KR20130105156A - Ship-building corrosion-resistant steel having excellent crevice corrosion resistance - Google Patents

Abstract

PURPOSE: A corrosion resistant steel for a ship with excellent crevice corrosion resistance is provided to have excellent crevice corrosion resistance in the paint film defect portion, and to improve the stability and lifespan of a ship. CONSTITUTION: A corrosion resistant steel for a ship with excellent crevice corrosion resistance includes: 0.02 to 0.25 wt% of C, 0.05 to 1.0 wt% of Si, 0.2 to 2.0 wt% of Mn, 0.05 to 2.0 wt% of Al, 0.1 to 0.5 wt% of Cu, 0.05 to 0.5 wt% of Mo, 0.01 to 0.3 wt% of Ti, 0.03 wt% less than of P, 0.03 wt% less than of S, 0.001 to 0.01 wt% of N, and the remains of Fe and the other unavoidable impurities; at least one selected from a group consisting of 0.1 to 2.0 wt% of Cr, 0.05 to 1.0% wt% of Ni, and 0.1 to 0.5 wt% of W; and at least one selected from a group consisting of 0.0005 to 0.005 wt% of Ca and 0.0005 to 0.005 wt% of Mg.

Description

Ship corrosion resistant steel with excellent corrosion resistance {SHIP-BUILDING CORROSION-RESISTANT STEEL HAVING EXCELLENT CREVICE CORROSION RESISTANCE}

The present invention relates to a corrosion resistant steel for ships used in ballast tanks and the like.

The ballast tank of the ship is used to balance the ship. Generally, the cargo is balanced evenly by loading the cargo evenly, but if only some of the cargo is unloaded or unloaded, each ballast tank is filled with seawater to reach the ship's minimum waterline for navigation. Will be corrected. As such, seawater flows into the ballast tank, and the ballast tank is placed in a very corrosive environment because the temperature inside the ballast tank rises to 60 ° C according to external conditions during operation. Therefore, the steel used in the ballast tank ensures corrosion resistance through the anticorrosive process.

In general, as the anticorrosive method, a method of forming an anticorrosive coating film by an epoxy paint and an anticorrosive method by an electric system are used in combination. When the coating film is damaged and the surface of the steel is exposed, some corrosion can be suppressed through the electric method, but since the corrosion rate is very fast, the corrosion of the steel cannot be completely prevented. In addition, after the seawater is removed from the ballast tank, the electric function does not work, so the damaged portion of the coating film is severely corroded by the remaining seawater. Therefore, development of corrosion resistant steels excellent in corrosion resistance of steels itself is desired.

In order to improve corrosion resistance of marine steels used in seawater environments such as ballast tanks, the following techniques have been proposed to date.

Patent document 1 relates to a marine corrosion resistant steel material which exhibits excellent corrosion resistance even under severe corrosive environments without being influenced by the surface state of the steel material, and mainly improves corrosion resistance using tungsten.

However, according to the tests of the present inventors with respect to Patent Document 1, the increase in corrosion resistance due to the addition of tungsten is insignificant, and tungsten is not preferable from an economical point of view because of its high price. In addition, antimony and tin are added to improve tensile strength, and the effect of these elements on corrosion resistance is minimal, and the elongation and impact value are reduced. In addition, since both elements are low melting points and cause hot brittleness, tempering brittleness, low temperature brittleness, the addition of these elements may cause problems in the steel manufacturing process.

Another technique is Patent Document 2, which relates to a ballast tank coated with a low-alloy corrosion resistant steel such as tar epoxy paint, pure epoxy paint, and urethane paint. Phosphorus does not have a large improvement in corrosion resistance relative to the amount added, but rather a problem of inhibiting weldability and weldability toughness.

Another technique is Patent Document 3, which is intended to improve the corrosion resistance by adding 0.2-5.0% by weight of chromium as a corrosion resistance improving element in steels having carbon of 0.15% by weight or less. There is a problem that the weldability is inferior, the weld section toughness decreases, and the manufacturing cost is high.

On the other hand, strict regulations on anti-corrosion coating are applied for the ballast under poor corrosive environment, but in general, the life of the anti-corrosion coating is less than half of the life of the ship. That is, since coating defects occur within 10 years under seawater environment and cause severe corrosion on the coating defects, there are efforts to provide corrosion resistance to the steel itself as a countermeasure to prevent them. The development of steel with excellent corrosion resistance is easy to prove its effect in the case of unpainted coating without coating, but in case of exposure to salt or constant temperature and high humidity such as seawater environment, even if the corrosion resistance is improved when using steel except stainless steel The use of unpainted corrosion resistant steel in ballast tanks is difficult because problems such as external appearance or marine environmental pollution occur due to the generation of rust.

Therefore, a method of strict control of the coating has also been proposed to prolong the life of the coating and to reduce maintenance, but a method of improving the resistance to crack corrosion of the steel itself has been proposed.

Gap corrosion is a form of local corrosion that occurs relatively quickly in small areas of the metal surface, with localized corrosion occurring in gaps such as film defects. Such gap corrosion is difficult to observe with the naked eye, so it penetrates to the end of the wall and forms a hole.

Therefore, there is a demand for the development of corrosion resistant steels having excellent resistance to crevice corrosion in paint defects as well as resistance to marine steels used in seawater environments such as ballast tanks.

Korean Patent Publication No. 2008-0090541 Japanese Patent Application Laid-Open No. 07-034197 Japanese Patent Application Laid-Open No. 07-034196

One aspect of the present invention is excellent in corrosion resistance at the coating defect in the environment exposed to salt or constant temperature and humidity by sea water, and excellent in corrosion resistance excellent in economic efficiency and production efficiency by improving the stability and life of the vessel Provide corrosion resistant steel for ships.

In the present invention, by weight%, C: 0.02 to 0.25%, Si: 0.05 to 1.0%, Mn: 0.2 to 2.0%, Al: 0.05 to 2.0%, Cu: 0.1 to 0.5%, Mo: 0.05 to 0.5%, Ti Provides corrosion resistant steel for ships having excellent corrosion resistance including 0.01 to 0.3%, P: 0.03% or less, S: 0.03% or less, N: 0.001 to 0.01%, balance Fe and other unavoidable impurities.

In addition, the solution of the above-mentioned problems does not list all the features of the present invention. The various features of the present invention and the advantages and effects thereof will be more fully understood by reference to the following specific embodiments.

According to the present invention, by optimizing the steel component, the corrosion rate is extremely low even at temperatures up to 60 ° C. higher than room temperature and normal temperature in the brine solution of seawater-like components, and at the same time, it is possible to prevent corrosion in the coating film during coating. Excellent resistance can be secured, and the stability and service life of the ship can be improved to reduce maintenance painting work, thereby obtaining corrosion resistant steel for ships with excellent economic efficiency and production efficiency.

1 is a schematic diagram illustrating the internal environment of a ballast tank.
Figure 2 (a) is a schematic diagram showing the specimen contained in the ballast tank, (b) is a schematic diagram showing a method of measuring the gap corrosion resistance.

The present inventors have overcome the problems that the above-described techniques have not solved, and have conducted research to develop steels excellent in corrosion resistance at coating defects even in poor corrosion environments such as ballast tanks of ships. And Ti as an essential element, and in addition, by containing chromium, nickel, tungsten, calcium and magnesium in an appropriate range, it was confirmed that the corrosion resistant steel having excellent crevice resistance can be produced and the present invention has been achieved. .

In general, steel used in ships is used after corrosion-proof coating is carried out for corrosion protection. Anticorrosive coating is generally coated with zinc primer to prevent rust before steel work and epoxy coating after assembly. In particular, in ballast tanks, the requirements for anticorrosive coating are difficult, so that the thickness of the coating layer is made very thick by applying epoxy coating more than once. In this anticorrosive coating layer, ships are serviced after construction, and defects such as cracks occur in the coating film during operation, and there are portions where the steel sheet is exposed due to peeling of the coating film or insufficient function as the coating film. In the cracks generated in the coating film, corrosion is generated not only from the front corrosion but also from the corrosion, and the corrosion is accelerated faster. This rapid corrosion plays a role in promoting the deterioration of the surrounding paint, thereby shortening the life of the coating. Corrosion-resistant steel of the present invention is to solve this problem, to improve the stability and service life of the ship and to reduce the maintenance painting work to have excellent corrosion resistance under poor corrosion environment, such as ballast tank of the ship.

Hereinafter, the corrosion resistant steel for ships excellent in corrosion resistance which is one side of this invention is demonstrated in detail.

In the present invention, by weight%, C: 0.02 to 0.25%, Si: 0.05 to 1.0%, Mn: 0.2 to 2.0%, Al: 0.05 to 2.0%, Cu: 0.1 to 0.5%, Mo: 0.05 to 0.5%, Ti Provides corrosion resistant steel for ships having excellent corrosion resistance including 0.01 to 0.3%, P: 0.03% or less, S: 0.03% or less, N: 0.001 to 0.01%, balance Fe and other unavoidable impurities.

Carbon (C): 0.02-0.25 wt%

The C is an element added to improve the strength, and increasing its content serves to improve the hardenability by improving the hardenability. In order to improve the resistance to corrosion and gap corrosion, it is necessary to reduce the C content, but when C is less than 0.02% by weight, it is difficult to secure the strength. On the other hand, when the carbon content exceeds 0.25% by weight, not only sufficient toughness may be secured but also the weldability is deteriorated, which is not preferable as steel for welding structures. Therefore, the carbon is preferably limited to 0.02 to 0.25% by weight. More preferably, the upper limit of C is limited to 0.12% by weight or less.

Silicon (Si): 0.05-1.0 wt%

The Si not only acts as a deoxidizer but also serves to increase the strength of the steel. In order to exhibit such an effect in the present invention, it is preferable that 0.05 wt% or more is included. In addition, it is advantageous to increase the content of Si because it contributes to the improvement of the front corrosion resistance, but if the content of Si exceeds 1.0% by weight, the toughness and weldability are inhibited and the peeling of the scale during the rolling is difficult. It causes surface defects. Therefore, the content of the silicon is preferably limited to 0.05 to 1.0% by weight. In order to improve corrosion resistance, it is more preferable to add 0.2 wt% or more of Si.

Manganese (Mn): 0.2-2.0 wt%

Mn is an element effective for solidifying steel. In the present invention, in order to exhibit such an effect, it is preferably included 0.2% by weight or more. When the content of manganese increases, the hardenability increases to increase the strength, but when the content of manganese exceeds 2.0% by weight, there is a problem in that it affects the corrosion resistance of the front surface and the weldability decreases. Therefore, the content of manganese is preferably limited to 0.05 to 2.0% by weight. It is more preferable to add manganese at 1.5% by weight or less in order to improve the front corrosion resistance.

Aluminum (Al): 0.05-2.0 wt%

The Al is an element that improves the corrosion resistance by forming an Al ₂ O ₃ layer on the surface of the steel over time when the steel is exposed to sea water, thereby slowing down the corrosion rate. In general, Al should be added at least 0.1% by weight in order to improve the corrosion resistance and the element added for deoxidation. Corrosion resistance improves as the amount of Al added increases, but the addition of Al may cause problems when playing steel, so the upper limit is limited to 2.0% by weight that can be played so far. More preferably the content is limited to 1.0% by weight or more.

Copper (Cu): 0.1-0.5 wt%

The Cu is an element that delays the elution of Fe from the acidic solution and improves corrosion resistance, thereby improving corrosion resistance under conditions in which the solution environment in the gap is acidified, such as a coating defect. In order to improve the corrosion resistance in such an acidic solution, at least 0.1% by weight should be added. Corrosion resistance is further increased as the amount of Cu is increased, but when it exceeds 0.5% by weight, it causes surface cracking during slab manufacture, thereby lowering local corrosion resistance.When reheating the slab for rolling, Cu having low melting point penetrates into the grain boundary of steel and is hot. Cracking occurs during processing. Therefore, the copper is preferably limited to 0.1 to 0.5% by weight.

Molybdenum (Mo): 0.05-0.5 wt%

Molybdenum is an element that contributes to the improvement of corrosion resistance and strength. If the molybdenum is included in less than 0.05% by weight it is difficult to show the effect. However, in order to improve corrosion resistance by molybdenum, molybdenum must be employed in steel materials. This is because molybdenum generates MoO ₄ ⁻ in the oxide layer formed on the surface, thereby preventing the penetration of Cl ⁻ ions. If it exceeds 0.5% by weight, molybdenum in excess of the solubility limit forms precipitates, forming ferrite and galvanic, which may increase the corrosion rate. If the precipitates are coarse, the pores formed in the precipitates and steel interfaces may cause local corrosion. It acts as a point of view.

Titanium (Ti): 0.01 ~ 0.3 wt%

In general, the Ti is an element showing excellent corrosion resistance even in a strong acid atmosphere, so that the solution is changed to a strong acid, such as a coating defect, thereby improving corrosion resistance in an environment, thereby increasing resistance to crevice corrosion. In order to exhibit such an effect in the present invention, it is preferable to include 0.01% by weight or more. However, when the content exceeds 0.3% by weight, the toughness and weldability are adversely affected. Therefore, the content of titanium is preferably limited to 0.01 to 0.3% by weight.

The remainder of the present invention is iron (Fe). However, in the ordinary manufacturing process, impurities which are not intended from the raw material or the surrounding environment may be inevitably incorporated, so that it can not be excluded. Since the son impurities are known to those skilled in the art, not all of them are specifically mentioned herein.

However, since phosphorus, sulfur, and nitrogen are generally referred to as impurities, this will be briefly described as follows.

Phosphorus (P): 0.03 wt% or less

The phosphorus is inevitably contained in the center of the steel sheet, so it is preferably segregated in the center of the steel sheet to lower toughness and significantly lower weldability. Therefore, the phosphorus is preferably controlled as low as possible in order to secure the low temperature impact toughness of the core material.

In theory, the phosphorus content is advantageously limited to 0%, but inevitably contained in the manufacturing process. Therefore, it is important to manage the upper limit, and in the present invention, the upper limit of the phosphorus content is preferably limited to 0.03% by weight.

Sulfur (S): 0.03 wt% or less

Sulfur is inevitably contained as an impurity and forms a nonmetallic inclusion by bonding with Mn or the like, thereby largely deteriorating the ductility, impact toughness and weldability of steel. Therefore, it is desirable to suppress the content to the maximum.

The theoretical sulfur content is advantageous to be limited to 0% but it is inevitably contained in the manufacturing process normally. Therefore, it is important to manage the upper limit, and in the present invention, the upper limit of the sulfur content is preferably limited to 0.03% by weight.

Nitrogen (N): 0.001 to 0.01 wt%

N is unavoidably contained impurity. Forming a nitride in combination with Al, Ti, Nb, V, etc., hinders the growth of austenite grains, thereby improving toughness and strength, but if the content is too high, there is a solid solution of N. Since it adversely affects toughness, the upper limit of the content is preferably limited to 0.01% by weight.

In addition, the steel of the present invention can further improve the effect of the present invention when additionally added at least one element selected from the group consisting of chromium, nickel and tungsten described below.

Chromium (Cr)

Cr is an element effective for improving corrosion resistance in a seawater environment. It is an element advantageous in forming a stable film on the surface which greatly contributes to the improvement of corrosion resistance. However, if the amount of Cr is sufficient at the level of stainless steel and a stable film is not formed, it becomes vulnerable to the formula under Cl ⁻ ion. Vulnerability to the formula will also adversely affect the same corrosion mechanism, crevice corrosion. Therefore, Cr may be added especially with Al to increase the corrosion resistance of the steel. In order to exhibit such an effect of the present invention, it should contain at least 0.1% by weight. On the other hand, if it exceeds 2.0% by weight, rather it promotes local corrosion as shown in the formula, thereby reducing the gap corrosion resistance. Therefore, the content of chromium is preferably limited to 0.1 to 2.0% by weight.

Nickel (Ni)

When Ni is added together with Cu, the Ni reacts with Cu to suppress the formation of a low melting point Cu phase, thereby suppressing the problem of cracking during hot working. Therefore, if surface cracks occur during rolling, Ni is also an effective element for improving the toughness of the base material. However, since it is an expensive element, the addition of more than 1.0% by weight is disadvantageous in terms of economics and weldability, so it is preferable to limit the content to 0.05 to 1.0% by weight. In addition, since the effect of Ni on corrosion resistance is not higher than that of Cu, it is more preferable to contain 1.5 times or less of Cu content to suppress surface cracking due to Cu addition rather than adding a large amount to improve corrosion resistance.

Tungsten (W)

W generates WO ₄ ⁻ in the corrosion product formed on the surface, thereby preventing the penetration of Cl ⁻ ions through the corrosion product to improve corrosion resistance. In order to exhibit this effect in the present invention, it should be added at least 0.1% by weight. However, in order to improve corrosion resistance, W must also be employed in steel materials. W may form precipitates when Mo exceeds the solid solution limit, thereby contributing to the increase in strength, but these precipitates may form ferrite and galvanic to increase the corrosion rate. In addition, when the precipitate is coarse, the cavities formed in the precipitate and the steel interface act as a starting point of local corrosion, thereby reducing the resistance to local corrosion. Therefore, the upper limit is preferably 0.5% by weight or less. Therefore, the W content is limited to 0.1 to 0.5% by weight.

In addition, the steel of the present invention can further improve the effect of the present invention when additionally added one or more elements selected from the group consisting of calcium and magnesium described below.

Calcium (Ca)

The Ca reacts with oxygen or sulfur in molten steel to form CaO or CaS. These CaO and CaS dissolve in water due to its deliquescent properties, and at this time, the pH of the solution is increased to decrease the acidity. This action prevents acidification of the solution in the gap to improve the corrosion resistance. To exhibit this effect, at least 0.0005% by weight must be added. However, MgO and MgS inhibit weldability, so the upper limit thereof is limited to 0.005%.

Magnesium (Mg)

The Mg reacts with oxygen or sulfur in molten steel to form MgO or MgS. These MgO or MgS is dissolved in water because of deliquescent, and at this time, the pH of the solution is increased to decrease the acidity. This action prevents acidification of the solution in the gap to improve the corrosion resistance. To exhibit this effect, at least 0.0005% by weight must be added. However, MgO and MgS inhibit weldability, so the upper limit thereof is limited to 0.005%.

Moreover, it is more preferable to apply the epoxy coating to the steel plate which has the above composition.

In the present invention, the steel slab satisfying the above-mentioned composition can be hot-rolled. The conditions of the hot rolling step are not particularly limited. In addition, if necessary, a process known in the art may be further performed.

Hereinafter, the present invention will be described more specifically by way of examples. It should be noted, however, that the following examples are intended to illustrate the invention in more detail and not to limit the scope of the invention. The scope of the present invention is determined by the matters set forth in the claims and the matters reasonably inferred therefrom.

(Example)

Steel slabs satisfying the component system shown in Table 1 below were heated to 1150 ° C. and hot rolled under normal conditions to prepare a thick steel sheet having a thickness of 20 mm. As shown in Figure 1 from the thick steel plate as described above, a specimen 100 of 5mmt (thickness) x 40mmW (width) x 50mmL (length) was prepared. After placing the specimen 100 on the specimen holder 200, it was immersed in artificial seawater (300) similar in composition to the general seawater. The immersion conditions of the sea water was used to heater 400 to simulate the interior of the ballast tank of the vessel to maintain the temperature at 60 ℃. After polishing the surface of the specimen 100 immersed in the above conditions for 45 days after removal of rust formed on the surface of the steel sheet to measure the weight loss and calculate the corrosion rate using the weight loss shown in Table 2 below.

In addition, it is shown in Table 2 by measuring the gap corrosion resistance generated in the coating film defect. As shown in (a) of FIG. 2, the method of evaluating the corrosion resistance is coated with a 300 m thick epoxy on the base material by spraying, and after the coating film is completely dried, the coating film has a length of 40 mm and a width of 0.1 mm. Artificial defects were created to expose the substrate. After fabrication of the defect, the immersion test was carried out under the same conditions as the base material, and as shown in FIG. 2B, the length of the largest couple of the coating deterioration parts around the defect was measured to evaluate the gap corrosion resistance.

No. C Si Mn P S Al Cu Mo Ti N Cr Ni W Mg Ca Inventory 1 0.071 0.25 0.95 0.015 0.0020 0.50 0.15 0.1 0.05 0.0050 0.15 0.20 0.001 Inventory 2 0.067 0.30 0.90 0.022 0.0030 0.15 0.20 0.1 0.04 0.0047 0.25 0.10 0.0015 Inventory 3 0.079 0.24 0.90 0.010 0.0025 0.33 0.18 0.15 0.05 0.0048 0.20 0.15 0.0012 Honorable 4 0.092 0.29 1.10 0.013 0.0018 0.58 0.19 0.12 0.06 0.0052 0.20 0.0014 Inventory 5 0.090 0.35 1.15 0.015 0.0025 0.19 0.24 0.20 0.05 0.0042 0.15 0.0020 Inventory 6 0.115 0.37 1.10 0.013 0.0020 0.38 0.30 0.15 0.10 0.0050 0.30 0.0015 Honorable 7 0.082 0.40 0.94 0.010 0.0030 0.69 0.35 0.10 0.11 0.0045 0.30 0.20 0.0014 Honors 8 0.071 0.14 1.25 0.014 0.0027 0.85 0.31 0.24 0.09 0.0039 0.12 0.0019 Proposition 9 0.105 0.25 1.20 0.017 0.0034 1.02 0.35 0.15 0.04 0.0060 0.4 0.21 0.0020 Inventory 10 0.126 0.19 1.24 0.010 0.0015 1.32 0.28 0.35 0.05 0.0045 0.15 0.0015 Exhibit 11 0.074 0.10 1.10 0.010 0.0020 1.24 0.40 0.20 0.06 0.0052 0.35 0.0021 Inventory 12 0.134 0.28 0.96 0.009 0.0021 0.75 0.31 0.10 0.10 0.0067 0.2 0.14 0.0023 Inventory 13 0.105 0.34 0.97 0.012 0.0029 0.67 0.47 0.08 0.15 0.0055 0.25 0.14 0.0015 Inventory 14 0.085 0.25 1.00 0.014 0.0032 0.72 0.25 0.25 0.07 0.0040 0.98 0.0014 Honorable Mention 15 0.099 0.40 1.08 0.013 0.0017 0.98 0.20 0.15 0.20 0.0041 0.25 0.0014 Inventory 16 0.090 0.31 1.25 0.010 0.0024 1.30 0.18 0.15 0.05 0.0038 0.24 0.0010 Inventory 17 0.071 0.23 1.4 0.008 0.0014 1.55 0.21 0.30 0.07 0.0047 0.30 0.10 0.0020 Inventory 18 0.135 0.19 1.35 0.015 0.0022 1.20 0.25 0.10 0.09 0.0055 0.15 0.0015 Inventive Example 19 0.121 0.24 1.25 0.014 0.0035 1.04 0.45 0.09 0.14 0.0064 1.05 0.10 0.0010 Inventive Example 20 0.060 0.26 1.06 0.015 0.0021 0.90 0.35 0.28 0.08 0.0055 0.15 0.0030 Comparative Example 1 0.160 0.17 0.94 0.012 0.0019 0.02 - 0.15 0.05 0.0045 1.25 Comparative Example 2 0.095 0.31 0.85 0.010 0.0018 0.01 0.25 - 0.17 0.0055 0.40 Comparative Example 3 0.105 0.32 1.25 0.011 0.0019 0.05 - - 0.04 0.0042 Comparative Example 4 0.145 0.41 1.17 0.009 0.0025 0.15 0.24 - 0.05 0.0055 0.50 Comparative Example 5 0.155 0.25 1.34 0.010 0.0036 0.08 0.19 0.20 - 0.0050 0.30 Comparative Example 6 0.950 0.21 1.40 0.012 0.0017 0.03 0.25 0.14 - 0.0047 0.23 Comparative Example 7 0.31 0.28 1.21 0.015 0.0027 0.68 - - 0.15 0.0052 Comparative Example 8 0.26 0.15 1.13 0.017 0.0038 - 0.63 - 0.34 0.0051 0.21 0.10

Inventive steels 1 to 20 are steel grades that satisfy both the component system and the composition range controlled by the present invention. On the other hand, Comparative Steels 1 to 8 are steel grades which do not satisfy the component system and composition range controlled by the present invention.

No. Weight loss after 45 days soaking (g) Corrosion rate (mm / year) Crevice Resistance (mm) Inventory 1 0.18 0.07 3.0 Inventory 2 0.22 0.10 1.5 Inventory 3 0.19 0.08 2.1 Honorable 4 0.18 0.07 1.5 Inventory 5 0.22 0.10 1.0 Inventory 6 0.23 0.11 1.6 Honorable 7 0.25 0.12 2.0 Honors 8 0.19 0.08 1.5 Proposition 9 0.23 0.10 1.2 Inventory 10 0.20 0.08 1.3 Exhibit 11 0.19 0.07 2.5 Inventory 12 0.18 0.06 1.8 Inventory 13 0.20 0.08 2.6 Inventory 14 0.20 0.08 3.4 Honorable Mention 15 0.18 0.07 1.8 Inventory 16 0.19 0.07 2.4 Inventory 17 0.17 0.06 2.5 Inventory 18 0.22 0.07 1.5 Inventive Example 19 0.34 0.11 2.4 Inventive Example 20 0.20 0.06 1.0 Comparative Example 1 0.58 0.18 18 Comparative Example 2 0.55 0.17 17 Comparative Example 3 0.47 0.16 20 Comparative Example 4 0.63 0.22 16 Comparative Example 5 0.59 0.18 17 Comparative Example 6 0.63 0.20 16 Comparative Example 7 0.59 0.18 15 Comparative Example 8 0.60 0.19 18

As shown in Table 2, Inventive Examples 1 to 20 to which Al, Cu, Mo, and Ti were added, it was confirmed that the corrosion rate was reduced by about 0.5 to 3.2 times the corrosion rate compared to Comparative Examples 1 to 8. In addition, it can be seen that the corrosion resistance of the inventive examples 1 to 8 is improved by an average of about 10 times compared to the comparative examples 1 to 8.

When the present invention does not include the components suggested by the present invention as in Comparative Examples 1 to 8, the weight loss value is larger than that of the Inventive Examples 1 to 20, and the corrosion rate is fast, so that corrosion resistance is not maintained even in seawater, resulting in large corrosion. Able to know.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

100: Psalms
200: specimen holder
300: artificial seawater
400: heater

Claims (4)

By weight%, C: 0.02-0.25%, Si: 0.05-1.0%, Mn: 0.2-2.0%, Al: 0.05-2.0%, Cu: 0.1-0.5%, Mo: 0.05-0.5%, Ti: 0.01- Corrosion-resistant steel for ships with excellent corrosion resistance including 0.3%, P: 0.03% or less, S: 0.03% or less, N: 0.001-0.01%, balance Fe and other unavoidable impurities.
The method of claim 1,
The corrosion resistant steel for ships excellent in corrosion resistance to corrosion which further contains at least one selected from the group consisting of Cr: 0.1 to 2.0%, Ni: 0.05 to 1.0%, and W: 0.1 to 0.5%.
The method of claim 1,
Ca: 0.0005 ~ 0.005%, Mg: 0.005 ~ 0.005% corrosion resistant steel for ships excellent in corrosion resistance corrosion resistance further comprises at least one selected from the group consisting of.
The method of claim 1,
The corrosion resistant steel for ships excellent in corrosion resistance including an epoxy coating layer on the surface of the steel.

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