JP2007119848A - Cold rolled ferritic stainless steel sheet having excellent press formability and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold rolled ferritic stainless steel sheet having high elongation and excellent press formability, and to provide its production method. <P>SOLUTION: A steel stock having a composition comprising, by mass, 0.010 to 0.045% C, 0.01 to 0.05% N, ≤1% Mn, 13 to 20% Cr and ≤0.01% Al, and also comprising C and N in such a manner that the volume ratio (v) of Cr carbonitride defined by v(%)=100×ä0.0196C+0.0015N}(wherein, (v): the volume ratio (vol.%) of Cr carbonitride, and C and N: the content (mass%) of each element) reaches ≤0.09% is heated to ≥1,000°C, is hot-rolled so as to be finished at ≥900°C, is coiled at ≥650°C, is subjected to hot rolled sheet annealing and pickling treatment, is cold-rolled at a draft of ≤90%, so as to be a cold-rolled sheet, and is thereafter subjected to continuous annealing at an annealing temperature of 800 to 900°C. In this way, the cold rolled stainless steel sheet having a ferrite single structure with a ferrite grain size of ≥10 μm in which Cr carbonitride of ≤50 pieces per ferrite grain is dispersedly precipitated, and having excellent ductility can be obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ferritic stainless steel cold-rolled steel sheet, and more particularly to an improvement in elongation characteristics that affect press formability.

  Ferritic stainless steel sheets are excellent in corrosion resistance and inexpensive, and are used in a wide range of applications such as building exterior materials, kitchen appliances, and chemical plants. Conventionally, in these applications, the ferritic stainless steel sheet is only required to have excellent corrosion resistance, and has not been required to be excellent in press formability. However, in recent years, even in these applications, the thin steel plate is often press-formed into a complicated three-dimensional shape, and it has been strongly demanded that the ferritic stainless steel plate be excellent in press formability.

  In response to such a request, for example, in Patent Document 1, C: 0.08% or less, Si: 0.70% or less, Mn: 1.00% or less, Cr: 15 to 20%, N: 0.04 to 0.12% (provided that C + N: A ferritic stainless steel plate comprising Fe and unavoidable impurities: remaining is proposed, and the use of this ferritic stainless steel plate is said to prevent the occurrence of stretch strain during press forming. However, the technique described in Patent Document 1 can prevent the occurrence of stretch strain and can eliminate surface polishing after molding, but C + N needs to be 0.08% or more, and the C and N contents are large, and the elongation itself Is low. For this reason, there is a problem that it is difficult to say that the steel sheet is suitable for press forming.

  Patent Document 2 discloses a composite of ferrite and martensite by heating and hot-rolling a stainless steel composition containing C: 0.02 to 0.05%, N: 0.02 to 0.05%, and Al: 0.10 to 0.30%. A hot-rolled sheet having a structure, and then the obtained hot-rolled sheet is subjected to high-temperature and short-term annealing in a temperature range of 850 to 980 ° C. to produce AlN, and then subjected to cold rolling and finish annealing. A method for manufacturing a ferritic stainless steel sheet excellent in the above has been proposed. However, the steel sheet obtained by the technique described in Patent Document 2 anneals martensite generated in the hot-rolled sheet for a short time, so that the martensite stretched in the rolling direction is not equiaxed and is significantly different. It is not suitable for press molding into a three-dimensional shape because it has a direction and may crack in one direction.

  In Patent Document 3, the mother molten steel is made of ferritic stainless steel containing Cr: 10 to 23% and a γ potential of 23% or less, and the γ potential is increased in the unsolidified part in the center of the mold during continuous casting. As a steel slab in which the particles containing the element to be injected are melted and dissolved and the γ potential of the slab inner layer is increased by 5% or more from the value of the mother molten steel, hot rolling, cold rolling and annealing are performed. There has been proposed a method for producing a ferritic stainless steel sheet, which is a ferritic stainless steel sheet having excellent ductility and ridging properties by the process of including. However, in the steel sheet obtained by the technique described in Patent Document 3, although the generation of ridging is reduced, the range of the region where the γ potential at the center of the slab is high is not constant, so that a stable effect cannot be obtained and the elongation is not achieved. There was a problem that the decrease in the r value was remarkable and it was difficult to say that the steel sheet was suitable for press forming.

Patent Document 4 includes hot rolling of a steel material including C: 0.01 to 0.12%, N: 0.01 to 0.12%, Cr: 11 to 18%, and V: 0.03 to 0.15%. After forming the plate, the hot-rolled sheet is subjected to 2-15% cold or warm pre-rolling to promote recrystallization and enable hot-rolled sheet annealing for a short time, followed by cold rolling and finish annealing. A method for producing a ferritic stainless steel cold-rolled steel sheet having excellent ridging resistance has been proposed.
JP 59-80753 A JP-A-9-111354 JP-A-10-99952 Japanese Patent Laid-Open No. 2001-107149

However, the steel sheet manufactured by the method described in Patent Document 4 has a high yield point and sufficient press formability because V carbonitride precipitates and refines crystal grains to harden the material. There was a problem that it was difficult to say that it was a steel plate.
An object of the present invention is to advantageously solve the above-described problems of the prior art, and to propose a ferritic stainless cold-rolled steel sheet having high elongation and excellent press formability and a method for producing the same. The term “excellent in press formability” as used in the present invention refers to a case where the elongation EL value shown when a tensile test is performed using a JIS No. 13 B test piece is 30% or more.

  In order to achieve the above-mentioned problems, the present inventors have made a detailed study on the relationship between the elongation and the structure that greatly affects the press formability of the ferritic stainless cold-rolled steel sheet, particularly the stretch formability. As a result, the present inventors have found that the elongation of the stainless cold-rolled steel sheet increases by activating the dislocation movement during deformation, and for that purpose, by suppressing the fine precipitation of AlN and by the fine AlN Reduces precipitation strengthening and coarsens crystal grains, and then disperses and precipitates in ferrite grains, adjusting the dispersion density of Cr carbonitrides that inhibit dislocation motion to a predetermined value or less, and dispersing Cr carbonitrides sparsely I found out that it would be good to. Plastic deformation is promoted when dislocations pass between sparsely dispersed Cr carbonitrides.

The present invention has been completed based on the above findings and further studies. That is, the gist of the present invention is as follows.
(1) In mass%, C: 0.010 to 0.045%, N: 0.01 to 0.05%, Mn: 1% or less, Cr: 13 to 20%, Al: 0.01% or less, and C and N (1 ) Formula v (%) = 100 x {0.0196C + 0.0015N} (1)
(Where, v: Cr carbonitride volume fraction (volume%), C, N: content of each element (mass%))
In which the volume fraction v of Cr carbonitride is 0.09% or less, the average grain size of ferrite grains is 10 μm or more, and Cr carbonitride is 50 per ferrite grain. A ferritic stainless cold-rolled steel sheet excellent in press formability, characterized by having a ferrite single structure dispersed in pieces or less.

  (2) In (1), the composition includes mass%, C: 0.010 to 0.045%, N: 0.01 to 0.05%, Mn: 1% or less, Cr: 13 to 20%, Al: 0.01% or less In addition, C and N are included so that the volume fraction v of Cr carbonitride defined by the formula (1) is 0.09% or less, Si: 0.4% or less, P: 0.05% or less, S: 0.010% A ferritic stainless steel cold-rolled steel sheet comprising: a balance Fe and inevitable impurities.

(3) A stainless steel material is subjected to a hot rolling process, a hot rolled sheet annealing process for performing hot rolled sheet annealing and pickling, a cold rolled process, and a cold rolled sheet annealing process, In the manufacturing method of the ferritic stainless steel cold rolled steel sheet, the stainless steel material is mass%, C: 0.010 to 0.045%, N: 0.01 to 0.05%, Mn: 1% or less, Cr: 13 to 20%, Al: Including 0.01% or less, and C and N in the following formula (1) v (%) = 100 × {0.0196C + 0.0015N} (1)
(Where, v: volume fraction of Cr carbonitride (volume%), C, N: content of each element (mass%))
A steel material having a composition including a volume fraction v of Cr carbonitride defined by ≦ 0.09%, and the hot rolling process is heated to 1000 ° C. or higher and hot rolled at a temperature of 900 ° C. or higher. Is finished, and then the hot rolled sheet is wound at a coiling temperature of 650 ° C. or more, and the cold rolling process is cold rolled at a cold reduction ratio of 90% or less. Ferritic stainless steel cold rolled excellent in press formability, characterized in that the cold rolled sheet annealing process is a process of subjecting the cold rolled sheet to a continuous annealing at an annealing temperature of 800 to 900 ° C. A method of manufacturing a steel sheet.

  (4) In (3), the stainless steel material is mass%, C: 0.010 to 0.045%, N: 0.01 to 0.05%, Mn: 1% or less, Cr: 13 to 20%, Al: 0.01% or less. And C and N so that the volume fraction v of Cr carbonitride defined by the above formula (1) is 0.09% or less, Si: 0.4% or less, P: 0.05% or less, S: A method for producing a ferritic stainless steel cold-rolled steel sheet, characterized by comprising a steel material having a composition comprising 0.010% or less, the balance being Fe and inevitable impurities.

  According to the present invention, it is possible to easily and inexpensively manufacture a stainless cold-rolled steel sheet having increased elongation and significantly improved press formability, particularly stretch formability, and has a remarkable industrial effect.

First, the reason for limiting the composition of the stainless cold-rolled steel sheet of the present invention will be described. Hereinafter, mass% in the composition is simply expressed as%.
C: 0.010-0.045%
C forms a solid solution in the steel and contributes to stabilization of the austenite phase during hot rolling, and is combined with Cr and precipitated as Cr carbide or Cr carbonitride in the crystal grains or in the grain boundaries. If the C content is less than 0.010%, the austenite phase fraction during hot rolling is lowered, and therefore, ridging is noticeably generated in the cold-rolled steel sheet as the product sheet, and the press formability is deteriorated. On the other hand, if the content exceeds 0.045%, the amount of Cr carbide or Cr carbonitride increases excessively, and the steel sheet becomes hard and the elongation decreases. For this reason, C was limited to the range of 0.010 to 0.045%. In addition, Preferably it is 0.010 to 0.030%.

N: 0.01-0.05%
N, like C, contributes to stabilization of the austenite phase during hot rolling by solid solution in steel, and combines with Cr to form Cr nitrides or Cr carbonitrides in crystal grains or crystal grains. Precipitate at the boundary. If the N content is less than 0.01%, the austenite phase fraction during hot rolling is lowered, and therefore, ridging is noticeably generated in the cold-rolled steel sheet, which is a product sheet, and press formability is deteriorated. On the other hand, if the content exceeds 0.05%, the amount of Cr nitride or Cr carbonitride increases excessively, and the steel sheet becomes hard and elongation decreases. For this reason, N was limited to the range of 0.01 to 0.05%. In addition, Preferably it is 0.01 to 0.035%.

C and N are contained so that the volume ratio v of Cr carbonitride defined by the formula (1) is 0.09% or less within the above range. In the present invention, since the Al content is reduced, C and N are combined with Cr to become Cr carbonitride. As used herein, Cr carbonitride refers to Cr ₂₃ C ₆ , Cr ₂ N, and composite precipitates thereof.
Cr carbonitride volume ratio v: 0.09% or less
The volume ratio v of Cr carbonitride is expressed by the following equation (1): v (%) = 100 × {0.0196 × C + 0.0015N} (1)
(Where, v: volume fraction of Cr carbonitride (volume%), C, N: content of each element (mass%))
Defined by When the volume ratio v of Cr carbonitride exceeds 0.09%, Cr carbonitride increases and it becomes difficult to make it 50 or less per ferrite grain. For this reason, Cr carbonitrides and dislocation motions interact during press forming, and the elongation decreases. For this reason, the volume ratio v of Cr carbonitride defined by the formula (1) is limited to 0.09% or less. Note that v is preferably 0.05 (%) or less.

In the formula (1), 0.0196C means the volume ratio of Cr carbide Cr ₂₃ C ₆ (calculated), and 0.0015N means the volume ratio of Cr nitride Cr ₂ N (calculated).
Mn: 1% or less
Mn is an element that affects the volume fraction of Cr carbonitrides, that is, the number of ferrite grains, in order to control the dispersion of Cr carbonitrides. In the present invention, it is desirable to contain 0.6% or more, but if it exceeds 1%, the steel is hardened and the press formability is lowered. For this reason, Mn was limited to 1% or less. In addition, Preferably it is 0.9% or less, More preferably, it is 0.70 to 0.85%. Moreover, it is preferable to make Mn / Si 2 or more from a viewpoint of form control of a deoxidation product.

Cr: 13-20%
Cr is an element that solidifies and strengthens steel and contributes to an improvement in corrosion resistance, and is an essential element for a stainless steel plate. However, if the Cr content is less than 13%, the corrosion resistance as stainless steel cannot be maintained. On the other hand, if the content exceeds 20%, the steel becomes too hard and the elongation decreases. For this reason, Cr was limited to the range of 13 to 20%.

Al: 0.01% or less
Al acts as a deoxidizer and combines with N in the steel and precipitates as AlN to harden the steel. AlN precipitates before Cr carbonitride and precipitates finely. Precipitation of fine AlN hardens the steel and reduces elongation. Therefore, in the present invention, Al is limited to 0.01% or less. In addition, Preferably it is 0.005% or less.

In the present invention, except for the components described above, it is preferable to limit to Si: 0.4% or less, P: 0.05% or less, and S: 0.010% or less.
Si: 0.4% or less
Si is an element that acts as a deoxidizing agent. In the present invention that limits the Al content to a low level, deoxidation is performed with Si. Si is a solid solution strengthening element, and a large amount of it hardens the steel. Si is a ferrite-forming element and increases the ferrite phase fraction during hot rolling. For this reason, the generation of ridging becomes significant when a large amount of Si is contained. In the present invention, Si is limited to 0.4% or less, preferably 0.2% or less, from the viewpoint of preventing ridging and preventing hardening of steel.

P: 0.05% or less P has an effect of solid strengthening and reinforces the steel remarkably. However, P is an element that segregates at the ferrite crystal grain boundary and embrittles the steel. % Is acceptable. In addition, in order to ensure a high elongation value, it is preferable to limit to 0.03% or less. In addition, More preferably, it is 0.02% or less.

S: 0.010% or less S forms sulfides in steel. When Mn is contained, it binds to Mn to form MnS. MnS expands by hot rolling or the like and exists as precipitates (inclusions) at ferrite grain boundaries. Such sulfide-based precipitates (inclusions) lower the elongation and particularly have a great influence on the occurrence of cracks during bending, so it is desirable to reduce S as much as possible, but it is acceptable up to 0.010%. In addition, Preferably it is 0.005% or less.

The balance other than the above components is Fe and inevitable impurities. Inevitable impurities include Ni: 0.5% or less, Cu: 0.05% or less, Mo: 0.1% or less, V: 0.05% or less, Nb: 0.03% or less, Ti: 0.03% or less, Ca: 0.01% or less, Mg: 0.01% or less is acceptable, but it goes without saying that the smaller the amount of inevitable impurities, the better.
Next, the reason for limiting the structure of the ferritic stainless steel cold rolled steel sheet according to the present invention will be described.

  The structure of the ferritic stainless steel cold-rolled steel sheet of the present invention is a single ferrite structure. As used herein, “ferrite single structure” refers to a structure composed of a ferrite phase and precipitates precipitated in ferrite crystal grains or at ferrite crystal grain boundaries. When a second phase such as a martensite phase, a bainite phase, or an austenite phase is mixed in addition to the ferrite phase, the steel becomes hard and a desired elongation cannot be obtained.

Average grain size of ferrite grains: 10 μm or more If the average grain size of ferrite is less than 10 μm, dislocations tend to proliferate from the grain boundaries due to the constraint of adjacent grains, and dislocation motion is easily inhibited by the interaction between dislocations, and plastic deformation is likely to occur. It doesn't progress and the elongation decreases. For this reason, the lower limit of the average grain size of the ferrite grains is set to 10 μm. Here, the “ferrite particle size” is an average value obtained according to a cutting method based on the provisions of JIS G 0552, and means the ASTM nominal particle size.

Cr carbonitride: 50 or less per ferrite grain If the number of Cr carbonitrides dispersed and precipitated in ferrite grains exceeds 50 per ferrite grain, the grains are formed by plastic deformation with the precipitated Cr carbonitride. Interaction with dislocations generated from the boundary occurs, and the dislocations cannot move between the Cr carbonitrides without hindrance, and the elongation decreases. For this reason, the number of Cr carbonitrides dispersed and precipitated per ferrite grain is limited to 50 or less. Here, “Cr carbonitride” is a general term for Cr carbide and Cr nitride, and when these are combined, the composite is counted as one. Here, Cr carbide mainly refers to Cr ₂₃ C ₆ , and Cr nitride mainly refers to Cr ₂ N. Even if a part of Cr ₂₃ C ₆ and Cr ₂ N is substituted with other elements such as Fe and Mn, there is no difference in effect as long as the crystal structure is equivalent to Cr ₂₃ C ₆ and Cr ₂ N. Here, the “number of Cr carbonitrides” includes only those dispersed in ferrite grains, and does not include those precipitated at grain boundaries.

Note that the number of Cr carbonitrides dispersed and precipitated per ferrite grain is determined from a structural photograph of a plate thickness section parallel to the rolling direction. As the number of Cr carbonitrides, an arithmetic average value of values measured for at least 20 grains adjacent in the cross-sectional structure is used.
Below, the preferable manufacturing method of the ferritic stainless steel cold-rolled steel plate of this invention is demonstrated.

The ferritic stainless steel cold-rolled steel sheet according to the present invention includes a hot-rolling process, a hot-rolled sheet annealing process, a cold-rolling process, a cold-rolling process, It is manufactured by applying a sheet annealing process.
After the molten stainless steel having the above composition is melted by a known melting method, a stainless steel material such as a slab is obtained by a known casting method, preferably a continuous casting method. In the present invention, the melting method and the casting method are not particularly limited. Any known method can be applied.

The obtained stainless steel material is then subjected to a hot rolling process.
In the hot rolling step, the stainless steel material is preferably heated to a temperature of 1000 ° C. or higher. When the heating temperature is less than 1000 ° C., the rolling load becomes excessive, and the steel material having a coarse grain structure is deteriorated in surface quality such as fine cracks, bevels, and surface gloss deterioration due to rolling. For this reason, it is preferable to limit the heating temperature of the steel material to 1000 ° C. or higher.

The heated stainless steel material is subjected to hot rolling at a temperature of 900 ° C. or higher to finish hot rolling to form a hot rolled sheet, and then winding the hot rolled sheet at a winding temperature of 650 ° C. or higher. .
When the end temperature of the hot rolling is less than 900 ° C., the rolling load increases, the surface roughness of the rolling roll increases, and the surface roughness of the hot rolled sheet increases accordingly, leading to deterioration of the surface quality of the steel sheet. For this reason, it is preferable that the completion | finish temperature of hot rolling shall be 900 degreeC or more.

When the coiling temperature is less than 650 ° C., the precipitation of Cr carbonitride is delayed during the hot rolling process, and Cr carbonitride is finely precipitated by hot-rolled sheet annealing in the subsequent process. It becomes difficult to ensure Cr carbonitride dispersion density. For this reason, it is preferable to limit the winding temperature of a hot-rolled sheet to 650 degreeC or more.
Subsequently, the hot-rolled sheet is subjected to a hot-rolled sheet annealing step for performing hot-rolled sheet annealing and pickling treatment. In the present invention, the hot-rolled sheet annealing and pickling treatment are not particularly limited, and it is preferable to use known hot-rolled sheet annealing conditions and pickling treatment conditions. As normal pickling conditions, a mixed acid aqueous solution is used, and preferable hot-rolled sheet annealing conditions can be box annealing from the viewpoint of uniformizing the hot-rolled sheet structure. The annealing temperature for box annealing is preferably 780 ° C. or higher, more preferably 800 ° C. or higher.

The hot-rolled sheet that has been subjected to the hot-rolled sheet annealing process is then subjected to a cold-rolling process to obtain a cold-rolled sheet. The cold rolling condition is not particularly limited as long as it can be a cold-rolled sheet having a desired thickness, but from the viewpoint of setting the ferrite grain size to 10 μm or more, the cold rolling ratio should be 90% or less. preferable. More preferably, it is 80% or less.
Next, the cold-rolled sheet is subjected to a cold-rolled sheet annealing process. In the present invention, in order to set the ferrite grain size to 10 μm or more, the cold-rolled sheet annealing step is preferably a step of performing a continuous annealing that holds the annealing temperature: 800 ° C. or more, more preferably 850 ° C. or more for 10 s or more. . When the annealing temperature is less than 800 ° C., the growth of ferrite grains becomes insufficient. On the other hand, when the annealing temperature is higher than 900 ° C., a part is austenitic and martensite after cooling. It is preferable from the viewpoint of surface properties that the temperature is maintained at the above temperature for 10 s or more, preferably 20 s or more, and then cooled to 400 ° C. or less at a cooling rate of 10 ° C./s or more.

  Note that after the cold-rolled sheet annealing step, temper rolling with an elongation of 1.5% or less, preferably 0.3% or more may be performed for the purpose of shape correction.

  Molten steel having the stainless steel composition shown in Table 1 was made into slabs. Subsequently, these slabs were subjected to a hot rolling process under the conditions shown in Table 2 to obtain hot rolled sheets. The obtained hot-rolled sheet was subjected to soaking at 840 ° C. for 8 hours as a hot-rolled sheet annealing, followed by box annealing that was held at 700 ° C. for 5 hours in the temperature lowering process, and then hot-rolling to pickle the hot-rolled sheet A plate annealing process was performed. Subsequently, the hot-rolled sheet was subjected to a cold-rolling process for performing cold rolling under the conditions shown in Table 2 to obtain a cold-rolled sheet having a thickness shown in Table 2. Subsequently, the cold-rolled sheet was subjected to a cold-rolled sheet annealing step under the conditions shown in Table 2 to obtain a cold-rolled annealed sheet.

The obtained cold-rolled annealed sheet was subjected to a structure test and a tensile test, and the structure and tensile properties were investigated. The test method was as follows.
(1) Microstructure test A test piece was taken from a cold-rolled annealed plate, the central portion of the plate thickness was polished with a cross-sectional thickness parallel to the rolling direction, and corroded with aqua regia to reveal the structure. The obtained structure was observed using a scanning electron microscope (magnification: 2000 times), the structure was imaged, and the number of Cr carbonitrides dispersed and precipitated in ferrite grains was measured by an image analyzer.

The number of Cr carbonitrides was measured for 100 ferrite grains in each specimen, the number of Cr carbonitrides obtained for each ferrite grain was averaged, and Cr carbonitride per ferrite grain in the steel sheet was measured. The number of objects.
In addition, the structure corroded with aqua regia is observed using an optical microscope (magnification: 100 times), a structure photograph is taken, and the grain diameter of ferrite is measured using the structure photograph in accordance with a cutting method compliant with JIS G 0552. Asked. On the structure photograph, draw a line with a length of 2 mm parallel to the plate surface and draw 5 lines in the thickness direction, and draw a line with a length of 0.5 mm perpendicular to the plate surface and 20 in the rolling direction. The number of ferrite grains cut at the line segment was measured. Then, the total line segment length is divided by the number of cut crystal grains, the length of the line segment per crystal grain is calculated, the ASTM nominal grain size is calculated by multiplying the coefficient 1.13, and the ferrite grain average in each steel plate The particle size was taken.
(2) Tensile test JIS 13B tensile test specimens were collected from the obtained cold-rolled annealed sheet so that the rolling direction was the tensile direction, and the tensile test was conducted in accordance with the provisions of JIS Z 2241. Properties (yield strength YS, tensile strength TS, elongation El) were determined.

  The obtained results are shown in Table 3.

  Each of the inventive examples has a structure in which the ferrite grain size is 10 μm or more and the number of Cr carbonitrides per ferrite grain is 50 or less, and El has an elongation characteristic of 30% or more (ductility). It can be inferred that it is excellent in press formability. On the other hand, in a comparative example in which any or all of the composition, the ferrite particle size, and the number of Cr carbonitrides are outside the scope of the present invention, the ductility is deteriorated when El is less than 30%.

Claims (4)

mass%
C: 0.010 to 0.045%, N: 0.01 to 0.05%,
Mn: 1% or less, Cr: 13-20%,
Al: has a composition containing 0.01% or less, C and N so that the volume fraction v of Cr carbonitride defined by the following formula (1) is 0.09% or less, and further the average crystal of ferrite grains A ferritic stainless steel cold-rolled steel sheet with excellent press formability, characterized by having a ferrite single structure having a particle size of 10 μm or more and 50 or less Cr carbonitrides dispersed per ferrite grain.
Record
v (%) = 100 × {0.0196C + 0.0015N} (1)
Where v: volume fraction of Cr carbonitride (volume%),
C, N: Content of each element (mass%) The composition is mass%,
C: 0.010 to 0.045%, N: 0.01 to 0.05%,
Mn: 1% or less, Cr: 13-20%,
Al: 0.01% or less, and C and N are included so that the volume fraction v of Cr carbonitride defined by the formula (1) is 0.09% or less, and
Si: 0.4% or less, P: 0.05% or less,
2. The ferritic stainless steel cold-rolled steel sheet according to claim 1, wherein the ferritic stainless steel cold-rolled steel sheet has a composition comprising S: 0.010% or less, the balance being Fe and inevitable impurities. A ferritic stainless steel material that is subjected to a hot rolling process, a hot rolled sheet annealing and pickling process, a cold rolled process, and a cold rolled sheet annealing process to form a stainless cold rolled steel sheet. In the manufacturing method of stainless steel cold-rolled steel sheet, the stainless steel material is mass%,
C: 0.010 to 0.045%, N: 0.01 to 0.05%,
Mn: 1% or less, Cr: 13-20%,
Al: A steel material having a composition containing 0.01% or less and C and N so that the volume fraction v of Cr carbonitride defined by the following formula (1) is 0.09% or less, and the hot rolling The process is heated to 1000 ° C. or higher, hot rolling is finished at a temperature of 900 ° C. or higher to form a hot-rolled sheet, and then the hot-rolled sheet is wound at a coiling temperature of 650 ° C. or higher. The process is a process of cold rolling with a cold rolling reduction of 90% or less to obtain a cold rolled sheet, and the cold rolled sheet annealing process is subjected to continuous annealing at an annealing temperature of 800 to 900 ° C. A method for producing a ferritic stainless cold-rolled steel sheet having excellent press formability, characterized by comprising a step.
V (%) = 100 × {0.0196C + 0.0015N} (1)
Here, v: Cr carbonitride volume fraction (volume%),
C, N: Content of each element (mass%) The composition is mass%,
C: 0.010 to 0.045%, N: 0.01 to 0.05%,
Mn: 1% or less, Cr: 13-20%,
Al: 0.01% or less, and C and N are included so that the volume fraction v of Cr carbonitride defined by the formula (1) is 0.09% or less, and Si: 0.4% or less, P: The method for producing a ferritic stainless steel cold-rolled steel sheet according to claim 3, wherein the composition contains 0.05% or less and S: 0.010% or less, and the balance is Fe and inevitable impurities.