Carbon potential, usually described as a percentage of carbon, is a measure of the furnace atmosphere’s capability to provide nascent carbon to the heated surface of the workpiece. It is controlled via oxygen sensing probes placed at designated locations within the furnace; the sensors provide feedback to a system which varies the input of natural gas and air to the furnace in order to balance the process gas appropriately, providing consistent heat treat results.

Part loading density is designed by IST. Each individual part number’s furnace loading is specified on work instructions; output is monitored and recorded from lot to lot. Belt furnace loading is defined as pounds per hour; batch and row furnace loading is defined as pounds per basket layer, the number of layers per basket, and, the number of baskets per load. Additionally, some parts may require stacking or racking in special or common fixtures that enable parts to be oriented relatively the same throughout the furnace load in order to achieve close tolerance dimensional results, or to minimize part contact during the heat treat process.

All of these variables, and others, are tightly controlled in order to achieve high Ppk and Cpk values from lot to lot.