TWI281505B - Excellent corrosion resistance steel for ship - Google Patents

Abstract

The present invention provides a steel for shipbuilding having excellent corrosion resistance which can be put to practical use even without applying coating or electrical protection, particularly a steel for shipbuilding with improved durability to crevice corrosion, and exhibiting excellent durability even to corrosion due to the sticking of salt caused by seawater and wet environment, and further exhibiting excellent corrosion resistance even when applied to a petroleum based liquid fuel tank. The corrosion resistant steel for shipbuilding has a composition comprising C of 0.01 to 0.30% by mass, Si of 0.01 to 2.0% by mass, Mn of 0.01 to 2.0% by mass, Al 0.005 to 0.10% by mass, and further comprising Se of 0.005 to 0.50% by mass, and the rest are Fe and inevitable impurities.

Description

(6) The tendency of 1281505 on the defective portion of rust is therefore a large effect of suppressing pH reduction for such local pH reduction. For this reason, 'the corrosion uniformity and the local corrosion resistance are improved by the inclusion of Se, but such an effect is obtained by Cu and Ni which are contained as needed to densify and stabilize the generated rust. And Ti coexist, it can be dramatically improved

In the steel material of the present invention, in order to conform to the basic characteristics of the steel material, it is necessary to appropriately adjust basic components such as C, Si, Μ, and A1. The reason for limiting the range of these components will be described below in conjunction with the effects of Se described above. C : 0 · 0 1 ～ 0 · 3 0 % C, which is the element required to ensure the strength of the material. To obtain the minimum strength of the structural member of the ship, that is, generally about 40 OMPa (but also depending on the thickness of the steel used), it is necessary to contain 0.01% or more. However, if it exceeds 0.30%, the toughness deteriorates. Therefore, the range of the C content is specified in 〇·〇1 to 0.30%. Further, a preferred lower limit of the C content is 0.02%, and more preferably 0.04% or more. Further, a preferred upper limit of the C content is 0.28%, and more preferably 0.26% or less. S i : 0.0 1 〜 2 · 0 %

Si, which is an element required for deoxidation and strength, cannot be ensured as the lowest strength of the structural member if it is less than 0.01%. However, if it exceeds 2·0%, the weldability deteriorates. Further, a preferred lower limit of the Si content is \S) -10- (7) 1281505 0.02%, and more preferably 0.05% or more. Further, a preferred upper limit of the Si content is 168%, and more preferably 1600% or less. Μ η : 0.0 1 to 2.0 % Μη, also like Si, is an element required for deoxidation and strength, and if it is lower than 〇 · 〇1%, it cannot be ensured as the lowest strength of the structural member. However, if it exceeds 2.0%, the toughness deteriorates. In addition, the content of Μη

A preferred lower limit is 0.05%, and more preferably 0.10% or more. Further, a preferred upper limit of the Μ η content is 1 · 80%, more preferably 1.7 % or less Α 1 : 0.005 〜 0· 1 0% Α1, and similarly to Mn and Si, it is deoxidized and ensures strength. If the required element is less than 0.005%, deoxidation has no effect. However, if it is added in excess of 0.10%, the range of the amount of addition of A1 is specified to be 0.005 to 0.10% because the weldability is impaired. Further, a preferred lower limit of the A1 content is 0.010%, and more preferably 15% or more. Further, a preferred upper limit of the A1 content is 0.040%, and more preferably 50% or less.

Se: 0.005 to 0.50% As described above, Se has a function of suppressing a decrease in pH at a point where a dissolution reaction causing corrosion occurs, suppressing a corrosion reaction, and improving corrosion resistance. By including such Se, it is difficult to cause local pH change, so that it has an effect of improving the uniformity of corrosion. In addition, it is easy to cause local PH drop when restricting the movement of substances -11 - 1281505

On the low (crack), the effect (local corrosion suppression effect) is effectively exerted for the above reasons. In order to ensure the required corrosion resistance in such an environment, the content of Se needs to be specified to be 0.05% or more. However, if it is excessively contained in excess of 0.5%, workability and weldability may deteriorate. Therefore, the Se content is specified to be 0.005 to 0.50%. Further, a preferred lower limit of the Se content is 0.006%, and more preferably 0.008% or more. Further, the preferred upper limit of the Se content is 0.45%, and more preferably 0.40% or less.

The basic components in the steel material for ship of the present invention are as described above, and the rest are composed of iron and unavoidable impurities (for example, P, S, ruthenium, etc.), but in addition to these, components which do not hinder the degree of characteristics of the steel material are also allowed (for example, Zr, N, etc.). However, if the content of these allowable components is too large, the toughness is deteriorated, so the degree should be controlled to 0.1% or less. Further, in the steel material for ship according to the present invention, in addition to the above components, (1) from: Cu: 0.01 to 5.0%, Cr: 0.01 to 5·0%, C 〇·· 0 · 0 1 to 5 · 0 %, N i : 0 · 0 1 ～ 5 · 0 % and T i : 0 · 0 0 5 ~ 0.20% of the selected group of more than one, (2) from La: 0.0005 to 0.15% , Ce : 0.0005 to 0.15 % , Ca : 0.0005 to 0.01 5% and Mg : 0.0005 to 0.01 5 % of the selected one or more of the groups, (3) Mo : 0·01 to 5.0%, (4) from Sb : 0.01 to 0.5%, As: 0·01 to 0.5%, Sn: 0.01 to 0.5%, Bi: 0.01 to 0.5%, and Te: 0·01 to 0.5%, one or more selected from the group consisting of ( 5) A group consisting of Β ·· 0 · 0 0 0 1 〜 0 · 0 1 0 %, V ·· 0 · 〇1 〇 〇 · 5 % and N b : 0.0 0 3 〜 0 · 5 0 % One or more selected, (6) Zn: 0.001 to 0.10 ° /. It is also effective, and the characteristics of the 1212 (9) 1281505 shipbuilding steel can be further improved depending on the type of components contained. Select from the group consisting of Cu: 0·01 ～5.0%, Cr: 0.01 ～5. 0%, Co: 0.01 ～5.0%, Ni: 0·01 ～5.0%, and Ti: 0.005~0·20% More than one

Cu, Cr, Co, Ni and Ti are all effective alizarins for improving corrosion resistance. Among them, Cu, Cr and Co are effective elements for forming a dense surface rust film which greatly contributes to an improvement in corrosion resistance. In addition, Co is an element that is effective in a high salinity environment. In order to exhibit the effects of these elements, it is preferable to contain 0.01% or more. However, if it is excessively contained, weldability or hot workability is deteriorated, so it is preferably 5.0% or less. A more preferred lower limit when Cu, Cr and Co are contained is 0.05%, and a more preferred upper limit is 4.50%.

Ni is an effective element for stabilizing a dense surface rust coating which greatly contributes to improvement in corrosion resistance. In order to exert such an effect, it is preferably contained in an amount of 0.01% or more. However, if the Ni content is excessive, the weldability or the hot workability is deteriorated, so it is preferably made 5.0% or less. A more preferred lower limit when Ni is contained is 0.05%, and a more preferred upper limit is 4.50%.

Ti is an element which densifies the surface rust coating which greatly contributes to the improvement of corrosion resistance, improves the environmental barrier properties, and suppresses corrosion inside the crack and also improves the crevice corrosion resistance. In order to ensure the corrosion resistance required in such an environment, it is preferable to contain 〇·〇〇 of 5% or more. However, if it is contained in excess of 0.20%, the workability and weldability are deteriorated. Therefore, a more preferable lower limit when Ti is contained is 0.00 8 %, and a more preferable upper limit is 0.1 5 %. (10) 1281505 From La: 0.0005 to 0.15°/. , Ce: 0.0005 to 0.15%, Ca: 0 · 0 0 0 5~0 · 0 1 5 % and M g : 0 · 0 0 0 5~0 · 1 5 % One or more selected from the group consisting of

These elements have a function of suppressing the pH lowering caused by the hydrolysis of Fe ions dissolved by the corrosion, and further have a function of promoting the effect of suppressing the local pH reduction by further forming the rust densification formed by the necessity or the like. The effect of one or more of these elements is 0.0005% or more, and it can be effectively exhibited. However, if La and Ce are excessively contained in excess of 0.15%, the excess content of Ca and Mg exceeds 0.015%. Further, the lower limit of the content of La and Ce is more preferably 0.0010%, and the more preferable upper limit is 0.10%. Further, the more preferable lower limit when Ca and Mg are contained is 0.0010%, A preferred upper limit is 0.010%. Μ 〇: 0 · 0 1 〜5 · 0 %

Mo has the effect of improving the uniformity of corrosion and suppressing the formation of perforations by local corrosion. In particular, it can exhibit a remarkable effect of improving uniform corrosion by being contained together with Cu, Cr, Co or the like. In order to exhibit such an effect, Mo is preferably contained in an amount of 0.01% or more. However, if it is excessively contained, the weldability is deteriorated, and therefore it is preferably 5.0% or less. A more preferable lower limit when these elements are contained is 0.02%, and a more preferable upper limit is 4.50%. Selected from the group consisting of Sb: 0·01 to 0.5%, As: 0.01 to 〇·5 %, Sn: 0.01 to 0.5%, :Bi: 0.0 1 to 0.5%, Te: 0.0 1 to 0.5% -14- (11) 1281505 One or more of these elements are elements which promote the rust densification of Cu or the like or the pH lowering action of La or the like to improve the corrosion resistance. In order to achieve such an effect, it is preferable to contain 〇·01% or more. However, if excessively contained 'deterioration in workability and weldability', it is preferably 0.5% or less. A more preferable lower limit when these elements are contained is 0. 02%, and a more preferable upper limit is 0. 40%.

From the group consisting of: 01: 0.0001 〇 〇 〇 10%, V: 〇·〇1 ～0.50% and Nb: 0.003 0.5 0%, one or more selected from the group of ship steels, depending on the part of the application It is also required to have high strength, and these elements are essential elements for improving strength. In the case where B' is contained in an amount of 0.000 1 % or more, the improvement of the hardenability is effective, but if it exceeds 〇·〇ι〇%, it is not preferable because it is excessively deteriorated due to the deterioration of the base material. V is more effective in increasing the strength by containing 0. 01% or more. However, if it exceeds 〇 · 5 〇%, excessive inclusion is caused to cause deterioration of the steel material, which is not preferable. Nb' is effective for improving strength by containing 0. 003% or more, but if it exceeds 0. 50%, excessive inclusion causes a deterioration in the edge of the steel. Further, a more preferable lower limit of these elements is 00·0 0 0 3 %, V is 〇.〇2%, and Nb is 0.005%. Further, a more preferable upper limit is 0 0·0 0 9 0%, V is 0 · 4 5 %, and N b is 0 · 4 5 %.

Zn : 0.001- 0.10%

Zn, which has a reaction with salt or sulfur, forms a sinking film of zinc chloride or sulfide bell on the surface of the steel, and separates the steel substrate from the water of the environment to inhibit the effect of corrosion -15-(12) 1281505 eclipse. In the coating film or the crack portion where the substance is restricted from moving, since zinc chloride or zinc sulfide is easily deposited on the surface of the steel material without splashing at sea, the corrosion inhibiting effect under the coating film or the crack portion is particularly good.

In order to achieve such an effect and to ensure the required corrosion resistance, the Zri content needs to be specified in 〇 · 〇 % or more. However, if it is excessively contained in excess of 0.10%, workability and weldability are deteriorated. Therefore, the Zn content is specified to be 0.001 to 0.10%. Further, a more preferred lower limit of the Zn content is 0.003%, and more preferably 0.005% or more. Further, a preferred upper limit of the Zn content is 0.09%, and more preferably 0.08% or less. In the case where a welded structure is formed by welding the steel material of the present invention, if normal welding conditions or welding materials are used, since the concentration of the above-mentioned effective element changes at the welded joint, corrosion resistance may not be found in the welded portion. In particular, in the case where the ratio of the Se content to the deposited metal and the base material (the Se content of the deposited metal/the Se content of the base material) is less than 0.3, the effect of suppressing the corrosion reaction formed by suppressing the decrease in pH is not found, and the fusion is performed. The metallized portion has insufficient corrosion resistance. Further, if the ratio is more than 3.0, the toughness of the welded portion is deteriorated, which is not preferable from the viewpoint of mechanical strength. Therefore, it is recommended to adjust the ratio in the range of 0.3 to 3.0, and more preferably in the range of 0.5 to 2.0. In addition, an effective element for improving corrosion resistance other than Se, that is, Cu,

Cr, Co, Ni, Ti, La, Ce, Ca, Mg, Mo, Sb, As, Sn,

In the case where these elements are also added, it is recommended to adjust the content ratio of the deposited metal to the base material (the content of the deposited metal/the content of the base material) in the range of 0.3 to 3.0, more preferably 0.5. Adjust within the range of ~2.0. 1281505

/^\ _ ft Other 1 1 1 1 1 丨Β:0·0012 1 1 Β:0·0001 1 1 V:0.011 1 1 1 1 1 1 ν··0·11, Nb:0.003 B:0.0099 1 1 1 1 I 1 1 I 1 1 1 1 1 1 I 1 1 1 1 Miscellaneous 1 1 1 1 1 1 1 1 1 1 1 瞧1 1 1 » 1 1 1 1 1 1 1 1 1 Review 1 1 1 1 » 1 1 1 1 1 1 1 1 c3 1 0.0048 Ray 1 I 0.0005 1 0.0022 1 0.018 0.0019 0.0022 0.0011 1 1 1 1 1 1 0.092 1 1 0.051 1 0.005 0.16 0.023 1 0.017 0.015 0.012 2 1 0.31 1 1 1 1 1 4.89 1 I 1 0.36 1 1 1.76 1 0.30 0.99 0.30 0.30 0.22 4ύΛ/ W ¥η ^〇1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 U 1 0.05 1 1 1 1 Fan 1 1 1 1 1 1 1 1 1 1 1 1 1 0.30 1 1 1 1 00 1 I 1 0.35 0·19 4.99 1 Flat 0.15 0.02 0.28 0.28 0.21 1 1 0.009 0.28 0.50 0.35 0.01 0.18 0.34 0.06 0.15 0.23 0.30 0.09 0.28 ! 0.25 0.27 0.35 0.34 0.21 < 0.012 0.013 0.021 0.017 0.018 0.011 0.032 0.015 1 0.015 0.016 0.008 0.006 0.015 0.016 0.015 ! 0.015 0.020 0.019 0.012 0.019 C 0.98 1.01 r—» (N 1.35 1.12 I 0.92 ο (Ν · —r—^ 0.99 1.07 00 rn vH 0.96 ! 1.18 1.31 1.31 ΰ5 0.20 0.32 0 .33 0.36 0.12 丨0.39 0.25 0.48 0.23 0.30 0.16 0.09 0.26 ! 0.34 : 0.45 0.19 0.28 0.32 0.33 0.29 U 0.18 0.15 0.16 0.17 0.18 0.15 0.15 0.20 0.14 0.15 0.16 0.17 0.17 1 0.15 0.15 0.12 0.09 0.17 0.17 0.15 6 2 (Ν m inch In VO 卜 00 Cs ο 2 (N inch s 〇 〇〇 〇〇 ON 1281505

_ tt Φ Others.- 1 Nb:0.018 1 Nb:0.49 1 1 1 B:0.0025, V:0.02 1 V:0.50 1 1 1 1 1 1 1 » 1 B:0.0006 1 cS 1 0.22 1 1 1 I 0.05 I 0.03 | 0.11 1 1 1 | 0.48 | 0.21 | 1 1 1 0.21 0.19 1 0.09 0.30 0.15 1 0.48 0.15 0.01 1 | 0.48 I 0.17 | 0.45 | I 0.09 I 0.05 ! 1 K 0.15 0.12 0.13 1 0.11 0.29 1 0.43 1 t 1 1 1 1 1 1 1 1 I 0.0049 II 0.0031 1 0.0007 1 0.0029 0.0028 0.0019 0.0200 0.0099 0.0045 ό 1 1 0.019 I 0.0055 0.0041 1 0.0044 0.0029 1 1 1 1 1 1 0.0018 0.0019 0.0024 0.0009 0.0010 0.011 0.0079 p 1 1 0.20 0.026 1 0.010 0.099 0.015 1 Plug 1 I 0.018 I 0.033 0.092 0.088 0.024 0.015 0.049 0.019 0.035 0.0]0 3.59 0.38 1 0.29 0.31 0.25 0.21 0.16 I 0.24 II 1.05 II 0.28 II 0.52 I 0.19 0.23 0.26 0.01 0.05 0.50 0.35 0.70 O 〇1 1 1 1 1 1 1 1 0.10 I 1 0.02 I 0.24 I 0.30 | t 1.01 4.97 0.19 0.21 0.56 0.09 sm U 〇1 1 1 1 1 1 1 1 〇\ r—i 1 1 0.02 0.14 4.88 1 1 1 0.22 0.98 0.26 S3 o 2.85 1 1 0.30 1 0.30 0.25 g 0.20 0.15 I 0.09 I 1 0.27 I 0.51 I 2.04 0.22 0.19 0.29 0.66 0.49 0.31 0.14 o 0 0 0.09 0.13 0.03 0.21 0.22 0.19 0.28 0.24 0.35 0.08 0.33 0.09 ! 0.15 0.18 0.39 0.26 0.20 0.09 0.24 0.17 0.18 < 0.018 0.020 0.021 0.009 0.015 0.014 0.016 1 0.012 0.012 I 0.022 I 0.017 0.016 0.016 0.010 0.011 I 0.015 0.013 0.052 0.018 0.015 0.029 Cs 〇〇rn 0.98 S 0.99 1.06 ON CN ST-t ——1.12 — o (N 1.19 0.93 I 0.92 I 0.98 1.00 ! 0.99 1.35 0.97 fN CNJ 0.33 0.34 0.18 0.47 0.12 1 1 0.28 —0.19 0.20 0.34 I 0.35 I | 0.23 I 0.25 0.31 | 0.12 0.18 o 0.22 0.39 0.26 0.20 0.19 〇 0.15 0.11 0.16 0.12 0.17 0.17 0.18 0.09 0.16 I 0.06 II 0.16 I 0.18 0.11 0.16 0.05 0.10 0.12 0.15 0.09 0.12 0.15 ό z (N oc (N <N m ri vn P: 00 C\ o -19- (16) 1281505 In addition, as shown in Fig. 2, make four small test pieces of 20x20x5 (mm) and large test pieces of 100x100x25 (mm) (the same as the above test piece eight) In contact with, a test piece B forming a crack portion was produced. The small test piece for forming the crack and the large test piece are steel materials having the same chemical composition, and the surface finish is the same as the above test piece A, and is specified as surface honing. Further, a hole of Φ 5 mm was opened at the center of the small test piece, and a screw hole was opened on the substrate side (large test piece side), and bolted with M4 plastic.

In the steel material of the present invention, the anti-corrosive paint may be used in combination. However, when the paint is damaged for some reason and the base steel material is exposed, the crack may be significantly formed in the crack portion of the coating film and the base steel material. Therefore, in order to verify the corrosion resistance improvement effect of the anticorrosive paint, a test piece C (Fig. 3) of a tar epoxy resin paint (primer: zinc-rich paint) having an average thickness of 25 μm was also used. On one side of the test piece C, a cut to the base body was formed by a cutting blade (length: l〇〇mm, width: about 〇.5 mm). For each of the samples having the chemical compositions shown in Tables 1 and 2, five test pieces A, test pieces B, and test pieces C were used for the corrosion test. The corrosion test method at this time is as follows. [Corrosion test method] First, the marine environment was simulated, and a composite cyclic corrosion test in which seawater spray, drying, and wetting were sequentially repeated was performed. In the seawater spray test, samples (each test piece A to C) were placed in a test tank at an inclination of 60° from the horizontal, and artificial seawater (saline) of 35 t was sprayed in a mist. The spray of brine is usually carried out continuously. At this time, in the test tank, 1.5 iterations of 0.3 mL of artificial seawater were taken at any position in a circular dish -20 - (17) 1281505 with a horizontal area of 80 cm2, and the amount of spray was adjusted in advance. During the drying process, the temperature in the test cell was maintained at 50 ° C and the humidity was maintained at 50% RT. During the wetting process, the temperature in the tank was maintained at 60 ° C and the humidity was maintained at 98%. The seawater is sprayed; the process takes 2 hours as one cycle, the drying process takes 3 hours as one cycle, and the wetting process takes 3 hours as one cycle, and these cycles are repeated to promote corrosion of the sample. The total test time was set at 6 months. In the corrosion test [hereinafter, referred to as "corrosion test I"], five test pieces A and test pieces B were used for evaluation. However, in the ballast tank, when the seawater is injected at an empty load, it is a seawater immersion state in which electric hysteresis is applied. However, when the crude oil is loaded (no seawater), it is a corrosive environment exposed to high temperature and high humidity. In addition, even in the vicinity of the sea surface of the outer panel, it is possible to prevent corrosion by electrical corrosion during seawater immersion, but in the case of exposing the sea surface, the electrical corrosion prevention does not act and is exposed to the humid corrosive environment of the atmosphere. Thus, in order to simulate the corrosive environment formed by repeating the electric anti-corrosion B# in the seawater and the atmospheric protective environment, the corrosion test was also carried out by repeating the cathodic electrolysis and the wet composite cycle in the artificial seawater. In electrolysis in artificial seawater, the electrode potential of each sample immersed in artificial seawater at a temperature of 30 °C was maintained at -800 mV (silver/silver chloride electrode standard) using a potentiostat. At this time, the counter electrode is made of platinum, and the control electrode is made of silver/silver chloride electrode. As an atmospheric protection environment, keep it at a constant temperature and humidity protection environment with a temperature of 60 ° C and a humidity of 95% RT. In the artificial seawater, the cathode is electrolyzed for one day as one cycle, and the atmospheric protective environment is used as one cycle for one day, and these cycles are repeated to promote corrosion of the sample. The total test time setting -21 - (18) 1281505 is 6 months. In the corrosion test [hereinafter, referred to as "corrosion test Π"], five test pieces A and test pieces C were used for evaluation.

(1) With respect to the test piece A, the weight change before and after the test was converted into the average plate thickness reduction amount D-ave (mm), and the average enthalpy of the five test pieces was calculated, and the total uranium property of each sample was evaluated. In addition, the maximum intrusion depth D-max (mm) of the test piece A was obtained by a stylus type three-dimensional shape measuring device, and normalized by the average plate thickness reduction amount [D-ave (mm)] (that is, D-max/ was calculated. D-ave), evaluation of the uniformity of uranium. In addition, the weight measurement and the thickness measurement after the test were carried out by removing a corrosion product such as rust by a cathodic electrolysis method [JIS K 82 84] in an aqueous solution of diammonium hydrogen citrate. (2) For the test piece B, visual observation of the cracked portion (contact surface) was carried out to investigate the occurrence of crevice corrosion. When the crevice corrosion was observed, the cathodic electrolysis method was used to remove the corrosion product, and the stylus type 3D was used. The shape determining device measures the maximum crack corrosion depth D - crev ( mm ). (3) The test piece C (cut portion) subjected to the painting treatment, and the ratio (bulk area ratio) of the coating film bulging area on the surface on which the cut portion was formed after the test was measured. The bulging area ratio was obtained by the lattice point method (grid spacing 1 m m ). That is, the enthalpy obtained by dividing the total number of grid points by the number of lattice points for confirming the bulging is defined as the blasting area ratio, and the average enthalpy of the five test pieces is obtained, and the caliper is used to measure the vertical direction of the cut. The film bulging width defines the maximum enthalpy of the five test pieces as the maximum bulging amplitude. In general corrosion resistance (D-ave), corrosion uniformity (D-max/D-ave), crevice corrosion resistance (D-crev), paint corrosion resistance (bulk area ratio and maximum bulging amplitude) The evaluation criteria are shown in Table 3 below. (19) 1281505 Tables 4 and 5 below show the results of the uranium test.

-23- 1281505

I

e« Judgment ◎ Below 〇· 〇5mm Below 1·5 Below 〇.〇5mm Below 1 mm 〇0.05mm or more below 0.10mm 1.5 or more is less than 2.0 0. 05mm or more is less than 〇·l〇mm 1mm The above is less than 2mm < 0.10mm or more and less than 〇.50mm 2.0 or more and less than 2.5 0.10mm or more and less than 0.50mm 2mm or more and less than 5mm X 0.50mm or more and 2.5 or more and 0.50mm or more 5_ or more of the measurement item D-ave (mm D-max/D-ave L-_ ........._______________ D-crev (mm) Maximum bulging amplitude (mm) Evaluation characteristics Resistance to general corrosion Corrosion uniformity Crack resistance Corrosion resistance paint test piece < 〇 -24 1281505

I

Inch «Comprehensive judgment XX < k △~〇△~〇△~〇△~〇△~〇△~〇△~〇| △~〇I △~〇〇△~〇〇△~〇〇〇〇〇〇〇〇〇〇Corrosion Test II (electrical anti-corrosion-wet) paint corrosion resistance XX <\ 0 << 〇〇〇0 〇〇〇〇〇〇〇〇〇〇i corrosion uniformity XXX <1 <<>;<〇< 0 〇<] 〇<3 〇〇〇〇Resistant to general corrosion X <] < 〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇 corrosion test I ( Seawater spray·dry-wet) crevice corrosion resistance XXX 〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇corrosion uniformity XXX <3 <3 <3 <<〇<3<!〇<3〇<3 全面Resistant general corrosion X <3 <<< 0 <<3<><<1<<><<1<< No. one (N 00 00 ON 〇一<N 卜〇〇ON 1281505

I

s«

Comprehensive judgment l_ 〇~◎ 〇~◎ 〇~◎ 〇~◎ 〇~◎ 〇~◎ 〇~◎ 〇~◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ Corrosion test II (electrical anti-corrosion-wet)涂 耐 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ Corrosion test Η seawater spray - dry - wet) crevice corrosion resistance ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ No. 5Q OC a ο <N mm rn m VO m P: 00 m On m O •26- (23) 1281505 Based on the above results, the following can be considered. In the Νο. 2 sample of the steel material of the conventional corrosion-resistant steel (corresponding to JIS SMA490) and the No. 3 sample having a Se content lower than the lower limit 规定 specified in the present invention, the steel (C-Si-Mn steel) of the prior art is used. Compared with the No. 1 sample, the overall corrosion resistance was slightly improved, but other corrosion resistances did not reach the acceptable level.

On the other hand, it was found that in the sample (Ν〇·4 to 41) containing an appropriate amount of Se, the corrosion resistance was improved by the effect of S e , and all the corrosion resistance was superior to that of the conventional steel (No. 1), especially It has excellent crevice corrosion resistance and is preferably used as a corrosion resistant steel for shipbuilding. Further, it has been found that the corrosion resistance of the steel material is further improved by including various elements which improve corrosion resistance. In particular, in samples containing Ca or Mg (No. 10, 13, 3, and the like), it was found that the corrosion uniformity was further improved, and it was considered that the inhibition of the local pH lowering of these elements synergistically functions. Further, in the sample to which Cii, Cr, Ni or Ti was added, the effect of particularly reducing the maximum bulging range of the lacquer sample (No. 7, 8, 9, etc.) was found, and it was judged that the p rust densification of these elements was obtained. It is used as a result of stabilizing the rust of the cut portion and suppressing the progress of corrosion. Further, it has been found that corrosion resistance (Νο·21, 22, etc.) can be greatly improved by including Sb or Sn. Example 2 A steel material having the chemical composition shown in the following Tables 6 to 8 was melted in a converter, and various steel sheets were produced by continuous casting and hot rolling. The obtained steel sheet was cut and subjected to surface honing to finally obtain a test piece (test piece D) having a size of 300 x 300 x 25 (mm). Fig. 4 shows the appearance of the test piece D. 1281505

9"

_ u Φ chain m other 1 Zr: 0.15 1 W: 0.10 Nb: 0.05, Cd: 0.02 | 1 Lu 1 1 1 1 1 1 | BiO.0010 1 1 | V: 0.011 | 1 Nb: 0.003 1 1 1 1 B :0.0002,V:0.09 1 1 1 W) 1 1 1 » 1 1 1 1 1 1 1 Fen 1 1 1 1 | 0.0148 | 1 1 0.0013 1 0.0006 I 0.0092 1 0.0031 ΰ Trial 1 1 1 1 1 K 1 1 I 1 1 1 1 1 I 0.0029 I 1 1 I 0.0006 I 1 I 0.0024 I 1 | 0.0147 0.0019 1 ( 1 1 1 1 1 1 1 1 1 KI 1 1 I 0.0014 I 1 1 1 0.0005 1 1 1 0.0182 0.0023 1 0.0082 0.1495 ►3 1 1 垂1 1 1 1 1 1 1 1 1 1 I 0.026 I 1 1 1 I 0.0022 1 I 0.1496 I 0.0020 1 1 1 0.0005 0.0231 ο % 1 o.oi I 0.05 0.04 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 - 1 0.18 1 0.09 1 1 1 1 0.199 1 I 0.019 II 0.012 I 1 | o.oio I 1 I 0.005 I 1 0.015 I | 0.012 ! 1 I 0.009 1 1 I 0.049 II 0.005 II 0.020 0.009 0.18 1 0.06 1 0.10 0.02 I 0.09 I 1 0.36 I 1 | 0.29 I 1 L U2 I 0.32 II 0.59 II 5.00 II 0.22 II 0.31 I 丨0.12 1 I 0.23 1 I 0.15 I 0.25 | 0.26 II 0.35 II 0.39 I 0.21 \ 0.29 § 41W SS I 1 1 1 1 1 1 1 with 1 1 1 1 1 Who 1 : 1 1 1 t 1 1 1 1 1 U 1 0.80 0.02 0.18 1 1 1 Stupid 1 1 1 1 1 1 Male 1 1 I 1 1 1 1 1 1 1 1 0.05 1 0.10 0.02 I 0.38 I 00 ON 1 I 0.20 1 丨 0.19 I 0.21 II 0.48 I 1 1 I 0.30 I | 0.13 | I o .oi II 0.15 I 0.25 I 0.24 I | 0.35 ! I 0.34 0.20 0.29 <υ C/D 1 1 II 0.004 I 0.18 II 0.009 I 0.38 1 0.22 1 | 0.496 I 0.30 I 0.27 I 1 0.14 I | 0.40 I 1 0.15 1 1 0.21 1 0.18 I 0.32 I | 0.089 II 0.10 II 0.055 I 1 0-14 1 l 0.Π 1 0.33 0.12 < 0.052 0.055 1 0.041 0.058 I 0.053 | 0.041 I 0.044 I | 0.053 1 0.042 1 I 0.005 I 0.012 I 0.029 I | 0.040 II 0.037 II 0.032 1 I 0.019 I 0.018 1 0.032 1 I 0.036 I | 0.034 ! | 0.032 0.036 | 0.030 0.032 0.019 C 0.98 0.95 0.80 | s 1.22 I VO I 0.92 1 0.96 1 I 0.99 I CO oo | 0.99 I 1 1-41 1 rn I 1.22 I | 0.95 | | 0.98 | (N | 0.99 o 0.21 0.20 1 0.21 0.20 I 0.20 I 0.28 I 049 0·21 1 0.21 1 I 0.39 I 0.19 0.19 L〇.19 — | 0.21 | __ 0.21... | 0.21 | | 0.18 1 | 0.20 | 00 〇· 00 d 00 d OO 〇· 00 d OO o 00 o U 0.18 0.16” 0.14 0.10 IL 0.17J — 0.18 1 1 0.17 II 0.28 1 1 0: 17 1 | 0.18 I 10.16 II 0.16 I LojiJ I 0.16 I | 0.26 | | 0.18 1 | 0.16 | | 0.18 1 | 0.15 | | 0.18 i LQ-12 1 0.15 0.14 No. One (Ν rn Ό 卜 oo ON o II (N VO 00 00 Cs (N (N -28- (25) (25)

1281505 卜« Chemical composition of the sample (% by mass) | 1 Other 1 V: 0.49 1 1 1 1 1 1 a 1 Nb: 0.49 00 〇 od od Os < N q j6 C/D As: 0.14 Sn: 0.12 s O o J6 Z 〇s c> s Te: 0.18 Sb: 0.13, Sn: 0.20 5 O hi 2 Bu O ω K 5 Ο Sb: 0.19, Bi: 0.02 5 ο g ο Sb: 0.09, Bi: 0.49 B : 0.0009, Nb: 0.12 Sb: 0.14, Sn: 0.49, Te: 0.09 Sb: 0.14, Sn: 0.20 Bi: 0.19, Te: 0.47 Sb: 0.14, As: 0.1, Sn: 0.21, Bi: 〇.19, Te :0.47 0.0019 0.0019 1 1 0.0019 0.0038 0.0023 0.0009 0.0068 0.0010 0.0021 1 1 0.0022 1 0.0019 0.0012 0.0150 I 0.0039 1 0.0027 0.0049 0.0012 0.0019 0.0030 0.0030 0.0009 0.0022 0.0042 0.0021 0.0010 1 0.0019 1 0.0099 0.0023 0.0020 0.0020 Review 0.0020 0.0035 0.0099 0.0129 I 1 ι 0.0035 0.0035 0.0020 0.0129 0.0054 1 1 1 0.0097 1 1 ί 0.0028 1 0.0109 1 1 1 0.0981 osoo 1 0.0018 0.0092 1 1 0.0015 1 1 0.0032 1 1 0.0012 1 | 0.0020 1 1 1 0.0012 0.0116 1 0.0034 1 1 0.0922 0.0320 1 1 0.0049 I 1 0.0546 t 0.0028 » 1 〇S 1 I 1 0.08 1 0.12 1 1 1 4.99 I 0.98 0.01 1 1 0.18 0.03 1 1 1 2.98 0.09 0.11 • Review 1 1 P 0.09 0.012 1 0.009 0.015 0.050 I 0.012 1 I 0.019 I | 0.012 I 0.009 | 0.078 1 0.049 | 0.108 I [0.005 II 0.009 II 0.087 I 1 0.009 I 0.028 0.050 0.032 1 0.087 0.036 2 1 0.32 1 1 3.48 1 1 0.35 | 0.25 II 0.50 I | 0.29 I | 0.32 | 1 0.30 I 1 0.22 I 0.11 L· 1 1 I 0.02 I 1 1 0.15 I 1 0.35 II 0.27 I Ι 0.29 1 0.19 0.33 0.40 0.35 0.36 0.34 ό II 1 1 oil 1 | 0.09 | 0.22 | I 0.01 I 1 4.98 I o' 1 1 1 I 0.49 I 1 L〇^2 | 0.08 | II 0·12— 0.14 3.23 0.12 0.05 ΰ 1 1 00 CN 1 1 | 4.96 | ! 1 | 0.09 | 1 | 0.02 | ί 0.28 I | 0.01 | Γ〇:78^ 1 | 0.38 | 1 1 | 0.09 | 1 L〇"2j 1 0.18 1 0.15 1 1 0.15 1 0.32 1 g | 0.68 | | 0.35 | | 0.25 | | 0.23 1 | 0.29 | 1 0.30 | 1,0.21 1 _9" | 0.20 1 1 0.48 1 1 1 | 0.13 | lQ-31 1 ί 0.26 1 Γ〇.18 1 1 0.20 ι 1 0.28 ι 0.19 0.24 0.30 0.29 <L> [Λ11___1 L〇j6 1 0.39 | 1 0.05 | ί 0.48 | 0.18 | S〇,llJ 0.22 I 015 J 014 1 ;0.18 | 0.40 | 1 0.09 | ! o.io | L〇J5j [0.12 1 ο ! 0.005 1 ί 019 ι ί 0.15 1 0.29 0.12 0.23 0.19 < 1 0.041 1 1 0.044 1 [0.052 | | 0.041 1 1 0.046 1 1 0.043 1 I 0.038 1 | 0.036 1 [0.019 | 1 0.029 ] 1 0.040 1 1 0.049 | | 0.035 | I 0.022 | | 0.029 1 | 0.031 1 | 0.032 ] 1 0.031 1 丨0.098 1 1 0.019 ι 1 0.027 1 0.048 0.032 0.019 0.022 c 2 1 0.98 1 1 0.92 1 L〇-97_l I 0.96 | g LL?i_ g I 0.99 | 1 0.97 1 1 0.92 1 1 0.93 1 LliU [0.95 | | 0.98 1 Os 1 0.97 ι 1 0.99 1 g 1 0.18 1 1 0.20 IL〇i2U LMLJ ! 0.25 | L〇J9j L〇J9j I 0.25 I | 0.22 1 1 0.23 1 | 0.18 | 1 0.20 1 LM2J | 0.18 1 imj 1 0.25 1 1 0.38 1 1 0.20 1 1 0.18 1 0.31 0.17 0.49 0.21 υ LMLJ OJ-L | 0.04 1 L-gJl. 0.16 | 0.05 1 L9J-L | 0.13 1 0.18 | 0.16 1 0.18 0.27 0.29 0.16 L〇JU 1 0.09 1 ο 0.10 0.13 0.12 o 0.14 No. a % rn rn $ 00 r^i OS mo ζί rn tn 5 -29- 1281505

(ο/OSSBlu) ιφ^ιψ^δ挂Μ00«

Remarks: The invention: Other Zn: 0.045 so CN oo Zn : 0.002 Zn: 0.039 CN S pd ώ 00" od Zn: 0.005 Zn: 0.069 Zn: 0.050 Zn: 0.029 Zn: 0.017 Zn: 0.034 » 〇〇d g" oo N Sb: 0.05, Zn: 0.015 sogo Te: 0.03, Zn: 0.020 0> 00 0.012 0.006 0.23 d 0.053 0.29 0.091 0.088 o 0.025 0.099 0.044 0.071 0.13 0.094 1 1 1 1 0.0019 1 1 0.0055 1 1 0.0093 1 1 1 0.0037 1 f 1 1 0.0022 1 0.0059 1 1 1 1 1 0.0032 1 1 1 1 1 Reference 1 1 1 I 0.0009 1 1 1 1 1 1 1 1 1 1 1 1 1 0.0039 1 1 1 1 1 1 1 1 - 1 1 0.022 0.009 1 1 1 0.019 1 I 1 0.019 1 0.024 0.019 1 1 1 0.09 1 I 1 0.08 1 1 1 1 1 1 0.09 〇2 1 1 1 1 1 1 1 0.09 2.09 0.12 0.57 1 1 0.05 1 » 1 5 1 1 | 0.92 1 1 1 1 1 1 1 1 1 0.29 0.21 0.09 1 0.18 1 1 1 0.19 Kang 1 0.20 ! 1 0.59 s δ 1 0.30 0.33 0.52 1 0.19 i 1 1 1 0.29 1 0.32 1 0.88 q < 0.024 0.015 0.024 0.029 0.009 0.033 0.027 0.018 0.026 0.049 0.030 0.024 0.032 0.028 C sso 0.95 q 0.98 0.99 sgs 0.99 s 0.98 q Ιλ 0.28 0.21 0.20 0.19 1_ 1 0.21 0.20 0.32 0.17 0.18 0 .20 0.19 0.28 0.22 0.19 0.18 U Γνί d rn O ddd fM d Γ-1 o ON o 0.24 0.19 0.13 0.14 0.10 0.16 0.15 d <N ro »〇5; in 00 SSSS -30- (28) 1281505 The same method The corrosion product is removed. (1) The test piece D' was converted into the average plate thickness reduction amount D-ave (mm) by the weight change before and after the test, and the average 値' of the five test pieces was calculated to evaluate the overall rotability of each sample. In addition, using the stylus type three-dimensional shape measuring device, the maximum uranium depth D-max (mm) of the test piece D is normalized by the average thickness reduction [D-ave (mm)] (that is, the D-max is calculated). /Dave ), evaluation of the uniformity of the rot.

(2) For the test piece E, the maximum crevice corrosion depth on the side of the large test piece was measured by a stylus type three-dimensional shape measuring device D-crev (mm) ° (3) Test piece F (with a cut portion) for performing the painting treatment Using a caliper to measure the bulging amplitude of the coating film in the vertical direction of the cut, 'the maximum 値 of the five test pieces is defined as the maximum bulging amplitude. The comprehensive corrosion resistance (average plate reduction: D_ave), corrosion uniformity (D-max/D-ave), crevice corrosion resistance (D-crev), paint corrosion resistance (maximum bulging width) The evaluation criteria are shown in Table 9 below. Tables 10 to 12 below show the results of the corrosion test. 1281505 i

Judgment ◎ Below 〇·l〇mm Below 1.5 Lower than 0.10mm Below 1 mm 〇0.10mm or more and less than 0.50mm 1.5 or more and less than 2.0 0·10mm or more and less than 0.50mm 1mm or more and less than 2mm <0.50mm The above is less than 3.00mm 2.0 or more and less than 5.0 0.50mm or more and less than 3.00mm 2mm or more and less than l〇mm X ! 3.00mm or more and 5.0 or more of 3.00mm or more and 10mm or more! Measurement item D-ave(mm) D-max/D -ave D-crev(mm) Maximum bulging amplitude (mm) ί Evaluation characteristics Corrosion resistance Corrosion resistance Rust resistance Corrosion resistance paint test piece Q Uh 19) -33- 1281505

I

Ol«

i: < ίπ 51 X < i < i < k <] 〇〇〇〇〇〇〇〇 ◎ l 〇 ◎ l 〇 ◎ l 〇 ◎ } 〇 ◎ l 〇 ◎ l 〇 ◎ l 〇 ◎ ? 〇 l l l l l l } } } } } } } } } & & X X X X X X X X X X ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ΠΤ gt <<]<]<3〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇陌#i mm X <<<< 〇〇〇〇〇〇 〇〇〇〇〇〇〇〇〇〇〇〇〇〇m 锢it _ #i| XXXX <〇〇〇〇<3 〇〇〇〇〇◎ ◎ 〇◎ ◎ ◎ ◎ ◎ ◎ ◎ ® ΠΤ) X <<>〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇陋靼i<W& mm X <3 < X 〇〇〇〇〇〇〇〇〇 〇〇〇〇〇〇〇〇〇〇〇〇mm XXXX < 〇〇〇〇〇〇〇〇 ◎ ◎ 〇〇 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ Yin Qi Si鳕切X <<<3 〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇mm making mm X <] <<<<> 〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇1 ΓΜ m VO 卜 00 Os o one (N m inch in VO oo Os fN -34- 1281505

一 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎背面 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ Wall paint corrosion resistance ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ 底板 底板 底板 底板 底板 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ 耐 耐 耐 耐 耐◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ No. $ 00 (N (N m Pi oc On O § -35- 1281505 _

Distillation <Π ◎ } 〇 ◎ 〇 ◎ 1 〇 ◎ 1 〇 ◎ l 〇 ◎ l 〇 ◎ } 〇 ◎ 1 〇 ◎ 1 〇 ◎ l 〇 ◎ l 〇 ◎ l 〇 ◎ ◎ ◎ 1rS 驷m B- mm 〇〇 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ 晅 mm mm 〇〇〇〇〇〇〇〇〇〇〇〇 ◎ ◎ ◎ 浙录, 激Ig ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ EsH sanctions mu 〇〇 ◎ ◎ 〇〇〇 ◎ 〇〇〇 〇 ◎ ◎ ◎ m 杂 mm 〇〇〇〇〇〇 ◎ ◎ 〇〇〇 ◎ ◎ ◎ ◎ -m _ ; 〇〇〇〇〇〇〇〇 ◎ ◎ ◎ ◎ ◎ ◎ ◎ mm mm mm 〇〇〇〇〇 ◎ ◎ ◎ i ?: < N 5; VO in 00 ON s S s -36- (33) 1281505 According to the above results, the following can be considered. In the conventional corrosion resistant steel (No. 2 to 4), the general corrosion resistance and the corrosion uniformity are slightly improved compared with the conventional steel No. 1 sample, but in terms of crevice corrosion resistance or paint corrosion resistance For the previous steel level, it is still insufficient as corrosion resistant steel. Further, in the sample No. 5 containing a small amount of Se, the crack-resistant uranium resistance was slightly improved, but since the Se content was less than the lower limit 规定 prescribed by the present invention, it was not effective.

On the other hand, it was found that in the sample (No. 6 to 65) containing an appropriate amount of Se, the corrosion resistance was improved by the effect of S e , and all the corrosion resistance was superior to that of the conventional steel (No. 1), and it was particularly excellent. The crevice corrosion resistance is preferably used as a corrosion resistant steel for shipbuilding. It has been found that, in particular, by containing various corrosion-improving elements (Cu, Cr, Co, Ni, Ti, etc.), in addition to resistance to general corrosion and corrosion uniformity, crevice corrosion resistance or paint corrosion resistance is greatly improved. Such an improvement effect of the corrosion resistance is judged to be an effect of suppressing the local pH reduction in the formation of Se, and synergistically acting on the formation of the above elements. In addition, it has been found that in a sample containing a suitable amount of La, Ce, or the like (Νο·14, 15 5, 18 to 27, etc.), it is found that the crevice corrosion resistance of the bottom plate is further improved, and a sample containing Ca or Mg in an appropriate amount is found ( No. 16, 17, 19 to 27, etc., greatly improve the paint corrosion resistance of the wall surface. Such an effect is presumed to promote the rust densification of Cu, Cr, Ni, and Ti formed by La, Ce, Ca, and Mg, and to promote the effect of suppressing the local pH reduction by the formation of Se. Mo is contained in an appropriate amount, and it also plays a role in improving the corrosion uniformity of the wall surface (for example, No. 31, 34, 35, etc.), and it is considered that the homogenization of the rust densification formed by the element acts. -37- (34) 1281505 In addition, by containing Sb, As, Sn, Bi or Te, it is obvious that the overall corrosion resistance is greatly improved (Νο·37~40, etc.), and it is inferred that these elements contribute to the above elements. The result of rust densification or pH mitigation. ~ In addition, in the sample (N 〇 . 5 1 , 5 2, 5 3 , etc.) to which Ζ η is added, the result also improves paint corrosion resistance or crevice corrosion resistance. For example, in addition to Cu, Ni, and Se, the maximum bulging amplitude of the test piece F on the wall surface is reduced as compared with the Νο·9 containing only Cu, Ni, and Se, and the result is improved. Paint corrosion resistance. As a result of the improvement of the corrosion resistance by the addition of Zn, it is estimated that the deposition film of zinc chloride or zinc sulfide is formed on the surface of the steel material, and the steel substrate is separated from the water in the environment to suppress the effect of corrosion. Example 3 Steel materials having the chemical composition shown in Table 13 below were smelted in a converter, and various steel sheets were produced by continuous casting and hot rolling. The obtained steel sheet was cut and subjected to surface honing to finally obtain a test piece G' having a size of 300 x 1 5 0 x 25 (mm). The solder joint material having the chemical composition shown in Table 14 was used for the creep arc welding, and the joint test piece G (Fig. 7) shown in the figure was produced by two D'. In addition, all the welding materials have a wire diameter of 4.8 mm and a groove shape of a V shape. The heat input is suitably adjusted within the range of 1 to 10 kJ/mm. Further, two small test pieces of 6 Ο X 6 Ο X 5 (mm ) were brought into contact with the welded portion of the test piece G to form a test piece 形成 contact (Fig. 8) in which the crevice portion was formed. The chemical composition of the small test piece for forming a crack was the same as that of the test piece D, and the surface finishing was also the same as that of the above test piece G, and it was defined as surface honing. Further, a hole of Φ 1 was opened at the center of the small test piece, and the maximum crevice corrosion on the side of the large test piece was measured using a stylus type three-dimensional shape measuring device on the substrate -38-(36) 1281505 (2) on the test piece Η. Depth D-crev ( mm ). (3) The test piece I (having a cut portion) for performing the painting treatment, and measuring the bulging amplitude (mm) of the coating film in the direction perpendicular to the cut portion by a caliper; defining the maximum 値 of the five test pieces as the maximum drum Out of range. The general corrosion resistance (average plate reduction: D-ave), corrosion uniformity (D-max/D-ave), crevice corrosion resistance (D-crev), paint corrosion resistance (maximum bulging The evaluation criteria of the amplitude are exactly the same as the evaluation criteria in the second embodiment shown in the above Table 9. Table 15 below shows the results of the corrosion test. However, in Table 15, I(Se) represents the Se content of the deposited metal / the Se content of the base material. The Se content on the welded portion did not conform to No. 66 of the relational formula (1), and in particular, the crack-resistant uranium resistance could not be satisfied. This is the result of corrosion progress on the portion of the weld metal. On the other hand, in the N 〇 · 6 7 to 7 5 in accordance with the relationship (1), it was found that all of the uranium properties were improved in uranium resistance, and as a result, it was found to be preferable as the corrosion resistance of the welded structure. Further, in the present embodiment, the welded portion by the hidden arc welding method is used as the evaluation object, but the same effect can be obtained by other welding methods such as the coating electric welding method or the electroslag welding method. In addition, the welding materials used are not limited to Table 14. (S) -40- 1281505

Ίι —1^1—el« Remarks Other 1 B of the present invention B: 0.0009 1 1 1 Bi: 0.09 Te: 0.08, Nb: 0.012 As: 0.02 Zn: 0.029 <1> 00 0.025 0.059 0.092 0.076 0.24 0.049 0.008 0.010 0.39 1 1 0.0051 1 0.0039 1 1 0.0055 1 1 1 1 1 1 I 0.0028 1 1 涵 涵1 1 1 1 1 1 0.0009 1 jd 1 1 1 1 0.0019 1 0.0039 1 1 P 1 0.019 0.022 I 1 1 0.048 1 1 1 1 1 0.09 1 0.11 1 1 1 os 1 1 1 0.08 0.19 1 1 0.98 0.03 ύ 1 1 1 1 1 1 0.22 1 1 1 0.70 1 0.09 0.36 0.24 1 0.06 1.05 1 0.68 0.33 1 0.35 0.20 1 0.05 0.99 < 0.014 0.021 0.020 0.017 0.011 0.039 0.009 0.018 i 0.018 cs 1.11 ο 0.99 0.98 (N VO Ιλ 0.21 0.22 0.25 0.17 0.18 0.23 0.19 0.24 0.22 〇0.11 0.12 0.11 0.12 0.12 0.15 0.10 0.11 0.10 di (N inch 5 VD s 卜 S 00 o. 2 -1ε- ΦΙ^ΙΙΙΕΙ^ϋ IX IX rest remaining 1 remaining I remaining 1 remaining 1 remaining 1 remaining I (3⁄4 ί 0.005 0.019 0.14 0.032 0.11 0.92 0.038 0.019 0.012 0.61 1 1.28 1.48 令 · 1.49 ON P; 0.99 1.41 0.21 | 0.20 1 (four) I | 0.21 I | 0.22 I 1 0.28 1 0.17 0.20 0.21 1 0.22 υ 0.10 0.11 I 0.12 1 0.12 I 0.12 0.14 0.12 丨0.14" I 0.09 i 0.12 d rj v〇 00 ON | W10 | -41 1281505

镒uj Distillation r Ϊ rt <lnfc! 〇〇〇 ◎ l 〇Ο ◎ l 〇 ◎ ◎ ◎ ◎ 〇〇 〇〇 〇 ◎ ◎ ◎ ◎ ◎ mm X 〇〇〇〇 ◎ ◎ ◎ ◎ ◎ rr >< 〇〇〇〇〇 ◎ ◎ ◎ ◎ mm < 〇〇〇〇〇 ◎ ◎ ◎ ◎ 00 (N o (NO oc O) d (N ΓΊ (N 〇Os 00 〇 · Gong ts St (N m 爹»〇 VO 00 ON Multi O 5 1? 03 si fN ss inch s VO 2 s 00 s ON S 6 Z s oc $ o (NP JJ JO (39) 1281505 In summary, the steel of the present invention, the oil film defect portion The local corrosion on the upper surface, the crevice corrosion of the structural crack portion, or the corrosion of the damaged portion of the coating film can exhibit excellent corrosion resistance, and can be suitably used as a corrosion resistant steel for oil tankers. [Schematic Description of the Drawing] Fig. 1 is a view showing an embodiment. 1 is an explanatory view of the external shape of the test piece A used in the corrosion resistance test 1.

Fig. 2 is an explanatory view showing the appearance of the test piece B used in the corrosion resistance test I of the first embodiment. Fig. 3 is an explanatory view showing the appearance of the test piece C used in the tamper resistance test II of the first embodiment. Fig. 4 is an explanatory view showing the appearance of the test piece D used in the corrosion resistance test of the second embodiment. Fig. 5 is an explanatory view showing the shape of the test piece E used in the corrosion resistance test of the second embodiment. Fig. 6 is an explanatory view showing the appearance of the test piece F used in the corrosion resistance test of the second embodiment. Fig. 7 is an explanatory view showing the appearance of the test piece 所 used in the corrosion resistance test of Example 3. Fig. 8 is an explanatory view showing the appearance of the test piece 所 used in the corrosion resistance test of Example 3. Fig. 9 is an explanatory view showing the appearance of the test piece 1 used in the corrosion resistance test of Example 3. -43-

Claims (1)

1281505 (1) X. Patent application No. 94120015 Patent application Amendment of Chinese patent application scope, seven jurisdictions i: January 15, 1996, revised the ship's steel with excellent corrosion resistance, characterized by There are: C: 0.01 to 0.30% (indicating mass %, the same below), Si: 0.01 to 2.0%, Μη: 0.01 to 2.0%, A1: 0.005 to 0.10%, and Se: 0.005 to 0.50%, and the rest It consists of Fe and unavoidable impurities. 2 · For shipbuilding steels according to item 1 of the patent application, which also contains: from Cu: 0.01 to 5.0%, Cr: 0.01 to 5.0%, Co: 0.01 to 5.0%, Ni: 0.0 1 to 5.0% and Ti : 0.005 to 0.20% of the selected group of more than one. 3. The steel material for ships of claim 1 or 2, which further comprises from La: 0.0005 to 0.15%, Ce: 0.0005 to 0.15%, Ca: 0.0005 to 0.015%, and Mg: 0.0005 to 0.015%. More than one of the groups selected. 4. For steel products for ships of the first or second patent scope, which also contains Mo: 0.01 to 5.0%. 5. For steel products for ships of the first or second patent scope, which also contain Sb: 0.01 to 0.5%, As: 0_01 to 〇_5%, Sn: 0.01 to 0.5%, Bi: 0.0 1 to 0.5 %, Te: One or more selected from the group consisting of 0.0 1 to 0.5%. 6. The steel material for ships of claim 1 or 2, further comprising a group consisting of B: 0.0001 to 0·01 〇%, V ··0.01 to 0.50%, and Nb: 0.003 to 0.50%. More than one choice. (2) 1281505 7, such as the ship's steel for the first or second patent application, which also contains Zn: 0.001 to 〇.1〇% by mass. 8 · A welded structure for ships with excellent corrosion resistance, characterized by: welding a steel structure as described in the first, second, third, fourth, fifth, sixth or seventh aspect of the patent application In the case of S e, the relationship is as follows: Se content of the 0.30S deposited metal / Se content of the base material ^ 3.0 9 • For steel materials for ships of the first or second patent application, which are used as materials for petroleum liquid fuel tanks. 1 0. A welded structure for ships as in claim 8 of the patent application, in which a material used as a petroleum liquid fuel tank is used. -2-