Who here knows all the current heat treating jargon out there? Raise your hand. Let’s face it. We have a lot going on in our lives and sometimes we pretend to know things we don’t. For example, my wife recently asked me if we needed an oil change. I know we are suppose to get one every few thousand miles, but I have no idea why. The same goes for heat treating. While you probably know what needs heat treating in your line of work and why, chances are you haven’t been exposed to all the ‘other’ heat treating terms that people like to throw around. Well, this blog is meant to give you the definitions of the most used terms that all the expert heat treating people like to drop at those fancy heat treating cocktail parties. Ok, those parties don’t exist, but you should still know the heat treating terminology. Enjoy
ANNEAL – To heat a material uniformly to a specific temperature that is within or above its critical range, then cooling it at a controlled rate to a temperature under its specified critical range. This process is used for many reasons including: to produce an exact microstructure in order for the material to perform optimally during the machining process, removing stresses, inducing malleability, and alter ductility.
SUB-CRITICAL ANNEAL – A tempering process for steel that is performed at high temperatures. The benefits include many of the same that annealing creates but without the controlled rate cooling.
SPHEROIDIZE ANNEAL – An annealing process, specific to steel, that entails a very long heat treating method. . the benefits of this procedure include increased ductility, improved performance during the machining process, increased softness, and the production of globular carbides .
NORMALIZE – An annealing process for steel where the material is heated at least 100° above its critical temperature. The results are grain recrystalization and refinement. The steel is strengthened by this process.
QUENCH – The process of rapidly cooling a material in air or liquid after its heated treatment.
TEMPER OR DRAW – To uniformly heat a material to a specific temperature below its critical range for a specific amount of time. The cooled material is then softened and ready for machining, has improved ductility and is free from stresses, or has the desired structure and properties.
STRESS RELIEVE TEMPER – A heat treating process designed to restore elasticity after a material has completed other heat treatment procedures that produces stresses.
CARBURIZE – This process includes transmitting a high carbon layer onto steel (a low carbon material) by heat transference. The quenching process hardens the outer high-carbon layer encasing the softer steel. This creates a strong, wear-resistant exterior best for manufacturing items like gears and camshafts.
NITROCARBURIZE – This practice uses carbon and nitrogen to create a hard case around steel known as the compound “white layer”. The inner layer called the diffusion zone, increases the products fatque properties, especially in alloys like steel. Nitrocarburizing is performed at temperature under the critical temperature range which helps to avoid distortion. The case depth thickness is less than .003 inches.
CARBONITRIDE – Similar to the carburizing process but with the introduction of ammonia added to the atmosphere to assimilate nitrogen into the case during production. This creates a stronger casing where lesser alloy grades can attain greater hardness and case thickness.
SOLUTION TREATMENT – The first phase of precipitation hardening treatment where a substance is heated to a specifid temperature and the temp. is maintained for long enough for the precipitates to dissolve. The result is a solid solution that can be made highly corrosive resistant like the 300 series stainless steels.
AGE – The next step in precipitation hardening where the material is heated moderately and remains at that temperature until the optimal precipitate size is reached and the desired mechanical properties are attained.
We hope these definitions help you understand the heat treating lingo. Good luck. Oh, and you should get an oil change every 3500 miles!