Spot welding specification of spot welding machine refers to the synthesis of process parameters that determine the process during the completion of a spot welding cycle. Welding specification is one of the important factors to determine the welding quality. When spot welding, the welding current is large and the power on time is short. Usually, it is customary to call a power on a current pulse. Each solder joint needs one or several main pulses to form the nugget. According to the requirements of material spot welding, sometimes there are auxiliary current pulses such as preheating and afterheating, as well as step electrode pressure or saddle electrode pressure. Therefore, there are single pulse specifications, double pulse specifications, multi pulse specifications and variable pressure specifications.
Spot welding specification parameters mainly include welding current, welding time, electrode pressure and electrode end size. The following focuses on the electrode pressure of the lower spot welding machine. If the electrode pressure is too large or too small, the load-carrying capacity of the solder joint will be reduced and the dispersion will be increased, especially the tensile load. When the electrode pressure is too small, due to the lack of plastic deformation range and deformation degree of the metal in the welding area, the heating speed increases due to the excessive current density, and the plastic ring is too late to extend, resulting in serious splashing. This not only changes the shape and size of the nugget, but also pollutes the environment and is not safe, which is absolutely not allowed. If the electrode pressure is too large, the contact area will increase, the total resistance and current density will decrease, and the heat dissipation of welding will increase, so the size of nugget will decrease, and in serious cases, there will be incomplete penetration defects.
It is generally considered that when increasing the electrode pressure, the welding current or welding time should be increased properly to keep the heating degree of the welding area unchanged. At the same time, due to the increase of pressure, it can eliminate the bad effects caused by the insufficient assembly clearance and rigidity of weldment. Therefore, not only the strength of solder joints remains unchanged, but also the stability is greatly improved. But the increase of electrode pressure is limited by the power of welding machine.
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