302 Stainless Steel: Properties and Key Applications

302 stainless steel is classified as an austenitic stainless steel, notable for its high chromium and nickel content. This grade is primarily alloyed with approximately 8% nickel and 18% chromium, which contribute to its excellent corrosion resistance, good formability, and high strength. The presence of nickel stabilizes the austenitic structure, making it non-magnetic and enhancing its toughness at both ambient and elevated temperatures.

Comprehensive Overview

302 stainless steel is widely recognized for its versatility and is often used in applications requiring a combination of good mechanical properties and resistance to oxidation and corrosion. Its inherent properties include:

• Corrosion Resistance: Excellent resistance to a variety of corrosive environments, including atmospheric conditions, and many organic and inorganic chemicals.
• Mechanical Strength: High tensile strength and yield strength, making it suitable for structural applications.
• Formability: Good workability, allowing for various fabrication processes such as welding and machining.

Advantages:
- High resistance to oxidation and corrosion.
- Good mechanical properties at both room and elevated temperatures.
- Non-magnetic in the annealed condition.

Limitations:
- Lower resistance to pitting corrosion in chloride environments compared to other stainless steels like 316.
- Not as strong as some other high-strength alloys, limiting its use in highly demanding structural applications.

Historically, 302 stainless steel has been a staple in the manufacturing of kitchen equipment, automotive parts, and various industrial applications due to its balance of properties and cost-effectiveness. Its market position remains strong, with widespread use across multiple industries.

Alternative Names, Standards, and Equivalents

Standard Organization	Designation/Grade	Country/Region of Origin	Notes/Remarks
UNS	S30200	USA	Closest equivalent to AISI 302
AISI/SAE	302	USA	Commonly used designation
ASTM	A240	USA	Standard specification for stainless steel plates
EN	1.4300	Europe	Equivalent to AISI 302 with minor compositional differences
JIS	SUS302	Japan	Similar properties, used in Japanese standards
GB	00Cr19Ni9	China	Equivalent with slight variations in composition
ISO	1.4300	International	General designation for this grade

Notes/Remarks: While grades like 316 stainless steel offer better resistance to chlorides, 302 remains a cost-effective choice for many applications where extreme corrosion resistance is not critical. The minor compositional differences between equivalent grades can affect performance in specific environments, making careful selection important.

Key Properties

Chemical Composition

Element (Symbol and Name)	Percentage Range (%)
C (Carbon)	0.15 max
Cr (Chromium)	17.0 - 19.0
Ni (Nickel)	8.0 - 10.0
Mn (Manganese)	2.0 max
Si (Silicon)	1.0 max
P (Phosphorus)	0.045 max
S (Sulfur)	0.03 max

The primary alloying elements in 302 stainless steel include chromium and nickel, which are crucial for enhancing corrosion resistance and mechanical properties. Chromium forms a passive oxide layer on the surface, providing protection against corrosion, while nickel improves toughness and ductility, particularly at low temperatures.

Mechanical Properties

Property	Condition/Temper	Typical Value/Range (Metric - SI Units)	Typical Value/Range (Imperial Units)	Reference Standard for Test Method
Tensile Strength	Annealed	520 - 750 MPa	75 - 109 ksi	ASTM E8
Yield Strength (0.2% offset)	Annealed	205 - 310 MPa	30 - 45 ksi	ASTM E8
Elongation	Annealed	40%	40%	ASTM E8
Hardness (Rockwell B)	Annealed	70 - 90	70 - 90	ASTM E18
Impact Strength	-	40 J (at -20°C)	30 ft-lbf (at -4°F)	ASTM E23

The combination of high tensile and yield strength, along with good elongation, makes 302 stainless steel suitable for applications that require both strength and ductility. Its impact strength at low temperatures ensures reliability in colder environments.

Physical Properties

Property	Condition/Temperature	Value (Metric - SI Units)	Value (Imperial Units)
Density	-	8.0 g/cm³	0.289 lb/in³
Melting Point/Range	-	1400 - 1450 °C	2550 - 2642 °F
Thermal Conductivity	20 °C	16.2 W/m·K	112 BTU·in/(hr·ft²·°F)
Specific Heat Capacity	20 °C	500 J/kg·K	0.12 BTU/lb·°F
Electrical Resistivity	20 °C	0.72 µΩ·m	0.72 µΩ·in
Coefficient of Thermal Expansion	20 - 100 °C	16.0 x 10⁻⁶ /K	8.9 x 10⁻⁶ /°F
Magnetic Permeability	-	Non-magnetic	Non-magnetic

The density and melting point of 302 stainless steel indicate its suitability for high-temperature applications. Its thermal conductivity and specific heat capacity make it effective in heat transfer applications, while its non-magnetic nature is advantageous in electronic and magnetic applications.

Corrosion Resistance

Corrosive Agent	Concentration (%)	Temperature (°C/°F)	Resistance Rating	Notes
Chlorides	0 - 10	20 - 60 / 68 - 140	Fair	Susceptible to pitting
Sulfuric Acid	0 - 50	20 - 60 / 68 - 140	Good	Requires passivation
Acetic Acid	0 - 50	20 - 60 / 68 - 140	Excellent	Resistant in low concentrations
Sea Water	-	20 - 60 / 68 - 140	Good	Risk of localized corrosion
Atmospheric	-	-	Excellent	Good resistance to oxidation

302 stainless steel exhibits excellent resistance to atmospheric corrosion and many organic and inorganic chemicals. However, it is susceptible to pitting corrosion in chloride environments, particularly in marine applications. Compared to 316 stainless steel, which contains molybdenum for enhanced chloride resistance, 302 may not perform as well in highly saline conditions.

Heat Resistance

Property/Limit	Temperature (°C)	Temperature (°F)	Remarks
Max Continuous Service Temp	870 °C	1600 °F	Suitable for high-temperature applications
Max Intermittent Service Temp	925 °C	1700 °F	Can withstand short-term exposure
Scaling Temperature	600 °C	1112 °F	Risk of oxidation beyond this temperature
Creep Strength considerations	600 °C	1112 °F	Creep resistance decreases at high temps

302 stainless steel maintains its mechanical properties at elevated temperatures, making it suitable for applications in heat exchangers and furnace components. However, prolonged exposure to temperatures above 600 °C can lead to oxidation and scaling, necessitating careful consideration in design.

Fabrication Properties

Weldability

Welding Process	Recommended Filler Metal (AWS Classification)	Typical Shielding Gas/Flux	Notes
TIG	ER308L	Argon	Good results with proper technique
MIG	ER308L	Argon + CO2	Requires careful control of heat input
Stick	E308L	-	Suitable for thicker sections

302 stainless steel is highly weldable using various processes, including TIG and MIG welding. Pre- and post-weld heat treatments are often recommended to minimize the risk of cracking and to ensure optimal mechanical properties. Care should be taken to avoid overheating during welding, which can lead to a loss of corrosion resistance.

Machinability

Machining Parameter	302 Stainless Steel	AISI 1212	Notes/Tips
Relative Machinability Index	50%	100%	Moderate machinability
Typical Cutting Speed (Turning)	30 m/min	60 m/min	Use carbide tools for best results

302 stainless steel has moderate machinability, often requiring slower cutting speeds and specialized tooling to achieve desired surface finishes. The use of high-speed steel or carbide tools is recommended to enhance performance.

Formability

302 stainless steel exhibits good formability, allowing for various processes such as bending, stamping, and deep drawing. However, it is essential to consider work hardening, which can affect the material's ductility during forming operations. Recommended bend radii should be adhered to in order to prevent cracking.

Heat Treatment

Treatment Process	Temperature Range (°C/°F)	Typical Soaking Time	Cooling Method	Primary Purpose / Expected Result
Annealing	1010 - 1120 / 1850 - 2050	1 - 2 hours	Air	Relieve stresses, improve ductility
Solution Treatment	1010 - 1120 / 1850 - 2050	1 hour	Water	Stabilize austenitic structure
Aging	650 - 800 / 1200 - 1470	1 - 2 hours	Air	Enhance strength and hardness

Heat treatment processes such as annealing and solution treatment are crucial for optimizing the microstructure of 302 stainless steel. These processes enhance ductility and strength while relieving internal stresses, making the material more suitable for demanding applications.

Typical Applications and End Uses

Industry/Sector	Specific Application Example	Key Steel Properties Utilized in this Application	Reason for Selection (Brief)
Food Processing	Kitchen Equipment	Corrosion resistance, formability	Hygiene and durability
Automotive	Exhaust Systems	High-temperature strength, oxidation resistance	Performance under heat
Chemical Industry	Storage Tanks	Corrosion resistance, mechanical strength	Safety and longevity
Aerospace	Aircraft Components	Lightweight, high strength	Performance and safety

Other applications include:

• • Medical devices
• • Architectural elements
• • Fasteners and fittings

302 stainless steel is chosen for these applications due to its excellent balance of properties, particularly its corrosion resistance and mechanical strength, which are critical in environments exposed to moisture and chemicals.

Important Considerations, Selection Criteria, and Further Insights

Feature/Property	302 Stainless Steel	316 Stainless Steel	304 Stainless Steel	Brief Pro/Con or Trade-off Note
Key Mechanical Property	Moderate Strength	High Strength	Moderate Strength	316 offers better corrosion resistance
Key Corrosion Aspect	Fair in Chlorides	Excellent	Good	316 is preferred for marine applications
Weldability	Good	Good	Excellent	304 is easier to weld
Machinability	Moderate	Moderate	Good	304 is often easier to machine
Formability	Good	Good	Excellent	304 has superior formability
Approx. Relative Cost	Moderate	Higher	Moderate	302 is cost-effective for many applications
Typical Availability	Widely Available	Widely Available	Widely Available	All grades are commonly found

When selecting 302 stainless steel, considerations such as cost-effectiveness, availability, and specific mechanical and corrosion resistance requirements are paramount. While 302 offers a good balance of properties, alternatives like 316 may be more suitable for environments with high chloride exposure. Additionally, 304 stainless steel is often chosen for its excellent formability and weldability, making it a popular choice in many applications.

In conclusion, 302 stainless steel remains a versatile and widely used material in various industries, providing a reliable option for applications requiring a combination of strength, corrosion resistance, and formability.