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 camshaft of a valve operating system for an internal combustion engine, is formed of iron-based alloy casting and has cam sections, each of which is in slidable contact with a heat resistant tip of a rocker arm. The cam section is formed at its surface portion with a surface hardened layer formed of an air-cooled chilled structure. The surface hardened layer is formed by remelting a part of the surface of the casting after preheating. An intermediate hardened layer of a heat affected zone is formed in contact with the surface hardened layer and has a thickness ranging from 0.5 to 2.0 mm. The intermediate hardened layer is formed of a mixed structure of bainite transformation phase and troostite and is formed by being thermally affected during the remelting.

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.