JP2000290728A - Manufacturing method of seamless steel pipe for steam injection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a high-temperature, high-pressure seamless steel pipe for high-temperature, high-pressure steam transportation having high-temperature resistance and high-pressure performance that can withstand high-pressure steam transportation more conventionally than before. SOLUTION: C: 0.05 to 0.15%, Si: 0.01 to 0.50%, Mn: 0.
50-1.50%, P: 0.025% or less, S: 0.008% or less, Cr: 0.10-0.
30%, Al: 0.01 to 0.10%, V: 0.01 to 0.12%, Ti: 0.01 to 0.05%
And a balance consisting of Fe and unavoidable impurities is hot-pierced to obtain a seamless steel pipe by hot rolling at a finishing temperature of the Ar ₃ transformation point or higher. And immediately (Ar3 points +5
(0 ° C) ~ 1100 ° C, soaked in a soaking furnace, quenched at a cooling rate of 5 ° C / sec or more, and subsequently tempered at a temperature of 550 ° C to A _C1 transformation point or less, so it is excellent in the medium temperature range. A high-temperature, high-pressure steam transport seamless steel pipe having excellent strength and excellent weldability can be manufactured at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to produce a seamless steel pipe for steam injection by direct quenching, in which steam is injected from a well to give fluidity to a highly viscous crude oil and the crude oil is directly collected from underground. About the method.

[0002]

2. Description of the Related Art Since high viscosity crude oil such as oil sand oil and heavy oil cannot be collected from an oil well as it is by a usual method, the viscosity of the crude oil is reduced by applying thermal energy to an oil reservoir. There is a method of collecting or increasing the collection rate. As a method of injecting the heat energy into the oil reservoir, there is a steam injection method in which high-temperature, high-pressure steam is injected through a steel pipe. The high-temperature, high-pressure steam to be injected at this time is generally at a high temperature of 300 to 400 ° C., 17.2
High pressure up to MPa.

[0003] Conventionally, steel pipes for pressure piping used at room temperature to about 450 ° C mainly include carbon steel pipes for pressure piping specified in JIS G3454, STPG370, 410, 480, and carbon steel for high pressure pipe specified in JIS G3455. STS370, 410, 480 for steel pipe, JIS G 34
STPT370, 410, 480 carbon steel pipes for high temperature piping specified in 56
Alternatively, carbon steel pipes such as ASTM.A106 grades A to C are used. When these carbon steel pipes were used as steam piping for steam injection, their strength was reduced, and they could not withstand the pressure of steam.

[0004] As a method for producing a steel pipe for steam injection with high strength in a temperature range of 200 to 450 ° C, C: 0.03 to 0.15%, Si: 0.01 to 0.80%, Mn: 0.50 to 2.00
%, Al: 0.001 to 0.10%, and one or both of Mo and V is 0.01 to 0.30% of Mo, and 0.005 to 0.1 of V
Pcm = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 2, including in the range of 0%, with the balance being Fe and unavoidable impurities
A seamless steel pipe having a composition with a Pcm value given by 0 + Mo / 15 + V / 10 + 5B (%) of 0.21% or less is subjected to high-temperature quenching immediately after the end of hot rolling, and thereafter, A _C1 transformation at 600 ° C. or more Tempering method at a temperature below the temperature (JP-A-56-166324), C: 0.05 to 0.1
5%, Si: 0.01 to 0.50%, Mn: 0.50 to 1.50%, P: 0.025% or less,
S: 0.008% or less, Cr: 0.10 to 0.30%, V: 0.01 to 0.10%, sol.A
l: 0.01 to 0.10%, Ti: 0.01 to 0.05%, the remainder is made of a round billet of steel substantially composed of Fe and made into a seamless steel pipe by the Mannesmann pipe manufacturing method, and then heated to 850 to 1000 ° C. Quenching, followed by tempering at 500-700 ° C
No. 41) has been proposed.

[0005]

Problems to be Solved by the Invention
In the method disclosed in Japanese Patent Application Laid-Open Publication No. H07-115, expensive Mo is added as an alloy component, so that there is still room for improvement in economic efficiency. In addition, when a seamless steel pipe is formed by applying the Mannesmann-type pipe manufacturing method, there is a problem of occurrence of poor pipe surface quality such as medium fog and outer fog. In addition, the method disclosed in Japanese Patent Publication No. 6-63041 makes it possible to manufacture a seamless steel pipe for steam injection at low cost, which has high temperature resistance and high pressure performance and has no pipe surface quality defects such as medium fog and outer fog.

However, in recent years, there has been a tendency to increase the pressure of steam in order to further increase the extraction rate of crude oil.
Further, high-strength steel pipes at high temperatures have become necessary.

[0007] An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a method for inexpensively producing a seamless steel pipe for steam injection having high temperature resistance and high pressure resistance capable of withstanding high-pressure steam transportation. To provide.

[0008]

The method for producing a seamless steel pipe for steam injection according to the present invention comprises the steps of: C: 0.05 to 0.15;
%, Si: 0.01 to 0.50%, Mn: 0.50 to 1.50%, P: 0.025% or less,
S: 0.008% or less, Cr: 0.10 to 0.30%, Al: 0.01 to 0.10%, V: 0.
From 01 to 0.12% Ti: contains 0.01 to 0.05%, the billet and the balance being Fe and inevitable impurities, and perforated with hot, and seamless steel pipe by rolling finishing temperature than the Ar ₃ transformation point of the heat, immediately After (Ar ₃ transformation point + 50 ° C.) C. to 1100 placed in soaking furnace of ° C. and soaking, quenched at a cooling rate 5 ° C. / sec or higher, subsequently 550 ° C. to a _{C 1} fired at transformation point temperature It is characterized by returning.

According to the method for producing a seamless steel pipe for steam injection of the present invention, it is possible to produce a seamless steel pipe for steam injection which can sufficiently withstand high-temperature and high-pressure steam transport and has excellent weldability. Can be.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the chemical components of steel in the present invention are as follows. C is an essential element to increase the strength of the steel, and by being precipitated as carbides of Cr and V, 0.05% or more is necessary to ensure sufficient strength in the medium temperature range, but 0.15% If it exceeds 50%, the strength of the base material becomes unnecessarily high and the weldability is impaired.

[0011] Si is an element required for deoxidation, it is necessary to secure 0.01% or more to improve the strength, but if it exceeds 0.50%, the toughness in the base metal and the weld heat affected zone , The content was reduced to 0.01 to 0.50%.

Mn is an element effective for securing the strength of steel, and is required to be 0.50% or more for securing the strength.
If it exceeds 0%, segregation tends to occur, and the toughness of the base material is reduced.

[0013] P is an element present in the steel as an impurity and lowers the toughness of the base material. Therefore, it is desirable that P be as low as possible. However, in consideration of the cost of de-P treatment for lowering the steel P,
0.025% or less.

[0014] S is an element which exists in steel as an impurity like P and lowers the toughness of the base material. Therefore, it is desirable that S be as low as possible. It is set to 0.008% or less in consideration of the balance.

[0015] Cr is an element necessary for securing sufficient strength in the medium temperature range, and when less than 0.10%, chromium carbide related to strength increase is most effective at a steel pipe operating temperature of 300 to 400 ° C. It cannot be precipitated in the form of precipitation,
If it exceeds 30%, not only the strength increasing effect is saturated, but also the cost is disadvantageous. Therefore, the content is set to 0.10 to 0.30%.

Al is an element necessary for deoxidation like Si, and if it is less than 0.01%, deoxidation becomes insufficient and steel quality is deteriorated. If it exceeds 0.10%, the effect of deoxidation hardly changes. Without
0.01 ~ 0.10% because inclusions increase and deteriorate toughness
And

V is an element necessary for ensuring sufficient strength in a medium temperature range, like Vr. When V is less than 0.01%, vanadium carbide related to an increase in strength is removed from the steel pipe at the operating temperature of 300%.
At ~ 400 ° C, it is impossible to precipitate in the form of the most effective precipitation, and if it exceeds 0.12%, the toughness is adversely affected.

Ti is an element having a precipitation strengthening effect and contributing to an increase in strength. If the content is less than 0.01%, the effect is not sufficient.
If it exceeds 0.05%, the toughness is adversely affected.
5%.

The other unavoidable impurity element amounts are not particularly limited.

The production of the billet used as the material of the present invention and the step of perforating the billet to form a hollow shell may use conventional techniques, and are not limited in any way. For example, a billet cast by a continuous casting machine may be heated to 1100 to 1300 ° C. to form a hollow shell using a punching machine such as an inclined roll mill.

[0021] The method of elongation rolling and finish rolling of the hollow shell is as follows.
Conventional techniques may be used, and there is no limitation. For example, as in the Mannesmann mandrel mill method, after elongating and rolling by a mandrel mill, finish rolling may be immediately performed by a sizer or a reducer to adjust the dimensions.

In the present invention, the finishing temperature in the pipe making step is set to the Ar ₃ transformation point or higher. The reason why the finishing temperature is set to the Ar ₃ transformation point or higher is to minimize the temperature difference between the various parts of the raw material when the steel is worked and to reduce the unevenness of the structure. The temperature drop during pipe production is due to contact with rolls and jigs and to heat radiation. Temperature drop due to contact with a roll or jig causes temperature unevenness. However, temperature decrease due to heat radiation is unlikely to cause temperature unevenness. Since the ratio of heat energy loss due to heat radiation increases dramatically as the temperature increases, the finishing temperature also decreases during the pipe making process.
Above the Ar ₃ transformation point, even if there is heat loss due to contact with a roll or a jig, the ratio is small and large temperature unevenness does not occur.

[0023] In direct quenching in which quenching is performed immediately after finish rolling, the structure after finish rolling is coarse, so that quenching properties are high and strength can be increased, but this is due to uneven temperature after finish rolling. There is a possibility that strength variations in the longitudinal direction and circumferential direction of the steel pipe may occur. For this reason, before quenching, it is put in a soaking furnace and soaked. However, if it cools to the Ar ₃ transformation point or less before loading into the soaking furnace after finish rolling, some ferrite precipitates and the required strength cannot be obtained, so the finishing temperature is set to the Ar ₃ transformation point or more. It is necessary to keep it. In addition, the temperature of the soaking furnace is the Ar ₃ transformation point +
Variations occur in the intensity is less than 50 ° C., the crystal grains grow to exceed 1100 ° C., in order to degrade the toughness, (Ar ₃ transformation point + 5
0 ° C) to 1100 ° C. Furthermore, the cooling rate during quenching
At less than 5 ° C / sec, the structure does not contain martensite and bainite to obtain the required strength.
sec or more.

[0024] The tempering treatment in the present invention follows the quenching.
It is carried out at a temperature of 550 ° C. or higher and an AC ₁ transformation point or lower. The reason is that 550 ° C is used to sufficiently precipitate Ti and V carbonitrides that were in a solid solution state during quenching without reheating, and to increase strength.
It is necessary. However, since lowering the rather strength exceeds A _C1 transformation point, tempering temperature was below 550 ° C. to A _{C 1} transformation point.

[0025]

EXAMPLES Example 1 Tests A and B of chemical components shown in Table 1 were melted in a 150-ton converter, then continuously cast into billets, and heated to 1250 ° C. in a rotary hearth heating furnace. Thereafter, a hollow shell was obtained using an inclined roll perforator. This hollow shell was hot-rolled using a mandrel mill and a sizer under the conditions shown in Table 2, and then immediately heat-treated to produce 10 seamless steel pipes each having an outer diameter of 406.4 mm and a wall thickness of 23.8 mm.

From each of the obtained seamless steel pipes, a tensile test piece was sampled in accordance with a tensile test piece of a metal material specified in JIS Z 2201, and the tensile strength, yield strength and weldability at room temperature and 200 to 350 ° C. were measured. It was measured. The results are shown in FIG. 1 for test A and FIG. 2 for test B. In addition, tensile strength at room temperature,
The measurement of the yield strength was performed in accordance with the metal material tensile test method specified in JIS Z 2241. The measurement of the tensile strength and the yield strength at 200 to 350 ° C. was performed in accordance with the high-temperature tensile test method for steel materials and heat-resistant alloys specified in JIS G 0567. The weldability was evaluated based on the cracking rate in a Battelle type bead under-cracking test using a cellulosic welding rod (E8010G).

[0027]

【table 1】

[0028]

[Table 2]

[0029] As shown in Fig. 1, the seamless steel pipe of test A manufactured by the direct quenching method of the present invention has a yield strength of 540MPa or more and a tensile strength of 647MPa or more in a medium temperature range of 200 to 350 ° C. Have. Also, there were no weld cracks. On the other hand, the seamless steel pipe of Test B manufactured by the conventional reheating quenching method, as shown in FIG.
It has a yield strength of 70MPa or more and a tensile strength of 590MPa or more.
As described above, the tensile strength is inferior to 57 MPa or more. In addition, no welding crack occurred.

Example 2 Steel Nos. 1 to 4 having the chemical components shown in Table 3 were melted in a 150-ton converter, then continuously cast into billets, and heated to 1250 ° C. in a rotary hearth heating furnace. A hollow shell was obtained using an inclined roll perforator. This hollow shell was subjected to hot rolling and heat treatment using a mandrel mill and a sizer under the conditions shown in Table 4 to produce ten seamless steel pipes each having an outer diameter of 406.4 mm and a wall thickness of 23.8 mm.

[0031] Tensile test pieces were obtained from each of the obtained seamless steel pipes in the same manner as in Example 1, and the tensile strength and the yield strength at 300 ° C were measured, and the weldability was evaluated. Table 5 shows the results.
Shown in

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

As shown in Tables 3 to 5, the seamless steel pipe of Test No. 1 manufactured by the direct quenching method of the present invention has a yield strength at 300 ° C. of 559 MPa or more and a tensile strength at 300 ° C. of 657 MPa.
The above is shown. Also, there were no weld cracks. On the other hand, the test No. 2 ~
The seamless steel pipe No. 4 has a yield strength at 300 ° C of 501 MPa or less and a tensile strength at 300 ° C of 624 MPa or less. More than 26% of weld cracks occurred. This shows that the seamless steel pipe manufactured by the method of the present invention can be used for steam injection.

[0036]

According to the method for producing a seamless steel pipe for steam injection of the present invention, a billet having the above-mentioned chemical composition is hot-pierced, and a seamless steel pipe is formed by hot rolling at a finishing temperature of the Ar ₃ transformation point or higher. Immediately (Ar ₃ transformation point + 50 ° C) ~ 1100
After heating in a soaking furnace at a temperature of 5 ° C, the cooling rate is 5 ° C / se.
By quenching at a temperature of c or more, and subsequently tempering at a temperature of 550 ° C. to an A _C1 transformation point or less, a seamless steel pipe having excellent strength in a middle temperature range and excellent weldability can be obtained. Therefore, it is extremely effective as a high-temperature, high-pressure steam transport pipe.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a tensile test temperature, a yield strength, and a tensile strength of a steel pipe of Test A manufactured by a direct quenching method of the present invention in Example 1.

FIG. 2 is a graph showing a relationship between a tensile test temperature, a yield strength, and a tensile strength of a steel pipe of Test B manufactured by a known reheating quenching method in Example 1.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 4K032 AA01 AA04 AA05 AA11 AA16 AA27 AA29 AA31 AA35 AA36 BA03 CA03 CC03 CC04 CD02 CD03 CE01 CE02 4K042 AA06 BA01 BA13 CA06 CA12 CA13 DA01 DA02 DE02 DE05

Claims (1)

[Claims] (Claim 1) C: 0.05 to 0.15%, Si: 0.01 to 0.50%, Mn: 0.5
0 to 1.50%, P: 0.025% or less, S: 0.008% or less, Cr: 0.10 to 0.3
0%, Al: 0.01 to 0.10%, V: 0.01 to 0.12%, Ti: 0.01 to 0.05%
With the balance being Fe and unavoidable impurities
The drill is hot pierced and the finishing temperature Ar_ThreeHot above the transformation point
Rolled into a seamless steel pipe, immediately (Ar _Three(Transformation point + 50 ℃) ~
After soaking in 1100 ° C soaking furnace, cooling rate 5
Rapid cooling at ℃ / sec or more, then 550 ℃ ~ A_C1Temperature below the transformation point
Steam injection characterized by tempering at a temperature
For manufacturing seamless steel pipes for