42CrMo attains through-hardening capability primarily through the deliberate addition of molybdenum alongside chromium. While 40Cr relies on chromium alone for hardenability, 42CrMo adds 0.15–0.30% Mo, a strong carbide former that dramatically pushes the C-curve rightward, enabling deep hardening in sections that 40Cr cannot fully penetrate.
Its oil-quenching critical diameter reaches 40–80 mm or more, allowing large-diameter fasteners to achieve uniform high strength from surface to core. After quenching and tempering, 42CrMo delivers tensile strength of at least 1080 MPa and yield strength of at least 930 MPa—substantially higher than 40Cr's 980 MPa and 785 MPa respectively. The molybdenum addition also suppresses temper embrittlement, maintaining toughness after high-temperature tempering. This ensures reliable performance in heavy-duty bolts, studs, and fasteners subjected to extreme loads, where a soft core would cause premature failure.
Just like you, 70% customers choose long-term cooperation with BBN steel not only for our good product and service quality, good reputation in the international market, but also for our experienced one-stop raw material supply and further steel processing!
