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Views: 0 Author: Site Editor Publish Time: 2026-09-16 Origin: Site
Welding deformation is a common issue in structural steel fabrication and steel construction. Excessive deformation can affect the dimensional accuracy of steel components, create difficulties during assembly and installation, and reduce the overall performance of the completed steel structure.
In severe cases, welding deformation may also introduce additional bending moments, secondary stresses, and alignment problems. Therefore, effective control of welding distortion is an important part of steel structure design, fabrication, and quality management.
During welding, the steel around the weld is heated rapidly and then cools unevenly. This uneven thermal expansion and contraction can cause:
Angular deformation
Longitudinal shrinkage
Transverse shrinkage
Bending deformation
Twisting
Local buckling
Overall dimensional deviation
The amount of deformation depends on factors such as plate thickness, weld size, heat input, joint design, welding sequence, restraint conditions, and material properties.
When weld quality and structural strength requirements can still be satisfied, the groove angle and root gap should be kept as small as reasonably possible.
Reducing the amount of deposited weld metal helps reduce heat input and welding shrinkage.
For suitable steels with yield strength below approximately 345 MPa and relatively low hardenability, excessive heat input should be avoided.
Where permitted by the applicable welding procedure, preheating and interpass temperatures should be appropriately controlled.
Low-heat-input welding processes, such as CO₂ gas-shielded welding, can help reduce thermal deformation.
All welding parameters should comply with approved welding procedures and applicable project standards.
For thick steel plates, multi-pass welding is generally preferred over depositing a large weld in a single pass.
Multi-pass welding provides better control of heat distribution and helps reduce excessive local deformation.
For longitudinal stiffeners and transverse stiffeners, intermittent welding can reduce the total amount of weld metal and heat input when permitted by structural design requirements.
However, continuous welding should be used where required by structural calculations, fatigue requirements, sealing requirements, or project specifications.
When both sides of a joint are accessible, a symmetrical double-sided groove should be considered.
For multi-pass welding, welds should be deposited symmetrically around the neutral axis of the component whenever possible.
This helps balance welding shrinkage and reduce angular distortion.
For thick T-joints or cruciform joints, groove welds may be more suitable than large conventional fillet welds.
When properly designed, groove welding can reduce the required weld metal volume while maintaining the necessary joint strength.
Pre-setting or reverse deformation can be introduced before welding to compensate for the expected angular distortion.
After welding and cooling, the component can return closer to the required geometry.
This method is commonly used for steel beams, H-sections, plates, and other fabricated components.
Dimensional allowances can be incorporated during fabrication to compensate for expected longitudinal and transverse shrinkage.
For example, fabricated H-sections may require additional length to compensate for longitudinal weld shrinkage.
The actual allowance should be determined according to:
Component dimensions
Plate thickness
Weld size
Welding process
Joint configuration
Fabrication experience
Approved welding procedures
Rather than relying on a single fixed value, shrinkage allowances should be verified according to actual production conditions.
For long steel members, twisting can often be reduced by improving the flatness of steel plates and the accuracy of component assembly.
Important factors include:
Accurate groove angles
Consistent root gaps
Correct member alignment
Proper weld positioning
Accurate electrode or welding torch direction
Consistent welding parameters
Maintaining uniform welding conditions along the entire component helps reduce uneven longitudinal and angular deformation.
During structural design, unnecessary welds should be avoided whenever possible.
Rolled steel sections, formed components, or standardized profiles may be used instead of heavily welded assemblies where appropriate.
Reducing the number and size of welds can help:
Reduce welding heat input
Minimize deformation
Reduce fabrication time
Lower correction costs
Improve production efficiency
Welds should be positioned as close as reasonably possible to the neutral axis or centerline of the section.
Symmetrical weld layouts can reduce bending deformation caused by unbalanced shrinkage.
Weld concentration should also be avoided because closely spaced welds can create excessive heat accumulation and local distortion.
For components with multiple welds, an appropriate welding sequence is essential.
Depending on the component design, suitable methods may include:
Symmetrical welding
Back-step welding
Skip welding
Segment welding
Welding from the center toward both ends
A well-planned sequence helps distribute heat more evenly and prevents deformation from accumulating in one direction.
The structural design should minimize unnecessary welded connections.
Where practical, rolled sections or formed steel components can replace fabricated welded parts, reducing the number of stiffeners and welded joints.
This can significantly reduce both welding deformation and subsequent straightening work.
For thick plate butt joints, an X-groove joint may require less deposited weld metal than a conventional V-groove joint.
Reducing weld metal volume helps reduce:
Welding heat input
Transverse shrinkage
Angular deformation
Residual stress
For T-joints that do not require large welds for structural strength, the minimum practical fillet weld size should be selected according to applicable design requirements.
Where structural conditions permit, intermittent welds may also help reduce deformation.
Welding deformation should be considered during the structural design stage rather than only during fabrication.
For thin steel plate structures, appropriate plate thickness, stiffener spacing, and weld size should be selected to improve structural stability and reduce wave deformation.
Simple and regular structural configurations are generally easier to fabricate and control than unnecessarily complex welded geometries.
In many welded structures, transverse shrinkage can be more significant than longitudinal shrinkage.
For this reason, weld orientation and location should be carefully considered during design.
Where possible, welds should:
Be arranged symmetrically
Be located close to the section centerline
Avoid excessive concentration
Be oriented to minimize deformation in critical directions
These measures help reduce bending, twisting, and dimensional deviations after welding.
Even with proper control measures, some deformation may still occur.
Common correction methods include:
Mechanical straightening
Controlled heat straightening
Press correction
Flame straightening where permitted
Local mechanical adjustment
Correction work should be carried out carefully to avoid damaging the steel, introducing cracks, or adversely affecting material properties.
Effective welding deformation control requires coordination between structural design, welding procedure development, fabrication, assembly, welding sequence, and quality inspection.
The most effective approach is to prevent excessive deformation before and during welding rather than relying heavily on correction after fabrication.
By controlling weld size, heat input, joint design, welding sequence, assembly accuracy, and shrinkage allowance, steel fabricators can achieve higher dimensional accuracy, better installation efficiency, and more reliable structural performance.
