FCAW: Chapter 12 review questions by:(7th edition by Larry Jeffus)

FCAW: Chapter 12 review questions by:(7th edition by Larry Jeffus) **Comparison with GMAW** FCAW is similar to GMAW in that it uses a constant-potential (CP) or constant-voltage (CV) power supply. What do these power supplies have in common? They are used in FCAW **Atmospheric Contamination** The major atmospheric contaminants of the molten weld metal are oxygen and nitrogen. What are the two main culprits? Oxygen and nitrogen **Slag Functionality** Slag helps an FCAW weld by protecting the hot metal from atmospheric effects, controlling bead shape by serving as a dam or mold, and slowing cooling rates. What does slag do? It helps with protection, control, and cooling **Welding Gun Cooling** Welding guns can be cooled using air or water. How can welding guns be cooled? By air or water **Excessive Drive Rollers Pressure** Excessive drive rollers pressure can cause crushed wire coverage, dropping flux inside the wire liner, and potentially causing stoppage and "birds nest" formation. What problems arise from excessive pressure? � � Crushed wire coverage, dropped flux, and potential stoppage **Large Diameter Electrodes** Large diameter electrodes are not suitable for all-position welding due to difficulty in controlling the arc. Why are large diameter electrodes not ideal? Difficulty in controlling the arc **Lime-Based Electrodes** Lime-based electrodes have low-temperature slag that is difficult to use in out-of-position welding. Why are lime-based electrodes challenging? Low-temperature slag **Slag Properties** Slag is called refractory because it solidifies at high temperatures. Why is slag considered refractory? It solidifies at high temperatures **Mill Scale** The thin dark gray or black layer on new hot-rolled steel is called mill scale. What is mill scale? A thin layer on new steel **Trapped Slag** When slag solidifies on the plate ahead of the weld, it will be trapped, causing slag inclusions. What happens to trapped slag? It causes inclusions **Atmospheric Contamination** Atmospheric contamination of the molten weld pool occurs as it travels across the arc gap and within the pool before it solidifies. When does atmospheric contamination occur? As it travels across the arc gap and within the pool **FCAW Power Supply** FCAW uses a constant-potential (CP) or constant-voltage (CV) power supply, similar to GMAW. What type of power supply is used in FCAW? Constant-potential (CP) or constant-voltage (CV) **Gas Formers** Gas formers force air around the weld zone away from the molten weld pool to prevent contamination. What do gas formers do? Force air away from the weld zone **Deposition Rate** FCAW is capable of depositing 25 lbs/hour (12kg/hour) of weld metal. How much weld metal can FCAW deposit per hour? 25 lbs/hour (12kg/hour) **Deoxidizers and Fluxing Agents**