Learning Objectives After studying this chapter, you will be able to: Describe the function of each component of an oxyfuel gas cutting outfi t. Correctly and safely assemble an oxyfuel gas cutting outfi t. Correctly and safely test the complete cutting outfi t for leaks. Describe the difference between a positive- pressure and injector-type cutting torch. Properly turn on and shut down an oxyacetylene cutting outfi t. Correctly select the proper cutting tip and working pressures for cutting a particular thickness of steel. Cut base metal using an oxyacetylene cutting torch. Distinguish between a well cut surface and a poorly cut surface, and be able to adjust where necessary to perform a good cut. Describe the gouging process and state when it is used. Pass a test on safe practices and procedures while oxyfuel gas cutting or gouging. List all the safety equipment that should be worn and used when oxyfuel gas cutting in various positions. In oxyfuel gas cutting of metal, an oxyfuel gas fl ame is used to heat the metal and an oxygen jet is used to perform the cutting. Oxyfuel gas cutting (OFC) and oxygen cutting (OC) are both AWS-approved terms. The art of oxyfuel gas cutting has progressed rapidly. It is now possible to accurately fl ame cut both very thin and very thick steel sections. For production work, many layers of metal can be cut at the same time (stack cutting). This process greatly reduces both time and costs. Oxyfuel gas cutting (OFC) is particularly useful when shape-cutting metal parts. Oxyfuel gas cutting can be done with great accuracy. It leaves the edges smooth enough to satisfy most fi nished job require- ments. Oxygen cutting (OC) can be done much faster than machine saw cutting. Standard rolled plates or sections may be used for many fabrications in shipbuilding, machine frames, and building struc- tures. They are cut to size, then welded together to form a solid steel structure. Such structures are strong, economical to build, and present an attractive appearance. 14.1 The Heat of Combustion of Steel In welding and cutting, burning is the rapid oxidation of a material. Virtually all materials burn, if they are fi rst heated to their ignition temperature in the presence of oxygen. Ignition temperature (or kindling point) is the lowest temperature in a normal atmosphere at which a given material will ignite spon- taneously without any external spark or fl ame. Steel is a combustible material, since it burns (oxidizes). During the process of burning, steel releases a consid- erable amount of heat that is measured in British 409
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