JPS59110765A - Cr-mo steel for pressure container excellent in hydrogen corrosion resistant characteristics and sr crack-resistant - Google Patents

Abstract

PURPOSE:To provide Cr-Mo steel for a pressure container enhanced in hydrogen corrosion resistant characteristics and SR crack resistance characteristics, in Cr-Mo steel having a specific composition, by especially limiting the value of S-parameter-P in impurities to a definite amount or less. CONSTITUTION:Cr-Mo steel consists of, on a wt. basis, 0.07-0.18% C, 0.05-1.0% Mn, 0.6-6.0% Cr, 0.3-1.5% Mo, 0.0003-0.010% B, 0.003-0.2% acid sol. Al, below 0.10% Si, according to necessity, one or more of elements selected from a group comprising 0.50% or less V, 0.20% or less Nb, 0.20% or less Ti and 0.20% or less Zr and the remainder of substantially Fe and the value of S-parameter-P of this steel shown by formula P=S-32/40 Ca-32/140 REM is limited to 0.0010% or less. By this steel composition, the hydrogen corrosion resistance characteristics and SR crack resistant characteristics of Cr-Mo steel for a pressure container used under a high temp. and high pressure hydrogen environment can be improved.

Description

[Detailed Description of the Invention] The present invention relates to a pressure-resistant Qr-MO steel with excellent hydrogen corrosion resistance and SR cracking resistance, and is particularly suited to advantageous use conditions in high-temperature, high-pressure hydrogen atmospheres. .

Petrochemical plants, petroleum refining plants, and coal liquefaction plants whose development is being considered in recent years operate in a high-temperature, high-pressure hydrogen atmosphere. In addition, in terms of efficiency, these plants are considering increasing the size of equipment and increasing operating conditions at high temperatures and high pressures, and for this reason, 0r-No. Steel is desired.

However, such a steel material that satisfies the above-mentioned characteristics and has excellent economic efficiency and weldability has not yet been developed.

For example, in order to manufacture thick-walled materials, it is necessary to take measures to improve hardenability in order to prevent deterioration of strength and toughness due to a decrease in the cooling relationship during quenching. Adding it is not acceptable from the viewpoint of weldability and cost.

On the other hand, B is attracting attention as an element that can economically improve hardenability, but for reasons unknown in B-added steel, Uru Cracks (SR cracks) are likely to occur.

In addition, in order to completely improve the hydrogen corrosion resistance, for example, CR
, It is said that it is effective to increase MO and add elements such as W and VZ that cause stable carbide formation.
These also have the advantage of increasing strength, but in any case, simply adding these elements poses problems in terms of economy and weldability.

From the above, Or-
There is a strong desire to develop No. 1 steel.

Regarding the above-mentioned problems, the inventors added 0 B to the Or-MO steel in order to improve the hardenability, and in particular reduced 81 as much as possible, and then reduced S or its degree. Depending on Oa
It has been found that by adding REM k, it is possible to particularly advantageously achieve both hydrogen corrosion resistance and SR cracking resistance.

This invention provides 0:0.07-0.18%, )4n
: 0.05'~], θ%, (3r:
0.6-6.0%, MO: 0.3-1.5%,
B: 0.0008-0.010% and acid soluble A
l: o, ooa ~ 0.20%, S1 content 01
10%, and in the following formula: S: Unavoidable amount of sulfur in the steel Ca: Calcium content REM: Rare earth element content Or-
Mo steel and O: 0.07 to 0.18%.

In: 0.05~1.0%, Cr: 0.6~
6.0%, MO: 10.8-1.5%, B:
0.0003-0.010% and acid-soluble Al: 0.
008 to 0.20%, and further ■: 0.50% or less, ) Jb: 0.20% or less, Ti: 0.2
0% or less and Zr: Q, at least one type selected from 20% or less, S1 content -i 0.10
to less than %.

and in the following formula: S: unavoidable amount of incorporation in steel Ga: calcium content RIM: value of S parameter P shown in rare earth element content Q less than 0.0010%,
The remaining part is essentially composed of Fe, which is an Or-No steel for pressure vessels with excellent hydrogen corrosion resistance and SR cracking resistance. It has achieved compliance with the conditions of use.

First, the reason why the components of the Cr-No steel are limited in this invention is as follows.

0: At least 0.07% is necessary from the viewpoint of strength, but the maximum content is set to 0.18% to prevent deterioration of toughness and weldability.

Mn: At least 0.05% is required from the viewpoint of strength, but
Is there a limit that does not pose a risk of increasing susceptibility to burning and embrittlement?

maximum] and 0%.

From the viewpoint of Cr2 strength and oxidation resistance, at least 0.6% is necessary, but from the viewpoint of economy and weldability, the maximum content is set to 6.0%.

M○2 At least 0.3% is necessary from the viewpoint of enforcement, but it is expensive and the highest limit that does not tend to deteriorate weldability is 1.
．． It was set at 5%.

B: A minimum of o, oooa% is necessary to improve hardenability, but too much will deteriorate toughness and weldability, so 0.0
The upper limit was 10%.

Acid-soluble Al: In order to secure the solid solution B necessary to improve hardenability, depending on the amount of N in the steel, B) tends to combine with N to form B) J. As a result, solid solution B To secure solid solution B by fixing part of the N as tAKIN and reducing BN, 0.008% is required under the normal N content in steel; If too much, the cleanliness and toughness deteriorate, so the maximum content was set at 0.20%.

This invention satisfies the above basic conditions and
content 0. ]03 and the following formula.

P=S --Oa --REM The value of parameter P 'i Q, 0 Since the reduction is lost as much as possible below 10%, O' is set to 085% or less. The experimental results of the Si content and the S parameter P are shown below.

0: 0.14%, Mn: 0.55%, ar
: 2.4%.

MO: 1.0%, B: 0.0015%, acid-soluble AA: 0.06%, N: 0.0060% In steel with all basic components, Si and S, (3a and HEM amount were changed) All steel materials (2 mm thick) were heat treated under the conditions shown in Table 1 and tested.

The results of the test are shown in Figures 1 and 2.

FIG. 1 shows the influence of Si, and the following is clear from this.

(11Si does not affect SR cracking susceptibility.

(2) Reduction of Si improves hydrogen attack resistance (
increase the absorbed energy after H2 immersion).

FIG. 2 shows the influence of the value of the S parameter P, and the following is clear from this.

(1) S parameter P, that is (S -32/Oa
-0 3 shades. By decreasing the value of REM ), the SR cracking susceptibility is reduced and the hydrogen attack resistance is also improved.

(2) Even if S is simply reduced or Oa or REM' is added, the S parameter P, that is (S-""/
400a −””/140 REM) nof+[JE
The same effect can be obtained by reducing fh.

Note that even if it contains aa and HEM, it is 0.0
Must be 85% or less.

From the results shown in Figures 1 and 2, 81 is less than 0.1θ% and the S parameter P is (s82.,;.aa3
27. It is clear that by reducing the value of REM) to less than 0.0010%, both the hydrogen corrosion resistance and the SR cracking resistance can be improved.

In the second invention, further V, Nb, Ti and z
Add one or more of r. All of these elements form stable carbides and contribute to strengthening as well as improving hydrogen corrosion resistance. However, if the amount is too large, the weldability will deteriorate even if the unique method of this invention for reducing the Si content and P value is used, so v, Nb, Ti, zr are each set at 0.
The upper limit was set to 1.1 at 50%, 0.20%, 0.20%, and 0.20%.

(]]] 306- The Qr-MO steel (20 mm thick) shown in Table 2 was subjected to the heat treatment shown in Table 1, and the hydrogen corrosion resistance and SR cracking resistance were investigated. The results are also listed in Table 2.

Comparative steel (A), (D), (E), (R)
, (U) versus the first invention steel (B) , (0) ,
(F) ~ (K), (S), (T, l.

(V) and (W) have excellent hydrogen corrosion resistance and SR cracking resistance. As is clear from the invention steel (K), even if the housing contains about 0.2% of O and Ni, the effects of the invention are not affected in any way.

Furthermore, this effect is more appropriately exhibited in the second invention steels (L) to (Q), especially in that SR cracking does not occur.

As described above, according to the present invention, it is possible to meet the demands for high temperature and high pressure of a pressure vessel used on a high temperature and high pressure water tank and on a ring platform by having both hydrogen corrosion resistance and SR cracking resistance. .

[Brief explanation of the drawing]

FIG. 1 is a graph showing the influence of Si content, and FIG. 2 is a graph showing the influence of is parameter P, that is, (S82/4o, . . 2/14ORFM).
□/11f Permit Applicant Kawasaki Steel Forest Company

Claims (1)

[Claims] 1 C as a chemical component expressed in weight percentage: 0.
07-0.18%, Mn: 0.05-1.0%. Qr: 0.6~6.0%, No: 0.8~1
．． 5%, B: o, oooa ~ 0.010% and acid-soluble Al: o, oooa ~ 0.20%, the S1 content is less than 0.10% 1..., and the following formula (1) A Qr-MO steel for pressure vessels with excellent hydrogen corrosion resistance and SR cracking resistance, in which the value of S parameter P 'i shown in is limited to less than 0.0010%, and the remainder is substantially composed of Fe. In the formula, S: Unavoidable amount of Iori in the steel (wt%) Oa: Calcium content (l), ・REM: Rare earth element content i (wt%) a As a chemical component expressed as a weight percentage, C: 0. 07-0.18%, Mn: 0
．． 05-1.0%, Or: 0.6-6.0%, MO:
0.8 ~], 5%, B: o, oooa ~ O, 010%
and acid-soluble KL: 0.00g-0.20%, and V: 0.50% or less. Contains at least one selected from Nb: 0.20% or less, T soil: 0.20% or less, and Zr: 0.20% or less, Si content 1 to less than 0.10%, and the following: The value of the S parameter P shown in equation (1) is 1...0
．． A Qr40 steel for pressure vessels with excellent hydrogen corrosion resistance and SR cracking resistance, with the remainder being substantially Fe. In the formula: S: Unavoidable amount of Iori in the steel (wt%) Oa:
Calcium content (') REM: Rare earth element content (1),.