Forging Alloy Steel 6140 & 6145

AISI 6140 AISI 6145
C Carbon
0.35 – 0.45
C Carbon
0.43 – 0.48
Mn Manganese
0.60 – 0.90
Mn Manganese
0.70 – 0.90
P Phosphorus
0.040 max
P Phosphorus
0.040 max
S Sulfur
0.040 max
S Sulfur
0.040 max
Si Silicon
0.20 – 0.35
Si Silicon
0.20 – 0.35
Cr Chromium
0.80 – 1.10
Cr Chromium
0.80 – 1.10
V Vanadium
0.15 min
V Vanadium
0.15 min

General Characteristics of AISI 6140 & 6145

These two alloys belong in the same family as 6150. They are both chromium-bearing types with a small vanadium addition.

Applications that use AISI 6140 & 6145 Forgings

AISI 6140 & 6145 are of a slightly lower strength level than type 6150 and both have in fact been superceded by it. They could be used in the same applications as 6150, namely as forged parts in automotive engineering and gear and engine construction.

Forging Temperatures of AISI 6140 & 6145

AISI 6140 & 6145 would be forged between 2150 and 1700ºF (1175 and 925ºC.) The alloys should be slow cooled after forging or transferred to a furnace around the ‘finishing’ temperature.

Heat Treatment

Annealing: As with 6150 alloy, the microstructure for AISI 6140 & 6145 to give optimum machinability is one of coarse lamellar pearlite to coarse spheroidite. This might be obtained by austenitizing at around 1380ºF (760ºC) followed by an iso anneal at 1250ºF (680ºC.)

Normalizing: A nominal normalizing temperature for this alloy is 1650ºF (900ºC.) This treatment is followed by air cooling.

Carburizing: The steels would be carburized at 1650-1740ºF (900-950ºC) followed by water quench for large components of simple shape only, otherwise oil quench.

Hardening: Austenitize at 1575-1650ºF (860-900ºC) and oil quench for small, intricate sections and water quench for large, simple sections.

Tempering: at a temperature that will give the required mechanical properties, based on past experience.

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