260 Steels: Metallurgy and ApplicationsTable 3.14Grade C% W% 114o% Cr% V%T1 0.75 18 4 1
M1 0.8 2 8 4 1
M2 0.85 6 5 4 2Table 3.15 Selection of high-speed steelsApplication Grade Composition (%)M1 0.8C, 2W, 8Mo, 4Cr, 1V
Normal duty M2 0.85C, 6W, 5Mo, 4Cr, 2V
T1 0.75C, 18W, 4Cr, 1V
M35 0.9C, 6W, 5Mo, 4Cr, 2V,
Higher speed cutting T4 0.75C, 18W 4Cr, 1V, 5Co
T6 0.8C, 20W, 4Cr, 1.5V, 12Co
Higher hardness M15 1.5C, 7W, 3Mo, 5Cr, 5V,
M42 1.3C, 9W, 3Mo, 4Cr, 3V,5Co5Co
lOCoMaraging steels
The term maraging relates to ageing (precipitation strengthening) reactions in
very low carbon martensitic steels for the development of ultra-high strengths,
i.e. 0.2% proof strength values of 1400-2400 N/mm 2. Maraging steels are char-
acterized by high nickel contents and a very important feature is that they exhibit
substantially higher levels of toughness than conventional high-carbon marten-
sitic grades of equivalent strength.
Work on these steels began in the United States in the 1950s at the Bayonne
Research Laboratory of the International Nickel Company and was directed
primarily to the development of a high-strength material for submarine hulls.
However, maraging steels proved unsuitable for this application and their main
usage has been in the areas of aerospace, tooling and machinery, and structural
engineering. An excellent summary of information on these steels is contained
in a publication by the American Society for Metals. 29Metallurgy
Maraging steels generally contain about 18% Ni and the carbon contents are
limited to 0.03% max. Typically, they are solution treated at a temperature of
820~ and air cooled to room temperature. This results in the formation of a
martensitic structure, even in large section sizes due to the high hardenability
effect conferred by the high nickel content and other alloying elements. In
the solution-treated condition, the low-carbon martensitic structures provide the
following range of properties: