Classes of Alloy Tool and Die Steels

Classes of Alloy, Tool and Die Steels.

Tungsten High Speed Steels

Type Spec. US
UK Comp. (%) Heat treatment, ^oC and hardness Rc Uses

Tungsten high-speed steel T1,
BS4659: BT1 0.75 C
4.25 Cr
18 W
1.2 V Double pre-heat: 600 and 850
Austenitise: 1290 - 1320
Quench into molten salt, oil, or air blast
Double or triple secondary harden / temper at about 565 for about 1 hour
Rc: 60 - 65 Cutting tools, particularly those likely to face shock load, ie: interrupted cutting

Molybdenum high-speed steel M2,
BS4659: BM2 0.83 C
4.25 Cr
6.5 W
1.9 V
5 Mo Double pre-heat: 600 and 850
Austenitise: 1250
Quench into molten salt, oil, or air blast
Double or triple secondary harden / temper at about 565 for about 1 hour
Rc: 60 - 65 Tougher than equivalent 18-4-1 tungsten HSS steel. Cutting tools, drills, punches, cold forging dies.

Cobalt high-speed steel T6,
BS4659: BT6 0.8 C
4.75 Cr
20 W
1.5 V
0.5 Mo
12 Co Double pre-heat: 600 and 850
Austenitise: 1300 - 1320
Quench into molten salt, oil, or air blast
Double or triple secondary harden / temper at about 565 for about 1 hour
Rc: 60 - 65 Has good red hardness and toughness. Tools for severe machining duties, eg on high tensile steels and cast irons.

Chromium hot-work steel H12,
BS4659: BH12 0.35 C
5 Cr
1.35 W
0.4 V
1.5 Mo
1 Si Preheat: 800
Austenitise: 1300 - 1320
Quench into molten salt, oil, or air blast
Double secondary harden / temper at about 500 to 600 for about 1 hour
Rc: 38 - 55 Suitable for hot die work. Low carbon content means tools can be water cooled without cracking. Extrusion dies, mandrels, hot forming and hot pressing tools

High-carbon, high-chromium, cold-work steel D3,
BS4659: BD3 2.1 C
12.5 Cr
0.3 Mn
1 max W
1 max V Preheat: 815
Austenitise: 925 - 980
Quench into molten salt, oil, or air blast (thin sections only)
Double secondary harden / temper at about 150 to 400 for about 1 hour
Rc: 54 - 61 Dies for blanking, forming, thread rolling. Rolls, slitter knives. Dies for moulding abrasive powders, eg ceramics.

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David J Grieve, 11th February 2003.

Type	Spec. US UK	Comp. (%)	Heat treatment, ^oC and hardness Rc	Uses
Tungsten high-speed steel	T1, BS4659: BT1	0.75 C 4.25 Cr 18 W 1.2 V	Double pre-heat: 600 and 850 Austenitise: 1290 - 1320 Quench into molten salt, oil, or air blast Double or triple secondary harden / temper at about 565 for about 1 hour Rc: 60 - 65	Cutting tools, particularly those likely to face shock load, ie: interrupted cutting
Molybdenum high-speed steel	M2, BS4659: BM2	0.83 C 4.25 Cr 6.5 W 1.9 V 5 Mo	Double pre-heat: 600 and 850 Austenitise: 1250 Quench into molten salt, oil, or air blast Double or triple secondary harden / temper at about 565 for about 1 hour Rc: 60 - 65	Tougher than equivalent 18-4-1 tungsten HSS steel. Cutting tools, drills, punches, cold forging dies.
Cobalt high-speed steel	T6, BS4659: BT6	0.8 C 4.75 Cr 20 W 1.5 V 0.5 Mo 12 Co	Double pre-heat: 600 and 850 Austenitise: 1300 - 1320 Quench into molten salt, oil, or air blast Double or triple secondary harden / temper at about 565 for about 1 hour Rc: 60 - 65	Has good red hardness and toughness. Tools for severe machining duties, eg on high tensile steels and cast irons.
Chromium hot-work steel	H12, BS4659: BH12	0.35 C 5 Cr 1.35 W 0.4 V 1.5 Mo 1 Si	Preheat: 800 Austenitise: 1300 - 1320 Quench into molten salt, oil, or air blast Double secondary harden / temper at about 500 to 600 for about 1 hour Rc: 38 - 55	Suitable for hot die work. Low carbon content means tools can be water cooled without cracking. Extrusion dies, mandrels, hot forming and hot pressing tools
High-carbon, high-chromium, cold-work steel	D3, BS4659: BD3	2.1 C 12.5 Cr 0.3 Mn 1 max W 1 max V	Preheat: 815 Austenitise: 925 - 980 Quench into molten salt, oil, or air blast (thin sections only) Double secondary harden / temper at about 150 to 400 for about 1 hour Rc: 54 - 61	Dies for blanking, forming, thread rolling. Rolls, slitter knives. Dies for moulding abrasive powders, eg ceramics.