【正文】 world39。Carbon steel and low alloy steel I. Overview In the steel production accounted for 85% of mediumcarbon steel, low alloy steel about 10%, the two together the world39。s total steel output more than 95%, and its importance is not difficult to imagine. In general, the carbon steel corrosion in all environments, performance is poor, does not belong to corrosion material. , Because its use is extremely broad understanding of carbon steel corrosion in all environments, behavior, proper selection of carbon steel and protection, to improve the economic benefits of the use is undoubtedly very important. As the name suggests, the performance of carbon steel depends on the amount of carbon content, and thus will be divided into lowcarbon steel carbon steel, medium carbon steel and high carbon steel. Low, medium carbon steel is mainly used for a variety of steel structures, it is also known as structural steel。s iron and steel materials, a major pillar, of which the Soviet Union had the largest share, nearly 20%, a total of 1500 lowalloy steel ponents around。s lowalloy steel output at close to 5 million tons, accounting for just % of output, lowalloy steel varieties of nearly 100 species. China39。 seawaterresistant steel。 and antihydrogen, antiN, antiammonia corrosion of steel and so on. (4)Of rail steel: China has the production of manganese, high silicon and copper highsilicon rails, antigang strength was more than 90kg/mm2. Mn lowalloy steel rail and linear curve on the rail for use on longer than carbon Su double rail about. Appropriately increasing the amount of phosphorus in steel, then in anticorrosion and wear resistance in the atmosphere have been improved accordingly. (5) Of reinforced steel: steel bars in China for more than two are lowalloy steel, and has formed series. Use of lowalloy steel for prestressed concrete reinforced with carbon steel pared to 4060% material savings. (6)Abrasion resistance, deep drawing steel: This type of steel wide range of uses, requirements vary. Is mainly used for agricultural machinery, mining machinery, construction machinery, automobile parts. The above classification is based on only the primary purpose of steel division, in fact many lowalloy steel is often both a variety of performance, usage is also very extensive. Ⅱ、 The corrosion characteristics of carbon steel the chemical position of the corrosion Ordinary carbon steel position is very simple, mainly carbon, silicon, manganese, sulfur, phosphorus and five conventional elements. C: Generally speaking, with the increase of carbon steel, carbon steel in acidic solution in the corrosion rate will also increase accordingly. However, in oxidizing ac id carbon to a certain extent, the corrosion rate worse. In the nonoxidizing acid, the carbon in the carbon content increases the amount of increase in carburizing, carburizing steel body and the basic potential difference, which constitutes a microbattery offers more opportunities, thereby increasing the corrosion. In other conditions the same, the carbon content of greater than %, corrosion apparent increase in trend. In oxidizing acid, as a cathode phase cementite the more able to promote just passivation. Sea water in the atmosphere and freshwater fish such as neutral solution, carbon little effect on the corrosion affecting the corrosion is the restrictive part of the role of oxygen depolarization. Thus, who can reach the steel surface to prevent the factors of oxygen will slow down the corrosion rate of steel. Si and Mn: Carbon steel, silicon and manganese content is not high, in the specification within the scope of what impact the little corrosion. It has been reported that the increase of manganese content in the acidic solution will just deteriorate the corrosion resistance, but because of Mn can improve the adverse effects of sulfur in the sea or the atmosphere, high manganese steel corrosion actually be improved. Only at a very high silicon content before it bees acid and high temperature oxidation resistance, which has does not belong to the scope of carbon steel and low alloy steels. S: Carbon steel, the sulfur is the negative factors affecting the corrosion resistance, cold dew 2 is too high, would greatly enhance the steel in acidic solution in the corrosion rate. In the atmosphere or a neutral aqueous solution, sulfide inclusions are localized corrosion induced by the source. Thus, carbon steel, the sulfur content should be as low as possible. P: phosphorus in the carbon steel against corrosion due to circumstance. In acidic solution, like phosphorus and sulfur is extremely harmful, then there is the fact that steel has phosphide, hydrogen evolution will lead to increased corrosion. However, the phosphorus in steel can effectively improve just right atmosphere, marine environment, corrosion resistance, have information that the phosphorus to improve the role of atmospheric corrosion of steel more than copper. However, like phosphorus and sulfur are the deterioration of the toughness of steel, in carbon steel in no other alloy elements can be offset or mitigate the crisp nature of the steel. Increase the amount of carbon in the phosphorus content is not under normal circumstances prevent advocated. In recent years, domestic and foreign steel in the heavy rail and by appropriately increasing the amount of phosphorus found on the rails are still the performance and wear resistance of the improvement in results. inclusions on the corrosion of On the carbon steel is concerned, various types of inclusions would immediately deteriorate the steel corrosion resistance. This is because: inclusion undermines the continuity and uniformity of steel, an increase of steel microbatteries, this nonuniformity caused by local