O.R.KAVITHA/ CE 312/ DSS WELDING Types of Welds and Welded Joints 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING DEFINITION OF WELDING “Welding is the process of joining together two pieces of metal so that bonding takes place at their original boundary surfaces”. When two parts to be joined are melted together, heat or pressure or both is applied and with or without added metal for formation of metallic bond. 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

TYPES OF WELDING PROCESS Welding process can also be classified as follows: Gas Welding 2. Arc Welding 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING Types of Welds and Welded Joints 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING Defects in welding The lack of training to the operator or careless application of welding technologies may cause discontinuities in welding. The Common weld defects include Porosity Lack of fusion Inclusions Cracking Undercut Lamellar tearing O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING Porosity Porosity occurs, when the solidifying weld metal has gases trapped in it. The presence of porosity in most of the welded joints is due to dirt on the surface of the metal to be welded or damp consumables. It is found in the shape of sphere or as elongated pockets. The region of distribution of the porosity is random and sometimes it is more concentrated in a certain region. By storing all the consumables in dry conditions and degreasing and cleaning the surface before welding, porosity can be avoided. Lack of Fusion Due to too little input or too slow traverse of the welding torch, lack of fusion arises. By increasing the temperature, by properly cleaning the weld surface before welding and by selecting the appropriate joint design and electrodes, a better weld can be obtained. On extending the fusion zone to the thickness of the joints fully, a good quality joint can be obtained 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING Inclusions Due to the trapping of the oxides, fluxes and electrode coating materials in the weld zone the inclusions are occurred. Inclusions occur while joining thick plates in several runs using flux cored or flux coated rods and the slag covering a run is not totally removed after every run and before the next run starts. By maintaining a clean surface before the run is started, providing sufficient space for the molten weld metal between the pieces to be joined, the inclusions can be prevented. 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING Cracking Due to thermal shrinkage, strain at the time of phase change, cracks may occur in various directions and in various locations in the weld area. Due to poor design and inappropriate procedure of joining high residual stresses, cracking is observed. A stage-wise pre-heating process and stage-wise slow cooling will prevent such type of cracks. This can greatly increase the cost of welded joints. Cracks are classified as hot cracking and hydrogen induced cracking. Undercutting The undercut is caused due to incorrect settings or using improper procedure. Undercutting can be detected by a naked eye and the excess penetration can be visually detected. 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING Lamellar Tearing Due to non metallic inclusions, the lamellar tearing occurs through the thickness direction. This is more evidently found in rolled plates. As the fusion boundary is parallel to the rolling plane in T and corner joints, the lamellar tearing occur. By redesigning the joint and by buttering the weld area with ductile material, the lamellar tearing can be minimized. O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

Welded joints and their advantages: A welded joint has following advantages: (i) Compared to other type of joints, the welded joint has higher efficiency. An efficiency > 95 % is easily possible. (ii) Since the added material is minimum, the joint has lighter weight. (iii) Welded joints have smooth appearances. (iv) Due to flexibility in the welding procedure, alteration and addition are possible. (v) It is less expensive. (vi) Forming a joint in difficult locations is possible through welding. 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING Types of Welded Joints Butt joint Corner joint Edge joint Lap joint T joint O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Square Butt Joints Used to butt weld light sheet metal. 1/16 to 3/16 thick metal. O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Butt Joints Butt joints: formed by placing the plates edge to edge and welding them. Grooves are sometimes cut (for thick plates) on the edges before welding. According to the shape of the grooves, the butt joints may be of different types, e.g., 􀂾 Square butt joint 􀂾 Single V-butt joint, double V-butt joint 􀂾 Single U-butt joint, double U-butt joint 􀂾 Single J-butt joint, double J-butt joint 􀂾 Single bevel-butt joint, double bevel butt joint Version O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Butt Joints O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Bevel Butt Joints Used to butt weld heavier pieces of metal together. 3/8 to ½ inch metal can welded using a single V or U joint. ½ Inch metal and up can be welded using a double V or U joint. O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Butt Joints . O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Lap or fillet joint obtained by overlapping the plates and welding their edges. The fillet joints may be single transverse fillet, double transverse fillet or parallel fillet joints O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Lap or fillet joint 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING Lap Joints Used to join two overlapping pieces of metal. Single lap joint welded from one side. Single lap joint welded from two sides develops full strength. Off set lap joint is used when two pieces of metal need to be joined in the same plain. O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Lap Joints Cont. A- single lap joint, one weld. B- single lap joint, two welds. C- offset lap joint. 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING OTHER TYPES OF WELDING O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Corner Joints Used to join to pieces of metal that are approximately right angles to each other. Closed corner joint is used on light sheet metal were strength is not a required at the joint. Half open corner joint is used on heavier metal when welding can only be done on one side. Used when load is not severe. O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Corner Cont. Open corner joint is used on heavy material. It is the strongest of the corner joints. Corner joints on heavy material are welded on both sides. The outside first them reinforced on the inside. O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Corners Cont. O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Edge Joints Used to join two parallel or nearly parallel pieces of metal. Not very strong. Used mainly to join edges of sheet metal, reinforce flanges of I beams, and mufflers. O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Tee Joints Used to join two pieces of metal that are approximately 90 degrees to each other, but the surface of one piece of metal is not in the same plain as the other metal. 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING Tee Joints Cont. A- plain tee B- single beveled C- double beveled D- single J E- double J 6/4/2018 O.R.KAVITHA/ CE 312/ DSS WELDING

O.R.KAVITHA/ CE 312/ DSS WELDING Fillet Welds O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

O.R.KAVITHA/ CE 312/ DSS WELDING Groove Welds O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018

Basic weld types and their symbols Basic weld types and their symbols O.R.KAVITHA/ CE 312/ DSS WELDING 6/4/2018