Impressive improvements in quenching of parts!
What is "heat treating" of metal?
Heat treating of metals can be defined as the controlled heating and cooling of metal parts to change the metallurgical structure to obtain desired characteristic in the parts such as hardness, softness, ductility, wear resistance, etc. To harden steel parts, the parts are first heated to the "transformation" temperature, above "critical point" (also called the hardening or "austenizing" temperature), usually between 1400oF to 2300oF (depending on the alloy content of the steel). Once the part is uniformly at temperature, the part is cooled rapidly or "quenched". The purpose of the quench is to achieve the desired metallurgical structure, usually hardened "martensite", while keeping distortion to a minimum. The heat treater must usually balance between the trade-off of hardness for distortion (or part cracking). Stated another way, the faster the steel part is quenched, the higher the "as-quenched" hardness and the deeper into the part the hardness is driven, but also the higher the probability of part distortion or of cracking. After quenching, the steel part is usually re-heated to a temperature well below the critical point, usually 350oF to 1200oF, to temper or "draw down" the hardness and give the part better ductility.
What is "Intensive Quenching" Using the IntensiQuench® Process?
About 35 years ago, Dr. Nikolai Kobasko, of the Ukraine, discovered the "intensive quenching" phenomenon. "Intensive quenching" can be defined as cooling, usually with pure water quenchant, at a rate several times higher than the rate of "normal" or conventional quenching. In contrast to conventional heat-treating practices, intensive quenching calls for very high cooling rates for parts within the martensite phase. Dr. Kobasko's research shows that very fast and very uniform part cooling actually reduces the probability of part cracking and distortion, while improving the surface hardness and durability of steel parts.
Since his discovery, Dr. Kobasko and his colleagues conducted literally hundreds of laboratory experiments and field validation tests. Dr. Kobasko and his team of researchers compiled this data and developed computer models for intensive quenching technology. Applications of intensive quenching are already in routine use in many production heat treating plants in countries of the former Soviet Union as well as in China and Bulgaria.
Why does the intensive quenching phenomenon work?
Due to very fast and very uniform cooling in the first step of the Intensi-Quench® process, the entire part surface reaches the martensite transformation region at the same time regardless of the part geometry and thickness variation. Therefore, the hardened martensitic structure starts forming in a matter of seconds simultaneously throughout the whole part surface area creating a firm case or shell with high compressive stresses on the part surface.
This compressive case acts as a "die" holding the part and minimizing distortion. After tempering, part toughness and fatigue life are improved over conventional quenching methods. The result is a SupR-STRONG part with little part distortion.
What Is The Difference Between Induction Case Hardening and IntensiQuench® Processes?
This is a very commonly posed question. Like IntensiQuench®, induction case hardening (ICH) provides the part with residual compressive surface stresses and with a wear resistant, martensitic surface. However, unlike intensive quenching processes, the ICH process only strengthens the part surface layer. The part core does not experience any phase transformations. If "core conditioning" is required, the part must be through heated, quenched and tempered prior to conducting ICH. This is in contrast to the IntensiQuench® method that provides high compressive surface stresses and at the same time strengthen the core. Secondly, the ICH process creates a hardness profile and residual stress profile that are much steeper than those after intensive quenching. And finally, intensive quenching is interrupted when residual surface compressive stresses are at their maximum value providing the part with an optimum hardened depth. The smoother hardness profile, the high residual stresses and the optimum depth of hardness after IQ processes result in better part performance characteristics - all in one process.