AWS Class RBCuZn-C MIG & TIG
RBCuZn-C Low Fuming Bronze Brazing Rod & Filler Wire - Copper-Zinc Braze Welding Alloy Supplier in India
Nicorex Alloys is an ISO 9001 and ISO 14001 certified Mumbai-based supplier and stockist of RBCuZn-C low-fuming bronze brazing rods and filler wire, classified under AWS A5.8 / ASME SFA-5.8 and also referred to as RCuZn-C under AWS A5.8 / ASME SFA-5.8. The UNS designation is C68100; the EN ISO 24373 equivalent is CuZn40FeSn.
RBCuZn-C is a copper-zinc (brass) brazing filler metal with approximately 58% Cu and 40% Zn, plus controlled additions of tin (0.80–1.10%), iron (0.25–1.20%), and silicon (0.04–0.15%). The silicon content is a critical feature, as it forms a thin SiO₂ film on the molten alloy surface that suppresses zinc vaporisation, significantly cutting toxic white fume generation. This fume-reduction mechanism earns the alloy its “low fuming bronze” name. RBCuZn-C is a braze-welding alloy; fillers are deposited into lap, tee, and butt joints rather than relying on capillary draw. Solidus sits at 866°C (1590°F), liquidus at 888°C (1630°F), and recommended brazing temperature ranges from 910 to 955°C (1670 to 1750°F). The typical tensile strength of a braze-welded joint reaches 386 MPa (56,000 psi).
Available as bare rods, flux-coated rods, and coils in diameters from 1.6 mm to 6.4 mm, this alloy joins carbon steel, cast iron, copper, brass, bronze, nickel alloys, stainless steel, and dissimilar combinations of these metals. Nicorex Alloys, as a trader and distributor of brazing consumables, supplies the complete RBCuZn family alongside matching AWS FB3-K class brazing fluxes. Every batch ships with MTC 3.1 per EN 10204 from our facility.
RBCuZn-C Low Fuming Bronze Specifications
The table below gives a full list of the technical standards and requirements that apply to RBCuZn-C low fuming bronze.
| AWS Classification | RBCuZn-C as per AWS A5.8 / ASME SFA-5.8 |
|---|---|
| UNS | C68100 |
| Primary Processes | Oxy-acetylene, TIG, furnace, induction brazing |
| Diameters | 1.6, 2.4, 3.2, 4.0, 4.8, 6.4 mm |
| Rod Length | 914 mm (36 in) |
| Forms | Bare rod, Flux-coated rod, Coils |
What Does RBCuZn-C Mean? - AWS A5.8 Classification Explained
Refer to this table for a detailed breakdown of the AWS A5.8 alphanumeric classification system for RBCuZn-C brazing rods.
| Prefix / Suffix | Meaning |
|---|---|
| R | Rod — bare filler for gas welding/brazing |
| B | Brazing filler metal |
| Cu | Copper — primary element (~58%) |
| Zn | Zinc — secondary element (~38–40%) |
| -C | Third variant in the CuZn family |
RBCuZn-A is a naval brass type, RBCuZn-B adds nickel for cast iron surfacing, and RBCuZn-D is a high-nickel bronze for tungsten carbide brazing. RBCuZn-C is the most popular variant, with its Si at 0.04–0.15% forms a SiO₂ skin on the molten pool, blocking zinc evaporation.
Deposit Chemical Composition of RBCuZn-C
Check the table below for the specific elemental percentages and chemical composition limits required for RBCuZn-C weld deposits.
| Specification | Copper (Cu) | Zinc (Zn) | Tin (Sn) | Iron (Fe) | Manganese (Mn) | Silicon (Si) | Aluminium (Al) | Lead (Pb) | Phosphorus (P) | Other |
|---|---|---|---|---|---|---|---|---|---|---|
| AWS A5.8 Req. (%) | 56.0–60.0 | Balance (~38–40) | 0.80–1.10 | 0.25–1.20 | 0.01–0.50 | 0.04–0.15 | 0.01 max | 0.05 max | 0.01 max | 0.50 max total |
Tin improves deposit strength. Iron and manganese increase hardness. Silicon is the critical addition, as its SiO₂ film suppresses zinc vaporisation, reducing toxic fumes by 50–70%. Low Pb, Al, and P limits keep joints porosity-free.
Mechanical Properties of RBCuZn-C Braze-Welded Joints
Review the following table for the typical mechanical performance data, including tensile strength, for joints using RBCuZn-C filler metal.
| Specification | Tensile Strength | Elongation | Hardness |
|---|---|---|---|
| Typical Value | ~386 MPa (56,000 psi) | Good (ductile deposit) | ~140–170 HB |
At 386 MPa, an RBCuZn-C braze weld reaches roughly 55% of mild steel’s base-metal strength. These joints suit maintenance and repair, but are not a substitute for full-strength fusion welds.
Base Metal Compatibility for RBCuZn-C Low Fuming Bronze
Refer to the following list for various base metals and alloys compatible with RBCuZn-C braze-welding filler rods.
| Base Metal | Joint Type | Notes | P-Number |
|---|---|---|---|
| Carbon Steel | Braze welding | Neutral/slightly oxidising flame; flux required | P1 |
| Low-Alloy Steel | Braze welding | Preheat for higher-carbon grades | P3 to P5 |
| Cast Iron | Repair and joining | Preheat 150–175°C; slow cool | N/A |
| Copper | Brazing | Neutral flame; excellent wetting | P31 |
| Brass | Composition brazing | Neutral flame to limit Zn loss | P32 |
| Bronze | Brazing | Good compatibility | P34 |
| Nickel Alloys | Brazing | Good wetting | P41 to P49 |
| Stainless Steel | Brazing | Flux essential | P8 |
| Dissimilar Metals | Steel-to-copper, cast iron-to-steel | Key advantage of RBCuZn-C | Varies |
Recommended Brazing Parameters for RBCuZn-C
See the table below for optimised heat settings and flame adjustment parameters recommended for successful RBCuZn-C brazing applications.
| Process | Amperage (A) | Voltage (V) | Gas / Shielding |
|---|---|---|---|
| Oxy-Acetylene | — | — | Neutral to Slightly Oxidising |
| TIG Brazing | 80–120 (Typical) | 10–15 | 100% Argon |
| Furnace / Induction | — | — | Vacuum or Controlled Atmosphere |
RBCuZn-C requires a strict 910–955°C range and AWS FB3-K flux across all processes, including TIG. It utilises a silicon-based mechanism to suppress toxic fumes. Engineers must ensure a “tinning” phase and hot water flux removal for structural integrity.
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Industrial Applications of RBCuZn-C Low Fuming Bronze
The following are the industrial applications for RBCuZn-C:
- Cast Iron Repair: Standard for fixing engine blocks and gearboxes. It prevents thermal shock and cracking in brittle grey or ductile iron during structural maintenance.
- HVAC & Plumbing: Creates leak-free, high-pressure joints between copper tubing and brass fittings. Ideal for refrigeration systems facing constant thermal cycling and vibration.
- Sheet Metal Fabrication: Perfect for thin-gauge steel or copper ducting. The low melting point ensures clean, strong joints without risking burn-through on delicate sections.
- Automotive Repair: Used for exhaust systems and radiator brazing. Its gap-filling ability makes it excellent for building up worn brackets and complex mechanical assemblies.
- Surfacing & Build-up: Restores worn valve seats and bearing surfaces. The bronze deposit provides a durable layer that remains easily machinable to original precision tolerances.
- Surfacing & Build-up: Restores worn valve seats and bearing surfaces. The bronze deposit provides a durable layer that remains easily machinable to original precision tolerances.
- Thermal Spray Coating: Serves as feedstock for arc spray metallising. It applies a wear-resistant, corrosion-protective bronze coating over large steel industrial substrates.
- Dissimilar Metal Joining: Bridges "unweldable" combinations like steel-to-copper or brass-to-cast iron. It provides a structural bond where fusion welding is technically impossible.
Storage and Handling of RBCuZn-C Brazing Rods
Proper storage is key to preventing the contamination that causes porosity.
- Store in original packaging, clean and dry (15–35°C, <60% RH).
- Flux-coated rods: protect from moisture; discard if wet.
- Bare rods: no heated storage needed. Clean with acetone if oxidised.
- Handle with clean gloves – skin oils cause porosity.
- Keep away from acids and ammonia vapours.
- Shelf life: bare rods indefinite if dry; flux-coated 12–24 months.
Available Forms, Diameters and Packaging of RBCuZn-C
RBCuZn-C brazing rods from Nicorex Alloys are supplied in three forms with batch traceability.
| Form | Diameters | Packaging |
|---|---|---|
| Bare Rod | 1.6, 2.4, 3.2, 4.0, 4.8, 6.4 mm | 5 / 10 / 25 kg packs, 914 mm length |
| Flux-Coated Rod | 2.4, 3.2, 4.0, 4.8 mm | 5 / 10 kg packs, 914 mm length |
| Coil | 2.4 mm | 11 kg (25 lb) / 23 kg (50 lb) coils |
How to Order RBCuZn-C Low Fuming Bronze from Nicorex Alloys
When ordering RBCuZn-C from Nicorex Alloys, specify these 10 details in your RFQ:
- Rod / Wire Type - Oxy-fuel / Torch / Furnace / Induction brazing; AWS A5.8 / ASME SFA-5.8: RBCuZn-C
- Size - Bare Rod: 1.6, 2.4, 3.2, 4.0, 4.8, 6.4 mm / 914 mm length; Flux-Coated: 2.4, 3.2, 4.0, 4.8 mm / 914 mm; Coil: 2.4 mm
- Current Type - Oxy-acetylene / Oxy-fuel torch; borax-boric acid flux required for bare rod
- Brazing Position - Flat and horizontal (H, V) only
- Material Grade - CuZn alloy; Cu 56–60%; UNS C68100; EN ISO 17672: CuZn40SnSi
- Quantity - Bare / Flux-Coated: 5 kg / 10 kg / 25 kg packs; Coil: 11 kg / 23 kg - specify form
- Standard - AWS A5.8 / ASME SFA-5.8; EN ISO 17672; ASME Section IX
- Documentation - MTC EN 10204 3.1; compliance certificate; TPI if required
- Packaging - Cardboard box / fibre tube packs; coils in moisture-resistant wrap - specify bare or flux-coated
- Delivery Destination - Domestic / International - specify port or delivery address
Frequently Asked Questions
What is the Difference between RBCuZn-C and RBCuZn-B?
Both are copper-zinc brazing alloys under AWS A5.8. Nickel (0.2–0.8%) in RBCuZn-B distributes iron evenly and improves cast iron colour. For fume control, RBCuZn-C has no nickel but more silicon. RBCuZn-C is affordable and more popular for general-purpose tasks.
Is Flux Required When Brazing with RBCuZn-C Bare Rods?
Yes. Borax-boric acid flux (AWS FB3-K) must be applied to joint surfaces and the rod tip. Without flux, a molten alloy will not wet the base metal. Flux-coated rods carry pre-applied flux, but extra flux is recommended for heavy sections.
Can RBCuZn-C be used for Cast Iron Repair?
Yes. Cast iron braze welding with RBCuZn-C is the standard foundry repair method. The brazing temperature (910–955°C) stays below cast iron’s melting point, avoiding thermal shock cracking. Preheat to 150–175°C and slow cool.
Can RBCuZn-C be used with a TIG Torch?
Yes. Bare rods work as TIG brazing filler with GTAW, 100% Argon, DCEN polarity. The objective is brazing, not fusion welding. Flux on joint surfaces is still required.
What Joint Designs Work with RBCuZn-C Braze Welding?
Because RBCuZn-C features minimal capillary action, the filler metal must be manually deposited into lap, tee, or butt joints with V-groove or bevel preparation using a clearance of 0.05 to 0.13 mm
When should RBCuZn-C not be used?
Avoid RBCuZn-C for structural joints needing full-strength fusion welds, service above 260°C (500°F) where copper-zinc alloys dezincify, ammonia or aggressive water environments, and poorly ventilated spaces without respiratory protection.