【正文】 s rich rareearth elements in the role of phosphorus greatly improved the steel brittle easily lead to adverse effects, of which Shanghai is the use of rare earth 10PcuRe developed the role and control the amount of steel in the aluminum ways in which the steel has good toughness. (B) sulfuric acid dew point corrosion resistant lowalloy steel The introduction of highsulfur heavy fuel oil or coal gas as fuel in the boiler, which often contain sulfur dioxide and sulfur trioxide. Low temperature in the boiler area, due to the role of sulfur trioxide with water vapor condenses into sulfuric acid, causing these parts of sulfuric acid dew point corrosion. The content of sulfur trioxide gas in up to 60ppm and above can make the environment of the dew point rises to 150 degrees. When the metal surface temperature is below the dew point, the sulfur trioxide with water vapor to form sulfuric acid will gather on it. Gas depends primarily on the concentration of sulfur trioxide in the sulfur content of fuel and air excess coefficient. Fuel sulfur content and excess air coefficient in turn depends on the conditions and plete bustion of fuel, hence the development of sulfuric acid dew point corrosion resistant lowalloy steel has a universal significance. Sulfuric acid dew point corrosion characteristics of their medium, are within the scope of industrial atmospheric corrosion, is oh, by the corrosion of sulfur dioxide pollution of the atmosphere, but can also in the corrosion of steel in sulfuric acid to carry out simulations. With the general atmospheric corrosion of different parameters are different in temperature, atmospheric corrosion is usually occurs at room temperature, and development, while the sulfuric acid dew point corrosion in the 60 degrees Celsius, and there is the role of carbon particles on the oxidation. In the sulfuric acid dew point corrosion occurred in an environment of lowalloy steel with corrosion resistance. Sulfuric acid dew point corrosion means that, in the use of highsulfur fuels (heavy oil, coal, etc.) contained in the boiler flue gas SO3, sulfuric acid dewpoint temperature in the lower parts of the boiler temperature (air preheater, flue and chimney, etc.), bined with water vapor as H2SO4, sulfuric acid condensation on the steel surface corrosion phenomenon. Corrosion mechanism on the sulfuric acid corrosion mechanism, the Japanese believe that a small, if so, with the boiler can be divided into three stages. Phase 1 (referring to the run early and demissioning) at a lower temperature (≤ 80 ℃ ) and low concentrations (≤ 60% H2SO4) sulfuric acid in the sulfuric acid corrosion, is in activation state electrochemical corrosion. Stage 2 (referring to the normal runtime) for hightemperature (~ 160 ℃ ), high concentration (about 85%) sulfuric acid corrosion, but also in the activation state of the electrochemical corrosion. Stage 3 of the temperature and concentration with the first two stages of the same, but contains large amounts of unburned carbon particles, carbon particles under the action of catalytic oxidation, so that care is oxidized to Fe ions Fe meal. Produce large amounts of Fe +3 ions, so that corrosion resistant steel (copper containing chromium or boron steel) appears 1st passivation, corrosion rate decreased, but the noncorrosion resistant steel is not passivated. Corrosion rate remains high. The role of alloying elements alloying elements in the above three stages, the corrosion resistance of different materials. In Phase 1 and effective elements are sulfur, tin, arsenic, antimony and silicon. When the sulfur content of % ~ % when the best results. Harmful elements phosphorus, yttrium, zirconium, tungsten, titanium and chromium ( 5%). In Stage 3 the effective elements of chromium and boron. In the CuCrsteel si ≥ %, a boron in the copper line in Steel V ≥ %, in the copper in the antimony and arsenic in steel more than %, it plays a harmful role. Although the alloy elements in the various stages of the corrosion process in the role of different, but as the first stage of a short time, little effect on the overall corrosion process, the sulfuric acid dew point corrosion rate of steel depends on 2 and 3 stage, especially Phase 3. Therefore the first two phases, in particular the first three stages of the alloying elements play a role in corrosion resistance is more important. Grades States to use sulfuric acid dew point corrosion resistant steel is mainly coppercontaining steel. Main brands are: China, 09Cu, 09CuWSn, Japan 10CrCu (CRIA), 12CrCuAl (TAICC) RS), 12CuSb (STer1), 12CrCuNiSbSn (NAC 1 1), 12CrCuNiNb (RIVERTEN41s) and the United States The carbon content of % or less of CuMo steel (A8361T) and so on. (C) seawater corrosionresistant lowalloy steel Oceans and seas constitute 71% of the earth39。 while the atmosphere in metallurgical industry, the steel increase in the amount of copper corrosion rate will decline further。s countries are trying to add a variety of small amount of the steel alloying elements to enhance the atmospheric corrosion resistant steel their ability to develop a group of lowalloy steel resistant to atmospheric corrosion. Corrosion of carbon steel in the atmosphere originally developed rapidly, when the rust layer formed, the average corrosion rate will be slowed. Because of this rust porous layer and its adhesion is poor, coverage is not uniform, unable to withstand wind and rain and the role of alternating wet and dry at any time by peeling off, so that corrosion, localized corrosion, especially the further development . Lowalloy steel corrosion in the atmosphere, mainly to improve the structure of the rust layer and improve the extent of the rust layer and the dense steel adhesion, enhanced the role of newly isolated with the air. Over the past decade, th