What is the blowhole in welding?

When welding, the bubbles in the molten pool failed to escape during solidification and remained, which is called blowhole. The pores on the weld surface are called surface pores, and the pores inside the weld are called internal pores.

The causes of blowholes are: the oil stain, dirt, rust, oxide scale and oxide film on the surface of welding wire and weldment are not cleaned up; The purity of acetylene or oxygen is too low; Improper selection of flame properties; Flux is wet or of poor quality; The swing speed of the welding gun is fast and the amplitude is large; The filling of welding locust is uneven; The wind around the welding site is strong; The welding speed is too fast, and the flame leaves the molten pool prematurely; The chemical composition of welding wire and base metal does not match.