Composition: Tool steel (1.40-1.50 C; 0.10-0.60 Mn; 11.0-12.0 Cr;  0.10- 0.60 Si; 0.7-1.20 Mo; < 0.03 P; < 0.03 S; 0.50-1.10 V).

Processing: Forging/rolling at 1050 ºC and slow cooling.

Etching: 20-40s immersion in 2% nital.

Technically, this is not a stainless steel. However, the high Cr concentration (11.5%) provides some corrosion protection. This is a high-carbon, high-chromium tool steel that is commonly used for stamping and forming dies, punches, forming rolls, shear blades and similar tools. The microstructures correspond to a hardness value of 310 HV and show the presence of coarse carbides that were already present during the forging process at 1050ºC. These carbides are rich in Cr and are aligned with the direction of rolling. Slow cooling after forging results in precipitation of fine globular carbides in a ferritic matrix. This steel can reach up to 63-65 HRC if carbides are uniformly distributed and the proper heat treatment is applied. For example, annealing up to 1050ºC and subsequent quenching in oil or air, in order to obtain a martensitic microstructure, followed by tempering at 500ºC to produce uniform and copious precipitation of chromium carbides in the martensitic matrix. 

F521 CCT diagram

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