Sanicro 28 Alloy | N08028 | 1.4563 | Super Austenitic | Fushun Metal

Sanicro 28 / N08028 / 1.4563 — Introduction

Sanicro 28, designated UNS N08028 and EN 1.4563 (also known as Alloy 28, Incoloy alloy 28, or Nicrofer 3127 LC), is an ultra-low-carbon, high-chromium super austenitic stainless steel occupying the performance gap between conventional 904L/254 SMO grades and full nickel-based corrosion alloys such as Inconel 625. With 26–28% chromium—one of the highest levels in any commercially available wrought austenitic grade—combined with 30–34% nickel, 3–4% molybdenum, and 0.6–1.4% copper, it delivers outstanding resistance to sulfuric acid, wet-process phosphoric acid, chloride pitting and crevice corrosion (PREN 32–35), and chloride stress corrosion cracking. Its iron-based matrix (Fe ~33–37%) provides significant cost advantages over pure nickel alloys while retaining near-immunity to Cl⁻-SCC, making it the most widely used high-alloy austenitic tubular material in sour gas well downhole service and phosphoric acid evaporation plants worldwide.

At Fushun Metal, Sanicro 28 is manufactured through a fully integrated triple-melt route under one roof. VIM primary melting under high vacuum ensures precise recovery of copper and ultra-low carbon content (≤0.020%), eliminating the risk of intergranular chromium carbide precipitation during welding or hot-forming. The VIM electrode passes to VAR, where controlled directional solidification yields chemically homogeneous, low-inclusion electrode stock with minimal micro-segregation—critical for the high chromium content. For the most demanding sour-service and phosphoric acid applications where sulfide-initiated pitting and fluoride-assisted crevice attack are the life-limiting mechanisms, we deploy PESR as the final stage, achieving deep desulfurization and oxide refinement through argon-shielded reactive slag chemistry.

Every heat is solution-annealed, quenched, and tested within Fushun Metal’s certified quality management system—ISO 9001 for manufacturing process control and AS9120B for aerospace distribution traceability. Full digital traceability links each production lot from melt heat number through remelt sequence, hot-working reduction ratio, and final annealing batch. Standard deliverables include intergranular corrosion testing per ASTM A262 Practice C, pitting corrosion testing per ASTM G48 Method A, ultrasonic inspection, chemical re-verification by optical emission and LECO combustion, and room-temperature tensile testing. Mill test certificates to EN 10204 3.1 or 3.2 accompany every shipment.

Equivalent Grades of Sanicro 28 Across International Standards

Sanicro 28 is codified under multiple national and international specification systems. The table below maps its designations and governing standards across major markets. Fushun Metal certifies to all listed specifications and can dual-certify heats where required.

Applications of Sanicro 28

Sanicro 28 fills the critical engineering gap where 904L and duplex stainless steels reach their corrosion limits but the cost of full nickel-based alloys such as C-276 or 625 cannot be justified. Its combination of ultra-high chromium for oxidizing-acid resistance, copper for reducing-acid passivation, and high nickel for chloride SCC immunity makes it the default specification for wet-process phosphoric acid plants and deep sour gas well production tubing and liners.

Sanicro 28 — Supply Range by Fushun Metal

Fushun Metal stocks and processes Sanicro 28 across all major mill forms from a single integrated facility. Our in-house 6000-ton hydraulic open-die press, 1800-ton precision radial forger (GFM), and multi-stand 850/550/350/250 rolling mills enable a broad dimensional envelope without outsourcing—ensuring uninterrupted lot traceability from melt to delivery under ISO 9001 and AS9120B. All material is supplied in the solution-annealed condition per ASTM B668 / B709 (typically 1070–1120°C, rapid water quench). Cold-worked high-strength tubulars for downhole sour-gas service are also available. Intergranular corrosion testing per ASTM A262 Practice C and pitting corrosion testing per ASTM G48 Method A are standard on every heat. Products are accompanied by mill test certificates to EN 10204 3.1 or 3.2. Welding consumable: ERNiCrMo-3 (Alloy 625 type) or ERNiCrMo-13 (Alloy 59 type) filler; matching ENiCrMo-3/ENiCrMo-13 electrodes.

Chemical Composition of Sanicro 28 — ASTM B668 / EN 10088-2

All heats produced by Fushun Metal are melted via VIM+VAR or VIM+PESR and verified against the composition limits below by optical emission spectrometry and LECO combustion analysis. Full chemical certificates are issued with every shipment under ISO 9001 and AS9120B quality management. The 26–28% chromium plateau is the highest available among commercial wrought super austenitic stainless steels and is the primary driver of the alloy’s exceptional oxidizing-acid and pitting resistance (PREN ≈ 32–35). The deliberate copper addition (0.6–1.4%) stabilizes the passive film in reducing-acid environments—particularly dilute to medium-concentration sulfuric acid—where chromium alone is insufficient.

Mechanical Properties of Sanicro 28 — Per Product Form

Sanicro 28 is a solid-solution-strengthened, fully austenitic alloy; all mechanical properties in the annealed condition are developed through solution annealing at 1070–1120°C followed by rapid water quenching. The alloy is not hardenable by precipitation heat treatment. Its high chromium content combined with the fully austenitic matrix provides a unique combination of strength, ductility, and corrosion resistance. For downhole sour-gas tubular applications, the alloy can be cold-worked to achieve minimum yield strengths of 110–140 ksi (760–965 MPa) while retaining adequate ductility and full NACE MR0175 / ISO 15156 compliance for H₂S service.

Fushun Metal performs all solution annealing in-house under calibrated furnace controls with rapid water-quench capability. The ultra-low carbon content (≤0.020%) eliminates the risk of sensitization during welding, and post-weld solution annealing is generally not required for corrosion resistance—though stress relief at 950–1000°C may be applied for cold-worked components. Welding parameters: ERNiCrMo-3 or ERNiCrMo-13 filler, heat input 0.5–1.5 kJ/mm, interpass temperature <100°C, argon-based shielding gas with backing purge. Post-weld pickling and passivation are recommended to restore full surface corrosion resistance.

Physical constants: Density 8.0 g/cm³; Melting range 1350–1410°C; Hardness ≤155 HB / 70–90 HRB (annealed condition); Modulus of elasticity 200 GPa at 20°C; Thermal conductivity 14.5 W/m·K at 20°C; Coefficient of thermal expansion ~15 μm/m·°C (20–100°C); PREN (Cr + 3.3Mo + 16N) 32–35. The alloy is non-magnetic due to its fully austenitic structure.