JPH0641697A - Fe-cr alloy excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To improve corrosion resistance to a greater extent by specifying Cr content in an Fe-Cr steel where respective contents of C, N, O, and S are reduced, increasing the degree of the above reduction of C, N, O, and S and adding specific amounts of P. CONSTITUTION:This Fe-Cr steel has a composition consisting of 5-60wt.% Cr, 100ppm or less of (C+N+O+S), 0.01-1.0wt.% P, and the balance Fe and has superior corrosion resistance. When P exceeds 1.0%, toughness as well as corrosion resistance is deteriorated. As deoxidizer, 1.0wt.% or less each of Al, Si, and Mn can be added to the steel. When one or more elements among Ti, Nb, Zr, V, Ta, W, and B are further added by the amounts satisfying inequality I, intergranular corrosion resistance and corrosion resistance in weld zone are improved. When 0.05-20% Mo is further added, pitting corrosion resistance and atmospheric corrosion resistance are improved. When one or more elements among Ni, Co, and Cu are further added by the amounts satisfying inequality II, acid resistance and atmospheric corrosion resistance are improved to greater extents. When one or more elements among Al, Si, and Mn are further added by the amounts satisfying inequality III, oxidation resistance is improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to Fe-C excellent in corrosion resistance.
r alloy.

[0002]

2. Description of the Related Art An Fe--Cr alloy is generally known as a material having excellent corrosion resistance, but C, N, O, and S in the Fe--Cr alloy may adversely affect the corrosion resistance for the following reasons. Are known. C, N: Appearance of Cr-deficient layer due to formation of Cr carbonitride at grain boundary. O, S: Increasing the starting point of rusting by increasing the amount of inclusions.

That is, it is already known that reduction of these impurity elements is effective for improving the corrosion resistance of the Fe-Cr alloy, and reduction of C, N, O and S and reduction of Ti and N.
Attempts have been made to remove the Cr-deficient layer by adding carbonitride elements such as b. The following is a conventional technique for improving the corrosion resistance of Fe-Cr alloys.

In Japanese Patent Laid-Open No. 61-186451, C
An Fe-Cr alloy having an r content of 25 to 50% by weight, particularly, an alloy excellent in sour resistance in which C, N are reduced to a specific amount and simultaneously Si, Mn and Mo are included in a specific amount, is proposed. .

Japanese Patent Publication No. 2-1902 discloses that Fe-C having a Cr content of more than 20.0% by weight and 25.0% by weight or less.
With r alloy, especially C and N are reduced and at the same time Mo and M
It proposes a corrosion-resistant ferritic stainless steel containing n and Nb in a specified amount, which is excellent in hot crack resistance during welding and excellent in weld toughness.

JP-A-3-2355 discloses a Fe-Cr alloy having a Cr content of 16.0 to 25.0% by weight.
In particular, it proposes a ferritic stainless steel containing Nb in a specific amount in the ratio of the total amount of C and N and having excellent cold workability, toughness, and corrosion resistance.

[0007]

However, the effect of improving the corrosion resistance in the Fe-Cr alloys proposed in these prior arts may not be sufficient. For example, a building material used in a severe corrosive environment such as near the coast, a chemical plant, and an automobile exhaust gas material that is required to have corrosion resistance at high temperatures are required to have further improved corrosion resistance.

[0008] Further, an attempt to add P to improve the corrosion resistance has been made in ordinary steel, and it has been put into practical use as a weather resistant steel. There is an application example to Cr-containing steel, but the corrosion resistance improving effect in the stainless steel. Is not enough.

That is, the object of the present invention is to use conventional Fe-C.
Fe-Cr with improved corrosion resistance compared to r alloy
It is to provide an alloy. In particular, the present invention aims to provide a highly corrosion-resistant steel suitable for stainless steel for building materials used in a severe corrosive environment such as near the coast, stainless steel for chemical plants, and stainless steel for exhaust gas materials for automobiles.

[0010]

As a result of intensive studies aimed at achieving the above object, the present inventor has found that the total amount of C, N, S and O existing as impurities in a conventional Fe-Cr alloy is remarkably increased. It was found that the Fe-Cr alloy containing a specific amount of P at the same time as the decrease was remarkably excellent in weather resistance.

Then, the above P-added Fe-Cr alloy is added with T
The intergranular corrosion resistance is further improved by adding a specific amount of one or more selected from i, Nb, V, Zr, Ta, W and B, and the pitting corrosion resistance is remarkably increased by adding a specific amount of Mo. I found that it improved. Also, N
It was found that the acid resistance is significantly improved by adding a specific amount of one or more selected from i, Co and Cu, and the oxidation resistance is improved by adding a specific amount of one or more selected from Al, Si and Mn. Therefore, the present invention has been completed.

That is, according to the first aspect of the present invention,
Cr content is 5 to 60% by weight, the total amount of C, N, O and S is 100 ppm or less, and the P content is 0.01 to 1.0.
An Fe-Cr alloy having excellent corrosion resistance is provided, which is characterized in that the content is wt% and the balance is Fe and inevitable impurities.

According to the second aspect of the present invention, in addition to the components of the first aspect, Al: 1.0 wt% or less, S
Provided is an Fe-Cr alloy having excellent corrosion resistance, containing i: 1.0 wt% or less and Mn: 1.0 wt% or less.

According to a third aspect of the present invention, Ti, N is further added in the first or second aspect.
F, which has excellent corrosion resistance, contains one or more selected from b, V, Zr, Ta, W and B in an amount satisfying the following formula (1).
An e-Cr alloy is provided. 0.01% by weight ≦ Ti + Nb + Zr + V + Ta + W + 20B ≦ 1.0% by weight (1)

According to a fourth aspect of the present invention, in addition to the above first or second aspect, Mo: 0.
Fe-Cr containing 0.5 to 20% by weight and excellent in corrosion resistance
An alloy is provided.

According to a fifth aspect of the present invention, in addition to the above first or second aspect, Mo: 0.
An Fe-Cr alloy excellent in corrosion resistance is provided which contains 05 to 20% by weight and one or more selected from Ti, Nb, V, Zr, Ta, W and B in an amount satisfying the following formula (1). 0.01% by weight ≦ Ti + Nb + Zr + V + Ta + W + 20B ≦ 1.0% by weight (1)

Further, according to a sixth aspect of the present invention, one or more selected from Ni, Co and Cu in the first, second, third, fourth or fifth aspect is represented by the following formula ( Fe-Cr with excellent corrosion resistance, containing 2)
An alloy is provided. 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (2)

According to a seventh aspect of the present invention, in the above first, third, fourth or fifth aspect, A
Provided is an Fe-Cr alloy having excellent corrosion resistance, containing at least one selected from 1, Si and Mn in an amount satisfying the following formula (3). 1.0 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt%… (3)

According to an eighth aspect of the present invention, in addition to the above-mentioned first, third, fourth or fifth aspect, N
Fe containing at least one selected from i, Co and Cu in an amount satisfying the following formula (2) and containing at least one selected from Al, Si and Mn in an amount satisfying the following formula (3) and having excellent corrosion resistance -Cr alloy is provided. 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (2) 1.0% by weight ≦ 3Al + 2Si + Mn ≦ 50% by weight (3)

[0020]

The present invention will be described in more detail with reference to the drawings. FIG. 1 shows the relationship between weather resistance and the total amount of C, N, O and S. This figure is for Fe-20% Cr-0.05% P alloy in the waterfront industrial area.
6 months atmospheric exposure within m (exposure at an angle of 36 degrees south)
After that, the results of visually evaluating the rusting degree in the following three stages are shown. 1: No rust 2: Stain-like corrosion occurs 3: Spot-like red rust occurs

The total amount of C, N, O and S is 100 pp
When it is less than m, no rusting occurs, and it is clear that the weather resistance is remarkably excellent.

In FIG. 2, the total amount of C, N, O and S is 1
Fe-18% Cr of 00ppm or less and 100ppm or more
Regarding the alloy, the relationship between the rusting degree after 1 year of atmospheric exposure and the P content is also shown. The degree of rusting was visually evaluated by the following four grades. 1: Slight stain-like corrosion 2: Overall stain-like corrosion 3: Spot-like corrosion with spot-like red rust 4: Full-scale red rust

From FIG. 2, the total amount of C, N, O and S is 1
It is apparent that the Fe content of the Fe-Cr alloy of 00 ppm or less is significantly excellent in weather resistance when the P content is 0.01% or more.

FIG. 3 shows the relationship between the total amount of C, N, O and S and the pitting potential (V'C _{, 10} (mVvsSCE)) for the Fe-18% Cr-0.02% P alloy. Is. It is clear that when the total amount of C, N, O and S is 100 ppm or less, the pitting corrosion resistance is excellent.

As described above, as shown in FIGS.
When the total amount of O and S is extremely low and the content of P is higher than a certain value, the corrosion resistance of the Fe-Cr alloy is dramatically improved.

In FIG. 4, the total amount of C, N, O and S is 10
Regarding the Fe-18% Cr-0.1% P alloy whose content is 0 ppm or less, the Mo content and the pitting corrosion potential (V'C _{, 10} (mVvs
SCE)). It is clear that when the Mo content is 0.05% by weight or more, the pitting corrosion resistance is further excellent.

In FIG. 5, the total amount of C, N, O and S is 1
It shows the relationship between the corrosion degree and the value of Ni + Co + 2Cu (% by weight) when immersed in boiling 1% HCl for 18 hours for an Fe-20% Cr 0.03% P alloy of 00 ppm or less. It is clear that when the above value is 0.01% by weight or more, the corrosion degree is reduced and the acid resistance is improved.

FIG. 6 shows that the total amount of C, N, O and S is 10
A Fe-20% Cr-0.06% P alloy of 0 ppm or less was subjected to a repeated oxidation test in which a cycle of heating at 1075 ° C. for 30 minutes and cooling for 12 minutes was set as one cycle, and the weight change was observed every 25 cycles. It shows the relationship between the number of cycles until the measurement and the above-mentioned oxidation (the number of cycles when the amount of increase in oxidation exceeds 5.0 mg / m ² ) and the value (% by weight) of 3Al + 2Si + Mn. 3Al + 2S
It is clear that when the value of i + Mn is 0.1% by weight or more, the oxidation resistance is remarkably excellent.

The structure of the present invention will be described in detail below. More preferred embodiments of the invention and the advantages derived therefrom will become apparent.

(First embodiment) Cr: 5 to 60% by weight, preferably 10 to 45% by weight. The Cr content within the above range is an essential condition for the alloy of the present invention to have excellent corrosion resistance. Excessive Cr content is not preferable because it causes deterioration of workability.

C, N, O and S: In the conventional Fe-Cr alloys, these elements were contained as unavoidable impurities in a total amount of several 100 ppm, but in the alloy of the present invention, they are 100 ppm or less, preferably 85 ppm. Below. This reduction of the total amount of these elements is essential for the purpose of improving the corrosion resistance of the present invention. If the content exceeds 100 ppm, the object of the present invention will not be achieved.

P: The alloy of the present invention contains P in an amount of 0.01 to 1.0.
%, Preferably 0.015 to 0.3% by weight. By including P in the above range, excellent corrosion resistance is imparted to the alloy of the present invention. However, 1.0
A content of more than wt% is not preferable because it not only lowers the corrosion resistance but also lowers the toughness and causes a problem in manufacturing.

The Fe content of the first embodiment of the present invention satisfying the above Cr content, the total content of C, N, O and S, and the P content.
Since the Cr alloy is excellent in corrosion resistance, it is preferably used for applications such as building exterior materials and vehicle exterior materials.

(Second Embodiment) In addition to the components of the first embodiment, Al, Si and Mn added as deoxidizing agents.
The composition of is added. That is, the steel ingot having the above-mentioned components sufficiently fulfills the object of the present invention even if the amounts of Al, Si, and Mn excessively administered are as follows. Al: 1.0 wt% or less. Preferably 0.5% by weight or less. Si: 1.0 wt% or less. Preferably 0.8% by weight or less. Mn: 1.0 wt% or less. It is preferably 0.7% by weight or less.

The inclusion of Al, Si and Mn beyond the above range is not preferable because the deoxidizing effect is saturated. The Fe—Cr alloy of the second aspect of the present invention satisfying the above requirements is excellent in corrosion resistance, and thus is preferably used for the same application as in the first aspect.

(Third Embodiment) In addition to the conditions of the first or second embodiment, one or more selected from Ti, Nb, V, Zr, Ta, W and B is represented by the following formula (1), preferably It is contained in an amount that satisfies the following formula (1a). 0.01 wt% ≦ Ti + Nb + Zr + V + Ta + W + 20B ≦ 1.0 wt%… (1) 0.03 wt% ≦ Ti + Nb + Zr + V + Ta + W + 20B ≦ 0.5 wt%… (1a)

An alloy excellent in corrosion resistance can be obtained even if these elements are not added. By satisfying the above range, an alloy further excellent in intergranular corrosion resistance can be obtained and at the same time the corrosion resistance of the welded portion is improved. To do. However, excessive inclusion of these elements is not preferable because the solid solution strengthening of the additional element itself lowers the workability. The content of each element is preferably in the following range for the same reason. Ti: 0.01-0.5 wt% Nb: 0.01-0.5 wt% Zr: 0.01-0.5 wt% V: 0.01-0.5 wt% Ta: 0.01- 0.5% by weight W: 0.01 to 0.5% by weight B: 0.0003 to 0.01% by weight

Fe of the third aspect of the present invention satisfying the above requirements
The -Cr alloy is excellent in corrosion resistance, and thus is not only preferably used for the same application as in the first embodiment, but also excellent in corrosion resistance of the welded portion, and thus is particularly advantageous as a member for welding.

(Fourth Embodiment) In addition to the conditions of the first or second embodiment, Mo is contained in an amount of 0.05 to 20% by weight, preferably 0.1 to 6.0% by weight. An alloy excellent in corrosion resistance can be obtained even if Mo is not added, but by satisfying the above range, an alloy with further improved pitting corrosion resistance and weather resistance can be obtained. Excessive content of more than 20% by weight is not preferable because the material hardens and the toughness of the base material decreases at the same time. Fe of the fourth aspect of the present invention satisfying the above
Since the -Cr alloy is excellent in corrosion resistance, it is preferably used for the same application as in the first aspect. Further, since it is excellent in pitting corrosion resistance, it is preferably used for a water heater tube body and the like.

(Fifth Mode) The conditions of the third mode, which is particularly excellent in corrosion resistance of welded parts, are added to the conditions of the fourth mode, which is particularly excellent in pitting corrosion resistance. That is, in addition to the conditions of the first or second aspect, Mo: 0.05 to 20% by weight, preferably 0.1 to 6.0% by weight, and at the same time Ti, Nb, V, Zr, Ta, At least one selected from W and B is represented by the following formula (1), preferably the following formula (1)
It is contained in an amount satisfying a). 0.01 wt% ≦ Ti + Nb + Zr + V + Ta + W + 20B ≦ 1.0 wt%… (1) 0.03 wt% ≦ Ti + Nb + Zr + V + Ta + W + 20B ≦ 0.5 wt%… (1a)

Ti, Nb, V, Zr, Ta, W and B
The preferable range of each individual element is as described in the third aspect, and therefore omitted. The reason for limiting the component ranges is also as described in the third and fourth aspects, and therefore omitted. Fe-Cr of the fifth aspect of the present invention satisfying the above
Since the alloy is excellent in corrosion resistance, it is preferably used as a member that requires the same application as in the first embodiment or welding.

(Sixth Aspect) In addition to the first, second, third, fourth or fifth aspect, at least one selected from Ni, Co and Cu is represented by the following equation (2), preferably the following equation: It is contained in an amount satisfying (2a). 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (2) 0.05% by weight ≦ Ni + Co + 2Cu ≦ 5% by weight (2a)

An alloy having excellent corrosion resistance can be obtained even if these elements are not added, but by adding one or more of these elements in a specific amount, an alloy having further improved acid resistance and weather resistance can be obtained. . If the blending amount of Ni, Co and Cu is less than the above range, the acid resistance is poor, and if it is large, the manufacturability of the alloy is poor. The preferable contents of Ni, Co and Cu are as follows, and the reason is the same as above. Ni: 0.05 to 5.0 wt% Co: 0.05 to 5.0 wt% Cu: 0.05 to 2.5 wt%

Fe of the sixth aspect of the present invention satisfying the above
The -Cr alloy is excellent in corrosion resistance and therefore is preferably used not only for the same application as in the first embodiment but also because it is excellent in acid resistance and is therefore preferably used as a material for chemical plants.

(Seventh Mode) In addition to the first, third, fourth or fifth mode, at least one selected from Al, Si and Mn is represented by the following formula (3), preferably the following formula (3)
It is contained in an amount satisfying a). 1.0% by weight ≤3Al + 2Si + Mn≤50% by weight (3) 3.0% by weight≤3Al + 2Si + Mn≤20% by weight (3a)

The seventh aspect is intended to add Al, Si and Mn positively, especially for the purpose of improving the oxidation resistance, and therefore its purpose is essentially different from that of the second aspect. Even if these elements are not added, an alloy having excellent corrosion resistance can be obtained, but by adding one or more of these elements in a specific amount, an alloy with further improved oxidation resistance can be obtained.
An excess content of more than 50% by weight causes oxide-based inclusions to be scattered in the alloy, lowers manufacturability and workability, and makes it difficult to manufacture the alloy, and therefore should be avoided. The preferable contents of each individual element and the reasons therefor will be described below. Al: 0.1 to 10.0% by weight If less than 0.1% by weight, it is effective, but not remarkable. 1
When it exceeds 0.0% by weight, the decrease in the productivity becomes conspicuous. Si: 0.1 to 10.0% by weight If less than 0.1% by weight, it is effective but not remarkable. 1
When it exceeds 0.0% by weight, the decrease in the productivity becomes conspicuous. Mn: 0.1 to 20.0% by weight If less than 0.1% by weight, it is effective but not remarkable. Two
When it exceeds 0.0% by weight, the decrease in the productivity becomes conspicuous. The Fe—Cr alloy of the seventh aspect of the present invention satisfying the above is excellent in corrosion resistance, and therefore is not only preferably used for the same application as in the first aspect, but is also excellent in oxidation resistance at high temperatures, and thus is excellent in automobiles. It is advantageous as a material for exhaust gas.

(Eighth Mode) The conditions of the sixth mode, which is particularly excellent in acid resistance, are added to the conditions of the seventh mode, which is particularly excellent in oxidation resistance. That is, in addition to the first, third, fourth or fifth aspect, at least one selected from Ni, Co and Cu is contained in an amount satisfying the following formula (2), preferably the following formula (2a). , Al, Si and Mn are contained in an amount satisfying the following formula (3), preferably the following formula (3a). 0.01 wt% ≦ Ni + Co + 2Cu ≦ 6 wt%… (2) 0.05 wt% ≦ Ni + Co + 2Cu ≦ 5 wt%… (2a) 1.0 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt%… (3 ) 3.0% by weight ≦ 3Al + 2Si + Mn ≦ 20% by weight (3a)

The preferable range of each individual element and the reason for limiting the component range are the same as those described in the sixth and seventh aspects, and therefore will be omitted.

The alloys of the present invention shown in the first to eighth aspects can be obtained by melting and casting in a high vacuum using a predetermined amount of a high-purity raw material obtained by an electrolysis method or the like. At this time, Al, Si and Mn may be used as the deoxidizing material. After smelting, the usual manufacturing process, that is, smelting-hot rolling-annealing-pickling-
It can be manufactured by cold rolling-annealing- (pickling)-(temper rolling).

Further, the alloy of the present invention is preferably Fe except for the above components. However, Ca, Mg, R
Even if one or more of the elements such as EM (rare earth element), Pb, Bi, Se and Te are contained in a total amount of less than 1%, the effect can be sufficiently obtained.

Further, the alloy of the present invention can sufficiently obtain the effect regardless of whether it is a hot rolled annealed sheet or a cold rolled annealed sheet used, and at the same time, the final surface finish is 2D, 2.
Any of B, BA, HL and polishing finish can sufficiently obtain the effect.

[0052]

EXAMPLES The present invention will be specifically described below with reference to examples. (Example) 30 kg small steel ingots of various Fe-Cr alloys having the chemical compositions shown in Table 1 were melted in an ultrahigh vacuum 50 kg high frequency furnace. In melting, the total amount of S, C, N, O is 10
Maximum vacuum degree at room temperature is 1 to suppress below 0ppm
An ultra-high vacuum furnace that exceeds 0 ⁻⁷ torr was used, and high-purity raw materials were also used. Further, for the purpose of suppressing contamination of impurity elements from the crucible as much as possible, the crucible was previously dissolved and washed with ultra-high purity iron for several charges, and then dissolved using strong stirring.

Each steel ingot was cut at a surface of 1 cm and removed, and then 110
After soaking for 1 hour at the optimum temperature selected in the temperature range of 0 to 1250 ° C., a hot rolled sheet of 4 mm was obtained and annealed for the purpose of recrystallization. After cutting and removing the carbonitriding layer on the surface,
Cold rolling and recrystallization annealing were repeated once or twice, and finally, the cold rolled annealed plate of 0.7 mm was used for the test. If necessary, the surface layer was removed by polishing before the test. The test pieces prepared by the above method were subjected to various corrosion resistance tests by the methods described below.

(Weather resistance test) After carrying out an atmospheric exposure test in a seaside industrial area for one year, (1) the appearance of the test piece was observed, and the degree of rusting was determined as follows.
It was classified into stages and evaluated. 1: No rusting 2: Very mild stain-like corrosion 3: Mild stain-like corrosion 4: Spot-like red rust with stain-like corrosion 5: Large tendency to red rust

(2) The gloss retention rate was measured using a gloss meter (HG-246) manufactured by Suga Test Instruments, and the gloss ratio before and after exposure to the atmosphere was determined as the gloss retention rate. Gloss retention (%) = {Gs (20) (after exposure) / Gs
(20) (Before exposure)} × 100

(Intergranular corrosion resistance test) JIS G 0575
The intergranular corrosion resistance was evaluated based on the presence or absence of cracks by performing a sulfuric acid / copper sulfate test on the stainless steel specified in.

(Pit corrosion resistance test) The pit corrosion potential was measured according to JIS G 0577. The pitting potential was expressed as the potential at which the current density reached 10 μA / cm ² .

(Acid resistance test) After the test piece was immersed in a boiling 0.5% HCl aqueous solution for 18 hours, the corrosion weight loss was measured and the acid resistance was evaluated according to the following four grades. ◎: less corrosion rate 0.1g / m ² · hr ○: corrosion rate 0.1~1g / m ² · hr △: Corrosion of 1~3g / m ² · hr ×: corrosion rate 3g / m ² · hr or more

(Oxidation resistance test) 3 at 1075 ° C. in air
A repeated oxidation test was conducted with one cycle consisting of 0 minute heating and 12 minute cooling, and the weight change was measured every 25 cycles, and the number of cycles until abnormal oxidation occurred (oxidation weight gain exceeded 5.0 mg / m ² ). The number of cycles) was measured.

[0060]

[Table 1]

[0061]

[Table 2]

[0062]

[Table 3]

[0063]

[Table 4]

[0064]

[Table 5]

[0065]

[Table 6]

[0066]

[Table 7]

[0067]

[Table 8]

The experimental results will be described below. (Example 1) Fe-2 is shown in Tables 2, 3, and 4, respectively.
0% Cr alloy, Fe-11% Cr alloy, Fe-40% C
The weather resistance test result of r alloy is shown.

[0069]

[0070]

[0071]

From Tables 2, 3 and 4, it is clear that the alloys of the present invention are remarkably excellent in weather resistance. If the total amount of C, N, O and S exceeds 100 ppm and is large, and if P is out of the range of the present invention, excellent weather resistance is not exhibited.

In Table 5, Fe- (4-20)% Cr-
The weather resistance test result of 0.1% P alloy is shown.

[0074]

The alloy of the present invention having a Cr content of 5% by weight or more exhibits excellent weather resistance. Comparative alloy 6 having a Cr content of 4.8% by weight showed a large amount of red rust, and could not be said to have a significantly low luster retention and weather resistance.

(Example 2) In Table 6, Fe-20% Cr-
7 shows the results of weathering test conducted on 0.02% P alloy.

[0077]

[Table 9]

For example, Al, Si, Mn used as a deoxidizing material, etc.
Even if is mixed, if the respective contents are 1.0% or less, sufficient weather resistance can be obtained by combining with the conditions of the Cr content, the total amount of C, N, O and S, and the P content. It is clear.

(Example 3) In Table 7, Fe-11% Cr-
The results of a weather resistance test and an intergranular corrosion resistance test conducted on a 0.1% P alloy (C + N + O + S ≦ 100 ppm) are shown.

[0080]

Β = Ti + Nb + Zr + V + Ta + W + 2
If the value of 0B is 0.01% by weight or more, the Cr content,
It is clear that, in combination with the conditions of the total amount of C, N, O and S and the P content, not only weather resistance but also intergranular corrosion resistance is excellent.

(Example 4) Table 8 shows Fe-20% Cr-
(0.01-0.4)% P- (0.001-6)% Mo
The results of the weather resistance test and pitting corrosion resistance test of the alloy are shown.

[0083]

[Table 10]

In addition to the conditions for the Cr content, the total content of C, N, O and S, and the P content, the steel of the present invention having a Mo content of 0.05% by weight or more is clearly excellent in pitting corrosion resistance. Is. Comparative Alloy 7 in which the total amount of C, N, O and S was more than 100 ppm and was inferior not only in weather resistance but also in pitting corrosion resistance.

Example 5 Table 9 shows the results of the weather resistance test, the intergranular corrosion resistance test and the pitting corrosion test of the invention alloy 26 and the invention alloy 27.

[0086]

In addition to the conditions of Cr content, total content of C, N, O and S, and P content, Mo content, Ti + Nb
The alloy of the present invention satisfying the range of + Zr + V + Ta + W + 20B is excellent in intergranular corrosion resistance and pitting corrosion resistance in addition to weather resistance.

Example 6 In Table 10, Fe-20% Cr-
The results of a weather resistance test and an acid resistance test of a 0.02% P alloy (C + N + O + S <100 ppm) are shown.

[0089]

From the results shown in Table 10, it is clear that the acid resistance is improved when the Ni + Co + 2Cu value exceeds 0.01% by weight.

Example 7 In Table 11, Fe-20% Cr-
0.015% P alloy (C + N + O + S <100ppm)
The results of a weather resistance test and an oxidation resistance test regarding are shown.

[0092]

From the results shown in Table 11, it is clear that the oxidation resistance is improved when the value of 3Al + 2Si + Mn exceeds 1.0% by weight.

(Example 8) In Table 12, Fe-20% Cr-
The results of a weather resistance test and an oxidation resistance test regarding a 0.02P alloy (C + N + O + S <100 ppm) are shown.

[0095]

From the results shown in Table 12, it is clear that the oxidation resistance and the acid resistance are excellent in the range of Embodiment 8 of the present invention.

[0097]

The Fe-Cr alloy of the present invention is excellent in corrosion resistance and is therefore preferably used in all applications of Fe-Cr alloys.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between weather resistance and the total amount of C, N, O and S.

FIG. 2 is a graph showing the relationship between weather resistance and P content.

FIG. 3 is a diagram showing the relationship between pitting corrosion resistance and the total amount of C, N, O and S.

FIG. 4 is a graph showing the relationship between pitting corrosion resistance and Mo content.

FIG. 5 is a diagram showing a relationship between acid resistance and a Ni + Co + 2Cu value.

FIG. 6 is a diagram showing a relationship between oxidation resistance and 3Al + 2Si + Mn value.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. Hei 4-136778 (32) Priority Date Hei 4 (1992) May 28 (33) Country of priority claim Japan (JP) (72) Inventor Yoshihiro Yazawa 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Technical Research Division, Kawasaki Steel Co., Ltd. (72) Inventor Toshio Togashi, 1st Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Technical Research Division, Kawasaki Steel Co., Ltd. (72) Inventor Yasushi Kato 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Corporation Technical Research Division (72) Inventor Satoshi Owada 1 Kawasaki-cho, Chuo-ku, Chiba Prefecture Kawasaki Steel Co., Ltd. Technical Research Division

Claims (8)

[Claims] 1. A Cr content of 5 to 60% by weight, C, N, O
And the total amount of S is 100 ppm or less, and the P content is 0.
Fe-C excellent in corrosion resistance, characterized in that it is 01 to 1.0% by weight and the balance is Fe and inevitable impurities.
r alloy. 2. Further, Al: 1.0 wt% or less, Si:
The Fe-Cr alloy excellent in corrosion resistance according to claim 1, containing 1.0% by weight or less and Mn: 1.0% by weight or less. 3. F which is excellent in corrosion resistance according to claim 1 or 2, which further contains one or more selected from Ti, Nb, V, Zr, Ta, W or B in an amount satisfying the following formula (1).
e-Cr alloy. 0.01% by weight ≦ Ti + Nb + Zr + V + Ta + W + 20B ≦ 1.0% by weight (1) 4. The Fe—Cr alloy having excellent corrosion resistance according to claim 1, which contains Mo: 0.05 to 20% by weight. 5. Mo: 0.05 to 20% by weight plus T
The Fe-Cr alloy excellent in corrosion resistance according to claim 1 or 2, which contains one or more selected from i, Nb, V, Zr, Ta, W and B in an amount satisfying the following formula (1). 0.01% by weight ≦ Ti + Nb + Zr + V + Ta + W + 20B ≦ 1.0% by weight (1) 6. The composition according to claim 1, which contains one or more selected from Ni, Co and Cu in an amount satisfying the following formula (2):
Fe-Cr excellent in corrosion resistance according to 2, 3, 4 or 5
alloy. 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (2) 7. An amount of one or more selected from Al, Si and Mn contained in an amount satisfying the following formula (3):
Fe-Cr alloy having excellent corrosion resistance as described in 3, 4, or 5. 1.0 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt%… (3) 8. One or more selected from Ni, Co and Cu is contained in an amount satisfying the following formula (2), and one or more selected from Al, Si and Mn is contained in an amount satisfying the following formula (3). The Fe-Cr alloy having excellent corrosion resistance according to claim 1, 3, 4, or 5. 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (2) 1.0% by weight ≦ 3Al + 2Si + Mn ≦ 50% by weight (3)