The potential difference between the weld seam of HFW welded pipe
and the heat affected zone and the base metal is the main cause of groove corrosion; through effective heat treatment, the microstructure of the weld, heat affected zone and the base metal can be uniform and grain refinement can be significantly reduced. Groove corrosion sensitivity coefficient; different heat treatment conditions, anti-groove corrosion sensitive properties for the quenched and tempered heat treatment> (medium frequency induction, resistance furnace) heating + water cooling> welding state.
HFW welded pipe has been widely used in downhole casing and oil and gas gathering pipelines because of its advantages such as economical efficiency and high dimensional accuracy. However, due to the difference in electrochemical performance between the weld zone and the base metal zone, the HFW welded pipe is prone to weld-groove-like selective corrosion under the service environment. Therefore, it is of great significance to study the electrochemical behavior of the groove corrosion of the welded pipe, the relationship between the heat treatment process and the microstructure, and to obtain a method for reducing the corrosion sensitivity of the groove of the welded pipe. The author chooses HFW welded pipe as the research object to study the effect of different heat treatment processes on the corrosion of the welded pipe groove, and provides a reasonable basis for effectively controlling the corrosion resistance of the HFW welded pipe against trenches.
The average values of channel corrosion sensitivity coefficient α of HFW pipes under different heat treatment processes were 1.32, 1.21, 1.18, 1.14 and 1.12, respectively. The non-heat-treated specimen has the highest sensitivity to trench corrosion; the material is austenitized by heating at intermediate frequency and resistance furnace, and after the water-controlled cold and heat treatment, the trench sensitivity of the weld is reduced.