Chapter 12 61 Copyright Goodheart-Willcox Co., Inc. May not be reproduced or posted to a publicly accessible website. Name ________________________________________________________________ Date ________________________ Class ________________ Assigned Job 12-5 Welding a V-Groove Butt Joint with Backing OBJECTIVE: You will learn to make an acceptable V-groove butt weld with backing. This job will help prepare you to take and pass a typical AWS D1.1 certification test. Do not attempt this job until: • •• You have read all safety precautions. •• You have satisfactorily completed the Shielded Metal Arc Welding (SMAW) Safety Test. • You have received permission from your instructor. NOTE Information relevant to this job: 1. This job requires you to prepare and weld a test plate similar to one specified in AWS D1.1. You will weld a groove weld in 3/8″ (9.5 mm) thick carbon steel plate with a 1/4″ to 3/8″ (6.4 mm to 9.6 mm) thick backing plate. A 1/8″ (3.2 mm) E7018 electrode will be used for all passes. Welding current will be 90A to 140A. 2. Your instructor, or a test supervisor when taking the real certification test, will inspect your work after preparing and tacking the plates, inspect your weld after the root pass is welded and ground, and a third time after the weld is completed. 3. A face-bend and a root-bend specimen will be cut out, prepared, tested, and evaluated. 4. The actual AWS D1.1 Certification is performed in the vertical, 3G, and the overhead, 4G, welding positions. Obtaining the AWS Welding Certification in the 3G and 4G positions will allow you to weld in all welding positions on similar material from 1/8″ to 3/4″ (3 mm to 19 mm) thick. 5. Welding in this job will be in the flat, 1G, position. The goal is to develop proper skills to be applied to other welding positions. Welding skills relevant to this job: 1. Welding skills developed in previous jobs have prepared you for this job. 2. This job uses a backing. A backing is a plate that is welded to the joint to control penetration. In the root pass, it is important to get penetration into each piece and into the backing plate. Poor penetration is a common cause of failure. There will not be a keyhole because of the backing. 3. The root pass can be welded in one of three ways. A Welding Procedure Specification (WPS) may specify which method to use. If not specified, you have three options: • Single stringer root pass. Use a higher welding current to run a wider weld bead. Make sure there is melting and fusion at each side of the two plates where they contact the backing plate. • Two stringers for the root pass. Use a lower welding current. Run one stringer pass, welding directly where one piece of base metal contacts the backing plate. Do not make a wide weld bead or there will not be room for the second root bead. All slag must be removed completely, especially between the weld bead and the backing plate. A power grinder with a wire wheel or an abrasive wheel can do this effectively. Once all slag is removed, weld a second root pass. Direct the arc to the joint where the second piece of base metal contacts the backing. This weld pass must fuse into the second piece of base metal, the backing, and into the first root weld pass. The current may need to be increased for this second root weld pass. • Weave bead for the root pass. Weld the root pass using a slight weave. Pause briefly at each side of the weave motion to melt into the base metal and the backing plate where they meet. 4. Clean all slag after each weld pass. Weld additional intermediate weld passes and cover pass to fill the joint. The weld face reinforcement is to be above flush and not to exceed 1/8″ (3 mm).