Shallow Cryogenic Treatment (SCT) Effects on the Mechanical Properties of High Cr Cast Iron: Low-Carbon Cast Steel Bimetallic Casting

摘要

The shallow cryogenic (subzero) treatment (SCT) effect on the mechanical properties of the bimetallic casting used in the crushing industry has been investigated. Examination methods include sand casting, heat treatment and SCT, Charpy impact test, optical microscope, scanning electron microscope, microanalysis of the chemical composition (energy dispersive spectroscopy-EDS), x-ray diffraction, and hardness measurement. Two bimetallic castings (single casting containing two layers, one of low-carbon cast steel-LCCS-back up part and other high Cr cast iron-HCCI-working part) have been prepared by the sand casting method. They have been subjected to diffusion annealing at 1040 degrees C for 5 h. One of them was quenched in pressurized air till 100 degrees C and was tempered at 270 degrees C for 3 h and, and the other one has been subjected to SCT at - 84 degrees C for 24 h and then tempered at 270 degrees C for 3 h. The impact toughness values before and after SCT are determined five Charpy specimens per point. Hardness values and metallography of samples have been analyzed and compared. A remarkable change was observed in hardness and impact energy/toughness before and after SCT.