Welding

By Don Geary and Rex Miller

LEARN THE ART OF WELDING FROM THE GROUND UP

Filled with step-by-step instructions and detailed illustrations, Welding, Second Edition provides an easy-to-follow introduction to oxyacetylene welding and cutting, soldering, and basic metal properties. You'll learn how to set up your workshop, properly use welding equipment, design projects, work safely, and get professional results--even if you have no experience. With coverage of the latest tools, materials, and techniques, this fully updated, hands-on guide serves as an ideal beginner's tutorial as well as an on-the-job reference for experienced welders.

Find out how to:

• Work with oxyacetylene welding fuels, equipment, and supplies
• Review other welding methods, including arc, tungsten inert gas, and gas metal arc welding
• Understand the properties and weldability of various metals
• Use the latest soldering tools and techniques
• Master brazing, braze welding, cutting metal, and welding thicker metals
• Follow welding safety procedures and troubleshoot problems
• Test your knowledge with end-of-chapter review questions
• Design and set up your own home workshop
• Build metal projects, including a gate, fireplace grate, and workbench

• Language: English
• Publisher: McGraw-Hill Education
• Release date: May 2, 2011
• ISBN: 9780071763882

Book preview

Introduction

Welding, Soldering, and Brazing Workers

More than two out of three welding jobs are found in the manufacturing industries. Training ranges from a few weeks of school or on-the-job training for low-skilled positions to several years of combined school and on-the-job training for highly skilled jobs. Employment is projected to grow more slowly than average. Job prospects should be excellent as employers report difficulty finding enough qualified people.

Nature of the Work

Welding is the most common way of permanently joining metal parts. In this process, heat is applied to metal pieces, melting and fusing them to form a permanent bond. Because of its strength, welding is used in shipbuilding, automobile manufacturing, repair, aerospace applications, and thousands of other manufacturing activities. Welding also is used to join beams when constructing buildings, bridges, and other structures, and to join pipes in pipelines, power plants, and refineries.

Welders use many types of welding equipment set up in a variety of positions, such as flat, vertical, horizontal, and overhead. They may perform manual welding, in which the work is entirely controlled by the welder, or semiautomatic welding, in which the welder uses machinery, such as a wire feeder, to perform welding tasks.

There are about 100 different types of welding. Arc welding is the most common type. Standard arc welding involves two large metal alligator clips that carry a high electrical current. One clip is attached to any part of the work piece being welded. The second clip is connected to a thin welding rod. When the rod touches the work piece, a powerful electrical circuit flows.

The massive heat created by the electrical arc causes both the work piece and the steel core of the rod to melt and run together. The hot metal cools quickly to form a solid bond. During welding, the flux that surrounds the rod’s core vaporizes, forming an inert gas that serves to protect the weld from atmospheric elements that might weaken it. Welding speed is important. Variations in speed can change the amount of flux applied, either weakening the weld or weakening the surrounding metal by increasing heat exposure.

Two common but advanced types of arc welding are Tungsten Inert Gas (TIG) and Metal Inert Gas (MIG) welding. TIG welding often is used with stainless steel or aluminum. TIG uses welding rods. The welder holds the welding rod in one hand and an electric torch in the other hand. The torch is used to simultaneously melt the rod and the work piece. MIG welding uses a spool of continuously fed wire, which allows the welder to join longer stretches of metal without stopping to replace the rod. The welder holds the wire feeder, which functions like the alligator clip in arc welding. Instead of using gas flux surrounding the rod, TIG and MIG protect the initial weld from the environment by blowing inert gas onto the weld.

Like arc welding, soldering and brazing use molten metal to join two pieces of metal. However, the metal added during the process has a melting point lower than that of the work piece, so only the added metal is melted, not the work piece. Soldering uses metals with a melting point below 800°F; brazing uses metals with a higher melting point. Because soldering and brazing do not melt the work piece, these processes normally do not create the distortions or weaknesses in the work piece that can occur with welding. Soldering commonly is used to join electrical, electronic, and other small metal parts. Brazing produces a stronger joint than soldering, and often is used to join metals other than steel, such as brass. Brazing can also be used to apply coatings to parts to reduce wear and protect against corrosion.

Skilled welding, soldering, and brazing workers generally plan work from drawings or specifications or use their knowledge of fluxes and base metals to analyze the parts to be joined. These workers then select and set up welding equipment, execute the planned welds, and examine welds to ensure that they meet standards or specifications. They are even examining the weld while they’re welding. By observing problems with the weld, they compensate by adjusting the speed, voltage, amperage, or feed of the rod. Highly skilled welders often are trained to work with a wide variety of materials in addition to steel, such as titanium, aluminum, or plastics.

Some welders have more limited duties, however. They perform routine jobs that already have been planned and laid out and do not require extensive knowledge of welding techniques.

Automated welding is used in an increasing number of production processes. In these instances, a machine or robot performs the welding tasks while monitored by a welding machine operator. Welding, soldering, and brazing machine setters, operators, and tenders follow specified layouts, work orders, or blueprints. Operators must load parts correctly and constantly monitor the machine to ensure that it produces the desired bond.

The work of arc, plasma, and oxy-gas cutters is closely related to that of welders. However, instead of joining metals, cutters use the heat from an electric arc, a stream of ionized gas (plasma), or burning gases to cut and trim metal objects to specific dimensions. Cutters also dismantle large objects, such as ships, railroad cars, automobiles, buildings, or aircraft. Some operate and monitor cutting machines similar to those used by welding machine operators. Plasma cutting has been increasing in popularity because, unlike other methods, it can cut a wide variety of metals, including stainless steel, aluminum, and titanium.

Working Conditions

Welding, soldering, and brazing workers often are exposed to a number of hazards, including the intense light created by the arc, poisonous fumes, and very hot materials. They wear safety shoes, goggles, hoods with protective lenses, and other devices designed to prevent burns and eye injuries and to protect them from falling objects. They normally work in well-ventilated areas to limit their exposure to fumes. Automated welding, soldering, and brazing machine operators are not exposed to as many dangers, however, and a face shield or goggles usually provide adequate protection for these workers.

Welders and cutters may work outdoors, often in inclement weather, or indoors, sometimes in a confined area designed to contain sparks and glare. Outdoors, they may work on a scaffold or platform high off the ground. In addition, they may be required to lift heavy objects and work in a variety of awkward positions: bending, stooping, or standing to perform overhead work.

Although about half of welders, solderers, and brazers work a 40-hour week, overtime is common, and some welders work up to 70 hours per week. Welders also may work in shifts as long as 12 hours. Some welders, solderers, brazers, and machine operators work in factories that operate around the clock, necessitating shift work.

Training, Other Qualifications, and Advancement

Training for welding, soldering, and brazing workers can range from a few weeks of school or on-the-job training for low-skilled positions to several years of combined school and on-the-job training for highly skilled jobs. Formal training is available in high schools, vocational schools, and postsecondary institutions, such as vocational-technical institutes, community colleges, and private welding schools. The Armed Forces operate welding schools as well. While some employers provide basic training, they prefer to hire workers with experience or more formal training. Courses in blueprint reading, shop mathematics, mechanical drawing, physics, chemistry, and metallurgy are helpful. An understanding of electricity is also very helpful. Knowledge of computers is gaining importance, especially for welding, soldering, and brazing machine operators, who are becoming more responsible for the programming of computer-controlled machines, including robots.

Some welders become certified, a process in which the employer sends a worker to an institution, such as an independent testing lab, equipment manufacturer, or technical school, to weld a test specimen according to specific codes and standards required by the employer. Testing procedures are based on the standards and codes set by industry associations with which the employer may be affiliated. If the welding inspector at the examining institution determines that the worker has performed according to the employer’s guidelines, the inspector will then certify that the welder being tested is able to work with a particular welding procedure.

Welding, soldering, and brazing workers need good eyesight, hand-eye coordination, and manual dexterity. They should be able to concentrate on detailed work for long periods and be able to bend, stoop, and work in awkward positions. In addition, welders increasingly need to be willing to receive training and perform tasks in other production jobs.

Welders can advance to more skilled welding jobs with additional training and experience. For example, they may become welding technicians, supervisors, inspectors, or instructors. Some experienced welders open their own repair shops.

Employment

Welding, soldering, and brazing workers held about 412,000 jobs in 2008. Of these jobs, more than 6 of every 10 were found in manufacturing. Jobs were concentrated in fabricated metal product manufacturing, transportation equipment manufacturing (motor vehicle body and parts and ship and boat building), machinery manufacturing (agriculture, construction, and mining machinery), architectural and structural metals manufacturing, and construction. Most jobs for welding, soldering, and brazing machine setters, operators, and tenders were found in the same manufacturing industries as skilled welding, soldering, and brazing workers.

Job Outlook

Employment of welding, soldering, and brazing workers is expected to experience little or no change, declining by about 2 percent over the 2008–2018 period. Despite this, job prospects should be excellent as employers report difficulty finding enough qualified people. In addition, many openings are expected to arise as a large number of workers retire over the next decade.

The major factor affecting employment of welders is the health of the industries in which they work. The manufacturing sector, which employs the most welding, soldering, and brazing workers, is expected to continue to decline as more manufacturing moves overseas. Because almost every manufacturing industry uses welding at some stage of manufacturing or in the repair and maintenance of equipment, this overall decline will affect the demand for welders, although some industries will fare better than others. The construction industry is expected to have solid growth over the next decade and an increasing demand for welders. Government funding for shipbuilding as well as for infrastructure repairs and improvements is expected to generate additional welding jobs.

Pressures to improve productivity and hold down labor costs are leading many companies to invest more in automation, especially computer-controlled and robotically controlled welding machinery. This will reduce the demand for some welders, solderers, and brazers because many repetitive jobs are being automated. The growing use of automation, however, should increase demand for welding, soldering, and brazing machine setters, operators, and tenders. Welders working on construction projects or in equipment repair will not be affected by technology change to the same extent, because their jobs are often unique and not as easily automated.

Despite slower-than-average job growth, technology is creating more uses for welding in the workplace and expanding employment opportunities. For example, new ways are being developed to bond dissimilar materials and nonmetallic materials, such as plastics, composites, and new alloys. Also, laser beam and electron beam welding, new fluxes, and other new technologies and techniques are improving the results of welding, making it useful in a wider assortment of applications. Improvements in technology have also boosted welding productivity, making welding more competitive with other methods of joining materials.

Earnings

The median hourly wage of welders, cutters, solderers, and brazers was $15.20 in May 2008. The middle 50 percent earned between $13.20 and $19.61. The lowest 10 percent had earnings of less than $10.85, while the top 10 percent earned over $23.92. The range of earnings of welders reflects the wide range of skill levels. The largest numbers of welders, cutters, solderers, and brazers in May 2008 were working in the:

Motor vehicle industry—parts manufacturing

Architectural and structural metals manufacturing

Commercial and industrial machinery and repair maintenance

The welders and these workers belong to a number of unions:

International Association of Machinists and Aerospace Workers

International Brotherhood of Boilermakers, Iron Ship Builders, Blacksmiths, Forgers and Helpers

International Union, United Automobile, Aerospace and Agricultural Implement Workers of America

United Association of Journeymen and Apprentices of the Plumbing, Pipefitting, Sprinkler Fitting Industry of the United States and Canada

United Electrical, Radio, and Machine Workers of America

Related Occupations

Welding, soldering, and brazing workers are skilled metal workers. Other metal workers include machinists; machine setters, operators, and tenders (in metal and plastic); computer control programmers and operators; tool and die makers; sheet metal workers; and boilermakers. Assemblers and fabricators of electrical and electronic equipment often assemble parts using solder.

Some of the additional related occupations that may employ welders, brazers, or solderers are:

Assemblers and fabricators

Boilermakers

Computer control programmers and operators

Plumbers, pipe layers, pipefitters, and steamfitters

Sheet metal workers

Tool and die makers

Projections for openings during the decade 2008–2018 are 126,300 in manufacturing and construction. The median wage in 2009, the latest information available, is $16.71 per hour or $34,750 annually.

Sources of Additional Information*

For information on training opportunities and jobs for welding, soldering, and brazing workers, contact local employers, the local office of the state employment service, or schools providing welding, soldering, or brazing training. Information on careers and educational opportunities in welding is available from:

American Welding Society, 550 N.W. Lejeune Rd., Miami, FL 33126. Internet: www.aws.org

Fabricators and Manufacturers Association, 833 Featherstone Road, Rockford, Illinois 61102. Internet: www.fmanet.org

* Courtesy of Bureau of Labor Statistics, U.S. Department of Labor, Occupational Outlook Handbook, 2010–2011 edition.

CHAPTER 1

Oxyacetylene Welding Fuels

Performance Objectives

After reading this chapter you should be able to:

Identify oxygen tanks by their color.

Understand how acetylene is produced.

Understand the process used to purify oxygen.

Know how to store acetylene and oxygen tanks properly.

Know how to safely handle acetylene and oxygen tanks.

Know how acetone is used with acetylene.

Know how to keep gas cylinders properly positioned.

Know at what temperature an acetylene tank’s safety plug melts.

Welding is a method used to join two or more pieces of metal in such a way as to make the finished piece as strong as the original metal. The oldest type of welding, oxyacetylene welding, was developed about 100 years ago. There have been many developments in metal joining processes since then.

Metal joining can be broken into three rather broad categories: gas welding, electric welding, and gas-electric welding. The home welder or farmer is not interested in production work or plasma welding.

History of Gas Welding

Gas welding is the oldest of all types of welding. It is very simple, in principle. Oxygen and acetylene are burned to produce a flame that is hotter than the melting point of most metals. The temperature of an oxyacetylene flame is generally accepted to be around 6,000°F.

Oxyacetylene is widely used and it is almost unbelievable that this process did not come into existence until the beginning of the 20th century. Oxyacetylene welding was first made possible through the experiments and discoveries of a French chemist, Henri Le Chatelier, in 1895. He was the first to discover that burning oxygen and acetylene produced a flame with a temperature far higher than that of any other flame in existence.

Once the capabilities of oxyacetylene became known to the industrial world, it was quickly put to use. After a workable way to store and transport oxygen and acetylene was developed, the road was cleared for widespread use of this new method of joining metals.

During World War I, the use of oxyacetylene welding accelerated. The pressures to supply an army and to repair existing heavy equipment brought worldwide attention to oxyacetylene welding. After the war, a need for greater controls over the welding process arose, and machines that could weld were developed.

The oxyacetylene welding-cutting process is a most versatile means of working with metals. No other equipment or process in use by the metal industries is capable of performing such a wide variety of work on most types and thicknesses of metals. Oxyacetylene welding is also the easiest to master and probably the most versatile for the farmer or other do-it-yourself welder. This book is primarily concerned with this type of welding.

The oxyacetylene process can be used for joining, heating, and cutting metals. Joining, or fusion, welding is an important application of the oxyacetylene process. Here, the two edges of a metal are heated to their melting points and fused together (Fig. 1.1).

FIGURE 1.1 Welding is a metalworking process. The joint metal is heated to the melting point and the pieces are fused together.

Heating with the oxyacetylene process is often used for forming metals into various shapes and heat treating metals in operations such as annealing, flame hardening, tempering, case hardening, and stress relieving (Fig. 1.2).

One last important use of oxyacetylene is to cut metals. In this application, a stream of pure oxygen is directed against an area of heated metal. This action causes the metal to oxidize, or burn, and thus be cut (Fig. 1.3).

It is obvious from the name oxyacetylene that this type of welding uses a combination of oxygen and acetylene. To understand these basic components, it may be helpful to discuss these two substances and explain their significance to the welding process.

FIGURE 1.2 Welding is often used to heat and shape metals, as is being done to this automobile fender.

Oxygen

Oxygen is present in small amounts in the air we breathe. About one-fifth of our atmosphere is oxygen. Oxygen used in the welding process is about as pure as possible—over 99 percent pure. The method used to produce pure oxygen for welding and medical purposes is called the liquid-air process.

Liquid-Air Process

The following is a simplified but adequate description of the liquid-air process. Atmospheric air, as mentioned earlier, consists of about 20 percent pure oxygen, 78 percent nitrogen, and 2 percent other gases (by volume). Oxygen and nitrogen have different boiling temperatures. In the liquid-air process, the two gases are separated by heating atmospheric air to a certain temperature and holding it at this temperature until the nitrogen, which has a boiling point of 295°, boils off. After the nitrogen has been removed from atmospheric air, oxygen and a small amount of other gases remain. These include carbon dioxide, argon, hydrogen, neon, and helium. Oxygen has the highest boiling point of all these gases; thus to separate it completely, the remaining mixture is further heated until only pure oxygen remains. The pure oxygen is then stored as either a gas or liquid, depending on its eventual use. The liquid-air process is probably the most widely used method of producing pure oxygen.

FIGURE 1.3 Metal cutting can be accomplished using welding equipment.

Cylinders

Oxygen is commonly sold in cylinders in three sizes: 244 cubic feet, 122 cubic feet, and 80 cubic feet (Fig. 1.4). There are very strict requirements for oxygen cylinders. They must be able to withstand over 1 ton of pressure per square inch. The Interstate Commerce Commission (ICC) has set up guidelines for oxygen cylinders. No part of the cylinder may be less than 1/4 inch thick. Each cylinder must be made or forged from a single piece of steel. The steel itself must be armor plate, high-carbon steel (Fig. 1.5).

FIGURE 1.4 The three most popular sizes of portable oxygen cylinders, left to right, are 244 cubic feet, 122 cubic feet, and 80 cubic feet.

Since the ICC requires periodic inspection of oxygen cylinders, which are shipping containers, very few oxygen cylinders are actually owned by private individuals. Oxygen supply houses, which own and lease oxygen cylinders, are responsible for complying with ICC regulations and inspections. This makes using the gases easier on the consumer.

The widely accepted color for oxygen cylinders, lines, and control knobs is green. However, there is no federal regulation that requires oxygen cylinders to be green; thus, many companies paint their oxygen cylinders a special identifying color. It will be to your advantage to become familiar with the color used by your dealer. Often two oxygen supply houses in the same city will have two different colors for their oxygen tanks.

FIGURE 1.5 A typical oxygen cylinder.

Safety Practices

Oxygen cylinders are not dangerous when used and stored according to generally accepted safety precautions. It is best to use only cylinders carrying ICC markings, however. You can be certain that cylinders of this type comply with the stringent regulations of the ICC.

Store cylinders only in a safe location, and fasten them in place. This will ensure that the cylinders cannot be knocked over. Keep tanks in an area away from stoves, radiators, furnaces, or other overly warm equipment or pipes. Oxygen cylinders should also be kept away from all combustible materials or liquids. If cylinders are stored in the open, they should be protected from water, heat, cold, and the sun’s direct rays.

Never use oxygen cylinders for any purpose other than holding oxygen. You should never use oxygen cylinders as rollers to help move large or heavy objects, for example. Nor should you use oxygen cylinders as supports.

Oxygen cylinders should be stored and used in an upright position. In most cases, a hand truck specifically designed to hold two cylinders (both oxygen and acetylene) is the best means for storing and using oxygen. The cylinders should be securely chained or strapped to the cart to prevent them from falling over, allowing the tanks to be transported safely (Fig. 1.6).

Never use the valve on top of the cylinder to lift the cylinder from a horizontal to a vertical position. The best way to lift a cylinder is to make sure that the valve protection cap is secured tightly. Then raise the cylinder by grasping the cap firmly and lifting (Fig.1.7).

FIGURE 1.6 Both oxygen and acetylene tanks should be chained to prevent their accidental falling.

QUICK >>> TIP

You can rent oxygen (as well as acetylene) cylinders for a fixed period of time. When you require more oxygen, you simply return the empty cylinder to the dealer, who replaces it with a full one. All you pay for is the oxygen. The oxygen itself is what you use. In most parts of the country a 20-year lease is available and quite reasonable. In our case, the cost of a cylinder for oxygen and a cylinder for acetylene costs about $10 a year. You can buy oxygen and acetylene to fill the tanks as you need them. In different parts of the country the price may vary.

Never allow oxygen cylinders to come in contact with live electrical wires or other electrical equipment. Keep cylinders away from welding and cutting work. Make certain that the hoses containing oxygen and acetylene do not lie under the work.

Open cylinder valves all the way when working, and always close cylinder valves when you have completed working. Never leave the cylinder valve open when you are not in the immediate vicinity. Cylinder valves should always be tightly closed when not in use—whether they are empty or full. If you stop working for lunch, for example, turn off the valves and bleed the lines. This procedure is explained later (see Fig.1.8).

Never use oxygen around oil or grease as these substances burn violently in the presence of pure oxygen under pressure. Do not use any oil or grease on the regulator fitting.

Never use oxygen for anything other than welding and cutting. Pure oxygen is not in itself flammable, but is an accelerant that can cause intense heat when added to a flame of even very small nature. There is a very real danger if it is used to dust off work or clothing. Similarly, oxygen should never be used for ventilation, pressure tests of any kind, or for any other similar purpose.

FIGURE 1.7 Whenever you pick up a cylinder of oxygen or acetylene, always lift it by the protective cap.

FIGURE 1.8 Always turn off the flow of both oxygen and acetylene at the tank when you stop work for more than 10 minutes.

Acetylene

Acetylene is produced by combining calcium carbide and water. When calcium carbide, commonly called carbide in the trade, is dropped into water, a reaction occurs that causes gas bubbles to rise. The gas is acetylene. It has a peculiar odor, and, if lighted, it burns with a black, smoky flame. After the action of the carbide has ceased, a whitish residue remains in the water. This end product is hydrated, or slaked, lime (calcium hydroxide), and it has many uses in the fertilizer industry.

It is interesting, as a side note, to mention that old-time miners’ headlamps are called carbide lamps, and they work simply by adding water to carbide pellets. A gas is formed in a special container and is forced out of a jet. This gas is ignited in front of a reflector plate, which throws a bright beam of light (Fig. 1.9).

FIGURE 1.9 A miner’s carbide lamp works on the same basic principle as does an acetylene generator.

Carbide-to-Water Generators

Acetylene is produced commercially by basically the same process as used in a miner’s headlamp, only on a much larger scale. Companies that use great amounts of acetylene will usually have their own generator that supplies them with all of the acetylene they can use. These generators are called carbide-to-water generators, and they are almost totally automated. In these types of generators, small amounts of calcium carbide are fed into a large sealed container of water. The heat given off