We are interested in the temperature of arc-welding spot. Does the camera work correctly under this intense light?

Yes, this will work, the camera needs a high temperature calibration which includes an attenuating filter.

The strong light from the arc is mostly UV that is far below the transmission band of the camera. Most of the radiation will not pass trough the optics.

However, please note that the melting point can reach 2000-3000°C. At close distance, radiation may heat the camera and optics above the operating range, or cause temporary temperature drift.