Rust-free nickel alloy steel pipes have two types of products - seamless tubes and sewn tubes. Seamless tubes and sewn tubes vary in general around the world: in the United States, the use of sewing tubes accounts for 95% of stainless steel tubes, in Europe it accounts for 60% of seamless tubes and 75% in Japan. Sales of seam pipes in Europe are now rising sharply, while seamless tubes are falling sharply.
In Asia, Taiwan and Indonesia have significantly increased the production of sewn pipes, resulting in a decline in seamless pipe sales in Japan. The development of sewing tubes began in the United States during World War II. Since almost all of the seamless pipe equipment was from Germany at the time, the United States used its own technology to produce pipelines as the war broke out and new equipment was not available. Trent and Carpenter were pioneers in the development of seam pipe production technology, creating a new industry. After the war Germany and Japan rebuilt their seamless pipe production technology industries, but they were decades behind The United States. Over the past two decades, sewing technology has been distributed to Italy, France, the Netherlands, England, Sweden, Taiwan, Indonesia, India and other small countries and regions.
Around the world, the application of sewing tubes has developed rapidly.
There is a difference between a seam tube and a seamless tube: Concentricity: The manufacturing process for seamless tubes is a hole in the stainless steel billet at a temperature of 2200 degrees F, at which the tool steel is softened and stretched to form from the hole by stamping and stretching. The wall thickness of the pipe is uneven and eccentric. As a result, ASTM allows the wall thickness difference of seamless tube solder to be larger than that of a sewn tube. The sewn tubes are made from precise cold-rolled plates (4-5 feet wide per roll). These cold-rolled plates typically have a largest wall thickness of 0.002 inches. The steel plate is cut into the width of the d, where d is the outer diameter of the pipe.
The tolerance of the thick seam pipe wall is very small, and the wall thickness of the whole circumference is very homogene. Welding performance: Generally there are seam pipes and seamless pipe chemical composition has a certain difference. The steel components for the production of seamless tubes are only the basic requirements for ASTM. Steel, which produces seam pipes, contains chemicals suitable for welding. For example, silicon, sulfur, manganese, oxygen and elements such as trigonoids can be mixed in a certain proportion to produce an easy-to-transfer heat welding melt during the welding process, so that the entire weld is welded through.
Steel pipes that lack the above chemical composition, such as seamless pipes, can produce various unstable factors during welding, are not easy to weld and are not transparent. Grain size: Usually, the grain size of a metal is related to the heat treatment temperature and the time it takes to maintain the same temperature. Therefore, the annealing treatment of sewing tubes and seamless tube grain size are the same.
If a seam tube is treated with minimal cold treatment, the grain size of the weld is smaller than the grain size of the welded metal, otherwise, the grain size is the same. Strength: The strength of the pipe depends on the alloy composition, so that the seamless tube with the same alloy and the same heat treatment and the sewing tube are essentially the same strength. After the pull test and the 3D vibration test, the tearing of the seam tube occurs almost all away from the welding point or the heated area. This is because the welds have fewer impurities and slightly higher nitrogen content, so the welds are stronger than others. However, ASME's Boiler and Pressure Vessels Association believes that seam pipes can only withstand 85% of the licensing pressure, mainly because data is collected earlier than the improved welding equipment used today. ASME requires that 100% of the sewn tubes that pass the ultrasound test are fully subject to licensing pressure. Similarly, Europe and Asia also require that the vortex test has a seam tube to ensure the quality of its welding performance, the vortex test is subject to legal procedures and licensed institutions. Trent's vortex tests were approved by Swedish Power.
ASME believes that the smaller current loss is based on the high quality performance of the sewn tube. Corrosion resistance: The quality of corrosion resistance also depends on the composition of the alloy. The chemical composition of the same seamless tube and completely heat-treated sewing tube corrosion resistance is consistent. The supplementary tests provided by ASTM demonstrate that the corrosion resistance at the welding is equivalent or superior to that of the welded metal. In the environment of acidic chlorides, corrosion at welding sites with sewn tubes that are not fully heat treated will accelerate, but this is only a need for corrosion testing, and the environment is not actually so harsh. Bending and elongation: The elongation at the weld can be verified by the following tests specified by ASTM: bend ingenage 45 degrees, then bend to 90 degrees, and then flatten along the weld; The standard of weld quality is that tearing or intercrystalline separation is not allowed with40 times magnification. The pipe bending radius is controlled by the composition of the alloy, and the minimum bending radius is generally 2D. The ideal welding condition is that the weld is neutral or under pressure.
Furthermore, the pipe should be annealed to reduce its hardness, thereby improving bending performance.
Price: The price of a sewing tube is usually only half that of a seamless tube. Wall thickness/diameter: Thin wall tubes with small thickness/diameter values are best produced by welding.
Thick wall tubes with large thickness/diameter values are best made of stamping. Comprehensive quality: Generally, the quality of the seam pipe is better than the seamless tube, because the seam pipe is made of a precise cold-rolled plate that has been tested and therefore any defects are limited to the welding. Seamless tubes are punched by stainless steel blanks, resulting in many tears in the walls of the tubes formed by the squeeze. The vortex test showed that the secondary rate with the seam tube was usually lower than the secondary rate of the seamless tube. With ultrasonic testing, the background noise of the seamless tube is so loud that it is difficult to detect its defects.
The background noise of the seam pipe is very low and the defect is easy to find. Summary: Comprehensive comparison of the above performance, there are seam pipe equivalent or better than seamless tube, and low price.
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