Essential Fused Quartz & Silica Products for Daegu Importers
Directly drawn, cut, flame-worked, and laser-machined in Donghai. Manufactured to KS (Korean Industrial Standards) and ASTM specifications with batch chemical certification.
Milky (Opaque) Quartz Tubes: Material Science & Engineering Thermodynamics
In thermal processing environments, standard transparent quartz transmits infrared radiation freely, which can cause excessive heat loss and uneven thermal zones in high-temperature industrial kilns. Milky quartz tubes (often designated as opaque fused silica tubes or translucent quartz tubing) solve this thermodynamic challenge through controlled micro-bubble dispersion, functioning simultaneously as a refractory structural chamber and an exceptional infrared thermal barrier.
Manufactured in Donghai County—China’s foremost quartz manufacturing center—our opaque milky quartz tubing is produced by precisely melting high-purity natural silica sand (SiO2 ≥ 99.98%) in specialized electric resistance or arc-fusion furnaces. During thermal fusion, microscopic gaseous inclusions (ranging from 5 to 50 μm in diameter) are uniformly suspended within the amorphous SiO2 glass matrix. These microscopic voids act as diffuse scattering centers for radiant energy.
When electromagnetic wavelengths between 1.0 μm and 4.5 μm (the primary infrared radiation spectrum generated by resistance heating coils) encounter these micro-bubbles, they undergo multiple internal refractions and diffuse back-scattering. This achieves an apparent infrared thermal emissivity exceeding 0.90, reducing radial thermal radiation loss by up to 38% compared to standard clear quartz tubes. For Daegu equipment manufacturers building horizontal diffusion systems, cathode calcination furnaces, or rapid thermal processing (RTP) equipment, this micro-structural characteristic directly translates into lower kilowatt-hour power consumption and precise isothermal chamber conditions.
Thermal & Viscosity Thresholds: Preventing High-Temperature Sagging
A frequent issue encountered by engineers in South Korea’s high-temperature processing sectors is devitrification (crystallization of amorphous silica into cristobalite) and tube sagging under sustained operational temperatures exceeding 1,050°C. Our milky quartz tubing utilizes natural Donghai quartz sand refined through 13 purification stages to achieve total conventional metallic impurities ≤ 20 ppm. Hydroxyl ([OH−]) content is rigorously controlled below 30 ppm through thermal vacuum degassing.
By maintaining low alkali metal concentrations (sodium [Na] ≤ 0.7 ppm, potassium [K] ≤ 0.6 ppm, and lithium [Li] ≤ 0.3 ppm), the nucleation rate of cristobalite is substantially arrested. The softening point is maintained at 1,683°C, with an annealing point of 1,215°C and a maximum continuous operating ceiling of 1,150°C (intermittent peak threshold: 1,300°C). Even when subjected to rapid thermal cycling—such as cycling from 1,100°C directly into 20°C chilled water—the near-zero linear thermal expansion coefficient (α = 5.5 × 10-7 /°C) ensures zero catastrophic fracturing.
| Material Property | Milky (Opaque) Quartz Tube | Clear Fused Quartz (JSC-1 Grade) | High-Alumina Ceramic (99.5% Al₂O₃) |
|---|---|---|---|
| Silicon Dioxide (SiO₂) Purity | ≥ 99.98% | ≥ 99.995% | N/A (Alumina based) |
| Apparent Density (g/cm³) | 2.06 – 2.18 | 2.20 – 2.22 | 3.85 – 3.92 |
| Coeff. of Thermal Expansion (CTE) | 5.4 × 10⁻⁷ /°C | 5.5 × 10⁻⁷ /°C | 8.0 × 10⁻⁶ /°C |
| Thermal Shock Resistance | ΔT > 1,100°C (Water Quench) | ΔT > 1,100°C (Water Quench) | ΔT ≈ 200°C – 250°C |
| Infrared (IR) Optical Behavior | Diffuse Scattering • Low Direct Transmittance | High Transmittance (>90% from 0.2–3.5 μm) | Opaque / High Thermal Absorption |
| Devitrification Point (Cristobalite) | > 1,180°C | > 1,220°C | No phase transition up to 1,600°C |
| Thermal Conductivity (at 800°C) | 1.38 W/(m·K) [Superior Insulator] | 2.15 W/(m·K) | 18.5 W/(m·K) |
Localized Application Scenarios Across Daegu & Gyeongbuk
Daegu Metropolitan City has transitioned into a major hub for secondary EV battery components, robotics, and advanced semiconductor packaging. Our milky quartz tubing is custom-engineered to meet the operational demands of facilities across Seongseo, Dalseong, and Gumi.
EV Battery Cathode Sintering
Opaque quartz heating muffle tubes and roller-hearth furnace liners designed for CAM/pCAM calcination. Resistant to corrosive lithium hydroxide [LiOH] vapors and rapid thermal expansion cycles.
Diffusion & Oxidation Furnaces
Large-bore milky quartz outer tubes (OD 250mm–520mm) functioning as outer thermal jackets around clear inner process tubes, establishing uniform thermal zones for silicon and SiC wafer batches.
Rapid Thermal Processing (RTP)
Opaque thermal reflector sleeves and halogen heating lamp housings. Employs micro-bubble diffuse scattering to eliminate localized hot spots and thermal stress during rapid silicon annealing.
Industrial Heating & Fiber Drying
Infrared emitter protection tubes and thermowell sheaths for Daegu’s high-performance technical textile, carbon-fiber composite curing, and precision metallurgy drying tunnels.
Market Trends Driving Daegu’s Shift to Chinese Quartz Suppliers
Korean procurement leaders in Daegu are realigning their critical component supply chains away from high-cost domestic intermediaries and Japanese suppliers in favor of direct Chinese factory partnerships.
1. Secondary Battery & Semiconductor Tooling Surge
With major battery material expansions (L&F, EcoPro BM) throughout the Daegu-Pohang belt, demand for high-durability thermal tubes has climbed 28% annually. Traditional domestic quartz processors in South Korea operate on prolonged lead times (8–14 weeks). Direct procurement from Donghai reduces production turnarounds to under 15 working days, expediting production schedules for local kiln builders.
2. Cost Rationalization Without Purity Compromise
Historical reliance on German and Japanese quartz fabricators created substantial cost overheads for Daegu OEMs competing globally. Donghai-based automated continuous drawing lines reduce tooling costs by 35% to 45% while matching chemical purity standards (≥99.99% SiO2, metallic impurities ≤20 ppm), supporting competitive bidding on export machinery.
3. Direct Lianyungang-to-Busan/Pohang Logistics
Situated in Lianyungang port, our manufacturing base offers streamlined maritime freight to Busan and Pohang ports with sailing transits of only 48 to 72 hours. Coupled with standardized shockproof wooden export crating, Daegu buyers experience rapid customs clearance, reliable delivery timelines, and lower transport risk compared to inland suppliers.
Why Daegu Industrial Buyers Partner with Our Donghai Works
Combining natural high-purity mineral reserves with provincial-level technical innovation to deliver reliable fused quartz solutions.
Integrated Donghai Source
Operating a 33,000 m² production complex with RMB 10M in fixed assets. Direct access to high-purity natural silica sand ensures strict raw-material impurity control (≤20 ppm total metals).
Large-Bore Continuous Drawing
Pioneered 320mm high-purity tubes under the Jiangsu Provincial S&T Support Project and industrialized 520mm large-diameter tubes for multi-wafer semiconductor and advanced calcination furnaces.
Precision Drawing & Flame-Working
In-house CNC glass cutting, slot milling, optical fire polishing, and specialized glass-blowing lathes for custom welded flanges, ground taper joints, flared ends, and closed-dome thermowells.
Export Crate Packaging
Every milky quartz tube is cushioned with custom pearl cotton sleeves, suspension brackets, and shock-resistant, fumigation-free plywood cases tailored for maritime, air, and express transport.
Frequently Asked Questions by Daegu Purchasing Managers
Technical, commercial, and logistics guidance for seamless cross-border importing from China into South Korea.
1. What outer diameter (OD) and wall thickness ranges are available for milky quartz tubes?
2. How does the thermal insulation of milky quartz compare to clear quartz in furnace applications?
3. Can your factory machine custom flanges, slots, or closed ends according to Korean CAD drawings?
4. How do you protect long, fragile quartz tubes against breakage during shipment to Daegu?
5. What quality certifications and inspection reports accompany each shipment to Korea?
6. What is the typical lead time from drawing sign-off to delivery at our Daegu warehouse?
7. What payment methods and trade terms are supported for Korean industrial entities?
8. What steps prevent milky quartz from devitrifying prematurely when running at 1,100°C?
Accelerate Your Daegu High-Temperature Tooling Project
Contact our bilingual technical sales team today. Provide your requested OD, ID, length, operating temperature profile, and drawing files to receive an itemized DDP Daegu quotation and engineering review within 2 hours.