Hot-dip aluminizing technique

Abstract

The invention relates to a hot-dip aluminizing technique for a heat exchanger tube bundle, which is characterized by comprising the following steps: aluminizing a heat exchanger tube bundle in an aluminum pot at 650-680 DEG C for 30-60 minutes; rotating and reciprocating the tube bundle in the aluminizing process; cooling the aluminized heat exchanger tube bundle; eliminating residual stress in the salt pan at 500 DEG C for 8 hours to implement high temperature annealing; increasing the flowability of the molten salt at 700-750 DEG C, wherein the melting point of the molten salt is 650 DEG C; and contacting the tube bundle in the rotating and reciprocating state with the salt liquid, ensuring uniformity and conformity of various components in the salt pan, and clearing impurities suspended in the salt liquid. The invention enables the heat exchanger tube bundle to have corrosion resistance, eliminates the welding and expanded joint residual stress, greatly controls the generation of stress corrosion, does not generate crevice corrosion, can eliminate induced vibration of the tube bundle, can not easily generate scale deposit in the application process, and enhances the service performance of the heat exchanger.

Description

technical field [0001] The invention relates to a process method for performing hot-dip aluminum plating on heat exchanger tube bundles. Background technique [0002] At present, domestic heat exchangers are widely used, and the tube bundles of heat exchangers are mostly made of carbon steel. Because the working medium of heat exchangers contains inorganic salts, sulfides, nitrides, organic salts, oxygen, carbon dioxide, moisture, etc. Corrosive impurities are affected by the oxygen polarization of dissolved oxygen in the cooling water, and the corrosion is extremely serious, so there is a low service life. The domestically produced tube sheets or heat exchange tubes produce residual welding stress near the welding joint or expansion joint through welding, expansion joint or expansion welding, or residual expansion tensile stress, and the tensile stress caused by the working pressure during equipment operation , so that the tube sheet and heat exchange tube joints form a vu...

AI Technical Summary

Problems solved by technology

[0002] At present, domestic heat exchangers are widely used, and the tube bundles of heat exchangers are mostly made of carbon steel. Because the working medium of heat exchangers contains inorganic salts, sulfides, nitrides, organic salts, oxygen, carbon dioxide, moisture, etc. Corrosive impurities are affected by the oxygen polarization of dissolved oxygen in the cooling water, and the corrosion is extremely serious, so there is a low service life

The domestically produced tube sheets or heat exchange tubes produce residual welding stress near the welding joint or expansion joint through welding, expansion joint or expansion welding, or residual expansion tensile stress, and the tensile stress caused by the working pressure during equipment operation , so that the tube sheet and heat exchange tube joints form vulnerable areas, which are prone to stress corrosion cracking in corrosive media

The gap that exists during the welding of the heat exchange tube and the tube sheet allows the electrolyte solution to enter the gap and stagnate in it, which intensifies the corrosion