Brass is a general term given to many different alloys of copper and zinc. Many established welders find it easy working with brass, however, brass welding can be problematic if you are just starting.
The key to welding brass the right way is to know the composition of zinc in the brass alloy you are working with.
In this super-specific guide we are going to cover:
- What is Brass and how to find out its composition?
- Different Brass Welding Processes
- Welding Brass to Steel, etc, and
- Some general tips for working with Brass
Let’s dive right in:
What Is Brass?
As already mentioned above, Brass is an alloy of copper and zinc, with a color ranging from light yellow to red-yellow depending on the copper content, which is between 56% and 90%.
Brasses with copper contents between 70% and 90% are called Tombac, the term brass for alloys with 56% to 80% copper is hardly used today.
Brass with a lower copper content is majorly used in pipe welding for pipes, building profiles, or fittings, while brass with a high copper content is used for exotic welding or micro welding i.e for jewelry and works of art.
Brass is characterized by high strength, good formability, and corrosion resistance and hence preferred for circumstances that require such profiles.
Composition Of Brass
Before talking about the brass welding processes, it is important to know the chemical composition of the Brass you are working with.
There are two ways to find out the composition of Brass:
- Using Brass that you know about.
- Getting the brass tested by a Chemist.
Most commonly used Brass with a chemical formula of Cu3Zn2 has a composition of 66% Copper and 34% Zinc.
Why Is It Important to Know the Composition of Brass for Welding?
Brass is an alloy of Copper and Zinc and Zinc affects the overall melting point of it.
For welding, it is absolutely important to know the melting point of the materials you are working with before starting the process.
Zinc has a lower melting point than Copper, and hence overheating can cause serious damages to the weld and from several discontinuities such a porous weld, cracking, etc.
Hence by knowing the composition of the Brass beforehand, you can easily know the melting point and the welding process you have to work with. Primarily oxy-acetylene welding is utilized, however, can be done with any of the welding processes.
If you know which Brass you are working with you can easily jump on the brass welding processes.
Brass Welding Processes
There are several suitable methods for welding brass. These include TIG( Tungsten Inert Gas) Welding, MIG(Metal Inert Gas) Welding or Wire Feed Welding, MAG(Metal Active Gas) Welding, Gas Welding or Oxy-Acetylene Welding, and Autogenous welding.
MIG/TIG Welding Brass
The TIG and MIG welding methods belong to the shielded arc welding processes. MAG welding is also similar to this, however, not commonly used for brass welding.
Here, an arc is formed between the electrode and workpiece and supplies the required heat. The electrode is surrounded by a nozzle from which shielding gas is supplied, protecting the arc and the weld from environmental contamination.
TIG and MIG utilize inert shielding gases such as helium, argon, or nitrogen, while MAG turns the gases into active gases by mixing carbon dioxide or oxygen, which forms a compound with the materials. The process which utilizes Argon gas for welding is called argon welding.
Another difference is the function of the electrode.
With MIG and MAG, the electrode performs two functions: it carries current and is a welding filler metal at the same time, whereas the tungsten electrode with TIG does not melt.
TIG Brass Welding
The TIG process delivers with similar additives even without a covering oxide skin rather low-pore.
The use of zinc-free additives i.e CuSi3Mn1, CuSn12, or CuAl8 electrodes further limits the zinc evaporation and improves the strength properties of the welded joints.
The use of fluxes remains limited in TIG welding to special cases, e.g. the protection of the seam root side in case of one-sided welding through.
Aluminium-containing multi-material alloys (e.g. CuZn20Al2As) are preferably TIG-welded with the high-frequency superimposed alternating current without flux and CuAl8 as filler material.
When applying the first welding layer of zinc-free additive, deeper burn-in into the base material is best avoided by using the brazing technique.
In this process, the base material is melted with the arc in such a way that the direct contact of the arc is limited to the beginning of the build-up of the weld.
To conclude for TIG Brass Welding, CuSn12 or CuAI8 electrodes would be the ideal choice. It is the best choice to get the closest end result you can keeping the color coordination in mind.
MIG Brass Welding
MIG welding requires zinc-free additives such as CuSn6 or CuAl8(consists of 8% Aluminum) similar to TIG brass welding.
However, MIG Brass Welding is best carried out with relatively thin wire electrodes because this shifts the ratio of penetration to deposition rate in favor of deposition rate. Further, the brazing technique described above is more important when applying the first welding layer. Fluxes are rarely used in MIG welding of copper-zinc alloys i.e brass.
The ideal wire for MIG Brass Welding would be CuAl8.
Oxy Acetylene Brass Welding
Besides, the brass can be welded by manual arc welding. Here too, an arc burns between the workpiece and the electrode. However, the electrode is sheathed and forms gases and a slag
when melting.
The gases protect the arc and the weld area, the slag counteracts the melting distortion.
An important point in the instructions for oxyacetylene welding is the flame, by which the workpiece is heated and joined directly or employing an alloyed welding rod. This flame is created by the combustion of acetylene and oxygen.
Oxy Acetylene Brass Welding is performed with oxidizing flame adjustment (up to 30% oxygen excess in copper-zinc alloys, up to 50% oxygen excess in multi-component alloys). Suitable fluxes must always be used for gas welding. In the case of multi-component alloys containing aluminum, excess oxygen due to aluminum oxide formation is not permissible.
If you are just starting out with brass welding, it is advised not to go ahead with gas welding or oxy acetylene as the zinc component of brass tends to vaporize due to high heat.
Zinc Oxide is formed in the process which causes porosity in the weld.
However, Phosphor bronze or Phosphor Bronze No 8 can be joined with oxy acetylene welding, Hence used by sculptors and some hobby welders on their backyard projects.
Electron Beam Brass Welding
Of all the beam welding processes, laser beam welding is suitable for copper-zinc alloys if the focusing optics are protected from the vaporizing zinc by inert gas devices such as a cross jet.
Good results are available with applications of solid-state lasers (Nd: YAG laser, fiber laser) and diode lasers.
Electron beam welding can only be carried out in the atmosphere (NV-EBW = Non-Vacuum Electron Beam Welding) at a short working distance of max. 25 mm. A cross jet is integrated into the beam nozzle protects it from the zinc vaporization.
Other Brass Welding Methods
The EBW likewise new fusion welding process “submerged arc welding” is not suitable for copper-zinc alloys.
All the resistance welding processes, butt welding, spot welding, and seam welding, as well as impulse and high-frequency welding, are well suited.
The same applies to explosive welding, friction, and diffusion welding for alloy thicknesses on the lower side.
Welding Brass To Steel
It’s extremely difficult to weld brass to steel, not impossible though. Still, it is advised to not go ahead with welding brass to steel, instead, brazing can be utilized.
Brazing is a fabrication process similar to welding which involves melting two different materials i.e Brass and Steel here and joining them together with the help of filler material.
Silicon Bronze rod would be the ideal filler rod for brazing of brass and steel.
Brass Welding Problems
Until now you have read about different welding processes used for brass welding and some prerequisites before jumping into the process.
Now:
Many possible problems may occur when welding brass especially if you are starting such as:
- When fusion welding brass, zinc evaporation is the most important factor to consider. If welding is not carried out properly, the evaporation can be very high due to the low boiling point of zinc (906°C). It obstructs the welder’s view, causes porosity, and impairs seam formation.
- Additional difficulties occur when welding brass base materials alloyed with lead if the lead content exceeds 1%. For such brass alloys, fusion weldability is no longer guaranteed due to shrinkage stresses. However, this influence can be reduced by suitable heat conduction and techniques.
- Gas and TIG welding are well suited for fusion welding, Having said that, MIG welding requires the use of zinc-free welding consumables and even then is only of limited use.
- Welding brass should be done with a relatively mild flame or soft arc. All fusion welding processes counteract zinc evaporation by restricting the penetration and avoiding overheating of the welding melt.
General Recommendations For Brass Welding
If you have reached this point, Congratulations, you know 90% more about brass welding than usual welders.
Now I will try to give some general recommendations for brass welding which may ease your selection process and overall method.
- The choice of the filler wire or the filler rod depends upon the composition of brass alloy.
- You should limit the preheat to less than 80 Celcius, going above that may alter the chemical structure of brass you are working with.
- SIFMIG 8 or Sifphosphor Bronze No8 is recommended as the first consideration for brass welding.
- If you couldn’t get hands on the above-mentioned brass types you can go for SIFMIG 328 and 968 or Sifbronze No 32 and Sifsilcopper No 968.
- If you are working on a process that requires a color match then Sifphosphor Bronze No 82 is recommended.
Conclusion
In this article, I tried to briefly explain how brass welding works.
You should make sure that you are well versed in the methods, and the brass pieces are well prepared and clean before jumping straight into processes.
Don’t forget your safety equipment, safety should always be your number one concern. Using welding booths would be the best choice if you are working in your garage.
Happy Welding!