JPH10195606A - Steel with excellent pickling and corrosion resistance - Google Patents

Abstract

(57) [Abstract] [Problem] To be excellent in pickling, and for example, 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 A steel having excellent corrosion resistance or a steel having excellent corrosion resistance and workability in a corrosive environment such as a corrosive environment. SOLUTION: In the steel of the present invention, Si: 0.01
To 3.0%, Mn: 0.1 to 3.0%, Cr: 2 to 9.
9%, Al: 1-10%, Ca + Mg: 10-500pp
m, to reduce C to 0.02% or less, P to 0.03% or less, S to 0.01% or less, and N to 0.02% or less. If necessary, Cu, Mo, Sb, Ni,
W, one or more rare earth elements, and if necessary, Nb, V, Ti, Zr, Ta, and Hf in a total of 0.0
1-0.5% is contained. Thereby, steel excellent in pickling properties and corrosion resistance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a steel excellent in pickling and corrosion resistance, and more particularly, to an exhaust system for an internal combustion engine,
Boiler exhaust system, low-temperature heat exchanger, high-temperature wet corrosion environment such as incinerator floor, bridges, columns, building interior and exterior materials, roofing materials, fittings,
Atmospheric corrosion environment of kitchen parts, various handrails, roof drains, railway cars, etc., soil corrosion environment of various storage tanks, columns, piles, sheet piles, etc., dew corrosion environment of cans, various containers, low temperature heat exchangers, bathroom members Includes corrosive environment in which freezing, wetting, and drying are combined), water storage tanks, water supply pipes, hot water supply pipes, can containers, various containers, tableware, cooking equipment, bathtubs, pools, vanities, and other tap water corrosive environments, can containers Excellent in corrosive environments such as drinking water corrosion environment of various containers, tableware, cooking equipment, etc., concrete corrosion environment of various reinforced structures, pillars, etc., seawater corrosion environment of ships, bridges, piles, sheet piles, marine structures, etc. Steel with good corrosion resistance and good pickling properties.

[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-containing steel and stainless steel for the purpose of improving the corrosion resistance of steel substrates has been increasing from the viewpoints of improving reliability, simplifying manufacturing and construction processes, making maintenance free, and saving resources. . 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 subjected to aluminum plating or zinc plating has been used in order to suppress corrosion from the inside or outside. Since a catalyst or the like is provided in the exhaust system for the purpose of purifying exhaust gas to suppress environmental pollution, such a plated steel material does not have sufficient corrosion resistance, and contains 5 to 10% Cr for the purpose of improving the corrosion resistance of the steel base. Steel is disclosed in JP-A-63-143240 and JP-A-6-143240.
It is proposed in Japanese Patent Publication No. 3-143241. Further, with the extension of the service period and the warranty period of vehicles in recent years, Cr is further contained up to about 18%, or M
High-grade stainless steels to which o has been added have come into wide 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.

[0006] In addition, corrosion-resistant steel often requires a great increase in load at the time of manufacture in exchange for improvement in corrosion resistance. 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, and Mo, which is conventionally generally used, greatly reduces pickling properties. Improving pickling properties is often an important issue from an economic viewpoint. Cr and Cu,
The steel plate with excellent corrosion resistance to which Mo is added is excellent in corrosion resistance, and at the same time, in terms of pickling properties, like conventional corrosion-resistant materials,
It is positioned as an acid-fast washable steel. Conventionally, in the manufacturing process of hard-to-pickling steel, strengthening and changing
Measures for improving the efficiency of deskew such as the use of electrolysis, the use of physical deskew such as shot blasting and grinding, or the combination of these means have been quite common. However, these means for improving pickling properties 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
In JP-A-12256, JP-A-6-212257, and JP-A-7-3388, steels in which Al is added to Cr for the purpose of improving corrosion resistance or improving corrosion resistance and workability are proposed. 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.

[0008]

SUMMARY OF THE INVENTION In view of these circumstances, the present invention provides 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, and a beverage. An object of the present invention is to provide a low-cost steel having a large corrosion resistance in a corrosive environment such as a water-corrosive environment and having excellent pickling properties.

[0009]

Means for Solving the Problems In order to achieve the above objects, the present inventors have developed a high temperature wet corrosion environment, dew condensation corrosion environment, atmospheric corrosion environment, tap water corrosion environment, soil corrosion environment, concrete corrosion environment, seawater environment. In order to develop steel that has excellent corrosion resistance in corrosive environments such as corrosive environments and drinking water environments,
The study was conducted from various viewpoints. First, as a result of various studies on means for improving corrosion resistance in each of the above-mentioned corrosive environments at the same time as excellent pickling properties, a steel containing 2 to 9.9% of Cr was added to a steel containing 1 to 10% of Al and 5 to 5% of Ca + Mg. That the steel added with 500 ppm has excellent pickling properties, and that it exhibits very good corrosion resistance in many of the corrosive environments described above;
Was found. There are many unclear points about the mechanism of the effect of simultaneous addition of Ca and Mg, but it has been found that under conditions where both coexist, excellent pickling properties and corrosion resistance that deviate from conventional knowledge are simultaneously achieved. .

[0010] Further, the inventors of the present invention have continued to study for a more excellent steel, and as a result, Cu, Mo, S
When b, Ni and W are added alone or in combination,
It is possible to obtain better corrosion resistance without impairing excellent pickling properties, and it is effective to improve corrosion resistance and processability without impairing excellent pickling properties by reducing C and N; Si and Mn are suitable as strengthening elements, and Nb, V, T
It has been found that when i, Zr, 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.

The present invention has been made on the basis of the above findings, and the gist of the invention is that, in terms of% by weight, C: 0.02% or less, Si: 0.01 to 3.0%, and Mn: 0. 1 to 3.0
%, Cr: 2 to 9.9%, Al: 1 to 10%, Ca + M
g: 5 to 500 ppm, P: 0.03% or less, S: 0.0
It is a steel excellent in pickling properties and corrosion resistance, characterized by being 1% or less, N: 0.02% or less, the balance being Fe and unavoidable impurities.

[0012] 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 improved.

Further, among the steels containing the basic component steel and the additional element, those which require workability include one or two selected from Nb, V, Ti, Zr, Ta and Hf. It contains 0.01 to 0.5% in total of the content of at least one kind of element, and is contained within a range satisfying the following formula. Nb / 93 + V / 51 + Ti / 48 + Zr / 91 + Ta
/181+Hf/179-0.8×(C/12+N/1
4) ≧ 0

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 2% or more of Cr, but if the content is less than 0.01%, the deoxidizing effect is not sufficient.
If the content exceeds 3.0%, the effect is saturated and, on the contrary, the pickling property and the processability are reduced. Therefore, the content range is limited to 0.01% or more and 3.0% or less.

Mn: Mn is 0.1% as a steel deoxidizing agent.
It is necessary to contain the above, but if the content exceeds 3.0%, the effect is not only saturated anymore, but if Mn is excessively contained, the workability is reduced. 0.0%.

Cr: Cr is 2 to ensure corrosion resistance.
%, It is necessary to contain 9.9% or more. However, if the content exceeds 9.9%, not only does the cost increase, but also the workability decreases, so the upper eye content is 9.9%.

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 are the most important elements along with Al in steel containing 2% or more of Cr and 1% or more of Al in order to secure not only corrosion resistance but also pickling properties. At present, there are many unknowns about the mechanism, but 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 corrosion resistance is improved. However, when the addition exceeds 500 ppm, the effect of improving the corrosion resistance is not only saturated, but also pickling. It has also been found that the Ca + Mg content is 5 ppm.
It is limited to at least 500 ppm.

C and N: C and N reduce the workability of the steel sheet, and also, C generates 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%. It is preferable that each of them is as small as possible.

P: Since a large amount of P decreases toughness when it is present in a large amount, 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: The presence of a large amount of S lowers the pitting corrosion resistance.
1%. 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-mentioned composition as a basic component, but further contains one or more of Cu, Mo, Sb, Ni, and W in order to further improve corrosion resistance.

Cu: Cu contains 2% or more of Cr,
1% or more, and 5 ppm to 500 ppm of Ca + Mg
Addition of 0.05% or more to the contained steel has the effect of improving the resistance to general corrosion without impairing the excellent pickling properties, but adding more than 5.0% lowers the pickling properties. , 0.05 to 5.0%.

Mo: Mo contains 2% or more of Cr,
1% or more, and 5 ppm to 500 ppm of Ca + Mg
When 0.05% or more is added to the contained steel, the effect of suppressing the generation and growth of pitting corrosion is observed without impairing the excellent pickling properties, but the effect is increased even if added over 3.0%. 0.05-3.
0%.

Sb: Sb also contains Cr at 2% or more,
1% or more, and 5 ppm to 500 ppm of Ca + Mg
When 0.01% or more is added to the contained steel, the effect of improving the resistance to pitting corrosion and general corrosion without impairing the excellent pickling property is recognized. , Since it reduces the hot workability, 0.01
To 0.5%.

Ni: Ni contains 2% or more of Cr,
1% or more, and 5 ppm to 500 ppm of Ca + Mg
When 0.01% or more is added to the contained steel, the effect of suppressing pitting corrosion is recognized without impairing excellent pickling properties, but the effect is not only saturated even if added over 6.0%. Since the hot workability is reduced, the content is set to 0.01 to 6.0%.

W: When W is added to steel containing 2% or more of Cr, 1% or more of Al, and 5 ppm to 500 ppm of Ca + Mg and added in an amount of 0.05% or more, excellent pickling properties can be obtained. The effect of suppressing the occurrence and growth of pitting corrosion is remarkably observed without impairing it. However, even if added in excess of 3.0%, not only the effect is saturated, but also the pickling property and processability are deteriorated. 0.05 to 3.0%.

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): The rare earth element contains 2% or more of Cr, 1% or more of Al, and 5 ppm of Ca + Mg.
When added in combination with steel containing 500 ppm, it is an element that is effective in improving hot workability and pitting corrosion resistance without impairing excellent pickling properties.
If it is less than 01%, the effect is not sufficient. If it is added more than 0.1%, coarse nonmetallic inclusions are generated, and conversely, hot workability and pitting resistance are deteriorated.
0.1%. In the present invention, the rare earth element refers to an element having an atomic number of 57 to 71 or 89 to 103 and Y.

In the steel comprising the above-mentioned steel components and having excellent pickling properties and corrosion resistance, if improvement of workability is also required if necessary, one or two of Nb, V, Ti, Zr, Ta and Hf may be used. The above is included.

Nb, V, Ti, Zr, Ta, Hf: N
b, V, Ti, Zr, Ta, and Hf contain at least 2% of Cr, at least 1% of Al, and 5 ppm to 5% of Ca + Mg.
By fixing C and N as carbides in the high Cr steel without impairing the excellent pickling properties of the basic component steel containing 00 ppm, 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. However, no effect is obtained if the total amount of the individual addition or the total addition of the composite addition is less than 0.01%. , More than 0.5% increases the cost and causes rolling flaws, etc., so that the total amount is 0.01 to 0.5%.
In addition, in order to effectively improve workability, Nb, V, T
It is necessary that the total amount of i, Zr, Ta, and Hf satisfies the following expression. Nb / 93 + V / 51 + Ti / 48 + Zr / 91 + Ta
/181+Hf/179-0.8×(C/12+N/1
4) ≧ 0 If the above expression is not satisfied, the fixation 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 an ingot, the steel is formed into an arbitrary shape such as a steel plate, a bar, a steel bar, a sheet pile by hot rolling, forging, cold rolling, or wire drawing. May be formed into a predetermined shape, and further processed and welded to be manufactured as a product, or a steel plate may be formed into a steel pipe, for example, as an ERW steel pipe, and then used for the product by secondary processing and welding. It is also possible to select an optimum product manufacturing process depending on costs and restrictions on existing manufacturing facilities, including other processes, and it is only necessary that the steel of the present invention can be manufactured regardless of which manufacturing process is selected.

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 to have a surface having a chemical composition within the range specified in the present invention. It may be made of steel.

The steel of the present invention can be used in a high temperature wet corrosion environment, a dew condensation corrosion environment, an atmospheric corrosion environment, a tap water corrosion environment, a soil corrosion environment,
The present invention can be applied to various corrosive environments in which these corrosive environments are combined, such as a corrosive environment for concrete, a corrosive environment for seawater, and a corrosive environment for drinking water.

[0035]

Embodiments of the present invention will be described below. 1) Evaluation of pickling properties Steels having the components shown in Tables 1 and 2 were melted, formed into a steel ingot by a normal steel 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 a 5% hydrochloric acid aqueous solution heated to 80 ° C. to remove the surface scale. The test results are shown in Tables 1 and 2. In the results of the pickling test, ◎ indicates that the pickling was completed within 20 seconds, and ○ indicates 4
Pickling was completed within 0 seconds, △ indicates that the pickling was completed within 60 seconds, and × indicates that the pickling was not completed even with a treatment time of 120 seconds or more. As is clear from Tables 1 and 2, the steel of the present invention shows good pickling properties, whereas the comparative steel is inferior in pickling properties.

2) Evaluation of corrosion resistance Steels having the components shown in Tables 1 and 2 were melted and formed 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 100ppm, 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 1 and 2. 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 1 and 2, symbols 1 to 72 in the steels of the present invention in Tables 1 and 2 show good corrosion resistance even in a very severe corrosive environment of high temperature wet containing chloride. On the other hand, the symbols A to Z in Tables 1 and 2, which are comparative steels, are inferior in corrosion resistance, or are inferior in pickling even if a certain degree of corrosion resistance is obtained.

The tap water environment corrosion test was a test in which a test piece was immersed in tap water and kept in an atmosphere at 40 ° C. for 3 months. The test results are shown in Tables 1 and 2. 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 1 and 2, symbols 1 to 72 in Tables 1 and 2 of the steel of the present invention show good corrosion resistance in a tap water corrosive environment, but are comparative steels. Table 1,
It can be seen that the symbols AZ in 2 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 spray zone for 12 months. Tables 1 and 2 show the test results.
Are also shown. ◎ in the corrosion test result is corrosion depth 0.05
mm indicates less than 0.1 mm, △ indicates less than 0.3 mm, and X indicates 0.3 mm or more.

As is clear from Tables 1 and 2, symbols 1 to 72 in Tables 1 and 2 of the steel of the present invention show good corrosion resistance in a seawater corrosive environment, whereas Tables 2 and 3 show comparative steels. One, two
It can be seen that the symbols A to Z in the figure 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 a test in which holding in an environment of -20 ° C. for 2 hours and holding in an environment of 90% humidity and 25 ° C. for 4 hours was repeated 1,000 times. Tables 1 and 2 show the test results.
Are also shown. 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 corrosion rate was 10% or more. Show.

As is clear from Tables 1 and 2, symbols 1 to 72 in Tables 1 and 2 of the steel of the present invention show good corrosion resistance in a dew-condensation corrosion environment, whereas Tables 1 and 2 show comparative steels. One, two
It can be seen that the symbols A to Z in the figure are inferior in corrosion resistance, or inferior in pickling even if a certain degree of corrosion resistance is obtained.

The atmospheric corrosion test was a test in which a test piece was exposed to a position about 500 m from the shore for about 700 days. The test results are shown in Tables 1 and 2. In the results of the corrosion test, ◎ 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 it was 10% or more.

As is clear from Tables 1 and 2, symbols 1 to 72 in Tables 1 and 2 of the steel of the present invention show good corrosion resistance in an atmospheric corrosive environment, whereas Tables 1 and 2 show comparative steels. One, two
It can be seen that the symbols A to Z in the figure are inferior in corrosion resistance, or inferior in pickling even if a certain degree of corrosion resistance is obtained.

In the soil corrosion test, the water content was 15% and the specific resistance was 5
A test piece was buried in sand adjusted to a content of sodium chloride of 00 Ω · cm and kept at 25 ° C. for about 700 days. The test results are shown in Tables 1 and 2. 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 1 and 2, symbols 1 to 72 in Tables 1 and 2 of the steel of the present invention show good corrosion resistance in a soil corrosive environment, whereas Tables 1 and 2 show comparative steels. One, two
It can be seen that the symbols A to Z in the figure are inferior in corrosion resistance, or inferior in pickling even if a certain degree of corrosion resistance is obtained.

The concrete corrosion test is performed by embedding a test piece in Portland cement kneaded with sea sand containing chloride to form a sample, solidifying the sample, immersing the sample in half in artificial sea water, and immersing the sample at 40 ° C. About 700 in the environment
The test was left to stand for a day. The test results are shown in Tables 1 and 2. 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 1 and 2, symbols 1 to 72 in Tables 1 and 2 of the steel of the present invention show good corrosion resistance in a corrosive environment in concrete, while they are comparative steels. The symbols A to Z in Tables 1 and 2 are inferior in corrosion resistance, or inferior in pickling even if a certain degree of corrosion resistance is obtained.

In the drinking water environmental corrosion test, the pH was adjusted to 2.8 using sodium hydroxide, high-purity nitrogen gas was passed therethrough to degas, and the temperature was maintained at 27 ° C., (a) 0.5% 850 cc solution of phosphoric acid solution, (b) 0.5% citric acid solution, (C) 0.5% citric acid-0.5% sodium chloride solution
The test piece was immersed in the solution for 20 days, and the test was performed to analyze the amount of iron ions eluted in the solution. The test results are shown in Tables 1 and 2. In the results of the corrosion test, ◎ indicates that the elution amount of iron ions into the solution was 1 ppm or less, Δ indicates less than 3 ppm, ○ indicates less than 5 ppm,
X shows that it was 5 ppm or more.

As is clear from Tables 1 and 2, symbols 1 to 72 in Tables 1 and 2, which are the steels of the present invention, show good corrosion resistance in a drinking water corrosive environment, whereas they are comparative steels. Table 1,
It can be seen that the symbols AZ in 2 are inferior in corrosion resistance, or inferior in pickling even if a certain degree of corrosion resistance is obtained.

As described above, the symbols 1 to 72 in Tables 1 and 2 of the steel of the present invention indicate high temperature wet corrosion environment, condensation corrosion environment, atmospheric corrosion environment, tap water corrosion environment, soil corrosion environment, concrete corrosion environment, Umemoto. Corrosion environment, good corrosion resistance in various corrosive environments such as drinking water corrosion environment, whereas the symbols A to Z in Tables 1 and 2, which are comparative steels, are inferior in corrosion resistance or have some degree of corrosion resistance. It can be seen that even if it is obtained, it is inferior in pickling properties.

3) Evaluation of workability A cylindrical drawing test with a drawing ratio of 1.8 was performed to determine whether there was a crack. The test results are also shown in Table 2. In the workability in Table 2, ○ indicates that the result of the cylindrical drawing test was good, and × indicates that cracks occurred in the cylindrical drawing test.

As is clear from Table 2, the symbols 37 to 72 in Table 2 which are the steels of the present invention show good pickling properties, and are subjected to high-temperature wet corrosion environment, dew condensation corrosion environment, atmospheric corrosion environment, tap water corrosion environment. It shows good corrosion resistance in various corrosive environments such as soil corrosive environment, concrete corrosive environment, seawater corrosive environment, drinking water corrosive environment, etc. and also has excellent workability. The symbols NZ indicate that pickling, corrosion resistance and workability cannot be simultaneously achieved.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

[0060]

[Table 4]

[0061]

Since the steel according to the present invention contains Cr, Al, and Ca + Mg, it has excellent pickling properties and corrosion resistance, and can be provided at low cost. More specifically, it has excellent pickling properties, 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. It can be used in corrosive environments.

Claims (4)

[Claims] C: 0.02% or less, Si: 0.01 to 3.0%, Mn: 0.1 to 3.0%, Cr: 2 to 9.9%, Al: Pickling characterized by comprising 1 to 10%, Ca + Mg: 5 to 500 ppm, P of 0.03% or less, S of 0.01% or less, N of 0.02% or less, and the balance of Fe and unavoidable impurities. Steel with excellent resistance and corrosion resistance. 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 pickling property and corrosion resistance according to claim 1, characterized in that it contains one or more of 6.0% and W: 0.05 to 3.0%, and the balance is Fe and unavoidable impurities. Excellent steel. 3. The steel excellent in pickling and corrosion resistance according to claim 1, further comprising 0.001 to 0.1% by weight of a rare earth element. 4. In addition, Nb, V, Ti, Z in% by 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
4. The steel excellent in pickling and corrosion resistance described in 1. Nb / 93 + V / 51 + Ti / 48 + Zr / 91 + Ta
/181+Hf/179-0.8×(C/12+N/1
4) ≧ 0