ARTICLE KB-MET-01
SUS304 vs SUS316 Metallurgy: Pitting Resistance & Beverage Longevity
Austenitic stainless steel is the foundation of high-performance insulated drinkware. However, the chemical formulation differences between standard SUS304 (18/8) and premium SUS316 (18/10) directly dictate product lifespan when exposed to aggressive acidic, chlorinated, or alkaline fluids.
| Steel Grade |
Chromium (Cr) |
Nickel (Ni) |
Molybdenum (Mo) |
Carbon (C max) |
PREN Value |
Recommended Drinkware Application |
| SUS304 (AISI 304) |
18.0 - 20.0% |
8.0 - 10.5% |
— |
0.08% |
18.0 - 20.0 |
Daily water bottles, standard 40oz tumblers, outer shells. |
| SUS316 (AISI 316) |
16.0 - 18.0% |
10.0 - 14.0% |
2.0 - 3.0% |
0.08% |
23.0 - 25.0 |
Kids bottles, coffee mugs, lemon/citrus tea vessels, sports nutrition. |
| Grade 1 Pure Ti |
<0.05% |
<0.05% |
— |
0.02% |
>45.0 (Bio-inert) |
Aerospace luxury drinkware, zero metal taste, permanent TiO₂ sterile layer. |
The Pitting Resistance Equivalent Number (PREN) Formula
PREN is calculated as PREN = 1 × %Cr + 3.3 × %Mo + 16 × %N. The addition of 2.5% Molybdenum in SUS316 increases pitting resistance by over 40% compared to SUS304. When citrus juice, carbonated cola, or hot saline soup sits inside a double-wall vessel for 12 hours, chloride ions attack the passive chromium oxide film. In SUS304, microscopic pitting can develop over months of repetitive use; in SUS316, the molybdenum atoms bond with chromium to reform an impenetrable self-healing barrier.
ARTICLE KB-THM-02
Thermodynamics of High Vacuum Brazing & Copper Radiation Shields
Heat transfers through three fundamental mechanisms: conduction, convection, and radiation. Understanding how UNIFAN double-wall engineering systematically eliminates all three modes is essential for evaluating thermal retention metrics.
Conduction: Nullified
By evacuating air in a continuous furnace down to 10⁻³ Pa, gas molecules between the inner and outer vessels are virtually eliminated, stopping molecular contact conduction.
Convection: Stopped
Without air molecules to circulate between the hot inner wall and cold outer wall, natural convection currents cannot form within the evacuated annular envelope.
Radiation: Reflected
Electromagnetic infrared radiation passes through vacuums. UNIFAN applies a 3μm electrolytic copper lining to the inner bottle's outer wall, reflecting 92% of IR waves back inward.
Furnace Brazing vs Cheap Mechanical Pinching:
Budget manufacturers use mechanical copper crimping with a tail pinch under coarse vacuum (10⁻¹ Pa). These crimps frequently develop micro-leaks after thermal shock or drops. UNIFAN utilizes tail-less continuous vacuum brazing at 1050°C using nickel-copper solder rings in a protective atmosphere, producing a permanent metallurgical fusion that preserves vacuum integrity for over 10 years.
ARTICLE KB-QC-04
Mil-STD-105E & ISO 2859-1 Sampling Protocol for Global Brands
UNIFAN operates under strict statistical quality control. For every mass production run (e.g., 20,000 units), standard Level II normal inspection sampling is deployed.
| Defect Classification |
AQL Threshold |
Criteria & Typical Defects |
Inspection Method |
Action Upon Breach |
| Critical Defects |
AQL 0.0 |
Sharp metal burrs, glass or foreign particulate contamination, vacuum breach (hot outer wall), cracked lid thread causing scald hazards. |
100% In-Line Vacuum Testing + Visual Examination |
Immediate Lot Rejection & 100% Re-inspection |
| Major Defects |
AQL 1.5 |
Coating peeling >1mm², logo color mismatch (ΔE > 1.5), capacity variation >3%, loose silicone gasket, dent >0.5mm on vessel body. |
ANSI/ASQ Z1.4 Level II Normal Sampling |
Full Rework & Secondary Sampling Audit |
| Minor Defects |
AQL 2.5 |
Removable lint or dust specks, minor packaging scuff, barcode print contrast <80%, slight adhesive label misalignment (<1mm). |
ANSI/ASQ Z1.4 Level II Normal Sampling |
Packaging Station Correction |
