4140 Alloy Steel

4140 Alloy Steel (UNS G41400) is a versatile, high-tensile, chromium-molybdenum low-alloy steel that has become an industry standard for applications requiring high fatigue strength, toughness, and torsional resistance. Often referred to in the trade as Alloy Steel 4140, this material is prized for its ability to maintain consistent hardness and strength through a cross-section of the metal after heat treatment.

At Specialty Steel, we provide premium 4140 Steel that meets the rigorous demands of the aerospace, oil and gas, and automotive sectors. Our inventory features Hot Rolled Heat Treated (HRHT) material, quenched and tempered to a Brinell Hardness of 269/341 (RC 28-34), ensuring it is stress-relieved and machine-straightened for immediate industrial use.

About 4140 Alloy Steel

The “41” in 4140 signifies that the steel is part of the chromium-molybdenum family. The chromium provides excellent hardness penetration and corrosion resistance, while the molybdenum ensures uniformity of hardness and high strength. This combination makes 4140 superior to standard carbon steels like 1045, offering significantly better impact resistance and durability under stress.

Key Specifications and Standards

To ensure the highest quality and compliance for B2B sourcing, our steel alloy 4140 is manufactured and tested to meet international standards including ASTM A29, A322, and A331.

Chemical Composition (AISI 4140)
The precise balance of elements in 4140 is what dictates its superior mechanical performance:

Because of its high strength-to-weight ratio and resistance to abrasion, 4140 is the “workhorse” of the industrial machining world. It is the material of choice for components that must withstand high stress and constant wear.

• Industrial Tooling: Drill collars, ejector pins, and tool holders.
• Automotive & Heavy Equipment: Axles, conveyor parts, steering knuckles, and crankshafts.
• Oil & Gas: High-pressure valves, drill bits, and pony collars.
• Fasteners: High-strength bolts, nuts, and studs (often meeting ASTM A193 Grade B7).
• Power Transmission: Gears, pinions, and sprocket shafts.

Available Forms and Sourcing Information

Specialty Steel Company maintains an extensive inventory of 4140 steel in multiple finishes and shapes to reduce your lead times. We specialize in hard-to-find sizes and custom lengths.

Stock Availability

• Available Lengths: 10/13 Ft, 20/26 Ft
• Custom Services: High-speed production sawing for Custom Cut-to-Length precision
• Finish: Hot Rolled, Quenched & Tempered, Stress Relieved, and Machine Straightened

4140 Alloy Steel Fabrication and Heat Treatment Guide

Understanding how to work with 4140 type steel is critical for achieving optimal part performance.

Machinability

In the heat-treated condition (RC 28-34), 4140 offers a balance of strength and workable machinability. While it is tougher than annealed material, it provides a superior surface finish and eliminates the need for further heat treatment after machining, reducing the risk of part distortion.

Welding

4140 can be welded using all conventional methods, but caution is required. Because of its hardenability, the material is susceptible to cracking in the heat-affected zone. Pre-heating to 400°F–600°F and post-weld stress relieving are mandatory for critical structural components.

Corrosion Resistance

While this type of steel contains chromium, it is not a stainless steel and will rust if exposed to moisture. We recommend storing material in dry, indoor locations on racks and applying protective oils or coatings for long-term storage.

Comprehensive Steel Supply

For over three decades, Specialty Steel has served as the backbone for comprehensive steel supply for commercial and industrial fabrication. As a certified steel distributor, we do more than just stock 4140 Alloy Steel; we provide a partnership built on material expertise and a commitment to uncompromising quality. Whether you are sourcing for a high-stakes aerospace component or large-scale industrial machinery, you can rely on our certified Material Test Reports (MTRs) and high-speed production sawing for precision cut-to-length accuracy.