Hard- Surfacing, Building Fusion Welding Carbon Welding Non-Ferrous Metals Heating & Heat Treating Braze Welding Welding Cast Iron Welding Ferrous Metals Brazing & Soldering Equipment Set-Up Operation Equipment For OXY-Acet Structure of Steel Mechanical Properties of Metals Oxygen & Acetylene OXY-Acet Flame Physical Properties of Metals How Steels Are Classified Expansion & Contraction Prep For Welding OXY-Acet Welding & Cutting Safety Practices Manual Cutting Oxygen Cutting By Machine Appendices Testing & Inspecting
6 Heating and Heat Treating. Probably every oxy-acetylene outfit in service today is used, at least occasionally, as a convenient source of heat for bending or forming metals, loosening ”frozen” nuts, and dozens of other jobs. For some of these uses, it is merely a convenient heat source, where the relatively high cost of acetylene is more than balanced by the time saved. Another widespread use for the heat of the oxy-acetylene flame is in the brazing of joints in copper tubing systems, where speed again gives it an advantage over lower-temperature flames which might be used. There are several industrial applications of the flame – for example, flame-hardening and flame- descaling, which will be covered in Chapter 19 – where the extremely high temperature of the flame is indispensable. Fig. 2-4. The oxy-acetylene flame-hardening process can be used to produce a hardened surface on a steel shaft, while permitting retention of a tough, ductile shaft core. In this application, the shaft is revolved in front of the flames for a few seconds. Then the flames are shut off, and a water quench applied immediately.