TWI374195B - - Google Patents

Description

1374195 IX. INSTRUCTIONS OF THE INVENTION [Technical Fields According to the Invention] The present invention relates to a steel material excellent in corrosion resistance, a building, an iron tower, a bridge, a construction machine, a steel pipe, and a material, and is particularly suitable for use in a large amount of sulfur oxides. A material for steel structures with excellent corrosion resistance. [Prior Art] Generally, in the heavy chemical industry, the environment contaminated by the atmosphere of burning coal and dust 'containing sulfur and sulfur, volcanic zones and other causes of severe corrosion of steel causes a weak acidic environment. As a suitable ring, alloy steel has been used in the past. The steel is improved in corrosion resistance by containing Cr and Ni, and is put into practical use in various forms of stainless steel. Usually, the high-valent element has a Cr content of 13% by mass or more, which is very high, so it is rarely applied to a structure or a structural surface. Regarding a corrosion-resistant steel material, in addition to stainless steel, low-alloy steel which has been subjected to corrosion by corrosion is used. Low alloy steel: weather resistant steel of Cr, Cu, P, etc. and contains Cr, Cu, and steel. Weather-resistant steel and seawater-resistant steel exhibit excellent corrosion resistance in the atmosphere. These low-alloy steels are cheaper than stainless steel and resistant to corrosion, so they are often used as structural members. However, it is suitable for hot springs that produce a large amount of oxysulfide as an atmospheric pollution environment of steel structures such as civil storage tanks. It is believed to be a material for uranium-resistant materials of sulfur oxidation, and it has long been mentioned. Cost variants and more. The other party also knows that it is not possible to generate weather resistance by protecting λ: fractionation = water-containing environment containing Mo, etc., and the energy in seawater is superior to ordinary steel, in an acid rain environment or -5 - 1374195. SOx environment. Steel has a special protective rust, so _ can not achieve the desired corrosion resistance. In addition, there is a kind of "sulfur-resistant steel j, which belongs to one of low-alloy corrosion-resistant steels, which is composed of adding Cu to steel and further adding a small amount of auxiliary elements (Sb, Sn, etc.). However, since 1975, Japan The concentration of S02 in the atmosphere is greatly reduced. The above-mentioned sulfur oxides cause severe corrosion, leaving only hot springs, etc., so no special materials have been developed. φ As mentioned above, in order to improve the corrosion resistance of iron, the common method is Add to

Corrosion improving elements such as Cr, Cu, and Ni. In general, the higher the amount of addition, the higher the corrosion resistance is obtained. However, as the amount of addition increases, the cutting property, mechanical properties, and weldability are often deteriorated, and the material cost is also increased. Therefore, it is preferable to suppress the element as much as possible. The amount added. In this way, there is a contradiction between the improvement of corrosion resistance and the characteristics of steel and material and the cost effect. In order to fully satisfy the two, although there are many discussions, they have to compromise at a certain balance point. On the other hand, equipment exposed to flue gases, chimneys, boiler air preheaters, etc., which are exposed to the combustion of heavy oil, coal, and garbage, can cause problems in the sulfuric acid dew point corrosive environment, using sulfuric acid dew point. Corrosive steel. When a sulfur-containing fuel is burned, SOx is generated in the exhaust gas, which is combined with water in the exhaust gas to produce sulfuric acid. When the exhaust gas temperature reaches a dew point of sulfuric acid, the sulfuric acid gas condenses and corrodes the steel. In the steel used in the sulfuric acid dew point corrosion environment, sulfuric acid dew point corrosion resistant steel which exhibits corrosion resistance in a sulfuric acid environment has been developed. It is generally practical to add a low alloy steel which is composed of Sb and Cu which are resistant to sulfuric acid corrosion. In recent years, it has also been proposed to add a low C-low S i -C u to the sulfuric acid dew point corrosion resistant steel (patent (£) -6 - 1374195 document 1). However, in recent years, with the rapid economic development in East Asia, energy demand has increased rapidly. Especially in mainland China, the production and consumption of coal has increased sharply. The emission of sulfur dioxide (S 02 ) is estimated to be 20 million tons per year and more than 20 times that of Japan. The atmospheric pollution in mainland China has been transported over long distances through atmospheric circulation, and in Japan it has also been observed to reduce the area of acid rain (below pH 4.5 due to SOx). However, the conventional steel material does not have excellent bare uranium resistance in an air pollution environment in which a large amount of sulfur oxide is generated by acid rain having a pH of 4.5 or less. Sexuality does not allow sufficient high corrosion resistance in response to the use of steel structures such as civil engineering and building 'iron towers, bridges, construction machinery, steel pipes, and storage tanks. In particular, steel materials used in Japan cannot provide sufficient corrosion resistance in response to such applications. Accordingly, an object of the present invention is to provide a steel material which exhibits excellent corrosion resistance even in an air pollution environment in which a large amount of sulfur oxide is generated by acid rain having a pH of 4.5 or less. In view of the foregoing, in order to solve the above problems, the present invention provides a steel material having excellent corrosion resistance as in the following 1 to 3. 1. Steels that meet the following (A) (B) (C) corrosion resistance: (A) In terms of mass%, the required components include c: 0.0 2 to 0.1 5 %,

Si: 0.10 to ι·〇%, Μη: 0.1 to 1.5%, S: 0.02 to 0.5%, Ti: 1374195 0.02 to 0.15%, Ca: 0.0001 to 0.01%, and Α1: 〇·〇1 to 0.50% t Further contains It is selected from at least one of Cu: 0.05 to 3.0% and Ni: 〇_〇5 to 6_0%; the remainder is composed of Fe and unavoidable impurities; and the contents of Ni, Cu, S, and Ti have the following formula (1) C (Ni + 4.5xCu)xSx2500xTi>5) (1) The relationship represented by: (B) The surface is covered with rust, and the rust contains S: 〇·3 to 5.0% by mass, and further contains a compound selected from Ti and Cu. At least one of Ni, Nb, Zr, and V is 0.5 to 10.0% by mass; (C) the grain size determined by the X-ray diffraction method for forming the 泠-FeOOH component on the surface is less than 5 Onm The rust layer and the specific surface area determined by the molecular adsorption method of the rust layer are l〇m 2 /g or more. 2. The steel material having excellent corrosion resistance as described in the above 1. further contains La: 0.0001 to 0.05% by mass, Ce: 0.0001 to 〇.〇5% by mass, Mg: 0.0001 to 〇_〇5% by mass, Mo : 0.05 to 3.0 mass%, :Nb: 0.005 to 0_5 mass%, V: 0·01 to 0.5 mass%, Zr: 0.005 to 0.5 mass%' B: 0.0003 to 0.003 mass%, and W: 0.05 to 3.0 mass% At least one of them. 3. The fraction of the amorphous component obtained by the X-ray diffraction method of the rust generated on the surface of the steel material having excellent corrosion resistance described in the above-mentioned 1 or 2. is 30% by mass or more, and 泠- The fraction of the FeOOH component was 30% by mass or less, and the embroidering fraction was a-FeOOH/Y-FeOOH> -8- 1374195 According to the steel of the above 1. In the air pollution environment, since the content of Cu, Ti and S has a specific relationship represented by the formula (1), a protective film composed of a unique insoluble sulfide film is formed, and Good corrosion resistance. That is, under atmospheric pollution containing a large amount of sulfur oxides, Ni, Cu, and Ti can be rust-producing, Cu: stable amorphous rust formation promotion, and α-rust generation promotion in normal atmospheric corrosion; T: stable The iS rust generation is controlled), and the sulfur-soluble sulphide is formed in the SOx environment to form a corrosion-resistant coating film. Further, by complying with the condition (B), the reproducibility is excellent in the high resistance in a corrosive environment. In addition, by complying with the above condition (C), even if the chloride ring contains a large amount of sulfur oxides, the atmosphere is polluted by the environment, and the corrosion ring of the environment does not cause flow rust and peeling rust, and can exhibit excellent performance. The uranium-resistance is further improved in corrosion resistance by containing at least one of a specific amount of E, Ce, Mg, Mo, Nb'V, Zr, B, and W in accordance with the steel of the above 2. Among them, La, Ce, and Mg can suppress the pH lowering of the corrosion end portion and suppress the formation of MnS (the starting point of corrosion and lower the weather resistance). In addition, Nb, V, Mo, and B are ribbed to promote the formation of protective rust, and Nb and V are quenched, which contributes to the improvement of strength. B also has the purpose of improving hardenability. According to the steel of the above 3., in the rust generated on the surface, the fraction of amorphous rust having an increase in corrosion resistance is 30% by mass or more, and the fraction of crystalline rust (call-FeOOH component) at the corrosion starting point is Below 30%, the rust fraction is in accordance with a -FeOOH / y-FeOOH > 0.6,

Ni, the environment can be obtained (Ni: it does not have the above-mentioned erosive or subtropical properties. It can be used as the pore Zr, and it can be used to help the quality. Therefore, -9- 1374195 can exert excellent corrosion resistance even if In the SOx environment, the protective rust can be maintained. The steel of the present invention can exhibit excellent corrosion resistance even in an air pollution environment in which a large amount of sulfur oxide is generated by acid rain of ρΗ4·5 or less. Materials for steel structures such as civil engineering, buildings, iron towers, bridges, construction machinery, steel pipes, storage tanks, etc., are particularly suitable for materials of steel structures requiring excellent corrosion resistance in an air pollution environment containing a large amount of sulfur oxides. Hereinafter, the steel material excellent in corrosion resistance of the present invention (hereinafter referred to as "steel material of the present invention") will be described in detail. In the present specification, all percentages defined by mass, etc., and percentages defined by weight respectively represent the same meaning. The steel material is an essential component of C, S i, Mn, S, Ti, Ca, and Α1, and contains at least one selected from the group consisting of Cu and Ni. The balance is Fe and an unavoidable impurity, and the content of Ni, Cu, S, and Ti has a specific relationship. The following describes the range of the content of each component constituting the steel material of the present invention, and the range of the number The reason for limitation, and the relationship between the contents of Ni, Cu, S, and Ti. C is a nutrient that contributes to the improvement of steel strength, and is an effective element for ensuring strength of 390 to 630 N/mm2 or higher, when C content When the content exceeds 0.15 mass%, the weldability and bare weatherability of the steel may deteriorate. On the other hand, when the C content is less than 0.02% by mass, it is difficult to ensure that the above strength is -10-1,195,195. The C content is set to 0.02 to 0 to 15% by mass, preferably 0.04 to 0.10% by mass.

Si is an element which is ribbed in the deoxidation and solid-solution strengthening of molten steel, and promotes the formation of a dense and stable rust layer, and has an effect of improving corrosion resistance such as bare weather resistance. However, when the Si content is less than 0.10% by mass, the equivalent is insufficient. Further, when the Si content exceeds 1.0% by mass, the weldability may be deteriorated. From this viewpoint, the Si content is set to 0.10 to 1.0% by mass, preferably 0.2 to 0.8% by mass. Μη is an element which contributes to the improvement of the strength of the steel, and is an effective element which replaces C to ensure a strength of 390 to 630 N/mm2 or higher, but when the Μη content exceeds 1.5% by mass, a large amount of MnS is generated in the steel. It may cause deterioration of corrosion resistance such as bare weather resistance. Further, when the Μη content is less than 0.1% by mass, it is difficult to secure the steel strength. From this viewpoint, the Μη content is set to 0.1 to 1.5% by mass, preferably 0.3 to 1.3% by mass. When the S content is too large, a large amount of corrosion starting points such as FeS and MnS are formed, and an element which is expected to reduce the content is conventionally used. However, in the steel material of the present invention, it can be formed in the SOx environment by coexisting with Cu, Ni, and Ti. Insoluble sulfides form a corrosion-resistant coating, which is an element that contributes to the improvement of corrosion resistance. However, when the content is more than 0.5% by mass, not only the mechanical properties are deteriorated, but also FeS, MnS or the like which is a starting point of corrosion is generated in the steel, and the formation of the above-mentioned stable rust layer is hindered, and the corrosion resistance may be deteriorated. Further, in the case where the content of Ni or the like is excessive, a low-melting NiS compound is precipitated at the grain boundary of the weld metal by the reaction with S, and the ductility of the grain boundary of the solidified metal is likely to be deteriorated. From this point of view, as long as the S content is 0.5 mass% or less; S) -11 - 1374195 or less, the above-mentioned low melting point NiS compound ' is not precipitated and 0 mesh contains a larger amount of Ni. Thus, the S content is set to 0.02 to 0.5 mass ° /. It is preferably 0.02 to 0.3% by mass.

Ti, which has the same effect as Cu and Ni, has an advantageous effect of promoting densification of rust formation to form a stable rust layer, and has excellent feed resistance. Therefore, it is very important in the present invention to add an element. In particular, it is an inhibitory component of yS-FeOOH which is produced in the sea or the marine environment and exhibits excellent effects when added in combination with Cu and Ni. At the same time, it has the advantage of purifying steel. This effect can be obtained by adding 〇·〇2 mass% or more, and the effect is remarkably improved when the amount of 〇.〇3 mass °/〇 is exceeded. However, when the excess is added, the effect tends to be saturated, resulting in poor economy. Further, it may cause an obstacle at the time of welding, so the upper limit of Ti is set to 0.15 mass%. In addition, although the above-mentioned matter is a case of a corrosion product of steel, the effect of improving the compactness is also contained in the corrosion product of zinc by the inclusion of Ti. Therefore, since the steel itself and the corrosion products of iron and zinc have an effect of improving corrosion resistance, it is also an important element based on this viewpoint. Therefore, the Ti content is set to 0.02 to 0.15 mass%, preferably 0.03 to 0.10 mass%.

Ca is an element that plays an important role in the corrosion of the defect portion of the coating film. That is, Ca has a function of buffering the pH drop in the coating film defect, and in the process of corrosion under the coating film, a slight melting is generated as the iron corrosion reaction is alkaline (the melt pH buffer of the anode melting end portion) effect). Therefore, 'Ca has an effect of suppressing crevice corrosion of the defect portion of the coating film, and raises the pH during melting to exhibit the effect of suppressing crevice corrosion. That is, in the front end portion of the corrosion -12- 1374195, if there is a Ca which can raise the pH during the melting of the iron, the crevice corrosion can be suppressed. From this viewpoint, the Ca content is set to 0.0001 to 0.01% by mass, preferably 0.0003 to 0.005% by mass. A1, by compounding with Ti, can further promote the formation of a stable rust layer, thereby further improving corrosion resistance. In addition, A1 also has the effect of improving the weldability. Furthermore, A1, as a deoxidizing element of molten steel, captures molten oxygen and prevents the occurrence of blowholes, which contributes to the initial rise of steel. Further, A1 forms an oxide on the surface layer, but the oxide particles of A1 are small and have few voids, and form a very stable dense scale, which contributes to laser cutting property. When the A1 content is less than 0.01% by mass, the effects are not sufficiently exhibited. On the other hand, when the A1 content exceeds 0.5% by mass, the effect of improving the corrosion resistance caused by the formation of the stable rust layer is saturated, but instead The weldability is deteriorated, or the toughness of the steel is deteriorated due to an increase in alumina-based inclusions. From this point of view, the A1 content is preferably from 0.01 to 0.5% by mass, more preferably from 0.1 to 0.5% by mass. Further, the steel material of the present invention contains at least one selected from the group consisting of Cu and Ni in addition to C, Si, Mn, S, Ti, Ca, and A1, and is composed of Fe and unavoidable impurities. In the steel material of the present invention, Cu is an element which contributes to improvement in corrosion resistance and weldability. That is, in terms of electrochemistry, Cu is an element which is more noble than iron, and can densify rust generated on the steel surface, promotes formation of a stable rust layer, and improves corrosion resistance such as weather resistance. At the same time, it helps to improve the weldability. In addition, although some of the surface layer will become an oxide, it is mostly concentrated in a solid solution state, and the surface scale is densified and the adhesion is improved, which is helpful for (S) -13 - 1374195 in laser cutting property. Upgrade. When the Cu content is less than 0.05% by mass, the effect of improving the corrosion resistance cannot be sufficiently exhibited. However, when the Cu content is more than 3.0% by mass, the effect of improving the corrosion resistance is saturated, and when the steel material is produced and subjected to hot rolling or the like, it may be caused. Embrittlement of materials (hereinafter also referred to as hot work embrittlement). From this point of view, in order to more reliably suppress the occurrence of the above-described hot work embrittlement, the Cu content is set to 0.05 to 3.0% by mass, preferably 0.3 to 1.5% by mass.

Ni is an element that contributes to corrosion resistance and weldability. Ni is the same as in the case of Cu, and it can densify the rust generated on the steel surface, promote the formation of a stable recording layer, improve the corrosion resistance such as weather resistance, and contribute to the improvement of the weldability. Further, 'Ni has the above-described effect of suppressing the hot work embrittlement. Therefore, by multiplying Ni and Cu together, the synergistic effect of both the corrosion resistance improving effect and the hot working brittleness suppressing effect can be expected. Ni is the same as Cu. Although some of the surface layer is an oxide, it is concentrated in a solid solution state, and the surface scale is densified and the adhesion is improved. This contributes to the laser cutting property. Improvement. When the Ni content is less than 0.05% by mass, the effect of improving the corrosion resistance cannot be sufficiently exerted. However, when the Ni content exceeds 6.0% by mass, the solid-liquid solidification temperature range of the complete Worthite iron structure becomes wider, which contributes to the low-melting impurity element toward the branch. The segregation of the grain boundary and the reaction with S precipitates a low-melting NiS compound at the grain boundary of the weld metal, which deteriorates the ductility of the grain boundary of the solidified metal, and further adversely affects the high-temperature crack resistance. Based on this point of view, in the case of containing Ni, the Ni content is set to be 0.05 to 6.0% by mass, preferably 0.5 to 5.0% by mass, more preferably 1.? to 3.0% by mass.

-14- 1374195 In the steel material of the present invention, it is necessary to have a relationship represented by the formula (1) between the contents of Ni, Cu, Si, and Ti. When the contents of Ni, Cu, Si and Ti are in accordance with the relationship of the formula (1), S and Ni, Cu and Ti form an insoluble sulfide film in the SOx environment to form a corrosion-resistant coating film, thereby obtaining high corrosion resistance. . (Ni+4.5xCu)xSx2500xTi>5 (1) In the steel material of the present invention, the following effects (a) to (d) can be exerted, wherein (a): generation of amorphous rust having good protection Promotion, (b): promotion of the formation of α rust with good protection and thermodynamic stability, (c): inhibition of the formation of corrosion resistance/3 rust generated in the chloride environment, (d): oxidation of a large amount of sulfur Corrosion resistance that enhances corrosion resistance in the atmosphere and dust environment (SOx environment) promotes the formation of the film. Therefore, the inventors of the present application have repeatedly conducted various experiments to know that the amount of each element required to conform to all items (a) to (d) must conform to the above formula (1) » In the steel of the present invention, Ni , Cu and Ti, can suppress the formation of rust under normal atmospheric corrosion (Ni, Cu: production of stable amorphous rust, promotion of α rust generation; Ti: inhibition of unstable formation of rust), In the range of 0.02 to 0.5% by mass of the S content, by coexisting with Ni, Cu, and Ti, it is possible to generate a large amount of sulfur oxides and dust in an atmosphere-polluting environment (SOx environment) due to combustion of coal in a heavy chemical industry zone. The corrosion resistance of the insoluble sulfide is increased to enhance the film, and excellent corrosion resistance is obtained. Further, in the steel material of the present invention, in order to further improve the corrosion resistance, it is preferred to contain at least one selected from the group consisting of La, Ce, Mg, Mo, Nb, V, Zr, B and W -15-1374195.

The action of La, Ce, and Mg is such that the pH of the corrosion end portion can be suppressed from being lowered, and the formation of MnS (which becomes a starting point of pitting corrosion and lowers weather resistance) can be suppressed. Furthermore, in the initial stage of corrosion, Zn and Fe have the effect of stabilizing corrosion. Therefore, in the case of containing La, Ce, or Mg, the La content is preferably 0.0001 to 0.05% by mass, the Ce content is preferably 0.0001 to 0.05% by mass, and the Mg content is preferably 0.0001 to 0.05% by mass.

Mo, Nb, V, Zr and B help promote the formation of protective rust, and Nb and V can improve the hardenability and contribute to the improvement of strength. B also has the effect of improving hardenability. Therefore, based on the improvement of corrosion resistance, in the case of containing Mo, Nb, V, Zr or B, the Mo content is preferably from 0.05 to 3.0% by mass, the Nb content is preferably from 0.005 to 0.5% by mass, and the V content is preferably 0.01. The content of 0.5% by mass and the Zr content is preferably 〇_〇〇5 to 0.5% by mass, and the B content is preferably 0.0003 to 0.003 mass%. Further, it is more preferable that the Mo content is 0.1 to 1.0% by mass, and the Nb content is 0.005 to 〇.1 〇 by mass. /〇, the V content is 0.01 to 0.20% by mass, the Zr content is 0.005 to 〇.1% by mass, and the B content is 0.0003 to 0.0030% by mass. Further, W is also an element contributing to the improvement of corrosion resistance, and contains W. In case, the W content is preferably from 0.05 to 3.0% by mass. Further, in the steel material of the present invention, in order to form an insoluble sulfide film in an S Οχ environment in which acid rain is lowered, an effect of improving uranium resistance is obtained, and it is preferable to contain a material selected from the group consisting of Be, As, Sb, Bi, Ge, Sn, Pb, and Se. At least one of Te, and Cd is 0.002 to 0.2% by mass in total. These elements are believed to avoid the formation of sulfides (cr, Ti • 16 - 1374195, ruthenium, etc.) which are insoluble in water and acid in the steel in place of Μη, so that they are dissolved in a corrosive environment accompanied by corrosion. The steel surface forms an insoluble sulfide film. Further, the steel material of the present invention can also contain p and Cr. P prevents chloride ions from invading the rust formed on the surface of the steel, and forms a dense and stable rust layer, which has an effect of improving corrosion resistance. Therefore, in the conventional weather-resistant steel, in order to exhibit the corrosion-improving effect, the content must be 0.05% by mass or more and 0.15% by mass or less. On the other hand, when P is contained in an excess of more than 0.15% by mass, the weldability is remarkably lowered. On the other hand, in the present invention, since a dense stable rust layer can be formed by containing Ti or the like, it is not necessary to contain an excessive amount of P. Therefore, in consideration of the improvement in weldability, in the case of containing p, the p content is preferably 0.001 to 0.15 mass%. Here, in general, P must be reduced in the production process of steel, but an element which is inevitably left in the steel. However, in the present invention, p is an element which contributes to the improvement of corrosion resistance. Therefore, in the manufacturing process of the steel material of the present invention, in order to increase the residual amount of p, the degree of P reduction can be alleviated.

Cr, which is added to stainless steel or the like, generally contributes to the improvement of corrosion resistance, but adversely affects the atmospheric chloride environment and the seaside environment. In this environment, the puncture resistance can be improved by lowering the Cr content. Such an improvement in the perforation resistance, the local corrosion resistance, and the improvement in the corrosion resistance in a salt environment are particularly effective in reducing the Cr content. From this point of view, in the case where the steel material of the present invention contains Cr, the Cr content is preferably 0.1% by mass. the following. Although it is more preferably Cr-free (Cr content is 0), excessive reduction may cause economic deterioration. In addition, in the manufacturing process of steel, Cr is an inevitable component of waste materials which are commonly used as raw materials. Therefore, in the invention of -17- 1374195, it is not preferable as the weather-resistant steel specified by the HS-SMA. Therefore, the content thereof is preferably less than 0.02% by mass. As described above, the steel material of the present invention contains C, Si, Μη, Ca, and Α1 as essential components, and further contains one selected from the group consisting of Cu and Ni, the remainder being Fe and unavoidable impurities, and Ni, and Ti. The specific relationship between the contents represented by the above formula (1) may include at least one selected from the group consisting of La, Ce, Mg, Mo, Nb, \B, and W, whereby a unique insoluble film may be formed. The film is protected to obtain good contact resistance. That is, under the atmospheric pollution environment of sulfur oxides, Ni, Cu, and Ti can generate rust during venting corrosion (Ni, Cu: stable amorphous rust, α rust generation promotion; Ti: unstable ^Inhibition of rust generation) and formation of an insoluble sulfide in an SOx environment to form an anti-corrosion film. Further, the steel material structure of the present invention is basically a mixed structure of fertilizer and iron, for example, a structural material such as a bridge or the like, which ensures a strength of 390 to 630 N/mm 2 or better, and has excellent strength. Corrosion resistance, the amount of ferrite should be more than 90%. The more the amount, the closer the steel structure is to the single layer of the ferrite grain iron phase, the steel structure forms a microbattery, and the corrosion resistance such as bare weather resistance can be improved. Therefore, the tissue is preferably more than 95% of the amount of fertilized iron. Next, the surface of the steel material of the present invention for the rust and rust layer on the surface of the steel material of the present invention is covered with rust containing S and at least one selected from the group consisting of Ti, Nb, Zr and V. Therefore, it is more difficult to add at least Cu's system of Cr, S, and Ti, or r, Zr, and sulfides in a large-scale formation to promote control, and the improvement of the iron and wave is difficult. , steel description. Cu, Ni can form dense and fine a-FeOOH rust and amorphous rust under the corrosion environment of salt CS) -18- 1374195 or in the atmosphere with a large amount of sulfur oxides, and can suppress cold-FeOOH as much as possible. Occurs, and reproducible to obtain high corrosion resistance. That is, in the steel surface or the steel rust layer, as long as the S is contained or present, and at least one selected from the group consisting of Ti, Cu, Ni, Nb, Zr, and V, the steel surface or the steel rust layer is in the atmosphere. The rust generated under the rust, whereby the elements can form dense and fine α-FeOOH rust and amorphous rust even in a salt corrosion environment or an air pollution environment, and can suppress as much as possible in this process. The occurrence of FeOOH. The effects of such Ti, S, etc. on rust formation are presumed as follows. That is, in the stage of formation and growth of rust, fine compound particles or fine precipitates having ionic or colloidal properties are obtained. (Ti hydroxide or oxygen-containing hydroxide which is produced by oxidation or hydrolysis of Ti or Ti ions, The influence of the form of an oxide or a reactive product with other substance elements may destroy the crystal structure of the rust and suppress the growth, and it may be prevented from being corroded or peeled off by the defect portion of the rust and the formation of a sulfide or the like. The starting point. In the rust which coats the surface of the steel, the S content is from 0.3 to 5.0% by mass. If S is contained in the rust layer, the rust layer itself becomes dense and has high corrosion resistance. Although the mechanism is unclear, it is believed that the corrosion resistance can be further improved by the insoluble sulfur compounds on the surface of the steel and the multiplication effect of the fine and dense rust containing s and Ni, Cu, and Ti. When the S content in the rust layer of the surface is less than 0.3% by mass, the effect of improving the corrosion resistance cannot be exhibited. When it exceeds 5% by mass, the corrosion start point may become, and the corrosion resistance may be deteriorated. -19- 1374195 The total amount of rust selected from the group consisting of Ti, Cu, Ni, Nb, Zr and V is 0.5 to 10.0% by mass. In the rust of the coated surface, the lower limit of the total content of at least one selected from the group consisting of Ti, Cu, Ni, Nb, Zr and V is preferably 2.0% by mass or more, and more preferably 3.0% by mass or more. In the rust layer formed on the surface of the steel material of the present invention, the grain size of the cold-FeOOH component determined by the X-ray diffraction method is less than 50 nm. Further, the specific surface area determined by the molecular adsorption method of the rust layer is 10 m 2 /g or more. Therefore, even in a harsh corrosive environment such as a chloride environment or an atmospheric pollution environment containing a large amount of sulfur oxides, flow rust and peeling rust do not occur, and excellent corrosion resistance can be exhibited and the appearance can be maintained. . Especially in the salt corrosion environment, although the stabilization of the rust layer depends on the presence of cold-FeOOH rust, the grain size of the /3 -FeOOH rust and the specific surface area of the rust particles determine the corrosion resistance of the rust layer. The grain size of the cold-FeOOH rust exceeds 5 Onm, and since the peeling rust layer is easily formed, the grain size of the /3 rust is set to less than 50 nm. In other words, the grain size of the rust particles constituting the rust layer is reduced as a result of the rust-free type, and the corrosion resistance is not remarkably improved. Therefore, in particular, the grain size of the spot rust is lowered to reduce the size thereof, and the corrosion resistance is improved. Promotion is very important. In the present invention, the main component of rust is composed of a-FeOOH and/or amorphous rust. Among them, in particular, amorphous rust can form a finer and denser stable rust layer than crystalline rust. Even if a "defective portion" is formed in the rust film, the amorphous rust portion has a "defect repair function". . Therefore, the higher the ratio (amorphism) of the amorphous rust in the rust, the higher the corrosion resistance (S > -20-1374195. Therefore, in the present invention, in the rust formed on the surface of the steel, the ray is irradiated The fraction of the amorphous component obtained by the diffraction method is preferably 30% by mass or more. On the other hand, other rust, in particular, crystalline rust such as cold-FeOOH, even if the rust is amorphous or Since the ratio of a-FeOOH is high and corrosion is still carried out starting from the rust, it is necessary to suppress as much as possible. Therefore, in the present invention, the rust formed on the surface of the steel material is determined by the X-ray diffraction method. The fraction of the FeOOH component is preferably 30% by mass or less. When the fraction of the rust amorphous component is less than 30% by mass and the fraction of the cold-FeOOH component (calling) exceeds 30% by mass, the aforementioned α-FeOOH There are many crystal rust components such as /3-FeOOH, γ-FeOOH, and Fe304. The rust on the surface of the steel cannot form a dense and stable rust layer, and the corrosion resistance of the steel may not be ensured. Crystal rust, which can be alpha rust (stable, easily formed in acid) and γ (unstable, easy to generate in neutrality) is compared to evaluate the protective property of rust. Therefore, in the steel material of the present invention, the fraction of rust is preferably a-FeOOH/Y-FeOOH>0-6. In the present invention, the surface of the steel The high corrosion resistance of the generated rust refers to the corrosion resistance of the steel in the SOx environment. Therefore, in order to ensure the high corrosion resistance, it is necessary to evaluate the atmospheric exposure of the steel for half a year or the acid rain spreading test in the simulated atmospheric environment. As a result, the corrosion resistance of the steel material is evaluated. In the present invention, as a means for measuring the degree of amorphousness of rust, "corrosion corrosion resistant 95C-306 (pp. 341 to 344)" "rust powder according to powder X-ray diffraction method" can be used. The powder X-ray-21 - 1374195 line diffraction method disclosed in the Quantification and Application thereof. This paper attempts to carry out the aforementioned rust component on the steel surface by powder x-ray diffraction method for weather resistant steel. Quantification, and the higher the proportion (amorphous degree) of amorphous rust in rust, the more dense and stable rust layer can be formed to improve corrosion resistance. Specific powder X-ray diffraction method, regarding internal standards, Yes A certain mass is more than the CaF2 or ZnO and the rust sample taken from the steel and is pulverized, and is identified by the usual X-ray diffraction method, and the integrated intensity ratio of the respective diffraction peaks of the above five rusts is determined. The calibration curve of each rust component obtained in advance is quantified, and the amount of the rust component of each crystal component is subtracted from the total amount of rust to calculate the ratio of the amorphous component. The integrated intensity ratio of the diffraction peak of the amorphous component itself is not easily determined, and it is difficult to quantify. Next, the method for producing the steel material of the present invention will be described. The steel material of the present invention can be produced by a usual thick steel plate. To manufacture. That is, after the steel is melted by continuous casting or agglomeration, heat processing such as block rolling, hot forging, or thick plate rolling is performed to produce a predetermined product thickness. These hot working conditions, cooling after hot working, and heat treatment conditions are appropriately selected according to the mechanical properties required for the steel (for example, the strength of the bridge is 390 to 630 N/mm 2 or higher). Decide. Therefore, in addition to the usual hot working, it is preferable to select a method for ensuring the mechanical properties such as the aforementioned strength after ensuring low alloying of the weldability or quantification of low carbon. For example, in order to make the amount of ferrite in the steel structure of the present invention to 90 ° /. As described above, forced cooling such as accelerated cooling after hot working or controlled rolling can be performed. Further, regarding the heat treatment after the hot working, direct quenching (S) -22- 1374195 fire (DQ) on the rolling line or quenching annealing (QT) outside the line may be appropriately performed as needed. EXAMPLES The following is a detailed description of an embodiment consistent with the requirements of the present invention and a comparative example not meeting the requirements of the present invention. The following examples are merely representative and the invention is not limited to the examples. (Example No. 1 to 16) Steel blocks having the chemical compositions shown in Table 1 were each atmospherically melted at a laboratory scale. The mold was cast using a square mold of 4 5 kgf using a thin plate to produce an ingot having the chemical composition shown in Table 1. Next, the ingots were subjected to rough rolling. The heating condition is maintained at 1 100 ° C for 30 minutes, and the heat-expansion roll process is not particularly limited, and is finished to a thickness of 25 mm x - a fixed width X length (the "certain width" herein means that the plate width is not limited. The width obtained by calendering is also the same for the length. The following are the same). Then, the gas was cut to prepare a sheet having a length of 300 mm. Then, 'the finishing process is performed. The heat extension condition is heating 1 l 〇〇 ° C x 2 hours 'rolling times 5 times, and the finishing temperature is 900 乞 ± 50. (: Finishing size is 6mm thick X - fixed width X length, cooling rate is 70 ° C / sec, stop temperature is 65 0 ° C. Then, keep the furnace at 60 (TC x 60 minutes for furnace cooling 'by making Steel plates. Each test piece was taken from these steel plates. (S) -23- 1374195

Φ chain I揪 parameter 〇〇〇〇ο Ό in ο ο rn rn ;13.08 1 14.93 1 23.32 16.33 29.57 51.71 29.03 68.31 1 37.97 1 150.89 Other La+Ce: 0.05 Nb: 0.05 Mo: 0.05 Ce: 0.003 Ta: 0.005 La+Ce: 0.05 Nb: 0.05 Hf: 0.003 B: 0.002 Mg: 0.008 W: 0.05 Ca: 0.004 La: 0.008 00 00 〇 oodo Nb: 0.05 V: 0.05 c3 Not added No added No added No added 0.004 0.005 丨 0.005 1 0.005 0.008 0.005 0.005 0.004 0.006 0.005 1 0.007 1 0.005 * 0.010 0.010 o.oio 1 0.045 1 1 o.oio 1 0.035 | 1 0.036 1 1 0.035 1 0.045 0.035 0.045 0.045 0.045 0.045 1 0.038 1 0.040 r ι A 0.030 0.030 0.030 1 0.030 1 1 0.030 1 0.030 | 1 0.030 1 1 0.030 1 0.070 0.030 0.070 0.060 1 0.070 0.070 1 0.030 0.050 〇〇ο ο ο ο do c5 Ο Ο S d 〇soo c5 os c5 ON 〇• 一〇Ο ο ο (Ν m ο ο md κη O VO rj sso c5 so On c5 00 ON o (N ri cn (N 〇〇 ο ρ ο ο ο ooo 芩ο ON ON Ο c> 〇〇ON og; oso S ON o On O) 〇C/D 0.003 0.003 0.005 0.003 0.003 0.028 ,0 028 1 0.031 1 0.041 0.038 0.052 0.082 0.061 0.092 | 0.059 CN 〇CU 0.015 0.015 1 "0_015 1 0.013 1 [0.010 "0.011 | 1 o.oio 1 1 o.oio 1 0.012 0.010 0.012 0.010 0.010 0.013 | 0.012 1 0.010 C ON ΓΟ 1—Η rH yn οο Ο 1-Η 〇rH (N (N CN rH s rH s CN m 〇(Ν CO ο ΓΟ ο CN m ο CN md (N m O CN m Ο m 〇omm 〇CN m 〇(N m O m O (N Md cn O (N m 〇Ο c5 爸爸ο g ο c5 dgo ο soso SOS oso O c5 sog c5 so Comparative Example 1 Comparative Example Comparative Example Comparative Example Comparative Example The present invention example of the present invention The present invention example EXAMPLES OF THE INVENTION Example 1 of the present invention Example of the invention Example of the invention Example of the invention Ο P ^ (Ν VO VO οο ON ο CN 寸 V £ > ! 1X00S (NXSX (5XS·inch + N): Gallium # : ii CS ) -24- 1374195 Next, a test piece of 50 mm x 50 mm wide x 3 mm thick was produced from the test piece taken, and the corrosion resistance was evaluated by the following test. Corrosion resistance evaluation test A 7-day compound cycle type promotion laboratory test was conducted. The composite cycle test '1 cycle consists of: spraying with artificial acid rain with pH = 3.5 for 2 hours, drying (temperature 60 °C, humidity 40%) for 2 hours, placed in a humid environment (temperature 40 ° C, humidity 9 5 %) 2 hours; 4 days for 4 cycles. After the test, the rust was removed by liquid calendering, and the weight was measured to determine the corrosion loss. The corrosion reduction amount of No. 1 was set to 1 Torr, and the amount of corrosion of each test piece was standardized. Analysis of generated rust A rust sample was taken from the test material after the corrosion resistance evaluation test, and the grain size of Lu-F e Ο Η Η rust (Miller index 1 1 〇) was measured by an X-ray diffraction method. For a part of the sample, the grain size of Y-FeOOH (y3 rust) (020) or magnetite (220) was measured. 'For the rust sample taken from the test material, the X-ray diffraction method was used to identify the integral of the diffraction peaks inherently based on the three kinds of rust of a-FeOOH, cold-FeOOH, γ-FeOOH and Fe3〇4. The intensity ratio and the calibration curve of each rust component obtained in advance are used to quantify each crystalline rust component. The amount of the rust component of each crystallinity is subtracted from the rust measurement to calculate the ratio of the amorphous component, and Rust fraction: a-FeOOH/Y-FeOOH. -25- 1374195 Specific surface area of rust layer The n2 isotherm was obtained from the liquid nitrogen temperature using an automatic volumetric adsorption device, and the adsorption isotherm was used for BET mapping to obtain the specific product. Elemental analysis in rust The test piece was cut, and the cross section was observed with a scanning electron microscope ( ) at a ratio of 100 to 2000 times, and the surface iron layer and the iron-adhered portion were arbitrarily taken out, and an electron beam probe micro analyzer was used. (ΕΡΜΑ) The degree (content) of the alloying elements (S, Ti, Cu, Ni, Nb, Zr, V) of the rust layer. Table 2 shows the results of the corrosion resistance evaluation test, the generated rust, the specific surface area of the rust layer, the pore diameter, and the elemental analysis in the rust. Adsorption surface SEM matrix determination concentration analysis , etc . -26- 1374195

账¥i(N« rust rate (α/γ) 1 0.53 0.55 0.51 0.56 0.56 0.78 0.89 0.86 0.91 0.95 ps 0.98 1.15 inch oo m (quality fl%) m ?; Os mv〇m inch inch CN 卜 inch m r-» amorphous component m&%) oo ON (N (N κη m 5 ΟΙ σ; (N in specific surface area of rust layer __(m2/g) in os 00 σ\ 〇ό CS 〇\ 〇 6 CN 22.3 25.6 19.7 1 25.3 39.4 inch · m Η 53.9 45.3 52.8 Grain size of cold gauge __0TM)__ g oo 00 vo 5 - o cn P; vn cn ft 舾m S , Π Total 0.15 0.17 0.26 (N 1.14 1.13 4.68 3.93 3.72 3.35 5.22 4.82 4.53 6.44 1 6.16 6.58 > ltll ( 1 tl 1 1 1 1 1 ι t 0.08 N 1 1 1 1 1 1 1 1 1 1 1 1 0.12 1 1 1 X) 1 1 1 1 1 1 1 1 0.12 ' 1 c> 1 1 1 1 0.09 0.01 0.01 0.03 0.34 0.31 1 0.61 2.98 1.31 0.78 0.54 0.68 g *- 2.31 2.16 2.89 i 1 3.01 a 0.02 0.06 0.01 0.62 0.69 0.09 m (N 1.89 oo O) w 1 cn oi 3.35 2.46 <N 2.98 2.34 κη p 0.01 0.01 0.01 0.05 0.01 0.04 0.05 0.04 0.06 0.04 0.06 0.06 0.05 0.05 0.04 0.06 00 o 0.09 0.21 »—· O 0.13 0.39 0.42 0.69 0.78 0.64 s 1 1.21 0.9 6 1 — , _ 0.89 1.89 Corrosion resistance o 00 〇 \ σ \ s rn Os v 〇 OS vn 00 Os Comparative example Comparative example Comparative example Comparative example Comparative example The present invention Example of the present invention Example of the present invention Example of the present invention EXAMPLES OF THE INVENTION Inventive Example I Inventive Example Inventive Example Inventive Example Inventive Example No. — (N inch v 〇 oo On Ο . 2 (N m inch -27- 1374195 as shown in Table 2, compared to In the examples (No. 1 to 5), the examples of the present invention (Νο·6 to 16) showed more excellent starvation resistance. The examples of the present invention are excellent in not only the saturability, but also the grain size of the g-FeOOH rust is small, and the specific surface area of the rust layer is large. That is, in the example of the present invention, the uranium resistance is excellent, the fraction of the amorphous component determined by the X-ray diffraction method is 30% by mass or more, and the fraction of the 泠-FeOOH component is 30%. Below %, and the fraction of rust (α -FeOOH / γ-FeOOH ) exceeds 0.6. On the other hand, the comparative example did not satisfy any of the conditions, and thus the scratch resistance was poor. Further, in the examples of the present invention (Nos. 6 to 16), S was contained in the rust layer, and an effective element such as Cu, Ni, or Ti was concentrated, and the results of the corrosion resistance test described above were confirmed. The present invention has been described in detail with reference to the specific embodiments thereof, and it is obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. In addition, this application is based on the Japanese invention application (Japanese Patent Application No. 2007-020522) filed on Jan. 31, 2007, and the Japanese Invention Application (Japanese Patent Application No. 2007-303333) filed on Nov. 22, 2007. The content is incorporated in the present invention. In addition, all the references cited herein are all the steel materials of the present invention, and can exhibit excellent corrosion resistance even in an air pollution environment in which a large amount of sulfur oxides are generated by lowering an acid rain of pH 4.5 or lower. . It is suitable for steel structures such as civil engineering, buildings, iron towers, bridges, construction machinery, steel pipes, storage tanks, etc. It is especially suitable for steels requiring excellent corrosion resistance in an air pollution environment containing a large amount of sulfur-oxygen-28- 1374195. Structure material

(S) -29

Claims (1)

1374195 Announcement ΙΒΓ1~ OB- Year of the 曰 Revision 097103510 Patent application Chinese patent application scope revision The Republic of China January 1, 2011 曰 Amendment 10, the scope of application for patent L - a steel with excellent corrosion resistance, at the same time The following conditions (A) (B)(C) are satisfied: (A) In terms of mass%, the essential components include C: 0·02 to 0.1 5%, Si: 0.1〇~ίο%, Μη: 0.1 to 1.5%, S : 0.02 to 0.5%, Ti: 002 to 0.15 %, Ca: 0.0001 to 0.01%, and A1: 0.01 to 0.50% t further containing at least one selected from the group consisting of Cu: 0.05 to 3.0% and Ni: 0.05 to 6.0%; The remainder is composed of Fe and unavoidable impurities; and the contents of Ni, Cu, S, and Ti have the relationship represented by the following formula (1) [(Ni + 4.5xCu) x Sx25 00xTi > 5] (1); (B) Surface The rust is rusted, and the rust contains S: 0.3 to 5.0% by mass, and further contains at least one selected from the group consisting of Ti, Cu, Ni, Nb, Zr, and V of 0.5 to 10.0% by mass; (C) surface a rust layer having a grain size of less than 50 nm obtained by an X-ray diffraction method for forming a /3-FeOOH component, and the rust layer is obtained by a molecular adsorption method The specific surface area is l〇m2/g or more. 2. The steel material excellent in uranium resistance according to the first aspect of the patent application, wherein the steel material further contains La: 0.0001 to 〇.〇5 mass%, Ce: 0.0001 to 0.05 mass%, and Mg: 0.0001 to 0.05 mass%. Mo: 5 to 3·〇% by mass, Nb: 0.005 to 0.5% by mass, V: 0.01 to 〇·5, 5% by mass, Zr: 0.005 to 〇·5 mass%, Β: 0.0003 to 0.003 mass%, and W · w. 〇 · 〇 5 to 3.0% by mass of at least one of them. 3. The steel material having excellent corrosion resistance as described in the first or second aspect of the patent application, wherein the fraction of the amorphous component obtained by the X-ray diffraction method of the rust generated on the surface is 30% by mass or more. Further, the fraction of the yS-FeOOH component was 30% by mass or less, and the fraction of rust was a -FeOOH / Y-FeOOH > 0.6.