JP5277393B2 - Strain-free laser bonding material manufacturing method, non-strained laser bonding structure forming method, and laser bonding material distortion occurrence prediction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser joining material free of thermal strain when iron-based metallic plates are continuously welded to each other, wherein each plate has a length of &ge;1 m along the welding direction, a width of 30-500 mm, and a thickness of 0.8-3 mm. <P>SOLUTION: When iron-based metallic plates are superimposed on each other, with the fillet continuously welded by laser; in a cross section vertical to the welding direction, fused end points A, B and deepest penetration point O in the thickness direction are connected to form and define a triangle AOB. Where x is the length of the side AB equivalent to a laser incident port, y, z are the length of other sides AO, BO respectively, and h is the length of a perpendicular from the point O to the side AB, laser joining is performed under the conditions; (x+y+z)/x multiplied by h/x, namely, the value of h(x+y+z)/x<SP>2</SP>&ge;2. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

The present invention relates to a distortion-free laser bonding material manufacturing method, a distortion-free laser bonding structure forming method, and a distortion of a laser bonding material , which are obtained in a state where there is no distortion when two metal plates are welded together using a laser. The present invention relates to an occurrence prediction method . In particular, the present invention relates to a laser bonding material obtained by laminating iron metal plates having a length of 1 m or more and laser welding the fillet.

  Laser welding is a welding method in which laser light is concentrated and irradiated on a welding target part of an object to be welded, and the welding target part is instantaneously melted and joined by the energy of the laser light. Generally, the work piece is fixed with a jig and a laser is irradiated so that the welding point does not move even if distortion occurs during welding, and a shielding gas for preventing oxidation is blown to the irradiation point. .

  The distortion occurs when the melted portion is stretched to the plastic deformation region by thermal expansion in the heat affected zone in addition to the solidification shrinkage of the melted portion, but actual welding is performed so as to suppress the influence as much as possible. Specifically, as described above, since the workpiece is fixed with a jig, most distortion is suppressed at this point, and cooling is performed by blowing a non-oxidizing gas such as argon or nitrogen to prevent oxidation. The effect is also taken into account. In addition, since the weight of the material is added when it is placed on a flat ground after welding, the force to warp upward in the vertical direction is suppressed downward, which also contributes to a reduction in distortion. Become. However, if the welding conditions are still not optimal, distortion remains when the material is removed from the jig after welding. This distortion varies depending on the force when the jig is fixed, and the current situation is that it cannot be expressed quantitatively.

  Although it is known that the solidification shrinkage rate of ferrous metals is 3 vol% for 0.25% C steel (Metal Data Book revised edition of the Japan Institute of Metals), the melted part is irradiated with laser. Since it is only a point and the others are solid, it is impossible to calculate the strain using that value, and as mentioned above, the material is pressed and fixed with a jig during welding, so that Considering the pressing weight, the influence of the dead weight, the cooling rate by the shield gas, etc., theoretical calculation is impossible. Therefore, a trial and error test is required to some extent depending on the shape and weight of the material, and it is the reality that providing an experimental index is the most economical, quick and simple method.

  Laser welding is a construction method that is relatively difficult to distort because the melting area is very small compared to arc welding. However, even if laser welding is used, it is necessary to develop a technology suitable for the product in order to eliminate any distortion. Therefore, many methods have been proposed for reducing the distortion in joining metal plates in accordance with the shape of each part.

  In Japanese Patent Laid-Open No. 2002-79389 “Laser Welding Method and Laser Welding Apparatus” (Patent Document 1), as a method for preventing distortion when a nozzle body and an injector housing are overlapped and laser joined in an injector that injects fuel into an intake system of an engine, A method for defining the laser irradiation angle has been proposed, and it is claimed that the technique can be applied to a planar member to be welded (specification, paragraph 0021). Further, in Japanese Patent Laid-Open No. 7-116875 “Beam Welding Method” (Patent Document 2), when laser welding an automobile inner panel and an outer panel, the end surface of one plate is irradiated with a laser to be melted and bent outward. A method has been proposed in which a melt is attached to the other panel surface that has been protruded and poured into the space, thereby suppressing the heat-affected zone and reducing distortion.

  In Japanese Patent Application Laid-Open No. 7-1000067 “Manufacturing Method of Sink” (Patent Document 3) or Japanese Patent Application Laid-Open No. 7-16776 “Laser Welding Method and Apparatus of Lap Joint” (Patent Document 4), There has been proposed a technique for preventing distortion by irradiating a laser from an inclined line direction having a minute angle with respect to the extension line, without melting unnecessary portions and melting only the contact surface. Specifically, the laser is incident from an angle of 0 to 5 ° (paragraph 0011 of Patent Document 3) or 10 to 20 ° (paragraph 0013 of Patent Document 4). That is, the feature of these techniques is that the incident angle is tilted to a specific range.

  Japanese Patent Laid-Open No. 6-328277 “Laser Welding Method” (Patent Document 5) proposes a method in which the heat-affected zone is suppressed to a narrow range as much as possible by spot irradiation at intervals. Japanese Patent Application Laid-Open No. 2003-112525 “Method for Manufacturing Automotive Door Frame” (Patent Document 6) proposes a method of suppressing a heat affected zone by melting a filler wire with a laser and filling a welded portion.

  Japanese Patent Laid-Open No. 6-297173 “Metal Welding Method by Laser Processing” (Patent Document 7) proposes a method for preventing distortion by quickly injecting water, mist, or argon gas or nitrogen gas to the welded portion to cool the welded portion. Has been.

Japanese Patent Application Laid-Open No. 2002-79389 “Laser Welding Method and Laser Welding Apparatus” JP-A-7-116875 “Beam Welding Method” Japanese Patent Laid-Open No. 7-100676 “Manufacturing method of sink” JP-A-7-16776 "Laser Welding Method and Apparatus for Lap Joint" Japanese Patent Laid-Open No. 6-328277 “Laser Welding Method” Japanese Patent Application Laid-Open No. 2003-112525 “Method for Manufacturing Door Frame for Automobile” JP-A-6-297173 “Metal Welding Method by Laser Processing”

  However, the object of the technology disclosed in Patent Document 1 is clearly limited to a cylindrical injector, and there is no specific example to apply to a flat plate (paragraphs 0010 to 0020). There is no information such as its melting shape. Therefore, if the length is 1 m or more as in the object of the present invention, the laser irradiation conditions must be re-examined from the beginning, which is not applicable. Further, in the technique disclosed in Patent Document 2, it is necessary to bend one end protrusion, and there is only a description that irradiation is performed near the end of the protrusion, and this is not applicable to a flat plate.

  The technologies disclosed in Patent Documents 3 and 4 are characterized only by tilting the incident angle. Therefore, even if this is applied to the object of the present invention, laser irradiation conditions such as pulse width, pulse energy, and irradiation diameter must be reexamined from the beginning by trial and error, and cannot be applied. Actually, when the techniques disclosed in Patent Documents 3 and 4 are applied to the welding of a plate material having a length of 1 m or more, which is a target material of the present invention, distortion (warpage) occurs in the longitudinal direction, which is the welding direction, and effective. The distortion could not be prevented.

  Furthermore, when the focal length is short and a nozzle for preventing oxidation is attached to the tip, such as a widely used YAG laser device, the nozzle is placed on the work piece or sample at such a low angle. Since this method cannot be applied in contact with a stand or the like, it is necessary to manufacture a nozzle in anticipation of the application of this method, or to change to a laser device with a long focal length, which requires improvement costs.

  In addition, the technique disclosed in Patent Document 5 cannot be applied to the continuous welding which is the subject of the present invention. In the technique disclosed in Patent Document 6, the use of consumables for the filler wire itself is costly, or the filler wire is melted. Because precise control such as positioning with the welding location is necessary, technology introduction is not easy and cannot be adopted.

  In the technique disclosed in Patent Document 7, when water or mist is jetted, it is necessary to sufficiently dry it, and quality deterioration such as rust and hydrogen embrittlement tends to occur. In addition, gas injection is usually performed as an antioxidant, and in the case of gas compared to liquid cooling, the cooling capacity is inferior. Therefore, it is applied to the object having the thickness and size as the object of the present invention. However, the distortion prevention effect cannot be expected.

  As described above, the technologies described in each of the patent documents described above are only method proposals, and the characteristics of the material itself such as the shape of the molten part after welding have not been proposed. There was no indicator. In addition, when the steel metal plates having a length in the welding direction of 1 m or more, a width of 30 to 500 mm, and a thickness of 0.8 to 3 mm are continuously welded with a laser like the object of the present invention. Even if these conventional methods are applied, problems occur in the shape of materials, the cost of consumables, quality, etc., and none of them can be applied.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and in the case of welding two metal plates by using a laser, it is possible to easily and reliably obtain a joint structure free from distortion. It is to provide a laser joining technique that can be performed, a laser joining material thereby, a method for predicting the presence or absence of distortion in the joining material, or a management technique relating to the occurrence of distortion. In particular, when laser welding the fillet by superimposing iron-based metal plates having a length of 1 m or more, a laser joining technique capable of easily and reliably obtaining a distortion-free joining structure and a laser joining material thereby obtained, And a technique for predicting the presence or absence of distortion in the bonding material or a management technique relating to the occurrence of distortion.

The inventor of the present application has intensively studied to solve the above-mentioned problems, and found that the problems can be solved based on defining the melt shape of the laser welding portion, and has reached the present invention. That is, the invention claimed or at least disclosed in the present application is as follows.
(1) Prior to obtaining a laser joining material by performing fillet welding of two iron-based metal plates with a thickness of 1 m or more in a thickness of 1 m or more with a laser, the welding conditions under which distortion does not occur are set. A distortion generation presence / absence prediction method performed to obtain the method,
A test piece of a laser joining material produced using the two iron-based metal plates is cut perpendicularly to the welding direction, and in a melting region by laser welding appearing on the cut surface or in a similar expression thereof (hereinafter referred to as melting) The end positions of the laser irradiation entrance of the laser irradiation entrance including the similar expression of the area are referred to as the first end point A and the second end point B, and the deepest position in the thickness direction is the deepest point O or both ends. The deepest point O is the deepest penetration point in the perpendicular direction to the incident width AB, which is a straight line connecting points A and B, and distortion evaluation is performed on the triangle AOB connecting the first end point A, the second end point B, and the deepest point O. In the distortion evaluation triangle AOB, the length of the incident width AB is x, the lengths of the other two sides AO and BO are y and z, respectively, and the perpendicular from the deepest point O to the incident width AB When the length or depth is h,
The sum x + y + z of the three sides of the triangle AOB is used as an index of the size of the molten shape of the cross section,
The ratio of x + y + z to the laser inlet length x, “(x + y + z) / x”, is defined as an index expressing the narrowness of the melted part,
On the other hand, the ratio “h / x” of the depth h to the laser inlet length x is defined as an index expressing the penetration depth, that is, the depth with respect to the melt width of the laser inlet portion,
Further, the product of the narrowness index “(x + y + z) / x” and the depth index “h / x” “h (x + y + z) / x ² ” is a distortion resistance value that is an index expressing the difficulty of distortion. And
Strain generation in the laser bonding material is calculated depending on the magnitude of the strain toughness value calculated based on the actual measurement value compared with a specific value based on the relationship between the strain actual measurement value and the strain toughness value obtained by measurement in advance. A method for predicting the presence or absence of distortion in a bonding material, characterized by predicting the presence or absence of a bonding material.
(2) When the strain resistance value is 2 or more, it is determined that there is no distortion even if laser welding is actually performed under the same conditions as in the test piece. (1) 2. A method for predicting whether or not the laser bonding material is distorted.
(3) A method of forming a laser joining structure in which two iron-based metal plates stacked with the thickness direction aligned are fillet welded with a laser at a length of 1 m or more,
The laser joining structure is obtained by using the laser welding conditions obtained by the method for predicting the presence or absence of distortion of the laser joining material according to (1) or (2),
A method for forming a strain-free laser joining structure, characterized in that a laser joining structure can be obtained in which no warpage occurs at both longitudinal ends of the two iron-based metal plates in a fillet weld.

(4) In a laser joining structure obtained by the above-described method for forming an unstrained laser joining structure, a molten region by laser welding that appears in an arbitrary cross section perpendicular to the welding direction or a similar representation thereof (hereinafter, a similar representation of the molten region) The non-strained laser-bonded structure forming method according to (3), wherein the “melting region” including the object satisfies the following [I].
[I] Both end positions of the laser irradiation entrance in the melting region are defined as first end point A and second end point B, the deepest position in the thickness direction is defined as deepest point O, and the first end point A, second end point B, and deepest point A triangle AOB formed by connecting the points O is set as a distortion evaluation triangle, the length of the incident width AB in the distortion evaluation triangle AOB is x, and the lengths of the other two sides AO and BO are y and z, respectively. when the point O the length or depth of the normal to the incident width AB is h, it is (x + y + z) / x and the product of h / x h (x + y + z) / value of ^{x 2} is 2 or more.
(5) The two iron-based metal plates each have a width of 30 to 500 mm and a thickness of 0.8 to 3 mm. The strain-free laser joining structure formation according to (3) or (4) Way .
(6) A distortion-free laser bonding material manufacturing method , wherein a distortion- free laser bonding material is obtained using the non-distortion laser bonding structure forming method according to any one of (3) to (5).

That is, according to the present invention, the melted region formed by laser welding (hereinafter also referred to as “melted part”) can be managed by providing an index of the material to be joined without distortion by formulating the melted shape. It has characteristics. A typical example of the laser joining material of the present invention is described as follows: “A length along the welding direction is 1 m or more, a width of 30 to 500 mm, and a thickness of 0.8 to 3 mm. When the fillet is continuously welded by laser, the melted part end points A and B and the deepest position in the plate thickness direction or deepest in the direction perpendicular to the welding direction are melted in the cross section perpendicular to the welding direction. In the triangle AOB formed by connecting the point O which is the position, the length of the side AB corresponding to the laser incident port is x, the lengths of the other sides AO and BO are y and z, respectively, and further from the vertex O When the length of the perpendicular to the side AB is h, the product of (x + y + z) / x and h / x, the value of h (x + y + z) / x ² is 2 or more, and there is no distortion laser bonding material Is.

  According to the present invention, there is no distortion in the formula of the present invention if the molten shape is defined as described above, and the cross section is cut and polished after the small test piece is welded and the dimension of the molten part is measured. It is possible to determine whether or not. After that, it is possible to perform the main test or product joining using a long sample exceeding 1 m in length, so that work and materials are not wasted or are considerably reduced and efficient. is there. In the conventional method patent, there is no provision concerning the product itself. For example, in order to know the strain when laser joining a length of 1 m or more, it is not known unless the material is actually joined. It was efficient. This can be solved by the present invention. Moreover, according to the present invention, it is easy to set and manage conditions, and it can be easily used in the field. In addition, since only the material is melted, consumables such as filler wires are not generated.

  As in the present invention, the details of specific laser irradiation conditions in individual laser welding implementations are effectively examined by grasping and considering the molten form in the molten part, and applying a specific index. And based on that, an efficient welding operation can be realized.

Hereinafter, the contents of the present invention will be described in detail.
FIG. 1 is an explanatory view for explaining a non-strained laser bonding structure of the present invention (hereinafter also referred to as “unstrained laser bonding material” or “laser-free laser bonding material”) with a cross-sectional photograph of one embodiment. .
FIG. 2 is an explanatory diagram illustrating a bonded structure of a laser bonding material in which distortion occurs as a comparative example, with a cross-sectional photograph, and is a cross-sectional view of the laser bonding material in which distortion is generated by 10 mm. FIGS. 1 and 2 both use photographs of the results of laser joining of the fillets of stainless steel having a length of 1.3 m, a width of 300 mm, and a thickness of 1.5 mm.

First, in the cross section in the direction perpendicular to the welding direction shown in this photograph, a triangle AOB formed by connecting the melting point A and B and the point O deepestly melted in the plate thickness direction is used as a strain evaluation triangle. It prescribes as In the triangle AOB, (x + y + z) / x where x is the length of the side AB corresponding to the laser entrance, and y and z are the lengths of the other sides AO and BO, respectively. One of the constituents is defined as an index expressing the so-called narrowness of the melted part.

In other words, x + y + z is the sum of the three sides of the triangle AOB and is used as an index because it is optimal for simply expressing the size of the melted shape of the cross section. For example, after the cross section is polished, the melted shape is subjected to a corrosion treatment using a corrosive solution obtained by dissolving ferric chloride in hydrochloric acid and then mixing it with alcohol. Judged by the difference in the degree of corrosion. For example, it is only necessary to print the microscope image on paper, draw a triangle connecting the A, O, and B points with a ruler and measure the length x, y, z of each side. It can be calculated by calculation. If the size of the melted part is expressed as an area, it cannot be calculated manually because of its complicated shape, and software and an electronic computer for performing image analysis and the like are required. In this case, the analysis is difficult unless the difference in color between the melted part and the non-melted part is clear when observed under a microscope, but in fact, the part other than the melted part is darkened with a corrosive liquid, or color unevenness occurs. For example, since the degree of corrosion varies depending on the skill level of the operator, only the melted portion cannot always be determined by image analysis. Therefore, the method of expressing by area is not simple.
The procedure for observing the shape of the melted portion from the cutting of the cross section may be as follows, for example.
[1] Cut into a mirror surface state or a state close thereto with a precision cutter or the like. Alternatively, after cutting with a general cutter, the surface is polished to a mirror finish.
[2] The cut surface or the polished surface is immersed in a corrosive liquid, and the shape of the melted part is raised from the difference in corrosion rate.
[3] Using an appropriate microscope such as an optical microscope or a microscope, observe the cross section where the shape of the melted part is raised.

x corresponds to the entrance (frontage) irradiated by the laser, and the shape of the melted portion is elongated in the shape of a wine cup or in the depth direction. In particular, when the incident light is incident at an angle, the shape of the fillet corresponding to x in FIG. 1 does not change. However, when incident from the vertically upward direction, the edge of the plate is melted to change the shape, and FIG. As shown in By dividing the sum of these three sides by x, the ratio of the length x to the size of the melted portion, that is, the narrowness can be expressed. That is, it can be expressed that the larger this value, the narrower the melting region of the laser entrance.

Next, h / x when the length of the perpendicular line from the vertex O to the side AB is h is an index indicating the penetration depth with respect to the melt width of the laser entrance portion, that is, the so-called depth . If this value is large, it is melted long and narrow. This is effective for reducing the size of the melted part, and is also an index because it tends to reduce the thermal strain.

Since it is possible to combine the above two indicators, it was (x + y + z) / x and h / x product h (x + y + z) / x 2 final index. The present inventors have intensively studied and found that when this value is 2 or more, there is no distortion.
FIG. 3 is a graph showing the relationship between the strain generation index according to the present invention and the actual strain amount in the laser bonding material. It is the result of the laser joining experiment of the superposition fillet in 1.5 mm-thick stainless steel with a length of 1.3 m and a width of 300 mm. and h (x + y + z) / x 2 is less than 2, it can be seen that the rapid distortion is likely to occur. For values of 2 and above, the distortion is always zero.

  The value of 2 is a number that can never be obtained from theoretical analysis as described above, and has been found as a result of repeated earnest experiments.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
Example 1 Welding Using Pulsed Wave YAG Laser
A SUS304 steel plate with a thickness of 0.8 to 3 mm, a welding direction length of 1.4 m, and a width of 50 mm, and a SUS304 steel plate with a plate thickness of 1.5 mm, a welding direction length of 1.4 m, and a width of 300 mm are stacked for a length of 20 mm. They were fixed together with a holding jig, and the fillet was welded with a pulsed YAG laser. The welding speed was 0.5 to 0.9 m / min. Irradiation was performed with a spot diameter of 0.4 mm, a pulse width of 10 ms, a repetition frequency of 14 Hz / s, and a laser irradiation angle (angle formed by the horizontal line and the laser) and pulse energy at the focal position.

Evaluation of distortion Evaluation of distortion after welding was performed based on the height in the vertical direction in which the joining material was allowed to stand on a flat ground and the edge of the plate floated from the ground. In addition, the height was made into the average value of both ends.
Table 1 shows test conditions and strain measurement results.

Examples 1-1 to 1-8 are invention, the value of h (x + y + z) / x 2 is 2 or more, any strain amount was 0 mm.

In Comparative Example 1-1, since the value of the pulse energy irradiated to SUS304 steel having a thickness of 0.8 mm was as large as 12 J, the value of h (x + y + z) / x ² was less than 2, and the distortion was also 12.2 mm. It was. The optimum conditions for this material are as in Example 1-1. As the pulse energy increased, the value of x increased and the value of h (x + y + z) / x ² decreased.

Similarly, also in Comparative Examples 1-2 to 1-6, the values of pulse energy irradiated to 1.0, 1.5, 2.0, 2.5, and 3.0 mm thick SUS304 steel were more than optimal conditions. for larger, the value of h (x + y + z) / x 2 is the result distortion has occurred less than 2.

Comparative Examples 1-7 to 1-9 are examples applied to 0.7 mm SUS304 steel. Since the thickness deviates from the thickness of 0.8 to 3.0 mm of the target material of the present invention, distortion occurs even when the welding speed is adjusted and the value of h (x + y + z) / x ² is changed. It was. Further, at a speed of 0.9 m / min in Comparative Example 1-9, the heat input was too small to join.

Comparative Examples 1-10 to 1-12 are examples applied to 3.2 mm SUS304 steel. Since the thickness is still different from the thickness of the target material of the present invention of 0.8 to 3.0 mm, distortion occurs even if the welding speed is adjusted and the value of h (x + y + z) / x ² is changed. It was. Moreover, at 0.8 m / min of Comparative Example 1-12, the heat input was too small to join.

Comparative Example 1-13 is a case where 1.5 mm SUS304 steel is irradiated with a laser at an irradiation angle of 90 °, that is, vertically above, the length corresponding to x increases, and the value of h (x + y + z) / x ² is Less than 2, a distortion of 10 mm was also generated.

Example 2 Welding Using Continuous Wave Fiber Laser
Instead of the YAG laser of Example 1, a continuous wave fiber laser was used, and SS400 was used as a sample. The spot diameter was 0.3 mm, and the heat input was changed by changing the output and welding speed at an irradiation angle of 50 °. In general, SS400 steel is coated with oil for the purpose of rust prevention. Table 2 summarizes the conditions and results of Example 2.

Examples 2-1 to 2-6 are invention, the value of h (x + y + z) / x 2 is 2 or more, any strain amount was 0 mm.

Comparative Example 2-1 is a case where laser joining is performed on SS400 steel having a thickness of 0.8 mm at a welding speed of 7 m / min. EXAMPLE slow minute heat input greater rate than 2-1, the value of h (x + y + z) / x 2 is less than 2, the distortion occurred even 11.2 mm. Optimal conditions for this material is as in Example 2-1, Comparative Example 2-1 the value of x is increased to slow welding speed than that, the value of h (x + y + z) / x 2 drops .

Similarly, in Comparative Examples 2-2 to 2-6, the welding speed was smaller than the optimum condition in SS400 steel of 1.0, 1.5, 2.0, 2.5, and 3.0 mm thickness, respectively. H (x + y + z) / x2 was less than ² , resulting in distortion.

Comparative Examples 2-7 to 2-9 are examples applied to 0.7 mm SS400 steel. Since the thickness deviates from the thickness of 0.8 to 3.0 mm of the target material of the present invention, distortion occurs even when the laser output is adjusted and the value of h (x + y + z) / x ² is changed. It was. In Comparative Example 2-9, the output was further reduced in order to reduce the heat input in order to reduce the distortion, but the heat input was too small to be joined.

Comparative Examples 2-10 to 2-12 are examples applied to 3.2 mm SS400 steel. Since the thickness is also different from the thickness of the target material of the present invention of 0.8 to 3.0 mm, even if the laser output is adjusted and the value of h (x + y + z) / x ² is changed, the distortion is occured. Further, in Comparative Example 2-12, as in Comparative Example 2-9, the heat input was too small to join.

  The present invention can be implemented as described above, and in a preliminary test using a small test piece, it is possible to easily confirm and set conditions without distortion if there is a metal cutting machine and a simple polishing device even at a work site. it can. By using the index of the present invention, it is possible to easily obtain the effect of eliminating the distortion of the metal plate that is overlap-welded with a laser, so that the invention is extremely highly applicable in the related industrial fields.

It is explanatory drawing explaining the unstrained laser joining structure of this invention with the cross-sectional photograph of one Example. As a comparative example, it is explanatory drawing explaining the joining structure of the laser joining material which produced the distortion with a cross-sectional photograph. The value of the index h (x + y + z) / x 2 of the distortion generator according to the present invention, is a graph showing the relationship between the actual amount of strain in the laser bonding material.

Claims (6)

In order to obtain welding conditions in which distortion does not occur prior to obtaining a laser joining material by performing fillet welding of two iron-based metal plates with the same thickness direction overlapped with a laser at a length of 1 m or more. A distortion generation presence / absence prediction method to be performed,
A test piece of a laser joining material produced using the two iron-based metal plates is cut perpendicularly to the welding direction, and in a melting region by laser welding appearing on the cut surface or in a similar expression thereof (hereinafter referred to as melting) The end positions of the laser irradiation entrance of the laser irradiation entrance including the similar expression of the area are referred to as the first end point A and the second end point B, and the deepest position in the thickness direction is the deepest point O or both ends. The deepest point O is the deepest penetration point in the perpendicular direction to the incident width AB, which is a straight line connecting points A and B, and distortion evaluation is performed on the triangle AOB connecting the first end point A, the second end point B, and the deepest point O. In the distortion evaluation triangle AOB, the length of the incident width AB is x, the lengths of the other two sides AO and BO are y and z, respectively, and the perpendicular from the deepest point O to the incident width AB When the length or depth is h,
The sum x + y + z of the three sides of the triangle AOB is used as an index of the size of the molten shape of the cross section,
The ratio of x + y + z to the laser inlet length x, “(x + y + z) / x”, is defined as an index expressing the narrowness of the melted part,
On the other hand, the ratio “h / x” of the depth h to the laser inlet length x is defined as an index expressing the penetration depth, that is, the depth with respect to the melt width of the laser inlet portion,
Further, the product of the narrowness index “(x + y + z) / x” and the depth index “h / x” “h (x + y + z) / x ² ” is a distortion resistance value that is an index expressing the difficulty of distortion. And
Strain generation in the laser bonding material is calculated depending on the magnitude of the strain toughness value calculated based on the actual measurement value compared with a specific value based on the relationship between the strain actual measurement value and the strain toughness value obtained by measurement in advance. A method for predicting the presence or absence of distortion in a bonding material, characterized by predicting the presence or absence of a bonding material. 2. The method according to claim 1, wherein when the strain resistance value is 2 or more, it is determined that no distortion occurs even if laser welding is actually performed under the same conditions as the conditions of the test piece. A method for predicting the presence or absence of distortion in a laser bonding material. A method of forming a laser joining structure in which two iron-based metal plates that are overlapped in the thickness direction are fillet welded with a laser at a length of 1 m or more,
The laser joining structure is obtained by using the laser welding conditions obtained by the method for predicting the presence or absence of distortion of the laser joining material according to claim 1 or 2,
A method for forming a strain-free laser joining structure, characterized in that a laser joining structure can be obtained in which no warpage occurs at both longitudinal ends of the two iron-based metal plates in a fillet weld. In the laser joining structure obtained by the method for forming an unstrained laser joining structure, a melted region by laser welding that appears in any one cross section perpendicular to the welding direction or a similar representation thereof (hereinafter including a similar representation of the molten region). The method for forming a strain-free laser joining structure according to claim 3, wherein the “melting region” satisfies the following [I].
[I] Both end positions of the laser irradiation entrance in the melting region are defined as first end point A and second end point B, the deepest position in the thickness direction is defined as deepest point O, and the first end point A, second end point B, and deepest point A triangle AOB formed by connecting the points O is set as a distortion evaluation triangle, the length of the incident width AB in the distortion evaluation triangle AOB is x, and the lengths of the other two sides AO and BO are y and z, respectively. when the point O the length or depth of the normal to the incident width AB is h, it is (x + y + z) / x and the product of h / x h (x + y + z) / value of ^{x 2} is 2 or more. 5. The method for forming a strain-free laser joining structure according to claim 3, wherein each of the two iron-based metal plates has a width of 30 to 500 mm and a thickness of 0.8 to 3 mm. A distortion-free laser bonding material manufacturing method , wherein a distortion- free laser bonding material is obtained using the non-strained laser bonding structure forming method according to claim 3.