No abstract

Considering the exhaust valve spindle consists of a valve head and a stem comprising the body, the use of different materials, that is, Nimonic 80A for the head and SNCrW for the stem, can reduce the manufacturing cost dramatically. The inertia welding was conducted to make the large exhaust valve for low speed marine diesel engines, superalloy Nimonic 80A for valve head of 540mm diameter and high alloy SNCrW for valve stem of 115mm diameter. Due to different properties of material like thermal conductivity and flow stress on the two sides of the weld interface, modeling is crucial in determining the optimal weld geometry and parameters. FE simulation was performed by the commercial code DEFORM-2D. A Good agreement between the predicted and actual welded shape was observed. It was expected that simulation will significantly reduce the number of experimental trials needed to determine the weld parameters, especially for welds of very expensive materials or large shaft. A variety of tests, including microstructure observation, tensile, hardness and fatigue test, are conducted to evaluate the quality of welded joints.