Friction Stir Welding of Steel
Friction Stir Welding (FSW) is an innovative welding technique that is becoming increasingly popular and widely used in the industry. This process involves the use of a non-consumable tool that is moved along the workpiece surface at a relatively high speed and with a pressure applied on the material at the contact points of the tool. This generates heat at the contact points and allows the materials to bond together.
The process is well suited to a wide range of materials, including steels, aluminium, magnesium, copper and various alloys, both in thin and thick sections. FSW is particularly attractive for welding steel due to its ability to achieve joints of the same quality as conventional welding with fewer defects.
A wide range of FSW process parameters enable welding of steel to be tailored to the specific requirements of the application. These parameters include the tool rotating speed, the axial feed speed, the traverse speed, and the tool geometry. Hence, FSW is suitable for a range of geometries and steel thicknesses.
As with any weld, it is essential to ensure that the materials to be joined are clean and free from contaminants, scale, rust and dirt. FSW also requires that the work pieces are securely held down to minimize vibration induced by the high speed movement of the tool. It is also important to use the correct tool geometry to ensure maximum joint penetration and optimal weld quality.
As with any weld, it is important to consider the distortion and shrinkage of the joint. FSW typically offers improved control over distortion compared to conventional welding due to the lower peak temperatures involved. This helps reduce residual stresses and cracking, as well as shrinking the heat affected zone and reducing the potential for distortion.
FSW of steel also provides good fatigue properties and fracture toughness. The reduced amount of heat input helps to minimize the grain growth around the weld, helping to improve the fatigue properties compared to traditional welding processes.
All of these advantages add to the cost effectiveness of FSW, with the joint quality and fatigue properties making it a cost-effective solution for a wide range of steel welding applications. It is also highly effective in welding applications in which access is limited or restricted, as the process is extremely efficient and can be completed without the need for a shielding gas.
From automotive manufacture, through to construction and pressure vessels, FSW of steel is increasingly used as a reliable and cost-effective method of joining steel components. The process offers improved control over joint properties and an enhanced ability to fabricate components with fine tolerances, whilst offering improved fatigue properties and good weld integrity. This makes FSW of steel well suited to a wide range of applications which require robust, reliable and cost-effective joints.
