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We are a world-class supplier of engineering raw materials. Our objective is to provide all our customers, from the small machine shop to the large multi-national corporation, a supply path that continuously delivers the highest levels of service, quality and value.

4340 (AMS A684, SAE 4340)

Chromium Nickel Molybdenum Alloy Steel

4340 Steel Alloy

AMS 6484 chromium-nickel-molybdenum alloy is a widely used deep-hardening constructional steel.

Remarkable Ductility

It is used at a variety of strength levels and at each level possesses remarkable ductility and toughness. With its high alloy content uniform hardness is developed by heat treatment in relatively heavy sections. High fatigue strength makes E-4340 ideal for highly stressed parts. It maintains its strength and hardness at elevated temperatures. This grade is available as electric furnace vacuum degassed steel to meet the high aircraft quality standards of AMS 2301. Thus, it is suitable for the fabrication of parts, which may be subjected to magnetic particle inspection.

Aerospace Sector

This grade is also available as a premium aircraft quality product. The regular aircraft quality material is re-melted in a vacuum using consumable electrode practice. This results in a much cleaner steel meeting the magnetic particle test requirements of AMS-2300 and insures a steel of the highest quality with excellent transverse ductility and toughness at high strength levels.


Aircraft landing gear, engine components, crankshafts, axles. Intended for parts with sections 3 Ā½ā€ or less in thickness at time of heat treatment, which require a through-hardening steel capable of developing minimum hardness of Rockwell ā€œCā€ 30. Premium aircraft quality is intended for use in the manufacturing of highly stressed parts at higher strength levels, such as 260/280 ksi and where a much cleaner steel is desired.

Typical Applications

Commercial applications for this engineering material include:

  • Premium aerospace product
  • Landing gears
  • Engineered components
  • Crankshafts and axles

We stock AMS 6484 (4340) in flats, round bar, plate, sheet, hollow bar and square bar.

Technical Assistance

Our knowledgeable staff and resident metallurgists will be pleased to assist you further on any technical topic. Smiths Metal Centres Limited also boasts an in-house UKAS Accredited Testing Laboratory which is unique within the multi-metal and plastic stockholding sector. We believe this underlines our total commitment to quality and our ethos of being the complete service provider.

Additional Info

A technical datasheet for AMS 6484 (4340) is available in PDF file format. To view and download, please click here.

We offer in-house processing options - for more information, please refer to our processing services.

Read our corporate brochure by clicking here.

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