Austenitizing temperatures for water-hardening tool steels normally vary from 760 to 845 °C (1400 to 1550 °F), as indicated in Table 2. Higher temperatures are sometimes used for special purposes (Fig. 2). Hardenability increases as austenitizing temperature increases. The optimum time at austenitizing temperature is from 10 to 30 min. Preheating is unusual except for very large tools or those with intricate cross sections. It is particularly important to protect shallow-hardening steels against scaling and decarburization. Severe scaling can interfere with heat transfer during quenching and slow the required high rate of cooling. Decarburization will produce a soft surface on any tool steel, but in a deep-hardening steel it can be ground off until the underlying hard high-carbon area is reached. Grinding a shallow-hardening steel will frequently expose the soft core.
For more information, click on the link below (subscription required). Then scroll to Figure 2.
Rafael Agnelli Mesquita; Reinhold Schneider; Cristiane Sales Gonçalves, Heat Treating of Cold-Work Tool Steels — Low- and Un-Alloyed Water and Oil Hardening Steels, ASM International, 2014. https://doi.org/10.31399/asm.hb.v04d.a0005972
