Effect of Steel Composition and Processing Parameters on the Penetration Depth of Microcracks in ZnFe‐Coated Boron Steels

Liquid metal assisted cracking (LMAC) and so-called microcracking are limiting the application of hot-dip galvanized boron steels in direct press hardening process. This study addresses role steel hardenability on behavior ZnFe-coated (galvannealed) 22MnB5 22MnMoB8. Several soaking times forming start temperatures range 800–520 °C examined using a laboratory equipment with hat-profiled tool. The results indicate that penetration depth microcracks can be reduced by improving steel, which enables hot austenitic state at exceptionally low even without accelerated cooling procedures. austenite decomposition leads easily to heterogeneous microstructure (ferrite + austenite/martensite) below coating/steel interface, promotes microcracks. crack is generally conversion-delayed 22MnMoB8 steel; however, crucial reduction attained only lowest 550 520 °C. uncouple effect high-temperature ferrite formation from mechanisms suggest embrittling zinc or zinc-rich intermetallic phases plays conventional 800–600