Laser Welding Distortion in Stainless Steel: Causes, Prevention Methods & Industrial Solutions

Controlling deformation is a systematic project. The best strategy is to optimize every link of welding.

Countermeasure 1: Use Rigid Fixation and Reasonable Fixtures

This is the most direct and effective method. Use strong external constraints to counteract the internal stress generated by welding.

• Use special welding fixtures: Design special fixtures with uniform clamping force and firm clamping according to the shape of the workpiece. The fixture should have sufficient rigidity and will not deform under the clamping force.

• Increase clamping points: For large-sized thin plates, multiple clamping points should be evenly distributed along both sides of the weld to prevent the plate from warping between two points.

• Copper pressing plate/pad: Copper has excellent thermal conductivity. Using copper pressing blocks or pads on the fixture can help quickly take away excess heat near the weld, reduce the heat-affected zone, and thus reduce deformation.

Countermeasure 2: Optimize Welding Process Parameters

Reasonable process parameters aim to use ” as little heat input as possible to complete high-quality penetration”.

• Increase welding speed: Increase welding speed as much as possible while ensuring full penetration. The faster the speed, the less heat input per unit length, and the smaller the deformation.

• Accurately control laser power: Avoid using power far exceeding the required power. Excessive power will unnecessarily increase the heat-affected zone.

• Use pulse waveforms: For heat-sensitive thin plates, use pulsed lasers with high peak power and short pulse width to melt the metal instantly while reducing the conduction of heat to the parent material.

• Adjust defocus: Appropriate positive defocus can obtain a larger spot and lower power density, which helps to form a wider and smoother weld, and sometimes helps to improve stress distribution.

Countermeasure 3: Optimize Weld Design and Welding Sequence

Through clever arrangements, the stresses generated can offset each other.

• Reduce weld cross-sectional area: Under the premise of meeting strength requirements, try to reduce the size of the weld (such as groove angle). The smaller the weld, the less metal is filled and the smaller the shrinkage.

• Use symmetrical welding: For symmetrical structures, use double-sided symmetrical welding so that the deformation stresses generated on both sides can offset each other.

• Segmented step-back welding method: Divide a long weld into several sections, and use a jump-type or welding method from the middle to both ends to make the heat and stress distribution more uniform and avoid stress accumulation in a single direction.

Countermeasure 4: Ensure Excellent Assembly Gap

Excessive gap is a common cause of increased deformation.

• Precise assembly: Ensure that the assembly gap before welding is uniform and as small as possible. An excessive gap will force you to use more filler wire or a slower speed to fill, which means greater heat input.

• Spot welding fixation: Before formal welding, firm spot welding positioning along the weld can effectively prevent gap changes caused by heat during welding.

Countermeasure 5: Choose High-Quality Raw Materials

An often overlooked but crucial factor is the material itself.

• Plate with good flatness: If the stainless steel plate used has internal stress or poor flatness, the heat of welding will become the “last straw that breaks the camel’s back”, releasing and aggravating these original deformations.

• Uniform thickness: Plates with uniform thickness can ensure the consistency of heat absorption and conduction during welding, and it is easier to obtain stable welding results.