Coated Sheet 


Galvanized Culvert Sheet
Fabrication Considerations
The fabricating characteristics of U.S. Steel Culvert Sheet are such that it can be readily corrugated, formed, and lock-seamed to any culvert or corrugated-pipe diameter. The sheet has good formability. It can be welded by the same methods and procedures used for U.S. Steel Galvanized Sheet.

Welding
Galvanized Culvert Sheet can be welded by many of the same methods used to weld conventional galvanized sheet. For metal-arc welding and other high temperature welding methods, precautions must be taken to avoid porosity and cracking of the weld that can be caused by penetration of zinc into the weld pool.

Zinc has a much lower melting point (787°F) than steel and a lower boiling point (about 1600°F). During welding, zinc vapor burns in the air to produce dense, white zinc oxide fumes. These fumes need to be adequately vented. Specific precautions are given in ANSI Publication Z49.1 Safety in Welding and Cutting. The thicker the zinc coating, the more fumes are generated. In general, resistance welding is preferred for joining galvanized sheet products because it results in less fuming than other types of welding

Electric Resistance Welding
	Seam Welding Because the galvanized coating has a lower surface contact resistance than bare steel, welding conditions for galvanized sheet will differ somewhat from those used for welding hot rolled or cold rolled sheet. Generally, higher electrode forces and higher welding currents and/or longer weld-cycle times are required to produce the same fused-zone area in galvanized sheet as achieved with uncoated sheet.  Zinc pickup on the electrodes during seam welding can cause fairly rapid electrode wear. To minimize zinc pickup, the electrodes should be kept as cool as possible by utilizing water cooling and controlling the rate of welding.  For all galvanized products, extremely high welding current is to be avoided, because excessive heating tends to cause expulsion of the zinc coating under the electrodes. The optimum setting of the welding parameters must be determined by trial and are dependent on the specific application and sheet characteristics such as thickness or coating weight.  Seam welding of galvanized steel sheet can be considered to be continuous spot welding; the guidelines for spot welding should be followed for seam welding. To produce acceptable welds, the procedures used for cold rolled sheet should be modified toward slightly narrower electrode width, higher electrode force, higher welding current and slightly lower welding speed.
Restoration of Weld Areas
	When good appearance and maximum corrosion resistance are desired in the weld area, oxides and fluxes from the welding operation should be removed by sand blasting, wire brushing or grinding. Satisfactory recoating methods are soldering, metal spraying or application of metallic-pigmented paints.

Typical Applications Application Considerations Fabrication Considerations Tolerances