Tool and Die Materials
177
Table 13.2 Influence of alloying elements on the characteristic properties of steels.
Medium-carbon steel. Medium-carbon steel has a carbon content of between 0.30 and 0.70. It is generally used in applications requiring higher strength than low-carbon steel, such as automotive, machin-
ery, and railroad equipment, and parts such as gears, axles, etc. High-carbon steel. High-carbon steel has more than 0.70 carbon. It is generally used for parts
requiring high strength and high hardness. The higher the carbon content of the steel, the higher its hard- ness, strength, and wear resistance after heat treatment.
13.2.4 Alloy Steels
These kinds of steels contain significant amounts of alloying elements and are usually made with more care than are carbon steels. Alloy steels are used in applications where strength, hardness,
resist- ance, and toughness are required. These steels may also be heat-treated to obtain the desired properties.
13.2.5 Machinability of Steels
The relative ease with which a given material may be machined, or cut with sharp edged tools, is called machinability. Machinability ratings are based on a tool life
of T
=
60 min. The standard is 1 1 12
steel,
178
Tool and Die Materials
Rating
which is given a rating of 100. Thus for a tool life
of
60 minutes, this steel should be machined at a cut-
ting speed of 100
A
higher speed will reduce tool life, and lower speeds will increase it. For example, tool steel
A2
has a machinability rating of 65. This means that when this steel is machined at a cutting speed of 65
0.325 tool life will be
60 minutes. Some materials have a machinability rating of more than
100. Nickel has a rating of 200, free-cutting brass of 300. In Table 13.3 ratings are given for some kinds of carbon and alloy steels.
1010 1020
1040 1060
3140 4340
6150 8620
55 65
60 53
55 45
50 60
CONDITION
13.2.6 Mechanical Properties
of Steels
Typical mechanical properties of selected carbon and alloy steels are given in Table 13.4.
UTS Elongation
Hardness
Table 13.4 Mechanical properties of selected carbon and alloy steels.
As-rolled 448
Normalized 44
Annealed 393
1020 330
36 143
346 35
131 294
36 111
As-rolled Normalized
Annealed As-rolled
Normalized Ann ea e d
Normalized Annealed
Normalized Annealed
Normalized Annealed
8620 813
482 17
341 775
420
18 229
625 372
22 179
965 586
12 293
1010 5 24
11 293
615 375
24 174
89 559
19 262
689 422
24 197
1279 86 1
12 229
744 472
22 197
939 615
21 269
667 412
23 197
,
Normalized Annealed
Normalized Annealed
As-rolled Normalized
Annealed
632 357
26 189
536 385
31 149
632 357
26 189
536 385
31 149
25
I
Tool and Die Materials
Table 13.5 Mechanical properties of quenched and tempered carbon and alloy steels.
179
1040
1060
1080
4340
6150 1875
1469 965
1931 1434
945 Tempering
temperature
1675 10
520 1365855
10 430
19 280
1689 8
538 1331
10 420
84 1 17
282 205
425 625
205 425
650
205 425
650
205 425
650
205 425
650 779
758 634
593 552
434
1076 800
524 23
229 1310
1289 889
979 95 1
600 12
13 21
388 375
255
Table 13.5 gives typical mechanical properties of selected carbon and alloy steels in quenched and
tempered condition.
Applications of Carbon and Alloy Steels
Characteristic and typical applications of various carbon and alloy steels are given in Table 13.6.
13.3 TOOL AND DIE STEELS
Tool and die steels are specially alloyed steels that are designed for high strength, impact toughness, and
wear resistance. They are commonly used in the forming and machining of metals at both room and ele- vated temperatures.
The steel for most types of tool and dies must be in a heat-treated state, generally hardened and tem-
pered, to provide the properties needed for the particular application. Thus, tool and die steels must be able to withstand heat treatment with a minimum of harmful effects, dependably resulting in the intended ben-
eficial changes in material properties.
13.3.1 Designation and Classification of Tool and Die Steels
The designation and classification system established by and SAE for tool and die steels has seven
basic categories. These categories are associated with the predominant application characteristics of the
