Glass that has been damaged from welding or grinding spatter can usually be resurfaced and repaired.
There are of course, always caveats when it comes to any repair, and this situation is not any different. What matters is the intensity of the damage vs the parameters of the glass.
Welding or grinding sparks are simply extremely hot and tiny pieces of metal. These tiny pieces – oh so tiny – are hot enough to melt glass, and rapidly cool down. The closer the glass, the more direct the impact, the deeper these pieces penetrate into the glass.
The greater the damage, the greater the cost to repair. Even if the repair CAN be performed, it might not be cost-effective. See the pricing page for a bit more detail on this.