What is weld overlay

What is the difference between cladding and weld overlay?

cladding :
Clad plate can be formed and fabricated using conventional techniques. The steel is welded using ordinary welding materials and practices. The clad material is welded
using high alloy filler metal. The techniques for welding clad steel are well developed. The explosive bonding process utilizes the high-energy impulse from an explosive charge to drive together the surfaces of the metals to be bonded. The plastic deformation of the metals during the high -energy collision forms a metallurgical bond between them. Explosive bonding can join almost any two (or more) metals. Explosive bonding can be used to fabricate plate, pipe, fittings, and other shapes. Cladding thicknesses for explosive bonding usually range from 1.5 mm to 2.5 cm.
Cladding with corrosion resistant alloys thinner than 1.5 mm is difficult. In some cases, explosive bonding is followed by hot rolling to improve the bond between the steel and corrosion resistant alloy. Weld overlaying is commonly used to clad the surfaces of fabricated steel structures. The actual weld overlay process used depends on many factors including access, welding position, the alloy applied, and economics. In some alloy combinations, dilution of the weld overlay material by the steel requires that more than one weld pass is required. Post weld heat treating to temper the backing steel may be required in some cases. Wallpapering, also known as sheet lining, was originally developed in the 1920’s to fabricate stainless steel clad steel vessels for the chemical process industry. In wallpapering, thin sheets of corrosion resistant alloy are edge welded to the carbon steel structure.
weld overlaying:
In some cases where larger wallpapering sheets are used, plug welds at intervals on the wallpapering sheet are also required. Wallpapering can be a very economical way to provide excellent corrosion resistance for steel structures. Both stainless steels and the more corrosion resistant nickel alloys can be economically applied to steel by wallpapering. Wallpapering has also been widely used to line interiors of stacks and ducting for flue gas desulfurization units in fossil fuel power plants. One major benefit of wallpapering and weld overlaying is that they can be used to repair or modify existing steel structures.



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