Thickness 5/8, 4340 Hot Rolled Annealed Alloy Steel

This is the "king" of the hardening grades of constructional alloy steels. Because of richer alloy content, 4340 possesses much deeper hardenability than the 4100 series. This advantage is realized principally where high strength is required in heavy sections. In addition, unusually high hardenability insures maximum toughness and ductility at the desired strength level. The fatigue-tensile ratio makes this grade ideal for highly stressed parts. It maintains its strength, ductility, and toughness at relatively high temperatures. It has remarkable non-distorting properties for an alloy steel. Thus, for high strength in heavy sections, or for highly stressed parts operating under the most severe conditions, or where the greatest margin of safety is desired, this is the steel to use.

Nickel-Chromium-Molybdenum Steel

UNS G43400

Unit of Measure

Specifications

Estimated Weight per Sq. In.	N/A .1773
Estimated Weight per Sq. Ft.	N/A 25.52

Analysis

N/A Carbon .38/.43
Manganese .60/.80
Phosphorus .035 Max.
Sulphur .04 Max.
Si. .15/.35
Cr. .70/.90
Ni. 1.65/2.00
Mo. .20/.30

Applications

N/A Automotive and marine crank shafts, diesel engine cranlc shafts and other heavy-duty shafting, axle shafts, dies, subs, gear shafts, gears, mine-drilling parts, oil-well fishing tools, perforating gun bodies, master hobs, etc.

Machinability

N/A This material has a machinability rating in the annealed condition of approximately 57% of 1212. Surface cutting speed is approximately 95 feet per minute.

Weldability

N/A Difficult to weld, but can be welded by any of the common welding processes providing the section is preheated and stress relieved after welding. The grade of welding rod to be used depends upon thickness of section, design, service requirements, etc.

Forging

N/A Heat to 2200°-2300°F

Normalizing

N/A Heat to 1600°-1700°F. Cool in air. Average Brinell Hardness, 363.

Annealing

N/A Heat to 1500°-1600°F. Cool slowly in furnace. Average Brinell Hardness, 197.

Hardening

N/A Standard hardening range is between 1475°-1575°F. Quench in oil. A wide range of mechanical properties can be obtained by tempering between 400° and 1200°F.