Welding of Carbon Steel
Carbon steel is a widely used material due to its high strength, mechanical properties and low cost. The ability to reliably weld carbon steel is essential for fabrication of many structural components. In order to properly weld carbon steel, some important considerations need to be taken into account. These considerations include welding equipment, electrode type and angle, welding parameters, weld joint design and post-weld heat treatment.
Welding Equipment
The type of welding equipment used for carbon steel depends on what application the welded joint will be used for. For example, shielded metal arc welding (SMAW) or gas metal arc welding (GMAW) is often used for general fabrication purposes. These welding processes add little or no filler metal, require fewer preparations, and are relatively simple and easy to operate. For more critical applications, shielding gas needs to be used, such as with tungsten inert gas (TIG) welding and metal active gas (MAG) welding. With these processes, the welder can control the weld pool and weld deposition rate precisely.
Electrode Type and Angle
When welding carbon steel, the appropriate type of electrode should be selected. This selection depends on the type of steel, thickness of the material, and desired welding process. For example, an E6013 or E7018 can be used for general purpose applications. But for more critical and higher strength applications, an E81T1-NI2 flux-cored wire can be used. The welding angle needs to be given careful attention throughout the welding process. Mainly, the angle and direction of the electrode should be the same as the plate being welded. This helps ensure that the weld pool forms properly.
Welding Parameters
Selecting the right welding parameters is essential for achieving good quality welds with carbon steel. Firstly, the amperage should be kept within the manufacturers’ parameters range. Too high or low an amperage could cause an underfilled or overfilled weld bead. Additionally, the polarity of the electrodes should also be adjusted as per the manufacturers’ instructions. Too little heat input will cause arc blow, while too much heat input can cause the welds to become over-penetrated.
Weld Joint Design
The weld joint design for carbon steel welds depends on the type of application it will be used for. Generally, the most common joint designs are T, K, lap and corner joints. The T-joint is the most versatile and widely used joint type, as it is used in many different welding processes. This joint allows access to all sides of the joint and welds can be completed on one or both sides. Furthermore, the joint should be designed to give uniform thickness and make sure the joint sides are properly aligned together.
Post-Weld Heat Treatment
Post-weld heat treatment (PWHT) is an important aspect of welding carbon steel. This method helps to influence the structures, hardness and strength of the welds. PWHT also promotes the benefits of yield strength and ductility as well as reducing the risk of fracturing. It should also be noted that if filler materials of different types are used in the welding process, the PWHT should be adjusted for optimal performance.
In conclusion, a number of important considerations need to be taken into account when welding carbon steel. This includes selection of welding equipment, the type and angle of the electrode, setting up of the welding parameters, weld joint design, and post-weld heat treatment. All of these steps are important to ensure quality welds and safe fabrication of the components.
