Physical Basics

Welding is based on several physical principles that affect how welding is performed and which materials and processes can be used. Some of the main physical principles of welding are explained below.

• Heat transfer: Heat transfer is a fundamental principle of welding. In welding, heat is generated to fuse and join materials together. The heat is generated either by arc, laser, electric current or gas flame. The heat is conducted through the material and results in a temperature rise that leads to the melting and vaporisation temperature of the material.
• Melting and solidification behaviour of materials: The melting and solidification behaviour of materials are important factors in welding. The melting temperature of the material must be reached for the material to melt and bond with other materials. The solidification temperature is the point at which the molten material re-hardens and bonds to the base material. Melting and solidification characteristics vary from material to material and affect the type of welding process that can be used.
• Electromagnetic interactions: Electromagnetic interaction is an important factor in welding. When an arc is generated, electromagnetic forces are created that affect the behaviour of the arc. These forces can cause the arc to be deflected in certain directions or vary the intensity of the arc. The electromagnetic forces also influence the type of welding process that can be used.
• Fluid mechanics: Another important factor in welding is fluid mechanics. Gas flows are used in welding to protect the weld metal from oxidation and contamination. Fluid mechanics affects the way the gas flows through the weld zone and can affect the quality of the weld.
• Thermodynamics: Thermodynamics is the study of heat and energy in systems. Welding generates energy in the form of heat to join materials together. Thermodynamics affects how this energy is generated and used to ensure that the weld is stable and durable.
• Metallurgy: Metallurgy is the study of the structure and properties of metals. Metallurgy affects the way materials react during welding. The various welding processes can affect the microstructure of the materials and therefore the strength and durability of the welded joint. It is important to consider metallurgy when welding to ensure that the welded joint meets the requirements.
• Thermal expansion: Another important factor in welding is thermal expansion. During the welding process, the material heats up and expands. The expansion of the material can cause deformation and distortion which can affect the quality of the welded joint. It is important that steps are taken during welding to minimise thermal expansion and ensure that the material retains its original shape and size after welding.
• Weld geometry: Weld geometry also plays an important role in welding. The way the materials are joined affects the strength and durability of the welded joint. Weld geometry can be influenced by a number of factors, including the type of welding process, welding position, welding speed and the size of the materials.
• Materials science: Materials science is the study of the properties of materials and their behaviour under various conditions. During welding, material properties must be taken into account to ensure that the welded joint meets the requirements. Material properties can change during the welding process, resulting in a change in the strength and durability of the welded joint.

Overall, welding is a complex process based on a variety of physical principles. Knowledge of these fundamentals is essential to the success of the welding process. By considering the various factors, welders can ensure that the welded joint meets requirements and is of high quality.