The surfacing welding technology is a kind of technology which is used to pile materials with certain mechanical ability on the welding surface of the base material. The purpose is not to directly weld with the base metal, but to obtain the surface of the weld with wear resistance, heat resistance, corrosion resistance and other special properties of the cladding metal welding surface, but also to restore or increase the size of the weld, the surfacing welding method has been widely used in manufacturing and repair.
Selection requirements for surfacing metals
The surfacing metal should first meet the use conditions of the welding base metal, then consider the surfacing metal welding mechanical ability is good, and then choose the most appropriate method.
Among the common welding methods, all-argon surfacing welding technology has the advantages of small heat input and small deformation. After welding, it has the advantages of small expansion coefficient, beautiful weld formation and good interlayer fusion ability, which are widely used in surfacing welding. Today I would like to introduce the requirements of surfacing welding technology.
Carbon steel and stainless steel surfacing welding
Welding example: pressure vessel flange face waterline seal disc. In order to ensure the large manhole flange surface corrosion resistance requirements, the carbon steel layer can not directly contact the chemical raw materials. Choose a layer of stainless steel surfacing on the carbon steel metal as the contact surface.
Welding material selection
ER309MO carbon steel Q345R hardfaced metal S31603. The surfacing welding thickness is 6mm and height is 6mm.
The two types of austenitic plus carbon steel are used in welding although the 309L wire can be used directly. However, due to the application in class 2 containers containing high temperature, corrosion medium, to choose some advanced MO ingredients.
The first welding current, 135A; The second layer 160A; The last layer is 150A. The heat input is related to the deformation capacity of the base metal. Strict control of the current is an important factor in welding.
First layer welding
When the first layer is welded, it is required to melt the deep metal as quickly as possible and move quickly. Keep the welding thickness of the first layer below 3 mm. Swing width to be small, after the completion of a round of welding in the second round of welding. When the first layer of overlaying is finished. Bring the temperature down to a second layer of soldering. Press the bead between each bead in 1/2 position of the first bead. Pressure channel control can not be too small, too small easy to cause low between layers. Too much will cause tension too concentrated crack defects.
When the second layer is welded, the current is slightly amplified so that the second layer and the first layer fuse well. The welding swing can be appropriately amplified. The number of press-down loops can be reduced between the second pass.
The last layer is welded
When welding the last layer, you should master the height of the welding. Height of 6mm allows stacking up to more than 8mm. The excess metal can be processed into surplus. Height less than 6 mm cannot be machined to turning tool. In order to avoid the processing is not in place due to the large welding pattern, the last layer can adopt the straight drawing method, so that the fusion between the weld intermediate layers is tight.
The gas flow is 12L
The gas flow is 12L. Argon flow control cannot be too small, which will cause too much oxidation and the molten iron cannot be spread out. The excessive flow of argon will cause the deviation of welding gas and thus generate arc ladle. The purity of argon is recommended to be high purity argon, and the protruding length of tungsten pole should be controlled below 6mm.
Weld from the outside in
When welding, weld from the outside in so that the resulting contraction force is directly in the circle. When there is a vertical fillet position, it is necessary to use direct melting welding without adding wire. Melt the weld at the included Angle and then wire weld.铜焊丝,Copper Welding Rods,铝焊丝,aluminium welding wire,镍焊条,Nickel electrode,药皮焊条,Flux Coated Brazing Welding Rods