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1.6582 34CrNiMo6 4340 EN24 Quenched Tempered +QT Alloy Steel Round Bar

Group Hardened Steel Bar
Min. Order 1 ton
Terms of Payment L/C, T/T
Update Time 2020-04-02
Item specifics
Diameter50-260mm
Delivery conditionHot rolled+QT
Surface conditionBlack, peeled

Description of 4340 steel:

4340 Steel is a heat treatable, low alloy steel containing nickel, chromium and molybdenum. It is known for its toughness and capability of developing high strength in the heat treated condition while retaining good fatigue strength. A very popular, versatile steel. It can be heat-treated to produce a wide range of tensile strength in moderate sections. We also supply quenched tempered alloy steel bar of 4130, 4140, 4145, 4145H, 4330V

Application of 4340 steel:

High voltage bolts and nuts, crankshafts, cam shafts, transmission axles, torsion bars, drive shafts, pump shafts, worm shafts, conveyor rollers, stems, pins, tie rods, clutch discs. Large-mass dies for hot stamping. 4340 Steel is widely used in the aerospace industry for structural parts of flaps assembly, fuselage and landing gear, propeller plane axles.

All Grades Comparison
Material no.
DIN
BS
ASTM
1.6580
30CrNiMo8
823M30
4340
AFNOR
ISO
ГOCT
JIS
30CND8
31CrNiMo8
3KH3M3F
SNCM431

Chemical Composition (%)

Steel Grade
C
Mn
Si
P
S
Cr
Ni
Mo
30CrNiMo8
0.26-0.34
0.50-0.80
0.40 max
0.025 max
0.035 max
1.80-2.20
1.80-2.20
0.30-0.50
4340
0.38–0.43
0.60-0.80
0.15-0.35
0.035 max
0.040 max
0.70-0.90
1.65-2.00
0.20-0.30
SNCM431
0.27-0.35
0.60-0.90
0.15-0.35
0.030 max
0.030 max
0.60-1.10
1.60-2.00
0.15-0.30
Mechanical Properties(T=20°C if not differently stated)
H
eat treatment state
Diameter(mm)
Rm (Mpa)
Rp0.2 (Mpa)
Fracture elongation A5 (%)
Notch impact energy ISO-V [J]
Hardness (HB)
SOFT ANNEALED
/
844 min
/
/
/
250 max
ISOTHERMAL ANNEALED
/
615-815
/
/
/
183-242
QUENCHED AND TEMPERED
16 max
880-1080
685 min
16 min
40 min
289-347
QUENCHED AND TEMPERED
16-40
930-1080
735 min
16 min
40 min
275-318
QUENCHED AND TEMPERED
40-100
880-1030
685 min
17 min
40 min
261-303
QUENCHED AND TEMPERED
100-250
785-935
635 min
18 min
35 min
233-276
QUENCHED AND TEMPERED
250-500
735-885
590 min
16 min
35 min
218-262
Heat treatment and hot plastic deformation temperatures
TEMPERATURE ° C
Cooling Medium
Hot plastic deformation
850-1100
/
Normalizing
850-880
air
Soft Annealing
650-690
air
Quenching
830-860
oil
Tempering
540-660
air

Heat Treatment of 4340 steel:

Annealing: Heat to 800 oC – 850 oC, hold until temperature is uniform throughout the section and cool in furnace.

Flame or Induction Hardening: 4340 steel 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.

Hardening: 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.

Nitriding: 4340 steel 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 steel.

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.

Tempering: 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.
Machinability
4340 steel in the hardened and tempered as supplied condition is still regarded as being readily machinable and operations such as turning and drilling etc. it can be carried out satisfactorily using machine manufacturers, recommendations for suitable tool type – feeds and speeds.
Welding
Welding of 4340 steel 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 steel 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).
Mill′s test certificate
EN 10204/3.1 with all relevant data reg. chem. composition, mech. properties and results of testing.