Stainless Steel Properties Industry Solutions

The development of stainless steel is due to its characteristics and ability to meet needs. The essential factor of stainless steel is corrosion resistance, but by no means only with corrosion resistance, but also have unique mechanical properties (yield strength, tensile strength, creep strength, high-temperature strength, low-temperature strength, etc.), physical properties (density, specific heat capacity, coefficient of linear expansion, thermal conductivity, electrical resistivity, magnetic permeability, coefficient of elasticity, etc.), process performance (molding performance, welding performance, cutting performance, etc.) and metallographic (phase composition, organizational structure, etc.) and so on. ) and metallographic (phase composition, organizational structure, etc).

一、Mechanical properties, strength (tensile strength, yield strength)

Various factors determine the strength of stainless steel, but the most fundamental factor is the addition of different chemical factors, mainly metal elements. Due to their chemical composition differences, other types of stainless steel have other strength characteristics.

1. Martensitic stainless steel

Martensitic stainless steel and ordinary alloy steel have the same hardening characteristics through quenching, so you can choose the grade and heat treatment conditions to get a wide range of different mechanical properties. From the significant aspect to distinguish, Martensitic stainless steel belongs to the iron-chromium-carbon stainless steel. Further, it can be divided into martensitic chromium stainless steel and martensitic chromium-nickel stainless steel. The martensitic chromium stainless steel, added chromium, carbon molybdenum, and other elements of the trend's strength, and the martensitic chromium stainless steel added nickel strength characteristics are described below.

Martensitic chromium stainless steel in the quenching-tempering conditions increases chromium content and can increase the ferrite content, reducing the hardness and tensile strength. Low-carbon martensitic chromium stainless steel is used in the annealing conditions, where the chromium content increases when the hardness increases, while the elongation decreases slightly. In the chromium content of a specific condition, the carbon content increases so that the steel's hardness increases after quenching while the plasticity is reduced. The primary purpose of adding molybdenum is to improve steel's strength, hardness, and secondary hardening effect. The addition of molybdenum is very effective after quenching at low temperatures. The content is usually less than 1%.

A certain amount of nickel in martensitic chromium-nickel stainless steel can reduce the δ ferrite content, achieving the maximum hardness value.

The chemical composition of martensitic stainless steel is characterized by adding molybdenum, tungsten, vanadium, and niobium based on different combinations of 0.1%-1.0%C, 12%-27%Cr. Due to the organization of the body-centered cubic structure, and thus at high temperatures, the strength of a sharp decline. At 600 ℃ below, high-temperature strength in all types of stainless steel is the highest, and creep strength is the highest.

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2. Ferritic stainless steel

According to the results of the study, when the chromium content of less than 25% ferrite organization will inhibit the formation of martensitic organization, and thus, with the increase in chromium content and its strength decreased, higher than 25% due to the solid solution strengthening of the alloy, the strength of a slight increase. Increasing molybdenum content can make obtaining ferrite organization easier, promoting precipitation of α'phase, б-phase, and x-phase, and after solid solution strengthens its strength. But also improve the notch sensitivity so that the toughness is reduced. Molybdenum to enhance the role of ferritic stainless steel strength rather than the role of chromium.

The chemical composition of ferritic stainless steel is 11% -30 % Cr, with added niobium and titanium. Its high-temperature strength in all types of stainless steel is the lowest but the most vigorous resistance to thermal fatigue.

3. Austenitic stainless steel

Austenitic stainless steel increases carbon content due to its solid solution strengthening effect, which improves strength.

Austenitic stainless steel's chemical composition is characterized by chromium, nickel-based addition of molybdenum, tungsten, niobium-titanium, and other elements. Because it organizes the face-centered cubic structure, it has high creep and creep strength at high temperatures. Also, the thermal fatigue strength of ferritic stainless steel is poor due to the significant linear expansion coefficient.

4. Duplex stainless steel

The chromium content of about 25% of the mechanical properties of duplex stainless steel research shows that the nickel content in the α + r duplex area increases when the r phase also increases. When the chromium content of steel is 5%, the yield strength reaches the highest value; when the nickel content is 10%, the strength of steel goes to the maximum value.

二、Creep strength

Due to the role of external forces with the increase in time, the deformation phenomenon is called creep. At a specific temperature, especially at high temperatures, the greater the load, the faster the creep rate; at a particular load, the higher the temperature, and the longer the possibility of creep is greater. In contrast, the lower the temperature, the slower the creep rate; in common to a specific temperature, creep is not a problem. This minimum temperature varies according to the steel, generally speaking, pure iron at 330 ℃ or so, and stainless steel because they have taken a variety of measures to strengthen. Hence, the temperature is 550 ℃ or more. Like other steels, the melting, deoxidation, solidification, heat treatment, and processing of stainless steel creep characteristics have a significant impact. In the United States, the 18-8 stainless steel creep strength test shows that, from the same nugget of the same part of the test material, the creep rupture time of the standard deviation is about 11% of the average value, and from different ingots of different parts of the standard deviation and the average value of the test material of the standard deviation and the average value of the difference between the more than two times. According to the results of the tests conducted in Germany, the strength of 0Cr18Ni11Nb steel in 10 of 5 power h time is less than 49MPa to 118MPa; the difference is enormous.

三、Fatigue Strength

High-temperature fatigue refers to the process of damage to the fracture of materials at high temperatures due to the action of cyclically changing stresses. The results of its research show that, at a specific high temperature, the fatigue strength of 10 to the 8th power of high temperature is 1/2 of the tensile strength at that temperature.

Thermal fatigue refers to the process of heating (expansion) and cooling (contraction); when the temperature changes and is subjected to external constraints, the internal deformation of the material corresponding to its expansion and contraction of the deformation of the material produces stress and causes material damage. When there is rapid and repeated heating and cooling of the stress of the impact, the resulting stress is greater than the usual situation when some materials are brittle and damaged. This phenomenon is called tie-up shock. Thermal fatigue and thermal shock are similar phenomena, but the former is mainly accompanied by considerable plastic strain, and the latter damage is especially brittle.

Stainless steel composition and heat treatment conditions impact high-temperature fatigue strength. Especially when the carbon content increases when the high-temperature fatigue strength increases significantly, solid solution heat treatment temperature also has a significant effect. Generally speaking, ferritic stainless steel has good thermal fatigue performance. In the austenitic stainless steel, the

High silicon and good elongation at high-temperature grades have good thermal fatigue performance in austenitic stainless steel.

The smaller the coefficient of thermal expansion, the smaller the strain under the same thermal cycle, the smaller the deformation resistance, and the higher the fracture strength, the longer the life. It can be said that the fatigue life of martensitic stainless steel 1Cr17 is the longest, while 0Cr19Ni9, 0Cr23Ni13, and 2Cr25Ni20 austenitic stainless steel fatigue life is the shortest. In addition, castings are more likely to occur than forgings due to thermal fatigue damage. At room temperature, 10 of the 7th power fatigue strength is 1/2 of the tensile strength. Compared with the fatigue strength at high temperatures, there is no significant difference in the fatigue strength from room temperature to high-temperature range.

四、Impact toughness

The material in the impact load, load-deformation curve includes the area known as impact toughness. For cast martensitic aging stainless steel, when the nickel content of 5% of its impact toughness is low. With the increase of nickel content, the strength and toughness of the steel can be improved, but if the nickel content is more significant than 8%, the strength and toughness values once again decline. Adding molybdenum can improve steel's strength and keep its toughness unchanged in martensitic chromium-nickel stainless steel.

Increasing the molybdenum content in ferritic stainless steel can improve its strength but also enhance notch sensitivity and decrease toughness.

In austenitic stainless steel with stable austenitic organization and chromium-nickel austenitic stainless steel, toughness (room-temperature toughness and low-temperature toughness) is very good. Thus, it is suitable for use in various environments, such as rooms and low temperatures, for stable austenitic organization and chromium-manganese austenitic stainless steel. The addition of nickel can further improve its toughness.

The impact toughness of duplex stainless steel improves with increased nickel content. Generally speaking, in the a + r two-phase region, its impact toughness stabilized in the range of 160-200J.

五、Stainless steel process performance

1. Forming properties

Stainless steel forming properties are due to the different steel grades, that is, the crystalline structure of the other, and significant differences. Such as ferritic stainless steel and austenitic stainless steel and forming properties due to the former crystal structure being body-centered cubic, while the latter crystal structure is face-centered cubic, and there are significant differences.

Ferritic stainless steel flange forming performance, n value (work hardening index), deep drawing performance, and r value (plasticity should change). The different production processes under the other organization determine the r-value. Are you taking some measures? Significantly reducing the solid solution carbon and solid solution nitrogen can improve the r value and dramatically enhance the deep drawing performance.

Austenitic stainless steel generally has an immense n value in the processing process due to plasticity-induced phase transformation and the generation of martensite, and therefore, has a more considerable n value and elongation and can be deep-drawn machining and flange forming. After some time, a part of austenitic stainless steel in the deep-drawn processing will produce longitudinal cracks consistent with the direction of the stamping, the so-called "aging cracks." The use of high nickel, low nitrogen, and low carbon austenitic stainless steel can avoid the occurrence of this defect.

Austenitic stainless steel does not contain nickel and can significantly reduce the tendency of cold work hardening of steel; the reason is that the stability of austenite can be increased to minimize or eliminate the martensitic transformation in the complex working process, reduce the rate of cold work hardening of the plant, strength reduction and plasticity improvement.

Increasing nickel content in duplex stainless steel can reduce the martensitic transformation temperature, thus improving the cold working deformation properties.

In evaluating stainless steel plate forming processability, generally, the integrated forming properties to mark. The integrated developing performance is characterized by the fracture limit of fracture resistance (deep-drawn performance, flange creating performance, edge extension performance, bending performance), marked by the forming mold and material compatibility with the anti-wrinkle, marked by the unloading of the shape of the fixed shape of the shape of the set and so on.

The main test methods for evaluating the process performance of stainless steel plates are as follows:

(1) tensile test;

(2) bending test;

(3) stamping forming test;

(4) flaring test;

(5) Impact test.

The process performance of stainless steel pipe is mainly evaluated in the following items:

(1) tensile test;

(2) Tube expansion test;

(3) flattening test;

(4) crushing test;

(5) Bending test.

2. Welding performance

Welding and cutting of stainless steel structures is inevitable in stainless steel applications. Due to the characteristics of stainless steel itself, the welding and cutting of stainless steel are particular to ordinary carbon steel, and it is easier to produce various defects in its welded joints and its heat-affected zone (HAZ). Pay special attention to the physical properties of stainless steel when welding. For example, the thermal expansion coefficient of Austenitic stainless steel is 1.5 times that of low carbon steel and high chromium stainless steel; The thermal conductivity is about 1/3 of low carbon steel, and the thermal conductivity of high chromium stainless steel is about 1/2 of low carbon steel; The specific resistance is more than four times that of low carbon steel, and high chromium stainless steel is three times that of low carbon steel. These conditions, together with the density of the metal, surface tension, magnetism, and other conditions, impact the welding conditions.

Martensitic stainless steel is generally represented by 13%Cr steel. When it is welded, a-r(M) phase transition occurs in the region heated above the phase transition point in the heat-affected zone, so there are problems such as low-temperature brittleness, low-temperature toughness deterioration, and ductility decline caused by hardening. Therefore, it is necessary to preheat the welding of general martensitic stainless steel. Still, preheating the welding materials with low carbon and nitrogen content and R-series welding materials is not required. The structure of the welding heat-affected zone is usually complex and brittle. For this problem, the toughness and flexibility can be restored by post-welding heat treatment. In addition, brands with low carbon and nitrogen content also have a certain toughness in the welding state.

Ferritic stainless steel is represented by 18%Cr steel. In the case of low carbon content, it has good welding performance, but welding crack sensitivity is also common. However, the grains of the welding heat affected zone (HAZ) heated to more than 900℃ are significantly coarsened, which makes it lack extensibility and toughness at room temperature and easy to crack at low temperatures. That is to say, generally speaking, ferritic stainless steel has 475℃ embrittlement, 700-800℃ for a long time heating of abnormal phase embrittlement, inclusions and grain coarsening caused by embrittlement, low-temperature embrittlement, carbide precipitation caused by corrosion resistance decline, and high alloy steel prone to delayed cracking and other problems. Generally, pre-welding and post-welding heat treatment should be carried out during welding, and welding should be carried out in a temperature range with good toughness.

Austenitic stainless steel is represented by 18%Cr-8%Ni steel. In principle, pre-welding and post-welding heat treatment are not required. Generally has good welding performance. However, high-alloy stainless steel with high nickel and molybdenum content can quickly produce high-temperature cracks when welding. In addition, it is also prone to phase embrittlement. The ferrite formed under the action of ferrite-forming elements causes low-temperature embrittlement, and the corrosion resistance is reduced and stress corrosion cracks and other defects. After welding, the mechanical properties of the welded joint are generally good. Still, when chromium carbide is on the grain boundary in the heat-affected zone, it is easy to form a chromium-poor and chromium-poor layer, and appearance will quickly produce intergranular corrosion during use. To avoid problems, low carbon (C ≤0.03%) grades or grades adding titanium and niobium should be used. To prevent high-temperature cracking of welding metals, it is generally considered that the control of δ ferrite in austenite must be effective. It is usually recommended to contain more than 5% δ ferrite at room temperature. Low-carbon and stable steel grades should be selected for steel whose primary use is corrosion resistance, and appropriate post-welding heat treatment should be carried out. The steel with structural strength as the primary purpose should not be subjected to post-welding heat treatment to prevent deformation and δ phase embrittlement due to precipitation of carbides. The welding crack sensitivity of duplex stainless steel is low. However, the increase of ferrite content in the heat-affected zone will increase the sensitivity of intergranular corrosion, which may lead to a decrease in corrosion resistance and the deterioration of low-temperature toughness. For precipitation-hardened stainless steel, there are problems such as softening of the welding heat-affected zone.

In summary, the welding performance of stainless steel is mainly manifested in the following aspects:

(1) High-temperature crack: the high-temperature crack mentioned here refers to the crack related to welding. High-temperature cracks can be roughly divided into solidification, microscopic, HAZ(heat-affected zone), and reheating cracks.

(2) Low-temperature cracking: Low-temperature cracking sometimes occurs in martensitic stainless steel and some ferritic stainless steel with martensitic structure. Since the main reason for its production is hydrogen diffusion, the degree of constraint of the welded joint and the hardened structure in it, the solution is mainly to reduce the diffusion of hydrogen during the welding process, appropriate preheating and post-welding heat treatment, and reduce the degree of constraint.

(3) Toughness of welded joints: To reduce the sensitivity of high-temperature cracks in austenitic stainless steel, the composition design usually leaves 5%-10% remaining ferrite. However, the presence of these ferrites leads to a decrease in low-temperature toughness. In welding duplex stainless steel, the Austenitic volume in the welded joint area is reduced, which affects the toughness. In addition, with the increase of ferrite, its toughness value decreased significantly.

It has been proved that the toughness of high-purity ferritic stainless steel welded joints decreases significantly due to the mixing of carbon, nitrogen, and oxygen. The increased oxygen content in the welded joints of some steels results in oxide inclusions, which become the source of cracks or the way of crack propagation and reduce the toughness. Some steel is due to the air mixed in the protective gas, in which the nitrogen content increases on the matrix cleavage surface {100} surface to produce strip Cr2N; the matrix hardens and makes the toughness decrease.

(4) Phase embrittlement: Austenitic stainless steel, ferritic stainless steel, and duplex stainless steel are prone to phase embrittlement. Due to the precipitation of a few percent of the phase in the tissue, the toughness is significantly reduced. The average phase is generally precipitated in the range of 600-900 ° C, especially around 750 ° C, and is the easiest to pour; as a preventive measure to prevent the production of the normal phase, Austenitic stainless steel should minimize the content offer.

(5)475℃ embrittlement: Fe-Cr is kept near 475℃ (370-540℃) for a long time

When the alloy is decomposed into a solid solution with low chromium concentration and a 'reliable solution with high chromium concentration, the deformation changes from sliding to twin deformation, and embrittlement occurs at 475℃.

六、Machinability

The machinability of different stainless steels is very different. Generally speaking, the machinability of stainless steel is worse than that of other steels, which refers to the poor machinability of Austenitic stainless steel. The severe work hardening of austenitic stainless steel and low thermal conductivity causes this. For this reason, water-based cutting coolant should be used in the cutting process to reduce cutting heat deformation. Especially when the heat treatment of welding is not good, no matter how much we try to improve the cutting accuracy, its deformation is inevitable. The cutting properties of other types of stainless steel, such as martensitic stainless steel and ferritic stainless steel, are not much different from carbon steel as long as they are not cut after quenching. However, the higher the carbon content of both, the worse the cutting performance. Precipitation-hardening stainless steel shows different thinning properties due to its other organization and treatment methods. Still, its cutting properties are generally identical in the annealed state with the same series and strength as martensitic stainless steel and austenitic stainless steel.

Adding sulfur, lead, bismuth, selenium, and tellurium can improve the cutting performance of stainless steel, like carbon steel. These elements can reduce tool wear and improve the cutting state.

Although adding sulfur can improve the machinability of stainless steel, the corrosion resistance is significantly reduced because it is present in the steel in the form of MnS compounds. To solve this problem, a small amount of molybdenum or copper is usually added.

七、Hardenability

Quenching and tempering heat treatment is generally required for martensitic chromium-nickel stainless steel. Different alloying elements and their added amounts affect hardenability in this process differently.

When quenching martensitic stainless steel, it is quenched from 925-1075℃. Due to the low phase change speed, oil and cold can be hardened. Also, in the tempering process that must be carried out, different mechanical properties can be obtained due to other tempering conditions.

Adding chromium can improve the hardenability of iron-carbon alloy in martensitic chromium stainless steel, so it is widely used in steels that need to be quenched. The primary function of chromium is to reduce the critical cooling rate of quenching so that the hardenability of steel is significantly improved. According to the C curve, because the addition of chromium slows down the transformation rate of austenite, the C curve shifts considerably to the right.

In martensitic chromium-nickel stainless steel, the addition of nickel can improve the hardenability and hardenability of the steel. Steel containing chromium close to 20% without the addition of nickel has no quenching capacity. The quenching capacity can be restored by adding 2%-4% nickel. However, the nickel content can not be too high; otherwise, the high nickel content will not only expand the R-phase region but also reduce the Ms temperature so that the steel becomes a single-phase austenitic structure and loses the quenching ability. The tempering stability of martensitic stainless steel can be improved, and the tempering softening degree can be reduced by choosing the appropriate nickel content.

In addition, adding molybdenum to martensitic chromium-nickel stainless steel can increase the tempering stability of the steel.

Although ferritic stainless steel cannot be hardened by quenching because it does not produce austenite at high temperatures, some martensitic phase changes occur in low-chromium steel.

Austenitic stainless steel belongs to the Fe-Cr-Ni and Fe-Cr-Mn series and is an austenitic structure.

Therefore, it shows high strength and good extensibility in a wide range from low to high temperatures. The solid solution treatment starting from 1000 ° C can obtain the non-magnetic austenitic structure for good corrosion resistance and maximum elongation.

八、Physical property

(1) General physical properties

Like other materials, the physical properties mainly include the following three aspects: thermal properties, such as melting point, specific heat capacity, thermal conductivity, and linear expansion coefficient; electromagnetic properties, such as resistivity, conductivity, and permeability; and mechanical properties, such as Young's elastic modulus and rigidity coefficient. These properties are generally considered inherent properties of stainless steel materials but are also affected by temperature, degree of processing, and magnetic field strength. Under normal circumstances, stainless steel has low thermal conductivity and considerable resistance compared with pure iron. At the same time, properties such as linear expansion coefficient and magnetic permeability vary according to the crystalline structure of stainless steel itself.

Table 4-1- Table 4-5 lists the physical properties of the primary grades of Martensitic stainless steel, ferritic stainless steel, Austenitic stainless steel, precipitation-hardened stainless steel, and duplex stainless steel, such as density, melting point, specific heat capacity, thermal conductivity, linear expansion coefficient, resistivity, permeability, longitudinal elastic coefficient, and other parameters.

(2) Correlation between physical properties and temperature

1. Specific heat capacity: With the change of temperature, the specific heat capacity will change, but in the process of temperature change, once the phase transition or precipitation occurs in the metal structure, the specific heat capacity will change significantly.

2. Thermal conductivity system: below 600 ° C, the thermal conductivity of various stainless steel is basically in the range of 10-30W/(m• ° C), and the thermal conductivity increases with the increase of temperature. At 100℃, the order of thermal conductivity of stainless steel from large to small is 1Cr17, 00Cr12, 2Cr25N, 0Cr18Ni11Ti, 0Cr18Ni9, 0Cr17Ni12Mo2, 2Cr25Ni20.500℃, the order of thermal conductivity from large to small is 1Cr13, 1Cr17, 2Cr25 N, 0Cr17Ni12Mo2, 0Cr18Ni9Ti and 2Cr25Ni20. The thermal conductivity of Austenitic stainless steel is slightly lower than that of other stainless steels, and compared with ordinary carbon steel, the thermal conductivity of Austenitic stainless steel is about 1/4 at 100 ° C.

3. Linear expansion coefficient: In the range of 100-900 ° C, the linear expansion coefficient of all kinds of stainless steel primary grades is basically in the minus six power of 10 to the minus six power of 20 ° C minus 1, and it shows an increasing trend with the rise of temperature. For precipitation-hardened stainless steel, the linear expansion coefficient is determined by the aging treatment temperature.

4. Resistivity: at 0-900℃, the specific resistance of all kinds of stainless steel primary grades is basically in the negative power of 70*10 to the negative energy of 130*10 Ωm, and with the increase of temperature, there is an increasing trend when used as a heating material, the material with low resistivity should be selected.

5. Permeability: The permeability of Austenitic stainless steel is minimal, so it is also known as a non-magnetic material, steel with stable austenitic structure, such as 0Cr20Ni10, 0Cr25Ni20, etc., even if it is processed with a large deformation of more than 80%, it will not be magnetic. In addition, high carbon, high nitrogen, high manganese Austenitic stainless steel, such as 1Cr17Mn6Ni5N, 1Cr18Mn8Ni5N series, and high manganese Austenitic stainless steel

In addition, ε phase transformation will occur under extensive pressure processing conditions, so it remains non-magnetic. Even magnetic solid materials lose their magnetism at high temperatures above the Curie point. However, for some austenitic stainless steels such as 1Cr17Ni7 and 0Cr18Ni9, because their organization is a metastable austenitic organization, martensitic phase transition will occur during extensive pressure cold processing or low-temperature processing, and they will have magnetic properties and their permeability will also increase.

6. Elastic modulus: At room temperature, the longitudinal elastic modulus of ferritic stainless steel is 200KN/mm square, and that of Austenitic stainless steel is 193KN/mm square, slightly lower than that of carbon structural steel. With the increase in temperature, the longitudinal elastic modulus decreases, Poisson's ratio increases, and the lateral elastic modulus (stiffness) decreases significantly. The longitudinal modulus of elasticity will impact work hardening and tissue aggregation.

7. Density: The density of ferritic stainless steel with high chromium content is small, and that of Austenitic stainless steel with high nickel and manganese content is significant. At room temperature, the density decreases as the lattice spacing increases.

(3) Physical properties at low temperatures

1. Thermal conductivity: The size of all kinds of stainless steel at very low temperatures is slightly different, but generally, it is about 1/50 of the thermal conductivity at room temperature. At low temperatures, the thermal conductivity increases with the increase in magnetic flux (magnetic flux density).

2. Specific heat capacity: Various stainless steels have different specific heat capacities at very low temperatures. The specific heat capacity is greatly affected by temperature, and at 4K, it can be reduced to less than 1/1 100 of the specific heat capacity at room temperature.

3. Thermal expansion: The shrinkage rate below 80K (relative to 273K) for Austenitic stainless steel is slightly different. The content of nickel has a specific effect on the shrinkage rate.

4. Resistivity: The difference in resistivity between grades increases at very low temperatures. The alloying elements significantly influence resistivity.

5. Magnetic: at low temperatures. The influence of mass magnetic susceptibility of Austenitic stainless steel on load magnetic field varies with different materials. The content of other alloy elements also varies.

There is no difference in permeability between different grades.

6. Elastic modulus: The Poisson ratio of magnetically transformed Austenitic stainless steel at low temperatures correspondingly produces extreme values.

九、Corrosion resistance

The corrosion resistance of stainless steel generally increases with chromium content. The basic principle is that when there is enough chromium in the steel, a very thin to dense oxide film is formed on the surface of the steel, which can prevent further oxidation or corrosion. The oxidizing environment can strengthen this film, and reducing the environment will inevitably destroy this film, resulting in steel corrosion.

(a) Corrosion resistance in various environments

1. Atmospheric corrosion: The resistance of stainless steel to atmospheric corrosion changes with chloride in the atmosphere. Therefore, proximity to the ocean or other chloride sources is essential for the corrosion of stainless steel. A certain amount of rain is essential only if it affects the chloride concentration on the steel surface.

Rural environment

1Cr13, 1Cr17, and Austenitic stainless steels can be adapted to various uses without significant changes in appearance. Therefore, the stainless steel used in rural exposure can be selected according to price, market supply, mechanical properties, production processing properties, and appearance.

Industrial environment

In the industrial environment without chloride pollution,1Cr17 and Austenitic stainless steel can work for a long time, basically maintain no rust, and may form a dirty film on the surface. However, when the dirty film is removed, it still retains the original bright appearance. In the industrial environment, chloride will cause corrosion of stainless steel. Marine environment

1Cr13 and 1Cr17 stainless steel will form a thin rust film in a short period but will not cause significant changes in size; austenitic stainless steel, such as 1Cr17Ni7, 1Cr18Ni9, and 0Cr18Ni9, when exposed to the Marine environment, there may be some rust. Rust is usually shallow and can be easily removed. 0Cr17Ni12M02 Molybdenum-containing stainless steel is basically corrosion resistant in the Marine environment.

In addition to atmospheric conditions, two other factors affect the atmospheric corrosion resistance of stainless steel—namely, surface state and production process. The finish grade affects the corrosion resistance of stainless steel in chlorinated environments. Matte surfaces (rough surfaces) are susceptible to corrosion. That is, standard industrial finishing surfaces are less vulnerable to rust. The level of surface finish also affects the removal of dirt and rust. It is easy to remove dirt and rust from highly finished surfaces but difficult to remove from matte surfaces. Regular cleaning is required for flat surfaces if the original surface state is to be maintained.

2. Fresh water: Fresh water can be defined as water that is not acidic, salty, or brackish and comes from rivers, lakes, ponds, or Wells.

The corrosiveness of fresh water is affected by the water's pH value, oxygen content, and scaling tendency. Scaling (hard) water. Its corrosion is mainly determined by the amount and type of scale formed on the metal surface—the scale forms due to the minerals and the temperature. Non-scaling (soft) water is generally more corrosive than hard water. It can be reduced by increasing the pH or decreasing the oxygen content. 1Cr13 stainless steel is significantly more resistant to freshwater corrosion than carbon steel and has excellent characteristics for use in freshwater. This steel is widely used in applications such as shipyards and DAMS, which require high strength and corrosion resistance. However, consideration should be given to particular circumstances. 1Cr13 May be moderately sensitive to pitting in fresh water. However, pitting can be avoided by cathodic protection. 1Cr17 and Austenitic stainless steels are almost entirely resistant to new water corrosion at room temperature (ambient temperature).

3. Acidic water: Acidic water refers to the polluted natural water precipitated from ore and coal, which is much more corrosive than natural freshwater due to its strong acidity. Due to the leaching effect of water on sulfide contained in ores and coal, acidic water usually contains a large amount of free sulfuric acid; in addition, this water contains a large amount of iron sulfate, which has a huge effect on the corrosion of carbon steel.www.juxinfasteners.com