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slag inclusion

Slag inclusions:- are nonmetallic solid material entrapped in weld metal or between weld and base metal. In a radiograph, dark, jagged asymmetrical shapes within the weld or along the weld joint areas are indicative of slag inclusions Skip to content Material Welding Slag inclusions are detected by the normal non-destructive testing methods, while non-metallic inclusions are observed in the weld microstructure at high magnification. Understanding what causes slag inclusion is key to reducing their occurrence and ensuring quality welds. Slag inclusion in rt film or a radiography film are visible as dark spot due to their low density compared to the base metal as shown in the below picture. Usually, slag inclusions have a three-dimensional elongated shape, but, in some, in cases, they can be both round and flat. Often slag inclusions are found along the boundaries between the base metal and the deposited metal. When performing multilayer seams, the formation of slag inclusions often occurs along the boundaries between the individual Layers. The cause of the formation of slag inclusions can be the presence of contaminants on welding edges (rust, slag, etc.), too little welding power current, and unnecessarily high welding speed. Slag inclusions in welding or casting can be: Elongated slag, Scattered Slag, Cluster slug. What causes slag inclusion in Welding? Slag inclusions in welds are caused when non-metallic materials are trapped within the weld, preventing it from fully fusing with the base material as shown in the below sketch. Why slag inclusion occur in welding is related to the good practices. Lack of proper interpass cleaning is the major cause of slag inclusion in welding. Other important causes of slag inclusion in welding are: Slag inclusion usually occurs in multi-pass welds due to imperfect cleaning of the slag between the deposition of successive passes. It may also be caused by heavy mill scale, loose rust, dirt, grit and other substances present on the surface of the base metal or bare electrode. Slag trapped in undercuts or between uneven preceding runs may give rise to elongated lines of included slag when a subsequent weld pass is deposited. Slag inclusion is caused by several factors such as improper cleaning of metals before welding, incorrect joint preparation and inadequate coating on welding rods. The melting characteristics of the welding consumable and particularly the viscosity of the resulting slag has an important bearing on inclusions. The molten slag should float freely to the surface of the weld pool and be easily removable on solidification. How can slag inclusions in welding be avoided? To avoid slag inclusions in welding, the following measures are necessary before & during the welding: Thorough cleaning of the surface of the welded edges and the surface of the inner layers of the weld seams during multilayer welding. Use weld weaving within limits. Excessive weld weaving will cause slag inclusion. Use proper welding consumables. Keep joint surfaces (especially gas cut surfaces) and bare filler wires perfectly clean. Avoid undercuts and gaps between deposited passes. Clean the slag thoroughly between weld passes. The strength of a welded joint may be considerably reduced if large irregular inclusions, or elongated lines of inclusions at the weld junction are present. These sometimes give rise to radiating hair-line cracks. The presence of small, isolated, globular inclusions may not however, seriously affect the static strength of a joint and these may normally be disregarded. To rectify this defect, the portions of weld-metal which contain slag inclusions must be removed and then filled with sound weld-metal. What is slag inclusion in casting? Slag inclusion in casting is a defect that occurs during the metal casting process. It is caused when molten slag infiltrates the mold and gets trapped inside the cast part. Slag inclusions weaken the casting overall soundness. The presence of slag in casting also causes an unsightly appearance, making it difficult to accept parts with slag defects. To prevent slag inclusion, proper gating design and maintenance should be employed when pouring molten metal into the mold cavity. This ensures that any slag created during melting does not enter alongside the molten metal. Additionally, appropriate fluxing materials need to be used so that any potential oxides created are removed before being poured into the mold cavity. Finally, operators must constantly check for signs of clogging or debris in order to maintain a smooth flow of molten metal into the molds. 1. #Slag inclusion in welding 2. $Welding defects 3. #Slag #inclusions prevention 4. Welding quality control 5. Welding #inspection 6. Metal fabrication 7. Welding techniques 8. Welding process 9. Welding #defects analysis 10. Welding industry best practices