Brazing Rod Guide: Silver, Aluminium and Bronze Rods in NZ

Choosing a brazing rod comes down to three things: the metals you are joining, the heat you can bring to the job, and the flux that suits the rod. For a silver brazing rod in NZ, the silver percentage sets the working temperature and the jobs it suits. Aluminium needs its own aluminium brazing rod, and bronze or nickel silver rods cover heavier steel and cast iron repairs.

Brazing vs soldering vs welding

All three join metal, but they do it differently:

• Welding melts the base metals themselves and fuses them, usually with a filler of a similar alloy.
• Brazing heats the parts without melting them and flows a filler alloy into the joint. The filler melts at a lower temperature than the base metals, so you can join dissimilar metals such as copper to steel.
• Soldering works the same way as brazing but with fillers that melt at much lower temperatures, such as tin/lead stick solder. Soldered joints are generally weaker than brazed ones and are used for sheet metal, electrical work and light plumbing.

If the joint has to carry load or vibration, or the parts are different metals, brazing is usually the better choice. If the parts are thin, heat-sensitive or electrical, soldering may be all you need.

Types of brazing rod

Silver brazing rods

Silver brazing rods are sold by silver content. The product data for our silver rods shows how the percentage changes the working range:

• 15% silver: 645-800°C. Described as having excellent flow and ductility, suited to joining ferrous and non-ferrous metals and to applications with higher vibration.
• 45% silver: 630-730°C. An economical general-purpose alloy.
• 56% silver: 620-650°C. Made for stainless steel in food and beverage work, with a good stainless steel colour match.

As the figures show, a higher silver content gives a lower and narrower melting range. That means less heat into the part and a filler that runs into the joint quickly once it reaches temperature. Lower-silver rods have a wider range, which suits general repair work.

The Silver Brazing Rod (sold per stick) comes in 15%, 34%, 45% and 56% silver at 1.5mm. The 15%, 34% and 45% sticks are 75cm long. A 2.4mm 15% stick and a 56% 1.5mm × 460mm stick are also sold separately.

Flux-coated vs bare rods

Bare rods need flux applied separately, either by dipping the hot rod into flux or by brushing flux onto the joint. Flux-coated rods carry it on the rod, so there is one less thing to manage on site. Our silver brazing rods are bare. Our nickel silver tinning rods are flux-coated. The Red Nickel Silver Tinning Rod 2.4mm uses a Safe Vue moisture-sealed coating. According to its listing, the coating reduces odour and glare, grips well on dirty steels and cast irons, and keeps longer than conventional sodium flux rods.

Bronze and nickel silver rods

Low Fuming Bronze Rod is a general-purpose copper-base brazing rod. It is used for gas brazing steel, copper alloys, cast iron, nickel alloys and stainless steel, and comes in 1.6mm and 2.4mm, with a 3.2mm 4.54kg pack also listed. The red nickel silver rod is listed for high-strength joining of steels, using either thin-flow or bead-form technique.

Aluminium brazing rods

Aluminium is a separate family. Silver, bronze and nickel silver rods are not the right filler for aluminium. Use a rod sold specifically for aluminium, such as the Aluminium Low Temp Brazing Rod. Aluminium forms a tough oxide skin and conducts heat away quickly, so clean the joint well and follow the rod maker's instructions on temperature and flux. If you have been searching for Tradeflame aluminium brazing rods, check the technique and flux needs on the packaging or datasheet of whichever rod you buy, because aluminium rods vary between makers.

Flux: matching it to the rod

Flux keeps oxides from forming while the joint heats, so the filler can wet and flow. Use the flux the rod is meant for:

• Brazing Flux Powder 303 (227g): an all-purpose powder for braze welding copper, brass, bronze and steel. It is listed to suit low fuming bronze, nickel silver, tobin bronze and silicon bronze rods.
• Weldbraze Flux Soldering Liquid 100ml: a general-purpose corrosive liquid flux for copper, bronze and low carbon steel. It contains zinc chloride, and the maker says to clean the surface thoroughly before applying it.

Silver brazing alloys are normally used with a flux made for silver brazing. Check the rod's datasheet for the recommended flux before you start. Whatever flux you use, remove the residue after brazing as the maker directs, especially with corrosive fluxes.

Compare the in-stock rods and fluxes

How to choose a rod by base metals

• Stainless steel, food and beverage gear: 56% silver, for the lower working range and stainless colour match.
• Copper to brass, or copper to steel: the 15% silver rod is listed for ferrous and non-ferrous metals and for vibration, so it suits mixed-metal joints such as fittings on machinery. For general bench work at a lower cost, 45% is the all-rounder.
• Copper to copper: the 15% rod is listed for non-ferrous metals, and the 45% is the general-purpose choice. A higher silver content means a lower working range, so less heat goes into the pipe or fitting.
• Steel and cast iron repairs, heavier sections: low fuming bronze with Flux Powder 303, or the flux-coated red nickel silver rod, which is listed as gripping well on dirty steels and cast irons.
• Aluminium: an aluminium brazing rod only.
• Light sheet metal or electrical: soldering may be enough. 50/50 Stick Solder is listed for sheet metal, non-potable plumbing, electrical and electronics, and is not for drinking water systems.

Tips for a good brazed joint

• Clean both parts back to bright metal and remove oil. Flux cannot make up for a dirty joint.
• Keep the gap close and even so the filler can draw through the joint.
• Heat the parts, not the rod. Let the work melt the filler so it flows towards the heat.
• Heat the heavier part more when joining thick to thin or copper to steel.
• Read the safety data sheet (SDS) for the rod and flux before use, and follow its ventilation and PPE advice.

FAQ

What silver percentage brazing rod should I buy?

For general repairs, 45% is the economical all-rounder. For mixed metals under vibration, use 15%. For stainless in food and beverage work, use 56%. A higher silver content gives a lower, narrower working range.

Can I use a silver brazing rod on aluminium?

No. Use a rod made for aluminium and follow its maker's guidance on flux and technique.

Do I need flux with a silver brazing rod?

Our silver rods are bare, so plan on a separate flux. Check the rod's datasheet for the recommended type.

What heat source do I need?

Brazing needs a gas torch that can bring the whole joint up to the rod's working range. For example, the 15% silver rod works at 645-800°C. Small parts can be done with a hand torch, while larger sections need an oxy or LPG brazing tip with more heat.

Is brazing as strong as welding?

A well-made brazed joint is strong for many repair and fabrication jobs and can join metals that cannot be welded together. Structural welds on steel should still be welded.

Browse silver, bronze and aluminium brazing rods and fluxes in the Duroweld range, or see soldering irons for lighter work.