Incur Seamless square tube Analysis of data elements of pitting corrosion

Alloy composition For seamless square tubes, elements 0, 10 and F are the main alloy elements that make the alloy have good pitting corrosion resistance. Some other elements may also have corresponding K and other elements will reduce the pitting corrosion resistance of seamless square tubes.

(1) It is certain that the effect of alloying elements on the pitting corrosion resistance of data can be summarized briefly into favorable effects. It is beneficial in solid solution, but it is harmful when it is precipitated as intermediate metal phase, 0 is good in solid solution, and it is harmful when it is precipitated as carbide, but it has slightly adverse effects.

(2) The study on cold working of austenitic seamless square tubes shows that the number of etch pits on the surface of the specimen increases and the size of the etch pits decreases after cold working. This is due to the increase of dislocation density during cold processing. Dislocation exposed on the surface is easy to cause corrosion pits. Cold processing tends to increase pitting corrosion.

(3) For a given alloy environment system, the element that determines the corrosion potential of alloy spots is the brightness of the data surface. In fact, it is meaningless to compare the corrosion tendency of stop points of alloys with different surface brightness. About the influence of surface brightness on the pitting corrosion performance of seamless square tubes. It indicates that in the same data environment system, if the surface brightness is different, the difference of pitting corrosion potential can be more than 14.

(4) The oxide formed by heating of the seamless square tube in the air may have a serious impact on the pitting corrosion performance. The microstructure of hot-dip galvanized square tubes plays an important role in the pitting corrosion resistance of alloys. Various phases, such as sulfide inclusion and 3-ferrite. Phase, sensitized grain boundary and weld may have a decisive impact on the pitting corrosion resistance of steel, and they are all sensitive parts to pitting corrosion.

For cast seamless square tubes with complex microstructure and martensite seamless square tubes with microstructure sensitive to heat treatment process, the relationship between pitting corrosion and constituent phases is closer. It is pointed out that the complex manganese sulfide inclusions are more sensitive to pitting corrosion. Therefore, the use of aluminum deoxidizer should be prevented when smelting seamless square tubes.

(5) The oxide film produced by welding may be detrimental to the pitting corrosion resistance of the alloy in strong chloride solution.

(6) The main function of passivation treatment is to dissolve the inclusions and infections on the surface of the seamless square tube to make it clean. It can also remove the manganese sulfide inclusions on the surface, which may become the source of pitting corrosion, thus improving the pitting corrosion resistance of the seamless square tube. It should be noted that the seamless square tube should be cleaned with sodium hydroxide solution after passivation treatment.

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