Book contents
- Frontmatter
- Contents
- Preface
- 1 Manual metal arc welding
- 2 Gas shielded metal arc welding
- 3 Tungsten electrode, inert gas shielded welding processes (TIG), and the plasma arc process
- 4 Resistance welding and flash butt welding
- 5 Additional processes of welding
- 6 Oxy-acetylene welding
- 7 Cutting processes
- 8 The welding of plastics
- Appendixes
- 1 Welding symbols: British, American
- 2 Simplified notes on the operation of a thyristor
- 3 Proprietary gases and mixtures
- 4 Tests for wear-resistant surfaces
- 5 Conversion factors
- 6 Low hydrogen electrode, downhill pipe welding
- 7 The manufacture of extruded MMA electrodes
- 8 Notes on fire extinguishing
- 9 Table of brazing alloys and fluxes
- 10 Latest plant and equipment
- 11 Refraction and reflection
- 12 Notes on the welding of Duplex and Super Duplex stainless steels
- 13 Welding fumes: health and safety
- 14 Lasers and laser welding
- City and Guilds of London Institute examination questions
- Index
13 - Welding fumes: health and safety
Published online by Cambridge University Press: 11 May 2010
- Frontmatter
- Contents
- Preface
- 1 Manual metal arc welding
- 2 Gas shielded metal arc welding
- 3 Tungsten electrode, inert gas shielded welding processes (TIG), and the plasma arc process
- 4 Resistance welding and flash butt welding
- 5 Additional processes of welding
- 6 Oxy-acetylene welding
- 7 Cutting processes
- 8 The welding of plastics
- Appendixes
- 1 Welding symbols: British, American
- 2 Simplified notes on the operation of a thyristor
- 3 Proprietary gases and mixtures
- 4 Tests for wear-resistant surfaces
- 5 Conversion factors
- 6 Low hydrogen electrode, downhill pipe welding
- 7 The manufacture of extruded MMA electrodes
- 8 Notes on fire extinguishing
- 9 Table of brazing alloys and fluxes
- 10 Latest plant and equipment
- 11 Refraction and reflection
- 12 Notes on the welding of Duplex and Super Duplex stainless steels
- 13 Welding fumes: health and safety
- 14 Lasers and laser welding
- City and Guilds of London Institute examination questions
- Index
Summary
The electric arc, used in MMA, MIG-MAG, TIG, and other welding processes, causes visible and invisible fumes to be given off by the melting flux when the arc is burning. These fumes can be harmful if inhaled through the nose and mouth of the welder. The content of the fumes may be either asphyxiating or toxic.
Asphyxiating fumes
Asphyxiating fumes are largely due to the shielding gases used around the arc. They are invisible and produce their effect by displacement of the surrounding air and thus, of its oxygen. (The air which we breathe consists mainly of nitrogen and oxygen, roughly in the ratio of four parts nitrogen to one part oxygen.) Asphyxiation begins when the oxygen content of the air falls below about 18%.
The gases usually used in welding are argon, carbon dioxide, helium and their mixtures. Argon and carbon dioxide are heavier than air (the mixtures are known under trade names). A mixture is selected to give the best welding conditions for a particular process. A simple mixture is the rutile coating for mild steel electrodes in the MMA welding of mild steel. The rutile gives a smooth arc, which is easily managed, but it gives off some hydrogen, which is absorbed by the molten metal and leads to hydrogen cracking under certain conditions of stress.
- Type
- Chapter
- Information
- The Science and Practice of Welding , pp. 449 - 457Publisher: Cambridge University PressPrint publication year: 1993