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Introduction Chemical Composition Physical Properties Mechanical Properties Thermal Properties Other Designations Fabrication and Heat Treatment Machinability Forming Welding Heat Treatment Forging Cold Working Annealing Tempering Hardening Applications
Alloy steels are designated by AISI four-digit numbers. They comprise different kinds of steels having composition exceeding the limitations of B, C, Mn, Mo, Ni, Si, Cr, and Va set for carbon steels.
AISI 4340 alloy steel is a heat treatable and low alloy steel containing chromium, nickel and molybdenum. It has high toughness and strength in the heat treated condition.
The following table shows the chemical composition of AISI 4340 alloy steel.
The physical properties of AISI 4340 alloy steel are given in the following table.
The mechanical properties of annealed AISI 4340 alloy steel are displayed in the following table.
The following table outlines the thermal properties of AISI 4340 alloy steel.
Other designations that are equivalent to AISI 4340 alloy steel include the following:
AISI 4340 alloy steel can be machined using all conventional techniques. Machining process can be performed in the annealed or normalized and tempered conditions.
AISI 4340 alloy steel has good ductility and formability in the annealed condition. It can be bent or formed by pressing or spinning in the annealed state.
AISI 4340 alloy steel can be welded using fusion or resistance welding methods. Preheat and post heat weld procedures are followed while welding this steel by established methods.
AISI 4340 alloy steel is heat treated at 830°C (1525°F) followed by quenching in oil.
AISI 4340 alloy steel is forged at 427 to 1233°C (1800 to 2250°F).
AISI 4340 alloy steel can be cold worked using all conventional methods in the annealed condition. It has high ductility.
AISI 4340 alloy steel is annealed at 844°C (1550°F) followed by cooling the furnace.
AISI 4340 alloy steel should be in the heat treated or normalized and heat treated condition before tempering. Tempering temperatures depend upon the desired strength level.
AISI 4340 alloy steel can be hardened by cold working or heat treatment.
AISI 4340 alloy steel is mainly used in power transmission gears and shafts, aircraft landing gear, and other structural parts.
Thanks for all the information. I have a question for you: We applied cadmium cyanide plating to avoid rusting of this material but after certain time, the material started to rust. We need to know what type of coating is compatible with the Cadmium Cyanide coating for a stronger rust protection system. Not Electro plating.
Chrome coating will be economic and efecctive solution with high corrosion resistance
Hello, ArmorGalv Thermal Diffusion Coating www.armorgalv.com should be considered. Zero chance of Hydrogen Embrittlement. Over 1,000 hours of salt spray resistance, high lubricity (replacement for cadmium plating), high ductility, various sealers either stand-alone coating or apply additional coatings such as paint, Teflon, etc. for specific applications. Over 60 world-wide applicators. Process requires 600-750 degrees F so only need to watch tempering temperatures, though consult with applicators.
Please why is the same shear modulus assumed for both forged carbon steel and alloy steel ?
Looking for characteristics magnetization curve for 4340 steel.
I'm looking for a B-H magnetization curve for 4340 steel
is it possible to weld grade 304stainless steel on AISI 4340 Alloy Steel
Yes, however the 4340 material needs to be purchased in the annealed or normalized condition. AISI 309L weld filler should be used. The material MUST be preheated to around 315°C and temperature in the welds zone must not be permitted to drop below 300°C during welding operations. Welded areas should be slow cooled over several hours. Typically this is done by reheating to 350-400°C then wrapping parts in insulation, or placing in a preheated furnace and furnace cooling. For complex parts with large amounts of welding, it's recommended to heat treat the assembly immediately after welding as finished and welds have been visually inspected. In general because if the very high strength of this material, welds must be of the utmost possible quality. Weld Undercutting, lack of fusion defects, cracks, porosity, and incomplete root penetration cannot be tolerated. It's strongly recommend to inspect welds for HAZ cracks and other defects by a variety of nondestructive testing methods. 100% of assemblies should be examined for weld defects.
I want to reference the Mill test of alloy steel 4340 (plate) (34CrNiMo-6). Who have it, please give me? Thank you so much. My email: [email protected]
is this possible to do case hardening and which type?
Can this steel be hot-dip galvanized? I will be using it as a structural pin in an outdoor industrial environment.
Yes. 4340 lends itself well to HDG in the quenched and tempered state because it has moderate tempering resistance. For the same reason it's sometimes bern used for hot-work tooling. Holding in the zinc bath while it heats to the galvanizing temperature will generally result in slight reduction in hardness and yield strength. However keep in mind that parts should be double tempered at slightly above the expected zinc bath temperature beforehand. Parts containing high residual stresses from quenching and high overall hardness may be subject to liquid metal embrittlement during HDG. Therefore consideration needs to be taken with regards to the tempering step. Lastly keep in mind that very high strength Q&T alloy steels are prone to hydrogen embrittlement. Certain corrosion conditions can lead to hydrogen production inside joint surfaces or crevices due to sacrificial corrosion of the thick zinc layer. This has been known to cause unexpected failures of hot-dipped fasteners, for example.
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