Haruyoshi Sumimoto

Effect of graphite morphology on decarburized cast iron

The decarburization of cast irons graphite has been studied as part of the process to make high-value-added cast iron. The aim is to develop new uses for cast irons. Once the graphite has been eliminated in a surface layer by high temperature oxidation in air, other materials conferring improved properties can be infiltrated into the resulting pores. The effects of holding time (3–48h), holding temperature (1023–1223K) and chemical composition (3.27–4.0%C, 2.0–4.0%Si) were investigated for each graphite morphology (flake graphite, compacted graphite, spheroidal graphite). As a result, it was found that the rate of formation of porosity (due to the decomposition of graphite) in cast iron obeyed the diffusion law. The rate of formation of porosity in flake graphite irons was faster than that for the other graphite morphologies, probably because flake graphite is continuous in the matrix, whereas spheroidal graphite exists as independent deposits. It has been found that the continuity of the graphite has a strong effect on the rate of formation of porosity.

Effects of heat treatment on the thermal expansion characteristics and mechanical properties in low expansion austenitic cast iron

Several kinds of heat-treatments were applied to a low thermal expansion austenitic flake graphite and spheroidal graphite cast irons. The effects of heat treatment on the average coefficient of li...

Low thermal-expansion gray cast iron strengthened by crystallizing dispersed carbide particles

Low thermal-expansion gray cast iron with high strength and hardness was produced by dispersing carbide particles by means of alloying carbide-stabilizing elements such as Nb, Cr, W, V, Ti and Mo up to 5 at.%. Increasing the alloying content of each element results in increasing the area fraction of carbide and decreasing in that of the graphite fraction, and it results in remarkable increasing in hardness. Tensile strength increases remarkably with increasing in alloying content of Cr or V, but it becomes maximum at some 1 at.% in the case of W or Nb. The increasing in tensile strength and hardness was discussed from such viewpoints as increasing in area fraction of carbide and increasing in effective sectional area ratio resulted from decreasing in area fraction of graphite. The coefficient of mean linear thermal-expansion at 373K increases largely with increasing alloying contents in the case of Cr, W or Mo, but it increases only slightly in the case of Ti, V or Nb.

Effects of tertiary elements on inter-graphite spacing of unidirectionally solidified Fe-C alloys

The effects of 0.004–0.108mass%S, 0.068–1.10 mass% Si, 0.047–0.177 mass% Ti, and 0.0350–0.078 mass% Zr on inter-graphite spacing λ of grey cast iron were investigated using a unidirectional solidif...

Effects of Sulphur, Titanium and Zirconium on the Shape of Solid-Liquid Interface in Fe-C binary alloys

The effects of sulphur, titanium and zirconium on the shape of the eutectic solidification interface in Fe-C binary alloys were investigated by the quenching into ice water during unidirectional solidification. The oscillatory schematic model for graphite branching is proposed by considering the shape of the solidification interface and the protuberance length of the graphite flakes. The specimens contain 0.012, 0.108, 0.37 mass % S, 0.177 mass % Ti, and 0.078 mass % Zr, respectively. They are 80 g in weight, 18 mm in diameter, and 55 mm in length. The temperature gradient at the solid-liquid interface is about 2.5 K/mm.

The Role of Graphite Nodules in the Deformation Behaviors of Spheroidal Graphite Cast Iron

When a ferritic Spheroidal Graphite Cast Iron(SG iron) is submitted to a large tensile load, the graphite nodules in the iron are deformed into oval shape. It has been recognized that a large deformation under tensile stress produces a kind of voids at the graphite edges. However, the breaking process of the graphite nodules has not been clarified yet.