Transcript Document
Welcome To WELDING PROCESSES. A Presentation by: John Clulow. SAPIS / APIU. T Today there are 4 main welding processes that are used in SAUDI ARAMCO. 1. G.T.AW. Gas Tungsten Arc Welding or TIG Process. Used mainly for root runs and small bore pipe work 2” and below. 2. S.M.A.W. Shielded Metal Arc Welding or Stick Welding. Used for all pipe work 3. G.M.A.W. Gas Metal Arc Welding or MIG. Used mainly in shop fabrication 4. S.A.W Submerged Arc Welding. Used in shop fabrication and production welding. An Overview 1 S.M.AW. Shielded Metal Arc Welding. Manual Metal Arc Welding or MMA is also known as shielded metal arc, stick welding, or electric arc welding. It is the oldest and most versatile of the various arc welding processes. An electric arc is maintained between the end of a coated metal electrode and the work piece. As molten metal droplets from the electrode are transferred across the arc and into the molten weld puddle, they are shielded from the atmosphere by the gases produced from the decomposition of the flux coating. The molten slag floats to the top of the weld puddle where it protects the weld metal from the atmosphere during solidification. The slag must be removed after depositing each weld run. Hundreds of different varieties of electrodes are produced, often containing alloys to add durability, strength and ductility to the weld. The process is mostly used for ferrous alloys in the structural steelwork, shipbuilding and general fabrication industries. Despite the relative slowness of the process, because of electrode changes and slag removal, it remains one of the most flexible techniques and has advantages in areas of restricted access. An Overview 1 Continued. S.M.AW. Shielded Metal Arc Welding. An Overview 2. G.TA.W. Gas Tungsten Arc Welding or TIG. Gas-Shielded Tungsten Arc Welding (also known as gas tungsten arc or TIG welding) is a process, which uses a non-consumable solid tungsten electrode. The electrode, the arc and the area surrounding the molten weld puddle are protected from the atmosphere by an inert gas shield. If a filler metal is necessary, it is added to the leading edge of the molten puddle. An Overview 2 Continued G.T.A.W. Gas Tungsten Arc Welding Continued. TIG welding produces exceptionally clean, high quality welds. As no slag is produced, the chance of slag inclusions in the weld metal is eliminated and the finished weld requires virtually no cleaning. TIG welding may be used for welding almost all metals and the process lends itself to both manual and automatic operation. TIG welding is most extensively used for welding aluminium and stainless steel alloys where weld integrity is of the utmost importance. It is widely used for high quality joints in the nuclear, chemical, aircraft and food industries. An Overview 3. G.M.A.W Gas Metal Arc Welding or MIG. With Gas-Shielded Metal Arc Welding (which is also known as gas metal arc, MIG or MAG welding) an arc is maintained between a continuous solid wire electrode and the work piece. The arc and weld pool are shielded by a stream of inert or active gas. The process is suitable for most materials and filler wires are available for a wide range of metals. An Overview 3 Continued G.M.A.W Gas Metal Arc Welding or MIG. An Overview 3 Continued. G.M.A.W Gas Metal Arc Welding or MIG. MIG/MAG welding is inherently more productive than MMA, where productivity losses occur each time a welder stops to replace a consumed electrode. Material losses also result from MMA welding when the stub of each electrode is thrown away. For every kilogram of coated stick electrode purchased, about 65 per cent becomes part of the weld (the rest being discarded). The use of solid wire and flux cored wire has increased this efficiency to 80-95 per cent. MIG/MAG welding is a versatile process, which can deposit weld metal at a very high rate and in all positions. The process is widely used on light to medium gauge steel fabrications and on aluminium alloy structures particularly where highrate manual operator production is required. The introduction of flux cored wires is finding increased application in heavy steel structures. An Overview 4 S.A.W. Submerged Arc welding. In Submerged Arc Welding an arc is struck between the work piece and the end of a consumable electrode, both of which are covered by a layer of granular flux (hence ‘submerged’ arc). The arc is therefore hidden. Some of the flux melts to provide a protective slag cover over the weld pool. The remainder is collected for re-use. An Overview 4 Continued. S.A.W. Submerged Arc welding. An Overview 4 Continued S.A.W. Submerged Arc welding. Submerged Arc Welding is principally carried out with fully automatic equipment, although there are hand-held welding guns for the process. To increase productivity an arrangement with several electrodes can be introduced. Because of its high metal deposition rate it is particularly suited to long straight joints of good quality in the flat position. It is widely used in the pressure vessel, chemical plant, heavy structural, repair and shipbuilding industries.