JPS607697B2 - Steel material for oil country tubular goods with tensile strength of 60Kg/mm↑2 or more with excellent sulfide stress corrosion cracking resistance - Google Patents

Description

Detailed Description of the Invention The present invention has a tensile strength of 6 with excellent sulfide stress corrosion cracking resistance.
It relates to steel materials for oil country tubular goods having a weight of 0 kg/sail 2 or more.

It has been known that a deterioration fracture phenomenon called sulfide stress corrosion cracking (hereinafter referred to as SSCC) occurs in high-strength steel used in an environment containing hydrogen sulfide.
In recent years, with the increase in energy consumption and the decrease in easily available high-quality oil resources, many sour gas fields and sour oil fields with high hydrogen sulfide content and deep wells have been developed.

For this reason, these developments require oil country tubular goods with excellent SSCO properties that can withstand harsh usage conditions.

Originally, SSCC is one of the hydrogen arm phenomena that occurs when hydrogen generated by the corrosion reaction of steel in an environment containing hydrogen sulfide infiltrates into the steel.The mechanism is still largely unknown, and the It is a phenomenon in which various factors such as metallurgical factors such as composition and structure and the state of stress applied to the steel are intricately related.

Therefore, due to steel composition, heat treatment, etc., SSC resistance has been
Although methods to improve C properties have been proposed, none of them are perfect measures, and some methods require the use of expensive alloying elements or complicated heat treatment, which significantly increases manufacturing costs. , the current situation is that it is unrealistic.

It is an object of the present invention to overcome the problems of the prior art and to provide a tensile strength of 60k9/side 2 with excellent sulfide stress corrosion cracking resistance.
The present invention provides steel materials for oil country tubular goods as described above.

This object of the present invention is achieved by any of the following eight inventions.

The gist of the first invention is as follows. That is, in terms of weight ratio, C: more than 0.2 to 0.5%, Si: 0.10
~0.35%, Mn: 0.5-1.90%, P: 0.0
15% or less, S: 0.010% or less, A: 0.01~
0.10%, Ca: 0.0010 to 0.0070%, and the remainder consists of Fe and inevitable impurities, and has excellent sulfide stress corrosion cracking resistance and a tensile strength of 60k9/Yanagi2 or more. This is a steel material for oil country tubular goods. The gist of the second invention is that, in addition to the basic composition of the first invention,
Furthermore, Cu: 0.20~0.60%, Ni: 0.10~
Cr: 0.60%, Cr: 0.1 to 2.0%, and at least one selected from the group consisting of 0.60% and Cr: 0.1 to 2.0%. It is a steel material for oil country tubular goods with excellent tensile strength of 60k9/skin 2 or higher. The gist of the third invention is that, in addition to the basic composition of the first invention, at least one selected from Mo: 0.5% or less, Nb: 0.05% or less, V: 0.10% or less A tensile strength of 60kg/sulfide with excellent stress corrosion cracking resistance, characterized by containing at least one sulfide at the same time, with the remainder consisting of Fe and unavoidable impurities.
Steel material for oil country tubular goods with side 2 or more. The gist of the fourth invention is that in addition to the basic composition of the first invention, B:0.
0005-0.005% or B: 0.0005-0
．． 005% and Ti: 0.01 to 0.10% at the same time, with the remainder consisting of Fe and inevitable impurities, and has excellent sulfide stress corrosion cracking resistance and a tensile strength of 60k9/Yanagi2 or more. steel material for oil country tubular goods.

The gist of the fifth invention is that in addition to the basic composition of the first invention, Cu: 0.20-0.60%, Ni: 0.
10 to 0.60%, Cr: at least one selected from 0.1 to 2.0%, Mo: 0.5% or less, N
Contains at least one selected from b: 0.05% or less, V: 0.10% or less, and the remainder is Fe.
and sulfide, which is characterized by consisting of unavoidable impurities. Excellent resistance to stress corrosion cracking. Tensile strength of 60 kg/leg 2.
The above steel materials for oil country tubular goods.

The gist of the sixth invention is that in addition to the basic composition of the first invention, Cu: 0.20-0.60%, Ni: 0.
10 to 0.60%, Cr: 0.1 to 2.0%, and B: 0.0005 to 0.
．． 005% or B: 0.0005 to 0.005% and Ti: 0.01 to 0.10% at the same time, with the remainder consisting of Fe and inevitable impurities. Excellent tensile strength of 60k
9/ side 2 or more steel material for oil country tubular goods.

The gist of the seventh invention is that, in addition to the basic composition of the first invention, the composition is further selected from among Mo: 0.5% or less, Nb: 0.05% or less, and V: 0.10% or less. At least one species and B: 0.0005 to 0.005% or B
:0.0005~0.005 and Ti:0.01~
This is a steel material for oil country tubular goods having a tensile strength of 60 kg/Yanagi 2 or more and having excellent sulfide stress corrosion cracking resistance and containing 0.10% of both at the same time, with the remainder consisting of Fe and unavoidable impurities. .

The gist of the eighth invention is that in addition to the basic composition of the first invention, Cu: 0.20 to 0.60%, Ni: 0
．． 10 to 0.06%, Cr: 0.1 to 2.0%, Mo: 0.5% or less, Nb: 0.05% or less, V: 0.10 % or less, and B: 0.0005~
A sulfide-resistant material containing 0.005% or both of B: 0.0005 to 0.005% and Ti: 0.01 to 0.10%, with the remainder consisting of Fe and inevitable impurities. Tensile strength with excellent stress corrosion cracking resistance,
60k9/Yanagi 2 or higher steel material for oil country tubular goods.

In other words, the present inventors focused on the fact that SSCC is a hydrogen arm phenomenon caused by hydrogen that penetrates and is absorbed into steel. We believe that this is an effective measure to improve the rolling process, and as a result of various studies, we have found that it is extremely possible to convert MnS-based inclusions, which tend to elongate in the rolling direction, into inclusions that do not elongate during hot rolling by adding Ca. This is due to the fact that it was found to be effective.

The feature of the present invention is that the addition of Ca improves the dispersion of inclusions, spheroidization, and structure, and this effect does not deteriorate even with other alloying elements or heat treatment, and it also improves the mechanical properties and weldability of steel. Resistant to SSCO without any negative effects
It is possible to produce copper with excellent properties. The reason for limiting the composition of the steel of the present invention is as follows.

Ca: At least 0.0010% is required for the dispersion of inclusions and spheroidization due to Ca addition, but it is technically difficult to add more than 0.020%, so 0.0010% to 0.
．． It was limited to a range of 0.020%.

Note that there are various methods of adding Ca, and it goes without saying that any of these methods may be used. S: If the S content exceeds 0.010%, even if Ca is added, the effect will be small.
It should be limited to 10% or less.

C: If C is less than 0.2%, it is difficult to obtain a steel material for oil country tubular goods with a tensile strength of 60k9/2 or more, and if it exceeds 0.5%, it is undesirable as it impairs the ballability of copper and causes dawn cracking. Savings 0. It was limited to a range of 0.5% to 0.5%.

Si: Si is an element necessary for deoxidation, but if it is less than 0.10%, there is no deoxidation effect, and if it exceeds 0.35%, there is a risk of deterioration of toughness, so it is in the range of 0.10 to 0.35%. limited to.

Mn: If Mn is less than 0.5%, it is not preferable to ensure the required strength, and if it exceeds 1.90%, the rutting property will be impaired, so it is set in the range of 0.5 to 1.90%.

P: If P is 0.015 or more, it tends to segregate into a segregation layer, potentially making the structure of the steel material non-uniform, and is also unfavorable for toughness, so it is limited to 0.015% or less.

A: A is necessary for deoxidation and is an element that improves the progress of Ca, but if it is less than 0.01%, it has no effect.
If it exceeds 0.1%, crystal grains will become coarse and the quality of the material will deteriorate, which is undesirable, so it is set in the range of 0.01 to 0.1%.

The basic components of the present invention are as described above, and the first invention has the above component range, but the second invention and the eighth invention further contain the following components to achieve the effects of the present invention. It will improve.

That is, the second invention includes Cu, Ni, and Cr in addition to the above basic components.
It contains one or more of the following.

The third invention contains one or more of Mo, Nb, and V in addition to the above basic components.

The fourth invention provides, in addition to the above basic components, B or B and Ti.
It contains.

The fifth invention provides that in addition to the above basic components, Cu, Ni, Cr
It contains one or more of these, and one or more of Mo, Nb, and V.

The sixth invention provides that in addition to the above basic components, Cu, Ni, Cr
It contains one or more of the following, B, or B and Ti.

The seventh invention contains, in addition to the above basic components, one or more of Mo, Nb, and V, and B or B and Ti.

The eighth invention provides that in addition to the above basic components, Cu, Ni
, Cr, one or more types of Mo, Nb, and V, and B or B and Ti.

However, next, these Cu, Ni, Cr, Mo, Nb,
The component ranges of V, B, and Ti will be explained.

Cu: At least 0.2% of Cu is required to improve corrosion resistance, but if it exceeds 0.6%, hot workability is impaired, so the content is set in the range of 0.2 to 0.6%.

Ni: Ni is an element that reduces SSCO resistance and is preferable to have a small amount, but it improves the toughness of steel, and Cu is an element in the range of 0.2 to 0.
When containing 6%, in order to prevent Cul
．． It is necessary to add it in a range of 10 to 0.06%.

Cr: Cr is effective in improving corrosion resistance, strength, and rice grain property, but if it is less than 0.1%, it has no effect, and if it exceeds 2.0%, it has a negative effect on workability, so it is 0.1 to 2.0%. % range.

Mo: Mo is effective in improving hardenability and strength, but addition of more than 0.5% actually causes deterioration of rutting properties, so 0.5
% or less.

Nb: Although Nb has almost the same effect as Mo, its content was set to 0.05% or less for the same reason as Mo.

V: Like Mo, V is also an effective element for preventing strength loss during competitive recovery, but if it exceeds 0.10%, it will cause arm formation, so 0.
．． It was set to 10% or less.

B: B is an element that improves hardenability, but 0.0005
If it is less than 0.0%, there is no effect, and if it exceeds 0.005%, the rutting property will be impaired.

Ti: Ti is effective in improving strength and corrosion resistance, and when it coexists with B, it has the effect of increasing the effect of B.
If it is less than 0.01, there is no effect, and if it exceeds 0.10%, the toughness deteriorates, so it is limited to 0.01 to 0.10%.

The present invention can be manufactured from molten steel melted in a converter or electric furnace through normal processes, and includes a steel melting method, an ingot making method,
The effects of the present invention are not impaired by differences in rolling methods.

EXAMPLE In order to clarify the improvement in SSCC properties due to the addition of Ca, the present inventors manufactured steels with varying amounts of Ca based on three types of conventional steels and conducted the tests described below.

Table 1 shows the components and mechanical properties of the samples tested. Test steel No. 1 to 5, No. 6-10, No. 11
-15 are the same heat, Ca is added with a Ca alloy wire between the ladle and the injection pipe during casting, and the Ca
Only the amount added was changed.

Also, test steel No. Comparative steels No. 16 and 17 are No. 11~
Sofuji (note) 0.50Y: 0.5% proof stress, HiT: tensile strength 15
However, due to the limited scope of the present invention, S
Ca is added to the slightly higher one.

The above steel is melted in a converter, subjected to ingot making and blooming processes to form a billet, rolled in a mandrel mill to form a seamless steel pipe, and then subjected to various heat treatments. Further, test steels 18 to 32 were experimental steel ingots melted in a 5q straw empty melting furnace, usually hot rolled, then subjected to various heat treatments, and tested as plates.

Test steels 1 to 5 and 18 to 20, 22, and 24 are 900
After heating for 900,001 hours, water quenching and tempering for 600,003 minutes to API standard C-75 class. Nos. 6 to 10 and 21, 22, 25 to 28 are heated for 900,001 hours, water quenching and tempering for 650qCI hours to meet API standard C-90 class. In, No. 11-17, 29-32, 900ko01
After heating for a time, water quenching and tempering at 630℃ for 90 minutes give the same result.
Adjusted to -110 class.

The results of these SSCO resistance tests will be described below.

In the test, a sample to which stress was applied using a constant strain four-point support bending method was immersed in hydrogen sulfide saturated 0.5% acetic acid + 5% saline for 3 weeks, and then the presence or absence of cracks was determined. The added stress is 0 for each sample.
．． Based on 5% yield strength, 0.2 to 1. Added the stress of sound. The results of these tests are shown in Table 2.

These test steels were tested according to API standards C-75C-90, P-1.
The relationship between Ca content, crack occurrence area, and Funen Yan Raiden for each of the 10 classes is shown in Figures 1 to 3, respectively.

As is clear from Figures 1 to 3 and Table 2, all of the steels of the present invention containing 0.0010% or more of Ca have significantly improved ship SCC properties compared to the comparative steel without Ca addition. It shows. Especially in the P-110 class shown in Figure 3, the effect is remarkable, and as the amount of Ca increases, the SSC resistance increases.
The C properties are markedly improved. However, comparative steel No.
If S exceeds 0.10% like IG 17, C
It can be seen that even if a large amount of 0.005% or more can be added, the effect is small. From the above results, it has become clear that the effect of Ca addition occurs even if the heat treatment and component system are different, and that Ca addition is very effective as a measure to improve SSCC resistance.

The steel of the present invention is 0.0010% lower than the conventional SSCC-resistant steel.
We were able to achieve a great effect in that excellent SSCC resistance could be obtained just by taking the inexpensive measure of adding ~0.020% of Ca.

In addition, since the effect of Ca addition can be obtained regardless of heat treatment or other alloy components, there is an advantage that when used in combination with the conventional method, the SSC resistance obtained by the conventional method can be further improved. Therefore, the present invention It is clear that the method can be applied not only to steel materials for oil country tubular goods, but also to other high-strength steels such as high-tensile bolt materials.

[Brief explanation of the drawing]

Figures 1, 2, and 3 show the additional stress (k9/
FIG. 2 is a correlation diagram showing the presence/absence of cracks in the SSCC test, which is shown by the relationship between C2) and the amount of Ca. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. C: more than 0.2 to 0.5% by weight, Si: 0.10
~0.35%, Mn: 0.5-1.90%, P: 0.0
15% or less, S: 0.010% or less, Al: 0.01~
0.10%, Ca: 0.0010 to 0.0070%, the remainder consisting of Fe and inevitable impurities, and has excellent sulfide stress corrosion cracking resistance and a tensile strength of 60 kg/mm^2 The above steel materials for oil country tubular goods. 2 C: more than 0.2 to 0.5%, Si: 0.10 in weight ratio
~0.35%, Mn: 0.5-1.90%, P: 0.0
15% or less, S: 0.010% or less, Al: 0.01~
0.10%, Ca: 0.0010-0.0070%, further Cu: 0.20-0.60%, Ni: 0.10
~0.60%, Cr: 0.1~2.0%, and at least one selected from Cr: 0.1~2.0%, with the remainder consisting of Fe and inevitable impurities. Tensile strength 60kg/mm^ with excellent crackability
2 or more steel materials for oil country tubular goods. 3 C: more than 0.2 to 0.5%, Si: 0.10 in weight ratio
~0.35%, Mn: 0.5-1.90%, P: 0.0
15% or less, S: 0.010% or less, Al: 0.01~
0.10%, Ca: 0.0010 to 0.0070%, further Mo: 0.5% or less, Nb: 0.05% or less,
V: Sulfide characterized by simultaneously containing at least one selected from 0.10% or less, with the remainder consisting of Fe and unavoidable impurities. Tensile strength of 60 kg with excellent stress corrosion cracking resistance. /mm^2 or more steel material for oil country tubular goods. 4 C: more than 0.2 to 0.5%, Si: 0.10 in weight ratio
~0.35%, Mn: 0.5-1.90%, P: 0.0
15% or less, S: 0.010% or less, Al: 0.01~
0.10%, Ca: 0.0010-0.0070%, and further B: 0.0005-0.005% or B:
0.0005-0.005% and Ti: 0.01-0
．． A steel material for oil country tubular goods having excellent resistance to sulfide stress corrosion cracking and a tensile strength of 60 kg/mm^2 or more, characterized by containing 10% of sulfide at the same time, and the remainder consisting of Fe and unavoidable impurities. 5 Weight ratio: C: more than 0.2 to 0.5%, Si: 0.10
~0.35%, Mn: 0.5-1.90%, P: 0.0
15% or less, S: 0.010% or less, Al: 0.01~
0.10%, Ca: 0.0010 to 0.0070%, Cu: 0.20 to 0.60%, Ni: 0.10 to
0.60%, Cr: at least one selected from 0.1 to 2.0%, Mo: 0.5% or less, Nb:
0.05% or less, V: 0.10% or less, and the remainder is Fe and unavoidable impurities. Excellent tensile strength 60kg/mm^2
The above steel materials for oil country tubular goods. 6 Weight ratio: C: more than 0.2 to 0.5%, Si: 0.10
~0.35%, Mn: 0.5-1.90%, P: 0.0
15% or less, S: 0.010% or less, Al: 0.01~
0.10%, Ca: 0.0010-0.0070%, further Cu: 0.20-0.60%, Ni: 0.10
~0.60%, Cr: at least one selected from 0.1 to 2.0%, and B: 0.0005 to 0.0
05% or B: 0.0005-0.005% and T
i: 0.01 to 0.10% of both at the same time, with the remainder consisting of Fe and unavoidable impurities Sulfide with excellent stress corrosion cracking resistance and tensile strength of 60 kg
/mm^2 or more steel material for oil country tubular goods. 7 C: more than 0.2 to 0.5%, Si: 0.10 in weight ratio
~0.35%, Mn: 0.5-1.90%, P: 0.0
15% or less, S: 0.010% or less, Al: 0.01~
0.10%, Ca: 0.0010 to 0.007%, further Mo: 0.5 or less, Nb: 0.05% or less, V:
At least one or more selected from 0.10% or less and B: 0.0005 to 0.005% or B: 0.0
005-0.005% and Ti: 0.01-0.10
A steel material for oil country tubular goods having excellent resistance to sulfide stress corrosion cracking and a tensile strength of 60 kg/mm^2 or more, characterized in that it simultaneously contains both of the following: 1. 8 C: more than 0.2 to 0.5%, Si: 0.10 in weight ratio
~0.35%, Mn: 0.5-1.90%, P: 0.0
15% or less, S: 0.010% or less, Al: 0.01~
0.10%, Ca: 0.0010-0.0070%, further Cu: 0.20-0.60%, Ni: 0.10
~0.60%, Cr: at least one selected from 0.1 to 2.0%, Mo: 0.5% or less, Nb:
at least one selected from 0.05% or less, V: 0.10% or less, and B: 0.0005 to 0.00.
5% or B: 0.0005-0.005% and T
i: 0.01 to 0.10% of both at the same time, with the remainder consisting of Fe and unavoidable impurities Sulfide with excellent stress corrosion cracking resistance and tensile strength of 60 kg
/mm^2 or more steel material for oil country tubular goods.