AISI 4000 Series 4135/4140/4145 is premium chromium-molybdenum alloy structural steel, graded by increasing carbon content for enhanced strength and hardness. Heat-treatable (quenched/tempered), it delivers exceptional tensile strength, toughness, wear resistance and fatigue performance, maintaining stability under heavy loads. Featuring good machinability, weldability with pre-treatment and precise dimensional tolerance, it’s available in customizable profiles and sizes. A cost-effective high-performance alloy steel, it’s the core material for heavy-duty industrial components requiring superior mechanical properties.