(1) the superior quality of billet High frequency welded pipe steel billet and SMLsteel pipe compared with the chemical composition design is more scientific and reasonable. Special ERW steel pipe has the characteristics of high purity. With S, P, degassing, Ca treatment methods such as S, P content can be controlled under 0.005%, N content can be controlled under 0.008%, the morphology of inclusions can be controlled for the ball, and its quantity is greatly reduced. C content is controlled under 0.1%, welding, including the construction process of ring welding has good welding performance, while the increase of strength by adding Nb, V, Ti micro alloy elements, to prevent the austenitic grain size grew up, at the same time increase the clearance to strengthen to improve the toughness and strength of steel. And SML pipe billet for A3, 20 steel, 16 commonly mh material, such as material purity is poorer, C content is higher, generally around 0.2%, is not conducive to the construction of the ring welding butt joint and strength, but toughness is poor. ERW steel pipe and steel tube billet of SML another big difference is that the former is made of hot-rolled steel strip cold rolling forming, while the latter is the garden of punch forming steel in hot rolling condition. Obviously, the formation of SML pipe hot rolling condition of grain size and organizational weave dense degree there is a difference compared with the ERW pipe, which can cause performance must also is very different. (2) the geometry size advantage In comparison with the data from, or data measured data contrast, ERW steel pipe are higher than the size precision of SML. This is because the steel seamless tube is a garden in the hot rolling unit continuous punch forming, and ERW steel tube is the forming of steel strip in cold rolling condition. ERW in terms of appearance size, by contrast, control is easier to implement than (SML). Because of this, the appearance of the ERW steel tube defects is less, the appearance quality is better than that of SML pipe. In addition, due to the use of computer flying saw, high-frequency welded pipe length rate and high precision of specified length. Due to the high frequency welded pipe is made with high precision of rolling of hot rolled steel belt, easy to control its thickness, according to the requirement of design production wall thickness is thinner and higher grade of steel pipe. Such as tube for west to east gas pipeline project, after a few repeated proof, now basically determined by the level of X70 steel, wall thickness at 14.7 mm, $ 1016 mm steel pipe, steel grade, wall thickness, relatively lower engineering investment, about 5 billion yuan. And wall thickness of the seamless pipe often is limited by perforation technology and the production cost, difficulty of thin-walled steel tube is very high.
