What is the effect of sulfur (S) in 16Mo3 steel plate on weldability?

Sulfur is often present in the form of iron sulfide in 16Mo3 steel, and it is distributed in the grain boundary in a network, thus significantly reducing the toughness of the steel. The eutectic temperature of iron and iron sulfide is relatively low (985°C). Therefore, during hot working, since the processing start temperature is generally 1150 to 1200°C, the eutectic of iron and iron sulfide has already melted, resulting in cracks during processing. This phenomenon is the so-called "hot brittleness of sulfur". This property of sulfur causes hot cracks in steel during welding. Therefore, the sulfur content in steel is generally strictly controlled. The main difference between ordinary carbon steel, carbon steel and steel lies in the content of sulfur and phosphorus.