Cracking of steel products during dip galvanizing

The tests were performed on industrial products made of 23MnNiCrMo5-2 steel, characterized by high internal stress generated in their production process during plastic working, heat treatment and calibration. Steel products were subjected to the process of metallization in a zinc bath and in a zinc bath with an addition of 2 wt. % of tin. They were then subjected to a breaking force load. The selected microareas of the resulting fractures were analysed qualitatively and quantitatively. It has been found that in the cases of galvanization of chains in a bath containing an addition of tin no narrowing on the link section was observed, as was the case with fractures of specimens subjected to metallization in a zinc bath. It has been concluded that links broke as a result of cracking and its propagation and penetration of liquid metal into the substrate material during the metallization process. It has also been found that tin concentration at the top of the crack is approximately eight times greater than in the area close to the surface of the coating.