Welding Machine Parts

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. Consequently, brazing with these alloys is carried out at the temperatures below beta-transus points of such base materials as Ti-6Al-4V or titanium Grade 2. We also produce Ti-15Cu-25Ni ( our brand is TiBraze15-25) that has lower brazing temperature than widely used Ti-15Cu-15Ni.

Compositions and brazing temperatures of these alloys are shown in Table 1. (All table entries are plus or minus 1 percent.)

Copper foil 0.0007 (17 microns) thick is supplied as a filler metal for vacuum brazing titanium to aluminum alloys A3003, A6061, and others. Liquid Al-Cu braze alloy is formed during brazing due to the eutectic reaction in contact of copper foil with the aluminum base metal. The Al-Cu liquid braze alloy reacts with titanium base metal too, providing excellent wetting of both base metals and flow in the joint gap. The structure of brazed joint is shown in picture below. Copper foil preforms can be used together with aluminum foils TiBrazeAl-600 (Al-12Si) or TiBrazeAl-665 (Al-2.5Mg) see Table 3-1, above. Titanium and aluminum parts to be brazed should be slightly compressed during brazing in order to provide contact of base metals with copper foil or aluminum-copper laminated foils that are used as filler metals. Compositions of brazing filler metals that can be obtained when using these three foils in different combinations are presented in Table 4.

We also have experience in the application of aluminum-based filler metals for brazing titanium at low temperature in vacuum or in air (Table 3-1) either for manufacturing structural joint or for repair purposes. These brazing filler metals are supplied in the form of wire or foil (Table 3-2). Strength of titanium brazed joints is presented in Table 3-3.

Aluminum-based brazing filler metals are based on Al-Cu, Al-Mg, Al-Cu-Si eutectics, and modified with Cr and Ti to refine microstructure of brazing joints, and with Beryllium to suppress an ignition during the torch brazing. These filler metals can be used for torch brazing of thin-wall titanium or aluminum articles, for example, for brazing tubing, and repairing fin-plate heat exchangers or honeycomb structures. Torch brazing is carried out with proprietary non-toxic fluxes TBF-42 or TBF-60 based on fluoride and chloride systems.

Brazing filler metals listed in Tables 3-1 and 4 are suitable for vacuum brazing of titanium at the temperatures significantly lower than conventional silver-based and titanium-based filler metals. For new applications and for brazing dissimilar metals, we still recommend evaluation of wetting and gap filling abilities of these new filler metals, as well as testing the strength of brazed joints.

Pictures followed after Tables represent examples of brazed joints made using Aluminum-based filler metals: titanium-to-titanium and titanium-to-copper.