Brazing Filler Metals · Technical Knowledge Base
Silver Brazing Alloys — The Complete AWS BAg Series Reference
01What makes a silver brazing alloy
Silver brazing joins metals by melting a filler that flows into a capillary gap and solidifies, without melting the parent parts. Silver lowers the melting range, wets most base metals readily, and gives joints useful strength and ductility.
Every commercial silver alloy balances silver content (price and wetting), brazing temperature, joint performance and regulatory status (restricted elements such as cadmium). Grades follow a classification system — the AWS A5.8 "BAg" designations being the most widely recognised — so a grade name means a defined composition and melting range, not a marketing claim.
02How to read a BAg designation
An AWS classification such as BAg-24 lists its constituents in order: "Ag 50, Cu 20, Zn 28, Ni 2" means 50 % silver, 20 % copper, 28 % zinc, 2 % nickel. Silver content is the main price indicator; the balance elements tune melting range, fluidity, colour and corrosion.
Compare four figures together:
Solidus / liquidus (°C) — fits your temperature limits and heat source.
Silver content (%) — the main cost driver and a rough proxy for wetting.
Restricted elements — cadmium, lead, RoHS and food-contact rules.
Base metals — some (copper, nickel, stainless) wet far more easily than others (aluminium, titanium).
03Full BAg series reference table
Compositions are nominal per AWS A5.8/A5.8M; melting values are solidus / liquidus in °C. Rows marked with a copper tag are analysed in the next section.
| AWS | Composition (Ag balance) | Solidus / Liquidus °C | Typical application | Silver % | Notes |
|---|---|---|---|---|---|
| BAg-24 | Cu 20, Zn 28, Ni 2 | 660 / 707 | Stainless (300-series), carbide, food & medical | 50 | Cadmium-free; Ni improves wetting & corrosion resistance |
| BAg-7 | Cu 22, Zn 17, Sn 5 | 618 / 652 | Copper, brass, stainless; food & potable water | 56 | Low zinc, very low melting range |
| BAg-22 | Cu 16, Zn 23, Mn 7.5, Ni 4.5 | 682 / 699 | Tungsten-carbide tools, sintered parts | 49 | Narrow range, strong carbide joints |
| BAg-8 | Cu 28 | 779 / 779 (eutectic) | Vacuum & atmosphere furnace, aerospace, electronics | 72 | Eutectic; no zinc/cadmium, clean vacuum use |
| BAg-5 | Cu 30, Zn 25 | 663 / 743 | General purpose, ferrous & non-ferrous, HVAC | 45 | Workhorse general-purpose alloy |
| BAg-28 | Cu 30, Zn 28, Sn 2 | 649 / 710 | Ferrous & non-ferrous, refrigeration | 40 | Tin-bearing cadmium-free family |
| BAg-34 | Cu 32, Zn 28, Sn 2 | 649 / 721 | HVAC & refrigeration, dissimilar metals | 38 | Cadmium-free replacement for low-temp work |
| BAg-18 | Cu 30, Sn 10 | 602 / 718 | Stainless, food equipment, elevated service | 60 | Low zinc; good for service to ~370 °C |
| BAg-20 | Cu 38, Zn 32 | 677 / 766 | HVAC, copper, nickel-silver | 30 | Higher temperature, economical on copper |
| BAg-35 | Cu 32, Zn 33 | 685 / 754 | Dissimilar metals, refrigeration tubing | 35 | Moderate temperature for ferrous & non-ferrous |
| BAg-36 | Cu 27, Zn 25, Sn 3 | 646 / 677 | Dissimilar metals, moderate flow | 45 | Tin-bearing, low melting range |
| BAg-37 | Cu 40, Zn 33, Sn 2 | 654 / 779 | General Ag-Cu-Zn-Sn work | 25 | Lowest silver of the Sn family |
| BAg-4 | Cu 30, Zn 28, Ni 2 | 671 / 779 | Stainless, tungsten-carbide | 40 | Ni improves stainless corrosion resistance |
| BAg-6 | Cu 34, Zn 16 | 688 / 774 | Electrical, dissimilar metals | 50 | Good conductivity and ductility |
| BAg-8a | Cu 28, Li 0.3 | liquidus 760 | Thin stainless, vacuum service | 71.7 | Lithium improves wetting |
| BAg-8b | Cu 28, Ni 0.5 | 779 / 788 | Stainless with improved corrosion | 71.5 | Nickel addition for stainless joints |
| BAg-9 | Cu 20, Zn 15 | 671 / 718 | Silversmithing, colour-matched silver | 65 | Good match to silver appearance |
| BAg-10 | Cu 20, Zn 10 | 691 / 738 | Sterling silver, step brazing | 70 | For jewellery and silverware |
| BAg-13 | Cu 40, Zn 5, Ni 1 | 718 / 857 | Furnace brazing, elevated service to ~370 °C | 54 | Low zinc, high service temperature |
| BAg-13a | Cu 42, Ni 2 | 771 / 893 | Furnace brazing, elevated service | 56 | Very low zinc, clean furnace atmosphere |
| BAg-19 | Cu 7.2, Li 0.23 | liquidus 891 | Vacuum, thin stainless | 92.5 | High silver, lithium-bearing |
| BAg-21 | Cu 28.5, Sn 6, Ni 2.5 | 690 / 801 | 400-series stainless, corrosion resistance | 63 | Designed to resist interface corrosion |
| BAg-23 | Mn 15 | liquidus 970 | High-temperature furnace brazing | 85 | Silver-manganese eutectic |
| BAg-26 | Cu 38, Zn 33, Mn 2, Ni 2 | 705 / 800 | Stainless, moderate service | 25 | Ni + Mn for stainless wetting |
Solidus and liquidus are rounded; some grades are quoted by liquidus only where the range is very narrow. Verify exact values against AWS A5.8 for your quality system.
04Melting ranges of the main commercial grades
Narrow ranges flow fast for furnace or automated work; wide ranges give torch operators more control. The chart below compares the solidus–liquidus spans of the most-quoted commercial grades.
Grade Solidus (°C) Liquidus (°C) Span (°C)
BAg-18 602 718 116
BAg-7 618 652 34
BAg-28 649 710 61
BAg-34 649 721 72
BAg-24 660 707 47
BAg-5 663 743 80
BAg-20 677 766 89
BAg-22 682 699 17
BAg-35 685 754 69
BAg-8 779 779 0
05High-demand grades, analysed
Demand concentrates where an alloy solves a recurring, high-value problem: corrosion-safe stainless in food and medical equipment, carbide tips in tooling, vacuum-tight aerospace joints, and the huge copper-brazing volume of HVAC. These grades carry most commercial volume.
The nickel-bearing cadmium-free alloy for stainless and tungsten-carbide, and the standard substitute where a cadmium-bearing grade was used before.
660 / 707 °C
300-series stainless, carbide tooling, nickel and copper alloys
Nickel suppresses interface corrosion that zinc-rich alloys can cause on stainless
Wire, strip, preforms, paste
Why it sells. It answers a recurring spec: a cadmium-free filler that wets stainless and survives food, medical and dental service. The 2 % nickel resists the galvanic corrosion plain Ag-Cu-Zn alloys can suffer on stainless, and as the accepted cadmium-free replacement for the older BAg-3, distributors stock it across the EU, North America and Asia. Quote it first for stainless tubing or carbide-tipped tools.
The low-zinc, low-melting cadmium-free alloy for copper, brass and stainless in food handling and potable-water systems.
618 / 652 °C
Copper, brass, bronze, stainless
Low zinc keeps the joint resistant in water and mild corrosive service
Wire, rings, preforms, flux-coated
Why it sells. Its 618 °C solidus is among the lowest of the cadmium-free series, protecting heat-sensitive base metals, and the low zinc resists the water-side corrosion that matters in potable-water and food contact. Often named for stainless-to-copper joints where a cadmium grade is no longer permitted, it is a steady line for refrigeration and food-processing customers.
The specialist for tungsten-carbide tips: saw segments, mining tools, lathe inserts and sintered-carbide assemblies.
682 / 699 °C
Tungsten carbide to steel, porous sintered parts, wire mesh
Manganese and nickel aid wetting on hard-to-wet carbide surfaces
Wire, strip, foil, preforms
Why it sells. Carbide brazing needs a filler that wets a sintered ceramic and a steel shank in one operation. BAg-22's very narrow 17 °C range gives fast, complete flow; manganese and nickel promote bonding to carbide. Named for carbide inserts, saw bodies and aluminium-bronze-to-steel joints, it is a recurring, margin-friendly line that also suits automated induction brazing.
The silver-copper eutectic for vacuum and atmosphere furnace brazing — the workhorse of aerospace and electronics.
779 °C (eutectic; melts at one temperature)
Steel, stainless, copper, nickel, and their alloys
No zinc or cadmium; clean, corrosion-resistant joints
Wire, foil, preforms, powder, paste
Why it sells. With no zinc or cadmium, BAg-8 works in controlled-atmosphere and vacuum furnaces without volatilising elements that contaminate the chamber or joint. It is named for aerospace, linear-beam tubes and electronics needing vacuum-tight joints; BAg-8a adds lithium for wetting thin stainless. Higher silver means higher unit value — volume trails HVAC, but each order is typically worth more.
The general-purpose 45 % silver alloy — the first grade many fabricators reach for when no specific filler is required.
663 / 743 °C
Steel, stainless, copper and copper alloys
Sound joints in indoor and mild outdoor service
Wire, rod, strip, rings, flux-coated
Why it sells. BAg-5 is the classic trade-off between silver cost and performance: enough silver to wet steel and stainless, with a melting range suited to torch brazing across most general fabrication. Quoted in job shops, maintenance and HVAC work more than any other single grade, it turns over in volume — the dependable default.
Tin-bearing cadmium-free alloys (38–45 % Ag) that recover the low melting temperatures of the old cadmium grades.
BAg-28: 649/710 · BAg-34: 649/721 · BAg-36: 646/677 °C
Copper, brass, stainless; ferrous & non-ferrous joints
Lower zinc than the BAg-5 family improves resistance in humid and mildly corrosive service
Wire, rings, preforms, flux-coated
Why they sell. As cadmium grades were phased out of HVAC and refrigeration, the industry needed low-temperature replacements. Tin lowers the melting range as cadmium once did, so these grades wet copper and brass at ~650 °C while staying RoHS and food-contact compliant. They now carry a large share of coil, condenser and refrigeration-pipe brazing volume.
A zinc-free, tin-bearing silver alloy for elevated service temperatures — a frequent choice for stainless and food equipment.
602 / 718 °C
Stainless steel, food-processing equipment
No zinc, so joints resist discolouration and corrosion in washdown service
Wire, rings, preforms
Why it sells. Specified where a joint must keep strength at elevated service temperature (commonly cited to about 370 °C) and where zinc is undesirable because it volatilises and stains. That profile fits the hygiene-focused industries that buy steadily — a quality-flagged line even if its volume trails the HVAC families.
Economical 30–35 % silver alloys for copper-to-copper HVAC work where a higher brazing temperature is acceptable.
BAg-20: 677/766 · BAg-35: 685/754 °C
Copper, brass, bronze, nickel-silver
Adequate for indoor HVAC and plumbing service
Wire, rings, flux-coated
Why they matter. On copper and brass, high silver is often wasted — the base metal wets well at lower levels. BAg-20 and BAg-35 cut silver cost while still joining copper plumbing and refrigeration parts, protecting margin on price-sensitive HVAC volume. Offer them for copper pipe when the joint does not need the lowest temperature.
06Cadmium-bearing grades (for completeness)
The original low-temperature alloys contained cadmium, which drastically lowered melting range; they remain in legacy specs and are produced where still permitted.
| AWS | Composition | Solidus / Liquidus °C | Comment |
|---|---|---|---|
| BAg-1 | Ag 45, Cu 15, Zn 16, Cd 24 | 607 / 618 | Lowest melting range of the series; close-clearance joints |
| BAg-1a | Ag 50, Cu 15.5, Zn 16.5, Cd 18 | 627 / 635 | Narrower range than BAg-1 |
| BAg-2 | Ag 35, Cu 26, Zn 21, Cd 18 | 607 / 702 | Broader range, larger joint gaps |
| BAg-3 | Ag 50, Cu 15.5, Zn 15.5, Cd 16, Ni 3 | 632 / 688 | Nickel aids stainless and carbide; legacy grade |
| BAg-27 | Ag 25, Cu 35, Zn 26.5, Cd 13.5 | 607 / 746 | Economical, wider range |
| BAg-33 | Ag 25, Cu 30, Zn 27.5, Cd 17.5 | 607 / 710 | Narrower range, needs careful heat control |
Cadmium-bearing grades are shown for reference only and are not recommended for new designs.
07Silver-phosphorus-copper (BCuP): the HVAC volume leader
Strictly a copper-phosphorus series, BCuP grades carrying 0–15 % silver are commonly grouped with silver brazing because the silver lowers melting temperature and improves flow on copper. On copper-to-copper joints they are self-fluxing — phosphorus reduces copper oxides — which is why they dominate air-conditioning and refrigeration brazing in enormous volume.
| AWS | Composition | Solidus / Liquidus °C | Typical use |
|---|---|---|---|
| BCuP-2 | Cu 92.75, P 7.25 | 710 / 793 | Copper–copper joints, fast flow, economical |
| BCuP-6 | Ag 2, Cu 91, P 7 | 643 / 788 | Silver lowers solidus; copper–copper HVAC |
| BCuP-7 | Ag 5, Cu 88.25, P 6.75 | 643 / 771 | Preform rings for heat exchangers |
| BCuP-4 | Ag 6, Cu 86.75, P 7.25 | 643 / 718 | Low melting, tight-clearance preforms |
| BCuP-5 | Ag 15, Cu 80, P 5 | 643 / 802 | Larger joint gaps, heat-exchanger preforms |
08Corrosion resistance by grade family
Corrosion is set less by the silver than by the alloying balance (especially zinc and nickel) and joint design. In general:
Zinc-free and low-zinc grades (BAg-8/8a/8b, BAg-13/13a, BAg-18, BAg-19) give the strongest water-side corrosion and staining resistance — for potable water and food contact.
Nickel-bearing grades (BAg-24, BAg-4, BAg-21, BAg-8b) resist the galvanic interface corrosion that can occur on stainless, making them preferable in humid or mildly aggressive service.
Zinc-rich grades (BAg-5, BAg-20, BAg-35) are adequate indoors and in mild atmospheres but can be attacked by dezincification or by coupling to more noble metals in wet service.
Silver content itself is not the deciding factor: a 45 % grade is not automatically more corrosion-resistant than a 30 % grade.
For seawater, strong chemicals or elevated temperatures, confirm the filler against the environment — a nickel- or palladium-bearing grade may suit better.
09Which grade for which base metal
| Base metal | Preferred grades | Notes |
|---|---|---|
| Copper & brass | BAg-20, BAg-35, BAg-7, BCuP-2/6 (copper only) | Copper wets easily; lower silver levels are adequate |
| Steel & carbon steel | BAg-5, BAg-28, BAg-34, BAg-6 | Flux required; standard silver-copper-zinc alloys wet well |
| Stainless steel (300-series) | BAg-24, BAg-7, BAg-8a, BAg-18, BAg-21 | Nickel or low-zinc grades resist interface corrosion |
| Tungsten carbide | BAg-22, BAg-4 | Narrow melting range for tool tips and inserts |
| Nickel & nickel alloys | BAg-8, BAg-24, BAg-6 | Silver wetting is generally good |
| Sterling silver / silverware | BAg-9, BAg-10 | Colour match and lower melting range for step brazing |
| Aluminium, titanium, magnesium | — (not silver brazed) | Need their own filler families; silver alloys do not wet them reliably |
Joint clearance matters: most silver alloys perform well with a capillary gap of about 0.05–0.15 mm; wider gaps need a broader melting range.
10Selection logic and cost perspective
Silver alloy is priced mainly by silver content, a traded commodity. The practical question is the same: what is the lowest silver level that will wet the joint and meet the service requirements?
Identify base metals and atmosphere. Copper-to-copper can use low-silver or silver-free BCuP; stainless usually needs a nickel-bearing or low-zinc grade; carbide needs BAg-22 or BAg-4.
Set the temperature ceiling. Thin, heat-sensitive or pre-heat-treated parts call for the lowest-temperature grade that still meets the other requirements (BAg-7, BAg-28, BAg-34, BAg-36).
Check compliance. For RoHS and food-contact markets, restrict selection to cadmium-free and, where water or food is involved, low-zinc grades.
Consider service temperature. Joints that run hot favour zinc-free grades such as BAg-18, BAg-13 and BAg-13a.
Match form to process. Torch work uses wire and rod; automated and furnace brazing use rings, preforms and paste, where narrow ranges pay off.
11Frequently asked questions
What does "BAg" mean?
The AWS A5.8 prefix for silver brazing filler metals; the number identifies a defined composition and melting range. Many grades have ISO 17672 and GB/T equivalents.
Is a higher silver content always better?
No. Higher silver improves wetting and can lower melting temperature, but it raises cost. Choose the lowest-silver, lowest-temperature alloy that wets the joint and meets corrosion, service and compliance needs.
Why are cadmium-free grades required?
Cadmium is restricted under EU RoHS and similar rules because of its toxicity. Cadmium-free alloys use tin, nickel and manganese to recover the low melting temperatures and wetting of the old cadmium grades.
Can silver alloys join steel to copper?
Yes — made with a general-purpose silver-copper-zinc alloy (e.g. BAg-5) or a tin-bearing grade with flux. BCuP alloys are limited to copper-to-copper work.
Do I always need flux?
Generally yes, except where the alloy is self-fluxing. On copper-to-copper joints, BCuP grades are self-fluxing; most other joints need a compatible flux to remove surface oxides and allow wetting.
What joint clearance is recommended?
Most silver alloys fill a capillary gap of about 0.05–0.15 mm well. Tight clearances favour free-flowing alloys; wider gaps need a broader melting range.
Need a grade matched to your joint?
Tell us the base metals, joining method (torch, induction, furnace), service environment and compliance requirements. We will recommend a grade, confirm the AWS / ISO classification, and quote the right form — wire, rod, strip, rings, preforms or paste — with composition and melting data.
Grades supplied against AWS A5.8, ISO 17672 and GB/T specifications
Composition and melting-range certificates with each batch
Cadmium-free and food-contact compliant options
Request a specification-based quote A reply within one business day
About this guide. This page is a general engineering reference to silver brazing alloys. Compositions and melting ranges are nominal values based on the AWS A5.8/A5.8M classification system, for selection guidance — not a substitute for the specification or qualification testing of your joint.
Material selection depends on base metal, joint design, process and service environment. Verify every grade against the current standard before production.
