Filler metal selection กำหนด joint quality, cost, regulatory compliance ของ HVAC brazing operation · BCuP (Cu-P-based) คือ default สำหรับ Cu-Cu joint แต่ ห้ามใช้กับ Steel/Ni · BAg (Silver-based) คือ universal solution แต่ ราคาสูง 5-10× · บทความนี้ comparing AWS A5.8 grades, regulatory Cd-free, cost trade-off
The Decision Tree — Base Material First
| Base Materials | Recommended Filler | Reason |
|---|---|---|
| Cu - Cu | BCuP-2 / BCuP-7 | Self-fluxing, low cost |
| Cu - Brass | BCuP + flux หรือ BAg | Zn vapor management |
| Cu - Steel | BAg-5 / BAg-7 (NO BCuP) | BCuP forms brittle Fe-P |
| Cu - Stainless | BAg-5 / BAg-22 / BNi | Wetting + ductility |
| Al - Al | BAlSi-4 (Al-Si 12%) | Aluminum filler match |
| Al - Cu | BAlSi + Cs-AlF₃ flux | Temp window 580-620°C |
BCuP — Copper-Phosphorus Family (AWS A5.8)
| Grade | Composition | Melt Range | HVAC Use |
|---|---|---|---|
| BCuP-2 | Cu 92.7% + P 7.3% | 710-790°C | Mass production, low-stress |
| BCuP-3 | Cu 86% + P 6% + Ag 5% | 645-815°C | Better gap-filling |
| BCuP-5 | Cu 80% + P 5% + Ag 15% | 645-815°C | Vibration / thermal cycle |
| BCuP-7 | Cu 88% + P 6.7% + Ag 5% | 645-770°C | HVAC mass production sweet-spot |
BAg — Silver-Based Family (AWS A5.8)
| Grade | Composition | Melt Range | Note |
|---|---|---|---|
| BAg-1 | Ag 45% + Cd 24% + Cu 15% + Zn 16% | 605-620°C | Cd toxicity — banned EU |
| BAg-5 | Ag 45% + Cu 30% + Zn 25% | 675-745°C | Cd-free common |
| BAg-7 | Ag 56% + Cu 22% + Zn 17% + Sn 5% | 620-655°C | Cd-free, low temp |
| BAg-22 | Ag 49% + Cu 16% + Zn 23% + Mn 7.5% + Ni 4.5% | 680-700°C | Stainless steel use |
Cadmium-Free Regulation — สำคัญสำหรับ EU Export
Cadmium = toxic heavy metal · BAg-1, BAg-1a, BAg-2, BAg-3 มี Cd 18-26% → ห้ามใช้ ในผลิตภัณฑ์ที่ส่งออก EU (RoHS, REACH) · ใช้แทนด้วย BAg-5/7/22 · OSHA, NIOSH (US) restrict workplace Cd exposure · Thailand DEDE recommend Cd-free สำหรับ industrial brazing
Filler Form — Wire, Ring, Paste, Pre-clad
- Wire (manual feed): flexible, operator-dependent, prototype/repair
- Pre-formed Ring: precise volume, repeatable, mass production HVAC standard
- Paste/Cream: automated dispense, complex geometry, microchannel
- Pre-clad (cladded sheet): filler bonded on base, furnace brazing
HVAC induction brazing ส่วนใหญ่ใช้ pre-formed ring — slip onto tube before joint assembly, fixed volume, repeatable Cpk
Flux Selection
| Flux Grade | Temp Range | Use With | Note |
|---|---|---|---|
| FB3-A | 565-870°C | BAg general | White paste/powder |
| FB3-C | 730-1150°C | BAg high temp | Stainless / Ni |
| FB3-D | 565-980°C | BAg + Mn | BAg-22 |
| Cs-AlF₃ (Nocolok) | 560-620°C | BAlSi (Al-Cu) | Activated, rinse off |
| None (self-fluxing) | - | BCuP on Cu | P reduces CuO |
Flux residue ต้อง wash off หลัง brazing — ไม่งั้นจะ corrode joint ระยะยาว · HVAC standard wash: hot DI water rinse + dry
Most Used Filler in Thai HVAC Plants
Filler metal ที่ HVAC OEM ในไทยใช้ทั่วไป (Cd-free standard)
Refrigerant tube
Service valve
Heat exchanger
Cost — Per Joint Reality Check
Filler cost per joint น้อยกว่าที่คิด เพราะใช้แค่ 1-3 g/joint:
- BCuP-2 ring 1 g: ~USD 0.03-0.05
- BCuP-7 ring 1 g (Ag 5%): ~USD 0.10-0.15
- BAg-5 ring 1 g (Ag 45%): ~USD 0.60-0.80
- BAg-7 ring 1 g (Ag 56%): ~USD 0.75-0.90
คิดจริง: 1 AC unit ใช้ ~50 joints — BCuP cost ~USD 2.5/unit · BAg cost ~USD 35/unit · ส่วนต่างชัดเจน เลือกตาม base material ก่อนเสมอ
SHINRAI Filler Metal Service
- Filler selection consultation (free) ตาม base material + application
- Sourcing BCuP/BAg/BAlSi จาก eldec-approved suppliers
- Pre-formed ring custom geometry
- Flux compatibility check + dispensing setup
- Sample test ที่ SHINRAI facility — ส่ง tube มา ทดลอง
- Inventory consignment option สำหรับ OEM volume
- Cd-free certification documentation
- [email protected], 098-978-9952