How to produce welding crack of laser welding equipment in Suzhou?

Suzhou laser welding equipment uses high-energy pulsed laser to focus and melt the target metal for welding between workpieces. The effect of this new welding technology is very good, but if the operation is improper, it will also cause hot or cold cracks. So how does Suzhou laser welding machine produce welding crack?

1. Metallurgical Factors

The unbalanced rapid heating and rapid cooling characteristics of laser welding make the whole joint in a complex stress state, which constitutes the mechanical factors of joint cracking; Laser welding is also the synthesis of a series of unbalanced processes. In the process of rapid metallurgical solidification, the inhomogeneous distribution of components and the hardened structure with low crack resistance will inevitably appear, which constitute the metallurgical factors to promote crack initiation.

2. Mechanical factors

There are mainly three kinds of cracks in the welding process of laser welding machine: product crack, liquefying crack and reheat like crack. The crystal crack is related to the inhomogeneity of composition in the macro region of the weld. The central region of the weld is the place where the liquid phase crystallizes the latest. The columnar crystals on both sides of the weld meet here. At the same time, a large number of impurities with low melting point also accumulate here, forming the centerline segregation, thus reducing the bonding strength. Under certain mechanical conditions, the cracks are generated in this part.

After the generation of cracks, we need to find and solve in time, so how to reduce the generation of laser welding machine welding cracks? There are two main measures: more knowledge of laser welding equipment

1. Changing the parameters of laser welding machine

The main reason of hot crack in pulse laser welding of Suzhou laser welding machine is: in the solidification process after laser welding, the weld passes through the temperature zone with low plasticity of metal, which is brittle temperature zone. The weld metal crystallizes under the action of tensile stress. This kind of tensile stress is caused by the reason that the welded metal is difficult to contract. The existence of tensile stress causes the elastic-plastic deformation of weld. If the weld metal of the welding equipment is in the brittle temperature zone, the plastic deformation exceeds the plasticity of the metal, and cracks are formed.

2. According to the nature of the crack, the alloy system of the material can be improved reasonably

The reason of cold crack: during the cooling process of pulsed laser welding, martensite structure is formed in the near seam area, and the stress state of welding stress and microstructure stress superimposed together is also formed. The metal with martensite structure has high strength and low plasticity, and residual stress appears during the cooling process of welding metal. The stress state of welded joint of ferritic or austenitic quenched steel is characterized by the formation of longitudinal compressive stress near the weld zone, which is caused by martensitic transformation in this zone during welding. These kinds of stresses will produce cold cracks.

The reason of hot crack: during laser welding, the hot crack depends on the chemical composition of weld metal and near weld zone, the conditions and characteristics of crystallization process, the extent of chemical and physical micro inhomogeneity, the size and growth rate of deformation, etc.

At present, the mechanism of crystal crack formation is described as follows: in the solidification process of plate bending machine, the weld of laser welding machine passes through the temperature zone with low plasticity of metal, which is the brittle temperature zone. The weld metal crystallizes under the action of tensile stress. This kind of tensile stress is caused by the reason that the welded metal is difficult to contract. The existence of tensile stress causes the elastic-plastic deformation of weld. If the weld metal of the welding equipment is in the brittle temperature zone, the plastic deformation exceeds the plasticity of the metal, and cracks are formed.