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SAE 8620 8620H ALLOY CASE HARDENING STEEL

aisi 8620 steel

Introduction:

SAE 8620 is a low Nickel Chromium Molybdenum case hardening (carburising) steel. Can Be supplied in “H” condition with controlled hardenability. Strict analytical limits provide controlled response from heat to heat, making it an ideal selection for production case hardened parts, where consistency in heat treatment is required. Typical core strength up to Rc41 Carburised, hardened and tempered.

Applications:

SAE 8620 finds wide application in the automotive industry and for ring gears, pinions, racks and  worms, helical gears, bearing races, pins and high tensile chains.

Quality Standard:

SAE J404-2000 Standard Specification for Alloy Steel.

All Grades Comparison:

AISI Material No. DIN BS970 JISG 4052 AFNOR UNI
8620 1.6523 21NiCrMo2 EN362/805M20 SNCM220H 20NCD2/22NCD2 20NiCrMo2

Size Range:

Hot Rolled: Dia16mm-320mm
Hot Forged: Dia100mm-600mm

Chemical Composition(%)

C Si Mn P S Cr Mo Ni
0.18-0.23 0.15-0.35 0.70-0.90 0.030 max 0.040 max 0.40-0.60 0.15-0.25 0.40-0.70

Mechanical Property Requirements(Quenched and Tempered at 200°C)

Dia(mm) Tensile Strength Rm (Mpa) Yield Strength R2 (Mpa) Elongation(%) Izod Impact (J) Hardness (BHN)
25 925 690 17 46 275
100 740 493 20 50 220

Machinability

Machining is done prior to carburizing to within as close a tolerance as possible. Finish machining, after heat treatment and/or carburizing, should be at a minimum so as not to impair the hardened case of the part. Machining may be done by conventional means prior to heat treatment – after carburizing machining is usually limited to grinding.

Forming: Forming characteristics of SAE 8620 alloy are good in the annealed condition.
Welding: The alloy may be welded by conventional methods, usually gas or arc welding. Preheating at 400 F is beneficial and subsequent heating after welding is recommended – consult the approved weld procedure for the method used.
Forging: The alloy may be forged at 2200 F down to 1800 F prior to the hardening heat treatment or carburizing.
Hot Working: Hot working may be accomplished prior to hardening or carburizing. Consult the alloy supplier for information as to temperatures.
Cold Working: The alloy may be cold worked in the annealed condition by conventional methods. Cold working, as with machining, should be done to as close a tolerance as possible before heat treatment or carburizing.

Heat Treatment:

This alloy may be hardened by heating to 1500 F followed by a water quench. Carburize at 1650 to 1700 F in an appropriate carburizing medium and oil quench to harden. Improved carburized case and core properties can be obtained by furnace cooling from carburizing at 1650 – 1700 F and then reheating to 1575 F.
Annealing: SAE 8620 may be given a full anneal at 1550 F and slow cooling at not more than 50 F per hour down to 850 F. From there it may be air cooled.
Tempering: Tempering of carburized parts is done at 250 to 300 F and this will result in the alloy having a core strength of approximately 135 ksi minimum with Rockwell C case hardness of 90. Tempering of heat treated and water quenched parts (not carburized) is done at 400 F to 1300 F with greater hardness the lower the tempering temperature.
Hardening: Hardening is done by oil quench from 1675 F. See “Heat Treatment”. Carburizing is accomplished at the same 1650 to 1700 F range in a carburizing “pack” or environment, followed by oil quench for thin sections or a furnace cool for heavier (over 3/4″) sections. Following carburizing of heavy sections a reheat at 1575 F will enhance both case and core properties of the alloy.

Mill′s test certificate:

EN 10204/3.1 with all relevant data reg. chem. composition, mech. properties and results of testing.

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