The Background of IntensiQuench
Some of the intensive water quenching methods have been around for at least 40 years. “Timed water quenching,” interrupted quenching, high velocity spray quenching with water have all been around for a long time. There is some confusion in the heat treating community as to where the IntensiQuench process fit into all of these methods. Suffice to say that the other methods of quenching do not combine all the elements that IntensiQuench has assembled to both limit part distortion and maximize compressive stresses. My partner in IQ Technologies Inc., Dr. Nikolai Kobasko, FASM, began his work with intensive quenching back in the 1970′s in the former Soviet Union. One of the main reasons that IntensiQuench is relatively unknown in North America is that approach in Western countries was to create “better alloys” with higher hardenability to get the properties that were needed from oil quenching of steel parts. The oil quench is very robust and relatively forgiving method of quenching most alloys of steel. The approach in the former Soviet Union was to try “to do more with less.” The steel plants in the USSR were very large facilities employing thousands of people making large quantities but fewer varieties of steel. Since the ability to tweak alloys was not market driven as in North America, the metallurgists got more creative with the processing methods for the alloys that were widely available.
Another reason that IntensiQuench processes has not flourished in heat treating practice is it flies in the face of most conventional heat treater’s wisdom – the faster the quench, the more likely you are to crack or distort the part. Even the renowned metallurgy Professor Jack Wallace at Case Western University, in Cleveland, Ohio, recoiled at the thought of quenching parts in cold water. In 1997, when my partner Dr. Michael Aronov was introducing the process to a gathering of heat treaters and metallurgists from the Cleveland area, and looking for a demonstration site, Professor Wallace told me “It will never work… the parts will explode in the quench.” (His grad assistant on the other side of Professor Wallace nodded in agreement.) Being a lawyer by training, and working in sales at Akron Steel Treating, I was too ignorant to know that you “cannot quench 52100 in water.” Several months later, under a project funded by the Edison Materials Technology Center (EMTEC) and the Ohio Department of Development, we did just that. We heated several 52100 bearing rings in a small atmosphere furnace at AST and intensively quenched the tapered rings (for the Dr. Kobasko determined number of seconds) in a relatively crude 500-gallon IntensiQuench system built at the AGA Research Labs in Cleveland, Ohio – where Michael Aronov worked at the time. After witnessing the trials at AST, Professor Wallace, in his early 80′s at the time, became one of our greatest supporters. Professor Wallace and his team at CWRU wrote several papers about the benefits of IntensiQuench. The benefits of rapid water quenching of S5 punches and H-13 dies was the subject of technical papers written with Professor Wallace.
The lack of computing power to optimize the compressive stress distribution and to predict by modeling the proper recipe to get the desired results from the higher quench rates. Dr. Kobasko created empirical models as well as mathematical models to predict the beneficial effects of intensive cooling rates during the martensitic phase transformation, versus traditional, less intensive, quenching methods. The advent of faster computer models to do the many calculations needed to stimulate the complex physics and thermodynamics that are going on simultaneously in the quenching of a steel part – temperature and phase transformation changes causing size changes – shrinking then growing; with shifting stress distribution changes; and all within the confines of the part covered. The newer 3-D finite element models, such as Deformation Control Technologies’ DANTE model are a tremendous help to IDT predicting what is going on during the quenching of various shaped parts made with various alloys.
Still an area of concern is lack of complete databases for different alloys of steel. More attention should be paid for developing these databases for cooling capacity of quenchants and optimized chemical composition of steels. But even with the lack of complete data base information, once the IntensiQuench trials are done for a particular part with the date from the high speed data loggers, the process is under precise control.
The surface case hardness uniformity in a load of carburized 8620 truck universal joint crosses in the 36″ X 72″ X 36″ AFC-Holcroft integral quench furnace equipped with IntensiQuench water tank is +/- 1 HRC point on the four truions checked at four point on each truion — that’s 2,000 Rockwell readings. The core is similarly uniform and with 8620 too hard — so 1018 is better (and lower cost) choice.
What goes on at the interface of the hot part surface and the water in the quench system in another area of complex events. IQ Technologies also works with Computational Fluid Dynamics (CFD) modeling company, Airflow Sciences Corporation of Michigan. Higher and higher water flow rates do not always translate into better quench uniformity and assure the elimination of dead zones in the quench. The newer modeling tools have enabled the application of IntensiQuench, uniformly, to more complex parts.
Obviously, there are practical limitations as to the sizes and the geometry of parts that can be uniformly intensively water quenched. Very small parts will not develop higher compressive residual surface stresses since they quench through almost instantaneously. Parts with blind holes can create real issue too. However, IntensiQuench equipment can and has been used to uniformly quench fasteners made of “water-hardening” grades of steel and even solution treat aluminum and titanium parts.
Over the years, IntensiQuench has had many successes. To date the greatest success of IntensiQuench is the application to carburized helicopter gears and through hardening gear rack steels. The small test gears treated with IntensiQuench withstood a 15% higher load for the same fatigue life. This means that the helicopter gear box should be able to safely do more work without major redesign of the helicopter platform.
The IntensiQuench S5 punches that outlast the oil-quenched punches by punching more than twice the number of holes in another success.
The reduction of the carburization cycle by 40% (or the reduction of alloy used for carburized parts) while still obtaining the same hardness gradient as oil quenching is a success. With “Optimal Hardenability” (“OH”) steels (very low alloy, medium carbon steels) coupled with IntensiQuench (“OH+IQ”) the carburization process can be eliminated entirely and the parts have a hardness profile and residual stress distribution that is very similar to that of carburized and oil quenched parts.
With the selection of the proper IntensiQuench, water-then-air cooling cycles, IntensiQuench is successfully applied to many types of gears, rollers, S5 punches, H-13 dies, gun barrels, axles, springs and the like. And because of the very high cooling rates of IntentiQuench, less alloy, lower hardenability steels, can often be substituted for higher alloy steels that are normally used with oil or gas quenching.
I feel that in the future, IntensiQuench will be come a more “mainstream” technology and capture a significant portion of the heat treating market. There are three drivers that will move IntensiQuench into the “mainstream” of the heat treating market of the 21st century.
Once is the ability to use lower alloy, lower hardenability, less expensive steel alloys with IntensiQuench versus oil or gas quenching and still obtain the needed part properties – tensile strength, ductility, hardened depth, etc. As alloy surcharges rise, so will the demand for ways to limit or eliminate the high cost alloying elements. Two is the ability to produce higher power density parts with IntensiQuench versus traditional quenching methods. Lighter, stronger parts with higher residual compressive stresses on the surface, with or without shot peening, are possible with IntensiQuench and the alloy of steel optimized for use with the process.
Three is the environmental benefits of elimination of the oil quench and the reduction (or elimination) of the energy intensive carburizing cycle. Since IntensiQuench uses plain water as the quenching media, it is an enabling technology for the heat treating of part (even case hardened parts) within the part manufacturing cell in a flexible, single part flow.
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