JPS62109950A - Steel for nonmagnetic drill collar - Google Patents

Abstract

PURPOSE:To develop a steel product having stable nonmagnetism and high yield strength and having excellent ductility, toughness, corrosion resistance, drilling workability and hot workability by using an Mn-Cr-V-N austenitic stainless steel having a specific compsn. as a steel for a nonmagnetic drill collar for excavation of oil wells. CONSTITUTION:The high-Mn nonmagnetic steel having the following compsn. is used as the steel material for the nonmagnetic drill collar for excavation of the oil wells and gas wells: The steel material having the compsn. contg., by wt%, 0.10-0.50% C, <2.0% Si, 20-30% Mn, 0.01-3.00% Ni, 12-20% Cr, [0.1XMn%-0.5]-[0.15XMn%-0.75]% V, 0.1-0.5% N, <0.030% P, <0.010 S, and 0.0005-0.030% in total of >=1 kinds among Ca, Mg, Y and rare earth elements or further contg. >=1 kinds among <1.5% Cu, 0.01-2.00% Mo, 0.01-1.00% Nb, <1.0% Al, and satisfying the formula 20XC%+20XN %+0.5XMn%+Ni%-1.5XV%>=20.5% is used.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a non-magnetic drill collar 111 for drilling oil and gas wells.

<Backlift technology> The energy situation in recent years has led to the active development of new oil and gas wells in all parts of the world, regardless of the availability of reserves. When drilling is necessary, the direction and slope of each well must be carefully planned to ensure the most efficient production from the multiple oil and gas formations. especially.

These plans need to be made more carefully if wells must be drilled from a production platform on the ground.

Moreover, in the case of the above-mentioned tilt valve, the orientation and inclination of the well are measured during actual drilling to confirm whether the drilling is proceeding as planned or not, and to check if the drilling is proceeding as planned or not. This necessitated troublesome work such as having to immediately make course corrections in such cases.

Therefore, in order to make this kind of work easier, recently attempts have been made to use magnetic sensors when drilling wells. In this case, the magnetic sensor is usually set in a drill collar that serves as an intermediate body for attaching the drilling bit to the drill pipe (2) and a drill collar that serves to load the required mold onto the drilling tool.

Therefore, it is desirable that the material for such a drill collar is non-magnetic so as not to reduce the search accuracy of the magnetic sensor, and at the same time, it should have a high proof strength enough to withstand the external force 1 during drilling. These required characteristics are summarized as follows. That is, a) magnetic permeability<1.01. 0.2 kSi (yield strength) ≧90 kSi (63,3K
qf/i) Elongation 230%, absorption energy ≧4, and the characteristics of gf-m, b) Drilling, easy to tear the drill collar product. C) Strong enough to survive the harsh corrosive environment deep underground.
Corrosion resistance (for example, stress corrosion resistance and corrosion resistance).

By the way, conventionally, Ni has been used as a material for non-magnetic drill collars.
-Cu alloy Monel and non-magnetic manganese steel have been used for a long time, but the following problems have been pointed out with these. a) K Monel is a Ni-Cu alloy (for example, "Monel -500" is 6
6 cl) based on Ni-291Cu) and is extremely expensive. ■ Conventional M+ Mn-based non-magnetic steels are made of 0.5 chloride to stabilize austenite, lower magnetic permeability, and increase strength.
．． A high content of C exceeding 50% is required, resulting in low ductility and toughness. Also, due to the high C content, machinability, especially drilling workability, is also poor. The content is low;
Therefore, it cannot withstand durability in deep, severe corrosive environments.

<Means for Solving the Problems> Based on the problems pointed out in the conventional non-magnetic drill collar materials as described above, the present inventors have developed an inexpensive, stable non-magnetic material with high proof strength. In particular, the present invention aims to provide a material for a non-magnetic drill collar that is fully satisfactory in terms of ductility, toughness, corrosion resistance, drilling workability, and hot workability.

○ Good balance between yield strength, ductility and toughness, ○ Relatively good drilling workability, ○ Relatively good corrosion resistance.

○ From the viewpoints of relatively good hot workability and low cost, etc. As a result of intensive research to ensure the above-mentioned requirements as a material for drill collars, we found that the
-V-N yarn I-fJ, Id"12, ensure 2 or more widths for Cr-containing rivers, adjust Mn content to a value exceeding 20 widths, and adjust C content to 0. 5
If the ratio is limited to 0 or less, high corrosion resistance can be obtained that can sufficiently withstand drilling of oil and gas wells in severe corrosive environments, mainly due to the Cr ratio of 12 or more.
Stable non-magnetism is ensured at a low cost due to high Mn (H), and machinability, toughness, and ductility are significantly improved due to the reduction in C content. By adjusting V@Ariharu to a specific value that takes into consideration the ``Or, ``simple short-time aging treatment after hot rolling'' is enough to achieve sufficient strength, making it possible to guarantee the decrease in strength due to the Cψ low range, and these factors are intertwined,
It was discovered that a steel suitable as a material for non-magnetic drill collars can be realized at a low cost, as it has excellent properties such as yield strength, ductility, toughness, corrosion resistance, and drilling workability, and also exhibits stable non-magnetism. It has come to this.

This invention was made based on the above-mentioned knowledge μC: non-magnetic drill collar steel, c: o, io ~ 0.50%, Si: 2. O Sorry, M
n: more than 20 to 30%.

Ni: 0.01-3.0.0fI et al., Cr: 12-20
6, V: [0,1xMn(4)-0,5]=[
0,15×Mn(%) −0,75] 4%N: 0.1
~0.5 Sorry, P: 0.030 Miito.

S: 0.010 I'm sorry.

A sword containing a total of 0.0005 to 0.030 pieces of Ca s Mg + Y and rare earth elements 1. Or further as necessary (2 Cu: 1
．． 5. F, MO: 0.01-2.00%, Nb: 0.01-1.00.

IJ: 1. It also contains one or more of O1 or less, and the remainder is substantially Fe.
It is characterized by having a THi component composition that satisfies the formula % formula % ().

Next, in the non-magnetic drill collar steel of the present invention, the reason why the content ratio of the constituent components is limited to two will be explained.

Al C The C component C= has the effect of stabilizing the austenite phase and ensuring its properties, as well as increasing the strength of the paper, but if the content is less than 0.104, the above There is a risk that the desired effect may not be obtained;
If the content exceeds 0'L, it will not only lead to poor ductility and toughness, but also cause a large amount of carbides to precipitate at the austenite grain boundaries, increasing the susceptibility to stress corrosion cracking. The amount was determined to be 0.10-0.50%.

fbl 5i Si is an element added as a deoxidizer for steel, and W
However, if the content exceeds 2.0 μm, the above effect will not only be saturated, but also non-metallic inclusions will increase, making it difficult to clean the steel for non-magnetic drill collars. Because it deteriorates the strength and also reduces the ductility and toughness,
S + ear-containing forgeries were determined to be below 2.0'l'QJ.

d Mn Mn is a low-cost element that is effective in stabilizing the austenite phase and making it non-magnetic, and also has the effect of improving ductility and toughness, but if its content is less than 20%, The desired effect cannot be obtained because the above production lacks conspicuousness in January. However, Mn increases the amount of solid solution of V precipitates, and
Since it reduces the strong C effect caused by precipitates, increasing Mnta requires a large amount of V for the strong f-force of the kabura, which in turn leads to stress and rise. 30
Since the risk of stress corrosion cracking is extremely high when the Mn content exceeds 20 to 30.

fdl Ni Ni1332 has the effect of stabilizing the austenite phase and improving the toughness of the austenite phase, but when its content is 0.01%, the desired effect based on the above effect cannot be obtained; Even if it is added in excess of 3.00%, the effect will be saturated and no further improvement can be expected, and it will also lead to an increase in Ni-containing dishes.
．． 01-3.00 section.

(el Cr Cr is an indispensable component for imparting high Mn m C = high yield strength and excellent corrosion resistance.
If the width is less than 2, the above effect will not be sufficient, while if the content exceeds 20, the effect will just become saturated.
, Cr-containing fine particles are 12 to 12%, since δ-ferrite is generated, increasing magnetic permeability and impairing non-magnetism.
20 regrets.

(Ge) ■ ■5+i, min has the effect of increasing the strength of the steel in addition to the microstructural fineness of the steel. Since it reduces the effect of V, in order to fully exhibit the effect of C2, Mnt
The V content must be defined in relation to l.

That is, Figure 1 shows the relationship between the strength and ductility/toughness balance of a series of specimen steels, which were air-cooled after being subjected to hot aE heating at 960°C with a total strength of 60 mm. The left half of the "○ marks" in the figure shows the strength status, and the right half shows the ductility/toughness status (in each case, "black" indicates the desired This indicates that the performance is not satisfied), but from this Figure 1, it can be seen that ■ the content is 0,1
It is clear that a good "strength-ductility/toughness balance" is exhibited when the relationship xMn($1-0.75 is satisfied).

In this way, ■ the content is [0, I
．． 5) If the content is less than -[0,15×Mn('1)-0bar5], the strength effect of V precipitates will be insufficient, while if it is added in excess of -[0,15×Mn('1)-0bar5], the ductility and toughness will deteriorate. Came here, vh et al., v3 observation is [: 0. I×Mn(%)−0
,5] to [0,15×Mn(%) −0,751%.

(gl N The N component is effective in stabilizing the austenite phase and making it non-magnetic, and I have heard that it also has the effect of increasing strength and improving stress corrosion cracking resistance, but its content 1 is effective in making it non-magnetic. If it is less than 0, it is difficult to obtain the desired effect based on the above action;
．． Addition 71D of more than 5% is extremely difficult to form and also causes a decrease in hot workability, so the N content should be set to 0.
It was set as 1-05.

(hlP, and S The reduction of P and S, which are unavoidable undesirable elements.

Not only is N-added effective in improving the hot workability of the reservoir, but it also contributes to further stabilization of the austenite phase, thereby overriding the effect of improving non-magnetic properties. These effects are noticeable by restricting p and o to less than 30% F and S content to less than 0010% (P and S), respectively, to 0. 03
04 and 0010%, respectively.

iii Ca , Mg r Y+ and red earth elements (R
EM) In order to prevent cracking during general production or hot working of the steel according to the present invention, the above-mentioned restrictions on P and S (= in addition, one or two of Ca, Mg, Y, and rare earth elements) are required. It is effective to add more than 0.05 to 0.03 [') of these components in total, but if the total content of these components is less than 0.00054, the above effect is not sufficient; ,
If the content exceeds 0.030 in total, the hot workability will actually deteriorate.

(jl Cu p Mo p Nb, and M These are all elements that are effective in increasing the strength of steel.
．． (j) When higher strength is required, one or more elements are added, and each element will be explained in detail below, including other effects.

1) Cu In addition to being effective in improving strength, Cu also has the effect of stabilizing the austenite phase and improving corrosion resistance, but if its content exceeds 1.5 years, hot processing becomes impossible. The Cu content was determined to be 1.5 mm or less, since it may lead to poor sexual performance. Incidentally, although Cu exhibits a certain effect even with a slight degree of υD, it is desirable to ensure a T content of 01'4 or more.

fi) Mo and Nb These components have the effect of improving the strength of steel as well as the corrosion resistance, but their content 1 is 0.0
If it is less than 1 liter, the desired effect cannot be obtained; on the other hand,
MO is 2. If OO'l and Nb are contained in excess of 1.004, hot workability and toughness are reduced.

Moa [fiha 0.01~2.004, Nbalir
tf was set at 0.01 to 1.004, respectively.

1ff) M M is effective in improving strength and is also a preferable element as a deoxidizing agent for steel, but if its content I exceeds 1.0, it may lead to poor toughness and increased magnetic permeability. Therefore, the 1M content was determined to be 1.0 or less.

(kl Combination of C, N, Mn, Ni, and V In this invention, controlling the content ends of CC, N, Mn, Ni, and V to satisfy the formula % formula % is a stable and non-containing material for steel. This is essential for ensuring magnetism, and if the value of the above formula is less than 20.5, it is impossible to suppress the magnetic permeability of steel to less than 1.01.

Figure 2 is a graph of magnetic permeability measured for steels whose compositions were adjusted so that the values of the above formula changed in various ways. Magnetic permeability 1 required for non-magnetic drill collar complex when .5 or more
．． It can be seen that less than 0.01 can be secured.

The non-magnetic steel for drill collars of the present invention has the above-described composition, and can secure the necessary properties as hot-worked or by simply subjecting it to a simple short-time aging treatment. In its production, the slab or steel slab with the above composition is subjected to hot working at a finishing temperature of 900°C or higher, and then cooled at a cooling rate equivalent to or higher than air cooling, or after cooling, it is further heated to a temperature of 750°C or lower. It is desirable to adopt a method of aging treatment under the following conditions.

This is because, in a temperature range below 900°C, the deformation resistance of the material increases, making hot working difficult and requiring large processing equipment.
For highly fertile component systems, hot working at temperatures below 900°C may cause Cr carbon particles to precipitate at grain boundaries, increasing susceptibility to stress corrosion cracking and deteriorating toughness. This is because there are concerns that this may occur.

Cooling at a cooling rate of half or more than the air cooling phase after hot working is effective in refining austenite grains, and also prevents deterioration in stress corrosion cracking resistance due to slow cooling. The above is also a highly recommended dormitory option.

Furthermore, when the aging treatment temperature for achieving even higher strength exceeds 750°C, the V precipitates that are effective for increasing strength become coarser and the strength improvement effect is lost. There is a risk that Cr carbide will precipitate and deteriorate the toughness and stress corrosion cracking resistance.Also, even if aging treatment is performed at a temperature of 750°C or less, the above [PLM] value of 20.5X103 If the conditions are exceeded, a so-called "over-aged state" will occur, which tends to result in a decrease in strength and poor toughness, so aging treatment after hot working should be carried out within the conditions mentioned above. 8 Next, the present invention will be explained using examples and comparing with comparative examples.

<Examples> Example 1 First, each of the test steels with individual numbers 1 to 25 shown in Table 1 was melted into a steel ingot by adjusting its composition, and then made into a steel billet by 1-blunt rolling. Finishing (finishing) @ 1030 to 930 degrees Celsius such that the total reduction rate (section reduction rate) is 50 mm.
The hot workability was first investigated by heating the hot rolled sheets and then cooling them under the conditions shown in Table 2 (2). A comprehensive judgment was made based on the occurrence of cracks on the end face, and a three-level evaluation was performed.

Next, other performance investigations were conducted on the test steels whose hot workability was not determined to be "eel" or "good", and the results are also shown in Table 2.

At this time, the tensile performance was investigated by cutting out a round bar tensile test piece with a parallel part of 14-φ, and the impact performance was investigated by cutting out a Charpy impact test piece with a 2 rm V-notch.

In addition, the following 1 single U-bend test method was adopted for the corrosion resistance investigation. In other words, 10 test pieces were cut out into a U-bend shape, and the U-bend test pieces were placed in artificial seawater at 80°C. After soaking for 4 weeks, the test piece is taken out and measured using an optical microscope to measure the maximum crack depth in the longitudinal section at the center of the U-bend.Table 2 shows the evaluation of corrosion resistance based on this result. This is indicated by a and an x mark, but here.

Circle: No stress corrosion cracking occurred in any of the 10 test pieces.

×: Stress corrosion cracking occurred in any or all of the 10 test specimens. Displayed in two stages.

Regarding drilling workability, the cut out test piece was
A (Boring and Trepanning
The holes were drilled using a processing machine (As5ociation), and comprehensively judged from the viewpoints of the rotational speed, feed rate, vibration status of the device, tool wear, and surface roughness, and displayed in a three-level evaluation.

The results shown in Table 2 also show that the steel of the present invention has a better balance of strength, toughness, gJ properties, corrosion resistance, drilling workability, hot workability, etc. than the comparative steels, and has a non-magnetic drill collar. It can be seen that it is suitable for use.

Example 2 A steel billet obtained by one-time block rolling of the invention steel 1 shown in Table 1 was hot-rolled so that the gold reduction ratio was 40, and then forced cooling was performed. (The two samples were further subjected to aging treatment and their tensile performance and impact performance were investigated.

The obtained results are also shown in Table 3 C.

Table 3: From the results shown, it can be seen that the steel of the present invention exhibits suitable performance as a steel for non-magnetic drill collars, regardless of the manufacturing method.

Overall Effects> As explained above, invention C2 has immeasurable industrial usefulness, such as a remarkable effect on improving the quality of non-magnetic drill collar steel and reducing costs. There is a car that is not there.

[Brief explanation of drawings]

Figure 1 shows the relationship between steel strength and ductility/toughness balance.
Figure 2 is a graph organized in relation to n(jt and V[1), and is a graph showing the relationship between magnetic permeability and steel composition. Applicant Sumitomo Metal Industries Co., Ltd. Agent Tomi 1) Kazuo et al. 2 Name [J-board! -1〕 1× Vt f(!Amount %n

Claims (2)

[Claims] (1) Weight percentage: C: 0.10-0.50%, Si: 2.0% or less, Mn
: more than 20 to 30%, Ni: 0.01 to 3.00%, Cr: 12 to 20%, V
: [0.1×Mn (%)-0.5] ~ [0.15×Mn
(%) -0.75]%, N: 0.1-0.5%, P: 0
．． 0.030% or less, S: 0.010% or less, one or more of Ca, Mg, Y, and rare earth elements: 0.030% or less in total.
0005 to 0.030%, the remainder substantially consists of Fe, and has the formula 20 x C (%) + 20 x N (%) + 0.5 x Mn (%)
A steel for a non-magnetic drill collar, characterized in that it has a composition satisfying +Ni (%) - 1.5 x V (%)≧20.5. (2) In weight percentage: C: 0.10 to 0.50%, Si: 2.0% or less, Mn
: more than 20 to 30%, Ni: 0.01 to 3.005, Cr: 12 to 205, V
: [0.1×Mn (%)-0.5] ~ [0.15×Mn
(%) -0.75]%, N: 0.1-0.5%, P: 0
．． 0.030% or less, S: 0.010% or less, one or more of Ca, Mg, Y, and rare earth elements: 0.030% or less in total.
0005 to 0.030%, and further contains Cu: 1.5% or less, Mo: 0.01 to 2.00%, Nb: 0.01 to 1.00%, M: 1.0% or less. and the remainder is substantially Fe.
and the formula 20 x C (%) + 20 x N (%) + 0.5 x Mn (%)
A steel for a non-magnetic drill collar, characterized in that it has a composition satisfying +Ni (%) - 1.5 x V (%)≧20.5.