
Chemical Analysis | |
---|---|
C% | Carbon 0.18 – 0.23 |
Mn% | Manganese 0.70 – 090 |
P% | Phosphorus 0.040 max |
S% | Sulfur 0.040 max |
Si% | Silicon 0.20 – 0.35 |
Ni% | Nickel 0.40 – 0.70 |
Cr% | Chromium 0.40 – 0.60 |
Mo% | Molybdenum 0.15 – 0.25 |
General characteristics of Alloy Steel 8620
Alloy steel 8620 is a case-hardening steel containing nickel, chromium and molybdenum as alloying elements. The alloy shows good strength and toughness properties, and has a higher core strength than grades 8615 and 8617.
Applications
This alloy may be used in the production of medium-strength parts such as forged camshafts, fasteners and gears.
Forging
This alloy is forged at a start temperature of around 2250ºF (1230ºC) and could be forged down to approximately 1700ºF(925ºC.) The alloy is air cooled after forging.
Heat treatment
Annealing:For optimum machinabilty, an as-forged structure is normally sufficient for this grade of alloy steel. If this proves not to be the case then an iso-anneal from around 1650ºF (900ºC) to 1225ºF (660ºC) will improve machinability.
Normalizing:1675ºF (910ºC) and air cool. This is another method of improving machinability in this grade; normalizing might also be used prior to case hardening.
Hardening:The alloy will be austenitized at around 1525ºF (830ºC) and oil or water quenched depending upon section size and intricacy.
Tempering:to desired hardness, using temperatures based on past experience, following water or oil quench.
Machinability:This grade of alloy is readily machined following suitable cooling from forging or subsequent heat treatment.
Weldability:This steel may be welded by normal fusion methods, but prior to carburizing or hardening and tempering.
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