Oxygen Potential

The oxygen potential describes how strongly the furnace atmosphere affects the workpiece. Too much oxygen burns the surface and pulls carbon out, making the weld brittle. Too little oxygen is also not good, then you won't achieve the desired decarburization and hardening suffers. So you have to set the furnace atmosphere to find a middle ground. Don't blindly rely on numbers, but go by the annealing condition of the material. If you work with protective gas, it usually handles this properly, but check the result on the workpiece, not just on the gauge.