Stainless steel, discovered in 1913, contains chromium that forms a thin chromium oxide layer on the surface, providing corrosion resistance. Passivation processes typically involve using nitric acid or citric acid to either create or facilitate the formation of this layer. Thorough cleaning is crucial to ensure contaminants, such as oils, spatter, or grease, do not interfere with the passivation process.
During stainless steel welding, heat input causes the material's color to change, indicating the formation of a heat affected zone. Depletion of chromium in this zone prevents the formation of the chromium oxide layer, requiring the removal of the oxidized layer to allow passivation to occur. Laser technology is now being used as a non-contact process to complement these methods and provide a cost-effective alternative.
When compared to traditional MIG and TIG welding, the quality and brilliance of fiber laser welding allows precise control of heat input in to the target materials. The high power density combined with wobble welding results in a more stable weld pool, which in turn results in a significant reduction in HAZ (heat affected zone) and reduced spatter around the weld joint.
Traditionally, pickling using strong acid solutions or mechanical methods like grinding and abrasive blasting have been employed for post-weld passivation. However, these methods have drawbacks such as toxicity, surface damage, and process variability. Laser cleaning with handheld laser devices offers an alternative approach that is repeatable, not affected by chemical degradation, and provides precise cleaning without line-of-sight limitations.
Laser cleaning involves rapidly scanning the laser beam over the joint surface, effectively removing oxidation from the weld joint. With handheld laser devices, the welding nozzle can be quickly exchanged for a laser cleaning nozzle, enabling cleaning up to 15mm wide. Tool-less tip exchange and preset cleaning parameters ensure consistent and reliable cleaning of various joint configurations. Laser cleaning also eliminates the need for hazardous chemicals and minimizes the use of abrasive media.
TTo validate the effectiveness of laser cleaning, welded steel coupons were tested independently by Sturbridge Metallurgical Services Inc. using ASTM B117-19 Salt Spray test, which measures corrosion resistance. The results demonstrated the benefits of laser cleaning for welded joints.
|Type of Salt and Water
|Morton Culinox 999 / DI Type IV
|Concentration of Salt
Sturbridge Metallurgical Services Test Conditions
The above image shows the comparison between two sides of a stainless steel coupon. The right side shows the piece after welding while the left side shows the piece after it was welded and laser cleaned.
Courtesy Sturbridge Metallurgical Services Inc.
IPG Photonics offers two handheld laser cleaning products, LightWELD XC and LightWELD XR which provides fabricators with many advantages for both welding and cleaning as compared with traditional methods:
Laser cleaning adds another option to a fabricator’s set of capabilities when considering post processing of welded assemblies. This non-contact method reduces the use of chemicals or abrasive blast media while being easy to use. HAZ is easily removed allowing the surface of the stainless steel to passivate restoring the rust resisting characteristics of the steel.
With its many advantages over traditional welding methods, hand-held laser welding can help improve the quality and consistency of your welds while reducing production time and costs. Contact us today to learn more about how we can help you implement laser welding and cleaning into your production process and take your products to the next level.
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