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Molybdenum Hex Cap Screws

Molybdenum hex cap screws possesses a very high melting point of 2620°C, a low coefficient of thermal expansion and a high level of thermal conductivity. Because molybdenum hex cap screws have the ability to withstand extremely high temperatures without changing shape, expanding or softening significantly, they are ideal for high strength / high temperature applications that are shielded from oxygen. Exposing molybdenum hex cap screws to oxygen above 600°C will cause them to readily oxidize.

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Molybdenum hex cap screws find their way into high temperature vacuum furnaces, glass production, military and space applications where oxygen is not present.

Extreme high temperature stability & strength
Maintains strength at elevated temperatures
Low distortion at high temperature
Molybdenum must be used in vacuum or inert gas at high temperatures

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RAYCHIN LIMITED

Name: Molybdenum Hex Cap Screws
SKU: 0

Molybdenum Hex Cap Screws · Hex Head Cap Screws · Finished Hex · Inch & Metric · Pure Mo / TZM / MoLa

Molybdenum Hex Cap Screws: Ultra-High Purity Refractory Metal Hex Head Cap Screws for Extreme Temperature Environments

Pure Mo (≥99.95%) | TZM (Mo-Ti-Zr-C) | MoLa (Mo-La₂O₃) | ASTM B386 / B387 | ISO 4017 / DIN 933

RAYCHIN LIMITED is a leading manufacturer of Molybdenum Hex Cap Screws – precision hex head fasteners produced from refractory molybdenum and its alloys, delivering exceptional high-temperature strength, thermal stability, and corrosion resistance in extreme environments. With a melting point of 2623°C (4743°F) and the ability to withstand temperatures up to 1700°C in vacuum or reducing atmospheres, molybdenum hex cap screws retain structural integrity where conventional materials fail. These screws feature a standard hex head design with flat washer facing, providing superior clamping pressure for critical high-temperature bolting applications. Our comprehensive product line includes molybdenum hex head cap screws, fully threaded hex cap screws, and partially threaded hex head bolts – all manufactured to the highest precision standards. Available grades include Pure Molybdenum (≥99.95%), TZM alloy (Mo-0.5Ti-0.08Zr-0.02C), and Molybdenum Lanthanum (MoLa) with enhanced recrystallization temperature. Our portfolio includes all standard and custom configurations manufactured to NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN and KS standards, including ASTM B386/B387, ISO 4017, DIN 933, and ASME B18.2.1. Whether you require molybdenum hex cap screws for high-temperature vacuum furnaces, semiconductor sputtering equipment, sapphire crystal growth systems, or aerospace propulsion components, RAYCHIN delivers precision, quality, and full traceability. All mechanical properties are presented in MPa and ksi (kilopound per square inch).

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Molybdenum Hex Cap Screws – Design & Configurations

Hex Head Cap Screws (Finished Hex)

Molybdenum hex head cap screws are precision fasteners featuring a flat washer facing under the bolt head, providing a larger bearing surface area and superior clamping pressure for critical high-temperature applications. Manufactured to ASME B18.2.1 (inch series), ISO 4017 / DIN 933 (fully threaded), and ISO 4014 / DIN 931 (partially threaded). Available in diameters from M1.6 to M48 (#0 to 2"). Precision forged heads and rolled threads for maximum strength at extreme temperatures.

Fully Threaded Hex Cap Screws

Molybdenum fully threaded hex cap screws (ISO 4017 / DIN 933) feature threads running the entire length of the screw shank. This design provides maximum thread engagement and is ideal for applications requiring precise length adjustment or through-hole fastening. Available in all standard metric sizes from M3 to M48 and inch sizes from #0 to 2". Precision rolled threads ensure superior fatigue life and consistent thread fit.

Thread Specifications

Molybdenum hex cap screws available with metric coarse threads (M1.6-M48) per ISO 4017/DIN 933, Unified Coarse (UNC), Unified Fine (UNF), and UNJF-3A (aerospace). Thread classes 2A, 3A, 6g. Standard metric pitches: M1.6 (0.35mm), M2 (0.4mm), M2.5 (0.45mm), M3 (0.5mm), M4 (0.7mm), M5 (0.8mm), M6 (1.0mm), M8 (1.25mm), M10 (1.5mm), M12 (1.75mm), M14 (2.0mm), M16 (2.0mm), M18 (2.5mm), M20 (2.5mm), M24 (3.0mm), M30 (3.5mm), M36 (4.0mm), M42 (4.5mm), M48 (5.0mm).

Alloy Grades: TZM & MoLa

TZM alloy hex cap screws (Mo-0.5Ti-0.08Zr-0.02C) offer higher recrystallization temperature (~1400°C), improved strength, and creep resistance compared to pure Mo. MoLa alloy hex cap screws (Mo doped with La₂O₃) exhibit enhanced ductility and high-temperature stability. Both alloys available across all diameters for applications exceeding 1400°C in vacuum or reducing atmospheres. These dispersion-strengthened grades maintain mechanical properties where pure molybdenum would recrystallize and weaken.

Aerospace & Military Standards

Our molybdenum hex cap screws meet applicable sections of NAS1802 (hex bolts), NASM 8830, MS16995, and AN42-AN73. Full compliance with ASTM B386 (plate/sheet/foil) and ASTM B387 (rod/bar/wire) for material and mechanical properties. Silver plating per AMS 2410 available for anti-galling. Cleanroom packaging available for semiconductor and aerospace applications.

Custom & Non-Standard Hex Cap Screws

Need special head configurations, proprietary drives, non‑standard lengths, or unique thread forms? RAYCHIN engineers design and produce custom molybdenum hex cap screws to your exact specifications – any grade (pure Mo, TZM, MoLa), any condition (stress relieved, recrystallized), with full material traceability. Prototype to production volumes supported. Available with cleanroom wash and packaging for sensitive applications.

Critical Applications of Molybdenum Hex Cap Screws

High-Temperature Vacuum Furnaces

Molybdenum hex cap screws are essential in vacuum furnace construction, including hot zones, heating element supports, heat shields, and hearth assemblies. They maintain structural integrity at temperatures exceeding 1700°C (3090°F) in vacuum or inert gas environments where superalloys fail. Used in sintering furnaces, brazing furnaces, and annealing furnaces. The hex head design allows for secure wrench tightening in high-temperature furnace assemblies.

Semiconductor & Sputtering Equipment

Molybdenum hex cap screws in semiconductor manufacturing equipment, including sputtering targets, PVD chambers, ion implanters, and wafer processing systems. Molybdenum's low coefficient of thermal expansion (5.1 × 10⁻⁶ /K), high thermal conductivity (142 W/m·K), and non-contaminating properties (no outgassing) make it ideal for ultra-high-vacuum (UHV) environments. Cleanroom packaging available for contamination control.

Sapphire Crystal Growth & Glass Melting

Molybdenum hex cap screws used in sapphire crystal growth furnaces (Kyropoulos, Czochralski) and glass melting electrodes. Molybdenum withstands molten glass corrosion and extreme temperatures required for LED sapphire substrate production. Screws secure crucible assemblies, heat shields, and electrode holders in aggressive molten environments. Outstanding resistance to molten glass makes them the preferred choice in the glass industry.

Aerospace & Defense

Molybdenum hex cap screws in rocket engine components, nozzle assemblies, re-entry vehicle heat shields, and supersonic aircraft skin elements. Molybdenum alloys maintain strength at extreme temperatures where other metals would soften or melt. Used in thrust vector control systems and high-temperature structural joints. The hex head design allows for secure wrench tightening in critical aerospace assemblies.

Nuclear Engineering

Molybdenum hex cap screws in nuclear reactors, particle accelerators, and experimental fusion devices. Molybdenum exhibits excellent resistance to radiation damage and retains mechanical properties under neutron irradiation. Used for fuel cladding supports, control rod mechanisms, and plasma-facing component fasteners. Resists corrosion by liquid metal coolants (lithium, sodium, potassium).

FPD Production & General Industrial

Molybdenum hex cap screws in flat panel display (FPD) production equipment and general industrial machines requiring heat resistance and vacuum compatibility. Their ability to withstand extreme thermal cycling without deformation makes them ideal for precision manufacturing equipment operating at elevated temperatures.

International Standards & Global Designations – Molybdenum Hex Cap Screws

RAYCHIN LIMITED manufactures molybdenum hex cap screws 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.

Designation	Standard / Specification	Description
Pure Molybdenum	Mo ≥99.9% – ≥99.95%	Unalloyed molybdenum, highest purity available; excellent thermal conductivity, low vapor pressure; melting point 2623°C
ASTM B386 / B386M-25	Molybdenum and Molybdenum Alloy Plate, Sheet, Strip, Foil, and Ribbon	Covers grades 360 (vacuum arc melted pure Mo), 361 (powder metallurgy pure Mo), 363 (TZM-VAM), 364 (TZM-PM)
ASTM B387 / B387M	Molybdenum and Molybdenum Alloy Bar, Rod, and Wire	Primary material specification for molybdenum hex cap screw stock; covers same grades as ASTM B386
TZM Alloy	Mo-0.5Ti-0.08Zr-0.02C	Molybdenum alloy with titanium, zirconium, carbon for enhanced strength and recrystallization temperature (~1400°C)
MoLa (Mo-La₂O₃)	Mo with 0.3-0.6% Lanthanum Oxide	Dispersion-strengthened molybdenum with improved ductility and high-temperature stability
ISO 4017:2011	Hexagon head cap screws – metric series (fully threaded)	Dimensional standard for molybdenum hex cap screws, M1.6 to M64; equivalent to DIN 933
ISO 4014 / DIN 931	Hexagon head bolts – metric series (partially threaded)	Dimensional standard for partially threaded molybdenum hex head bolts
DIN 933	Hexagon head cap screws – metric series (fully threaded)	German standard for fully threaded hex cap screws, interchangeable with ISO 4017
ASME B18.2.1	Square and hex bolts (inch series)	Dimensional standards for inch-series hex cap screws
JIS B 1180	Hexagon head bolts – metric series	Japanese Industrial Standard for hex cap screws

ASTM B386 ASTM B387 Pure Mo 99.95% TZM MoLa ISO 4017 ISO 4014 DIN 931 DIN 933 ASME B18.2.1

Chemical Composition (Weight %) – Molybdenum Alloys for Hex Cap Screws

Our molybdenum hex cap screws 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%

Element	Min %	Max %	Typical
Molybdenum (Mo)	99.9	Balance	99.95
Iron (Fe)	—	0.010	0.004
Nickel (Ni)	—	0.005	0.002
Silicon (Si)	—	0.010	0.0013
Carbon (C)	—	0.030	0.0028
Oxygen (O)	—	0.0070	0.005
Nitrogen (N)	—	0.002	0.002
Aluminum (Al)	—	0.002	0.0005
Calcium (Ca)	—	0.002	<0.001
Magnesium (Mg)	—	0.002	<0.0005

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

Element	Min %	Max %	Typical
Molybdenum (Mo)	Balance	Balance	~99.0
Titanium (Ti)	0.40	0.55	0.50
Zirconium (Zr)	0.06	0.12	0.08
Carbon (C)	0.01	0.04	0.02
Iron (Fe)	—	0.010	0.005
Nickel (Ni)	—	0.005	0.002
Silicon (Si)	—	0.010	0.005
Oxygen (O)	—	0.0030	0.002
Nitrogen (N)	—	0.002	0.001

MoLa Alloy (Mo with Lanthanum Oxide)

Element	Min %	Max %	Typical
Molybdenum (Mo)	Balance	Balance	~99.5
Lanthanum Oxide (La₂O₃)	0.3	0.6	0.4
Other impurities	—	0.10	<0.05

Metallurgical note: Molybdenum is a refractory metal with a body-centered cubic (BCC) crystal structure. Pure molybdenum hex cap screws are typically supplied in stress-relieved condition (recrystallization temperature ~1100°C). 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 hex cap screws 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 Hex Cap Screws (MPa / ksi)

Molybdenum hex cap screws are supplied in various conditions (hard/stress relieved, soft/annealed) per ASTM B387. Data represent typical values based on industry standards and are compared with SUS304 stainless steel for reference.

Mechanical Properties – Pure Molybdenum vs. SUS304

Property	Pure Molybdenum	SUS304 Stainless Steel	Notes
Tensile Strength (N/mm² or MPa)	515	520 or more	Comparable at room temperature
0.2% Proof Load (MPa)	380	205 or more	Molybdenum ~85% stronger
Elongation (%)	15	40 or more	Stainless steel more ductile
Tensile Breaking Load (M6 screw)	11,000 N	—	For reference
Tensile Breaking Load (M5 screw)	7,810 N	—	For reference

Mechanical Properties – TZM Alloy Hex Cap Screws

Condition	Tensile Strength (MPa)	Tensile Strength (ksi)	Yield Strength 0.2% (MPa)	Yield Strength 0.2% (ksi)	Elongation (%)	Hardness
Stress Relieved	860-1035	125-150	690-860	100-125	8-15	300 HV
Recrystallized	620-760	90-110	550-620	80-90	15-25	230 HV

Physical Properties – Pure Molybdenum vs. SUS304

Property	Pure Molybdenum	SUS304 Stainless Steel	Notes
Specific Gravity (g/cm³)	10.2	7.93	Molybdenum ~28% denser
Melting Point (°C)	2620-2623	1400-1450	Molybdenum much higher
Longitudinal Elastic Modulus (GPa)	327	193	Molybdenum ~70% stiffer
Electrical Resistivity (µΩ·m)	0.056-0.058	0.7	Molybdenum 12x more conductive
Thermal Conductivity (W/(m·K))	142	17	Molybdenum ~8x higher
Linear Expansion Coefficient (K⁻¹)	5.1-5.2 × 10⁻⁶	17.3 × 10⁻⁶	Molybdenum much lower CTE
Poisson's Ratio	0.293	0.29
Atomic Number	42	—
Atomic Mass (g/mol)	95.94	—

High‑Temperature Performance of Molybdenum Hex Cap Screws

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. Molybdenum has a melting point of 2623°C (4743°F), making it ideal for the highest temperature environments. However, molybdenum oxidizes rapidly above 600°C in air, forming volatile MoO₃, limiting use to vacuum, inert gas, or reducing atmospheres unless protected by coatings.

Elevated Temperature Capabilities

Property	Pure Molybdenum	TZM Alloy	MoLa Alloy
Melting Point (°C)	2620-2623	~2600	2623
Max Service Temp (vacuum/inert)	1700°C (3090°F)	1400-1500°C (2550-2730°F)	1700°C (3090°F)
Recrystallization Temp	1100-1200°C (2010-2190°F)	1400°C (2550°F)	1300-1500°C
Oxidation Onset in Air	600°C (1110°F) – sublimation begins in oxidizing atmosphere
Boiling Point (°C)	4612-4639	—	—

Molybdenum hex cap screws support use with vacuum equipment in high-temperature environments. In oxidizing atmospheres above 600°C, sublimation will occur; use is therefore recommended only in vacuum, inert gas, or reducing atmospheres. For air applications, protective coatings (MoSi₂, Al₂O₃, Y₂O₃) may be applied.

Corrosion Resistance of Molybdenum Hex Cap Screws

Molybdenum exhibits excellent resistance to many corrosive media, particularly in reducing environments and in the absence of oxidizing agents. However, rapid oxidation occurs in air above 600°C. Its stability in various chemical environments makes it suitable for specialized applications.

Oxidation Resistance: Forms volatile MoO₃ above 600°C in air; requires protective atmosphere or coating for high-temperature air service.
Acid Resistance: Excellent resistance to hydrochloric acid (HCl) at moderate temperatures. High solubility in concentrated sulphuric acid and nitric acid. Resists most non-oxidizing mineral acids.
Liquid Metals: Excellent resistance to liquid lithium, sodium, potassium, and bismuth, making it valuable in nuclear coolant systems.
Hydrogen: Excellent resistance to hydrogen attack even at high temperatures.
Glass Corrosion: Outstanding resistance to molten glass, widely used in glass melting electrodes and stirrers.
Environmental Stability: Molybdenum occurs naturally in fresh water and sea water as MoO₄²⁻ in oxidised environments.

Manufacturing Standards – Molybdenum Hex Cap Screws

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

ASTM B386ASTM B387ISO 4017ISO 4014DIN 931DIN 933ASME B18.2.1JIS B 1180NAS1802MS16995EN 10204 3.1/3.2

We offer surface finishes: black (as-machined), chemical cleaned, ground, polished, and passivated. Special coatings (MoSi₂, Al₂O₃, Y₂O₃) available for oxidation protection. Cleanroom wash and cleanroom packaging available for semiconductor, medical, and aerospace applications – batch cleanroom packing provided for orders containing multiple items of the same size. Full traceability and destructive/non‑destructive testing available (UT, PMI, MPI). ISO 9001, AS9100D, ISO 13485 certified.

Why RAYCHIN LIMITED – The Molybdenum Hex Cap Screw Authority

Refractory metal expertise: Decades of experience with molybdenum, TZM, and MoLa alloys. We ensure precise processing: stress relieving, recrystallization annealing, and surface finishing per ASTM B386/B387 standards. In‑house PMI verifies chemistry of every heat. Our molybdenum hex cap screws achieve full traceability and certified properties.

Global certifications: ISO 9001, AS9100D, ISO 13485 (medical), PED, API Q1, NADCAP accredited processes. All hex cap screws supplied with EN 10204 3.1/3.2 certifications, material test reports, and NACE compliance when required. Cleanroom packaging certified for semiconductor and medical applications.

Precision heading & thread rolling: CNC cold heading and precision thread rolling ensure accurate hex head geometry and thread form per ASME, ISO, and DIN standards. Class 2A/3A/6g thread fit. 100% inspection available. Special tooling for molybdenum's unique machining characteristics (brittle behavior at room temperature).

Custom solutions: Special head configurations, proprietary drives, non‑standard lengths, and tailored packaging. In-house metallurgical laboratory and failure analysis capabilities. Prototype to production volumes supported. Cleanroom wash and packaging available for sensitive applications.

Contact the molybdenum hex cap screw experts

Request a quotation for molybdenum hex cap screws, hex head cap screws – any standard (ASME B18.2.1, ISO 4017, DIN 933, JIS B 1180) – any grade (Pure Mo, TZM, MoLa) – any condition (stress relieved, recrystallized), any quantity. Global delivery. Mechanical data in MPa/ksi available for all products.

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