4340 steel (36CRNIMO4)

Sullivan Steel Stocks 4340 VAR Tube

A low alloy steel, 4340 is known for its strength and toughness. The steel can be carburized or induction-hardened but is more often used as a through-hardening grade.

Typically, 4340 is used in applications when other low alloy steel varieties don’t have sufficient hardenability, ductility, toughness, or strength. 4340 has a high nickel content, giving it superior hardness. This grade of steel can often be used as an alternative to 4140.

4340 steel is well-suited to aerospace and industrial applications for components that require high strength and toughness, such as gears, shafts, etc.

FOR REQUIREMENTS: High strength, high hardness
AMS 6414
UNS: G43400
Euro Number: 1.6511
Boeing: BMS 7-28

Get 4340 VAR Tube At Sullivan Steel

4340 steel is typically available in bar stock and tubing. Sullivan Steel currently stocks VAR tubing and we expect to expand our offerings. Contact us to inquire about ordering other forms, such as bar, wire, or sheets.

Request 4340 VAR Tube

Chemical Composition – VAR

  C Mn Si P Cr Ni Mo S Cu
Min. 0.38 0.65 0.15 0.70 1.65 0.20
Max. 0.43 0.90 0.35 0.010 0.90 2.00 0.30 0.010 0.35

The nickel content in 4340 gives the alloy more strength compared to other low alloy steels, such as 4140, when used in similar applications.

Equivalent Grades

 The steel grade 4340 is often compared to 4140 and 4130 but can achieve superior hardness. 4340 is also similar to NC310YW—an alloy with similar properties and a higher silicon content.

Heat Treatment

Heat treating 4340 steel improves the alloy’s hardness significantly. It can be carburized or induction hardened but is mostly used as a through hardening grade.

The usual heat treatment for 4340 is to quench and temper for the desired hardness. Heat treating 4340 can produce hardness in excess of HRC 50 (see the hardenability data in TimkenSteel Practical Data for Metallurgists).

Sullivan Steel supports customers with guidance and documentation for heat treating 4340 to help ensure it meets their requirements.


While in the annealed condition, 4340 is ductile and machinable using standard methods, including sawing, turning, drilling, cutting, and boring. Machining is not recommended after heat treatment due to increased hardness.


4340 steel is used for components and machinery where high hardenability and toughness are a priority. Typical applications include truck and aircraft parts with large cross-sections, such as gears and shafts.

When through hardened, 4340 has superior strength compared to similar low alloy grades and may be used as an alternative for parts made from 4130 or 4140.

● Gears
● Shafts
● Flanges
● Die blocks
● Pressure vessels
● Fasteners

Sullivan Steel has 4340 var tube in Stock

At Sullivan, we carry 4340 tubing. Contact us if you’re looking for bar, sheets, wire, or a hard-to-find size. Through our connections with the major mills, we can help with finding the 4340 stock that fits your requirements.

We support the steel we sell with guidance and technical support to ensure your steel can achieve the properties needed for your application.

Request 4340 VAR Tube