JPWO2018147149A1 - Ferritic stainless steel sheet - Google Patents

Abstract

A ferritic stainless steel sheet having excellent corrosion resistance and capable of further improving the corrosion resistance of a weld bead when butt welding is performed with SUS304. In mass%, C: 0.020% or less, Si: 0.05 to 1.00%, Mn: 0.05 to 1.00%, P: 0.040% or less, S: 0.030% or less, Al: 0.001 to 0.150%, Cr: 20.0 to 23.0%, Ni: 1.60 to 3.00%, Nb: 0.40 to 1.00%, and N: 0.020 % Or less, and the balance has a component composition consisting of Fe and inevitable impurities.

Description

  The ferritic stainless steel sheet of the present invention has excellent corrosion resistance and excellent corrosion resistance of butt welds with SUS304 (18 mass% Cr-8 mass% Ni steel) which is an austenitic stainless steel.

  Ferritic stainless steel (for example, SUS430 (16% by mass Cr steel)) is less expensive than austenitic stainless steel (for example, SUS304), and is therefore applied to various applications including kitchen appliances. Yes. However, when SUS430 is welded together, a phenomenon called sensitization occurs, and there is a problem that the corrosion resistance of the welded portion is greatly deteriorated.

  It is known that the sensitization phenomenon described above occurs by the following mechanism. In the weld bead portion formed by welding, Cr carbonitride precipitates and grows. For the growth of Cr carbonitride, Cr is supplied from the grain boundary where Cr is relatively easy to diffuse. In contrast to this supply, the diffusion of Cr from within the crystal grain to the crystal grain boundary is slow, thereby forming a region called a chromium-deficient layer in which the Cr content is locally reduced and the corrosion resistance is degraded at the crystal grain boundary. Is done.

  In order to solve this problem, carbonization and nitrogen reduction are performed using a refining technique typified by VOD (Vacuum Oxygen Decarburization), and an element called a stabilizing element typified by Ti or Nb is contained. Ferritic stainless steel has been developed that is less susceptible to sensitization. Since the stabilizing element has high affinity with C and N, it precipitates as carbonitride in preference to Cr, and suppresses precipitation and growth of Cr carbonitride that induces sensitization. Typical examples are SUS430LX (16 mass% Cr-0.2 mass% Ti), SUS430J1L (19 mass% Cr-0.5 mass% Cu-0.4 mass% Nb), SUS436L (18 mass% Cr- 1.0 mass% Mo-0.3 mass% Ti), SUS443J1 (21 mass% Cr-0.4 mass% Cu-0.3 mass% Ti) and the like, and are widely used for automobile parts and the like.

  However, the various ferritic stainless steels described above also have a problem that sensitization may occur when welded with austenitic stainless steel. This is because the austenitic stainless steel has a high carbon and nitrogen content, so a large amount of C and N is dissolved from the austenitic stainless steel side into the molten pool formed during welding, and the C content and N This is because the content is increased, and in the weld bead, the concentration of the stabilizing element contained in the ferritic stainless steel is decreased by the penetration of the austenitic stainless steel, so that the precipitation of the Cr carbonitride cannot be sufficiently suppressed.

  It is known that, by optimizing the welding conditions, it is possible to prevent sensitization of the welded portion between the ferritic stainless steel and the austenitic stainless steel. This mainly controls the penetration rate of the austenitic stainless steel into the weld bead. That is, the chemical composition of the weld bead is determined by the mixing of the steel components of the two types of steel that are welded by welding. Sensitization can be prevented by optimizing. However, in actual welding construction, it is difficult to always properly control the penetration rate.

  Parts and products using stainless steel are often manufactured by joining members produced using a plurality of stainless steel plates. In recent years, the movement to replace some members from austenitic stainless steel to ferritic stainless steel has been accelerated for the purpose of reducing the price of parts and products. In this movement, there is a demand for a ferritic stainless steel that has excellent corrosion resistance and does not deteriorate in corrosion resistance, that is, does not cause sensitization even when butt-welded to austenitic stainless steel. Therefore, the inventors aimed to develop a ferritic stainless steel that does not deteriorate its corrosion resistance even when butt-welded with SUS304, which is most commonly used among austenitic stainless steels.

  Ferritic stainless steels that are less susceptible to sensitization in welding with austenitic stainless steels are disclosed in, for example, Patent Documents 1 and 2.

  In Patent Document 1, in mass%, C: 0.02% or less, Si: 3% or less, Mn: 1% or less, P: 0.04% or less, S: 0.03% or less, Ni: 3% Hereinafter, Cr: 18 to 26%, Mo: 0.3 to 2%, Nb: 0.1 to 0.6%, N: 0.025% or less, the balance consists of Fe and inevitable impurities, “A value = Cr% + Mo% + 1.5 (Si%) + 0.5 (Nb%) + 0.9 (Mn%) + 1.5 (Ni%)” A ferritic stainless steel excellent in corrosion resistance of a welded portion with an austenitic stainless steel characterized by having a composition prepared is disclosed.

  In Patent Document 2, in mass%, C: 0.030% or less, N: 0.030% or less, (C + N): 0.050% or less, Si: 0.15 to 0.60%, Mn: 0 50% or less, Al: 0.010% or less, Cr: 20.5 to 22.5%, Cu: 0.03 to 1.00%, Ni: 0.10 to 1.50%, Nb: 0.0. 30 to 0.70%, P: 0.040% or less and S: 0.010% or less, and these components satisfy the relationship of “Nb / (C + N + 0.06) ≧ 4”, and the balance Discloses a ferritic stainless steel sheet excellent in the corrosion resistance of a welded part of a dissimilar material with austenitic stainless steel, characterized by comprising Fe and inevitable impurities.

JP 2010-202916 A JP 2008-179885 A

  The technique disclosed in Patent Document 1 is intended for welding with SUS316L. The present inventors made a plurality of steel plates by the method described in Patent Document 1, and performed TIG butt welding with SUS304 under conditions where the penetration rate of SUS304 was 20 to 80%. Sensitization was observed in the welds of the steel plates. That is, the technique disclosed in Patent Document 1 is insufficient to prevent sensitization when welding with SUS304.

  In the technique disclosed in Patent Document 2, butt welding with SUS304 is being studied. However, the examination of the penetration rate of SUS304 in the weld bead portion is insufficient. The present inventors made a plurality of steel plates by the method described in Patent Document 2, and performed TIG butt welding with SUS304 under the condition that the penetration rate of SUS304 was 20 to 80%. Depending on the penetration rate, sensitization may be observed in the welds of some steel plates.

  The present invention has been developed in view of the above problems, and provides a ferritic stainless steel sheet that is excellent in corrosion resistance and can further improve the corrosion resistance of a weld bead when butt welding is performed with SUS304. The purpose is to do.

Here, in the present invention, “excellent corrosion resistance” means that a steel plate is polished with No. 600 emery polishing paper, sprayed with 7.0 mass% NaCl aqueous solution (2 hours, 35 ° C., 98% RH), dried ( 4 hours, 60 ° C., 30% RH), wet (2 hours, 40 ° C., 95% RH) as one cycle, and 50 cycles of corrosion test results indicate that the soot area ratio is 20% or less. .
Further, in the present invention, “the corrosion resistance of the weld bead when butt welding with SUS304 can be further improved” means that the penetration rate of SUS304 is 10% when the plate thickness is 1.0 mm. More than 30%, less than 30%, less than 30%, less than 50%, 50% or more, less than 70%, 70% or more and less than 90%, butt welding with SUS304 of the same plate thickness (plate thickness 1.0mm) The conditions are a welding current of 70 A, a welding voltage of 11 V, a welding speed of 40 cm / min, a shielding gas of argon, a torch side of 15 L / min, and a back side of 10 L / min. As a result, it indicates that the flaw area ratio in the weld bead portion is 5% or less at any penetration rate.

The present inventors have studied a ferritic stainless steel sheet that is excellent in corrosion resistance and can further improve the corrosion resistance of the weld bead portion when butt-welded with SUS304. As a result, the following knowledge was obtained.
The C content is 0.020% or less, the N content is 0.020% or less, the Cr content is 20.0% or more and 23.0% or less, and the Ni content is 1. 60% or more and 3.00% or less and the Nb content is 0.40% or more and 1.00% or less, so that the corrosion resistance is excellent and the corrosion resistance of the weld bead portion when butt welding is performed with SUS304. It has been found that can be further improved.

The mechanism is considered as follows.
When a ferritic stainless steel plate and SUS304 are welded under conditions where the penetration rate of SUS304 is low, the weld bead portion has a ferrite single-phase structure. In this state, a sufficient amount of Nb is contained in the ferritic stainless steel plate, and the amount of C and N in the ferritic stainless steel plate is sufficiently reduced, so that C and N contained in the weld bead portion are Nb. Precipitate as carbonitride. Thereby, in the weld bead part, the production | generation of Cr carbonitride is suppressed and sensitization is suppressed.
On the other hand, when the ferritic stainless steel plate and SUS304 are welded under conditions where the penetration rate of SUS304 is high, the weld bead portion has an austenite single phase structure. In this state, C and N contained in the weld bead portion are dissolved in the steel. Thereby, in the weld bead part, the production | generation of Cr carbonitride is suppressed and sensitization is suppressed. The reason why C and N described above dissolve in the steel is that a large amount of C and N are dissolved in the austenite phase as compared with the ferrite phase.

  In addition, in the intermediate condition between the two welding conditions described above, the weld bead portion has a ferrite-austenite two-phase structure. The weld bead portion in this state contains a large amount of C and N dissolved from SUS304, and further does not have a sufficient austenite phase to dissolve them, so that conventional steel is likely to be sensitized. When Nb is contained in the ferritic stainless steel plate, Nb is precipitated as carbonitride in the weld bead portion, and a part of C and N in the ferrite phase can be fixed. However, Nb increases the amount of C and N in the ferrite phase because it suppresses the formation of the austenite phase in the weld bead. For this reason, sensitization under welding conditions in which the weld bead portion has a ferrite-austenite two-phase structure cannot be prevented only by increasing the Nb content in the ferritic stainless steel sheet.

  On the other hand, by containing an appropriate amount of Ni in the ferritic stainless steel, sensitization can be prevented even under welding conditions in which the weld bead has a ferrite-austenite two-phase structure. This is due to the following mechanism. First, by containing an appropriate amount of Ni, austenite phase generation in the weld bead portion is promoted. Thereby, the quantity of C and N which dissolves in the austenite phase in a weld bead part increases. This means that the amount of C and N in the ferrite phase in the weld bead portion is reduced. Most of the C and N in the ferrite phase whose amount is reduced in this way is precipitated as carbonitride together with Nb, the formation of Cr carbonitride is suppressed, and sensitization is suppressed.

  Thereby, in any case where the weld bead portion has a ferrite single-phase structure, a ferrite-austenite two-phase structure and an austenite single-phase structure, sensitization is prevented. That is, the corrosion resistance of the weld bead portion when butt welding with SUS304 can be further improved.

The present invention is based on the above findings, and the gist of the present invention is as follows.
[1] By mass%, C: 0.020% or less, Si: 0.05 to 1.00%, Mn: 0.05 to 1.00%, P: 0.040% or less, S: 0.030 %: Al: 0.001 to 0.150%, Cr: 20.0 to 23.0%, Ni: 1.60 to 3.00%, Nb: 0.40 to 1.00%, and N: A ferritic stainless steel sheet containing 0.020% or less and having a composition comprising the balance of Fe and inevitable impurities.
[2] Further, in terms of mass%, Cu: 0.01 to 0.80%, Co: 0.01 to 0.50%, Mo: 0.01 to 1.00%, and W: 0.01 to 0 The ferritic stainless steel sheet according to [1] above, containing one or more selected from 50%.
[3] Furthermore, by mass%, one selected from Ti: 0.01 to 0.80%, V: 0.01 to 0.80%, and Zr: 0.01 to 0.80% Or the ferritic stainless steel plate as described in said [1] or [2] containing 2 or more types.
[4] Further, by mass%, B: 0.0003 to 0.0030%, Mg: 0.0005 to 0.0100%, Ca: 0.0003 to 0.0030%, Y: 0.001 to 0.001. 20% and REM (rare earth metal): The ferrite system according to any one of the above [1] to [3], containing one or more selected from 0.001 to 0.10% Stainless steel sheet.
[5] Furthermore, the above-mentioned [1] containing, in mass%, one or two selected from Sn: 0.001 to 0.50% and Sb: 0.001 to 0.50% ~ Ferritic stainless steel sheet according to any one of [4].

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in corrosion resistance and can improve the corrosion resistance of the weld bead part at the time of performing butt welding with SUS304.

Hereinafter, the present invention will be specifically described.
The ferritic stainless steel sheet of the present invention is, in mass%, C: 0.020% or less, Si: 0.05 to 1.00%, Mn: 0.05 to 1.00%, P: 0.040% or less. S: 0.030% or less, Al: 0.001 to 0.150%, Cr: 20.0 to 23.0%, Ni: 1.60 to 3.00%, Nb: 0.40 to 1. 00% and N: 0.020% or less, with the balance being a component composition composed of Fe and inevitable impurities, excellent corrosion resistance, and corrosion resistance of the weld bead when butt welding is performed with SUS304 Can be further improved.

  First, the reason why the component composition is limited to the above range in the present invention will be described. In addition, about% which shows the component of a steel plate, unless otherwise indicated, means mass%.

C: 0.020% or less C is an element effective for increasing the strength of steel. Since the effect is obtained by setting the C content to 0.003% or more, the C content is preferably 0.003% or more. However, if the C content exceeds 0.020%, the corrosion resistance and workability are remarkably lowered, and when welding with SUS304, sensitization occurs at the weld bead portion. Therefore, the C content is 0.020% or less. The C content is more preferably 0.004% or more, and further preferably 0.005% or more. Further, the C content is preferably 0.016% or less, more preferably 0.012% or less.

Si: 0.05-1.00%
Si is not only effective in increasing the corrosion resistance of the welded portion, but also has an effect of concentrating C in the austenite phase generated in the weld bead portion to suppress sensitization when welding with SUS304. However, if the Si content exceeds 1.00%, when welding with SUS304, the formation of the austenite phase at the weld bead portion is suppressed and sensitization is likely to occur. Therefore, the Si content is set to 0.05 to 1.00%. The Si content is more preferably 0.08% or more. Moreover, Si content becomes like this. Preferably it is 0.50% or less, More preferably, it is 0.18% or less.

Mn: 0.05-1.00%
Mn has a deoxidizing action. This effect is obtained by making the Mn content 0.05% or more. Moreover, when welding with SUS304, there exists an effect which promotes the production | generation of the austenite phase in a weld bead part and suppresses sensitization. On the other hand, if the Mn content exceeds 1.00%, precipitation and coarsening of MnS are promoted, resulting in a decrease in corrosion resistance. Therefore, the Mn content is 0.05 to 1.00%. The Mn content is preferably 0.10% or more, more preferably 0.15% or more. Further, the Mn content is preferably less than 0.30%, more preferably 0.25% or less.

P: 0.040% or less P is an element that lowers corrosion resistance. Moreover, P reduces hot workability by segregating at the grain boundaries. Therefore, the P content is desirably as small as possible, and is set to 0.040% or less. Preferably, the P content is 0.030% or less.

S: 0.030% or less S forms Mn and precipitate MnS. This MnS becomes a starting point of corrosion, and the corrosion resistance is lowered. Therefore, it is desirable that the S content is small, and the content is 0.030% or less. Preferably, the S content is 0.020% or less.

Al: 0.001 to 0.150%
Al is an effective element for deoxidation. This effect can be obtained by making the Al content 0.001% or more. On the other hand, when the Al content exceeds 0.150%, when welding with SUS304, the formation of the austenite phase is suppressed at the weld bead portion, and sensitization is likely to occur. Therefore, the Al content is 0.001 to 0.150%. The Al content is preferably 0.005% or more, and more preferably 0.010% or more. Moreover, Al content becomes like this. Preferably it is 0.100% or less, More preferably, it is 0.050% or less.

Cr: 20.0-23.0%
Cr is an element that improves the corrosion resistance by forming a passive film on the surface. If the Cr content is less than 20.0%, sufficient corrosion resistance cannot be obtained. On the other hand, since Cr suppresses the formation of an austenite phase, when the Cr content exceeds 23.0%, sensitization is likely to occur when welding with SUS304. Therefore, the Cr content is 20.0 to 23.0%. The Cr content is preferably 20.5% or more, more preferably 21.0% or more. Further, the Cr content is preferably 22.5% or less, and more preferably 22.0% or less.

Ni: 1.60 to 3.00%
Ni has the effect of suppressing sensitization when welding with SUS304. This is because Ni promotes the formation of the austenite phase in the weld bead. In the produced austenite phase, a large amount of C and N are dissolved. For this reason, the precipitation of C and N in the ferrite phase is suppressed and the sensitization is suppressed by promoting the formation of the austenite phase. This effect is obtained by setting the Ni content to 1.60% or more. On the other hand, if the Ni content exceeds 3.00%, the steel becomes hard and the workability decreases. Furthermore, a trace amount of austenite phase is generated in the structure of the steel sheet, the amount of Cr in the austenite phase is lowered, and the corrosion resistance is lowered. Therefore, the Ni content is 1.60 to 3.00%. The Ni content is preferably 1.70% or more, and more preferably 1.80% or more. Moreover, Ni content becomes like this. Preferably it is 2.60% or less, More preferably, it is 2.40% or less.

Nb: 0.40 to 1.00%
Nb is an element that fixes C and N in the weld bead portion and prevents sensitization by Cr carbonitride when welding with SUS304. The effect is acquired by making Nb content 0.40% or more. On the other hand, when the Nb content exceeds 1.00%, Nb carbonitride precipitates excessively, which becomes a starting point of corrosion, thereby reducing the corrosion resistance of the steel itself. Furthermore, sensitization is likely to occur when welding with SUS304. This is because Nb suppresses the formation of the austenite phase in the weld bead portion. Therefore, the Nb content is set to 0.40 to 1.00%. The Nb content is preferably 0.50% or more, and more preferably 0.60% or more. Further, the Nb content is preferably 0.80% or less, and more preferably 0.75% or less.

N: 0.020% or less N is an element inevitably mixed in steel. However, when the N content exceeds 0.020%, the corrosion resistance and workability are remarkably lowered, and when welding with SUS304 is performed, the weld bead is sensitized. Therefore, the N content is 0.020% or less. Preferably, the N content is 0.016% or less. More preferably, the N content is 0.012% or less.

  The balance other than the above components is Fe and inevitable impurities. Typical examples of the inevitable impurities mentioned here include Zn, Ga, Ge, As, Ag, In, Hf, Ta, Re, Os, Ir, Pt, Au, and Pb. About these elements, 1 type or 2 types or more of these elements can be included in 0.3% or less of total.

  In the present invention, in addition to the basic components described above, Cu: 0.01 to 0.80%, Co: 0.01 to 0.50%, Mo: 0.01 to 1.00%, and W: 0.0. You may contain 1 type, or 2 or more types chosen from 01 to 0.50%. In the present invention, one or two selected from Ti: 0.01 to 0.80%, V: 0.01 to 0.80%, and Zr: 0.01 to 0.80% You may contain the above. In the present invention, 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 metal): one or more selected from 0.001 to 0.10% may be contained. Moreover, in this invention, you may contain 1 type or 2 types chosen from Sn: 0.001-0.50% and Sb: 0.001-0.50%.

Cu: 0.01 to 0.80%
Cu is an element that reinforces the passive film and improves the corrosion resistance. On the other hand, if Cu is excessively contained, ε-Cu is likely to be precipitated, and the corrosion resistance is lowered. Therefore, when it contains Cu, it is preferable to make Cu content into 0.01 to 0.80%. The Cu content is more preferably 0.30% or more, and further preferably 0.40% or more. Moreover, Cu content becomes like this. More preferably, it is 0.50% or less, More preferably, it is 0.45% or less.

Co: 0.01 to 0.50%
Co is an element that improves the crevice corrosion resistance of stainless steel. On the other hand, if Co is contained excessively, the workability of the welded portion is lowered. Therefore, when Co is contained, the Co content is preferably 0.01 to 0.50%. The Co content is more preferably 0.03% or more, and still more preferably 0.05% or more. Further, the Co content is more preferably 0.30% or less, and still more preferably 0.10% or less.

Mo: 0.01 to 1.00%
Mo has the effect of improving the crevice corrosion resistance of stainless steel. On the other hand, when Mo is contained excessively, when welding with SUS304, the formation of the austenite phase is suppressed at the weld bead portion, and sensitization is likely to occur. Therefore, when Mo is contained, the Mo content is preferably 0.01 to 1.00%. The Mo content is more preferably 0.03% or more, and still more preferably 0.05% or more. Moreover, Mo content becomes like this. More preferably, it is 0.50% or less, More preferably, it is 0.30% or less.

W: 0.01 to 0.50%
W is an element that improves the crevice corrosion resistance of stainless steel. On the other hand, when W is excessively contained, the workability of the welded portion is lowered. Therefore, when it contains W, it is preferable to make W content into 0.01 to 0.50%. The W content is more preferably 0.03% or more, and even more preferably 0.05% or more. Moreover, W content becomes like this. More preferably, it is 0.30% or less, More preferably, it is 0.10% or less.

Ti: 0.01 to 0.80%
Ti, like Nb, is an element that fixes C and N and prevents sensitization. On the other hand, if Ti is excessively contained, an oxide is generated in the weld bead and weldability is lowered. Therefore, when Ti is contained, the Ti content is preferably 0.01 to 0.80%. The Ti content is more preferably 0.02% or more, and further preferably 0.03% or more. Further, the Ti content is more preferably 0.10% or less, and still more preferably 0.05% or less.

V: 0.01 to 0.80%
V, like Nb, is an element that fixes C and N and prevents sensitization. On the other hand, when V is contained excessively, a hot crack in welding occurs, and the toughness of the welded portion decreases. Therefore, when V is contained, the V content is preferably 0.01 to 0.80%. The V content is more preferably 0.02% or more, and further preferably 0.03% or more. Moreover, V content becomes like this. More preferably, it is 0.10% or less, More preferably, it is 0.05% or less.

Zr: 0.01 to 0.80%
Zr, like Nb, is an element that fixes C and N and prevents sensitization. On the other hand, if Zr is excessively contained, an oxide is generated in the weld bead portion and weldability is lowered. Therefore, when Zr is contained, the Zr content is preferably 0.01 to 0.80%. The Zr content is more preferably 0.02% or more, and further preferably 0.03% or more. The Zr content is more preferably 0.10% or less, and still more preferably 0.05% or less.

B: 0.0003 to 0.0030%
B has the effect of improving the strength of the weld. On the other hand, when B is contained excessively, the toughness of the welded portion decreases. Therefore, when it contains B, it is preferable to make B content 0.0003 to 0.0030%. The B content is more preferably 0.0010% or more. Further, the B content is more preferably 0.0025% or less.

Mg: 0.0005 to 0.0100%
Mg forms Mg oxide together with Al in molten steel and acts as a deoxidizer. On the other hand, if Mg is excessively contained, an oxide is generated in the weld bead portion and weldability is lowered. Therefore, when it contains Mg, it is preferable to make Mg content 0.0005 to 0.0100%. The Mg content is more preferably 0.0010% or more. Moreover, Mg content becomes like this. More preferably, it is 0.0050% or less, More preferably, it is 0.0030% or less.

Ca: 0.0003 to 0.0030%
Ca forms an oxide in the molten steel and acts as a deoxidizer. However, if Ca is contained excessively, an oxide is generated in the weld bead portion and weldability is deteriorated. Therefore, when Ca is contained, the Ca content is preferably 0.0003 to 0.0030%. The Ca content is more preferably 0.0005% or more, and further preferably 0.0007% or more. Moreover, Ca content becomes like this. More preferably, it is 0.0025% or less, More preferably, it is 0.0015% or less.

Y: 0.001 to 0.20%
Y is an element that decreases the viscosity reduction of the molten steel and improves the cleanliness. On the other hand, when Y is contained excessively, the workability of the welded portion is lowered. Therefore, when Y is contained, the Y content is preferably 0.001 to 0.20%. The Y content is more preferably 0.10% or less.

REM (Rare Earth Metals): 0.001-0.10%
REM (rare earth metal: elements having atomic numbers 57 to 71 such as La, Ce, and Nd) is an element that decreases the viscosity of molten steel and improves cleanliness. On the other hand, when REM is contained excessively, the workability of the welded portion is lowered. Therefore, when it contains REM, it is preferable to make REM content 0.001-0.10%. The REM content is more preferably 0.005% or more. The REM content is more preferably 0.05% or less.

Sn: 0.001 to 0.50%
Sn is effective for suppressing roughening of the work surface by promoting the generation of deformation bands during rolling. On the other hand, when Sn is contained excessively, the workability of the welded portion is lowered. Therefore, when it contains Sn, it is preferable to make Sn content 0.001 to 0.50%. The Sn content is more preferably 0.003% or more. The Sn content is more preferably 0.20% or less.

Sb: 0.001 to 0.50%
Similar to Sn, Sb is effective in suppressing roughening of the processed skin by promoting deformation band generation during rolling. On the other hand, when Sb is contained excessively, the workability of the welded portion is lowered. Therefore, when it contains Sb, it is preferable to make Sb content into 0.001 to 0.50%. The Sb content is more preferably 0.003% or more. The Sb content is more preferably 0.20% or less.

Next, the suitable manufacturing method of the ferritic stainless steel plate of this invention is demonstrated. Steel having the above component composition is melted by a known method such as a converter, electric furnace, vacuum melting furnace or the like, and further subjected to secondary refining by the VOD method. Thereafter, a steel material (slab) is obtained by a continuous casting method or an ingot-bundling method. The steel material is heated to a temperature of 1200 to 1250 ° C., and then hot-rolled so that the finishing temperature is 700 to 1000 ° C. and the plate thickness is 2.0 to 6.0 mm. The hot-rolled sheet thus produced is annealed at a temperature of 1000 to 1100 ° C. and pickled, and then cold-rolled and cold-rolled sheet is annealed at a temperature of 950 to 1050 ° C. After cold-rolled sheet annealing, pickling is performed to remove scale. Skin pass rolling may be performed on the cold-rolled sheet from which the scale has been removed.
The steel sheet of the present invention is effective not only as a cold-rolled sheet product as described above but also as a hot-rolled sheet product.

After the stainless steel having the composition shown in Table 1 was melted in a 100 kg steel ingot, it was heated to 1200 ° C. and hot-rolled to obtain a hot rolled sheet having a thickness of 3.0 mm. Then, no. Except for 54, annealing was performed at 1000 ° C. for 5 minutes in an air atmosphere, and after shot blasting, pickling was performed with a sulfuric acid solution, followed by pickling with a mixed solution of hydrofluoric acid and nitric acid. This annealed pickled plate was cold rolled to a plate thickness of 1.0 mm, annealed at 1000 ° C. for 1 minute in the air atmosphere, and electrolytically pickled in a sodium sulfate solution, then hydrofluoric acid and nitric acid Immerse it in a mixed solution and pickle it. 1 to 53, 55, 56 ferritic stainless steel cold-rolled annealed pickling plates were produced.
Test No. 54 is SUS304 equivalent steel. Test No. 54, SUS304 equivalent steel cold-rolled annealed pickling plate, except that the hot-rolled plate was annealed at 1150 ° C for 5 minutes, and the annealed pickled plate was annealed at 1050 ° C for 1 minute. Produced in the same manner.

(1) Corrosion resistance of steel plate Test No. obtained under the above production conditions. 1 to 53, 55, 56 ferritic stainless steel cold-rolled annealed pickling plates were cut into a length of 80 mm and a width of 60 mm by shearing. After cutting out, it was polished with a 600th emery polishing paper so as to have polishing marks in the length direction, and degreased with acetone. The end portion and the back surface of the obtained steel plate were sealed, placed in a cyclic corrosion tester at an inclination of 60 °, with the width direction being transverse. In the corrosion tester, 7.0 mass% NaCl aqueous solution spray (2 hours, 35 ° C., 98% RH), dry (4 hours, 60 ° C., 30% RH), wet (2 hours, 40 ° C., 95%) RH) was taken as one cycle, and 50 cycles of corrosion tests were conducted. After the test, the test piece was photographed, and the wrinkle area ratio was measured by image analysis for a 50 mm × 50 mm center portion of the test piece. The case where the heel area ratio was 10% or less was “◯” (pass: excellent), the case where it was over 10% and 20% or less was “□” (pass), and the case where it was over 20% was “ It was evaluated as “▲” (failed).

(2) Corrosion resistance of the weld bead part. 1 to 53, 55, 56 ferritic stainless steel cold-rolled annealed pickling plates were cut into 35 mm × 400 mm, and the end surfaces were processed smoothly to obtain welding materials. With respect to the obtained welding material, the test No. TIG welding of an I-shaped groove with a welding material (hereinafter referred to as SUS304 plate) produced from No. 54 was performed to produce a welding material. TIG welding conditions were a welding current of 70 A, a welding voltage of 11 V, and a welding speed of 40 cm / min. Argon was used as the shielding gas, and the torch side was 15 L / min and the back side was 10 L / min.
In producing the welding material, the torch position is shifted from the position just above the butt portion to the SUS304 plate side to increase the penetration rate into the weld bead portion of SUS304, or to the other material side to shift to the weld bead portion of SUS304. The penetration rate is reduced by 10% or more and less than 30% (Condition 1), 30% or more and less than 50% (Condition 2), 50% or more and less than 70% (Condition 3), 70% More than 90% (condition 4) was adjusted to 4 conditions. Since the torch moves in parallel with the butted portion of the I-shaped groove, the amount of shift is the same from the welding start end to the end. In this experiment, the amount was 1.2 to -0.2 mm on the SUS304 plate side.
About the welding material, in order to confirm that the penetration rate by the side of the SUS304 board in the weld bead part became said 4 conditions, it analyzed as follows.
First, of the welded materials, only the bead portion (molten metal portion) of the welded portions (the front side and the rear side of the weld bead portion) in contact with the region where the corrosion resistance evaluation test of the welded portion described later is performed. Each was cut into “bead width × 100 mm”. About two obtained bead parts, the scale was grind | polished and removed, Then, component analysis was performed by the wet analysis, and Ni content was measured. The Ni content of the two bead portions was averaged to obtain “Ni content contained in weld bead portion (C below)”. Then, assuming that the Ni content of the steel to be tested is A, the Ni content of the SUS304 plate is B, the Ni content contained in the weld bead portion is C, and the penetration rate of the welding material of the SUS304 plate is D, “D = The penetration rate (D) of the welding material for the SUS304 plate was obtained from {(CA) / (BA)} × 100 ”. The unit of D is%.

  With respect to the welding materials obtained under the above conditions (four samples each having a different penetration rate with respect to the welding material produced from the ferritic stainless steel cold-rolled and annealed pickling plates of each test No.), the corrosion resistance of the welded portion was determined. evaluated. A test piece was cut into a length of 80 mm and a width of 60 mm so that the weld bead passed through the width center by shearing from the center of the welded material. After cutting out, the surface on the front bead side was polished until the unevenness formed by welding disappeared, and further polished with No. 600 emery polishing paper so that the polishing marks entered in the direction perpendicular to the weld bead, and degreased with acetone. . The end portion and the back surface of the obtained steel plate were sealed, placed in a cyclic corrosion tester at an inclination of 60 °, with the length direction being transverse. In the corrosion tester, 7.0 mass% NaCl aqueous solution spray (2 hours, 35 ° C., 98% RH), dry (4 hours, 60 ° C., 30% RH), wet (2 hours, 40 ° C., 95%) RH) was 1 cycle, and 12 cycles of corrosion tests were conducted. After the test, according to the same image analysis as the above (1) for the area of the weld bead portion 50 mm × 1 mm at the center of each test piece, the weld bead portion having a wrinkle area ratio of 5% or less is “◯” and exceeds 5%. Was rated as “▲”. Furthermore, in any of the above conditions 1 to 4, a case where the wrinkle area ratio of the weld bead portion is 5% or less is comprehensively evaluated as “◯” (pass), and the wrinkle area ratio exceeds 5% under any of the conditions. Was evaluated as a comprehensive evaluation “▲” (failed).

  The obtained results are shown in Table 1.

The steel of the present invention (Test Nos. 1 to 45, 55, 56) has a corrosion resistance evaluation of “◯” or “□”, and the corrosion resistance of the weld bead by welding with SUS304 (“SUS304” in the table) The overall evaluation of (corrosion resistance of the welded part) was “◯”, and it was found that the corrosion resistance and the welded part corrosion resistance with SUS304 were excellent.
In particular, the steel according to the present invention having a Cr content of 21.0% or more and a Ni content of 1.80% or more was evaluated as “◯”.
Test No. Since the content of Cr was lower than the component range of this invention, 46 comparative examples were inferior in corrosion resistance.
Test No. In Comparative Example 47, since the Cr content was higher than the component range of the present invention, the welded portion corrosion resistance with SUS304 was inferior.
Test No. In Comparative Example 48, since the Ni content was lower than the component range of the present invention, the welded portion corrosion resistance with SUS304 was inferior.
Test No. The 49 comparative examples were inferior in corrosion resistance because the Ni content was higher than the component range of the present invention.
Test No. Since the Nb content was lower than the component range of the present invention, the comparative example of 50 had poor weld corrosion resistance with SUS304.
Test No. In Comparative Example 51, the Nb content was higher than the component range of the present invention, so the corrosion resistance was inferior and the welded part corrosion resistance with SUS304 was inferior.
Test No. In Comparative Examples 52 and 53, the contents of C and N were higher than the component range of the present invention, respectively, so that the corrosion resistance was inferior and the welded part corrosion resistance with SUS304 was inferior.

  According to the present invention, since it has excellent corrosion resistance and excellent corrosion resistance at the welded portion with SUS304, it is a part for household appliances, industrial machine parts, building interior / exterior materials, elevator parts, water tank parts, automotive parts, Suitable for kitchen equipment and the like.

Claims (5)

% By mass
C: 0.020% or less,
Si: 0.05-1.00%,
Mn: 0.05 to 1.00%,
P: 0.040% or less,
S: 0.030% or less,
Al: 0.001 to 0.150%,
Cr: 20.0-23.0%,
Ni: 1.60 to 3.00%
A ferritic stainless steel sheet containing Nb: 0.40 to 1.00% and N: 0.020% or less, with the balance being composed of Fe and inevitable impurities. Furthermore, in mass%,
Cu: 0.01 to 0.80%,
Co: 0.01 to 0.50%
Mo: 0.01-1.00%, and W: 0.01-0.50%
The ferritic stainless steel sheet according to claim 1, comprising one or more selected from among the above. Furthermore, in mass%,
Ti: 0.01-0.80%
V: 0.01 to 0.80%, and Zr: 0.01 to 0.80%
The ferritic stainless steel sheet according to claim 1 or 2, comprising one or more selected from among the above. Furthermore, in mass%,
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 metal): 0.001 to 0.10%
The ferritic stainless steel sheet according to any one of claims 1 to 3, comprising one or more selected from among the above. Furthermore, in mass%,
Sn: 0.001 to 0.50%, and Sb: 0.001 to 0.50%
The ferritic stainless steel sheet according to any one of claims 1 to 4, comprising one or two selected from among them.