Acid-resistant steel plate and method for manufacturing same

Abstract

An acid-resistant steel plate, according to one embodiment of the present invention, comprises, by weight %, 0.10% or less (excluding 0%) of C, 0.20% to 0.35% of Cu, 0.23% to 0.40% of Ni, 0.05% to 0.15% of Sb, and 0.07% to 0.22% of Sn, with the remainder being iron (Fe) and other unavoidable impurities.

Description

Acid-resistant steel plate and its manufacturing method

[0001] This relates to acid-resistant steel plates and their manufacturing methods. Specifically, it relates to steel plates with excellent corrosion resistance and surface properties against corrosion caused by various acids, and a manufacturing method thereof.

[0002] Fossil fuels contain various impurity elements such as S and Cl. Since these fossil fuels are burned, there is always a problem of deterioration due to corrosion of the pipes and equipment that are the passages through which the combustion gases pass. This corrosion phenomenon is called condensate corrosion, and typical applications where pipes and equipment are exposed to this corrosive environment include flue gas pipes and environmental equipment of thermal power plants, and automobile exhaust systems. A type of condensate corrosion is SO2, which is formed when sulfur contained in the flue gas is burned. x In particular, there is corrosion by sulfuric acid condensate, which is formed when SO3 meets moisture in the flue gas and forms sulfuric acid; corrosion by hydrochloric acid condensate, which is formed when chlorine contained in the flue gas or industrial water reacts to produce hydrochloric acid through various reactions; and corrosion by sulfuric acid / hydrochloric acid complex condensate, which occurs when sulfuric acid and hydrochloric acid are mixed in a complex manner. The starting temperature of this acid condensation is related to the temperature of the flue gas itself, the content of SOx and Cl in the flue gas, and the content of water vapor.

[0003] Recently, there has been a persistent demand to lower the temperature of flue gas itself in power plants and other applications, either to improve power generation efficiency or to utilize waste heat released externally. Generally, when the flue gas temperature drops to the temperature at which sulfuric acid begins to condense, the sulfuric acid formed in the flue gas liquefies and condenses on the steel surface, causing increased corrosion. Furthermore, if the flue gas temperature drops even lower than the temperature at which hydrochloric acid can condense, combined sulfuric and hydrochloric acids condense, resulting in combined corrosion.

[0004] Provided are acid-resistant steel plates and a method for manufacturing the same. Specifically, the present invention provides steel plates with excellent corrosion resistance and workability against corrosion caused by various acids, and a method for manufacturing the same.

[0005] An acid-resistant steel sheet according to one embodiment of the present invention contains, in wt%, C: 0.10% or less (excluding 0%), Cu: 0.20 to 0.35%, Ni: 0.23 to 0.40%, Sb: 0.05 to 0.15%, Sn: 0.07 to 0.22%, and the remainder includes iron (Fe) and other unavoidable impurities.

[0006] According to one embodiment of the present invention, the acid-resistant steel plate may further include at least one of Mn: 0.5 wt% or less, Al: 0.1 wt% or less, P: 0.01 wt% or less, S: 0.01 wt% or less, and N: 0.01 wt% or less.

[0007] An acid-resistant steel plate according to one embodiment of the present invention may further include at least one of Cr: 0.1 wt% or less, Nb: 0.1 wt% or less, and Mo: 0.1 wt% or less.

[0008] An acid-resistant steel plate according to one embodiment of the present invention includes a concentrated layer positioned from the surface of the steel plate toward the inside of the steel plate, and the maximum Sn content in the concentrated layer may be 5.0 wt% or less, and the maximum Ni content may be 2.0 to 5.0 wt%.

[0009] The sum of the maximum Sn content and the maximum Ni content in the concentrated layer may be 7 wt% or less.

[0010] According to one embodiment of the present invention, when an acid-resistant steel plate is immersed in a 50 wt% sulfuric acid aqueous solution at 70°C for 6 hours, the average corrosion rate is 30 mg / (cm 2 ·hr) may be less.

[0011] According to one embodiment of the present invention, when an acid-resistant steel plate is immersed in an aqueous solution containing 28.5 wt% sulfuric acid and 0.5 wt% hydrochloric acid at 60°C for 6 hours, the average corrosion rate is 2.0 mg / (cm 2 ·hr) may be less.

[0012] According to one embodiment of the present invention, the acid-resistant steel plate may have a crack length of 5 mm or less on the side.

[0013]

[0014] A method for manufacturing an acid-resistant steel plate according to one embodiment of the present invention comprises the steps of: heating a slab containing, in wt%, C: 0.10% or less (excluding 0%), Cu: 0.20 to 0.35%, Ni: 0.23 to 0.40%, Sb: 0.05 to 0.15%, and Sn: 0.07 to 0.22%, with the remainder being iron (Fe) and other unavoidable impurities; and hot-rolling the slab to manufacture a hot-rolled steel plate.

[0015] In the step of heating the slab, the heating temperature may be 1230℃ or lower.

[0016] The step of manufacturing a hot-rolled steel sheet includes a rough rolling step and a finish rolling step, and the rough rolling finishing temperature may be 960°C or higher, and the finish rolling finishing temperature may be 910°C or higher.

[0017] The step of manufacturing a hot-rolled steel sheet further includes a step of coiling the hot-rolled steel sheet, and the coiling step can be performed at 450 to 750°C.

[0018] After the step of manufacturing the hot-rolled steel sheet, a step of cold rolling the hot-rolled steel sheet may be further included.

[0019] After the step of manufacturing the hot-rolled steel sheet, a step of annealing heat treatment at 750 to 880°C may be further included.

[0020] An acid-resistant steel plate according to one embodiment of the present invention has excellent acid resistance and surface properties.

[0021] An acid-resistant steel plate according to one embodiment of the present invention can obtain excellent acid resistance and surface properties without adding expensive alloy components such as Cr.

[0022] An acid-resistant steel plate according to one embodiment of the present invention has a concentrated layer formed thereon, and thus has excellent corrosion resistance in an acid-based corrosive environment, thereby effectively extending the life of the material.

[0023] The acid-resistant steel plate according to one embodiment of the present invention can be effectively utilized as a raw material for pipes through which exhaust gas passes after combustion of fossil fuels, hot-rolled products for fossil fuel combustion facilities, and cold-rolled products.

[0024] In addition, it is possible to prevent surface and side saw marks that occur during the steel manufacturing process, thereby ensuring safety during the manufacturing process, transportation, and processing.

[0025] Figure 1 is a schematic cross-section of an acid-resistant steel plate according to one embodiment of the present invention.

[0026] Figure 2 is a surface photograph of an acid-resistant steel plate manufactured in Invention Example 1.

[0027] Figure 3 is a surface photograph of the acid-resistant steel plate manufactured in Comparative Example 1.

[0028] Figure 4 is a surface photograph of the acid-resistant steel plate manufactured in Comparative Example 4.

[0029]

[0030] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0032] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0033] In one embodiment of the present invention, the inclusion of additional elements means including the remaining iron (Fe) in an amount equivalent to the additional amount of the additional elements.

[0034] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0035] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0036]

[0037] An acid-resistant steel plate according to one embodiment of the present invention is a steel plate used in an environment where acid corrosion occurs. The material for this purpose must be corrosion-resistant in acid environments to extend its service life, while also suppressing the formation of saw-tooth cracks on the steel surface and sidewalls.

[0038] In one embodiment of the present invention, by adding Cu, Sb, Sn, etc. in combination during the steel composition, corrosion resistance in high-concentration sulfuric acid and sulfuric acid / hydrochloric acid complex condensation environments can be significantly improved simultaneously, thereby dramatically increasing the corrosion resistance of equipment in a condensate corrosion environment. At the same time, by appropriately controlling the steel composition and manufacturing conditions, the formation of sawtooth-shaped cracks (commonly referred to as "saw ears") on the steel surface and side surfaces of the steel material can be significantly reduced, while improving the corrosion resistance.

[0039] An acid-resistant steel sheet according to one embodiment of the present invention contains, in wt%, C: 0.10% or less (excluding 0%), Cu: 0.20 to 0.35%, Ni: 0.23 to 0.40%, Sb: 0.05 to 0.15%, Sn: 0.07 to 0.22%, and the remainder includes iron (Fe) and other unavoidable impurities.

[0040] Below, each component is explained in detail.

[0041]

[0042] Carbon (C): 0.10 wt% or less

[0043] The carbon content of the acid-resistant steel plate according to one embodiment of the present invention is 0.10 wt% or less. If the carbon content in the steel is too high, excessive carbide formation may result in a decrease in corrosion resistance, particularly a decrease in sulfuric acid / hydrochloric acid combined corrosion resistance. More specifically, C may be included in an amount of 0.001 to 0.100 wt%. More specifically, C may be included in an amount of 0.01 to 0.09 wt%.

[0044]

[0045] Copper (Cu): 0.20 to 0.35 wt%

[0046] Copper (Cu) is a representative element that prevents further corrosion by concentrating between the steel surface and corrosion products when exposed to acid immersion. To achieve this effect, an appropriate amount of Cu can be added. However, excessive addition can cause cracking during manufacturing due to the low melting point of Cu. Therefore, the content is limited to 0.35 wt% or less. More specifically, Cu can be included in an amount of 0.25 to 0.33 wt%.

[0047]

[0048] Nickel (Ni): 0.23% to 0.40 wt%

[0049] When only Cu is added to steel without Ni, the low melting point of Cu can cause liquid Cu to penetrate the grain boundaries, causing cracks. Ni is added to raise the melting point and limit the occurrence of cracks. In addition, Ni suppresses the surface enrichment of Sn, Sb, Cu, etc. that are generated during the steel manufacturing process in the form of Ni itself being enriched. This plays an important role in preventing sawtooth defects that occur during the manufacturing process. However, if too much Ni is added, Ni itself can enrich on the surface of the steel, causing surface cracks and defects, so the upper limit is limited to 0.4 wt%. More specifically, Ni can be included in an amount of 0.25 to 0.37%. More specifically, it can be included in an amount of 0.27 to 0.35%.

[0050]

[0051] Antimony (Sb): 0.05 to 0.15 wt%

[0052] Sb, like Cu, is added to form a stable concentrated layer on the surface. If the Sb content is too low, a sufficient concentrated layer may not be formed. Conversely, if the Sb content is too high, surface cracks may occur due to surface concentration during the manufacturing process. More specifically, Sb may be included in an amount of 0.07 to 0.13 wt%.

[0053]

[0054] Tin (Sn): 0.07 to 0.22 wt%

[0055] Sn, like Cu and Sb, is added to form a stable concentrated layer on the surface. In particular, Sn is preferentially dissolved in acid immersion environments such as sulfuric acid, significantly improving the corrosion resistance of steel. When a steel plate is immersed in an environment of sulfuric acid or a mixed acid, Sn and Cu dissolve, but Sn dissolves before Cu. As Sn dissolves before Cu, Sn dissociates in the solution. The dissociated Sn lowers the corrosion potential of the solution, thereby partially delaying the corrosion of the steel plate. Here, the corrosion potential refers to the potential with respect to the reference electrode of the metal undergoing corrosion. In addition, a corrosion retardation layer may be formed during the re-fusion process of Sn dissolved on the surface of the steel plate, and this corrosion retardation layer can delay the corrosion of the steel plate. If Sn is included too little, a sufficient corrosion retardation layer may not be formed. If Sn is added too much, serious surface cracking may occur during the production process. More specifically, Sn may be included in an amount of 0.073 to 0.220 wt%.

[0056] According to one embodiment of the present invention, an acid-resistant steel plate may further include at least one of Mn: 0.1 to 0.5 wt%, Al: 0.1 wt% or less, P: 0.01 wt% or less, S: 0.01 wt% or less, and N: 0.01 wt% or less.

[0057]

[0058] Manganese (Mn): 0.5 wt% or less

[0059] Manganese (Mn) is an element that prevents hot shortness caused by solid solution S by combining with solid solution S in steel and precipitating as MnS. To achieve this effect, Mn may be additionally included. However, if Mn exceeds 0.5 wt%, the material may harden and reduce ductility. More specifically, Mn may be included in an amount of 0.10 to 0.50 wt%. More specifically, Mn may be included in an amount of 0.15 to 0.35 wt%.

[0060]

[0061] Aluminum (Al): 0.1 wt% or less

[0062] Al is an element with a very strong deoxidizing effect, and it reacts with nitrogen in steel to precipitate AlN, thereby preventing the deterioration of formability due to dissolved nitrogen, so it can be included in more amounts. However, since ductility deteriorates rapidly when added in large amounts, the content is limited to 0.1 wt% or less. More specifically, 0.01 to 0.05 wt% of Al can be included.

[0063]

[0064] Phosphorus (P): 0.01 wt% or less

[0065] Addition of P below a certain amount does not significantly reduce the ductility of steel and is an element that can increase strength, but if added in excess of 0.01 wt%, it segregates at grain boundaries and hardens the steel, so it can be limited to 0.01 wt% or less. More specifically, P can be further included in an amount of 0.001 to 0.01 wt%.

[0066]

[0067] Sulfur (S): 0.01 wt% or less

[0068] Since S is an element that causes red-hot embrittlement during employment, the addition of Mn should induce the precipitation of MnS. However, excessive precipitation of MnS is undesirable because it hardens the steel. Therefore, the upper limit of S is limited to 0.01 wt%. More specifically, S may be further included in an amount of 0.001 to 0.01 wt%.

[0069]

[0070] Nitrogen (N): 0.01 wt% or less

[0071] Nitrogen is often contained as an unavoidable element in steel, and N that is not precipitated but remains in a solid solution reduces ductility, worsens aging resistance, and reduces workability. Therefore, the upper limit is limited to 0.01 wt%. More specifically, N may be further included in an amount of 0.001 to 0.005 wt%.

[0072]

[0073] In addition to the aforementioned alloy composition, the remainder includes iron and unavoidable impurities. However, in one embodiment of the present invention, the addition of other compositions is not excluded. The unavoidable impurities may be unintentionally mixed from raw materials or the surrounding environment during a typical steel manufacturing process, and thus cannot be excluded. Those skilled in the art of typical steel manufacturing will understand the unavoidable impurities. For example, the alloy may further include one or more of Cr: 0.1 wt% or less, Nb: 0.1 wt% or less, and Mo: 0.1 wt% or less.

[0074]

[0075] Fig. 1 schematically illustrates a cross-section of an acid-resistant steel plate according to one embodiment of the present invention. As shown in Fig. 1, a thickened layer (20) exists inward from the surface of the acid-resistant steel plate (10). In Fig. 1, the thickened layer (20) is shown as being located on one side, but it may also be located on both sides.

[0076] The maximum Sn content in the concentrated layer (20) may be 5.0 wt% or less, and the maximum Ni content may be 2.0 to 5.0 wt%.

[0077] Here, the concentrated layer (20) refers to a surface portion where Cu, Sb, Sn, and Ni are concentrated, and in other respects, it is similar to the point where oxidation generally begins. In one embodiment of the present invention, the concentrated layer (20) is defined as a position where the total amount of Cu, Sb, Ni, and Sn from the surface of the steel plate in the inward direction is up to four times the total amount of Cu, Sb, Ni, and Sn at the center of the steel plate (at 1 / 2 the thickness). At this time, the maximum content refers to the content at the part where the concentration of the corresponding element is highest within the concentrated layer, and in most cases, the outermost surface portion has the highest concentration. It was confirmed that the concentrated layer composed of Ni, Sb, Sn, and Cu exists on the surface of the steel and corrosion products at a total amount of 10 to 20 wt%. Meanwhile, the thickness of the concentrated layer (20) may be 20 μm to 30 μm. In one embodiment of the present invention, the concentration layer (20) and the content of elements within the concentration layer (20) can be measured by measuring the distribution of elements from the surface to the inside of a steel plate specimen using a glow discharge spectrometer (GDS). The formation of an appropriate concentration layer (20) can be achieved by controlling the steel composition as described above and controlling conditions during hot rolling.

[0078] The maximum Sn content in the concentrated layer (20) may be 5.0 wt% or less. As mentioned above, Sn is an element that retards corrosion, but if Sn is included in large amounts in the concentrated layer (20), it may cause sawtooth cracking. Therefore, the maximum Sn content in the concentrated layer (20) may be limited. More specifically, the maximum Sn content in the concentrated layer may be 1.0 to 4.7 wt%.

[0079] The maximum Ni content in the concentrated layer (20) may be 2.0 to 5.0 wt%. When a large amount of Sn is included in the steel, the concentration of Sn cannot be avoided, and in one embodiment of the present invention, Ni is concentrated instead of Sn, thereby reducing the concentration of Sn in the concentrated layer. However, since Ni may also cause sawtooth cracking when concentrated excessively, the maximum Ni content in the concentrated layer (20) is limited as described above. More specifically, the maximum Ni content in the concentrated layer (20) may be 2.0 to 4.8 wt%.

[0080] The sum of the maximum Sn content and the maximum Ni content in the concentrated layer (20) may be 7 wt% or less. As described above, Ni is added to suppress the concentration of Sn, but if Ni is added in excessive amounts, Ni may rather cause sawtooth cracking, so the upper limit of the sum of the maximum Sn content and the maximum Ni content in the concentrated layer (20) may be limited. More specifically, the sum of the maximum Sn content and the maximum Ni content in the concentrated layer (20) may be 3.5 to 6.7 wt%.

[0081] The maximum Sb content within the concentrated layer (20) may be 10 wt% or less. Similar to Sn, if Sb is concentrated in large amounts on the surface, it may cause sawtooth cracking. In one embodiment of the present invention, Ni is concentrated to reduce the Sb concentration within the concentrated layer. More specifically, the maximum Sb content within the concentrated layer (20) may be 3.0 to 8.5 wt%.

[0082] The maximum Cu content within the concentrated layer (20) may be 13 wt% or less. Similar to Sn, if Cu is concentrated in large amounts on the surface, it may cause sawtooth cracking. In one embodiment of the present invention, Ni is concentrated to reduce the Cu concentration within the concentrated layer. More specifically, the maximum Cu content within the concentrated layer (20) may be 3.0 to 8.5 wt%.

[0083] According to one embodiment of the present invention, the acid-resistant steel plate may have a crack length of 5 mm or less on the side surface. As described above, in one embodiment of the present invention, the crack length can be reduced by concentrating Ni instead of Sn, Sb, and Cu.

[0084] A crack means a groove with a depth of 5 mm or more formed from the surface of the steel plate, and the length of the crack means the length in the direction perpendicular to the end of the surface of the steel plate.

[0085] In one embodiment of the present invention, corrosion resistance against sulfuric acid and a composite acid of sulfuric acid and hydrochloric acid is simultaneously excellent.

[0086] Specifically, when an acid-resistant steel plate according to one embodiment of the present invention is immersed in a 50 wt% sulfuric acid aqueous solution at 70°C for 6 hours, the average corrosion rate is 30 mg / (cm 2 ·hr) or less. More specifically, 10 to 28 mg / (cm 2 ·hr) may be.

[0087] According to one embodiment of the present invention, when an acid-resistant steel plate is immersed in an aqueous solution containing 28.5 wt% sulfuric acid and 0.5 wt% hydrochloric acid at 60°C for 6 hours, the average corrosion rate is 2.0 mg / (cm 2 ·hr) or less. More specifically, 0.30 to 2.00 mg / (cm 2 ·hr) may be.

[0088]

[0089] A method for manufacturing an acid-resistant steel plate according to one embodiment of the present invention includes a step of heating a slab; and a step of hot-rolling the slab to manufacture a hot-rolled steel plate.

[0090] Below, each step is explained in detail.

[0091] First, heat the slab.

[0092] The alloy composition of the slab has been described in the previously mentioned acid-resistant steel plate, so a duplicate description will be omitted. Since the alloy composition does not substantially change during the manufacturing process of acid-resistant steel plate, the alloy composition of the acid-resistant steel plate and the alloy composition of the slab are substantially identical.

[0093] The slab heating temperature can be lower than 1230℃. If the slab heating temperature is too high, star cracks originating from the copper element can occur at temperatures similar to the melting point of copper, resulting in sawtooth cracks in the hot-rolled sheet. Furthermore, temperatures higher than 1150℃ may be required to re-dissolve most of the precipitates present in the steel.

[0094] Next, the slab is hot rolled to produce hot-rolled steel sheets.

[0095] The steps for manufacturing hot rolled steel sheets include a rough rolling step and a finish rolling step, and the rough rolling finish temperature may be 960°C or higher, and the finish rolling finish temperature may be 910°C or higher. At the above-mentioned rough rolling finish temperature and finish rolling finish temperature, the enrichment of Ni instead of Sn or Sn may be promoted. More specifically, the rough rolling finish temperature may be 960 to 1050°C, and the finish rolling finish temperature may be 910 to 1000°C.

[0096] The step of manufacturing a hot-rolled steel sheet further includes a step of coiling the hot-rolled steel sheet, and the coiling step can be performed at a temperature of 450 to 750°C. If the coiling temperature is too low, the final cold rolling may become difficult due to an increase in the initial strength of the hot-rolled steel sheet, while if the coiling temperature is too high, buckling and a decrease in strength may occur due to phase transformation in the coiling section.

[0097] The hot rolled sheet thickness can be 2.5 to 5.5 mm.

[0098] Afterwards, a step of pickling the coiled hot-rolled steel sheet may be included.

[0099] After the step of manufacturing the hot-rolled steel sheet, a cold-rolling step may be additionally included. The reduction ratio may range from 54% to 70%. If the reduction ratio is too low, it may be difficult to ensure complete recrystallization during cold rolling, which can lead to a decrease in the material's elongation and the development of cracks during subsequent customer processing. Conversely, if the reduction ratio is too high, the rolling process may not proceed due to excessive motor load.

[0100] Additionally, an annealing step may be added after the step of manufacturing the hot-rolled steel sheet. The annealing temperature may be between 750 and 880°C. If the annealing temperature is too low, complete recrystallization may be difficult to achieve, leading to a decrease in the material's elongation and the potential for cracking during subsequent customer processing. Conversely, if the annealing temperature is too high, it may be difficult to secure the steel sheet's strength.

[0101] Even if cold rolling and annealing heat treatment are performed, the concentrated layer (20) that existed in the hot-rolled steel sheet remains the same.

[0102]

[0103] The present invention will be described in more detail below through examples. However, these examples are intended only to illustrate the present invention and are not intended to limit the present invention.

[0104]

[0105] Example 1

[0106] First, a steel slab containing the alloy components summarized in Table 1 below was manufactured. The slab was heated at 1200°C (SRT) for 200 minutes and then hot-rolled to a thickness of 3.5 mm to manufacture a hot-rolled sheet. The rough rolling temperature (RDT) was 1000°C, the finish rolling temperature (FDT) was 950°C, and coiling was performed at 650°C.

[0107] The element distribution from the surface to the interior of the hot-rolled specimen was measured using GDS and summarized in Table 2.

[0108] After manufacturing the steel plate, an immersion test was performed using the method described in the ASTM G31 standard. The immersion test was performed by preparing a 50 wt% sulfuric acid aqueous solution and immersing the steel plate at 70°C for 6 hours. After immersion, the weight loss after cleaning was measured using the ASTM G1 specimen surface cleaning method, thereby determining the weight loss per unit time and per unit surface area.

[0109] In addition, to simulate the combined sulfuric acid / hydrochloric acid condensation that occurs during low-temperature condensation in Korean thermal power plants, a mixed aqueous solution containing 28.5 wt% sulfuric acid and 0.5 wt% hydrochloric acid was prepared, and a test was conducted in which the mixture was immersed at 60°C for 6 hours. After immersion, the weight loss after washing was measured using the specimen surface washing method of ASTM G1 in the same manner as above, and the weight loss per unit time and per unit surface area was measured.

[0110] Edge cracks were measured using a magnifying glass to determine the longest length of cracks that occurred from the edge toward the inside of the steel plate.

[0111] The results are shown in Table 3 below.

[0112] (Wt%)CCuNiSbSnInvention Example 10.070.300.300.100.15Invention Example 20.070.300.230.100.15Invention Example 30.070.300.250.100.15Invention Example 40.070.300.350.100.15Invention Example 50.070.300.400.100.15Invention Example 60.070.300.300.100.07Invention Example 70.070.300.300.100.22Invention Example 80.070.200.300.100.10Invention Example 90.070.350.300.100.10Invention Example 100.100.300.300.100.15 Invention example 110.070.300.300.050.15 Invention example 120.070.300.300.150.15 Comparative example 10.070.300.200.100.15 Comparative example 20.070.300.500.100.15 Comparative example 30.070.300.300.100.05 Comparative example 40.070.300.300.100.30 Comparative example 50.070.150.300.100.15 Comparative example 60.070.400.300.100.15 Comparative example 70.150.300.300.100.15Comparative example 80.070.300.300.020.15Comparative example 90.070.300.300.180.15

[0113] (Wt%) SnNiSbCuNi+SnTotalInvention Example 12.53.55.56.56.018.0Invention Example 24.52.15.46.56.618.5Invention Example 32.52.35.46.54.816.7Invention Example 42.53.85.46.56.318.2Invention Example 51.54.85.34.06.315.6Invention Example 61.32.53.55.53.812.8Invention Example 73.93.04.35.56.916.7Invention Example 82.52.54.54.05.013.5Invention Example 91.53.54.38.55.017.8Invention Example 102.53.55.54.56.016.0Invention example 112.52.53.54.55.013.0Invention example 121.53.08.05.04.517.5Comparative example 16.51.04.58.07.520.0Comparative example 21.05.54.55.56.516.5Comparative example 30.85.04.34.55.814.6Comparative example 48.01.03.54.59.017.0Comparative example 52.52.05.52.04.512.0Comparative example 61.51.53.515.03.021.5Comparative example 72.53.54.52.56.013.0Comparative example 81.52.52.53.54.010.0Comparative example 91.53.510.25.55.020.7

[0114] Corrosion loss ratio (mg / cm) 2 / hr.)Edge crack occurrence length (mm)Sulfuric acid onlyComplexInvention example 118.50.450.0Invention example 218.00.522.0Invention example 318.10.632.0Invention example 422.01.201.0Invention example 523.51.503.5Invention example 622.52.000.0Invention example 717.50.803.0Invention example 826.51.200.0Invention example 917.80.754.5Invention example 1028.01.890.0Invention example 1122.51.950.0Invention example 1217.50.383.5Comparative example 119.00.557.5Comparative example 235.01.855.5Comparative Example 322.03.201.0Comparative Example 421.00.359.5Comparative Example 535.02.100.0Comparative Example 618.50.657.5Comparative Example 736.52.300.0Comparative Example 832.05.500.0Comparative Example 918.50.536.5

[0115] As shown in Tables 1 to 3, it can be confirmed that the steel composition containing Cu, Ni, Sn, and Sb in appropriate amounts has excellent corrosion resistance and suppresses the occurrence of sawtooth burrs.

[0116] On the other hand, it can be confirmed that Comparative Examples 3, 5, and 8, which contain less Sn, Sb, and Cu, have inferior corrosion resistance.

[0117] In addition, in the case of Comparative Examples 4, 6, and 9, which contained excessive amounts of Sn, Sb, and Cu, it was confirmed that these were excessively concentrated on the surface, resulting in the occurrence of a large amount of sawtooth.

[0118] Meanwhile, it can be confirmed that Comparative Example 7, to which a large amount of C was added, has poor corrosion resistance due to excessive carbide formation.

[0119] In the case of Comparative Example 1, which contains too little Ni, Sn was concentrated in large quantities, and sawdust was generated in large quantities. In the case of Comparative Example 2, which contains too much Ni, Ni was concentrated in large quantities, and sawdust was generated in large quantities.

[0120] Figures 2 to 4 show photographs of the steel plate surfaces in Inventive Example 1, Comparative Example 1, and Comparative Example 4, respectively. In the case of Comparative Example 1 and Comparative Example 4, it can be confirmed that a large number of cracks occur compared to Inventive Example 1.

[0121]

[0122] Example 2

[0123] The same procedure as in Invention Example 1 of Example 1 was followed, but the hot rolling conditions were changed as shown in Table 4 below.

[0124] The corrosion reduction ratio and edge crack length were measured in the same manner as in Example 1 and summarized in Table 4. The maximum content of each element in the surface concentrated layer is summarized in Table 5 below.

[0125] Hot rolling conditions (℃) Corrosion loss ratio (mg / cm2 / hr.) Edge crack (mm) SRTRDTFDT Sulfuric acid only Composite invention example 11200100095018.50.450.0 Comparative example 101250100095017.50.557.5 Comparative example 11120095095018.50.555.5 Comparative example 121200100090019.50.48.5

[0126] (Wt%)SnNiSbCuNi+SnTotalInvention Example 12.53.55.56.5621.5Comparative Example 102.53.54.518.5632.5Comparative Example 116.53.55.54.51023.5Comparative Example 128.52.56.55.51125.5

[0127] Comparative Example 10 shows that the slab heating temperature is too high, resulting in excessive Cu enrichment and a large amount of sawdust. Comparative Examples 11 and 12 show that the rough rolling finishing temperature and the finishing rolling temperature are low, respectively, resulting in excessive Sn enrichment and a large amount of sawdust.

[0128]

[0129] The present invention is not limited to the embodiments described herein, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

[0130] [Explanation of symbols]

[0131] 10: Acid-resistant steel plate,

[0132] 20: Concentrated layer

Claims

An acid-resistant steel sheet comprising, in weight%, C: 0.10% or less (excluding 0%), Cu: 0.20 to 0.35%, Ni: 0.23 to 0.40%, Sb: 0.05 to 0.15%, and Sn: 0.07 to 0.22%, with the remainder being iron (Fe) and other unavoidable impurities. In the first paragraph, Acid-resistant steel sheet further comprising at least one of Mn: 0.5 wt% or less, Al: 0.1 wt% or less, P: 0.01 wt% or less, S: 0.01 wt% or less, and N: 0.01 wt% or less. In the first paragraph, Acid-resistant steel sheet further comprising at least one of Cr: 0.1 wt% or less, Nb: 0.1 wt% or less, and Mo: 0.1 wt% or less. In the first paragraph, Contains a concentrated layer positioned from the surface of the steel plate toward the inside of the steel plate, An acid-resistant steel plate having a maximum Sn content of 5.0 wt% or less and a maximum Ni content of 2.0 to 5.0 wt% in the above-mentioned concentrated layer. In paragraph 4, An acid-resistant steel plate having a sum of the maximum Sn content and the maximum Ni content in the above-mentioned concentrated layer of 7 wt% or less. In the first paragraph, When immersed in a 50 wt% sulfuric acid aqueous solution at 70°C for 6 hours, the average corrosion rate was 30 mg / (cm 2 · Acid-resistant steel plate with a temperature of less than hr. In the first paragraph, When immersed in an aqueous solution containing 28.5 wt% sulfuric acid and 0.5 wt% hydrochloric acid at 60°C for 6 hours, the average corrosion rate was 2.0 mg / (cm 2 · Acid-resistant steel plate with a temperature of less than hr. In the first paragraph, Acid-resistant steel plate with a crack length of 5 mm or less on the side. A step of heating a slab containing, in wt%, C: 0.10% or less (excluding 0%), Cu: 0.20 to 0.35%, Ni: 0.23 to 0.40%, Sb: 0.05 to 0.15%, and Sn: 0.07 to 0.22%, with the remainder being iron (Fe) and other unavoidable impurities; and A method for manufacturing an acid-resistant steel plate, comprising: a step of hot-rolling the above slab to manufacture a hot-rolled steel plate. In Article 9, A method for manufacturing an acid-resistant steel plate, wherein the slab is heated to 1230°C or lower in the step of heating the slab. In Article 9, The step of manufacturing the above hot rolled steel sheet includes a rough rolling step and a sand rolling step, A method for manufacturing an acid-resistant steel sheet, wherein the above rough rolling finishing temperature is 960°C or higher, and the above sintering finishing temperature is 910°C or higher. In Article 9, The steps for manufacturing the above hot rolled steel plate are Further comprising a step of coiling the hot rolled steel plate, The above-mentioned coiling step is a method for manufacturing an acid-resistant steel plate by coiling at 450 to 750°C. In Article 9, After the step of manufacturing the above hot rolled steel plate, A method for manufacturing an acid-resistant steel sheet further comprising the step of cold rolling the hot-rolled steel sheet. In Article 9, After the step of manufacturing the above hot rolled steel plate, A method for manufacturing an acid-resistant steel sheet, further comprising a step of annealing at 750 to 880°C.

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