409不锈钢是汽车排气口用不锈钢，用于前管、消音器以及转化器，有良好的

409 stainless steel is used for automobile exhaust port, used for front pipe, muffler and converter, has good corrosion resistance and high temperature performance, and has very good application value. In this paper, five different 409 ferritic stainless steels The optical morphology (OM) and scanning electron microscope (SEM) were used to analyze the morphology and inclusion composition of the experimental materials, and the five types of 409 stainless steel were investigated at 3.5 wt.% By scanning vibration electrode technology such as polarization curve. NaCl solution, corrosion performance in 100ppm chloride ion concentration solution. <br>Optical micrographs of the metallographic structure of five 409 stainless steels at different magnifications show that the five stainless steels are all equiaxed crystals formed after recrystallization annealing, which is a recrystallization structure. Among them, A409, B409, C409, and E409 stainless steels The grain size is similar, the grain size is about 60 ~ 90 μm. The grain size of D409 is obviously different from the other four stainless steels, and the size is about 15 ~ 45 μm. Scanning electron microscopy combined with EDS spectrometer analysis can be concluded that there are more Ti and N elements in A409, C409 and D409, so it can be inferred that the inclusions are mainly Ti-containing nitrides, among which C409 also has more Nb element, the inclusion may also be Nb-containing nitride. There are more Si elements in B409, but few O elements, so it is inferred that the inclusions are elemental Si, while the inclusions in E409 may be oxides of Al and Ca. Long-term immersion experiments show that the order of pitting resistance of the five stainless steels is: E409> D409> A409> B409> C409; and the pitting potential of these five 409 stainless steels in 3.5 wt.% NaCl solution also follows a similar sequence: E409> D409> A409> B409> C409. In addition, by measuring the critical pitting temperature of these five 409 stainless steels, it can also be seen that the corrosion resistance of these stainless steels also follows this order. However, the number of inclusions of D409 and E409 is similar and the smallest, so the two should have the highest resistance to pitting corrosion, but the grain of D409 is finer, and the grain boundary can be used as the source of pitting corrosion, so its resistance to pitting corrosion is low At E409.

409 stainless steel is the automotive exhaust port stainless steel, used in the front pipe, muffler and converter, has good corrosion resistance and high temperature performance, has very good application value, this paper selects five different 409 ferrite stainless steel, through optical microscope (OM) and scanning electron microscope (SEM) to analyze the tissue profile of experimental materials, the composition of the inclusion, and through polarization curve and other scanning vibration electrode technology to explore five models of 409 stainless steel solution Corrosive energy in a solution with a concentration of 100 ppm chloride ions.<br>Optical microscope photos of the five 409 stainless steel strains under different magnifications show that five kinds of stainless steel are isometric crystals formed after recrystallization annealing, which is a recrystallized tissue, of which A409, B409, C409, E409 four stainless steel grain size similar size, grain size of about 60 to 90 sm. The Size of the D409 grain is significantly different from the other four stainless steels, which are approximately 15 to 45 sm in size. Using scanning electron microscope combined with EDS energy spectrometer analysis, it can be concluded that A409, C409 and D409 all exist more Ti and N elements, so it can be inferred that the inclusion is mainly Ti-containing nitride, of which C409 also has more Nb elements, inclusion may also be containing Nb nitride. The B409 has more Si elements, but few O elements, so it is inferred that the inclusion is a single-mass Si, while the E409 is mixed with oxides that may be Al and Ca. Long-term immersion experiments show that the size order of the pitting forces of 5 stainless steels is: E409 , D409 , B409 , C409, and the five 409 stainless steel pitting potentials in 3.5 wt.% NaCl solution follow a similar order: E409 , D409 , B409 , C409. In addition, by measuring the temperature of these five 409 stainless steel critical point erosion, it can also be seen that the corrosion resistance of these stainless steels can follow the same sequence. However, D409 and E409 are equal in number and minimal, so they should have the highest pitting resistance, but D409 grain is smaller, and the crystal boundary can be used as the source of pitting, so its resistance to pitting is lower than E409.

409 stainless steel is a kind of stainless steel used for automobile exhaust port, which is used for front pipe, muffler and converter. It has good corrosion resistance and high temperature performance, and has very good application value. In this paper, five different 409 ferritic stainless steels are selected. The microstructure and inclusion composition of the experimental materials are analyzed by OM and SEM The corrosion behaviors of five types of 409 stainless steel in 3.5 wt.% NaCl solution and 100 ppm chloride solution were investigated by polarization curve and other scanning vibration electrode techniques.<br>The optical micrographs of the metallographic structure of five kinds of 409 stainless steels at different magnification show that all the five kinds of stainless steels are equiaxed crystals formed after recrystallization annealing, which are recrystallized structures. The grain sizes of a409, b409, c409 and e409 are similar, and the grain sizes are about 60 ~ 90 μ M. The grain size of D409 is obviously different from that of other four kinds of stainless steel. The grain size is about 15 ~ 45 μ M. It can be concluded by SEM and EDS that there are more ti and n elements in a409, c409 and D409, so it can be inferred that the inclusions are mainly Ti containing nitrides, among which there are more NB elements in c409, and the inclusions may also be Nb containing nitrides. There are more Si elements but less o elements in b409, so it is inferred that the inclusions are simple Si, while the inclusions in e409 may be oxides of Al and ca. The long-term immersion test showed that the order of pitting resistance of five kinds of stainless steel was e409 > D409 > a409 > b409 > c409, and the pitting potential of these five kinds of stainless steel in 3.5 wt.% NaCl solution followed a similar order: e409 > D409 > a409 > b409 > c409. In addition, through the measurement of critical pitting temperature of these five kinds of 409 stainless steels, it can be seen that the corrosion resistance of these kinds of stainless steels also follows this order. However, the number of inclusions in D409 and e409 is almost the same and the least, so they should have the highest pitting resistance, but the grain size of D409 is smaller, and the grain boundary can be the source of pitting, so its pitting resistance is lower than e409.<br>