AISI 4340 Steel | 36CrNiMo4 | 1.6511 | EN24 | 817M40 | SNCM439

AISI 4340 Steel | 36CrNiMo4 | 1.6511 | EN24 | 817M40 | SNCM439

Short Description:

AISI 4340 steel is a medium carbon, low alloy steel known for its toughness andstrength in relatively large sections. AISI 4340 is also one kind ofnickel chromium molybdenum steels. 4340 alloy steel is generallysupplied hardened and tempered in the tensile range of 930 – 1080 Mpa.Pre hardened and tempered 4340 steels can be further surface hardened by flame or induction hardening and by nitriding. The 4340 steel has goodshock and impact resistance as well as wear and abrasion resistanc...


  • Length: 3-5.8mm or Customization
  • Surface: black, peeled, or rough turned
  • Heat treatment: air-cooling, normalized, annealed, Q&T
  • Smelting process: EAF+LF+VD
  • Product Detail

    Product Tags

    AISI 4340 steel

    is a medium carbon, low alloy steel known for its toughness and
    strength in relatively large sections. AISI 4340 is also one kind of
    nickel chromium molybdenum steels. 4340 alloy steel is generally
    supplied hardened and tempered in the tensile range of 930 – 1080 Mpa.
    Pre hardened and tempered 4340 steels can be further surface hardened by

    flame or induction hardening and by nitriding. The 4340 steel has good
    shock and impact resistance as well as wear and abrasion resistance in
    the hardened condition. AISI 4340 steel properties offer good ductility
    in the annealed condition, allowing it to be bent or formed. Fusion and
    resistance welding is also possible with our 4340 alloy steel. ASTM 4340

    material is often utilized where other alloy steels do not have the
    hardenability to give the strength required. For highly stressed parts
    it is excellent choice. AISI 4340 alloy steel can also be machined by
    all customary methods.


    Due to availability the ASTM 4340 grade steel is often substituted
    with European based standards 817M40/EN24 and 1.6511/36CrNiMo4 or Japan
    based SNCM439 steel. You have the detailed data of 4340 steel below.

    1. AISI 4340 Steel Specification and Relevant Standards

    Country USA Britain Britain Japan
    Standard ASTM A29 EN 10250 BS 970 JIS G4103
    Grades 4340 36CrNiMo4/
    1.6511
    EN24/817M40 SNCM 439/SNCM8

    2. ASTM 4340 Steels And Equilvalents Chemical Composition

    Standard Grade C Mn P S Si Ni Cr Mo
    ASTM A29 4340 0.38-0.43 0.60-0.80 0.035 0.040 0.15-0.35 1.65-2.00 0.70-0.90 0.20-0.30
    EN 10250 36CrNiMo4/
    1.6511
    0.32-0.40 0.50-0.80 0.035 0.035 ≦0.40 0.90-1.20 0.90-1.2 0.15-0.30
    BS 970 EN24/817M40 0.36-0.44 0.45-0.70 0.035 0.040 0.1-0.40 1.00-1.40 0.20-0.35
    JIS G4103 SNCM 439/SNCM8 0.36-0.43 0.60-0.90 0.030 0.030 0.15-0.35 1.60-2.00 0.60-1.00 0.15-0.30

    3. AISI Alloy 4140 Steel Mechanical Properties

    Mechannical Properties

    (Heat Treated Condition )

    Condition Ruling section
    mm
    Tensile Strength MPa Yield Strength
    MPa
    Elong.
    %
    Izod Impact
    J
    Brinell
    Hardness
    T 250 850-1000 635 13 40 248-302
    T 150 850-1000 665 13 54 248-302
    U 100 930-1080 740 12 47 269-331

    V 63 1000-1150 835 12 47 293-352
    W 30 1080-1230 925 11 41 311-375
    X 30 1150-1300 1005 10 34 341-401

    Y 30 1230-1380 1080 10 24 363-429
    Z 30 1555- 1125 5 10 444-

    Thermal Properties

    Properties Metric Imperial
    Thermal expansion co-efficient (20°C/68°F, specimen oil hardened, 600°C (1110°F) temper 12.3 µm/m°C 6.83 µin/in°F
    Thermal conductivity (typical steel) 44.5 W/mK 309 BTU in/hr.ft².°F

    4. Forging of 4340 Alloy Steel

    Preheat

    the steel 4340 first, heat up to 1150°C – 1200°C maximum for forging,
    hold until temperature is uniform throughout the section.

    Do not forge

    below 850 °C. 4340 has good forging characteristics but care must be
    taken when cooling as the steel shows susceptibility to cracking.
    Following forging operation the work piece should be cooled as slowly as

    possible. And cooling in in sand or dry lime is recommended etc.

    5. AISI 4340 Steel Grade Heat Treatment

    • Stress Relieving

    For

    pre-hardened steel stress relieving is achieved by heating steel 4340
    to between 500 to 550°C. Heat to 600 °C – 650 °C, hold until temperature

    is uniform throughout the section, soak for 1 hour per 25 mm section,
    and cool in still air.

    • Annealing

    A

    full anneal may be done at 844°C (1550 F) followed by controlled
    (furnace) cooling at a rate not faster than 10°C (50 F) per hour down to

    315°C (600 F). From 315°C 600 F it may be air cooled.

    • Tempering

    AISI

    4340 alloy steel should be in the heat treated or normalized and heat
    treated condition before tempering. The tempering temperature for
    depends upon the strength level desired. For strength levels in the 260 –

    280 ksi range temper at 232°C (450 F). For strength in the 125 – 200
    ksi range temper at 510°C (950 F). And don’t temper the 4340 steels if
    it is in the 220 – 260 ksi strength range as tempering can result in
    degradation of impact resistance for this level of strength.

    Tempering should be avoided if possible within the range 250 °C – 450 °C due to temper brittleness.

    • Flame or Induction Hardening

    As mentioned above, pre-hardened and tempered 4340 steel bars or plates can be further surface hardened by either the flame or induction hardening

    methods resulting in a case hardness in excess of Rc 50. AISI 4340
    steel parts should be heated as quickly as possible to the austenitic
    temperature range (830 °C – 860 °C) and required case depth followed by
    an immediate oil or water quenching, depending upon hardness required,
    workpiece size/shape and quenching arrangements.

    Following
    quenching to hand warm, tempering at 150°C – 200°C will reduce stresses
    in the case with minimal effect on its hardness.

    All de-carburised surface material must first be removed to ensure best results.

    • Nitriding

    Hardened

    and tempered 4340 alloy steel can also be nitrided, giving a surface
    hardness of up to Rc 60. Heat to 500°C – 530°C and hold for sufficient
    time (from 10 to 60 hours) to develop the depth of case. Nitriding

    should be followed by slow cooling (no quench) reducing the problem of
    distortion. The nitrided grade 4340 materials can therefore be machined
    to near final size, leaving a small grinding allowance only. The tensile

    strength of the 4340 steel material core is usually not affected since
    the nitriding temperature range is generally below the original
    tempering temperature employed.

    Surface hardness achievable is 600 to 650HV.

    6. Machinability

    Machining

    is best done with the alloy steel 4340 in the annealed or normalized
    and tempered condition. It can be readily machined by all conventional
    methods such as sawing, turning, drilling etc. However in the high
    strength conditions of 200 ksi or greater the machinability is only from

    25% to 10% that of the alloy in the annealed condition.

    7. Welding

    Welding

    of steel 4340 in the hardened and tempered condition (as normally
    supplied), is not recommended and should be avoided if at all possible,
    because of the danger of quench cracking, as the mechanical properties
    will be altered within the weld heat affected zone.

    If welding

    must be carried out, pre-heat to 200 to 300°C and maintain this while
    welding. Immediately after welding stress relieve at 550 to 650°C, 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 °C

    below the original tempering temperature.

    8. Application of 4340 Steel

    AISI

    4340 steel is used in most industry sectors for applications requiring
    higher tensile/yield strength than 4140 steel can provide.

    Some typical applications such as:

    • Aircraft Landing Gear

    • Automotive,

    • Oil and Gas Drilling,

    • Forging,

    • Warm and Cold Forming,

    • Machine Building,

    • Transfer Systems, like power transmission gears and shafts.

    • General

      engineering industries and structural use applications, such as: heavy
      duty shafts, gears, axles, spindles, couplings, pins, chucks, molds etc.


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