Understanding Welding Stress: Causes and Elimination | MachineMFG

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Understanding Welding Stress: Causes and Elimination


Are you tired of dealing with welding stress and its negative impacts on your weldments? Are you struggling to find effective ways to eliminate welding stress and improve the performance of your welded components? Look no further!

We have the solution you need to alleviate your pain points and achieve optimal welding results. Our comprehensive method for eliminating welding residual stress, known as Hawking energy aging, can eliminate up to 100% of stress and significantly improve the fatigue strength, corrosion resistance, and dimensional stability of your weldments.

Unlike other stress relief methods, Hawking energy aging is versatile, efficient, and convenient, making it ideal for use in construction sites, welding processes, and welding repairs.

With its ability to directly process weld reinforcement, pits, and undercuts, and remove microcracks and slag defects, Hawking energy aging is the most effective method for improving weld fatigue performance currently available.

Say goodbye to the hazards of welding stress and hello to optimal welding results with Hawking energy aging. Don’t let welding stress hold you back any longer – try our solution today and experience the difference for yourself!

1. What is welding stress

Welding stress refers to the stress generated during the welding process in welded components. This stress is caused by the thermal process of welding and the resulting internal stress and changes in the shape and size of the weldment.

The root cause of welding stress and deformation is the uneven temperature field during welding and the resulting local plastic deformation and differences in microstructure with varying specific volumes.

Transient welding stress and deformation occur when the temperature field from welding has not yet dissipated. On the other hand, residual welding stress and deformation refer to the stress and deformation that remain after the welding temperature field has dissipated.

In the absence of external forces, welding stress is balanced within the weldment. However, under certain conditions, welding stress and deformation can impact the functionality and appearance of the weldment.

What is welding stress

2. Hazards of welding stress

Welding residual stress has six effects on weldments:

① Effect on strength:

Serious defects in areas with high residual tensile stress can negatively impact the static load strength of the weldment if it operates below the brittle transition temperature. The presence of residual tensile stress at stress concentration points under cyclic stress will reduce the fatigue strength of the weldment.

The fatigue strength of weldments is not only dependent on the magnitude of residual stress, but also on factors such as the stress concentration factor, stress cycle characteristic coefficient, and the maximum value of cyclic stress. The influence of residual stress decreases as the stress concentration factor decreases and intensifies as the stress cycle characteristic coefficient decreases, but decreases as the cyclic stress increases.

When the cyclic stress approaches the yield strength, the effect of residual stress gradually diminishes.

② Effect on stiffness:

The combination of welding residual stress and stress from external loads can result in early yielding and plastic deformation in specific areas of the weldment. This will result in a reduction in the stiffness of the weldment.

③ Influence on the stability of pressure weldment:

When a welded rod is subjected to pressure, the welding residual stress combines with the stress from external loads, potentially causing local yielding or instability, and reducing the overall stability of the rod.

The impact of residual stress on stability depends on the geometry and distribution of internal stress within the member. The influence of residual stress on non-closed sections, such as I-sections, is greater than its influence on closed sections, such as box sections.

④ Influence on machining accuracy:

The presence of welding residual stress can affect the machining accuracy of weldments to varying degrees. The lower the stiffness of the weldment, the larger the machining amount, and the greater its impact on accuracy.

⑤ Influence on dimensional stability:

Welding residual stress and the size of the weldment both change over time, and this can affect the dimensional stability of the weldment. The stability of residual stress also influences the dimensional stability of the weldment.

⑥ Effect on corrosion resistance:

The combination of welding residual stress and load stress can result in stress corrosion cracking.

Influence of welding residual stress on structure and member:

Welding residual stress is the initial stress on a member before it bears any loads. During the use of the member, the residual stress overlaps with the working stress caused by other loads, leading to secondary deformation and a re-distribution of residual stress.

This not only decreases the stiffness and stability of the structure, but also significantly impacts its fatigue strength, resistance to brittle fracture, stress corrosion cracking, and high temperature creep cracking under the combined effects of temperature and the environment.

Hazards of welding stress

3. Elimination method of welding stress

Currently, there are three methods used to eliminate stress: vibration aging, thermal aging, and houckner PT aging. Vibration aging can eliminate 30% to 50% of stress, thermal aging can eliminate 40% to 70% of stress, and houckner PT aging can eliminate 80% to 100% of stress.

Vibration aging

Vibration aging treatment is a common method for reducing internal residual stress in engineering materials. The process involves subjecting the material to vibration, which causes a small amount of plastic deformation in the material when the combined residual stress and additional vibration stress exceeds the yield strength of the material, thereby reducing the internal stress.

Vibration aging

Thermal aging

Thermal aging is a process of reducing residual stress in a workpiece by heating it to its elastic-plastic transition temperature, holding it at that temperature for a specified period of time, and then slowly cooling it down. This process results in the workpiece being in a low-stress state after cooling.

However, if the process parameters for heating, insulation, and cooling are not properly selected or if the operational procedures are not followed strictly, the stress elimination process may not be effective, and the stress on the workpiece may even increase. This has been demonstrated through production experience.

Hawking energy aging

Hawke is currently the most comprehensive method for eliminating welding residual stress and producing ideal compressive stress. It can eliminate 80% to 100% of the stress and has several benefits.

Hawke can increase the fatigue strength of welded joints by 50% to 120% and prolong their fatigue life by 5 to 100 times. Additionally, the corrosion resistance of metal in corrosive environments is increased by about 400%.

Hawke is a versatile method for stress relief treatment and can replace heat treatment and vibration aging. The treatment process is straightforward, and the results are stable and reliable. It is not limited by the material, shape, structure, thickness, weight, or location of the workpiece, making it especially convenient for use in construction sites, welding processes, and welding repairs.

Hawke can directly process weld reinforcement, pits, and undercuts at the weld toe into a smooth geometric transition, reducing the stress concentration factor. It can also remove microcracks and slag defects at the weld toe to prevent early crack initiation.

Hawke improves multiple factors affecting weld fatigue performance, such as residual stress, microcracks, defects, weld toe geometry, and surface strengthening, making it the most effective method for improving weld fatigue performance currently available.

It is well-suited for stress relief treatment of site welds, ultra-high and low welds, and welding repair welds of large structural parts. Hawke is environmentally friendly, energy-efficient, safe, and non-polluting, making it a flexible and convenient option for use on construction sites.

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