Seam welding head forming process (intermittent), each solder joint also should pass preloading, electricity, heating and cooling crystallization three stages. But because the roller when the seam welding machine electrodes and welding pieces of the relative position between the rapid change, make the three stage not as obvious as to distinguish when spot welding. Can be thought of: 1) under the wheel electrode pressure directly, the metal is heated by electricity, in the "electrical heating stage". 2) entering roller under the electrode adjacent metal, preheating and roller electrode parts by pressure effect, in "preloading" stage. 3) just came out from the roller under the electrode adjacent metal, on the one hand begins to cool, and at the same time by electrode part of roller pressure effect, is in the "cooling crystallization phase". Therefore, is in the midst of a welding roller under the electrode area and adjacent it on both sides of the metal material, at the same time will be at different stages, respectively. For weld on any of the solder joints, from under the wheel by is also undergoing the process of the "preloading, electrical heating, cooling crystallization" three stages of the process. Because the process is under the dynamic, during the period of preloading and cooling crystallization pressure enough, should make the quality of seam welding head is usually better than spot welding machine time, easy to appear crack, shrinkage cavity defects, etc.
According to the wheel was rotated electrodes (mobile) weldment and welding current through the cooperate way (electricity) of machine, electricity, can be divided into the following three.
1. Straight seam welding
Roller continuous rotating electrode, the welding speed move, welding current through continuously, each half cycle to form a solder joint. Welding speed can reach 10 ~ 20 m/min due to poor surface quality of the weld, the practical application is limited.
2. Intermittent seam welding
Weldment continuous constant movement, through the discontinuous welding current, every "connect - off" form a solder joint. According to the thickness of welding speed can reach 0.5 ~ 4.3 m/min is used widely, mainly in the production of black metal gas, water, oil seal weld.
3. Step-by-step welding
Weldment intermittent movement, through welding current in the weldment resting, every "open - shift" form a solder joint, and forging pressure. Formation and spot welding machine joint is very approximate. Welding speed is low, only 0.2 ~ 0.6 m/min is only used in the manufacture of aluminum alloy and magnesium alloy such as seal weld.
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