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Metal – Processing

Metal – Processing. Welding. Oxy-acetylene.

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Metal – Processing

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  1. Metal – Processing Welding

  2. Oxy-acetylene This uses a mixture of oxygen and acetylene to create a flame that will at a temperature of around 2500°C at the hottest point. This will clearly be sufficient to melt mild steel at the joint, allowing the melting of a filler rod to fuse the joint edges together. Advantages of Oxy-Acetylene Welding : ·        It's easy to learn. ·        The equipment is cheaper than most other types of welding rigs (e.g. TIG welding) ·        The equipment is more portable than most other types of welding rigs (e.g. TIG welding) ·        OA equipment can also be used to "flame-cut" large pieces of material. Disadvantages of Oxy-Acetylene Welding : ·     OA weld lines are much rougher in appearance than other kinds of welds, and require more finishing if neatness is required. ·     OA welds have large heat affected zones (areas around the weld line that have had their mechanical properties adversely affected by the welding process) Materials Suitable for OA Welding: Most steels Brass

  3. Electric arc An Electric arc generates sufficient heat to melt mild steel at the joint edges by creating an electric current through a gap (arc) between the materials being joined and the filler rod (electrode). The electrode is coated in a flux which, when melted, prevents the joint area becoming oxidised. Today, is commonly used in industries such as the automobile industry for its quality, versatility and speed. Advantages • Versatility - suitable for a variety of positions and applications • Capable of relatively high deposition rates • Enables "one process" operation for individual projects - simplifies training, supervision and logistics Disadvantages • If the weld is not applied in the right place the weld could be weak. • Potential for lack-of-fusion type defects if welding parameters are incorrect or misalignment occurs • Fume extraction may be required

  4. MIG / TIG More refined forms of electric arc welding can be used to join thin sheet material. MIG (Metal Inert Gas) and TIG (Tungsten Inert Gas) welding use a gas jet around the filler wire to prevent oxidation of materials. Different gases are used with different materials, for examples argon is used with aluminium. TIG Welding Advantages •  Superior quality welds •  Welds can be made with or without filler metal •  Precise control of welding variables (heat) •  Free of spatter •  Low distortion TIG Welding Problems • Erratic arc • Excessive electrode consumption • Oxidized weld deposit • Arc wandering • Difficult arc starting MIG Welding Benefits •  All position capability •  Higher deposition rates •  Less operator skill required •  Long welds can be made without starts and stops •  Minimal post weld cleaning is required MIG Welding Problems You need for both of these welding methods a wire feed, different thicknesses of wire needed for different welds which also changes the power and speed needed to correctly weld.

  5. Spot & Seam Both spot welding and seam welding use an electrical current as the heat source. Spot welding, as the name suggests, provides a spot of heat to fuse the metal together. It is usual to fins a series of spot welds in a structure like a car body shell. Advantages ‘spot’ • The process involves less maintenance cost. • Skill of the operator does not influence the quality of spot welds obtained by this process. • The process is normally free from smoke and spatter. Disadvantages ‘spot’ • To achieve low cost of construction, the weld production rate is not very high. • The process proves un-economical as compared to other welding methods. Industrial Spot-welder

  6. Seam Seam welding; a typical application for this type of joining method is thin coated mild steel for food and drinks cans. Advantages of Seam Welding • It can produce gas tight or liquid-tight joints. • Overlap can be less than for spot or projection welds. • A single seam weld or several parallel seams may be produced simultaneously. Disadvantages of Seam Welding • Welding can be done only along a straight or uniformly curved line. • It is difficult to weld a thicknesses greater than 3 mm. • A change in the design of electrode wheels is required to avoid obstructions along the path of the wheels during welding. Diagram of Seam welder.

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