The forms of failure are fatigue fracture and excessive deformation. Usually, the parts of fatigue fracture are three high stress areas on the connecting rod.

The working conditions of MG Roewe Maxus Engine require the connecting rod to have high strength and fatigue resistance, and sufficient stiffness and toughness.

The material of forged connecting rods is mainly non-quenched and tempered steel, which is very sensitive to stress concentration. Therefore, there are strict requirements on the shape and transition fillet of the connecting rod.

In the production of connecting rod forgings, common problems include decarburization, creases, errors, cutting edges and pull marks, expansion and fracture slag, etc.

⑴The problem has occurred. Decarburization generally requires the connecting rod to be ≤0.3mm (some products require decarburization ≤0.2mm), and complete decarburization is not allowed. During the production process, non-quenched and tempered steel connecting rods are prone to decarburization. Bare Engine that exceed the standard decarburization layer will affect their service life.

The main reasons for decarburization are: too high blank temperature, too long heating time, accumulation of high-temperature materials in the box or long-term insulation in the furnace, multiple heating, and a sharp rise in the temperature of the electric heating furnace.

⑵Solutions

1) Strengthen the quality control of the production process to avoid excessive material temperature, multiple heating, and stuffy materials;

2) Improve the heating furnace to shorten the heating time and avoid air gaps in the furnace connection;

3) Add a high-temperature rod cooling conveyor belt to avoid high-temperature rod accumulation.