JPH0641696A - Fe-cr alloy excellent in workability, pitting corrosion resistance, and corrosion resistance in weld zone - Google Patents

Abstract

PURPOSE:To provide an Fe-Cr alloy excellent in workability, pitting corrosion resistance, and corrosion resistance in weld zone and also provide an Fe-Cr alloy excellent in acid resistance and oxidation resistance besides the above. CONSTITUTION:The Fe-Cr alloy is an Fe-Cr alloy having a composition which contains, by weight, 5-60% Cr and 0.5-20% Mo and where C+N+O+S+P is regulated to 100ppm or less and Ti+Nb+Zr+V+Ta+W+50B is also regulated to 1% or less, and further, an Fe-Cr alloy having a composition where, besides the above, Ni+Co+2Cu is regulated to 0.01-6%, and further, an Fe-Cr alloy having a composition where, besides the above, 3Al+2Si+Mn is regulated to 0.1-50% and/or 4Ca+4MG+REM is regulated to 0.001-0.2%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Fe-Cr alloy having excellent workability, corrosion resistance, particularly pitting corrosion resistance, weld corrosion resistance (intergranular corrosion resistance), acid resistance and oxidation resistance.

[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 JP-A-62-267450, a high-purity ferritic stainless steel which is an 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 an Fe-Cr alloy having a Cr content of 25.0 to 30.0% by weight, and in particular, it contains a specific amount of Mo and is excellent in biofouling resistance and seawater resistance. Ferritic stainless steel is proposed.

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.

[0009]

In these Fe-Cr alloys, since the corrosion resistance is important first, Cr is used in a relatively large amount. As a result, ductility deteriorates and workability is not always sufficient, and when it is applied to a sink of a domestic sink, exterior material for construction, exterior material for automobiles, etc., cracks occur during processing, and it is difficult to process. When conditions are required, there is a problem that processing becomes difficult, and further improvement in processability has been desired.

Further, although these Fe-Cr alloys are excellent in corrosion resistance, they are still insufficient, and especially water heater can bodies and automobile muffler materials, which are required to have pitting corrosion resistance and weld corrosion resistance (intergranular corrosion resistance). There is a demand for improvement in these properties for the use of, and further for applications such as chemical plants where acid resistance is required.

Thus, the first object of the present invention is Fe, which has improved workability and is excellent in pitting corrosion resistance and weld corrosion resistance.
-Providing a Cr alloy.

A second object of the present invention is to provide a Fe-Cr alloy having improved acid resistance and / or oxidation resistance, in addition to the above-mentioned improvement of properties.

[0013]

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
By adding a specific amount of Mo to the alloy, the pitting corrosion resistance is remarkably improved, and further Ti, Nb, Zr, V, Ta,
It has been found that the corrosion resistance of the weld zone (intergranular corrosion resistance) is remarkably improved by adding a specific amount of one or more of W and B.

In addition to the above elements, Ni, Co,
We have found a series of facts that the acid resistance is significantly improved by adding a specific amount of one or more Cu. Further, it has been found that the oxidation resistance is remarkably improved by adding a specific amount of one or more of Si, Mn and Al and / or one or more of Ca, Mg and REM instead of the above elements, and the present invention has been completed. It was

That is, according to the present invention, the Cr content is 5-6.
0% by weight, and the total amount of C, N, O, P and S is 1
00ppm or less, Mo content is 0.5 to 20% by weight, and contains at least one selected from Ti, Nb, Zr, V, Ta, W and B in an amount satisfying the following formula (1),
Fe- which is excellent in workability, pitting corrosion resistance and weld corrosion resistance, characterized by comprising the balance Fe and unavoidable impurities
A Cr alloy is provided. 0.01 wt% ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 1.0 wt% ………… (1)

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, the Mo content is 0.5 to 20% by weight, and At least one selected from Ti, Nb, Zr, V, Ta, W and B satisfies the following formula (1), and Ni, Cu
Fe having excellent workability, pitting corrosion resistance, weld corrosion resistance and acid resistance, characterized by containing at least one selected from Co and Co in an amount satisfying the following formula (2) and consisting of balance Fe and inevitable impurities. -Cr alloy is provided. 0.01% by weight ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 1.0% by weight (1) 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (2)

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 Ti, Nb, Zr, V, Ta, W and B is contained in an amount satisfying the following formula (1). ,
And an amount of one or more selected from Si, Mn and Al satisfying the following formula (3) and / or an amount of one or more selected from Ca, Mg and a rare earth element (REM) satisfying the following formula (4). Provided is an Fe-Cr alloy having excellent workability, pitting corrosion resistance, weld corrosion resistance, and oxidation resistance, which is characterized by containing the balance Fe and inevitable impurities. 0.01 wt% ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 1.0 wt% …… (1) 0.1 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt% …… (3) 0.001 wt% ≦ 4Ca + 4Mg + REM ≦ 0.2 wt% …… (4)

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 is 0.5 to 20% by weight, and one or more selected from Ti, Nb, Zr, V, Ta, W and B is contained in an amount satisfying the following formula (1). ,
Further, one or more selected from Ni, Cu and Co is contained in an amount satisfying the following formula (2), and one or more selected from Si, Mn and Al is contained in an amount satisfying the following formula (3) and / or Ca, Mg and rare earth elements (REM)
Fe- which is excellent in workability, pitting corrosion resistance, weld corrosion resistance and oxidation resistance, characterized in that it contains at least one selected from the following formula (4) in an amount satisfying the following formula (4) and is composed of the balance Fe and inevitable impurities. A Cr alloy is provided. 0.01 wt% ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 1.0 wt% …… (1) 0.01 wt% ≦ Ni + Co + 2Cu ≦ 6 wt% …… (2) 0.1 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt% ………… (3) 0.001% by weight ≤ 4Ca + 4Mg + REM ≤ 0.2% by weight ... (4)

[0020]

The present invention will be described in more detail below. (I) First, the Fe-Cr alloy excellent in workability, pitting corrosion resistance and weld corrosion will be described. In FIG. 1, Fe-
For the 18% Cr alloy, the total amount of C, N, O, P and S and the result of the tensile test at room temperature are shown to be 500 p
It is shown based on the conventional alloy of about pm.
It can be seen that when the content is 100 ppm or less as compared with the conventional alloy, the elongation value is improved, the yield strength is remarkably reduced, and the ductility is improved.

The method for preparing the test piece and the measuring method are as follows. Specimen: 10kg melting in a vacuum furnace, casting, 4m hot
After rolling to a thickness of m, recrystallization annealing, descaling, and cold rolling to a thickness of 0.8 mm and recrystallization annealing were performed to obtain a test material. Measurement method: Evaluated by a tensile test according to JIS Z-2241. The test piece was sampled from the L direction, the X direction, and the C direction, and was calculated by (L + C + 2 × X) / 4. In Fig. 1, the change in elongation (%) and the change in proof stress (yield strength) (N / mm ² ) are C + N + O + S + P = 500 for each alloy component.
The difference in tensile properties from that of ppm is shown. The basic tensile properties are as follows. Fe-18Cr, C + N + O + S + P = 500ppm, elongation 30%, yield strength 330N / mm ² Fe-30Cr, C + N + O + S + P = 500ppm, elongation 25%, yield strength 450N / mm ²

FIG. 2 shows the relationship between the Mo content and the pitting corrosion potential 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. When the Mo content is 0.5% by weight or more, it is clear that the pitting corrosion potential is rapidly improved and the pitting corrosion resistance is excellent.

The method for preparing the test piece and the measuring method are as follows. Specimen: 10kg melting in a vacuum furnace, casting, 4m hot
After rolling to m thickness, recrystallization annealing, descaling, cold rolling to 0.8 mm thickness, recrystallization annealing, and surface emery # 800 polishing were performed to obtain test pieces. Measurement method; 1000 ppm Cl ^-in solution JIS G0
According to 577, the anodic polarization curve was determined and Vc of 10 μA was used as the pitting potential.

FIG. 3 shows the intergranular corrosion test results of the TIG welded portion for the Fe-20% Cr alloy in which the total amount of C, N, O, P and S is 100 ppm or less (Ti + Nb).
+ Zr + V + Ta + W + 50 × B) value (% by weight) is shown. According to this, it is clear that when the above value is 0.01% or more, the weld corrosion resistance (intergranular corrosion resistance) is significantly improved.

The method for preparing the test piece and the measuring method are as follows. Specimen: 10kg melting in a vacuum furnace, casting, 4m hot
After rerolling to m thickness, recrystallization annealing, descaling, cold rolling to 0.8 mm thickness, recrystallization annealing, and surface emery # 500 polishing, TIG welding (bead-on) was applied to the sample. And Measurement method: Welding part bending test (r = 2t, 180 ° C. bending) after sulfuric acid-copper sulfate test based on JIS G-0572
It was evaluated by the presence or absence of cracks due to.

In FIG. 4, the total amount of C, N, O, P and S is 100 ppm or less, and Fe- (25 to 45)
The relationship between the corrosion rate obtained by the immersion test of the 5% Cr alloy plate in a 5% by weight HCl aqueous solution and the (Ni + Co + 2Cu)% by weight was shown. From this graph, (Ni + Co + 2C
It is apparent that when the value of u) is 0.01% by weight or more, the corrosion rate sharply decreases and the acid resistance improves.

The method for preparing the test piece and the measuring method are as follows. Specimen: 10kg melting in a vacuum furnace, casting, 4m hot
After rolling to m thickness, recrystallization annealing, descaling, cold rolling to 0.8 mm thickness, recrystallization annealing, and surface emery # 500 polishing were performed to obtain test pieces.

Next, the composition of the alloy of the present invention will be described. Cr: 5 to 60% by weight, preferably 10 to 35% by weight. When the Cr content is in this range, the corrosion resistance of the alloy is excellent. If the content of Cr exceeds 60% by weight and is excessive, the effect of improving the corrosion resistance is almost saturated, which is economically unreasonable and also the workability is deteriorated.

C, N, O, P, S: The total amount of these elements is 100 ppm or less. As described in the section [Operation], when it is 100 ppm or less, excellent ductility is exhibited and workability is excellent. Mo: 0.5 to 20% by weight, preferably 1 to 10% by weight
contains. If it is 0.5% by weight or more, pitting corrosion resistance is excellent, but excessive content is uneconomical and not preferable. Ti, N
b, Zr, V, Ta, W, B: The alloy of the present invention contains one or more of these elements, and the content thereof satisfies the following formula (1). It is preferable to satisfy the formula (1a). 0.01 wt% ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 1.0 wt% …… (1) 0.05 wt% ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 0.5 wt% …… (1a) Corrosion resistance of weld zone The alloy of the present invention having an excellent intergranular corrosion property is obtained. However, excessive inclusion of these elements is not preferable because the workability is deteriorated due to the solid solution strengthening of the additional elements themselves.

The content of Ti, Nb, Zr, V, Ta, W or B is preferably in the following range. Ti: Ti ≦ 5 (C% + N%) Nb: 0.01 to 0.5 wt% Zr: 0.01 to 0.5 wt% V: 0.01 to 0.5 wt% Ta: 0.01 to 0.5% by weight W: 0.01 to 0.5% by weight B: 0.0003 to 0.01% by weight

The Fe-Cr alloy satisfying the above conditions is excellent in workability, pitting corrosion resistance and weld part corrosion resistance (intergranular corrosion resistance), and can be used in water heater can bodies, automobile muffler materials and the like. It can be preferably used for various purposes.

(II) Next, the Fe-Cr alloy of the present invention which is excellent in workability, pitting corrosion resistance, weld corrosion and acid resistance will be described. In addition to the above condition (I), N
By containing at least one of i, Cu, and Co and satisfying the following expression (2), the alloy becomes excellent in acid resistance. It is preferable to satisfy (2a). 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (2) 0.05% by weight ≦ Ni + Co + 2Cu ≦ 5% by weight (2a)

Excessive composition of Ni, C3 and Cu in excess of the formula (2) means that these elements are austenite stabilizing elements and a large amount is required to finally obtain a ferrite single phase as in the present invention. Cr and Mo are added, which is not preferable.

The preferred 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% Nu: 0.05 to 2.5 wt%

An alloy satisfying the above conditions (I) or (II) is excellent in workability, and is also extremely excellent in pitting corrosion resistance, weld corrosion resistance (intergranular corrosion resistance), and acid resistance. It is suitable for various uses such as muffler materials, water heater cans and materials for chemical plants.

F described in (I) or (II) of the present invention
As a raw material for producing an e-Cr alloy, first, high-purity electrolytic iron, electrolytic Cr, metal Mo, metal Ti, metal Nb, metal Zr, metal V, metal Ta, metal W, high purity (Fe-
B), electrolytic Ni, electrolytic Cu and metallic Co are used. 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 10 ⁻⁷ torr or more in order to remove this oxygen.

(III) Further, the Fe-Cr alloy of the present invention which is excellent in workability, pitting corrosion resistance, weld corrosion and oxidation resistance will be described. FIG. 5 shows Fe- (15 to 30) in which the total amount of C, N, O, P and S is 100 ppm or less.
% Cr alloy, oxidation resistance test (1350K in air,
It is a graph which shows the result of the weight reduction after 12 hr scale removal. It is clear that when (3Al + 2Si + Mn) is 0.1% by weight or more, the oxidation resistance is excellent.

FIG. 6 shows Fe- (15-30)% Cr in which the total amount of C, N, O, P and S is 100 ppm or less.
For alloys, oxidation resistance test (1350K in air, 12h
It is a graph which shows the result of the weight reduction after r scale removal. It is clear that when (4Ca + 4Mg + REM) is 0.001% by weight or more, the oxidation resistance is excellent.

The components and embodiments of the alloy composition of the present invention will be described below. The Fe-Cr alloy excellent in workability 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 10 to 40% by weight. When the Cr content is in this range, it is combined with other conditions to form an alloy having excellent oxidation resistance. Excessive Cr content is not preferable because it causes deterioration of workability and saturates the effect of improving the oxidation resistance.

C, N, O, P, S: The total amount of these elements is 100 ppm or less, preferably 85 ppm or less. By satisfying this condition, abnormal oxidation is suppressed. Then, these conditions are combined with other conditions to form an alloy exhibiting excellent oxidation resistance and, at the same time, an alloy having excellent ductility and good workability.

Mo: 0.5 to 20% by weight, preferably 1
Contains 10 to 10% by weight. If it is 0.5% by weight or more, pitting corrosion resistance is excellent, but excessive content is uneconomical and not preferable. Ti, Nb, Zr, V, Ta, W, B: The alloy of the present invention contains one or more of these elements, and the content thereof satisfies the following formula (1). It preferably satisfies (1a). 0.01 wt% ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 1.0 wt% …… (1) 0.05 wt% ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 0.5 wt% …… (1a) Corrosion resistance of weld zone The alloy of the present invention having an excellent intergranular corrosion property is obtained. However, excessive inclusion of these elements is not preferable because the workability is deteriorated due to the solid solution strengthening of the additional elements themselves. The Fe-Cr alloy satisfying the above conditions has excellent workability, and also has excellent pitting corrosion resistance and weld zone corrosion resistance (intergranular corrosion resistance),
It can be preferably used for various purposes such as a water heater can and an automobile muffler material.

Si, Mn, Al: The alloy of this embodiment contains at least one of these elements, and the content satisfies the following formula (3), preferably (3a). 0.1 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt% (3) 0.5 wt% ≦ 3Al + 2Si + Mn ≦ 25 wt% (3a) Due to such a range, in combination with other conditions,
The alloy is remarkably excellent in oxidation resistance. If these elements are contained excessively and the value of 3Al + 2Si + Mn exceeds the range of the formula (3), it becomes difficult to produce an alloy, so that the excessive content of these elements should be avoided.

The preferred contents of each individual element and the reasons therefor will be described below. Si: 0.1 to 10.0% by weight If less than 0.1% by weight, it is effective but not remarkable. 10.
If it exceeds 0% by weight, the decrease in manufacturability becomes noticeable. Mn: 0.1 to 5.0% by weight If less than 0.1% by weight, it is effective but not remarkable. When it exceeds 5% by weight, the productivity is conspicuously deteriorated. Al: 0.1 to 4.0% by weight If less than 0.1% by weight, it is effective but not remarkable. 10.
If it exceeds 0% by weight, the decrease in manufacturability becomes noticeable.

The Fe-Cr alloy satisfying the above conditions is excellent in oxidation resistance and workability.
It can be suitably used for pipes and the like used in a high temperature repeated oxidation environment.

(2) Second embodiment of the present invention With respect to the Cr content, the contents of C, N, O, P and S, and the preferable content of Fe, what has been described in the first embodiment is also applied to the present embodiment. To be done. In the alloy of the second aspect,
It contains one or more selected from Ca, Mg and REM. And the contents of these elements are expressed by the following formula (4),
It preferably satisfies (4a). 0.001 wt% ≦ 4Ca + 4Mg + REM ≦ 0.2 wt% (4) 0.005 wt% ≦ 4Ca + 4Mg + REM ≦ 0.15 wt% (4a)

By satisfying this condition, in combination with other conditions, an Fe-Cr alloy having excellent oxidation resistance and good workability can be obtained.

These elements remarkably improve the protective property of the oxide film formed on the surface of the alloy of the present embodiment, suppress the abnormal oxidation that is apt to occur in the ultrathin material, and improve the adhesion between the oxide film and the base material. Has the function of improving

However, if these elements are excessively contained and the value of (4Ca + 4Mg + REM) exceeds 0.2% by weight, surface defects of the alloy are likely to occur, which is not preferable.

The more preferable contents of each of Ca, Mg and REM and the reasons therefor are as follows. Ca: 0.002 to 0.01% by weight Even if less than 0.002% by weight, there is an effect but it is not remarkable.
If it exceeds 0.01% by weight, the decrease in manufacturability becomes noticeable. Mg: 0.002 to 0.01% by weight If less than 0.002% by weight, the effect is obtained but not remarkable.
If it exceeds 0.01% by weight, the decrease in manufacturability becomes noticeable. REM: 0.005 to 0.1% by weight If less than 0.005% by weight, there is an effect but not remarkable.
If the amount exceeds 0.1% by weight, the effect will be saturated and the cost will increase.

Such an alloy of the second aspect of the present invention is
It can be used for the same purpose as the alloy of the first aspect.

(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 detailed above, that is, the Cr content is 5 to 60% by weight, the total amount of C, N, O, P and S is 100 ppm or less, the Mo content is 0.5 to 20% by weight, and Ti, Nb, Z
It contains at least one selected from r, V, Ta, W and B in an amount satisfying the above formula (1), and contains 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 in order to remove this oxygen, the Fe-Cr of the present invention was obtained by melting and casting under ultra-high vacuum of higher than ^10-5 torr.
Alloys can be produced.

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

Like the invention of (III), this invention has three aspects, C + N + O + P ≦ 100 ppm, and Cr:
5 to 60% by weight, Mo: 0.5 to 20% by weight, 0.01% ≦ Ti + Nb + Zr + V + W + 50B ≦
In addition to 1%, only the changing portion will be described below for each mode. (1) First embodiment of the present invention One or more kinds selected from Ni, Co and Cu are contained in an amount satisfying the following formula (2). 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (2) One or more kinds selected from Si, Mn and Al are contained in an amount satisfying the following formula (3). 0.1% by weight ≤3Al + 2Si + Mn≤50% by weight (3) Preferably, 0.5% by weight≤3Al + 2Si + Mn≤25% by weight (3a)

(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 (2). 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (2) One or more selected from Ca, Mg and a rare earth element (REM) are contained in an amount satisfying the following formula (4). 0.001 wt% ≦ 4Ca + 4Mg + REM ≦ 0.2 wt% (4) Preferably, 0.005 wt% ≦ 4Ca + 4Mg + REM ≦ 0.15 wt% (4a)

(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 (2). 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (2) One or more kinds selected from Si, Mn and Al are contained in an amount satisfying the following formula (3). 0.1% by weight ≤3Al + 2Si + Mn≤50% by weight (3) Preferably, 0.5% by weight ≤3Al + 2Si + Mn≤25% by weight (3a) selected from Ca, Mg and rare earth elements (REM). One or more kinds are contained in an amount satisfying the following formula (4). 0.001 wt% ≦ 4Ca + 4Mg + REM ≦ 0.2 wt% (4) Preferably, 0.005 wt% ≦ 4Ca + 4Mg + REM ≦ 0.15 wt% (4a)

Since the manufacturing method of the alloy of the present invention is exactly the same as the above, detailed description thereof will be omitted.

[0059]

EXAMPLES The present invention will be described in more detail below with reference to examples. (Example 1) 10k of alloy having the chemical composition shown in Table 1
g Melt in a vacuum melting furnace, cast, and hot rolled to a plate thickness of 4 m
m hot-rolled sheet, subjected to hot-rolled sheet annealing for the purpose of recrystallization, cold-rolled after descaling to a cold rolled sheet having a thickness of 0.7 mm, finally recrystallized annealed, cold-rolled annealed sheet And

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

(Workability) Invention alloys 1 and 2 and comparative alloy 1,
2 was used to measure the elongation value by a tensile test according to 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 5 to 6%.

(Pit Corrosion Resistance and Intergranular Corrosion Resistance) Using a sample obtained by polishing the surface of the test piece with Emery # 500, the pitting corrosion resistance is shown in Table 2 from the corrosion weight loss after 4 hours of immersion in an FeCl ₃ + HCl aqueous solution. Evaluated by the calculated corrosion rate, the intergranular corrosion resistance was evaluated by applying JIG welding (bead-on) to the above sample,
The presence or absence of cracks was evaluated by a welded bending test (r = 2t, 180 ° bending) after a sulfuric acid-copper sulfate test based on ISG-0572. ○ No cracks at all △ Micro cracks present × Large cracks are shown in Table 2.

(Grain boundary corrosion resistance and acid resistance) Samples were prepared in the same manner as above, and the intergranular corrosion resistance was evaluated by the same evaluation as above. The acid resistance was evaluated by the corrosion rate calculated by the corrosion weight loss after immersion in the HCl aqueous solution for 24 hours shown in Table 2. The results are shown in Table 2.

(Oxidation test) The oxidation test was carried out in air at 135
It was heat-treated at 0 k for 12 hours, and evaluated by weight reduction after removing the scale. The results are shown in Table 2.

(Changes in elongation and proof stress) With respect to the obtained test materials, changes in elongation and proof stress (yield strength) were examined. Change in elongation (%), change in proof stress (yield strength) (N /
mm ² ) means C + N + O + S + P = for each alloy component.
The difference in tensile properties from that of 500 ppm is shown. The basic tensile properties are as follows. Fe-18Cr, C + N + O + S + P = 500ppm, elongation 30%, yield strength 330N / mm ² Fe-30Cr, C + N + O + S + P = 500ppm, elongation 25%, yield strength 450N / mm ²

By adding Mo within the range of the present invention, the pitting corrosion resistance is remarkably improved, and Ti, Nb, V, Ta, W,
It can be seen that when Zr and B are added in appropriate amounts, the intergranular corrosion resistance at the welded portion is improved. Further, it is clear that the acid resistance is remarkably improved by adding an appropriate amount of Ni, Co and Cu. Furthermore, it is also clear that the addition of one or more of Si, Mn, Al and / or one or more of Ca, Mg, REM improves the oxidation resistance.

[0068]

[Table 1]

[0069]

[Table 2]

[0070]

[Table 3]

[0071]

[Table 4]

[0072]

[Table 5]

[0073]

[Table 6]

[0074]

[Table 7]

[0075]

[Table 8]

[0076]

[Table 9]

[0077]

[Table 10]

[0078]

[Table 11]

[0079]

[Table 12]

[0080]

The total amount of C, N, O, P and S of the present invention is 100 ppm or less, and Mo and Ti, Nb, Zr,
Fe-containing a specific amount of one or more of V, Ta, W, and B
The Cr alloy is excellent in workability, and is also extremely excellent in pitting corrosion resistance and weld corrosion resistance (intergranular corrosion resistance).

Further, the Fe--Cr alloy containing a specific amount of one or more of Ni, Cu and Co is remarkably excellent in acid resistance. Further, the addition of one or more of Si, Mn and Al and / or one or more of Ca, Mg and REM further improves the oxidation resistance. These steel sheets are useful in various applications.

[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 (Ti + Nb + Zr + V + Ta + W + 50 ×
9B is a graph showing the relationship between weight% and intergranular corrosion resistance.

FIG. 4 is a graph showing the relationship between (Ni + Co + 2Cu) wt% and acid resistance.

FIG. 5 is a graph showing the relationship between (3Al + 2Si + Mn) and oxidation resistance.

FIG. 6 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,
The total amount of P and S is 100 ppm or less, the Mo content is 0.5 to 20% by weight, and Ti, Nb, Z
R, V, Ta, W and B are contained in an amount satisfying the following formula (1), and the balance Fe and unavoidable impurities are included in the workability, pitting corrosion resistance and welded portion. Fe-Cr alloy with excellent corrosion resistance. 0.01 wt% ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 1.0 wt% ………… (1) 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 Ti, Nb, Z
at least one selected from r, V, Ta, W and B satisfies the following formula (1), and further contains at least one selected from Ni, Cu and Co in an amount satisfying the following formula (2),
An Fe-Cr alloy having excellent workability, pitting corrosion resistance, weld corrosion resistance and acid resistance, which is characterized by comprising the balance Fe and inevitable impurities. 0.01% by weight ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 1.0% by weight (1) 0.01% by weight ≦ Ni + Co + 2Cu ≦ 6% by weight (2) 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 Ti, Nb, Z
Contains one or more selected from r, V, Ta, W and B in an amount satisfying the following formula (1), and contains Si, Mn and A.
1 or more selected from 1 is contained in an amount satisfying the following formula (3) and / or one or more selected from Ca, Mg and a rare earth element (REM) is contained in an amount satisfying the following formula (4), and the balance Fe And an inevitable impurity, which is excellent in workability, pitting corrosion resistance, weld corrosion resistance and oxidation resistance. 0.01 wt% ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 1.0 wt% …… (1) 0.1 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt% …… (3) 0.001 wt% ≦ 4Ca + 4Mg + REM ≦ 0.2 wt% …… (4) 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 Ti, Nb, Z
An amount containing one or more selected from r, V, Ta, W and B in an amount satisfying the following formula (1), and an amount containing one or more selected from Ni, Cu and Co in the following formula (2). And / or Ca, M containing at least one selected from Si, Mn and Al and satisfying the following formula (3):
g and one or more selected from rare earth elements (REM) in an amount satisfying the following formula (4), and the balance Fe and unavoidable impurities: processability, pitting corrosion resistance, weld corrosion resistance, Fe with excellent acid resistance and oxidation resistance
-Cr alloy. 0.01 wt% ≦ Ti + Nb + Zr + V + Ta + W + 50B ≦ 1.0 wt% …… (1) 0.01 wt% ≦ Ni + Co + 2Cu ≦ 6 wt% …… (2) 0.1 wt% ≦ 3Al + 2Si + Mn ≦ 50 wt% (3) 0.001% by weight ≤ 4Ca + 4Mg + REM ≤ 0.2% by weight ... (4)