Chapter 1. Introduction Delmar, Cengage Learning

Transcription

1 Chapter 1 Introduction

2 Objectives After completing this chapter, you will be able to: Discuss the role welding plays in the manufacture of modern products today Explain the primary steps used in welding fabrication Describe the most popular welding and cutting processes

3 Objectives (cont d.) Discuss the importance of careful and accurate part assembly for welding fabrication List the types of jobs available in the welding industry Convert from standard units to metric (SI) units and from SI units to standard units

4 Important concepts Introduction Forge welding (FOW) Joining smaller pieces of metal that can be heated in a forge and hammered together Metal fabrication Building, shaping, and assembling of a product, equipment, or machine from raw metal stock Welded metal fabrication: assembled using welding, thermal cutting, or brazing Weldment: assembly in which all parts are joined by welding

5 FIGURE 1-2A This all-riveted bridge was built in 1922, and is still in use today in San Antonio, Texas. Larry Jeffus

6 FIGURE 1-2B Riveted boiler used in a gold mine in Eagle Nest, New Mexico. Larry Jeffus

7 Welding Applications Modern welding techniques Employed in construction of numerous products Ships, buildings, bridges, and recreational rides Used in space exploration Experiments aboard the Space Station Used in manufacturing Automobiles, farm equipment, home appliances, computer components, mining equipment, etc.

8 Fabrication Steps Process of metal fabrication Layout Cut out Assembling Welding Finishing FIGURE 1-4 One way to lay out parts is to trace them. Larry Jeffus

9 FIGURE 1-5 Oxyacetylene torch cutting a two-inch thick steel plate. Larry Jeffus

10 FIGURE 1-6 Magnetic alignment clamp used to hold pipe in the correct placement for welding. Larry Jeffus

11 FIGURE 1-7 Gas tungsten arc welding was used to join this stainless steel flange to pipe. Larry Jeffus

12 FIGURE 1-8 Angle grinding a weld to prepare it for finish painting. Larry Jeffus

13 Welding Defined American Welding Society s (AWS) definition A localized coalescence of metals or nonmetals produced either by heating the materials to the required welding temperatures, with or without the application of pressure, or by the application of pressure alone, and with or without the use of filler materials

14 Weld Quality The higher the welding standard The higher cost to produce a weld to that standard Fit for service Reasonable expectation that the weld will never fail FIGURE 1-11 (A) Welded in 1945, using bare metal electrodes. (B) Welded in 2008 with GTA welding. A B Larry Jeffus

15 FIGURE 1-12 Farm trailer, 3 miles per hour. Larry Jeffus FIGURE 1-13 Formula 1 race car, 300 miles per hour. Larry Jeffus

16 Welding and Cutting Processes Popular welding and cutting processes Gas metal arc welding(gmaw) Flux cored arc welding (FCAW) Shielded metal arc welding (SMAW) Gas tungsten arc welding (GTAW) Oxyacetylene welding (OAW) Torch or oxyfuel brazing (TB) Oxyacetylene cutting (OAC) Plasma arc cutting (PAC)

17 Gas Metal Arc Welding Uses a solid electrode wire Continuously fed from a spool, through welding cable assembly, and through gun Extremely fast and economical Produces long welds rapidly Used to weld metal ranging in thickness Thin gauge sheet metal to heavy plate metal

18 Flux Cored Arc Welding Uses a flux core electrode wire Continuously fed from a spool, through welding cable assembly, and out through gun GMA and FCA welding Classified as semiautomatic processes Filler metal is automatically fed into welding arc Welder manually moves welding gun

19 FIGURE 1-14 Gas metal arc (GMA) and/or flux cored arc (FCA) welding equipment. Cengage Learning 2012

20 Shielded Metal Arc Welding Uses a 14-inch long consumable stick electrode FIGURE 1-15 Shielded metal arc (SMA) welding equipment. Cengage Learning 2012

21 Gas Tungsten Arc Welding Uses a nonconsumable electrode made of tungsten FIGURE 1-16 Gas tungsten arc (GTA) welding equipment. Cengage Learning 2012

22 Oxyacetylene Welding, Brazing, and Cutting FIGURE 1-17 Oxyfuel gas welding (OFW) and oxyfuel cutting (OFC) equipment. Cengage Learning 2012

23 Thermal Cutting Processes Oxyfuel gas cutting (OFC) Uses high-temperature flame to heat the surface of a piece of steel Forceful stream of oxygen flows out a center hole in the tip Hot steel burns away Plasma arc cutting (PAC) Uses a stiff, highly ionized, extremely hot column of gas Almost instantly vaporizes the metal

24 FIGURE 1-18 Plasma arc cutting (PAC) equipment. Cengage Learning 2012

25 Demonstrations, Practices, and Projects In this textbook: Demonstrations Show how something works, reacts, or how to perform a task Practices Help develop a specific skill Projects Help improve welding skills and develop fabricating skills

26 Demonstrations, Practices, and Projects (cont d.) Assembling the parts May be simple or complicated May require clamps, jigs, or fixtures to hold the parts in place Time spent accurately positioning the part is not wasted Selection of joining process Many processes can be used Consider amount of welds required, metal thickness, and joint design

27 FIGURE 1-19 Motorcycle frame clamped in a welding jig. Larry Jeffus

28 Occupational Opportunities in Welding Widespread growth Welders and tack welders Welding operators and welders helpers Welder assemblers and inspectors Welding shop supervisors and owners Welding salespersons and engineers Metric units Both standard and metric (SI) units are given in this text

29 Table 1-2 Metric Conversion Approximations By using an approximation for converting standard units to metric, it is possible to quickly have an idea of how large or heavy an object is in the other units. For estimating, it is not necessary to be concerned with the exact conversions.

30 Summary This chapter reviewed: The role welding plays in the manufacture of modern products today Primary steps in welding fabrication Popular welding and cutting processes Features of this text Occupational opportunities in welding