JP4673343B2 - Stainless steel sheet excellent in corrosion resistance, weldability and surface properties and method for producing the same - Google Patents

Description

The present invention corrosion-resistant, stainless steel plate having excellent weldability and surface properties and a manufacturing method thereof.

  Fe-Ni-Cr stainless steel is widely used as a highly corrosion-resistant alloy in kitchen equipment, chemical plants, and the like. However, it is known that the nonmetallic inclusions present on the surface of the stainless steel serve as a starting point for corrosion such as rust, and the speed of the corrosion varies depending on the composition and amount of the nonmetallic inclusions. In addition, nonmetallic inclusions may cause surface defects depending on the composition, particularly when the composition is alumina.

To deal with this problem, for example, in Patent Document 1, after a small amount of Al or Si is added to molten steel and preliminary deoxidation is performed, the form of inclusions is controlled by adding Ti and performing deoxidation. In addition, a technique is disclosed in which an appropriate amount of Ca is added to control inclusions that do not cause surface flaws and do not adversely affect corrosion resistance (see Patent Document 1). However, this prior art method has a problem that the added Ti bonds with N to form hard TiN, and surface flaws called stringers are likely to occur. In addition, the addition of Al and Ca has a problem of adversely affecting weldability.
JP 2000-1759 A

  As described above, depending on the amount and composition of the nonmetallic inclusions contained in the steel, sufficient corrosion resistance and weldability may not be obtained. In addition, when the inclusion composition is alumina, surface defects due to the clusters are generated. Furthermore, when trying to avoid these problems by adding Ti, there is a problem that stringers are easily generated.

An object of the present invention, corrosion resistance, while providing excellent stainless steel plate weldability and surface quality, is to propose a method of inexpensively manufactured using a general-purpose production equipment the stainless steel plate.

Inventors for solving the problems of the above prior art, the amount and composition of non-metallic inclusions especially contained in a stainless steel plate, the corrosion resistance of stainless steel plate, the effect on weldability and surface quality, The following examination was conducted.

First, an Fe-18 mass% Cr-8 mass% Ni alloy is melted in a laboratory using a magnesia crucible or an alumina crucible, and CaO—SiO ₂ —Al ₂ O ₃ —MgO—F slag is dissolved in the molten steel. After the addition, any one or more of Si, Mn, Al, Ca and Mg was added and deoxidized, and then cast to obtain steel ingots having various inclusion compositions. . This ingot was forged and hot-rolled, and then cold-rolled to obtain a steel plate having a thickness of 3 mm. Test pieces were collected from this steel sheet and investigated for corrosion resistance and weldability.

  For the corrosion resistance, the above test piece was polished and finished with # 600, then degreased, and subjected to a salt spray test (SST) for 4 hours under conditions (50 ° C.) in accordance with JIS Z2371, to check for rusting.

  Further, the weldability was evaluated by performing TIG welding on the test piece under the conditions of a current value of 120 A and a welding speed of 200 mm / min, and the presence or absence of black spots generated on the beads. This black spot is an oxide defect generated on the bead, and when this defect exists, the corrosion resistance of the part is deteriorated or an appearance defect is caused. Simultaneously with this test, the presence or absence of surface flaws was also examined visually.

Results of the test, the inventors have found that when non-metallic inclusions, a _{C aO-SiO 2 -Al 2 O} 3 -MgO-MnO based oxide (silicate) or Ranaru composition, corrosion resistance, weldability It was also found that stainless steel with excellent surface properties can be obtained.

  In addition, it was found that when the Ca content exceeds 0.01 mass%, the composition of inclusions becomes CaO alone, and the corrosion resistance deteriorates, and at the same time, black spots are generated during welding. The cause is considered to be that CaO is water-soluble and unstable in terms of corrosion resistance, and that in terms of weldability, CaO-based inclusions float and concentrate in the molten pool. Furthermore, the Ca concentration in the steel is also related to the O concentration, and it was also found that when the O becomes lower than 0.0001 mass%, the Ca exceeds 0.01 mass%.

Also, if the Al concentration in the steel exceeds 0.1 mass%, the composition of inclusions becomes Al ₂ O ₃ (alumina), forming clusters, generating surface defects, and generating black spots during welding. I understood.

  Furthermore, it was found that when the O concentration is higher than 0.01 mass%, the cleanliness specified in JIS G0555 exceeds 0.05, so that the amount of inclusions on the steel sheet surface increases and the corrosion resistance deteriorates. . It has also been found that if S is lowered to less than 0.0002 mass%, the penetration property during welding is deteriorated.

This invention was developed based on the said knowledge, Comprising: C <= 0.1mass%, Si: 0.01-2.0mass%, Mn: 0.01-3.0mass%, Cr: 13. 0 to 26.0 mass%, Ni: 2.0 to 30.0 mass%, Mo: 0.01 to 5.0 mass%, Co ≦ 3 mass%, Al: 0.001 to 0.1 mass%, S: 0.0002 -0.02 mass%, Mg: 0.00005-0.01 mass%, Ca: 0.00005-0.01 mass%, O: 0.0050-0.01 mass%, N: 0.01-0.3 mass%, in a stainless steel plate the balance of Fe and unavoidable impurities, non-metallic inclusions contained in the stainless steel plate in the, CaO: 1~40mass% or _less, SiO 2: _{10~70mass%, l 2 O 3: 5~40mass%,} MgO: 0.1~25mass%, MnO: consists 0.1~2.5mass%, CaO-SiO _{2 to Cr} 2 _{O 3} and FeO is contained less 20 mass% in total corrosion, characterized in that it consists -Al ₂ O ₃ -MgO-MnO based oxide, a stainless steel plate having excellent weldability and surface properties.

In a stainless steel plate of the present invention, before Symbol _{CaO-SiO 2 -Al 2 O 3} -MgO-MnO based oxide is preferably present as a glassy in slab or ingot in after casting.

Further, non-metallic inclusions in the steel in a stainless steel plate of the present invention is in the form of a B system and C system defined in JIS G0555, and, at a defined cleanliness in JIS G0555 is 0.05 or less Preferably there is.

Further, the present invention is that when manufacturing the stainless steel plate, and dissolved by charging raw materials into an electric furnace, and decarburization by吹精the Ar or nitrogen and oxygen in the AOD and / or VOD, then, limestone and fluorite was _{charged, CaO: 30~80mass%, SiO 2} ≦ 20mass%, Al 2 O 3: 5~40mass%, MgO: CaO-SiO having a composition of 1～30Mass% and F ≦ 20 mass% _2- Al ₂ O ₃ —MgO—F-based slag is formed, and after addition of Al or Al and ferrosilicon to perform chromium reduction, deoxidation and desulfurization, slabs are formed by a continuous casting method or a normal ingot-making method. corrosion resistance characterized by, proposes a method for producing a stainless steel plate having excellent weldability and surface properties.

  The ordinary ingot forming method of the present invention is preferably a method in which a steel ingot obtained by casting is hot forged into a slab.

According to the present invention, has excellent corrosion resistance, the stainless steel plate having excellent characteristics in weldability and surface properties, it can be produced inexpensively by using a general-purpose production equipment, extremely effective industrially The effect can be expected.

First, the reason why each component composition of the stainless steel according to the present invention is limited to the above range will be described.
C ≦ 0.1 mass%
C is an austenite stabilizing element, but if present in a large amount, it combines with Cr and Mo to form carbides, lowers the amount of solid solution Cr and Mo contained in the base material, and degrades corrosion resistance. Therefore, the C content is set to 0.1 mass% or less. In addition, Preferably it is 0.08 mass% or less, More preferably, it is 0.07 mass% or less.

Si: 0.01-2.0 mass%
Si is an element effective for improving acid resistance and pitting corrosion resistance, and also effective for deoxidation. However, when the Si content is less than 0.01 mass%, the effect is not sufficiently obtained. On the other hand, when the Si content exceeds 2.0 mass%, generation of a sigma phase composed of Fe, Cr, (Mo) is not achieved. Promotes and causes embrittlement, and reduces weldability. Therefore, the Si content is defined as 0.01 to 2.0 mass%. In addition, Preferably it is 0.02-1.8 mass%, More preferably, it is 0.03-1.7 mass%.

Mn: 0.01 to 3.0 mass%
Mn is an element effective for deoxidation. If the Mn content is less than 0.01 mass%, the effect is not sufficiently obtained. Conversely, if the Mn content exceeds 3.0 mass%, the formation of a sigma phase is promoted similarly to Si, leading to embrittlement. Therefore, the Mn content is defined as 0.01 to 3.0 mass%. In addition, Preferably it is 0.02-2.5 mass%, More preferably, it is 0.03-2.0 mass%.

Cr: 13.0-26.0 mass%
Cr is an element that forms a passive film, which is indispensable to ensure corrosion resistance, on the surface of a steel sheet, and is a base material for improving acid resistance, pitting corrosion resistance, crevice corrosion resistance, and stress corrosion cracking resistance Is the most important element. However, if the Cr content is less than 13.0 mass%, sufficient corrosion resistance cannot be obtained. Conversely, if the content exceeds 25 mass%, a sigma phase is generated and embrittlement occurs. For the above reasons, the Cr content is defined as 13.0 to 26.0 mass%. In addition, Preferably it is 15.0-25.5 mass%, More preferably, it is 16.0-25.0 mass%.

Ni: 2.0-30.0 mass%
Ni has an effect of improving pitting corrosion resistance, crevice corrosion resistance and stress corrosion cracking resistance in a solution environment containing chloride. In order to acquire the effect, 2.0 mass% or more is required. However, the effect of adding 30.0% by mass or less is sufficient, and beyond that, the cost is increased, which is not preferable. Therefore, the Ni content is defined as 2.0 to 30.0 mass%. In addition, Preferably it is 3.0-25.0 mass%, More preferably, it is 4.0-23.0 mass%.

S: 0.0002 to 0.02 mass%
S is an effective element that improves the penetration at the time of welding. However, when there is too much content, it will couple | bond with Mn and will produce | generate MnS and will reduce corrosion resistance and hot workability. Therefore, the S content is set in the range of 0.0002 to 0.02 mass%. In addition, Preferably it is 0.0005-0.015 mass%, More preferably, it is 0.001-0.01 mass%.

Al: 0.001 to 0.1 mass%
Al is an indispensable element for deoxidation. If the Al content is less than 0.001 mass%, the oxygen concentration will increase (O> 0.01 mass%), the cleanliness specified in JIS G0555 will be higher than 0.05, and corrosion resistance, especially pitting corrosion resistance will be increased. Reduce. However, if the content exceeds 0.1 mass%, not only black spots are generated and weldability is deteriorated, but also the composition of inclusions becomes alumina, and surface defects due to clusters are generated. Therefore, the content of Al is defined as 0.001 to 0.1 mass%. In addition, Preferably it is 0.003-0.08 mass%, More preferably, it is 0.005-0.05 mass%.

Mg: 0.00005 to 0.01 mass%
Mg controls the composition of non-metallic inclusions in steel to a component system that does not adversely affect corrosion resistance, that is, MgO.Al ₂ O ₃ , MgO or CaO—SiO ₂ —Al ₂ O ₃ —MgO—MnO oxide It is a useful element to do. The effect cannot be obtained if the content is less than 0.00005 mass%. Conversely, if the content exceeds 0.01 mass%, nozzle clogging of a continuous casting machine is caused and operation is hindered. Furthermore, there is also a problem of causing bubble defects due to Mg in the steel. Therefore, Mg content was prescribed | regulated as 0.00005-0.01 mass%. Preferably it is 0.0001-0.005 mass%, More preferably, it is 0.0001-0.002 mass%. More preferably, it is 0.0002 to 0.002 mass%.

Ca: 0.00005 to 0.01 mass%
Ca, like Mg, is a component system that does not adversely affect the corrosion resistance of the composition of nonmetallic inclusions in steel, that is, CaO—Al ₂ O ₃ oxide or CaO—SiO ₂ —Al ₂ O ₃ —MgO—. It is an element necessary for controlling the MnO-based oxide. The effect cannot be obtained when the content is less than 0.00005 mass%. Conversely, when the content exceeds 0.01 mass%, inclusions composed of simple CaO are generated, and the corrosion resistance and weldability are deteriorated. Therefore, the Ca content is specified to be in the range of 0.00005 to 0.01 mass%. Preferably it is 0.0001-0.005 mass%, More preferably, it is 0.0001-0.002 mass%. More preferably, it is 0.0002 to 0.002 mass%.

O: 0.0050 to 0.01 mass%
If O is present in the steel in an amount exceeding 0.01 mass%, the amount of non-metallic inclusions is remarkably increased, the cleanliness specified in JIS G0555 exceeds 0.05, and the pitting corrosion resistance is reduced. On the contrary, when the content is less than 0.0001 mass%, CaO present in the slag is reduced and the Ca concentration in the molten steel exceeds 0.01 mass%, so that CaO inclusions are formed, resulting in corrosion resistance and weldability. Adversely affect. For this reason, the O concentration must be controlled to an appropriate value, and in the present invention, it is defined within the range of 0.0050 to 0.01 mass%. Preferably it is 0.0050-0.008 mass%.

  In the present invention, in addition to the above essential components, Mo and / or N may be added for the purpose of improving the corrosion resistance of the steel sheet. In this case, the respective addition amounts are preferably within the following ranges.

Mo: 0.01-5.0 mass%
Since Mo is an important element for ensuring corrosion resistance such as acid resistance, stress corrosion cracking resistance, crevice corrosion resistance and pitting corrosion resistance, it is preferably contained in the steel in an amount of 0.01 mass% or more. However, if the Mo content is too high, the generation of the sigma phase is promoted and the base material becomes brittle. Therefore, the Mo content is defined as 0.01 to 5.0 mass%. Preferably it is 0.01-4.8 mass%, More preferably, it is 0.02-4.5 mass%.

N: 0.01-0.3 mass%
N is a component effective for improving corrosion resistance, and the effect is obtained when it is contained in an amount of 0.01 mass% or more. However, if the content exceeds 0.3 mass%, the refining time becomes remarkably long because it approaches the melting limit of N in molten steel, resulting in an increase in cost. Therefore, the N content is defined as 0.01 to 0.3 mass%. In addition, Preferably it is 0.01-0.25 mass%, More preferably, it is 0.02-0.20 mass%.

  In the present invention, P and / or Ti can be contained. However, these contents are preferably as low as possible, and can be added within the following range.

P ≤ 0.05 mass%
P is a harmful element that reduces corrosion resistance and hot workability. For this reason, the P content is preferably as low as possible, and is preferably 0.05 mass% or less. In addition, More preferably, it is 0.04 mass% or less, More preferably, it is 0.035 mass% or less.

  Furthermore, in the present invention, one or more of B, Ce and La may be added within a range of 0.01 mass% or less for the purpose of improving hot workability.

In the present invention, in order to prevent the nonmetallic inclusions from adversely affecting the corrosion resistance, weldability, and surface properties, the nonmetallic inclusions are CaO—SiO ₂ —Al ₂ O ₃ —MgO—MnO. It is an essential requirement to be composed of a system oxide. Since this inclusion basically does not form a large cluster like alumina, it does not adversely affect the surface properties of the steel sheet, and this inclusion is insoluble and stable in corrosive aqueous solutions. Therefore, the corrosion resistance is not deteriorated because a local battery is not formed or a corrosive substance is not generated from inclusions.

In order for the non-metallic inclusions to have the above characteristics, the properties of the CaO—SiO ₂ —Al ₂ O ₃ —MgO—MnO-based oxide preferably satisfy the following conditions.
Since the CaO—SiO ₂ —Al ₂ O ₃ —MgO—MnO-based oxide crystallizes and crystallizes CaO alone and deteriorates the corrosion resistance, its properties are preferably glassy. For this purpose, the composition of the CaO—SiO ₂ —Al ₂ O ₃ —MgO—MnO-based oxide is set so that the cooling rate (0.1 to 10,000) of the slab after continuous casting or the steel ingot obtained in the ordinary ingot forming process is obtained. (° C./sec), and a composition that vitrifies is preferable. To satisfy this condition, the composition of the oxides forming the above _{inclusions, CaO: 1~40mass%, SiO 2} : 10~70mass%, Al 2 O 3: 5~40mass%, MgO: 0. 1～25Mass% and MnO: is preferably in the range of 0.1 to 2.5 mass%. Moreover, even if this composite oxide contains about 20 mass% or less of Cr ₂ O ₃ and FeO in total, vitrification is not affected.

  In addition, in order for the steel of the present invention to have characteristics excellent in corrosion resistance, weldability and surface properties, inclusions present in a steel sheet rolled to a thickness of about 10 mm or less are B-series specified in JIS G0555. It is preferable that the cleanliness of the steel sheet is 0.05 or less, as defined in JIS G0555. The reason is shown below.

Inclusion Form When non-metallic inclusions present in a hot-rolled or cold-rolled steel sheet are present as A-based inclusions defined in JIS G0555, such as MnS, the corrosion resistance is adversely affected. Therefore, in this invention, the nonmetallic inclusion in steel is limited to what shows the type of B system or C system prescribed | regulated to JISG0555.

Cleanliness: 0.05 or less When the cleanliness of steel specified in JIS G0555 exceeds 0.05, the starting point of pitting corrosion is remarkably increased and the pitting corrosion resistance is reduced. Therefore, in the stainless steel according to the present invention, the cleanliness is defined as 0.05 or less, preferably 0.045 or less, more preferably 0.04 or less.

Next, a method for manufacturing the stainless steel plate according to the present invention.
Basically, a method for producing a stainless steel plate consisting of components defined as above, the raw material was dissolved was charged into an electric furnace, the AOD and / or VOD, and吹精the Ar or nitrogen and oxygen After decarburizing and refining, limestone and fluorite are added to form slag, and further, Al or Al and ferrosilicon are added to perform chromium reduction, deoxidation and desulfurization, and then by continuous casting method or ordinary ingot casting method. It is a manufacturing method of stainless steel excellent in corrosion resistance, weldability and surface properties, characterized by being a slab. In the present invention, a hot forging method is used as a method for obtaining a slab from an ingot in a normal casting method. Moreover, the said slab is hot-rolled or cold-rolled further, and the stainless steel plate excellent in the corrosion resistance of the desired board thickness, weldability, and surface property can be obtained. This will be specifically described below.

  The melting raw material is not particularly limited, but is preferably selected as appropriate from, for example, ferronickel, pure nickel, ferrochrome, chromium, iron scrap, stainless steel scrap, and Fe—Ni alloy scrap. In particular, Ni sources (ferronickel, stainless steel scrap, Fe—Ni alloy scrap, pure nickel) often contain Co, but Co is almost equivalent to Ni, so in the present invention, it is about 3%. It may be contained as long as it is below. Thus, in the present invention, a relatively inexpensive Ni source can be used, which is advantageous in terms of cost. On the other hand, since it is difficult to remove P during the refining process, it is preferable to select the melting raw material so that it falls within the range defined in the present invention.

After melting the raw material in an electric furnace or the like, decarburization refining is performed by blowing Ar or nitrogen and oxygen in AOD and / or VOD, and C is set to 0.03 mass% or less. Here, the refractory used in the AOD furnace, VOD pan or ladle supplies the appropriate MgO concentration in the slag and controls the inclusions to the above-described composition. From the viewpoint of imparting good melt resistance, it is preferable to select appropriately from MgO—C, Al ₂ O ₃ —MgO—C, dolomite and magnesia chromium brick.

  Thereafter, the oxide of Cr, which is a valuable metal that has shifted to the slag phase, is recovered by chromium reduction by introducing Al or Al and ferrosilicon. In addition, when Al or Al and ferrosilicon are slag formed by adding limestone and meteorite, Al and Si are Al: 0.001 to 0.1 mass%, Si: 0.01 to 1.5 mass, respectively. It is preferable to add so that it may become in the range of%. This is because these deoxidizers (Al or Si) act as a deoxidizer for Cr oxide as described above, and reduce CaO or MgO present in the slag and recover it in molten steel as Ca or Mg. This is because the reduction of Ca and Mg can be facilitated by introducing a deoxidizer onto the slag. In addition, when content of Ca or Mg is less than the range prescribed | regulated to this invention, you may add suitably auxiliary materials, such as Ca-Si, Ca-Al, and Ni-Mg.

The slag composition is preferably a CaO—SiO ₂ —Al ₂ O ₃ —MgO—F system, and the composition range is within the concentration range defined in the present invention for Al, Ca and Mg in molten steel. composition suitable for controlling, for _{example, CaO: 30~80mass%, SiO 2} ≦ 20mass%, Al 2 O 3: 5~40mass%, MgO: is preferably 1～30Mass% and F ≦ 20 mass%. As other components, FeO, S, P and TiO ₂ may be included in a total range of 5% or less. In addition, since the refractory is a magnesia-based material, magnesia brick waste may be appropriately added to the slag in order to protect the refractory.

  Thereafter, deoxidation and desulfurization are performed by blowing Ar or N gas and stirring, so that the O concentration is within the range of 0.0001 to 0.01 mass%, and the S concentration is 0.0002 to 0.02 mass%. Control within range. When the O concentration is reduced to less than 0.0001 mass%, CaO inclusions are generated as described above, which adversely affects corrosion resistance and weldability. Therefore, the O concentration is preferably controlled so that the CaO concentration in the slag does not exceed 80 mass%. According to this method, it is possible to suppress the slag basicity from becoming too high and deoxidation to proceed excessively. The S concentration is basically desulfurized using slag and is reduced to 0.02 mass% or less. However, as described above, when the S concentration is reduced to less than 0.0002 mass%, the penetration property during welding is deteriorated. Therefore, it is preferable to adjust by adding an appropriate amount of an S source such as FeS.

  Thus, the molten steel which controlled the component and the nonmetallic inclusion composition is cast by a continuous casting method or a normal ingot casting method. In the case of continuous casting, it is preferable to cast using a vertical continuous casting machine. This is because this steel type has a relatively high high-temperature strength, and therefore there is a risk of causing slab cracking in a continuous casting machine including a curved portion. Further, the superheat degree of the molten steel at this time is preferably 10 to 60 ° C. in the case of the continuous casting method and 30 to 150 ° C. in the case of the ordinary ingot casting method in consideration of its manufacturability. Further, the inside of the tundish in the continuous casting method and the ingot in the ordinary ingot casting method are preferably sealed with Ar or N gas in order to prevent oxidation of active components in molten steel such as Al, Mg and Ca. In the case of the ordinary ingot-making method, it is preferable that a steel ingot obtained by casting is hot forged into a slab. Moreover, the hot rolling and cold rolling performed in order to obtain a steel plate from a slab can be performed by a conventional method.

After melting ferronickel, pure nickel, ferrochrome, iron scrap, stainless steel scrap, and Fe-Ni alloy scrap as raw materials in an electric furnace with a capacity of 60 tons, oxidative refining is performed with AOD, and then limestone and meteorite are added. , CaO—SiO ₂ —Al ₂ O ₃ —MgO—F-based slag is generated, aluminum and / or ferrosilicon is added, chromium reduction, deoxidation and desulfurization are performed, and then continuous casting or normal An ingot obtained by the ingot-making method was hot forged to obtain a slab. In some cases, refining was performed only with VOD. Thereafter, the slab was hot-rolled and cold-rolled to obtain a steel plate having a thickness of 3 mm.

The cold rolled steel sheet thus obtained was evaluated as follows.
(1) Chemical components: For O and N in the sample cut out from the steel plate, oxygen and nitrogen simultaneous analyzer (inert gas-impulse heating melting method: EMGA-520 manufactured by Horiba, Ltd.), C and S was analyzed using a simultaneous carbon / sulfur analyzer (combustion in oxygen stream-infrared absorption method: EMIA-520 manufactured by Horiba, Ltd.), and other elements were analyzed using a fluorescent X-ray analyzer.

(2) Nonmetallic inclusion composition: A sample cut out from a steel plate was mirror-polished, and inclusions were randomly analyzed 20 points using EDS.

(3) Form of inclusions and cleanliness: A cross section parallel to the rolling direction was observed with an optical microscope at a magnification of 400 and 60 fields of view, and measured according to “JIS G0555”.

(4) Surface properties: The total length of the front and back surfaces of the coil was observed visually, and the number of surface defects was counted.

(5) Corrosion resistance test: The test piece was degreased after # 600 polishing, and a salt spray test (SST) was conducted for 4 hours under conditions (50 ° C.) in accordance with “JIS Z2371” to investigate the presence or absence of rusting.

(6) Weldability: TIG welding was performed under the conditions of an electric current of 120 A and a welding speed of 200 mm / min, and the presence or absence of black spots generated on the beads was visually evaluated.

Table 1 shows the analysis results of the steel plate components, Table 2 shows the measurement results of the composition of non-metallic inclusions, the form of inclusions, and the cleanliness, and Table 3 shows the investigation results of the surface properties, corrosion resistance test, and weldability. According to the results of Tables 1 to 3, Example No. No. 9 satisfied the composition range defined by the present invention, and there were no problems in terms of surface properties, corrosion resistance and weldability. On the other hand, in the comparative example, any one or more of the terms was outside the specified composition range, so that many surface flaws were generated, the required corrosion resistance was not obtained, or black spots were observed during welding. Furthermore, in some cases, manufacturability was remarkably poor and there was a charge (No. 17) in which a product could not be obtained.

Claims (5)

C ≦ 0.1 mass%, Si: 0.01 to 2.0 mass%, Mn: 0.01 to 3.0 mass%, Cr: 13.0 to 26.0 mass%, Ni: 2.0 to 30.0 mass% , Mo: 0.01-5.0 mass%, Co ≦ 3 mass%, Al: 0.001-0.1 mass%, S: 0.0002-0.02 mass%, Mg: 0.00005-0.01 mass%, Ca: 0.00005~0.01mass%, O: 0.0050~0.01mass %, N: 0.01~0.3mass%, in a stainless steel plate the balance of Fe and unavoidable impurities, said stainless steel non-metallic inclusions contained in the plates, CaO: 1~40mass% or _{less, SiO 2: 10~70mass%, Al} 2 O 3: 5~40mass%, MgO: 0.1~2 5 mass%, MnO: 0.1 to 2.5 mass%, and comprising CaO—SiO ₂ —Al ₂ O ₃ —MgO—MnO-based oxide containing ₂₀ mass% or less of Cr ₂ O ₃ and FeO in total. corrosion, wherein, weldability and stainless steel plate having excellent surface properties. The _{CaO-SiO 2 -Al 2 O 3} -MgO-MnO based oxide, stainless steel plate according to claim 1, characterized in that present as glassy in slab or ingot in after casting. Wherein the non-metallic inclusions in the steel in the stainless steel plate is in the form of a B system and C system defined in JIS G0555, and defined cleanliness in JIS G0555 is 0.05 or less stainless steel plate according to claim 1 or 2,. In producing the stainless steel plate according to any one of claims 1 to 3 raw material was dissolved was charged into an electric furnace, and吹精the Ar or nitrogen and oxygen in the AOD and / or VOD decarburized, then, limestone and fluorite was _{charged, CaO: 30~80mass%, SiO 2} ≦ 20mass%, Al 2 O 3: 5~40mass%, MgO: the 1～30Mass% and F ≦ 20 mass% After forming a CaO—SiO ₂ —Al ₂ O ₃ —MgO—F-based slag having a composition and further introducing Al or Al and ferrosilicon to perform chromium reduction, deoxidation and desulfurization, a continuous casting method or ordinary corrosion, characterized in that a slab by ingot making method, the production method of the stainless steel plate having excellent weldability and surface properties. The ordinary Zokatamariho method for manufacturing a stainless steel plate according to claim 4, characterized in that the cast-obtained steel ingot is a method for the hot forging to the slab.