This chromium nickel molybdenum alloy is a widely used deep-hardening constructional steel. 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.
This grade is also available as a Premium Aircraft Quality product. The regular aircraft quality material is remelted 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.
N/AIntended for parts with sections 3 1/2" or less in thickness at time of heat treatment, which require a through-hardening steel capable of developing minimum hardness of Rockwell "C" 30. Premium Aircraft Quality is intended for use in the manufacturing of highly stressed parts at higher strength levels, such as 260/280,000 psi and where a much cleaner steel is desired.
Hardening
N/AEnd-quench hardenability values for this grade are Rockwell "C" 50 minimum at 20/16" and Rockwell "C" 45 minimum at 3 2/16"
Heat Treating
N/ANormalize—1650°F
Austenitize—1500°F
Quench—Oil, 140 °F maximum
Temper—400/500°F for 260,000 psi strength level
725°F minimum for lower strength levels
