The customer size strip lamination steel sheet has a low carbon content, generally 0.18% or less, its high strength and good mechanical properties, by adding various heat treatments through alloying elements, high quenching and tempering strength, and good toughness. The resulting low carbon improvement, low carbon martensite and a portion of the lower bainite obtained.
The complexity of such a composite steel plate alloy system, the hardening is large, and the softened HAZ of the heat-affected zone is a customer size strip lamination steel sheet which is softened by customizable size due to the accumulated material which is heated and whose temperature is usually higher than the tempering temperature range. The softening of the weld heat affected zone without quenching and tempering is an unavoidable problem. The task of the welding process parameters is to control the heat input to obtain a good softened zone width and a suitable degree of softening.
Welding cold cracking and embrittlement in the heat-affected zone are two contradictory aspects, and the combination of the same situation produces this contradiction around the cooling rate. The customer size strip lamination steel sheet has large hardenability and large cold cracking tendency, but due to low carbon content, it is welded and formed with high-transition temperature low-carbon martensite, and cooling is relatively slow at this temperature, martensite is produced. "Self-tempered" cold cracks can be avoided. If such a fast martensite transformation to martensite does not "self-tempering" cold cracking tendency, it must be increased
In order to obtain an appropriate cooling rate and control the heat affected zone, these factors must take into account the soldering method, solder matching of the heat input, preheating and softening of the interlayer temperature.