Annealing is an acceptable practice, but it is necessary to take care with the rate of cooling.

Hot-work tool steels must have the ability to resist deteriorating core-hardness values when operating under high-temperature, hot-forming operating conditions.

During the past 100 years or so carburizing has developed into a science.
 

In part 1, we discussed what happens when refractory is contaminated by the carbon-rich furnace atmosphere.

Furnace atmosphere burnout is a controversial subject among both captive and commercial heat treaters.

Atmosphere control is critical to the success of heat-treat practices, especially with the carburizing process.

The carbon potential in the process furnace atmosphere to ensure a good carburized case should be determined by the type of steel to be treated and the carburizing process temperature.

If it has been ascertained that the endothermic generator is functioning correctly, then the next step is to observe the process furnace atmosphere conditions.

Protective atmospheres for heat-treatment shops (captive or commercial) can fall into five categories: endothermic, blended gases, exothermic, elemental gases, vacuum and air.

We resume our discussion of furnace gases (see part 1).