Nickel base weld overlays are commonly used in the Power Industry to extend the life of equipment subjected to aggressive corrosion enviroments. As boiler conditions have become more aggressive over the years,Nickel base alloy overlays have become more commonly used,not just for repair and maintenance purposes,but also as a cost effective solution for new boiler installations.
Our company mainly adopts gas shielded surfacing technology. Compared with other surfacing methods, gas shielded surfacing has the following advantages:
(1) Gas shielded welding is a kind of open arc welding. During the welding process, the heating and melting of arc and molten pool can be clearly seen, which is convenient to find problems and timely adjust, so the welding process and weld quality are easy to control.
(2) Gas shielded welding usually does not need to use tubular welding wire, so there is no slag in the welding process and no slag cleaning after welding, which saves the auxiliary labor hours of slag cleaning and reduces the welding cost.
(3) Wide range of application, high production efficiency, easy to carry out all-position welding and realize mechanization and automation.
(4) Suitable for welding most metal and alloy, most suitable for welding carbon steel and low alloy steel, stainless steel, heat resistant alloy, aluminum and aluminum alloy, copper and copper alloy and magnesium alloy.
There is a wide range of weldable metal thicknesses, with the thinest about 1mm and the thickest almost unlimited.
(5) The adaptability is also strong, and the welding efficiency is the highest when flat welding and horizontal welding.
| | | Steel clad with Alloy 625 |
Membrane wall in combustion room – lower area | | |
Membrane wall in combustion room – higher area | | |
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| | » Pipe walls and single tubes in P235GH, 15Mo3, 13CrMo44, 10CrMo910 |
| | » Alloy 622 (US), alloy 625, alloy 686 (super heater tubes)
» Coating alternatives under investigation: metal powder, ceramic, galvanizing |
| | » 4-component shielding gas: He = 32 %, H2 = 2 %, CO2 = 0.05 %, remainder Ar » Alternative choices of shielding gas |
| | » GMAweldingequipmentwithpulsed-currentpowersources » Automatic burner processing |
| | » Vertical down position preferred, layer width 15 - 20 mm |
| | » On-site in the boiler with mobile welding equipment, minimum wall thickness 3 mm » Welding in the workshop weld metal overlay on new pipe walls and single tubes |
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» Overlay thickness 2mm -
» Two layers preferred -
» Sandblastingoftheweldingsurface -
» Water circulation in the tubes -
» Content of Fe in welding surface < 5 % -
» Content of Fe in welding material < 1 % -
» Consider shrinkage -
» End of cladding round-welded with TIG, notch-free |
