astm a240 grade 304n (S30451) stainless steel plate supplier

ASTM A240 Grade 304N (S30451) Stainless Steel Plate

When strength meets corrosion resistance in demanding applications like nuclear reactors or cryogenic tanks, ASTM A240 Grade 304N (S30451) stainless steel plate provides a nitrogen-enhanced austenitic solution. We also call it A240 Gr 304N in technical circles (Gr for Grade), A240 SS 304N (SS for stainless steel), A240 TP 304N (TP for tubing plate, frequent in piping specs), or the classic AISI 304N plate (from the American Iron and Steel Institute). Whatever term you searched, you're likely after a material that boosts the yield strength of standard 304 through 0.10-0.16% nitrogen addition, while keeping low carbon for weldability and a PREN of 20-22 for mild corrosives. At Gangsteel, we refine it via AOD + VOD for precise nitrogen control, rolling plates up to 100 mm thick in finishes from 2B to mirror polish.

With over 25 years as a leading Chinese manufacturer and exporter, Gangsteel supplies ASTM A240 Grade 304N to nuclear, chemical, and cryogenic industries worldwide, certified to ASTM A240 and ASME SA240. This nitrogen-alloyed grade offers interstitial strengthening for higher tensile without molybdenum's cost, resisting deformation in high-stress, low-temp settings. It bridges 304 and 304LN, with better ambient strength than low-carbon variants. Dive into our guide below. Explore our austenitic nitrogen grades in the ASTM A 240/A 240M stainless steel plate portfolio, including ASTM A 240 Gr 304LN for similar N-boost and ASTM A 240 Gr 304 for base.

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1. What is ASTM A240 Grade 304N (S30451)?

ASTM A240 Grade 304N (UNS S30451) is a nitrogen-strengthened, low-carbon austenitic stainless steel under ASTM A240 for chromium-nickel plates, sheets, and strips in pressure vessels and general service. It modifies standard 304 by adding 0.10-0.16% nitrogen for solid-solution hardening, increasing yield strength by 20-30% while maintaining excellent ductility and weldability—ideal for high-stress applications where phase stability is crucial, like nuclear fuel elements or cryogenic vessels. Low carbon (≤0.08%) curbs sensitization in the 425-870°C HAZ, passing ASTM A262 Practice E without annealing in many cases.

Born from needs for stronger 304 in the 1970s nuclear boom, 304N uses N to interstitially strengthen without carbides or exotics. At Gangsteel, we use ladle refining for N solubility >0.12%, yielding grain size ASTM 6-8 and ferrite <5% for toughness. The 18-20% Cr, 8-10.5% Ni base delivers non-magnetic status, high elongation (>40%), and formability for spins. Thermal expansion 17.3 × 10⁻⁶/°C, conductivity 16.2 W/m·K suit mixed joints.

Searches for “A240 SS 304N” often focus on its edge: yield >240 MPa vs 205 MPa in 304, with PREN 20-22 for mild acids/atmospheres. Weld with 308LSi; low input preserves N. Compared to ASTM A 240 Gr 304L, 304N adds strength without Mo. For Mo+N, see ASTM A 240 Gr 316L.

In nuclear cladding or pressure piping, A240 304N's strength cuts weight 15-20% vs 304, per our Asian client data.

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2. ASTM A240 Grade 304N Chemical Composition

The composition of ASTM A240 Grade 304N is engineered for strength and stability, per Table 1.

Nitrogen's interstitial role boosts yield without ductility loss. Low C curbs carbides for welds. Cr/Ni for passivity. Gangsteel keeps N 0.12-0.14%, with <0.02 mm pitting after 1000h salt fog.

Note: Vs ASTM A 240 Gr 304, added N for strength. MTRs with analysis.

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. ASTM A240 Grade 304N Mechanical Properties

Mechanics of A240 Grade 304N highlight N-strengthening, annealed at 1010-1120°C.

N pushes yield 15-20% above 304; cryo toughness 200J Charpy. Fatigue ~250 MPa at 10^7 cycles.

Vs ASTM A 240 Gr 304L, higher yield without Mo.

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4. ASTM A240 Grade 304N Allowable Stress

Stresses per ASME BPVC Table 1A.

N stabilizes for higher loads. Certs with data.

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5. ASTM A240 Grade 304N Equivalent Materials

Equivalents for sourcing.

Gangsteel dual-certs.

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6. ASTM A240 Grade 304N vs ASTM A 240 Gr 304, ASTM A 240 Gr 304L, and ASTM A 240 Gr 304LN

Vs ASTM A 240 Gr 304, ASTM A 240 Gr 304L, ASTM A 240 Gr 304LN.

• 304N vs 304: 304N N boosts yield 20%; same corrosion—304N for stress.
• 304N vs 304L: 304N higher strength; 304L low C for welds—304N for strength welds.
• 304N vs 304LN: Both N; 304LN low C for better welds—similar, 304N for general.

Choose 304N for strengthened 304, 304 ambient, 304L welds, 304LN low C N.

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7. ASTM A240 Grade 304N Specifications

Gangsteel tailors with ±0.05 mm.

7.1 Plate and Sheet

• Thickness: 0.3-100 mm (plate), 0.2-6 mm (sheet)
• Width: 1000-3000 mm
• Length: 2000-12000 mm/coils
• Surface: 2B, BA, No.4; Ra <0.4 μm
• Standards: ASTM A240, ASME SA240, AMS 5647
• Uses: Plates for vessels, sheets for cryo

7.2 Bar and Rod

• Diameter: 5-400 mm
• Length: Up to 12000 mm
• Finish: Drawn, ground
• Standards: ASTM A276, ASME SA479
• Uses: Fasteners, shafts

7.3 Custom Components

• Types: Heads, tubesheets
• Processes: Forged, machined
• Certs: NORSOK, API
• Uses: Nuclear custom

700 tons stock; 10 days.

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8. Applications of ASTM A240 Grade 304N

304N for strengthened corrosives:

• Nuclear: Fuel cladding; high yield low temp.
• Cryogenics: LNG tanks; tough at -196°C.
• Chemical: Piping; stress resistant.
• Aerospace: Structures; strength/weight.
• Pressure Vessels: Heads; N for load.

Vs 304, 304N for high stress.

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9. Price of ASTM A240 Grade 304N

November 2025: USD 3-5/kg FOB, hot-rolled $3.5/kg, cold $4.5/kg, per data. N adds 10% over 304; Ni ~$17k/ton. Gangsteel discounts bulk.

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10. FAQ for ASTM A240 Grade 304N Stainless Steel Plate

Q: What is the difference between ASTM A240 304N and 304?

A: ASTM A240 304N adds 0.10-0.16% nitrogen to the base 304 composition for interstitial strengthening, increasing yield strength from ≥205 MPa to ≥240 MPa while maintaining similar corrosion resistance (PREN 20-22) and weldability; 304N is preferred for high-stress applications like nuclear or cryogenic, where 304 suffices for general fabrication at lower cost.

Q: Is ASTM A240 304N suitable for cryogenic applications?

A: Yes; nitrogen enhancement provides excellent toughness at low temperatures, with Charpy impact >200J at -196°C and yield strength ≥400 MPa, making it ideal for LNG tanks or cryogenic piping where deformation resistance is critical without brittleness.

Q: What welding filler for ASTM A240 304N?

A: Use ER308LSi or E308L filler for GTAW/SMAW; low heat input (<1.5 kJ/mm) preserves nitrogen and avoids distortion; no preheat or post-weld anneal needed for most joints—the weld retains strength and corrosion resistance.

Q: Can ASTM A240 304N resist corrosion?

A: Moderately; good in atmospheric and dilute acids (<0.02 mm/year in 10% HNO3), with PREN 20-22 for mild pitting resistance; not for chlorides—use 316 grades; nitrogen subtly aids in some reducing environments.

Q: Is ASTM A240 304N magnetic?

A: Non-magnetic in annealed condition; cold work induces slight magnetism (5-15% martensite)—anneal at 1010°C to restore full austenite.

Q: What sizes for ASTM A240 304N plates?

A: Thickness 0.3-100 mm plates, 0.2-6 mm sheets; widths to 3000 mm, lengths to 12000 mm; custom with ±0.05 mm tolerance via laser/plasma.

Q: How does 304N compare to 304LN?

A: Both nitrogen-strengthened; 304LN has lower carbon (≤0.03% vs ≤0.08%) for better weld IGC resistance without annealing; 304N offers slightly higher ambient strength for general use, while 304LN excels in cryo welds.

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11. Why Choose Gangsteel?

Gangsteel’s 25+ years, 500+ experts, N-control tech. 120k tons/year, ABS/TUV certified. For 304N: 100% PMI, custom N, global ship. Explore ASTM A 240 Gr 316.

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12. Conclusion

ASTM A240 304N (S30451) is the N-strengthened austenitic stainless for high-stress, weldable duties in nuclear and cryo. With equivalents like EN 1.4315 and mechanics for endurance, at $3-5/kg in November 2025, it’s strengthened value. Contact Gangsteel for quotes or data on this or ASTM A 240 Gr 304H. Strengthen with us.