| Steel reflects the comprehensive national power of a country, and the thirdgeneration advanced high strength steel is one of the most promising trends for theautomotive steels. In this paper, a novel process which combined deformation inducedferrite transformation technical and the quenching-partition process is investigated.This process will result in a sophisticated microstructure containing lath martensite,ferrite and retained austenite which will get a good mechanical property.This novel process contains two main steps: hot stamping to get deformationinduced ferrite and the following Q&P process. Here is the detail: firstly the specimenswere austenitized under the established conditions to form a desired austenite grain size,then cooled to the deformation temperature which around the Ae3temperature. It wasimmediately followed by compression at a strain proper rate to a prescribed strain.After deformation, the specimens were immediately quenched to the temperaturebetween the martensitic starting temperature (Ms) and the martensitic finishingtemperature (Mf), partitioning within a few seconds at the temperature equal to orabove the quenching temperature, and then quenched to room temperature. After allthis steps, the specimens will get a sophisticated microstructure.In this research, two typical steels are treated by the novel process and both have agood mechanical property. Both steels have a product of strength and strain above20000MPa%. Also, the process parameters are investigated such as hot stampingtemperature, strain and partition time. Finally the deformation induced ferrite wasfounded in TRIP780whose diameters were5μm in average and was well-distributed.In22MnB5, the deformation induced ferrite transformation is hard to occur. Thetransformation could happen when the specimen were hot stamped at750℃with thestrain of about60%. After all, this novel process is a promising process to get advancedhigh strength steels. |
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