24 July 2021 Mould Steel Bar
SAE8620H Mould Steel Bar
SAE 8620H is American Standard alloy steel used for mould, gear, shafts etc, belongs to standard ASTM A29/A29M-04 . Equivalent to the Chinese standard 20NiCrMo2 steel, is a Cr-Ni-Mo case hardening steel widely used in carburizing and carbonitriding. SAE 8620H has high hardenability, no temper brittleness, good weldability, little tendency to form cold cracks, good machinability and cold strain plasticity. Generally used in quenched and tempered or carburized and quenched state, it is used to manufacture high-pressure pipes and various fasteners that work in non-corrosive media and media containing nitrogen and hydrogen mixtures with a working temperature of less than 250 ℃, and higher-level infiltration Carbon parts, such as gears, shafts, etc.
Chemical Composition:
| C(％) | Si(％) | Mn(％) | P(％) | S(％) | Cr(％) | Ni(％) | Mo(％) | Cu(%) |
|---|---|---|---|---|---|---|---|---|
| 0.18～0.23 | 0.15～0.35 | 0.70～0.90 | ≤0.035 | ≤0.035 | 0.40～0.60 | 0.40 ~ 0.70 | 0.15～0.25 | ≤0.30 |
Mechanical Propoerties:
| Yield Strength Rp0.2(MPa) | Tensile Strength Rm(MPa) | Impact Energy KV(J) | Elongation at Fracture A(%) | Reduction in Cross Section on Fracture Z(%) | Impact toughness value αkv (J/cm2) | Hardness |
|---|---|---|---|---|---|---|
| ≥ 785(80) | ≥ 980(100) | ≥ 47 | ≥ 9 | ≥ 40 | ≥ 59(6) | ≤197HB |
Welding:
Pre-heat welding area to 250-450°C and maintain this temperature while welding with a low hydrogen electrode. Cool at a maximum rate of 100°C per hour. Weld before carburising.
Case Hardening Steel Bar SAE 8620H:
After final machining, heat in carburising atmosphere (blank carburise) to 880 to
960°C and hold for sufficient time at temperature to produce the required case depth. The time at temperature during the blank carburising process determines the depth of case achieved.
After completion of blank carburisation treatment, re-heat to 860-900°C, hold until uniform and then quench in oil as rapidly as practical.
A refining treatment is necessary to improve the structure of the case and its hardness. Heat slowly to 780-820°C, hold until uniform and then quench in oil.
Single quench treatment may also be possible where components are quenched directly from 820 to 840°C.
Minimum tempering time is 1 hour, but a tempering period of 1 hour per 25mm of section is recommended. If the steel is to be direct hardened, in general, a carburising temperature of 950°C should not be exceeded. After case hardening a typical case hardness of 61 HRC can be achieved.
Case Hardening Steel Bar SAE 8620H:
Small diameter gear parts exposed to low-medium stress. Typical components include gears, planet wheels, drive pinions, shafts.
Hardenability Diagram Curve SAE 8620H (20NiCrMo2):
Hardenability Diagram Curve(SAE 8620H):
SAE 8620H Technical Specification Data Sheet