9310 Steel: Properties and Key Applications Overview

9310 steel is classified as a medium-carbon alloy steel, primarily known for its high strength and toughness. It is commonly used in applications requiring high fatigue resistance and impact strength, making it suitable for components subjected to dynamic loads. The primary alloying elements in 9310 steel include chromium, nickel, and molybdenum, which enhance its mechanical properties and resistance to wear and corrosion.

Comprehensive Overview

9310 steel is a low-alloy steel that falls under the AISI/SAE classification system. Its composition typically includes approximately 0.07-0.15% carbon, 0.80-1.20% chromium, 1.00-1.50% nickel, and 0.15-0.25% molybdenum. These alloying elements contribute significantly to the steel's overall performance, particularly in terms of strength, toughness, and hardenability.

The most significant characteristics of 9310 steel include its excellent tensile strength, good ductility, and high fatigue resistance. These properties make it ideal for applications in the aerospace and automotive industries, where components are often subjected to high-stress conditions.

Advantages (Pros):
- High strength-to-weight ratio
- Excellent fatigue resistance
- Good toughness and ductility
- Suitable for hardening through heat treatment

Limitations (Cons):
- More expensive than standard carbon steels
- Requires careful heat treatment to achieve desired properties
- May exhibit lower corrosion resistance compared to stainless steels

Historically, 9310 steel has been used in critical applications such as aircraft landing gear, gears, and shafts, highlighting its importance in high-performance engineering sectors. Its market position is robust, with a steady demand in industries that prioritize safety and reliability.

Alternative Names, Standards, and Equivalents

Standard Organization	Designation/Grade	Country/Region of Origin	Notes/Remarks
UNS	G93100	USA	Closest equivalent to AISI 9310
AISI/SAE	9310	USA	Commonly used designation
ASTM	A829	USA	Specification for alloy steel
EN	1.6580	Europe	Equivalent grade in European standards
JIS	SCM435	Japan	Similar properties but different composition
ISO	9310	International	Standardized designation

The table above outlines various standards and equivalents for 9310 steel. Notably, while SCM435 is similar, it has a slightly different composition that may affect its performance in specific applications, particularly in terms of hardenability and toughness.

Key Properties

Chemical Composition

Element (Symbol and Name)	Percentage Range (%)
C (Carbon)	0.07 - 0.15
Cr (Chromium)	0.80 - 1.20
Ni (Nickel)	1.00 - 1.50
Mo (Molybdenum)	0.15 - 0.25
Mn (Manganese)	0.40 - 0.70
Si (Silicon)	0.15 - 0.40
P (Phosphorus)	≤ 0.025
S (Sulfur)	≤ 0.025

The primary alloying elements in 9310 steel play crucial roles in its performance:
- Chromium: Enhances hardenability and resistance to wear.
- Nickel: Improves toughness and ductility, especially at low temperatures.
- Molybdenum: Increases strength and resistance to softening at high temperatures.

Mechanical Properties

Property	Condition/Temper	Typical Value/Range (Metric)	Typical Value/Range (Imperial)	Reference Standard for Test Method
Tensile Strength	Quenched & Tempered	930 - 1,080 MPa	135 - 156 ksi	ASTM E8
Yield Strength (0.2% offset)	Quenched & Tempered	780 - 930 MPa	113 - 135 ksi	ASTM E8
Elongation	Quenched & Tempered	12 - 15%	12 - 15%	ASTM E8
Reduction of Area	Quenched & Tempered	45 - 55%	45 - 55%	ASTM E8
Hardness (Rockwell C)	Quenched & Tempered	30 - 40 HRC	30 - 40 HRC	ASTM E18
Impact Strength (Charpy)	-40°C	30 - 50 J	22 - 37 ft-lbf	ASTM E23

The mechanical properties of 9310 steel make it particularly suitable for applications requiring high strength and toughness. Its ability to withstand dynamic loads without failure is critical in aerospace and automotive components.

Physical Properties

Property	Condition/Temperature	Value (Metric)	Value (Imperial)
Density	-	7.85 g/cm³	0.284 lb/in³
Melting Point	-	1,400 - 1,540 °C	2,552 - 2,804 °F
Thermal Conductivity	20°C	45 W/m·K	31 BTU·in/(hr·ft²·°F)
Specific Heat Capacity	-	460 J/kg·K	0.11 BTU/lb·°F
Electrical Resistivity	-	0.00065 Ω·m	0.00038 Ω·in
Coefficient of Thermal Expansion	20-100°C	11.5 x 10⁻⁶ /°C	6.4 x 10⁻⁶ /°F

Key physical properties such as density and thermal conductivity are important for applications where weight and heat dissipation are critical. The relatively high melting point indicates good performance under elevated temperatures.

Corrosion Resistance

Corrosive Agent	Concentration (%)	Temperature (°C)	Resistance Rating	Notes
Chlorides	3-5	25	Fair	Risk of pitting corrosion
Sulfuric Acid	10	50	Poor	Not recommended
Sea Water	-	25	Fair	Moderate resistance
Atmospheric	-	-	Good	Generally resistant

9310 steel exhibits moderate corrosion resistance, particularly in atmospheric conditions. However, it is susceptible to pitting in chloride environments and should not be used in highly corrosive applications without protective coatings. Compared to stainless steels like 304 or 316, 9310's corrosion resistance is significantly lower, making it less suitable for marine or chemical processing applications.

Heat Resistance

Property/Limit	Temperature (°C)	Temperature (°F)	Remarks
Max Continuous Service Temp	300	572	Suitable for prolonged exposure
Max Intermittent Service Temp	400	752	Short-term exposure
Scaling Temperature	600	1,112	Risk of oxidation beyond this temp
Creep Strength considerations begin	400	752	Not recommended for high creep applications

At elevated temperatures, 9310 steel maintains its strength but may begin to oxidize if not properly protected. Its performance in high-temperature applications is adequate, but care must be taken to avoid prolonged exposure to temperatures above 300 °C.

Fabrication Properties

Weldability

Welding Process	Recommended Filler Metal (AWS Classification)	Typical Shielding Gas/Flux	Notes
MIG	ER80S-Ni1	Argon	Good for thin sections
TIG	ER80S-Ni1	Argon	Requires preheat
Stick	E8018-C3	-	Suitable for thicker sections

9310 steel can be welded using various processes, but preheating is often recommended to reduce the risk of cracking. Post-weld heat treatment may also be necessary to relieve stresses and restore toughness.

Machinability

Machining Parameter	9310 Steel	AISI 1212	Notes/Tips
Relative Machinability Index	60	100	Moderate machinability
Typical Cutting Speed (Turning)	40 m/min	60 m/min	Use carbide tools for best results

Machinability of 9310 steel is moderate, requiring appropriate tooling and cutting speeds to achieve optimal results. Care should be taken to avoid overheating during machining.

Formability

9310 steel exhibits good formability, allowing for both cold and hot working processes. However, it may work-harden quickly, necessitating careful control of forming parameters to avoid cracking.

Heat Treatment

Treatment Process	Temperature Range (°C/°F)	Typical Soaking Time	Cooling Method	Primary Purpose / Expected Result
Annealing	600 - 700 / 1,112 - 1,292	1 - 2 hours	Air	Softening, improving ductility
Quenching	800 - 850 / 1,472 - 1,562	30 minutes	Oil	Hardening
Tempering	400 - 600 / 752 - 1,112	1 hour	Air	Reducing brittleness, improving toughness

The heat treatment processes significantly affect the microstructure of 9310 steel, enhancing its hardness and strength while maintaining ductility. Proper control of these processes is essential to achieve the desired mechanical properties.

Typical Applications and End Uses

Industry/Sector	Specific Application Example	Key Steel Properties Utilized in this Application	Reason for Selection (Brief)
Aerospace	Aircraft landing gear	High strength, fatigue resistance	Critical safety component
Automotive	Gears and shafts	Toughness, wear resistance	High-performance requirements
Oil & Gas	Drill bits	Hardness, impact strength	Durability in harsh conditions

Other applications include:
- Military components
- Heavy machinery parts
- High-stress fasteners

9310 steel is chosen for these applications due to its excellent mechanical properties, which are crucial for components that must withstand high loads and fatigue over time.

Important Considerations, Selection Criteria, and Further Insights

Feature/Property	9310 Steel	AISI 4140	AISI 4340	Brief Pro/Con or Trade-off Note
Key Mechanical Property	High strength	Moderate strength	High strength	9310 offers better toughness than 4140
Key Corrosion Aspect	Fair	Poor	Fair	9310 is less corrosion-resistant than 4340
Weldability	Good	Fair	Poor	9310 is easier to weld than 4340
Machinability	Moderate	Good	Fair	9310 is more challenging to machine than 4140
Formability	Good	Fair	Poor	9310 has better formability than 4340
Approx. Relative Cost	Moderate	Low	High	9310 is more expensive than 4140 but offers better performance
Typical Availability	Good	Excellent	Fair	9310 is widely available in various forms

When selecting 9310 steel, considerations include its cost-effectiveness, availability, and suitability for specific applications. Its balance of strength, toughness, and weldability makes it a preferred choice for high-performance components, particularly in the aerospace and automotive sectors. However, its lower corrosion resistance compared to stainless steels may limit its use in certain environments.

In summary, 9310 steel is a versatile alloy that offers a unique combination of properties, making it suitable for demanding applications where performance and reliability are paramount.