1090 Steel: Properties and Key Applications

1090 steel is classified as a medium-carbon steel, primarily composed of iron with a carbon content of approximately 0.90%. This steel grade falls under the AISI/SAE classification system and is known for its high strength and hardness, making it suitable for various engineering applications. The primary alloying element in 1090 steel is carbon, which significantly influences its mechanical properties, particularly its tensile strength and hardness.

Comprehensive Overview

1090 steel is characterized by its excellent wear resistance and ability to be hardened through heat treatment processes. The carbon content allows for a fine balance between strength and ductility, making it a versatile material for applications requiring high strength and toughness.

Advantages:
- High Strength and Hardness: The elevated carbon content provides superior tensile strength and hardness compared to lower carbon steels.
- Good Wear Resistance: Ideal for applications where abrasion resistance is critical.
- Heat Treatable: Can be hardened through quenching and tempering processes, enhancing its mechanical properties.

Limitations:
- Reduced Ductility: The high carbon content can lead to brittleness, especially in the hardened state.
- Weldability Issues: 1090 steel can be challenging to weld due to its carbon content, which may lead to cracking.
- Corrosion Susceptibility: It is more prone to corrosion than lower carbon steels, necessitating protective coatings in certain environments.

Historically, 1090 steel has been used in various applications, including automotive components, tools, and machinery parts, due to its favorable mechanical properties. Its market position is notable in industries requiring high-performance materials, although it is less common than other grades like 1045 or 1080 steel.

Alternative Names, Standards, and Equivalents

Standard Organization	Designation/Grade	Country/Region of Origin	Notes/Remarks
UNS	G10900	USA	Closest equivalent to AISI 1090
AISI/SAE	1090	USA	Medium-carbon steel with high carbon content
ASTM	A108	USA	Standard specification for cold-finished carbon steel bars
EN	C90E	Europe	Minor compositional differences to be aware of
JIS	S45C	Japan	Similar properties but with different alloying elements

The table above highlights various standards and equivalents for 1090 steel. Notably, while S45C is similar, it may contain different alloying elements that could affect performance in specific applications.

Key Properties

Chemical Composition

Element (Symbol and Name)	Percentage Range (%)
C (Carbon)	0.85 - 0.95
Mn (Manganese)	0.60 - 0.90
Si (Silicon)	0.15 - 0.40
P (Phosphorus)	≤ 0.04
S (Sulfur)	≤ 0.05

The primary alloying element in 1090 steel is carbon, which enhances hardness and strength. Manganese contributes to hardenability and improves toughness, while silicon aids in deoxidation during steelmaking. Phosphorus and sulfur are kept to low levels to maintain ductility and prevent brittleness.

Mechanical Properties

Property	Condition/Temper	Test Temperature	Typical Value/Range (Metric)	Typical Value/Range (Imperial)	Reference Standard for Test Method
Tensile Strength	Annealed	Room Temp	620 - 850 MPa	90 - 123 ksi	ASTM E8
Yield Strength (0.2% offset)	Annealed	Room Temp	350 - 600 MPa	51 - 87 ksi	ASTM E8
Elongation	Annealed	Room Temp	15 - 20%	15 - 20%	ASTM E8
Hardness (Rockwell C)	Quenched & Tempered	Room Temp	50 - 60 HRC	50 - 60 HRC	ASTM E18
Impact Strength	Quenched & Tempered	-20 °C	30 - 50 J	22 - 37 ft-lbf	ASTM E23

The mechanical properties of 1090 steel make it suitable for applications requiring high strength and toughness. The combination of tensile and yield strength indicates its ability to withstand significant loads, while the hardness values suggest excellent wear resistance.

Physical Properties

Property	Condition/Temperature	Value (Metric)	Value (Imperial)
Density	Room Temp	7.85 g/cm³	0.284 lb/in³
Melting Point	-	1425 - 1540 °C	2600 - 2800 °F
Thermal Conductivity	Room Temp	45 W/m·K	31 BTU·in/(hr·ft²·°F)
Specific Heat Capacity	Room Temp	0.46 kJ/kg·K	0.11 BTU/lb·°F
Coefficient of Thermal Expansion	Room Temp	11.5 x 10⁻⁶/K	6.4 x 10⁻⁶/°F

The density of 1090 steel indicates its substantial mass, which contributes to its strength. The melting point is relatively high, allowing it to maintain structural integrity at elevated temperatures. The thermal conductivity and specific heat capacity are important for applications involving heat transfer.

Corrosion Resistance

Corrosive Agent	Concentration (%)	Temperature (°C/°F)	Resistance Rating	Notes
Atmospheric	-	-	Fair	Risk of rusting without protection
Chlorides	3-5	20-60 °C (68-140 °F)	Poor	Susceptible to pitting corrosion
Acids	10-20	Room Temp	Poor	Not recommended for acidic environments
Alkaline	5-10	Room Temp	Fair	Moderate resistance, but protective measures needed

1090 steel exhibits moderate corrosion resistance, particularly in atmospheric conditions. However, it is susceptible to pitting in chloride environments and should not be used in acidic applications. Compared to stainless steels, such as 304 or 316, 1090 steel's corrosion resistance is significantly lower, necessitating protective coatings or finishes in corrosive environments.

Heat Resistance

Property/Limit	Temperature (°C)	Temperature (°F)	Remarks
Max Continuous Service Temp	300 °C	572 °F	Beyond this, properties degrade
Max Intermittent Service Temp	400 °C	752 °F	Short-term exposure only
Scaling Temperature	600 °C	1112 °F	Risk of oxidation at this temp

At elevated temperatures, 1090 steel maintains its strength but may begin to lose hardness and toughness. Oxidation can occur at high temperatures, leading to scaling, which can affect surface integrity.

Fabrication Properties

Weldability

Welding Process	Recommended Filler Metal (AWS Classification)	Typical Shielding Gas/Flux	Notes
MIG	ER70S-6	Argon + CO2	Preheat recommended
TIG	ER70S-2	Argon	Requires post-weld heat treatment

Welding 1090 steel can be challenging due to its high carbon content, which may lead to cracking. Preheating before welding and post-weld heat treatment are recommended to mitigate these issues.

Machinability

Machining Parameter	1090 Steel	AISI 1212	Notes/Tips
Relative Machinability Index	60	100	1212 is easier to machine
Typical Cutting Speed (Turning)	30-50 m/min	60-80 m/min	Adjust based on tooling

1090 steel has moderate machinability. Optimal cutting speeds and tooling should be used to achieve the best results, as it can work-harden quickly.

Formability

1090 steel is less formable than lower carbon steels due to its higher carbon content. Cold forming is possible but may require more force and can lead to work hardening. Hot forming is more feasible, allowing for better shaping without compromising material integrity.

Heat Treatment

Treatment Process	Temperature Range (°C/°F)	Typical Soaking Time	Cooling Method	Primary Purpose / Expected Result
Annealing	600 - 700 °C / 1112 - 1292 °F	1 - 2 hours	Air	Softening, improving ductility
Quenching	800 - 900 °C / 1472 - 1652 °F	30 minutes	Oil or Water	Hardening
Tempering	200 - 600 °C / 392 - 1112 °F	1 hour	Air	Reducing brittleness, improving toughness

Heat treatment processes significantly affect the microstructure of 1090 steel. Quenching increases hardness, while tempering is essential to reduce brittleness and enhance toughness.

Typical Applications and End Uses

Industry/Sector	Specific Application Example	Key Steel Properties Utilized in this Application	Reason for Selection
Automotive	Drive shafts	High strength, wear resistance	Durability under load
Tooling	Cutting tools	Hardness, edge retention	Performance longevity
Machinery	Gears	Toughness, fatigue resistance	Reliability in operation

Other applications include:
- Shafts and axles in machinery
- Spring components
- High-strength fasteners

1090 steel is chosen for these applications due to its ability to withstand high stress and wear, making it ideal for components that require durability and performance.

Important Considerations, Selection Criteria, and Further Insights

Feature/Property	1090 Steel	AISI 1045	AISI 1080	Brief Pro/Con or Trade-off Note
Key Mechanical Property	High Strength	Moderate Strength	High Strength	1090 offers better hardness than 1045
Key Corrosion Aspect	Fair	Fair	Poor	1090 is less corrosion-resistant than 1080
Weldability	Challenging	Moderate	Poor	1045 is easier to weld than 1090
Machinability	Moderate	Good	Poor	1045 is easier to machine than 1090
Approx. Relative Cost	Moderate	Low	Moderate	Cost varies with market demand
Typical Availability	Moderate	High	Moderate	1045 is more commonly available

When selecting 1090 steel, considerations include its mechanical properties, potential for corrosion, and challenges in fabrication. While it offers high strength and wear resistance, its weldability and machinability may limit its use in certain applications. Understanding these trade-offs is crucial for engineers and designers when specifying materials for projects.

In summary, 1090 steel is a robust medium-carbon steel with distinct advantages and limitations. Its applications span various industries, making it a valuable material for high-performance components.