About the metal welding repair
Publish Time: 2016-10-09 Origin: Site
A, the choice of welding current
Generally low carbon steel parts of the welding current, and the relation between the electrode diameter is: I = (3555), d (type I - welding current (amps); d - electrode diameter (mm).
Several kinds of commonly used specifications acid electrode welding when the welding current, commonly used acid electrode of flat welding electrode and current selection table of alkaline welding rod welding current is commonly 90 with specifications acid electrode.
Compared with the same condition of low carbon steel, medium carbon steel, alloy steel welding current general should be smaller.
Second, non-ferrous metal parts welding points
(1) of aluminium and aluminium alloy welding repair
Welding aluminum parts are difficult, this is because, when heat melting aluminum, easy to generate the undissolved alumina membranes, this layer of alumina membrane hinder the continuing heating of aluminum, aluminum oxide can also affect the existence of the combination of metal in welding material and the substrate;Of thermal conductivity of aluminum fairly quickly, so the welding place is not easy to melt.And because the expansion coefficient of aluminium is very big, so deformation is big;Aluminum itself to lose strength during melting, molding not easily under the action of gravity;Aluminum from heated to melt the process, no change color, the operator is difficult to determine the starting time of the temperature and the melting;The sand casting aluminum internal, increased the difficulty of welding.Therefore, neutral flame should be used when welding repair or slightly carbonizing flame welding heat welding, welding nozzle should be chosen than welded steel parts of the same size, caused by the thermal conductivity of the aluminum is strong to overcome the temperature of the loss.But when welding thin-wall parts, with a smaller welding mouth, in case burn through.Electrode had better choose silk, 311, in the case of a request is not high, can be used with a composition similar to that of welding rod (cut off a piece of weldment as electrode can be), or use the same as the welding materials of scrap melting casting into a diameter of 3.5 ~ 6 mm of homemade cast aluminium welding, for convenience of slag, can add a small amount of zinc oxide.Flux must be used (401) aluminium welding powder to prevent metal by oxidation, and absorb the impurity in the molten pool.When using, can weld powder tune into a paste coating on electrode, can be used after drying, also can dip in with the electrode in the welds for use.When heated to melting point, can be found that the surface oxidation film slightly wrinkled and matrix metals have a wave phenomenon, the welds.When the workpiece melting, churn with high melting point metal molten pool, the oxide film damage and allocated impurities and sand.After welding, weld to wash with hot water and its surrounding.
(2) of copper and copper alloy welding repair
Copper and copper alloy welding is difficult than low carbon steel.Like aluminum, the performance and the expansion coefficient of thermal conductivity of copper is bigger also, prone to deformation, in the process of welding, the molten mass easy oxidation, reduce weld strength and toughness.
Copper and copper alloy welding is normally used.Should use neutral flame, when welding the copper and bronze welding general appropriate USES oxidizing flame welding brass, zinc evaporation can prevent welding repair.Borax flux by dehydration or copper welding powder powder (i.e., 301).