Classification of the hazards of welding defects

1.Non fusion
Welding between the weld channel and the base material or between the weld channel and the weld channel is not completely fused part of the unfused can be divided into bevel unfused, weld channel between the unfused, the root of the weld is not fused, according to the composition of the different between them, divided into white unfused and black unfused.
2. Incomplete penetration
The welding current is too small, the speed is too fast, the groove angle is too small, the root blunt edge is too thick, the arc is too long or partial blowing.
The danger of under-welding depends on the shape, length and depth of the defect, which not only reduces the strength of the weld, but also tends to expand into cracks in the under-welded area, leading to fracture.

3.Slag inclusion
It refers to the defects caused by the residual foreign solid material in the weld metal, and the metal particles remaining in the weld after welding. Slag inclusion is a defect that is easy to appear in the welding process, especially the slag caused by the flux remaining in the weld metal.
Flux inclusion is the inclusion caused by flux remaining in the weld metal and metal particles remaining in the weld metal.
4. Porosity
Porosity refers to the welding process, the molten pool of bubbles in the solidification process failed to escape and the formation of cavities, which can be divided into worm-like pores, pinholes and column holes, pores produced by the part and shape of the inner pores and outer pores of two kinds of pores, pores are due to the gas in the liquid metal melting, reduces the degree of melting of the metal when cooling, some of the gas into the atmosphere to meet the resistance of the metal crystals can not successfully escape and stay in the metal, the formation of Internal porosity.

The main reason for porosity is that the metal or filler material surface rust, oil and other uncleaned electrode, arc energy is too small or welding speed is too fast, the weld metal deoxygenation is insufficient.
Residual porosity in the weld will reduce the effective cross-section of the weld metal, thereby reducing the strength of the welded joint, especially dense porosity will make the weld is not dense, reduce the plasticity of the joint, resulting in leakage at the weld.
Porosity compared with unwelded, less harmful, the standard allows a limited presence, but to strive for welds without porosity or reduce the number of porosity.