Welding is basically a joining process. Ideally a weld should achieve a complete continuity between the parts being joined such that the joint is indistinguishable from the metal in which the joint is made. Such an ideal situation is unachievable but welds giving satisfactory service can be made in several ways. The choice of a particular welding process will depend on the following factors.

1. Type of metal and its metallurgical characteristics

2. Types of joint, its location and welding position

3. End use of the joint

4. Cost of production

5. Structural (mass) size

6. Desired performance

7. Experience and abilities of manpower

8. Joint accessibility

9. Joint design

10. Accuracy of assembling required

11. Welding equipment available

12. Work sequence

13. Welder skill

Frequently several processes can be used for any particular job. The process should be such that it is most, suitable in terms of technical requirements and cost. These two factors may not be compatible, thus forcing a compromise. Table 2.1 of chapter 2 shows by “x” marks the welding process, materials and material thickness combinations that are usually compat­ible. The first column in the table shows a variety of engineering materials with four thickness ranges. The major process currently in use in industry are listed across the top of the table. The information given is a general guide and may not necessarily be valid for specific situa­tions.