AISI 4140 Alloy Steel Bars

Product Description

AISI 4140 (UNS G41400) is one of the most widely used versatile chromium-molybdenum "chromoly" steels. It is a medium-carbon alloy steel known for its exceptional balance of strength, toughness, and wear resistance.

Commonly supplied as round bars or rods, it can be through-hardened to achieve high mechanical properties, making it a staple for components subjected to high stress.

1. Core Technical Profile

The addition of Chromium provides hardness and corrosion resistance, while Molybdenum ensures uniform hardness and high strength.

2. Heat Treatment & Conditions

The properties of 4140 bars vary significantly depending on their "condition":

• Annealed (+A): Maximum softness for easier machining. Ideal if you plan to do heavy milling before final hardening.

• Normalized (+N): Heated and air-cooled to create a uniform grain structure with moderate strength.

• Quenched & Tempered (Q&T / HT): Often sold as "Pre-hardened" (usually 28“32 HRC). This allows you to machine the part and put it straight into service without further heat treat.

3. Popular AISI 4140 Bar Options

If you are looking for specific stock for a project, these are common commercial forms:

OnlineMetals 4140 Cold-Finished Round Bar

This is a high-performance cold-finished bar that meets ASTM A108 standards. Being annealed, it is optimized for high-stress applications like gears and shafts where precision dimensions are required.

• Condition: Annealed / Cold Finished

• Key Feature: Superior surface quality and dimensional accuracy.

4140 Alloy Steel Round Bar (link{product_id:3762867778937849423})

[Forged 4140 Round Bar

For larger diameters (typically over 100mm), forged bars are preferred. The forging process improves the internal grain structure, providing better impact resistance and reliability for heavy machinery parts.

• Condition: Forged / As-Rolled

• Key Feature: High fatigue strength and abrasion resistance.