Method of welding Welding

CHAPTER 2 LITERATURE REVIEW

2.1 Welding

Joining process plays important role in the manufacturing industries, especially in the assembly sector. The term for joining process is widely in range, covering many aspects of process that may includes brazing, soldering, adhesive bonding, mechanical fastening, and welding. Welding is a joining process which involves metal parts. This process includes melting and joining parts of metal together to form new item or product. Balchin 1991 defines welding as uniting pieces of metal part at joint faces. The faces are melted by heating it with additional similar composition filler metal. Later, the melted faces which are put close together will stick when it cooled. O’con 2000 extend the definition by saying that welding is not just sticking metals together, but it is a total science and the main method of construction and manufacturing used world wide.

2.1.1 Method of welding

A weld occurs when pieces of metal are joined due to the melting at the interface of metal and combine it before it is solidified. This process may be caused by heat, pressure or a combination of both. There are many methods of welding used currently which follow previously described principles. Kalpakjian and Schmid 2006 have divide welding into three methods, which is Fusion Welding, Solid-state Welding and, Brazing and Soldering. 4 When heat alone is used the process is called fusion welding. Referring to Houldcroft 2001, the metal to be weld is melt to form a bridge between the combining parts and will united after it solidifies. Adapted from his book, Figure 2.1 shows that the metal which is melted can come exclusively from the parts to be joined. In other hand extra metal know as filler metal may also included if welded metal is too thick. The name ‘fusion welding’ is used due to the metal workpiece that has to be melted to make joint. Figure 2.1: Fusion welding courtesy of www.llnl.gov Solid-state Welding or Pressure welding usually involves heating the surfaces to a plastic state and then forcing the metal together. The heating can be by electric current or by friction resulting from moving one surface relative to the other. This statement is proven by Rufe 2001, taking resistance welding as an example, defined that the process of this welding is forming of combined metals from the heat obtained by resistance of electric current and by the application of pressure. Spot welding as shown in Figure 2.2 in the next page, is the most common resistance type welding that applies previously stated principles 5 . Figure 2.2: Resistance spot welding courtesy of www.substech.com According to Kalpakjian and Schmid 2006 which defined, Brazing and Soldering can considered as welding and these types of joining require lower temperature than welding. Filler metals are placed in the joint and are melted using external source of heat. When it is solidified, a strong joint is obtained. Figure 2.3 is an example of the two joining process. Both brazing and soldering are different in the temperature used, where needed temperature and joint strength of soldering is lower then brazing. Figure 2.3: Brazing and Soldering courtesy of http:openlearn.open.ac.uk 6 Weman 2003 has provided a schematic presentation of the most common welding method used world wide shown in the Figure 2.4 below. In this figure, brazing and soldering is not listed. Pressure welding Fusion welding Resistance Friction Spot Seam Projection Butt Ultrasonic Cold Pressure Induction Gas Arc Power Beam Process Laser Electron Beam Metal Arc Gas Shield Arc Manual Metal Arc Submerged Arc Gas Metal Arc Gas Tungsten Arc Plasma Flash Welding Figure 2.4: Most common welding methods

2.1.2 Advantages of Welding