Abstract
Cast iron becomes porous after repeated heating and cooling above and below the A1 transformation point, and when oil is impregnated into the pores, it can be used as quality of oil-less bearing. The oil content of grown cast iron is almost proportional to the growth rate. As it is considered that the bearing performance is influenced by oil content, a series of bearing performance tests were carried out.
The results of the thrust journal bearing tests showed that the bearing performance rose rectilinealy up to 14 repeated heating and cooling treatments, 4% of growth rate, and about 1% of oil content. The Load capacity of thus treated cast iron was 10 times superior than that of nontreated cast iron. The bearing performance of the grown cast iron were constant in the oil content from 1 to 2%, but the load capacity decreased when oil content was more than 2%. It is considered that the fall of the load capacity is due to the deterioration of the material strength.
The bearing performances at higher sliding speeds improved by making the surface roughness of the mating material fine, whereas at lower sliding speeds, better results were obtained when the surface roughness was rather rough. It was observed that the friction surface was coated by the graphite in the grown cast iron.
