Heat Treatment Guide
Ovako Heat Treatment Guide is a tool developed to increase the understanding of how different alloying elements influence steel hardness after quenching and/or tempering. For most steels, hardness after quenching depends on the cooling rate (sometimes expressed as the time between 800 and 500℃). Hardenability is usually presented in a CCT-diagram or a Jominy-curve. Other, simplified ways to present the hardenability also exist, such as DI-value. Following the quenching process most steels are tempererd, for low and medium alloyed steels the hardness is reduced by tempering. Whereas for example certain tool steels and PH-steels the hardness can be maintained or increased after tempering/aging process.
This calculation tool calculates:
- CCT-diagram (hardness as a function of cooling rate)
- Jominy-curve & DI-value
- Core hardness after quenching of a bar with a user-specified diameter (water, oil and air quenching)
- Tempering diagram (hardness and strength as a function of tempering temperature)
This tool has been developed to be valid for most steel grades (carbon steels, engineering steels, tool steels, maraging steels, PH-steels, stainless steels etc).
The input needed to perform a calculation is the alloy composition, with the following elements included: carbon (C), silicon (Si), manganese (Mn), chromium (Cr), nickel (Ni), molybdenum (Mo), copper (Cu), titanium (Ti), aluminium (Al), boron (B), vanadium (V), tungsten (W) and cobalt (Co).
The austenitization time and temperature is assumed to be appropriate in order to achieve maximum hardness after a fast quench (for example, for a bearing steel with 1%C, a hardness of approx. 65HRC following a fast quench, is expected, provided austenitization is performed correctly). For the tempering diagrams, hardness before tempering is assumed to be as high as possible for the given steel grade. The tempering time is “short”, approx. 1-3hours.
