Page 167 - Manufacturing Engineering and Technology - Kalpakjian, Serope : Schmid, Steven R.

|46 Chapter 5 Ferrous Metals and Alloys: Production, General Properties, and Applications

TABl.E 5.7
Processing and Service Characteristics of Common Tool and Die Steels
Resistance Resistance Approximate Resistance Resistance
AISI to to hardness to to
designation decarburization cracking (HRC) Machinability Toughness softening wear
M2 Medium Medium 60-65 Medium Low Very high Very high
T1 High High 60-65 Medium Low Very high Very high
T5 Low Medium 60-65 Medium Low Highest Very high
H11, 12, 13 Medium Highest 38-55 Medium Very high High Medium
to high
A2 Medium Highest 57-62 Medium Medium High High
A9 Medium Highest 35-56 Medium High High Medium
to high
D2 Medium Highest 54-61 Low Low High High to very
high
D3 Medium High 54-61 Low Low High Very high
H21 Medium High 36-54 Medium High High Medium
to high
H26 Medium High 43-58 Medium Medium Very high High
P20 High High 28-37 Medium High Low Low to medium
to high
P21 High Highest 30-40 Medium Medium Medium Medium
\X/1, W2 Highest Medium 50-64 Highest High Low Low to medium

5.1.l High-speed Steels
High-speed steels (HSS) are the most highly alloyed tool and die steels. First devel-
oped in the early 19005, they maintain their hardness and strength at elevated oper-
ating temperatures. There are two basic types of high-speed steels: the molybdenum
type (M-series) and the tungsten type (T-series).
The M-series steels contain up to about 10% molybdenum with chromium,
vanadium, tungsten, and cobalt as other alloying elements. The T-series steels con-
tain 12 to 18% tungsten with chromium, vanadium, and cobalt as other alloying
elements. The M-series steels generally have higher abrasion resistance than T-series
steels, undergo less distortion in heat treatment, and are less expensive. The M-series
constitutes about 95% of all the high-speed steels produced in the United States.
High-speed steel tools can be coated with titanium nitride and titanium carbide for
improved Wear resistance.

5.7.2 Die Steels
Hot-work steels (H-series) are designed for use at elevated temperatures. They
have high toughness, as well as high resistance to wear and cracking. The alloying
elements are generally tungsten, molybdenum, chromium, and vanadium. Cold-
Work steels (A-, D-, and O-series) are used for cold-working operations. They gen-
erally have high resistance to Wear and cracking. These steels are available as
oil-hardening or air-hardening types. Shock-resisting steels (S-series) are designed
for impact toughness and are used in applications such as header dies, punches,
and chisels. Other properties of these steels depend on the particular composition.
Various tool and die materials for a variety of manufacturing applications are pre-
sented in Table 5.8.