Age Hardenable Tempers - This term means the material can be strengthened by simple heat treatment after stamping or forming. The strength level will be roughly doubled by optimum heat treatment.
ASTM Designation Description Name
TB00
TD01
TD02
TD04
Annealed
Quarter Hard
Half Hard
Hard
A
1/4 H
1/2 H
H

Heat Treated Tempers - These tempers describe the resulting strength after optimum heat treatment of their age hardenable counter parts.
ASTM Designation Description Name
TF00
TH01
TH02
TH04
Annealed & Heat Treated
Quarter Hard & Heat Treated
Half Hard & Heat Treated
Hard & Heat Treated
AT
1/4 HT
1/2 HT
HT

Mill Hardened Tempers - These tempers have been heat treated through carefully controlled processing to develop a strength level between age hardenable and fully heat treated tempers. They are normally formed and put into service at this strength. They are also used to provide sturdy, miniature parts for subsequent full heat treatment. This approach protects small parts from damage and improves dimensional stability during final heat treatment.
ASTM Designation Name
TM00
TM01
TM02
TM04
TM05
TM06
TM08
AM
1/4 HM
1/2 HM
HM
SHM
XHM
XHMS