JPS6010574B2 - Inspection method for resistance welds - Google Patents

Description

[Detailed description of the invention] This invention relates to a method for inspecting resistance welds.

FIG. 1 is a schematic diagram showing a general resistance welding method. The first material to be welded 1 and the second material to be welded 2 have a pair of electrodes 3 joined to their respective inner surfaces, and a pair of electrodes 3 joined to their respective outer surfaces.
4. Days of the first and second materials to be welded,
When current is applied between the pair of electrodes 3 and 4 in a state in which the electrodes 2 are in pressure contact with each other, a point P on the inner surface of each of the first and second materials to be welded 1 and 2 is resistance welded. In such resistance welding, the conventional inspection method for resistance welds involves non-destructive inspection of the resistance part during the resistance welding process. a pair of electrodes 3.4 that vary according to changes in thermal expansion of at least one of the materials to be welded 1 and 2;
Measure the change in at least one of these displacements, and measure the maximum displacement (maximum thermal expansion of the material to be welded).

Hereinafter, this will be referred to as the maximum displacement amount. ), or the rate of change of at least one of the pair of electrodes 3 and 4 at the initial stage of energization, that is, the rate of change of the amount of displacement (days.) with respect to the passage of a certain time (T,), day, /T,, The first and second
The quality of the welded parts of the welded materials 1 and 2 was determined. FIG. 2A is a characteristic curve diagram showing the relationship between the displacement pattern between the electrodes 3 and 4 and the welding current applied between the pair of electrodes 3 and 4.

A characteristic curve A in FIG. 2 is a displacement pattern between the electrodes 3 and 4, and a curve B at the beginning of FIG. The conventional inspection method for resistance welds is based on the maximum displacement Ho during the energization period T determined from the characteristic curve A in FIG. The strength of the welded part of the first and second welded materials 1 and 2 is estimated from the value (Q=day./T,), and the strength of the welded part of the first and second welded materials is estimated from the estimated value. The quality of the welding conditions of 1 and 2 is determined. However, if at least one of the first and second materials to be welded 1 and 2 has a narrow plate shape, the pressure conditions for the pair of electrodes 3 and 4 and the pressure conditions for the pair of electrodes 3 and 4 Due to the energization conditions during the energization period, the plastic deformation of the plate-shaped first and second welded materials 1 and 2 during the energization period T is significant, and the electrode 3 shown in FIG.
, 4, the maximum displacement amount Ho between electrodes 3 and 4 is detected during energization, and then the displacement amount between electrodes 3 and 4 contracts. The inspection method has a drawback that it is not possible to determine the quality of the welded portions of the first and second materials to be welded 1 and 2. This drawback will be explained with reference to FIGS. 4 and 5. Note that the curve D at the beginning of FIG. 3 shows the waveform of the welding current during the energization period T during which the current is applied between the pair of electrodes 3 and 4. Figure 4 shows the first and second welding materials 1.
92. FIG.

That is, the first material to be welded is a rail-shaped material with a width of 5 mm at the upper and lower ends, 2 ribs in the center, and a height of IQ ■, and the second material to be welded is a plate-shaped material with a thickness of 0.8 The energization period T is 10 cycles, and the welding current is 7.A to 10K.
When welding under welding conditions A, the first and second
The relationship between the maximum displacement amount Ho of the welded materials 1 and 2 and the tensile breaking load of the welded portion of the first and second welded materials 1 and 2 is as shown in Fig. As is clear from FIG. 5, although the maximum displacement Ho at point A is approximately 50 mm, the tensile breaking load of the welded portion at this time is approximately 400 kg. Also, the maximum displacement Ho of the point opening is about 50 degrees, same as point A, but the tensile breaking load of the welded part at this time is very small, about 20 k9.
In this way, regardless of the quality of the welded portion, in other words, regardless of the tensile breaking load of the welded portion, the maximum amount of displacement Ho during the energization period T was almost constant. Therefore, there is a drawback that it is not possible to determine the quality of the welded portion by determining the maximum amount of displacement Ho. Further, even if the fluctuation rate Q between the electrodes 3 and 4 at the initial stage of energization was determined, it was not possible to similarly determine the quality of the welded portion. The reason why sufficient judgment could not be made as described above is that the conventional inspection method only captures the welding phenomenon at the initial stage of energization and the welding phenomenon up to the period when the maximum displacement amount Ho occurs.

In other words, as shown by characteristic curve C in Figure 3A, the maximum displacement amount Ho is detected during energization, and the welding conditions (changes in welding current, changes in pressurizing force) during the subsequent contraction process are important for the welding result. However, in spite of this, conventional inspection methods do not grasp the welding phenomenon of the shrinkage process during the energization period T after the maximum displacement amount Ho is detected, so it is difficult to judge whether the weld is good or bad. The drawback was that the judgment accuracy was extremely low. This invention was made based on new knowledge and in order to eliminate the drawbacks of the conventional method.
o is detected and the amount of contraction occurring during the energization period T in the L pan-raku is also measured, and the first . By capturing the thermal expansion and contraction phenomena of the second materials 1 and 2 to be welded, a method for inspecting a resistance welded part is provided, which significantly improves the accuracy of determining the quality of the welded part.

The present invention will be explained below with reference to the drawings. FIG. 6 is a characteristic diagram showing the relationship between the tensile breaking load and the sum of the maximum displacement amount shown in FIG. 3A and the shrinkage amount day 2 obtained by the inspection method according to the present invention.

That is, the first and second welded materials to be welded 2 are of the shape shown in the diagram, and in detail, the first welded material 1 has a width of 5 at the upper and lower ends and a height of 2 from the center width. 1. Using a rail-shaped material with a thickness of 0.8 as the second material to be welded 2, the retention period T is 10 cycles, and the welding current is 7. When welding is performed under the welding conditions for shoes A to 1 plate A, the displacement pattern between the electrodes 3 and 4 is as shown by the characteristic curve C in FIG. 3A. In this characteristic curve C, measure the maximum displacement Ho and the contraction amount 2 that occur during the energization period T, calculate the sum of the maximum displacement 2 and the contraction amount 2, and add this sum to the tensile fracture of the weld. The relationship with load was determined. In Figure 6, the sum of the maximum displacement day and contraction day 2 at point C is approximately 27
0 Yamakawa, and the tensile breaking load of the weld at this time is approximately 40
0k9 appears. Furthermore, the sum of the maximum displacement Ho at point 2 and the shrinkage amount 2 is about 50 mm, and the tensile breaking load of the weld at this time is about 20 k9. In this way, the maximum displacement amount Ho that occurs during the entire energization period T and the contraction amount day 2 that occurs during the energization period after the detection of the maximum displacement amount Ho are determined, and from the sum of this maximum displacement amount Ho and the contraction amount day 2. The method of the present invention for determining the quality of a welded part is to grasp the welding phenomenon up to the detection of the maximum displacement Ho during the energization period T, and to determine the maximum displacement Ho.
Since the welding phenomenon of the shrinkage process during the energization period after the detection of can also be grasped, it is possible to accurately determine the quality of the welded part.

In addition, the characteristic diagram shown in Figure 6 shows a method for determining the quality of the welded part based on the sum of the maximum displacement and the shrinkage ratio, but as shown in characteristic curve C in Figure 3, the maximum displacement When the displacement Ho is detected and the welding phenomenon during the subsequent shrinkage process has an important effect on the welding result, the quality of the weld may be determined only by the shrinkage amount ratio, as shown in Fig. 7. . 7th
The figure is a characteristic diagram showing the relationship between the tensile breaking load and the shrinkage amount day 2 obtained by the inspection method according to the present invention.

That is, the first workpiece 1 having the shape shown in FIG. 4 is a rail-like material with a width of 5 columns at the upper and lower ends, a width of 2 bars at the center, and a height of IQ, the energization period T is 10 cycles, and the welding current is is 7. When shoes A to 1 are welded under the hot twill conditions of Fox A, the displacement pattern of the electrode 3 is as shown by the characteristic curve C in FIG. 3A. Figure 7 shows the amount of contraction &
was measured, and the relationship between the amount of shrinkage (day 2) and the tensile breaking load of the welded portion was determined. As is clear from this characteristic diagram, even in this case, it is possible to accurately determine the quality of the welded portion. Further, in the above embodiment, the case of resistance welding was explained, but during the energization period T, the first
, Projection welding is a type of resistance welding in which only plastic deformation of the first and second welded materials 1 and 2 occurs, as shown in FIG. 8, rather than thermal expansion of the second welded materials 1 and 2. It is clear that the same effects as in the above embodiment can also be obtained. FIG. 8 is a schematic diagram showing a projection welding method.

That is, when the second material to be welded 2 having a projection (protrusion) is brought into contact with the first welding material 1 in the form of a flat plate, and the pair of electrodes 3 and 4 are pressed against each other and energized, welding occurs at one point P. As described above, according to the present invention, the maximum amount of hot air acid tension of the material to be welded that occurs during the energization period and the amount of contraction of the material to be welded that occurs during the energization period after the maximum amount of thermal expansion are determined, and Since the quality of the weld is judged based on the sum of the expansion amount and the shrinkage amount, or the shrinkage amount, it is possible to grasp the welding phenomenon during the energization time of the father bee with the maximum expansion amount L, and it is possible to determine the quality of the welded part with high accuracy. It has the effect that can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a general resistance welding method. FIGS. 2 and 3 are time charts showing the relationship between the displacement pattern of the electrode and the welding current. FIG. 4 is a perspective view showing the material to be welded. FIG. 5 is a characteristic diagram of the tensile breaking load with respect to the maximum displacement of the electrode according to the secondary inspection method. FIG. 6 is a characteristic diagram of the tensile breaking load with respect to the sum of the maximum displacement amount and the shrinkage amount of the electrode according to the inspection method of the present invention. FIG. 7 is a characteristic diagram of the tensile breaking load with respect to the shrinkage amount of the electrode according to the inspection method of the present invention. FIG. 8 is a side view showing another example of welding according to the present invention. In the figure, 1, 2
is a material to be welded, and 3 and 4 are electrodes. Diamond diagram Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. Both inner surfaces of a first material to be welded and a second material to be welded are joined, both outer surfaces of the first and second materials to be welded are sandwiched between a pair of electrodes, and the Pressure is applied to a pair of electrodes in a direction sandwiching the first and second materials to be welded, and electricity is applied between the pair of electrodes to weld both inner surfaces of the first and second materials to be welded. In resistance welding, the amount of maximum thermal expansion of at least one of the first and second materials to be welded that occurs during the energization period;
The amount of contraction of at least one of the first and second materials to be welded that occurs during the energization period after at least one of the second materials to be welded has reached its maximum thermal expansion, and A method for inspecting a resistance welded part, characterized in that the state of the welded part of the first and second materials to be welded is tested based on the sum of the amount of expansion and the amount of contraction. 2 Both inner surfaces of the first and second materials to be welded are joined, both outer surfaces of the first and second materials to be welded are sandwiched between a pair of electrodes, and the pair of electrodes is connected to the In resistance welding, the first and second materials to be welded are pressurized in a direction in which they are sandwiched, and current is applied between the pair of electrodes to weld both inner surfaces of the first and second materials to be welded. , the first material that occurs during the energization period after at least one of the second materials to be welded has reached its maximum thermal expansion.
, the amount of shrinkage of at least one of the second materials to be welded is determined, and the state of the welded portion of the first and second materials to be welded is inspected from the value of the amount of shrinkage. Inspection method for resistance welds.