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How can you reduce or eliminate residual stress in welded components?

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\nWelding is a common and versatile process for joining metal parts, but it can also introduce residual stress in the welded components. Residual stress is the internal stress that remains in a material after the external forces that caused it are removed. Residual stress can affect the performance, quality, and durability of welded components, as well as increase the risk of distortion, cracking, and failure. Therefore, it is important to understand how residual stress is generated in welding and how it can be reduced or eliminated.

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Simon Krismer

Structural Maintenance Welding and Welder Competency Expert
Yuri Kudryavtsev

Tech. Executive

1 Sources of residual stress

Residual stress in welding is mainly caused by two factors: thermal expansion and contraction, and phase transformation. Thermal expansion and contraction occur when the weld metal and the base metal are heated and cooled during the welding process, creating different thermal gradients and strains in different regions of the component. Phase transformation occurs when the weld metal and the base metal undergo changes in their crystal structure due to the high temperature and cooling rate, resulting in different volume changes and stresses. These factors create a complex distribution of residual stress in the welded component, which can be divided into three types: longitudinal, transverse, and normal.

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2 Effects of residual stress

Residual stress can have both positive and negative effects on the welded components, depending on the magnitude, direction, and location of the stress. Positive effects include increasing the strength and fatigue resistance of the component, as well as improving the dimensional stability and shape memory. Negative effects include reducing the ductility and toughness of the component, as well as enhancing the corrosion and cracking susceptibility. The negative effects of residual stress can be more pronounced when the component is subjected to external loads, temperature changes, or aggressive environments.

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Simon Krismer

Structural Maintenance Welding and Welder Competency Expert
举报内容
The "positive" effects are incorrect. In almost all cases, residual stresses reduce fatigue resistance. Residual stresses have no effect on "strength" - this is fundamental to the material type. Residual stresses cause dimensional instability - hence why stress relieving is required prior to machining

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3 Methods of reducing or eliminating residual stress

To reduce or eliminate residual stress in welded components, depending on the design, material, and application, methods such as preheating, post-weld heat treatment (PWHT), mechanical methods, and thermal methods can be utilized. Preheating the base metal before welding can reduce the thermal gradient and the cooling rate while PWHT involves heating the welded component to a certain temperature and holding it for a certain time followed by controlled cooling. Mechanical methods involve applying external forces or vibrations to the welded component while thermal methods involve applying localized heating or cooling. These methods can improve the hardness, toughness, fatigue resistance, and corrosion resistance of the component, as well as induce compressive residual stress that can counteract tensile residual stress.

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Aarthi K

Assistant Manager at FLsmidth
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Welding speed is an another governing factor, as well as welding fixture frame. Plate thickness less than 12mm will not be affected much.

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4 Selection of methods

The selection of the most suitable method to reduce or eliminate residual stress in welded components depends on several factors, such as the type, magnitude, and distribution of the residual stress, the material, geometry, and function of the component, the welding process and parameters, the cost and availability of the equipment and resources, and the standards and specifications of the industry and customer. Therefore, it is essential to conduct a thorough analysis and evaluation of the component and its requirements before choosing a method. It is also advisable to consult with experts and conduct tests and experiments to verify the effectiveness and feasibility of the method.

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Yuri Kudryavtsev

Tech. Executive
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Ultrasonic Impact Treatment (UIT) is relatively new and promising process for residual stress relief and fatigue improvement of parts, welded elements and structures. UIT is also known in industrial applications as Ultrasonic Peening (UP). The beneficial effect of UIT is achieved mainly by relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of material and also on smaller scale by decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material (Yuri Kudryavtsev. Ultrasonic Impact Treatment - 30 Years of Practical Application. International Institute of Welding (IIW). IIW Document XIII-2803-19. 2019).

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5 Benefits of reducing or eliminating residual stress

Reducing or eliminating residual stress in welded components can have significant benefits for the manufacturing engineering process and the final product, such as improving quality and reliability, enhancing performance and durability, increasing efficiency and productivity, and meeting industry standards. These advantages can help reduce defects and rework, extend service life, reduce maintenance and repair costs, save time and energy, gain a competitive edge and reputation.

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6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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How can you reduce or eliminate residual stress in welded components?

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3

4

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1 Sources of residual stress

2 Effects of residual stress

3 Methods of reducing or eliminating residual stress

4 Selection of methods

5 Benefits of reducing or eliminating residual stress

6 Here’s what else to consider

Manufacturing Engineering

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How can you reduce or eliminate residual stress in welded components?

1

2

3

4

5

6

1 Sources of residual stress

2 Effects of residual stress

3 Methods of reducing or eliminating residual stress

4 Selection of methods

5 Benefits of reducing or eliminating residual stress

6 Here’s what else to consider

Manufacturing Engineering

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