JPS59104447A - High ni-alloy containing cr with high stress corrosion cracking resistance - Google Patents

Abstract

PURPOSE:To enhance the stress corrosion cracking resistance of a high Ni-alloy containing C, Si, Mn, Cr, Ni, Al, Ti and Nb and comprising the remainder of substantially Fe, by respectively adjusting the amounts of C and impurities P and S to specific amount or less. CONSTITUTION:The composition of this Ni-alloy contg. Cr having high stress corrosion cracking resistance is prescribed as mentioned hereinbelow. That is, a composition containing 0.05% or less C, 1.0% or less Si, 1.0% or less Mn, 25-35% Cr, 50-74% Ni, 1.0% or less Al, 0.05-1.0% Ti and 0.05-1.0% Nb and, as impurities, 0.010% or less P and 0.005% or less S and comprising the remainder of substantially Fe is prepared. This alloy shows excellent stress corrosion cracking resistance in welding or even after succeeding annealing treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to welding and subsequent SR (5tressres).
Engineering ief) Tubes and containers for nuclear power-related and various chemical fluids that are used in high-temperature, high-pressure water environments containing pure water or alkalis, etc., regarding Or-containing high N1 alloys that exhibit excellent stress corrosion cracking resistance even after heat treatment. In recent years, 30% Cr-60% N1 has been used as a material for various other accessories.
These alloys have attracted attention and are currently being put into practical use. This is because the stress corrosion cracking resistance (hereinafter referred to as SCC resistance) of the 30%0r-60%N1 type is excellent.

However, even with this 30%Cr-60%Nj-based alloy,
During use under the above-mentioned environment, the risk of SCC occurring in the base metal cannot be sufficiently avoided when welding the thermal acoustic zone.

As a result of this (zeta), Cr carbide precipitates at the grain boundaries and Cr near the grain boundaries. N deficiency occurs, resulting in sensitization of the alloy and SCC
This is because it is more likely to occur.

Therefore, it is an object of the present invention to provide an alloy that has the excellent SCC resistance inherent to the 30%Cr-60%Ni system, and that does not substantially become sensitized or deteriorate in SCC resistance even after welding or subsequent SR heat treatment. That is.

That is, the gist of the present invention is that
Below, 5j-1,0% or less, Mn 1.0 X or less,
0r25-35%, N150-80%, AAl, 0% or less, T10.05-160%, Nb0.05-1.0%
containing P and S'iz as impurities, Po and 0, respectively.
Niroru is a Cr-containing high N1 alloy consisting of 10% or less, 5O80055A or less, and the balance iFe and unavoidable impurities.

In the case of 30%Cr-60%Ni alloy, products such as plates and thatch are generally subjected to cold treatment of 30X or less after part processing.
As the final heat treatment, the manufacturing process is performed by performing annealing at a heating temperature of 950 to 1100°C and a holding time of about 05 to 2 hours. In such an alloy system, precipitation of carbides after annealing must be suppressed as much as possible in order to avoid sensitization during SR treatment. In other words, if there is a large amount of carbide precipitation, S
The precipitation of Cr carbide caused by the R treatment is likely to cause aggravation and sensitization due to Cr deficiency.

Precipitation of undissolved carbides decreases because the higher the annealing temperature, the higher the solid solubility of C. On the other hand, with regard to cold working before annealing, the lower the degree of working, the less the introduction of nullif "bands, which are the core of carbide precipitation, and thus the precipitation of carbides tends to be suppressed.

For the above reasons, the manufacturing method described above is applied to the 30-light Cr-60 light N1 system.

On the premise of application of this manufacturing method, the inventors
We experimentally tried various improvements to the composition system of the %0r-60%N1 alloy, and as a result, we limited the amount of C to 0.05% or less, and lowered the P and Si in the alloy to below the general level.
We have found that lowering O,0010% or less and So,005% or less is extremely effective in preventing SCC. That is, (1) C(4) is preferably as low as possible since it contributes to the precipitation of Cr carbide at grain boundaries, which causes sensitization to SCC.

■ S cracks, which precipitate and segregate at grain boundaries during annealing, and the subsequent S
R9) It has the function of promoting the precipitation of cr carbide due to the 4-dimensional process, etc., and must be reduced as much as possible in order to suppress SCC.

(2) Like S, P also precipitates and segregates at grain boundaries during SR heat treatment, increasing SCC susceptibility8, so it is necessary to reduce it as much as possible in order to improve SCC resistance.

■ and ■ above are clearly swords).

The reasons for limiting each alloy component in the present invention will be described below.

C: Since it is an element harmful to the SCC properties of the above-mentioned (2), it was limited to 0.05% or less.

Si, Mn, AA: All are deoxidized by the deoxidizing element, and when each upper limit is exceeded, the cleanliness of the alloy deteriorates, perhaps because the effect is saturated.

N1: Highly effective in improving corrosion resistance, especially against nitric hydrofluoric acid and alkali!
SC in high-temperature, high-pressure water environments containing J (NaOH, etc.)
65.50% as a basic element that improves resistance to C
Extremely high corrosion resistance can be obtained with the above content. On the other hand, 80
If the Ni content exceeds 80%, the effect not only reaches saturation but also limits the amount of Or that can be added.

Cr is an essential element for improving metametallic corrosion properties, and if it is less than 25%, sufficient effects will not be exhibited, while if it exceeds 35%, hot workability will be significantly impaired.

T work: If it is less than 0.005%, hot workability may deteriorate.

On the other hand, if it exceeds 1.0%, the effect is saturated and is meaningless.

N'l): A stabilizing element for C, which fixes C and is effective in suppressing the precipitation of Cr carbide, which is harmful to SCC resistance. However, if it is less than 0.05%, the effect of fixing C cannot be expected, and on the other hand, if it is added in excess of 1.0%, the effect is saturated. Therefore, Nb was set to 0.005% to 1.0%.

S: As mentioned above (DK), it is an element that is harmful to SCC resistance and must be kept at 0.005% or less.OP: As explained in ■, like S, it is an element that is harmful to SCC resistance. From that point of view, it is necessary to limit P to 0.010% or less. This restriction on P is effective only under the above-mentioned condition of 80005% or less.

As is clear from the above, the Cr-containing high N1 alloy of the present invention is made of ordinary 30% Cr760.
As with the %N1 series, during production, hot working and cold working of about 30% or less may be performed to obtain a temperature of 950 to 950 b.

Next, the superiority of the alloy of the present invention will be specifically explained with reference to examples.

Alloy 117k having each component of (1) to α■ shown in Table 1
g After melting in a short vacuum, forging, hot rolling, and heat treatment, 30% cold working was performed, followed by final annealing at 1100° C. for 30 minutes WQ (water cooling).

This as-annealed material was further subjected to 550 x 20 hours of low-temperature heat treatment (simulating the base material receiving only SR treatment) or TIG welding (using tank stainless steel wire).
10■, about 50A with nano twice) Juka low? 'l From the material subjected to passion treatment (simulating a weld), 2a
Two test pieces each measuring 75 mm thick x 1 shoulder long and shoulder length were taken and subjected to the following SCC test. That is, by bending it into a U-shape and constraining it to the awn with a 51TW, the so-called sing/l/
A U-bend test piece was prepared, and this was placed in a 30 CA'NaOH solution (325°C) stored in an autoclave.
A time immersion test was conducted, and after the test, the crack depth of the U-shaped specimen was measured under a microscope.

The results were as shown in Table 2.

In the upper table of Table 2, at C0.05% or less, P, Si satisfies pkuo, oto%, s<o, oo% fcL,,7:l-
All alloys of the present invention containing N'be are as-annealed,
At both stages after low-temperature heat treatment corresponding to SR treatment and after welding + low-temperature heat treatment, the maximum depth of sCc showed an extremely small value on the order of the second decimal place. In contrast, C<0.05%, P<0. Q10%, S〈0
．． 005%, NbO, any one of the conditions of 05 to 1.0%
Comparative Example (9) to α East, which does not satisfy one or more conditions, shows a significant SCC of more than one decimal place at the maximum depth in any of the above conditions. From the above comparison, it is clear that the implementation effect of the present invention is 1.

As is clear from the above explanation, the Cr-containing high Ni
The base alloy has the excellent SCC resistance inherent to the 30%Cr-60%Ni system, and the cam also has SR treatment and common joint ten SR.
It has the great advantage of maintaining its excellent resistance to 5CC8E even after treatment, and can be said to be particularly effective when applied to various equipment and parts used in pure water or alkaline environments.

Sumitomo Metal Industries, Ltd. Voluntary Procedural Amendment September 16, 1980 Kazuo Wakasugi, Commissioner of the Patent Office 1. Indication of the case 1982 Patent Application No. 212299 2. Name of the invention Good stress corrosion cracking resistance Cr-containing high N1 alloy 3, relationship with the amended case Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Name (2)
11) Sumitomo Metal Industries Co., Ltd. Representative Norifumi Kumagai 4 Agent (Document sending date: Month, Day, 1939) 6. “Claims” column and “Detailed description of the invention” column of the specification subject to amendment 7. Contents of the amendment (1) Please attach the claims of the specification to the attached sheet.

(2) “Ni5
0 to 80%, and correct the stop to rN150 to 74%.

(3) In the 12th line of page 5 of the same document, the phrase ``On the other hand, if it exceeds 80%...'' is corrected to ``On the other hand, if it exceeds 74%...''.

(4) Same as above, page 5, line 14 ['N'L(ζ80
% or less. ” was changed to “Ni was set to 74% or less.

”.

(5) In the 4th line of page 6 of the same document, the phrase ``In the case of addition of more than 1.0% on the other side,'' is amended to ``In the case of addition of more than 1.0% on the other side.''

(6) From the second line to the third line from the bottom of page 6 of the same page, the phrase "Final annealing of the raw material for about 2 hours at 950-1100℃" is changed to "Final annealing for about 2 hours at 950-1100℃". Correct it to...''.

(7) "S<0.0" in the fourth row from the bottom of page 9 of the specification
00% is satisfied, and the correction is made to ``stop rskuo, oo5% is satisfied''.

(Note 2) The amendment to increase the N1 amount from 80% to 74% is simply a correction of a writing error and does not constitute a change in the basic content of the invention.
C'r The sum of the components is always 11?11 in relation to the scenery.
It is clear that it will exceed 00%. ) (Attachment) Claims (1) CO, 055X or less, Sl 1.0X or less,
Mni, below ox, Or 25-85x, Nj-50
--74X, At 1.0% or less, Tl O, 05-1
．． O') 6, N'b O, 05-1, ON 'it: P and S as impurities are po and o i, respectively.
.

% or less, So, 0.05% or less, the balance Fe and unavoidable impurities 71% or less, an Or-containing high N1 alloy with good stress corrosion cracking resistance.

Claims (1)

[Claims] (1) C0.05% or less, 811.0% or less, Mn
1.0% or less, cr25-85%, N1.50-80%
, At 1.0% or less, TiO, 05-1.0%, Nb0
．． Contains 05 to 1.0%, P and S as impurities are PO, 010% or less, So, 005% or less, and the balance is Fe and inevitable impurities.Or content high N1 with good stress corrosion cracking resistance. alloy.