Crankshaft is one of the most important parts of internalcombustion engine and its service life determines IC engine’s service life. In1920 newly invented induction heating technology was applied to hardening ofcrankshaft neck by CLARCOR USA which improved wearing resistance of crankshaftand lifetime of IC engine greatly.

In recent decades fatigue fracture of crankshaft hasbecame a serious problem and fatigue fracture often happens at the filletpositon of inner crankshaft neck. So many crankshaft manufacturers requiredimproving the fatigue strength of crankshaft. The key of improving the fatiguestrength of crankshaft is to improving the residual stress of crankshaftfillet. The induction quenching of crankshaft fillet(including neck) is thefirst choice of making fillet get >600MP residual stress.

One Japanese company did a series of experiments aboutfatigue bending of IC engine’s crankshaft which showed the fillet has thehighest fatigue strength (996MPa) after induction heating, 890MPa after rollingand 720MPa after nitriding. And some US companies also got the similar data.Generally induction quenching of crankshaft fillet uses” half-ring inductor”,namely Elotherm quenching--- putting inductor on crankshaft neck and doingheating and shower cooling under rotation(or after neck being heated to thepointed temperature and put crankshaft into water tank for cooling). Thismethod is not only easy for crankshaft in and out of inductor, but alsosimplifies the quenching machine’s movement, meanwhile solves problems of oilhole crack, uneven hardening area and depth case by using traditional inductor.Most industry insiders think Elotherm quenching is one of the big progress incrankshaft induction quenching. The data makes clear that crankshaft neckinduction quenching can improve engine lifetime to 8000 hours and neck andfillet quenching can improves lifetime to 10000 hours. The key technology ofrealizing fillet quenching is power distribution technology. ” Half-ringinductor” quenching of crankshaft involves a lot of technologies like variablefrequency power, quenching machine, inductor, etc. These technologies whichwere preliminarily realized in China in the early 80’s.

I still remember when my colleagues and I were doingcrankshaft fillet quenching research we had a problem: when inner filletreached pointed quenching temperature via using ” half-ring inductor” quenchingthe outer shoulder already melted. That is because of the crankshaft structure.There’s a big difference in quality environment of crankshaft’s fillet corner. Theinner fillet is “deeper” with more thermal capacity and when surface of filletreached the quenching temperature also there’s some heat transferred inside;but the other area of fillet is “thinner” with less thermal capacity, whensurface of fillet reached the quenching temperature, the same heat is transferredinside, however because of “thinner” area it can accept limited thermalcapacity so heat accumulated and the shoulder melted. Apparently to do a goodquenching on crankshaft’s fillet the heating power should change, namely thepower inside of crankshaft hand is bigger than the one outside, this technologyis called power distribution. It’s a pity at that time in China we didn’t havesuch technology. In middle 90’s Heatking pioneered the development of thistechnology and successfully used it in fillet quenching of big and smallcrankshafts. This technology means providing 100% power when doing heatinginside of handle and 60% or 70% power when doing heating outside of handle,increasing(or reducing) some power every 15° turn of crankshaft rotation. Inrecent years Heatking has sold over 10 set of induction quenching machines forcrankshaft which process millions of crankshafts. Most of these crankshafts areexported to USA. Nowadays ideas like energy-saving, environmental protectionbecame a general agreement, almost all the IC engine manufacturers are pursuingminiaturization, lightweight and longevity. And quenching technology ofcrankshaft’s fillet provides powerful technical support and it has a broadmarket prospect.