Failure of steel castings welded to heavy truck axles

Minor changes in steel chemistry can have a significant affect on weld quality. Weld procedures performed in a manufacturing environment are usually developed based on the steel composition required in a material specification. This is done to consistently produce acceptable weld properties without developing a high hardness heat-affected zone (HAZ) in the adjacent base metal. Fatigue cracks were visually detected in cast steel suspension brackets after operators reported noticing looseness in the rear suspension system. These trucks were associated with a particular vocation that resulted in significant loads transferred through the torque rods that position the rear axles. It was discovered that the carbon equivalent (chemistry) in the steel castings had increased slightly over a period of time which ultimately resulted in a higher than expected hardness in the HAZ. Underbead cracks had formed in the HAZ of the casting that subsequently propagated by fatigue that could have resulted in detachment of the castings from the axle housing. (C) 2003 Elsevier Ltd. All rights reserved.