Diffusion welding process for heat exchanger core

Abstract

The invention discloses a diffusion welding process for a heat exchanger core. The diffusion welding process comprises the following steps: (1) pre-welding pre-treatment: feeding the well assembled heat exchanger core into a diffusion welding furnace, and vacuumizing the interior of the furnace to be below 0.01 Pa; (2) diffusion welding: raising the temperature to 800-850 DEG C at the speed of 15-20 DEG C/min, keeping the temperature for 30 min, after that, raising the temperature to 1,100-1,150 DEG C at the speed of 10-15 DEG C/min, keeping the temperature for 3 h, and performing vacuum cooling to the room temperature, wherein the pressure (8-9.5 MPa) exerted before is kept in the first 2 h and reduced to 4-6 MPa in the last 1 h; and (3) postweld heat treatment: raising the temperature of the heat exchanger core to 1,150-2,000 DEG C, keeping the temperature for at least 20 h, and after that, reducing the temperature in a water quenching manner. According to the diffusion welding process, such parameters as welding temperature, diffusion time and pressure are controlled, the step of heat treatment after diffusion welding is added, so that brittle phases easily generated during diffusion welding are reduced, and the quality of a welded joint of the heat exchanger core is improved.

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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