Brazing brass is a thermal process of joining metals or alloys through capillary action. This process uses a filler metal which is melted at temperatures of more than 450 degrees Celsius to join base metals. During the heating of a filler metal a flux chemical has to be used so that it can facilitate the wetting of the metal rather than the formation of oxides. Brazing is normally conducted using hand torches although HF conduction, fixed burners, and resistance heating can also be used.
How to Braze Brass
The brazing of brass is mostly based on capillary action which is the flow of liquid through a narrow space or a tube and against the forces of gravity. When brazing brass to brass there are three metals which are involved, two of these are the metals which are to be joined, called the base metals. The third metal is a filler material which is used to join the base metals.
The first step in looking at how to braze brass involves the setting of a good fit between the base metals so that adequate space in left in a gap. This is a sensitive step which requires skill so that filler metal correctly distributes itself over a clearance. The tensile strength of the joined brass metals is influenced by the distribution of the filler metal; with a narrow clearance the resulting joint becomes stronger. This does not mean that the gap between the brass metals is the best with the least amount of clearance. Instead a balance should be achieved so that a clearance which is too narrow does not inhibit the flow of filler metal and one which is too wide does not reduces the forces of capillary action. In both cases the joint strength is reduced.
The next step in brazing brass is for all the metals to be checked for dust, oil, and grease. Effective joining of the filler to the base brass metals can only work if there is uninhibited contact with all surfaces. Joint formation will be affected by dirt particles on the brass base metals since they will prevent the filler metal from adhering to the surface.
Caution should be practised so that cleaning chemicals do not further contaminate the base metals since this will affect the capillary action. Immediately after cleaning the filler metal should be applied on the brass metals.
Fluxing must be included in the process of brazing brass. In this step a flux chemical is applied on the surfaces of the brass metals so as to seal them from air. This is necessary because during the heating of the base metals oxidation can occur as the heat comes into contact with oxygen. The choice of flux for this type of brazing should be compatible with the brass; it should also be applied immediately before brazing so that it does not dry out.
The base brass metals have to be positioned properly for heating. Supports can be added to give stability to the metals but they supports should be made of poor conductors of heat such as ceramic and stainless steel. Heating is then done broadly over the base metals. Interestingly it is not the filler metal which is heated rather it is the base metals which are exposed to a heat source. On bringing the filler material to contact with the base metals it heats, melts, spreads, and cools to form a joint. The trick brazing brass is to use a filler metal which melts at a lower temperature than the base metals. This way only the filler material melts while the base metals remain in solid form.
The last step in the brazing of brass metals involves the cleaning of the surfaces to remove excess flux and to get rid of oxides scales from the surfaces, if any.
Advantages of Joining brass by Brazing
Brazing is a preferred process of joining metals such as brass, because of the following advantages;
- The metal is easy to work with and it is economical due to compatibility with other metals and alloys. For instance brazing brass to stainless steel or brazing brass to copper can be done with little or no difficulty even though the materials have different components and masses.
- The joints which result from brazing brass are good conductors of heat, they are smooth, and are best suited for liquid and gas leakages.
- Because of the high melting point of brass metals they are not damaged with heating, only the filler metals are affected in this process.
Notes to be taken on the Brazing of Brass
- Caution should be taken not to use leaded brass since it melts before the brazing is started. Also the leaded brass has a tendency to crack during brazing thus leading to poor joint formation.
- A reducing flame and a quality chemical flux should be used to prevent zinc oxide formation.
Rods for Brazing Brass
Amazon.com has a wide selection of bras brazing rods which can be purchased at the lowest prices.
The Bernzomatic NS3 Brazing Rods come with the compatibility for high temperature fuel torches and oxygen torch kits. They are particularly effective for brazing brass to copper. The rods are recommended for use in small brazing applications involving brass metals especially for repair purposes. They are portable and are suited for induction heating.
Other models of brazing rods can also be found at amazon.com. They include the Bernzomatic AL3 Brazing Rods, Import Er 70s 2 1/8 * 36 10lb Tig/ Brazing Rod, and Bernzomatic WB5 Brazing Rods. All these come with improved features for brazing as well as for cutting, soldering, and welding. With the use of these products there is a guarantee of higher quality from brazing brass.
Before any of these products are purchased buyers should be keen to find out if they meet the standard specifications for brazing equipment and if they are fitted for strength and durability. Otherwise the products pose health and safety risks.