Abstract
21-4N is a typical heat resistant steel used as the material of exhaust valves. The application of cross wedge rolling to manufacture preform for valves has the advantages of higher efficiency and better quality. In this study, cross wedge rolling of 21-4N with an area reduction ratio of 65% was experimentally studied. Twelve groups of different tool parameters of cross wedge rolling tests were carried out. It is found that a larger stretching angle or a smaller forming angle is better for surface quality. When the stretching angle is 7° and the forming angle is less than 25°, a smooth surface can be obtained. Furthermore, the influence of stretching angle on central quality is not obvious, but a greater forming angle is prone to get a better central quality. When the forming angle is larger than 30°, no central damage was found in the workpieces. Considering the balance of surface quality and central quality, a stretching angle of 7° and a forming angle of 30° is a suitable combination for cross wedge rolling of 21-4N with an area reduction ratio of 65%.
Highlights
The valve is one of the key parts used in diesel engines
Austenitic alloy and superalloys are used for exhaust valves [1]. 21-4N is a typical heat resistant steel used as a material for exhaust valves in the automobile industry
A team in the University of Science and Technology Beijing (USTB) proposed a new method to produce the preform of valves by cross wedge rolling (CWR), which has higher production efficiency and better control of product quality [4,5,6]
Summary
The valve is one of the key parts used in diesel engines. It works under a corrosive environment with high temperatures and high pressure. 21-4N is a typical heat resistant steel used as a material for exhaust valves in the automobile industry. Austenitic alloy and superalloys are used for exhaust valves [1]. It has good properties of tensile strength, yield strength, wear resistance and corrosion resistance. Valves are formed by electric upsetting and forging. In this process, electric upsetting is used to manufacture the preform for forging. A team in the University of Science and Technology Beijing (USTB) proposed a new method to produce the preform of valves by cross wedge rolling (CWR), which has higher production efficiency and better control of product quality [4,5,6]
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