Is 304 stainless A2 or A4?

Is 304 Stainless Steel A2 or A4?

SA 240 GR 304 stainless steel is equivalent to A2in the context of fastener grades, as defined by standards like ISO 3506 (for corrosion-resistant stainless steel fasteners). The A2 and A4 designations are primarily used for fasteners (e.g., bolts, screws, nuts) and are not directly applicable to plates or sheets like plat stainless 304. However, they indicate stainless steel grades with specific compositions and corrosion resistance properties.

• A2 (Austenitic Grade 2): Corresponds to AISI 304 (or SA 240 GR 304, UNS S30400, 1.4301), an austenitic stainless steel with 18-20% chromium and 8-10.5% nickel. It offers excellent corrosion resistance in mild environments and is SA 240 304 non magnetic in the annealed state. A2 is commonly referred to as "A2-70" or "A2-80" (indicating tensile strength levels in decanewtons per mm²).
• A4 (Austenitic Grade 4): Corresponds to AISI 316 (or SA 240 GR 316, UNS S31600, 1.4401), which includes 2-3% molybdenum for enhanced pitting and crevice corrosion resistance in chloride-rich environments (e.g., marine settings). Like A2, it’s austenitic and non-magnetic, often labeled as A4-70 or A4-80.

Key Clarification: SA 240 GR 304 is A2, not A4, due to its lack of molybdenum, which distinguishes 316 (A4). For fastener applications, A2 (304) is suitable for general use, while A4 (316) is preferred for harsh, chloride-heavy conditions.

Properties of SA 240 GR 304 (A2 Equivalent)

Since SA 240 GR 304 aligns with A2, its properties reflect its suitability for both plates and fasteners.

Chemical Composition

• Chromium: Provides corrosion resistance via a passive oxide layer.
• Nickel: Enhances ductility and SA 240 304 non magnetic properties.
• Carbon: Limited to ≤0.08% for weldability, though SA 240 GR 304L (≤0.03%) is preferred for critical welds. See sa 240 gr 304l.

Mechanical Properties (Annealed Plates, 8-75 mm thick)

For fasteners (A2-70), tensile strength is ~700 MPa, reflecting cold-worked conditions.

Physical Properties

• Density: 8.00 g/cm³ (SA 240 GR 304 density).
• Melting Point: ~1400-1450°C.
• Thermal Conductivity: 16.2 W/m·K.
• Coefficient of Thermal Expansion: 17.2 × 10⁻⁶/K.

Corrosion Resistance and Weldability

SA 240 GR 304 (A2) offers excellent corrosion resistance in:

• Atmospheric conditions, freshwater, and mild acids (food-grade).
• General environments, outperforming SS204 vs SS 304.

It’s less resistant to chloride-induced pitting compared to SA 240 GR 316 (A4). Weldability is good with ER308 fillers, but SA 240 GR 304L is preferred for critical welds. For chloride-heavy environments, explore sa 240 gr 316l.

Applications

• SA 240 GR 304 (A2): Used in food processing (tanks, plat stainless 304), chemical equipment, SA 240 GR 304 pipe, and architecture. A2 fasteners are common in general construction and indoor applications.
• SA 240 GR 316 (A4): Preferred for marine, coastal, and chemical applications requiring chloride resistance. A4 fasteners are used in harsh environments.

For high-temperature applications, explore sa 240 gr 304h or sa 240 gr 321.

Pricing and Availability

As of October 14, 2025, SA 240 GR 304 plate prices (2B finish, 3-6mm) range from $1.55-$3.50/kg globally, while 316 (A4) is $2.50-$3.50/kg. Gangsteel offers SA 240 GR 304 at $1.60/kg FOB (MOQ 1 ton) for sa 240 gr 304 plates, including sizes like plate 2 mm SUS 304.

Why Choose Gangsteel?

Gangsteel provides certified SA 240 GR 304 (A2 equivalent) plates with competitive SS 304 plate price and sizes like plat stainless 304. For quotes or to learn what is SA 304, visit our astm a 240 stainless plate page or email admin@gangsteel.com.