3. Grain size
The grain size of the metal is related to the heat treatment temperature and the time for maintaining the same temperature. The grain size of the annealed seamed stainless steel pipe and the seamless stainless steel pipe is the same. The grain size of the weld is smaller than the grain size of the metal being welded if the seamed pipe is subjected to the minimum cold treatment, otherwise the grain size is the same.
4. Pipe strength
The strength of the pipe depends on the alloy composition, so seamless stainless steel pipes and seamed stainless steel pipes containing the same alloy and the same heat treatment are essentially the same strength. After tensile testing and three-dimensional vibration testing, the tear of the seamed stainless steel pipe almost always occurs away from the welding point or the heated area. This is because there are fewer impurities and a slightly higher nitrogen content at the weld, so the strength of the weld is better than other parts. However, ASME believes that seamed stainless steel pipe can only withstand 85% of the allowable pressure, mainly because the data was collected earlier than the improved welding equipment in use today.
