KR20210139296A - stainless steel plate - Google Patents

Abstract

C: 0.001 to 0.03%, Si: 0.05 to 1.5%, Mn: 0.10 to 3.00%, Cr: 22.00 to 27.00%, Ni: 4.00 to 7.00%, Mo: 0.50 to 2.50%, W: 0 to 1.50%, N : With a two-phase stainless steel sheet containing 0.10 to 0.25% and satisfying Equation 1 and Equation 2, even if solution heat treatment is omitted, corrosion resistance sufficient to be applied to structures such as river structures, industrial machinery, and chemical industry tanks , it is possible to obtain a steel sheet having strength and toughness equal to or greater than that of SUS304N2-X.
PREW=Cr+3.3(Mo+0.5W)+16N (Equation 1)
TS(℃)=4Cr+25Ni+11(Mo+W)×(Mo+W)+41(Mo+W)+5Si-6Mn-30N+550 (Equation 2)

Description

stainless steel plate

The present invention relates to stainless steel. For example, SUS304N2-X, which is an austenitic stainless steel, and SUS329J4L, which is a two-phase stainless steel, can be substituted.

In river structures, industrial machinery, chemical industry tanks, and the like, stainless steel is used as a countermeasure against corrosion. When stainless steel is used as a structural member, a high-strength material is required for weight reduction by thinning, etc., so SUS304N2-X austenitic stainless steel containing N in SUS304 and omitting solution heat treatment is used. there may be cases

However, the corrosion resistance of SUS304N2-X is inferior to that of SUS316L, so it may not be applicable in terms of corrosion. Cr and Mo are known as elements for improving corrosion resistance, but in order to form an austenite phase single phase, in addition to these elements, the content of Ni as an austenite phase forming element must also be increased simultaneously, leading to a significant increase in cost.

Compared with the austenitic stainless steel, the two-phase stainless steel has a low Ni content, which is expensive, and has high strength. However, the two-phase stainless steel subjected to the solution heat treatment does not achieve the strength of SUS304N2-X. In addition, since SUS329J4L, which is a typical steel type of two-phase stainless steel, cannot avoid precipitation of σ phase during hot rolling, if solution heat treatment is omitted to obtain strength, σ phase remains in the product and corrosion resistance and toughness are greatly deteriorated.

As a two-phase stainless steel in which the strength was increased by omitting the solution heat treatment, the stainless steel shown in Patent Document 1 is proposed. This steel is focused on reducing Mo and suppressing the precipitation of Cr nitride.

Japanese Patent Laid-Open No. 2012-153953

River structures, industrial machinery, chemical industry tanks, etc. may become a severe corrosive environment by chloride ions or acids in the fluid in contact. In such a place, the amount of Cr is small and the desired corrosion resistance cannot be ensured in SUS304N2-X which does not contain Mo.

In the hot-rolled steel sheet disclosed in Patent Document 1, attention is focused on suppressing the precipitation of Cr nitride, but in the two-phase stainless steel with large Cr and Mo contents, the sigma phase precipitation greatly affects the toughness and corrosion resistance. Cr nitride is a compound that precipitates due to the interaction of Cr and N, and reduction of N and inclusion of austenite phase forming elements (eg, Ni, Mn) are effective for suppressing precipitation of Cr nitride. On the other hand, the sigma phase is an intermetallic compound precipitated by the interaction of Cr and Mo, and Ni accelerates the precipitation of the sigma phase. In addition, although Mn is effective in suppressing Cr nitride precipitation, it is an element which deteriorates corrosion resistance. Therefore, in the two-phase stainless steel having a large content of Cr and Mo, the influence of elements containing Ni and Mn on the formation of precipitates, intermetallic compounds, and corrosion resistance is significantly different. That is, since the hot-rolled steel sheet disclosed in Patent Document 1 does not take into consideration deterioration in toughness and corrosion resistance due to precipitation of σ phase, there is a limit in corrosion resistance, and a steel sheet having enhanced corrosion resistance and also toughness is required.

The present inventors have a problem to obtain a stainless steel sheet having sufficient corrosion resistance to be applied to structures such as river structures, industrial machinery and chemical industry tanks, and also having strength and toughness equivalent to or higher than that of SUS304N2-X under this background.

In order to solve the above problems, the present inventors have designed a component that can avoid σ phase precipitation during hot rolling while ensuring corrosion resistance, so that a stainless steel sheet having high strength even if solution heat treatment is omitted, and also excellent in corrosion resistance and toughness thought to be obtained. That is, an estimation equation is newly found for the σ phase precipitation temperature TS, and by this equation, using steel materials having different TS, the entry temperature TF of the final finishing rolling pass of hot rolling, and 800°C to 600°C after the completion of hot rolling The strength, impact characteristics, and corrosion resistance were evaluated for the hot-rolled steel sheet obtained by changing the cooling rate in each section.

Through the above experiments, the present invention specified for a stainless hot-rolled steel sheet in which solution heat treatment is omitted has been reached.

That is, the gist of the present invention is as follows.

[One]

in mass %,

C: 0.001 to 0.030%;

Si: 0.05 to 1.50%,

Mn: 0.10 to 3.00%;

Cr: 22.00 to 27.00%,

Ni: 4.00 to 7.00%;

Mo: 0.50 to 2.50%,

W: 0 to 1.50%,

N: 0.10 to 0.25%,

Co: 0 to 1.00%,

Cu: 0 to 3.00%,

V: 0 to 1.00%,

Nb: 0 to 0.200%,

Ta: 0 to 0.200%,

Ti: 0 to 0.030%,

Zr: 0 to 0.050%,

Hf: 0 to 0.100%,

B: 0 to 0.0050%,

Al: 0 to 0.050%,

Ca: 0 to 0.0050%,

Mg: 0 to 0.0050%,

REM: 0 to 0.100%, and

Sn: contains 0 to 0.100%,

the balance is Fe and unavoidable impurities,

as an impurity

O: 0.006% or less;

P: 0.05% or less;

S: steel limited to 0.003% or less,

PREW obtained in Equation 1 is 25.0 or more and 36.0 or less,

The σ phase precipitation temperature TS (°C) obtained from Equation 2 is 800°C or higher and 950°C or lower,

0.2% yield strength of 450 MPa or more,

The Charpy impact value at -20°C is 70 J/cm 2 or more,

The official potential measured at 50°C is 0.40V vs. SSE or higher

Stainless steel sheet, characterized in that.

PREW=Cr+3.3(Mo+0.5W)+16N (Equation 1)

TS(℃)=4Cr+25Ni-11(Mo+W)×(Mo+W)+100(Mo+W)+5Si-6Mn-30N+550 (Equation 2)

However, each element symbol in Formula 1 and Formula 2 shows content (mass %) of the said element, and when not containing, 0 is substituted.

[2]

The component in the stainless steel sheet is in mass%,

Co: 0.01 to 1.00%,

Cu: 0.01 to 3.00%,

V: 0.01 to 1.00%,

Nb: 0.005 to 0.200%,

Ta: 0.005 to 0.200%,

Ti: 0.001 to 0.030%,

Zr: 0.001 to 0.050%,

Hf: 0.001 to 0.100%,

B: 0.0001 to 0.0050%;

Al: 0.003 to 0.050%,

Ca: 0.0005 to 0.0050%,

Mg: 0.0001 to 0.0050%,

REM: 0.005 to 0.100%, and

Sn: 0.005 to 0.100%

The stainless steel sheet according to [1], containing one or two or more of them.

The stainless steel sheet obtained by this invention has the intensity|strength equal or more than SUS304N2-X, and toughness sufficient as a structural material, and has corrosion resistance exceeding SUS304N2-X. On the other hand, the economical efficiency is also good in that the alloy cost is also reasonable. As a result, by using the stainless hot-rolled steel sheet according to the present invention for river structures, industrial machines, chemical industry tanks, etc., improvements are made in both performance and cost, and the contribution to the industrial and environmental aspects is very large.

The reason for limitation of the component composition of the stainless steel which concerns on this invention is demonstrated. In addition, unless otherwise specified in this specification, % regarding a component represents mass %.

C is limited to a content of 0.030% or less in order to secure the corrosion resistance of stainless steel. When it contains more than 0.030%, Cr carbide will generate|occur|produce at the time of hot rolling, and corrosion resistance and toughness will deteriorate. On the other hand, 0.001% is made into a lower limit from a viewpoint of the cost of reducing the C content of stainless steel.

Si is contained in an amount of 0.05% or more for deoxidation. Preferably, what is necessary is just to set it as 0.20 % or more. On the other hand, when it contains exceeding 1.50 %, toughness will deteriorate. Therefore, it is set as 1.50% or less. Preferably, it is good to set it as 1.00% or less.

Mn may be contained in an amount of 0.10% or more in order to have the effect of increasing the austenite phase and lowering the sigma phase precipitation temperature. On the other hand, since Mn is an element that reduces the corrosion resistance of stainless steel, Mn may be set to 3.0% or less. Preferably, it is 2.50% or less, 2.00% or less, 1.50% or less, 1.00% or less, 0.50% or less, 0.45% or less, 0.40% or less, or 0.35% or less.

Cr is contained 22.00% or more in order to secure basic corrosion resistance. Preferably 23.00% or more, 24.00% or more, 25.00% or more, 25.10% or more, 25.20% or more, 25.30% or more, 25.40% or more, or 25.50% or more. On the other hand, since Cr is an element that promotes the precipitation of the σ phase, the content is limited to 27.00% or less. Preferably, it is 26.90% or less, 26.80% or less, 26.70% or less, 26.60% or less, or 26.50% or less.

Ni is an element that promotes the formation of an austenite structure, has an effect of suppressing the formation of Cr nitride, and has an effect of improving corrosion resistance to various acids. Therefore, what is necessary is just to make it contain 4.00% or more. Preferably, what is necessary is just to contain 4.50% or more, 5.00% or more, 5.10% or more, 5.20% or more, 5.30% or more, 5.40% or more, or 5.50% or more. On the other hand, Ni is an element that promotes the precipitation of the sigma phase, and when the sigma phase is precipitated, a Cr-depleted phase is formed and the local corrosion resistance deteriorates. Preferably, it is 6.90% or less, 6.80% or less, 6.70% or less, 6.60% or less, or 6.50% or less.

Mo is a very effective element for improving the corrosion resistance of stainless steel, and in order to provide corrosion resistance of 304N2-X or more, it is good to contain it in 0.50% or more. Preferably, 1.00% or more, 1.30% or more, 1.35% or more, 1.40% or more, 1.45% or more, 1.50% or more, 1.55% or more, 1.60% or more, 1.65% or more, or 1.70% or more. On the other hand, Mo is an element that promotes the precipitation of the sigma phase, and since the local corrosion resistance deteriorates, it is sufficient to contain it in an amount of 2.50% or less. Preferably, it is good to set it as 2.40 % or less, 2.30 % or less, 2.10 % or less, and 2.00 % or less.

W, like Mo, has the effect of improving the corrosion resistance of stainless steel. What is necessary is just to contain 1.50% as an upper limit for the purpose of improving corrosion resistance in this invention steel. On the other hand, since it is also an expensive element, it is not necessary to contain it in particular. A preferable content may be 0.02% or more.

Since N (nitrogen) is an effective element which improves the intensity|strength and corrosion resistance of stainless steel, what is necessary is just to contain it 0.10% or more. Preferably, it is good to set it as 0.15% or more. On the other hand, in order to produce Cr nitride and to impair corrosion resistance, what is necessary is just to make the content into 0.25 % or less. Preferably, what is necessary is just to set it as 0.20 % or less.

The remainder is Fe and unavoidable impurities. An unavoidable impurity is an element contained in a raw material, an element contained unintentionally during manufacture, etc. Among the impurities, O, P, and S are restricted for the following reasons.

O (oxygen) is an element that is unavoidably mixed, and is an element that impairs the hot workability, toughness, and corrosion resistance of stainless steel, so it is preferable to make it as small as possible. Therefore, the O content may be 0.006% or less.

P is an element that is unavoidably mixed from the raw material, and in order to deteriorate hot workability and toughness, it is preferable that there is as little as possible, and it is limited to 0.05% or less. Preferably, what is necessary is just to set it as 0.03 % or less.

S is an element that is unavoidably mixed from raw materials, and in order to also deteriorate hot workability, toughness, and corrosion resistance, it is good that there is as little as possible, and what is necessary is just to make an upper limit 0.003 % or less.

Moreover, you may contain 1 type, or 2 or more types of the following elements (Co, Cu, V, Nb, Ta, Ti, Zr, Hf, B, Al, Ca, Mg, REM, Sn) instead of Fe. Since it is not necessary to contain these elements, the range of content also includes 0%.

Co is an effective element in order to improve the corrosion resistance of steel, and you may contain it. Since Co is an expensive element even if it contains exceeding 1.00 %, since the effect suitable for cost will not be exhibited, what is necessary is just to contain 1.00 % or less. Preferably, what is necessary is just to contain 0.50% or less. In order to acquire the effect, what is necessary is just to contain 0.01% or more, Preferably it is good to contain 0.03% or more.

Since Cu is an element which additionally improves the corrosion resistance with respect to the acid of stainless steel, you may contain it. When Cu is contained in excess of 3.0%, εCu is precipitated in excess of solid solubility during cooling after hot rolling, and embrittlement occurs, so it is sufficient to contain not more than 3.00%. Preferably, what is necessary is just to contain 2.00% or less. When it contains Cu, in order to acquire the effect, what is necessary is just to contain 0.01% or more, Preferably it is good to contain 0.20% or more.

Since V, Nb, and Ta are elements that form carbides and nitrides in steel and additionally improve corrosion resistance, they may be contained. On the other hand, if the content of V, Nb, and Ta is set to 1.00% or less, 0.200% or less, and 0.200% or less, respectively, since toughness is impaired by excessively formed carbides and nitrides when contained in a large amount. When these elements are contained, what is necessary is just to contain 0.01% or more, 0.005% or more, and 0.005% or more, respectively, in order to acquire the effect.

Since Ti, Zr, and Hf are elements that form carbides and nitrides in steel to refine crystal grains, they may be contained. On the other hand, since the excessively formed carbides and nitrides impair toughness when contained in large amounts, the content of Ti, Zr, and Hf may be set to 0.030% or less, 0.050% or less, and 0.100% or less, respectively. When these elements are contained, what is necessary is just to contain 0.001 % or more, 0.001 % or more, and 0.001 % or more, respectively, in order to acquire the effect.

B is an element which improves the hot workability of steel, and you may contain it. On the other hand, when it is contained in a large amount, the nitride of B is precipitated and the toughness is impaired. For this reason, what is necessary is just to make the content into 0.0050 % or less. When it contains B, in order to acquire the effect, what is necessary is just to contain 0.0001% or more, Preferably it is good to contain 0.0005% or more.

Al is an element for deoxidation of steel, and may be contained. On the other hand, when it is contained in excess, Al nitride is generated and toughness is impaired. For this reason, what is necessary is just to make the content into 0.050 % or less. Preferably, it is good to set it as 0.030% or less. In the case of containing Al, in order to obtain the effect, the content may be 0.003% or more, preferably 0.005% or more.

Ca and Mg may be contained in order to improve hot workability. On the other hand, when it contains excessively, it is good to set the content of Ca and Mg to 0.0050% or less and 0.0050% or less, respectively, from the viewpoint of inhibiting hot workability on the contrary. When these elements are contained, what is necessary is just to set it as 0.0005 % or more and 0.0001 % or more, respectively, in order to acquire the effect.

Since REM is an element which improves the hot workability of steel, you may contain it. On the other hand, excessive phosphorus content reduces hot workability and toughness on the other hand. Therefore, when REM is contained, the content may be 0.100% or less. When containing REM, in order to acquire the effect, you may contain 0.005% or more. Here, the content of REM is the total content of lanthanoid-based rare earth elements such as La and Ce.

Since Sn is an element which improves the corrosion resistance with respect to the acid of steel, you may contain it. On the other hand, if it contains excessively, hot workability will be impaired. For this reason, when Sn is contained, what is necessary is just to set it as 0.100 % or less. What is necessary is just to set it as 0.005 % or more in order to acquire the effect when it contains Sn.

PREW is an index for the pitting resistance of stainless steel, and is calculated from Equation 1 using the content (%) of alloying elements Cr, Mo, W, and N. If the PREW of stainless steel is less than 25.0, corrosion resistance in a chloride ion environment, such as brackish water and seawater environment, and a chemical industry tank, cannot be exhibited. Although an upper limit is not specifically limited, Since cost will become high when an alloy element is contained exceeding 36.0, what is necessary is just to make the range of PREW 25.0 or more and 36.0 or less.

PREW=Cr+3.3(Mo+0.5W)+16N (Equation 1)

However, each element symbol in Formula 1 shows content (mass %) of the said element, and when not containing, 0 is substituted.

In river structures, industrial machinery, chemical industry tanks, etc., chloride ions become a corrosion factor and corrosion occurs. In order to ensure sufficient corrosion resistance in the said environment, what is necessary is just to make the value of PREW 25.0 or more by containing Cr, Mo, N, and W. From the viewpoint of ensuring corrosion resistance, the lower limit of PREW may be 26.0, 27.0, 28.0, 29.0, 29.5, 30.0, 30.5 or 31.0. On the other hand, if the content of Cr and Mo is excessively increased in order to increase the PREW, as described above, precipitation of the σ phase is caused, and if the content of N is excessive, adverse effects such as deterioration of toughness appear. In consideration of the influence on these characteristics, it is preferable that the upper limit of PREW be 36.0.

In a general stainless steel sheet (especially a two-phase stainless steel sheet), even when a sigma phase is precipitated in hot rolling, the sigma phase is lost in the subsequent solution heat treatment. However, since the strength is lowered by the solution heat treatment, in order to secure the strength, the solution heat treatment may be omitted and the strain introduced into the steel during hot rolling may remain in the final product.

The precipitation temperature of the σ phase is determined by the chemical composition of the steel, and the temperature range at which the σ phase can precipitate in a chemical equilibrium state can be estimated by thermodynamic calculation. For example, it can be calculated using commercially available software called Thermocalc (registered trademark) and a thermodynamic database (FE-DATA version6, etc.). The present inventors obtained Equation 2 for estimating the upper limit of the sigma phase precipitation temperature range (hereinafter referred to as sigma phase precipitation temperature and denoted by TS) using the above software and database. Moreover, in order to suppress precipitation of a sigma phase and obtain a desired characteristic, TS should just be 950 degrees C or less. Preferably, TS should just be 930 degrees C or less or 910 degrees C or less. The lower the TS, the more difficult it is to precipitate the σ phase, but it leads to a decrease in Cr, Mo, and W, resulting in insufficient corrosion resistance. Therefore, what is necessary is just to set the lower limit of TS to 800 degreeC. Preferably, what is necessary is just to set it as 820 degreeC or more, 830 degreeC or more, or 840 degreeC or more.

TS(℃)=4Cr+25Ni-11(Mo+W)×(Mo+W)+100(Mo+W)+5Si-6Mn-30N+550 (Equation 2)

However, each element symbol in Formula 2 shows content (mass %) of the said element, and when not containing, 0 is substituted.

In addition, the following formula 2' may be used for the estimation formula of the sigma phase precipitation temperature TS. As long as it is within the scope of the present invention, Formula 2' is also equivalent to Formula 2.

TS(℃)=4Cr+25Ni+71(Mo+W)-11.4(Mo-1.3)*(Mo-1.3)+5Si-6Mn-30N+569 (Formula 2')

A hot rolling process is demonstrated below.

What is necessary is just to determine the slab heating temperature before a rolling start suitably, for example, the range of 1150-1250 degreeC, etc. may be sufficient.

Next, with respect to the pass schedule, if the finishing temperature TF (the surface temperature of the steel material at the entrance of the final pass of hot rolling) is too high and close to the solution heat treatment temperature, sufficient deformation does not remain in the hot rolled steel sheet, so that the desired hardness can be obtained. none. On the other hand, if TF is too low, precipitation of the sigma phase is unavoidable. However, since TS is an estimated value of the sigma phase precipitation temperature in a case where the steel sheet is held in a chemical equilibrium state, that is, for an infinite time, since the actual hot rolling ends in a finite time, TF does not need to exceed TS. If it is the range of components prescribed|regulated by this invention, what is necessary is just to satisfy Formula 3. In addition, conditions other than the finishing temperature are not specifically limited, For example, the rolling-reduction|draft amount for each pass, etc. may just be set according to the capability of a rolling mill.

TF-TS≥-100 (Equation 3)

After hot rolling, in order to suppress sigma phase precipitation in the cooling process, if it is the component range prescribed|regulated by this invention, what is necessary is just to cool at a cooling rate of 1 degreeC/s or more in the range of 800 degreeC to 600 degreeC. The cooling method is not particularly limited, and water cooling or air cooling may be used depending on the plate thickness. As described above, the hot-rolled steel sheet obtained in this way does not need to be subjected to solution heat treatment.

The strength may be equal to or greater than that of SUS304N2-X, ie, 0.2% yield strength of 450 MPa or more. Preferably, what is necessary is just 480 MPa or more.

Stainless steel is outdoors for river structures, and for chemical plants, it is used together with cooling equipment and is sometimes exposed to temperatures lower than room temperature. In order to use it as a structural member in such an environment, toughness at low temperature is required, and specifically, the Charpy impact value at -20 degreeC of a hot-rolled steel sheet should just be 70 J/cm<2> or more.

In the above application, sufficient corrosion resistance is required for chloride ions, which are factors of corrosion, and specifically, the pitting potential at 50° C. is 0.40V vs. 0.40V vs. SSE or higher. Here, vs. SSE indicates that it is a potential with reference to a silver-silver chloride reference electrode using a saturated aqueous KCl solution at 25°C as an electrolyte.

Among the precipitated σ phases, those that affect corrosion resistance are those precipitated during hot rolling and subsequent cooling. Therefore, from the difference ΔCr between the Cr extraction residual amount of the hot-rolled steel sheet and the Cr-extraction residue amount of the steel sheet obtained by water-cooling the hot-rolled steel sheet after solution heat treatment at 1000 to 1100° C., The impact was quantified. As a result, when ΔCr exceeds 0.010% in terms of Cr content in the steel sheet, the corrosion resistance of the hot-rolled steel sheet tends to decrease. Therefore, preferably, ΔCr may be 0.010% or less.

Example

Examples are described below. Table 1 shows the chemical composition, PREW, and TS of the test steel. Among the components of the steel, components not shown in Table 1 are Fe and unavoidable impurity elements. These steels are obtained using vacuum furnaces. About the components shown in Table 1, the part whose content is not described is an unavoidable impurity level. REM means a lanthanoid-based rare earth element, and the content represents the sum of those elements. After heating the slab obtained by these vacuum melting at 1200 degreeC for 2 hours, the steel ingot of a predetermined|prescribed shape was obtained by hot forging. Here, the shape of the steel ingot was 110 mm width x 150 mm length x 100 mm thickness when the plate thickness after finish rolling was 20 mm or less, 110 mm width x 150 mm length x 60 mm thickness, and what exceeded 20 mm.

Table 2 shows the conditions of the hot rolling and subsequent cooling rate performed to use the steel ingot as a steel sheet, and the values of the 0.2% yield strength, Charpy absorbed energy, and pitting potential of the obtained hot-rolled steel sheet. In manufacture of a hot-rolled steel sheet, the steel ingot obtained by the forging mentioned above was cracked at 1200 degreeC for 60 minutes first. Then, it reduced so that TF might become the temperature shown in Table 2, and it cooled so that it might become the value shown in the table|surface in the cooling rate of the 800 degreeC to 600 degreeC section. The cooling method was set as water cooling.

A method for measuring 0.2% yield strength is described. The No. 4 test piece described in JIS Z2241:2011 was cut out by machining rather than the steel plate after hot rolling. The measuring method was implemented based on JIS Z2241:2011.

A method for measuring the Charpy absorbed energy is described. The test piece described in JIS Z2242:2018 was cut out by machining from the steel plate after hot rolling. The notch shape was made into a V notch. When a standard test piece could not be sampled because the sheet thickness of the steel sheet was not sufficient, a sub-size test piece was sampled as shown in Table 2. The measurement was performed based on JIS Z2242:2018. However, the test temperature was -20 degreeC.

Describe the method for measuring the formula potential. A sample having a thickness of 15 mm width × 30 mm length × 2 mm from the surface layer of the steel sheet after hot rolling was cut out by machining, and after grinding 0.5 mm from the surface layer, a test piece having a #600 wet polishing finish was prepared. Resin was applied to this test piece leaving a 10 mm x 10 mm part of the measurement surface. Using this test piece, it tested according to the method of JIS G0577:2014. However, in JIS G0577:2014, the thing of 30 degreeC was made into 50 degreeC test temperature. The measurement was carried out until the anode current density reached 1 mA/cm 2 , and the pitting potential was defined as the potential when the current density exceeded 100 μA/cm 2 .

As can be seen from the above examples, it was clarified that a stainless hot-rolled steel sheet having strength and toughness suitable for structural members, excellent corrosion resistance and good economic feasibility can be obtained according to the present invention.

The stainless steel sheet according to the present invention has a strength equal to or higher than that of conventional stainless steel (SUS304N2-X or SUS329J4L), has toughness and corrosion resistance suitable as a structural member, and is excellent in economic efficiency, so that it can be used for river structures, chemical plants, etc. , can be used for all industrial equipment and structures.

Claims (2)

in mass %,
C: 0.001 to 0.030%;
Si: 0.05 to 1.50%,
Mn: 0.10 to 3.00%;
Cr: 22.00 to 27.00%,
Ni: 4.00 to 7.00%;
Mo: 0.50 to 2.50%,
W: 0 to 1.50%,
N: 0.10 to 0.25%,
Co: 0 to 1.00%,
Cu: 0 to 3.00%,
V: 0 to 1.00%,
Nb: 0 to 0.200%,
Ta: 0 to 0.200%,
Ti: 0 to 0.030%,
Zr: 0 to 0.050%,
Hf: 0 to 0.100%,
B: 0 to 0.0050%,
Al: 0 to 0.050%,
Ca: 0 to 0.0050%,
Mg: 0 to 0.0050%,
REM: 0 to 0.100%, and
Sn: contains 0 to 0.100%,
the balance is Fe and unavoidable impurities,
as an impurity
O: 0.006% or less;
P: 0.05% or less;
S: steel limited to 0.003% or less,
PREW obtained in Equation 1 is 25.0 or more and 36.0 or less,
The σ-phase precipitation temperature estimation formula TS (°C) obtained from Equation 2 is 800°C or more and 950°C or less,
0.2% yield strength of 450 MPa or more,
Charpy impact value at -20°C is 70 J/cm 2 or more,
The official potential measured at 50°C is 0.40V vs. SSE or higher
Stainless steel sheet, characterized in that.
PREW=Cr+3.3(Mo+0.5W)+16N (Equation 1)
TS(℃)=4Cr+25Ni-11(Mo+W)×(Mo+W)+100(Mo+W)+5Si-6Mn-30N+550 (Equation 2)
However, each element symbol in Formula 1 and Formula 2 shows content (mass %) of the said element, and when not containing, 0 is substituted. The composition according to claim 1, wherein the component in the stainless steel sheet is, by mass%,
Co: 0.01 to 1.00%,
Cu: 0.01 to 3.00%,
V: 0.01 to 1.00%,
Nb: 0.005 to 0.200%,
Ta: 0.005 to 0.200%,
Ti: 0.001 to 0.030%,
Zr: 0.001 to 0.050%,
Hf: 0.001 to 0.100%,
B: 0.0001 to 0.0050%;
Al: 0.003 to 0.050%,
Ca: 0.0005 to 0.0050%,
Mg: 0.0001 to 0.0050%,
REM: 0.005 to 0.100%, and
Sn: 0.005 to 0.100%
A stainless steel sheet containing one or two or more of them.