Heat exchangers, surfacing, heat treatment, ferrite testing
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This post was last edited by *nchen on 2015-7-28 at 13:34. There is a heat exchanger with tube banks that have been surfaced with weldments (carbon steel + stainless steel); there are partition plates in between, and the tube banks require heat treatment. Question: 1. According to the technical requirements for the tube banks, heat treatment is to be carried out after the surfacing of the transition layer is completed. . . . . So, after welding the face layer and the partition plates, does the tube box need to be heat-treated again? 2 Before heat treatment, it is necessary to determine the ferrite content – is this really required? When should it be done? What is the purpose? Thank you
This medium shouldn’t be necessary, right?
The determination of ferrite content must be carried out before heat treatment (the ferrite content decreases after heat treatment). Generally, it is not necessary to measure the ferrite content in the transition layer, unless it is a single-layer surfacing.
Generally, ferrite determination is carried out on the facing layer. Stress-relief heat treatment must definitely be carried out after welding the surfacing transition layer. However, whether heat treatment is necessary after welding the surface layer and partitions depends on the requirements of the equipment. If stainless steel is used for surfacing due to its high-temperature resistance, heat treatment is possible; but if corrosion resistance is the priority, it is better not to undergo heat treatment, as it can affect the corrosion resistance properties.