1、 Precision resistance spot welding
The above elements are related to the heat generation Q and heat generation location, which means that the factors affecting the welding effect during spot welding include: current I, energization time t, contact resistance R, current density (electrode tip), and electrode material. The contact resistance R decreases with the increase of applied pressure. The above elements are known as the five major elements of resistance spot welding.
The resistance caused by the thin oxide layer generated on the surface of the workpiece (skin resistance) and the resistance caused by the cross-section of the current flow (concentrated resistance).
3、 The role of electrodes
1. Conduct high current.
2. Apply pressure.
3. Improve the cooling effect of welding points.
4. Stabilize the current density.
The electrode has the above functions, and here we will explain the current density related to quality management.
Current density refers to the value of current per unit cross-section. If the current density is kept stable, welding defects can be prevented. Due to the need to conduct high currents (electrode action 1), the top of the electrode will generate heat; Due to the need for pressure, the electrode tip will widen and the current density will decrease. Therefore, as the number of welding cycles increases, the weld nugget will become smaller (poor welding). Therefore, electrode management (replacing or grinding the electrode after a certain number of welding cycles) becomes very important in welding quality management.
4、 Induction of Resistance Spot Welding Principle
1. Resistance spot welding method is a metal connection method that uses the resistance of the workpiece itself, the applied pressure on the workpiece, and the large current conducted to generate Joule heat at the contact part of the workpiece and perform melting.
2. The five key factors that determine welding quality:
[1] Current value
[2] Power on time
[3] Add pressure
[4] Current density
[5] Electrode material
5、 Selection of welding specifications
5-1. Selection of electrode materials
Principles of Selection:
① Workpieces with high intrinsic resistance ->Choose materials with low intrinsic resistance as electrodes
② Workpieces with low intrinsic resistance ->Choose materials with high intrinsic resistance as electrodes
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