JPH0665691A - High ni alloy sheet strip excellent in corrosion resistance and its production - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a high Ni alloy sheet strip to a greater extent by effectively using a direct sheet casting process. CONSTITUTION:This sheet strip has a composition consisting of <=0.2% C, 30-70% Ni, 10-30% Cr, one or >=2 kinds selected from 1-20% Mo, 0.1-5.0% Ti, 0.1-5.0% Cu, 0.1-5.0& Nb, 0.1-5.O% W, and 0.1-5.0% Al, and the balance Fe with inevitable impurities. As to the texture in the sheet surface shown by the peak intensity by X-ray diffraction, the relationship in inequality I211/(I211+ I111+I110+I100)<=0.30 (where I means the peak intensity of each crystal plane and each figure in the lower right hand of I represents a crystal plane) is satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high Ni alloy thin strip having excellent corrosion resistance and a method for producing the same. Particularly, the present invention is intended to further improve the corrosion resistance of the high Ni alloy thin strip by effectively utilizing the thin plate direct casting method. Is.

[0002]

2. Description of the Related Art High Ni alloys are widely used in various fields as gas turbine components, chemical plant pipes, and recently as dust incinerator components. Recently, the corrosion resistance has been further improved due to deterioration of the operating environment. Is desired. In order to meet the above demands, for example, Japanese Patent Publication No. 64-9392 discloses a high Ni-Cr alloy, in particular Δ ₁ = [Cr + 1.5 Mo.
+0.8 Ti +0.5 Cu-100 C], the value of Δ ₁ is 25
After adjusting to the above composition, the solubilization treatment is performed by the following formula: Tf
≦ 60 Δ ₂ −550 << where Δ ₂ = Ni − [{(Cr + 1.5 Mo−2
0) it has proposed a ^{2/12} -35C-27N +} 14 ] "be carried out at a temperature which satisfies. The above-mentioned manufacturing method is an attempt to improve the corrosion resistance by the combination of the component adjustment and the heat treatment.
A number of complicated steps of hot rolling-heat treatment-intermediate rolling-heat treatment are required.

By the way, in recent years, a technique for directly manufacturing a thin strip from molten steel by utilizing a thin plate direct casting method such as a twin roll method or a single roll method has been developed (for example, Japanese Patent Publication No. 4-2338). Gazette). However, the steel types that have been attempted to be produced by the above-mentioned thin plate direct casting method are SUS304 and SUS4.
It is a stainless steel centered on 30 grade (Japanese Patent Publication No. 4-24413 and Japanese Patent Publication No. 4-24414), and there is no example applied to a high Ni alloy.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to the production of a high Ni alloy thin strip using the above-mentioned thin sheet direct casting method, and by utilizing the features of such a thin sheet direct casting method, it is possible to reduce the number of steps. First, the corrosion resistance of the high Ni alloy thin strip is further improved. Note that in applying the thin plate direct casting method, it is necessary to specify the manufacturing conditions in consideration of the metallurgical characteristics of the applied steel type, the manufacturing conditions in the conventional process as they are, and further, the same thin plate direct casting method. Needless to say, the manufacturing conditions of other steel types cannot be used as they are.

[0005]

That is, the present invention provides C:
0.2 wt% or less (hereinafter simply indicated as%), Ni: 30 to 70% and
Cr: 10 to 30% included, Mo: 1 to 20%, Ti: 0.1 to 5.
0%, Cu: 0.1 to 5.0%, Nb: 0.1 to 5.0%, W: 0.1
.About.5.0% and Al: 0.1 to 5.0%, containing one or more selected from the rest, Fe and unavoidable impurities in the balance, and the texture of the plate surface expressed by the peak intensity by X-ray diffraction. , The following equation (1)

[Equation 2] Of high Ni with excellent corrosion resistance characterized by satisfying the relationship
It is an alloy thin strip.

In the present invention, C: 0.2% or less, Ni: 30-
70% and Cr: 10 to 30%, Mo: 1 to 20%, Ti:
0.1 to 5.0%, Cu: 0.1 to 5.0%, Nb: 0.1 to 5.0%,
W: 0.1 to 5.0% and Al: 0.1 to 5.0%, containing one or more selected from the rest, and the balance from molten steel having a composition of Fe and unavoidable impurities by a thin plate direct casting method.
Thickness: 0.1 to 20mm When manufacturing thin strip, hold for 10s or more from solidification temperature to 800 ℃, and continue 800
Cooling in the temperature range of ~ 600 ℃ at a rate of 50 ℃ / s or more, then cold rolling without hot rolling at a reduction rate of 10% or less or 40% or more, and then finish annealing. A method for producing a high Ni alloy thin strip having excellent corrosion resistance.

The present invention will be specifically described below. First, the clarification process of the present invention will be described. Now, the inventors
In the course of research on the production of high Ni alloy strip by the direct casting method, it was found that the corrosion resistance is strongly correlated with the texture of the sheet surface. Therefore, in the present invention, the relationship between the texture of the plate surface and the corrosion resistance was investigated. Here, the texture of the plate surface can be represented by the peak intensity I _hkl of each crystal plane (hkl) when the plate surface is subjected to X-ray diffraction. For example, I ₁₀₀ is the peak intensity of the (100) plane. Is. FIG. 1 shows the results of examining the relationship between each crystal plane and corrosion resistance of Incoloy 800 alloy. As is clear from the figure, the (211) plane has a particularly high critical current density and is inferior in corrosion resistance as compared with the (111), (110), (100) plane and the like.

Therefore, the present invention intends to improve the corrosion resistance by suppressing the generation of the (211) plane, in other words, by suppressing the peak intensity of the (211) plane to a certain value or less. ) Surface diffraction peak intensity I
₂₁₁ is the diffraction peak intensity (I ₂₁₁ + I ₁₁₁₎ from all crystal planes.
+ I ₁₁₀ + I ₁₀₀ ) was examined to find out how much it should be suppressed to obtain good corrosion resistance. as a result,
(211) plane diffraction peak intensity I ₂₁₁ total diffraction peak intensity (I
Ratio of ₂₁₁ + I _{11 1} + I ₁₁₀ + I ₁₀₀ ) I ₂₁₁ /
It has been clarified that the desired corrosion resistance can be obtained by setting (I ₂₁₁ + I ₁₁₁ + I ₁₁₀ + I ₁₀₀ ) to 0.30 or less. It should be noted that the thin strip having the texture as described above cannot be manufactured by the conventional normal process. I mean,
This is because the (211) plane is strongly developed when hot-rolled, and it is difficult to reduce the (211) plane by any subsequent treatment.

[0009]

In the present invention, the reason why the component composition is limited to the above range will be described below. C: 0.2% or less C is added in order to secure a desired strength, but if the content exceeds 0.2%, carbides are easily generated and corrosion resistance is deteriorated. Therefore, C is contained in a range of 0.2% or less. I decided.

Ni: 30 to 70% Ni is a useful component added to improve strength, corrosion resistance and creep strength, but if it is less than 30%, its effect is not sufficient, while if it exceeds 70%, it is The effect reaches saturation and is rather expensive, so it is limited to 30-70%.

Cr: 10 to 30% Cr is an essential element for improving the corrosion resistance, but if it is less than 10%, the effect of improving the corrosion resistance is poor.
When it exceeds 30%, its effect reaches saturation, so 10-30%
Limited to the range.

Mo: 1 to 20%, Ti: 0.1 to 5.0%, Cu: 0.
1 to 5.0%, Nb: 0.1 to 5.0%, W: 0.1 to 5.0%, A
l: 0.1-5.0% Mo, Ti, Cu, Nb, W and Al are all in the γ'phase [Ni ₃ (A
(l, Ti)] and the like are dispersed and precipitated to improve the strength of the alloy by dispersion strengthening, but if the addition amount is less than the lower limit, the addition effect is poor, and if the addition amount exceeds the upper limit, workability deteriorates. , These elements are added within the above ranges.

Next, the reason why the manufacturing conditions are limited as described above will be explained. In general, the thin plate direct casting method strongly develops the (100) plane during solidification, which is advantageous in forming a texture having a small number of (211) planes, which is the target of the present invention. However, the subsequent rolling process
The amount of (211) planes increases. Therefore, in the method of the present invention, not only hot rolling is omitted, but before the cold rolling,
The (100) plane was sufficiently developed, and the growth of the (211) plane due to the subsequent cold rolling was suppressed as much as possible.

First, the thin plate direct casting method applied to the present invention may be any one as long as it can cast a strip to the extent of direct cold rolling from molten steel, such as a twin roll method, a single roll method and a twin roll method. Any conventionally known method such as a belt method can be applied. Here, the slab thickness needs to be 0.1 to 20 mm. This is because if the thickness is less than 0.1 mm, the solidification rate is too fast and the (100) plane is not sufficiently developed, and in some cases it becomes amorphous. Because it is not practical.

Next, it is necessary to hold for at least 10 seconds from the solidification temperature to 800 ° C. This is because if the retention time is less than 10 s, the (100) plane will not be sufficiently developed and the (211) plane may be induced in the subsequent step.

In the temperature range from 800 ° C. to 600 ° C., it is necessary to cool at a rate of 50 ° C./s or more. This temperature range is the temperature range in which the γ'phase, etc. precipitate, but since the γ'phase deteriorates the subsequent cold workability,
This is because it is preferably not present during solidification, but if the above temperature range is cooled at a rate of 50 ° C./s or more, the precipitation of such a precipitation phase can be substantially suppressed.

Then, cold rolling is applied to the thin strip having the (100) plane sufficiently developed as described above. In order to suppress the growth of the (211) plane in this cold rolling. The reduction rate is especially important. FIG. 2 shows the reduction ratio and I ₂₁₁ of cold rolling in Incoloy 800 alloy.
FIG. 3 shows the results of the examination of the relationship between the / (I ₂₁₁ + I ₁₁₁ + I ₁₁₀ + I ₁₀₀ ) ratio, and FIG. 3 shows the results of the examination of the relationship between the cold rolling reduction and the corrosion amount of the same alloy. In each figure, the results indicated by the broken lines are the results of investigations on alloys obtained according to the conventional process. As is clear from Figs. 2 and 3, when the rolling reduction is more than 10% and less than 40%,
The (211) plane has developed and {I ₂₁₁ / (I ₂₁₁ + I ₁₁₁ + I
_{As a result of 110} + I ₁₀₀ }> 0.30, corrosion resistance is deteriorated.

Therefore, in the present invention, the rolling reduction in cold rolling is limited to the range of 10% or less or 40% or more. In the present invention, cold rolling is not limited to one time, and cold rolling may be performed a plurality of times depending on the desired strip thickness. However, the reduction ratio during each cold rolling needs to satisfy the above conditions (10% or less or 40% or more).

Finally, the finish annealing may be carried out in a temperature range usually used, that is, a temperature range of 950 to 1200 ° C. Also, an aging treatment can be applied if necessary.

[0020]

[Examples] Molten steels having various compositional compositions shown in Table 1 were melted by 10 kg in a high-frequency induction furnace, and cast into 2.0 mm thick slabs by twin-roll type thin plate direct casting method. Made into a thin plate. The final annealing is 1000 ℃, 20 minutes,
The same with water cooling. Table 2 also shows the results of examining the corrosion resistance of the thus obtained high Ni alloy thin plate. Further, in Table 2, for comparison, 18-ton ordinary ingot-press slab-hot rolling (4.0 mm thickness) -heat treatment (1000 ° C) -cold rolling (3.
(0 mm thickness) -Survey results of products manufactured by the conventional process consisting of heat treatment (1000 ° C) are also shown. The corrosion resistance is
Corrosion loss of 65 ℃, 15% HCl and 80 ℃, 15% H ₂ SO ₄ (mm / y)
It was evaluated by.

[0021]

[Table 1]

[0022]

[Table 2]

As is clear from Table 2, all of the high Ni alloy thin plates obtained according to the present invention are I ₂₁₁ / (I ₂₁₁ +
I ₁₁₁ + I ₁₁₀ + I ₁₀₀ ) was 0.30 or less, and good corrosion resistance was obtained, whereas all of the high Ni alloy thin plates I ₂₁₁ / (I ₂₁₁ + I ₁₁₁ + I ₁₁₀ + I ₁₀₀ ) obtained by the conventional method were
It exceeded 0.30, and as a result, sufficient corrosion resistance was not obtained.

[0024]

[Effect] Thus, according to the present invention, it is possible to obtain a high Ni alloy thin strip which is more excellent in corrosion resistance than conventional ones, in combination with the process saving, and its industrial significance is extremely large.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between each crystal plane of Incoloy 800 alloy and the critical current density in 5% H ₂ SO ₄ .

FIG. 2 Cold rolling reduction of Incoloy 800 alloy and I ₂₁₁ /
6 is a graph showing the relationship with the (I ₂₁₁ + I ₁₁₁ + I ₁₁₀ + I _{10 0} ) ratio.

[Fig. 3] Cold rolling reduction and corrosion resistance of Incoloy 800 alloy (65
2 is a graph showing the relationship with the corrosion amount in 15% HCl).

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[Procedure amendment]

[Submission date] May 21, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

[0021]

[Table 1]

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location C22C 30/00 38/50 C22F 1/10 H

Claims (2)

[Claims] 1. C: 0.2 wt% or less, Ni: 30 to 70 wt% and Cr: 10 to 30 wt% are included, and Mo: 1 to 20 wt%, Ti: 0.1 to 5.0 wt%, Cu: 0.1 to 5.0 wt%. %, Nb: 0.1 to 5.0 wt%, W: 0.1 to 5.0 wt% and Al: 0.1 to 5.0 wt%, and one or more selected from the rest, the balance being Fe and inevitable impurities, The texture of the plate surface expressed by the peak intensity by X-ray diffraction is expressed by the following equation (1) Of high Ni with excellent corrosion resistance characterized by satisfying the relationship
Alloy thin strip. 2. C: 0.2 wt% or less, Ni: 30 to 70 wt% and Cr: 10 to 30 wt%, Mo: 1 to 20 wt%, Ti: 0.1 to 5.0 wt%, Cu: 0.1 to 5.0 wt% %, Nb: 0.1 to 5.0 wt%, W: 0.1 to 5.0 wt% and Al: 0.1 to 5.0 wt%, and one or more selected from Al, 0.1 to 5.0 wt% with the balance being Fe and inevitable impurities. When manufacturing a thin strip with a thickness of 0.1 to 20 mm from molten steel by direct casting method, hold the temperature from solidification temperature up to 800 ℃ for 10 s or more, and continue the temperature range from 800 to 600 ℃.
Cooling at a rate of 50 ° C / s or more, then cold rolling without hot rolling at a rolling reduction of 10% or less or 40% or more, followed by finish annealing. High corrosion resistance. Ni alloy thin strip manufacturing method.