JP2007239095A - Acid corrosion resistant steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acid corrosion resistant steel exhibiting excellent corrosion resistance even in any environment of low temperature/low sulfuric acid concentration environments and high temperature/high sulfuric acid concentration environments without adding large quantities of various alloy elements. <P>SOLUTION: The acid corrosion resistant steel has a composition comprising, by mass, 0.001 to 0.2% C, 0.01 to 3.0% Si, 0.01 to 3.0% Mn, 0.001 to 0.3% Al, 0.01 to 2.0% Cu, 0.01 to 2.0% Cr and 0.01 to 0.2% Co, in which the content of P is regulated to ≤0.035% and the content of S is regulated to ≤0.030%, and, if required, further comprising prescribed amounts of one or more kinds of elements selected from the group consisting of Ni, Mo, W, Sb, Sn, Se, Pb, Nb, V, Ti, Ta, Zr, B, Mg, Ca, Y, La and Ce, and the balance Fe with inevitable impurities. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an acid-corrosion-resistant steel made of low alloy steel, and more particularly to an acid-corrosion-resistant steel suitable for applications in which sulfuric acid corrosion occurs, such as a flue gas treatment apparatus of a thermal power plant and a sulfuric acid tank.

  In a flue gas treatment facility of a thermal power plant, sulfuric acid dew point corrosion is likely to occur due to SO3 contained in the exhaust gas. In particular, the heat transfer element of the rotary regenerative heat exchanger is prone to sulfuric acid dew point corrosion at low temperatures, and the heat transfer element is made of a thin cold-rolled steel sheet with a plate thickness of about 1 mm. There is also the problem of being short. For this reason, in such a use, steel excellent in sulfuric acid dew point corrosion resistance is strongly demanded.

  Conventionally, low-alloy corrosion-resistant steel has been widely used in an environment where sulfuric acid dew point corrosion is likely to occur (for example, see Patent Documents 1 and 2). In Patent Document 1, in mass%, C: 0.01 to 0.15%, Si: 0.1 to 0.5%, Mn: 0.1 to 0.5%, P: 0.03% or less , S: 0.01% or less, Cu: 0.2 to 1.0%, Ni: 0.5% or less, Cr: 2.0% or less, Al: 0.1% or less, Sn and Sb Or the total of the two types is 0.01 to 1.0%, B: 0.0050% or less, V: 0.2% or less, Nb: 0.2% or less and Ti: 0.2% or less, A steel excellent in acid dew point corrosion resistance has been proposed, with the balance being Fe and inevitable impurities.

  Similarly, in Patent Document 2, by mass%, C: 0.15% or less, Si: 1% or less, Mn: 0.2 to 1.5%, P: 0.03% or less, S: 0.03 % Or less, Al: 0.01 to 0.1%, Cu: 0.2 to 1.0% and Co: 0.02 to 0.2%, with the balance being composed of Fe and inevitable impurities Cold-rolled steel sheets having excellent sulfuric acid corrosion resistance have been proposed.

Japanese Patent Application Laid-Open No. 09-025536 US Pat. No. 6,773,518

  However, the conventional techniques described above have the following problems. That is, in sulfuric acid dew point corrosion, when the steel sheet temperature is relatively low, 40 to 70 ° C., sulfuric acid having a relatively low concentration of about 20 to 50% by mass is generated (hereinafter, this environment is referred to as low temperature / low sulfuric acid concentration This low concentration of sulfuric acid contributes to corrosion. On the other hand, when the steel plate temperature is relatively high at 80 to 140 ° C., sulfuric acid having a high concentration of about 60 to 80% by mass is generated (hereinafter, this environment is referred to as a high temperature / high sulfuric acid concentration environment). Of sulfuric acid is involved in corrosion. Therefore, steels exhibiting excellent corrosion resistance under both low temperature / low sulfuric acid concentration environment and high temperature / high sulfuric acid concentration environment are ideal for such applications.

  In contrast, the inventions disclosed in Patent Document 1 and Patent Document 2 have good corrosion resistance in either one of a low temperature / low sulfuric acid concentration environment and a high temperature / high sulfuric acid concentration environment. There is a problem that the corrosion resistance is poor in the environment. In an actual flue gas treatment facility, a low temperature / low sulfuric acid concentration environment or a high temperature / high sulfuric acid concentration environment is formed depending on the operating state, and therefore, development of steel exhibiting excellent corrosion resistance in both environments is awaited.

  The present invention has been devised in view of the above-described problems, and can be used in both low temperature / low sulfuric acid concentration environments and high temperature / high sulfuric acid concentration environments without adding a large amount of various alloy elements. An object of the present invention is to provide an acid corrosion resistant steel exhibiting excellent corrosion resistance.

  The acid corrosion resistant steel according to the present invention is in mass%, C: 0.001 to 0.2%, Si: 0.01 to 3.0%, Mn: 0.01 to 3.0%, P: 0.00. 035% or less, S: 0.030% or less, Al: 0.001-0.3%, Cu: 0.01-2.0%, Cr: 0.01-2.0% and Co: 0.01 It is characterized in that it contains ˜0.2% and the balance consists of Fe and inevitable impurities.

  This acid-corrosion resistant steel is further, in mass%, Ni: 0.01-2.5%, Mo: 0.01-2.5%, W: 0.01-2.5%, Sb: 0.01 One or two selected from the group consisting of ˜0.3%, Sn: 0.01 to 0.3%, Se: 0.01 to 0.3% and Pb: 0.01 to 0.3% The above elements can also be contained.

  Furthermore, by mass%, Nb: 0.002-0.2%, V: 0.005-0.5%, Ti: 0.002-0.2%, Ta: 0.005-0.5%, You may contain the 1 type (s) or 2 or more types of element selected from the group which consists of Zr: 0.005-0.5% and B: 0.0002-0.005%.

  Furthermore, in mass%, Mg: 0.0001-0.01%, Ca: 0.0005-0.01%, Y: 0.0001-0.1%, La: 0.005-0.1% and Ce: One or more elements selected from the group consisting of 0.005 to 0.1% can also be contained.

  Moreover, it is preferable that the acid corrosion-resistant steel of the present invention is mass% and the S content is 0.005 to 0.030%.

  According to the present invention, Cu—Cr—Co is added to low carbon steel in combination and the content of each element is optimized. Therefore, in both low temperature / low sulfuric acid concentration environment and high temperature / high sulfuric acid concentration environment. Excellent corrosion resistance can be obtained.

  Hereinafter, the best mode for carrying out the present invention will be described in detail. In order to solve the above-mentioned problems, the present inventor diligently studied the corrosion mechanism of steel in a low temperature / low sulfuric acid concentration environment and a high temperature / high sulfuric acid concentration environment and the effects of trace alloy elements. As a result, it has been found that when low carbon steel is used as a base and Cu—Cr—Co is further added, the corrosion resistance is improved in both low temperature / low sulfuric acid concentration environment and high temperature / high sulfuric acid concentration environment. Moreover, it discovered that corrosion resistance improved further by optimizing the mass ratio (Cr / Co) of Cr and Co to add. As a result of further study, the present inventor has found that Cr is an element that accelerates the corrosion rate of steel in a low temperature / low sulfuric acid concentration environment, but when Cr and Co are added together, the dissolved Co ions cause corrosion by Cr. It was found that the acceleration action is remarkably suppressed. In addition, in order to ensure corrosion resistance in a high temperature / high sulfuric acid concentration environment, it is indispensable to add Cu-Cr in combination, but if Co is added in combination, the steel surface is likely to be in a quasi-passivated state. It has been found that this further suppresses the corrosion rate of steel.

  Furthermore, as a result of examining the influence of additive elements on the corrosion resistance of Cu-Cr-Co steel, the corrosion resistance of steel in a low temperature / low sulfuric acid concentration environment is further improved by making S, which is an impurity, 0.005% or more. It was found that it improved.

  The acid-corrosion resistant steel of the present invention (hereinafter also simply referred to as steel) is based on the above knowledge, and in mass%, C: 0.001 to 0.2%, Si: 0.01 to 3 0.0%, Mn: 0.01-3.0%, P: 0.035% or less, S: 0.030% or less, Al: 0.001-0.3%, Cu: 0.01-2. It contains 0%, Cr: 0.01-2.0% and Co: 0.01-0.2%, with the balance being composed of Fe and inevitable impurities.

  First, each component element and its content in the steel of the present invention will be described. In the following description, mass% in the composition is simply described as%.

C: 0.001 to 0.2%
C has an effect of increasing the strength of the steel, but when C is added excessively, weldability and joint toughness deteriorate. Specifically, if the C content exceeds 0.2%, weldability, joint toughness, and the like deteriorate, which is not preferable as a steel for welded structures. On the other hand, de-C conversion until the C content is less than 0.001% significantly hinders industrial economic efficiency. Therefore, the C content is set to 0.001 to 0.2%. In addition, when using C as a reinforcement | strengthening element, it is preferable that the content shall be 0.002% or more. Further, from the viewpoint of weldability, the C content is preferably 0.18% or less. Furthermore, since C is also an element that lowers the sulfuric acid resistance, it is more preferable that the C content is 0.15% or less from the viewpoint of corrosion resistance. Furthermore, when it is used as a cold-rolled steel sheet and it is particularly necessary to impart workability, the C content is more preferably 0.002 to 0.1%. Furthermore, when used as a steel sheet for welded structure, the C content is more preferably 0.05 to 0.15%.

Si: 0.01-3.0%
Si is a deoxidizing element, but when its content is less than 0.01%, the deoxidizing effect is not exhibited. On the other hand, when Si is excessively contained, specifically, when the Si content exceeds 3.0%, the hot-rolled scale is fixed (decrease in scale peelability), and scale-induced wrinkles increase. Therefore, the Si content is set to 0.01 to 3.0%. Si is an element effective for improving both sulfuric acid corrosion resistance under a low temperature / low sulfuric acid concentration environment and a high temperature / high sulfuric acid concentration environment. Preferably, the Si content is 1.0% or more in order to obtain a remarkable effect of improving the corrosion resistance by Si. Moreover, in the case of steel with severe requirements for corrosion resistance as well as weldability and base metal and joint toughness, the upper limit of Si content is preferably 0.5%.

Mn: 0.01 to 3.0%
Mn has the effect of increasing the strength of the steel, but if the content is less than 0.01%, the strength of the steel cannot be ensured. On the other hand, if the Mn content exceeds 3.0%, the weldability deterioration and the grain boundary embrittlement susceptibility increase, which is not preferable. Therefore, in the steel of the present invention, the range of Mn content is limited to 0.01 to 3.0%. Since Mn is an element that hardly affects the corrosion resistance, it can be adjusted by the Mn content when the carbon equivalent is limited particularly for use in a welded structure.

P: 0.035% or less P is an impurity element. If its content exceeds 0.035%, the weldability and sulfuric acid corrosion resistance under a low temperature / low sulfuric acid concentration environment are remarkably lowered. The content is limited to 0.035% or less. In addition, it is preferable that P content shall be 0.015% or less, and this can make weldability favorable. Moreover, although manufacturing cost increases, when more excellent corrosion resistance is required, the P content is more preferably 0.005% or less.

S: 0.030% or less S is also an impurity element, and if its content exceeds 0.030%, mechanical properties, particularly ductility, are significantly deteriorated, so the S content is 0.030% or less. In addition, when S content is less than 0.005%, the sulfuric acid corrosion resistance in low temperature / low sulfuric acid concentration environment and high temperature / high sulfuric acid concentration environment may fall. In particular, in a low temperature / low sulfuric acid concentration environment, the precipitation amount of CuS that supports the sulfuric acid corrosion resistance may be significantly reduced, and the corrosion resistance of the steel may be reduced. Therefore, the S content is preferably 0.005% or more.

Al: 0.001 to 0.3%
Al is a deoxidizing element, but when its content is less than 0.001%, a deoxidizing effect cannot be obtained. On the other hand, when Al exceeds 0.3% and contains excessively, a coarse oxide will be formed and ductility and toughness will be deteriorated. Therefore, the Al content is limited to a range of 0.001% to 0.3%.

Cu: 0.01 to 2.0%
Cu has an effect of improving sulfuric acid corrosion resistance under a low temperature / low sulfuric acid concentration environment and a high temperature / high sulfuric acid concentration environment, and is the most important element in the steel of the present invention together with Cr and Co. However, when the Cu content is less than 0.01%, the above-described effect of improving the sulfuric acid corrosion resistance cannot be obtained. On the other hand, when Cu is contained exceeding 2.0%, adverse effects such as the promotion of surface cracking of steel slabs and deterioration of joint toughness become apparent. Therefore, in the steel of the present invention, the Cu content is set to 0.01 to 2.0%. Even if Cu is added over 0.5%, the improvement in sulfuric acid corrosion resistance is almost saturated. Therefore, considering both sulfuric acid corrosion resistance and manufacturability, the Cu content is 0.01 to 0. 0.5% is preferable.

Cr: 0.01 to 2.0%
Cr has an effect of improving the sulfuric acid corrosion resistance under a high temperature / high sulfuric acid concentration environment depending on the amount added, but if the Cr content is less than 0.01%, the effect cannot be obtained. On the other hand, when Cr is added exceeding 2.0%, sulfuric acid corrosion resistance in a low temperature / low sulfuric acid concentration region environment is lowered, and weldability is lowered and cost is increased. Therefore, the Cr content is set to 0.01 to 2.0%.

Co: 0.01 to 0.2%
Co has the effect of improving the sulfuric acid corrosion resistance under high temperature / high sulfuric acid concentration environment. When Co is added to the Cr-added steel, the sulfuric acid corrosion resistance under low temperature / low sulfuric acid concentration environment is dramatically improved. Improve. However, when the Co content is less than 0.01%, these effects cannot be obtained. On the other hand, even if Co is added over 0.2%, the improvement in corrosion resistance is saturated. Therefore, the Co content is set to 0.01 to 0.2%.

  The above are the basic requirements regarding the chemical composition of the steel of the present invention and the reasons for its limitation. In the present invention, the elements and parameters that may be selectively added are further limited for the purpose of improving various properties. be able to.

  First, in order to improve the corrosion resistance, it is preferable to control the ratio ([Cr] / [Co]) between the Cr content ([Cr]) and the Co content ([Co]) as described below. . Specifically, when [Cr] / [Co] exceeds 50, Co becomes insufficient, and the resistance to sulfuric acid corrosion under a low temperature / low sulfuric acid concentration environment and a high temperature / high sulfuric acid concentration environment decreases. On the other hand, in a Cr-added steel with a constant Cr content, even if the amount of Co is increased so that [Cr] / [Co] is less than 10, the low-temperature / low sulfuric acid concentration environment and the high-temperature / high sulfuric acid concentration environment Improvement in sulfuric acid corrosion resistance is saturated. Therefore, the ratio of Cr content to Co content ([Cr] / [Co]) is preferably 10-50.

  In the steel of the present invention, in addition to the above components, Ni: 0.01 to 2.5%, Mo: 0.01 to 2.5%, W: 0.01 to 2.5% , Sb: 0.01 to 0.3%, Sn: 0.01 to 0.3%, Se: 0.01 to 0.3% and Pb: 0.01 to 0.3% One or more elements may be added.

  Ni is an element effective in preventing hot cracking in the Cu-added steel, and improving the toughness of the base metal and the weld heat affected zone (HAZ), but when the Ni content is less than 0.01%, The effect cannot be obtained. On the other hand, Ni is an expensive element, and it is economically inappropriate to contain it in excess of 2.5%, and excessive addition of Ni causes deterioration of weldability. Therefore, in the steel of the present invention, when Ni is contained, the content is limited to 0.01 to 2.5%. In addition, from the viewpoint of corrosion resistance, weldability, and economy, the Ni content is preferably 0.2 to 0.6%.

  Mo and W are effective in improving hydrochloric acid resistance. However, when the Mo content and the W content are each less than 0.01%, the hydrochloric acid resistance improving effect cannot be obtained. On the other hand, when Mo or W is contained exceeding 2.5%, weldability and toughness deteriorate. Therefore, when it contains Mo and / or W, the content is limited to 0.01 to 2.5%, respectively. In addition, since Mo and W are expensive elements, from the viewpoint of corrosion resistance, weldability, and economy, it is preferable that both elements be 0.02 to 0.1%.

  Furthermore, Sb, Sn, Se, and Pb have an effect of further improving the sulfuric acid corrosion resistance under a low temperature / low sulfuric acid concentration environment and a high temperature / high sulfuric acid concentration environment. However, when the content of these elements is less than 0.01%, the sulfuric acid corrosion resistance improving effect cannot be obtained. Moreover, even if Sb, Sn, Se, and Pb are each contained in excess of 0.3%, the effect is saturated, and there is a concern of adverse effects on other characteristics. Therefore, in consideration of economy and the like, when Sb, Sn, Se and / or Pb is contained, the contents are limited to 0.01 to 0.3%, respectively. In addition, when comprehensively considering corrosion resistance, economy, and manufacturability, the contents of Sb, Sn, Se, and Pb are more preferably 0.01 to 0.15%, respectively.

  Further, the steel of the present invention has Nb: 0.002-0.2%, V: 0.005-0.5%, Ti: 0.002-0.2%, Ta: It is also possible to add one or more elements selected from the group consisting of 0.005 to 0.5%, Zr: 0.005 to 0.5% and B: 0.0002 to 0.005% it can.

  Nb, V, Ti, Ta, Zr, and B are elements that have the effect of improving the strength of the steel by adding a small amount, and are contained as needed for strength adjustment. In addition, in the case of a cold-rolled steel sheet, the addition of Nb and Ti has an effect of improving workability by fixing C and N in the steel as well as an effect of lowering C. However, Nb content is less than 0.002%, V content is less than 0.005%, Ti content is less than 0.002%, Ta content is less than 0.005%, Zr content is 0.005%. And when the B content is less than 0.0002%, these effects are not exhibited. On the other hand, Nb content exceeds 0.2%, V content exceeds 0.5%, Ti content exceeds 0.2%, Ta content exceeds 0.5%, If the Zr content exceeds 0.5% or the B content exceeds 0.005%, the toughness deterioration becomes remarkable, which is not preferable. Therefore, if Nb, V, Ti, Ta, Zr and / or B are contained as required, the Nb content is 0.002 to 0.2% and the V content is 0.005 to 0.5. %, Ti content is 0.002 to 0.2%, Ta content is 0.005 to 0.5%, Zr content is 0.005 to 0.5%, and B content is 0.0002 to 0%. Limited to 0.005%.

  Furthermore, the steel of the present invention has Mg: 0.0001-0.01%, Ca: 0.0005-0.01%, Y: 0.0001-0.1%, La: 0.005-0. One or two or more elements selected from the group consisting of 1% and Ce: 0.005 to 0.1% may be contained.

  Mg, Ca, Y, La, and Ce are effective elements for improving the morphology of inclusions and improving ductility, and are also effective for improving the HAZ toughness of high heat input welded joints. Since the sludge generation suppressing effect due to this is weak, it is contained as necessary. In that case, Mg content is less than 0.0001%, Ca content is less than 0.0005%, Y content is less than 0.0001%, La content is less than 0.005%, and Ce content is 0.005. If it is less than%, the effect of adding each element does not appear. On the other hand, if the Mg content or Ca content exceeds 0.01%, or if the Y content, La content or Ce content exceeds 0.1%, the inclusions become coarse and mechanical properties are increased. Particularly adversely affects ductility and toughness. Therefore, when adding Mg, Ca, Y, La and / or Ce, the content is respectively Mg: 0.0001-0.01%, Ca: 0.0005-0.01%, Y: 0.00. 0001 to 0.1%, La: 0.005 to 0.1%, and Ce: 0.005 to 0.1%. In addition, it is preferable that Mg content shall be 0.0005%-0.01%, and this can improve the protection property of a rust layer of a base iron.

  In the steel of the present invention, the N content is not particularly limited, but is preferably 0.001 to 0.01%. N is not preferable because it adversely affects the ductility and toughness in the solid solution state, but on the other hand, it binds with V, Al or Ti and effectively works for austenite grain refinement and precipitation strengthening. It is effective for improving characteristics. Further, it is impossible to remove N in steel completely industrially, and reducing it more than necessary is not preferable because it places an excessive load on the manufacturing process. For this reason, the lower limit of the range in which the adverse effects on ductility and toughness can be tolerated and industrially controllable and the load on the manufacturing process can be tolerated is about 0.001%. Further, N has an effect of slightly improving the corrosion resistance, but if contained excessively, the solid solution N increases, which may adversely affect the ductility and toughness. Therefore, the upper limit as an allowable range is 0.01%. Is preferred.

  As described above in detail, the steel of the present invention is obtained by adding Cu-Cr-Co to a low carbon steel and optimizing the content of each element. Excellent corrosion resistance can be obtained in both environments of high sulfuric acid concentration. As a result, if the acid-corrosion resistant steel of the present invention is applied to an application that causes sulfuric acid corrosion, such as a flue gas treatment device of a thermal power plant and a sulfuric acid tank, the life of the equipment and equipment can be greatly extended, and the maintenance cost is greatly increased. Therefore, the industrial contribution is extremely large.

  Hereinafter, the effect of the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to the following Example. In this example, the steels having the compositions shown in Tables 1 and 2 below were melted and cast into ingots, then hot-rolled until the wall thickness became 4 mm, and further subjected to pickling and cold rolling. Annealing was performed to produce a cold-rolled steel sheet having a thickness of 1 mm, which was used as a test material. The balance in Tables 1 and 2 below is Fe and inevitable impurities. Moreover, the underline in the following Table 1 and Table 2 shows that it is outside the scope of the present invention.

  In this Example No. A1-No. A35 and Comparative Example No. C1-No. Test pieces having a length of 50 mm and a width of 50 mm were taken from a C6 cold-rolled steel sheet, subjected to a dipping test in sulfuric acid, and the amount of corrosion per unit time and unit area was measured. The test conditions at that time are as follows: low temperature / low sulfuric acid concentration environment, condition (a): temperature 40 ° C., sulfuric acid concentration 20%, and condition (b): temperature 70 ° C., sulfuric acid concentration 50%. As the sulfuric acid concentration environment, conditions (c): temperature 80 ° C., sulfuric acid concentration 60%, and conditions (d): temperature 140 ° C., sulfuric acid concentration 80% were adopted. The results are summarized in Table 3 below.

  As shown in Table 3 above, Comparative Example No. C1-No. The C6 cold-rolled steel sheet does not satisfy the requirements of the present invention. A1-No. Corrosion resistance was inferior to that of A35 cold-rolled steel sheet. Specifically, Comparative Example No. Since the C1 cold-rolled steel sheet has a Cr content less than the lower limit of the present invention, the corrosion resistance in a high temperature / high sulfuric acid concentration environment was inferior. On the other hand, Comparative Example No. The C2 cold-rolled steel sheet has a Cr content that exceeds the upper limit of the present invention, and a Co content that is less than the lower limit of the present invention. Therefore, in a low temperature / low sulfuric acid environment and a high temperature / high sulfuric acid environment. The corrosion resistance of was poor. Comparative Example No. Since the C3 cold-rolled steel sheet had a Cu content less than the lower limit of the present invention, the corrosion resistance under low temperature / low sulfuric acid concentration environment and high temperature / high sulfuric acid concentration environment was inferior. Further, Comparative Example No. C4-No. Since the C6 cold-rolled steel sheet has a Co content less than the lower limit of the present invention, the corrosion resistance in a low temperature / low sulfuric acid concentration environment was inferior.

  On the other hand, Example No. within the scope of the present invention. A1-No. All of the A35 cold-rolled steel sheets exhibited excellent corrosion resistance under both a low temperature / low sulfuric acid concentration environment and a high temperature / high sulfuric acid concentration environment. In particular, Example No. having an S content of 0.005%. The cold-rolled steel sheet of A31 has an S content of 0.001%, and the other contents are No. Example No. which is the same as A31. Corrosion resistance was superior to A32 cold-rolled steel sheet. Thereby, it was confirmed that corrosion resistance improves more by making S content into 0.005-0.030%.

  Moreover, Example No. which is mutually equal except Co content. Cold rolled steel sheet of A10 and Example No. Except for the cold rolled steel sheet of A29 and the Cr content, Example No. Cold rolled steel sheet of A13 and Example No. When compared with the cold-rolled steel sheet of A30, [Cr] / [Co] is 50 or less. A10 and No. The cold-rolled steel sheet of A13 has a [Cr] / [Co] of more than 50 in Example No. A29 and No. Corrosion resistance was excellent in both low temperature / low sulfuric acid concentration environment and high temperature / high sulfuric acid concentration environment than A30 cold-rolled steel sheet. From this result, it was confirmed that the corrosion resistance under low temperature / low sulfuric acid concentration environment and high temperature / high sulfuric acid concentration environment is further improved by setting [Cr] / [Co] to 50 or less.

Claims (5)

% By mass
C: 0.001 to 0.2%,
Si: 0.01-3.0%,
Mn: 0.01 to 3.0%,
P: 0.035% or less,
S: 0.030% or less,
Al: 0.001 to 0.3%,
Cu: 0.01 to 2.0%,
Cr: 0.01 to 2.0%,
Co: 0.01 to 0.2%,
An acid-corrosion-resistant steel characterized in that the balance consists of Fe and inevitable impurities.   Furthermore, in mass%, Ni: 0.01-2.5%, Mo: 0.01-2.5%, W: 0.01-2.5%, Sb: 0.01-0.3%, Contains one or more elements selected from the group consisting of Sn: 0.01-0.3%, Se: 0.01-0.3% and Pb: 0.01-0.3% The acid-corrosion-resistant steel according to claim 1.   Furthermore, by mass%, Nb: 0.002-0.2%, V: 0.005-0.5%, Ti: 0.002-0.2%, Ta: 0.005-0.5%, The element according to claim 1 or 2, comprising one or more elements selected from the group consisting of Zr: 0.005 to 0.5% and B: 0.0002 to 0.005%. The acid-corrosion resistant steel described.   Furthermore, in mass%, Mg: 0.0001-0.01%, Ca: 0.0005-0.01%, Y: 0.0001-0.1%, La: 0.005-0.1% and The acid-corrosion-resistant steel according to any one of claims 1 to 3, comprising one or more elements selected from the group consisting of Ce: 0.005 to 0.1%.   The acid-corrosion resistant steel according to any one of claims 1 to 4, wherein S is 0.005 to 0.030% in mass%.