| 摘要 |
PURPOSE:To obtain a superior wear resistant material in which the shapes of carbide are changed and the hardness of matrix is increased by subjecting high Cr cast iron to the special heat treatment which increases C, adds Si, Mo, V, etc. and cools mists at specific cooling rates. CONSTITUTION:High Cr cast iron contg. by %, 3.0-4.0 C, 0.5-2.5 Si, 15.0-30.0 Cr, 1.0-30.0 Mo and V, Nb is heated. While the moisture content in blast is controlled, said cast iron is cooled with mists at 10-100 deg.C/min cooling rate. Here, if the C is below the lower limit, the absolute quantity of barbide is small and wear resistance cannot be assured. If in excess of the upper limit, the car bide of the initial crystal is too much to be maintained. The Si and the Mo improve the hardness of the matrix, and the V improves its toughness. The cooling rate is required to be in the above-described range in order to allow the carbide on the surface to be used to deposet in the form of columns as shown. Such high cooling rate cannot be obtained with furnace cooling, air cooling or blast cooling except for extra small-sized products. On the other hand, with water cooling and oil cooling, the cooling rate is so high that retained austenite is formed and hardness decreases considerably; therefore, the mist cooling is employed. |
