Stainless Steel EFW Welded Pipe is a type of stainless steel pipes that is produced through electric fusion welding. The electric fusion welding is a process in which high voltage electricity is passed onto the material to heat and melt it. These pipes are welded by rolling the plates and welding the seam and then cleaning the weld flash with scarfing blades.
Since the material is fully melted, pressurization is not required after the process. X ray welding is relatively new in the electric fusion welding technology. X-rays require special conditions to be used. So the room requirements are higher and costly with X-ray welding. But as a compliment, the X-rays focus on smaller spot with accuracy and can melt the metal faster. This allows the impacted zone to be as minimal as possible.
So the mechanical properties of the material remain intact for the most part. Usually with electric fusion welding there could be a small deformation of the pipes. With X-rays, the deformation is little to none. So the pipe does not need additional treatments in terms of wall thickness, absolute roughness or the shape. For these reasons, manufacturers are turning to X-ray welding for efw pipes.
ASTM A 358/A 358M Specification for Electric-Fusion-Welded Austenitic Chromium-Nickel Alloy Steel Pipe for High-Temperature Service.
Five Classes of pipes are covered :
ASTM A358 Class 1 - Pipe shall be double welded by processes employing filler metal in all passes and shall be completely radiographed.
ASTM A358 Class 2 - Pipe shall be double welded by processes employing filler metal in all passes. No radiography is required.
ASTM A358 Class 3 - Pipe shall be single welded by processes employing filler metal in all passes and shall be completely radiographed.
ASTM A358 Class 4 -Pipe Same as ASTM A358 Class 3 except that the weld pass exposed to the inside pipe surface may be made without the addition of filler metal.
ASTM A358 Class 5 - Pipe shall be double welded by processes employing filler metal in all passes and shall be spot radiographed.
ASTM A409/SA409 Welded Large Diameter Austenitic Steel Pipe for Corrosive or High Temperature Service
ASTM A 778 Specification for Welded, Unannealed Austenitic Stainless Steel Tubular Products
ASTM A789/A789M, ASME SA789/SA789M Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing for General Service
ASTM A790/A790M, ASME SA790/SA790M Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe
ASTM A813/A813M Standard Specification for Single- or Double-Welded Austenitic Stainless Steel Pipe
ASTM A814/A814M Standard Specification for Cold-Worked Welded Austenitic Stainless Steel Pipe
DIN 17455 Welded circular stainless steel tubes with general quality requirements -Technical delivery conditions
DIN 17457 Welded circular austenitic stainless steel tubes subject to special requirements
EN 10216-5 Welded Stainless Steel Tube
EN 10296-2 Welded circular steel tubes for mechanical and general engineering purposes - Part 2: Stainless steel
JIS G3468 Large Diameter Welded Stainless Steel Pipes
JIS G3446 Stainless Steel Pipes for Machine and Structural Purposes