D6AC High Strength Alloy Steel
D6AC is a medium carbon low alloy steel that is melted as AOD + VAR which improved hardenability as compared to 4340 low alloy steel. This alloy has very high strength and offers excellent notch toughness. D6AC has excellent deep hardening characteristics which lend itself well to larger components. This grade is also widely used in the aerospace industry as landing gear, shafts, and axles requiring a good combination of toughness and strength.
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| Chemical Composition Limits | |||||||
| Weight% | C | Si | Mn | Cr | Ni | Mo | V |
| D-6AC Vac Melt N&T | 0.46 | 0.25 | 0.75 | 1.10 | 0.60 | 1.00 | 0.10 |
SPECS USAP PRODUCES TO:
AMS 6431
AMS-S-8949
General Dynamics FMS-1011
Grumman GM-1013
Lockheed LCM 05-2190
Lockheed STM 05-500
MIL-S-8949
Don’t see the spec you’re looking for? Not all specs are listed so please submit an inquiry!
INDUSTRY / TRADE NAMES
UNS K24728
Alloy D6AC Vac Melt N&T (D6AC VAC ARC ®) is available in bar (round bar). For all stock availability contact Sales.
Typical Mechanical Properties
| Material | Tempering Treatment | Ultimate Tensile Strength (Mpa) | 0.2 % Yield Strength (Mpa) | % Elongation | % Reduction of Area | Hardness HRC |
| D6AC VAC ARC | 316°C (600°F) | 1931 | 1724 | 7 | 23 | 53 |
| D6AC VAC ARC | 510°C (950°F) | 1572 | 1345 | 7 | 25 | 46 |
| Heat Treatment before temper. A ustenitized at 1650°F (899°C). Oil quenched and air cooled, or salt quenched at 400-425°F (204-218°C) for ten minutes and air cooled | ||||||
General Characteristics
D6AC alloy is a medium-carbon low-alloy ultra high strength steel that was primarily developed for high strength structural applications requiring ultimate tensile strength values up to 280 ksi. The steel has a high yield to ultimate strength ratio, while retaining good ductility. It has good hardenability and excellent impact strength down to –210ºF (-134ºC.)
Applications
D6AC is used where its excellent strength, ductility and toughness properties come into play, primarily in structural applications. The alloy’s good hardenability makes it suitable for use in fairly large sections.
Forging
Forging of this grade may be carried out from 2000 to 2250ºF (1090 to 1230ºC,) the actual temperature depending upon complexity of the part and the reduction required. A minimum finishing temperature of 1700ºF (930ºC) is recommended. Following forging an equalization treatment at 1200-1300ºF (650-705ºC) is recommended, followed by a furnace cool to 1000ºF (540ºC) and subsequent air cool.
Heat Treatment
Annealing: Heat uniformly to 1500-1550ºF (815-845ºC) and furnace cool at 50ºF (28ºC) per hour to 1000ºF (540ºC) then air cool to room temperature.
Hardening : Austenitize at 1550-1650ºF (845-900ºC). Small sections up to 1 in (25mm) may be air cooled, but larger sections should be cooled in oil or brine.
Tempering: Temper at 300 – 1200ºF (150-650ºC) for desired properties, using appropriate times according to section size. Double tempering is recommended.
Machinability
The alloy D6AC has a machinability rating 50-55 percent of that of B1112 screw stock. Either high speed steel or carbide cutting tools are recommended.
Weldability
The alloy is weldable, even in heavy sections. Preheat and postheat treatments are applicable here for the carbon content in question.
Property
Density: 0.284
Specific Gravity: 7.8
Specific Heat: 0.116
Melting Point: 2600
Thermal Conductivity: 30
MCTE: 7
MoETensile: 32
