JPS62182252A - Corrosion resistant metal coating material for equipment relating to oil production - Google Patents

Abstract

PURPOSE:To remarkably improve corrosion resistance of oil well tube, etc., used in corrosive atmosphere, by coating the surface thereof with Fe-Cr-Ni-Mo alloy steel having a specified compsn. CONSTITUTION:For improving corrosion resistance of equipment relating to oil production used in corrosive circumstance such as oil well pipe, piping in oil refining equipment, alloy steel having the following compsn. is coated by thermal spraying. Namely, alloy steel composed of, by weight 20-35% Cr, 22-60% Ni, 1-10% Mo, <=0.005% C, <=1.0% Si, <=1.0% Mn, <=0.02% P, <=0.01% S and the balance Fe and satisfying the following inequality 60>=Cr+3XMo>=35 as compsn. condition of component elements and having adjusted components so that value DELTA obtd. by an equation [1] is attained to >=7 is coated. By the coating, corrosion resistance of equipment relating to oil production is remarkably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coating material for coating oil production-related equipment such as oil country tubular goods and piping in oil refining equipment with a corrosion-resistant metal.

[Conventional technology and its problems]

In recent years, with the development of deep sour gas wells and oil wells, the corrosive environment for equipment such as oil country tubular goods has become increasingly severe.
For this reason, these devices have higher corrosion resistance (pitting corrosion resistance, stress corrosion cracking resistance (hereinafter referred to as SCC resistance)).
Now it's my turn to be required.

This type of equipment requires not only high corrosion resistance as described above, but also strength to withstand internal pressure and its own weight.For this reason, conventionally, highly corrosion-resistant materials such as duplex stainless steel and high Ni austenite alloys have been used for cooling. The partially processed one is used.

However, such conventional materials use a large amount of expensive materials, and have the disadvantage that they are extremely expensive because they involve cold working difficult-to-process materials to increase strength.

To solve this problem, for example, by fitting a plate made of a corrosion-resistant alloy inside the tube and hot extruding it, or by thermally spraying a corrosion-resistant alloy inside the tube (plasma spraying, etc.),
A method of coating the surface of equipment such as oil country tubular goods with a corrosion-resistant alloy is known, and this method has the advantage that the amount of expensive corrosion-resistant alloy used can be reduced and products can be obtained at low cost.

However, when coating with a corrosion-resistant alloy as described above, there is a major problem in that the hot extrusion method cannot use materials with poor workability for the main body to be coated.

In addition, although there are no restrictions on the workability of a single body in the thermal spraying method, there is a problem in that the corrosion-resistant alloy coated becomes a solidified structure, and the corrosion resistance of alloys with conventionally known compositions is significantly deteriorated. At present, no metal material for coating that has sufficient corrosion resistance under the intended usage conditions has yet been proposed.

[Means to solve the problem]

The present invention was made in view of such conventional problems,
It is an object of the present invention to provide a corrosion-resistant metal coating material that can obtain a high degree of corrosion resistance when coated by thermal spraying or the like.

Therefore, in the present invention, C4: 20 to 35 wt%, Nt
: 22-60 wt%, Mo: 1-1 (1 wt%,
C: 0.05wt96 or less, Si: 1.0wt
9b or less 1Mn: 1.0wt% or less, P:
0.02wt% or less, S: 0.01wt% or less.

The remainder consists of Fe and unavoidable impurities, Cr and Mo satisfy the following conditions: 60 > r + 3
-19)''/12}+13] The basic feature is that the composition has a Δ value of 7 or more.

Below, the reason for limiting the component composition of the present invention will be explained in detail.

Cr is an element necessary to maintain pitting corrosion resistance, and if its content is less than 20 wt%, sufficient pitting corrosion resistance cannot be obtained. However, if Cr is added in an amount exceeding 35 wt%, a σ phase is generated, and the corrosion resistance is significantly deteriorated. Therefore, Cr is added in a range of 20 to 35 vrt%.

Ni is an effective element for improving SCC resistance,
The effect becomes noticeable when the strain is 22wt or more.

On the other hand, even if the content exceeds 60 wt%, no further effect can be expected, and on the contrary, it will impair economic efficiency. Therefore, Nl is set in the range of 22 to 60 wt.

Mo is an element that greatly improves pitting corrosion resistance and corrosion resistance, and its effect becomes noticeable when the content exceeds 1 wt%, but when it is contained in excess of 10 wt%, it forms a σ phase and significantly deteriorates the corrosion resistance. Because of this! 7IO is 1-1
It is set to 0wt%.

C forms carbides during solidification of the coating material and significantly deteriorates corrosion resistance, so 0.05wt%
It can be kept below.

Although St and Mn do not have a large direct effect on corrosion resistance, St deteriorates hot workability, and Mn
There is a problem that precipitates such as manganese sulfide easily become the starting point of pitting corrosion, and therefore 1. The upper limit is 0 wt%.

P and s are elements that are harmful to corrosion resistance and must be reduced as much as possible. Therefore, P is 0.02wt% and S is 0.0%.
The upper limit is IWt'%.

In the present invention, it is necessary to satisfy the following conditions in addition to the composition conditions of the component elements as described above.

First, Cr and Mo must satisfy the following condition (11).

60〉cr+3×Mo≧35・・・・・・・・・・・・
(1) If the value of Cr + 3 X Mo is less than 35, sufficient pitting corrosion resistance of the coating material, which is a solidified structure, cannot be obtained. On the other hand, if the above value exceeds 60.

This results in the formation of a σ phase, which significantly deteriorates corrosion resistance.

Figure 1 shows the relationship between the value expressed by equation (1) above and the pitting corrosion resistance (corrosion degree) after coating. The judgment was based on the reduction in heavy sound after immersion in water for 24 hours. In addition, results regarding rolled materials are also shown. As is clear from the figure, the coating materials targeted by the present invention contain Cr+
When the value of 3XMo (%) exceeds 35, the pitting corrosion resistance of the coating material is significantly improved.

Furthermore, in the present invention, Δ=on+aoc+25N)−C((cr+1.s
Mo-19)” /12) + 13] ・・−
(The compositional conditions must be adjusted so that Δ defined by the formula 2J is 7 or more, and if this Δ value is not satisfied in the compositional conditions, sufficient SCC resistance cannot be obtained in the H2S environment.

Figure 2 shows the relationship between the above Δ value and the SCC resistance after coating, with (Cr+1.5Mo) on the X axis.

Also, (Ni + 30C + 25N) is expressed on the Y axis, and in this case, SCC susceptibility is measured by applying stress to a test piece in a 20% NaCl solution at 230°C in equilibrium with 1 atm of hydrogen sulfide gas for 720 hours. Soaking 77? After that, the judgment was made by Kokichi, who checked for cracks.

As is clear from the figure, satisfactory SCC resistance is obtained in the p range of Δ>7, and in order to fully satisfy the SCC resistance aimed at by the present invention, at least the above composition conditions must be satisfied. It turns out that it has to be done.

〔Example〕

Table 1 shows examples of the present invention, among which No.
Nos. 1 to 14 show the corrosion resistance of materials coated with the material according to the present invention by low-pressure plasma bath perforation. All of the materials of the present invention have a pitting corrosion value of 05 when determined in a ferric chloride solution.
? /m”hr or less, indicating that they have excellent pitting corrosion resistance.Also, regarding stress corrosion cracking resistance determined under the conditions shown in Figure 2, none of the materials exhibited cracking.・On the other hand, marks 15 to 20 indicate the corrosion resistance of conventional materials coated with severe pitting corrosion or stress corrosion cracking. It can be seen that

〔Effect of the invention〕

According to the present invention described above, it is possible to obtain a high degree of corrosion resistance even when coated by thermal spraying, and since it is possible to coat any material by thermal spraying, processing is easy. Moreover, by coating an inexpensive material with a corrosion-resistant metal, it is possible to obtain petroleum-related equipment such as oil country tubular goods with excellent corrosion resistance at a low cost.

[Brief explanation of drawings]

FIG. 1 shows the relationship between the value of (Cr+3xMo) and the pitting corrosion resistance after coating. Figure 2 shows the relationship between Δ value and SCC resistance after coating. Patent applicant: Nippon Kokan Co., Ltd. Inventor: Jun Sakai
Yutaka Naganawa 1
Figure Cr+3M.

Claims (1)

[Claims] Cr: 20 to 35 wt%, Ni: 22 to 60 wt%, M
o: 1 to 10 wt%, C: 0.05 wt% or less, Si:
1.0 wt% or less, Mn: 1.0 wt% or less, P: 0.
02wt% or less, S: 0.01wt% or less, the balance consists of Fe and unavoidable impurities, and Cr and Mo are 60≧Cr
+3×Mo≧35 and Δ=(Ni+30C+25N)−[{(Cr+1.5M
o-19)^2/12}+13] A corrosion-resistant metal coating material for oil production-related equipment having a composition in which the value of Δ determined by the following is 7 or more.