1, the surface of the hot press molded product is irradiated with laser light to form an oxide film. After removing by vaporization, the adhesion of the coating film is enhanced by performing a coating process.

JP, 2015-105422, A

  By the way, when welding a hot press molded article by spot welding, if an oxide film adheres to the surface of the hot press molded article, the electrode tip will press and hold the hot press molded article to conduct electricity. The electrical resistance between the tip surface of and the hot press molded product is increased by the oxide film. Therefore, the current supply path becomes unstable and a shunt occurs, and the quality of the formed weld varies.

  In order to cope with this, after removing the oxide film adhering to the surface of the hot press molded product by a method of irradiating a laser beam as disclosed in Patent Document 1, the quality of the welded portion is stabilized by spot welding. Is considered.

  However, although Patent Document 1 describes the method of removing the oxide film by laser light for enhancing the adhesion of the coating film, it is by laser light for stabilizing the quality of the weld formed by spot welding. Naturally, how to remove the oxide film is not considered.

  This invention is made in view of such a point, The place made as the objective provides the welding method of the hot press molded article which can stabilize the quality of a welding part, when spot welding is implemented. It is.

  In order to achieve the above object, according to the present invention, only a partial region of the oxide film adhering to the surface of the hot press molded article is removed by laser light, and the region from which the oxide film has been removed It is characterized in that a level difference is generated between the two.

  That is, in the first invention, after a hot press-formed product is obtained by hot press forming from a steel plate having a galvanized layer or an alloyed galvanized layer on the surface, a plurality of spot welds on the surface of the hot pressed formed product The laser irradiation is applied to the area to be welded which encloses the planned parts to be rectangular or circular, and the oxide film adhering to the area to be welded is vaporized and removed by irradiating the laser beam using a laser oscillator, Alternatively, the film thickness of the oxide film may be reduced, and then another press-formed product or steel plate may be superimposed on the hot press-formed product, and spot welding may be performed on the planned portion to be hit in the respective welding scheduled areas. Do.

  In a second invention, in the first invention, the region to be welded has a circular shape corresponding to the tip surface of the electrode tip used at the time of spot welding, and adheres to the region to be welded on the surface of the hot press molded article The laser beam is irradiated to the above-mentioned welding planned area so that the film thickness of the oxide film to be formed becomes thinner than the film thickness of the oxide film adhering to the area except the welding planned area and the thickness of a predetermined amount remains. It is characterized by

  In the first invention, the oxide film adhering to each of the regions to be welded on the surface of the hot press molded product is eliminated or the amount of the oxide film to be adhered is reduced, and each region to be welded on the surface of the hot press molded product and the other A step is generated between the area. Then, when a hot press molded product is pressurized and held by the electrode tip and electricity is applied, the electric resistance between the tip surface of the electrode tip and the hot press molded product is reduced, and each welding schedule on the surface of the hot press molded product Since the difference in electrical resistance between the region and the other regions is large, it is possible to prevent current diversion and to stabilize the quality of the weld.

  In the second invention, when the electrode tip is pressed and held by the electrode tip in the portion to be subjected to the hitting point, the peripheral portion of the tip surface of the electrode tip is at a position corresponding to the step portion of the oxide film. Therefore, when current flows between the front end surface of the electrode tip and the hot press molded product, the current flow is concentrated on the portion to be subjected to the hitting point, which makes it possible to reliably prevent the diversion, and the welding portion Can further stabilize the quality of In addition, since the laser beam is irradiated so that a predetermined amount of the oxide film adhering to the area to be welded remains, the laser beam does not directly strike the galvanized layer or the alloyed galvanized layer or the base material. Therefore, it is possible to prevent the galvanized layer or the alloyed galvanized layer from being damaged or affecting the hardness of the base material, and the corrosion resistance, corrosion resistance, and rigidity are high even after spot welding. It can be made into a hot press molded article.

It is a layout figure of the production line where the welding method concerning Embodiment 1 of the present invention was applied. It is a block diagram of the production line where the welding method concerning Embodiment 1 of the present invention was applied. It is III arrow line view of FIG. It is sectional drawing in the IV-IV line of FIG. It is a photograph which shows the cross section of the hot press molded article before removing an oxide film. It is a photograph which shows the cross section of the hot press molded article after removing an oxide film. It is a graph which shows the hardness of the base material before and behind removing an oxide film in a hot press molded article. Hot-press molded articles with various oxide film removal conditions when oxide films are removed while changing laser output with respect to hot press molded articles molded under maximum heating conditions, and hot-pressed molded articles with oxide film removed under various oxide film removal conditions It is the graph which showed the relationship with the resistance value between electrode tips when carrying out pressurization holding | maintenance by a pair of electrode tip. Hot-press molded articles with various oxide film removal conditions when oxide films are removed while changing laser output with respect to hot press molded articles molded under the minimum heating conditions, and hot-pressed molded articles with the oxide film removed under the various oxide film removal conditions It is the graph which showed the relationship with the resistance value between electrode tips when carrying out pressurization holding | maintenance by a pair of electrode tip. The hot press molded article from which the oxide film was removed under various oxide film removal conditions when the oxide film was removed while changing the processing speed with respect to the hot press molded item molded under the maximum heating condition It is the graph which showed the relationship with the resistance value between electrode tips when carrying out pressurization holding | maintenance by a pair of electrode tip. The hot press molded article from which the oxide film was removed under various oxide film removal conditions when the oxide film was removed while changing the processing speed with respect to the hot press molded article molded under the minimum heating condition It is the graph which showed the relationship with the resistance value between electrode tips when pressing and holding with a pair of electrode tips It is the graph which showed the relationship between the electric current value when performing spot welding with respect to the hot press molded article to which an oxide film adheres, and the nugget diameter of a welding part. It is the graph which showed the relationship between the electric current value when performing spot welding with respect to the hot press molded article which removed the oxide film, and the nugget diameter of a welding part. It is the FIG. 4 equivalent view which concerns on Embodiment 2. FIG.

  Hereinafter, embodiments of the present invention will be described in detail based on the drawings. The following description of the preferred embodiments is merely exemplary in nature.

Embodiment 1 of the Invention
FIG. 1 shows a production line 1 according to Embodiment 1 of the present invention. In the production line 1, the vehicle body frame B1 is to be produced, and as shown in FIG. 2, in the order from the upstream side of the production line 1, it has a galvanized layer G1 (or an alloyed galvanized layer) on the surface. A hot press-formed product P1 is formed from the steel sheet S1 heated in the heating step 3 and the heating step 3 for heating the steel plate S1 carried in from the carry-in step 2 Hot pressing step 4 and a film removing step 5 for removing the oxide film W1 (see FIG. 4) adhering to the surface of the hot press molded product P1 during hot press molding, and a hot press molded product after removing the oxide film A welding step 6 for obtaining the vehicle body frame B1 by integrating spot P1 and a flat press plate P2 (steel plate) by spot welding is disposed on a straight line.

  As shown in FIG. 1, the loading step 2 has a pallet 20 on which a plurality of steel plates S1 are placed in a stacked state.

  Between the carry-in step 2 and the heating step 3, a first robot R1 is provided which sequentially carries the plurality of steel plates S1 stacked on the pallet 20 into the heating step 3.

  The heating step 3 includes a heating furnace 30 extending along the upstream side and the downstream side of the production line 1, and the heating furnace 30 includes a lower furnace body 30a installed on the floor and an upper side of the lower furnace body 30a. And an upper furnace body 30b disposed opposite to each other.

  The lower furnace body 30a is provided with a plurality of transport rollers (not shown) for conveying the steel plate S1, while the upper furnace body 30b is provided with an atmosphere between the upper furnace body 30b and the lower furnace body 30a. A heater (not shown) for raising the gas is attached, and the heating furnace 30 is configured to raise the temperature of the steel plate S1 to approximately 800 to 1000 ° C. when the steel plate S1 is transported.

  Between the heating step 3 and the hot pressing step 4, a second robot R 2 for conveying the steel sheet S 1 heated by the heating furnace 30 to the hot pressing step 4 is disposed.

  The hot press process 4 includes a mold 40 for hot press molding having an upper mold 41 and a lower mold 42, and a hydraulic press 43 for servo motor control, and the hydraulic press 43 comprises the upper mold 41 and a lower mold. It is made to go up and down to 42.

  An upper pressing surface 41a having a substantially concave cross section is formed on the upper die 41, and a lower pressing surface 42a having a substantially convex cross section corresponding to the upper pressing surface 41a is formed on the lower die 42.

  Then, the steel plate S1 is set along the upper pressing surface 41a and the lower pressing surface 42a by setting the heated steel plate S1 on the lower pressing surface 42a of the lower die 42 and lowering the upper die 41 to the bottom dead center. While forming into a molded article having a substantially hat-shaped cross section, the molded article is subjected to pressure holding by the upper mold 41 and the lower mold 42 and cooled to quench the molded article to obtain a hot press molded article P1. It has become.

  Between the hot pressing step 4 and the film removing step 5, a third robot R 3 for sequentially transporting the hot press molded product P 1 formed in the hot pressing step 4 to the film removing step 5 is disposed.

  The film removing step 5 includes a mounting table 50 on which the hot press molded product P1 can be mounted, and a film removing device 51 disposed on the side of the mounting table 50.

  The film removing apparatus 51 is connected to a fourth robot R4 which is an industrial robot, a fiber laser oscillator 51a disposed on the side of the fourth robot R4, and the fiber laser oscillator 51a via a fiber cable 51b. The galvano scanner head 51c attached to the tip end of the arm of the fourth robot R4 enables the laser beam L1 excited by the fiber laser oscillator 51a to scan the object with respect to the object It has become.

  As shown in FIG. 3, a plurality of spot execution planned portions X1 for spot welding are preset in the flange portion F1 of the hot press molded product P1 mounted on the mounting table 50, and the film removing device 51 As shown in FIG. 4, an oxide film W1 attached to each welding scheduled area A1 by irradiating the welding planned area A1 surrounding each welding spot implementation planned portion X1 in a rectangular shape while scanning the laser light L1. Is to be vaporized and removed.

  The hot press molded article P1 after the oxide film removal is conveyed to the welding process 6 by an industrial robot not shown.

  In the welding step 6, as shown in FIG. 1, a jig 61 capable of positioning the hot press molded article P1 after removal of the oxide film and the press plate P2 in an overlapping manner and positioned sideways of the jig 61 The fifth robot R5 has a welding gun T1 attached thereto, and spot welding is performed on each planned spot X1 using the welding gun T1 to integrate the hot press molded article P1 with the press plate P2. Thus, the vehicle body frame B1 is obtained.

  Next, the operation of removing the oxide film W1 in the hot press-formed product P1 and the operation of welding the hot press-formed product P1 after the removal of the oxide film W1 will be described in detail.

  On the surface of the hot press molded article P1 obtained in the hot press process 4, as shown in FIG. 5, an oxide film W1 having a film thickness of about 2 to 5 μm is attached.

  In the film removing step 5, when the hot press molded article P1 to which the oxide film W1 adheres is placed on the mounting table 50, the fourth robot R4 moves the galvano scanner head 51c above the flange portion F1 of the hot press molded article P1. .

  Next, when the galvano scanner head 51c reaches above the predetermined welding area A1 before removing the oxide film W1 in the flange portion F1, the laser light L1 excited by the fiber laser oscillator 51a is welded from the galvano scanner head 51c. The light is emitted toward the scheduled area A1. Specifically, as shown in FIG. 3 and FIG. 4, with respect to the welding planned area A1 of an area of 30 mm × 30 mm, the scanning width is 30 mm and the processing speed (moving speed in the arrow Z1 direction in FIG. The laser beam L1 with an output of 100 W is scanned at 30 mm / sec. Then, as shown in FIG. 6, the oxide film W1 attached to the surface of the hot press-formed product P1 is removed. The welding planned area A1 may have other dimensions.

  Next, when the removal work of the oxide film W1 in the predetermined welding planned area A1 in the galvano scanner head 51c is finished, the fourth robot R4 turns the galvano toward the upper side of the welding planned area A1 where the removal work of the oxide film W1 is next performed. The scanner head 51c is moved. Thus, the removal operation of the oxide film W1 in all the welding planned area | regions A1 is performed in order.

  When the removal operation of the oxide film W1 in all the planned welding regions A1 is completed, as shown in FIG. 1, the hot press molded article P1 after the removal of the oxide film W1 is transported to the welding step 6 by a robot not shown, It is superimposed on the press plate P2 set on the upper side and positioned in the jig 61.

  Then, the fifth robot R5 moves the welding gun T1 to carry out spot welding on each planned portion X1 of the hot-press formed article P1. Then, the hot press-formed product P1 and the press plate P2 are integrated to obtain the vehicle body frame B1.

  Next, hardness evaluation of the hot press-formed product P1 after the removal operation of the oxide film W1 will be described.

  FIG. 7 is a graph showing the results of measuring the hardness before and after removing the oxide film W1 in the welding scheduled area A1 in the hot press molded article P1, wherein the horizontal axis represents the hot press molded article P1. The depth from the surface and the vertical axis are hardness. From this result, there is no change in the hardness of the base material before and after removing the oxide film W1 in the hot press molded article P1, and the removing operation of the oxide film W1 in the film removing step 5 of the present invention is hot press forming It could be confirmed that it did not affect the hardening effect at the time.

  Next, the heating condition in heating step 3 is 910 ° C. and the hot press molded article P1 obtained by hot press molding, and the heating condition in heating step 3 is 890 ° C. and the hot press molded article obtained by hot press molding The experiment which performed the removal operation of oxide film W1 of each welding plan area | region A1 on various oxide film removal conditions in P1 is demonstrated.

  The removal operation of the oxide film W1 is performed according to the conditions A to F in which the combination of the output of the laser beam L1 irradiated from the galvano scanner head 51c, the processing speed, and the frequency is changed, and the planned welding area after the oxide film W1 is removed A1 was sandwiched by a pair of electrode tips and pressurized with a pressure of 5.88 kN, and the operation of checking the resistance value between the electrode tips was performed multiple times. The thickness of each of the hot press-formed product P1 and the press plate P2 is 1.8 mm.

  Then, when the processing speed and frequency of the laser beam L1 are made the same condition and the output is changed, as shown in FIG. 8 and FIG. 9, the laser beam L1 is used for both hot press molded articles P1 whose heating conditions are changed. It was found that the resistance value between the electrode tips was low and stable when the output of 100 W was 100 W.

  Further, when the processing speed is changed while making the output and the frequency of the laser beam L1 the same condition, as shown in FIGS. 10 and 11, the laser beam L1 is obtained for both of the hot press molded articles P1 whose heating conditions are changed. It was found that the resistance between the electrode tips was low and stable when the processing speed of 30 mm / sec.

  Next, an experiment in which spot welding was performed on each of the hot press-formed products P1 before and after removing the oxide film W1 will be described.

  Spot welding was carried out while changing the current value to be applied to the hot press molded product P1, and the nugget diameter of the weld formed was measured. In addition, other welding conditions of spot welding were made into pressurization pressure: 5.88kN, electrode tip diameter: phi6R40mm, energization time 24 cycles, and holding time 2 cycles.

  As shown in FIG. 12, when spot welding is performed on the hot press-formed product P1 before removing the oxide film W1, the range of current values satisfying the reference value of the nugget diameter which can ensure welding quality (appropriate current range) Was found to be very narrow.

  On the other hand, as shown in FIG. 13, when spot welding is performed on the hot press-formed product P1 after removing the oxide film W1, the range of current values satisfying the reference value of the nugget diameter which can ensure welding quality (appropriate current It has been found that the range can be broadened.

  As mentioned above, according to Embodiment 1 of the present invention, the oxide film W1 adhering to each welding scheduled area A1 of the surface in the hot press molded article P1 disappears, and as shown in FIG. 4, each on the surface of the hot press molded article P1. A step is generated between the welding scheduled area A1 and the other areas. Then, when pressing and holding the hot press molded article P1 with the electrode tip and supplying electric current, the electric resistance between the front end surface of the electrode tip and the hot press molded article P1 decreases and the surface of the hot press molded article P1 Since the difference in electrical resistance between the respective areas A1 to be welded and the other areas becomes large, diversion at the time of energization can be prevented, and the quality of the weld can be stabilized.

Embodiment 2 of the Invention
FIG. 14 shows a state in which the oxide film W1 is removed from the surface of the hot press-formed product P1 in the film removal step 5 of the production line 1 according to Embodiment 2 of the present invention. The second embodiment is the same as the first embodiment except that the method of removing the oxide film W1 is different from the first embodiment. The same parts as the first embodiment are indicated by the same reference numerals. , Only the different parts will be described in detail.

  The planned welding area A1 of the second embodiment has a circular shape corresponding to the tip surface of the electrode tip used at the time of spot welding.

  In the second embodiment, when the welding planned area A1 is irradiated with the laser light L1, the film thickness H1 of the oxide film W1 attached to the welding planned area A1 on the surface of the hot press molded article P1 excludes the welding planned area A1. In order to be thinner than the film thickness H2 of the oxide film W1 attached to the region, a predetermined amount of thickness is left.

  From the above, according to Embodiment 2 of the present invention, when pressing and holding the hot press molded product P1 with the electrode tip in the planned spot application portion X1, the peripheral portion of the tip surface of the electrode tip corresponds to the step portion of the oxide film W1. Position. Therefore, when current flows between the front end face of the electrode tip and the hot press molded product P1, the flow of current is concentrated on the spot implementation planned portion X1, so that diversion can be surely prevented. The quality of welds can be further stabilized.

  In addition, since the laser beam L1 is irradiated so that a predetermined amount of the oxide film W1 attached to the area to be welded A1 remains, the laser beam L1 does not directly strike the galvanized layer G1 and the base material. Therefore, it is possible to prevent the galvanized layer G1 from being damaged or to exert an influence on the hardness of the base material, and a hot press-formed product P1 having high corrosion resistance, corrosion resistance, and rigidity even after spot welding. Can be

  In Embodiments 1 and 2 of the present invention, the flat press plate P2 is superimposed on the hot press molded article P1 and integrated by spot welding, but a non-flat press molded article is a hot press molded article It may be integrated by spot welding while being superimposed on P1.

  In the first and second embodiments of the present invention, the fiber laser oscillator 51a is used as an oscillator for oscillating the laser light L1, but the laser light L1 may be oscillated using a YAG laser oscillator.

  Furthermore, in the first and second embodiments of the present invention, the laser beam L1 is irradiated to the welding scheduled area A1 using the galvano scanner head 51c, but the laser beam L1 is irradiated to the welding scheduled area A1 using other laser processing heads. You may make it irradiate.

  The present invention is suitable for a method of welding a hot press-formed product obtained by hot pressing.

A1 Welding planned area G1 Galvanized layer L1 Laser light P1 Hot press molded article P2 Pressed plate (steel plate)
S1 Steel sheet W1 Oxide film X1

Claims (2)

  After a hot press-formed product is obtained by hot press forming from a steel plate having a galvanized layer or an alloyed galvanized layer on the surface, are the planned portions to be spot-welded at the surface of the hot press-formed product rectangular? Alternatively, the oxide film adhering to the area to be welded is vaporized and removed by irradiating the area to be welded enclosed with a circular shape with laser light using a laser oscillator, or the thickness of the oxide film is Then, another press-formed product or steel plate is superimposed on the hot press-formed product, and spot welding is performed on a portion to be subjected to hitting in each of the planned welding regions, and a welding method for the hot press-formed product. . In the method of welding a hot press-formed product according to claim 1,
The area to be welded is a circular shape corresponding to the tip surface of the electrode tip used at the time of spot welding,
The thickness of the oxide film attached to the area to be welded on the surface of the hot press molded article is thinner than the thickness of the oxide film to be attached to the area excluding the area to be welded, and only a predetermined amount of thickness A method of welding a hot press-formed product, comprising irradiating the laser light to the region to be welded so as to remain.