Machinery's Handbook, 31st Edition
Special Tool Steels 455 guide for this category, keeping in mind that whereas higher carbon content results in deeper hardness penetration, it also reduces toughness. The general system distinguishes the following four grades, listed in the order of decreasing quality: 1) special; 2) extra; 3) standard; and 4) commercial. The differences between these grades, which are not offered by all steel mills, are defined in principle only. The distinguishing characteristics are purity and consistency resulting from different degrees of process refinement and inspection steps applied in making the steel. Higher qualities are selected for assuring dependable uniformity and performance of the tools made from the steel. The groups with higher carbon content are more sensitive to heat-treatment defects and are generally used for the more demanding applications, so the better grades are usually chosen for the high-carbon types and the lower grades for applications where steels with lower carbon content only are needed. Water-hardening tool steels, although the least expensive and quite acceptable in many types of applications, have several drawbacks. Some limiting properties are the tendency to deformation in heat treatment due to harsh effects of the applied quenching medium, the sensitivity to heat during the use of the tools made of these steels, the only fair degree of toughness, and the shallow penetration of hardness. However, this last-mentioned property may prove a desirable characteristic in certain applications, such as cold-heading dies, because the relatively shallow hard case is supported by the tough, although softer, core. The AISI designation for water-hardening tool steels is W, followed by a numeral indi cating the type, primarily defined by the chemical composition, as shown in Table 11. Table 11. Water-Hardening Tool Steels—Identifying Chemical Composition and Heat-Treatment Data Chemical Composition in Percent AISI Types W1 W2 W5 C 0.60–1.40 0.60–1.40 1.10 Varying carbon content may be available V … 0.25 … Cr These elements are adjusted to satisfy the hardening requirements 0.50 Mn Si Heat-Treatment Data
0.60–0.80% 0.85–1.05% 1.10–1.40%
1450–1500 ° F (788–816 ° C ) 1425–1550 ° F (774–843 ° C ) 1400–1525 ° F (760–829 ° C )
Hardening Temperature Ranges Varying with Carbon Content
Quenching Medium
Brine or Water
Tempering Temperature Range
350–650 ° F (177–343 ° C )
Approx. Tempered Hardness, RC (Rockwell C scale)
64–50
Relative Ratings of Properties (A = greatest to E = least)
Characteristics in Heat Treatment
Service Properties
Safety in Hardening
Depth of Hardening
Resistance to Decarburization
Stability of Shape in Heat Treatment Machinability
Hot Hardness
Wear Resistance Toughness
D C/D Water-Hardening Type W1 (Plain Carbon) Tool Steels, Recommended Applications: Group I (C 0.70 to 0.90%): This group is relatively tough and therefore preferred for tools that are subjected to shocks or abusive treatment. Used for such applications as hand tools, chisels, screwdriver blades, cold punches, and nail sets, and fixture elements, vise jaws, anvil faces, and chuck jaws. C A E A E D/E Group II (C 0.90 to 1.10%): This group combines greater hardness with fair toughness, resulting in improved cutting capacity and moderate ability to sustain shock loads. Used for such applications as hand tools, knives, center punches, pneumatic chisels, cutting
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