4340/34CrNiMo6/EN24/817M40/SNCM439/1.6565 Hot Rolled Steel Bar ,
High Tensile Steel Bar
1.Specification:
Dia:10-320mm
Length: as your request:
2.Description:
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.
3.APPLICATIONS:
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.
4.Chemical Composition(%):
| C | Si | Mn | P(max) | S(max) | Mo | Ni | Cr |
| 0.37-0.44 | 0.17-0.37 | 0.50-0.80 | 0.04 | 0.04 | 0.15-0.25 | 1.25-1.85 | 0.60-0.90 |
5.Process: EAF+LF+VOD+ Rolled +Heat Treatment(optional)
6.Test: Ultrasonic test according to SEP 1921-84 3Cc
7.Heat Treatment
Annealing
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.
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.
*Temper immediately while still hand warm.
Nitriding
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.
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..
