A Diffusion Welding Process for Heat Exchanger Core

Abstract

The invention discloses a diffusion welding process of a heat exchanger core, which comprises the following steps: (1) Pretreatment before welding: sending the assembled heat exchanger core into a diffusion welding furnace, and vacuumizing the furnace to 0.01 Below Pa; (2) Diffusion welding: heat up to 800-850°C at a rate of 15-20°C / min, hold for 30 minutes; The previously applied pressure was 8-9.5MPa, and then reduced to 4-6MPa in the next 1h; then vacuum cooled to room temperature; (3) Post-weld heat treatment: raise the temperature of the heat exchanger core to 1150-2000°C, and keep it warm for more than 20h. Then cool down by water quenching. The invention controls the welding temperature, diffusion time, pressure and other parameters, and adds the post-diffusion welding heat treatment step at the same time, reduces the brittle phase that is easy to appear in the diffusion welding, and improves the quality of the welding joint of the heat exchanger core.

Description

technical field [0001] The invention relates to a stainless steel heat exchanger suitable for petrochemical, aerospace, gas turbine, high-temperature gas-cooled reactor and other fields with high-temperature and high-pressure service requirements, in particular to a diffusion welding process for the heat exchanger core. Background technique [0002] Compact and high-efficiency heat exchangers are widely used in petrochemical, aerospace and other fields. In a special service environment, such as a high-temperature gas-cooled reactor, the service temperature of the heat exchanger reaches about 600°C, and the pressure reaches about 7MPa. It also needs to withstand cyclic thermal stress, and has high heat transfer performance and compactness. These requirements limit The use of compact and high-efficiency heat exchangers in similar harsh conditions. The plate-fin heat exchanger is formed by superimposed brazing, and has limited high-temperature and high-pressure service capacit...

AI Technical Summary

Problems solved by technology

The longer the welding time, the higher the welding rate of the joint, but too long holding time will cause brittle phases to form in the joint area, resulting in a decrease in the mechanical properties of the joint

Increased pressure is beneficial to improve welding quality, but too high pressure can easily cause core deformation, so the diffusion welding process is greatly affected by these process parameters

Due to the very high temperature of stainless steel diffusion welding, it is difficult to obtain a stable clamping pressure in this environment, the heating and cooling speed of diffusion welding is greatly affected by tooling, the assembly accuracy is not high, and brittle phases are prone to appear in the process of stainless steel diffusion welding, all of which are Easy to produce welding defects, resulting in reduced yield

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