Exhaust poppet valve and solution heat treatment method of the same

摘要

A forged exhaust poppet valve and a method of solution heat treating the same are provided. The forged exhaust poppet valve (10) includes a head portion (12) which has a seat portion (14) on the outer periphery thereof and is integral with a diametrically tapered neck portion (16) connected to a stem portion (18). Using a radio-frequency heating apparatus, a solution heat treatment is given to a predetermined transitional region (A) of the neck portion and the stem portion that is exposed to exhaust air during a valve opening period such that the grain size in the region (A) does not exceed ASTM 10, thereby securing a necessary high-temperature creep strength in the region (A) and a necessary hardness (wear resistance) in the seat portion (14) and thereby rendering the exhaust poppet valve highly durable.