Slit and Seamless Stainless Steel Pipe
Posted: 03/09/2016 05:19:10 Hits: 217
Stainless steel pipe is a hollow long round steel, and is widely used in industrial pipeline and mechanical structure parts such as petroleum, chemical, medical, food, light industry, machinery instrument etc. In addition, as to the bending and torsional strength, it is lighter, and it is widely used in the manufacture of machinery parts and engineering structures. It is used for the production of various kinds of conventional weapons, barrel, shells, etc.
1, the concentricity
Seamless tube manufacturing process is under the temperature of 2200 °, stamping out a hole in the stainless steel billet. Under the high temperature and after the stamping and drawing, the pipe becomes soft and spiral. So the thickness of pipe wall differs and has high degree of eccentricity. Thus ASTM allows the thickness difference of seamless tube more than the thickness of tube wall.
A seam pipe is made by precise manufacture (width is 4 to 5 feet per roll). Usually these manufacture's biggest wall thickness difference is 0.002 inches. The width of the steel plate is cut into the width of πd, where d for pipe diameter. The wall thickness of the slit pipe is very little, and the circumferential wall thickness is even.
2, welding performance
Generally, there are some differences between seamed pipe and seamless pipe in chemical composition. The composition of seamless steel pipe has just reached the basic requirement of ASTM. While the steel use for producing seamed pipe contains chemical composition which is applicable for welding. For example, silicon, sulfur, oxygen and the angle iron, manganese, ferrite and other elements, when mixed together, can produce a kind of weld material easy to transfer heat to make the weld penetration. When lacking chemical composition above, unstable factors in the welding process will arise, and make it hard to weld.
1, the concentricity
Seamless tube manufacturing process is under the temperature of 2200 °, stamping out a hole in the stainless steel billet. Under the high temperature and after the stamping and drawing, the pipe becomes soft and spiral. So the thickness of pipe wall differs and has high degree of eccentricity. Thus ASTM allows the thickness difference of seamless tube more than the thickness of tube wall.
A seam pipe is made by precise manufacture (width is 4 to 5 feet per roll). Usually these manufacture's biggest wall thickness difference is 0.002 inches. The width of the steel plate is cut into the width of πd, where d for pipe diameter. The wall thickness of the slit pipe is very little, and the circumferential wall thickness is even.
2, welding performance
Generally, there are some differences between seamed pipe and seamless pipe in chemical composition. The composition of seamless steel pipe has just reached the basic requirement of ASTM. While the steel use for producing seamed pipe contains chemical composition which is applicable for welding. For example, silicon, sulfur, oxygen and the angle iron, manganese, ferrite and other elements, when mixed together, can produce a kind of weld material easy to transfer heat to make the weld penetration. When lacking chemical composition above, unstable factors in the welding process will arise, and make it hard to weld.
3, grain size
The grain size of the metal is relevant with heat treatment temperature and time maintenance. After annealing treatment, the seamed and seamless steel pipe has the same size. If the seamed pipe uses cold treatment, the grain size of welded part will be less than the size of welded metal; otherwise, the grain size is the same.
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