What is UNS S41500? SS Properties Explained

What is UNS S41500? SS Properties Explained

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

Stainless steel grades can feel like a maze, but UNS S41500 stands out as a versatile workhorse in the martensitic family, blending toughness, corrosion resistance, and ease of fabrication into one reliable alloy. As a leading producer and exporter based in China, Gangsteel has melted, forged, and shipped tens of thousands of tons of UNS S41500 material to industries worldwide—from subsea oil rigs battling saltwater corrosion to power plants enduring high-pressure steam. If you've ever wondered what makes this grade tick, or how its properties stack up for your next project, you're in the right place. We'll unpack exactly what UNS S41500 is, dive into its key stainless steel (SS) properties, and share real-world insights from our mill floors to help you decide if it's the fit for your needs.

Picture this: In a 2024 overhaul of a Gulf Coast refinery, our UNS S41500 forgings formed critical valve components that withstood 200°C sour gas flows without a hint of cracking or pitting—extending maintenance intervals by 40%, as per client audits. Often known as F6NM or AISI 415, this grade isn't flashy like super duplexes, but its balanced properties make it a go-to for engineers who need strength without overkill. Let's break it down step by step, from its origins to practical applications, all grounded in our hands-on experience producing this alloy to ASTM, ASME, and EN standards.

Defining UNS S41500: The Basics of This Martensitic SS

UNS S41500 is a Unified Numbering System designation for a low-carbon martensitic stainless steel, primarily used in forged or wrought forms for high-strength, moderately corrosion-resistant components. Developed as an improvement over basic martensitic grades like 410, it incorporates nickel and molybdenum to enhance toughness and pitting resistance, making it suitable for environments where standard carbon steels would fail prematurely. The "martensitic" label comes from its microstructure, which forms hard, needle-like crystals after heat treatment, giving it superior hardness and strength compared to austenitic SS like 304.

At its core, UNS S41500 is designed for applications requiring a balance of mechanical prowess and environmental endurance. It's not fully austenitic (soft and ductile) nor ferritic (magnetic and less tough)—instead, it's a soft martensitic type that can be hardened through quenching and tempering. This makes it ideal for parts that need to be machined soft then hardened for service. Gangsteel produces this grade in various forms, including bars, plates, and forgings, adhering to specs like ASTM A182 (for flanges), A240 (plates), A473 (forgings), and A479 (bars). Its UNS code ensures global traceability, but you'll often see it cross-referenced as EN 1.4313, AISI 415, or simply F6NM (Forged 6% Nickel Martensitic).

What sets it apart from other SS? Unlike 300-series austenitics that prioritize corrosion over strength, UNS S41500 flips the script: high tensile (up to 950 MPa in practice) with good resistance to mild acids, chlorides, and H2S—perfect for oil & gas or chemical processing. From our perspective, it's the "Goldilocks" grade: not too soft, not too brittle, just right for demanding yet cost-sensitive projects.

Chemical Composition: The Building Blocks of Its Properties

The magic of UNS S41500 lies in its carefully tuned chemistry, which minimizes carbon for weldability while alloying with chromium, nickel, and molybdenum for enhanced performance. This composition ensures the steel can be heat-treated to achieve desired properties without unwanted phases like delta ferrite or sigma that could compromise toughness.

Here's a breakdown of the typical chemical makeup (percentages by weight, based on heat analysis maxima unless ranged):

This formula results in a Carbon Equivalent (CE) typically under 0.40, which is key for weldability—more on that later. At Gangsteel, we melt UNS S41500 using advanced processes like AOD (Argon Oxygen Decarburization) to achieve ultra-low impurities, often beating spec maxima by 50% for P and S, enhancing properties like fatigue resistance in cyclic loads.

Mechanical Properties: Strength, Toughness, and Durability

UNS S41500's real appeal shines in its mechanical profile, which can be tailored through heat treatment to suit specific needs. In the annealed state, it's relatively soft for machining; quenched and tempered, it hardens for strength while retaining good ductility—a hallmark of martensitic SS.

Key mechanical properties (minimum values in quenched and tempered condition, per common specs like ASTM A182 or A479):

These properties hold up well in service: at elevated temps up to 425°C, tensile drops less than 10%; in cryogenic down to -196°C, yield increases while maintaining impact. Heat treatment is key—quench from 1010-1120°C, then temper at 565-760°C for 2 hours to fine-tune hardness and toughness. From our experience, tempering at the lower end (around 600°C) yields the best balance for NACE MR0175 sour service compliance, where hardness must stay under 22 HRC (converted from HRB).

Thermal properties add to its appeal: thermal conductivity around 25 W/m·K, specific heat 460 J/kg·K, and expansion coefficient 10.5 × 10^-6 /°C—stable for thermal cycling without warping.

Corrosion Resistance and Weldability: Practical SS Traits

UNS S41500 offers moderate corrosion resistance, better than carbon steels but not as robust as 300-series austenitics. Its 11.5-14% Cr forms a passive film effective against atmospheric rust, mild acids, and wet CO2, while Mo (0.5-1%) enhances pitting resistance in chlorides—PREN typically 18-20. It's particularly strong in H2S environments (NACE-approved), making it ideal for oil & gas.

Weldability is a standout: low C and CE (<0.40) allow welding with E410NiMo fillers, preheat 150-200°C for thick sections, and PWHT at 620°C to restore properties without sigma phase. From our welding trials, joints achieve 90% of base metal strength, with no reported cracking in over 100 client projects.

Machinability is fair—similar to 4140 alloy steel—using carbide tools at 80-120 SFM with coolant. Forging and hot working are straightforward at 1100-1180°C, finishing above 900°C to avoid strain hardening.

Applications: Where UNS S41500 SS Thrives

UNS S41500's properties make it versatile across industries requiring strength and moderate corrosion:

• Oil & Gas: Valves, pumps, and wellhead components in sour service; its hardness and toughness handle H2S without sulfide stress cracking.
• Petrochemical: Pressure vessels, heat exchangers, and reactors; withstands thermal cycling and mild acids.
• Power Generation: Turbine blades, shafts, and boiler parts; high yield for high-temp strength.
• Marine & Offshore: Propeller shafts and risers; resists seawater pitting.
• Mining & Heavy Equipment: Drill bits and crusher parts; abrasion resistance from tempered hardness.
• General Engineering: Bolts, fasteners, and structural components where SS is needed but 300-series is overkill.

Gangsteel has supplied this grade for a Brazilian ethanol plant's reactors, where its properties reduced erosion by 30%, or for U.S. fracking tools that doubled service life in abrasive muds. It's not for extreme corrosives (use duplex there), but excels in balanced demands.

Equivalents and Standards: Global Cross-References

UNS S41500 aligns with several equivalents, easing international sourcing:

• EN/DIN: 1.4313 (X3CrNiMo13-4) – Nearly identical chemistry and properties; common in Europe.
• AISI/SAE: 415 – Legacy U.S. name, matching in strength.
• AFNOR: Z6CND13-04 – French standard for similar toughness.
• JIS: SUSF415 – Japanese equivalent for forging apps.
• BS: 416S21 – British variant with comparable hardness.

Standards: ASTM A182 (forgings), A240 (plates), A473 (forgings), A479 (bars). For metric, see A240M. At Gangsteel, we offer dual-cert material to bridge specs, like UNS S41500 to EN 1.4313 for EU clients.

Explore our full range, including ASTM A240 /A240M plates or ASME SA240/SA240M for pressure vessel needs.

Buying Guide: Sourcing UNS S41500 from Gangsteel

Ready to source? Gangsteel makes it straightforward with mill-direct quality.

Step 1: Define Your Needs

Specify form (plate, bar, forging), standard (A182, A240), and condition (annealed, tempered). Need equivalents? We cross-reference free.

Step 2: Stock and Customization

We hold 100+ tons in stock, thicknesses 1-200mm, custom-cut or heat-treated. Density calcs and hardness mapping available.

Step 3: Pricing and Certifications

Current price: $2,600-2,800 USD per ton FOB Tianjin, depending on volume and form. Includes EN 10204 3.1/3.2 certs, UT/RT per A388, and third-party inspections (SGS/BV).

Step 4: Logistics and Support

Global delivery: 7-30 days sea/air, DDP to major ports. 24/7 support for property queries or equivalent swaps.

Why Gangsteel? Competitive pricing, zero-defect guarantees, and expertise in tailoring properties—saving clients 15-25% vs. Western suppliers. Quote today for your UNS S41500 project.

FAQ: UNS S41500 SS Properties Answered in Detail

Q: What exactly is UNS S41500 stainless steel?

A: UNS S41500 is a martensitic stainless steel grade known for its high strength, good toughness, and moderate corrosion resistance. It's low-carbon (0.05% max) with alloying elements like chromium (11.5-14%), nickel (3.5-5.5%), and molybdenum (0.5-1%) that allow it to be heat-treated for optimized properties. Often called F6NM or AISI 415, it's used in forged or wrought forms for components needing durability in mildly corrosive environments. At Gangsteel, we produce it to standards like ASTM A182 and A240, where its martensitic structure provides better hardness than austenitic grades like 304 while maintaining weldability.

Q: What are the key mechanical properties of UNS S41500?

A: In quenched and tempered condition, UNS S41500 boasts minimum tensile strength of 795 MPa, yield strength of 620 MPa, elongation of 15%, and hardness of 32 HRB max (or around 260 HB). It also offers excellent impact toughness, with Charpy V-notch values of at least 27 J at -18°C. These properties make it suitable for high-stress applications, and they can be adjusted via tempering—lower temperatures for higher hardness (up to HRC 32), higher for better ductility. From our testing, it retains over 90% strength at 300°C and shows minimal loss in cryogenic conditions, making it versatile for extreme environments.

Q: How does the chemical composition affect UNS S41500's properties?

A: The composition is designed for balance: low carbon prevents brittleness and improves weldability, chromium provides corrosion resistance through passivation, nickel enhances toughness by stabilizing the microstructure during heat treatment, and molybdenum boosts pitting resistance in chlorides. Impurities like phosphorus and sulfur are capped at 0.03% to maintain ductility and avoid cracking. This setup gives UNS S41500 a low Carbon Equivalent (under 0.4), reducing welding risks, and a PREN of 18-20 for moderate environmental protection. In our production, we often achieve even tighter controls, resulting in superior fatigue life and consistency.

Q: What are the corrosion resistance properties of UNS S41500?

A: UNS S41500 offers good resistance to atmospheric corrosion, mild acids, and wet CO2, thanks to its chromium content forming a stable oxide layer. It's particularly effective in H2S-containing environments (NACE MR0175 compliant when hardness is controlled), with better pitting resistance than 410 SS due to molybdenum. However, it's not suited for highly aggressive media like strong acids or high-chloride seawater without additional protection. In tests, it shows corrosion rates under 0.1 mm/year in mild conditions, and our clients in petrochemicals report extended service life in sour gas compared to carbon steels.

Q: How is UNS S41500 heat treated, and what properties does it affect?

A: Typical treatment involves austenitizing at 1010-1120°C, quenching in air or oil, and tempering at 565-760°C for 2 hours. This process transforms the structure to tempered martensite, adjusting hardness (from HRB 32 max annealed to HRC 25-32 tempered), strength, and toughness. Lower temper temps increase hardness and yield but reduce ductility; higher temps do the opposite. For NACE, temper to keep hardness below 22 HRC. In our mill, this yields consistent properties, with elongation often exceeding 18% and impact over 35 J at -46°C, enhancing its use in cold climates.

Q: What are common applications for UNS S41500 SS?

A: UNS S41500 is widely used in oil & gas for valves and wellheads (due to sour service resistance), petrochemicals for pressure vessels and reactors, power generation for turbine parts, marine for shafts and risers, and mining for wear-resistant components. Its properties suit environments needing strength (620 MPa yield) and moderate corrosion without the cost of duplex SS. Gangsteel has supplied it for Brazilian ethanol plants (reducing erosion 30%) and U.S. fracking tools (doubling life in abrasives), proving its versatility in balanced-demand scenarios.

Q: What are the equivalents of UNS S41500?

A: Common equivalents include EN 1.4313 (X3CrNiMo13-4) for Europe, AISI 415 for U.S. legacy, AFNOR Z6CND13-04 for France, JIS SUSF415 for Japan, and BS 416S21 for UK. These share similar chemistry and properties, allowing substitution in most cases—e.g., 1.4313 for CE-marked parts. Always check standards; Gangsteel offers dual-cert material to bridge gaps, like UNS S41500 to EN 1.4313 for EU exports.

Q: How does UNS S41500 compare to other SS grades?

A: Compared to austenitic 304 (better corrosion but lower strength at 205 MPa yield), UNS S41500 offers higher yield (620 MPa) but moderate corrosion. Vs. 410 martensitic (similar strength but poorer toughness and pitting resistance), it excels with added Ni/Mo. Duplex 2205 beats it in corrosion (PREN 35) but costs more and is harder to weld. UNS S41500 is the cost-effective choice for balanced needs; our tests show it outperforming 410 in impact by 30% while matching 304's machinability.