Use of low-hardenability steel in small-scale production
Low-hardenability steels developed for induction hardening can also be used for bulk hardening with furnace heating for small-scale production.
The following conditions were found to be optimal for steel 55PP: Furnace heating to 790–800°C with holding 15 min, quenching in 10% NaCl, thrusting the piece into the quenching tank or dropping it into a tank of sufficient depth, and tempering 60 min at 150°C.
The structure of samples quenched in 10% NaCl consists of fine and medium-size martensite needles (grade 5–6) in the outer zone, martensite and temper troostite in the transition zone (the quality of troostite increasing toward the core), and sorbite with sections of martensite and separate grains of ferrite in the core.
KeywordsFurnace Ferrite Martensite Transition Zone Sorbite
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