Special Alloy Steel:Application in the Automotive Industry

From the core components of the engine to the body safety structure, special alloy steel is everywhere due to its superior performance.

How does it work in different parts? What kind of amazing performance does it have?

Today, let’s take a look at the application of special alloy steels commonly used in the automotive industry.

SAE 4140 Steel

SAE 4140 steel is a crucial medium-carbon alloy structural steel in the automotive industry. It is typically used in a quenched and tempered state to achieve the optimal combination of strength, toughness, and fatigue limit.

The application of SAE 4140 steel in automobiles is primarily concentrated in core components that need to withstand heavy loads, impacts, and torsion.

SAE 4140 Steel Applications

Crankshafts and Connecting Rods:Forged 4140 crankshafts and connecting rods can withstand reciprocating impacts and alternating torsional loads.
Steering knuckle: After quenching and tempering, 4140 provides the required high strength, toughness and fatigue life to withstand torsion and impact.

SAE 8620 Steel

As a typical carburizing alloy structural steel, SAE 8620 steel achieves high hardness and wear resistance through surface carburizing and quenching, while its core, due to its low carbon content, retains extremely high ductility, toughness, and impact resistance.

The application of SAE 8620 steel in automobiles is mainly concentrated in gear parts that require extremely wear-resistant surfaces and impact-resistant cores.

SAE 8620 Steel Applications

Gearbox Gears/Differential Gears:This is the most core application of SAE 8620 in the automotive industry.After carburizing, SAE8620 steel has a high surface hardness (HRC58-62) to resist wear and pitting, while maintaining good core toughness to withstand external impact overloads.
Camshaft/Spline Shaft:SAE 8620 steel, after carburizing, has a wear-resistant surface and impact-resistant core, meeting the requirements for axle-type parts in the automotive industry.

SAE 4340 Steel

SAE4340 steel is a high-end, high-strength alloy structural steel used in the automotive industry. After quenching and tempering, its strength, toughness, and fatigue resistance reach extremely high levels of overall performance.

The applications of SAE 4340 steel in automobiles are primarily concentrated in high-performance core components requiring heavy loads, high impacts, and extreme conditions.

SAE 4340 Steel Applications:

High-performance crankshafts and connecting rods: Used in top-tier racing cars, heavy-duty vehicles, and off-road vehicles.Forged 4340 steel withstands ultra-high speeds and alternating tensile and compressive stresses, effectively absorbing impact energy to prevent fracture while maintaining extremely high strength.
Half-shafts/Drive shafts: This is one of the most typical applications of the 4340 in automobiles. Shafts made of 4340 are used to transmit huge torques while absorbing huge external impact energy to ensure safety.

SAE 5140 Steel

5140 steel is currently the most widely used medium-carbon alloy structural steel in the automotive industry, covering a large number of automotive components with medium loads and comprehensive mechanical properties due to its excellent cost performance.

The application of SAE 5140 steel in automobiles is mainly concentrated in components that need to withstand medium loads.

SAE 5140 Steel Applications:

Steering knuckle：This is the largest application of 5140 steel, requiring components to withstand bending, torsion, and certain impact loads. After quenching and tempering, 5140 steel is sufficient to handle the complex stresses under normal driving and general impact conditions.
Fasteners: Fasteners in automobiles, especially those of grade 10.9 and below, are largely made of 5140 steel.

SAE 52100 Steel

SAE 52100 steel is a high-carbon chromium bearing steel. After quenching and tempering, it exhibits extremely high hardness, excellent contact fatigue life, and good dimensional stability.

SAE52100 steel is the core special steel for various automotive bearings, and it is also used in high wear-resistant precision parts.

SAE 52100 Steel Applications:

Bearings:This is the most basic application of the 52100, covering the vast majority of rolling bearings in the entire vehicle.
Precision assembly:The wear resistance and contact fatigue resistance of 52100 steel ensure the sealing performance and lifespan of the parts.