Alloy Steel 20X2H4A Round Bar 20X2H4A Bars 20X2H4A Rods

Product Description

20X2H4A or 20H2N4A) is a premium, high-quality Russian GOST standard (GOST 4543) chrome-nickel alloy structural steel designed primarily for case-hardening (carburizing).

Characterized by its exceptionally high Nickel (~3.5%) and Chromium (~1.5%) content, it is engineered for heavy-duty components that require extreme surface hardness (up to 60+ HRC after carburizing and heat treatment) combined with outstanding core toughness, fatigue strength, and deep hardenability in large cross-sections.

Technical Specifications & Chemical Composition

The "A" at the end of the GOST designation signifies a high-quality steel with strict limits on impurities like phosphorus and sulfur, which maximizes impact toughness and minimizes embrittlement.

Chemical Composition (Weight % per GOST 4543)

Mechanical Properties (Quenched & Tempered Core Properties)

Even before case-hardening, the core of a 20X2H4A round bar retains extraordinary yield strength and fracture toughness, resisting heavy shock loads without catastrophic failure.

Typical Mechanical Characteristics (Tested on $\le$ 15 mm section)

Global Cross-Reference Equivalents

When sourcing materials across global projects, 20X2H4A aligns closely with heavy-duty nickel-chrome case-hardening grades:

• USA (AISI/SAE): AISI E3316 / SAE 3316

• Europe (EN / DIN): 18NiCrMo14-6 / 1.3533 / 17NiCrMo14

• China (GB/T): 20Cr2Ni4A

• France (AFNOR): 18NiCrMo14 / F-1556

Heat Treatment Guidelines

20X2H4A is a highly responsive steel requiring careful thermal management to achieve its optimum dual-phase properties (hard case, ultra-tough core):

• Forging / Hot Rolling: 1220°C – 850°C

• Normalizing: 860°C – 880°C (air cooling)

• Soft Annealing: 640°C – 680°C (to lower hardness below 269 HBW for easier machining)

• Carburizing Temperature: 870°C – 950°C

• Double Hardening Cycle (Recommended for ultimate grain refinement):

  1. First Quench: Heat to 845°C – 875°C, quench in oil. (Refines the core)

  2. Second Quench: Heat to 760°C – 800°C, quench in oil. (Refines the carbon-rich case)

• Low-Temperature Tempering: 150°C – 210°C (relieves internal quenching stresses while retaining maximum surface HRC)

Key Applications of 20X2H4A Round Bars & Rods

Because it retains high core performance across large section diameters, 20X2H4A round bars are primarily chosen for heavy machinery, aerospace, and defense applications involving severe stress, impact, and wear friction:

• Heavy-Duty Transmission Gears: Large sprockets, bevel gears, planetary pins, and ring gears for mining equipment and heavy trucks.

• High-Stress Shafts: Main drive shafts, multi-diameter turbine shafts, crankshafts, and heavy-duty industrial axles.

• Aerospace & Defense: Highly loaded fasteners, engine connecting rods, rocker arms, and structural pins in aircraft framing.

• Machinery Components: Highly wear-resistant bushings, piston pins, and cold-working dies where surface indentation cannot be tolerated.

Processing Note: Due to its chemical profile and susceptibility to air-hardening cracks, 20X2H4A is not considered weldable. Components should be joined via mechanical means, or structural welding should be strictly avoided.