TWI580502B - A spot welding method for lap-joint of multi-metal sheets - Google Patents

Description

Multi-layer metal sheet spot welding method

The invention relates to a method for lap jointing of a multi-layer metal sheet, in particular to a method for lapping a multi-layer metal sheet by a high resistivity active agent combined with a resistance spot welding technique.

Multi-layer metal plate lap joint technology has been widely used in industry, especially in the automotive industry, the steel plate jointing operation is more popular, and the resistance spot welding technology is the most used for multi-layer metal plate lap joints.

However, in the welding process of multi-layer metal plate parts by resistance spot welding technology, in addition to factors such as electrode holding force, welding current and welding time, it is often limited by the material, thickness and surface between the metal plates. The condition and other factors require the multi-pass welding or high electrode holding force or high welding current to complete the joining of the multi-layer metal plates. In this way, not only the multi-pass welding procedure is excessively complicated, but also due to high welding current or high electrode holding force, abnormal phenomena such as expulsion or excessive depression may occur at the joint of the metal plate member, and it is easier to be welded. The internal heat energy distribution is uneven or the local cooling rate of the weld nugget is different, which causes the weld nugget to have defects such as center shrinkage, incomplete melting and cracks; even, due to the difference in contact resistance between adjacent metal plates, it is easy to cause electricity The latter resistance heat energy is concentrated on the higher contact resistance value, so that the subsequent weld nugget grows with an offset condition and reduces the weld nugget diameter or weld nugget fusion area, which seriously affects the spot welding quality of the multi-layer metal plate.

In addition, the high temperature effect brought by the high-current resistance spot welding often leads to the loss of the strength or hardness of the metal plate itself, so that the upper and lower electrodes hold the metal plate Under the influence of the high force applied, 遂 is easy to cause depression on the outer surface of the metal plate. Even when the depth of the dent is more than 20% of the thickness of the metal plate (commonly known as 〝 weld nugget), it will easily cause metal. The lack of lap joint strength is greatly reduced.

In view of the above, it is indeed necessary to develop a multi-layer metal plate lap joint method different from the prior art described above in order to effectively perform spot welding of a multi-layer metal sheet member while solving various problems as described above.

The main object of the present invention is to improve the above disadvantages to provide a multi-layer metal sheet spot welding method capable of changing the contact resistance value between any two adjacent metal sheets to increase the diameter of the weld nugget or the weld core fusion area. Better welding results.

The second object of the present invention is to provide a multi-layer metal sheet spot welding method, which is capable of adopting a lower welding current effect, avoiding defects such as central shrinkage, melt incompleteness and cracks in the weld nugget, or capable of adopting a lower electrode holding force. Avoid the phenomenon of over-pressure of the weld nugget, which can effectively improve the quality of the weld nugget.

In order to achieve the foregoing object, the method for spot welding a multi-layer metal sheet according to the present invention comprises: applying an active agent having a high electrical resistivity to a joint between two adjacent metal sheets to cover a surface of the sheet to form a a welding work area; and the upper and lower electrodes jointly hold the welding working area, and pass current to the welding working area, and the high-resistance heat generated by the high-resistivity active agent is used to make the joint of the two adjacent metal plates Bonded by heat fusion; wherein the resistivity of the high resistivity active agent is much higher than the resistivity of the metal plate member, and the high resistivity active agent is a mixture of a plurality of constituent powders and an organic solvent, and None of the two adjacent metal sheets coated with the high resistivity active agent contact the upper electrode.

Wherein, the multi-component powder is composed of a metal and a non-metal compound, and the weight ratio of the multi-component powder to an organic solvent is 2:3.

Wherein, the multi-component powder may be an oxide, a sulfide, a carbonate compound, and a halide, preferably a silicon oxide, a titanium oxide, an iron oxide, a molybdenum sulfide, a manganese carbonate, and a halide; The solvent may be methanol, ethanol, isopropyl alcohol or acetone.

Wherein, the high resistivity active agent is 30-50% by weight of silicon oxide, 20-40% of titanium oxide, 5-20% of iron oxide, 10 ~25% molybdenum sulfide, 10-15% manganese carbonate and 5-10% halides are mixed with methanol to make the high resistivity activity The agent is in the form of a slurry.

Wherein, the resistivity of the high resistivity active agent is in particular different from the resistivity of the metal plate member by 10 ¹⁵ ~ 10 ²⁵ .

Wherein, the coating amount per unit area of the high resistivity active agent is from 0.00009 g/cm ² to 0.00099 g/cm ² . Moreover, the coating width of the high resistivity active agent is greater than the diameter of the end portions of the upper and lower electrodes.

The invention can not only increase the diameter of the weld nugget or the molten area of the weld nugget through the stable resistance heat action, but also avoid the abnormal phenomena such as abnormal flying or excessive depression caused by the high welding current or the high electrode holding force, so as to The welding procedure has better welding effect; even, the spot welding method of the multi-layer metal sheet of the invention can avoid various defects such as central shrinkage, smelting and cracking of the weld nugget under the action of low welding current, or can take lower Under the action of the electrode holding force, the phenomenon of over-pressure of the weld nugget is avoided, thereby effectively improving the quality of the weld nugget and relatively improving the spot welding strength of the multi-layer metal plate.

〔this invention〕

1, 1a, 1b, 1c‧‧‧ metal plate

2a‧‧‧Upper electrode

2b‧‧‧ lower electrode

P‧‧‧High Resistivity Active Agent

A‧‧‧ welding work area

Ra, Rab, Rbc, Rc, Ra', Rab', Rbc', Rc', Ra", Rab", Rbc", Rc"‧‧‧ resistivity

Ta, Tab, Tbc, Tc, Ta', Tab', Tbc', Tc', Ta", Tab", Tbc", Tc" ‧ ‧ temperature values

Figure 1a: Schematic representation of the coating of the high resistivity active agent of the present invention.

Figure 1b is a schematic view of a spot welding method for a multilayer metal sheet according to the present invention.

Figure 2a: One of the three-layer metal plate spot welding diagram.

Figure 2b: Schematic diagram of the resistance distribution of the three-layer metal plate in Figure 2a.

Figure 2c: Schematic diagram of the temperature distribution of the three-layer metal plate in Figure 2a.

Figure 3a: Two of the three-layer metal plate spot welding diagram.

Figure 3b: Schematic diagram of the resistance distribution of the three-layer metal plate in Figure 3a.

Figure 3c: Schematic diagram of the temperature distribution of the three-layer metal plate in Figure 3a.

Figure 4a: Three of the three-layer metal plate spot welding diagram.

Figure 4b: Schematic diagram of the resistance distribution of the three-layer metal plate in Figure 4a.

Figure 4c: Schematic diagram of the temperature distribution of the three-layer metal plate in Figure 4a.

Figure 5(a)~5(d): Sectional view of spot welds of multi-layer metal sheets.

The above and other objects, features, and advantages of the present invention will become more apparent and understood. The method can be applied to the welding of metal plates of different materials and thicknesses, especially the high-strength steel plate of the automobile, and the welding spot welding technology can be widely used in the transportation industry to improve the welding efficiency of the multi-layer metal plates. And welding nuclear quality.

The term "weld core" as used herein refers to the area where the current is caused by the resistance spot welding process. This is a common term in the art and should be understood by those skilled in the art and will not be described again.

The multi-layer metal sheet spot welding method comprises the following steps: as shown in FIG. 1a, a high-resistivity active agent P is first applied to a joint between any two adjacent metal sheets 1 to cover the The surface of the panel 1 forms a welding work area A. Wherein, the resistivity of the high resistivity active agent P is much higher than the resistivity of the metal plate member 1 (for example, the typical resistivity of the cerium oxide powder is 1.0×10 ¹⁸ Ω-cm; the typical resistivity of the titanium dioxide powder is 1.0×10 ¹² Ω-cm; the typical resistivity of high-strength steel sheet is 2.8×10 ^-5 Ω-cm; the typical resistivity of stainless steel sheet is 7.4×10 ^-5 Ω-cm), and the high resistivity active agent It is preferable that the resistivity of P and the metal plate member 1 differ by about 10 ¹⁵ to 10 ^{25 in} order to effectively increase the contact resistance between the metal plate members 1. Furthermore, the high-resistivity active agent P may be selected from a mixture of a multi-component powder composed of a metal and a non-metal compound, and an organic solvent, and the weight of the multi-component powder is compared with the weight of the organic solvent. Preferably, the multi-component powder may comprise oxides, sulfides, carbonic acid compounds and halides, such as silicon oxide, titanium oxide, iron oxide, and molybdenum sulfide. Various metal or non-metal compounds having a higher electrical resistivity with respect to the plate member 1 such as (molybdenum sulfide), manganese carbonate, and halides, and the organic solvent may be selected from methanol or Various volatile liquids such as ethanol, isopropyl alcohol or acetone.

In detail, the high-resistivity active agent P of the present embodiment is particularly selected from the group consisting of 30-50% by weight of silicon oxide, 20-40% of titanium oxide, and 5-20%. a multi-component powder of iron oxide, 10 to 25% molybdenum sulfide, 10 to 15% manganese carbonate, and 5 to 10% halides. And the appropriate amount of methanol (the multi-component powder: methanol = 2:3) blended, so that the high-resistivity active agent P is in the form of a slurry; continued as shown in Figure 1a three-layer metal sheet spot welding [ The metal plate members 1a, 1b, 1c are exemplified to apply the high-resistivity active agent P in the form of a slurry between the interlayers of any two adjacent metal plate members 1a, 1b or 1b, 1c (i.e., the surface) The upper surface of the metal plate members 1b, 1c is shown to form a welding work area A covering the high resistivity active agent P on the upper surfaces of the metal plate members 1b, 1c, and to cause the metal plate members 1b of each layer, The welding work area A of 1c is stacked in the opposite position, and then the metal plate 1a of the uppermost layer is laminated together.

Wherein, the high-resistivity active agent P is covered by the surface gloss which can be applied to the metal plate member 1, and the unit area coating amount of the high-resistivity active agent P is preferably maintained at 0.00009 g/cm. ² ~ 0.00099g / cm ² , also known as complete and uniform coverage of the welding work area, in order to improve the accuracy of current through the welding work area A.

In particular, the high-resistivity active agent P may be uniformly applied to each layer of the metal plate member 1. The person skilled in the art shall finely adjust the high-resistivity active agent P according to the material and thickness of the metal plate member 1. The coating position and thickness are to improve the weld nugget diameter or weld nugget area between thick metal plates.

When the high-resistivity active agent P is coated between the metal plate members 1 and stacked according to the respective welding work area A, as shown in FIG. 1b, the upper and lower electrodes 2a, 2b are held together. The working area A is welded and an electric current is supplied to the welding working area A to force the joint of the two adjacent metal sheets 1 to be thermally melted and joined via the high-resistance heat generated by the high-resistivity active agent P. Wherein, the coating width of the high resistivity active agent is greater than the diameter of the end portions of the upper and lower electrodes. In this embodiment, the medium frequency DC resistance spot welding equipment is selected, and the end diameter is 6.0 mm, the highest welding current is 6.1 kA, and the electrode holding force is 350 kgf for better implementation.

As described above, the upper electrode 2a and the lower electrode 2b jointly hold the outermost metal plate members 1a, 1c, and the electrode tips of the upper electrode 2a and the lower electrode 2b are located in the welding work area A, and are properly adjusted. After the welding current and the electrode holding force, the current is introduced into the welding work area A. When the high-resistivity active agent P is not coated between the metal plate members 1a, 1b and 1c (as shown in Fig. 2a), the resistance value and the temperature value thereof are as shown in Figs. 2b and 2c, wherein Ra And Ta is a resistance value and a temperature value measured by the surface of the metal plate member 1a contacting the upper electrode 2a, and Rab and Tab are resistance values and temperature values measured by the contact faces of the metal plate members 1a and 1b. Rbc and Tbc are resistance values and temperature values measured by the contact faces of the metal plates 1b and 1c, and Rc and Tc are resistance values and temperatures measured by the metal plate member 1c contacting the surface of the lower electrode 2b. value. It can be seen from Figures 2b and 2c that Rab and Rbc are larger than Ra and Rc, and Tab and Tbc are larger than Ta and Tc. And between the metal plate members 1a and 1b, and the metal plate members 1b and 1c The high resistivity active agent P is applied to the soldering work area A (please refer to FIG. 3a), and the current passing through the soldering work area A is limited by the high resistivity active agent P. The insulation resistance characteristic causes high resistance heat between the metal plate members 1a and 1b and between the metal plate members 1b and 1c, as shown in Fig. 3b, between the metal plate members 1a and 1b, and Between the metal plate members 1b and 1c, the resistance values Rab' and Rbc' are significantly higher than the uncoated resistance values Rab and Rbc, and the temperature values Tab' and Tbc' are also lower than the uncoated temperature values. Tab and Tbc are high so that the joints of the metal sheets 1a, 1b, 1c are melted by heat, and the sheet metal parts 1a, 1b, 1c can be forced to be completed under the pressure of the upper and lower electrodes 2a, 2b. Tightly joined.

Referring to FIG. 4a, in addition, when the metal plate members 1a and 1b are not coated with the high resistivity active agent P, and the high resistivity active agent P is applied between the metal plate members 1b and 1c. (In other words, the high-resistivity active agent P) is applied only between the metal plate members 1b and 1c which are not in contact with the upper electrode 2a, and the high-resistance active agent P can also effectively promote the metal plate members 1a and 1b. Between the metal plates 1b and 1c, high resistance heat is generated (refer to Figures 4b and 4c), and the joints of the metal plates 1a, 1b, and 1c may be heated and melted to make the metal The panels 1a, 1b, 1c complete the tight joint.

In this way, the multi-layer metal sheet spot welding method of the present invention can improve the contact resistance value between adjacent metal plates by the high-resistivity active agent to significantly improve the resistance heat energy. In other words, since the resistance spot welding process tends to concentrate the generated resistance heat on the position where the contact resistance is more significant, so that the resistance heat distribution is uneven, when the present invention selectively coats the high resistivity active agent, the contact resistance is relatively insignificant. When the two adjacent metal plates are between the two, the contact resistance between the two adjacent metal plates can be improved by the high insulation resistivity of the active agent to achieve stable and uniform resistance heat under the action of low current. Multi-layer metal plate parts welding process.

Based on the foregoing technical concept, the difference between the conventional resistance spot welding technique and the present invention is compared here, and the metallographic cross-section of the weld is presented in the fifth (a) to fifth (d). As can be seen from the figure, when the welding current of the output is 5.0kA, it is soldered by conventional resistance spot welding technology, as shown in Figure 5(a). The center of the weld metal plate of the metal plate obviously has defects such as shrinkage holes and cracks, and even more incomplete melting phenomenon occurs at the outer metal plate member; in contrast, after the welding according to the present invention, the weld nugget as shown in Fig. 5(b) is Presents good quality without defects. Moreover, when the welding current of the output is increased to 6.1 kA, the welding core of the conventional resistance spot welding still has the shrinkage defect as shown in Fig. 5(c), and after the action of the invention, the multi-layer metal sheet is spot-welded. The weld nugget diameter or weld nugget area is significantly improved as shown in Figure 5(d), and the weld nugget quality is significantly better.

In this regard, the multi-layer metal plate member is subjected to the welding current of different outputs and after spot welding, and the difference in the diameter of the weld nugget is evaluated by a peel test, as shown in Table 1 below.

It can be seen from Table 1 that after the action of the high resistivity active agent of the present invention, it is only necessary to increase the diameter of the weld nugget of the spot welding of the multi-layer metal sheet with a lower welding current.

In summary, the present invention can not only increase the diameter of the weld nugget or the molten area of the weld nugget through the action of stabilizing resistance heat, but also avoid the abnormal phenomena such as abnormal flying or excessive depression caused by high welding current or high electrode holding force. This one-time welding procedure has better welding results; even, the multi-layer metal sheet spot welding method of the invention can avoid various defects such as central shrinkage, melt incompleteness and cracks under the action of low welding current, or can Under the action of lower electrode holding force, avoiding the phenomenon of over-pressure of the weld nugget, thereby effectively improving the quality of the weld nugget and relatively reaching Improve the effect of spot welding strength of multi-layer metal sheets.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

1, 1a, 1b, 1c‧‧‧ metal plate

2a‧‧‧Upper electrode

2b‧‧‧ lower electrode

P‧‧‧High Resistivity Active Agent

A‧‧‧ welding work area

Claims (9)

A multi-layer metal sheet spot welding method comprises: uniformly applying an active agent with high resistivity to a joint between two adjacent metal plates to cover a surface of the plate to form a welding work area; And the lower electrode jointly holds the welding working area, and applies current to the welding working area, and the high-resistance heat generated by the high-resistivity active agent causes the joints of the two adjacent metal sheets to be melted by heat fusion; The resistivity of the high resistivity active agent is much higher than the resistivity of the metal plate member, and the high resistivity active agent is formed by mixing a plurality of constituent powders with an organic solvent, and applying the high resistance therebetween. The two adjacent metal sheets of the active agent are not in contact with the upper electrode. The multi-layer metal sheet spot welding method according to claim 1, wherein the multi-component powder is composed of a metal and a non-metal compound, and the weight ratio of the multi-component powder to the organic solvent is 2:3. The multi-layer metal sheet spot welding method according to claim 2, wherein the multi-component powder is an oxide, a sulfide, and a carbonic acid compound and a halide. The multi-layer metal sheet spot welding method according to claim 3, wherein the multi-component powder is silicon oxide, titanium oxide, iron oxide, molybdenum molybdenum Sulfide), manganese carbonate and halides. The method of spot welding of a multi-layer metal sheet according to claim 4, wherein the high-resistivity active agent is 30-50% by weight of silicon oxide and 20-40% of titanium oxide. (titanium oxide), 5 to 20% iron oxide, 10 to 25% molybdenum sulfide, 10 to 15% manganese carbonate, and 5 to 10% halide (halides) And co-mixing with the organic solvent to make the high-resistivity active agent into a slurry. The method of spot welding of a multi-layer metal sheet according to claim 1, 2, 3, 4 or 5, wherein the resistivity of the high resistivity active agent is different from the resistivity of the metal sheet by 10 ¹⁵ 10 ²⁵ . The method of spot welding of a multi-layer metal sheet according to claim 1, wherein the organic solvent is methanol, ethanol, isopropyl alcohol or Acetone (acetone). The method of spot welding of a multi-layer metal sheet according to claim 1, 2, 3, 4 or 5, wherein the coating amount per unit area of the high-resistivity active agent is 0.00009 g/cm ² to 0.00099 g. /cm ² . The multi-layer metal sheet spot welding method according to claim 1, 2, 3, 4 or 5, wherein the coating width of the high-resistivity active agent is larger than the diameter of the end portions of the upper and lower electrodes.