Welding of aluminum and its alloys with copper.
Also significant differences in physical and chemical properties of aluminum and copper welding of metals, the formation of brittle intermetallic difficult phase.
Usually perform TIG welding in argon and the layer of flux. To improve the process of welding on copper after cleaning is necessary to apply the coating, which activates the surface of a refractory metal, improves wetting the surface of copper with aluminum. The best is the zinc coating thickness of 50-60 microns, applied by electroplating. Welding technology of aluminum and copper, such as aluminum and steel, ie, the shift in the arc of a heat-conducting metal, in the case of copper, the thickness of 0.5-0.6 base metal.
Bond strength is the strength of commercial aluminum ( kgf/mm2 8.10), the resistivity is slightly higher weld (0.037 Ohm-mm2 / m) than aluminum (0.0313 ohms-mm2 / m). Welds do not change their strength during prolonged heating to a temperature of 150 deg. C. At higher heating bond strength decreases due to the sharp increase in the brittle intermetallic layer. On the border of the connection of the copper intermetallic layer is formed (GuAl2) thickness of 10.3 microns, by a strip of aluminum solid solution of copper in aluminum of the same size. Microhardness of intermetallic layer adjacent to the copper reaches 450-550 kgf/mm2. The presence of this zone causes a relatively low bond strength. If the thickness of the intermetallic layer is less than 1 micron, it does not affect the bond strength. strength of the connection, as well as in steel-aluminum compounds, increases with the doping of the weld metal silicon (4-5%) and zinc (6-8%), as these elements inhibit the growth of intermetallic layer. To ensure the stable strength of welded joints on weld bevel edge of the copper is needed at an angle of 45-60 degrees. When welding aluminum with copper Ml grade A5 layer on a standard flux used for welding aluminum (AN-A1) with metal thickness up to 20 mm, use the wire mark AD1 2.5 mm in diameter. When welding electrode is necessary to shift from the bevel to 5-7 mm in the direction of copper. When welding on a layer of flux strength of welded joints is 7-8 kgf/mm2, the electrical conductivity remains at the level of electrical conductivity of aluminum.
Welding of aluminum alloy with titanium OT4. usually used argon-arc welding with tungsten, titanium front edge which is purified from a layer and pollution and alitiruyut in pure aluminum at a temperature of aluminum, 800 - 830 deg. C for 1-3 min. In this case, during the formation of a connection between aluminum and titanium is less than the period of retardation and brittle intermetallic compounds along the line did not have time to form. edges are pre-cut up (V - shaped cutting) Before welding on the edge of the overlay layer is aluminized pure aluminum (5-8 mm) using a wire mark AB00 5-8 mm. The connection is welded by the usual method, as an aluminum alloy. Tensile strength of welded joints of alloys OT4 + AMg6 depends on the layer of aluminum and is 11-27 kgf/mm2, bending angle 17-30 degrees.
Welding of titanium and copper and its alloys. Welding difficult properties and a large difference in the formation of brittle intermetallic compounds. The most successful fusion welding using intermediate insertion of a specially melted alloys of titanium alloyed with molybdenum, niobium or titanium, which lower the temperature of the transformation of al; P and provide the uniform titanium alloy with a stable structure that is not very different from the structure of the copper. You can use the combination of paste alloy Ti + 30% Nb alloy, and VT15. These alloys for welding copper to provide a tensile strength of MH connection 22-22,5 kgf/mm2 and bending angle of 140-180 degrees., and welding with bronze 26 - 28 kgf/mm2 and the bending angle 100-160Q. In the interlayer of the line connecting the hardness reaches 470 - 480 kgf/mm2 at a hardness of bronze BrH 0.8 120 kgf/mm2. Welding of niobium, tantalum and molybdenum alloy steel and nonferrous metals. The theoretical possibility of welding of niobium, tantalum and molybdenum from the steel and nonferrous alloys, partly shown above, since these metals are used as intermediates in welding titanium inserts with steel, aluminum and copper.
Tantalum and niobium on the characteristics are close to titanium welding and with it form a solid solutions without the fragile connections. Niobium is also satisfactorily welded with copper and copper alloys, which forms a limited solutions. Tantalum and copper solutions and does not form compounds. Typically used beryllium bronze BrB2. Performed TIG welding in inert gas-shielded, often in chambers with controlled atmosphere and the electron beam.
Welding bimetals. now known application of bimetallic billets of carbon and corrosion-resistant steel, aluminum alloys, steel and copper-nickel alloy MNZH 5 -1 12X18H9T steel and titanium alloy OT4, OT4-1 for welding dissimilar metals. In bimetallic rolled carbon and low alloy steels and aluminum alloys AMg3 and AMg6 thickness ratio in the package 1: 1 and 1.5: 1. Aluminum alloy is connected with the steel at the box office on the sublayer of pure aluminum. Tensile strength of bimetal by the slice, and 9.7 kgf/mm2 Peel 10-15 kgf/mm2. strength of welded joints is highly dependent on the strength of adhesion layers of bimetal and, consequently, on the area of bi-metallic insert. However, non-constructive node connectivity and the lack of quality control of adhesion layers of bimetal often lead to the fact that the compounds of this type do not have the vacuum density. To prevent the occurrence of brittle intermetallic compounds within the bimetal in heating during the welding process must be strictly withstand welding mode. For the bi-metal thickness of 10 - 12 mm we recommend the following regime: by argon-arc welding of aluminum alloy tungsten electrode on the mode I = 140 -160 A, Ud = 14 - 18; v St = 6-7m / h from steel welding in CO2 on the mode I = 100 - 130 A, Ud = 18 - 20 V, v = St. 17 - 20 m / h is most likely the formation of brittle intermetallic compounds in the bimetal StZsp, 12X18H9T AMg6 and alloy when heated above the line of junction temperature of 450 deg. C. When heated to a temperature of 550 deg. C and above bimetal fibers. It is recommended to start from the welding of aluminum, and after cooling the entire site - from the steel.
See also:
Welding of Aluminum
Welding of Titanium
Welding of Copper
Welding of Steel and Aluminum
Welding Steel with Copper
Dissimilar Metals, Nonferrous
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