RAYCHIN LIMITED

Zirconium Shoulder Bolts – Design & Configurations

Critical Applications of Zirconium Shoulder Bolts

International Standards & Global Designations – Zirconium Shoulder Bolts

RAYCHIN LIMITED manufactures zirconium shoulder bolts from vacuum arc remelted (VAR) or electron beam melted material conforming to the most widely used national and international specifications. All material is traceable to the mill with complete certifications.

Chemical Composition (Weight %) – Zirconium Alloys

Our zirconium shoulder bolts are produced from vacuum arc remelted (VAR) or electron beam melted material conforming to the limits of applicable ASTM B493 and B550 standards.

Zirconium 702 (UNS R60702) – Commercially Pure

Zirconium 705 (UNS R60705) – Zr-2.5%Nb Alloy

Metallurgical note: Zirconium is a refractory metal with a hexagonal close-packed crystal structure at room temperature. It exhibits exceptional corrosion resistance due to the formation of a stable, adherent, and self-healing oxide layer (ZrO₂) that provides protection in the most aggressive acidic environments. Zirconium is virtually immune to attack by hydrochloric acid at all concentrations up to boiling, outperforming all other engineering metals. In sulfuric acid, zirconium is resistant to concentrations up to 70% at temperatures well above boiling. It also exhibits excellent resistance to nitric acid, phosphoric acid, and most organic acids. Zirconium has the lowest thermal neutron absorption cross-section of all common structural metals (0.18 barns), making it the material of choice for nuclear reactor core components. The addition of 2-3% niobium in Zr 705 provides solid solution strengthening, increasing tensile strength by approximately 50% while maintaining excellent corrosion resistance.

Complete Mechanical & Physical Properties – Zirconium Alloys (MPa / ksi)

Zirconium shoulder bolts are supplied in annealed condition per applicable ASTM specifications. Data represent typical values based on ASTM B493 and B550 standards.

Mechanical Properties – Zirconium Alloys (Annealed Condition)

Physical Properties – Zirconium Alloys

High-Temperature Mechanical Properties – Zr 705

Maximum continuous service temperature in corrosive environments: 400°C (752°F). Zirconium begins to oxidize rapidly above 500°C in air.

Exceptional Corrosion Resistance of Zirconium Shoulder Bolts

Zirconium is renowned for its outstanding corrosion resistance, often outperforming all other engineering metals in aggressive acidic environments. The material forms a stable, adherent, and self-healing oxide layer (ZrO₂) that provides protection against a wide range of corrosive media. Zirconium exhibits virtually zero corrosion rate in hydrochloric acid at all concentrations up to boiling – a performance unmatched by any other metal except tantalum. In sulfuric acid, zirconium is resistant to concentrations up to 70% at temperatures well above boiling, significantly outperforming nickel alloys and stainless steels.

Corrosion Resistance to Common Media

• Hydrochloric Acid: Zirconium shoulder bolts exhibit corrosion rates less than 5 mpy (0.13 mm/year) in 37% HCl at 130°C (266°F). This performance is unmatched by any other engineering metal with the exception of tantalum. In 10% HCl at boiling point, Hastelloy C276 experiences 288 mpy corrosion while zirconium exhibits nil corrosion even when aerated.
• Sulfuric Acid: Excellent resistance to sulfuric acid up to 70% concentration at temperatures well above boiling. Outperforms Alloy 20 and C-276 in sulfuric acid service.
• Nitric Acid: Zirconium can be used in all concentrations of nitric acid up to 90% and temperatures up to 200°C – comparable to tantalum and superior to most stainless steels.
• Organic Acids: Excellent resistance to acetic acid, formic acid, oxalic acid, and other organic acids at all concentrations up to boiling.
• Alkali Resistance: Good resistance to dilute alkalis, but zirconium is attacked by strong alkalis (NaOH >40%) and is not recommended for concentrated caustic service.
• Limitations: Zirconium is rapidly attacked by hydrofluoric acid, ferric chloride, cupric chloride, and other oxidizing halides. Even small amounts of fluoride ions (as low as 5 ppm) can cause accelerated corrosion. Process control of upstream contaminants is critical for maintaining corrosion resistance.
• Oxidation Behavior: Zirconium begins to oxidize rapidly above 500°C in air. High-temperature service requires vacuum, inert atmosphere, or protective coatings.
• Galvanic Corrosion: Zirconium is noble and can be safely coupled with most metals, but may accelerate corrosion of less noble materials. Avoid coupling with graphite or noble metals in conductive electrolytes.

Manufacturing Standards – Zirconium Shoulder Bolts

All zirconium shoulder bolts are manufactured and tested to meet the following standards:

We offer surface finishes: plain (as-machined), passivated, or electropolished. Controlled annealing processes per ASTM specifications ensure consistent mechanical properties. Shoulder bolts are manufactured with precision-ground shoulders to tight diametrical tolerances (h8/h9 standard, custom tolerances available down to ±0.0005"). Specialized CNC turning, thread rolling, and centerless grinding ensure accurate geometry per ASME, ISO, and DIN standards. Class 2A/3A/6g thread fit. 100% inspection available including dimensional inspection, hardness testing, and non-destructive examination. Full traceability and material test reports (MTR) with mill certifications available per EN 10204 3.1. AS9100 and ISO 9001:2015 certified quality management. ISO 13485 certified for medical applications with cleanroom packaging available. Build-to-print specials to customer specifications are available.