Electric resistance welding method for different kinds of materials

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to an electric resistance welding method for dissimilar materials in which materials having different conductivity and thermal conductivity are joined by electric resistance welding.

【0002】

[Conventional technology]

Conventionally, it has been known that it is effective to use a light metal, particularly aluminum, as a panel material constituting a vehicle body in order to promote reduction of the vehicle weight. However, since aluminum has a lower strength than the steel materials that are usually used, it is difficult to secure the rigidity of the car body if the car body is entirely made of aluminum, and it is necessary to make a major change in the car body structure. There was a drawback that there was. Further, aluminum has the disadvantages that the material is more expensive than the iron material and the processing cost is increased due to the difficulty in processing. In order to solve the above drawbacks, steel materials are used for the parts where strength is required (for example, underbody of chassis frame, floor panel, etc.), and the parts where relatively strength is not required (for example, side frame panel, roof panel, etc.). It is conceivable to use an aluminum material for the upper body), but since the potential difference between steel and aluminum is different, there is a risk of electrolytic corrosion at the joint when the two are joined, and steel and aluminum Welding was extremely difficult. Therefore, as a technique for welding dissimilar materials, for example, the one described in Japanese Patent Application Laid-Open No. 3-294071 has a relay material having an intermediate conductivity between the high conductive material and the high resistance material. However, since the potential difference between the highly conductive material and the relay material and the potential difference between the high resistance material and the relay material are different from each other, there is a problem that electrolytic corrosion is likely to occur. .. In order to solve this problem, the invention described in Japanese Patent Application No. 4-210243, which the applicant filed earlier, is used to join two dissimilar materials having different potential differences by welding. By interposing the clad material formed in (1) between dissimilar materials so that the same kind of materials are in contact with each other and performing resistance welding, welding of dissimilar materials is facilitated and the occurrence of electrolytic corrosion is prevented.

【0003】

[Problems to be Solved by the Invention]

However, in the above-mentioned conventional electric resistance welding method of dissimilar materials, for example, a material having high conductivity and thermal conductivity and a clad material are welded first, and then a material having high conductivity and thermal conductivity and a clad material are welded. It is conceivable to weld the welded material and the material with low conductivity and thermal conductivity in this order, but the required welding current is large, the total amount of power consumption is large, and the heat generated by the electrode is large, so that the electrode There was a problem of shortening the life of the. Looking at the heat generation of the electrodes and the total amount of power consumption that affects the life of the electrodes, two dissimilar materials with different potential differences and a clad material formed of the two dissimilar materials are welded at once. The method is the most preferable, but this method has a problem that three members must be positioned and held at the same time, it is difficult to handle parts, and work efficiency is lowered. Therefore, in the present invention, it is premised that two members are welded at a time in order to improve weldability while facilitating the handling of parts.

【0004】

An object of the present invention is a welding method in which two dissimilar materials having different conductivitys and thermal conductivitys are joined with a clad material interposed therebetween, and the total amount of power consumption can be reduced while maintaining the handleability of parts. It is an object of the present invention to provide an electric resistance welding method of dissimilar materials capable of suppressing the heat generation of the electrode and improving the durability of the electrode.

【0005】

[Means for solving problems]

In order to achieve the above object, the electric resistance welding method of dissimilar materials of the present invention comprises a first material having high conductivity and thermal conductivity, and a second material having lower conductivity and thermal conductivity than the first material. A method of welding a clad material made of the same type of material as the first material and the second material by arranging the clad materials in the middle so that the same type of materials face each other and polymerizing them. And the clad material are welded first, and the second material and the clad material are welded together, and the first material is welded.

【0006】

[Action]

By welding the second material and the clad material first in terms of conductivity and thermal conductivity, the conductivity between the second material and the same type of clad material is low, so the amount of heat generated increases with a small current, and the energized location Since heat is not dissipated from the welding current, welding at the energized part is performed with a small welding current. Next, by welding the welded second material and the clad material and the first material having higher conductivity and thermal conductivity than the second material, the heat between the second material and the same kind of clad material is generated. Since the conductivity is low, it is possible to suppress the dissipation of heat generated during welding of the first material and the same type of clad material, maintain a high temperature, and reduce the welding current. In addition, since welding is performed for each of the two members, good parts handling can be maintained.

【0007】

[Example]

An embodiment in which the present invention is applied to a vehicle body of an automobile will be described with reference to the drawings. In FIG. 3, the underbody and the upper body are formed of materials having different potential differences in the vehicle body of the automobile, and in FIG. 2, the underbody assembly 1 located below the side sill including the floor panel, chassis frame, etc. And the underbody A consisting of the cowl dash upper 2 located in front of the front body is formed of steel plate to ensure the rigidity of the car body, and the upper body can be made of either steel or aluminum. Can be standardized. In addition, the upper body B consisting of side frame assembly 3, roof panel 4, front header 5, rear header 6, package tray 7, rear end panel 8 and rear skirt 9, which is located above the side sill and behind the front body, is 5000 series. It is made of aluminum material to reduce the weight of the car body. The 5000 series aluminum material corresponds to the first material having high conductivity and thermal conductivity, and the steel plate corresponds to the second material having lower conductivity and thermal conductivity than the first material.

【0008】

As shown in FIG. 2, the side sill portion has a side sill outer 100 formed at the lower end of the side frame outer 10 constituting the side frame assembly 3, and a flange 101 is provided at the lower end of the side sill outer 100. The side sill inner 12 which is joined to the end of the floor panel constituting the underbody A and forms a closed cross section of the side sill together with the side sill outer 100 is formed of a steel plate (second material), and a flange 121 is attached to the lower end of the side sill inner 12. , A flange 122 is provided at the upper end. The reinforcement 11 arranged so as to cross the closed cross section of the side sill is the same material as the side sill outer 100 (5000 series aluminum material, that is, the first material) on the first material side (for example, 1000 series aluminum material). It is formed of a clad material consisting of 11A and the side silina 12 (cold-rolled steel plate, that is, the second material) and the second material side (for example, cold-rolled steel plate) 11B, which is the same material, and is formed by the lower end of the reinforcement 11. Flange 111 on top, flange 112 on top Is formed. The first material side 11A (1000 series aluminum material) of the above reinforcement 11 (clad material) is attached to the side sill outer 100 (5000 series aluminum material), and the second material side 11B (cold rolled steel plate) is attached to the side sill inner 12 (cold-rolled steel plate). It is joined so as to face the cold-rolled steel plate).

【0009】

With the above configuration, the clad material is interposed and joined between the flange portions of the dissimilar material panels so as to cross the closed cross section so that the panel members and the same type of materials face each other, so that the end face of the clad material is joined. Is located only on the outside and does not exist in the closed cross section, so that the end face of the clad material is completely covered with paint, and the end face of the clad material is not electrolytically corroded. It is possible to completely block the contact of the panels and surely prevent the occurrence of electrolytic corrosion between panels of different materials.

【0010】

As shown in FIG. 1, the welding method of the present invention first welds the second material side 11B (cold-rolled steel plate) of reinforcement 11 and the side silina 12 (cold-rolled steel plate) by resistance welding (for example, spot welding). The first material side 11A (1000 series aluminum material) of the reinforcement 11 and the side sill outer 100 (5000 series aluminum material) joined to the side sill inner 12 are joined by resistance welding.

【0011】

With this configuration, the side sill inner 12 made of a second material (cold-rolled steel plate) having low conductivity and thermal conductivity and the second material side 11B (cold-rolled steel plate) of reinforcement 11 (clad material) are welded first. By doing so, the conductivity between the side sill inner 12 made of the second material (cold-rolled steel plate) and the second material side 11B (cold-rolled steel plate) of the reinforcement 11 (clad material) is low, so the amount of heat generated with a small current is small. As the heat is not dissipated from the energized part, welding of the energized part is performed with a small welding current. After that, the first material side 11A (1000 series aluminum material) of the reinforcement 11 joined to the side sill inner 12 made of the second material (cold-rolled steel plate) and the above-mentioned second material having high conductivity and thermal conductivity. By welding the side sill outer 100 made of the first material (5000 series aluminum material), which is higher than (cold-rolled steel plate), the side sill inner 12 and reinforcement 11 (clad material) made of the second material (cold-rolled steel plate) are welded. ) 2nd material side 11B (cold-rolled steel plate) has low thermal conductivity, so side sill outer 100 made of 1st material (5000 series aluminum material) The heat generated during welding with the first material side 11A (1000 series aluminum material) of reinforcement 11 is suppressed to maintain a high temperature, and heat is generated by welding the second materials, so small welding Since welding can be performed with an electric current, the power consumption is finally small, and the heat generation of the electrode is small, so that the durability of the electrode can be improved. The following is a comparison of the conductivity, thermal conductivity, and required welding current between the 5000 series aluminum material (first material) and cold-rolled steel sheet (second material) used in the above examples, using the cold-rolled steel sheet as a reference. It is shown in Table 1 of. [table 1] Conductivity Thermal conductivity Required welding current Cold-rolled steel sheet 1 1 1 Aluminum 4 ~ 5 3 ~ 5 3 ~ 5 [0012]

Here, the welding experiment results will be described. A 1.0 mm thick 5000 series aluminum material (AL) is used as the first material, and a 0.8 mm thick cold-rolled steel plate (ST) is used as the second material. A 1000 series aluminum material, 11B on the second material side, formed of a 0.6 mm thick cold-rolled steel plate is used. The above 5000 series aluminum material (AL) and clad material (CL), 5000 series aluminum material (AL) and clad material (CL) and cold-rolled steel plate (ST), clad material (CL) and cold-rolled steel plate (ST) The results obtained by performing resistance welding at only one point are shown in Table 2 below. [Table 2] Suitability Welding current Welding time Welding average voltage Power consumption (kA) (cyc) (V) (kW) AL / CL 19.0 9 0.64 12.2 AL / CL / ST 14.5 9 0.80 11.6 CL / ST 11.0 9 0.68 7.5 Further, in each of the above combinations, the relationship between the welding current (kA) and the nugget diameter d (mm) of the welded portion is shown in FIG.

【0013】

From the results in Table 2 and Fig. 4, looking at the total amount of power consumption that affects electrode heat generation and electrode life, 5000 series aluminum material (AL), clad material (CL), and cold-rolled steel sheet (ST) The method of welding the three members at once is the most preferable, but this method requires that the three members be positioned and held at the same time, which makes it difficult to handle the parts and may reduce the work efficiency. Therefore, in the present invention, the welding of two members is performed in order to improve the weldability while facilitating the handling of parts.

【0014】

Next, the welding method of the present invention will be described with reference to Table 2 and FIG. 4, with the second material (cold-rolled steel plate) side and the cold-rolled steel plate (second material) of the clad material having low conductivity and thermal conductivity. Welded first, and then the 1000 series aluminum material (1st material) and 5000 series aluminum material (1st material), which are clad materials whose conductivity and thermal conductivity are higher than those of the 2nd material (cold-rolled steel sheet). By welding, the total power consumption is that the 1000 series aluminum material (first material) side of the clad material and the 5000 series aluminum material (first material) are first welded, and then the second material of the clad material (first material). It is smaller than the method of welding the cold-rolled steel plate) side and the cold-rolled steel plate (second material).

【0015】

[Effect of the invention]

Since the present invention is configured as described above, the effects described below are obtained. By welding the second material and the clad material, which have low conductivity and thermal conductivity, first, the heat generation amount increases with a small current because the conductivity of the second material and the same type of clad material is low, and energization is performed. Since heat is not dissipated from the location, welding at the energized location is performed with a small welding current. Next, by welding the welded second material and the clad material and the first material having higher conductivity and thermal conductivity than the second material, the heat between the second material and the same kind of clad material is generated. Since the conductivity is low, it is possible to suppress the dissipation of heat generated during welding of the first material and the same type of clad material, maintain a high temperature, and reduce the welding current. Since the heat generation of the electrode is small, the durability of the electrode can be improved. In addition, since the second material and the clad material are welded, and the second material and the clad material are welded and the first material is welded in the order of each of the two members, the parts can be easily handled during the welding work, and the parts can be handled easily. Can be maintained well.

[Simple explanation of drawings]

[Figure 1]

It is explanatory drawing which shows the Example of this invention.

[Figure 2]

It is sectional drawing of the side sill part to which this invention was applied.

[Fig. 3]

It is a schematic assembly drawing of the vehicle body of the automobile to which this invention is applied.

[Fig. 4]

It is a graph which shows the relationship between a welding current and a nugget diameter.

[Explanation of symbols]

10 Side frame outer (1st material: 5000 series aluminum material) 11 Reinforcement (clad material) 11A 1st material side (1000 series aluminum material) 11B 2nd material side (cold steel sheet) 12 Side sill inner (second material: cold-rolled steel plate)