JPH11335789A - Corrosion resisting steel excellent in acid-cleaning - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the corrosion resisting steel which exhibits an excellent corrosion resistance in corrosive environments such as a high-temp., wet corrosive environment, a corrosive environment caused by dew condensation, an atmospheric corrosive environment, a corrosive environment caused by city water, soils, concrete, sea water, drinking water or the like and which is also excellent in acid-cleaning. SOLUTION: The objective steel contains, by weight, 0.01-3.0% Si, 0.1-3.0% Mn, 10-30% Cr, 1-10% Al and 5-500 ppm Ca+Mg, wherein, the contents of C, P, S and N are reduced to amounts of <=0.02%, <=0.03%, <=0.01% and <=0.02%, respectively. The addition of at least one selected from Cu, Mo, Sb, Ni, W and rare earth elements to the above mentioned composition causes the corrosion resistance of the steel to increase. Moreover, the addition of 0.01-1% by total weight of Nb, V, Ti, Zr, Ta and Hf causes the corrosion resistance and workability of the steel to increase further.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion-resistant steel having excellent pickling properties, and more particularly, to a high-temperature wet corrosion environment such as an exhaust system for an internal combustion engine, a boiler exhaust system, a low-temperature heat exchanger, an incinerator floor, and a bridge. , Struts, building interior and exterior materials, roofing materials, fittings, kitchen components, various handrails, roof drains, atmospheric corrosion environments such as rail cars, various storage tanks, soil corrosion environments such as struts, piles, sheet piles, cans, various containers , Low-temperature heat exchangers, dew-corrosion environments such as bathroom components (including corrosive environments where freezing, wetting and drying are combined), water storage tanks, water supply pipes, hot water supply pipes, can containers, various containers, tableware, cooking equipment, bath tubs, pools Corrosion environment of tap water such as washstands, corrosive environment of drinking water such as cans, various containers, tableware, cooking equipment, etc., concrete corrosion environment of various reinforced structures, columns, ships, bridges, piles, sheet piles, marine construction Rot such as seawater corrosive environment It has excellent corrosion resistance in the environment, and to a corrosion resistant steel having good pickling.

[0002]

2. Description of the Related Art Steels used in corrosive environments such as high temperature wet corrosive environments, dew condensation corrosive environments, atmospheric corrosive environments, tap water corrosive environments, soil corrosive environments, concrete corrosive environments, seawater corrosive environments, drinking water corrosive environments, etc. Often, some anti-corrosion measures are used together. In recent years, the use of Cr alloy steel and stainless steel for the purpose of improving the corrosion resistance of steel substrates has been increasing from the viewpoint of improving reliability, simplifying the manufacturing and construction processes, making maintenance free, and saving resources. I have. However, in the conventional technology, the improvement in corrosion resistance leads to an increase in material cost, and is often not a practical measure from the viewpoint of economy. In addition, improvement of corrosion resistance, such as reducing the workability of the material,
It can also cause side problems.

[0003] For example, in the exhaust system of an internal combustion engine mainly for automobiles, steel in which ordinary steel is plated with aluminum or zinc has been used in order to suppress corrosion from the inside or outside. Since a catalyst or the like was provided in the exhaust system for the purpose of purifying exhaust gas to suppress environmental pollution, such a plated steel material did not have sufficient corrosion resistance, and contained 5 to 10% Cr for the purpose of improving the corrosion resistance of the steel substrate. Steel is disclosed in JP-A-63-143240 and JP-A-63-143241. However, with the extension of the service period and the warranty period of vehicles in recent years, high-grade stainless steel further containing about 18% of Cr or further adding Mo has come into use.

[0004] However, even such a high-grade stainless steel does not always have sufficient corrosion resistance, such as the occurrence of pitting-like local corrosion. In addition, such high-grade stainless steel is poor in workability because it contains a large amount of Cr and Mo, and it is extremely difficult to manufacture a complicated shape such as an exhaust system member, and the manufacturing process is remarkably difficult. There is a disadvantage that the processing cost increases due to the complexity. Or it may not be applicable depending on the shape. And,
Material costs are also high.

As can be seen from the above-mentioned example, in general, steel containing a certain amount of Cr is liable to cause local corrosion when the corrosion environment becomes severe, and in order to improve the resistance to corrosion, it is necessary to further improve the resistance to corrosion by using Cr or Mo. Increasing the content of was a very common technical measure. In addition, corrosion-resistant steel, in exchange for improved corrosion resistance,
In many cases, a large increase in load is required during manufacturing. That is, in order to obtain a corrosion resistant material, it is well known that addition of a corrosion resistance improving element such as Cr, Cu, or Mo, which has been generally used in the past, greatly reduces pickling properties. Improving pickling properties is often an important issue from an economic viewpoint. A steel sheet excellent in corrosion resistance to which Cr, Cu, and Mo are added is excellent in corrosion resistance, and at the same time, it is positioned as a pickling resistant steel in terms of pickling properties, similarly to conventional corrosion-resistant materials. Conventionally, in the manufacturing process of hard-to-pick steel, the descaling efficiency has been enhanced by strengthening or changing the pickling liquid, using electrolysis, using physical descaling such as shot blasting or grinding, or combining these means. Improvement measures were very common. However, these pickling-improving means involve a great deal of equipment investment and an increase in process load in taking measures, resulting in an increase in steel manufacturing costs.

In recent years, Japanese Patent Application Laid-Open Nos. Hei 5-279791, Hei 6-179949, Hei 6-179950
JP, JP-A-6-179951, JP-A-6-2
JP-A-12256, JP-A-6-212257 and JP-A-7-3388 disclose steels in which Al is added to Cr for the purpose of improving corrosion resistance or improving corrosion resistance and workability. These steels are recognized to be effective to some extent in improving corrosion resistance or corrosion resistance and workability. However, as with conventional corrosion-resistant materials, they are regarded as difficult to pickle, as in conventional corrosion-resistant materials. At present, it has not been resolved.

[0007]

SUMMARY OF THE INVENTION In view of these circumstances, the present invention has been developed in consideration of the high-temperature wet corrosion environment, condensation corrosion environment, atmospheric corrosion environment, tap water corrosion environment, soil corrosion environment, concrete corrosion environment, seawater corrosion environment, beverage An object of the present invention is to provide a low-cost corrosion-resistant steel having high corrosion resistance in a corrosive environment such as a water-corrosive environment and excellent in pickling properties.

[0008]

Means for Solving the Problems In order to achieve the above objects, the present inventors have developed a high-temperature wet corrosion environment, a dew condensation corrosion environment, an atmospheric corrosion environment, a tap water corrosion environment, a soil corrosion environment, a concrete corrosion environment, a seawater corrosion environment. In order to develop a corrosion resistant steel having excellent corrosion resistance in the corrosive environment such as the environment and drinking water corrosive environment, the study was conducted from various viewpoints. First, as a result of studying various means for improving corrosion resistance in each of the above-mentioned corrosive environments simultaneously with excellent pickling properties, a steel containing 10 to 30% of Cr was added with 1 to 10% of Al and 5 to 500 ppm of Ca + Mg.
It has been found that the added steel has excellent pickling properties and that it exhibits very good corrosion resistance in many of the corrosive environments described above. Although there are many unclear points about the mechanism of the effect of simultaneous addition of Ca and Mg, it has been found that under conditions where both coexist, excellent pickling properties and corrosion resistance deviating from conventional knowledge are simultaneously achieved. .

Further, the present inventors have continued their studies to find a more excellent steel, and as a result, have found that the above-mentioned steel has Cu, Mo, S
When b, Ni and W are added alone or in combination, more excellent corrosion resistance can be obtained without impairing the excellent pickling property, and when C and N are reduced, the corrosion resistance and processing can be obtained without impairing the excellent pickling property. Effective in improving sex,
Si and Mn are suitable as deoxidizing and strengthening elements, and Nb, V, Ti, Z after reducing C and N
It has been found that when r, Ta, and Hf are added so as to satisfy specific conditions, it is effective in improving corrosion resistance and workability without impairing excellent pickling properties.

[0010] The present invention has been made based on the above findings, and in terms of% by weight, Si: 0.01% to 3.0%;
Mn: 0.1 to 3.0%, Cr: 10 to 30%, Al:
1% to 10%, Ca + Mg: 5 to 500 ppm, balance Fe
And unavoidable impurities, of which C is limited to 0.02% or less, P is limited to 0.03% or less, S is limited to 0.01% or less, and N is limited to 0.02% or less. Corrosion-resistant steel with excellent pickling characteristics.

[0011] In the above invention steel, further, by weight%,
Cu: 0.05 to 5.0%, Mo: 0.05 to 3.0
%, Sb: 0.01-0.5%, Ni: 0.01-6.
0%, W: 0.05 to 3.0%, by containing one or more of them, without impairing the pickling properties,
Further improvement in corrosion resistance is obtained.

Further, by adding the rare earth element: 0.001 to 0.1% by weight in the invention steel, hot workability and corrosion resistance can be further improved. Furthermore, among the above-mentioned basic component steels and steels containing additional elements, those which require particularly high workability are one or two selected from Nb, V, Ti, Zr, Ta and Hf. The total content of the above elements is 0.01 to 1%, and the content is within a range satisfying the following expression.

Nb / 93 + V / 51 + Ti / 48 + Zr
/91+Ta/181+Hf/179-0.8×[C/
12 + N / 14] ≧ 0

[0014]

The reasons for limiting the range of each component in the present invention will be described below. Si: It is effective to add Si as a deoxidizing agent and a strengthening element to steel containing 10% or more of Cr, but if the content is less than 0.01%, the deoxidizing effect is not sufficient, and If the content exceeds 0%, the effect is saturated and, on the contrary, the pickling property and the processability are lowered. Therefore, the content range is limited to 0.01% or more and 3.0% or less.

Mn: Mn is used as a steel deoxidizing agent in an amount of 0.1%.
However, if the content exceeds 3.0%, the effect is not only saturated, but if Mn is excessively contained, the processability is reduced. 3.0%. Cr: It is necessary to contain 10% or more of Cr in order to ensure corrosion resistance. However, if the content of more than 30% increases the cost, the content of the upper limit is 30%. I do. When workability is further emphasized, the upper limit content is more preferably set to 25%.

Al: Al is an important element in addition to Ca + Mg and Cr in order to secure corrosion resistance in the present invention. The content of Al depends on the amount of Ca + Mg required to secure corrosion resistance and pickling properties. 1% or more is necessary to ensure the content of 5 ppm or more stably, and if the content of Al is less than 1%, the effect of suppressing the occurrence of pitting corrosion is not sufficient, and on the other hand, it exceeds 10%. If added, the effect is saturated, but the workability and pickling properties are reduced, so the Al content is limited to 1% or more and 10% or less.

Ca + Mg: Ca and Mg contain 10% of Cr.
% In steel containing 1% or more of Al, is the most important element along with Al in order to secure not only corrosion resistance but also pickling properties. At present, there are many unclear points about the mechanism,
If the total of both is less than 5 ppm, good pickling properties cannot be obtained. On the other hand, from the viewpoint of corrosion resistance, when the total amount is 10 ppm or more, the corrosion resistance is further improved. With the increase in the total amount, the improvement in corrosion resistance is recognized. It has been clarified that the property also decreases, and the content of Ca + Mg is limited to 5 ppm or more and 500 ppm or less.

C and N: C and N reduce the workability of the steel sheet, and also, C forms carbides with Cr to lower the corrosion resistance, and N lowers the toughness. Is desirably small, and the upper limit of the content is set to 0.02%. The smaller the number, the better.
It is advisable to use as little steelmaking technology as possible. P: If P is present in a large amount, the toughness is reduced. Therefore, it is desirable that P is small, and the upper limit content is 0.03%.
It is preferable to minimize the content that is inevitably mixed.

S: Since the presence of a large amount of S lowers the pitting corrosion resistance, the smaller the amount, the better.
01%. As with P, it is preferable that the inevitable mixing amount of S be as small as possible. The steel of the present invention has the above-described component composition as a basic component. In order to further improve corrosion resistance, one or more of Cu, Mo, Sb, Ni, and W are further contained.

Cu: Cu contains 10% or more of Cr, 1% or more of Al, and 5 ppm to 50% of Ca + Mg.
When 0.05% or more is added to steel containing 0 ppm, an excellent effect of improving resistance to general corrosion without impairing excellent pickling properties is observed, but when added in excess of 5.0%, pickling properties are reduced. Therefore, the content is set to 0.05 to 5.0%. Mo: Mo contains 10% or more of Cr and 1% of Al
When 0.05% or more is added to steel containing 5 ppm to 500 ppm of Ca + Mg, the effect of suppressing the generation and growth of pitting corrosion is observed without impairing excellent pickling properties, but 3.0%. Is added, the effect is not only saturated, but also the workability is deteriorated. Therefore, the content is set to 0.05 to 3.0%.

Sb: Sb also contains 10% or more of Cr, 1% or more of Al, and 5 ppm to 50% of Ca + Mg.
Addition of 0.01% or more to steel containing 0 ppm has the effect of improving resistance to pitting corrosion and general corrosion without impairing excellent pickling properties. However, adding more than 0.5% results in pickling. Performance and hot workability
0.01% to 0.5%.

Ni: Ni contains 10% or more of Cr, 1% or more of Al, and 5 ppm to 50% of Ca + Mg.
When 0.01% or more is added to steel containing 0 ppm, the effect of suppressing pitting corrosion is recognized without impairing excellent pickling properties, but the effect is only saturated when added over 6.0%. Or lowers hot workability.
%.

W: W contains 10% or more of Cr;
1% or more, and 5 ppm to 500 ppm of Ca + Mg
When added to steel containing steel at a content of 0.05% or more, the effect of suppressing the occurrence and growth of pitting corrosion is noticeably observed without impairing the excellent pickling properties, but added in excess of 3.0%. Even so, the effect is not only saturated, but also the pickling property and the processability deteriorate, so that the content is set to 0.05 to 3.0%.

[0024] In the steel of the present invention, a rare earth element (REM) is selectively contained as an element for further improving the corrosion resistance. Rare earth element (REM): Rare earth element is Cr
10% or more, Al 1% or more, Ca + M
g is added to steel containing from 5 ppm to 500 ppm, which is an element that is effective for improving hot workability and pitting corrosion resistance without impairing excellent pickling properties. If less than 0.001%, the effect is not enough,
If added in excess of 0.1%, coarse non-metallic inclusions are formed and conversely degrade hot workability and pitting corrosion resistance.
0.001 to 0.1%. In the present invention, the rare earth element has an atomic number of 57-71 and 89-10.
Indicates the third element and Y.

In the case of a steel comprising the above-described steel components and having excellent pickling properties and corrosion resistance, if particularly high workability is also required, Nb, V, Ti, Zr, Ta, Hf may be used as necessary.
One or more of these. Nb, V, Ti, Zr, Ta, Hf: Nb, V, T
i, Zr, Ta, and Hf contain 10% or more of Cr,
1% or more, and 5 ppm to 500 ppm of Ca + Mg
Without impairing the excellent pickling properties of the contained basic component steel,
By fixing C and N in the high Cr steel as carbides, a remarkable effect on improvement of corrosion resistance and workability is recognized. Of these, each element can be added alone or two or more elements can be added in combination.
If it is less than 1%, there is no effect, and if it exceeds 1%, the cost is increased and roll flaws are caused. Therefore, the total amount is set to 0.01 to 1%. In addition, in order to effectively improve workability, Nb, V, Ti, Zr, Ta, H
It is necessary that the total amount of f added satisfies the following expression.

Nb / 93 + V / 51 + Ti / 48 + Zr
/91+Ta/181+Hf/179-0.8×[C/
12 + N / 14] ≧ 0 If the above formula is not satisfied, the immobilization of C and N becomes insufficient, and it becomes difficult to obtain the effect of improving workability. When the steel of the present invention is used, for example, after being manufactured as a steel ingot, it is hot-rolled, forged, cold-rolled, drawn by wire or the like into an arbitrary shape such as a steel sheet, a sheet steel, and the like. It may be formed into a shape, further processed and welded to be manufactured as a product, or a steel plate may be used as a product by secondary processing and welding after forming the steel tube into a shape such as an ERW steel tube first, An optimum product manufacturing process can be selected depending on costs, restrictions on existing manufacturing facilities, and the like, including other processes. Whatever manufacturing process is selected, it is sufficient that the steel of the present invention can be manufactured.

The steel of the present invention has an A
l or an Al alloy containing a further necessary element is deposited by a method such as a plating method or a cladding method, and the element is diffused by an appropriate treatment such as a heat treatment. good. The steel of the present invention can be used in various kinds of corrosion, such as high temperature wet corrosion environment, condensation corrosion environment, atmospheric corrosion environment, tap water corrosion environment, soil corrosion environment, concrete corrosion environment, seawater corrosion environment, drinking water corrosion environment, etc. Can be applied to the environment.

[0028]

Embodiments of the present invention will be described below. 1) Evaluation of pickling properties Steels having the components shown in Tables 1 and 3 were melted, formed into a steel ingot by a normal ingot manufacturing process, and then subjected to hot rolling to obtain a sample having a thickness of 2.5 mm. Next, test pieces having a width of 50 mm and a length of 70 mm were sampled from these steel sheets and subjected to an acid pickling test.

In the pickling test, a test piece was immersed in an 8% hydrochloric acid aqueous solution heated to 85 ° C. to remove the surface scale. The test results are shown in Tables 2 and 4. In the results of the pickling test, ◎ indicates that the pickling was completed within 20 seconds, ○ indicates that the pickling was completed within 40 seconds, Δ indicates that the pickling was completed within 60 seconds, and x indicates 120. It indicates that the pickling was not completed even with a treatment time of not less than seconds.

As is clear from Tables 2 and 4, the steels of the present invention (Nos. 1-36, 50-85) show good pickling properties, while the comparative steels (Nos. 37-49,86). ~ 9
8) is inferior in pickling properties. 2) Evaluation of corrosion resistance Steels having the components shown in Tables 1 and 3 were melted and made into a steel plate having a thickness of 1 mm by a normal steel plate manufacturing process such as hot rolling or cold rolling.
Annealed at 50mm width and 70mm length from these steel plates
mm test pieces were collected and subjected to various corrosion tests described below.

The high-temperature wet corrosion test was carried out with a sulfate ion of 100 pp.
m, chloride ion 350ppm, bicarbonate ion 500ppm
The test piece was immersed in half in an aqueous solution (50 cm ³⁾ in which the test solution was added in the form of an ammonium salt, and the entire test container was kept at 130 ° C. to ensure that the test solution completely evaporated and evaporated.
The test was repeated twice. The test results are shown in Tables 2 and 4. In the results of the corrosion test, ◎ indicates that the maximum corrosion depth is less than 0.20 mm, ○ indicates less than 0.3 mm, Δ indicates less than 0.4 mm, and × indicates 0.4.
mm or more.

As is clear from Tables 2 and 4, the steels of the present invention (Nos. 1 to 36, 50 to 85) show good corrosion resistance even in a very severe corrosive environment of high temperature wet containing chloride. On the other hand, comparative steels (Nos. 37 to 49,86
-98) are inferior in corrosion resistance, or inferior in pickling even though some degree of corrosion resistance is obtained. The tap water environmental corrosion test was a test in which a test piece was immersed in tap water and kept in a 45 ° C. atmosphere for 12 months. The test results are shown in Tables 2 and 4. In the results of the corrosion test, ◎ indicates that no corrosion was observed, は indicates that the rusting area ratio was less than 5%, Δ indicates that the rusting area ratio was less than 10%, and X indicates that the rusting area ratio was 10% or more. .

As is clear from Tables 2 and 4, the steels of the present invention (Nos. 1-36, 50-85) show good corrosion resistance in tap water corrosive environments, while the comparative steels (Nos.
49, 86 to 98) are inferior in corrosion resistance or inferior in pickling even if a certain degree of corrosion resistance is obtained. The seawater environment corrosion test was a test in which a test piece was exposed to a shore splash zone for 17 months. The test results are shown in Tables 2 and 4.
In the results of the corrosion test, ◎ indicates that the corrosion depth was less than 0.05 mm, ○ indicates less than 0.1 mm, Δ indicates less than 0.3 mm, and × indicates 0.3.
mm or more.

As is clear from Tables 2 and 4, the steels of the present invention (Nos. 1-36, 50-85) show good corrosion resistance in a seawater corrosive environment, while the comparative steels (Nos. 37-4)
9, 86 to 98) are inferior in corrosion resistance, or inferior in pickling even if a certain degree of corrosion resistance is obtained. The dew condensation corrosion test was conducted at a humidity of 95%
The test was repeated 1,300 times to maintain the environment at 25 ° C. for 4 hours. The test results are shown in Tables 2 and 4. ◎ in the corrosion test results indicates that no corrosion was observed,
○ indicates that the rusting area ratio was less than 5%, △ indicates that the rusting area ratio was less than 10%, and X indicates that the rusting area ratio was 10% or more.

As is evident from Tables 2 and 4, the steels of the present invention (Nos. 1-36, 50-85) show good corrosion resistance in a dew-corrosion environment, while the comparative steels (Nos. 37-4)
9, 86 to 98) are inferior in corrosion resistance, or inferior in pickling even if a certain degree of corrosion resistance is obtained. In the atmospheric corrosion test, a test piece was placed about 350 m from the coast at about 70 m.
The test was performed with 0 day exposure. The test results are shown in Tables 2 and 4. In the results of the corrosion test, ◎ indicates that no corrosion was observed, は indicates that the rusting area ratio was less than 5%, and △ indicates that the rusting area rate was 10%.
%, And X indicates 10% or more.

As is clear from Tables 2 and 4, the steels of the present invention (Nos. 1 to 36, 50 to 85) show good corrosion resistance in an atmospheric corrosion environment, while the comparative steels (Nos. 37 to 4) have good corrosion resistance.
9, 86 to 98) are inferior in corrosion resistance, or inferior in pickling even if a certain degree of corrosion resistance is obtained. The soil corrosion test was conducted by embedding a test piece in sand adjusted to a water content of 15% and a specific resistance of 400 Ω · cm with a sodium chloride content.
A test was performed in which the temperature was maintained at 0 ° C. and left for about 700 days. The test results are shown in Tables 2 and 4. In the results of the corrosion test, ◎ indicates that the maximum corrosion depth was less than 0.05 mm, ○ indicates that the depth was less than 0.1 mm, Δ indicates that the depth was less than 0.5 mm, and x indicates that the depth was 0.5 mm or more.

As is clear from Tables 2 and 4, the steels of the present invention (Nos. 1-36, 50-85) show good corrosion resistance in a soil corrosive environment, while the comparative steels (Nos. 37-4)
9, 86 to 98) are inferior in corrosion resistance, or inferior in pickling even if a certain degree of corrosion resistance is obtained. The corrosion test in concrete is performed by embedding a test piece in Portland cement kneaded with sea sand containing chloride to form a sample, solidifying it, immersing the sample in artificial seawater by half, and placing it in a 50 ° C environment. It was a test that was left for about 700 days. The test results are shown in Tables 2 and 4. In the results of the corrosion test, ◎ indicates that no corrosion was observed, は indicates that the rusting area ratio was less than 5%, △ indicates that the rusting area ratio was less than 10%, and × indicates that the rusting area ratio was less than 10%.
0% or more.

As is clear from Tables 2 and 4, the steels of the present invention (Nos. 1-36, 50-85) show good corrosion resistance in a corrosive environment in concrete, while the comparative steels (Nos. 49, 86 to 98) are inferior in corrosion resistance or inferior in pickling even if a certain degree of corrosion resistance is obtained. The drinking water environmental corrosion test uses sodium hydroxide
The pH was adjusted to 2.5, degassed by passing high-purity nitrogen gas, and kept at 27 ° C. (a) 0.5% phosphoric acid solution,
(B) A test piece was immersed in a 850 cc solution of 0.5% citric acid solution, (c) 0.5% citric acid-0.5% sodium chloride solution for 25 days, and the amount of iron ions eluted in the solution Was a test for analyzing The test results are shown in Tables 2 and 4. In the results of the corrosion test, ◎ indicates that the elution amount of iron ions into the solution was 1 ppm or less, ○ indicates less than 3 ppm, Δ indicates less than 5 ppm, and × indicates 5 p.
pm respectively.

As is clear from Tables 2 and 4, the steels of the present invention (Nos. 1 to 36, 50 to 85) show good corrosion resistance in a drinking water corrosive environment, whereas the comparative steels (Nos.
49, 86 to 98) are inferior in corrosion resistance or inferior in pickling even if a certain degree of corrosion resistance is obtained. That is, the steel of the present invention (Nos. 1-36, 50-85) is a high temperature wet corrosion environment, dew condensation environment, atmospheric corrosion environment, tap water corrosion environment, soil corrosion environment, concrete corrosion environment, seawater corrosion environment, drinking water corrosion environment, etc. Shows good corrosion resistance in various corrosive environments, whereas the comparative steels (Nos. 37 to 49,8)
6 to 98) are inferior in corrosion resistance or poor in pickling even if a certain degree of corrosion resistance is obtained.

3) Evaluation of workability The steel having the components shown in Table 3 was subjected to a cylindrical drawing test with a drawing ratio of 1.8, and the presence or absence of cracks was judged. The steels having the components shown in Table 3 were melted and formed into steel sheets having a thickness of 1.0 mm by ordinary steel plate manufacturing processes such as hot rolling and cold rolling, and were annealed at 850 ° C. A 100 mm test piece was sampled and used for the test. The test results are shown in Table 4. In the workability column of Table 4, ○ indicates that the result of the cylindrical drawing test was good, and × indicates that cracks were generated in the cylindrical drawing test.

As is clear from Table 4, the steels of the present invention (Nos. 50 to 85) exhibit good pickling properties, and have a high-temperature wet corrosion environment, a dew condensation corrosion environment, an atmospheric corrosion environment, a tap water corrosion environment, and a soil corrosion environment. It shows good corrosion resistance in various corrosive environments such as concrete corrosive environment, sea water corrosive environment, drinking water corrosive environment, etc. and has excellent workability, whereas the comparative steel (No. 86-98) has pickling properties. It can be seen that corrosion resistance and workability cannot be simultaneously achieved.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

[Table 5]

[0047]

The corrosion-resistant steel of the present invention has excellent pickling properties and corrosion resistance by containing Cr, Al, and Ca + Mg, and can be provided at low cost. Yes, in detail, excellent for use in corrosive environments such as high temperature wet corrosive environment, dew condensation corrosive environment, atmospheric corrosive environment, tap water corrosive environment, soil corrosive environment, concrete corrosive environment, seawater corrosive environment, drinking water corrosive environment It has excellent corrosion resistance and at the same time has excellent pickling properties.

Claims (4)

[Claims] 1. wt%, Si: 0.01 to 3.0%, Mn: 0.1 to 3.0%, Cr: 10 to 30%, Al: 1 to 10%, Ca + Mg: 5 to 500 ppm The balance consists of Fe and inevitable impurities, and of the inevitable impurities, C is limited to 0.02% or less, P is limited to 0.03% or less, S is limited to 0.01% or less, and N is limited to 0.02% or less. Corrosion-resistant steel with excellent pickling characteristics. 2. Further, in terms of% by weight, Cu: 0.05 to 5.0%, Mo: 0.05 to 3.0%, Sb: 0.01 to 0.5%, Ni: 0.01 to The corrosion-resistant steel having excellent pickling properties according to claim 1, comprising one or more of 6.0% and W: 0.05 to 3.0%. 3. The corrosion-resistant steel having excellent pickling properties according to claim 1, further comprising: 0.001 to 0.1% by weight of a rare earth element. 4. The method according to claim 1, further comprising Nb, V, Ti, Z in weight%.
4. The method according to claim 1, wherein one or more elements selected from r, Ta, and Hf are contained in a total content of 0.01 to 1% and satisfy the following expression. Or 3
Corrosion-resistant steel excellent in pickling properties described in 1. Nb / 93 + V / 51 + Ti / 48 + Zr / 91 + Ta
/181+Hf/179-0.8×[C/12+N/1
4] ≧ 0