steel - Nouvelle page 1 - Free

MMPDS-01
31 January 2003
2.4.2 9NI-4CO-0.20C
2.4.2.0 Comments and Properties — The 9Ni-4Co-0.20C alloy was developed specifically
to have excellent fracture toughness, excellent weldability, and high hardenability when heat-treated to 190
to 210 ksi ultimate tensile strength. The alloy can be readily welded in the heat-treated condition with preheat
and post-heat usually not required. The alloy is through hardening in section sizes up to at least 8 inches
thick. The alloy may be exposed to temperatures up to 900EF (approximately 100EF below typical tempering
temperature) without microstructural changes which degrade room temperature strength.
The heat treatment for this alloy consists of normalizing at 1650 ± 25EF for 1 hour per inch of cross
section, cooling in air to room temperature, heating to 1525 ± 25EF for 1 hour per inch of cross section,
quenching in oil or water, hold at -100 ± 20EF for 2 hours within 2 hours after quenching, and double
tempering at 1035 ± 10EF for 2 hours.
A material specification for 9Ni-4Co-0.20C steel is presented in Table 2.4.2.0(a). Room temperature
mechanical and physical properties are shown in Table 2.4.2.0(b). The effect of temperature on thermal
expansion is shown in Figure 2.4.2.0.
Table 2.4.2.0(a). Material Specification for
9Ni-4Co-0.20C Steel
Specification
Form
AMS 6523
Sheet, strip, and plate
2.4.2.1 Heat-Treated Condition — Effect of temperature on various mechanical properties
is presented in Figures 2.4.2.1.1, 2.4.2.1.2, and 2.4.2.1.4. Typical tensile stress-strain curves at room and
elevated temperatures are shown in Figure 2.4.2.1.6(a). Typical compression stress-strain and tangentmodulus
curves are presented in Figure 2.4.2.1.6(b).
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