JPS6252669B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for resistance seam welding parts of different thickness. Resistance seam welding is generally used for welding thin plates and joints that require airtightness due to efficiency considerations. However, if there is a significant difference in the plate thickness of the joint, unwelded parts are likely to occur, and if the heat input is increased to prevent this, a sound weld cannot be obtained, such as surface flaking, and resistance seam welding is not recommended. Recruitment was extremely difficult. For example, part of an automobile's exhaust gas system involves lap joint welding between a flexible tube and a cap, but since the flexible tube is thin and the cap is thick,
When resistance seam welding is performed, if there is insufficient heat input, non-welding will occur, if there is too much heat input, surface dust will occur, and in severe cases, hole formation will occur, making it impossible to perform a satisfactory weld. Ta. For this reason, in such cases, fusion welding such as TIG welding is currently used, which is less efficient than resistance seam welding. This difficulty is especially true when the thickness of the thinner member is 0.5 mm.
This is noticeable when: The present invention overcomes this difficulty and provides a resistance seam welding method for joining members of different thickness together. The method of the present invention is applicable to welding between members in which the thickness of the members to be welded is different, the thickness of the thinner member is 0.5 mm or less, and the thickness of the thicker member is more than three times the thickness of the thinner member. In this method, the thickness of the thinner member is t ₁ and the thickness of the thicker member is t _2. When both members are overlapped, the thickness of the thinner member is This method is characterized by superimposing a backing member having a thickness t _x defined as T _x >1/3t ₂ −t ₁ on the outside and performing resistance seam welding. The term member above actually refers to a material of constant thickness consisting of a plate or tube. Furthermore, the thicker member may be made of two or more layers. In this case, t ₂ is the total thickness of two or more stacked members. The above relational expression was derived experimentally, and if this relational expression is not satisfied considering the heat capacity, thermal conductivity, etc. of the material, surface dust etc. will occur and a good weld will not be obtained. This is what I learned that it cannot be done. Although the present invention will be specifically explained below mainly regarding stainless steel (partly carbon steel), this method is not limited to the type of metal. Hereinafter, the present invention will be specifically explained with reference to Examples. The members to be welded were all cold-rolled steel plates manufactured using normal processes, and the steel types used were SUS304, SUS410, and some mild steel. As shown in the attached schematic diagram, welding is performed by overlapping a thick member (in the illustrated case, it consists of two sheets 1 and 2) and a thin member 3, and overlapping a third backing member 4 on the top surface of the thin member 3. The entire stack was sandwiched between disk electrodes 5 and resistance seam welding was performed by a conventional method. The materials, welding conditions, and results are summarized in the table below.

[Table] As seen in this table, execution numbers 1 to 4 are the methods of the present invention, and A ₁ , A ₂ , B ₁ , B ₂ , C ₁ , and C ₂ are comparative examples. Further, 1, A ₁ , and A ₂ are cases where there is one thick plate, and the others are cases where there are two thick plates. In the latter case, the respective thicknesses of the two sheets are t ₂₁ and t ₂₂ , and t ₂ =t ₂₁ +t ₂₂ . The welding current was varied according to the plate thickness. The welding results were judged based on the presence or absence of surface dust and the presence or absence of unwelded parts on the thinner member, and those with no surface dust or unwelded parts were judged as "good". When stacking two sheets, by comparing 1 with A ₁ and A ₂ , it was found that by stacking 0.2 mm thin plates (covering members) as in the method of the present invention, surface dusting does not occur and there is no welding. However, in the comparative example, the current of _A1 is 10000Amp.
It can be seen that surface dust occurs in A ₂ at 9000 Amp., but surface dust does not occur, but there are unwelded areas, making it impossible to weld soundly. In addition, by comparing B ₁ and B 2 with B 1 and B ₂ , it was found that the method of the present invention can perform good welding even when three sheets are stacked, whereas the comparative example of B ₁ and B ₂ does not allow for sound welding. I understand that. In addition, in the method of the present invention, the material of the abutting member placed on the thinner member may be the same material as shown in Example No. 3, but depending on the conditions, it may be made of the same material as shown in Example No. 4. Different materials (in this case SUS410 versus mild steel) may be used. This abutment member only needs to be slightly larger than the welding width, and therefore the economic disadvantage of using this abutment member is slight. As described above, the present invention prevents the occurrence of surface dust and unwelded parts by overlapping a support member on the thinner workpiece in lap joint welding of members of different thicknesses. This method makes it possible to perform overlapping resistance seam welding of members with different thicknesses, which was previously considered impossible, and has the excellent effect of significantly improving work efficiency.

[Brief explanation of the drawing]

The accompanying drawings are schematic diagrams illustrating embodiments of the method of the invention. 1, 2... together with the thicker member to be welded, 3...
Thinner member to be welded, 4...Abutting member, 5...Disc electrode.

Claims (1)

[Claims] 1. The thickness of the members to be welded is different, the thickness of the thinner member is 0.5 mm or less, and the thickness of the thicker member is more than three times the thickness of the thinner member. This is a method of resistance seam welding two members together, where the thickness of the thinner member is t ₁ and the thickness of the thicker member is t _2. When both members are overlapped, the thinner A method characterized by superimposing a backing member having a thickness _tX defined as _tX >1/ _3t2 - _t1 on the outside of the member and performing resistance seam welding. 2. The method according to claim 1, in which the thicker member is made of two layers, and where the thickness of each layer is t ₂₁ and t ₂₂ , t ₂ = t ₂₁ + t ₂₂ .