Times Have Changed

Many years ago, part manufacturers almost always heat treated their parts in their own heat treating department. In most cases there were no better alternatives – no one had sophisticated temperature and atmosphere controls; and the cost of energy was really not as much of a concern. (Natural gas pricing was regulated, controlled at thirty-two cents per MCF. In 2009, it is about $10.00 per MCF delivered to your burner tip.) The capital costs for the basic furnace and material handling equipment were relatively low. Other complexities not faced by in-house heat treaters were the myriad of OSHA, and environmental regulations; many that are specific to heat treating operations. There were fewer types of heat treating processes and fewer quality requirements for heat treated products. So the captive heat treating department, just like the in-house electricians and pipe-fitters, made sense for many manufacturers.

Just as CNC controls have revolutionized the part manufacturing processes, the computerized furnace controls, job tracking software and material handling automation have all changed the way heat treating is done. Atmosphere controls have gone from dew point testers, with manual testing of atmospheres once a shift, to real-time oxygen probes with computer controlled feedback loops tweaking the gas atmosphere every few seconds. The paper chart recorders have been replaced by computerized data logging systems. Job shop routers are kept in the computer for 10 years and can be found with a couple of keystrokes. (See, "JobbShoppe™" / "SpecView©" / " Certification" links.) Many heat treat operations use automated charge cars to move the work into and out of the furnaces. Quenching is done under protective atmospheres without excessive smoke or fumes. Vacuum furnaces eliminate all the smoke and contain most of the heat inside the vessel.

Fire safety has always been a concern for the heat treating industry. The fire suppression systems for oil quenching have been taken from the plant floor (outside the furnace) to automated nitrogen gas purge systems that fill the inside of the furnace vestibule over the quench oil to smother any quench oil fire before it starts.

Years ago, quality in heat treating had a lot to do with the “black art” of blacksmithing, such as, “eyeballing” temperature by color, and using experience to tweak the process. Unfortunately, practicing an “art” is not the best way to insure uniformity of the product and consistently high quality parts.

Today, as with most manufacturing disciplines, modern heat treating of metals is a science. The science of metallurgy has come a long way from the days of the blacksmith, and even the heat treaters of the mid to late 1900’s. The scanning electron microscope has opened up the inner workings of many metallurgical processes, so metallurgists can actually “see” the changes to the molecular structures that take place during the heat treating process. AST’s in-house metallography and micro-hardness testing lab allows us to diagnose the underlying cause of costly part failures and makes sure they do not happen again. Since heat treating is done to a mostly finished product, mistakes near the end of the part making process are very costly.