I have to wonder why you gave up on gas fired ovens for a healing profiles. You will likely need a different arrangement of nozzles and plumbing but it should be cheaper to operate.

Ive worked on a number of different ovens and furnaces over the years and frankly tight tolerances on temperature require air circulation via a fan or other method. Frankly I wouldn’t put something like a pin in an oven that is round and expect it to maintain an even temperature profile. Without a fan you would want a rectangular oven that would keep the pins evenly away from the elements.

as the other responder mentioned temperature profiles in industrial ovens can be huge. Even in the case of much lower temperatures in ovens used for specific processes operating at much lower temperatures getting a flat profile in the oven is a chore. The higher the operating temperature the bigger the potential errors. In an oven with static air you would need to keep the element distance from the workpiece as constant as possible. Note we are talking simply about issues of temperature control here. This has little to do with knowing the optimal annealing profile.

here in is the next issue, I really doubt that those pins and such are plain carbon steels. Maybe maybe not. In some cases they may not be through hardened as toughness might be the goal so a “case” or outer hard layer might be in place. Some of these steels May machine well once through the outer hard shell.

by the way you wouldn’t be the first person to throw a piece of steel into a fire to soften it. Totally uncontrolled but it does work for some simple steels. By fire I mean a substantial coal or wood fire that can be fed with air. The steel is brought up to temp and the fire allowed to cool and burn out.