Study of the applicability of 22MnB5 sheet metal as protective masks to improve tool life in hot forging process

Abstract

Low boron steels are the only class of steel capable of forming a fully martensitic microstructure after hot stamping when a cooled tool is used, and the maximum stress can reach 1500 MPa. The purpose of this work is to study the applicability of 22MnB5 sheet metal as protective masks in hot forging dies. Sheets that were 1.3 mm thick were cut in samples of 110 mm diameter and heat treated in conditions similar to direct hot stamping and placed on the hot forging die. Cycles of 25, 50, 75, and 100 forgings were performed, and at each cycle, the metallic mask was replaced for characterization. Microhardness profiles, micrographic analysis by optical and electron microscopy, and profilometry profiles were used to determine the occurrence of surface wear on the masks after each forging cycle. The main types of superficial wear were abrasive and plastic deformation. However, the masks showed high resistance to wear and did not present failures that would make them unusable until the studied condition of a cycle of 100 forgings.