D-7 is a high carbon-high chromium die steel with added carbon and vanadium for unexcelled abrasion resisting qualities. It was developed especially for applications involving extreme abrasive wear.

Because of its high alloy content and abrasion resisting properties, D-7 is difficult to grind when hardened; so, fabrication should include a machining operation which leaves little final grinding required. D-7 has excellent size change properties, so that in many cases, final grinding may be omitted when adequate surface protection is available during heat treatment.

D-7 has important secondary hardening properties, and this factor may be taken advantage of reducing size change on hardening as well as improving toughness and performance at temperatures up to 800°F.  D-7 can be used for semi-hot work applications but not when extreme operating temperatures are involved. This grade is susceptible to heat checking and thermal stresses as a consequence of its high alloy, wear resisting qualities.

Preheat D-7 at 1400-1500°F, then transfer to a furnace 1950-2000°F for maximum hardness and abrasion resisting qualities, or to 1875-1925°F for dies and tools which require a better balance of toughness and abrasion resistance. To hold size change to an absolute minimum, hold as close to the 1900°F hardening temperature as possible.

Quench the pieces in still air. Extremely heavy sections may require an oil quench to develop maximum hardness. If an oil quench is used, flash quench into oil until the pieces loses color, then complete the quench in air. Temper as soon as the pieces have cooled to room temperature.

When the pieces have cooled to room temperature, transfer to the tempering furnace. If the 1950-2000°F hardening room was used, select a low temperature temper from 250-300°F so that maximum hardness and abrasion resistance will be maintained. If the 1875-1925°F range was used for hardening, temper in the 350-400°F range for most applications, or in the 950-975°F secondary hardness range for semi-hotwork applications. Double tempering of large section sizes is recommended.

Hardening happens between 1875°F- 2000°F.

D-7 is an oversized material,

+/- .015 up to .040 on thickness

+/- .080 up to .125 on width

Up to 1" +/- .007 up to .018

1" up to 6" +/- .015 up to .040

6" and up +/- .0625 up to .250

Preheat Forging:     1450°F thru 1550°F