Inspection of welding quality

Reply to 1# Yu Yun: TIG welding produces no slag, offers good sealing properties, and makes it less likely for pipelines to get clogged

First, examine the appearance to check for issues such as trachoma, edge biting, or incomplete welding; then, according to the process requirements, determine whether penetrant testing or flaw detection is necessary

It is recommended to download AWS; the images there are very clear. Whether to use TIG welding or arc welding, a WPS should be prepared in advance, following the relevant guidelines.

TIG welding provides better sealing properties, and it is generally required for higher standards; TIG welding is used as a base layer in pipeline welding. Welding is used for sealing outside the pipeline. :victory:

11. Manual arc welding: Manual arc welding is the earliest-developed among various arc welding methods, and it remains the most widely used welding technique to this day. It uses a welding rod coated with flux as the electrode and filler metal, with the arc burning between the end of the welding rod and the surface of the workpiece to be welded. Under the action of arc heat, the coating can produce gases to protect the arc; it can also generate slag that covers the surface of the molten pool, preventing interaction between the molten metal and the surrounding gases. Another important role of slag is to undergo physical and chemical reactions with the molten metal or to add alloying elements, thereby improving the mechanical properties of the weld. Manual arc welding equipment is simple, lightweight, and flexible to operate. It can be used for welding short seams in maintenance and assembly, especially for welding in areas that are difficult to access. Glove welding, using the appropriate electrodes, can be applied to most industrial carbon steels, stainless steels, cast irons, copper, aluminum, nickel, and their alloys. 2. Tungsten inert gas arc welding: This is a type of non-consumable electrode gas shielded arc welding, in which the arc between the tungsten electrode and the workpiece is used to melt the metal and form a weld seam. During welding, the tungsten electrode does not melt; it merely serves as an electrode. At the same time, argon or helium is supplied through the nozzle of the welding torch for protection. Additional metals can also be added as needed. It is commonly known internationally as TIG welding. Tungsten inert gas arc welding is an excellent method for joining thin metal sheets and for performing root welding, as it allows for good control of heat input. This method can be used for joining almost all metals, especially suitable for welding metals such as aluminum and magnesium that form refractory oxides, as well as reactive metals like titanium and zirconium. This welding method produces welds of high quality, but its welding speed is slower compared to other arc welding methods.

There’s no rush; non-destructive testing will do. If it’s urgent, colored testing can be used~

Tubes with small diameters are suitable for PT or MT, while the welds of tubes with large diameters are inspected using RT.

Inspection is necessary before piping welding; care should be taken to ensure that grooves are made on the pipes. For pipes made of materials such as titanium and nickel, TIG welding is used, and color flaw detection is typically applied to such pipes. For pipes made of carbon steel, TIG welding is used for the root layer while electric welding is used for the outer layers. The focus is on checking whether there are any defects such as pores, cracks, or undercuts on the surface of the welds. For some important pipes, flaw detection is required as part of the manufacturing process

Welding quality inspection is divided into visual inspection and internal non-destructive testing. I won’t discuss topics in material mechanics such as strength here. Visual inspection generally includes visual defects such as burrs and weld beads, which can be observed with the naked eye. Non-destructive testing includes the five conventional methods: RT, UT, PT, MT, and ET. TIG welding enables full penetration at the root of the weld, preventing defects such as unwelded areas. The welding quality of TIG welding is higher than that of manual arc welding.