Din 1.2581 is a king of hot work tool steel for oil or air solidifying to grow high hot quality, maintenance of hardness, and warmth checking resistance. This is mostly utilized as hot work devices, instruments for manufacture of hollows, screws, rivets, nuts and bolts. Die casting tools, forming dies, die inserts, hot shear blades.
Round: dia.10-700 mm
Flat: 6-120 x 40-1200 mm
Block: 80-600 x 100-1600 mm
EAF+LF+VD+(ESR), Hot rolled or Forged, Annealed, Black surface or Machined surface, UT SEP1921 Class3 D/d
| DIN / W.Nr | JIS | GB | |
| H21 | 1.2581 | SKD5 | 3Cr2W8V |
| Steel Grade | C | Si | Mn | P | S | Cr | V | W |
| 1.2581 | 0.25-0.35 | 0.10-0.40 | 0.15-0.45 | ≤ 0.030 | ≤ 0.020 | 2.50-3.20 | 0.30-0.50 | 8.50-9.50 |
| H21 | 0.30-0.40 | 0.15-0.30 | 0.20-0.40 | ≤ 0.030 | ≤ 0.030 | 3.00-3.75 | 0.30-0.50 | 8.75-10.00 |
1. Highly stressed hot work tools, such as mandrels, dies and containers for metal tube and rod extrusion; hot extrusion tools;
2. Tools for the manufacture of hollows, screws, rivets, nuts and bolts.
3. Die casting tools, forming dies, die inserts, hot shear blades.
| Start Forging Temperature | Finish Forging Temperature | Cooling Method | |
| 1130-1160 °C | 1080-1120 °C | 900-850 °C | Slow cooling in furnace or thermoinsulating material |
Annealing
750 to 800°C (1382 to 1472°F)
Slow controlled cooling in furnace at a rate of 10 to 20°C/hr (50 to 68°F/hr) down to approx. 600°C (1112°F), further cooling in air.
Hardness after annealing: max. 235 HB.
Hardening
1070 to 1150°C (1958 to 2102°F)
Oil, salt bath (500 - 550°C / 932-1022°F), air
Holding time after temperature equalization: 15 to 30 minutes.
Obtainable hardness:
48 - 52 HRC in oil or salt bath,
44 - 48 HRC in air.
Stress relieving
600 to 650°C (1112 to 1202°F)
Slow cooling in furnace; intended to relieve stresses set up by extensive machining, or in complex shapes.
After through heating, hold in neutral atmosphere for 1 - 2 hours.
Tempering
Slow heating to tempering temperature immediately after hardening / time in furnace
1 hour for each 20 mm of work piece thickness, but at least 2 hours / cooling in air.
It is recommended to temper at least twice. A third tempering cycle for the purpose of stress relieving may be advantageous.
1st tempering approx. 30°C (86°F) above maximum secondary hardness.
2nd tempering to desired working hardness.
3rd for stress relieving at a temperature 30 - 50°C (86 to 122°F) be low highest tempering temperature.
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