Sulfur segregation bands
Sulfur segregation stringers are line-shaped accumulations of manganese sulfides and accompanying elements parallel to the forming direction, caused by non-uniform solidification. They cause reduced toughness in the transverse direction.
Physical-Chemical Mechanism of Action
Sulfur segregation streaks form when manganese sulfides and accompanying elements concentrate at certain locations during forming. This happens due to uneven solidification, where certain areas solidify faster than others. The concentration of sulfur and manganese leads to local segregation and the formation of streak-like structures parallel to the forming direction.
Metallurgical Relevance & Welding Risks
Sulfur segregation streaks can reduce the material's toughness in the transverse direction. This can lead to cracks and deformations, especially when the material is under mechanical stress. During welding, this can cause weak points in the weld, as the segregation streaks interfere with stress relief.
Workshop Practice & Action Instructions
To minimize sulfur segregation streaks, clean the material well before forming. You can achieve even solidification through controlled forming speeds and temperatures. When welding, it's important to keep the voltage and travel speed optimal to avoid forming segregation streaks. In general, set the temperature and voltage so no local hardness differences occur.