CN113817960A

CN113817960A - N80 petroleum casing pipe steel and preparation method thereof

Info

Publication number: CN113817960A
Application number: CN202110913507.6A
Authority: CN
Inventors: 张晓磊; 刘妍; 刘恩泽; 杨维宇; 王亚男
Original assignee: Baotou Iron and Steel Group Co Ltd
Current assignee: Baotou Iron and Steel Group Co Ltd
Priority date: 2021-08-10
Filing date: 2021-08-10
Publication date: 2021-12-21

Abstract

The invention discloses steel for an N80 petroleum casing pipe and a preparation method thereof, wherein the yield strength is 566-627 MPa by taking low C, Mn and Si as the basis and through the reasonable proportioning of micro alloy elements such as Nb and Ti and the like and through the processes of steelmaking, rolling, heat treatment and the like; the tensile strength is 643-718 MPa; a low-alloy high-strength hot-rolled coil with 0 ℃ impact of 69.3-147.7J and-20 ℃ impact value of 61-116.1J. The medium-low carbon microalloying component design ensures the mechanical property and the mechanical property of a welded seam after welding.

Description

N80 petroleum casing pipe steel and preparation method thereof

Technical Field

The invention relates to the field of metallurgical materials, in particular to steel for an N80 petroleum casing pipe and a preparation method thereof.

Background

The special petroleum pipe is mainly used for drilling oil wells and gas wells and conveying oil wells and gas wells. It comprises an oil drill pipe, an oil casing pipe and an oil pumping pipe. The petroleum drill pipe is mainly used for connecting a drill collar and a drill bit and transmitting drilling power. The petroleum casing pipe is mainly used for supporting the well wall in the drilling process and after well completion so as to ensure the normal operation of the whole oil well after the drilling process and the well completion. The oil pumping pipe mainly conveys oil and gas at the bottom of the oil well to the ground.

Three types of casing are mainly used in oil production processes: surface casing, technical casing and reservoir casing. The sleeves can be divided into different steel grades according to the strength of steel, namely J55, K55, N80, L80, C90, T95, P110, Q125, V150 and the like. The steel grade adopted is different according to different well conditions and well depths. In corrosive environments, the casing itself is also required to have corrosion resistance. Where geological conditions are complex, the casing is also required to have collapse resistance.

The petroleum casing pipes are classified into seamless petroleum casing pipes and electric resistance welded pipe (ERW) petroleum casing pipes according to the production process. Compared with a seamless petroleum casing pipe, the ERW petroleum casing pipe has the advantages of good welding seam toughness, excellent anti-extrusion performance and high dimensional precision. Meanwhile, the quality is easy to control and the manufacturing cost is low. Compared with other welding methods, the ERW sleeve welding seam has no metal filler, and the welding seam performance depends on welding and subsequent heat treatment processes. The ERW technology combines welding, thermal tension reducing and whole-tube heat treatment technologies, namely, TMCP hot-rolled coils are welded, a welded tube blank is rapidly heated to the austenite phase transition temperature Ac3 (900-1100 ℃) through medium-frequency induction heating, and then is reduced to the required specification through a plurality of roller sets, so that deformation heat treatment is carried out on the whole tube (base metal and welding seams).

The steel with the grade of N80 designed by the invention is used for ERW petroleum casing pipes, the chemical components of the steel are adjusted, and the hardness and the tensile strength of the steel are improved, which is a main measure for solving the problem of sticking.

Disclosure of Invention

The invention aims to provide N80 petroleum casing steel and a preparation method thereof, wherein the yield strength is 566-627 MPa by taking low C, Mn and Si as the basis and through the reasonable proportion of micro alloy elements such as Nb and Ti and the like and through the processes of steelmaking, pipe rolling processing and the like; the tensile strength is 643-718 MPa; a low-alloy high-strength hot-rolled coil with 0 ℃ impact of 69.3-147.7J and-20 ℃ impact value of 61-116.1J. The medium-low carbon microalloying component design ensures the mechanical property and the mechanical property of a welded seam after welding.

In order to solve the technical problems, the invention adopts the following technical scheme:

the steel for the N80 petroleum casing pipe comprises the following chemical elements in percentage by mass: 0.10 to 0.15 percent of C; 0.18 to 0.2 percent of Si; 1.2 to 1.7 percent of Mn; p is less than or equal to 0.017 percent; s is less than or equal to 0.004 percent; nb is less than or equal to 0.15; ti is less than or equal to 0.03; the balance of Fe and inevitable impurities.

Further, the chemical elements and the mass percentage content thereof are as follows: 0.12 percent of C; 0.2 percent of Si; 1.5 percent of Mn; p is less than or equal to 0.017 percent; s is less than or equal to 0.004 percent; 0.15 percent of Nb; 0.03 percent of Ti0; the balance of Fe and inevitable impurities.

The preparation method of the steel for the N80 petroleum casing pipe comprises the following steps of:

quenching and tempering heat treatment are carried out, the quenching heating temperature is 880 ℃, the heat preservation is 40min, the tempering temperature is 650 ℃, 625 ℃, 600 ℃, 575 ℃, 550 ℃, 525 ℃, and the furnace time is 50 min.

Furthermore, the tempering temperatures of the 127# and 128# steels are 525 ℃ and 550 ℃, respectively.

Compared with the prior art, the invention has the beneficial technical effects that:

according to the invention, the high-strength petroleum casing steel with low alloy consumption and without subsequent heat treatment can be realized by optimally proportioning the microalloy elements and matching with a proper rolling process and heat treatment. Low cost, easy production, high efficiency and high performance.

Drawings

The invention is further illustrated in the following description with reference to the drawings.

FIG. 1 is the variation trend of the yield strength of experimental steel with tempering temperature;

FIG. 2 is the variation trend of the tensile strength of the experimental steel with the tempering temperature;

FIG. 3 is the variation trend of the elongation of the experimental steel with the tempering temperature;

FIG. 4 is a metallographic structure of experimental steel at different tempering temperatures;

FIG. 5 shows the yield strength, tensile strength and-20 ℃ impact strength of the experimental steel.

Detailed Description

The steel for the N80 petroleum casing pipe comprises the following chemical elements in percentage by mass: c0.12; 0.2 of Si; mn 1.5; p is less than or equal to 0.017; s is less than or equal to 0.004; nb 0.15; ti0.03; the balance of Fe and inevitable impurities, and the mass fraction is 100 percent.

The rolling experiment of the experimental steel is carried out according to the hot rolling unit in the rolling laboratory, and the rolling process parameters and the control condition are shown in the table 1.

TABLE 1 Rolling Process parameters

The target and actual smelting components are shown in Table 2:

TABLE 2 melting chemistry of the experimental steels wt.%

The rolling experiment of the experimental steel is carried out by the hot rolling mill group in the laboratory, and the rolling process parameters and the control condition are shown in the table 3.

TABLE 3 Rolling Process parameters

And carrying out quenching and tempering heat treatment tests on the samples rolled by No. 127 and No. 128, wherein the quenching heating temperature is 880 ℃, the heat preservation time is 40min, and the tempering temperature is 650 ℃, 625 ℃, 600 ℃, 575 ℃, 550 ℃, 525 ℃ and the furnace time is 50 min. The samples in the quenched and tempered state are subjected to mechanical property inspection, and the changes of yield strength, tensile strength and elongation of the four-furnace-number experimental steel along with the tempering temperature are shown in figures 1-3.

With the increase of the tempering temperature, the yield strength and the tensile strength of the experimental steel are obviously reduced, and the elongation is slightly increased, but the strength and the elongation of 2 components are not greatly different at the same tempering temperature. The heat treatment protocol can be substantially determined; and (3) carrying out metallographic structure inspection on samples of 127# and 128# experimental steels at the tempering temperature of 525 ℃ and 550 ℃, wherein the structure type after tempering is tempered sorbite as shown in figure 4.

The mechanical properties of the rolled and heat treated samples were measured and the results are shown in FIG. 5.

The mechanical property and the metallographic structure obtained by rolling and heat treatment meet the design requirements.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims

1. The steel for the N80 petroleum casing pipe is characterized by comprising the following chemical elements in percentage by mass: 0.10 to 0.15 percent of C; 0.18 to 0.2 percent of Si; 1.2 to 1.7 percent of Mn; p is less than or equal to 0.017 percent; s is less than or equal to 0.004 percent; nb is less than or equal to 0.15; ti is less than or equal to 0.03; the balance of Fe and inevitable impurities.

2. The steel for N80 oil casing pipes according to claim 1, wherein the steel comprises the following chemical elements in percentage by mass: 0.12 percent of C; 0.2 percent of Si; 1.5 percent of Mn; p is less than or equal to 0.017 percent; s is less than or equal to 0.004 percent; 0.15 percent of Nb; 0.03 percent of Ti0; the balance of Fe and inevitable impurities.

3. The method for preparing the steel for N80 oil casing according to claim 1 or 2, wherein the rolling process parameters and control conditions are shown in the following table:

quenching and tempering heat treatment: the quenching heating temperature is 880 ℃, the temperature is kept for 40min, the tempering temperature is 650 ℃, 625 ℃, 600 ℃, 575 ℃, 550 ℃, 525 ℃ and the furnace time is 50 min.

4. The method for preparing steel for N80 oil casing pipes according to claim 1, wherein the tempering temperatures of the 127# and 128# steels are 525 ℃ and 550 ℃, respectively.