AISI SAE 8620 Steel Properties, Chemical Composition, Equivalent, Heat Treatment

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AISI SAE 8620 Steel (UNS G86200)

AISI SAE 8620 steel is a commonly used low-alloy material for carburizing, with excellent carburizing response, good hardenability for most section sizes, it has many extensive applications due to its low cost, better machinability, and availability.

SAE AISI 8620 Steel Properties

The tables below summarize SAE AISI 8620 steel properties, and specification including chemical composition, mechanical properties, hardness, heat treatment, etc.

Chemical Composition

AISI SAE 8620 steel chemical composition is listed in the table below.

SAE AISI 8620 Chemical Composition, %
Standard Steel Grade (UNS) C Si Mn P, ≤ S, ≤ Cr Ni Mo Cu, ≤  O, ≤ Al, ≤
ASTM A322;
ASTM A29/A29M
8620 (UNS G86200) 0.18-0.23 0.15-0.35 0.70-0.90 0.035 0.040 0.40-0.60 0.40-0.70 0.15-0.25
ASTM A534 8620H 0.17-0.23 0.15-0.35 0.60-0.95 0.025 0.015 0.35-0.65 0.35-0.75 0.15-0.25 0.3 0.002 0.05

Mechanical Properties

AISI SAE 8620 material mechanical properties are listed in the following tables including yield strength (yield stress), tensile strength, impact strength and hardness, etc.

Notes:

  • 1 MPa = 1 N/mm2
  • 1 GPa = 1 kN/mm2
8620 alloy steel mechanical properties
Steel (UNS) Tensile strength, Mpa (ksi), ≥ Yield strength, Mpa (ksi), ≥ Elongation in 50 mm (2 in.), %, ≥ Reduction in area, %, ≥ Hardness, HB Izod impact strength, J (ft·lbf) Condition or treatment
8620 (UNS G86200) 633 (92) 357 (52) 26.3 59.7 183 100 (74) Normalized at 915 °C (1675 °F)
536 (78) 385 (56) 31.3 62.1 149 115 (83) Annealed at 870 °C (1600 °F)

Machinability ratings: 65% for cold-finished bars based on the machinability rating of 1212 steel of 100%, microstructure composed mainly of acicular pearlite and bainite. Brinell hardness: 179-235 HB.

Hardness

Effect of mass on hardness of normalized 8620 alloy steel
Grade (UNS) Normalizing temperature, °C (°F) Bar with diameter, mm (in.) Hardness, HB
8620 (UNS G86200) 915 (1675) 13 (1/2) 197
25 (1) 183
50 (2) 179
100(4) 179
Effect of mass on oil quenched hardness (HRC) of low-alloy 8620 steel of various diam bar.
Alloy 13 mm (0.5 in) 25 mm (1 in.) 50 mm (2 in.) 100 mm (4 in.)
Surface 1/2 radius Center Surface 1/2 radius Center Surface 1/2 radius Center Surface 1/2 radius Center
8620, 8620H 43 43 43 29 27 25 23 22 97 HRB 22 95 HRB 93 HRB

Alloy 8620 Heat Treatment

Approximate transformation temperatures of 8620 alloy steels
Grade Transformation temperature on heating at 28 °C/h (50 °F/h) Transformation temperature on cooling at 28 °C/h (50 °F/h)
8620 (UNS G86200) Ac1 Ac3 Ar3 Ar1 Ms
730 (1350) 830 (1525) 770 (1415) 660 (1220) 395 (745)
Hardening temperatures for low-carbon, low-alloy 8620 steel after carburizing
SAE steels Treatment Temperature, °C (°F) Note
8620, 8615, 8617, 8622, 8625, 8720 Carburizing 900-955 (1650-1750)
Reheat 800-830 (1475-1525) When case hardness only is paramount
830-855 (1525-1575) When higher core hardness is desired
Tempering 120-175 (250-350) Optional (For partial stress relief and improved resistance to cracking from grinding operations.)
Cooling medium: Oil
Austenitizing temperatures and quenching media for direct hardening 8620 low-alloy steel
AISI Austenitizing temperature, °C (°F) Quenching medium Temper, °C (°F)
8620 (UNS G86200) 845 (1550) Oil or Austenitize at 830 °C (1525 °F) for water quench 200-650 (390-1200)
Full annealing cycles for 8620 alloy carburizing steel
AISI Conventional process Isothermal process
Annealing temperature, °C (°F), Hold for 45 min Cooling Annealing temperature, °C (°F) Isothermal temperature, °C (°F) Hold, h
8620 870 (1600) Furnace Cool 885 (1625) 660 (1220 ) 4
8620 material usually do not require a full anneal. Normalizing or an isothermal treatment will provide the best structures for machining.
Important carburizing parameters for some of 8620 gear steel grade
AISI Heat Treatment Temperature, °C (°F)
8620 Normalizing 870-930 (1600-1700)
Annealing 860 (1575)
Carburizing 930 (1700)
Reheat 775-840 (1425-1550)
Ms 395 (745)
Typical heat treatment for carburizing of 8620 alloy steel
AISI Normalize Carburizing temperature, °C (°F) Cooling method Tempering temperature, °C (°F)
8620 steel Should be at least as high as the carburizing temperature followed by air cooling 900-925 (1650-1700) Quench in Oil 120-175 (250-350)
Note:
Carburizing: The usual practice is to reduce the carburizing temperature to approximately 845°C (1550°F) before quenching to minimize deformation and retain austenite.
Tempering: Optional. Tempering is usually used to relieve some of the stress and improve the crack resistance of the grinding operation. In some application cases, use a temperature higher than the indicated temperature.
Typical applications of 8620 martempering steel parts in salt
Part Grade Maximum section thickness, mm (in.) Weight, kg (lb) Martempering conditions
Temperature of salt, °C (°F) Minimum time in salt, min
Screw-machine spindle 8620 Carburized 10.2 (0.40) 6.35 (14.0) 205 (400) 3
Screw-machine sprocket 38.1 (1.50) 9.07 (20.0) 205 (400) 3
Typical applications of martempering 8620 steel parts in oil
Part Grade Maximum section thickness, mm (in) Outside diameter, mm (in) Weight, kg (lb) Carburizing temperature, °C (°F) Depth of case, μm (0.001 in) Quenching temperature, °C (°F) Temperature of martempering oil, time in oil ≥5 min. Surface hardness, HRC
Splined shaft 8620 steel 50.8 (2) 50.8 (2) 5.1 (11.25) 925 (1700) 1525-1725 (60-68) 925 (1700) 165 58-62
8625 steel 44.4 (1.75) 44.4 (1.75) 2.0 (4.5) 190 58-62
65.0 (2.559) 65.0 (2.559) 6.8 (15) 165 58-62
Typical applications of liquid carburizing in cyanide baths
Material Part Weight, kg (lb) Depth of case, mm (in.) Temperature, °C (°F) Time, h Quench Subsequent treatment Rockwell hardness, HRC
8620 steel Bearing races 0.9-36 (2-80) 2.3 (0.090) 925 (1700) 14 AC 61-64
Bearing rollers 0.20 (0.5) 2.3 (0.090) 925 (1700) 14 AC 61-64
Coupling 0.03 (0.06) 0.25-0.4 (0.010-0.015) 845 (1550) 2 Oil File-hard
Crankshaft 0.9 (2) 1.0 (0.040) 915 (1675) 6.5 AC 60-63
Gear 0.34 (0.75) 1.0 (0.040) 915 (1675) 6 AC 60-63
0.03 (0.06) 0.075-0.13 (0.003-0.005) 845 (1550) 0.5 Oil File-hard
Idler shaft 0.45 (1) 0.75 (0.030) 915 (1675) 5 58-63
Pintle 4.5-86 (10-190) 1.5 (0.060) 925 (1700) 12 58-63
Piston 0.20 (0.5) 1.3 (0.050) 915 (1675) 8 AC 60-63
Plunger 0.45-82 (1-180) 1.3 (0.050) 915 (1675) 8 58-63
Ram 2.3-23 (5-50) 1.1 (0.045) 915 (1675) 7 58-63
Spool 0.45-54 (1-120) 1.3 (0.050) 925 (1700) 7 58-63
Thrust cup 0.20 (0.5) 1.1 (0.045) 915 (1675) 7 58-63
Thrust plate 5.4 (12) 2.3 (0.090) 925 (1700) 14 AC 60-64
Universal socket 1.8 (4) 1.5 (0.060) 915 (1675) 10 AC 58-63
Valve 0.01 (0.03) 0.4-0.5 (0.015-0.020) 845 (1550) 4 Oil ≥60
Valve seat 0.20 (0.5) 1.1 (0.045) 915 (1675) 7 AC 60-63
Wear plate 0.45-3.6 (1-8) 1.3 (0.050) 915 (1675) 7 AC 60-63
Notes:

  • ① Tempered at 165 °C (325 °F).
  • ② Reheated at 845 °C (1550 °F), quenched in salt at 175 °C (350 °F).
  • ③ Reheated at 775 °C (1425 °F), quenched in salt at 195 °C (380 °F).
  • ④ Quenched directly in salt at 175 °C (350 °F).
  • ⑤ Tempered at 165 °C (325 °F) and treated at -85 °C (-120 °F)
Typical applications of liquid carburizing in noncyanide baths
Alloy Part Weight, kg (lb) Depth of case, mm (in.) Temperature, °C (°F) Time, h Quench Subsequent treatment Rockwell hardness, HRC
4620, 8620 steel Screw machine spindles 0.8 (1.8) 0.89 (0.035) Preheat at 840 °C (1545 °F); carburize at 920 °C (1690 °F) 6 Molten salt, 205 °C (400 °F) 60-63

Carburizing

A common carburizing method of AISI SAE 8620 steel is to heat up to 925 °C (1700 °F) at a potential of 0.9% C in a prepared carbon-containing atmosphere, hold for about 4 hours (to reach a depth of 1.3 mm [0.050 in]), and reduce the temperature to 845 °C (1555 °F). The carbon potential is close to eutectoid, maintaining a 1 h diffusion period, quenching in oil, and then tempering at 150°C (300 °F). If the hardness loss at higher tempering temperatures can be tolerated, a slightly higher tempering temperature can be used to increase toughness.

Carbonitriding

A typical SAE AISI 8620 material carbonitriding process involves heating to 845 °C (1555 °F) with 10% (volume) anhydrous ammonia in a carburizing atmosphere for 45 minutes, then quenching in oil to produce a 0.305 mm (0.012 in.) deep shell. The time and temperature can be adjusted to change the depth of the case. The temperature is usually between 790 and 900 °C (1455 to 1650 °F). After carbonitriding, it is recommended to temper at 150 to 260 °C (300 to 500 °F).

Applications

The applications of AISI SAE 8620 steel including: Differentials (automotive and off-highway), drives (industrial, tractor accessory), engines, equipment (off-highway, steel or paper mill, mining), starters. Gears, steering mechanism, gear box and transmission components for cars.

Carburized gears, pinions, shafts, differential rings, steering worms, engine crankshafts, spline shafts, chains, air drill parts, chuck jaws, oil well bit and reamer cutters, piston pins, pneumatic chucks, heavy-duty bolts, fasteners, and hand tools.

SAE AISI 8620 Equivalent Material

SAE AISI 8620 material equivalent to European EN (Germany DIN, British BSI, French NF…), ISO, Japanese JIS and Chinese GB standard (For reference).

SAE AISI 8620 Equivalent Material
US China Japan European Union ISO
Standard Grade (UNS) Standard Grade (UNS) Standard Grade Standard Steel name (Steel number) Standard Grade
AISI SAE;
ASTM A322;
ASTM A29/A29M
8620 (UNS G86200) GB/T 3077 20CrNiMo (A50202) JIS G4053 SNCM220

Related material: 5160 Steel, SAE AISI 1080 Steel, AISI 1018 Steel, AISI 1045 Steel, AISI 1020 Steel, SAE AISI 52100 Steel

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