vii What’s New? This edition of Modern Welding includes updated content and coverage of new welding top- ics in order to align the textbook with both SENSE Level I and Level II standards. In addi- tion, organization of the arc welding sections of the book has been improved. In this edition, gas tungsten arc welding material is presented in its own section. Coverage of fl ux cored arc welding has been expanded as well. Chapter 31, Procedure and Welder Qualifi cations, has been greatly expanded and revised. A Quick Reference table of contents has been added. The Quick Reference lists useful tables of information that students will likely need to reference repeatedly as they learn to weld. The listed tables help students with tasks such as selecting the proper electrodes, determin- ing proper machine settings, and setting gas fl ow rates. The entries in the Quick Reference are divided into sections based on welding process. End-of-chapter questions have been divided into three headings. “Know and Understand” questions test recall of subject matter, “Apply and Analyze” short-answer questions ask the student to describe, explain, compare, differentiate, etc., and “Critical Thinking Questions” require deeper thinking and engage higher-order thinking skills. In addition, an "Experiment" has been added to the end of each chapter. These experiments encourage students to further explore welding concepts with hands-on activities. This edition also includes new features. Employability features have been added in sev- eral chapters to provide information pertaining to seeking employment and succeeding in a career. Pro Tip features call out work practices and advice. The Nonstandard Terminology fea- tures differentiate between AWS-approved terminology and the nonstandard terms often encountered on the job. Color Code Many of the drawings in Modern Welding are color coded for quick identifi cation of the compo- nents shown. By comparing the color of a component in a drawing to the following color code key, the student can determine the function of the component. In fi gures, travel angles are shown in red and work angles are shown in black to help differentiate between these important angles. Shielding gas (1) high-pressure low-pressure Shielding gas (2) high-pressure low-pressure Air high-pressure vacuum Gases Oxygen high-pressure low-pressure Fuel gas high-pressure low-pressure Weld Base metal or plastic Molten metal or plastic Welding rod Weld bead or surfacing material Flame, arc, or plasma Electrode Flux Slag Fumes Direction or motion Welding machines/equipment Wires, leads, graph curves Water Other Materials Special features, materials, or components not otherwise color-coded How to Use the Key Colors are used throughout Modern Welding to help show the fl ow of different gases and to indicate various materials or equipment features. The following key shows what each color represents.