Rex 734 UGIPURE 4472 High Nitrogen Steel Round Bar, Rods & Bars

Product Description

Rex 734—also commercialized under trade names such as UGIPURE 4472—is a high-nitrogen, fully austenitic stainless steel specifically vacuum-arc remelted or electroslag remelted for high-purity medical implants, surgical instruments, and critical engineering components. It is designated under international standards as UNS S31675, ISO 5832-9, ASTM F1586, and DIN Werkstoff Nr. 1.4472 (X2CrNiMoN21-16-5-4).

Unlike standard austenitic stainless steels that rely primarily on carbon or nickel for strength, Rex 734 uses a deliberate high-nitrogen addition (0.25 to 0.50 percent) in solid solution. This nitrogen addition significantly enhances mechanical strength, fatigue endurance, and resistance to pitting and crevice corrosion without sacrificing ductility or biocompatibility.

Standards and Designations

• UNS: S31675

• DIN Werkstoff Nr.: 1.4472

• DIN En Name: X2CrNiMoN21-16-5-4

• Medical / Surgical Specifications: ASTM F1586, ISO 5832-9

• Trade Names: Rex 734, UGIPURE 4472, Chronifer M-1586

Chemical Composition Limits (Percent Weight)

The chemical matrix is characterized by low carbon, elevated chromium and molybdenum for pitting resistance, high manganese to increase nitrogen solubility, and niobium for grain refinement:

• Chromium: 19.50 to 22.00 percent

• Nickel: 9.00 to 11.00 percent

• Molybdenum: 2.00 to 3.00 percent

• Manganese: 2.00 to 4.25 percent

• Nitrogen: 0.25 to 0.50 percent

• Niobium: 0.25 to 0.80 percent

• Carbon: 0.030 percent maximum

• Silicon: 0.75 percent maximum

• Phosphorus: 0.025 percent maximum

• Sulfur: 0.010 percent maximum

• Copper: 0.25 percent maximum

• Iron: Balance

Physical and Thermal Properties

• Density: 7.88 grams per cubic centimeter (0.285 pounds per cubic inch)

• Elastic Modulus in Tension: 200 gigapascals

• Magnetic Permeability: Less than 1.005 (fully non-magnetic in all conditions, including heavy cold work)

• Pitting Resistance Equivalent Number (PREN): 33.0 to 38.0 (significantly higher than standard 316L stainless steel)

Mechanical Properties (ASTM F1586 / ISO 5832-9 Bar Standards)

Mechanical performance varies based on delivery condition, ranging from annealed stock to high-strength cold-worked bar forms used for bone screws and orthopaedic pins:

Solution Annealed Condition

• Tensile Strength: Minimum 740 megapascals (107 ksi)

• Yield Strength (0.2 Percent Offset): Minimum 430 megapascals (62 ksi)

• Elongation: Minimum 35 percent

• Hardness: 200 to 250 Brinell

Cold-Worked / High-Strength Condition

• Tensile Strength: Minimum 1000 megapascals (145 ksi)

• Yield Strength (0.2 Percent Offset): Minimum 750 megapascals (109 ksi)

• Elongation: Minimum 10 to 15 percent

• Hardness: 30 to 38 Rockwell C

Primary Applications

• Medical Implants: Orthopaedic trauma pins, bone plates, intramedullary nails, spinal fixation systems, and joint replacement components requiring superior fatigue strength.

• Surgical Tools: High-precision instruments requiring non-magnetic behavior and high corrosion resistance during sterilization cycles.

• Specialty Hardware: High-stress components operating in halide or marine environments where 316L exhibits localized pitting or crevice attack.