Heat Treatment And Defect Analysis Of Auto Connecting Rod

Automobile connecting rod is one of important components in the reciprocating internal combustion engines. When internal combustion engine works, connecting rod small end moves to and fro along the central line of the cylinder together with piston, and connecting rod big end and crankshaft shank revolve together. Therefore, besides upward and downward movement, the connecting rod body has also complex planar motion of right and left swing. Connecting rods bear mostly combustion gas breakout inflation pressure applied on piston and compressive and tensile stress caused by reciprocating inertia force. Furthermore, because of its slightness, connecting rod will bend along the planes parallel and vertical crankshaft axis shaft under compression. Since angular acceleration and rotating inertia during connecting rod swing will produce inertia moment, connecting rod body would be impressed additive bending stress and moment. Otherwise, above-mentioned working loads are alternating, so there is impact property. Therefore, the steel material for manufacturing connecting rod should have enough strength and certain plasticity and resilience.For the technical parameters are very important in such steps as feed preparation,blanking,forming,heat treatment and strengthening etc, it is quite difficult to deform high-precision connecting rod. The main form of failure in connecting rod is fatigue fracture. In order to maintain high-speed running crankshaft on balance state, quality tolerance of connecting rod is required to limit in a certain range. Meantime, connecting rod body can not be machined after die forging, otherwise the fiber formed during die forging will be cut off and then the heads of fibers will be seen, which affects fatigue property.