TY - BOOK

T1 - High Temperature Oxidation of Steel, Aluminum and Copper Alloys under the Influence of a Sustainable Energy-Efficient Combustion in Industrial Furnaces

AU - Sobotka, Christina

N1 - no embargo

PY - 2015

Y1 - 2015

N2 - The metal industry has to face diverse challenges such as higher cost effectiveness, increased throughput capacities, pressure to cut fuel and reduce emissions (especially of CO2). Implementing oxygen into the combustion process of burner heated industrial reheating and forging furnaces is a perfect possibility to solve most of these challenges in an effective way. The most important issue of the usage of oxygen burners is the substantially increasing melting rate by lowering the specific production costs because of the higher combustion efficiency. Nevertheless, the change from air combustion burners to oxygen-enriched or oxy-fuel heating systems is a big change in the metallurgical process for forging and steel plants. The major aim of the production is the quality of the product which should not be affected in a negative way. The implementation of oxygen in the burner system increases the heat transfer process beneficially, but also leads to a higher amount of CO2 and H2O in the furnace atmosphere. In this thesis, the influence of oxygen-enhanced and oxy-fuel combustion on the scale formation is investigated and compared to oxidation in conventional air fired furnaces. The oxidation mechanisms of several steel grades, aluminum and copper alloys were investigated. These materials come into contact with the combustion atmosphere during the production process (e.g. steel and aluminum) and in their application area (e.g. steel, copper). Steel grades from low alloy mild steel, Cr-Mo steel (42CrMo4, 1.7225), Cr-Cr/Ni steel (1.4301, X5CrNi18-10), Cr-Ni-Mn steel (H525, 1.4841, X15CrNiSi2521) and Cr-Al steel (Kanthal) were investigated in a temperature range from 750-1200 °C. The aluminum oxidation experiments of the alloys EN AW 1050, EN AW 5005, EN AW 5086, EN AW 5019 and EN AW 6082 were performed up to a temperature of 600 °C and the oxidation of the copper alloys Cu-ETP (CW004A), CuZn37 (CW508L), CuZn39Pb3 (CW614N) and CuAl10Ni5Fe4 (CW307G) was analyzed from 500 °C up to 900 °C. The oxidation results were evaluated with respect to activation energies, kinetics reaction behavior, parabolic or linear oxidation rate and scale morphology. High temperature oxidation is either limited by diffusion processes or by phase surface reaction and supply of oxidizing components to the reaction interface. The mild steel, Cr-Mo and Cr-Cr/Ni steel grades changed their reaction behavior and the oxidation kinetics significantly above 1050 °C. Under that temperature, oxygen implementation in the combustion has no remarkable effect on the oxidation. Higher temperatures increase the diffusion rate; therefore, above 1050 °C the gas composition becomes more important. Copper and aluminum alloys formed an adherent and dense oxide layer, which led to a decrease in oxidation rate. The reaction was diffusion-limited and the concentration of oxidizing components and the combustion method had no significant impact on the reaction rate. The Cr-Al and Cr-Ni-Mn steel grades showed the same kinetic behavior and the oxidation was not altered by adding oxygen to the combustion process. The results of this work enable optimization of the combustion process, without fearing disadvantages in the product quality, and form requirements for an energy-efficient and sustainable process optimization.

AB - The metal industry has to face diverse challenges such as higher cost effectiveness, increased throughput capacities, pressure to cut fuel and reduce emissions (especially of CO2). Implementing oxygen into the combustion process of burner heated industrial reheating and forging furnaces is a perfect possibility to solve most of these challenges in an effective way. The most important issue of the usage of oxygen burners is the substantially increasing melting rate by lowering the specific production costs because of the higher combustion efficiency. Nevertheless, the change from air combustion burners to oxygen-enriched or oxy-fuel heating systems is a big change in the metallurgical process for forging and steel plants. The major aim of the production is the quality of the product which should not be affected in a negative way. The implementation of oxygen in the burner system increases the heat transfer process beneficially, but also leads to a higher amount of CO2 and H2O in the furnace atmosphere. In this thesis, the influence of oxygen-enhanced and oxy-fuel combustion on the scale formation is investigated and compared to oxidation in conventional air fired furnaces. The oxidation mechanisms of several steel grades, aluminum and copper alloys were investigated. These materials come into contact with the combustion atmosphere during the production process (e.g. steel and aluminum) and in their application area (e.g. steel, copper). Steel grades from low alloy mild steel, Cr-Mo steel (42CrMo4, 1.7225), Cr-Cr/Ni steel (1.4301, X5CrNi18-10), Cr-Ni-Mn steel (H525, 1.4841, X15CrNiSi2521) and Cr-Al steel (Kanthal) were investigated in a temperature range from 750-1200 °C. The aluminum oxidation experiments of the alloys EN AW 1050, EN AW 5005, EN AW 5086, EN AW 5019 and EN AW 6082 were performed up to a temperature of 600 °C and the oxidation of the copper alloys Cu-ETP (CW004A), CuZn37 (CW508L), CuZn39Pb3 (CW614N) and CuAl10Ni5Fe4 (CW307G) was analyzed from 500 °C up to 900 °C. The oxidation results were evaluated with respect to activation energies, kinetics reaction behavior, parabolic or linear oxidation rate and scale morphology. High temperature oxidation is either limited by diffusion processes or by phase surface reaction and supply of oxidizing components to the reaction interface. The mild steel, Cr-Mo and Cr-Cr/Ni steel grades changed their reaction behavior and the oxidation kinetics significantly above 1050 °C. Under that temperature, oxygen implementation in the combustion has no remarkable effect on the oxidation. Higher temperatures increase the diffusion rate; therefore, above 1050 °C the gas composition becomes more important. Copper and aluminum alloys formed an adherent and dense oxide layer, which led to a decrease in oxidation rate. The reaction was diffusion-limited and the concentration of oxidizing components and the combustion method had no significant impact on the reaction rate. The Cr-Al and Cr-Ni-Mn steel grades showed the same kinetic behavior and the oxidation was not altered by adding oxygen to the combustion process. The results of this work enable optimization of the combustion process, without fearing disadvantages in the product quality, and form requirements for an energy-efficient and sustainable process optimization.

KW - Oxidation

KW - Verbrennung

KW - Oxidationskinetik

KW - Sauerstoffanreicherung

KW - 23 %

KW - 30 %

KW - Sauerstoffbrenner

KW - Oxyfuel

KW - Luftbrenner

KW - Einfluss Wasserdampf

KW - lineares Zeitgesetz

KW - parabolisches Zeitgesetz

KW - 42CrMo4

KW - Kanthal

KW - Stahl

KW - Aluminium

KW - Kupfer

KW - Baustahl

KW - H525

KW - EN AW 1050

KW - EN AW 5005

KW - EN AW 6082

KW - EN AW 5086

KW - EN AW 5019

KW - CW004A

KW - Cu-ETP

KW - CW614N

KW - CuZn39Pb3

KW - CW508L

KW - CuZn37

KW - CW307G

KW - CuAl10Ni5Fe4

KW - Oxidation

KW - Steel

KW - Aluminum

KW - Copper

KW - Combustion

KW - Industrial Furnace

KW - Kinetics

KW - Parabolic Rate Law

KW - Linear Rate Law

KW - Oxygen-enriched Combustion

KW - 23 %

KW - 30 %

KW - Oxygen Combustion

KW - Oxyfuel

KW - Air-fuel

KW - Influence Water Vapor

KW - 42CrMo4

KW - Kanthal

KW - Mild Steel

KW - H525

KW - EN AW 1050

KW - EN AW 5005

KW - EN AW 6082

KW - EN AW 5086

KW - EN AW 5019

KW - CW004A

KW - Cu-ETP

KW - CW614N

KW - CuZn39Pb3

KW - CW508L

KW - CuZn37

KW - CW307G

KW - CuAl10Ni5Fe4

M3 - Doctoral Thesis

ER -