Abstract: In a process of casting a rocker arm as one piece from high chrome cast iron, a Ca-Si base addition agent is added to the molten metal in an amount of 0.3 to 0.6% by weight. The agent is effective as a globulizer to round high-hardness carbide precipitates directing toward the casting surface.

Abstract: A high strength high chromium cast iron contains fine particle precipitated hard carbide. The precipitated hard carbide has an average particle size of 20 .mu.m or less and hardness of Hv 500 or more in martensite base matrix, and has area ratio in a range of 30% or more and 45% or less. The precipitated hard carbide has spheroidal ratio (surface area of sphere circumscribing the precipitated hard carbide versus actual surface area of precipitated hard carbide) of 40% or more.

Abstract: A high temperature wear resistant sintered alloy suitable for the material of a valve seat in an automotive vehicle engine. The matrix of the sintered alloy consists essentially of carbon ranging from 0.45 to 1.15% by weight, nickel ranging from 5.4 to 27% by weight, molybdenum ranging form 0.4 to 2.7% by weight, cobalt ranging from 4.2 to 7.2% by weight and balance being substantially iron. The matrix is formed of a mixture of at least one of sorbite structure and bainite structure and austenite structure. Furthermore, the matrix includes hard phase dispersed therein and containing at least silicon, molybdenum and cobalt. The sintered alloy of such a structure can exhibit high strength and wear resistance at high temperatures regardless of type of engine and kind of fuel in case of being used as the material of the valve seat, while maintaining production cost thereof lower.

Abstract: A heat resistant and wear resistant iron-base sintered alloy to be used as the material of a valve seat and a valve face of an engine valve and a waste gate valve of a turbocharger for an internal combustion engine. The iron-base sintered alloy consists essentially of at least one of molybdenum and tungsten, ranging from 3 to 25% by weight, chromium ranging from 1 to 10% by weight, silicon ranging from 0.1 to 0.9% by weight, manganese ranging not more than 0.7% by weight, phosphorus ranging not more than 0.05% by weight, carbon ranging from 0.1 to 2.5% by weight, boron ranging from 0.5 to 2.0% by weight, intermetallic compound of TiAl ranging from 0.3 to 20% by weight, and balance including iron and impurities. In the sintered alloy, carbide, boride and/or carbide boride and TiAl are uniformly dispersed in the matrix, thereby strengthening grain boundary.

Abstract: A wear resistant iron-base sintered alloy consists essentially of at least one selected from the group consisting of molybdenum and tungsten, ranging from 5 to 20% by weight, chromium ranging from 2 to 10% by weight, silicon ranging from 0.1 to 0.9% by weight, manganese ranging not more than 0.7% by weight, phosphorus ranging not more than 0.05% by weight, carbon ranging from 0.1 to 0.8% by weight, boron ranging from 0.5 to 2.0% by weight, and balance including iron and an impurity, so that fine multiple carbide, multiple boride, and/or multiple carbide-boride can be homogeneously dispersed as hard grains in the structure of a matrix, thereby exhibiting excellent wear resistance, scuffing resistance and pitting resistance.

Abstract: A rocker arm of a valve mechanism of an automotive internal combustion engine is composed of a rocker arm tip secured to a rocker arm main body. The rocker arm tip includes a sheet type sintered alloy adhered to a steel substrate. The sintered alloy includes a joining phase of martensite stainless steel, and a hard phase of boride and/or multiple boride of at least one, including iron, of elements capable of forming boride and/or multiple boride. The hard phase is homogeneously dispersed in the joining phase. The sintered alloy contains boron ranging from 3.0 to 5.0% by weight, and the hard phase ranging from 40 to 62% by weight. Additionally, the sintered alloy has a maximum grain size of the boride and/or multiple boride ranging not larger than 50 .mu.m, a Rockwell A-scale hardness number ranging not less than 80, and a deflective strength ranging not lower than 175 kgf/mm.sup.2.