The effectiveness of intense spray quenching

Conclusions

• 1. The use of spray quenching for hardening parts of low- and medium-carbon unalloyed and low-alloy steels ensures considerable strengthening not attainable by other quenching methods.

• 2. To attain high strength characteristics the most important factor is to prevent tempering of martensite during the course of its formation.

• 3. For steel 25 with 0.22–0.28% C the cooling rate in the lower temperature range that is sufficient to prevent decomposition of martensite during quenching must be above 600–700 deg/sec. When a water spray is used this rate is attained in the center of parts of diameter D ^min_cr =7–8.5 mm or thickness δ ^min_cr =2.3–2.8 mm (cooling from one side).

• 4. For steel 45 with 0.42–0.48% C the cooling rate in the lower temperature range that is sufficient to prevent decomposition of martensite during quenching must be above 300–350 deg/sec. This rate is attained in the center of parts with diameter D ^min_cr =9–12 mm or thickness δ ^min_cr =3–4 mm (cooling from one side).

• 5. With quenching of low- and medium-carbon steels in a water spray, identical rates of heat transfer from the inner layers can be attained in any temperature range and also equal strength characteristics, with D ^min_cr /δ ^min_cr =3.