Joining processes can be broadly classified into two categories—permanent joining processes and temporary joining processes. A permanent joint is one that does not allow easy dismantling of assembled parts; while a temporary joint allows easy dismantling of assembled parts without rupturing the components. However, a permanent joint is adequately sound, inherently leak-proof, and can sustain much higher load. Welded joint and riveted joints are common examples of permanent joint, while fasteners are temporary joints.

By definition, welding is one of the manufacturing processes by which two or more similar or dissimilar materials can be joined permanently by coalescence formation with or without the applications of external pressure, heat or filler material. There are hundreds of different welding processes; some of them are manual metal arc welding, tungsten inert gas welding, resistance spot welding, diffusion welding, forge welding, etc.

Various features of welded joints are:

  • It is one type of manufacturing process.
  • It is a permanent joining process.
  • It can join two or more parts together.
  • It can join similar or dissimilar components together.
  • Joining occurs by coalescence or weld bead formation.
  • It may or may not require filler metal.
  • Application of either heat or pressure is required for joining.

Introduction to welding

Few basic things related to welding are discussed in this topic. Such discussion includes a concise definition of welding with explanation of each terms, Complete list of welding processes, Classification of a large number of welding processes in various ways, Advantages and disadvantages of welding processes with comparison to other joining processes, Concepts of autogenous, homogeneous, and heterogeneous welding—their examples, advantages and disadvantages, Concepts of fusion welding and solid-state welding—relative pros and cons, comparison, etc. To see all such topics, you may browse all topics.

Polarity in arc welding

In the context of arc welding, polarity indicates the way electrical connections are made with power source. With DC power sources, when electrode is connected with positive terminal of power source and work plates are connected with negative terminal, it is termed as reverse polarity, and the opposite connection is called straight polarity.

Consequently, arc welding can be performed with three different polarities—Direct Current Straight Polarity (DCSP), Direct Current Reverse Polarity (DCRP) and Alternating Current (AC) polarity. Their effects on arc welding performance, relative pros and cons, applications, etc. are discussed in this topic. It also discusses which polarity is suitable for which purposes such as to achieve maximum penetration, better oxide cleaning, maximum deposition rate, etc. To see all such topics, you may browse all topics.