A hybrid welding method for duplex stainless steel heat exchange plates based on residual stress control

Abstract

The invention relates to the technical field of plate and shell heat exchangers, and provides a composite welding method for duplex stainless steel heat exchange plates based on residual stress regulation. Welding residual stress of the heat exchanger core, and adjust the dual-phase ratio of the duplex stainless steel welded joints to avoid the precipitation of brittle phases and improve the resistance to pitting corrosion; the hybrid welding method of resistance welding and argon arc welding can effectively reduce the residual stress, To control the deformation of the plate, the second argon arc welding is performed after the first resistance welding, in addition to the role of double sealing, the sealing effect is better, and the medium leakage caused by the failure of one welding seam is avoided; argon arc welding The heat input can also effectively play a metallurgical role, promote the precipitation of austenite phase, reduce the ferrite content, optimize the ratio of the two phases, improve the mechanical properties of the welded joint, and enhance the stress corrosion cracking resistance of the welded joint.

Description

Technical field[0001]The invention relates to the technical field of plate and shell heat exchangers, in particular to a compound welding method for duplex stainless steel heat exchange plates based on residual stress control.Background technique[0002]Heat exchangers are widely used in nuclear power, petroleum and petrochemical industries because of their ability to exchange heat between media at different temperatures. Plate and shell heat exchangers have higher heat exchange efficiency and more compact structure than tubular heat exchangers. ,; Compared with the plate heat exchanger, the plate and shell heat exchanger has better sealing performance, higher temperature resistance and higher pressure capability. Under the same pressure loss, its area is only one-fifth of the traditional shell-and-tube heat exchanger, but its heat transfer coefficient is more than 5 times that of the shell-and-tube heat exchanger, and the heat recovery rate can reach 98% , The pressure resistance can...

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Problems solved by technology

However, in the current welding method, the ferrite content of the weld seam is too high after welding, resulting in a greatly reduced corrosion resistance and impact toughness of the welded joint, which may lead to failure of the heat exchanger

[0005] At present, the method that can effectively improve the phase ratio of two-way stainless steel welded joints is post-weld heat treatment, but at present, the heat exchanger is developing towards large-scale, and it is unrealistic to conduct overall heat treatment on the core of the heat exchanger due to the limited size. The sheet is very thin, and the folded edge where the weld is located is small and it is not easy to achieve local heat treatment, so real-time control of welding must be considered

[0006] At present, methods that can effectively reduce welding residual stress include heat treatment, ultrasonic impact method, vibration aging, etc. The above-mentioned heat treatment method is not applicable, and other methods are not applicable because the thickness of the heat exchanger plate is too low to cause greater deformation.

Post-weld residual stress relief method not only wastes time, but also invests a lot of manpower and material resources

[0007] For plate-shell heat exchanger plate welding, there are mainly the following technical problems. Generally, resistance welding, argon arc welding, electron beam welding, plasma welding, etc. are used. Because the thickness of the heat exchanger plate is too small, the above welding method is easy to produce Problems such as excessive welding residual stress and excessive deformation of the plate affect the welding quality of the product, thereby affecting the service life of the product; the weld seam of the existing technology is poorly formed, and the product is prone to problems such as burn-through and undercut, and the product quality is difficult to guarantee. High production cost; due to excessive welding heat input and too fast cooling rate, the weld seam and heat-affected zone have no time to precipitate austenite, resulting in excessive ferrite content, which greatly reduces the plasticity, impact toughness and corrosion resistance of the welded structure. Leading to the failure of the heat exchanger plates, the medium leaks and flows; the traditional single-pass sealing welding may have welding defects and lead to sealing failure. Due to the overall welding structure of the core of the plate-shell heat exchanger, one failure may cause the entire heat exchange end-of-life

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