20Cr square steel is a versatile low-alloy structural material widely utilized across industrial sectors for its balanced mechanical properties and cost-effectiveness. As a member of the chromium steel family, it merges the strength of carbon steel with enhanced wear and corrosion resistance, making it a preferred choice for components demanding durability and reliability. The chemical composition of 20Cr steel is precisely controlled to deliver its key characteristics. It typically contains 0.17–0.24% carbon, which contributes to hardness and tensile strength; 0.70–1.00% chromium, the core alloying element that forms a protective oxide layer to boost wear and corrosion resistance; 0.50–0.80% manganese, which enhances strength and ductility; and small amounts of silicon (0.17–0.37%) for deoxidation and grain refinement. Phosphorus and sulfur are limited to ≤0.035% each to minimize brittleness. Manufacturing 20Cr square steel involves several stages. Raw materials like iron ore and scrap steel are smelted in electric arc or blast furnaces to form molten steel, which is then cast into billets via continuous casting. These billets are hot-rolled into square sections of varying dimensions (from 10mm×10mm to 100mm×100mm). For high-performance applications, heat treatments such as quenching (rapid cooling) and tempering (reheating to lower temperatures) refine the microstructure, elevating tensile strength and toughness. Mechanical properties of 20Cr square steel shine after heat treatment: tensile strength reaches ~835 MPa, yield strength exceeds 540 MPa, and elongation is at least 10%, indicating good ductility. Its Charpy V-notch impact toughness is ~47 J at room temperature, resisting sudden loads. Physically, it has a density of 7.85 g/cm³ and a melting point of ~1450°C. While not fully stainless, chromium gives it better corrosion resistance than plain carbon steels. Applications span automotive manufacturing (gears, shafts, axles—parts enduring friction and stress), machinery (spindles, bolts, linkage components in heavy equipment), construction (structural supports in industrial buildings), and tooling (low-load dies). Its excellent machinability simplifies cutting, drilling, and milling, reducing fabrication time. Compared to plain carbon steels like 1045, 20Cr offers superior wear resistance without high costs. It is more affordable than high-alloy steels while delivering adequate strength and flexibility. Its square shape streamlines assembly, further lowering production expenses. In summary, 20Cr square steel is a reliable, cost-effective material balancing strength, wear resistance, and machinability. Its wide use across automotive, machinery, and construction underscores its versatility, making it a staple for engineers seeking performance and value.