Hardening treatment to ductile iron could increase the surface hardness of castings, to make the casting with good hardness and abrasive resistance.
The normal quenching and tempering treatment could increase the surface hardness to about HRC 30 to HRC 40 of Rockwell Hardness, this process includes the heat heated to 880-930 centigrade, then quenching in the oil, then do the tempering treatment in 500-600 centigrade. As our dandong foundry experience, this process could get high hardness, improve the mechanical properties, and abrasive performance.
If you want higher hardness, and better abrasive resistance, then consider to do this process in the carburizing furnace, then could increase the surface hardness to HRC 50 to HRC 55. The hardness depth will be about 2mm. Our Dandong foundry can not do this heat treatment by ourselves, but we could entrust our local heat treatment workshop to complete this process.
Why do you need carburizing furnace for ductile iron? For the mild steel, because of its low carbon content 0.10% to 0.30%, so it must be treated in the carburizing furnace, to increase its carbon content on the surface. This is the normal acknowledge. For ductile iron, because its carbon content is high enough, 3.00% to 3.90%, so no need to increase its carbon content, but during heat treatment, its carbon content will be reduced, so normal quenching and tempering process can only increase its hardness to about HRC 30 to HRC 40. However, if heating them in the carburizing furnace, the carbon content will be kept, so the hardness can be increased to HRC 50 to HRC 55.
This article is from our Dandong Foundry's Ductile Iron Hardening Treatment.
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