Naslov
Influence of Heat Transfer Dynamics on Hardness Distribution after Quenching

Autori
Liščić, Božidar

Izvornik
Kovine, zlitine, tehnologije = Metals, alloys, technologies (1318-0010) 31 (1997), 6; 521-528

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Quenching; Heat Transfer

Sažetak
The pattern of hardness distribution on round bars' cross-section after quenching was studied in relation to the change of heat transfer on the workpiece surface. It was found that a "delayed quenching", producing a discontinuous change of cooling rate, may result in higher hardness in the core, than at the surface. This phenomenon called "inverse hardening" has been theoretically expllained by Shimizu and Tamura. It depends on: hardenability of the steel, cross-section size of the workpiece and on quenching condition, and is related to the incubation period consumed before the cooling rate was changed. own experiments using cylindrical specimens of 50 mm Dia, made of AISI-4140 steel, have shown that Controllable Delayed Quenching (CDQ) technology has a great potential to increase the depth of hardening, compared to conventional quenching practice. Bending fatigue tests with inverse hardened and tempered specimens have shown a significant increase of the fatigue life compared to specimens having normal hardness distribution after quenching. CDQ-technology and "inverse hardening" can reproducibly be realized using adequate steel hardenability and cross-section size of the workpiece, by quenching in PAG polymer-solution of high concentration, or high pressure-circulated gases.

Izvorni jezik
Engleski

Znanstvena područja
Strojarstvo

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