Difference between large-diameter LSAW steel pipe and SSAW steel pipe

Large-diameter LSAW steel pipe and SSAW steel pipe are both welded steel pipes. They are widely used in national production and construction. Large-diameter LSAW steel pipe and SSAW steel pipe have many differences due to different production processes. The following specifically discusses the difference between large-diameter LSAW steel pipe and SSAW steel pipe.

The production process of LSAW steel pipe is relatively simple. The main production processes are high-frequency welding large-diameter LSAW steel pipe and submerged arc welding large-diameter LSAW steel pipe. Straight seam pipe has high production efficiency, low cost and rapid development.

The strength of spiral welded pipe is generally higher than that of LSAW steel pipe. The main production process is submerged arc welding. SSAW steel pipe can use the same width of billet to produce welded pipes with different diameters, and can also use narrower billets to produce welded pipes with larger diameters. However, compared with the same length of straight seam pipe, the weld length increases by 30~100%, and the production speed is lower. Therefore, smaller-diameter welded pipes are mostly welded by straight seam welding, while large-diameter welded pipes are mostly welded by spiral welding. When producing large-diameter LSAW steel pipes in the industry, T-welding technology is used, that is, short sections of large-diameter LSAW steel pipes are butt-jointed to meet the length required by the project. The probability of defects in T-welded large-diameter LSAW steel pipes is also greatly increased, and the welding residual stress at the T-weld is large. The weld metal is often in a triaxial stress state, which increases the possibility of cracks.

General process of LSAW steel pipe production
LSAW steel pipes are increasingly used in industrial production to replace seamless welded pipes due to their high yield rate, low price and gradually improved performance. At present, most domestic welded pipe companies can only produce small and medium-diameter welded pipes. Because foreign companies keep technology confidential in my country and only sell equipment but not technology, large-diameter welded pipe manufacturers in China are still unable to independently develop corresponding welded pipe production processes and design rollers. The development of new processes and new products still depends on foreign companies. Research on welded pipe production processes and roller design can improve the production technology level and international competitiveness of my country's welded pipes and meet the requirements of national economic development.
The forming methods of welded pipes mainly include continuous roll forming and row roll forming. At present, the more advanced one in the world is flexible forming. The advantage of continuous roll forming is good forming effect, but the disadvantage is poor roll versatility, large consumption, high number of spare rolls and high production cost. The advantage of row roll forming is good versatility, but poor forming effect. Research shows that row roll forming can only produce thin-walled steel pipes, and it is easy to produce instability. Flexible forming is a mixed forming method, which has the advantages of good versatility of row roll forming and high quality of continuous roll forming. Its disadvantage is that it has high requirements for roll processing accuracy and high control accuracy of structural adjustment. At present, this technology has been adopted on large-diameter welded pipe mills introduced in China. China currently does not have the ability to produce large-diameter welded pipe mills using flexible forming methods.
Welded pipe production occupies an important position in steel pipe production. The output of welded pipes in foreign industrial countries generally accounts for 60%-70% of the proportion of steel pipes, and modern welded pipe technology is developing in the direction of improving the quality of pipe blanks, developing forming technology, controlling welding processes, strengthening weld processing, and improving online detection methods.
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