JPH0649604A - Fe-cr alloy excellent in workability and pitting corrosion resistance - Google Patents

Abstract

PURPOSE:To provide an Fe-Cr alloy excellent in workability and oxidation resistance and to provide an Fe-Cr alloy excellent in acid resistance and/or oxidation resistance as well as workability and pitting corrosion resistance. CONSTITUTION:The alloy includes Fe-Cr alloy constituted of 5wt.%<=Cr<=60 wt.%, C+N+O+S+P<=100ppm and 0.5wt.%<=Mo<=20wt.%; Fe-Cr alloy constituted of 0.01wt.%<=Ni+Co+2Cu<=6wt.% in addition to the same; and moreover Fe-Cr alloy constituted of 0.1wt.%<=3Al+2Si+Mn<=50wt.% and/or 0.001wt.%<=4 Ca+4Mg+REM<=0.2wt.% in addition to the same.

Description

Detailed Description of the Invention

[0001]

The present invention relates to Fe, which is excellent in workability, corrosion resistance, particularly pitting corrosion resistance, acid resistance and oxidation resistance.
-Cr alloy.

[0002]

2. Description of the Related Art Generally, Fe--Cr alloy is known as a material having excellent corrosion resistance, but various improvements such as corrosion resistance and workability of the Fe--Cr alloy have been proposed as shown below. ing.

In Japanese Examined Patent Publication No. 63-58904, an Fe-Cr alloy having a Cr content of 11.0 to 16.0% by weight, particularly a ferritic stainless steel having a Ti content as a specific amount and being excellent in overhanging property and secondary workability Proposing steel.

Japanese Examined Patent Publication No. 64-6264 discloses a Fe-Cr alloy having a Cr content of 8.0 to 35.0% by weight, especially S
It proposes a stainless steel bright annealed material containing i, Mn and Mb in specific amounts and having excellent rust resistance.

In Japanese Patent Publication No. 2-1902, an Fe-Cr alloy having a Cr content of more than 20.0% by weight and 25% by weight or less, in particular, Mo, Mn and Mb are contained in specific amounts respectively, so that the resistance to welding is improved. We propose a corrosion-resistant ferritic stainless steel with excellent hot cracking and weld toughness.

In Japanese Patent Laid-Open No. 61-186451, Cr is used.
Fe-Cr alloy with a content of 25 to 50% by weight, especially S
It has been proposed an alloy having a specific sourness of i, Mn and Mo and having excellent sour resistance.

In JP-A-62-267450, a high-purity ferritic stainless steel which is a Fe-Cr alloy having a Cr content of 16 to 19% by weight and which is particularly excellent in intergranular corrosion resistance because it contains a specific amount of Mo. Proposing steel.

JP-A-2-232344 discloses a Fe--Cr alloy having a Cr content of 25.0 to 30.0% by weight, and particularly containing a specific amount of Mo, is excellent in biofouling resistance and seawater resistance. Ferritic stainless steel is proposed.

In Japanese Patent Laid-Open No. 3-2355, the Cr content is 1
A ferritic stainless steel having a Fe-Cr alloy content of 6.0 to 25.0% by weight, particularly 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. Proposing steel.

In JP-A-1-287253, Fe-C having a Cr content of 15 to 26% by weight and an Al content of 4 to 6% by weight is disclosed.
It is an r-Al alloy, and proposes an Al-containing ferritic stainless steel containing a small amount of a rare earth element and having excellent oxidation resistance and manufacturability.

In Japanese Patent Application Laid-Open No. 3-2355, the Cr content is 1
A ferritic stainless steel having a Fe-Cr alloy content of 6.0 to 25.0% by weight, particularly 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. Proposing steel.

[0012]

In these Fe-Cr alloys, since the corrosion resistance is important first, Cr is used in a relatively large amount. As a result, ductility is reduced and workability is not always sufficient, and when it is applied to applications requiring workability such as automobile exterior materials, building exterior materials and structures, cracks occur during processing, or processing conditions are There has been a problem that it is severe and very difficult to process, and further improvement in processability has been desired.

Further, although these Fe-Cr alloys have excellent corrosion resistance, they are still insufficient, and are particularly used for automobile exterior materials and building exterior materials for which pitting corrosion resistance is required, and further for chemical plants where acid resistance is required. There is a demand for improvements in structural materials for automobiles.

Further, these Fe-Cr alloys are not sufficient in strength and oxidation resistance at high temperatures, and further improvement is required when they are used for applications such as automobile exhaust gas pipes which are exposed to high temperatures. .

Thus, the main object of the present invention is to provide an Fe--Cr alloy having improved workability and excellent pitting corrosion resistance.

Another object of the present invention is to provide a Fe-Cr alloy having improved acid resistance, in addition to the above-mentioned improvement of properties.

Still another object of the present invention is to provide a Fe-Cr alloy which is excellent in workability and is also excellent in acid resistance and oxidation resistance.

[0018]

As a result of intensive studies to achieve the above object, the present inventor has surprisingly found that the conventional Fe-
It has been found that a Fe-Cr alloy having a very small amount of impurities such as C, N, O, P, and S, which were present in the Cr alloy, is remarkably excellent in ductility and also excellent in corrosion resistance.

Fe-Cr having the above-mentioned amount of impurities reduced
It has been found that the addition of a specific amount of Mo to the alloy significantly improves the pitting corrosion resistance, and the addition of a specific amount of one or more of Ni, Co and Cu significantly improves the acid resistance.

Then, if one or more selected from Al, Si and Mn is added in a specific amount and / or one or more selected from Ca, Mg and REM is further added in a specific amount, the oxidation resistance is remarkably improved. The findings led to the completion of the present invention.

That is, according to the present invention, the Cr content is 5
~ 60 wt%, the total amount of C, N, O, P and S is 10
0ppm or less, Mo content is 0.5 to 20% by weight,
An Fe-Cr alloy comprising the balance Fe and unavoidable impurities is provided.

According to the present invention, the Cr content is 5-6.
0% by weight, the total amount of C, N, O, P and S is 100 p
pm or less, Mo content of 0.5 to 20% by weight, and further N
At least one selected from i, Cu, and Co is represented by the following formula (1)
Provided is an Fe-Cr alloy excellent in workability, pitting corrosion resistance, and corrosion resistance, which is characterized by containing a sufficient amount of Fe and unavoidable impurities. 0.01 wt% ≦ Ni + Co + 2Cu ≦ 6 wt% (1)

According to the present invention, the Cr content is 5-6.
0% by weight, the total amount of C, N, O, P and S is 100 p
pm or less, Mo content is 0.5 to 20% by weight, and one or more selected from Al, Si and Mn satisfy the following formula (2) and / or Ca, Mg and rare earth element (REM). An Fe-Cr alloy having excellent workability, pitting corrosion resistance and oxidation resistance, characterized in that it contains one or more selected from the following formula (3) in an amount satisfying the following formula (3), and the balance is Fe and inevitable impurities. It 0.1 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt% (2) 0.001 wt% ≦ 4Ca + 4Mg + REM ≦ 0.2 wt% (3)

Further, according to the present invention, the Cr content is 5 to.
60% by weight, the total amount of C, N, O, P and S is 100
ppm or less, Mo content of 0.5 to 20% by weight, and further N
At least one selected from i, Cu, and Co is represented by the following formula (1)
An amount satisfying the following formula (2) and / or one or more selected from Al, Si and Mn and / or one or more selected from Ca, Mg and a rare earth element (REM). ), The balance Fe
Fe-C excellent in workability, pitting corrosion resistance, acid resistance and oxidation resistance, characterized by being composed of unavoidable impurities
An r alloy is provided. 0.01 wt% ≦ Ni + Co + 2Cu ≦ 6 wt% (1) 0.1 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt% (2) 0.001 wt% ≦ 4Ca + 4Mg + REM ≦ 0.2 wt% (3)

[0025]

The present invention will be described in more detail below. (I) First, F of the present invention which is excellent in workability and pitting corrosion resistance
The e-Cr alloy will be described. In Figure 1, Fe-18%
Regarding the cold rolled annealed plate of Cr alloy, JIS Z-2241
The effect of the total amount of C, N, O, P, S on the change in elongation and the change in yield strength obtained by the tensile test specified in 1. Quantity 10
It is clear that when the content is 0 ppm or less, the ductility is remarkably excellent, and the YS is also low and the softening is achieved.

In FIG. 1, the change in elongation (%) and the change in proof stress (yield strength) (N / mm ² ) were calculated for each alloy component as C + N + O.
It shows the difference in tensile properties from that of + S + P = 500 ppm. The basic tensile properties are as follows. Fe-18Cr, C + N + O + S + P = 500ppm elongation 30
%, Yield strength 330 N / mm ² Fe-30Cr, C + N + O + S + P = 500ppm, elongation 25
%, Yield strength 450 N / mm ²

FIG. 2 shows the content of Mo and the pitting potential (JIS G 0) in the cold-rolled annealed sheet of Fe-16% Cr alloy in which the total amount of C, N, O, P and S is 100 ppm or less.
5), the pitting potential is significantly improved when the Mo content is 0.5 wt% or more.
It is clear that it has excellent pitting corrosion resistance.

Next, the composition of the alloy of the present invention will be described. Cr: 5 to 60% by weight, preferably 10 to 40% by weight. When the Cr content is in this range, the corrosion resistance is excellent. Excessive Cr content saturates the effect of improving corrosion resistance, which is not economically rational, and even if (S + P + O + N +
Even if C) ≦ 100 ppm, a decrease in workability is likely to occur due to solid solution strengthening of Cr itself, which is not preferable.

C, N, O, P, S: The total amount of these elements is 100 ppm or less. As explained above,
Excellent ductility due to 100 ppm or less,
Excellent in workability.

Mo: 0.5 to 20% by weight, preferably 0.5 to 5% by weight. If it is 0.5% by weight or more, pitting corrosion resistance is excellent, but excessive content is uneconomical and not preferable. An Fe-Cr alloy satisfying the above conditions has excellent workability and excellent pitting corrosion resistance.

(II) Next, the Fe-Cr alloy of the present invention which is excellent in workability, pitting corrosion resistance and acid resistance will be explained.
In FIG. 3, the total amount of C, N, O, P and S is 100 p.
pm or less, the corrosion rate of the Fe-16% Cr alloy plate in a 0.3 wt% HCl aqueous solution and (Ni + Co + 2C
u) The relationship with% by weight is shown. From this graph (Ni +
It is clear that when the value of Co + 2Cu) is 0.01% by weight or more, the corrosion rate decreases and the acid resistance improves.

As for the contents of Cr, C, N, O, P, S and Mo, the description in (I) is applied as it is. The alloy of the embodiment (II) further contains at least one of Ni, Cu, and Co, and the content thereof satisfies the following formula (1), preferably formula (1a), so that the alloy is resistant to acid. It is an excellent alloy. 0.01 wt% ≦ Ni + Co + 2Cu ≦ 6 wt% (1) 0.1 wt% ≦ Ni + Co + 2Cu ≦ 4 wt% (1a)

Excessive blending of Ni, Co, and Cu beyond the formula (1) is not preferable because these elements are austenite-stabilizing elements, which causes a disadvantage in finally obtaining a ferrite single-phase structure.

The alloy of the embodiment (II) satisfying the above conditions is excellent in workability as well as remarkably excellent in pitting corrosion resistance and acid resistance.

Fe described in (I) and (II) of the present invention
To produce a —Cr alloy, first, high-purity electrolytic iron, electrolytic Cr, metallic Mo, electrolytic Ni, electrolytic Cu, and metallic Co are used as raw materials. The main impurity of any of the raw materials is oxygen, and in order to remove this oxygen, the Fe-based alloy of the present invention is produced by melting and casting under ultrahigh vacuum higher than 10 ^-7 torr.
A Cr alloy can be manufactured.

It is needless to say that the alloy of the present invention can achieve its effect in hot-rolled and annealed sheets. Furthermore, the final surface finish can be sufficiently obtained by any of BA, 2B, 2D, HL, polishing and the like.

(III) Further, the Fe-Cr alloy of the present invention excellent in workability, pitting corrosion resistance and oxidation resistance will be described. FIG. 4 relates to a Fe- (15-30)% Cr alloy,
It is a graph which shows the result of the oxidation resistance test (1350K in air | atmosphere, weight reduction after 12 hr scale removal). (3Al +
It is clear that the oxidation resistance is excellent when 2Si + Mn) is 0.1% by weight or more.

FIG. 5 is a graph showing the results of an oxidation resistance test (1350 K in air, weight loss after 12 hr scale removal) for a Fe- (15-30)% Cr alloy.
It is clear that when (4Ca + 4Mg + REM) is 0.001% by weight or more, the oxidation resistance is excellent.

The alloy composition and embodiments of the present invention will be described below. The Fe-Cr alloy excellent in workability, pitting corrosion resistance and oxidation resistance of the present invention has the following three aspects, and each of them will be described.

(1) First embodiment of the present invention Cr: 5 to 60% by weight, preferably 5 to 45% by weight. Within the above range, in combination with other conditions of the present invention,
Although the alloy has excellent oxidation resistance, an excessive content of more than 60% by weight is not preferable because of high cost.

C, N, O, P, S: The total amount of these elements is 100 ppm or less, preferably 85 ppm or less. Under these conditions, the ductility of the alloy, that is, the workability is improved, and at the same time, it is combined with the conditions of the Cr content defined above and is excellent in the oxidation resistance. If the total amount exceeds 100 ppm, such an excellent effect is not exhibited.

Mo: Mo content is 0.5 to 20% by weight, preferably 0.5 to 5% by weight. By including Mo in the alloy within this range, the pitting corrosion resistance is improved. 20
Excessive content exceeding 5% by weight is not preferable because of high cost.

Al, Si, Mn: One or more of these elements are contained, and the content is added so as to satisfy the following formula (2), preferably (2a). 0.1 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt% (2) 0.3 wt% ≦ 3Al + 2Si + Mn ≦ 30 wt% (2a) By containing these elements in the above range, the oxidation resistance is significantly improved. However, if added excessively, 3Al +
If the value of 2Si + Mn exceeds 50% by weight, the workability deteriorates, which is not preferable. The preferable contents of Al, Si or Mn are as follows. Al: 0.1-4 wt% Si: 0.3-3 wt% Mn: 0.5-10 wt%

(2) Second embodiment of the present invention With respect to the Cr content, the contents of C, N, O, P and S, and the content of Mo, what has been described in the first embodiment is also applicable to this embodiment. In the alloy of the second aspect, Ca, M
g and REM.

Ca, Mg, REM: When these elements are contained in the alloy of the present invention so as to satisfy the following formula (3), the oxidation resistance is further improved and preferable results are obtained. 0.001% by weight ≦ 4Ca + 4Mg + REM ≦ 0.2% by weight (3) The preferred content of each of Ca, Mg or REM is as follows. Ca: 0.0002 to 0.03 wt% Mg: 0.0003 to 0.03 wt% REM: 0.0005 to 0.15 wt%

The alloy of the present invention described in (II), which satisfies the above conditions, is excellent in workability, and is excellent in pitting corrosion resistance and oxidation resistance, and therefore suitable for applications such as automobile exhaust gas pipes.

To produce the Fe-Cr alloy of the present invention, ultrahigh-purity electrolytic iron and electrolytic Cr are used as raw materials. The main impurity of any of the raw materials is oxygen, and the Fe—Cr alloy of the present invention can be produced by melting and casting under an ultrahigh vacuum higher than 10 ⁻⁷ torr to remove this oxygen.

(3) Third Aspect of the Invention An alloy satisfying both the conditions of the alloy of the first aspect of the invention and the conditions of the alloy of the second aspect of the invention described above, that is, the Cr content is 5 ˜60 wt%, the total amount of C, N, O, P and S is 100 ppm or less, the Mo content is 0.5 to 20 wt%, and Si, Mn and A
1 or more selected from 1 is contained in an amount satisfying the above formula (2), and Ca, Mg and a rare earth element (REM)
The Fe-Cr alloy containing at least one selected from the above in an amount satisfying the formula (3) is also an alloy having further excellent oxidation resistance and workability, and is preferably used for the above-mentioned applications.

Fe of the present invention including these three embodiments
In order to produce a —Cr alloy, ultra-high purity electrolytic iron, electrolytic chromium, zone melting method silicon, molten salt electrolytic manganese, molten salt electrolytic aluminum, molten salt electrolytic calcium, electrolytic reduced magnesium, electrolytic reduced rare earth metal are used as raw materials. . The main impurity of any of the raw materials is oxygen, and the Fe—Cr alloy of the present invention can be produced by melting and casting under an ultrahigh vacuum of higher than 10 ⁻⁵ torr to remove this oxygen.

(IV) Finally, in addition to workability and pitting resistance,
The Fe-Cr alloy of the present invention having excellent acid resistance and oxidation resistance will be described. This alloy of the present invention has an alloy composition having excellent acid resistance as described in (II) and an alloy composition having excellent oxidation resistance as described in (III).
Therefore, only the mode will be shown below, and detailed description thereof will be omitted because it is as described in (II) and (III).

The present invention has three modes as in the case of (III), C + N + O + P ≦ 100 ppm, and Cr:
In addition to 5% to 60% by weight, Mo: 0.5 to 20% by weight, and 0.01% ≦ Ni + Co + 2Cu ≦ 6%, only the changed portion will be described below for each embodiment.

(1) First Aspect of the Present Invention One or more kinds selected from Ni, Co and Cu are contained in an amount satisfying the following formula (1). 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (1) One or more kinds selected from Si, Mn and Al are contained in an amount satisfying the following formula (2). 0.1% by weight ≦ 3Al + 2Si + Mn ≦ 50% by weight (2)

(2) Second Aspect of the Present Invention One or more kinds selected from Ni, Co and Cu are contained in an amount satisfying the following formula (1). 0.01 wt% ≦ Ni + Co + 2Cu ≦ 6 wt% (1) One or more kinds selected from Ca, Mg and rare earth elements (REM) are contained in an amount satisfying the following formula (3). 0.001 wt% ≦ 4Ca + 4Mg + REM ≦ 0.2 wt% (3)

(3) Third Embodiment of the Present Invention One or more kinds selected from Ni, Co and Cu are contained in an amount satisfying the following formula (1). 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (1) One or more kinds selected from Si, Mn and Al are contained in an amount satisfying the following formula (2). 0.1% by weight ≦ 3Al + 2Si + Mn ≦ 50% by weight (2) One or more kinds selected from Ca, Mg and rare earth elements (REM) are contained in an amount satisfying the following formula (3). 0.001 wt% ≦ 4Ca + 4Mg + REM ≦ 0.2 wt% (3)

Since the manufacturing method and the like of the alloy of the present invention are exactly the same as those described above, detailed description thereof will be omitted.

[0056]

EXAMPLES The present invention will be specifically described below based on examples. (Example 1) Corresponding to invention alloys 1 to 10 and comparative alloys 1 to 7 ... Corresponding to claims 1 and 2 Alloys having the chemical compositions shown in Table 1 were melted and cast in a 10 kg vacuum melting furnace, and hot rolled. To a hot-rolled sheet with a thickness of 4 mm, subjected to hot-rolled sheet annealing for the purpose of recrystallization, and after descaling to a cold-rolled sheet with a sheet thickness of 0.7 mm, finally recrystallized and annealed. It was annealed sheet.

The following tests were conducted on the alloy plate thus obtained.

(Workability) Invention alloys 1 and 6 and comparative alloy 1,
6, the elongation value was measured by a tensile test in accordance with JIS Z-2241, and after 50% cold rolling, 1 in the C direction.
The state of cracks when the 80 ° C. adhesion bending test was performed was observed. The evaluation was performed as follows. ○ No cracks at all △ Micro cracks present × Large cracks The results are shown in Table 2.

The total amount of C, N, O, P and S is 100.
It can be seen that below 50 ppm, no cracks occur due to the C-direction contact bending after 50% cold rolling, whereas above 100 ppm cracks occur and the workability deteriorates.
Also, the elongation is C, when comparing the same amount of Cr and the same amount of Mo,
It can also be seen that when the total amount of N, O, P and S exceeds 100 ppm, the amount decreases by about 7 to 8%.

(Pit Corrosion Resistance and Acid Resistance) The surface of the test pieces of Comparative Alloy 2 and Invention Alloys 1 and 7 was polished with Emery # 500, and the pitting corrosion resistance was 30 ° C. (2% FeCl ₃ +1/20).
HCI) was evaluated by the corrosion rate calculated from the corrosion weight loss after immersion in an aqueous solution for 4 hours, and the acid resistance was determined to be 0.1% by weight HCl.
The corrosion rate calculated from the corrosion weight loss after immersion in the aqueous solution for 4 hours was evaluated. The results are shown in Table 2.

Samples were prepared in the same manner as above for Comparative Alloy 5, Invention Alloy 10, and Invention Alloy 6, and the pitting corrosion resistance was 30.
℃, (5% FeCl ₃ + 1 / 20N HCl) was immersed in an aqueous solution for 4 hours and then evaluated by the corrosion rate calculated by the corrosion weight loss, acid resistance after immersion in a 0.3 wt% HCl aqueous solution for 4 hours The corrosion rate calculated from the corrosion weight loss was evaluated. The results are shown in Table 2.

Samples were prepared for Comparative Alloy 4, Invention Alloy 4, and Invention Alloy 5 in the same manner as described above, and the pitting corrosion resistance was 30 ° C.
(5% FeCl ₃ + 1 / 20N HCl) in water 4
The corrosion rate was evaluated by the corrosion rate calculated by the corrosion weight loss after immersion for a period of time, and the acid resistance was evaluated by the corrosion rate calculated by the corrosion weight loss after immersion for 4 hours in a 0.3 wt% HCl aqueous solution. The results are shown in Table 2.

Samples were prepared for Comparative Alloy 3, Invention Alloy 2, and Invention Alloy 8 in the same manner as above, and the pitting corrosion resistance was 80.degree.
(5% FeCl ₃ + 1 / 20N HCl) in water 4
The corrosion rate was evaluated by the corrosion rate calculated from the corrosion weight loss after immersion for a period of time, and the acid resistance was evaluated by the corrosion rate calculated from the corrosion weight loss after immersion in a 5 wt% HCl aqueous solution for 4 hours. The results are shown in Table 2.

Samples were prepared in the same manner as above for Comparative Alloy 7, Invention Alloy 3, and Invention Alloy 9, and the pitting corrosion resistance was 80 ° C.
(10% FeCl ₃ + 1 / 20N HCl) was evaluated by the corrosion rate calculated from the corrosion weight loss after 4 hours of immersion in an aqueous solution, and the acid resistance was calculated from the corrosion weight loss after immersion in a 5% by weight HCl aqueous solution for 4 hours. The corrosion rate was evaluated. The results are shown in Table 2.

It can be seen that the inclusion of Mo in the range of the present invention significantly improves the pitting corrosion resistance, and the inclusion of Ni, Co and Cu in the range of the present invention further improves the acid resistance.

(Example 2) Corresponding to invention alloys 11 to 25 and comparative alloys 8 to 11 ... Corresponding to claim 3 The alloys having the compositions shown in Table 1 were used with ultra-high-purity electrolytic iron, electrolytic Cr, and high-purity metal materials. Melted in an ultrahigh vacuum of 10 ⁻⁷ Torr or more.

After heating this to about 1200 ° C., it is hot-rolled to a thickness of about 5 mm, and finally cold-rolled to 1.0 to 2.0 ^t mm, followed by recrystallization and adjustment of the crystal grain size. Annealing for 5
It was applied at 00 to 1100 ° C.

From this, tensile test pieces at room temperature and high temperature were cut out and subjected to respective tests in accordance with JIS (room temperature tensile test pieces were JIS No. 5, high temperature tensile was J
According to ISG0567).

The oxidation test was carried out by heating in an electric furnace at 1350 k for 12 hr in the air, then air-cooling to room temperature, and the weight loss when the scale on the surface of the sample was removed was measured and used as an index of oxidation resistance. Al, Si, Mn or Ca, M
It can be seen that the oxidation resistance is remarkably improved by including g, REM or both in the range of the present invention.

(Example 3) Inventive alloys 26, 27 ... Corresponding to claim 4 An alloy having the composition shown in Table 1 was used in an amount of 10 ^-7 Torr or more by using ultra-high purity electrolytic iron, electrolytic Cr and a high-purity metal material. It was melted in a high vacuum.

After heating this to about 1200 ° C., it is hot-rolled to a thickness of about 5 mm, and finally cold-rolled to 1.0 to 2.0 ^t mm, followed by recrystallization and adjustment of the crystal grain size. Annealing for 5
It was applied at 00 to 1100 ° C. It was evaluated as acid resistance and oxidation resistance in the same manner as in the above example. It is clear that the alloys of the present invention show excellent properties. The test results are shown in Table 2.

(Changes in elongation and proof stress) With respect to the test materials obtained in all of the above-mentioned examples, changes in elongation (%) and proof stress (yield strength) (N / mm ² ) About C
It shows the difference in tensile properties from those of + N + O + S + P = 500 ppm. The basic tensile properties are as follows. Fe-18Cr, C + N + O + S + P = 500ppm elongation 30
%, Yield strength 330 N / mm ² Fe-30Cr, C + N + O + S + P = 500ppm, elongation 25
%, Yield strength 450 N / mm ²

[0073]

[Table 1]

[0074]

[Table 2]

[0075]

[Table 3]

[0076]

[Table 4]

[0077]

[Table 5]

[0078]

[Table 6]

[0079]

[Table 7]

[0080]

[Table 8]

[0081]

INDUSTRIAL APPLICABILITY The alloy of the present invention is excellent in workability and pitting corrosion resistance and, in addition to these, is excellent in acid resistance and / or oxidation resistance, and therefore, it is suitably used for applications such as automobile exhaust gas pipes.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the total amount of C, N, O, P and S and the tensile properties.

FIG. 2 is a graph showing the relationship between the Mo content and the pitting potential.

FIG. 3 is a graph showing the relationship between (Ni + Co + 2Cu) wt% and acid resistance.

FIG. 4 is a graph showing the relationship between (3Al + 2Si + Mn) and oxidation resistance.

FIG. 5 is a graph showing the relationship between (4Ca + 4Mg + REM) and oxidation resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fusao Togashi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Technical Research Division (72) Yoshihiro Yazawa Chuo-ku, Chiba, Chiba Kawasaki-cho No. 1 Kawasaki Steel Co., Ltd. Technical Research Division (72) Inventor Yasushi Kato No. 1 Kawasaki-cho Chuo-ku, Chiba City Chiba Prefecture Kawasaki Steel Co., Ltd. Technical Research Division (72) Inventor Satoshi Owada Chiba Chiba 1 Kawasaki-cho, Chuo-ku, Yokohama-shi Kawasaki Steel Corporation Technical Research Division

Claims (4)

[Claims] 1. A Cr content of 5 to 60% by weight, C, N, O,
An Fe-Cr alloy excellent in workability and pitting corrosion resistance, characterized in that the total amount of P and S is 100 ppm or less, the Mo content is 0.5 to 20% by weight, and the balance is Fe and inevitable impurities. 2. A Cr content of 5 to 60% by weight, C, N, O,
The total amount of P and S is 100 ppm or less, the Mo content is 0.5 to 20% by weight, and one or more kinds selected from Ni, Cu, and Co are contained in an amount satisfying the following formula (1), and the balance Fe and unavoidable. Fe-Cr alloy excellent in workability, pitting corrosion resistance and acid resistance, which is characterized in that it is made of specific impurities. 0.01 wt% ≦ Ni + Co + 2Cu ≦ 6 wt% (1) 3. A Cr content of 5 to 60% by weight, C, N, O,
The total amount of P and S is 100 ppm or less, the Mo content is 0.5 to 20% by weight, and Al, Si and Mn.
Containing one or more selected from the following formula (2) and / or one or more selected from Ca, Mg and rare earth elements (REM) in an amount satisfying the following formula (3):
Fe-Cr excellent in workability, pitting corrosion resistance and oxidation resistance, characterized by being composed of balance Fe and unavoidable impurities
alloy. 0.1 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt% (2) 0.001 wt% ≦ 4Ca + 4Mg + REM ≦ 0.2 wt% (3) 4. A Cr content of 5 to 60% by weight, C, N, O,
The total amount of P and S is 100 ppm or less, the Mo content is 0.5 to 20% by weight, and one or more kinds selected from Ni, Cu and Co are contained in an amount satisfying the following formula (1), and Al and Si. And one or more selected from Mn and / or one or more selected from Ca, Mg and a rare earth element (REM) in an amount satisfying the following formula (3), and the balance Fe and An Fe-Cr alloy excellent in workability, pitting corrosion resistance, acid resistance and oxidation resistance, which is characterized by comprising unavoidable impurities. 0.01 wt% ≦ Ni + Co + 2Cu ≦ 6 wt% (1) 0.1 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt% (2) 0.001 wt% ≦ 4Ca + 4Mg + REM ≦ 0.2 wt% (3)