I've used 400 speed 35mm film black and white and came away with striking images. Timing is the big thing. Just wait until flames are really going and let it rip.
I'd use 400 film as well. The few times I've shot in blacksmith shops the lighting was a challenge, with lots of dark corners and trying to balance the exposure with flames/fire in the scene.
You want to be able to use high-enough shutter speeds to prevent motion blur, but a tripod is probably a must.
This will be a very high contrast lighting environment. Super bright flames, dark irons, etc.
Take an incident reading near his face with the fire up high to at least get a solid exposure there. You may want to bring a 500W shop light just to bounce a little light into the shadows.
I would also suggest a compensating developer like Diafine to help keep that contrast in check. Or, just give it a good healthy exposure and under develop the roll about 20%.