RAYCHIN LIMITED

Tantalum Hex Cap Screws – Design & Configurations

Critical Applications of Tantalum Hex Cap Screws

International Standards & Global Designations – Tantalum Hex Cap Screws

RAYCHIN LIMITED manufactures tantalum hex cap screws from electron-beam melted or vacuum-arc melted material conforming to the most widely used national and international specifications. All material is traceable to the mill.

Chemical Composition (Weight %) – Tantalum Grades

Our tantalum hex cap screws are produced from electron-beam melted (EB) or vacuum-arc remelted (VAR) material conforming to the limits of applicable ASTM specifications [citation:3].

Commercially Pure Tantalum – UNS R05200

Tantalum 2.5% Tungsten – UNS R05252

Metallurgical note: Tantalum is a refractory metal with a body-centered cubic (BCC) crystal structure [citation:4]. It exhibits exceptional corrosion resistance due to the formation of a stable, adherent oxide layer (Ta₂O₅) that protects the base metal from chemical attack [citation:2]. This oxide layer is self-healing in oxidizing environments and provides immunity to virtually all acids and chemicals except hydrofluoric acid, hot concentrated alkalis, and fuming sulfuric acid (oleum) [citation:2]. Tantalum's high melting point (2996°C) makes it suitable for high-temperature applications in vacuum or inert atmospheres, though it may embrittle when exposed to oxygen above 300°C [citation:2]. The addition of 2.5% tungsten provides solid solution strengthening, increasing tensile and yield strength while maintaining excellent corrosion resistance [citation:7]. Tantalum is fully biocompatible, non-toxic, and radio-opaque, making it ideal for medical implant applications [citation:4].

Complete Mechanical & Physical Properties – Tantalum (MPa / ksi)

Tantalum hex cap screws are supplied in annealed condition per applicable ASTM specifications. Strain-hardened (cold worked) conditions available upon request. Data represent typical values based on industry standards.

Mechanical Properties – Tantalum (Annealed Condition)

Physical Properties – Tantalum

High-Temperature Mechanical Properties – Tantalum

Note: High-temperature testing in vacuum or inert atmosphere. Tantalum may embrittle in oxygen above 300°C [citation:2].

High‑Temperature Performance of Tantalum Hex Cap Screws

Tantalum is a refractory metal with exceptional high-temperature strength and stability in vacuum or inert atmospheres. The material maintains useful mechanical properties up to 2000°C (3632°F) in non-oxidizing environments, making it suitable for extreme temperature applications in vacuum furnaces, rocket engines, and aerospace propulsion systems [citation:2]. Tantalum's melting point of 2996°C (5425°F) is among the highest of all metals, exceeded only by tungsten and rhenium [citation:2]. The recrystallization temperature of tantalum is approximately 1200-1400°C, depending on purity and prior cold work [citation:3]. In oxidizing atmospheres, tantalum forms a protective oxide layer (Ta₂O₅) at moderate temperatures but may embrittle above 300°C due to oxygen diffusion [citation:2]. Therefore, tantalum hex cap screws are typically specified for high-temperature applications in vacuum, inert gas, or reducing atmospheres. Ta-2.5W alloy offers improved high-temperature strength compared to pure tantalum while maintaining similar oxidation behavior [citation:7].

Elevated Temperature Capabilities

Exceptional Corrosion Resistance of Tantalum Hex Cap Screws

Tantalum is renowned for its outstanding corrosion resistance, often described as similar to glass but with the mechanical properties of a metal [citation:2]. The material forms a stable, adherent, and self-healing oxide layer (Ta₂O₅) that provides protection against virtually all acids and chemicals except hydrofluoric acid, hot concentrated alkalis, and fuming sulfuric acid (oleum) [citation:2]. Tantalum exhibits zero or near-zero corrosion rates in most aggressive media, making it the material of choice for critical chemical processing applications where other materials fail [citation:1].

Corrosion Resistance to Common Media

The following list represents media to which tantalum exhibits nil or negligible corrosion (rates <0.05 mm/year) at temperatures up to at least 150°C (302°F) [citation:2]:

• Acetic acid
• Acetic anhydride
• Acetone
• Alcohols
• Aluminum chloride
• Aluminum sulfate
• Ammonium chloride
• Ammonium nitrate
• Ammonium phosphate
• Ammonium sulfate
• Aqua regia
• Barium chloride
• Benzoic acid
• Body fluids
• Boric acid
• Bromine (dry, <300°C)
• Butyric acid
• Calcium chloride
• Calcium hydroxide
• Carbolic acid
• Carbon dioxide
• Chloric acid
• Chlorinated brine
• Chlorine (dry, <250°C)
• Chlorine (wet, <350°C)
• Chloroacetic acid
• Chromic acid
• Citric acid
• Copper salts
• Fatty acids
• Ferric chloride
• Ferric sulfate
• Food stuffs
• Formaldehyde
• Formic acid
• Glycerine
• Hydrobromic acid
• Hydrocarbons
• Hydrochloric acid
• Hydrogen bromide (<400°C)
• Hydrogen chloride (<350°C)
• Hydrogen peroxide
• Hydrogen sulfide
• Lactic acid
• Magnesium chloride
• Magnesium sulfate
• Maleic acid
• Mercuric chloride
• Methyl alcohol
• Milk
• Mineral oils
• Mixed acids (sulfuric-nitric)
• Nickel salts
• Nitric acid
• Nitric acid (fuming)
• Nitric oxides
• Nitrogen (<300°C)
• Nitrous acid
• Organic acids
• Oxalic acid
• Oxygen (<300°C)
• Petroleum products
• Phenol
• Phosphoric acid (<4ppm F, <180°C)
• Pickling acids (except HNO3-HF)
• Potassium bromide
• Potassium chloride
• Potassium dichromate
• Potassium nitrate
• Potassium permanganate
• Potassium sulfate
• Propionic acid
• Refrigerants
• Sea water
• Silver nitrate
• Sodium acetate
• Sodium bisulfate (solution)
• Sodium bromide
• Sodium chlorate
• Sodium chloride
• Sodium cyanide
• Sodium dichromate
• Sodium hypochlorite
• Sodium nitrate
• Sodium nitrite
• Sodium phosphate
• Sodium silicate
• Sodium sulfate
• Sodium sulfide
• Sodium sulfite
• Sodium thiosulfate
• Stearic acid
• Succinic acid
• Sugar
• Sulfamic acid
• Sulfur (<500°C)
• Sulfur dioxide
• Sulfuric acid (<175°C)
• Sulfurous acid
• Tannic acid
• Tartaric acid
• Zinc chloride
• Zinc sulfate

Media to Avoid with Tantalum Fasteners

• Hydrofluoric acid (HF) – any concentration, any temperature [citation:2]
• Hot concentrated alkalis – sodium hydroxide (NaOH), potassium hydroxide (KOH) above 50°C [citation:2]
• Fuming sulfuric acid (oleum) – rapid attack at elevated temperatures [citation:2]
• Ammonium hydroxide – limited resistance
• Fluoride salts – may cause attack
• Hydrogen >300°C – may cause embrittlement
• Oxygen >300°C – may cause embrittlement [citation:2]

Manufacturing Standards – Tantalum Hex Cap Screws

All tantalum hex cap screws are manufactured and tested to meet the following standards:

We offer surface finishes: plain (as-machined), chemically cleaned, passivated, or electropolished for medical applications. Controlled annealing processes per ASTM specifications ensure consistent mechanical properties. Specialized CNC heading and thread rolling for accurate hex head geometry with proper washer facing. Class 2A/3A/6g thread fit. 100% inspection available including dimensional inspection, thread verification, and non-destructive examination. Full traceability and material test reports (MTR) with mill certifications available. AS9100 and ISO 9001:2015 certified quality management. ISO 13485 certified for medical applications with cleanroom packaging available [citation:1]. Build-to-print specials to customer specifications are available.