LightWELD: The Welds Look Great, But Are They Strong?

NOTE: We are continuing to conduct in-depth laser weld strength testing and working on WPS and PQR documentation to meet additional AWS codes. Can’t wait? We’ll publish the data as soon as we can but don’t hesitate to reach out to one of our laser welding experts with any strength-related questions.

An ugly weld is rarely a good weld. At best, an ugly weld is workable with a lot of extra grinding and, at worst, an ugly weld is also defective (and a possible source of embarrassment). But is the reverse true? Is a pretty weld always a good weld?

Despite an undeniable correlation between weld appearance and weld strength, most welders will tell you it’s not that simple. A weld that looks good on the surface can suffer from over or under penetration, insufficient fusion, and even non-visible cracks and porosity. It is both reasonable and expected that welders aren’t usually sold on handheld laser welding based on looks alone.

There is no question that lasers are more than capable of producing excellent welds. Look no further than the automotive industry, which increasingly relies on automated laser welding for everything from precision battery welding to welding structural components of vehicle bodies. But industrial automation is one thing and manual fabrication is another – so, do the advantages of laser welding extend to the handheld devices currently on the market?

Putting Laser Welds to the Test

To answer this question, we used LightWELD to laser weld some samples before sending them to a local materials testing lab for an independent and unbiased evaluation. The lab, Sturbridge Metallurgical Services, offered the experience and accreditation to test our samples to Class A of AWS D17.1:2017. For our readers that have not memorized every AWS standard, D17.1 is very demanding and used for critical aerospace welds where a single failure can mean lost or damaged equipment (or worse).

We ended up welding a series of butt joints in stainless steel plates of various thicknesses (0.036”, 0.075”, and 0.120”). Next, we sent SMS our samples for preparation and examination of some cross sections. Across all 26 cross sections that they inspected there was no sign of incomplete fusion or defects like cracking, porosity, and inclusions. The weld profiles also passed, demonstrating sufficient penetration and throat while avoiding problems like undercut and overlap.

Butt joint in 0.120″ 304 stainless steel plate

Next, it was time to test the tensile strength. Seven samples were prepared for evaluation. Of those seven, just one failed at the weld joint while the other six failed at the base material. Still, all the weld samples were found to be acceptable to the demanding AWS D17.1:2017 Class A standards. We would call that a success.

All but one of the butt-welded samples failed at the base material during pull tests.