Nittan Valve Co., Ltd.

Hisanaga Yokoyama

Yasuhito Tanaka

Shigeru Uchida

Masanami Iio

A method and an apparatus for supplying inert gas into a poppet valve intermediate are provided that are capable of properly filling the inert gas without waste into the poppet valve intermediate of any size. After a negative pressure is achieved by suction in an internal space (Win) of a poppet valve intermediate (W) as compared to an ambient pressure (Pa) of the poppet valve intermediate (W), the inert gas is supplied into the internal space (Win) until a pressure (F) of the internal space (Win) reaches the ambient pressure (Ps) of the poppet valve intermediate (W).

Method for supplying inert gas into poppet valve intermediate and apparatus for supplying inert gas into poppet valve intermediate

[Problem] To provide an engine valve which satisfies predetermined characteristics with respect to impact resistance, abrasion resistance and high-temperature corrosion resistance all of which meet or exceed predetermined levels required to resist severe use environments, while also minimizing the content ratios of predetermined rare metals. [Means for Solving the Problem] An engine valve is configured to include an engine valve base body having a stem portion and a head portion provided at one end portion of the stem portion, which engine valve comprises: a build-up portion formed by seat welding to encircle the head portion; and a seat obtained by forming a surface-hardened layer on the build-up portion, wherein the build-up portion is formed of a seat weld material constituted of a Ni&#x2014;Fe&#x2014;Cr alloy containing W at 8.0 to 40.0 mass %, Mo at a total together with W in a range of 20.0 to 40.0 mass %, Fe at 20.0 to 50.0 mass %, Cr at 12.0 to 36.0 mass %, B at 1.0 to 2.5 mass %, and a balance of Ni and inevitable impurities, and wherein the surface-hardened layer is formed by effecting nitriding treatment on the entire valve to form a nitride layer on a machined surface formed on the seat, thereby ensuring predetermined characteristic while minimizing rare metal content ratio.

Engine valve

A forged exhaust poppet valve and a method of solution heat treating the same are provided. The forged exhaust poppet valve () includes a head portion () which has a seat portion () on the outer periphery thereof and is integral with a diametrically tapered neck portion () connected to a stem portion (). 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 () and thereby rendering the exhaust poppet valve highly durable.

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Kanagawa, Japan

Hisanaga Yokoyama