EN362 Alloy Steel Chrome Moly Bars

Product Description

EN362 is a historic and highly regarded British standard (BS 970: 1955) specification for a low-carbon, Nickel-Chromium-Molybdenum triple-alloy steel bar. Primarily engineered as a case-hardening (carburizing) steel, it is the metallurgical twin to the modern British standard 805M20 and North America’s widely utilized AISI 8620.

When specified in bar form (round, hex, or square), EN362 bridges the gap between basic carbon steels and high-alloy steels. It provides moderate hardenability, a clean machining profile, and an exceptional balance of wear-resistant case hardness and shock-resistant core toughness.

1. Chemical Formula Breakdown

The multi-alloy chemistry of EN362 bars is balanced precisely to favor surface carbon absorption while ensuring a highly stable, impact-resistant underlying core:

2. Structural Heat Treatment Strategy

Because an EN362 bar contains only $\sim$0.20% baseline carbon, direct quenching will not result in a high-hardness skin. Instead, it is subjected to a classic dual-state case-hardening process:

1. Carburizing ($880^\circ\text{C} - 950^\circ\text{C}$): The machined component is baked in a carbon-rich gas or plasma atmosphere. Carbon atoms diffuse into the surface layer, driving the outer "case" carbon content up to $\sim$0.80%.

2. Quenching & Low-Tempering ($\sim150^\circ\text{C} - 200^\circ\text{C}$): The components are oil-quenched and stress-relieved.

• The Final Properties: The outer shell reaches a glass-hard 58 to 62 HRC for superb resistance to abrasion and surface pitting, while the core remains a robust structural matrix boasting a tensile strength of 700 to 1100 MPa (depending on the section diameter).

3. Core Delivery and Machining States

From the mill, EN362 bars are typically supplied in two standard configurations:

• As-Rolled / Soft Annealed State: Delivered with a maximum hardness of $\le$ 240–280 HBW. In this softer state, the material exhibits outstanding machinability. It chips predictably, leaves an incredibly smooth surface finish on CNC lathes, and preserves the lifespan of drilling, milling, and hobbing inserts.

• Uncarburized (Hardened & Tempered State): While primarily a case-hardening grade, EN362 bars can be purchased pre-hardened without surface carbon enrichment. In this state, it acts as a reliable high-tensile structural steel (up to $\sim$800 MPa tensile strength) that can be easily nitrided to yield a hard surface skin without thermal distortion.

4. Primary Industrial Applications

EN362 bars are heavily utilized across the automotive, heavy machinery, and power transmission sectors for light-to-medium stressed parts subject to intense friction:

• Powertrain Elements: Differential pinions, automotive camshafts, light-duty crankshafts, ratchets, and splined transmission shafts.

• Mechanical Assemblies: High-load bushings, guide pins, kingpins, steering joints, and heavy-duty sleeves.

• Tooling Support: Machine arbors, collet holders, and specialized gear shafts.

5. Direct Global Cross-References

If you are sourcing material globally, auditing an old blueprint, or validating Mill Test Certificates (MTCs), EN362 lines up directly with:

• United States: AISI 8620 / SAE 8620 / UNS G86200

• United Kingdom (Modern): BS 970 805M20

• Germany / Europe: DIN 1.6523 / 20NiCrMo2-2 / 21NiCrMo2

• Japan: JIS SNCM220 / SNCM220H

• France (AFNOR): 20NCD2

• Russia: GOST 20KhNM (20ХНМ)

• China: GB 20CrNiMo

6. Sourcing & Fabrication Realities

⚠️ Technical Considerations

• Flame/Induction Quenching Caution: If you plan to leave the steel uncarburized, do not attempt surface induction or flame hardening. Due to the low baseline carbon window, it will not respond satisfactorily. Use nitriding instead.

• Favorable Weldability: Thanks to its low base carbon footprint, EN362 is considerably easier to weld than high-carbon structural alloys like EN19 (AISI 4140). A moderate preheat ($150^\circ\text{C} - 200^\circ\text{C}$) for thick bar cross-sections is sufficient to avoid hydrogen cracking in the heat-affected zone (HAZ).