| 摘要 |
PURPOSE:To reduce the manufacturing cost by inserting into a hole of a heat resistant steel billet with the 1st core material such as a lightweight material and the 2nd core material such as titanium, etc. under an overlapped state, and forming a stem and a head by hot extrusion and hot press upsetting, respec tively. CONSTITUTION:The inside of a hole 3 formed in a heat resistant steel billet 4 by warm extrusion is inserted with the 1st core material 7 consisting of a fluid, deformable lightweight substance such as graphite and the 2nd core mate rial 8 such as titanium, etc. having a strength and corrosion resistance under an overlapped state. Then, the billet 4 is heated, the stem 11 is formed by hot forward extrusion, and a billet part 12 is formed into a valve head 15 by hot press upsetting. At that time, the core material 8 and 7 are positioned in the head 15 and 11, respectively. In this method, the complicated and accurate boring process is eliminated, so that the manufacturing cost of the hollow valve is reduced.
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