Common surfacing process methods and characteristics
Surfacing is a cost-effective and rapid process for the surface modification of materials. In order to effectively exert the effect of surfacing layer, it is hoped that the surfacing method has a smaller base metal dilution rate, a higher deposition rate and an excellent heap Solder layer performance, that is, high quality, high efficiency, low dilution rate of surfacing technology.
Almost any kind of welding method can be used for surfacing, from the earliest use of gas welding, surfacing electrode welding, so far has developed a variety of semi-automatic, automated surfacing method. Each method of surfacing has its own advantages and disadvantages, commonly used surfacing methods are as follows:
1.Welding electrode surfacing has the advantages of simple equipment, flexible operation, good accessibility, but the workpiece temperature gradient, prone to cracks, and high dilution rate, suitable for small batch and irregular workpiece welding and field repair.
2.TIG welding surfacing with good visibility, easy to control the shape of surfacing, arc stability, no spatter, surfacing quality, manual welding TIG welding workpiece less heat, the advantages of small deformation, Automatic TIG welding to obtain a higher quality surfacing layer, surfacing materials can be solid wire, flux cored wire, but the welding efficiency is low, suitable for welding small and complex shape of the workpiece.
3.Melting gas protection arc surfacing visibility, semi-automatic or fully automatic welding. Process specifications directly affect the dilution rate, short-circuit transition shallow penetration, the dilution rate of only 10%; spray transition dilution rate of 40%, to the molten pool into the auxiliary filler metal, can reduce the penetration, the dilution rate can be reduced to 3% -5%, and improve the deposition efficiency. Self-protection flux cored welding, wire length can be extended, wire diameter available 2.4mm, help to improve the deposition efficiency.
4.Submerged arc welding surfacing has no spatter, no arc radiation, good working conditions, the appearance of smooth, easy mechanization and automation. Can be divided into monofilament, multifilament, with a single pole, with many submerged arc surfacing. Large area corrosion resistant surfacing is the most used with submerged arc welding, submerged arc surfacing than the wire has a lower dilution rate and higher deposition rate, the bandwidth has been developed from 30mm to 60mm, 75mm or even 120mm broadband pole. As bandwidth increases, the device must have a magnetron to prevent biting defects due to magnetic deflection.
5.Electroslag surfacing is the use of conductive slag resistance heat to melt the surfacing material and base metal surfacing process. Currently used more with electroslag surfacing, with submerged arc submerged arc welding with 50% higher production efficiency and lower dilution rate (can be controlled below 10%) and good weld formation, not easy There are slag and other defects. Surface roughness is less than 0.5mm, single layer surfacing to meet the requirements, without machining. Suitable for large area pressure vessel wall surfacing. Electroslag surfacing for surfacing welding work in the hydrogen medium, due to lower welding speed, heat input is larger, resulting in the base metal and surfacing between the coarse grain boundary layer, the surfacing layer resistance Hydrogen induced stripping performance decreased. Because of its heat input is larger, generally only applies to the welding of thick-walled workpiece greater than 50mm.