Welcome To Aluminium Brazing Blog

aluminiumWelcome To Aluminium Brazing Blog
 
Then I let the parts cool, it`s best to let the metals cool slowly in the air.  Copper content above 60% yields reduced strength and liquidus above 900 °C. Silver content above 85% yields reduced strength, high liquidus and high cost. Silver-rich brazes (above 67.5% Ag) are hallmarkable and used in jewellery; alloys with lower silver content are used for engineering purposes. Alloys with copper-zinc ratio of about 60:40 contain the same phases as brass and match its color; they are used for joining brass. Addition of cadmium yields Ag-Cu-Zn-Cd alloys with improved fluidity and wetting and lower melting point; however cadmium is toxic. Wider melting range than Au-Cu alloys but better corrosion resistance and improved wetting.Torch brazing copper tubing is one of the most common-but widely misunderstood-joining processes.  Copper may be added to lower gold proportion, chromium to compensate for loss of corrosion resistance, and boron for improving wetting impaired by the chromium. Makes the joint less prone to fail due to intergranular penetration when brazing alloys of nickel, molybdenum, or tungsten. High affinity to oxygen, promotes wetting of copper in air by reduction of the cuprous oxide surface film. When present in alloys being joined, may destabilize the surface oxide layer (by oxidizing and then volatilizing) and facilitate wetting. Diffusion away from the braze increases its remelt temperature; exploited in diffusion brazing.We produce Ti-Zr-Cu-Ni near-eutectic alloys having the lowest melting points and brazing temperatures amid all conventional filler metals for vacuum joining of titanium.  Rapidly diffuses to base materials, may lower their melting point; especially a concern when brazing thin materials. Particularly useful for alloys of four or more components, where the other additives compromise flow and spreading. Deoxidizer, decomposes copper oxide; phosphorus-bearing alloys can be used on copper without flux. In some cases, especially for vacuum brazing, high-purity metals and alloys are used.Silver brazing is a joining process whereby a non-ferrous filler metal, alloy is heated to melting temperature (above 800°F) and distributed between two or more close-fitting parts by capillary attraction.  Forms brittle phosphides with some metals, e.g. nickel (Ni3P) and iron, phosphorus alloys unsuitable for brazing alloys bearing iron, nickel or cobalt in amount above 3%. The phosphides segregate at grain boundaries and cause intergranular embrittlement. The tinning of the alu plate was much much easier than the doing the copper tube, very astounding.Self fluxing copper based brazing alloys containing phosphorus thereby facilitating brazing on copper to copper in air without the use of a flux.  Care must be taken to not introduce deleterious impurities from joint contamination or by dissolution of the base metals during brazing. When the brazing temperature is suitably high, brazing and heat treatment can be done in a single operation simultaneously. For successful wetting, the base metal must be at least partially soluble in at least one component of the brazing alloy. The molten alloy therefore tends to attack the base metal and dissolve it, slightly changing its composition in the process. Alloys that do not significantly attack the base metals are more suitable for brazing thin sections.
 
For example, some alloys dissolve both silver and copper; dissolved silver lowers their melting point and increases fluidity, copper has the opposite effect. As the remelt temperature can be increased by enriching the alloy with dissolved base metal, step brazing using the same braze can be possible. Nonhomogenous microstructure of the braze may cause non-uniform melting and localized erosions of the base metal. Wetting of base metals can be improved by adding a suitable metal to the alloy.Copper wets ferrous metals that silver does not attack, copper-silver alloys can therefore braze steels silver alone won`t wet. The effect works both ways; there can be detrimental interactions between the braze alloy and the base metal. I used your method to solder 10mm copper Tubing to an Aluminium plate(as a water cooling device for an Video card).Presence of phosphorus in the braze alloy leads to formation of brittle phosphides of iron and nickel, phosphorus-containing alloys are therefore unsuitable for brazing nickel and ferrous alloys. That works always on dirty (oil saturated for example) metals impossible to weld with TIG or MIG, as the flux fluorides are nasty but very effective for cleaning the alu. It melts first then the wire melts and that`s how it fluxes the joint to be welded.I have repaired a Honda gear box carter, after 4 attempts by other shops using MIG and TIG, with my good old aviation torch; the welding was a breeze with a fluoride flux and 4047 rods. Aluminum melts at 660 degrees C and is normally done with a MIG welder with Argon gas and aluminum filler wire, eg roo bars on 4WD and trucks. I just felt the need to clearly explain the different ways of joining the metal with heat and without heat.The strength of a soldered joint depends on so many variables that you simply can`t rely on it. Today`s techniques for advanced boat building is not to weld anything at all but to design a seam that can be glued using heat curable adhesive similar to that used in some aircraft construction. If the area being joined is heated hot enough in the presence of a reducing substance, such as excess acetylene, then the oxide layer will be stripped away leaving the reactive metal. For the soldering that is subject of this instructable, there needs to be a flux or other reducing agent to remove the oxygen.