Forging. Heat to I I50 “C (2 100 “F). Do not forge below 8 I5 “C ( 1500 ‘F)
Recommended Heat Treating Practice
Normalizing. Heat to 855 “C (1570 “F). Cool in air
In aerospace practice. parts are normalized at 900 “C ( 1650 “F)
Annealing. As is generally true for all high-carbon steels, bar stock
supplied by mills in spheroidized condition. Annealed with structure of fine
spheroidal carbides in ferrite matrix. When parts are machined from bars
in this condition. no normalizing or annealing required. Forgings should
always be normalized. Anneal by heating to 800 “C (1475 OF). Soak
thoroughly. Furnace cool to 650 “C ( I200 “F), at a rate not to exceed 28 “C
(50 “F) per h. From 650 “C ( I200 “F) to ambient temperature, cooling rate
is not critical. This relatively simple annealing process will provide predominantly
spheroidized structure, desired for subsequent heat treating or
machining.
ln aerospace practice. parts are annealed at 815 “C (1500 “F) and
allowed to cool to below 510 “C (I000 “F)
Hardening. Heat to 800 “C (l-l75 “FL Carbonitriding and austempering
are suitable processes. Quench in water. brine. or aqueous polymers. Oil
quench rounds under A.7 mm (0. I9 in.) for full hardening. Responds well
to austempering (same procedure as for 1090).
In aerospace practice, parts are austenitized at 800 “C (1475 “F). and
quenched in oil or polymers
Tempering. As-quenched hardness as high as 66 HRC. Hardness can be
reduced by proper tempering. When quenching with oils or polymers, parts
may be tempered at a number of different temperatures to get specitic
ranges of tensile strengths as follows: 675 “C (I 245 OF) for 620 to 860 MPa
( 90 to 125 ksi); 620 “C (I I50 “F) for 860 to 1035 MPa ( I25 to I50 ksi);
540 “C ( 1000 “F) for 1035 to I I70 MPa ( I50 to I70 ksi): 480 “C (895 “F)
for 1170 to I240 MPa ( I70 to I85 ksi); 425 “C (795 “F) for 1240 to I380
MPa (185 to 200 ksi); 370 “C (700 “F) for I380 to I520 hiPa ( 200 IO 220
ksi)
Austempering. Responds well to austempering (bainitic hardening).
Austenitize at 800 “C (1475 “F). Quench in agitated molten salt bath at 3 I5
“C (600 “F). Hold for 2 h. Cool in air