Heat exchange tubes of a heat exchanger are formed of an alloy containing Mn (0.2 to 0.3 mass %), Cu (0.1 mass % or less), and Fe (0.2 mass % or less), the balance being Al and unavoidable impurities. A Zn diffused layer is formed in an outer surface layer portion of the peripheral wall of each heat exchange tube. T200, 0.57A1.5, D/T0.55, and 0.0055A/D0.025 are satisfied, where T is the thickness [m] of the peripheral wall of the heat exchange tube, A is the Zn concentration [mass %] at the outermost surface of the outer surface layer portion, and D is the maximum depth [m] of the Zn diffused layer. The spontaneous potential of the Zn diffused layer is lower than that of a portion of the peripheral wall located on the inner side of the Zn diffused layer.

A process for brazing of aluminium magnesium alloys is described applying a flux which comprises KAlF.sub.4 or CsAlF.sub.4 or both as major constituent. The flux further comprises at least one alkaline or alkaline earth metal compound selected from the group consisting of KAlF.sub.4, CsAlF.sub.4, Li.sub.3AlF.sub.6, CaF.sub.2, CaCO.sub.3, MgF.sub.2, MgCO.sub.3, SrF.sub.2, SrCO.sub.3, BaF.sub.2, and BaCO.sub.3. Preferably the flux comprises or consists of KAlF.sub.4, CsAlF.sub.4, and Li.sub.3AlF.sub.6 and optionally contains also BaF.sub.2.

The invention concerns a flux for brazing, a process for brazing metal parts employing said flux, a flux composition containing said flux, aluminum parts coated with said flux or said flux composition, a process for brazing and a brazed metal object obtainable by said brazing process. The flux is high in KAlF.sub.4 and low in K.sub.3AlF.sub.6.

A flux (55) for superalloy laser welding and additive processing (20, 50), including constituents which decompose when heated in a laser induced plasma or to a melt temperature of the superalloy (42), creating one or more gases (46) that blanket the melt to protect it from air, while producing not more than 5 wt. % of slag relative to the weight of the flux. Embodiments may further include compounds providing one or more functions of surface cleaning, scavenging of impurities in the melt, and elemental additions to the superalloy.

A method and resulting gas turbine engine component (40) having a protective layer of metallic glass (14) deposited over a superalloy substrate (12). A further layer of ceramic insulating material (42) may be deposited over the metallic glass. The metallic glass functions as a bond coat to provide thermal insulation and mechanical compliance. The metallic glass may be deposited onto the substrate by a flux mediated laser deposition process wherein powdered alloy material (18) is melted together with powdered flux material (20). The flux material can facilitate the glass forming process by adding to the solidification confusion effect and/or by providing an active cooling effect.

A method of fabricating a joining preform includes the step of printing a self-fluxing joining alloy. Joining includes brazing and soldering. The self-fluxing joining alloy contains at least one of phosphorus, boron, fluorine, chlorine, or potassium. Another printing step prints a non-phosphorous joining alloy. Both printing steps are performed by an additive manufacturing or 3D printing process. The printing a self-fluxing joining alloy step may be repeated until the non-phosphorous joining alloy is substantially encapsulated by the self-fluxing joining alloy. The self-fluxing joining alloy may be a BCuP alloy, a CuP alloy, a CuSnP alloy, a CuSnNiP alloy or a CuAgP alloy. The non-phosphorous joining alloy may be a BAg alloy, a BNi alloy or a BAu alloy.

A flux-cored wire comprising a flux which is a core and a hoop which is an outer skin or sheath is described. The flux includes a strong deoxidizing metal element containing Mg and Al, and a fluoride powder. At least 60 mass % of a strong deoxidizing metal powder related to the strong deoxidizing metal element has a grain size of at most 150 m. At least 60 mass % of the fluoride powder has a grain size of at most 75 m. The flux is present at a concentration of 10-30 mass % relative to a total mass of the flux-cored wire. The flux-cored wire also requires a specific composition of elements.

A flux-cored wire for arc welding, including a steel sheath filled with flux, where the wire contains, relative to a total mass of the wire, Cr: 16.0 to 22.0 mass %, Ni: 6.0 to 11.0 mass %, Mn: 0.7 to 2.6 mass %, Si: 0.1 to 1.1 mass %, Zr: 0.2 to 0.8 mass %, Fe: 45.0 to 65.0 mass %, TiO.sub.2: 5.0 to 9.0 mass %, SiO.sub.2: 0.1 to 2.0 mass %, ZrO.sub.2: 0.5 to 3.0 mass %, and Bi: less than 0.0020 mass %. Where by mass %, a Si content is denoted by [Si] and a Zr content is denoted by [Zr], a value of parameter A expressed by A=[Si]+2[Zr] satisfies 1.4 to 2.5.

Low melting temperature flux materials for brazing applications and methods of brazing using the same are provided. A low melting temperature flux material for brazing applications includes as a majority constituent, a Cs-containing flux material, as a first minority constituent, a eutectic blend composition, and, optionally, as a second minority constituent, a mediating compound. The second minority constituent is present in the low melting temperature flux material in a lesser amount with respect to the first minority constituent.

A flux for electroslag welding used for electroslag welding may include a basic oxide, an amphoteric oxide, an acidic oxide, and a fluoride. With respect to a total mass of the flux, the basic oxide may include 5.1 mass % or more and 30.0 mass % or less of CaO, the acidic oxide includes 17 mass % or less of SiO.sub.2, and the fluoride includes 35 mass % or more and 73 mass % or less of CaF2. A content of the CaO is 30 mass % or more with respect to a total mass of the basic oxide, a content of the SiO.sub.2 is 80 mass % or more with respect to a total mass of the acidic oxide, a content of the CaF.sub.2 is 80 mass % or more with respect to a total mass of the fluoride, and a value of (2[CaF.sub.2]+[CaO])/[SiO.sub.2] is 5 or more and 56 or less.