The stainless steel seamless pipe is manufactured by punching a hole in a stainless steel billet at a temperature of 2,200 °F. At this high temperature, the tool steel is softened and spirally formed from the hole by punching and drawing. In this way, the wall thickness of the pipe is uneven and the degree of partial pain is high. Therefore, astm promises that the wall thickness difference of the seamless steel pipe is larger than the wall thickness of the seamed pipe.
There are generally certain differences in the chemical composition of the seamed tube and the seamless tube. The steel components that produce seamless pipes are only the basic requirements for reaching astm. Steels with seams contain chemical components suitable for welding. For example, the mixing of silicon, sulfur, manganese, oxygen, and elements such as triangular ferrite in a certain ratio can result in a weld melt that tends to transfer heat during the welding process to allow the entire weld to penetrate.
The seamed tube is made from an accurate cold rolled sheet (4-5 feet per roll width). These cold rolled sheets generally have a maximum wall thickness difference of 0.002 inches. The steel plate is cut to a width of πd, during which d is the outer diameter of the pipe. The public service with the wall thickness of the seam is small and the wall thickness of the entire circumference is very uniform.
Steel pipes with fewer chemical components, such as seamless pipes, have various unstable elements in the welding process, and are not easily welded and cannot be welded. 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 inherently strength.
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