Sheet Metal Forming

1.5 Tool Materials (Ref 1.13) 
Tool material is selected based on the number 
of parts to be blanked before regrinding the tool. 
Commonly used tool materials include different 
tool steels, cemented carbides, steel-bonded car-
bides, or powder metallurgy tools. Tool coatings 
are also instrumental in increasing tool life.
Cast irons hardenable to ~60 HRC are used to 
blank softer materials and at slower speeds. 
Among tools steels, A2, M2, and D2 are used. 
A2 is used for producing parts on the order of 
thousands, while M2 is used for larger quantities 
on the order of 100,000. High-speed tool steels 
have been shown to produce smaller burrs than 
D2 steels. Carbides clearly give a longer tool life 
than tool steels. Steel-bonded carbides and high-
vanadium carbide powder metallurgy tools, such 
as CPM 10V, are considered for critical applica-
tions. Cemented tungsten carbide tooling is con-
sidered when long tool life between regrinding 
or high-volume blanking is required. The com-
position of cobalt and tungsten is varied to ob-
tain the required toughness and wear resistance. 
Coatings and surface treatments include ni-
triding, hard facing with nickel-base alloys, bo-
ronizing, vapor deposition coating, and hard-
chromium coating. Tool life at least doubles with 
coatings and treatments. Chemical vapor deposi-
tion (CVD) coating with TiC is well known. 
Tools coated with TiC also greatly improve the 
surface roughness of fine-blanked parts. Physi
-
cal vapor deposition of hard coatings is also use-
ful, with better dimensional control and lower 
treatment temperature but less resistance to abra-
sive wear than CVD coatings.
Fig. 1.18
 
Schematic of forces during snap-thru. Source: Ref 1.11

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