Hot-Work Tool Steel Softening Resistance
How four hot-work tool steels — H13, H21, H23 and H26 — hold their hardness after 100 hours at temperatures from 480 to 760 °C. This is the “temper resistance” data behind hot-work die life: how much hardness a die retains during long exposure to hot metal.
| Type | Original hardness, HRC | 480 °C (900 °F) | 540 °C (1000 °F) | 595 °C (1100 °F) | 650 °C (1200 °F) | 705 °C (1300 °F) | 760 °C (1400 °F) |
|---|---|---|---|---|---|---|---|
| H13 | 50.2 | 48.7 | 45.3 | 29.0 | 22.7 | 20.1 | 13.9 |
| 41.7 | 38.6 | 39.3 | 27.7 | 23.7 | 20.2 | 13.2 | |
| H21 | 49.2 | 48.7 | 47.6 | 37.2 | 27.4 | 19.8 | 15.2 |
| 36.7 | 34.8 | 34.9 | 32.6 | 27.1 | 19.8 | 14.9 | |
| H23 | 40.8 | 40.0 | 40.6 | 40.8 | 38.6 | 33.2 | 25.8 |
| 38.9 | 38.9 | 38.0 | 38.0 | 37.1 | 32.5 | 25.6 | |
| H26 | 51.0 | 50.6 | 50.3 | 47.1 | 38.4 | 26.9 | 21.3 |
| 42.9 | 42.4 | 42.3 | 41.3 | 34.9 | 26.4 | 21.1 |
- (a) At room temperature.
Table notes
Hardness after 100 hours at temperature, measured again at room temperature — the standard way to rank hot-work steels for resistance to softening (“temper resistance”) in die-casting, extrusion and forging service.
The source lists two test rows per steel; the original hardness differs between the two rows, and both are shown as printed.
The tungsten grades H21, H23 and H26 retain the most hardness above 650 °C, while H13 holds its hardness through the 540-595 °C range and falls more sharply above it — data to weigh against toughness and cost when specifying a hot-work grade.
Reference data for comparison — response varies with the exact hardening and tempering cycle. Verify with the applicable heat treatment before service.
Related reference pages
H13 tool steel · H11 tool steel · H10 tool steel · H21 tool steel · Hot-work tool steels · Hot-work tool steel applications · Selection of tool steel for hot forging dies · Tool steel hot hardness chart · Tool steel hardening and tempering chart · Tool steel properties chart
Source: ASM Handbook, Volume 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys, Table 6 “Resistance of four hot-work steels to softening at elevated temperatures” (10th ed.). Reference data for comparison — verify the applicable heat treatment before service.