CN113166891A - Low Cr ferritic stainless steel having excellent formability and high temperature characteristics and method for manufacturing the same - Google Patents

Low Cr ferritic stainless steel having excellent formability and high temperature characteristics and method for manufacturing the same Download PDF

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CN113166891A
CN113166891A CN201980081706.6A CN201980081706A CN113166891A CN 113166891 A CN113166891 A CN 113166891A CN 201980081706 A CN201980081706 A CN 201980081706A CN 113166891 A CN113166891 A CN 113166891A
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stainless steel
high temperature
ferritic stainless
low
temperature characteristics
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郑壹酂
林珍佑
柳汉振
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Posco Holdings Inc
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Posco Co Ltd
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
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    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/004—Dispersions; Precipitations
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    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

Abstract

Disclosed are a low Cr ferritic stainless steel having excellent formability and high temperature characteristics, and a method for manufacturing the same. Embodiments of the present invention can provide a low Cr ferritic stainless steel having excellent high temperature strength and high temperature oxidation resistance corresponding to a high Cr ferritic stainless steel and ensuring formability and a method of manufacturing the same, by optimizing the amounts of Ci, Si, Sn and using solid solution strengthening and precipitation strengthening without increasing the amount of Cr or adding Nb.

Description

Low Cr ferritic stainless steel having excellent formability and high temperature characteristics and method for manufacturing the same
Technical Field
The present disclosure relates to a low Cr ferritic stainless steel, and more particularly, to a low Cr ferritic stainless steel capable of securing formability while having excellent high temperature strength and high temperature oxidation resistance, and a method of manufacturing the same.
Background
Ferritic stainless steel has excellent corrosion resistance while adding cheaper alloying elements, and has price competitiveness higher than that of austenitic stainless steel. In particular, the low Cr ferritic stainless steel of 9% to 14% has excellent cost competitiveness and is used for exhaust system components (muffler, exhaust manifold, collector cone, etc.) corresponding to an exhaust temperature range of room temperature to 800 ℃.
However, the high temperature strength and the high temperature oxidation resistance are inferior to those of the steel having high Cr and added with Nb, and thus there is a limitation in the expansion of the use. Increasing the Cr content or adding Nb to improve the high temperature strength and the high temperature oxidation resistance causes an increase in manufacturing costs. Therefore, development is required that can improve high temperature characteristics without adding Nb to low Cr ferritic stainless steel.
Disclosure of Invention
Technical problem
Embodiments of the present disclosure provide a low Cr ferritic stainless steel having excellent formability corresponding to a high Cr ferritic stainless steel and excellent high temperature strength and high temperature oxidation resistance, and a method of manufacturing the same, without increasing Cr content or adding Nb, by optimizing Ci, Si, Sn content and utilizing solid solution strengthening and precipitation strengthening.
Technical scheme
According to one aspect of the present disclosure, a low Cr ferritic stainless steel having excellent formability and high temperature characteristics includes, in weight percent (%) of the entire composition: c: 0.005% to 0.015%, N: 0.005% to 0.015%, Si: 0.5 to 1.5%, Mn: 0.1 to 0.5%, Cr: 9 to 14%, Ti: 0.1 to 0.3%, Cu: 0.3% to 0.8%, Al: 0.01 to 0.05%, Sn: 0.005% to 0.15%, the balance of Fe and other unavoidable impurities, and satisfying the following formulae (1) and (2).
(1)Cu+Si＝1.3
(2)Si+Cu+10*Sn≤＝3.0
Here, Si, Cu, and Sn mean the content (wt%) of each element.
The low Cr ferritic stainless steel may further comprise: ni: 0.3% or less, P: 0.04% or less, and S: 0.002% or less.
The ferritic stainless steel may contain 0.03% or more of Cu precipitates having a size of 1nm to 500nm in the matrix.
The high temperature strength at 900 ℃ may be 12MPa or greater.
The elongation may be 30% or more.
The low Cr ferritic stainless steel may satisfy the following formula (3).
(3)(Si+5*Sn)/Ti＝5.0
According to one aspect of the present disclosure, a method of manufacturing a low Cr ferritic stainless steel having excellent formability and high temperature characteristics includes: subjecting a ferritic stainless steel cold-rolled steel sheet to a cold-rolling annealing heat treatment, the ferritic stainless steel cold-rolled steel sheet comprising, in weight percent (%): c: 0.005% to 0.015%, N: 0.005% to 0.015%, Si: 0.5 to 1.5%, Mn: 0.1 to 0.5%, Cr: 9 to 14%, Ti: 0.1 to 0.3%, Cu: 0.3% to 0.8%, Al: 0.01 to 0.05%, Sn: 0.005% to 0.15%, the balance of Fe and other unavoidable impurities, and satisfying the following formulas (1) and (2); and rapidly cooling to a temperature range of 450 ℃ to 550 ℃ and holding for 5 minutes or more.
(1)Cu+Si＝1.3
(2)Si+Cu+10*Sn≤＝3.0
Here, Si, Cu, and Sn mean the content (wt%) of each element.
The cold-rolled annealed steel sheet may contain 0.09% or more of Cu precipitates having a size of 1nm to 500nm in the matrix.
The high temperature strength at 900 ℃ of the cold-rolled annealed steel sheet may be 14.5MPa or more.
The cold-rolled steel sheet may satisfy the following formula (3).
(3)(Si+5*Sn)/Ti＝5.0
Advantageous effects
The low Cr ferritic stainless steel according to the embodiment of the present disclosure may improve high temperature strength by 30% or more compared to the existing high temperature strength by distributing fine Cu precipitation phases along with the solid solution strengthening effect of Si and Cu, and may also improve high temperature oxidation resistance by surface concentration of Si and Sn.
In addition, poor formability due to an increase in the content of alloying elements may be prevented, and high temperature strength characteristics may be more excellent when the manufacturing method according to the present disclosure is applied.
Drawings
Fig. 1 is a graph showing the correlation between the high temperature characteristics of equations (1) and (3) according to the present disclosure.
Detailed Description
A low Cr ferritic stainless steel having excellent formability and high temperature characteristics according to an embodiment of the present disclosure includes, in weight percent (%): c: 0.005% to 0.015%, N: 0.005% to 0.015%, Si: 0.5 to 1.5%, Mn: 0.1 to 0.5%, Cr: 9 to 14%, Ti: 0.1 to 0.3%, Cu: 0.3% to 0.8%, Al: 0.01 to 0.05%, Sn: 0.005% to 0.15%, the balance of Fe and other unavoidable impurities, and satisfying the following formulae (1) and (2).
(1)Cu+Si＝1.3
(2)Si+Cu+10*Sn≤＝3.0
Here, Si, Cu, and Sn mean the content (wt%) of each element.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following embodiments are provided to convey the technical concept of the present disclosure to those of ordinary skill in the art. However, the present disclosure is not limited to these embodiments, and may be embodied in other forms. In the drawings, portions irrelevant to the description may not be shown in order to clearly illustrate the present disclosure, and furthermore, the sizes of components are more or less exaggeratedly shown in order to facilitate understanding.
In addition, when a portion "includes" or "includes" an element, the portion may also include other elements, not excluding the other elements, unless there is a description specifically contrary thereto.
Unless the context clearly dictates otherwise, expressions used in the singular include plural expressions.
As a result of conducting various studies to improve the high-temperature strength and the high-temperature oxidation resistance of low-cost low-Cr ferritic stainless steel, the present inventors have been able to obtain the following knowledge.
Generally, Nb is added to ferritic stainless steel for exhaust systems for high-temperature strength. The addition of niobium is not a desirable development since the raw material cost of Nb is relatively expensive and results in increased manufacturing costs. It is known that alternative solid solution strengthening elements are effective for improving high temperature strength. In particular, when an alternative solid solution strengthening element is added, the greater the difference in weight and atomic radius compared to Fe and Cr, the stronger the solid solution strengthening effect. In the periodic table, alloying elements such as Si, Cu, Sn, etc. are far from Fe, Cr, and there are differences in weight and atomic radius. Therefore, it was determined that it can replace existing Nb and be subjected to composition optimization to improve high-temperature strength.
Meanwhile, the Cr content is generally increased in order to improve the high-temperature oxidation resistance. However, since Cr also has high raw material cost and causes an increase in manufacturing cost, increasing the content of chromium is not a desirable development direction. With respect to high temperature oxidation resistance, when exposed to high temperatures for a long period of time, some elements are densely concentrated on the surface to inhibit the formation of an iron oxide film. In the present disclosure, Si, Cu, and Sn are selected as candidate elements that can be concentrated on the surface, and composition optimization is performed to improve high-temperature oxidation resistance.
Including the above, the present disclosure must satisfy the following component system conditions and formulas.
A low Cr ferritic stainless steel having excellent formability and high temperature characteristics according to an embodiment of the present disclosure includes, in weight percent (%): c: 0.005% to 0.015%, N: 0.005% to 0.015%, Si: 0.5 to 1.5%, Mn: 0.1 to 0.5%, Cr: 9 to 14%, Ti: 0.1 to 0.3%, Cu: 0.3% to 0.8%, Al: 0.01 to 0.05%, Sn: 0.005% to 0.15%, the remainder being Fe and other unavoidable impurities.
Hereinafter, the reason for the numerical limitation of the contents of the alloy component elements in the embodiments of the present disclosure will be described. Hereinafter, unless otherwise specified, the unit is weight%.
The content of C is 0.005% to 0.015%.
When the C content exceeds 0.015%, it combines with Cr to form Cr23C6Precipitates, which reduce the high temperature oxidation resistance due to local Cr consumption in the matrix. Further, in order to control the C content to less than 0.005%, the VOD process for steel making increases in cost, which is not preferable. Therefore, the content of C is limited to the range of 0.005% to 0.015%.
The content of N is 0.005% to 0.015%.
When N in the steel exceeds 0.015%, the concentration of dissolved N reaches its limit, and it combines with Cr to form Cr2N precipitates, resulting in a decrease in high temperature oxidation resistance due to local Cr consumption in the matrix. In addition, in order to control the N content to less than 0.005%, the VOD process for steel making is increased in cost,this is not preferred. Therefore, the content of N is limited to the range of 0.005% to 0.015%.
The content of Si is 0.5% to 1.5%.
Si is a solid solution strengthening element for improving high temperature strength, and also improves high temperature oxidation resistance by forming a Si-rich oxide film on the surface layer. For both effects described above, the minimum Si content is required to be 0.5% or more, and if it exceeds 1.5%, workability of the material is greatly deteriorated, and thus the Si content is limited as described above.
The Mn content is 0.1% to 0.5%.
Mn is an impurity inevitably contained in steel, and plays a role of stabilizing austenite. If the Mn content in the low Cr ferritic stainless steel exceeds 0.5%, reverse austenite transformation may occur during an annealing heat treatment after hot rolling or cold rolling, which adversely affects elongation. Therefore, the content of Mn is limited as described above.
The content of Cr is 9-14%.
Cr is an essential element added to form a passive film that suppresses oxidation in stainless steel. In order to form a stable passivation film, 9% or more of Cr should be added. However, since the present disclosure is directed to developing low cost steels with reduced Cr, the upper limit is limited to 14%. More preferably, it may be in the range of 10.5% to 12.5%.
The content of Ti is 0.1 to 0.3 percent.
Ti should be added at least 0.1% to increase the corrosion resistance of the weld. Ti combines with C and N to form Ti (C, N) precipitates, thereby reducing the amount of solid-soluted C and N and suppressing the formation of a Cr-depleted layer. However, when the Ti content exceeds 0.3%, the Ti component of the surface layer reacts with oxygen, causing yellowing. Therefore, the Ti content is limited as described above.
The Cu content is 0.3% to 0.8%.
Cu is an element that contributes to high-temperature strength by substituting Nb as a solid-solution strengthening element. Further, when Cu produces fine precipitates by an appropriate heat treatment, additional high-temperature strength can be expected due to the precipitation strengthening effect. Thus, it is added at least 0.5%. However, if too much Cu is added, the high-temperature hot workability may be impaired, so the amount is limited to 0.8% or less.
The content of Al is 0.01-0.05%.
Al is an element added for deoxidation during steel making. When the Al content exceeds 0.05%, Al in the surface layer reacts with oxygen to form an uneven oxide layer, which adversely affects high-temperature oxidation resistance. Therefore, the Al content is limited as described above.
The content of Sn is 0.005% to 0.15%.
Sn is a solid solution strengthening element for improving high-temperature strength, and at the same time, it improves high-temperature oxidation resistance by forming a Sn-rich oxide film on the surface layer. For both effects, at least 0.005% or more of Sn should be added. However, if it exceeds 0.15%, Sn may segregate at grain boundaries during hot rolling, thereby weakening the intergranular bonding force, causing microcracks in the surface layer. Therefore, the upper limit of the Sn content is limited to 0.15% or less.
Further, according to an embodiment of the present disclosure, may further include: ni: 0.3% or less, P: 0.04% or less, and S: 0.002% or less.
The content of Ni is 0.3% or less. Ni is an impurity inevitably contained in steel, may be contained in an amount of 0.01% or more, and plays a role of stabilizing austenite. When the Ni content in the low Cr ferritic stainless steel exceeds 0.3%, reverse austenite transformation may occur during an annealing heat treatment after hot rolling or cold rolling, which adversely affects elongation. Therefore, the content of Ni is limited as described above.
The content of P is 0.04% or less. P is an inevitable impurity contained in the steel, and the content thereof is adjusted to 0.04% or less because it causes intergranular corrosion or impairs hot workability during pickling.
The content of S is 0.002% or less. S is an inevitable impurity contained in steel, and because it segregates at grain boundaries and impairs hot workability, its content is limited to 0.002% or less.
The remainder of the ferritic stainless steel other than the above-mentioned alloying elements is composed of iron and other unavoidable impurities.
Meanwhile, the low Cr ferritic stainless steel having excellent formability and high temperature characteristics according to one embodiment of the present disclosure may satisfy the following formulas (1) to (3).
(1)Cu+Si＝1.3
The high temperature strength is generally affected by solid solution strengthening and precipitation strengthening. Since Cu and Si are representative solid solution strengthening elements, they are preferably added to improve high temperature strength. When Cu precipitates as a Cu precipitate phase, the high-temperature strength is more effectively improved due to the precipitation strengthening effect. Further, as the Si content increases, the solubility limit of Cu decreases, so that the precipitation of the Cu precipitate phase becomes easier. Therefore, 0.03 wt% or more of a Cu precipitate phase having a size of 1nm to 500nm can be precipitated in the matrix. Therefore, the Cu + Si content is controlled to be in the range of 1.3% or more.
Through the above solid solution strengthening and precipitation strengthening effects, the low Cr ferritic stainless steel according to the present disclosure may exhibit a high temperature strength of 12MPa or more at 900 ℃.
(2)Si+Cu+10*Sn＝3.0
The Si, Cu and Sn alloying elements have a positive effect on the high temperature strength or the high temperature oxidation resistance, respectively, but the material is too hard, resulting in poor elongation and poor formability. In the present disclosure, when Si and Cu improve high temperature strength while satisfying formula (3), 30% or more of elongation may be secured to prevent poor formability. Therefore, in order to ensure the workability of the material, the relationship among the contents of Si, Cu and Sn is controlled within the above range.
(3)(Si+5*Sn)/Ti＝5.0
In the high-temperature oxidation, when Si and Sn are added to the low Cr ferritic stainless steel, a uniform oxide film of Si and Sn is first formed to suppress abnormal oxidation. However, when Ti is added, a Ti oxide film is not uniformly formed, and since the Ti oxide film itself is yellow, high-temperature discoloration occurs. Therefore, the high temperature oxidation resistance can be improved by controlling the contents of Si, Sn, and Ti within the above ranges.
Next, a method of manufacturing a low Cr ferritic stainless steel having excellent formability and high temperature characteristics according to an embodiment of the present disclosure will be described.
The method of manufacturing a low Cr ferritic stainless steel having excellent formability and high temperature characteristics of the present disclosure may manufacture a cold-rolled steel sheet through a conventional manufacturing process, and includes: cold-rolling annealing heat treatment of a ferritic stainless steel cold-rolled steel sheet containing the above alloy composition and satisfying formulas (1) to (3); and rapidly cooling to a temperature range of 450 ℃ to 550 ℃ and holding for 5 minutes or more.
For example, a cold-rolled steel sheet may be manufactured by hot rolling a steel slab including the above alloy composition, annealing the hot-rolled steel sheet, and cold rolling.
After the typical recrystallization heat treatment in the cold-rolling annealing process, the cold-rolled steel sheet may be rapidly cooled to a temperature range of 450 ℃ to 550 ℃ and maintained for 5 minutes or more. By this cooling and holding, the precipitation of the Cu precipitated phase in the same component system can be increased, and the high-temperature strength can be further improved.
Therefore, the cold-rolled annealed steel sheet may contain 0.09 wt% or more of a Cu precipitated phase having a size of 1nm to 500nm in the matrix, and the high-temperature strength of 900 ℃ may be 14.5MPa or more.
Hereinafter, more detailed description will be made by preferred embodiments of the present disclosure.
Examples
Using stainless steel laboratory scale melting and ingot production equipment, 20mm bar samples were prepared with the alloy composition system shown in table 1 below. After reheating at 1200 ℃ and hot rolling to 6mm, hot rolling annealing was performed at 1100 ℃. And annealing heat treatment at 1100 ℃ after cold rolling to 2.0 mm. For only some inventive examples, cold-rolled annealed steel sheets were manufactured by rapidly cooling to 500 ℃ after heat treatment, holding for 7 minutes, and performing air cooling. The remaining inventive examples and comparative examples were air-cooled after the annealing heat treatment.
< Table 1>
Distinguishing C N Si Mn Cr Ti Cu Al Sn
Comparative example 1 0.005 0.010 0.41 0.21 11.4 0.21 0.05 0.02 0
Comparative example 2 0.006 0.008 0.6 0.21 12.1 0.19 0.15 0.02 0.05
Comparative example 3 0.007 0.007 0.2 0.21 11.1 0.18 0.24 0.03 0.06
Comparative example 4 0.006 0.008 1.1 0.20 11.7 0.20 0.08 0.02 0.1
Comparative example 5 0.006 0.007 1.31 0.20 11.9 0.21 0.41 0.02 0.18
Comparative example 6 0.005 0.009 0.6 0.19 11.3 0.15 0.76 0.02 0.21
Inventive example 1 0.006 0.009 0.64 0.21 11.5 0.22 0.73 0.02 0.03
Inventive example 2 0.006 0.008 1.1 0.16 11.8 0.24 0.65 0.02 0.11
Inventive example 3 0.005 0.010 0.86 0.21 12.2 0.22 0.75 0.02 0.08
Inventive example 4 0.007 0.008 0.96 0.21 12.0 0.16 0.49 0.03 0.14
Inventive example 5 0.006 0.008 1.1 0.21 11.8 0.24 0.65 0.02 0.11
Inventive example 6 0.005 0.009 0.86 0.23 12.2 0.22 0.75 0.02 0.08
Inventive example 7 0.007 0.008 0.96 0.20 12.0 0.16 0.49 0.02 0.14
For each cold-rolled annealed steel sheet, the fraction of Cu precipitated phase was measured, and it was examined whether discoloration occurred after 1 hour at 500 ℃. In addition, the high temperature strength at 900 ℃ and the elongation at room temperature were also measured and are shown in Table 2.
< TABLE 2 >
Figure BDA0003108778510000101
In the comparative examples and inventive examples listed in table 1, the contents of Cu, Si, and Sn were changed, and the alloying elements such as C, N, Cr and Ti were controlled within the range of the contents of the present disclosure.
In comparative examples 1 to 4, the content of Cu was less than 0.3%, and the value of formula (1) was less than 1.3, so the amount of fine Cu precipitate phase was low. It was confirmed that the high temperature strength was less than 12MPa due to the lack of solid solution strengthening and precipitation strengthening effects.
Comparative examples 1 to 3 showed that formula (3) was not satisfied because the contents of Si and Sn were less than that of Ti, and high-temperature discoloration occurred because Si-rich and Sn-rich oxide films on the surfaces were not sufficiently formed. Comparative example 4 satisfied formula (3) due to its low Cu content but high Si content, so no discoloration occurred, and it was confirmed that high-temperature oxidation resistance was secured according to formula (3).
In comparative examples 5 and 6, the value of formula (2) exceeded 3.0 due to the high Sn content, and as a result, it was determined that the elongation was reduced by 5.0% as compared with the other comparative examples.
Inventive example 1 satisfies the composition of the present disclosure and formulas (1) and (2). Discoloration occurred at high temperature, but 0.05 wt% of Cu precipitates were precipitated by satisfying formula (1), and the high temperature strength was 12MPa or more. Further, it was confirmed that the high temperature strength was ensured by satisfying formula (2), and the elongation was measured to be 33.3%, indicating excellent formability.
Inventive examples 2 to 4 satisfied all of formulae (1) to (3) by optimizing the contents of Si, Cu and Sn. As a result, high-temperature strength of 13.5MPa or more and elongation of 30.8% or more were exhibited, and high-temperature discoloration did not occur.
Inventive examples 5 to 7 show that all formulas (1) to (3) are satisfied by optimizing the Si, Cu and Sn contents, and that the cooling scheme after the heat treatment according to the present disclosure is applied. An elongation of 30.3% or more is ensured, and as a result of satisfying the rapid cooling and holding time after the heat treatment, 0.09 wt% or more of a fine Cu precipitate phase is precipitated, and the high-temperature strength is 14.6MPa or more. In particular, inventive examples 5 and 6 exhibited high temperature strength of 15MPa or more.
Fig. 1 is a graph showing values of formula (1) and formula (3) according to an embodiment of the present disclosure. The correlation between the formula (1) and the formula (3) with respect to the high temperature strength and the high temperature oxidation resistance can be determined by fig. 1.
As described above, although the exemplary embodiments of the present disclosure have been described, the present disclosure is not limited thereto, and those having ordinary knowledge in the related art may not depart from the spirit and scope of the appended claims. It will be understood that various changes and modifications are possible.
INDUSTRIAL APPLICABILITY
The ferritic stainless steel according to the present disclosure can improve high temperature characteristics of existing steels by 30% or more without increasing Cr content and without adding Nb. Therefore, the cost of raw materials can be reduced.

Claims (10)

1. A low Cr ferritic stainless steel having excellent formability and high temperature characteristics, the ferritic stainless steel comprising, in weight percent (%): c: 0.005% to 0.015%, N: 0.005% to 0.015%, Si: 0.5 to 1.5%, Mn: 0.1 to 0.5%, Cr: 9 to 14%, Ti: 0.1 to 0.3%, Cu: 0.3% to 0.8%, Al: 0.01 to 0.05%, Sn: 0.005% to 0.15%, the remainder being Fe and other unavoidable impurities, and
satisfying the following formulae (1) and (2)
(1) Cu+Si＝1.3
(2) Si+Cu+10*Sn≤＝3.0
Here, Si, Cu, and Sn mean the content of each element in wt%.
2. The low Cr ferritic stainless steel with excellent formability and high temperature characteristics according to claim 1, further comprising: ni: 0.3% or less, P: 0.04% or less, and S: 0.002% or less.
3. The low Cr ferritic stainless steel having excellent formability and high temperature characteristics according to claim 1, wherein the ferritic stainless steel contains 0.03% or more of Cu precipitates having a size of 1nm to 500nm in a matrix.
4. The low Cr ferritic stainless steel having excellent formability and high temperature characteristics according to claim 1, wherein the high temperature strength at 900 ℃ is 12MPa or more.
5. The low Cr ferritic stainless steel having excellent formability and high temperature characteristics according to claim 1, wherein the elongation is 30% or more.
6. The low Cr ferritic stainless steel having excellent formability and high temperature characteristics according to claim 1, wherein the low Cr ferritic stainless steel satisfies the following formula (3)
(3) (Si+5*Sn)/Ti＝5.0
Here, Si, Sn and Ti mean the contents of the respective elements in wt%.
7. A manufacturing method of a low Cr ferritic stainless steel having excellent formability and high temperature characteristics, the manufacturing method comprising:
subjecting a ferritic stainless steel cold-rolled steel sheet to a cold-rolling annealing heat treatment, the ferritic stainless steel cold-rolled steel sheet comprising, in weight percent (%): c: 0.005% to 0.015%, N: 0.005% to 0.015%, Si: 0.5 to 1.5%, Mn: 0.1 to 0.5%, Cr: 9 to 14%, Ti: 0.1 to 0.3%, Cu: 0.3% to 0.8%, Al: 0.01 to 0.05%, Sn: 0.005% to 0.15%, the balance of Fe and other unavoidable impurities, and satisfying the following formulas (1) and (2); and
rapidly cooling to a temperature range of 450 ℃ to 550 ℃ and holding for 5 minutes or more
(1) Cu+Si＝1.3
(2) Si+Cu+10Sn≤＝3.0
Here, Si, Cu, and Sn mean the content of each element in wt%.
8. The method of manufacturing a low Cr ferritic stainless steel having excellent formability and high temperature characteristics according to claim 7, wherein the cold-rolled annealed steel sheet contains 0.09% or more of Cu precipitated phases having a size of 1nm to 500nm in a matrix.
9. The method of manufacturing a low Cr ferritic stainless steel having excellent formability and high temperature characteristics according to claim 7, wherein the 900 ℃ high temperature strength of the cold rolled annealed steel sheet is 14.5MPa or more.
10. The method for manufacturing a low Cr ferritic stainless steel having excellent formability and high temperature characteristics according to claim 7, wherein the cold-rolled steel sheet satisfies the following formula (3)
(3)(Si+5*Sn)/Ti＝5.0
Here, Si, Sn and Ti mean the contents of the respective elements in wt%.
CN201980081706.6A 2018-12-10 2019-02-20 Low Cr ferritic stainless steel having excellent formability and high temperature characteristics and method for manufacturing the same Pending CN113166891A (en)

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