金属腐蚀与防护英文专题

1、carbon steel and low alloy steeli. overview in the steel production accounted for 85% of medium-carbon steel, low alloy steel about 10%, the two together the worlds total steel output more than 95%, and its importance is not difficult to imagine. in general, the carbon steel corrosion in all environ

2、ments, 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. a

3、s the name suggests, the performance of carbon steel depends on the amount of carbon content, and thus will be divided into low-carbon 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 structu

4、ral steel; high-carbon steel is mainly used to manufacture a variety of tools. carbon steel is divided into ordinary carbon steel and two types of high-quality carbon steel, ordinary steel and carbon steel have group b divided steel. and high-quality carbon steel will not only guarantee the mechanic

5、al properties, there is need to ensure that chemical composition, the phosphorus in steel mixed with sulfur than conventional low-pass steel. the various types of carbon steel in a carbon content of 0.2% of the a3 steel or steel production 20 largest and most widely used. of such steel is greater th

6、an the tensile strength of the general 400mpa, the yield strength is greater than 240mpa. carbon content of less than 0.1% of the steel can produce boiling steel. in addition to boiling steel, the steel required to use silicon, manganese alloys deoxidation, and their removal of deoxidation products

7、of most of the floating, but always remains a part of a non-metallic inclusions. in terms of the carbon steel, carbon steel, non-metallic inclusions in the type, quantity, morphology and distribution, just the heat treatment system, steel surface conditions, the corrosion would have an impact. this

8、effect is only in the corresponding conditions is comparable, and can only be statistical data have actual meaning. low-alloy steel in the 19th century, 70 years in industry began to apply, but it develops slowly, aware of the late 20th century, 50, because of advances in technology and industrial p

9、roduction of low-alloy steel increased the demand that prompted its rapid and vigorous developed, and now it has become the worlds iron and steel materials, a major pillar, of which the soviet union had the largest share, nearly 20%, a total of 1500 low-alloy steel components around; other countries

10、, low-alloy steel production usually accounts for steel production of 7-10%, in 1983 chinas low-alloy steel output at close to 5 million tons, accounting for just 11.5% of output, low-alloy steel varieties of nearly 100 species. chinas production of low-alloy steel to the following categories: (1) h

11、igh-strength steel: about two-thirds of the total low-alloy steel for more than 18 steel has been officially included in the national standard. yield strength from 300mpa to 700mpa, initially formed a strength series. such a wide use of steel to be used for the construction of the nanjing yangtze ri

12、ver bridge, 100 tons of mine dump trucks, 300,000 tons of ammonia synthesis tower, 220,005 1000 kilowatts hydro scroll, 10000-ton ocean-going vessels and military ships chemical system, high-pressure container and so on. (2) low-temperature steel: -40-105 degree has taken initial shape of the temper

13、ature series, and for oxygen equipment and ethylene devices. (3) the corrosion resistance of steel: this type of steel, including resistance to atmospheric corrosion and corrosion-resistant steel for sulfuric acid dew point; seawater-resistant steel; used in fertilizer and oil resistance to hydrogen

14、 sulfide steel; and anti-hydrogen, anti-n, anti-ammonia corrosion of steel and so on. (4)of rail steel: china has the production of manganese, high silicon and copper high-silicon rails, anti-gang strength was more than 90kg/mm2. mn low-alloy steel rail and linear curve on the rail for use on longer

15、 than carbon - su double rail about. appropriately increasing the amount of phosphorus in steel, then in anti-corrosion and wear resistance in the atmosphere have been improved accordingly. (5) of reinforced steel: steel bars in china for more than two are low-alloy steel, and has formed series. use

16、 of low-alloy steel for prestressed concrete reinforced with carbon steel compared to 40-60% 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, au

17、tomobile parts. the above classification is based on only the primary purpose of steel division, in fact many low-alloy steel is often both a variety of performance, usage is also very extensive.、the corrosion characteristics of carbon steel1、 the chemical composition of the corrosion ordinary carbo

18、n steel composition 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 acid carbon

19、to a certain extent, the corrosion rate worse. in the non-oxidizing 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 micro-battery offers more opportunities, thereby increasing the c

20、orrosion. in other conditions the same, the carbon content of greater than 0.6%, 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 fresh-water fish such as neutral solution, carbon little e

21、ffect 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 s

22、pecification 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 mangane

23、se steel corrosion actually be improved. only at a very high silicon content before it becomes 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 resi

24、stance, 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: phosphor

25、us 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

26、 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 o

27、ffset 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

28、still the performance and wear resistance of the improvement in results.2、 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

29、 steel, an increase of steel micro-batteries, this non-uniformity caused by localized corrosion has been confirmed by a large number of experiments and practice. carbon steel or low alloy steel in sulfide inclusions on the corrosion effects are harmful, the only difference lies in the different cate

30、gories of sulfide differ on the extent of corrosion only. ; sulfide inclusions are plastic, like the distribution of clusters along the rolling direction; steel during solidification or fast cooling after welding, resulting in enrichment of sulfur in mns around so as to further promote the intensifi

31、cation of localized corrosion. this year the jet developed a new metallurgical process to reduce the sulfur content in steel, changing the shape and distribution of sulfide inclusions have good results, so that it can significantly improve the corrosion resistance of carbon steel or low alloy steel

32、performance.3、the steel on the corrosion of the organization steel chemical composition of the organization not only by the impact, but also with the heat-treatment procedure. in general, the lower the carbon content, the lower the impact of heat treatment; the higher the carbon content, the greater

33、 the impact of heat treatment. this is because with the increase in carbon content of steel is also a corresponding increase in cementite, different heat treatment systems, the number of cementite precipitates is different from carbon as the cathode of a mixture of carbon steel for non-passive syste

34、m, the cathode efficiency increases, will inevitably lead to an increase in corrosion rate. in the carbon content under the same conditions, pearlite morphology and distribution of corrosion to a certain extent, for example, spherical than the flaky pearlite pearlite good corrosion resistance, and i

35、ts greater dispersion, the average corrosion rate of the more great. some of the carbon steel, low alloy steel after heat treatment, materials, mechanical properties and corrosion studied the relationship between that extension of the high rate of steel corrosion resistance of the material useful, a

36、nd the steel strength, hardness, brittleness and impact the value of changes, and corrosion almost no effect. elimination of stress and high temperature annealing heat treatment, proved to be useful to reduce the corrosion rate of steel in the original state of the effect of heat treatment has a dir

37、ect relationship.4、carbon steel corrosion in the general environment tend to carbon steel construction, machinery, transport, daily necessities, the most fundamental institution of conventional weapons materials, uses a very wide, with the exception of part of surface treatment, most of them are dir

38、ectly related to environmental exposure, such as air, industrial water, sea water, mud , fertilizer and so on. therefore, to understand the environment in the carbon steel corrosion in the above trend, with practical significance. carbon steel in the general atmosphere of dry air or corrosive than t

39、he moist air is small, such as the ocean-atmosphere climate than the mainland serious corrosion. carbon steel corrosion rate with changes in environmental factors have changed a lot. in the atmosphere, for example, because of its composition, humidity, temperature, airflow and light of the different

40、 corrosion rate can be 0.1-4mm / a varied between. but the majority of cases, 0.2-0.5mm / a. corrosion in aqueous solution was more complex than the atmosphere, most acid, alkali, salt water solution are highly corrosive to carbon steel. only the strong oxidation of concentrated sulfuric acid, dilut

41、e acetic acid, sulfur, saltpeter mixed acid, alkaline hydroxides, alkaline cyanide, alkaline sulfide, as well as nitrate, carbonate, chromate, acetate and ammonia solution and so on, may use the carbon steel at room temperature. in addition, organic solvents such as hydrocarbons, alcohols, amines, a

42、ldehydes and ketones, can also be used to make carbon steel containers. tap water, river water, sea water, distilled water so the corrosion of carbon steel, and water dissolved oxygen, flow, ph value, temperature, bacteria, etc. is different, they are very different; the same time, with the steel su

43、rface state related.、 low-alloy steel corrosion resistance corrosion resistance of low-alloy steel is a low-alloy steel is an important branch of the class. add the main alloying elements to improve the corrosion of steel in different environments in the corrosion resistance. however, for this purpo

44、se to add a small amount of multi-alloy steel is often the same time, the mechanical properties and process performance of the larger impacts, both beneficial side also has a negative side, which to the corrosion of low alloy steel and production increased the difficulties. corrosion is still a deve

45、loping low-alloy steel in the steel type, there is no uniform classification. now more mature and effective corrosion resistance of low-alloy steel are: (1) the atmospheric corrosion-resistant low-alloy steel. (2) sulfuric acid dew point corrosion resistant low-alloy steel. (3) seawater corrosion-re

46、sistant low-alloy steel. (4) milk sulfide corrosion of low-alloy steel. (5) other corrosion resistant low-alloy steel. in other corrosion resistant low-alloy steel, there are high-temperature, high pressure, hydrogen, nitrogen, and corrosion-resistant low-alloy steel, etc. bittern. chinas high-stren

47、gth low-alloy steel with the corrosion of low-alloy steel has been around 30 years of history, and achieved considerable results.(a) atmospheric corrosion-resistant low-alloy steel without the protection of ordinary carbon steel under the conditions of exposure to the atmosphere, the corrosion, the

48、corrosion rate and the relationship between environmental factors greatly. atmospheric corrosion is usually a typical environment, there are three types: the rural atmosphere, industrial atmosphere and ocean atmosphere. among them, rural countryside of atmospheric corrosion of mild steel; and indust

49、rial air vary widely, affecting different; oceanic and atmospheric corrosion of steel is the biggest. air pollution in rural areas due to a lesser extent, affecting a major factor in corrosion of steel is precipitation, annual mean temperature and relative humidity. corrosion of steel in the atmosph

50、ere is due to the surface of steel is conducive to the formation of the wet film electrochemical reaction, resulting in corrosion to proceed. industrial atmosphere of the steel corrosion rate of the influencing factors, primarily in the pollution of the atmosphere composition and content, such as su

51、lfur dioxide. in the atmosphere is also inevitably contain moisture, which greatly increased the corrosion of steel. steel corrosion in the marine atmosphere is much more serious than the former two kinds of environments, mainly because of the ocean-atmosphere contains a large number of chloride par

52、ticles, such as the sea fog particles falling in the steel surface, forming a layer of electrolyte of the wet film . just in the marine atmospheric corrosion by the high plane distance is the proximity and the coastline, wind speed, wind direction and other factors. nightside is usually steel surfac

53、e corrosion than steel yang greater degree, because rain can put a positive salt washed out. in order to prevent atmospheric corrosion of steel, usually paint or metal plating, so that the steel surface and moist air separation, but this surface treatment is not once and for all. the past 20-30 year

54、s, the worlds 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 low-alloy steel resistant to atmospheric corrosion. corrosion of carbon steel in the atmosphere originally devel

55、oped 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

56、 corrosion, especially the further development . low-alloy 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, the united st

57、ates ambassador to the successful development of rust color with an artistic low-alloy steel, not paint directly exposed to the use of a building with a beautiful tan.1、 alloy elements on corrosion resistance of steels in the impact of atmospheric atmospheric corrosion-resistant low-alloy steel, the

58、 effective alloying elements are mainly copper, phosphorus, chromium, nickel, etc., these elements are enriched in the surface of steel and formed amorphous layer increases in the atmospheric environment in the steel corrosion resistance. cu: copper atmospheric corrosion resistant steel has an obvio

59、us effect of a large number of domestic and international experimental study and confirmed the effectiveness of long-term use. steel containing 0.2% - 0.5% cu, both in the rural atmosphere, industrial atmosphere or oceans in the atmosphere, have a more general superior corrosion resistance of carbon steel, copper steel normal industrial atmosphere in the marine atmosphere and the atmospheric environment than in rural areas corrosion r