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1、 Welding quality inspection

There are generally two methods for inspecting welding quality: visual inspection and destructive inspection.
Visual inspection is the inspection of each item shown in Figure 1. If using microscopic (mirror) photographs for metallographic examination, it is necessary to cut and extract the weld nugget and grind the corrosion (as shown in Figure 2). However, it is not sufficient to draw a conclusion based solely on visual inspection. Please conduct destructive experiments.
Destructive testing is usually carried out by tearing open the welding base material for confirmation, as shown in Figures 3 and 4 (circular holes appear on one side and button shaped residues appear on the other side)
In addition, there is also a method of using a tensile tester for tensile strength testing.

2、 Quality assurance measures
Although resistance spot welding is the most suitable welding method for mass production, improper quality management can cause huge losses. At present, due to the inability to achieve online non-destructive welding quality inspection, it is necessary to strengthen the management of quality assurance.
1. Pressure detection
The heat generation of welding is greatly affected by the contact resistance between the electrode and the workpiece. During the welding process, the pressure must remain constant, so it is necessary to frequently use a pressure tester to test the welding

2. Electrode grinding
The increase in welding frequency will aggravate the wear on the electrode surface. Rough electrode surface can cause splashing and rough marks on the workpiece surface, affecting the appearance of the workpiece. Therefore, it is necessary to prepare more ground electrodes and replace them appropriately according to the number of welding cycles. It is better to use the discarded workpiece for debugging before using the new electrode.
3. Electrode overheating
Overheating of electrodes not only shortens their lifespan but also leads to uneven welding quality of workpieces.
4. Workpiece accuracy
The phenomenon of welding defects often occurs due to neglecting changes in workpiece thickness, coating thickness, metal composition, etc. The stability of the quality of the workpiece itself is also an important factor affecting the welding quality.
5. Current monitoring
Current monitoring is essential for welding. The main factors affecting current changes include: fluctuations in power supply voltage, overheating caused by overloading of welding machines resulting in reduced current output, poor contact of workpieces leading to reduced current, and poor performance of welding machines.
       
In order to prevent adverse welding results caused by the above reasons, it is necessary to regularly monitor the welding current. If the monitoring of welding current can be ensured, other factors that affect welding quality can be easily identified, thereby further improving the reliability of welding quality.