4340 cold drawn steel bar

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US $950-1,500 / Metric Tons | 3 Metric Ton/Metric Tons (Min. Order)
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Quick Details
Steel Grade:
Dia 10-90mm
Place of Origin:
Jiangsu, China (Mainland)
Brand Name:
Unite Steel
Model Number:
Tolerance: H8/H9/H10/H11/K12
Cold Drawn
Structural Steel Bar
Alloy Or Not:
Is Alloy
Special Use:
Cold Heading Steel
Alloy Steel Bar
EAF/LD+LF+VOD+ Rolled+Cold Drawn
SEP 1921-84
cold drawn steel bar
Round Section
Product Name:
cold drawn steel bar
Peeled Finish or Smooth Finish
Supply Ability
Supply Ability:
2000 Metric Ton/Metric Tons per Month cold drawn steel bar
Packaging & Delivery
Packaging Details
Seaworthy package
Lead Time :
Within 10 - 45 days after confirmed



4340 is a 1.8% nickel - chromium - molybdenum high hardenability high tensile steel - generally supplied hardened and tempered in the tensile range of 930 - 1080 Mpa (condition U) - (Rc 28 - 36).
Characterised by high strength and toughness in relatively large sections.
Pre hardened and tempered 4340 can be further surface hardened by flame or induction hardening and by nitriding.
4340 is used in most industry sectors for applications requiring higher tensile/yield strength than 4140 can provide.



Components for the aircraft, automotive, general engineering industries, Propeller shafts, connecting rods, gear shafts, and other automobile parts, Heavy forgings, Rotors, shafts, discs. Pulley shafts, gears, pins and axles, Heavy-duty axles, shafts, heavyduty gears, spindles, pins, studs, collets, bolts, couplings, sprockets, pinions, torsion bars, connecting rods, crow bars, conveyor parts etc. Used where higher yield and tensile strength than 4140 is required.



Australia AS 1444-2007 4340

Germany W.Nr 1.6565 34CrNiMo6

Great Britain BS970 1955 EN24

BS970 Part 3:1991 817M40

BS EN10083:1-1991 817M40

USA ASTM A29A29M 1991 4340

ASTM A322 4340

SAE 4340

UNS G43400

Japan JIS G 4103 SNCM439

JIS G 4103 SNCM8

Werkstoff 1.6565 40NiCrMo6


Chemical Composition(%):

Carbon 0.37-0.44

Silicon 0.17-0.37

Manganese 0.50-0.80

Phosphorus 0.04 max

Sulphur 0.04 max

Chromium 0.60-0.90

Molybdenum 0.15-0.25

Nickel 1.25-1.85


Process: EAF/LD+LF+VOD+ Rolled+Cold Drawn




Cold Drawn: 10mm-90mm 



Black, Peeled K12, Cold Drawn, Turned & Polished H10, H11, Precision Ground H9, H8


Test: Ultrasonic test according to SEP 1921-84


Heat to 1150 oC - 1200 oC maximum, hold until temperature is uniform throughout the section.
Do not forge below 850 oC.
Following forging operation the work piece should be cooled as slowly as possible in sand or dry lime etc.

Heat Treatment
Heat to 800 oC - 850 oC, hold until temperature is uniform throughout the section and cool in furnace.
Flame or Induction Hardening
4340 hardened and tempered bar can be further surface hardened by either the flame or induction hardening methods resulting in a case hardness in excess of Rc 50. Parts should be heated as quickly as possible to the austenitic temperature range (830 oC - 860 oC) and required case depth followed by an immediate oil or water quench, depending upon hardness required, workpiece size/shape and quenching arrangements.
Following quenching to hand warm, most components should be tempered between 150 oC - 200 oC to remove quenching stresses in the case. This will have little effect on case hardness.
Heat to 830 oC - 860 oC, hold until temperature is uniform throughout the section, soak for 10 - 15 minutes per 25 mm section, and quench in oil, water, or polymer as required.
*Temper immediately while still hand warm.
4340 hardened and tempered bar can also be successfully nitrided, giving a surface hardness of up to Rc 60. Nitriding is carried out at 490 oC - 530 oC, followed by slow cooling (no quench) reducing the problem of distortion. Parts can therefore be machined to near final size, leaving a grinding allowance only. The tensile strength of the core is usually not affected since the nitriding temperature range is generally below the original tempering temperature employed.
N.B. Nickel is inert to the action of nitrogen and in general resists its diffusion into steel. This can result in lower case hardness or longer nitriding cycle times for steels containing nickel such as 4340.
Stress Relieving
Heat to 600 oC - 650 oC, hold until temperature is uniform throughout the section, soak for 1 hour per 25 mm of section, and cool in still air.
Re-heat to 450 oC - 660 oC as required, hold until temperature is uniform throughout the section, soak for 1 hour per 25 mm of section, and cool in still air.
N.B. Tempering should be avoided if possible within the range 250 oC - 450 oC due to temper brittleness.
Notes on Heat Treatment
Heating temperatures, rate of heating, cooling and soaking times will vary due to factors such as work piece size/shape also furnace type employed, quenching medium and work piece transfer facilities etc..

4340 in the hardened and tempered as supplied condition is still regarded as being readily machinable and operations such as turning and drilling etc. can be carried out satisfactorily using machine manufacturers, recommendations for suitable tool type - feeds and speeds.

Welding of 4340 in the hardened and tempered condition (as normally supplied), is not recommended and should be avoided if at all possible, as the mechanical properties will be altered within the weld heat affected zone. It is preferred that welding be carried out on 4340 while in the annealed condition, and that the work piece, immediately on cooling to hand warm, is then stress relieved at 640 oC - 660 oC prior to hardening and tempering.
If welding in the hardened and tempered condition is really necessary, then the work piece, immediately on cooling to hand warm, should be if possible stress relieved at 15 oC below the original tempering temperature (if known).


Certificate of Quality: issued in English, in addition the normal terms, production process, the mechanical property yield strength, tensile strength, elongation and hardness, forged ratio, UT test result, Grain size, heat treatment methods and the sample of is shown on the Certificate of Quality.


Marking: Heat No. will be cold stamped and Steel grade, diameter mm, length mm, and the manufacturer LOGO and weight kg is painted