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Cyclical ultrasonic impact process for maintaining welding joint

A technology for welding joints and maintenance, which is applied in the field of life extension of magnesium alloy welded structures, can solve the problems of low fatigue life of magnesium alloy welded structures, and achieve the effect of prolonging the service life

Inactive Publication Date: 2016-06-08
EAST CHINA JIAOTONG UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to solve the problem of low fatigue life of magnesium alloy welded structures. The present invention provides a repair process for regular cycle maintenance of MB8 magnesium alloy welded joints in service

Method used

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  • Cyclical ultrasonic impact process for maintaining welding joint
  • Cyclical ultrasonic impact process for maintaining welding joint
  • Cyclical ultrasonic impact process for maintaining welding joint

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0036] (1) Grind the welding area and welding wire with fine sandpaper to fully remove the oxide film on the surface; clean the surface of the workpiece and welding wire with acetone to remove oil and dirt; then dry the surface of the workpiece and welding wire with a dry cotton cloth and let it stand.

[0037] (2) The 8mm thick MB8 magnesium alloy plate is TIG welded with Φ3mm MB3 welding wire. The welding process parameters are shown in Table 2.

[0038] Table 2 welding process parameters

[0039]

[0040] (3) Choose a cylindrical impact head with a diameter of 3 mm and a semicircular head. The welding seam and the heat-affected area adopt double rows of impact heads with at least 4 needles, and the weld toe area adopts a single needle. Ultrasonic impact treatment is performed on the weld seam, weld toe and heat-affected zone of the welded joint. When impacting the weld toe, the impact gun reciprocates along the welding direction; when impacting the weld seam, the impa...

Embodiment 2

[0050] (4) Apply a tension-tension alternating fatigue load in the form of a sine wave of 55Mpa to the welded joint after impact, and the stress ratio R(σ min / σ max )=0.1, loading frequency f=110~115Hz, effect 0.5×0.763513×10 6 times (half of the post-weld impact fatigue life) to stop the load.

[0051] (5) Grind and clean the surface of the weld seam and the heat-affected zone with fine sandpaper to remove the scale and other dirt formed during use.

[0052] (6) Choose a cylindrical impact head with a diameter of 3 mm and a semicircular head. The welding seam and the heat-affected area adopt double rows of impact heads with at least 4 needles, and the weld toe area adopts a single needle. The impact speed is 15mm / min~20mm / min, and the number of reciprocating impacts is 4 times. Ultrasonic impact frequency is 18KHz. Excitation current: 1.0A.

[0053] (7) Implement ultrasonic impact treatment on the weld toe to make the transition between the base metal and the weld as s...

Embodiment 3

[0059] (4) Apply a tension-tension alternating fatigue load in the form of a sine wave of 60Mpa to the welded joint after impact, and the stress ratio R(σ min / σ max )=0.1, loading frequency f=110~115Hz, effect 0.5×0.437742×10 6 times (half of the post-weld impact fatigue life) to stop the load.

[0060] (5) Grind and clean the surface of the weld seam and the heat-affected zone with fine sandpaper to remove the scale and other dirt formed during use.

[0061] (6) Choose a cylindrical impact head with a diameter of 3 mm and a semicircular head. The welding seam and the heat-affected area adopt double rows of impact heads with at least 4 needles, and the weld toe area adopts a single needle. The impact speed is 15mm / min~20mm / min, and the number of reciprocating impacts is 4 times. Ultrasonic impact frequency is 18KHz. Excitation current: 1.0A.

[0062] (7) Implement ultrasonic impact treatment on the weld toe to make the transition between the base metal and the weld as s...

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Abstract

The invention discloses a cyclical ultrasonic impact process for maintaining a welding joint. According to the process, in the process of using a magnesium alloy welding structure, cyclical ultrasonic impact treatment is performed on the welding joint, so as to recover surface quality and performance reduction in the welding joint manufacturing and using process caused by process, load and environment factors and the like and part of microdefects in recovery use, and thus the service life is prolonged.

Description

technical field [0001] The invention relates to a method for maintaining the MB8 magnesium alloy welded joints in use (in service), repairing the surface quality of the magnesium alloy welded joints through cyclic ultrasonic impact, thereby prolonging the fatigue life of the joints, belonging to the life extension technology of magnesium alloy welded structures . Background technique [0002] Magnesium alloy has the advantages of low density, high specific strength, good impact resistance, good shock absorption, easy recycling and no pollution, and has become the third largest metal structural material after steel and aluminum alloy materials. In recent years, with the improvement of production capacity and technical level, and the decline of production cost, magnesium alloy has been mainly used in defense and aerospace products, and has expanded to automobiles and other civilian fields. However, due to the characteristics of lively nature, low melting point, fast heat cond...

Claims

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Application Information

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IPC IPC(8): B23P9/04
CPCB23P9/04
Inventor 于影霞江明明何柏林
Owner EAST CHINA JIAOTONG UNIVERSITY
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