1. Key Properties:
High Strength: SAE 4340 QT is a high-strength, quenched and tempered alloy steel, offering enhanced tensile and yield strength compared to the standard SAE 4340, making it suitable for demanding and heavy-duty applications.
Improved Toughness: The quenching and tempering processes significantly improve the toughness, ensuring excellent impact resistance and performance under shock loads.
Enhanced Hardness: Quenching increases hardness, providing high wear and abrasion resistance, which is essential for parts exposed to heavy wear.
Fatigue Resistance: SAE 4340 QT is highly resistant to fatigue, making it ideal for components exposed to cyclic stresses and dynamic loading.
Weldability: While the material has good weldability, thicker sections may require preheating and post-weld heat treatment to prevent cracking and ensure optimal results.
Corrosion Resistance: It has moderate corrosion resistance, which can be further enhanced by coatings or protective treatments in certain environments.
2. Applications/Industries:
Aerospace: Used for aerospace components that require high strength, toughness, and fatigue resistance, including landing gear, turbine blades, and structural elements.
Automotive: Employed in automotive parts such as axles, crankshafts, gears, and suspension components that require high strength and wear resistance.
Oil & Gas: Commonly used for high-pressure equipment such as drill pipes, blowout preventers, and other critical oilfield applications where strength and impact resistance are paramount.
Heavy Machinery: SAE 4340 QT is used in the production of gears, shafts, and other high-stress components for heavy machinery, mining equipment, and construction tools.
Military: Used in military applications, including armored vehicle parts, weapons systems, and structural components, requiring high strength and durability.
3. Certifications/Standards:
SAE J403: SAE 4340 QT conforms to the SAE J403 standard for alloy steels, ensuring it meets the required chemical composition and mechanical properties.
ASTM A519: This standard applies to seamless carbon and alloy steel mechanical tubing, which is applicable to SAE 4340 QT pipes.
ISO 9001: Quality management system certification.
4. Chemical Composition:
Carbon (C): 0.38% – 0.43%
Manganese (Mn): 0.60% – 0.80%
Chromium (Cr): 0.70% – 0.90%
Nickel (Ni): 1.65% – 2.00%
Molybdenum (Mo): 0.20% – 0.30%
Silicon (Si): 0.15% – 0.30%
Phosphorus (P): 0.035% max
Sulfur (S): 0.035% max
Iron (Fe): Balance
5. Technical Specifications:
Yield Strength:
SAE 4340 QT: 690 MPa (minimum)
Tensile Strength:
SAE 4340 QT: 850–1000 MPa
Hardness:
SAE 4340 QT: Approximately 220–300 HB (Brinell hardness), depending on the specific quenching and tempering process.