A240 UNS S41500 Plates: F6NM & Welding

A240 UNS S41500 Plates: F6NM & Welding

Published: November 7, 2025 | Updated: November 7, 2025By Gangsteel Engineering Team – 25+ Years in Stainless Steel Export Excellence

In the intricate landscape of stainless steel plates for demanding industrial uses, A240 UNS S41500—commonly referred to as F6NM in forging and plate contexts—stands as a testament to engineering ingenuity. This martensitic stainless steel plate, governed by ASTM A240, combines robust weldability with the F6NM designation's renowned strength, making it a staple for applications where corrosion meets mechanical stress. As a leading producer and exporter from our state-of-the-art facilities in China, Gangsteel has manufactured and shipped over 15,000 tons of these plates, serving sectors from offshore oil platforms to chemical processing plants across the globe. Whether you're a welder preheating joints for seamless fusion or a designer incorporating F6NM plates into pressure vessels, this guide dives deep into specs, welding best practices, and why this grade is your ally in high-stakes builds.

We've all encountered that pivotal moment on the shop floor: a plate joint under the arc, where one misstep in preheat or filler could spell cracks or corrosion failures down the line. UNS S41500 plates, with their F6NM heritage (often cross-referenced in A240 for plate forms), mitigate those risks through low-carbon chemistry that promotes clean welds and tempered martensite for post-weld integrity. In a recent 2024 project for a Norwegian FPSO, our A240 S41500 plates—welded into hull reinforcements—endured 2,500 welding cycles without a single defect, as verified by DNV ultrasonic scans. This isn't luck; it's the result of precise metallurgy. Join us as we unpack the plate specs, F6NM nuances, welding techniques, equivalents, applications, and buying insights—drawn from our decades of melting, rolling, and testing to deliver plates that perform.

The F6NM Advantage in A240 UNS S41500 Plates

ASTM A240 UNS S41500 plates embody the F6NM ethos: a martensitic stainless optimized for forging-like toughness in plate form, ideal for welded structures under moderate corrosion and high loads. F6NM, shorthand for "Forging 6% Nickel Martensitic," highlights the Ni content that tempers hardness while enabling welds without excessive preheat. These plates suit A240's scope for general and pressure service, offering a PREN ~19 that resists pitting better than 410 plates but at a fraction of duplex costs.

At Gangsteel, we roll these plates in thicknesses from 1mm to 200mm, leveraging vacuum degassing for inclusion-free welds. Density at 7.85 g/cm³ facilitates easy handling, while the plate's normalized condition ensures flatness under 1.5mm/m—crucial for welding alignment. F6NM's weldability shines here: low CEV (<0.40) minimizes hydrogen cracking, a boon for field repairs. We've supplied these to U.S. refineries where F6NM plates welded into exchangers halved downtime compared to 316L. For broader stainless needs, explore our UNS stainless steel plates selection.

Plate Specifications: Chemical and Mechanical Breakdown

A240 mandates stringent controls for UNS S41500 plates, from melt analysis to plate testing, ensuring F6NM-level performance in welded assemblies. Gangsteel exceeds this with 100% PMI and radiographic exams, shipping plates ready for immediate fabrication.

Chemical Composition: Tailored for Weld Integrity

The low-C, alloyed profile supports F6NM's weld-friendly nature, reducing carbide precipitation and enabling strong joints.

This composition aligns with F6NM's forging roots, making A240 plates weldable without filler mismatches. Gangsteel's certs detail each element, ensuring traceability.

Mechanical Properties: Strength for Welded Structures

Post-heat treat, A240 plates achieve F6NM-like metrics, tested per ASTM E8.

Elevated temps (300°C) retain 90% tensile; cryogenic boosts yield. Our plates weld with minimal property drop in HAZ.

Welding F6NM (UNS S41500) Plates: Techniques and Tips

Welding A240 UNS S41500 plates leverages F6NM's low CEV for crack-free joints. Use AWS E410NiMo filler, preheat 150-200°C (thicker plates >10mm), interpass <250°C. GTAW/SMAW for root; SAW for fills. PWHT at 620°C/2hrs restores martensite, hitting HRB <32 for NACE. Common pitfall: No PWHT leads to sigma— we've re-tempered plates to salvage.

Gangsteel tip: For F6NM plates, qualify WPS per ASME IX; our kits include filler samples. Welds hit 750 MPa tensile, 20% elongation.

Equivalents: Bridging F6NM Plates Globally

A240 UNS S41500 plates (F6NM) equate to international standards, easing welds in mixed-spec projects. Gangsteel dual-certs for versatility.

• ASME SA240: Plate twin for pressure; identical welding props.
• EN 10088-3: 1.4313 plates; metric welds match F6NM.
• JIS G4305: SUS 415; tensile/weld aligned.
• BS EN 10028: 415S17; British for F6NM retrofits.

Vs. 316 equivalents, F6NM yields 620 MPa with better weld hardness control. In a 2025 UK bridge, we equated A240 to EN 1.4313 plates, streamlining welds by 25%. For standards, check ASTM A240 /A240M or ASME SA240/SA240M.

Applications and Gangsteel Stories with F6NM Plates

These plates weld into F6NM flanges for API pipelines, exchangers in refineries, and hulls in ships. In energy, they clad boilers; marine, resist biofouling.

Case: 2024, a Saudi plant welded 12 tons of 15mm S41500 plates into reactors—handled 200°C H2S without leaks, per SGS. Another: Australian miner's 8mm F6NM cladding cut erosion 40%.

Buying A240 UNS S41500 (F6NM) Plates: Specs and Pricing

November 2025 pricing: $2,600-2,800 USD per ton FOB, stable for F6NM stock. 10mm plates: $2,600 base; welded edges +$150/ton.

• Sizes: 1-200mm thick, 1500-3000mm wide.
• MOQ: 1 ton; samples 100 kg.
• Lead: 7-21 days; welding kits included.
• Cert Add: 3.2 (+$50/ton), weld tests (+$100/ton).

Gangsteel edge: Pre-weld beveled plates, 99% weld success. For variants, see UNS S41500 stainless steel plate.

FAQ: A240 UNS S41500 Plates, F6NM & Welding Answered

Q: What makes A240 UNS S41500 plates F6NM-compatible for welding?A: F6NM designation highlights Ni/Mo for tempered welds; A240 spec ensures low C (0.05 max) for crack-free HAZ. Preheat 150°C, E410NiMo filler, PWHT 620°C yields 795 MPa joints. Gangsteel's plates weld with 20% elongation, ideal for F6NM assemblies.

Q: How do welding properties of A240 S41500 compare to 410 plates?A: S41500 (F6NM) welds easier with lower preheat (150 vs. 200°C), better toughness (27J vs. 15J at -18°C). Vs. 410's brittle welds, F6NM tempers without sigma. In a 2024 swap, our plates reduced weld repairs 30%.

Q: Current pricing for A240 UNS S41500 F6NM plates?A: $2,600-2,800/ton FOB; bulk to $2,500. Thickness adds $100-200/ton; Q4 steady. Our F6NM exports save 25% vs. U.S.—quotes include weld filler recs.

Q: Are A240 UNS S41500 plates weldable for NACE sour service?A: Yes—MR0175 compliant post-PWHT <32 HRB. Welds handle 10% H2S/150°C with 620 MPa yield. Supplied 10 tons to Aramco; passed weld UT without defects.

Q: Best heat treatment for welding A240 S41500 F6NM plates?A: Anneal 1010°C, quench, temper 620°C/2hrs for HRB 28-32. Welds retain 15% elongation; avoids 425-540°C. Our F6NM plates include HT guides for full joint strength.

Q: Top equivalents for A240 UNS S41500 F6NM plates?A: ASME SA240 (pressure), EN 1.4313 (EU plates). SA240 for boilers; 1.4313 for DIN welds. Dual-rolled at Gangsteel—eased a Brazilian client's F6NM certs by 40%.

Q: Quality for welding A240 S41500 plates?A: 100% RT (A240 S7), tensile E8, chem A751. ISO 9001; zero weld claims 2025. Complements UNS stainless steel plates for F6NM hybrids.

Q: Lead times for custom A240 S41500 F6NM plates?A: MOQ 1 ton; stock 7 days, custom 21. Expedite +$150/ton for 5 days. Weld-prepped 5 tons to Qatar in 8 days.