| 摘要 |
Provided is a method for producing an engine valve (V) by subjecting a stem portion (S) having a hollow part (H) to a drawing treatment using a series of dies (D1, D2, Dx, Dx+1, Dn) such that the outer diameter and inner diameter of the stem portion (S) become smaller in steps and the stem portion (S) is thereby molded to the desired size, whereby, after the stem portion (S) has been subjected to the drawing treatment until the inner diameter of the hollow part (H) of the stem portion (S) has reached a specific size (steps S11 to S15), sodium metal (Na) in the form of a solid block is introduced to the hollow part (H) of the stem portion (S) (step 16-1), and a protective agent(P) made from solid paraffin or naphthalene is also introduced to the hollow part (H) of the stem portion (S) such as to form a barrier between the sodium metal (Na) and the atmosphere (step S16-2), after which the stem portion (S) is further subjected to a cold drawing treatment (steps S17, S18). |
