Precision-Ground Tungsten Rod
- High purity W ≥ 99.95% with density 19.3 g/cm³
- High surface finish: Ra 0.1–0.4μm (standard), Ra 0.05–0.1μm (high-precision), Ra ≤ 0.01μm (ultra-polished)
- Tight diameter tolerances: ±0.01mm (standard), ±0.005mm (high-precision), ±0.002mm (ultra-precision)
- Excellent straightness: ≤0.05mm/m (standard), ≤0.02mm/m (high-precision)
- Highest melting point among all metals — 3,410–3,422°C
- Centerless ground finish for precise diameter control
- Diameter range: 0.5–100.0mm, length up to 2,000mm
Description Of Precision-Ground Tungsten Rod
Precision-Ground Tungsten Rod, also known as ground tungsten bar, centerless ground tungsten rod, or polished tungsten rod, is a high-purity tungsten product manufactured through precision grinding and polishing processes to achieve exceptional surface finish and tight dimensional tolerances. Unlike as-sintered (black) or alkali-washed tungsten rods, ground tungsten rods undergo centerless grinding to remove all surface coatings, oxides, and processing lubricants, achieving precise diameter control and a smooth, clean surface.
The manufacturing process begins with high-purity tungsten (purity ≥99.95%) in the form of sintered or hot-rolled rods. These are then processed through precision CNC cylindrical grinding using diamond or CBN grinding wheels, with progressive grit sizes from coarse (#180–#400) to fine (#600–#1200). The grinding process is carefully controlled with feed rates of 0.005–0.02mm per pass to prevent edge chipping due to tungsten's inherent brittleness, and specialized cooling oils are used to prevent thermal stress cracking. For applications requiring mirror-like surfaces, additional mechanical polishing with diamond polishing paste (0.5–3μm) or electrolytic polishing (EP) can achieve surface roughness as low as Ra < 0.01μm.
Precision-ground tungsten rods inherit all the exceptional physical properties of tungsten. With a melting point of approximately 3,410–3,422°C — the highest among all metals — they can withstand extreme temperatures without softening or deformation. The material offers a density of 19.3 g/cm³, excellent thermal and electrical conductivity, a low coefficient of thermal expansion, and extremely low vapor pressure at elevated temperatures.
Key Manufacturing Process Of Precision-Ground Tungsten Rod
Raw Material Selection: High-purity tungsten (≥99.95%) rods in sintered or hot-rolled condition, with diameters ranging from 1mm to 100mm and lengths up to 1,000mm.
Precision Grinding: CNC cylindrical grinding machines equipped with diamond or CBN grinding wheels. Progressive grinding from coarse grit (#180–#400) to fine grit (#600–#1,200). Feed rate controlled at 0.005–0.02mm per pass to prevent edge chipping. Specialized cooling oil applied to prevent thermal stress cracking.
Ultra-Precision Polishing (Optional): Mechanical polishing with diamond paste (0.5–3μm) and non-woven polishing wheels achieves Ra ≤ 0.05μm. Electrolytic polishing (EP) using NaOH or KOH electrolyte at 5–20V achieves Ra < 0.01μm for ultra-smooth surfaces.
Inspection and Packaging: Laser diameter measurement (±0.002mm accuracy), roundness measurement (≤0.005mm), white light interferometer for surface roughness (Ra), and electron microscopy for micro-crack detection. Vacuum or inert gas anti-oxidation packaging.
Applications Of Precision-Ground Tungsten Rod
Semiconductor and Electronics Industry: Precision-ground tungsten rods are essential components in semiconductor manufacturing. They are used as probe cards for wafer testing, requiring surface roughness Ra < 0.05μm. They also serve as sputtering target support shafts, where high straightness (≤0.01mm/m) ensures coating uniformity. Additional applications include ion implantation parts, printer needles, lead wires, and support wires.
Medical Devices and Healthcare: Tungsten's high density and precision-ground surfaces make it ideal for radiation therapy collimators and multi-leaf collimators (MLC), where surface finish directly affects radiation focusing accuracy. Gamma knife core components also benefit from high-density, high-polish tungsten to reduce scatter radiation.
High-Temperature Furnace and Industrial Heating: Precision-ground tungsten rods are widely used as heating elements, support pillars, feeders, and fasteners in high-temperature vacuum furnaces, sapphire crystal growth furnaces, and single crystal furnaces. They withstand temperatures exceeding 2,000°C and maintain dimensional stability under extreme thermal conditions.
TIG Welding Electrodes: Ground tungsten rods serve as the raw material for manufacturing high-quality TIG (GTAW) welding electrodes, providing precise diameter control essential for consistent arc performance.
Aerospace and Defense: Precision-ground tungsten rods are used in kinetic energy penetrators (Φ5–20mm), where precision grinding improves ballistic consistency. They are also used in rocket engine components and high-temperature structural parts.
Rare Earth and Glass Industries: Tungsten rods serve as electrodes in rare earth metal smelting and glass melting furnaces, where their corrosion resistance and high-temperature stability ensure reliable performance.
Scientific Research and Synchrotron Radiation: Ultra-high straightness tungsten rods are used for X-ray guidance in synchrotron radiation beamlines.
Specifications Of Precision-Ground Tungsten Rod