Project Description
431 (UNS S43100 / 1.4057 / X17CrNi16-2 / SUS431 / 20Х17Н2) is a nickel-bearing martensitic stainless steel bar engineered for high-strength service in corrosive environments. With roughly 16% chromium and 2% nickel, it delivers the best corrosion resistance among standard martensitic grades while retaining heat-treatable strength up to 1,100 MPa. SHUNFU METAL supplies this grade as a core product line for the global oil and gas sector, leveraging ISO 9001 and API Q1 certified manufacturing to ensure batch-to-batch consistency across all heat treatment conditions.
431 Stainless Steel — Martensitic Grade Overview
431 stainless steel belongs to the martensitic family — alloys that gain strength through quenching and tempering rather than cold working. Unlike common 410 or 420 grades, the deliberate nickel addition (1.25–2.50%) in 431 improves hardenability and corrosion resistance significantly, making it suitable for sections that must withstand both mechanical load and mildly aggressive media. SHUNFU METAL produces this grade via AOD refining followed by precisely controlled forging or hot-rolling, achieving clean microstructure and minimal inclusion levels. Every heat is spectrometrically verified before release, with full traceability maintained under the ISO 9001 quality framework.
A key advantage of 431 over austenitic grades is its hardenability: in the quenched-and-tempered condition (+QT800 or +QT900 per EN 10088-3), tensile strength reaches 800–1,050 MPa, roughly double that of annealed 304. This makes it the material of choice where austenitic stainless would require excessive section thickness to carry the same load. SHUNFU METAL routinely delivers 431 bars in both annealed (+A) and hardened-and-tempered (+QT) conditions, cut to customer-specified lengths and protected with anti-corrosion wrapping for transit.
Equivalent Grades of 431 Across International Standards
| Standard | Designation |
|---|---|
| ASTM A276 / A479 | 431 (UNS S43100) |
| AMS 5628 | 431 |
| EN 10088-3 | X17CrNi16-2 (1.4057) |
| DIN | X17CrNi16-2 |
| JIS G4303 / G4304 | SUS431 |
| GOST 5632 | 20Х17Н2, 14Х17Н2 |
| BS 970 | 431S29 |
| GB/T 1220 | 17Cr16Ni2 (S43120) |
| ISO 15510 | X17CrNi16-2 (4057-431-00-X) |
| AIR 9160/C (Aerospace) | Z15CN17-03 |
Oil & Gas Industry Applications
431 stainless steel bars serve across upstream, midstream, and downstream oil and gas operations where high tensile strength must coexist with resistance to produced water, H2S-bearing fluids, and chlorides at moderate concentrations. SHUNFU METAL supplies 431 bars to OEM workshops and service centers that machine finished components for drilling systems, wellhead assemblies, refining equipment, and subsea hardware. ISO 9001 and API Q1 certified production guarantees dimensional accuracy and metallurgical integrity for these safety-critical parts.
Pump Shafts
Centrifugal and multi-stage pump shafts in crude transfer and injection service.
Valve Stems & Trim
Gate, globe, and choke valve stems; seat rings and discs in wellhead valves.
Compressor Shafts
Rotating shafts for reciprocating and centrifugal gas compressors.
Drill Collars & Subs
Non-magnetic variants and crossover subs for bottom-hole assemblies.
High-Strength Fasteners
Stud bolts, nuts, and tensioning bolts for flanged connections and pressure vessels.
Couplings & Connectors
Shaft couplings, pup joints, and adapter spools for pump and compressor trains.
Actuator Components
Drive shafts and gear racks for pneumatic and hydraulic valve actuators.
Downhole Tool Bodies
Mandrels, fishing tools, and packer bodies for wireline and coiled-tubing operations.
Heat Exchanger Parts
Tie rods, baffle supports, and tube-sheet bolting for shell-and-tube exchangers.
Supply Range of 431 Stainless Steel Bar
SHUNFU METAL manufactures and stocks 431 stainless steel in bar form across a broad dimensional window. Production routes include hot-rolling, hot-forging, peeling, and precision centerless grinding. Each bar undergoes ultrasonic testing, dimensional inspection, and hardness verification prior to dispatch. The ISO 9001 and API Q1 quality management system ensures full material traceability from heat number to final delivery documentation.
| Product Form | Diameter / Section Range | Length | Surface Condition |
|---|---|---|---|
| Hot-Rolled Round Bar | ⌀5 mm – ⌀300 mm | 3,000 – 6,000 mm | Black / Peeled / Ground |
| Forged Round Bar | ⌀80 mm – ⌀1,000 mm | 2,000 – 8,000 mm | Rough Machined / Peeled |
| Hot-Rolled Flat Bar | 3–100 mm thick × 20–610 mm wide | 3,000 – 6,000 mm | Black / Pickled |
| Forged Flat / Block | 50–500 mm thick × 200–1,500 mm wide | 1,000 – 5,000 mm | Rough Machined |
| Bright Bar (Cold-Drawn) | ⌀3 mm – ⌀80 mm | 3,000 / 6,000 mm | Bright / H8–H11 Tolerance |
Non-standard diameters, stepped shafts, hollow bars, and custom-cut pieces are available on inquiry. SHUNFU METAL also supplies 431 in forged ring, disc, and open-die forging configurations for clients requiring near-net shapes prior to final machining.
Chemical Composition of 431 (EN 10088-3 / ASTM A276)
The chemistry of 431 stainless steel is specified under two widely used norms. SHUNFU METAL controls each heat within the tighter overlap of both standards through AOD refining and ladle metallurgy, verified by optical emission spectrometry on every cast. API Q1 procedures mandate retained samples and independent rechecks for critical orders.
| Element | EN 10088-3 X17CrNi16-2 | ASTM A276 UNS S43100 |
|---|---|---|
| Carbon (C) | 0.12 – 0.22 | ≤ 0.20 |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 |
| Manganese (Mn) | ≤ 1.50 | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.040 | ≤ 0.040 |
| Sulfur (S) | ≤ 0.015 (bar) | ≤ 0.030 |
| Chromium (Cr) | 15.0 – 17.0 | 15.0 – 17.0 |
| Nickel (Ni) | 1.50 – 2.50 | 1.25 – 2.50 |
All values in weight percent (wt%). Cast analysis per respective standard. SHUNFU METAL product analysis typically meets the tighter EN limits even when certified to ASTM.
Mechanical Properties — Quenched & Tempered Conditions
431 achieves its service strength through austenitizing at 950–1,050°C followed by oil or air quenching and tempering at 600–800°C. Two standard delivery conditions (+QT800 and +QT900 per EN 10088-3) cover the majority of oilfield requirements. SHUNFU METAL’s in-house heat treatment furnaces, calibrated under ISO 9001 and API Q1 protocols, ensure uniform through-section properties. Temperatures between 425°C and 600°C are avoided in practice due to known temper embrittlement in this grade.
| Condition | Diameter (mm) | Tensile Strength (MPa) | Yield Strength Rp0.2 (MPa) | Elongation A5 (%) | Impact KV2 (J) | Hardness (HB) |
|---|---|---|---|---|---|---|
| +A (Annealed) | All | ≤ 950 | ≤ 295 HB | Soft condition for machining; not for final service | ||
| +QT800 | ≤ 60 | 800 – 950 | ≥ 600 | ≥ 14 | ≥ 25 | – |
| 60 < d ≤ 160 | 800 – 950 | ≥ 600 | ≥ 12 | ≥ 16 | – | |
| Bright bar ≤ 10 | 850 – 1,100 | ≥ 750 | ≥ 7 | – | – | |
| +QT900 | ≤ 60 | 900 – 1,050 | ≥ 700 | ≥ 12 | ≥ 16 | – |
| 60 < d ≤ 160 | 900 – 1,050 | ≥ 700 | ≥ 10 | ≥ 15 | – | |
Data per EN 10088-3. Mechanicals measured on longitudinal specimens at room temperature. Additional heat treatment conditions and custom properties available through SHUNFU METAL’s technical team.