RAYCHIN LIMITED

Molybdenum Threaded Rods – Design & Configurations

Critical Applications of Molybdenum Threaded Rods

International Standards & Global Designations – Molybdenum Threaded Rods

RAYCHIN LIMITED manufactures molybdenum threaded rods from vacuum arc melted (VAR) or powder metallurgy (PM) material conforming to the most widely used national and international specifications. All material is traceable to the mill.

Chemical Composition (Weight %) – Molybdenum Alloys for Threaded Rods

Our molybdenum threaded rods are produced from vacuum arc melted (VAR) or powder metallurgy (PM) material conforming to ASTM B386/B387 and industry standards.

Pure Molybdenum (Grade 360 / 361) – Mo ≥99.95%

TZM Alloy (Grade 363 / 364) – Mo-0.5Ti-0.08Zr-0.02C

MoLa Alloy (Mo with Lanthanum Oxide)

Metallurgical note: Molybdenum is a refractory metal with a body-centered cubic (BCC) crystal structure. Pure molybdenum threaded rods are typically supplied in stress-relieved condition (recrystallization temperature ~1100°C) or soft/annealed condition. TZM alloy offers significantly higher recrystallization temperature (~1400°C) and improved creep strength through carbide dispersion strengthening. MoLa (lanthanated molybdenum) maintains ductility after high-temperature exposure due to oxide dispersion pinning grain boundaries. All molybdenum threaded rods should be handled with care due to limited ductility at room temperature, becoming more ductile above ductile-to-brittle transition temperature (DBTT).

Complete Mechanical & Physical Properties – Molybdenum Threaded Rods (MPa / ksi)

Molybdenum threaded rods are supplied in various conditions (hard/stress relieved, soft/annealed) per ASTM B387. Data represent typical values based on industry standards.

Mechanical Properties – Pure Molybdenum Threaded Rods

Mechanical Properties – TZM Alloy Threaded Rods

Physical Properties – Molybdenum (vs Stainless Steel SUS304)

High‑Temperature Performance of Molybdenum Threaded Rods

Molybdenum and its alloys are renowned for exceptional high-temperature strength and stability. Pure molybdenum maintains useful mechanical properties up to 1700°C (3090°F) in vacuum or reducing atmospheres, with TZM extending capability further through carbide strengthening. However, molybdenum oxidizes rapidly above 600°C in air, forming volatile MoO₃, limiting use to vacuum, inert gas, or reducing environments unless protected by coatings. At 980°C, molybdenum's creep strength (~17.5 kg/mm²) exceeds that of conventional heat-resistant alloys.

Elevated Temperature Capabilities

Molybdenum alloys are capable of long-time operation at temperatures of 1200-1300°C under low loads. For applications requiring protection against oxidation in air above 600°C, protective coatings such as MoSi₂, Al₂O₃, Y₂O₃, or Cr-Ni double layer deposits may be applied. Molybdenum is considered a main structural material for nuclear thermionic converters due to its low vapor pressure in vacuum.

Corrosion Resistance of Molybdenum Threaded Rods

Molybdenum exhibits excellent resistance to many corrosive media, particularly in reducing environments and in the absence of oxidizing agents. Its stability in various chemical environments makes it suitable for chemical processing equipment and research applications.

• Acid Resistance: Excellent resistance to hydrochloric acid (HCl), sulfuric acid (H₂SO₄) up to 60% concentration at moderate temperatures, and phosphoric acid (H₃PO₄). Resists most non-oxidizing mineral acids. Rapid attack in nitric acid (HNO₃) and other oxidizing acids. The beneficial action of Mo against pitting corrosion in neutral chloride solutions is attributed to its presence as MoO₄²⁻ in the passive film.
• Alkalis: Stable in alkaline solutions (sodium hydroxide, ammonia), resisting corrosion effectively.
• Liquid Metals: Excellent resistance to liquid lithium, sodium, potassium, and bismuth, making it valuable in nuclear coolant systems. Resists molten aluminum and zinc.
• Halogens: Resistant to fluorine, chlorine, and bromine at moderate temperatures; forms halides at higher temperatures.
• Oxidation: Forms volatile MoO₃ above 490-600°C in air; requires protective atmosphere or coating for high-temperature air service.
• Hydrogen: Excellent resistance to hydrogen attack even at high temperatures (unlike steel).
• Sulfur Compounds: Good resistance to sulfur, hydrogen sulfide, and sulfur dioxide.
• Glass Corrosion: Outstanding resistance to molten glass, widely used in glass melting electrodes and stirrers.
• Halide Salts: Resistant to corrosion and pitting attack by chlorides.
• Biocompatibility: Recent studies indicate molybdenum shows progressively advantageous long-term corrosion behavior in simulated body fluids with the smallest corrosion rate and most uniform mode compared to Mg, Zn, and Fe, suggesting potential as a new type of bio-metal.
• Neutron Irradiation: Excellent resistance to radiation damage, retaining mechanical properties under neutron flux.

Manufacturing Standards – Molybdenum Threaded Rods

All molybdenum threaded rods are manufactured and tested to meet the following standards:

We offer surface finishes: black (as-machined), chemical cleaned, ground, polished, and passivated. Special coatings (MoSi₂, Al₂O₃, Y₂O₃, Cr-Ni double layer) available for oxidation protection. Full traceability and destructive/non‑destructive testing available (UT, PMI, MPI). ISO 9001, AS9100D, ISO 13485 certified with cleanroom packaging available for semiconductor and medical applications.