CN111593266B - Medium chromium type ferritic stainless steel - Google Patents
Medium chromium type ferritic stainless steel Download PDFInfo
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
Abstract
The invention discloses a medium-chromium ferritic stainless steel, which comprises the following chemical components in percentage by mass: c: 0.001% -0.05%; n: 0.001% -0.05%; si: 0.02% -0.6%; cr: 16% -20%; p is less than or equal to 0.04 percent; s is less than or equal to 0.003 percent; al: 0.005% -0.15%; mn: 0.05 percent to 0.5 percent; cu: 0.015% -0.15%; the rest is Fe and inevitable impurities; wherein the contents of Mn and Cu also satisfy 0.4<(wMn+8wCu)×100<1.5. The medium-chromium ferrite stainless steel can greatly reduce the corrosion rate of the medium-chromium ferrite stainless steel after pitting corrosion on the premise of not influencing the processability of the medium-chromium ferrite stainless steel, thereby having excellent corrosion resistance and processability and being applied to common humid environments and acid environments such as household appliances, automobile exhaust system silencers, tail pipes and the like.
Description
Technical Field
The invention relates to the technical field of steel manufacturing, in particular to medium-chromium ferritic stainless steel.
Background
The chromium content is 16-22% (by mass)Percentage by weight) ferritic stainless steel is generally called medium-chromium ferritic stainless steel, and the ferritic stainless steel accounts for more than half of the annual output of domestic ferritic stainless steel due to the characteristics of good corrosion resistance, processability and economy, and is mainly applied to household appliances, kitchen equipment, automobile exhaust systems, exterior decorations of buildings and the like. The corrosion environment of the medium-chromium ferritic stainless steel mainly takes a common humid environment and an acid environment at medium and low temperature, such as two types of medium-chromium ferritic stainless steel, namely 022Cr18Ti and 022Cr18NbTi, used for a silencer and a tail pipe at the cold end of an automobile exhaust system, the service environment temperature of the medium-chromium ferritic stainless steel is lower than 400 ℃, and a corrosion medium is NH-containing4 +、CO3 2-、SO4 2-、Cl-And a condensate of an organic acid; for example, the 10Cr17 and 022Cr17NbTi medium chromium type ferritic stainless steels used by the inner cylinder of the washing machine in China are used in a water system with the temperature lower than 60 ℃ for a long time, and corrosion media mainly comprise tap water containing hypochlorous acid and various detergents. The medium-chromium ferritic stainless steel has the characteristics of wide application field and diversified and complicated forming modes, and has the processing types of punching, deep drawing, spinning, flaring, bulging and the like after pipe making besides simple shearing and bending, so that the medium-chromium ferritic stainless steel has both corrosion resistance and processability and is the basis of the components and process design of the medium-chromium ferritic stainless steel.
In the prior art, a great deal of literature data suggests that the corrosion resistance of ferritic stainless steel is controlled by an index w (Cr) +3.3 xw (Mo) (w represents mass percent), and the higher the index is, the better the uniform corrosion resistance, pitting corrosion resistance and crevice corrosion resistance are. Therefore, in designing steel grades, researchers often improve the corrosion resistance of medium chromium type ferritic stainless steels by adjusting the contents of Cr and Mo elements while ensuring that the workability is not affected. However, in tests conducted by some users to simulate actual conditions, it has been found that, at present, even medium-chromium ferritic stainless steel plates having the same brand number and even the same Cr and Mo contents often show greatly different corrosion degrees. Through investigation, the inventors found that the difference of the corrosion degree of the parts is mainly caused by the difference of the corrosion rate of the substrate after pitting corrosion occurs on the surface of the medium chromium ferritic stainless steel plate.
Accordingly, there is a need in the art for a new medium chromium ferritic stainless steel that eliminates or at least alleviates all or some of the above-mentioned deficiencies of the prior art.
Disclosure of Invention
In view of the above problems in the prior art, an object of the present invention is to provide a medium-chromium ferritic stainless steel which can greatly reduce the corrosion rate of the medium-chromium ferritic stainless steel after pitting corrosion without affecting the workability of the medium-chromium ferritic stainless steel, thereby having both excellent corrosion resistance and workability, and can be applied to general humid environments and acidic environments such as home appliances, automobile exhaust system mufflers, tail pipes, and the like.
It is emphasized that, unless otherwise indicated, the terms used herein correspond to the ordinary meanings of the various technical and scientific terms in the art, and the meanings of the technical terms defined in the various technical dictionaries, textbooks, etc.
The corrosion type of the medium chromium ferritic stainless steel in the actual working condition is mainly pitting corrosion, and the corrosion process is mainly divided into two stages of pitting corrosion on the surface and corrosion (pit growth) of the matrix, so that the pitting corrosion resistance of the stainless steel plate in the actual working condition can be comprehensively evaluated through the following two aspects, namely the number of rusts on the surface of the stainless steel plate, the macroscopic rusty area of the surface of the part after the simulation test and the qualitative evaluation on the corrosion rate of the matrix.
The inventor finds that when the medium-chromium type ferritic stainless steel substrate corrosion rate is quantitatively evaluated, if a standard corrosion test method is adopted, such as GB/T17987-. Therefore, the inventor selects a laboratory non-standard method, namely a sodium chloride hydrochloride solution soaking method (test conditions are 35 ℃, 5% NaCl +1mol/LHCl and soaking time is 2 hours), and measures the uniform corrosion rate of the medium chromium ferrite stainless steel plate after the surface is polished, and the result shows that the method can accurately reflect the difference of the matrix corrosion rates of the medium chromium ferrite stainless steel with the same mark but different trace alloy element contents and is consistent with the user feedback result.
The inventor finds that the technical measures adopted for controlling the surface rust point quantity of the medium-chromium ferritic stainless steel and the corrosion rate of the matrix are not completely the same through long-term experimental research and user tracking.
The key to the corrosion resistance of stainless steel is that a colorless and transparent Cr-rich oxide layer (i.e. a passive film) with the thickness of nanometer level is formed on the surface of the stainless steel in air or an oxidizing medium. The thicker and more stable the passivation film, the higher the Cr content, the less the pitting corrosion will occur. Mo can remarkably promote the enrichment of Cr in the passive film, thereby enhancing the pitting corrosion resistance of the passive film. Stainless steel undergoes various oxidation-reduction reactions in the smelting, pouring and molten steel solidification processes, and steel slag, refractory materials and the like are mixed into the steel, so that the stainless steel plate inevitably contains various oxide and sulfide inclusions. The inclusions are exposed on the surface of the stainless steel, so that a passive film cannot be normally formed, and the positions of the inclusions in the corrosion medium preferentially become pitting corrosion sources.
Once the passive film on the surface of the stainless steel is damaged, pitting hole-shaped nuclei are formed, and the corrosion rate of a matrix determines the propagation speed of pitting corrosion. Besides being easy to cause pitting corrosion sources, the inclusions and the stainless steel matrix have a potential difference of about hundred millivolts, and in a corrosion medium, the inclusions and the matrix respectively serve as a cathode and an anode of an electrochemical reaction to accelerate the corrosion of the matrix. The inclusions in the medium chromium ferritic stainless steel are usually MgO and Al2O3Oxide inclusions of the type CaO, etc., the total oxygen content in the steel in the test, To]The level of inclusions in the stainless steel is represented, and the purpose of controlling the total oxygen content and reducing the inclusions can be achieved by controlling the contents of Mg, Al, Ca and other elements in the stainless steel plate. The invention can realize the total oxygen content T [ O ] in the medium-chromium ferritic stainless steel by controlling the contents of the elements such as Mg, Al, Ca and the like]A technical effect of less than 35 ppm. The experimental study shows that when the total oxygen quantity T [ O ]]When the content of the chromium-containing ferritic stainless steel is increased from 18ppm to 27ppm, the uniform corrosion rate of the chromium-containing ferritic stainless steel in the sodium chloride hydrochloride solution can be improved by 20 percent.
Further, the inventors have found that the synergistic effect of the complex addition of trace alloying elements such as Mn, Cu, Al and the like is exhibited, and the synergistic effect plays a critical role in reducing the corrosion rate of the medium-chromium ferritic stainless steel sheet after pitting corrosion, without affecting the workability of the stainless steel sheet. FIG. 1 shows the uniform corrosion rate vs. (w) of medium chromium ferritic stainless steel 022Cr18Ti measured in NaCl HCl solutionMn+8wCu) X 100. In FIG. 1, wMnRepresents the mass percent of Mn, wCuRepresents the mass percent of Cu. As can be seen from FIG. 1, when (w)Mn+8wCu) When the value of x 100 is less than 1.0, the corrosion rate is dependent on (w)Mn+8wCu) An increase of x 100 decreases rapidly followed by a slow decrease. FIG. 2 shows (w)Mn+8wCu) Anodic polarization curves of two medium chromium ferritic stainless steels 022Cr18Ti at room temperature in 3.5% NaCl solution with x 100 of 0.2 and 1.1, respectively. NaCl and pure water are selected to prepare 3.5 percent (mass fraction) NaCl solution, the experiment temperature is room temperature, during the test, the working electrode is stabilized for 10min under open-circuit potential to form a stable test system, and then the potential polarization measurement is carried out. Measuring key parameters i in the polarization process of two samplesc,0(cathodic exchange Current), ia,0(anodic exchange Current), Ec,0(cathode balance electrode potential), Ea,0(anode balance electrode potential) and the like are plotted in an evans (Evens) diagram, as shown in fig. 3. Based on the results of electrochemical tests, the inventor finds that the corrosion rate is faster when the difference of the exchange current densities of the stainless steel cathode and anode reactions is larger, and the composite addition of Mn and Cu greatly reduces the exchange current densities of the cathode and anode reactions and reduces the difference of the exchange current densities of the cathode and anode reactions, so that the corrosion of a matrix is macroscopically delayed, and the rust area after part simulation tests is also greatly reduced.
To this end, according to an embodiment of the present invention, there is provided a medium-chromium ferritic stainless steel, wherein the medium-chromium ferritic stainless steel includes the following chemical components in percentage by mass:
c: 0.001% -0.05%; n: 0.001% -0.05%; si: 0.02% -0.6%; cr: 16% -20%; p is less than or equal to 0.04 percent; s is less than or equal to 0.003 percent; al: 0.005% -0.15%; mn: 0.05 percent to 0.5 percent; cu: 0.015% -0.15%; the rest is Fe and inevitable impurities;
wherein the contents of Mn and Cu also satisfy 0.4<(wMn+8wCu)×100<1.5, wherein wMnRepresents the mass percent of Mn, wCuRepresents the mass percent of Cu.
Further, in an embodiment, the medium-chromium ferritic stainless steel may further include any one or any two of the following chemical composition combinations by mass percent:
Ti：0.001％～0.8％；Nb：0.001％～0.8％；V：0.001％～0.8％。
further, in an embodiment, the medium chromium type ferritic stainless steel may further include the following chemical components by mass percent:
Ni：0.05％～0.5％；Mo：0.0015％～2％；
wherein the Ni content also satisfies 0.18<(wNi+4wCu) X 100 < 1, wherein wNiRepresents the mass percentage of Ni.
Further, in an embodiment, the medium chromium type ferritic stainless steel may further include any combination of the following chemical components by mass percent:
B：0.0001％～0.0015％；Ca＜0.0015％；Mg＜0.001％。
further, in an embodiment, the medium chromium type ferritic stainless steel may include the following chemical components in percentage by mass: p: 0.01 to 0.04 percent; s: 0.0005 to 0.003 percent.
Further, in one embodiment, the total oxygen content T [ O ] of the medium chromium type ferritic stainless steel is less than or equal to 35 ppm.
Further, in one embodiment, the steel plate made of the medium chromium type ferritic stainless steel can be subjected to surface grinding and then soaked in a 5% NaCl +1mol/L HCl solution at 35 ℃ for 2 hours, and the uniform corrosion rate of the steel plate is lower than 40 g/(m)2×h)。
The medium chromium ferritic stainless steel according to any of the above embodiments can be applied to home appliances, kitchen appliances, mufflers and tail pipes of automobile exhaust systems, products, and exterior decorations of buildings. The medium-chromium ferritic stainless steel can also be applied to other common humid environments and acid environments.
The medium-chromium ferritic stainless steel provided by the embodiment of the invention has the following beneficial effects:
according to the invention, on the premise of not influencing the processability of the medium-chromium ferritic stainless steel plate, through the compound addition of trace alloy elements such as Mn, Cu and Al and the like and the synergistic effect of the trace alloy elements, the corrosion rate of the medium-chromium ferritic stainless steel plate after pitting corrosion can be greatly reduced, so that the medium-chromium ferritic stainless steel has excellent corrosion resistance and processability.
Tests show that the ferritic stainless steel plate made of the medium-chromium ferritic stainless steel can utilize the sodium chloride hydrochloride solution soaking method to perform uniform corrosion rate test, after surface grinding, the ferritic stainless steel plate is soaked in 5% NaCl +1mol/L HCl solution at 35 ℃ for 2 hours, and the results show that the uniform corrosion rate can be lower than 40 g/(m)2Xh) compared with the similar steel plate in the prior art, the corrosion rate can be obviously reduced, even can be reduced by more than 40%.
Drawings
The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 shows the uniform corrosion rate vs. (w) of medium chromium ferritic stainless steel 022Cr18Ti measured in NaCl HCl solutionMn+8wCu) X 100 plot;
FIG. 2 shows (w)Mn+8wCu) Anodic polarization curves of two medium chromium ferritic stainless steels 022Cr18Ti with x 100 of 0.2 and 1.1, respectively, in a 3.5% NaCl solution at room temperature;
FIG. 3 shows (w)Mn+8wCu) Two medium chromium ferritic stainless steels 022Cr18Ti with x 100 of 0.2 and 1.1 respectively at room temperature 3.5%And uniformly corroding corresponding Evans (Evens) graphs in the NaCl solution.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention and the accompanying drawings. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The technical solution provided by the embodiment of the present invention is illustrated in the following with reference to the accompanying drawings.
First, the respective main conditions of the present invention will be described in detail.
Note that in this context, "%" of the content of each element represents "mass%" or mass percentage.
C and N are harmful elements in medium-chromium ferritic stainless steel, are easily combined with Cr to form a chromium carbonitride second phase, and the processability and corrosion resistance are reduced along with the increase of the content of C and N. Therefore, the upper limit of the content of both C and N can be controlled below 0.05 percent; the lower limits of the contents of C and N are both 0.001 percent and are limited by equipment capacity and smelting cost.
Si is added as a deoxidizing element, but a small amount of Si is dissolved in a matrix in a solid solution manner, so that the yield and tensile strength of the medium-chromium ferrite stainless steel can be improved, and the service life of parts is prolonged; excessive addition leads to poor shaping, so the upper limit can be controlled at 0.6%, and the extreme decrease of Si content greatly increases the smelting cost, so the lower limit can be controlled at 0.02%.
Cr is a key element for ensuring the basic corrosion resistance of the medium-chromium ferritic stainless steel, and the content can be controlled to be 16-20% in comprehensive consideration of corrosion resistance, processability and cost.
P is an impurity element in the medium-chromium ferritic stainless steel, and P is dissolved in the matrix to improve the strength, but P is easily segregated in the grain boundary, thereby weakening the intergranular action, lowering the toughness of the stainless steel and causing cold brittleness, so that P can be controlled to 0.04% or less, and preferably 0.01% to 0.04% in view of the smelting cost.
S is an impurity element in the medium-chromium ferrite stainless steel, and is easy to form MnS inclusions with Mn elements in a matrix to become a pitting corrosion source, so that the corrosion resistance is deteriorated, the equipment capacity and the desulfurization cost are considered, and the S is preferably controlled to be 0.0005-0.003%.
Al is an important deoxidizing element in the medium-chromium ferritic stainless steel and is an important element for ensuring that the total oxygen T [ O ] in the steel plate is less than or equal to 35 ppm; the addition of Al can also improve the yield of Ti in the Ti-containing ferritic stainless steel and reduce the cost, so the lower limit of the Al content can be 0.005 percent. However, since excessive addition of Al deteriorates workability and weldability of ferritic stainless steel, the upper limit of Al is controlled to 0.15%.
Mn is an inevitable element in the raw material alloy for stainless steel smelting, and Mn is a solid solution strengthening element, so that the strength of the medium-chromium ferritic stainless steel can be improved. However, the research results of fig. 1 show that the composite addition of Mn and Cu can greatly reduce the uniform corrosion rate of the steel sheet, and the lower limit of the Mn content can be controlled to 0.05% in order to ensure that the uniform corrosion rate targeted by the present invention is obtained. When the content of Mn exceeds 0.5%, the effect on the uniform corrosion rate is saturated, and the excessive addition of Mn increases brittleness and deteriorates workability of the ferritic stainless steel, so that the upper limit of the Mn content can be controlled to 0.5%.
Cu is an element for remarkably reducing the corrosion rate of the medium-chromium ferritic stainless steel plate after pitting corrosion by utilizing the composite effect with Mn, as shown in fig. 1. In addition, a small amount of copper element is beneficial to improving the workability of the ferritic stainless steel, but excessive Cu addition increases the cost and is not beneficial to the stress corrosion resistance of the ferritic stainless steel. In order to obtain the uniform corrosion rate of the invention, the synergistic effect of Mn and Cu can be exerted, the harmful effect of Cu can be avoided, the Cu content can be controlled to be 0.015-0.15%, and simultaneously, when the Mn and Cu contents are selected, 0.4 can be ensured<(wMn+8wCu)×100<1.5.
Ti, Nb and V are elements fixed C, N in the medium chromium type ferritic stainless steel, and one or two of them may be selectively added. The addition of Ti, Nb and V can not only improve the workability of the ferritic stainless steel, but also inhibit the intergranular corrosion of the welding part of the steel. When Ti is excessively added, TiN chain-like inclusions and titanium oxide-like inclusions are easily formed, the toughness and corrosion resistance of the ferritic stainless steel are reduced, and the surface quality of the steel plate is deteriorated; the excessive addition of Nb can improve the strength of the ferritic stainless steel and reduce the shaping, which is unfavorable for the processability; v is a noble metal, and excessive addition can increase the manufacturing cost. Combining the above factors, the optimal control ranges of Ti, Nb and V can be respectively Ti: 0.001% -0.8%; nb: 0.001% -0.8%; v: 0.001 to 0.8 percent.
Both Ni and Mo are elements for further reducing the uniform corrosion rate of the medium-chromium ferritic stainless steel by utilizing the composite effect of the Ni and the Mo with Mn and Cu, and both the elements belong to expensive metals. Ni also contributes to the improvement of the workability of ferritic stainless steel, but the composite addition of the Ni and the Cu can increase the stress corrosion sensitivity of the medium-chromium ferritic stainless steel after being processed, and by combining the above influencing factors, the optimal control range of Ni can be 0.05-0.5%, the optimal control range of Mo can be 0.0015-2%, and the Ni content also meets 0.18<(wNi+4wCu)×100＜1。
B is an element for improving the grain boundary strength of the medium-chromium ferritic stainless steel, and the addition of a small amount of B can contribute to the improvement of the deep drawing ratio of the steel. However, the B element is enriched in the grain boundary to inhibit the growth of crystal grains, and the addition of trace B element can obviously increase the strength of the ferritic stainless steel plate and reduce the shaping. Therefore, the B content can be preferably controlled to 0.0001% to 0.0015%.
Ca and Mg are deoxidizing elements in medium-chromium ferritic stainless steel, and both the Ca and the Mg exist in the form of metal oxides in the stainless steel plate, so that the lower the content of the Ca and the Mg is, the better the content is to reduce the influence of inclusions on corrosion resistance, but the Ca content can be controlled to be less than 0.0015% and the Mg content can be controlled to be less than 0.001% respectively in consideration of smelting cost.
According to the medium chromium ferritic stainless steel of the embodiment of the invention, the total oxygen amount T [ O ] in the steel sheet can be controlled to be less than 35ppm by controlling the content of deoxidizing elements such as Si, Al, Ca, Mg and the like in the steel, and the corrosion rate of the medium chromium ferritic stainless steel after pitting corrosion can be greatly reduced by compositely adding elements such as Mn, Cu, Ni and the like, so that the medium chromium ferritic stainless steel of the invention has the target of excellent corrosion resistance and processability.
Examples
The medium chromium type ferritic stainless steel according to the embodiment of the present invention will be described below by way of example.
Table 1 shows the chemical compositions of seven examples of the medium chromium type ferritic stainless steel according to the present invention and three comparative examples thereof. Table 2 shows the results of the evaluation of the corrosion resistance and the workability of each of the ten test steels in table 1.
Ferritic stainless steels having chemical compositions shown in table 1, including examples 1 to 7 according to the present invention, and comparative examples 1 to 3, were produced by smelting. Firstly, preparing a round rod with the diameter of 5mm in a smelting ingot; next, obtaining total oxygen amount T [ O ] in the steel plate by an oxygen-nitrogen analyzer; and next, subjecting the continuous casting slab to hot rolling, hot rolled plate annealing, cold rolling and cold rolled plate annealing to manufacture a medium-chromium ferritic stainless steel plate with the thickness of 0.5 mm.
The steel sheets of examples 1 to 7 and comparative examples 1 to 3 described above were each subjected to a test of formability index, for example, a test of a parameter indicating workability of a stainless steel sheet, using an electronic tensile tester. The parameter for characterizing the workability of the stainless steel sheet may include elongation A50mmA plastic strain ratio r and a strain hardening exponent n.
The corrosion resistance of the sample can be tested by adopting a sodium chloride hydrochloride solution soaking method, GB/T17987-.
The sodium chloride hydrochloride solution soaking method and GB/T17987-. The third method, GB/T10125-1997 salt fog test for Artificial atmosphere Corrosion test, can have a specimen size of 50X 80mm, which can be designated as the third specimen. The first, second and third specimens may each have a thickness of 0.5 mm.
For testing, all surfaces of the first, second and third test specimens may be first polished, and then these specimens may be washed in an alcohol solution for use.
Next, a test solution of 5% NaCl +1mol/L HCl may be prepared, heated in a water bath to 35 ℃, and then the first sample may be placed in the test solution to be soaked for 2 hours, after which the first sample is taken out to measure its uniform corrosion rate.
Next, a 6% ferric chloride hydrochloride solution may be prepared, heated in a water bath to 35 ℃, and then a second sample may be placed in the test solution for 1.5 hours, after which the second sample is removed to measure its pitting rate.
Next, the salt spray corrosion may be performed using a 5% NaCl solution, the temperature in the salt spray box may be 35. + -.2 ℃, and the spraying is continued for 168 hours, after which a third sample is taken out to measure its pitting corrosion rate.
The results of the three tests are shown in table 2.
On the one hand, as can be seen from Table 2, the uniform corrosion rates of 7 ferritic stainless steel sheets prepared according to the compositions of examples 1 to 7 of the present invention after surface grinding in the aforementioned conditions of 35 ℃ in the NaCl HCl solution immersion method, 5% NaCl +1mol/L HCl solution for 2 hours were less than 40 g/(m)2X h). Compared with the similar steel plates of the comparative examples, the corrosion rate can be obviously reduced, even reduced by more than 80 percent.
For example, the results of the corrosion resistance tests of comparative examples 2 and 3 show that, although there is no significant change in the salt spray corrosion and corrosion rates in the ferric trichloride solution, the uniform corrosion rate is significantly increased. In particular, the difference between the corrosion rates of example 5 and comparative example 2 according to the present invention was 57.8 g/(m)2Xh), the corrosion rate of example 5 according to the invention can be reduced by 82.4%. The comparative test results show that the corrosion rate after pitting corrosion can be reduced by compositely adding trace alloying elements such as Mn, Cu, Al and Ni and exerting the synergistic effect of the trace alloying elements.
Thus, based onAccording to the comparative test results, the total oxygen content T [ O ] in the steel plate can be controlled by controlling the contents of four deoxidizing elements of Si, Al, Ca and Mg]The uniform corrosion rate is controlled to be below 35ppm, and the uniform corrosion rate is controlled to be 40 g/(m) by compositely adding elements such as Mn, Cu, Ni and the like2X h) or less, the corrosion resistance is remarkably improved.
On the other hand, as can be seen from table 2, the 7 medium chromium type ferritic stainless steel plates prepared using the compositions of inventive examples 1 to 7 in table 1 can have the following beneficial property value ranges: elongation A50mmGreater than 28%; the plastic strain ratio r is more than 1.6; the strain hardening exponent n is greater than 0.19. The numerical ranges of the above parameters indicate that all of the 7 medium chromium type ferritic stainless steel sheets prepared according to the composition of examples 1 to 7 of the present invention have excellent formability.
In comparison, in comparative example 1, the contents of Al, Mn and B elements exceed the composition ranges of 7 kinds of medium-chromium ferritic stainless steel plates prepared according to the present invention, and the elongation A is50mmThe plastic strain ratio r value and the strain hardening index n value are all significantly reduced, and the workability is deteriorated. In comparative examples 2 and 3, (w)Mn+8wCu) X 100 does not satisfy the requirement of "less than 1.5 and more than 0.4", and the Al content in comparative example 2 is lower than the composition requirement range of the medium chromium type ferritic stainless steel plate prepared according to the present invention.
The above comparative test results show that the medium chromium-based ferritic stainless steel according to the examples of the present invention and the medium chromium-based ferritic stainless steel plate manufactured therefrom can combine excellent corrosion resistance and workability.
In contrast, the ferritic stainless steel of comparative example 1 has a good uniform corrosion rate of 13.2 g/(m)2Xh) but its elongation A)50mmThe r value of the plastic strain ratio and the n value of the strain hardening index are all obviously reduced, and the processability is deteriorated; the ferritic stainless steels of comparative examples 2 and 3 have good elongation A50mmA plastic strain ratio r value, and a strain hardening index n value, but the uniform corrosion rate thereof is significantly increased. Therefore, none of the ferritic stainless steels of comparative examples 1, 2, and 3 has both good corrosion resistance and workability.
The medium-chromium ferritic stainless steel in the embodiment of the invention can be applied to household appliances, kitchen equipment, silencers and tail pipes of automobile exhaust systems, products and exterior decorations of buildings. However, the medium chromium type ferritic stainless steel according to the present invention is not limited to the above-mentioned application, and may be applied to other suitable general wet environments and acidic environments.
Finally, it should be noted that: the above examples are only for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
TABLE 1
TABLE 2
Claims (6)
1. The medium-chromium ferritic stainless steel is characterized by comprising the following chemical components in percentage by mass:
c: 0.001% -0.05%; n: 0.001% -0.05%; si: 0.02% -0.6%; cr: 16% -20%; p is less than or equal to 0.04 percent; s is less than or equal to 0.003 percent; al: 0.005% -0.15%; mn: 0.35 to 0.4 percent; cu: 0.08% -0.09%; the rest is Fe and inevitable impurities;
wherein the contents of Mn and Cu also satisfy 0.4<（wMn+8wCu）×100<1.5, wherein wMnRepresents the mass percent of Mn, wCuRepresents the mass percent of Cu;
the paint also comprises any one or any two of the following chemical composition combinations in percentage by mass:
Ti：0.001%～0.8%；Nb：0.001%～0.8%；V：0.001%～0.8%；
the paint also comprises the following chemical components in percentage by mass:
Ni：0.11%～0.18%；Mo：0.0015%～2%；
wherein the Ni content also satisfies 0.18<（wNi +4 wCu) X 100 < 1, wherein wNiRepresents the mass percentage of Ni.
2. The medium chromium ferritic stainless steel of claim 1 further comprising any combination of the following chemical compositions in mass percent:
B：0.0001%~0.0015%； Ca＜0.0015%；Mg＜0.001%。
3. the medium chromium ferritic stainless steel of claim 2 comprises the following chemical composition in mass percent:
P：0.01%~0.04%；S：0.0005%~0.003%。
4. a medium chromium ferritic stainless steel as set forth in claim 1 wherein the total oxygen amount T [ O ] is not more than 35 ppm.
5. The medium chromium ferritic stainless steel of claim 1 wherein the uniform corrosion rate of the steel sheet made of the medium chromium ferritic stainless steel is less than 40 g/(m) after being surface ground and then immersed in a 5% NaCl +1mol/L HCl solution at 35 ℃ for 2 hours2×h)。
6. The medium chromium ferritic stainless steel according to any one of claims 1 to 5, which is used for home appliances, kitchen appliances, mufflers and tail pipes of automobile exhaust systems, and exterior decorations of buildings.
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| CN101899625A (en) * | 2009-05-25 | 2010-12-01 | 宝山钢铁股份有限公司 | Ferrite stainless steel and manufacturing method thereof |
| CN105874092A (en) * | 2014-01-08 | 2016-08-17 | 杰富意钢铁株式会社 | Ferritic stainless steel and method for producing same |
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| CN101899625A (en) * | 2009-05-25 | 2010-12-01 | 宝山钢铁股份有限公司 | Ferrite stainless steel and manufacturing method thereof |
| CN105874092A (en) * | 2014-01-08 | 2016-08-17 | 杰富意钢铁株式会社 | Ferritic stainless steel and method for producing same |
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