ISSUE 1/2010

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Gutte, H.; Radtke, M.; Weiss, A.; Scheller, P. R.
Stainless, austenitic, cast steel with a TRIP effect

For the first time, investigations of meta-stable, austenitic and austenitic-martensitic steels serve as a basis for developing austenitic, cast steel alloys with a TRIP effect. The TRIP effect in these cast steel alloys serves as a stretching reserve during subjection to mechanical stress, e. g. in the event of a crash. CrMnNi cast steel alloys were produced and then underwent tensile and notched-impact bending tests at various temperatures. Three alloy variants with differently scaled TRIP effects and exhibiting typical strengths and tenacities were compared with conventional, reference cast steel GX 5CrNi 19 10 (1.4308). Due to the TRIP effect, the new cast steel alloys possess improved characteristics in terms of strength and tenacity. The additional strength and strain values attributable to the TRIP effect are quantified. Metallographic investigations document the martensite induced by deformation and resulting in the TRIP effect. Similar to metastable, austenitic CrNi steels with a TRIP effect, deformation-induced martensite in TRIP cast steel leads to a temperature anomaly in the tenacity characteristics; this anomaly is manifested as a maximum. Current density/potential curves serve for evaluation of the corrosion resistance of TRIP cast steel alloys. Given similar corrosion characteristics, much higher strength and tenacity values are registered in comparison with the reference cast steel GX 5CrNi 19 10 (1.4308). Furthermore, a drop of more than 50 % in the nickel content allows notable savings in alloy costs. The developed cast steel alloys with a TRIP effect hence widen the scope of applications for austenitic and austenitic-martensitic, cast steel

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