1. Special Metals Fabrication and Welding Processes TSM 233 Unit 15

2. TSM 233 Metallurgy and Welding Processes Objectives: The purpose of this unit of instruction is to provide an overview of the following topics which we do not have an opportunity to do during the laboratory sessions: Additional fabrication processes Additional weld testing methods

3. TSM 233 Metallurgy and Welding Processes Electrical Resistance Welding A welding process that uses the heat produced from electrical resistance to weld metals together. Contacts, usually copper, touch the metal surfaces on opposing sides, electrical current briefly flows across the contacts. Use a step-down electrical transformer Some forms of spot welders use resistance welding http://www.medar.com/video/re sweldvideo.html

4. TSM 233 Metallurgy and Welding Processes Seam Welding Uses electrical current flow across a metal seam as the metal is being formed/rolled. Many forms of metal tubing and pipe are seam welded. Requires very specialized equipment, largely a production type process.

5. TSM 233 Metallurgy and Welding Processes Plasma Arc Welding Same processes as plasma arc cutting without the high forces of the air/gases used to cut the metals. Very similar to GTAW, uses the same processes. Since, we teach GTAW, and the processes are so similar, we do not spend time plasma arc welding in the lab.

6. TSM 233 Metallurgy and Welding Processes Submerged Arc Welding A common weld production technique. Uses an electric arc, and the weld area is covered with solidified, granular flux. Very fast, uses coils of consumable electrode. Can use more than one electrode at a time. Either a semi-automatic or fully automatic process. http://www.matter.org.uk/steel matter/manufacturing/saw_vide o.html

7. TSM 233 Metallurgy and Welding Processes Forge Welding Very old process, still used today in many metal production applications. Metal pieces are heated to forging range (yellow heat for steel) and the two surfaces hammered (forged) together. Drop forging is used to produce many products such as tools, crankshafts. http://science.howstuffworks. com/question376.htm

8. TSM 233 Metallurgy and Welding Processes Friction Welding Metals are “rubbed” against opposing pieces, creates heat, and the pieces bond together. A spinning metal lathe can be used to spin one piece of metal on a stationary piece. Pressure is also used to force the heated metals pieces together.

9. TSM 233 Metallurgy and Welding Processes Plastic Welding While not metals, many plastics can be welded together. Use a heat source, usually an electric heating iron. And, provide a plastic filler material.

10. TSM 233 Metallurgy and Welding Processes Welding Testing Two basic types of weld testing” Non-destructive examinations Destructive testing

11. TSM 233 Metallurgy and Welding Processes Non-Destructive Examinations Visual inspections Magnetic particle inspection – “Magnaflux” – magnetic fields are created and particles will “lineup” surrounding a weld area. Liquid penetrant inspection – Commercial liquid dyes are applied to a weld area to observe defects and uniformity. Ultrasonic testing – uses sound waves “bounced” off of a weld area to record fluctuations. Eddy Current Inspections – electrical current flow patterns are observed. X-Ray Inspections – uses x-ray energy waves to look for weld pattern flaws.

12. TSM 233 Metallurgy and Welding Processes Destructive Tests Bend tests – a test weld is bent to determine weld strength and possible failure. Root bend test. Face bend test.

13. TSM 233 Metallurgy and Welding Processes Destructive Tests Tensile tests – a test weld is pulled apart, determines: Tensile strength Yield point Ductility

14. TSM 233 Metallurgy and Welding Processes Destructive Tests Impact/Hardness tests – hardness testers are used to test the relative hardness of a test weld.