304 stainless steel, welded to seamless difference in what place?
The strength of the pipeline depends on the alloy composition, which contains the same alloy and the same heat treatment of stainless steel seamless pipe and welded stainless steel pipes essentially consistent strength.After the tensile test and three-dimensional vibration test, welded stainless steel pipes tearing almost all occurred in the region far away from the welding point or local heating. 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, ASME (American Society of Mechanical Engineers) that welded stainless steel pipes 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 permit pressure through ultrasonic testing of welded stainless steel pipe. Similarly, Europe and Asia also stipulates that can ensure the quality of welding performance by eddy current testing of welded stainless steel tube for 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.
The grain size of the metal is related to the temperature of heat treatment and the time of keeping the same temperature. The welded stainless steel pipe and seamless stainless steel tube as the annealed 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.
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.
The seamless tube is made by pressing a hole in a stainless steel billet at a temperature of 2200 degrees F. At this high temperature, the tool steel is made soft and spirally shaped from the hole by stamping and drawing. 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.
