Seam and Seamless Pipe

Seam and seamless pipe difference
Concentricity: seamless manufacturing process at a temperature of 2200 °f punched a hole in the stainless steel billet, and at this temperature, tool steel becomes soft and stamped and drawing a spiral shape from Kong Zhongcheng come out. Such non-uniform wall thickness of the pipe and eccentric high. Thus astm allow seamless tube wall thickness difference than to have a large difference in the thickness of the pipe joints. Pipe joints is (4-5 feet per roll width) made by precision cold-rolled sheet. Cold-rolled sheet is usually the biggest difference between the wall thickness of 0.002 inches. Steel plate was cut into a width of πd, where d is the outer diameter of the pipe. Slit pipe wall thickness tolerance is small, and the entire circumference of the wall thickness is very uniform.

Welding performance: general chemical composition of seamless pipe and tube joints have some differences. Production of seamless steel components simply meet the basic requirements of astm. It produced the steel pipe joints contain chemicals suitable for welding. Such as silicon, sulfur, manganese, oxygen, and other elements of the triangle ferrite produces an easily transferring heat weld material during the welding process by mixing a certain proportion, so that the entire weld penetration. Missing more than the chemical composition of the steel pipe, seamless pipe, for example, the welding process will produce a variety of uncertainties, not easy to weld and solder impervious.

Grain size: typically, the metal grain size and heat treatment temperature and time to maintain the same temperature related. Thus, annealed and slit pipe seamless grain size are the same. If the pipe joints with a minimum of cold treatment, the weld on the grain size is smaller than the grain size of the weld metal, otherwise, the grain size is the same.

Strength: the strength of the pipeline depends on the alloy composition, which contains the same alloy and heat treatment of the same seamless and seamed pipes essentially uniform intensity. After tensile tests and three-dimensional vibration testing, pipe joints tear occurs almost exclusively in the area away from the welding point or heat the place. This is because the weld fewer impurities and the nitrogen content is higher, and thus the strength of the weld is better than the other region. However asme boiler and pressure vessel Association believes pipe joints can only bear 85% of the allowable pressure, mainly due to the collection of data as early as from the improved welding equipment in use today. asme provisions by 100% ultrasonic testing pipe joints are fully licensed to withstand pressure. Similarly, Europe and Asia also provides through the slit pipe eddy current testing can ensure quality, eddy current testing is required by legal procedures and permit its institutions were weldability. trent's eddy current testing by the Swedish licensing power section. asme think current loss is based on a smaller pipe joints high performance.

Corrosion resistance: resistance to corrosion is good or bad depends on the composition of the alloy of the same. The same chemical composition of seamless pipe and heat treatment have been completely slit pipe corrosion resistance is consistent. Supplementary test astm provide proof weld corrosion resistance equivalent to or better than the metal being welded. Under acidic chloride environments, incomplete heat treatment at a seam welded pipe corrosion will accelerate, but this is only required corrosion tests, in fact, the environment is not so bad. Bending and stretching properties: extension of the weld may be prescribed following tests to verify through astm: bent 45 °, then bent to 90 °, and then along the weld flattening; then turn around pipe joints to repeat the steps above to the weld curved inner diameter reaches 180 °. Weld quality standard is adopted at a magnification of 40 times between the situation allowed to tear or separation of the grain. Pipeline bend radius is controlled by the composition of the alloy, the general minimum bend radius 2d. Seam welding conditions are ideal in a neutral or compression. Further, the pipe should be annealed to reduce its hardness, thereby improving the bending performance.