Precious Metal BVAg-8b
UNS P07728
BVAg-8b is the vacuum-grade, lithium-modified 72Ag-28Cu eutectic braze filler (UNS P07728); the lithium addition reduces surface oxides so the alloy self-fluxes, while low-vapor-pressure purity limits keep outgassing low.
Reference datasheet — BVAg-8b is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
BVAg-8b tempers and conditions
BVAg-8b is supplied in one standard condition, AS-BRAZED.
Supply forms, finishes and certifications
Ways BVAg-8b is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
FOIL | Foil / shim, rolled and annealed | Supply form |
PREFORM | Stamped/formed preform | Supply form |
WIRE-H | Wire, hard drawn | Supply form |
WIRE-ODefault | Wire/rod, annealed | Supply form |
PASTE | Braze paste | Printing process |
POWDER | Atomized powder | Printing process |
What is BVAg-8b?
BVAg-8b is the vacuum-grade, lithium-modified 72Ag-28Cu eutectic braze filler (UNS P07728); the lithium addition reduces surface oxides so the alloy self-fluxes, while low-vapor-pressure purity limits keep outgassing low. It is used for flux-free vacuum brazing of stainless steels, superalloys and other oxide-forming metals, and is supplied as annealed and hard wire, foil, preforms, powder and paste. As-brazed values are roughly 300 MPa tensile, 165 MPa yield, 28% elongation and 70 HB. Lithium makes it more sensitive to storage and handling contamination than plain BVAg-8, which remains the choice for clean copper and nickel-plated joints. BVAg-8b has a density of 9.9 g/cm³ (0.358 lb/in³), lighter than 70% of precious metal grades. It melts at 766°C (1,411 °F). BVAg-8b has a yield strength of 165 MPa (23.9 ksi) and a tensile strength of 300 MPa (43.5 ksi) — weaker than 65% of precious metal grades. Elongation at break is 28% and the elastic modulus is 85 GPa (12.3 Msi).
What is BVAg-8b used for?
- vacuum furnace brazing without flux
- stainless steel and superalloy joints
- aerospace vacuum assemblies
Advantages
- High electrical conductivity — 87 % IACS, better than 93% of precious metal grades
- Conducts heat well — 355 W/m·K (205.1 BTU/hr·ft·°F), better than 92% of precious metal grades
BVAg-8b properties
Typical room-temperature values; bars are the position among precious metal grades.
Physical3
BVAg-8b has a density of 9.9 g/cm³ (0.358 lb/in³), lighter than 70% of precious metal grades. It melts at 766°C (1,411 °F).
Mechanical10
BVAg-8b has a yield strength of 165 MPa (23.9 ksi) and a tensile strength of 300 MPa (43.5 ksi) — weaker than 65% of precious metal grades. Elongation at break is 28% and the elastic modulus is 85 GPa (12.3 Msi).
Thermal6
BVAg-8b is rated for continuous service to 370°C (698 °F). It conducts heat at 355 W/m·K (205.1 BTU/hr·ft·°F), better than 92% of precious metal grades. Thermal expansion is 19.6 µm/m·K (10.9 µin/in·°F).
Electrical3
BVAg-8b conducts electricity at 87 % IACS, better than 93% of precious metal grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), worse than 66% of precious metal grades.
Sustainability3
Producing a kilogram of BVAg-8b takes about 1,100 MJ of energy and emits 95 kg of CO₂ — less than 71% of precious metal grades. Typical recycled content is 35%.
Manufacturability6
BVAg-8b's machinability is fair (40/100, worse than 60% of precious metal grades); formability excellent (85/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the precious metal family
Yield strength against density for every precious metal grade FabDigit runs. BVAg-8b is highlighted; hover a dot for its name, or open the interactive family chart.
Working with BVAg-8b
Is BVAg-8b easy to machine?
Rarely machined — soft and gummy; supplied as drawn wire, rolled foil or stamped preforms, sheared/blanked rather than turned.
Can BVAg-8b be welded?
Not a structural weld metal; it is the filler itself — vacuum or dry-hydrogen furnace braze at roughly 780–900 °C with 0.025–0.075 mm joint clearance and no flux.
Can BVAg-8b be formed, bent or molded?
Highly ductile: drawn to fine wire, rolled below 0.05 mm foil and stamped into rings/washers; interanneal to avoid work-hardening cracks.
BVAg-8b chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Ag | 71 – 73 | 72 |
| Liactive element; reduces surface oxides for self-fluxing action | 0.15 – 0.3 | 0.22 |
| Cdvacuum-grade limit (low vapour pressure) | ≤ 0 | |
| Znvacuum-grade limit | ≤ 0 | |
| Pvacuum-grade limit | ≤ 0 | |
| Pbvacuum-grade limit | ≤ 0 | |
| other (total)total of all other elements | ≤ 0.15 | |
| Curemainder, nominally ~27.8 % | balance |
What surface finishes work on BVAg-8b?
Keep parts and filler oil- and sulfur-free before brazing; as-brazed fillets can be lightly brushed or passivated with the base metal, and silver-rich fillets will tarnish in sulfur-bearing air.
Equivalent designations
Standards and trade names that resolve to Precious Metal BVAg-8b in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- P07728
- Also called
- BAg-8a
How much does BVAg-8b cost?
BVAg-8b is a high-cost precious metal ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
BVAg-8b — frequently asked
What is BVAg-8b used for?
BVAg-8b is typically used for vacuum furnace brazing without flux, stainless steel and superalloy joints and aerospace vacuum assemblies. In short: self-fluxing eutectic filler; brazes stainless without flux; vacuum-purity BAg-8 variant.
What is the yield strength of BVAg-8b?
BVAg-8b has a typical yield strength of 165 MPa (23.9 ksi) and a tensile strength of 300 MPa (43.5 ksi) — weaker than 65% of precious metal grades.
Is BVAg-8b easy to machine?
Not especially — machinability is rated fair (40/100, worse than 60% of precious metal grades). Rarely machined — soft and gummy; supplied as drawn wire, rolled foil or stamped preforms, sheared/blanked rather than turned.
Can BVAg-8b be welded?
Not a structural weld metal; it is the filler itself — vacuum or dry-hydrogen furnace braze at roughly 780–900 °C with 0.025–0.075 mm joint clearance and no flux.
What surface finishes work on BVAg-8b?
Keep parts and filler oil- and sulfur-free before brazing; as-brazed fillets can be lightly brushed or passivated with the base metal, and silver-rich fillets will tarnish in sulfur-bearing air.
Can BVAg-8b be formed, bent or molded?
Highly ductile: drawn to fine wire, rolled below 0.05 mm foil and stamped into rings/washers; interanneal to avoid work-hardening cracks.
What is the maximum service temperature of BVAg-8b?
BVAg-8b is rated for continuous use to about 370°C (698 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does BVAg-8b cost?
BVAg-8b is a high-cost precious metal ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- AWS A5.8/A5.8M — Specification for Filler Metals for Brazing and Braze Welding — American Welding Society (2019)
- ASM Handbook Vol. 6 — Welding, Brazing, and Soldering — ASM International (1993)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Ag-Cu system) — ASM International (1990)
- Silver-copper-lithium vacuum brazing filler metal data (Cusil-ABA/Cusil family bulletins) — Morgan Advanced Materials (Wesgo Metals) (2022)
- BVAg vacuum-grade brazing alloy product data — Lucas-Milhaupt / Handy & Harman (2021)
- GB/T 10046 (2018)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.