JPWO2014157066A1 - Ferritic stainless steel sheet excellent in punching workability and manufacturing method thereof - Google Patents

Abstract

One aspect of this ferritic stainless steel sheet is mass%, C: 0.016% or less, Si: 1.0% or less, Mn: 1.0% or less, P: 0.010 to 0.035%, S : 0.005% or less, Al: 0.50% or less, N: 0.018% or less, Cr: 15.6 to 17.5%, Cu: 0.10 to 0.50%, Sn: 0.01 -0.3%, Ti: 0.05-0.30% or less, Nb: 0.05-0.40%, Mo: 0.05-0.50% or less, and Ni: 0.05-0 1 or more selected from .50%, the balance is made of Fe and inevitable impurities, the Cu concentration on the steel sheet surface is 15% or more in terms of cation fraction, and the ferrite grain size is 30 μm or less.

Description

The present invention relates to a ferritic stainless steel sheet having excellent punching workability used in kitchens, household electric appliances, instruments, coins, containers, and the like, and a method for producing the same.
This application claims priority based on Japanese Patent Application No. 2013-062077 filed in Japan on March 25, 2013 and Japanese Patent Application No. 2013-069772 filed in Japan on March 28, 2013. The contents are incorporated herein.

  Ferritic stainless steel sheets are excellent in design and corrosion resistance, and are therefore used in various applications such as buildings, transportation equipment, household electrical appliances, and kitchen appliances. These products (structures) are usually manufactured through steps of cutting, forming, and joining steel plates. In cutting, a shearing process is usually performed because of high productivity. At this time, a so-called “burl” is generated on the cut surface. If this burr is large, when the cut product is automatically inserted into the press machine, the `` burr '' part will be caught inside the machine, causing poor loading, and even if it can be inserted, There may be a problem that a gap is generated due to “bounce” and burnout occurs. In particular, ferritic stainless steel sheets tend to have a large “kaeri”, which has been an impediment to expanding applications.

For example, Patent Document 1 discloses a technique for eliminating the shortage of recrystallization of a hot-rolled sheet that causes roving (also referred to as ridging), which is a surface irregularity defect, by properly combining chemical components and hot-rolling coiling temperature. Is disclosed. This technology reduces the content of C, P, and S forming FeTiP, Ti ₄ C ₂ S ₂ and TiC, which are precipitates in steel, and winds the steel sheet after hot rolling at a high temperature. The precipitate is coarsened. However, although the steel sheet obtained by this technique has improved formability and roving resistance, it has a problem of large burr during shearing because of the small amount of precipitates that become the starting point of fracture during shearing. .

  Patent Document 2 discloses a ferritic stainless steel having excellent stretch formability and a method for producing the same by regulating the amount of solid solution elements and coarsening precipitates and crystal grains. ing. However, the steel sheet obtained by this technique has a problem that the burr is large because the ferrite grains are large and the deformed ferrite grains directly form the burr of the shear plane.

Patent Document 3 is excellent in workability and corrosion resistance by adding a sufficient amount of Ti while reducing the amount of TiO ₂ and Al ₂ O ₃ that cause surface scratches, and has few surface defects. A ferritic stainless steel sheet is disclosed. However, the steel sheet obtained by this technique also has a problem that a large burr is generated by shearing because the ferrite grain size is large and the amount of inclusions as a starting point of fracture is small.

  Patent Document 4 discloses that ductile fracture during shearing is achieved by appropriately dispersing FeTiP in steel and generating cracks during shearing starting from FeTiP and reducing the ferrite grain size to 30 μm or less. A steel sheet that suppresses deformation of the part and further suppresses work hardening and suppresses deformation of ferrite grains until breakage is disclosed by setting the yield ratio to 0.65 or more. However, in this technique, there is a problem that the existing FeTiP promotes the wear of the shearing tool and the tool life is shortened.

JP-A-10-204588 JP 2002-249857 A JP 2002-012955 A JP 2008-308705 A

  It is an object of the present invention to provide a ferritic stainless steel sheet that is not only excellent in corrosion resistance but also excellent in punching workability that has not been sufficiently improved by the prior art and a method for producing the same.

Regarding the first aspect of the present invention, the inventors conducted a punching test using various ferritic stainless steel sheets, and investigated in detail the occurrence of burr generated during processing and the tool surface used for punching. .
As a result, the following matters were found.
(A) Cu is concentrated in an appropriate amount on the steel sheet surface.
(B) The state where the burr height is small can be maintained only when the average ferrite grain size of the steel sheet is 30 μm or less.
That is, the following matters were found and the present invention was completed.
(A ′) By appropriately concentrating Cu on the surface of the steel sheet, a lubrication effect when contacting with the punching tool at the time of shearing is expressed, and a starting crack is stably generated.
(B ′) The deformation of the ductile fracture portion during shearing is suppressed by reducing the ferrite grain size to 30 μm or less. This is effective in reducing burr size and extending tool life.

The gist of the first aspect of the present invention is as follows.
(1) C: 0.016 mass% or less, Si: 1.0 mass% or less, Mn: 1.0 mass% or less, P: 0.010 to 0.035 mass%, S: 0.005 mass% or less Al: 0.50 mass% or less, N: 0.018 mass% or less, Cr: 15.6 to 17.5 mass%, Cu: 0.10 to 0.50 mass%, Sn: 0.01 to 0 Further, Ti: 0.05 to 0.30 mass%, Nb: 0.05 to 0.40 mass%, Mo: 0.05 to 0.50 mass%, and Ni : Containing one or more selected from 0.05 to 0.50% by mass, the balance being Fe and inevitable impurities, Cu concentration on the steel sheet surface is 15% or more in terms of cation fraction, ferrite grain size Is a ferritic stainless steel sheet having an excellent punching workability of 30 μm or less.
(2) Further, in mass%, B: 0.001 mass% or less, V: 0.50 mass% or less, W: 0.50 mass% or less, Co: 0.50 mass% or less, Mg: 0.01 mass % Or less, Ca: 0.003 mass% or less, Zr: 0.30 mass% or less, REM (rare earth metal): 0.02 mass% or less, Ta: 0.50 mass% or less, Sb: 0.001- The ferritic stainless steel sheet having excellent punchability according to (1), which includes one or more selected from 0.3% by mass and Ga: 0.0002 to 0.1% by mass.
(3) A steel slab having the component composition described in (1) or (2) is heated to 1100 ° C. or higher, and then hot-rolled at a finish rolling finish temperature of 900 ° C. or higher is performed at 450 to 600 ° C. A rolled hot-rolled sheet is obtained, and then the hot-rolled sheet is annealed at 800 to 950 ° C., pickled, cold-rolled, and then at a temperature of 820 to 950 ° C. and an oxygen concentration of 1% or more. A method for producing a ferritic stainless steel sheet that is excellent in punching workability, in which final annealing is performed in an atmosphere and then cooling is performed at a cooling rate of 30 ° C./s or higher in a temperature range up to 600 ° C.

Regarding the second aspect of the present invention, the inventors conducted a punching test using various ferritic stainless steel sheets, and investigated in detail the occurrence of burr generated during processing and the tool surface used for punching. .
As a result, the following matters were found.
(C) Cu is concentrated on the steel sheet surface in an appropriate amount.
(D) The steel sheet has an average ferrite particle size of 30 μm or less, and can maintain a small burr height only when the surface hardness HV1 satisfies 140 to 180.
That is, the following matters were found and the present invention was completed.
(C ′) By appropriately concentrating Cu on the surface of the steel plate, a lubrication effect when contacting with the punching tool at the time of shearing is expressed, and the starting crack is stably generated.
(D ′) The ferrite grain size is reduced to 30 μm or less and the surface hardness HV1 is set to 140 to 180, thereby suppressing the sticky deformation of the ductile fracture portion during shearing. This is effective in reducing the burr size and extending the tool life by suppressing wear.

The gist of the second aspect of the present invention is as follows.
(4) C: 0.020 mass% or less, Si: 0.80 mass% or less, Mn: 1.0 mass% or less, P: 0.010 to 0.035 mass%, S: 0.005 mass% or less Al: 0.50 mass% or less, N: 0.020 mass% or less, Cr: 15.6 to 17.5 mass%, Cu: 0.50 to 2.00 mass%, Sn: 0.001 to 0 0.1% by mass, and further selected from Ti: 0.05 to 0.30% by mass or less, Nb: 0.05 to 0.40% by mass, and Ni: 0.05 to 0.50% by mass. And the balance is Fe and inevitable impurities, the Cu concentration on the steel sheet surface is 15% or more in terms of cation fraction, the ferrite grain size is 30 μm or less, and the surface hardness is 140 to 180 A ferritic stainless steel sheet with excellent punchability.
(5) Further, in terms of mass%, Mo: 0.01 to 0.50 mass%, B: 0.001 mass% or less, V: 0.50 mass% or less, W: 0.50 mass% or less, Co: 0 50 mass% or less, Mg: 0.01 mass% or less, Ca: 0.003 mass% or less, Zr: 0.30 mass% or less, REM (rare earth metal): 0.02 mass% or less, and Ta: 0 Ferrite excellent in punching workability according to (4), which includes one or more selected from Sb: 0.001 to 0.3% by mass, Ga: 0.0002 to 0.1% by mass Stainless steel sheet.
(6) A steel slab having the composition described in (4) or (5) is heated to 1100 ° C. or higher, and then the rolling rate during finish rolling is 80 to 90% and the end temperature is 900 ° C. or higher. Hot rolling is performed to obtain a rolled hot rolled sheet at 400 to 500 ° C., then the hot rolled sheet is annealed, pickled, cold rolled, and then at a temperature of 850 ° C. to 950 ° C. and oxygen A method for producing a ferritic stainless steel sheet excellent in punching workability, in which final annealing is performed in an atmosphere having a concentration of 1% or more, and then cooling is performed at a cooling rate of 50 ° C./s or more in a temperature range up to 500 ° C.

  According to the first and second aspects of the present invention, it is possible to provide a ferritic stainless steel sheet that is not only excellent in corrosion resistance but also excellent in punching workability and a method for manufacturing the same. Therefore, according to this invention, it becomes possible to expand the use of a ferritic stainless steel plate.

FIG. 1 is a graph showing the relationship between the Cu concentration of the surface layer and the burr height of the ferritic stainless steel sheet of the first embodiment. FIG. 2 is a graph showing the relationship between the ferrite grain size and the 20th burr height of the ferritic stainless steel sheet of the first embodiment. FIG. 3 is a graph showing a measurement example of the surface layer Cu concentration of the ferritic stainless steel sheet of the first embodiment, and is a graph showing the relationship between the Cu concentration and the distance from the outermost layer. FIG. 4 is a diagram showing the relationship between the Cu concentration of the surface layer of the ferritic stainless steel plate of the second embodiment and the 20th burr height. FIG. 5 is a diagram showing the relationship between the ferrite grain size of the ferritic stainless steel sheet of the second embodiment and the 20th burr height. FIG. 6 is a graph showing a measurement example of the surface layer Cu concentration of the ferritic stainless steel plate of the second embodiment, and is a graph showing the relationship between the Cu concentration and the distance from the outermost layer.

(First embodiment)
The component composition of the ferritic stainless steel sheet according to the first embodiment will be described. In addition, unit% which shows content of an element means the mass%.

(C: 0.016 mass% or less)
C forms Cr carbide and causes sensitization. Therefore, in this embodiment, Ti or Nb is added to form carbides and fix C. TiC is fine and has an effect of promoting work hardening by precipitation strengthening of steel. However, if the C content exceeds 0.016% by mass, it is necessary to add a large amount of Ti. Therefore, the C content is set to 0.016% by mass or less. Preferably, it is 0.012 mass% or less. From the viewpoint of avoiding deterioration of corrosion resistance and the like due to C, the content is preferably as small as possible. However, excessive reduction of the amount of C leads to an increase in the refining cost, so 0.001% by mass or more is preferable. Furthermore, considering production costs and the like, it is desirable that the content be 0.002 mass% to 0.009 mass%.

(Si: 1.0% by mass or less)
Si is a solid solution strengthening element, hardens steel and reduces ductility. When the ductility is lowered, the deformability at the time of punching breakage is lowered. For this reason, the region of the punching conditions in which the burr height is low and stable is narrow, and the burr height is significantly increased by increasing the number of punches. In addition, since Si has a characteristic of being easily oxidized, Si is concentrated in the oxide scale due to heat treatment conditions, and the descaleability is deteriorated. As a result, it is necessary to increase the amount of cutting during the final descale. Excessive cutting will also cut the concentrated Cu layer on the surface, which is inappropriate in this embodiment. Therefore, in this embodiment, it is necessary to make Si content 1.0 mass% or less. The amount of Si is preferably 0.50% by mass or less, and more preferably 0.25% by mass or less. Further, Si is an element that may be added as a deoxidizing element, and considering the manufacturing cost and the like, the Si amount is preferably 0.01% by mass or more.

(Mn: 1.0% by mass or less)
Mn is an element that degrades corrosion resistance, and is also an element that constitutes MnS. When a large amount of MnS is precipitated or MnS is coarsened, punching workability is deteriorated. MnS precipitates in the form of flakes at the ferrite grain boundaries, and the ferrite grains are expanded to increase the burr during punching. Therefore, in this embodiment, it is necessary to make Mn content 1.0 mass% or less. The amount of Mn is preferably 0.50% by mass or less, and more preferably 0.30% by mass or less. Further, Mn is an element that may be added as a deoxidizing element, and in view of manufacturing costs, it is preferable to set it to 0.01% by mass or more.

(P: 0.010-0.035 mass%)
P has a function of forming FeTiP to promote the generation and development of cracks during punching and to reduce the height of burr. This effect is manifested by containing 0.010% by mass or more of P.
However, if added over 0.035% by mass, the material becomes brittle, so the P content is made 0.035% by mass or less. Preferably, it is the range of 0.020-0.025 mass%.

(S: 0.005 mass% or less)
S forms MnS or TiS, suppresses equiaxed ferrite grains, and promotes extension, thus promoting the occurrence of burr. In order to prevent this phenomenon, the S content needs to be 0.005% by mass or less. Preferably, it is 0.003 mass% or less. However, since excessive reduction leads to an increase in refining costs, the S amount is preferably 0.0001% by mass or more.

(Al: 0.50 mass% or less)
Al is a component added as a deoxidizer and is preferably added in an amount of 0.02% by mass or more in order to improve the cleanliness of steel. However, when a large amount of Al is added, AlN is precipitated, which promotes softening of the ferrite grains and causes the ferrite grains to expand in the rolling direction. Therefore, in the present embodiment, the Al content is set to 0.50% by mass or less. Preferably, it is 0.10 mass% or less. Further, Al may be added as a deoxidizing element, and improves high temperature strength and oxidation resistance. Since the action is expressed from 0.01% by mass, the Al content is preferably 0.01% by mass or more.

(N: 0.018 mass% or less)
N is an element that is easily bonded to Ti to form TiN. In particular, when the N content exceeds 0.018% by mass, a large amount of coarse rectangular parallelepiped TiN precipitates in the steel, which causes surface flaws on the steel sheet. Therefore, N content shall be 0.018 mass% or less. Preferably, it is 0.008 to 0.014 mass% or less.

(Cr: 15.6 to 17.5% by mass)
Cr is an important element that forms a passive film on the surface of stainless steel and improves corrosion resistance. In order to maintain the corrosion resistance of the end face, it is necessary to contain 15.6% by mass or more. However, if it exceeds 17.5% by mass, the hardening by Cr becomes remarkable, the work hardening coefficient decreases, and the ferrite grains easily extend in the punching direction, so that the burr becomes large. Therefore, Cr content shall be 17.5 mass% or less. Preferably, it is the range of 16.0-17.3 mass%.

(Cu: 0.10 to 0.50 mass%)
Since Cu acts to reduce the friction with the punching tool by concentrating on the surface of the steel sheet, Cu plays an important role in this embodiment. By containing Sn and adding 0.10% by mass or more of Cu, Cu concentration on the steel sheet surface is stabilized, reducing burr and suppressing tool wear. On the other hand, if added over 0.50% by mass, hardness increases due to solid solution strengthening, and Cu precipitates at the grain boundaries and the ferrite grains tend to become brittle, which may impair manufacturability. Therefore, the amount of Cu shall be 0.50 mass% or less. Preferably, it is 0.10 to 0.30 mass% or less.

(Sn: 0.01-0.30 mass%)
Sn is an important element in the present embodiment because Sn exhibits an effect of promoting concentration of Cu on the steel sheet surface when coexisting with Cu. The effect of promoting the surface concentration of Cu due to the coexistence of Sn and Cu is exhibited by adding 0.01% by mass or more of Sn. However, Sn is also a solid solution strengthening element, and if added excessively, the work hardening constant increases, so the Sn amount is set to 0.3% by mass or less. Sn is also an element that improves corrosion resistance. The effect of improving the corrosion resistance is exhibited at 0.03% by mass or more. Therefore, it is preferable to make Sn into the range of 0.03-0.25 mass%. More preferably, it is the range of 0.10-0.20 mass%.

  In the steel plate of the present embodiment, Ti: 0.05 to 0.30% by mass or less, Nb: 0.05 to 0.40% by mass, Mo: 0.05 to 0.50% by mass or less, and Ni: 1 type or more selected from 0.05-0.50 mass% is contained.

(Ti: 0.05-0.30 mass%)
Ti combines with C, N, and S to form carbides, nitrides, and sulfides. When the amount of Ti is 0.05% by mass or more, the effect of fixing these elements is exhibited. Therefore, it is necessary to add 0.05% by mass or more of Ti. On the other hand, if the amount of Ti exceeds 0.30% by mass, a large amount of TiN precipitates and wrinkles on the steel sheet surface occur. Therefore, the Ti amount is set to 0.30% by mass or less.
Preferably, the amount of Ti is in the range of 0.08 to 0.20 mass%. More preferably, the amount of Ti is 0.08 to 0.15 mass%.

(Nb: 0.05-0.40 mass%)
Nb is an element that improves moldability and corrosion resistance. Formability and corrosion resistance are improved by adding 0.05 mass% or more of Nb. On the other hand, excessive addition of Nb brings about defects such as surface defects and gloss unevenness, and a decrease in ductility. Therefore, Nb is set to a range of 0.05 to 0.40 mass%. Furthermore, in consideration of manufacturability and ductility, the Nb amount is preferably in the range of 0.10 to 0.30 mass%.

(Mo: 0.05 to 0.50 mass%)
Mo is an element that improves corrosion resistance, and it is desirable to add it in applications where corrosion resistance is required. By adding 0.05% by mass or more of Mo, the effect of improving the corrosion resistance is exhibited. On the other hand, addition of an excessive amount of Mo results in deterioration of formability, particularly ductility. Therefore, it is preferable to set it as the range of 0.05-0.50 mass%. Furthermore, when manufacturability, steel plate strength, and the like are taken into consideration, the range of 0.05 to 0.20 mass% is more preferable. The amount of Mo is more preferably in the range of 0.05 to 0.10% by mass.

(Ni: 0.05 mass% or more and 0.5 mass% or less)
Ni is an element that improves the corrosion resistance. However, when a large amount of Ni is added, the steel is hardened and the ductility is lowered. Therefore. Ni content shall be 0.5 mass% or less. Preferably, it is 0.25 mass% or less. Moreover, when adding Ni, in order to fully exhibit the effect which improves corrosion resistance, adding 0.05 mass% or more is desirable. More preferably, it is 0.10 mass% or more.

  In this embodiment, you may contain the following elements as needed.

(B: 0.001 mass% or less)
B is an element that segregates at the grain boundary and increases the grain boundary strength, and stabilizes the end face properties during the punching process. However, the addition of an excessive amount of B forms a low melting point boride and significantly reduces hot workability. Therefore, when adding B, it adds in 0.001 mass% or less. In order to stably obtain the effect of B, the amount of B is preferably 0.0002% by mass or more, and more preferably 0.0003% by mass or more.

(Co: 0.50 mass% or less)
Co, like Ni, is an element that improves the corrosion resistance, but if added in a large amount, it hardens the steel and decreases the ductility. Therefore. Co content shall be 0.50 mass% or less. The amount of Co is preferably 0.1% by mass or less. In order to stably obtain the effect of Co, the amount of Co is preferably 0.005% by mass or more, and more preferably 0.01% by mass or more.

(V, W: 0.50 mass% or less)
V and W combine with C in the same manner as Ti to form carbides. If the amount of V or W added exceeds 0.50% by mass, precipitation of TiN is promoted to induce wrinkles on the surface of the steel sheet. Accordingly, when V and W are added, the respective amounts are preferably 0.50% by mass or less, preferably 0.10% by mass or less, and further 0.05% by mass or less. More preferred. In order to stably obtain the effects of V and W, each of the V amount and the W amount is preferably 0.005% by mass or more, and more preferably 0.01% by mass or more.

(Mg: 0.01% by mass or less)
Mg is a component added as a deoxidizer. However, if added in a large amount, it precipitates as MgO and causes nozzle clogging during steelmaking. Therefore, in the present embodiment, the Mg amount is 0.01% by mass or less, and more preferably 0.002% by mass or less. In order to stably obtain the effect of Mg, the amount of Mg is preferably 0.0001% by mass or more, and more preferably 0.0003% by mass or more.

(Ca: 0.01% by mass or less)
Ca is a component added as a deoxidizer. However, when a large amount of Ca is added, it precipitates as CaO or CaS, and causes rust. Therefore, in the present embodiment, Ca is 0.01% by mass or less. In order to stably obtain the effect of Ca, the Ca content is preferably 0.0001% by mass or more, and more preferably 0.0003% by mass or more.

(Zr: 0.30 mass% or less)
Zr is added in an amount of 0.01% by mass or more as needed in order to form carbonitrides to suppress the formation of Cr carbonitrides and improve corrosion resistance, like Nb and Ti. Moreover, even if it adds exceeding 0.30 mass%, the effect will be saturated, and since it will also cause a surface flaw by formation of a large sized oxide, it adds at 0.01-0.30 mass%. The upper limit is more preferably 0.20% by mass. Since it is an expensive element compared with Ti and Nb, it is desirable to set it as 0.02 mass%-0.05 mass% when manufacturing cost is considered.

(REM (rare earth metal): 0.02 mass% or less)
Like REM, REM (rare earth metal) is an element that increases the grain boundary strength and stabilizes the end face properties at the time of punching, but its action is saturated at 0.02% by mass. Therefore, the REM amount (total amount of rare earth metals) is set to 0.02% by mass or less. In order to exhibit the effect, the lower limit of the REM amount is preferably 0.002% by mass. In addition, REM (rare earth element) refers to a generic name of two elements of scandium (Sc) and yttrium (Y) and 15 elements (lanthanoid) from lanthanum (La) to lutetium (Lu) according to a general definition. It may be added alone or as a mixture.

(Ta: 0.50 mass% or less)
Ta is an element that improves the high-temperature strength and can be added as necessary. However, addition of an excessive amount of Ta causes a decrease in normal temperature ductility and a decrease in toughness, so 0.50% by mass is made the upper limit of the Ta amount. In order to achieve both high temperature strength and ductility / toughness, the Ta content is preferably 0.05% by mass or more and 0.5% by mass or less.

(Sb: 0.001 to 0.3% by mass)
Sb is effective in improving the corrosion resistance, and may be added in an amount of 0.3% by mass or less as necessary. In particular, from the viewpoint of crevice corrosion, the lower limit of the amount of Sb is set to 0.001% by mass. Furthermore, it is preferable that the amount of Sb is 0.01% by mass or more from the viewpoint of manufacturability and cost. From the viewpoint of cost, the upper limit of the amount of Sb is preferably 0.1% by mass.

(Ga: 0.0002 to 0.1% by mass)
Ga may be added in an amount of 0.1% by mass or less in order to improve corrosion resistance and suppress hydrogen embrittlement. From the viewpoint of the formation of sulfides and hydrides, the lower limit of Ga content is 0.0002% by mass. Furthermore, the amount of Ga is preferably 0.0020% by mass or more from the viewpoint of manufacturability and cost.

  Although it does not prescribe | regulate especially in this embodiment about another component, in this embodiment, you may add Hf, Bi, etc. in the quantity of 0.001-0.1 mass% as needed. Note that the amount of generally harmful elements such as As and Pb and impurity elements is preferably reduced as much as possible.

  The balance other than the above components in the ferritic stainless steel sheet of the present embodiment is Fe and inevitable impurities.

  Next, the surface Cu concentration and the ferrite particle size in the ferritic stainless steel sheet according to the present embodiment will be described.

(Cu concentration on the steel sheet surface is 15% or more in terms of cation fraction)
It has been found that the Cu concentration on the surface of the ferritic stainless steel sheet has an important function of reducing the coefficient of friction with the tool during punching, suppressing the occurrence of burr, and suppressing tool wear. When Cu is concentrated on the surface, Cu exists as a constituent edge at the tip of the tool when it comes into contact with the punching tool, and wear of the tool is suppressed. Further, since Cu is excellent in thermal conductivity, it diffuses the processing heat accumulated in the tool and suppresses softening due to a rise in the temperature of the steel sheet, thereby reducing the burr on the end face. In order to express this effect, it is necessary that Cu is concentrated so that at least the Cu concentration of the steel sheet surface layer is 15% or more in terms of the cation fraction. Below this, the friction coefficient between the steel sheet and the tool increases, the burr becomes larger and the tool wear is promoted. In order to concentrate Cu on the product surface, it is better that the amount of Cu added as an alloy element is large. However, it was revealed that Cu coexists with Sn, so that Cu is concentrated on the surface even with a small Cu concentration. The addition of an excessive amount of Sn or Cu promotes embrittlement of the ferritic stainless steel, so that the effect needs to be expressed with a small addition amount. In order to concentrate Cu so that the Cu content is in the range of 0.1 to 0.5% and the Cu concentration on the surface is 15% or more, 0.01% or more of Sn is required.

  FIG. 1 is a diagram showing the relationship between the Cu concentration of the surface layer and the burr height. In FIG. 1, white circle plot points indicate examples in which the ferrite grain size is 30 μm or less. An example in which the black dot plot points exceed 30 μm. In the test example in FIG. 1, the steel having the component composition of this embodiment (steels 1-1, 1-6, and 1-9 of Example 1) is cooled when manufactured according to the manufacturing method of this embodiment. It is an example manufactured by changing the heat treatment conditions of the plate. The ferrite grain size was controlled to 30 μm or less under the thermomechanical treatment conditions, and the Cu concentration on the steel material surface was changed under a combination of the cold rolled sheet heat treatment atmosphere, the cooling rate, and the pickling conditions. As a result, if the Cu concentration on the steel sheet surface is 15% or more, the burr height can be stably reduced to 50 μm or less. Even when the ferrite grain size was 35 μm and the Cu concentration on the steel sheet surface was less than 15%, the burr height was sometimes 50 μm or less. In this example, the burr height at the 20th round was 50 μm. Out of the following range.

(Ferrite particle size: 30 μm or less)
When the ferrite grain size is large, the amount of deformation of each ferrite grain that occurs at the time of punching becomes large, and therefore burr becomes large. Therefore, the ferrite particle size needs to be 30 μm or less. The ferrite particle size is preferably 25 μm or less, more preferably 20 μm or less.

  FIG. 2 is a graph showing the relationship between the ferrite grain size and the 20th burr height. In FIG. 2, the white circle plot points are examples in which the Cu concentration on the steel sheet surface is 15% or more in terms of cation fraction, and the black circle plot points are examples in which the Cu concentration on the steel sheet surface is less than 15% in terms of cation fraction. is there. These are the hot-rolled sheet and the steel having the component composition of the present embodiment (steel Nos. 1-1, 1-6 and 1-9 of Example 1) according to the production method of the present embodiment. It is the example manufactured by changing the conditions of annealing of a cold-rolled sheet. The Cu concentration on the steel surface is controlled to 15% or more and less than 15% by the combination of the annealing atmosphere of the cold rolled sheet and the pickling condition, and the ferrite grain size is changed by the annealing condition of the hot rolled sheet and the cold rolled sheet. I let you. When the Cu concentration on the steel sheet surface is high at 15% or more, the burr height at the 20th round can be controlled by the ferrite grain size. The smaller the particle size, the smaller the burr height. Further, when the Cu concentration on the steel sheet surface is less than 15% and low, the burr height is high even if the ferrite grain size is small.

Next, the manufacturing method of the ferritic stainless steel plate which concerns on this embodiment is demonstrated.
As described below, the manufacturing method of the present embodiment winds up at a relatively low temperature after hot rolling, performs hot-rolled sheet annealing at a relatively low temperature, and increases the cooling rate after the final annealing. Thereby, precipitation of ε-Cu is avoided and solid solution Cu is secured. By the manufacturing method of this embodiment, it is possible to moderately concentrate Cu on the steel sheet surface and refine the ferrite grain size to 30 μm or less. Below, it demonstrates for every manufacturing process.

  A generally known method can be used for manufacturing the steel slab as a material for the ferritic stainless steel sheet of the present embodiment. For example, steel is melted in a converter, electric furnace or the like, and secondary refining is performed in an RH degasser, AOD furnace, VOD furnace or the like as necessary to adjust to the above component composition. Thereafter, the slab is preferably formed by a continuous casting method or an ingot-bundling rolling method.

The subsequent hot rolling needs to be performed under the following conditions.
(Slab heating temperature: 1100 ° C or higher)
The heating temperature of the slab prior to hot rolling needs to be 1100 ° C or higher. If heating temperature is less than 1100 degreeC, a hot rolling structure will remain easily on a hot-rolled sheet. This makes it easy for the ferrite grains to expand in the rolling direction and increases burr.

(Finish rolling finish temperature: 900 ° C or higher)
The finish rolling finish temperature in the hot rolling needs to be 900 ° C. or higher. When the finishing temperature of finish rolling is less than 900 ° C., the material becomes difficult to recrystallize during hot rolling, and as a result, the ferrite grains easily spread.

(Winding temperature: 450-600 ° C)
The coiling temperature after hot rolling is important for controlling grain boundary segregation and precipitates in the hot-rolled sheet, and needs to be in the range of 600 ° C. or less. When the coiling temperature exceeds 600 ° C., Cu precipitates as an ε-Cu phase, and the Cu concentration effective for concentration on the surface decreases. On the other hand, when the coiling temperature is less than 450 ° C., the hardness of the steel sheet is remarkably increased due to the influence of Cu or Sn, which causes a defective file shape of the wound shape during winding. For this reason, winding temperature shall be 450 degreeC or more. The coiling temperature is preferably in the range of 500 to 550 ° C.

  Hot-rolled sheet annealing, pickling, and cold rolling are performed on the hot-rolled sheet obtained as described above. Thereafter, final annealing for recrystallization is performed. At this time, the annealing temperature and the final annealing temperature of the hot-rolled sheet are set as follows.

(Annealing temperature of hot-rolled sheet: 800-950 ° C)
The annealing temperature of the hot-rolled sheet is preferably in the range of 800 to 950 ° C. When the annealing temperature of the hot-rolled sheet is less than 800 ° C., recrystallization of the hot-rolled sheet is insufficient and the ferrite grains are expanded. When the annealing temperature of the hot-rolled sheet reaches 800 ° C. or higher, the ε-Cu phase dissolves, and an amount of Cu concentrated on the surface after the final annealing of the cold-rolled sheet can be secured. On the other hand, when the annealing temperature of the hot-rolled sheet exceeds 950 ° C., the coarsening of the ferrite grains is promoted, and the ferrite grains of the product are coarsened. For this reason, it is necessary to set it as 950 degrees C or less.

(Final annealing temperature: 820 to 950 ° C. or less)
The final annealing temperature after cold rolling is 820 ° C. or higher. When the final annealing temperature is less than 820 ° C., the cold rolled structure stretched in the rolling direction tends to remain and burr becomes large. Furthermore, precipitation of the ε-Cu phase starts, the amount of solid solution Cu becomes insufficient, and the Cu concentration on the surface becomes low. On the other hand, when the final annealing temperature exceeds 950 ° C., the ferrite grains become coarse and the ferrite particle diameter exceeds 30 μm. A preferable final annealing temperature is in the range of 850 to 920 ° C.

(Atmosphere of final annealing: oxygen concentration 1% or more)
Moreover, since the oxidation state of the steel sheet surface affects the Cu concentration on the product surface, the oxygen concentration in the atmosphere during the final annealing is set to 1% or more. When a scale is formed with Mn oxide or Fe oxide together with Cr oxide, the number of elements that form oxide near the surface layer decreases. For this reason, the amount of Cu increases as a relative ratio. In general, in descaling, since the steel plate matrix is dissolved together with the oxide scale with an acid solution, concentration of the surface is promoted together with Cu concentrated on the surface by diffusion during final annealing. The final annealing may be performed in the atmosphere. That is, the oxygen concentration in the atmosphere (about 21%) may be set as the upper limit of the oxygen concentration in the atmosphere.

(Cooling rate to 600 ° C: 30 ° C / s or more)
Cu precipitates as an ε-Cu phase during cooling after the final annealing. Once the ε-Cu phase is precipitated, it does not re-dissolve in subsequent steps. In order to concentrate Cu to the surface layer, it is necessary to suppress precipitation. For this purpose, it is necessary to cool at a cooling rate of 30 ° C./s or more in a temperature range up to 600 ° C. If the cooling rate is high, the precipitation behavior can be suppressed, but there is a problem that shape defects are likely to occur. Therefore, the cooling rate is preferably in the range of 35-60 ° C./s.

  Descaling is performed on the cold-rolled sheet after final annealing by pickling. Subsequently, the product may be used as it is, and then temper rolling may be performed as necessary. The temper reduction ratio at this time is preferably in the range of 0.3 to 1.2%.

(Second Embodiment)
The component composition of the ferritic stainless steel sheet according to the second embodiment will be described.

(C: 0.020 mass% or less)
C forms Cr carbide and causes sensitization. Therefore, in this embodiment, Ti or Nb is added to form carbides and fix C. TiC is fine and has an effect of promoting work hardening by precipitation strengthening of steel. However, if the C content exceeds 0.020% by mass, a large amount of Ti or Nb needs to be added, so the C content is set to 0.020% by mass or less. Preferably, it is 0.012 mass% or less. From the viewpoint of avoiding deterioration of corrosion resistance and the like due to C, the content is preferably as small as possible. However, excessive reduction leads to an increase in refining cost, and thus it is preferably 0.001% by mass or more. Furthermore, considering the manufacturing cost and the like, the content is preferably 0.005% by mass to 0.010% by mass.

(Si: 0.80 mass% or less)
Si is a solid solution strengthening element, hardens steel and reduces ductility. When the ductility is lowered, the deformability at the time of punching breakage is lowered. For this reason, the region of the punching conditions in which the burr properties are stable is narrow, and the punching conditions deviate from the stable region due to the increase in the number of punches, and the burr height is increased. Therefore, in this embodiment, the Si content needs to be 0.80% by mass or less. The amount of Si is preferably 0.30% by mass or less, more preferably 0.25% by mass or less. Further, Si is an element that may be added as a deoxidizing element, and considering the manufacturing cost and the like, the Si amount is preferably 0.01% by mass or more.

(Mn: 1.0% by mass or less)
Mn is an element that degrades corrosion resistance, and is also an element that constitutes MnS. When a large amount of MnS is precipitated or MnS is coarsened, punching workability is deteriorated. MnS precipitates in the form of flakes at the ferrite grain boundaries, and the ferrite grains are expanded to increase the burr during punching. Therefore, in this embodiment, it is necessary to make Mn content 1.0 mass% or less. Preferably, it is 0.50 mass% or less. More preferably, it is 0.30 mass% or less. Further, Mn is an element that may be added as a deoxidizing element, and in view of manufacturing costs, it is preferable to set it to 0.01% by mass or more.

(P: 0.010-0.035 mass%)
P has a function of forming FeTiP to promote the generation and development of cracks during punching and to reduce the height of burr. This effect is manifested by containing 0.010% by mass or more of P.
However, if added over 0.035% by mass, the material is embrittled, so the content is made 0.035% by mass or less. Preferably, it is the range of 0.020-0.025 mass%.

(S: 0.005 mass% or less)
S forms MnS or TiS, suppresses equiaxed ferrite grains, and promotes extension, thus promoting the occurrence of burr. In order to prevent this phenomenon, the S content needs to be 0.005% by mass or less. Preferably, it is 0.003 mass% or less. However, excessive reduction leads to an increase in the refining cost, so 0.0001% by mass or more is preferable.

(Al: 0.50 mass% or less)
Al is a component added as a deoxidizer and is preferably added in an amount of 0.02% by mass or more in order to improve the cleanliness of steel. However, when a large amount of Al is added, AlN is precipitated, which promotes softening of the ferrite grains and causes the ferrite grains to expand in the rolling direction. Therefore, in the present embodiment, the Al content is set to 0.50% by mass or less. Preferably, it is 0.10 mass% or less. Further, Al may be added as a deoxidizing element, and improves high temperature strength and oxidation resistance. Since the action is expressed from 0.01% by mass, the Al content is preferably 0.01% by mass or more.

(N: 0.020% by mass or less)
N is an element that is easily bonded to Ti to form TiN. In particular, when the N content exceeds 0.020% by mass, a large amount of coarse rectangular parallelepiped TiN precipitates in the steel, which causes surface flaws on the steel sheet. Therefore, N content shall be 0.020 mass% or less. Preferably, it is 0.07-0.012 mass%.

(Cr: 15.6 to 17.5% by mass)
Cr is an important element that forms a passive film on the surface of stainless steel and improves corrosion resistance. In order to maintain the corrosion resistance of the end face, it is necessary to contain 15.6% by mass or more. However, if it exceeds 17.5% by mass, the hardening by Cr becomes remarkable, the work hardening coefficient decreases, and the ferrite grains easily extend in the punching direction, so that the burr becomes large. Therefore, Cr content shall be 17.5 mass% or less. Preferably, it is the range of 16.0-17.3 mass%.

(Cu: 0.50 to 2.00% by mass)
Since Cu acts to reduce the friction with the punching tool by concentrating on the surface of the steel sheet, Cu plays an important role in this embodiment. By containing Sn and adding 0.50% by mass or more of Cu, Cu concentration on the steel sheet surface is stabilized, reducing burr and suppressing tool wear. On the other hand, if added over 2.00% by mass, the hardness is increased due to solid solution strengthening, and Cu precipitates at the grain boundaries and the ferrite grains tend to become brittle, which may impair manufacturability. Moreover, precipitation of an ε-Cu phase is caused, and an increase in hardness due to dispersion strengthening promotes tool wear. Therefore, the upper limit of Cu is 2.00% by mass. Preferably, it is more than 0.50 mass% and 2.00 mass% or less, more preferably 0.8 to 1.2 mass% or less.

(Sn: 0.001 to 0.1% by mass)
Sn is an important element in the present embodiment because Sn exhibits an effect of promoting concentration of Cu on the steel sheet surface when coexisting with Cu. The effect of promoting the surface concentration of Cu due to the coexistence of Sn and Cu is exhibited by adding Sn in an amount of 0.001% by mass or more, and the effect is more prominent at 0.01% by mass or more. Practically, it may be 0.003% by mass or more. However, Sn is also a solid solution strengthening element. Accordingly, if added excessively, the work hardening constant increases, so the Sn content is 0.1% by mass or less. Sn is also an element that improves corrosion resistance. The effect of improving the corrosion resistance is exhibited at 0.01% by mass or more, and the effect is more pronounced at 0.03% by mass or more. Therefore, in order to promote the surface concentration of Cu by Sn, 0.003 to 0.01% by mass is sufficient.
When the effect of improving corrosion resistance is also required, Sn is preferably in the range of 0.03 to 0.08 mass%. More preferably, it is the range of 0.04-0.06 mass%.

  The steel plate of this embodiment is further selected from Ti: 0.05 to 0.30 mass% or less, Nb: 0.05 to 0.40 mass%, and Ni: 0.05 to 0.50 mass%. Contains one or more.

(Ti: 0.05-0.30 mass%)
Ti combines with C, N, and S to form carbides, nitrides, and sulfides. When the amount of Ti is 0.05% by mass or more, the effect of fixing these elements is exhibited. Therefore, it is necessary to add 0.05% by mass or more of Ti. On the other hand, if the amount of Ti exceeds 0.30% by mass, a large amount of TiN precipitates and wrinkles on the steel sheet surface occur. Therefore, the Ti amount is set to 0.30% by mass or less. Preferably, the amount of Ti is in the range of 0.15 to 0.25% by mass.

(Nb: 0.05-0.40 mass%)
Nb is an element that improves moldability and corrosion resistance. Formability and corrosion resistance are improved by adding 0.05 mass% or more of Nb. On the other hand, excessive addition of Nb brings about defects such as surface defects and gloss unevenness, and a decrease in ductility. Therefore, Nb is set to a range of 0.05 to 0.40 mass%. Furthermore, in consideration of manufacturability and ductility, the Nb content is preferably in the range of 0.07 to 0.20 mass%.

(Ni: 0.05 to 0.50 mass%)
Ni is an element that improves corrosion resistance, and exhibits an effect when added in an amount of 0.05% by mass or more. On the other hand, if added in a large amount, the steel is hardened and the ductility is lowered. Therefore, the Ni content is 0.50 mass or less. Preferably, it is 0.25 mass% or less.

  In this embodiment, you may contain the following elements as needed.

(B: 0.001 mass% or less)
B is an element that segregates at the grain boundary and increases the grain boundary strength, and stabilizes the end face properties during the punching process. However, the addition of an excessive amount of B forms a low melting point boride and significantly reduces hot workability. Therefore, the B amount is 0.001% by mass or less. In order to stably obtain the effect of B, the amount of B is preferably 0.0002% by mass or more, and more preferably 0.0003% by mass or more.

(Co: 0.50 mass% or less)
Co, like Ni, is an element that improves the corrosion resistance, but if added in a large amount, it hardens the steel and decreases the ductility. Therefore, the Co content is 0.50 mass% or less. The amount of Co is preferably 0.10% by mass or less. In order to stably obtain the effect of Co, the amount of Co is preferably 0.005% by mass or more, and more preferably 0.01% by mass or more.

(Mo: 0.01 to 0.50 mass%)
Mo is an element that improves corrosion resistance, and is added in applications where corrosion resistance is required. By adding 0.01% by mass or more of Mo, the effect of improving the corrosion resistance is exhibited. On the other hand, addition of an excessive amount of Mo results in deterioration of formability, particularly ductility. Therefore, it is preferable to set it as the range of 0.01-0.50 mass%. More preferably, the upper limit is 0.30% by mass. Furthermore, when manufacturability, strength, and the like are taken into consideration, the range of 0.05 to 0.20% by mass is more preferable. More preferably, it is 0.05-0.15 mass%.

(V, W: 0.50 mass% or less)
V and W combine with C in the same manner as Ti to form carbides. If the addition amount of V or W exceeds 0.50 mass%, precipitation of TiN is promoted and wrinkles on the surface of the steel sheet are induced. Therefore, when V or W is added, the respective amounts are preferably 0.50% by mass or less, preferably 0.10% by mass or less, and further 0.05% by mass or less. More preferred. In order to stably obtain the effects of V and W, each of the V amount and the W amount is preferably 0.005% by mass or more, and more preferably 0.01% by mass or more.

(Mg: 0.01% by mass or less)
Mg is a component added as a deoxidizer. However, if added in a large amount, it precipitates as MgO and causes nozzle clogging during steelmaking. Therefore, in the present embodiment, the Mg amount is 0.01% by mass or less, and more preferably 0.002% by mass or less. In order to stably obtain the effect of Mg, the amount of Mg is preferably 0.0001% by mass or more, and more preferably 0.0003% by mass or more.

(Ca: 0.003 mass% or less)
Ca is a component added as a deoxidizer. However, if added in a large amount, it precipitates as CaO or CaS, which also causes rust. Therefore, in the present embodiment, Ca is 0.003% by mass or less. In order to stably obtain the effect of Ca, the Ca content is preferably 0.0001% by mass or more, and more preferably 0.0003% by mass or more.

(REM (rare earth metal): 0.02 mass% or less)
Like REM, REM (rare earth metal) is an element that increases the grain boundary strength and stabilizes the end face properties at the time of punching, but its action is saturated at 0.02% by mass. Therefore, the REM amount (total amount of rare earth metals) is set to 0.02% by mass or less. In order to exhibit the effect, the lower limit of the REM amount is preferably 0.002% by mass. In addition, REM (rare earth element) refers to a generic name of two elements of scandium (Sc) and yttrium (Y) and 15 elements (lanthanoid) from lanthanum (La) to lutetium (Lu) according to a general definition. It may be added alone or as a mixture.

(Ta: 0.50 mass% or less)
Ta is an element that improves the high-temperature strength and can be added as necessary. However, addition of an excessive amount of Ta causes a decrease in normal temperature ductility and a decrease in toughness, so 0.50% by mass is made the upper limit of the Ta amount. In order to achieve both high temperature strength and ductility / toughness, the Ta content is preferably 0.05% by mass or more and 0.5% by mass or less.

(Sb: 0.001 to 0.3% by mass)
Sb is effective in improving the corrosion resistance, and may be added in an amount of 0.3% by mass or less as necessary. In particular, from the viewpoint of crevice corrosion, the lower limit of the amount of Sb is set to 0.001% by mass. Furthermore, it is preferable that the amount of Sb is 0.01% by mass or more from the viewpoint of manufacturability and cost. From the viewpoint of cost, the upper limit of the amount of Sb is preferably 0.1% by mass.

(Ga: 0.0002 to 0.1% by mass)
Ga may be added in an amount of 0.1% by mass or less in order to improve corrosion resistance and suppress hydrogen embrittlement. From the viewpoint of the formation of sulfides and hydrides, the lower limit of Ga content is 0.0002% by mass. Furthermore, the amount of Ga is preferably 0.0020% by mass or more from the viewpoint of manufacturability and cost.

(Zr: 0.30 mass% or less)
Zr is added in an amount of 0.01% by mass or more as necessary in order to form carbonitrides to suppress the formation of Cr carbonitrides and improve corrosion resistance, like Nb and Ti. Moreover, even if it adds exceeding 0.30 mass%, the effect will be saturated, and since it will also cause a surface flaw by formation of a large sized oxide, it adds at 0.01-0.30 mass%. More preferably, it is 0.20 mass% or less. Since Zr is an expensive element compared to Ti and Nb, considering the manufacturing cost, it is desirable that Zr be 0.02 mass% to 0.05 mass%.

  Although it does not prescribe | regulate especially in this embodiment about another component, in this embodiment, you may add Hf, Bi, etc. in the quantity of 0.001-0.1 mass% as needed. Note that the amount of generally harmful elements such as As and Pb and impurity elements is preferably reduced as much as possible.

  The balance other than the above components in the ferritic stainless steel sheet of the present embodiment is Fe and inevitable impurities.

  Next, the surface Cu concentration and the ferrite particle size in the ferritic stainless steel sheet according to the present embodiment will be described.

(Cu concentration on the steel sheet surface is 15% or more in terms of cation fraction)
It has been found that the Cu concentration on the surface of the ferritic stainless steel sheet has an important function of reducing the coefficient of friction with the tool during punching, suppressing the occurrence of burr, and suppressing tool wear. When Cu is concentrated on the surface, Cu exists as a constituent edge at the tip of the tool when it comes into contact with the punching tool, and wear of the tool is suppressed. Further, since Cu is excellent in thermal conductivity, it diffuses the processing heat accumulated in the tool and suppresses softening due to a rise in the temperature of the steel sheet, thereby reducing the burr on the end face. In order to express this effect, it is necessary that Cu is concentrated so that at least the Cu concentration of the steel sheet surface layer is 15% or more in terms of the cation fraction. Below this, the friction coefficient between the steel sheet and the tool increases, the burr becomes larger and the tool wear is promoted. In order to concentrate Cu on the product surface, it is better that the amount of Cu added as an alloy element is large. By containing Cu in an amount of 0.5% or more, Cu tends to be concentrated so that the Cu concentration on the surface becomes 15% or more. However, it was confirmed that the Cu concentration on the surface was less than 15% depending on the manufacturing conditions. For this reason, the concentration of Cu on the surface is stabilized by adding Sn that easily coexists with Cu. In order to stabilize the Cu concentration on the surface to 15% or more, it is necessary to add 0.001% or more of Sn.

  FIG. 4 is a diagram showing the relationship between the Cu concentration of the surface layer and the burr height at the 20th time. When the Cu concentration of the surface layer exceeds 15%, the burr height is stabilized, and the burr height at the 20th time is 50 μm or less. In FIG. 4, even if the surface Cu concentration is 15% or more, the burr height may exceed 50 μm. The black dot plot points in the figure show examples where the ferrite grain size is 30 μm or less but the surface hardness is less than 140 or more than 180. White triangular plot points indicate examples where the particle size is greater than 30 μm. These change the heat treatment conditions of the cold-rolled sheet when manufacturing the steel having the component composition of this embodiment (Steel 2-1 and 2-7 of Example 2) according to the manufacturing method of this embodiment. This is an example manufactured. The ferritic grain size is controlled to 30 μm or less under the thermomechanical treatment conditions, the surface hardness is controlled to 140 to 180, and the Cu concentration on the steel material surface is changed by combining the heat treatment atmosphere of the cold-rolled sheet and the pickling conditions. It was. As a result, when the Cu concentration on the steel sheet surface is 15% or more, the burr height can be stably reduced to 50 μm or less.

(Ferrite particle size: 30 μm or less)
When the ferrite grain size is large, the amount of deformation of each ferrite grain that occurs at the time of punching becomes large, and therefore burr becomes large. Therefore, the ferrite particle size needs to be 30 μm or less. The ferrite particle size is preferably 25 μm or less, more preferably 20 μm or less.

  FIG. 5 is a diagram showing the relationship between the ferrite grain size and the 20th burr height. In FIG. 5, white triangle plot points are examples in which the Cu concentration on the steel sheet surface is 15% or more in terms of cation fraction, but the surface hardness is less than 140 or more than 180. The black dot plot points are examples where the Cu concentration is less than 15%. These are manufactured by changing the conditions of hot-rolled sheet and cold-rolled sheet annealing when manufacturing steels of the component composition of the present embodiment (Examples Steels 1 and 7) according to the manufacturing method of the present embodiment. This is an example. Controlling the Cu concentration on the steel surface to 15% or more and controlling the surface hardness to 140 to 180 under the combined conditions of the cold-rolled sheet annealing atmosphere and pickling conditions, the ferrite grains under the cooling rate conditions for cold-rolled sheet annealing The diameter was changed. When the Cu concentration on the surface of the steel sheet is 15% or more, the burr height at the 20th round can be controlled by the ferrite grain size, and the burr height is smaller as the grain size is smaller. When the surface layer Cu concentration is low, the burr height of the 20th time is high even if the particle size is small.

(Surface hardness 140-180)
Surface hardness is an important factor affecting the deformation and tool life in stamping. When the hardness is high, it becomes difficult to deform but becomes brittle, and the ratio of the shear fracture surface to the ductile fracture surface changes. A ductile fracture surface is less likely to occur, which is effective in reducing the burr height, but the tool life is significantly reduced. Therefore, the upper limit of the surface hardness is set to 180. On the other hand, when the surface hardness is low, sagging is likely to occur, and deformation accompanying sagging increases the height. In particular, when the surface hardness is low, the increase in the burr height is significant, so the surface hardness is the standard. Further, there is a correlation between the crystal grain size and the surface hardness, and in order to reduce the surface hardness, the coarsening of the crystal grains is an effective means.
In order to stably satisfy the crystal grain size of 30 μm or less, the surface hardness is set to 140 or more. In addition, the surface hardness in this embodiment is Vickers hardness.

Next, the manufacturing method of the ferritic stainless steel plate which concerns on this embodiment is demonstrated.
As described below, the manufacturing method of the present embodiment winds up at a relatively low temperature after hot rolling, performs hot-rolled sheet annealing at a relatively low temperature, and increases the cooling rate after the final annealing. Thus, precipitation of ε-Cu is avoided to ensure solid solution Cu, and the crystal grain size and material hardness are controlled. By the manufacturing method of this embodiment, it is possible to moderately concentrate Cu on the steel sheet surface and refine the ferrite grain size to 30 μm or less. Below, it demonstrates for every manufacturing process.

  A generally known method can be used for manufacturing the steel slab as a material for the ferritic stainless steel sheet of the present embodiment. For example, steel is melted in a converter, electric furnace or the like, and secondary refining is performed in an RH degasser, AOD furnace, VOD furnace or the like as necessary to adjust to the above component composition. Thereafter, the slab is preferably formed by a continuous casting method or an ingot-bundling rolling method.

The subsequent hot rolling needs to be performed under the following conditions.
(Slab heating temperature: 1100 ° C or higher)
The heating temperature of the slab prior to hot rolling needs to be 1100 ° C or higher. When the heating temperature of the slab is less than 1100 ° C., the hot rolled structure tends to remain on the hot-rolled sheet. This makes it easy for the ferrite grains to expand in the rolling direction and increases burr.

(Rolling ratio during finish rolling: 80-90%)
The finish rolling rate in hot rolling needs to be in the range of 80 to 90%. If the rolling rate is less than 80%, the cast structure cannot be completely pulverized. For this reason, defects such as ridging due to the coarse solidified structure occur in the surface characteristics of the final product. On the other hand, if the rolling rate exceeds 90%, the temperature at the end of the plate is remarkably lowered, and there is a high possibility that problems such as lashes and ear cracks will occur.

(Finish rolling finish temperature: 900 ° C or higher)
The finish rolling finish temperature in the hot rolling needs to be 900 ° C. or higher. When the finishing temperature of finish rolling is less than 900 ° C., the material becomes difficult to recrystallize during hot rolling, and as a result, the ferrite grains easily spread. The expanded ferrite grains cause a mixed grain structure including coarse grains, and the hardness tends to be low, so strict management is required.

(Winding temperature: 400-500 ° C.)
The coiling temperature after hot rolling is important for controlling grain boundary segregation and precipitates in the hot-rolled sheet, and needs to be in a range of 500 ° C. or less. With the amount of Cu in the steel of the present invention, when the coiling temperature exceeds 500 ° C., Cu begins to precipitate as an ε-Cu phase. In order to secure a solid solution Cu amount effective for concentrating Cu on the surface, the amount of precipitation should be as small as possible. On the other hand, if the coiling temperature is less than 400 ° C., the hardness of the steel sheet is remarkably increased due to the effect of dissolving Cu and Sn, which causes defective winding and flaws during winding. The coiling temperature is preferably in the range of 450 to 500 ° C.

  Hot-rolled sheet annealing, pickling, and cold rolling are performed on the hot-rolled sheet obtained as described above. Thereafter, final annealing for recrystallization is performed. At this time, the annealing temperature and the final annealing temperature of the hot-rolled sheet are set to the following ranges.

(Annealing temperature of hot-rolled sheet: 850 to 950 ° C.)
The annealing temperature of the hot-rolled sheet is preferably in the range of 850 to 950 ° C. When the annealing temperature of the hot-rolled sheet is less than 850 ° C., recrystallization of the hot-rolled sheet is insufficient and the ferrite grains are expanded. When the annealing temperature is 850 ° C. or higher, the ε-Cu phase is dissolved, and the amount of Cu concentrated on the surface after the final annealing of the cold rolled sheet can be secured. On the other hand, when the annealing temperature exceeds 950 ° C., the coarsening of the ferrite grains is promoted, and the ferrite grains of the product are coarsened. For this reason, it is necessary to set it as 950 degrees C or less.

(Final annealing temperature: 850 to 950 ° C. or less)
The final annealing temperature after cold rolling is 850 ° C. or higher. When the final annealing temperature is less than 850 ° C., the cold rolled structure stretched in the rolling direction tends to remain, and the burr becomes large. Furthermore, precipitation of the ε-Cu phase starts, the amount of solid solution Cu becomes insufficient, and the Cu concentration on the surface becomes low. On the other hand, when the final annealing temperature exceeds 950 ° C., the ferrite grains become coarse and the ferrite particle diameter exceeds 30 μm. A preferred final annealing temperature is in the range of 880-920 ° C.

(Atmosphere of final annealing: oxygen concentration 1% or more)
Moreover, since the oxidation state of the steel sheet surface affects the Cu concentration on the product surface, the oxygen concentration in the atmosphere during the final annealing is set to 1% or more. When a scale is formed with Mn oxide or Fe oxide together with Cr oxide, the number of elements that form oxide near the surface layer decreases. For this reason, the amount of Cu increases as a relative ratio. In general, in descaling, since the steel plate matrix is dissolved together with the oxide scale with an acid solution, concentration of the surface is promoted together with Cu concentrated on the surface by diffusion during final annealing. The final annealing may be performed in the atmosphere. That is, the oxygen concentration in the atmosphere (about 21%) may be set as the upper limit of the oxygen concentration in the atmosphere.

(Cooling rate to 500 ° C: 50 ° C / s or more)
Cu precipitates as an ε-Cu phase during cooling after the final annealing. Once the ε-Cu phase is precipitated, it does not re-dissolve in subsequent steps. Further, when finely dispersed, the hardness is increased. In order to concentrate Cu on the surface layer and suppress the increase in hardness, it is necessary to control the precipitation state. For this purpose, it is necessary to cool at a cooling rate of 50 ° C./s or more in a temperature range up to 500 ° C. If the cooling rate is high, the precipitation behavior can be suppressed, but there is a problem that shape defects are likely to occur. Therefore, the cooling rate is preferably in the range of 55 to 65 ° C./s.

  Descaling is performed on the cold-rolled sheet after final annealing by pickling. Subsequently, the product may be used as it is, or after that, temper rolling may be performed as necessary. The temper reduction ratio at this time is preferably in the range of 0.3 to 1.2%.

Example 1
Examples corresponding to the ferritic stainless steel sheet of the first embodiment are shown below.
Component No. having the component composition shown in Table 1A and Table 1B. Steels 1-1 to 1-38 were melted into steel ingots. Subsequently, it hot-rolled on the conditions shown in Table 2A, Table 2B, and Table 2D, and was set as the hot-rolled board whose board thickness is 4 mm. The hot-rolled sheet was subjected to hot-rolled sheet annealing by continuous annealing at 890 ° C. After pickling, it was cold-rolled to obtain a cold-rolled sheet having a thickness of 1 mm.
Next, the cold-rolled sheet was finally annealed at the temperatures shown in Tables 2A, 2B, and 2D to obtain cold-rolled annealed sheets. About the cold-rolled annealing board obtained as mentioned above, it used for the following test.

(Evaluation of punchability)
The cold-rolled annealed plate was punched with a 12 mmφ hole with a clearance of 10%, and the burr height of the sheared surface was measured. This punching test was repeated, and the burr height after punching 50 times continuously was measured. The burr height at the time of continuous punching depends on the contact with the tool at the initial stage of punching. For this reason, it has been found that a stable burr height is maintained unless a large burr occurs after 20 to 30 machining operations. Therefore, the punchability was evaluated at the 20th burr height as an index that does not impair the productivity. The first burr height was also an evaluation item.

(Measurement of ferrite crystal grain size)
In the sheet thickness section parallel to the rolling direction of the cold-rolled annealed sheet, the center part of the sheet thickness was mirror-polished and corroded with aqua regia to reveal the structure. The ASTM nominal particle diameter of the ferrite grains was measured by a cutting method defined in JIS G0552. The particle size was measured according to the following procedure. Five lines with an actual length of 800 μm were drawn on the photograph in the sheet thickness direction and five in the rolling direction. The intersections of these line segments and ferrite grain boundaries were counted. The total length of the line segments cut at the ferrite grain boundary in the plate thickness direction was determined by dividing the total length of the line segments in the plate thickness direction by the number of intersections. Similarly, the average length of the cut line segment in the rolling direction was also obtained. The average value of these was multiplied by 1.13 to obtain the ASTM nominal particle size.

(Measurement of Cu concentration on steel sheet surface)
A test piece having a size of 20 mm square was cut out from the cold-rolled annealed plate. Using Rigaku's Spectrum GDA750 / Glow Discharge Optical Emission Spectrometer (GDS), analysis diameter: 4 mm, measurement pitch: 2.5 mm / min, analysis time: 20 sec. The Cu concentration was measured continuously. From the measurement results, a cation element was extracted, the amount of the cation element was converted into an abundance ratio, and an internal concentration profile was obtained from the outermost layer. From the obtained profile, the Cu concentration at the 5 nm portion from the outermost layer was defined as the surface Cu concentration. FIG. 3 is a diagram showing a measurement example of the surface layer Cu concentration. As shown in FIG. 3, it can be seen that Cu is significantly concentrated in the vicinity of the surface layer.

The measurement results are shown in Table 2C and Table 2E. From Tables 1A, 1B, and 2A to 2E, the following can be understood.
Test No. In the steel plates 1-1 to 1-30, the component ranges satisfy the conditions related to the composition of the embodiment, but the steel plates not satisfying other conditions (Test Nos. 1-6, 1-7, 1-10) 1-14, 1-15, 1-17, 1-22, 1-24, 1-25, 1-27, 1-29, 1-30), the burr height during the punching test exceeds 50 μm. Or the burr height of the 20th time was over 50 μm.
Test No. 1-1 to 1-5, 1-8, 1-9, 1-11 to 1-13, 1-16, 1-18 to 1-21, 1-23, 1-26, 1-28, 1- In the 30-1 and 1-30-2 steel plates, all the conditions satisfied the range of the present embodiment, and the initial burr height of the punching test and the burr height of the 20th time are both good, 50 μm or less. Met.
Test No. Since the components 1-31 to 1-51 did not satisfy the range of the present embodiment, the burr height of the 20th round was large.

Test No. In 1-6, 1-7, 1-14, 1-17, and 1-24, the hot rolling conditions are changed with components that satisfy the range of the present embodiment.
Test No. In 1-6, the rolling end temperature at the time of hot rolling was out of the range of this embodiment. For this reason, the ferrite particle diameter exceeded 30 μm, and the burr height of the 20th time was increased.
Test No. In 1-14, in hot rolling, the rolling end temperature was low and the coiling temperature was high, which was outside the range of the present embodiment. For this reason, the Cu concentration of the surface layer was low, and the ferrite grain size was also large, and the initial burr height and the 20th burr height of the punching test were large.
Test No. In 1-7 and 1-17, the coiling temperature of the hot rolling was high and was outside the range of this embodiment. For this reason, the Cu concentration of the steel sheet surface layer was low, and the initial burr height and the 20th burr height of the punching test were large.
Test No. In 1-24, the rolling end temperature was low, the final annealing temperature of the cold-rolled sheet was high, and was outside the range of this embodiment. For this reason, the ferrite grain size was also large and the burr height at the initial stage of the punching test was low, but the burr height was high in the 20th punching test.

Test No. 1-10 and 1-30 are examples in which the annealing temperature of a hot-rolled steel sheet having a component composition suitable for this embodiment is changed.
Test No. In 1-10, the annealing temperature of a hot-rolled sheet is low and the Cu concentration in the surface layer is also low. For this reason, the initial burr height and the 20th burr height of the punching test were increased.
Test No. In 1-30, since the annealing temperature of the hot-rolled sheet was high, the surface Cu concentration was less than 15%. For this reason, the initial burr height and the 20th burr height of the punching test were increased.
Test No. 1-22, 1-25 are examples in which the final annealing temperature of a cold-rolled steel sheet having a component composition suitable for this embodiment is changed.
Test No. In 1-22, the final annealing temperature is low and the Cu concentration of the surface layer is also low. For this reason, the initial burr height and the 20th burr height of the punching test were increased.
Test No. In 1-25, since the final annealing temperature was high, ferrite grains grew coarsely. For this reason, the burr height of the 20th time became large.

Test No. 1-27 is an example in which the cooling rate at the time of final annealing of the steel whose component composition conforms to the present embodiment is changed. Test No. In 1-27, since the cooling rate was slow, Cu precipitated. For this reason, Cu density | concentration of the surface layer became low. Furthermore, the ferrite grain size increased due to the high annealing temperature. As a result, both the initial burr height and the 20th burr height of the punching test were increased.
Test No. 1-29 is an example in which the oxygen concentration at the time of final annealing of the steel whose component composition conforms to the present embodiment is changed. Test No. In 1-29, since the oxygen concentration at the time of final annealing was low, the oxide scale was thin and the main component was Cr oxide. For this reason, the element change near the surface layer was slight, and Cu concentration was reduced. Therefore, the initial burr height and the 20th burr height of the punching test were increased.

(Example 2)
Hereinafter, examples corresponding to the ferritic stainless steel plate of the second embodiment will be shown below.
Component No. having the component composition shown in Table 3A and Table 3B. Steels 2-1 to 2-36 were melted to form steel ingots. Subsequently, it hot-rolled on the conditions shown in Table 4A, Table 4B, and Table 4D, and set it as the hot-rolled board whose board thickness is 4 mm. The hot-rolled sheet was subjected to hot-rolled sheet annealing by continuous annealing. After pickling, it was cold-rolled to obtain a cold-rolled sheet having a thickness of 1 mm.

  Next, the cold-rolled sheet was finally annealed under the conditions shown in Table 4A, Table 4B, and Table 4D to obtain a cold-rolled annealed sheet. About the cold-rolled annealing board obtained as mentioned above, it used for the following test.

(1) Evaluation of punchability The cold-rolled annealed plate was punched into a 12 mmφ hole with a clearance of 10%, and the burr height of the sheared surface was measured. This punching test was repeated, and the burr height after punching 20 times continuously was measured. The burr height at the time of continuous punching depends on the contact with the tool at the initial stage of punching. For this reason, a stable burr height is maintained unless a large burr occurs in 20 to 30 machining operations. Therefore, the 20th burr height was measured as an index that does not impair the productivity.

(2) Measurement of ferrite crystal grain size In the thickness cross section parallel to the rolling direction of the cold-rolled annealed plate, the central portion of the plate thickness was mirror-polished and corroded with aqua regia to reveal the structure. The ASTM nominal particle diameter of the ferrite grains was measured by a cutting method defined in JIS G0552. The particle size was measured according to the following procedure. Five lines with an actual length of 800 μm were drawn on the photograph in the sheet thickness direction and five in the rolling direction. The intersections of these line segments and ferrite grain boundaries were counted. The total length of the line segments cut at the ferrite grain boundary in the plate thickness direction was determined by dividing the total length of the line segments in the plate thickness direction by the number of intersections. Similarly, the average length of the cut line segment in the rolling direction was also obtained. The average value of these was multiplied by 1.13 to obtain the ASTM nominal particle size.

(3) Measurement of surface hardness The surface of the cold-rolled annealed plate was polished with # 600, and the surface hardness was measured by a method defined in JIS Z 2244 using a Vickers hardness meter. The test force at the time of measurement was 9.807 N, and five points were measured and the average value was defined as the surface hardness.

(4) Measurement of cation fraction of Cu concentration on steel plate surface A test piece having a size of 20 mm square was cut out from the cold-rolled annealed plate. Using Rigaku's Spectrum GDA750 / Glow Discharge Optical Emission Spectrometer (GDS), in the depth direction while Ar sputtering from the surface under the conditions of analysis diameter: 4 mm, measurement pitch: 2.5 mm / min, analysis time: 20 sec. Cu concentration was measured continuously. From the measurement results, a cation element was extracted, the amount of the cation element was converted into an abundance ratio, and an internal concentration profile was obtained from the outermost layer. From the obtained profile, the Cu concentration in the 5 nm portion from the outermost layer was assumed to be the surface Cu concentration. FIG. 6 is a diagram illustrating a measurement example of the surface layer Cu concentration. It can be seen that Cu is remarkably concentrated in the vicinity of the surface layer.

The measurement results are shown in Tables 4C and 4E. From Tables 3A, 3B, and 4A to 4E, the following can be understood.
Test No. In the steel sheets of 2-1 to 2-25, the component range satisfies the conditions relating to the composition of the present embodiment, but in the steel sheets not satisfying other conditions, the burr height of the 20th punching test exceeds 50 μm. ing. Test No. Steel sheets of 2-1, 2-5 to 2-8, 2-10, 2-11, 23-13 to 2-15, 2-17 to 2-19, 2-22, 2-24 are all conditions. However, the range of this embodiment is satisfied, and the burr height is good at 50 μm or less.

Test No. In 2-2, 2-9, 2-12, 2-16, and 2-20, the hot rolling conditions are changed with components that satisfy the range of the present embodiment.
Test No. In 2-2 and 2-9, since the finish rolling rate during hot rolling is out of the range of the present embodiment, the burr is large.
Test No. In 2-12, in hot rolling, the rolling end temperature is low, and is outside the range of the present embodiment. For this reason, the Cu concentration in the surface layer is low, and the burr height is large.
Test No. In 2-16 and 2-20, the coiling temperature of the hot rolling is out of the range of the present embodiment. For this reason, test no. In No. 2-16, the Cu concentration on the steel sheet surface layer was low, and In 2-20, the ferrite particle size exceeds 30 μm. Both have a high burr height.

Test No. 2-3, 2-4, 2-21, and 2-23 are examples in which the conditions of the cold-rolled sheet annealing of the steel in which the component composition is adapted to the present embodiment are changed.
Test No. In 2-3, since the cooling rate after cold-rolled sheet annealing was slow, ferrite grains grew coarsely and an ε-Cu phase precipitated. For this reason, the Cu concentration of the surface layer is lowered, and the burr of the 20th time is large.
Test No. In 2-4, the annealing temperature is low. For this reason, the Cu concentration and the ferrite particle size of the surface layer satisfy the range of the embodiment, but the surface hardness is high. For this reason, the burr is large.
Test No. In 2-21, the cooling rate after cold-rolled sheet annealing was slow, and the ε-Cu phase was precipitated. For this reason, Cu density | concentration of a surface layer falls and the bounce of the 20th time is large.
Test No. In 2-23, since the final annealing temperature of a cold-rolled sheet is high, surface hardness falls and the 20th burr is large.

  Test No. 2-25 is an example in which the oxygen concentration at the time of the final annealing of the steel whose component composition conforms to the present embodiment is changed. Since the oxygen concentration was low, the oxide scale was thin and the main component was Cr oxide. For this reason, the element change near the surface layer is slight, and the Cu concentration is reduced. Therefore, the burr is getting bigger.

  Test No. Since the steel sheet of 2-26 to 2-46 does not satisfy the range of this embodiment, the burr height is large.

The ferritic stainless steel sheet of the first embodiment is excellent in corrosion resistance and can reduce burr at the time of punching. For this reason, the ferritic stainless steel plate of the first embodiment can be applied to the fields of kitchens, household electric appliances, equipment, containers, medical instruments, and water storage devices.
The ferritic stainless steel sheet of the second embodiment is excellent in corrosion resistance and can reduce burr at the time of punching. For this reason, the ferritic stainless steel plate of the second embodiment can be applied to the fields of medical instruments and construction hardware.

[0035]

[0044]

［０１２０］[0045]
[0119]
[Table 2C]

[0120]

The gist of the first aspect of the present invention is as follows.
(1) C: 0.016 mass% or less, Si: 1.0 mass% or less, Mn: 1.0 mass% or less, P: 0.010 to 0.035 mass%, S: 0.005 mass% or less Al: 0.50 mass% or less, N: 0.018 mass% or less, Cr: 15.6 to 17.5 mass%, Cu: 0.10 to 0.50 mass%, Sn: 0.01 to 0 Further, Ti: 0.05 to 0.30 mass%, Nb: 0.05 to 0.40 mass%, Mo: 0.05 to 0.50 mass%, and Ni : Containing one or more selected from 0.05 to 0.50% by mass, the balance being Fe and inevitable impurities, Cu concentration on the steel sheet surface is 15% or more in terms of cation fraction, ferrite grain size Is a ferritic stainless steel sheet having an excellent punching workability of 30 μm or less.
(2) Further, in mass%, B: 0.001 mass% or less, V: 0.50 mass% or less, W: 0.50 mass% or less, Co: 0.50 mass% or less, Mg: 0.01 mass % Or less, Ca: 0.003 mass% or less, Zr: 0.30 mass% or less, REM (rare earth metal): 0.02 mass% or less, Ta: 0.50 mass% or less, Sb: 0.001- The ferritic stainless steel sheet having excellent punchability according to (1), which includes one or more selected from 0.3% by mass and Ga: 0.0002 to 0.1% by mass.
(3) A steel slab having the component composition described in (1) or (2) is heated to 1100 ° C. or higher, and then hot-rolled at a finish rolling finish temperature of 900 ° C. or higher is performed at 450 to 600 ° C. A rolled hot-rolled sheet is obtained, and then the hot-rolled sheet is annealed at 800 to 950 ° C., pickled, cold-rolled, and then at a temperature of 820 to 950 ° C. and an oxygen concentration of 1% or more. Last atmosphere annealing, to have a row of cooling to the cooling rate 30 ° C. / s or higher in a temperature range of up to then 600 ° C., then excellent the descaling by pickling in a row cormorants punching workability (1) or (2) The manufacturing method of the ferritic stainless steel plate of description .

The gist of the second aspect of the present invention is as follows.
(4) C: 0.020 mass% or less, Si: 0.80 mass% or less, Mn: 1.0 mass% or less, P: 0.010 to 0.035 mass%, S: 0.005 mass% or less Al: 0.50 mass% or less, N: 0.020 mass% or less, Cr: 15.6 to 17.5 mass%, Cu: 0.50 to 2.00 mass%, Sn: 0.001 to 0 0.1% by mass, and further selected from Ti: 0.05 to 0.30% by mass or less, Nb: 0.05 to 0.40% by mass, and Ni: 0.05 to 0.50% by mass. And the balance is Fe and unavoidable impurities, the Cu concentration on the steel sheet surface is 15% or more in terms of cation fraction, the ferrite grain size is 30 μm or less, and the surface Vickers hardness is 140 A ferritic stainless steel sheet having excellent punchability of ~ 180.
(5) Further, in terms of mass%, Mo: 0.01 to 0.50 mass%, B: 0.001 mass% or less, V: 0.50 mass% or less, W: 0.50 mass% or less, Co: 0 50 mass% or less, Mg: 0.01 mass% or less, Ca: 0.003 mass% or less, Zr: 0.30 mass% or less, REM (rare earth metal): 0.02 mass% or less, and Ta: 0 Ferrite excellent in punching workability according to (4), which includes one or more selected from Sb: 0.001 to 0.3% by mass, Ga: 0.0002 to 0.1% by mass Stainless steel sheet.
(6) A steel slab having the composition described in (4) or (5) is heated to 1100 ° C. or higher, and then the rolling rate during finish rolling is 80 to 90% and the end temperature is 900 ° C. or higher. Hot rolling is performed to obtain a rolled hot rolled sheet at 400 to 500 ° C., then the hot rolled sheet is annealed, pickled, cold rolled, and then at a temperature of 850 ° C. to 950 ° C. and oxygen final annealing at a concentration of 1% or more atmosphere, have rows cooling to the cooling rate 50 ° C. / s or higher in a temperature range of up to then 500 ° C., then excellent the descaling by pickling in a row cormorants punching workability (4) Or the manufacturing method of the ferritic stainless steel sheet as described in (5) .

Claims (6)

C: 0.016 mass% or less, Si: 1.0 mass% or less, Mn: 1.0 mass% or less, P: 0.010 to 0.035 mass%, S: 0.005 mass% or less, Al: 0.50 mass% or less, N: 0.018 mass% or less, Cr: 15.6 to 17.5 mass%, Cu: 0.10 to 0.50 mass%, Sn: 0.01 to 0.3 mass %
Further, Ti: 0.05 to 0.30 mass% or less, Nb: 0.05 to 0.40 mass%, Mo: 0.05 to 0.50 mass% or less, and Ni: 0.05 to 0.50 Containing one or more selected from mass%,
The balance consists of Fe and inevitable impurities,
A ferritic stainless steel sheet excellent in punching workability, in which the Cu concentration on the steel sheet surface is 15% or more in terms of cation fraction and the ferrite particle diameter is 30 μm or less.   Furthermore, in mass%, B: 0.001 mass% or less, V: 0.50 mass% or less, W: 0.50 mass% or less, Co: 0.50 mass% or less, Mg: 0.01 mass% or less, Ca: 0.003 mass% or less, Zr: 0.30 mass% or less, REM (rare earth metal): 0.02 mass% or less, Ta: 0.50 mass% or less, Sb: 0.001 to 0.3 mass % And Ga: 0.002 to 0.1% by mass or more selected from ferritic stainless steel sheets with excellent punchability according to claim 1.   The steel slab having the component composition according to claim 1 or 2 is heated to 1100 ° C or higher, and then hot-rolling at a finish rolling finishing temperature of 900 ° C or higher is performed and wound at 450 to 600 ° C. After obtaining a hot-rolled sheet, the hot-rolled sheet is annealed at 800 to 950 ° C, pickled, cold-rolled, and then at a temperature of 820 to 950 ° C and an oxygen concentration of 1% or more. A method for producing a ferritic stainless steel sheet excellent in punching workability, in which final annealing is performed and then cooling is performed at a cooling rate of 30 ° C./s or higher in a temperature range up to 600 ° C. C: 0.020 mass% or less, Si: 0.80 mass% or less, Mn: 1.0 mass% or less, P: 0.010 to 0.035 mass%, S: 0.005 mass% or less, Al: 0.50 mass% or less, N: 0.020 mass% or less, Cr: 15.6 to 17.5 mass%, Cu: 0.50 to 2.00 mass%, Sn: 0.001 to 0.1 mass% %
Furthermore, Ti: 0.05 to 0.30% by mass or less, Nb: 0.05 to 0.40% by mass, and Ni: 0.05 to 0.50% by mass selected,
The balance consists of Fe and inevitable impurities,
A ferritic stainless steel sheet having excellent punching workability, in which the Cu concentration on the steel sheet surface is 15% or more in terms of cation fraction, the ferrite particle size is 30 μm or less, and the surface hardness is 140 to 180.   Further, in terms of mass%, Mo: 0.01 to 0.50 mass%, B: 0.001 mass% or less, V: 0.50 mass% or less, W: 0.50 mass% or less, Co: 0.50 mass% % Or less, Mg: 0.01 mass% or less, Ca: 0.003 mass% or less, Zr: 0.30 mass% or less, REM (rare earth metal): 0.02 mass% or less, Ta: 0.50 mass% The ferritic stainless steel sheet having excellent punchability according to claim 4, comprising at least one selected from Sb: 0.001 to 0.3% by mass and Ga: 0.0002 to 0.1% by mass. .   A steel slab having the component composition according to claim 4 or 5 is heated to 1100 ° C or higher, and then hot-rolled under conditions of a rolling rate of 80 to 90% and a finish temperature of 900 ° C or higher during finish rolling. To obtain a hot rolled sheet wound up at 400 to 500 ° C., then annealing, pickling and cold rolling the hot rolled sheet, and then at a temperature of 850 ° C. to 950 ° C. and an oxygen concentration of 1% A method for producing a ferritic stainless steel sheet excellent in punching workability, in which final annealing is performed in the above atmosphere, followed by cooling to a cooling rate of 50 ° C./s or higher in a temperature range up to 500 ° C.

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