Automotive

Carbon steel covers general structural and non-critical stressed parts. S20C carburized gives high surface hardness with a tough core for transmission and idler gears. S45C suits crankshafts, steering knuckles, and pedal levers requiring moderate strength. S55C's higher carbon content delivers better hardness for brake discs and clutch plates. S355J2, a low-alloy high-strength structural steel with excellent low-temperature impact toughness and weldability, is used for frames, sub-frames, and trailer chassis that must maintain structural integrity under long-term dynamic loading without heat treatment.

Alloy steels are the backbone of critical automotive components. SCM420 carburized and quenched is the standard for differential and transmission gears — extremely high surface hardness delivers long gear-face wear life. SNCM220 (8620), favored by North American and European OEMs, provides hard case and tough core for heavily impacted drive gears. Hardenability-guaranteed grades SCM420H, SNCM220H, and 8620H ensure every bar in a batch falls within the specified Jominy band, keeping gear meshing noise and service life consistent across production.

Cold heading steel plays a larger role in automotive than most realize. A single vehicle contains thousands of bolts — from cylinder head bolts to chassis suspension bolts — almost all cold-formed. 10B33, the go-to for 8.8-grade flange bolts, uses trace boron to greatly increase hardenability, reaching required strength after Q&T. 50BV30 suits high-strength fasteners and elastic elements with boron-vanadium addition balancing hardenability and grain refinement. 40ACR covers chassis and wheel hub bolts requiring higher post-cold-forming strength and fatigue resistance. Cold forming aligns metal fiber flow with part geometry, giving superior fatigue life over machined parts — a critical advantage for fasteners under repeated vibration.