1. Key Properties:
High Strength: SAE 4140 QT is a quenched and tempered alloy steel, offering enhanced strength and hardness compared to standard SAE 4140. It’s ideal for applications requiring high tensile strength.
Improved Toughness: The heat treatment process (quenching and tempering) significantly enhances the toughness of SAE 4140 QT, making it resistant to shock loads and impact.
Enhanced Hardness: The quenching process increases the hardness of the steel, providing excellent wear and abrasion resistance.
Weldability: While SAE 4140 QT has good weldability, preheating may be necessary for thicker sections to reduce the risk of cracking during welding.
Corrosion Resistance: Moderate resistance to corrosion in industrial environments; however, protective coatings may be required for harsher conditions.
Heat Treatable: SAE 4140 QT can be further heat-treated to fine-tune its properties, allowing for increased hardness or strength for specific applications.
2. Applications/Industries:
Automotive: Ideal for high-stress components such as gears, axles, crankshafts, and suspension parts in high-performance automotive applications.
Heavy Machinery: Frequently used in the production of machinery components, including shafts, gears, and other parts that must endure heavy loads and extreme working conditions.
Oil & Gas: Commonly used in high-pressure environments such as oilfield drilling equipment, pipelines, and pressure vessels.
Aerospace: Used in aerospace components like landing gears, structural elements, and critical engine parts that require both high strength and toughness.
Tooling & Dies: SAE 4140 QT is widely used in tooling and die applications, providing durability and wear resistance for molds and press tools.
3. Certifications/Standards:
SAE J403: SAE 4140 QT conforms to the SAE J403 standard for alloy steels, ensuring that it meets specific mechanical properties and chemical composition.
ASTM A519: The standard applies to seamless carbon and alloy steel mechanical tubing, which is relevant for SAE 4140 QT pipes.
ISO 9001: Quality management system certification.
4. Chemical Composition:
Carbon (C): 0.38% – 0.43%
Manganese (Mn): 0.60% – 0.90%
Chromium (Cr): 0.80% – 1.10%
Molybdenum (Mo): 0.15% – 0.25%
Silicon (Si): 0.20% – 0.35%
Phosphorus (P): 0.035% max
Sulfur (S): 0.035% max
Iron (Fe): Balance
5. Technical Specifications:
Yield Strength:
SAE 4140 QT: 485 MPa (minimum)
Tensile Strength:
SAE 4140 QT: 655–850 MPa
Hardness:
SAE 4140 QT: Approximately 220–300 HB (Brinell hardness), depending on the specific quenching and tempering process.