Method for improving welded joint fatigue strength following chilling treatment after weld toe TIG refusion

A technology for fatigue strength and welded joints, which is applied to the welded structure of low-alloy steel, low-carbon steel, and post-weld treatment. The effect of wide range, lower energy consumption, lower manufacturing cost

Inactive Publication Date: 2008-09-24
DALIAN JIAOTONG UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The former requires special equipment, and the effect of removing residual stress is very limited; the latter has a better effect of eliminating residual stress, but the overall annealing process consumes a lot of energy and has low efficiency

Method used

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  • Method for improving welded joint fatigue strength following chilling treatment after weld toe TIG refusion

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0022] Chilling treatment process after TIG remelting of welding toes of railway vehicle bogie welding frame T-shaped corner joints. The material is Q345-C low-alloy structural steel (thickness 14mm), welding toe TIG remelting process parameters: tungsten pole diameter φ3.2mm, nozzle diameter φ12mm, argon gas flow rate 10L / min, current 170-180A, voltage 14-18V, Speed ​​13~16cm / min. During TIG remelting, the angle between the welding torch and the vertical plate is about 30°, and the arc axis is located 1 to 1.5 mm outside the welding toe. Weld toe TIG remelting layer chilling treatment process: When the temperature of the welding toe TIG remelting layer drops to no less than 500°C, water flow with a certain pressure is sprayed onto the surface of the welding toe remelting zone through a special nozzle for chilling treatment. Keep an appropriate distance from the TIG welding torch to ensure that the temperature of the remelting layer at the spraying position is not lower than ...

Embodiment 2

[0024] Chilling treatment process after TIG remelting of weld toe of plate butt joint. 16MnR low-alloy steel (thickness 14mm) was selected as the material, and the technological parameters of the TIG remelting of the weld toe and the chilling treatment of the remelting layer were the same as those in Example 1. During TIG remelting, the torch welds the test plate vertically, and the arc axis is located 0.5-1.0mm outside the welding toe. The residual stress test results are: in the welded state, σx = 215MPa, σy = 164MPa; after TIG remelting of the welding toe, σx = 155MPa, σy = 129MPa; after TIG remelting of the welding toe, spraying treatment when cooling to 550°C, σx = -209MPa, σy=-198MPa. It can be seen that after treatment by this process, a bidirectional compressive stress field that is conducive to improving fatigue strength is also formed in the weld toe area.

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Abstract

The invention discloses an after-welding processing method by using a welding joint after being remelted by a welding toe TIG to follow a spray chilling treatment to adjust the residual stress field of the weld toe to transfer the original residual tension stress field of the TIG remelting area into a compression stress field which is beneficial to improve the endurance strength of the joint. The method integrates both the advantages of improving the geometrical shape of the welding toe by TIG remelting and improving the residual stress state of the welding toe by the chilling treatment in the remelting area; besides, the method has the advantages of simple device, convenient operation, remarkable effect, easily checked and controlled quality, no noise, no environment pollution, etc. The method can be applied to the non-quenching steels like mild steel low alloyed steel, etc., as well as the welding structures of the metals like aluminum alloy and titanium alloy. The method can be popularized and applied in the industrial fields of shipping and ocean platforms, rolling stocks, railroad bridges, cranes, oil pipelines and chemical containers.

Description

technical field [0001] The invention belongs to the field of welding technology and engineering, and mainly relates to a post-welding treatment method for improving the fatigue strength of welded joints by adjusting the residual stress field on the surface of welding toes for welding structures of low-carbon steel and low-alloy steel. Background technique [0002] Weld toe TIG remelting (melting repair) process is a post-weld treatment method recommended by the International Institute of Welding (IIW) to improve the fatigue strength of welded joints. Defects such as undercut and microscopic slag inclusions may exist, and at the same time, a remelting zone with uniform transition is formed to achieve a smooth transition between the weld and the base metal, reduce stress concentration, and improve the fatigue strength of the joint. Compared with other methods for improving the fatigue strength of welded joints, TIG remelting technology has the advantages of simple process, con...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22F1/00
Inventor 史春元丁成钢朱平焦建强
Owner DALIAN JIAOTONG UNIVERSITY
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