Laser Welding Steel

Yes, laser welding is as strong as MIG welding, and often stronger. MIG suffers from three main problems which reduce its strength:
a.  Lack of penetration.  MIG welds can look nice but not penetrate very far.  To get more penetration you need to vee out the joint, or create a gap, then spend time feeding molten wire in.  Laser welding is best without gaps, and no preparation is required.  Simply hit our pre-sets and weld away to get full penetration.
b.  Excess heating of the material.  As mentioned above, MIG welding puts a lot of heat into the joint.  This large amount of heat anneals the metal, removing the strength that was engineered into the metal via alloying, heat treatment and/or cold working such as rolling.  In contrast, laser welding uses a much smaller, focused heat source to melt the metal.  This cools more quickly, giving a smaller more refined grain structure, with less change from the parent material.
c.  MIG’s large heat input causes distortion of the components.  This distortion or waviness can reduce the geometrical strength.  In comparison, laser welding has about 1/4 the distortion, and often no noticeable distoration.

MIG welding’s one advantage is the large amount of filler wire used gives a larger fillet, but testing on TIG welded parts with large fillet showed they were weaker than laser welded parts with a much smaller filler, as the weakening of the parent material was the key factor.  Laser welding should cause you to rethink the old concept “that’s a good weld because the parent material failed, not the weld”.

Laser welding works well on steel.  Steel absorbs a lot of infrared (IR) even in the solid state.  This means it melts quickly when hit with a fiber laser beam.

We find steel responds well to focus changes, which change the power density.