Cracking reason of welded joint of steam header in cement plant

The cracking phenomenon of the inner surface of the weld occurred during the operation of the steam header in a cement plant. The causes of weld cracking were analyzed by means of macroscopic observation, mechanical property test, metallographic examination, scanning electron microscopy and energy spectrum analysis, X-ray diffraction and other methods. The results show that the weld spacing in the repair welding area of the cylinder was too small, which led to the formation of overheating zone in this area and the mechanical properties of the material decreased. There were misalignment and undercut defects on the weld surface, and welding residual stress was formed locally. There were a large number of alkali metal salts in the steam, which formed an alkaline corrosion environment in the material. Under the combined action of welding residual stress and alkali metal environment, the weld seam underwent alkali stress corrosion cracking.