Prevention of decarburization in Annealing of high carbon steel
Tóm tắt
High carbon steel products must frequently be annealed without decarburization. At annealing temperatures, CO2 and H2O readily react with carbon in the steel to form CO and H2. Hydrogen itself can cause decarb, forming methane. Depending on temperature, the carbon in the steel can be present as cementite or as solute in the α- and γ-iron phase. Each of the forms requires different atmosphere considerations. The condition of the material to be treated (lubricants, oxides, etc.) and the condition of the annealing furnaces can substantially alter the atmosphere composition in the furnace. Outside the γ-iron region, annealing is done at nonequilibrium atmosphere conditions. This makes the control of the process difficult. By considering the various conditions and the dynamics of the different reactions, high carbon steel can be annealed without decarburization.
Tài liệu tham khảo
L. S. Darken and R. W. Gurry:Physical Chemistry of Metals, New York, NY, 1953, McGraw-Hill Book Company, Chapter 16.
R. W. Gurry: “Composition of Atmospheres Inert to Heated Carbon Steel,”Transaction AIME, 1950, vol. 188, pp. 671–87.
G. Krauss: “Principles of Heat Treatment of Steel,” American Society for Metals, 1980.
H. J. Grabke: “Kinetics and Mechanics of Surface Reactions during Carburizing and Decarburizing of Iron in Gases,” Archive Eisenhuttenwesen, 1975, vol. 46, pp. 75–81.
Metals Handbook, 8th ed., American Society for Metals, vol. 8, pp. 180, 275, 276.
Nassheuer:Schutzgas Taschenbuch, 3. Auflage, Vulkanverlag, 1979.
F. E. Purkert: “Using N2 atmospheres to anneal high carbon steel without decarb,” Heat Treating, vol. 14, no. 3, March 1982, pp. 32–34.