TW201718909A - Ferrite stainless steel sheet - Google Patents

Abstract

Provided is a ferrite stainless steel sheet which has excellent corrosion resistance and which simultaneously achieves reduction in surface defects and improvement in toughness. The ferrite stainless steel sheet is characterized by: containing, in mass%, 0.020% or less of C, 0.05-0.40% of Si, 0.05-1.00% of Mn, 0.040% or less of P, 0.030% or less of S, 0.001-0.15% of Al, 20.0-23.0% of Cr, 0.01-0.80% of Ni, 0.30-0.80% of Cu, 0.10-0.50% of Ti, 0.010-0.150% of Nb, 0.005-0.150% of Zr, and 0.020% or less of N; satisfying formula (1); and the balance being Fe and incidental impurities. Zr ≤ Nb ≤ Ti (1) (note that, in formula (1), Zr, Nb, and Ti each mean the contained amount (mass%) of the respective component).

Description

Fertilizer iron stainless steel plate

The present invention relates to a ferrite-based iron-based stainless steel sheet which is excellent in corrosion resistance, has few surface defects, and is excellent in toughness.

Since the ferrite-based iron-based stainless steel sheet does not contain a large amount of Ni, it is a material which is inexpensive and has excellent price stability as compared with an austenite-based stainless steel sheet. Moreover, since the ferrite-based stainless steel sheet is excellent in rust resistance, it is used for various purposes such as construction materials, transportation equipment, home electric appliances, and kitchen equipment.

That is, in the ferrite-rich iron-based stainless steel sheet, SUS443J1 (JIS G 4305) also contains 20.0 to 23.0% by mass of Cr, 0.3 to 0.8% by mass of Cu, and a sufficient amount of stable elements (Ti, Nb, and Zr). In addition, it has excellent corrosion resistance equivalent to SUS304 (JIS G 4305, 18% by mass of Cr-8 mass% Ni) which is a stainless steel of the Vostian system, and is therefore applied to a particularly corrosive environment.

That is, in the case of SUS443J1, it is also generally SUS443J1 which mainly contains Ti as a stabilizing element. This steel promotes the development of texture by containing Ti, and is excellent in workability. Further, compared with those containing Nb, even if the cold-rolled sheet is annealed at a relatively low temperature, it is sufficiently softened. Therefore, it can be manufactured by passing through a cold-rolled sheet annealed pickling line common to ordinary steel. Good sex. However, in the case of SUS443J1 containing Ti, there is a case where a fringe pattern (surface defect) which impairs the appearance is caused on the surface. It is known that the above-described stripe pattern is caused by the coarse TiN formed on the surface at the time of casting. Further, in SUS443J1 containing Ti, there is also a problem that the toughness is low. The reason is that A coarse TiN that is the starting point of destruction is generated.

The prevention of surface defects or the improvement of toughness of the ferrite-based stainless steel containing Ti are described in Patent Document 1 or Patent Document 2.

Patent Document 1 discloses a method for producing a ferrite-based iron-based stainless steel which is excellent in rope resistance and has excellent surface properties. In Patent Document 1, the solidification temperature, the casting temperature, and the TiN precipitation temperature of the steel are controlled so as to be in a specific relationship, thereby controlling the precipitation of TiN at the time of casting of the molten steel, thereby preventing the cold rolled annealed sheet. Surface defects.

Patent Document 2 discloses a ferrite-grained stainless steel sheet which is excellent in toughness, has excellent corrosion resistance, and is excellent in productivity and economy, and a method for producing the same. In Patent Document 2, the toughness of the hot rolled annealed sheet and the cold rolled annealed sheet is improved by allowing the nitride in the steel to exist in the form of ZrN.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. Hei 1-118341

Patent Document 2: Japanese Patent Laid-Open Publication No. 2011-214060

In recent years, with the diversification of home appliances, it is required to take into consideration both the excellent corrosion resistance and the fat-grained iron-based stainless steel sheets which have both the reduction of the surface stripe pattern and the excellent toughness.

However, in the method disclosed in Patent Document 1, in order to obtain an effect of improving the equiaxed crystal ratio of the slab, TiN is intentionally precipitated, and therefore, sufficient toughness improvement effect cannot be obtained. And the reduction effect of surface defects. Further, in the method disclosed in Patent Document 2, the formation of TiN in the steel cannot be sufficiently suppressed, and the effect of improving the toughness and the effect of reducing the surface defects cannot be obtained.

An object of the present invention is to provide a ferrite-based iron-based stainless steel sheet which has both a reduction in surface defects and an increase in toughness, and further uses a cold-rolled sheet at a temperature equivalent to that of the conventional Ti-containing SUS443J1. Annealing is also sufficiently soft and excellent in corrosion resistance.

In order to solve the above problems, the inventors have conducted a comprehensive study for achieving both reduction in surface defects and improvement in toughness. As a result, it has been found that by adding an appropriate amount of Zr and Nb to the SUS443J1 containing Ti, it is possible to improve the precipitation form of TiN which causes a decrease in toughness without changing the annealing temperature of the cold-rolled sheet, thereby improving the SUS443J1 containing Ti. toughness. Further, it has been found that the Ti-based interpolymer can be finely dispersed and precipitated by this effect, and the surface defects of the steel sheet caused by TiN can be reduced.

Specifically, it is found that the stabilizing elements (Ti, Nb, and Zr) of the ferrite-based stainless steel sheet of SUS443J1 are set to have a main component of 0.10 to 0.50% by mass of Ti, and further preferably 0.010 to 0.150% by mass. In the range of Nb having a Ti content or less and further containing a Zr content of not less than the Nb content in the range of 0.005 to 0.150% by mass, it is possible to anneal the cold-rolled sheet at the same temperature as the case where the composition of the stabilizing element is only Ti. Fully softened, taking into account both the reduction of surface defects and the achievement of higher toughness. It can be speculated that the mechanism is as follows.

By compounding Nb and Zr in steel, it is a composite carbonitride of Ti, Zr and Nb which is smaller in size than TiN produced in Ti-based ferrite-based stainless steel. Ti, Zr, and Nb) (C, N)) are dispersed and precipitated, thereby achieving an improvement in toughness and a reduction in surface defects.

The present invention is based on the above-mentioned knowledge, and its main constitution is as follows.

[1] A ferrite-based iron-based stainless steel sheet comprising C: 0.020% or less, Si: 0.05 to 0.40%, Mn: 0.05 to 1.00%, P: 0.040% or less, and S: 0.030% by mass%. Hereinafter, Al: 0.001 to 0.15%, Cr: 20.0 to 23.0%, Ni: 0.01 to 0.80%, Cu: 0.30 to 0.80%, Ti: 0.10 to 0.50%, Nb: 0.010 to 0.150%, Zr: 0.005 to 0.150% And N: 0.020% or less, and satisfy the following formula (1), and the remainder contains Fe and unavoidable impurities.

Zr≦Nb≦Ti (1)

(Further, Zr, Nb, and Ti in the formula (1) means the content (% by mass) of each component)

[2] The ferrite-based iron-based stainless steel sheet according to [1], which further comprises, in mass%, a selected from the group consisting of Co: 0.01 to 0.50%, Mo: 0.01 to 0.30%, and W: 0.01 to 0.50%. One or two or more.

[3] The ferrite-based iron-based stainless steel sheet according to [1] or [2], which further comprises, in mass%, a selected from the group consisting of V: 0.01 to 0.50%, B: 0.0003 to 0.0030%, and Mg: 0.0005 to 0.0100. %, Ca: 0.0003 to 0.0030%, Y: 0.001 to 0.20%, and rare earth metal (REM, Rare Earth Metals): one or more of 0.001 to 0.10%.

[4] The ferrite-based iron-based stainless steel sheet according to any one of [1] to [3], which further comprises, in mass%, selected from the group consisting of Sn: 0.001 to 0.50% and Sb: 0.001 to 0.50%. 1 or 2 types.

According to the present invention, it is possible to obtain a ferrite-grained stainless steel sheet which is excellent in corrosion resistance, has few surface defects, and is excellent in toughness.

Further, since the cold-rolled sheet annealing at the same temperature as the case where the composition of the stabilizing element is only Ti is sufficiently softened, the productivity of the ferrite-grained stainless steel sheet is high.

Figure 1 is a graph showing the effect of Ti and Nb content on the amount of toughness and surface defects under the conditions of Zr≦Nb.

Fig. 2 is a graph showing the effect of the contents of Nb and Zr on the amount of toughness and surface defects under the conditions of Nb≦Ti.

Hereinafter, embodiments of the present invention will be described. Furthermore, the present invention is not limited to the following embodiments.

The component composition of the ferrite-based iron-based stainless steel sheet of the present invention contains C: 0.020% or less, Si: 0.05 to 0.40%, Mn: 0.05 to 1.00%, P: 0.040% or less, and S: 0.030% or less in mass%. Al: 0.001 to 0.15%, Cr: 20.0 to 23.0%, Ni: 0.01 to 0.80%, Cu: 0.30 to 0.80%, Ti: 0.10 to 0.50%, Nb: 0.010 to 0.150%, Zr: 0.005 to 0.150%, and N: 0.020% or less, and the following formula (1) is satisfied, and the remainder contains Fe and unavoidable impurities.

Zr≦Nb≦Ti (1)

Further, Zr, Nb and Ti in the formula (1) mean the content (% by mass) of each component.

In addition, the component composition may further contain one or more selected from the group consisting of Co: 0.01 to 0.50%, Mo: 0.01 to 0.30%, and W: 0.01 to 0.50% by mass.

Further, the component composition may further include, in mass%, a selected from the group consisting of V: 0.01 to 0.50%, B: 0.0003 to 0.0030%, Mg: 0.0005 to 0.0100%, Ca: 0.0003 to 0.0030%, and Y: 0.001 to 0.20%, and REM (rare earth metal): one or more of 0.001 to 0.10%.

In addition, the component composition may further contain one or two selected from the group consisting of Sn: 0.001 to 0.50% and Sb: 0.001 to 0.50% by mass%.

Hereinafter, each component will be described. The "%" of the content of the component means mass% unless otherwise specified.

C: 0.020% or less

The C system is an effective element for increasing the strength of steel. This effect can be obtained by setting the C content to 0.001% or more. However, when the C content exceeds 0.020%, the corrosion resistance and workability are remarkably lowered. Therefore, the C content is set to 0.020% or less. Further, it is preferable to set the C content to 0.015% or less. Further preferably, it is 0.010% or less.

Si: 0.05~0.40%

Si is an element useful as a deoxidizer. This effect can be obtained by setting the Si content to 0.05% or more. However, when the Si content exceeds 0.40%, the steel is hardened and the workability is lowered. Moreover, when the Si content exceeds 0.40%, the formation of a scale on the upper surface of the slab having a lubricating effect during hot rolling is suppressed, and the surface defects are increased. Therefore, the Si content is limited to the range of 0.05 to 0.40%. More preferably, it is in the range of 0.05 to 0.25%. The lower limit of the Si content is more preferably 0.08% or more. The upper limit of the Si content is more preferably 0.15% or less.

Mn: 0.05~1.00%

Mn has a deoxidation effect. This effect can be obtained by setting the Mn content to 0.05% or more. On the other hand, when the Mn content exceeds 1.00%, precipitation and coarsening of MnS are promoted, and corrosion resistance is lowered. Therefore, the Mn content is limited to the range of 0.05 to 1.00%. The lower limit of the Mn content is preferably 0.10% or more, and more preferably 0.15% or more. Regarding the upper limit, a more preferable Mn content is less than 0.30%, more preferably 0.25% or less.

P: 0.040% or less

P is an element that reduces corrosion resistance. Further, since P is segregated at the grain boundary, the hot workability is deteriorated. Therefore, the P content is desirably as low as possible and is set to be 0.040% or less. It is preferably 0.030% or less.

S: 0.030% or less

The S system forms a precipitate MnS with Mn. The interface between the MnS and the stainless steel base material becomes the starting point of the etched holes, and the corrosion resistance is lowered. Therefore, the S content is desirably low, and is set to 0.030% or less. It is preferably set to 0.020% or less.

Al: 0.001~0.15%

Al is an element that is effective for deoxidation. This effect can be obtained by having an Al content of 0.001% or more. On the other hand, when the Al content exceeds 0.15%, the formation of scale on the upper surface of the steel slab having a lubricating effect during hot rolling is suppressed, and surface defects are increased. Therefore, the Al content is limited to the range of 0.001 to 0.15%. With respect to the lower limit, the Al content is preferably 0.005% or more, more preferably 0.01% or more. The upper limit is preferably 0.10% or less, more preferably 0.05% or less.

Cr: 20.0~23.0%

Cr is an element which forms a passive film on the surface to improve corrosion resistance. If the Cr content is less than 20.0%, sufficient corrosion resistance cannot be obtained. On the other hand, when the Cr content exceeds 23.0%, the toughness is liable to be lowered by the influence of the σ phase or the 475 ° C brittleness. Therefore, the Cr content is set to 20.0 to 23.0%. Regarding the lower limit, the Cr content is preferably 20.5% or more. The upper limit is preferably 22.0% or less, more preferably 21.5% or less.

Ni: 0.01~0.80%

Ni suppresses an anodic reaction caused by an acid and maintains a passive state even at a lower pH. That is, Ni improves the effect of the crevice corrosion resistance, and remarkably suppresses the progress of corrosion in the active dissolved state to improve the corrosion resistance. This effect can be obtained by having a Ni content of 0.01% or more. On the other hand, when the Ni content exceeds 0.80%, the steel is hardened and the workability is lowered. Therefore, the Ni content is limited to the range of 0.01 to 0.80%. The lower limit is preferably 0.05% or more, and more preferably 0.10% or more. The upper limit is preferably 0.40% or less, more preferably 0.25% or less.

Cu: 0.30~0.80%

Cu is an element that enhances the passive film and improves corrosion resistance. On the other hand, when Cu is excessively added, ε-Cu is easily precipitated, and corrosion resistance is lowered. Therefore, the Cu content is set to be 0.30 to 0.80%. The lower limit is preferably 0.35% or more, and more preferably 0.40% or more. The upper limit is preferably 0.60% or less, more preferably 0.45% or less.

Ti: 0.10~0.50%

Ti is an element that fixes C and N to prevent sensitization by Cr carbonitride and improve corrosion resistance. However, TiN generated by the addition of Ti causes a decrease in toughness. As described below, in the present invention, the above-described toughness reduction is suppressed by the combined effect of Nb and Zr. The corrosion resistance improving effect obtained by using Ti is obtained by having a Ti content of 0.10% or more. On the other hand, when the Ti content exceeds 0.50%, the stainless steel sheet is hardened and the workability is lowered. In addition, when the Ti content is more than 0.50%, it is difficult to control the precipitation form of the Ti-based intermediate material by the addition of Nb or Zr, and the surface quality is lowered. Therefore, the Ti content is set to 0.10 to 0.50%. The scope. The lower limit is preferably 0.15% or more, and more preferably 0.18% or more. The upper limit is preferably 0.35% or less, more preferably 0.26% or less.

Nb: 0.010~0.150%

Nb is an element which fixes C and N similarly to Ti, and prevents sensitization by Cr carbonitride, and improves corrosion resistance. Further, Nb improves the toughness by the combined effect with Zr described below, thereby suppressing the occurrence of surface defects. This effect can be obtained by having a Nb content of 0.010% or more. On the other hand, when the Nb content exceeds 0.150%, the stainless steel sheet is hardened and the workability is lowered. Moreover, when the Nb content exceeds 0.150%, the recrystallization temperature is increased and the manufacturability is lowered. Therefore, the Nb content is set to be in the range of 0.010 to 0.150%. The lower limit of the Nb content is preferably 0.030% or more, and more preferably 0.070% or more. With respect to the upper limit, the Nb content is preferably less than 0.100%, more preferably 0.090% or less.

Zr: 0.005~0.150%

Zr is an element which fixes C and N in the same manner as Ti and prevents sensitization by Cr carbonitride to improve corrosion resistance. Further, Zr improves the toughness by the combined effect with Nb described below, thereby suppressing the occurrence of surface defects. In order to obtain such effects, it is necessary to contain 0.005% or more of Zr. On the other hand, when the Zr content exceeds 0.150%, a Zr-based intermediate is precipitated on the surface, which causes an increase in surface defects. Therefore, the Zr content is limited to the range of 0.005 to 0.150%. The lower limit of the Zr content is preferably 0.010% or more, and more preferably 0.030% or more. With respect to the upper limit, the Zr content is preferably less than 0.100%, more preferably 0.080% or less.

In the present invention, it has been found that by adding Nb and Zr in a composite manner to SUS443J1 containing only Ti as a stabilizing element, the same applies to the case where the composition of the stabilizing element is only Ti. When the cold-rolled sheet is annealed at a temperature, it can be sufficiently softened, thereby suppressing the occurrence of surface defects and improving the toughness. Specifically, it has been found that the stable elements (Ti, Nb, and Zr) of SUS443J1 are contained in the range of 0.10 to 0.50% of Ti, 0.010 to 0.150% of Nb, and 0.005~ by the following formula (1). The composition of 0.150% of Zr can be sufficiently softened by annealing the cold-rolled sheet at the same temperature as when the composition of the stabilizing element is only Ti, thereby achieving both reduction of surface defects and high toughness. It can be speculated that the mechanism depends on the following.

It is considered that by compounding Nb and Zr in steel, it is a composite carbonitride of Ti, Zr and Nb which is smaller in size than TiN which is formed by separately adding Ti-based ferrite-based stainless steel. ((Ti, Zr, Nb) (C, N)) is dispersed and precipitated, and the toughness is improved and the surface defects are reduced. In order to sufficiently generate the above ((Ti, Zr, Nb) (C, N)), the following formula (1) must be satisfied.

Zr≦Nb≦Ti (1)

Further, Zr, Nb and Ti in the formula (1) mean the content (% by mass) of each component.

The relationship between Ti and Nb is preferably Ti≧1.5Nb, and further preferably Ti≧2Nb. The relationship between Nb and Zr is preferably Nb ≧ 1.3Zr, and further preferably Nb ≧ 1.5Zr.

N: 0.020% or less

The N system inevitably mixes into the elements in the steel. However, when the N content exceeds 0.020%, the corrosion resistance and workability are remarkably lowered. Therefore, the N content is set to 0.020% or less. More preferably, it is 0.015% or less.

Although the basic components have been described above, the above-described elements may be appropriately contained in the present invention as described above.

Co: 0.01~0.50%

Co is an element that improves the crevice corrosion resistance of stainless steel. This effect is obtained by having a Co content of 0.01% or more. However, if the content exceeds 0.50%, the effect is saturated and the workability is deteriorated. Therefore, in the case of adding Co, the Co content is set to 0.01 to 0.50%. The lower limit is preferably 0.02% or more, and more preferably 0.03% or more. The upper limit is preferably 0.30% or less, more preferably 0.10% or less.

Mo: 0.01~0.30%

Mo has the effect of improving the crevice corrosion resistance of stainless steel. This effect is obtained by a content of Mo content of 0.01% or more. However, when the Mo content exceeds 0.30%, the effect is saturated, and a coarse intermetallic compound is formed to lower the toughness. Therefore, when Mo is added, the Mo content is set to 0.01 to 0.30%. The lower limit is preferably 0.02% or more, and more preferably 0.03% or more. The upper limit is preferably 0.20% or less, more preferably 0.10% or less.

W: 0.01~0.50%

The W system is an element that improves the crevice corrosion resistance of stainless steel. This effect is obtained by having a W content of 0.01% or more. However, if the content exceeds 0.50%, the effect is saturated and the workability is lowered. Therefore, when W is added, the W content is set to 0.01 to 0.50%. The lower limit is preferably 0.02% or more, and more preferably 0.03% or more. The upper limit is preferably 0.30% or less, more preferably 0.10% or less.

V: 0.01~0.50%

The V system improves the resistance of the stainless steel to crevice corrosion. The effect can be obtained by the V content Obtained from 0.01% or more. However, if the content exceeds 0.50%, the effect is saturated and the workability is lowered. Therefore, when V is added, the V content is set to 0.01 to 0.50%. More preferably, it is in the range of 0.01 to 0.30%. Further, it is preferably in the range of 0.01 to 0.10%.

B: 0.0003~0.0030%

B is an element that improves hot workability or secondary workability, and B is added to steel in which Ti is added. This effect is obtained by having a B content of 0.0003% or more. On the other hand, if the B content exceeds 0.0030%, the toughness is lowered. Therefore, when B is added, the B content is set to be in the range of 0.0003 to 0.0030%. With respect to the lower limit, the B content is preferably 0.0015% or more. Regarding the upper limit, the B content is preferably 0.0025% or less.

Mg: 0.0005~0.0100%

Mg is formed in a molten steel together with Al to form a Mg oxide and functions as a deoxidizing agent. This effect is obtained by having a Mg content of 0.0005% or more. On the other hand, when the Mg content exceeds 0.0100%, the toughness of the steel is lowered and the manufacturability is lowered. Therefore, in the case of adding Mg, the Mg content is limited to the range of 0.0005 to 0.0100%. With respect to the lower limit, the Mg content is preferably 0.0010% or more. The upper limit is preferably 0.0050% or less, more preferably 0.0030% or less.

Ca: 0.0003~0.0030%

Ca is an element that improves hot workability. This effect can be obtained by having a Ca content of 0.0003% or more. On the other hand, if the Ca content exceeds 0.0030%, the toughness of the steel decreases. Moreover, corrosion resistance also falls due to precipitation of CaS. Therefore, in the case of adding Ca, the Ca content is limited to the range of 0.0003 to 0.0030%. Regarding the lower limit, the preferred Ca content is 0.001%. the above. Regarding the upper limit, the Ca content is preferably 0.002% or less.

Y: 0.001~0.20%

Y is an element that reduces the viscosity of molten steel and improves the cleanliness. This effect can be obtained by having a Y content of 0.001% or more. On the other hand, when the Y content exceeds 0.20%, the effect is saturated and the workability is deteriorated. Therefore, in the case of adding Y, the Y content is limited to the range of 0.001 to 0.20%. More preferably, it is in the range of 0.001 to 0.10%.

REM (rare earth metal): 0.001~0.10%

REM (rare earth metal: an element of atomic numbers 57 to 71 such as La, Ce, and Nd) is an element which improves high temperature oxidation resistance. This effect can be obtained by having a REM content of 0.001% or more. On the other hand, if the REM content exceeds 0.10%, not only the effect is saturated, but also surface defects occur during hot rolling. Therefore, in the case of adding REM, the REM content is limited to the range of 0.001 to 0.10%. Regarding the lower limit, a preferred REM content is 0.005% or more. Regarding the upper limit, a preferred REM content is 0.05% or less.

Sn: 0.001~0.50%

Sn is effective in improving ridging due to the promotion of deformation band formation at the time of rolling. This effect is obtained by the content of Sn being 0.001% or more. However, when the content of Sn exceeds 0.50%, not only the effect is saturated, but also the workability is lowered. Therefore, when Sn is added, the content thereof is set to 0.001 to 0.50%. Regarding the lower limit, the Sn content is preferably 0.003% or more. Regarding the upper limit, the Sn content is preferably 0.20% or less.

Sb: 0.001~0.50%

Sb is effective in improving wrinkles by promoting deformation zone formation during rolling. This effect is obtained by the content of Sb being 0.001% or more. However, when the content of Sb exceeds 0.50%, not only the effect is saturated, but also the workability is lowered. Therefore, when Sb is added, the content is set to 0.001 to 0.50%. The lower limit of the Sb content is preferably 0.003% or more, and the upper limit is preferably 0.20% or less.

The remainder except the above components are Fe and unavoidable impurities. Representative examples of the unavoidable impurities herein include H, O (oxygen), Zn, Ga, Ge, As, Ag, In, Hf, Ta, Re, Os, Ir, Pt, Au, Pb, and the like. Among these elements, H and O (oxygen) may be contained in a range of 0.05% or less. For other elements, other elements may be included in the range of 0.3% or less.

Next, a preferred method of producing the ferrite-based stainless steel sheet of the present invention will be described. The steel of the above composition is melted by a known method such as a converter, an electric furnace, and a vacuum melting furnace, and a steel material (steel billet) is produced by a continuous casting method or an ingot-spinning method. After the steel material is heated to 1000 ° C to 1200 ° C, hot rolling is performed so as to have a thickness of 2.0 mm to 5.0 mm under the conditions of a completion temperature of 700 ° C to 1000 ° C. The hot-rolled sheet produced in this manner is annealed at 800 ° C to 1100 ° C for pickling, followed by cold rolling, and cold-rolled sheet annealing is performed at a temperature of 700 ° C to 1000 ° C. After the cold rolled sheet is annealed, pickling is performed to remove the scale. It is also possible to perform skin pass rolling on the cold-rolled sheet from which the scale has been removed.

Further, the present invention is not limited to the cold-rolled sheet product as described above, and is also effective as a hot-rolled sheet product.

[Examples]

It will have Table 1 (combining Table 1-1 and Table 1-2 as Table 1), Table 2 (combining Table 2-1 and Table 2-2 as Table 2), and Table 3 (Table 3) -1 and Table 3-2 together as the composition shown in Table 3), the ferrite-based iron-based stainless steel is melted into a 100 kg steel ingot and heated to a temperature of 1200 ° C. Hot rolling was performed to obtain a hot rolled sheet having a thickness of 4.0 mm. Thereafter, annealing at 1100 ° C and pickling by a usual method are carried out, followed by cold rolling to a thickness of 2.0 mm, annealing at 900 ° C, and pickling by a usual method.

Corrosion resistance was evaluated by performing pitting corrosion potential measurement (JIS G 0577) on the obtained cold rolled annealed sheet. When the pitting potential was 290 mV (vs. SCE) or more, it was set to "○" (passed), and those who did not exceed 290 mV were set to "▲" (failed).

Further, with respect to the obtained cold-rolled annealed sheet, a test piece (JIS B 7722 V notch) was collected in the rolling direction, and a Charpy impact test was performed to evaluate the toughness of the steel sheet. When the Charpy impact value at 25 ° C was 200 J/cm ² or more, it was set to "○" (pass), and the less than 200 J/cm ² was set to "▲" (failed).

Further, the amount of surface defects was evaluated by measuring the density of the striped pattern on the surface by observing the surface of the cold rolled annealed sheet. Ten sheets of each of the steel sheets of the respective compositions were produced, and the number of stripe patterns having a length in the L (length) direction of more than 10 mm was measured for a region having a width of 200 mm × a length of 200 mm in the center portion of the front surface of each steel sheet, and the average number was 1 The following is set to "○" (passed), and more than one is set to "▲" (failed) and evaluated.

Further, the cold-rolled steel sheet before the annealing was used, and it was evaluated whether or not it was sufficiently softened even in the annealing at 880 ° C for 20 s. The evaluation was carried out at 1000 ° C for the hardness (a) of the steel sheet after the cold rolling, the hardness (b) of the steel sheet which was annealed at 880 ° C for 20 s, and the index when it was sufficiently softened. The hardness (c) of the annealed steel sheet of 20 s was compared and evaluated. In the evaluation, three steel sheets each having a length of 15 mm and a width of 20 mm were cut, and for the test pieces measuring b and c, after performing the above various annealing, the steel sheet was cut into a size of 15 mm in length × 10 mm in width, and used from the section. The Vickers hardness was measured. When annealing is performed, the hardness of the steel sheet changes from a toward c, and 90% or more of the softening is borrowed. The evaluation was made by annealing at 880 ° C for 20 s, that is, c + 0.1 × (a - c) ≧ b was set to "○" (passed) and evaluated. In addition, the evaluation was made by setting "▲" (failed).

The results obtained are shown in Tables 1, 2 and 3. It can be seen that the evaluation of the pitting corrosion potential of the inventive steel system, the evaluation of the Charpy impact value, the evaluation of the surface defects, and the evaluation of the softening temperature are all "○", the corrosion resistance and the toughness are good, the surface defects are small, and the manufacturing is small. There is no problem with sex.

The comparative example of Test No. 34 was inferior in corrosion resistance because the Cr content was lower than the range of the present invention.

The comparative example of Test No. 35 was inferior in toughness because the Cr content was higher than the range of the present invention.

The comparative example of Test No. 36 was inferior in corrosion resistance because the Ni content was lower than the range of the present invention.

The comparative example of Test No. 37 was inferior in corrosion resistance because the Ti content was lower than the range of the present invention.

The comparative example of Test No. 38 was that the Ti content was higher than the range of the present invention, so that the toughness was poor and the surface defects were large.

The comparative example of Test No. 39 was that the Nb content was lower than the range of the present invention, so that the toughness was poor and the surface defects were large.

In the comparative example of Test No. 40, since the Nb content was higher than the range of the present invention, the softening temperature was high and the manufacturability was poor.

In the comparative example of Test No. 41, since the Zr content was lower than the range of the present invention, the toughness was poor and the surface defects were large.

The comparative example of Test No. 42 has a large surface defect because the Zr content is higher than the range of the present invention.

In the comparative example of Test No. 57, since both the Nb content and the Zr content were lower than the range of the present invention, the toughness was poor and the surface defects were large.

In the comparative example of Test No. 58, since the Ti content and the Zr content are lower than the range of the present invention, and the Al content and the Nb content are higher than the range of the present invention, the toughness is poor and the surface defects are large, and the softening temperature is high. Poor manufacturability.

Further, a comparative example of Test Nos. 43 to 54, 67, and 68 will be described below with reference to FIGS. 1 and 2 .

In Fig. 1, the results of the examples of the present invention and the results of the comparison examples (No. 43 to 48) satisfying Nb ≧ Zr and satisfying Ti ≧ Nb within the scope of the present invention are evaluated for the Charpy impact value. The surface defects were evaluated by taking the Ti content on the horizontal axis and the Nb content on the vertical axis. In addition, the evaluation of the surface defects of all the Charpy impact values of the steel plate shown in the figure is also acceptable, and the evaluation of the surface defects of the unsatisfactory results of the Charpy impact value is also unsatisfactory. As shown in Fig. 1, Ti≧Nb must be satisfied in order to achieve both excellent toughness and surface defects in the composition range of the present invention.

In Fig. 2, the results of the examples of the present invention and the results of the comparative examples (No. 49 to 54, 67, 68) satisfying Ti≧Nb and satisfying Nb≧Zr within the scope of the present invention are directed to Xiabi. The evaluation of the impact value and the evaluation of the surface defects are summarized in the figure by taking the Nb content on the horizontal axis and the Zr content on the vertical axis. As shown in Fig. 2, Nb≧Zr must be satisfied in order to achieve both excellent toughness and surface defect reduction within the composition range of the present invention. Further, from Fig. 1 and Fig. 2, it is understood that in order to achieve both the excellent toughness and the reduction in surface defects in the composition range of the present invention, it is necessary to satisfy both Ti≧Nb and Nb≧Zr, that is, satisfy Zr≦Nb≦Ti.

Further, regarding the comparative examples of Test Nos. 55 and 56, the composition is within the scope of the present invention, and does not satisfy both Ti≧Nb and Nb≧Zr, and neither the Charpy impact value nor the surface defect evaluation is satisfied. qualified.

(industrial availability)

The ferrite-grained stainless steel sheet of the present invention is preferably used as an interior decoration represented by an inner panel of an elevator, a duct cover, an exhaust pipe tail throat, and a locker because of excellent toughness and less surface defects. , parts for home appliances, parts for business products, parts for automotive interiors, piping for automobile exhaust, building materials, drain cover, containers for marine transportation, utensils, kitchen equipment, interior and exterior materials for buildings, auto parts, escalators, The rail vehicle and the outer panel of the electric device housing are centrally required to have corrosion resistance, and may be used as a member requiring toughness or design.

Claims (4)

A ferrite-based iron-based stainless steel sheet characterized by containing C: 0.020% or less, Si: 0.05 to 0.40%, Mn: 0.05 to 1.00%, P: 0.040% or less, S: 0.030% or less, and Al by mass%. : 0.001 to 0.15%, Cr: 20.0 to 23.0%, Ni: 0.01 to 0.80%, Cu: 0.30 to 0.80%, Ti: 0.10 to 0.50%, Nb: 0.010 to 0.150%, Zr: 0.005 to 0.150%, and N : 0.020% or less, and satisfying the following formula (1), the remainder containing Fe and unavoidable impurities; Zr≦Nb≦Ti (1) (again, Zr, Nb, and Ti in the formula (1) means each Content of the ingredients (% by mass)). The ferrite-based iron-based stainless steel sheet of the above-mentioned claim 1 further contains one or more selected from the group consisting of Co: 0.01 to 0.50%, Mo: 0.01 to 0.30%, and W: 0.01 to 0.50% by mass%. . The ferrite-based iron-based stainless steel sheet according to claim 1 or 2, further comprising, in mass%, selected from the group consisting of V: 0.01 to 0.50%, B: 0.0003 to 0.0030%, Mg: 0.0005 to 0.0100%, and Ca: 0.0003 to 0.0030 %, Y: 0.001 to 0.20% and REM (rare earth metal): one or more of 0.001 to 0.10%. The ferrite-based iron-based stainless steel sheet according to any one of claims 1 to 3, which further comprises, in mass%, one or two selected from the group consisting of Sn: 0.001 to 0.50% and Sb: 0.001 to 0.50%.