Nittan Valve Co., Ltd.

Fukuda Metal Foil & Powder Co., Ltd.

Kazunori Kurahashi

Maiku Mikami

Shinichi Nishimura

Katsunori Otobe

Atsuyuki Ichimiya

Yoshihiro Takahashi

A method of manufacturing an engine valve intermediate product with a boss portion formed in integral fashion at an outer circumferential surface at an intermediate location on a stem forming portion. The manufacturing method may comprise a stem retaining operation in which an intermediate location of the stem forming portion is retained by a plurality of intermediate jigs removably installable radially with respect to a center of the stem forming portion, and a base end portion is retained by a base end jig. The manufacturing method may further comprise a stem enlarging operation in which compressive forces are applied from both ends of the intermediate product and the boss portion is formed as the intermediate product is made to rotate and alternating loads that cause tensile forces and compressive forces to act in repeated and alternating fashion at the outer circumferential surface of the stem forming portion are applied.

Method of manufacturing engine valve intermediate product with boss portion

A method for manufacturing a poppet valvefrom an intermediate valve products is disclosed. The intermediate valve products have an intermediate valve head' with a pressing protrusions. A peakof the pressing protrusionsis located in a normal direction Xof the seat surface N, which is positioned on a normal line Xpassing a reference point Pset on a line segment K connecting a base point Pin an inner side and a base point Pin an outer side of the seat surface N; a position of the reference point Pis set such that a relation between a length Lfrom the base point Pto the reference point Pand a length Lfrom the base point Pto the reference point Pmeets a formula of L/L&#x2264;0.5.

Poppet valve and method for manufacturing same

There is provided a surface-coating material having excellent cracking resistance and peeling resistance, and having excellent high-temperature corrosion resistance properties; and a poppet valve coated with the surface-coating material. The Ni&#x2014;Cr&#x2014;Co-based alloy comprises 40.0 to 50.0 mass % of Cr, 10.0 to 20.0 mass % of Co, 0.5 to 5.0 mass % of Nb, 0.01 to 5.0 mass % of Fe and 0.1 to 3.0 mass % of Si, with the remainder being 26.0 to 40.0 mass % of Ni and unavoidable impurities. The Ni&#x2014;Cr&#x2014;Co-based alloy may additionally comprise one or more elements selected from Mo, W, Mn, Ti, Al, B and C in a total amount of 5.0 mass % or less. The content of each of Ti and Al is 3.0 mass % or less and the content of each of B and C is 1.0 mass % or less. In the poppet valve, at least a face portion is coated with the Ni&#x2014;Cr&#x2014;Co-based alloy.

Ni-Cr-Co-based alloy having high-temperature corrosion resistance, and poppet valve surface-modified with the same

A method of forming a poppet valve having a stem, a valve head and a valve seat while concurrently maintaining compressive residual stress without grain coarsening on both the valve body and the valve seat. The method includes forming a rounded cladded part on the valve head of the poppet valve by welding and forming a valve seat surface at a predetermined aperture angle and cutting the cladded part to form a smooth surface which is subjected to uniform contact pressure at a temperature less than the recrystallization temperature of the base material or cladding material, whichever is lower, to enhance the durability of the valve seat.

Poppet valve with a formed seat, and method of making

A surface hardening material being excellent in impact resistance and having abrasion resistance is provided. Provided are: a high-toughness cobalt-based alloy containing 25.0 to 40.0 mass % of Cr, 0.5 to 12.0 mass % of a sum of W and/or Mo, 0.8 to 5.5 mass % of Si, and 0.5 to 2.5 mass % of B, 8.0 mass % or less of each of Fe, Ni, Mn, and Cu, and 0.3 mass % or less of C, the sum amount of Fe, Ni, Mn, and C being 10.0 mass % or less, and the remainder comprising 48.0 to 68.0 mass % of Co and unavoidable impurities; and an engine valve coated with the same.

High-toughness cobalt-based alloy and engine valve coated with same

A surface hardening material being excellent in abrasion resistance and having impact resistance is provided. Provided are: a wear-resistant cobalt-based alloy containing 20.0 to 30.0 mass % of a sum of Mo and/or W, 0.8 to 2.2 mass % of B, 5.0 to 18.0 mass % of Cr, 5.0 mass % or less of a sum of Fe, Ni, Mn, Cu, Si and C, 1.0 mass % or less of Si, and 0.3 mass % or less of C, and the remainder comprising 55.0 to 70.0 mass % of Co and unavoidable impurities; and an engine valve coated with the same.

Wear-resistant cobalt-based alloy and engine valve coated with same

A method of manufacturing a valve for an internal combustion engine, comprises: (i) a primary step of forging a bulging portion at one end of a rod material to form a generally disk-shape valve head of the valve having a tapered periphery; (ii) an thickness adjustment step of machining an excessively thick portion of the valve head; and (iii) a secondary step of forging a peripheral region of the valve head to create radial slip deformations therein to form a valve face of the valve head. In the step of thickness adjustment, only the front end of the disk-shape valve head is machined without harming dense grain flow lines induced in the tapered face () in the primary forging while advantageously saving the valve material and reducing thickness adjustment time. In the secondary forging, the hardness of the valve face is further enhanced.

Method of manufacturing a valve for an internal combustion engine

A method of manufacturing a valve () is provided, in which an intermediate valve product having a generally disk-shape valve head is formed by a die unit (). The valve head is then machined to have a proper thickness and a tapered face on the periphery of the disk-shape valve head. The valve head is repeatedly forged in secondary forging by means of a die unit () equipped with a die () and a press punch () while angularly displacing the tapered face relative to the die () through a predetermined angle. Since the die () has protruding pressing sections and grooves () along the circumference of the die, a uniformly deformed and hardened valve face () is formed on the valve head.

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Hadano, Japan

Kazunori Kurahashi