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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%.

Experimental Study on Cross Wedge Rolling of 21-4N Heat Resistant Steel