A Method for Reducing Invar Steel Welding Hot Cracking Tendency by Layered Pulse Laser

Abstract

The invention provides a method for lowering the hot cracking tendency of invar welding through layered pulse lasers and belongs to the technical field of laser welding. According to the method, the layered pulse lasers are used for controlling laser energy, and preheating, welding and post-welding post-heating are achieved during each laser period, wherein the preheating lasers play a role in lowering the welding temperature gradient; the welding lasers achieve connection of weld metal; the post-welding post-heating lasers play a role in reducing the cooling rate of the post-welding weld metal. The layered laser energy is controlled to control the preheating temperature, the preheating temperature range, the welding heat input amount and the post-welding post-heating energy by adjusting the power and pulse width of the layered lasers; the welding temperature gradient and the post-welding cooling speed are adjusted in combination with control over the pulse frequency so that the welding stress of invar laser welding can be reduced, and the problem of hot cracks of invar welding can be solved. By means of the method, the welding speed can be greatly increased, and the hot cracking tendency of invar welding can be lowered. The welding speed can reach 500-800 mm / min, and the cooling rate of the post-welding weld metal is reduced by 50-80 DEG C / s.

Description

technical field [0001] The invention relates to a method for reducing the thermal cracking tendency of invar steel welding by layered pulse laser, and belongs to the technical field of laser welding. Background technique [0002] Invar steel (Invar steel, also known as Invar steel) is a FeNi36 alloy, and its coefficient of linear expansion at room temperature is lower than 1.6×10 -6 k -1 , about one-tenth of low carbon steel, and has little change in a large temperature range, so it is widely used in precision measurement devices, electronics industry and liquefied natural gas ships. As the status of natural gas in the energy field becomes more and more important, the LNG ship for long-distance transportation of natural gas has developed rapidly as a difficult and high value-added ship type, and the liquid cargo tank welded by Invar steel film The insulation system shield is the most difficult part to build. [0003] Invar steel has a single-phase austenitic structure and...

AI Technical Summary

Problems solved by technology

By adjusting the layered laser power and pulse width to control the layered laser energy to control the preheating temperature and range, welding heat input and post-weld heat energy, combined with pulse frequency control to adjust the welding temperature gradient and post-weld cooling rate, to achieve The purpose of reducing the welding stress of invar steel laser welding is to solve the problem of thermal cracking in invar steel welding

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