JP2008119708A - Laser beam welding method for metal plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam welding method for a metal plate by which production efficiency is improved without complicating and upsizing a laser beam welding apparatus. <P>SOLUTION: Welding is performed by taking the spot diameter of a laser beam 17 which irradiates a butt part 12 of the metal plates 11, 11 as not smaller than the absolute minimum spot diameter which is calculated by a formula; d<SB>min</SB>=(α-β*t)*g. Where, d<SB>min</SB>is the absolute minimum spot diameter (mm) of the laser beam, t is the thickness (mm) and g is the amount (mm) of the clearance in the butt part. Furthermore, α and β are constants, 2.5≤α≤3.0 and 0≤β≤0.15. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser welding method for a metal plate material.

  In laser welding, a laser beam, which is a high-density energy beam, is irradiated from one side to the joint of the work piece, and the work piece is melted by penetrating the laser beam, thereby forming beads on the front and back of the work piece. To weld. The joint portion of the workpiece is cut and butted by a shearing device before welding. In laser welding, filler metal or the like may be added to compensate for the amount of weld metal and fill the gap in the weld. This laser welding can perform high-speed welding and has a small thermal effect on the workpiece. In particular, with regard to the continuous welding process line of steel plates, it is possible to ensure the welding strength characteristics necessary for passing through high-alloy component special steel, which was difficult with the conventional flash butt welding method. Due to such excellent characteristics, the use of laser welding has increased in recent years.

  However, laser welding is performed by focusing a laser beam transmitted from a laser oscillator through a reflection mirror, an optical fiber or the like to a beam having a very small diameter of about 0.2 to 0.8 mm using a concave mirror, an optical lens, or the like. For this reason, when the gap between the joints of the work piece is large, the laser beam passes through the gap, and the work piece cannot be sufficiently melted. The strength of was not obtained. In this case, the focus of the laser beam is shifted from the surface of the workpiece (hereinafter referred to as “defocus”), and the diameter of the laser beam on the surface of the workpiece (hereinafter referred to as “spot diameter”) is increased. It was. However, by shifting the focus of the laser beam, the energy density is lowered and the welding speed is lowered, so that there is a problem that the production efficiency is lowered.

In order to solve this problem, the invention described in Patent Document 1 discloses a laser beam welding apparatus including a coupling unit that couples a strip clamping device and a shearing device that cuts an end of the strip. According to this technique, the straightness of the cut surfaces of both strips is improved, and high-quality welding is obtained. The invention described in Patent Document 2 discloses a laser welding method in which laser welding is performed after flattening a butt portion between thin plates with a pressing member, and a laser welding apparatus including a pressing member and a supporting member. According to such a technique, it is said that the gap amount can be significantly reduced by eliminating the level difference of the butt portion and pushing the burr into the gap of the butt portion, thereby preventing the occurrence of poor welding. Yes. In the invention described in Patent Document 3, a laser welding method is disclosed in which a laser beam is scanned without defocusing. According to such a technique, it is said that a laser having a high energy density can be widely irradiated. In the invention described in Patent Document 4, there is a laser welding method for adjusting a condensing diameter of a laser beam and a traveling speed of the torch by detecting a gap amount of a butt portion of an object to be welded by an image sensor preceding the torch. It is disclosed. According to such a technique, even if the amount of gap increases, it is said that welding defects can be prevented by immediately responding and expanding the focal spot diameter of the laser beam.
Japanese Patent Laid-Open No. 4-200986 JP-A-1-118389 JP-A-3-234388 JP 61-46389 A

  However, the invention described in Patent Document 1 has a problem that the laser beam welding apparatus is complicated and the shear apparatus is enlarged and the equipment cost is increased by including a coupling unit that couples the clamp apparatus and the shear apparatus. was there.

  In the invention described in Patent Document 2, since the pressing member and the supporting member are provided, there is a problem that the laser beam welding apparatus becomes complicated and the equipment cost increases.

  In the invention described in Patent Document 3, since a device for scanning a laser beam is required, there is a problem that the device around the laser irradiation head becomes complicated and the equipment cost increases.

  In the invention described in Patent Document 4, the condensing diameter of the laser beam and the traveling speed of the torch are adjusted only according to the measured gap amount of the butting portion, and the influence of the plate thickness is not taken into consideration. Since the diameter of the laser beam expands after reaching the focused diameter at the focal point, if the spot diameter is adjusted only in accordance with the gap amount of the butted portion, the diameter of the laser beam passing through the work piece depends on the plate thickness. That's it. Therefore, the spot diameter of the laser beam can be reduced by considering the plate thickness. Furthermore, the spot diameter of the laser beam may be smaller as the plate thickness is larger even with the same gap amount. Therefore, in particular, a workpiece to be welded with a large plate thickness has a problem that the spot diameter of the laser beam is increased more than necessary, so that the welding speed is excessively lowered and the production efficiency is lowered.

  Accordingly, an object of the present invention is to provide a laser welding method for a metal plate that can improve the production efficiency without complicating and increasing the size of the apparatus in order to solve the above problems.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appropriately added in parentheses, but the present invention is not limited to the illustrated embodiment.

The invention according to claim 1 is a laser beam spot for a metal plate material laser welding method in which the end faces of the metal plate materials (11, 11) are butted and the butted portion (12) is welded by irradiating a laser beam (17). The problem is solved by providing a laser welding method for a metal plate material, characterized in that welding is performed with a diameter equal to or larger than a necessary minimum spot diameter of a laser beam calculated by the following equation (1).
d _min = (α−β · t) · g (1)
Here, d _min is a necessary minimum spot diameter (mm) of the laser beam, t is a plate thickness (mm) of the metal plate material, and g is a gap amount (mm) of the butted portion. Α and β are constants, and 2.5 ≦ α ≦ 3.0 and 0 ≦ β ≦ 0.15. The “laser beam spot diameter” is the diameter of the laser beam on the surface of the workpiece.

According to a second aspect of the present invention, there is provided a laser beam spot in a laser welding method of a metal plate material in which end faces of the metal plate materials (11, 11) are butted and the butted portion (12) is welded by irradiating a laser beam (17). The upper limit of the diameter is compared with the required minimum spot diameter of the laser beam calculated by the following equation (1). If the upper limit of the spot diameter is equal to or larger than the required minimum spot diameter, the spot diameter is set to the required minimum spot. The above-mentioned problem is achieved by providing a method for laser welding of a metal plate material, characterized in that welding is performed with a diameter greater than or equal to, and when the upper limit value of the spot diameter is less than the required minimum spot diameter, filler wire is added for welding. To solve.
d _min = (α−β · t) · g (1)
Here, d _min is a necessary minimum spot diameter (mm) of the laser beam, t is a plate thickness (mm) of the metal plate material, and g is a gap amount (mm) of the butted portion. Α and β are constants, and 2.5 ≦ α ≦ 3.0 and 0 ≦ β ≦ 0.15.

  According to a third aspect of the present invention, in the laser welding method for the metal plate members (11, 11) according to the first or second aspect, the laser beam (17) is oscillated by a YAG-based solid excitation medium. And

  Here, YAG is an abbreviation for yttrium aluminum garnet.

  According to a fourth aspect of the present invention, in the laser welding method for the metal plate (11, 11) according to the third aspect, the shape of the solid excitation medium is a fiber shape or a disk shape.

  According to the first aspect of the invention, the spot diameter of the laser beam can be set according to the plate thickness by obtaining the necessary minimum spot diameter using the plate thickness of the metal plate material. Thereby, especially in a workpiece having a large plate thickness, it is possible to prevent the welding speed from being excessively lowered and the production efficiency from being lowered due to an unnecessarily large spot diameter.

  According to the second aspect of the present invention, when the upper limit value of the spot diameter of the laser beam is equal to or larger than the necessary minimum spot diameter, the laser is used without using the filler wire by setting the spot diameter to be larger than the necessary minimum spot diameter. Welding is possible. Thereby, since re-welding due to poor welding and fracture of the welded portion are reduced, it is possible to improve production efficiency. Further, since laser welding can be performed without using a filler wire, the cost of the filler wire is reduced and the welding speed is increased. On the other hand, when the upper limit value of the spot diameter of the laser beam is less than the required minimum spot diameter, laser welding can be performed by adding a filler wire. Therefore, by using the value of the necessary minimum spot diameter as a criterion, it is possible to perform reliable production, and it is possible to reduce production costs and improve quality by preventing unnecessary filler wire addition.

  According to the third aspect of the present invention, by using a YAG solid excitation medium as the laser beam oscillation source, the spot diameter can be adjusted by exchanging the optical lens as described later. Thereby, a spot diameter can be made larger than other laser beams, such as a carbon dioxide laser. Therefore, since the spot diameter is larger than the necessary minimum spot diameter in a wide range, laser welding of a metal plate material is possible without using a filler wire. Even when the upper limit value of the spot diameter is less than the required minimum spot diameter, the amount of filler wire used can be reduced by setting the spot diameter as the upper limit value. Furthermore, since the spot diameter can be adjusted without defocusing, a decrease in production efficiency can be prevented even when the spot diameter is increased.

  According to the fourth aspect of the present invention, the YAG laser beam in which the solid excitation medium has a fiber shape or a disk shape has a large output and excellent light quality. Therefore, high-speed and high-quality welding is possible.

  Hereinafter, based on the embodiment shown in the drawings, as an example of a method for producing a metal sheet according to the present invention, a case where steel plates are laser welded to each other will be described. However, what is described below is an example of an embodiment of the present invention. The present invention is not limited to the following description as long as the gist thereof is not exceeded.

  FIG. 1 is a diagram schematically showing a laser welding apparatus 10 used in the method for manufacturing a metal plate material according to the present invention. Fig.1 (a) is the figure which looked at the laser welding apparatus 10 from the welding direction. FIG. 1B is a right side view of FIG. The steel plates 11 and 11 are arranged with their end faces abutted against each other. Above the abutting portion 12 of the steel plates 11, 11, a machining head 13 that can move in the vertical direction, the welding direction, and a horizontal direction orthogonal to the welding direction, and a gap amount measuring device 14 are provided. The machining head 13 and the gap amount measuring device 14 are connected to a welding machine control device 15. The welding machine control device 15 is connected to a host PLC 16 or a personal computer (not shown; hereinafter referred to as “PC”). In FIG. 1A, illustration of the welding machine control device 15 and the host PLC 16 is omitted.

With this configuration, the gap amount measuring device 14 and the machining head 13 are disposed above the abutting portion 12. Then, the gap amount measuring device 14 moves the butt portion 12 in the welding direction in advance of the machining head 13 and transmits the measured gap amount g to the welding machine control device 15. On the other hand, the welding machine control device 15 acquires material information such as the plate thickness t of the steel plates 11 and 11 from the host PLC 16. And the welding machine control apparatus 15 calculates | requires the required minimum spot diameter _dmin of a laser beam by following (1) Formula from this board thickness t and the gap | interval amount g.
d _min = (α−β · t) · g (1)
Here, d _min is the required minimum spot diameter (mm) of the laser beam, t is the plate thickness (mm) of the metal plate material, and g is the gap amount (mm) of the butted portion. Α and β are constants, and 2.5 ≦ α ≦ 3.0 and 0 ≦ β ≦ 0.15.

And the welding machine control apparatus 15 compares the calculated _| required required minimum spot diameter _dmin and the upper limit of the spot diameter d of a laser beam. As a result of the comparison, when the upper limit value of the spot diameter d is equal to or larger than the necessary minimum spot diameter d _min , the processing head 13 is configured so that the spot diameter d of the laser beam 17 becomes equal to or larger than the necessary minimum spot diameter d _min by defocusing. Adjust the vertical position. Then, laser welding is performed when the processing head 13 irradiates the butted portion 12 with the laser beam 17 without using the filler wire.

As a result, the required minimum spot diameter d _min is obtained using the plate thickness t of the metal plate material, whereby the spot diameter d of the laser beam corresponding to the plate thickness t is set. Therefore, particularly in a workpiece to be welded having a large plate thickness t, it is possible to prevent the welding speed from being excessively lowered and the production efficiency from being lowered by increasing the spot diameter d more than necessary. Moreover, since a favorable bead shape is formed in the welded portion by setting the spot diameter d to be _{equal to} or larger than the necessary minimum spot diameter _dmin , re-welding due to poor welding and fracture of the welded portion are reduced, and the production efficiency is improved. Further, since no filler wire is used, the production cost can be reduced and the welding speed can be increased.

On the other hand, when the gap amount g increases due to factors such as deterioration of the shear knife, the required minimum spot diameter d _min of the laser beam increases. In this case, since the defocus amount DF of the laser beam is limited, the upper limit value of the spot diameter d may be less than the necessary minimum spot diameter d _min . At this time, the laser beam 17 passes through the gap and the work piece cannot be sufficiently melted, so that the necessary bead thickness is not formed, and the strength of the joint cannot be obtained. Therefore, filler wire is added and laser welding is performed. Thus, by using the value of the necessary minimum spot diameter d _min as a criterion for adding filler wire, reliable production can be performed and unnecessary filler wire addition can be prevented. Therefore, it is possible to reduce production costs and improve quality.

The spot diameter d is preferably the same as the required minimum spot diameter d _min . According to this, since the energy density of the laser beam 17 is the highest within a range where a good bead shape can be obtained, the production efficiency can be maximized by increasing the welding speed. However, in the butt portion of the steel plates 11 and 11, the gap amount g is partially increased due to variations in cutting quality in the welding direction, small scratches on the cutting blade, etc., so that a good bead shape can be obtained at the necessary minimum spot diameter d _min. There may be a part that cannot be obtained. In this case, in order to increase the amount of molten metal and stabilize the bead shape, it is preferable to apply a spot diameter d larger than the necessary minimum spot diameter d _min or add a filler wire. On the other hand, since the upper limit value of the spot diameter d is less than the required minimum spot diameter d _min , it is preferable to set the spot diameter d as the upper limit value when adding filler wire and performing laser welding. According to this, since the addition amount of filler wire becomes the minimum, the production cost can be reduced.

  FIG. 2 is a plan view of the abutting portion 12 of the steel plates 11 and 11. When the abutting portion 12 is cut with a shear device, the gap amount g of the abutting portion often changes in the welding direction as shown in FIG. This is due to the rigidity of the shear device and the clamp device. Therefore, as the plate thickness t is increased and the plate width L is increased, the linearity of the cut surface is lost as the cutting force of the steel plate 11 is increased, and the gap amount g of the butt portion 12 tends to increase.

Thus, when the gap amount g varies depending on the position of the abutting portion 12, it is preferable to change the spot diameter d of the laser beam 17 (see FIG. 1) in accordance with the gap amount g. For this purpose, the gap amount g at each position in the butt portion 12 is measured, and the required minimum spot diameter d _min is obtained for each position of the butt portion 12 by the welding machine control device 15 (see FIG. 1). Then, the vertical position of the machining head 13 (see FIG. 1) is controlled at each position of the abutting portion by the welding machine control device 15 so that the spot diameter d is _{equal to} or greater than the determined d _min and defocused. According to this, a good bead shape can be obtained at all positions of the abutting portion 12 and the welding speed becomes the fastest, so that the production efficiency can be improved. Note that the gap amount g of the abutting portion 12 is usually measured by scanning the abutting portion 12 with a gap amount measuring device 14 (see FIG. 1) such as a laser displacement meter, for example, such a measuring device. If there is no gap, the gap amount may be periodically measured with a gap amount measuring jig such as a filler gauge.

Further, when the spot diameter d is not changed at each position of the abutting portion 12, the necessary minimum spot diameter d _min of the laser beam 17 may be obtained from the measured maximum value of the gap amount g at each position of the abutting portion 12. . According to this, by performing welding after adjusting the spot diameter d of the laser beam 17 to the required minimum spot diameter d _min or more, a good bead shape can be obtained at all positions of the butt portion 12. The required minimum spot diameter d _min is a value obtained by multiplying the maximum value of the gap amount g by a predetermined ratio or the gap amount g at each position of the butted portion 12 according to the strength required for the welded portion. You may obtain | require from a value etc.

In consideration of the fact that the gap amount g varies depending on the position of the abutting portion 12 as shown in FIG. 2, the laser welding apparatus 10 is designed with the widest and thickest metal plate material assumed to be laser-welded. A material having a large thickness t is cut with a shearing device, the gap amount g is measured, the required minimum spot diameter d _min is obtained using the gap amount g, and a spot diameter d equal to or greater than the required minimum spot diameter d _min is obtained. It is preferable to design.

  FIG. 3 shows the relationship between the spot diameter d, the gap amount g, the plate thickness of the steel plate 11 (see FIG. 1) to be laser-welded (hereinafter sometimes simply referred to as “plate thickness”) t, and the bead shape after welding. It is a figure which shows the result. For the investigation, a 10 kW carbon dioxide laser and a fiber laser with the same output were used as the laser oscillator. The spot diameter d can be adjusted in the range of 0.1 mm to 0.8 mm by changing the defocus amount DF or the optical lens focal length. The steel plate 11 to be laser welded has three types of low carbon steels having a thickness t of 2, 4, and 6 mm (composition ratio C: 0.05%, Si: 0.005%, Mn: 0.2%, the balance is Steel plates 11 and 11 having the same thickness were laser welded using Fe and inevitable impurities). For the steel plates 11 and 11 having respective thicknesses t, the gap amount g was changed to 0.1, 0.2, and 0.25 mm, and laser welding was performed while changing the spot diameter d. And evaluation of the bead shape after welding is considered good when the bead thickness hb is 70% or more of the thickness hs of the steel plate 11 from the viewpoint of the process line passing plate, and the bead thickness hb is the thickness of the steel plate 11. When it was less than 70% of the length hs, it was regarded as defective.

As shown in FIG. 3, the minimum spot diameter d (required minimum spot diameter d _min ) at which a good bead can be obtained becomes larger as the gap amount g becomes wider at any thickness t. On the other hand, when the gap amount g is the same, the minimum spot diameter d (required minimum spot diameter d _min ) at which a good bead is obtained increases as the plate thickness t decreases. From this, it was found that the plate thickness t, the gap amount g, and the necessary minimum spot diameter d _min can be arranged by the following equation (1).
d _min = (α−β · t) g (1)
Here, α and β are constants obtained from the investigation results of FIG. 3, and are as shown in the following equations (2) and (3).
2.5 ≦ α ≦ 3.0 (2)
0 ≦ β ≦ 0.15 (3)
Thereby, a favorable bead shape is obtained when the spot diameter d satisfies the following formula (4).
d ≧ d _min (4)

  FIG. 3 shows a straight line when α = 3.0 and β = 0.1. If 2.5 ≦ α ≦ 3.0 and 0 ≦ β ≦ 0.15, A good bead shape can be obtained. When the constant α is large, since the spot diameter d is sufficiently large with respect to the gap amount g, a good bead shape can be obtained. However, as described above, the energy density of the laser beam is reduced, and an unnecessary reduction in welding speed is caused. Therefore, the upper limit of α is set to 3.0. On the other hand, when α is small, the calculated spot diameter d can be equal to or smaller than the gap amount g. When the spot diameter d is smaller than the gap amount g, it is difficult to uniformly melt both end faces of the butted portion 12 (see FIG. 1) through the gap even if the amount of weld metal is compensated with a filler wire or the like. A good bead shape cannot be obtained. Therefore, the spot diameter d needs to be larger than the gap amount g. Therefore, the lower limit of α is set to 2.5.

  Further, as shown in FIG. 3, the larger the spot diameter d, the wider the range of the gap amount g in which a good bead shape can be obtained. However, in order to obtain a large spot diameter d, it is necessary to defocus the focus of the laser beam. Thereby, since the energy density of the laser beam is lowered, it is necessary to reduce the welding speed, and the production efficiency is lowered. Therefore, the spot diameter d is preferably 0.8 mm or less. In general, the gap amount g in the continuous process line of the steel sheet is 0.3 mm or less, which is a value that is satisfactory from the viewpoint of forming a good bead shape. In consideration of the accuracy of the butting position and the welding position in the process line, or the weld longitudinal direction linearity of the butting portion, the spot diameter d is preferably 0.4 mm or more.

  Furthermore, in the above, from the viewpoint of the process line through plate, the formulas (1) to (3) are defined as good when the bead thickness hb which is common in the metal plate material is 70% or more of the metal plate material thickness. The evaluation of the bead shape after welding can be individually determined from the strength required for the welded portion. Therefore, it is possible to change the ranges of the constants α and β by setting a value different from 70% of the steel plate thickness hs as the bead thickness according to the required strength. The bead shape can also be evaluated based on criteria other than the bead thickness.

The laser used in the method for producing a metal sheet according to the present invention is not particularly limited as long as the effects of the present invention can be achieved. A gas laser such as CO ₂ , CO, CF ₄ , HF, and iodine; Liquid laser used; solid laser such as YAG, YLF, glass, Ti sapphire, CrLiSAF; GaAs, (InGa) As, InP, In (PAs), CdSnP ₂ , GaSb, Cd ₃ P ₂ , InAs, PbS, InSb, PbTe , PbSe, (PbSn) Se, or other semiconductor lasers; or free electron lasers, etc., but from the viewpoint described later, a laser beam oscillated by a YAG-based solid excitation medium (hereinafter simply referred to as “YAG-based laser beam”). It is preferable to use.

As main lasers having the capability (output) applicable to the present invention, there are YAG laser and carbon dioxide laser. Among these, in the laser welding method of the metal plate material according to the present invention, it is preferable to use a YAG-based laser beam because optical fiber transmission is possible and a condensing lens is provided. The spot diameter d (mm) of the YAG laser beam can be expressed by the following equation (5).
d = Dcore × Lf / Lc × DF / 100 (5)
Here, Dcore is the core diameter (mm) of the transmission fiber cable, Lf is the focal lens focal length (mm), Lc is the collimating lens focal length (mm), and DF is the defocus amount (%). Note that 100% ≦ DF ≦ the upper limit value in the possible range, and when there is no defocus, the calculation is performed as DF = 100%. As shown in the above equation (5), the spot diameter d of the YAG laser beam can be easily adjusted by changing the Lf and Lc by exchanging the optical lens in addition to defocusing. The degree is great.

Therefore, since the spot diameter d is not less than the minimum required spot diameter d _min in a wide range, laser welding of a metal plate material is possible without using a filler wire. Further, even when the spot diameter d cannot be made larger than the required minimum spot diameter d _min , the amount of filler wire used can be reduced by setting the spot diameter d as the upper limit value, thereby reducing the production efficiency. Can be prevented.

The YAG-based laser beam has a remarkable effect especially in welding in a continuous process line of a hot-rolled coil or a hot-rolled coil subjected to pickling treatment. The material of the hot rolled coil is not particularly limited, and examples thereof include extremely low carbon steel, low carbon steel, high tensile steel, high carbon steel, high Si steel, and stainless steel. The hot-rolled coil is generally thicker than the process after cold rolling, with a plate thickness t of 1.2 to 6.0 mm, and the plate width L is as wide as about 2000 mm, so the gap between the butted portions 12 (see FIG. 1). The amount g tends to increase to 0.2 mm or more. Previously in the commonly applied it has a carbon dioxide gas laser, since the spot diameter d of the laser beam 17 (see FIG. 1) is about 0.2 to 0.3 mm, the spot diameter d than necessary minimum spot diameter _{d min} It may not be possible to cause welding defects. On the other hand, with a YAG-based laser beam, the spot diameter d can be set to a necessary minimum spot diameter d _min or more in a wide range by appropriately selecting an optical lens. Therefore, the steel material 11 (see FIG. 1) is used without using a filler wire. ) Laser welding is possible. Thereby, poor welding can be prevented.

  The YAG-based solid excitation medium is preferably in the form of a fiber or a disk. These pumping mediums can provide an output equal to or higher than that of the rod-shaped YAG solid pumping medium, and the rod-shaped YAG solid pumping is performed at the power level required for welding the metal plate material targeted by the laser welding method according to the present invention. The light quality is superior to that of a YAG laser beam using a medium. Therefore, high-speed and high-quality welding is possible.

  It is also possible to directly measure the spot diameter d of the laser beam without calculating it as shown in equation (5). As an example of the measuring method, a spot diameter d of the laser beam at the surface position of the welding material is obtained by placing an acrylic plate at the position of the welding material, irradiating the laser beam 17 (see FIG. 1) and taking a burn pattern. Measure.

(Example 1)
In Example 1, the laser welding method of the present invention was applied to an existing laser welding machine, and the effect was verified. For metal sheets to be laser welded, low-carbon steel sheets with a thickness t of 2 mm, 4 mm, and 6 mm (composition ratio C: 0.05%, Si: 0.005%, Mn: 0.2%, the balance being Fe and inevitable) Then, it was cut into a cut plate shape having a weld length of 300 mm using a shearing device. Then, the end face to be welded was finished into a rectangle by machining, this end face was abutted and the gap amount g was accurately adjusted with a filler gauge, and then fixed with a clamp. The gap amount g was changed at intervals of 0.05 mm between 0.10 mm and 0.25 mm. Using the plate thickness t and the gap amount g, the necessary minimum spot diameter d _min of the laser beam was obtained by the above-described equation (1). As for the constants, α was 2.5 or 3.0, and β was 0.1.

  As the laser oscillation source, a fiber laser having an output of 10 kW or a carbon dioxide gas laser having the same output was used. A fiber laser having a transmission fiber cable core diameter Dcore of 0.2 mm or 0.3 mm is used, and the spot diameter d is adjusted by changing the Lf and Lc by changing the optical lens and adjusting the defocus amount. Changed.

  Under the above conditions, laser welding was performed while changing the spot diameter d, the gap amount g, and the welding speed, and the bead thickness after welding was examined. The bead thickness was a ratio of the bead thickness hb to the thickness hs of the steel sheet (hb / hs × 100 (%)), and was obtained from cross-sectional observation. And it was considered as good when the bead thickness was 70% or more. Table 1 shows the results. The conditions other than those described in Table 1 were all the same.

In Examples 1-1 to 1-12, when laser welding was performed with the spot diameter d set to the required minimum spot diameter d _min or more, the bead thickness was 70% or more in all cases. On the other hand, laser welding was performed using a fiber laser in Comparative Examples 1-1 and 1-2, and using a carbon dioxide laser in Comparative Examples 1-3 and 1-4, with the spot diameter d being less than the required minimum spot diameter d _min . However, in all cases, the bead thickness was less than 70%. Thereby, it was confirmed that by setting the spot diameter d to be _{equal to} or greater than the necessary minimum spot diameter d _min , the bead thickness becomes 70% or more and a good bead shape is formed.

(Example 2)
In Example 2, a plurality of types of steel plates were laser welded by the laser welding method of the present invention. As the steel plate, an extremely low carbon steel plate, a low carbon steel plate, a high tensile steel plate, a high carbon steel plate, a high Si steel plate, and a stainless steel plate were used. When the end faces of these steel plates were cut with a shearing device and the gap amount g at the butt portion was measured, the maximum gap amount g was 0.24 mm for a steel material having a thickness t of 6 mm. Using the plate thickness t and the gap amount g, the necessary minimum spot diameter d _min of the laser beam enabling laser welding was obtained by the above-described equation (1). As for the constants, α was 3.0 and β was 0.1. As a result, the required minimum spot diameter d _min was 0.58 mm.

A 10 kW fiber laser was used as the laser oscillation source, the transmission fiber core diameter Dcore was 0.3 mm, the focus lens focal length Lf was 300 mm, the collimator lens focal length Lc was 150 mm, and the defocus amount DE was 100%. As a result, when calculated from the above equation (5), the spot diameter d of the laser beam was 0.60 mm, which was not less than the necessary minimum spot diameter d _min . The bead thickness was determined to be good when it was 70% or more in the same manner as described above.

  When laser welding was performed under the above conditions, a bead thickness of 70% or more was good in all steel sheets at a welding speed of 4 to 10 m / min without using a filler wire, and stable welding was possible. Thereby, it has confirmed that this invention was applicable regardless of a material.

(Example 3)
In Example 3, a YAG laser beam with an output of 5 kW is used in the laser welding apparatus 10 of FIG. 1 to produce steel plates such as an ultra-low carbon steel plate, a low carbon steel plate, a high tensile steel plate, a high carbon steel plate, a high Si steel plate, and a stainless steel plate. Laser welded. The YAG laser beam has a transmission beam core diameter Dcore of 0.3 mm, a focus lens focal length Lf of 250 mm, a collimator lens focal length Lc of 150 mm, and a defocus DF of 100 to 110%. The lower limit value was 0.50 mm, and the upper limit value was 0.55 mm. From the thickness t of each steel material and the gap amount g measured by the gap amount measuring device 14, the required minimum spot diameter d _min of the laser beam was obtained by the above-described equation (1). As for the constants, α was 3.0 and β was 0.1. The bead thickness was determined to be good when it was 70% or more in the same manner as described above.

When the required minimum spot diameter d _min was 0.55 mm or less, defocusing was performed, and laser welding was performed with the spot diameter d set to the required minimum spot diameter d _min or more. When the required minimum spot diameter was more than 0.55 mm, the spot diameter d was set to 0.55 mm, and a filler wire was supplied to perform laser welding. As a result, the bead thickness was as good as 70% or more for all the steel materials. Therefore, it was confirmed that the filler wire supply target was greatly reduced and the cost of the filler wire was reduced. In addition, the welding speed was increased and the production capacity was improved.

  In the above embodiment and examples, the metal plate material is described as a steel plate, but the present invention is also applicable to other metal plate materials such as aluminum and titanium.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. However, the present invention can be modified as appropriate without departing from the scope or spirit of the invention that can be read from the claims and the entire specification, and a laser welding method for such a metal plate with such changes is also included in the technical scope of the present invention. Must be understood as being.

It is the figure which showed typically the laser welding apparatus used for the manufacturing method of the metal plate material which concerns on this invention. It is a top view of the butt | matching part of a steel plate. It is a figure which shows the result investigated about the relationship between the spot diameter d, the gap | interval amount g, plate | board thickness t, and the bead shape after welding.

Explanation of symbols

g Gap amount 10 Laser welding device 11 Steel plate 12 Gap portion 13 Processing head 14 Gap amount measuring device 15 Welding machine control device 17 Laser beam

Claims (4)

In a laser welding method for a metal plate material in which the end surfaces of the metal plate material are butted and welded by irradiating the butted portion with a laser beam, the spot diameter of the laser beam is set to be equal to or larger than the required minimum spot diameter of the laser beam calculated by A laser welding method of a metal plate material characterized by welding.
d _min = (α−β · t) · g
Where d _min : the required minimum spot diameter of the laser beam (mm)
t: Metal plate thickness (mm)
g: Amount of gap at the butting portion (mm)
2.5 ≦ α ≦ 3.0, 0 ≦ β ≦ 0.15 In a laser welding method for a metal plate material, in which the end faces of the metal plate material are butted and irradiated by irradiating a laser beam to the butted portion, an upper limit value of the spot diameter of the laser beam and a necessary minimum spot diameter of the laser beam calculated by the following formula When the upper limit value of the spot diameter is equal to or larger than the necessary minimum spot diameter, welding is performed with the spot diameter being equal to or larger than the necessary minimum spot diameter, and the upper limit value of the spot diameter is equal to the necessary minimum spot diameter. When the diameter is less than the diameter, a filler metal wire is added and welding is performed.
d _min = (α−β · t) · g
Where d _min : the required minimum spot diameter of the laser beam (mm)
t: Metal plate thickness (mm)
g: Amount of gap at the butting portion (mm)
2.5 ≦ α ≦ 3.0, 0 ≦ β ≦ 0.15 3. The laser welding method for a metal plate material according to claim 1, wherein the laser beam is oscillated by a YAG-based solid excitation medium. The metal plate material laser welding method according to claim 3, wherein the solid excitation medium has a fiber shape or a disk shape.

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