What is the difference between the stainless steel pipe welded pipe and seamless pipe?
Welding performance: chemical composition of seamed pipe and seamless pipe are different. The production of seamless steel components only meets the basic requirements of astm. The production of seamed tube steel containing suitable for chemical composition of welding. For example, the mixing of silicon, sulfur, manganese, oxygen, and a certain proportion of elements such as the triangle ferrite can produce a welding flux which is easy to transfer heat during welding, so as to make the whole weld be welded well. The lack of steel pipe above the chemical components, such as seamless tube, can produce all kinds of unstable factors in the process of welding, welding and welding penetration is not easy.
Concentricity: seamless tube manufacturing process is the temperature of 2200 degrees F in stainless steel billet stamping a hole, at this high temperature, tool steel by stamping and drawing become soft and spiral form from the hole. Thus, the wall thickness of the pipeline is uneven and the eccentricity is high. Thus ASTM allows seamless pipe wall thickness ratio of the wall thickness difference of seamed tube. Through the seamed tube cold rolling plate precision (per roll width is 4-5 feet) made. These cold rolled plates usually have a maximum wall thickness of 0.002 inches. The steel plate is cut into a width of PI D, in which D is the outer diameter of the pipe. Tube wall thickness tolerance is very small, and the entire circumference of the wall thickness is very uniform.
Grain size: usually, the grain size of the metal is related to the heat treatment temperature and the time at which the metal is kept at the same temperature. Therefore, the welded pipe and seamless tube annealing of the same grain size. If the minimum tube cold treatment, the grain size of the weld metal is smaller than the grain size, welding or grain size is the same.
Seamless tube is a strip of steel with a hollow cross section and no seams at all. The general is rolled into a cylindrical tube plate welding.
Strength: the strength of the pipeline in the composition of the alloy and alloy containing the same and the same heat treatment of seamless tube and seamed tube essentially consistent strength. After the tensile test and three-dimensional vibration test, tube tearing almost all occurred in the welding point or away from the heated area where. This is because there is little impurity in the weld and the nitrogen content is slightly higher, so the strength of the welded joint is better than that of other parts. However, the ASME Boiler and Pressure Vessel Association believes that the seamed tube can withstand 85% of the allowable pressure, which is mainly due to improved welding equipment data collection prior to today. The provisions of ASME 100% completely under license by ultrasonic testing pressure tube. Similarly, Europe and Asia also stipulates that can ensure the quality of welding performance by eddy current test tube, the eddy current testing is subject to legal procedures and licensed institutions. Trent's eddy current test was approved by the Swedish power division. ASME believes the current loss is relatively small, high-quality performance based on the seamed tube.
