TWI638055B - Ferrous iron series stainless steel plate - Google Patents

Abstract

The present invention provides a ferrous iron-based stainless steel sheet that has both reduced surface defects and improved toughness, and has excellent corrosion resistance.

A ferrous iron-based stainless steel plate characterized in that it contains, by mass%, 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, 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, satisfying the following formula (1), and the remainder contains Fe and inevitable impurities.

Zr ≦ Nb ≦ Ti (1)

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

Description

Ferrous iron series stainless steel plate

The present invention relates to a ferrous iron-based stainless steel plate having excellent corrosion resistance, few surface defects, and excellent toughness.

Since the ferrous iron-based stainless steel plate does not contain Ni in a large amount, it is a material that is cheaper than the austenite-based stainless steel plate and has excellent price stability. In addition, the ferrous iron-based stainless steel plate is used in various applications such as building materials, transportation equipment, home appliances, and kitchen equipment because of its excellent rust resistance.

Even in the ferrous stainless steel plate, 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 stabilizing elements (Ti, Nb, and Zr). It has the same excellent corrosion resistance as SUS304 (JIS G 4305, 18 mass% Cr-8 mass% Ni), which is a stainless steel of the Wastfield system. Therefore, it is used in corrosive environments.

Even in SUS443J1, it is usually SUS443J1 mainly containing Ti as a stabilizing element. This steel promotes the development of texture by containing Ti, and is excellent in workability. Furthermore, compared with those containing Nb, even cold-rolled sheet annealing at a lower temperature will be sufficiently softened, so it can be manufactured and produced through the annealing and pickling line of cold-rolled sheet common with ordinary steel Sex is good. However, in SUS443J1 containing Ti, a stripe pattern (surface defect) that impairs the appearance may be generated on the surface. It is known that the above-mentioned stripe pattern results from coarse TiN generated on the surface during casting. In addition, SUS443J1 containing Ti has a problem of low toughness. The reason is that A coarse TiN will be generated, which is the starting point of the preferred destruction.

Patent Literature 1 or Patent Literature 2 describes prevention of surface defects or improvement of toughness of a ferritic iron-based stainless steel containing Ti.

Patent Document 1 discloses a method for producing a ferritic iron-based stainless steel with added Ti which is excellent in roping resistance and has good surface properties. In Patent Document 1, by controlling the solidification temperature, casting temperature, and TiN precipitation temperature of the steel in a specific relationship, the precipitation of TiN at the time of casting the molten steel is controlled, thereby preventing the cold-rolled annealed plate. Surface defects.

Patent Document 2 discloses a ferritic iron-based stainless steel sheet having excellent toughness, good corrosion resistance, and excellent 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 causing the nitrides in the steel to exist in the form of ZrN.

[Prior technical literature] [Patent Literature]

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

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

In recent years, along with the diversification of household appliances, in addition to excellent corrosion resistance, a ferrous iron-based stainless steel sheet that has both a reduction in a stripe pattern on the surface and an excellent toughness is required.

However, in the method shown in Patent Document 1, in order to obtain the effect of improving the equiaxed crystal ratio of the slab, TiN is intentionally precipitated, and therefore, a sufficient effect of improving toughness cannot be obtained. And the effect of reducing surface defects. Furthermore, in the method shown in Patent Document 2, the generation of TiN in steel cannot be sufficiently suppressed, and thus sufficient effects of improving toughness and reducing effects of surface defects cannot be obtained.

The object of the present invention is to provide a ferritic iron-based stainless steel plate, which takes into account the reduction of surface defects and the improvement of toughness, and even uses a cold-rolled plate at the same temperature as the conventional Ti-containing SUS443J1. Annealing is also sufficiently softened and has excellent corrosion resistance.

The inventors have conducted a comprehensive study in consideration of the above-mentioned problems to reduce both surface defects and toughness. As a result, it was found that by adding appropriate amounts of Zr and Nb to SUS443J1 containing Ti, it is possible to change the precipitation morphology of TiN that causes a decrease in toughness without increasing the annealing temperature of the cold-rolled sheet, thereby improving the SUS443J1 containing Ti. toughness. Furthermore, it has been found that by this effect, Ti-based intermediaries can be finely dispersed and precipitated, so that it is possible to reduce surface defects of the steel sheet caused by TiN.

Specifically, it was found that, with respect to the stabilizing elements (Ti, Nb, and Zr) of the ferrous iron-based stainless steel plate of SUS443J1, the main component was set to 0.10 to 0.50% by mass of Ti, and then 0.010 to 0.150% by mass. The composition containing Nb below the Ti content and further containing Zr below the Nb content in the range of 0.005 to 0.150% by mass can be annealed with a cold-rolled sheet at the same temperature as when the composition of the stabilizing element is only Ti. Fully softened, and then both the reduction of surface defects and the realization of higher toughness are taken into account. The mechanism is speculated as follows.

By compositely containing Nb and Zr in steel, the composite carbonitride of Ti, Zr, and Nb becomes smaller in size compared to TiN generated in the ferritic iron-based stainless steel in which Ti is added alone (( Ti, Zr, Nb) (C, N)) are dispersed and precipitated, thereby improving the toughness and reducing the surface defects.

The present invention is based on the above-mentioned insights, and its gist structure is as follows.

[1] A ferrous iron-based stainless steel plate, characterized in that it contains C: 0.020% or less, Si: 0.05 ~ 0.40%, Mn: 0.05 ~ 1.00%, P: 0.040% or less, and S: 0.030% by mass% Below, 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 satisfying the following formula (1), the remainder contains Fe and inevitable impurities.

Zr ≦ Nb ≦ Ti (1)

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

[2] The ferrous iron-based stainless steel plate according to [1], further characterized by containing, in mass%, a member 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% 1 or more.

[3] The ferrous iron-based stainless steel plate according to [1] or [2], further characterized by containing, in mass%, a member 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 ~ 0.0030%, Y: 0.001 ~ 0.20%, and rare earth metals (REM, Rare Earth Metals): 0.001 ~ 0.10%, one or more kinds.

[4] The ferrous iron-based stainless steel plate according to any one of [1] to [3], further comprising, in mass%, a member selected from the group consisting of Sn: 0.001 to 0.50% and Sb: 0.001 to 0.50% 1 or 2 species.

According to the present invention, a ferrous iron-based stainless steel sheet having excellent corrosion resistance, few surface defects, and excellent toughness can be obtained.

In addition, the cold-rolled sheet can be sufficiently softened by annealing at the same temperature as when the composition of the stabilizing element is only Ti, so that the ferritic iron-based stainless steel sheet has high productivity.

Figure 1 is a graph showing the effects of Ti and Nb contents on the amount of toughness and surface defects under the condition of Zr ≦ Nb.

FIG. 2 is a graph showing the effect of the content of Nb and Zr on the amount of toughness and surface defects under the condition of Nb ≦ Ti.

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

The composition of the ferrous iron-based stainless steel plate 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, S: 0.030% or less by 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, satisfying the following formula (1), and the remainder contains Fe and inevitable impurities.

Zr ≦ Nb ≦ Ti (1)

In addition, Zr, Nb, and Ti in the formula (1) refer to the content (% by mass) of each component.

Further, the above-mentioned component composition may further contain one or two or more kinds selected from Co: 0.01 to 0.50%, Mo: 0.01 to 0.30%, and W: 0.01 to 0.50% in mass%.

Further, the above-mentioned component composition may further contain, 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%, Ca: 0.0003 to 0.0030%, Y: 0.001 to 0.20%, and REM (rare earth metals): 0.001 to 0.10% of one or more.

Further, the above-mentioned 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% in mass%.

Hereinafter, each component is demonstrated. "%", Which refers to the content of the ingredients, means% by mass as long as it is not particularly limited.

C: 0.020% or less

C is an element that is more effective for improving the strength of steel. This effect can be obtained by setting the C content to 0.001% or more. However, if the C content exceeds 0.020%, the corrosion resistance and processability are significantly reduced. Therefore, the C content is set to 0.020% or less. The C content is desirably 0.015% or less. Furthermore, it is preferably 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, if the Si content exceeds 0.40%, the steel system will be hardened and the workability will decrease. In addition, if the Si content exceeds 0.40%, generation of scale on the upper surface of the slab having a lubricating effect during hot rolling is suppressed, and surface defects become large. Therefore, the Si content is limited to the range of 0.05 to 0.40%. A more preferable range is 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 deoxidizing effect. This effect can be obtained by setting the Mn content to 0.05% or more. On the other hand, if the Mn content exceeds 1.00%, the precipitation and coarsening of MnS are promoted, and the corrosion resistance is reduced. Therefore, the Mn content is limited to the range of 0.05 to 1.00%. Regarding the lower limit, a more preferable Mn content is 0.10% or more, and still more preferably 0.15% or more. Regarding the upper limit, a more preferable Mn content is less than 0.30%, and more preferably 0.25% or less.

P: 0.040% or less

P is an element that reduces corrosion resistance. In addition, segregation of P at the grain boundaries causes a decrease in hot workability. Therefore, the P content is preferably as low as possible, and is set to 0.040% or less. It is preferably 0.030% or less.

S: 0.030% or less

S system and Mn form a precipitate MnS. The interface between the MnS and the stainless steel base material becomes the starting point of pitting, which reduces the corrosion resistance. Therefore, the S content is preferably as low as 0.030% or less. The content is preferably 0.020% or less.

Al: 0.001 ~ 0.15%

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

Cr: 20.0 ~ 23.0%

Cr is an element that 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 tends to decrease due to the influence of the σ phase or the brittleness at 475 ° C. Therefore, the Cr content is set to 20.0 to 23.0%. Regarding the lower limit, the preferable Cr content is 20.5% or more. Regarding the upper limit, the preferred Cr content is 22.0% or less, and more preferably 21.5% or less.

Ni: 0.01 ~ 0.80%

Ni is an element that suppresses the anode reaction caused by acid and can maintain a passive state even at a lower pH value. That is, the Ni-based effect of improving the interstitial corrosion resistance significantly suppresses the progress of corrosion in an active dissolved state and improves the corrosion resistance. This effect can be obtained when the Ni content is 0.01% or more. On the other hand, when the Ni content exceeds 0.80%, the steel is hardened and its workability is reduced. Therefore, the Ni content is limited to the range of 0.01 to 0.80%. Regarding the lower limit, the Ni content is preferably 0.05% or more, and more preferably 0.10% or more. Regarding the upper limit, the Ni content is preferably 0.40% or less, and more preferably 0.25% or less.

Cu: 0.30 ~ 0.80%

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

Ti: 0.10 ~ 0.50%

Ti is an element that fixes C and N, prevents sensitization by Cr carbonitride, and improves corrosion resistance. However, TiN generated by Ti addition causes a decrease in toughness. As described below, in the present invention, the aforementioned reduction in toughness is suppressed by the composite effect of Nb and Zr. The effect of improving the corrosion resistance by Ti is obtained when the Ti content is 0.10% or more. On the other hand, when the Ti content exceeds 0.50%, the stainless steel plate is hardened, and workability is reduced. In addition, if the Ti content exceeds 0.50%, it becomes difficult to control the precipitation form of the Ti-based intermediary even with the addition of Nb or Zr, and the surface quality decreases. Therefore, the Ti content is set to 0.10 to 0.50%. Range. Regarding the lower limit, the preferred Ti content is 0.15% or more, and more preferably 0.18% or more. Regarding the upper limit, the preferred Ti content is 0.35% or less, and more preferably 0.26% or less.

Nb: 0.010 ~ 0.150%

Nb is an element that fixes C and N similarly to Ti, prevents sensitization by Cr carbonitride, and improves corrosion resistance. Furthermore, Nb improves toughness by a compound effect with Zr described below, thereby suppressing the occurrence of surface defects. This effect can be obtained when the Nb content is 0.010% or more. On the other hand, when the Nb content exceeds 0.150%, the stainless steel plate becomes hard and workability is reduced. If the Nb content exceeds 0.150%, the recrystallization temperature will increase, and the manufacturability will decrease. Therefore, the Nb content is set in the range of 0.010 to 0.150%. Regarding the lower limit, the Nb content is preferably 0.030% or more, and more preferably 0.070% or more. Regarding the upper limit, the Nb content is preferably less than 0.100%, and more preferably 0.090% or less.

Zr: 0.005 ~ 0.150%

Zr is an element that fixes C and N like Ti, prevents sensitization by Cr carbonitride, and improves corrosion resistance. Furthermore, Zr improves toughness by a compound effect with Nb described below, thereby suppressing the occurrence of surface defects. In order to obtain these effects, Zr must be contained in an amount of 0.005% or more. On the other hand, if the Zr content exceeds 0.150%, Zr-based intermediaries are precipitated on the surface, and an increase in surface defects is caused. Therefore, the Zr content is limited to the range of 0.005 to 0.150%. Regarding the lower limit, the Zr content is preferably 0.010% or more, and more preferably 0.030% or more. Regarding the upper limit, the preferred Zr content is less than 0.100%, and more preferably 0.080% or less.

It has been found in the present invention that by adding Nb and Zr to SUS443J1 containing only Ti as a stabilizing element in combination, the use is the same as when the composition of the stabilizing element is only Ti. Annealing the cold-rolled sheet at such a temperature can sufficiently soften, further suppress the occurrence of surface defects, and improve toughness. Specifically, it was found that by stabilizing the elements (Ti, Nb, and Zr) of SUS443J1 within the limits of the following formula (1), it was set to contain 0.10 to 0.50% of Ti, 0.010 to 0.150% of Nb, and 0.005 to The composition of Zr of 0.150% can be fully softened by annealing a 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 realization of high toughness. It is speculated that the mechanism depends on the following.

It is considered that the composite carbonitride of Ti, Zr, and Nb becomes smaller in size as compared with TiN produced by adding Ti-based ferritic iron-based stainless steel by compositely containing Nb and Zr in steel. ((Ti, Zr, Nb) (C, N)) is dispersed and precipitated, thereby realizing improvement in toughness and reduction in surface defects. In order to sufficiently generate the above-mentioned ((Ti, Zr, Nb) (C, N)), the following formula (1) must be satisfied.

Zr ≦ Nb ≦ Ti (1)

In addition, Zr, Nb, and Ti in the formula (1) refer to the content (% by mass) of each component.

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

N: 0.020% or less

N is an element that is inevitably mixed into steel. However, if the N content exceeds 0.020%, the corrosion resistance and processability are significantly reduced. Therefore, the N content is set to 0.020% or less. It is more preferably 0.015% or less.

The basic components have been described above, but as described above, the following elements may be appropriately contained in the present invention in addition to the above.

Co: 0.01 ~ 0.50%

Co is an element that improves the interstitial corrosion resistance of stainless steel. This effect is obtained when the Co content is 0.01% or more. However, when the content exceeds 0.50%, the effect is saturated, and the workability is further reduced. Therefore, when Co is added, the Co content is set to 0.01 to 0.50%. Regarding the lower limit, the Co content is preferably 0.02% or more, and more preferably 0.03% or more. Regarding the upper limit, the Co content is preferably 0.30% or less, and more preferably 0.10% or less.

Mo: 0.01 ~ 0.30%

Mo has the effect of improving the interstitial corrosion resistance of stainless steel. This effect is obtained with a Mo content of 0.01% or more. However, when the Mo content exceeds 0.30%, the effect is saturated, and coarse intermetallic compounds are formed, which reduces the toughness. Therefore, when Mo is added, the Mo content is set to 0.01 to 0.30%. Regarding the lower limit, the Mo content is preferably 0.02% or more, and more preferably 0.03% or more. With regard to the upper limit, the Mo content is preferably 0.20% or less, and more preferably 0.10% or less.

W: 0.01 ~ 0.50%

W is an element that improves the interstitial corrosion resistance of stainless steel. This effect is obtained when the W content is 0.01% or more. However, when the content exceeds 0.50%, the effect is saturated, and the workability is further reduced. Therefore, when W is added, the W content is set to 0.01 to 0.50%. Regarding the lower limit, the W content is preferably 0.02% or more, and more preferably 0.03% or more. Regarding the upper limit, the W content is preferably 0.30% or less, and more preferably 0.10% or less.

V: 0.01 ~ 0.50%

V is an element that improves the interstitial corrosion resistance of stainless steel. This effect can be achieved by the V content as Obtained above 0.01%. However, when the content exceeds 0.50%, the effect is saturated, and the workability is further reduced. Therefore, when V is added, the V content is set to 0.01 to 0.50%. A more preferable range is 0.01 to 0.30%. It is more 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. B is more effective when added to Ti-added steel. This effect is obtained when the B content is 0.0003% or more. On the other hand, if the B content exceeds 0.0030%, the toughness decreases. Therefore, when B is added, the B content is set to the range of 0.0003 to 0.0030%. Regarding the lower limit, the preferable B content is 0.0015% or more. Regarding the upper limit, the preferred B content is 0.0025% or less.

Mg: 0.0005 ~ 0.0100%

Mg forms a Mg oxide together with Al in the molten steel, and functions as a deoxidizer. This effect is obtained when the Mg content is 0.0005% or more. On the other hand, if the Mg content exceeds 0.0100%, the toughness of the steel decreases and the manufacturability decreases. Therefore, when Mg is added, the Mg content is limited to the range of 0.0005 to 0.0100%. Regarding the lower limit, the preferable Mg content is 0.0010% or more. Regarding the upper limit, the Mg content is preferably 0.0050% or less, and more preferably 0.0030% or less.

Ca: 0.0003 ~ 0.0030%

Ca is an element that improves hot workability. This effect can be obtained when the Ca content is 0.0003% or more. On the other hand, if the Ca content exceeds 0.0030%, the toughness of the steel decreases. In addition, corrosion resistance is also reduced due to precipitation of CaS. Therefore, when Ca is added, 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 preferable Ca content is 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 when the Y content is 0.001% or more. On the other hand, when the Y content exceeds 0.20%, the effect is saturated, and the workability is further reduced. Therefore, when Y is added, the Y content is limited to the range of 0.001 to 0.20%. A more preferable range is 0.001 to 0.10%.

REM (rare earth metals): 0.001 ~ 0.10%

REM (rare earth metals: elements with atomic numbers 57 to 71 such as La, Ce, Nd) is an element that improves high temperature oxidation resistance. This effect can be obtained when the REM content is 0.001% or more. On the other hand, when the REM content exceeds 0.10%, not only the effect is saturated, but also surface defects are generated during hot rolling. Therefore, when REM is added, the REM content is limited to the range of 0.001 to 0.10%. Regarding the lower limit, a preferable REM content is 0.005% or more. Regarding the upper limit, a preferable REM content is 0.05% or less.

Sn: 0.001 ~ 0.50%

Sn is effective in improving the ridging caused by the promotion of the formation of deformed bands during rolling. This effect is obtained when the content of Sn is 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, its content is set to 0.001 to 0.50%. Regarding the lower limit, a preferable Sn content is 0.003% or more. Regarding the upper limit, a preferable Sn content is 0.20% or less.

Sb: 0.001 ~ 0.50%

Sb is effective in improving wrinkles by promoting the formation of deformed bands during rolling. This effect is obtained when the content of Sb is 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, its content is set to 0.001 to 0.50%. Regarding the lower limit, the preferred Sb content is 0.003% or more, and as for the upper limit, the preferred Sb content is 0.20% or less.

The remainder other than the above components are Fe and inevitable impurities. Representative examples of the inevitable impurities referred to here 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. Regarding other elements, other elements may be included in a range of 0.3% or less.

Next, a preferred method for manufacturing the ferrous iron-based stainless steel plate of the present invention will be described. The steel with the above-mentioned composition is melted by a known method such as a converter, an electric furnace, and a vacuum melting furnace, and a steel material (slab) is produced by a continuous casting method or an ingot-split method. After heating this steel material to 1000 ° C. to 1200 ° C., hot rolling is performed so as to have a sheet 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 way is annealed and pickled at a temperature of 800 ° C to 1100 ° C, followed by cold rolling, and annealed at a temperature of 700 ° C to 1000 ° C. After the cold-rolled sheet is annealed, pickling is performed to remove scale. Skin pass rolling may also be performed on the cold-rolled sheet from which the scale has been removed.

In addition, the present invention is not limited to the cold-rolled sheet products described above, and it is also effective to make hot-rolled sheet products.

[Example]

In 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 (combining Table 3 -1 is combined with Table 3-2 to form the ferritic iron-based stainless steel with the composition shown in Table 3). After melting into a 100 kg steel ingot, it is 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 were performed, followed by cold rolling to a plate thickness of 2.0 mm, annealing at 900 ° C, and pickling by a usual method.

The obtained cold-rolled annealed sheet was subjected to pitting corrosion potential measurement (JIS G 0577), and the corrosion resistance was evaluated. The evaluation was performed with a pitting potential of 290 mV (vs. SCE) or more as "○" (pass) and a value of less than 290 mV as "▲" (fail).

Further, for 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. A Charpy impact value at 25 ° C of 200 J / cm ² or more was evaluated as "○" (Passed), and those below 200 J / cm ² were evaluated as "▲" (Failed).

Furthermore, by observing the surface of the cold-rolled annealed sheet, the density of the striped pattern on the surface was measured, and the amount of surface defects was evaluated. Ten steel plates of each composition were made, and the number of stripe patterns whose length in the L (length) direction exceeded 10 mm was measured for an area having a width of 200 mm × a length of 200 mm at the central portion of the front surface of each steel plate, and the average number was 1 The following were evaluated as "○" (pass) and more than 1 as "▲" (fail).

Furthermore, using the cold-rolled steel sheet before the annealing was performed, it was evaluated whether it was sufficiently softened even in the annealing at 880 ° C. for 20 s. The evaluation is performed on the hardness (a) of the steel sheet maintained in the state after cold rolling, the hardness (b) of the steel sheet annealed at 880 ° C for 20 s, and performed at 1000 ° C as an index when sufficiently softened. The hardness (c) of the annealed steel sheet after 20s was compared and evaluated. In the evaluation, three steel plates with a length of 15 mm × a width of 20 mm were cut, and for the test pieces for measurement b and c, after performing the various annealing described above, the steel plates were cut into a size of 15 mm × 10 mm in width and used from this section. The Vickers hardness was measured. If annealing is performed, the hardness of the steel sheet changes from a to c, and more than 90% of this softening is borrowed. Those who achieved the annealing at 880 ° C for 20 s were evaluated as "○" (pass) if c + 0.1 × (a-c) ≧ b. In addition, the evaluation was performed by setting the case to "▲" (Failure).

The obtained results are shown in Tables 1, 2, and 3. It can be seen that the evaluation of the pitting corrosion potential measurement, the Charpy impact value evaluation, the surface defect evaluation, and the softening temperature evaluation of the invention steel are all "○". The corrosion resistance and toughness are good, and the surface defects are few. 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 is inferior in toughness because the Cr content is higher than the range of the present invention.

The comparative example of Test No. 36 is inferior in corrosion resistance because the Ni content is 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 is because the Ti content is higher than the range of the present invention, the toughness is poor, and there are many surface defects.

The comparative example of test No. 39 is because the Nb content is lower than the range of the present invention, the toughness is poor, and there are many surface defects.

The comparative example of test No. 40 is because the Nb content is higher than the range of the present invention, the softening temperature is high, and the manufacturability is poor.

The comparative example of test No. 41 is because the Zr content is lower than the range of the present invention, the toughness is poor, and there are many surface defects.

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

The comparative example of Test No. 57 is because the Nb content and the Zr content are both lower than the range of the present invention, the toughness is poor, and there are many surface defects.

The comparative example of Test No. 58 is because 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. Therefore, the toughness is poor and there are many surface defects, and the softening temperature is higher. Poor manufacturability.

The comparative examples 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 comparative examples (No. 43 to 48) that satisfy Nb ≧ Zr and do not satisfy Ti ≧ Nb within the scope of the present invention are evaluated for the Charpy impact value. And the evaluation of surface defects, the content of Ti is taken on the horizontal axis, and the content of Nb is taken on the vertical axis, and they are summarized in the figure. In addition, the steel plate shown in the figure is all qualified for the evaluation of the surface defects of the Charpy impact value, and those who fail the result of the Charpy impact value are also unqualified for the surface defect. As shown in FIG. 1, in order to balance excellent toughness and reduction of surface defects within the composition range of the present invention, it is necessary to satisfy Ti ≧ Nb.

In FIG. 2, the results of the examples of the present invention and the results of comparative examples (No. 49 ~ 54, 67, 68) that satisfy Ti ≧ Nb and do not satisfy Nb ≧ Zr within the scope of the present invention are directed to Charpy. The evaluation of the impact value and the evaluation of the surface defect 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, in order to balance excellent toughness and reduction of surface defects in the composition range of the present invention, it is necessary to satisfy Nb ≧ Zr. Furthermore, according to FIG. 1 and FIG. 2, in order to achieve both excellent toughness and reduction of surface defects within the composition range of the present invention, it is necessary to satisfy both Ti ≧ Nb and Nb ≧ Zr, that is, satisfy Zr ≦ Nb ≦ Ti.

Furthermore, the comparative examples of Test Nos. 55 and 56 are within the scope of the present invention and do not satisfy both Ti ≧ Nb and Nb ≧ Zr. Neither the results of the Charpy impact value nor the evaluation of surface defects. qualified.

(Industrial availability)

The ferrous iron-based stainless steel plate of the present invention is preferably used as an interior decoration represented by an inner plate of an elevator, a duct cover, an exhaust pipe tail throat, and a storage cabinet because of its excellent toughness and few surface defects. , Parts for household electrical appliances, parts for business supplies, parts for automobile interiors, pipes for automobile exhausts, building materials, gutter covers, containers for marine transportation, utensils, kitchen equipment, building interior and exterior materials, automobile parts, escalators, Railroad cars and electrical equipment housings are required to have corrosion resistance as the center, and they can also be used as members requiring toughness or design.

Claims (5)

A ferrous iron-based stainless steel plate characterized in that it contains, by mass%, 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, 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: 0.030 to 0.150%, Zr: 0.005 to 0.150%, and N : 0.020% or less, and satisfying 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) refer to each Content of ingredients (% by mass)). For example, the ferrous iron-based stainless steel sheet according to claim 1, further comprising one or two 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% in terms of mass%. . For example, the ferrous iron-based stainless steel plate of claim 1 or 2 further includes, in mass%, a material 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 ~ 0.20%, and REM (rare earth metal): 0.001 ~ 0.10%, one or more kinds. For example, the ferritic iron-based stainless steel plate of claim 1 or 2 further contains Sb in a mass% of 0.001 to 0.50%. For example, the ferritic iron-based stainless steel plate of claim 3 further contains Sb in a mass% of 0.001 to 0.50%.