Development of Fracture Split Steel Connecting Rods

Fracture split steel connecting rod has been developed for new passenger diesel engines for its advantages in cost saving and better performance. The splitting type of steel con rod is made of high carbon micro-alloyed steel with no additional heat treatment after hot forging. This con rod blank is forged in one-die mold and later fracture splitted. Unlike the conventional types where the rods and caps are separately forged and machined, this steel split con rod needs no additional rod/cap contact face milling which means a substantial savings in machining cost. Besides, a firm contact between rod and cap improves stiffness and compatibility with other crank-train moving parts - a definite merit in engine performance.

Our research work focuses on optimizing the two major technologies in this subject - microstructural analysis of controlled cooling (high carbon micro-alloyed steels) and detailed fracture splitting parameters and test results. We are now expecting up to a 25% reduction in cost as well as a significant improvement in engine performance (stiffness increase of at least 10%, weight tolerance of forge blank less than ±1%).