How To Weld

Todd Bridigum

• Editore: Motorbooks
• Anno: 2008
• ISBN:
  9781616730697
• Argomento: Technology & Engineering
• Categoria: Mechanical Engineering

Welding is a skill that any do-it-yourself enthusiast needs in his or her arsenal. How to Weld is the perfect introduction for newbies and an excellent refresher for veteran welders—a work so comprehensive that most readers won't need any further instruction.

In How to Weld, a bestselling installment in the Motorbooks Workshop series, AWS- certified welding instructor Todd Bridigum thoroughly describes process and art of fusing metals, including:

• Tools and equipment commonly used
• T ypes of metals and their weldability
• Welding techniques
• Shop and site s afety
• Types of joints

In addition, all popular types of welding variants are covered, including gas welding, shielded metal arc (or stick ) welding, gas metal arc welding ( MIG ), gas tungsten arc welding ( TIG ), brazing, soldering, and even metal cutting. Each skills section concludes with a series of exercises, each illustrated with captioned sequential color photography, to fully explain and detail the techniques learned.

Mechanics, automotive enthusiasts, farmers, metalworkers, and other DIYers who can't bond metal can't make repairs and they can't create—in short, they can't do much of anything except bolt together pre-made parts. With this thorough and completely illustrated all-color tutorial by an experienced college-level instructor, readers can get on the path fabricating and fixing metals on their own. How To Weld is the only book about welding they'll ever need. The Motorbooks Workshop series covers topics that engage and interest auto and motorcycle enthusiasts. Written by subject-matter experts and illustrated with step-by-step and how-it's-done reference images, Motorbooks Workshop is the ultimate resource for how-to know-how.

CHAPTER 1
HISTORY AND PROCESS OVERVIEW

Here is a fun way to think about how important welding and metal fabrication are to our standard of living today. What if all the welds in the world came apart at one time and welders weren’t available to repair them? Society as we know it would fall apart, or at least electricity would go away. Power plants are held together by welds and maintained by pipefitters, ironworkers, boilermakers, and machinists. All of us rely on electricity and on those skilled professionals for our standard of living. What about wind and solar panels? Each of these relies on manufacturing processes and welding to be fabricated and installed.

I believe metal fabrication is the single largest influence on how the world looks today, from the cities to the country and even into space. Today we tend to think in the short term, which is understandable since our computers, cell phones, cars, and televisions seem to be outdated or obsolete every few years. If we back up and look at the larger picture in the context of welding, the technology available to work and join metals is extraordinary.

Humankind moved from the Stone Age into the Bronze Age about 5,500 years ago. Copper was the first metal to be worked because it exists in its pure form in nature, and using it didn’t require separating iron from ore. About 3,200 years ago, people discovered how to separate iron from rock and the Iron Age began. Forge welding, the first metal-joining process, was developed during the Iron Age. The people able to transform rock into usable iron tools through forge welding, known to us today as blacksmiths, were thought to possess magical powers a few millennia ago. It took a lot of time, work, and skill to fabricate metal, and for thousands of years that is all we had.

Then, in the late 1800s and early 1900s, gas, arc, and resistance welding were discovered. These breakthroughs, combined with Bessemer’s furnace (which enabled industry to make large quantities of high–quality steel) led the world through the last stages of the Industrial Revolution and into the modern age. Yet if we look at the Brooklyn Bridge and Eiffel Tower, both were constructed during the 1880s and both are riveted together, not welded. In those days, welding processes produced hard, brittle welds that were not suitable for joining large sections of iron or steel under heavy loads. The development of a flux coating on the welding rod was the key to making arc welding more usable, but that took another 50 years to perfect. By the 1930s, welding was being used to construct ships, pipelines, and skyscrapers. For better or worse, war has been the main factor in the advancement of many technologies, including metalworking. The biggest wars—World Wars I and II and the Cold War—precipitated the biggest advances in welding. Research and development of new technologies has trickled down to civilian use.

Modern equipment allows us to easily do welding jobs at home that would take a blacksmith weeks to complete. You can find high–quality steel, aluminum, and other metals in almost any structural shape and size at the local steel yard. Joining them is as easy as pulling the trigger of a wirefeed gun.

Still, welding is a skill difficult to master. Think of it like this: I can put a band–aid on someone’s cut and give them an aspirin, but that doesn’t make me a doctor. I can change a light fixture and its switch in my home, but that doesn’t make me an electrician. Just because someone can lay a bead does not make him or her a welder.

The good news is we no longer have to dedicate our lives to the craft in order to join metals. But we should recognize the difference between what we know how to do and a professional who has spent most of his life learning and working in the trade. New ways of processing, refining, and combining metals, as well as the further development of new welding processes using lasers, electron beams, and friction, indicate that the rate of new discoveries and applications of different metal–joining processes will continue into the foreseeable future. The Internet and books are great resources to learn more about the history of welding and metalworking.

WELDING PROCESSES OVERVIEW

Welding processes can be divided into two basic categories: manual and automated. This book deals with the former, the manual processes, the ones in which the person doing the work has a direct influence on how the weld turns out. This puts the pressure on the person operating the equipment to produce a good weld.

Some of the manual processes are considered semiautomatic, in which one or several aspects of the weld is controlled by the machine. For example, in wirefeed welding the wire is automatically electrified and fed into the molten puddle by the machine. Two processes, which can be manually operated but are more commonly automated, are not covered in this book: plasma arc welding (PAW) and submerged arc welding (SAW). Both have applications in industry, but are not common in most metal fabrication shops because of lack of need or cost of equipment.

Automated is not the best term to describe the wide variety of welding processes in which there is no manual control over the welding process, but the welding does occur in an automatic manner. The only influence an operator has in these cases is to set up the equipment and materials properly.

Some examples of automated process welding are...