Research Of Low-temperature Toughness Of -70℃～-101℃ Steel SAW Deposited Metal

With the rapid development of "petroleum chemical industry" and "coal chemical industry",-70℃-101℃pressure to the direction of havey-duty and low-temperature, the application of SAW in this field is more and more important. It is difficult to guarantee the low-temperature toughness and its stability. In order to keep higher safety of the low-temperature pressure vessel, domestic manufacturing units put forward higher request of low-temperature toughness of welding deposited metal of low-temperature steel. Because of the vessel is more and more big, the wall thickness of the pressure vessel is more and more thick, the original welding parameter and PWHT cannot meet the requirements of production. Therefore, this paper focus on welding parameter and welding heat treatment process and other factors to the low-temperature toughness of SAW deposited metal of -70℃--101℃steel.There are many factors affects the low-temperature toughness, this paper focuses on the following aspects of SAW deposited metal of -70℃--101℃steel commence special research:study tempering parameter (P) of low-temperature impact toughness of the deposited metal and the relationship of parameter P and low-temperature toughness of the deposited metal, find out that the better temper parameter of -70℃--101℃steel is between 17.24 and 18.5;orthogonal analysis the relationship between temperature, welding current, welding speed and low-temperature impact value of the deposited metal, find out that the interpass temperature greatly affects low-temperature toughness of welding deposited metal of -70℃--101℃steel, recommended interpass temperature is less than 100℃; analyze the relationship of welding power, impact toughness of the deposited metal, tensile strength and hardness of the deposited metal; study the relationship of the contents of O,N of the deposited metal and low-temperature toughness of the deposited metal, and find out that the content of O greatly affects low-temperature toughness of the deposited metal; Using different welding materials, in the recommended welding parameter and PWHT process, the deposited metal of different thickness steel gets good toughness, it indicates that the welding parameter and PWHT process can be recommended to get better low-temperature impact toughness.It has certain effect, through control of Si content in the wire, on deoxidizing the deposited metal, but the increment of O still has a large rage to improve; in addition, there sill needs a further analysis of microstructure and fracture. These will be the key work in the future.