SAE AISI 4340 Steel Properties, Heat Treatment, Equivalent, Hardness Chart, Density, Machinability

0 5,124

SAE AISI 4340 Steel (UNS G43400)

AISI 4340 steel (UNS G43400) is an ultra-high strength medium carbon low alloy steel, which combines deep hardenability, high ductility, toughness and strength, and has high fatigue resistance and creep resistance. It is not particularly affected by tempering and embrittlement, and exhibits good strength retention at high temperatures and is not easily softened. In thin sections, this steel is air-hardened. In practice, it is usually oil quenched.

4340 Alloy Steel Datasheet

The following tables and lists give 4340 alloy steel datasheet and specification including chemical composition, physical properties and mechanical properties, heat treatment, welding, etc.

Chemical Composition

AISI 4340 steel material chemical composition is listed in the following table based on cast analysis.

4340 Chemical Composition, %
ASTM Steel Grade (UNS) C Si Mn P (≤) S (≤) Ni Cr Mo Notes
ASTM A29/A29M 4340 alloy steel (UNS G43400) 0.38-0.43 0.15-0.35 0.60-0.80 0.035 0.04 1.65-2.00 0.70-0.90 0.20-0.30 Steel Bars, Carbon and Alloy, Hot-Wrought
ASTM A322 Steel Bars, Alloy, Standard Grades
ASTM A519/A519M Seamless Carbon and Alloy Steel Mechanical Tubing
ASTM A646/A646M Premium Quality Alloy Steel Blooms and Billets for Aircraft and Aerospace Forgings

AISI 4340 Steel Properties

The tables below list AISI 4340 steel properties, including physical and mechanical properties.

Physical Properties

4340 alloy steel physical properties are given in the following lists, including density, thermal expansion, elastic modulus, thermal conductivity, specific heat capacity and electrical resistance.

Notes:

  • 10-6·K-1 = 10-6/K
  • 1 Ω·mm²/m = 1 μΩ·m
  • 1 g/cm3 = 1 kg/dm3 = 1000 kg/m3
  • 1 GPa = 1 kN/mm2
  • 1 MPa = 1 N/mm2
Physical Properties
Density, g/cm3 (lb/in.3) 7.85 (0.284) Conditions
Melting point, °C (°F) 1505 (2740)
Specific heat capacity, J/kg·K (Btu/lb ·°F) 475 (0.114) at 20℃
Modulus of Elasticity, GPa (ksi) 205 (29700)
Bulk Modulus, GPa (ksi) 140 (20300)
Poisson’s Ratio 0.29
Shear Modulus, GPa (ksi) 80 (11600)
Thermal conductivity, W/m·K (Btu/ft · h ·°F) 44.5 (25.73)
Coefficient of thermal expansion, 10-6/K (μin./in. ·°F) 12.3 at 20-100 ℃ (68-212 °F) Oil hardened, tempered 600 °C (1110 °F)
12.7 at 20-200 ℃ (68-392 °F)
13.7 at 20-400 ℃ (68-752 °F)
14.5 at 20-600 ℃ (68-1112 °F)
11.2 at -100 to 20 °C (-148 to 68 °F) Oil hardened, tempered 630 °C (1170 °F)
10.4 from -150 to 20 °C (-238 to 68 °F).
12.4 at 20-200 ℃ (68-392 °F)
13.6 at 20-400 ℃ (68-752 °F)
14.3 at 20-600 ℃ (68-1112 °F)

Mechanical Properties

4340 steel mechanical properties are listed in the following tables.

AISI 4340 Mechanical Properties
Steel Condition Tensile strength, MPa (ksi), ≥ Yield strength, MPa (ksi), ≥ Elongation in 50 mm (2 in.), ≥ Reduction in area, %, ≥ Hardness, HB, ≤
4340 Normalized at 870 °C (1600 °F) 1282 (186) 862 (125) 12.2 36.3 363
Annealed at 810 °C (1490 °F) 745 (108) 470 (68) 22.0 50.0 217
Oil quenched from 800 °C (1475 °F) and tempered at 540 °C (1000 °F) 1207 (175) 1145 (166) 14.2 45.9 352
Effects of mass on the mechanical properties of 4340 steel
Oil quenched and tempered: Austenitized at 845 °C (1550 °F); tempered at 425 °C (800 °F).
Section diameter Tensile strength, ≥ Yield strength, ≥ Elongation in 50 mm (2 in.), ≥ Reduction in area, ≥ Hardness, ≤
mm (in.) MPa (ksi) MPa (ksi) % % HB
13 (0.5) 1460 (212) 1380 (200) 13 51
38 (1.5) 1450 (210) 1365 (198) 11 45
75 (3) 1420 (206) 1325 (192) 10 38
Water quenched and tempered: 75 mm (3 in.) diam bar austenitized at 800 °C (1475 °F); 100 and 150 mm (4 and 6 in.) diam bars austenitized at 815 °C (1500 °F). All sizes tempered at 650 °C (1200 °F). Test specimens taken at midradius.
Section diameter Tensile strength, ≥ Yield strength, ≥ Elongation in 50 mm (2 in.), ≥ Reduction in area, ≥ Hardness, ≤
mm (in.) MPa (ksi) MPa (ksi) % % HB
75 (3) 1055 (153) 930 (135) 18 52 340
100 (4) 1035 (150) 895 (130) 17 50 330
150 (6) 1000 (145) 850 (123) 16 44 322
Typical mechanical properties of 4340 steel
Oil quenched from 845 °C (1550 °F) and tempered at different temperatures
Tempering temperature Tensile strength, ≥ Yield strength, ≥ Elongation in 50 mm (2 in.), ≥ Reduction in area, ≥ Hardness, ≤ Hardness Izod impact energy
°C (°F) MPa (ksi) MPa (ksi) % % HB HRC J (ft · lbf)
205 (400) 1980 (287) 1860 (270) 11 39 520 53 20 (15)
315 (600) 1760 (255) 1620 (235) 12 44 490 49.5 14 (10)
425 (800) 1500 (217) 1365 (198) 14 48 440 46 16 (12)
540 (1000) 1240 (180) 1160 (168) 17 53 360 39 47 (35)
650 (1200) 1020 (148) 860 (125) 20 60 290 31 100 (74)
705 (1300) 860 (125) 740 (108) 23 63 250 24 102 (75)
Transverse tensile properties of air-melted and vacuum arc remelted 4340 alloy steel, billet size and amount of hot reduction were not available.
Tempering temperature Tensile strength, ≥ Yield strength, ≥ Elongation in 50 mm (2 in.), ≥ Reduction in area, ≥
°C (°F) MPa (ksi) MPa (ksi) %, ≥ %
Air melted
230 (450) 1945 (282) 1585 (230) 6.0 14
480 (900) 1380 (200) 1190 (173) 8.0 16
540 (1000) 1240 (180) 1125 (163) 10.0 22
Vacuum arc remelted
230 (450) 1930 (280) 1635 (237) 6.5 17
480 (900) 1380 (200) 1210 (175) 9.0 20
540 (1000) 1240 (180) 1100 (160) 10.5 24
Longitudinal mechanical properties of bar stock made from remelted 4340 steel
Melting method Tensile strength, MPa (ksi), ≥ Yield strength, MPa (ksi), ≥ Elongation in 4D, %, ≥ Reduction in area, %, ≥ Charpy V-notch impact energy at -12 °C (10 °F), J (ft · lbf) Hardness, HRC
Vacuum arc remelted 1210 (175) 1120 (163) 16.4 61.2 65 (48) 37
Bars were normalized at 900 °C (1650 °F), oil quenched from 845 °C (1550 °F), and tempered 2 h at 541 °C (1005 °F). All specimens taken from midradius.
Cyclic and monotonic properties of as-received and heat-treated 4340 alloy steel
SAE steel Condition Ultimate tensile strength Reduction in area, ≥ Modulus of elasticity Yield strength Cyclic strain hardening exponent
Grade Brinell hardness, HB MPa (ksi) % Gpa (106 psi) MPa (ksi)
4340 242 As-received 825 (120) 43 192 (27.8) 467 (67.7) 0.17
409 Quenched + Tempered 1467 (213) 38 200 (29) 876 (127) 0.13
Relative gouging abrasion resistance in the ASTM G 81 jaw crusher test
Steel Heat Treatment Laboratory A Laboratory B
Wear ratio Hardness, HB Wear ratio Hardness, HB
4340 steel Oil Quenched and Tempered (650 °C, or 1200 °F) 0.788 321 0.716 340
Oil Quenched and Tempered (205 °C, or 400 °F) 0.262 555 0.232 520
The ratio of the weight loss of the sample to the weight loss of the standard material martensitic T-1 steel plate. High values indicate poor abrasion resistance.

4340 Steel Heat Treatment

Alloy steel 4340 heat treatment including: normalizing, annealing, hardening, tempering, spheroidization, stress relief, etc. (4340 heat treat)

  • Normalizing: Heat to 845 to 900 °C (1550 to 1650 °F) and hold for a period of time, which depends on the thickness of the section; air cooling.
  • Annealing: Heating to 830 to 860 °C (1525 to 1575 °F) and maintaining it for a period of time, which depends on the thickness of the section or furnace load; furnace cooling.
  • Spheroidization: The preferred schedule is to preheat to 690 °C (1275 ° F) for 2 h, increase the temperature to 745 °C (1375 °F) for 2 h, and cool to 650 °C (1200 °F) ) And hold for 6 hours, cool the furnace to about 600 °C (1100 °F), and finally air-cool to room temperature. Another arrangement is to heat the temperature to 730 to 745 °C (1350 to 1375 °F), hold it for several hours, and then cool the furnace to room temperature.
  • Hardening: Heat to 800 to 845 °C (1475 to 1550 °F) for 15 minutes (minimum 15 minutes) per 25 mm (1 inch) thickness; oil quench to below 65 °C (150 °F), or quench in fused salt at 200 to 210 °C (390 to 410 °F), hold for 10 minutes, and then air-cool to below 65 °C (150 °F).
  • Tempering: Hold at 200 to 650 °C (400 to 1200 °F) for at least 1/2 hour; air cooling. The temperature and the time at the temperature mainly depend on the required final hardness.
  • Stress Relief: After straightening, forming or processing, the stress of the part can be released at a temperature of 650 to 675 °C (1200 to 1250 °F).
  • Baking: To avoid hydrogen embrittlement, the plated parts must be baked at least 8h at a temperature of 185 to 195 °C (365 to 385 °F) as soon as possible after plating.
  • Forging: 4340 steel is usually forged at a temperature of 1065 to 1230 °C (1950 to 2250 °F); after forging, the parts can be air-cooled in a dry place, or preferably with a furnace.

Welding of AISI 4340 Steel

AISI 4340 steel has good weldability. It can be easily gas or arc welded, but electrodes of the same composition should be used. Since 4340 alloy steel is air hardened, the welded parts should be either annealed or normalized and tempered shortly after welding.

The high hardness of 4340 alloy steel requires that the material be welded in the annealed or tempered state and then heat treated to resist martensite formation and cold cracking. However, as in motor shaft applications, under quenching and tempering conditions, 4340 steel typically use high preheating in low hydrogen processes. Preheating or interpass heating of weld metal and heat affected zones is recommended. Hydrogen control is also essential to prevent cracks in the weld. Extremely clean vacuum smelted steel is the first choice for welding.

Preheating and interpass temperature °C (°F) range for indicate section thickness
Steel ≤13 mm (0.5 in.) 13-25 mm (0.5-1 in.) 25-50 mm (1-2 in.)
4340 290-345 (550-650) 315-370 (600-700) 315-370 (600-700)
Data are for low-hydrogen welding processes and low-hydrogen filler metals.
Typical transverse tensile properties of selected low alloy steel quenched and tempered ARC welded joints
Steel Welding Process Thickness, mm (in.) Filter Metal Tempering temperature, °C (°F) Welded joint Elongation in 50mm (2 in.), % Approximate base metal tensile strength, MPa (ksi)
Tensile strength, MPa (ksi) Yield strength, MPa (ksi)
4340 Gas Metal Arc Welding (GMAW) 25.4 (1) 4340 510 (950) 1307 (189.5) 1251 (181.5) 11 1310 (190)

Machinability and Machining

Hardness and machinability ratings (cold-drawn steel)
Steel (UNS) Machinability rating Condition Range of typical hardness, HB Microstructure type
4340 (UNS G43400) 50 Annealed and cold drawn 187/241 B, A
E4340 (UNS G43406)
Based on cutting with high-speed tool steels and a machinability rating of 100% for 1212 steel. Type A: predominantly lamellar pearlite and ferrite; Type B: predominantly spheroidized.
Nominal speeds and feeds for turning a variety of steels and cast irons with high-speed steel (HSS) single-point and box tools
Material Hardness, HB Condition Depth of cut, mm (in) High-speed steel tool Tool material
Speed Feed
m/min sfm mm/rev in./rev ISO AISI
4340, 1340, 1345, 4042, 4047, 4140, 4142, 4145, 4147, 50B40, 50B44, 5046, 50B46, 5140, 5145, 5147, 81B45, 8640, 8642, 8645, 86B45, 8740, 8742 175-225 Hot rolled, annealed, or cold drawn 1 (0.04) 41 135 0.18 0.007 S4, S5 M2, M3
4 (0.15) 32 105 0.4 0.015
8 (0.30) 24 80 0.5 0.02
16 (0.625) 20 65 0.75 0.03
High-strength wrought steels: 4340, 300M, 4330V, 4340Si, 98BV40, D6ac, H11, H13 225-300 Annealed 1 (0.04) 26 85 0.18 0.007 S4, S5 M2, M3
4 (0.15) 20 65 0.4 0.015
8 (0.30) 15 50 0.5 0.02
16 (0.625) 12 40 0.75 0.03
Nominal speeds and feeds for turning a variety of steels and cast irons with carbide-tipped single-point and box tools
Material Hardness, HB Condition Carbide tool
Uncoated Coated
Speed Feed Tool material grade Speed Feed Tool material grade
Brazed Indexable
m/min sfm m/min sfm mm/rev in./rev ISO C m/min sfm mm/rev in./rev ISO C
Medium carbons: 4340, 1340, 1345, 4042, 4047, 4140, 4142, 4145, 4147, 50B40, 50B44, 5046, 50B46, 5140, 5145, 5147, 81B45, 8640, 8642, 8645, 86B45, 8740, 8742 175-225 Hot rolled, annealed, or cold drawn 115 375 150 500 0.18 0.007 P10 C-7 200 650 0.18 0.007 CP10 CC-7
90 300 120 400 0.50 0.020 P20 C-6 160 525 0.40 0.015 CP20 CC-6
73 240 95 315 0.75 0.030 P30 C-6 120 400 0.50 0.020 CP30 CC-6
58 190 76 250 1.00 0.040
High-strength wrought steels: 4340, 300M, 4330V, 4340Si, 98BV40, D6ac, H11, H13 225-300 Annealed 105 350 135 450 0.18 0.007 P10 C-7 185 600 0.18 0.007 CP10 CC-7
84 275 105 350 0.40 0.015 P20 C-6 135 450 0.40 0.015 CP20 CC-6
66 215 84 275 0.50 0.020 P30 C-6 105 350 0.50 0.020 CP30 CC-6
52 170 69 225 0.75 0.030 P40 C-6
Nominal speeds and feeds for turning a variety of steels and cast irons with ceramic tools
Material Hardness, HB Condition Depth of cut, mm (in) Speed Feed Type of ceramic
m/min sfm mm/rev in./rev
4340, 1340, 1345, 4042, 4047, 4140, 4142, 4145, 4147, 50B40, 50B44, 5046, 50B46, 5140, 5145, 5147, 81B45, 8640, 8642, 8645, 86B45, 8740, 8742 175-225 Hot rolled, annealed, or cold drawn 1 (0.040) 520 1700 0.13 0.005 Cold-pressed alumina
4 (0.150) 350 1150 0.25 0.010 Cold-pressed alumina
8 (0.300) 260 850 0.40 0.015 Hot-pressed cermet
High-strength wrought steels: 4340, 300M, 4330V, 4340Si, 98BV40, D6ac, H11, H13 225-300 Annealed 1 (0.040) 440 1450 0.13 0.005 Hot-pressed cermet
4 (0.150) 265 875 0.25 0.010 Hot-pressed cermet
8 (0.300) 205 675 0.40 0.015 Hot-pressed cermet
Nominal speeds and feeds for turning a variety of steels and cast irons with high-speed steel and carbide cutoff and form tools
Material Hardness, HB Condition Speed Feed, mm/rev (in./rev) Tool material grade
Cutoff tool width Form tool width
m/min sfm 1.5 mm (0.062 in.) 3 mm (0.125 in.) 6 mm (0.250 in.) 12 mm (0.500 in.) 18 mm (0.750 in.) 25 mm (1.00 in.) 35 mm (1.50 in.) 50 mm (2.00 in.) ISO AISI or C
Medium carbon steel 4340, 1340, 1345, 4042, 4047, 4140, 4142, 4145, 4147, 50B40, 50B44, 5046, 50B46, 5140, 5145, 5147, 81B45, 8640, 8642, 8645, 86B45, 8740, 8742 175-225 Hot rolled, annealed, or cold drawn 29 95 0.038 (0.0015) 0.046 (0.0018) 0.056 (0.0022) 0.046 (0.0018) 0.041 (0.0016) 0.038 (0.0015) 0.033 (0.0013) 0.028 (0.0011) S4, S5, P40, M40 M2, M3, C-6
95 305
4340, 300M, 4330V, 4340Si, 98BV40, D6ac, H11, H13 225-300 Annealed 18 60 0.036 (0.0014) 0.043 (0.0017) 0.053 (0.0021) 0.043 (0.0017) 0.038 (0.0015) 0.036 (0.0014) 0.030 (0.0012) 0.025 (0.001) S4, S5, P40, M40 M2, M3, C-6
58 190
Speeds and feeds for the deep-hole trepanning of various steels with high-speed tool steels and carbide tools
Material Hardness, HB Condition Speed Feed Tool material grade
m/min sfm mm/rev in./rev ISO AISI or C
Medium carbon steel 4340, 1340, 1345, 4042, 4047, 4140, 4142, 4145, 4147, 50B40, 50B44, 5046, 50B46, 5140, 5145, 5147, 81B45, 8640, 8642, 8645, 86B45, 8740, 8742 175-225 Hot rolled, annealed, or cold drawn 18 60 0.15 0.006 S4, S5 M2, M3
115 375 0.15 0.006 P30 C-6
325-375 Normalized or quenched and tempered 9 30 0.10 0.004 S9, S11 T15, M42
90 300 0.13 0.005 P30 C-6
Feeds and speeds for broaching various steels with high-speed tool steels and carbide tools
Material Hardness, HB Condition Speed, m/min (sfm) Chip load, mm/tooth (in./tooth) Tool material grade, ISO (AISI or C)
Medium carbon steels: 4340, 1330, 1335, 1340, 1345, 4027, 4028, 4032, 4037, 4042, 5155, 5160, 51B60, 6150, 81B45, 8625, 4047, 4130, 4135, 4137, 4140, 4142, 4145, 4147, 4150, 8627, 8630, 8637, 8640, 8642, 8645, 4161, 4427, 4626, 50B40, 50B44, 5046, 50B46, 50B50, 86B45, 8650, 8655, 8660, 8740, 8742, 5060, 50B60, 5130, 5132, 5135, 5140, 5145, 5147, 5150, 9254, 9255, 9260, 94B30;
Low carbon steels: 4012, 4023, 4024, 4118, 4320, 4419, 4422, 4615, 4617, 4620, 4621, 4718, 4720, 4815, 4817, 4820, 5015, 5115, 5120, 6118, 8115, 8617, 8620, 8622, 8822, 9310, 94B15, 94B17;
High carbon steels: 50100, 51100, 52100, M-50
125-175 Hot rolled, annealed, or cold drawn 7.5 (25) 0.075 (0.003) S4, S2 (M2, M7)
325-375 Normalized, or quenched and tempered 3 (10) 0.05 (0.002) S9, S11 (T15, M42)
175-225 Hot rolled, annealed, or cold drawn 6 (20) 0.10 (0.004) S4, S2 (M2, M7)
325-375 Normalized, or quenched and tempered 3 (10) 0.05 (0.002) S9, S11 (T15, M42)
175-225 Hot rolled, annealed, or cold drawn 6 (20) 0.10 (0.004) S4, S2 (M2, M7)
325-375 Normalized, or quenched and tempered 3 (10) 0.05 (0.002) S9, S11 (T15, M42)

Applications

SAE AISI 4340 steel is usually used in places where severe conditions exist and heavy parts requiring high strength, and can be widely used as billet, bar, bar, forging, sheet, pipe and welding wire. AISI 4340 steel can also be produced as light plates and castings. Typical applications include bolts, screws and other fasteners. Gears, pinions, shafts and similar mechanical components; crankshafts and piston rods of engines; and landing gear and other key structural components of aircraft.

Equivalent

ASTM AISI 4340 steel equivalent to SAE, European (German DIN, British BSI, France NF), Japanese JIS and Chinese GB standard (for reference).

AISI 4340 equivalent
US European Union China Japan ISO
Standard Grade (UNS) Standard Grade Standard Steel name (Steel number) Standard Grade Standard Grade Standard Grade
AISI
SAE;
ASTM A29/A29M;
ASTM A322;
ASTM A519/A519M;
ASTM A646/A646M
4340 (UNS G43400) SAE AMS6414 GB/T 3077 40CrNi2Mo JIS G 4053 SNCM439

Get real time updates directly on you device, subscribe now.

Leave A Reply

Your email address will not be published.

We use cookies to improve your experience on our website. By browsing this website, you agree to our use of cookies. Accept Read More