Tool Steel Forging Temperature Guide
Heating, start, stop and post-forging cooling temperatures for the common cold-work, shock-resisting, hot-work and stainless tool steel grades, as published in the mill and forge-shop datasheets. Use this table to set the forging window before hot working a billet, and to check the slow-cooling practice each grade needs after forging.
| Calificación | Tipo | Heating before forging | Start forging | Stop forging (not below) | Cooling after forging |
|---|---|---|---|---|---|
| Cold work tool steels | |||||
| D2 | 1.2379 | Heat uniformly to the start temperature | 1052–1093 °C (1925–2000 °F) | 927 °C (1700 °F) | Small, simple forgings: slow in lime. Large: furnace at 843 °C (1550 °F), soak, shut off heat, cool slowly in the furnace (1) |
| D3 | 1.2080 | Heat slowly and uniformly to the start temperature | 1052–1093 °C (1925–2000 °F) | 927 °C (1700 °F) | Small, simple forgings: slow in lime. Large: furnace at 843 °C (1550 °F), soak, shut off heat, cool slowly (1) |
| A2 | 1.2363 | Heat uniformly to the start temperature | 1066–1121 °C (1950–2050 °F) | 927 °C (1700 °F) | Small, simple forgings: slow in lime. Large: furnace at 843 °C (1550 °F), soak, shut off heat, cool slowly (1) |
| O1 | 1.2510 | Heat slowly and uniformly to the start temperature | 982–1038 °C (1800–1900 °F) | 816 °C (1500 °F) | Slowly in ashes, lime or in the furnace (1) |
| DC53 | — | Not published in the mill catalogue | 900–1100 °C (1650–2010 °F) | 900 °C (1650 °F) | Not stated in source — annealing after forging is recommended (3) |
| Shock-resisting tool steels | |||||
| S7 | — | Heat uniformly to the start temperature | 1066–1121 °C (1950–2050 °F) | 927 °C (1700 °F) | Small, simple forgings: dry lime, ashes or other insulating material. Large: furnace at 760 °C (1400 °F), soak, shut off heat, cool in the furnace (1) |
| Hot work tool steels | |||||
| H13 | 1.2344 | Preheat slowly to 750 °C, then raise more rapidly to the start temperature | 1050–1100 °C | 850 °C | Slow — in a furnace or in vermiculite (2) |
| H11 | 1.2343 | Hot forming range below | 1100–900 °C (4) | 850 °C (4) | Slow — in a furnace or in vermiculite (4) |
| Stainless (corrosion-resistant) tool steels | |||||
| 420 | 1.2083 / 1.4021 | Preheat to 760–816 °C (1400–1500 °F), then heat uniformly to the start temperature | 1097–1204 °C (2000–2200 °F) | 900 °C (1650 °F) | Furnace at 843 °C (1550 °F) if possible; otherwise warm dry lime or ashes. Air cooling may cause cracking (1)(5) |
| 440C | 1.4125 | Preheat to 760–816 °C (1400–1500 °F), then heat slowly and uniformly to the start temperature | 1038–1149 °C (1900–2100 °F) | 927 °C (1700 °F) | Furnace if possible, otherwise warm dry lime or ashes (1) |
- (1) Carpenter Technology (CarTech) datasheets for D2, D3, A2 (No. 484), O1, S7, 420 and 440C. Values are quoted from the forge section of each datasheet.
- (2) West Yorkshire Steel X40CrMoV5-1 (H13) datasheet. A peer-reviewed study on H13 hot working reports a heating temperature of 1120–1150 °C, start forging at 1050–1100 °C and a terminal forging temperature of 850–900 °C, which supports the same window.
- (3) Daido Steel DC53 catalogue, as reproduced in the distributor’s technical bulletin: forging temperature 900–1100 °C; annealing after forging is recommended to minimise stress.
- (4) European mill datasheets for 1.2343 publish a hot-forming range of 1100–900 °C rather than a separate start/stop pair. Some producers quote a narrower window with a higher floor — confirm against the mill certificate for the heat you are working.
- (5) “AISI 420” strictly refers to UNS S42000 / EN 1.4021 (X20Cr13, ~0.2 %C). The 1.2083 / X42Cr13 grade is the higher-carbon “420 modified” mould steel. Forging data for both is listed in the same family; check which one your drawing specifies.
- Stop temperature conventions differ. North American datasheets state a single minimum (“do not forge below”), while European mill datasheets publish a hot-forming range whose lower bound can sit lower — for D2 and D3, for example, European data gives a hot-forming range of 1050–850 °C against the US minimum of 927 °C. Both are published values; the machining and heat-treatment route decides which applies to your order.
- Reheating. Every datasheet in this table allows reheating as often as necessary to stay inside the forging window. The stop temperature is a floor, not a target.
Cooling down is not annealing
The slow cool after forging does not replace an anneal. The datasheets state this explicitly: after the forging is cold it must still be annealed before machining and hardening.
Reheat to stay in the window
As the billet loses heat it drops below the forging window. Reheat as often as necessary — working below the stop temperature is what produces cracking and internal defects.
Stainless grades need slower cooling
420 y 440C are cooled in a furnace where possible, or in warm dry lime or ashes. Air cooling 420 may cause cracking, and both grades must be annealed after forging.
Where the numbers come from
Values are quoted from mill and forge-shop datasheets (Carpenter Technology, West Yorkshire Steel, Daido Steel). Where producers differ, the difference is shown rather than averaged away.
Before you set the forging window
Forging temperatures are published as typical values for the grade family. The exact window depends on the grade specification, the mill that produced the steel, the billet size and the forging equipment. Confirm the figures against the mill certificate for the heat you are working before production.
All grades in this table must be annealed after forging and cooled to room temperature before annealing. Cooling rate, soak time and the annealing cycle are covered on the individual grade heat-treatment pages — for example D2 heat treatment, H13 heat treatment, 420 heat treatment y 440C heat treatment.
Data source: Carpenter Technology (CarTech) datasheets for D2, D3, A2, O1, S7, 420 and 440C · West Yorkshire Steel X40CrMoV5-1 datasheet for H13 · Daido Steel DC53 catalogue via distributor technical bulletin · European mill datasheets for 1.2343 (H11). Reviewed 2026.