Production method of steel for high-strength sucker rod

Abstract

The invention discloses a production method of steel for a high-strength sucker rod. The production process specifically comprises the steps of molten iron pretreatment, converter smelting, LF furnace refining, square billet continuous casting production, heating, bar continuous rolling unit rolling and air cooling. The steel for the sucker rod comprises the following chemical components in percentage by weight: 0.18 to 0.23 percent of C, 0.65 to 0.85 percent of Si, 1.30 to 1.40 percent of Mn, less than or equal to 0.018 percent of P, less than or equal to 0.015 percent of S, 0.08 to 0.10 percent of V, less than or equal to 0.006 percent of Nb, 0.01 to 0.025 percent of Ti, 0.001 to 0.002 percent of B, 0.90 to 1.00 percent of Cr, 0.11 to 0.21 percent of Mo and the balance of iron impurities. The mechanical properties of the high-strength steel for the sucker rod meet the requirements that the tensile strength is larger than or equal to 1000 MPa, the percentage elongation after fracture is larger than or equal to 13%, and the percentage reduction of area is larger than or equal to 55%.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical materials, and in particular relates to a production method of high-strength steel for pumping rods. Background Art

[0002] In the development of the human world, oil and natural gas play a vital role. As important energy resources, oil and natural gas are the focus of national energy security. Since the beginning of the 21st century, the growing demand for oil and natural gas has further aggravated the depletion of oil and gas resources, so the international oil industry is facing a more severe situation.

[0003] Sucker rods are important components used to connect ground pumping units and downhole pumps in the oil field production system during oil extraction operations. They are also important consumable materials in the oil extraction process. With the frequent and excessive exploitation of oil fields in my country, the wells are getting deeper and deeper, and the difficulty of exploitation is getting greater and greater. Therefore, the strength, toughness and fatigue resistance requirements of the sucker rods are getting higher and higher. Nowadays, the increase in oil field maintenance costs and the decline in production efficiency have made the development of low-cost, high-strength, high-toughness steel for sucker rods an urgent need for domestic oil field users.

[0004] According to the manufacturing process, high-strength sucker rods are divided into two types: process type (HY type) and material type (HL type). HY type uses quenching + tempering process to meet the use requirements, while HL type is that the sucker rod manufacturer only performs mechanical processing without heat treatment, and fully utilizes the performance of the material itself, which is guaranteed by chemical composition or appropriate tempering treatment after rolling. Summary of the invention

[0005] The purpose of the present invention is to provide a production method for high-strength steel for pumping rods, so that its mechanical properties meet the following requirements: tensile strength ≥1000MPa, elongation after fracture ≥13%, and section shrinkage ≥55%.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention discloses a production method for high-strength steel for pumping rods, and the production process specifically comprises: molten iron pretreatment - converter smelting - LF furnace refining - billet continuous casting production - heating - bar continuous rolling unit rolling - air cooling; wherein:

[0008] Before smelting, the molten iron is first desulfurized to reduce the sulfur content in the molten steel, reduce the pressure of the refining furnace, and ensure that the tapping w[S] is ≤0.025%; in order to meet the high-drawing re-blowing operation and avoid overoxidation of the molten steel, the w[Si] is required to be 0.46%-0.56% and the temperature is greater than 1250℃; in the converter smelting process, the slag washing process is adopted, lime and refining slag are added, and the good dynamic conditions of the converter steel are used to prepare the pre-slag for the refining furnace smelting;

[0009] During the LF refining process, lime, refined slag and fluorite are added, and argon is blown from the bottom for stirring throughout the process; the tapping temperature is 1600℃~1610℃ for the first pouring furnace and 1590℃~1600℃ for the continuous pouring furnaces;

[0010] After LF steel is tapped, the temperature is measured on the continuous casting platform and Ar is blown. The intensity of Ar blowing is based on the condition that the steel surface is not exposed. The Ar blowing time is ≥8min~15min. The existing low-carbon and low-basicity covering agent is still used in the tundish. The covering agent should be added in time and should not be exposed or turn red.

[0011] The casting machine is used to produce continuous casting billets. The continuous casting process adopts full-process protection casting to prevent secondary oxidation of molten steel. The H content in the billet is less than 2.5ppm, and the composition and gas content of the finished continuous casting billet meet the design requirements.

[0012] The heating furnace adopts blast furnace gas regenerative combustion technology. The gas pressure and flow rate should be adjusted at any time during the heating process to ensure good heating quality. The heating temperature of the steel billet is between 1100℃ and 1180℃. The furnace temperature of heating stage I is controlled above 900℃, and the furnace temperature of heating stage II is controlled between 1150℃ and 1210℃. The heating time above 950℃ is ≥1.0h. The steelmaking rhythm and heating time are strictly controlled. The heating time of the continuous casting billet above 1100℃ should not exceed 3h.

[0013] During the steel rolling process, the technical parameters controlled in the high-speed wire rolling process are:

[0014] Rolling temperature: 1150±20℃;

[0015] Final rolling temperature 920±20℃;

[0016] The cooling beds are closely packed and the spacing is less than 10mm;

[0017] The chemical composition percentage of the steel for sucker rod is: C: 0.18-0.23%, Si: 0.65-0.85%, Mn: 1.30-1.40%, P: ≤0.018%, S: ≤0.015%, V: 0.08-0.10%, Nb: ≤0.006%, Ti: 0.01-0.025%, B: 0.001-0.002%, Cr: 0.90-1.00%, Mo: 0.11-0.21%, and the rest are iron and inevitable trace chemical elements.

[0018] Furthermore, the chemical composition percentages of the sucker rod steel are: C: 0.21%, Si: 0.71%, Mn: 1.32%, P: 0.012%, S: 0.013%, V: 0.08%, Nb: 0.005%, Ti: 0.02%, B: 0.0017%, Cr: 0.90%, Mo: 0.14%, and the rest are iron and inevitable trace chemical elements.

[0019] Furthermore, the chemical composition percentages of the sucker rod steel are: C: 0.21%, Si: 0.72%, Mn: 1.37%, P: 0.011%, S: 0.012%, V: 0.09%, Nb: 0.005%, Ti: 0.02%, B: 0.0017%, Cr: 0.94%, Mo: 0.18%, and the rest are iron and inevitable trace chemical elements.

[0020] Furthermore, the chemical composition percentages of the sucker rod steel are: C: 0.21%, Si: 0.75%, Mn: 1.39%, P: 0.014%, S: 0.008%, V: 0.10%, Nb: 0.006%, Ti: 0.024%, B: 0.0015%, Cr: 0.99%, Mo: 0.20%, and the rest are iron and inevitable trace chemical elements.

[0021] Furthermore, its mechanical properties meet the following requirements: tensile strength ≥ 1000 MPa, elongation after fracture ≥ 13%, and cross-sectional shrinkage ≥ 55%.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are:

[0023] The steel for the pumping rod produced by the present invention has higher tensile strength and yield strength and better impact performance. DETAILED DESCRIPTION

[0024] Below in conjunction with embodiment, the present invention is described in further detail:

[0025] The purpose of the present invention is to provide a production method for high-strength steel for pumping rods, so that its tensile strength is ≥1000MPa, elongation after fracture is ≥13%, and cross-sectional shrinkage is ≥55%. The method comprises the steps of molten iron pretreatment, converter smelting, LF furnace refining, billet continuous casting production, heating, bar continuous rolling unit rolling, and air cooling.

[0026] The specific ingredients of each embodiment are as follows:

[0027] Embodiment 1: The chemical composition percentage of the sucker rod steel is: C: 0.21%, Si: 0.71%, Mn: 1.32%, P: 0.012%, S: 0.013%, V: 0.08%, Nb: 0.005%, Ti: 0.02%, B: 0.0017%, Cr: 0.90%, Mo: 0.14%, and the rest are iron and inevitable trace chemical elements.

[0028] Embodiment 2: The chemical composition percentage of the sucker rod steel is: C: 0.21%, Si: 0.72%, Mn: 1.37%, P: 0.011%, S: 0.012%, V: 0.09%, Nb: 0.005%, Ti: 0.02%, B: 0.0017%, Cr: 0.94%, Mo: 0.18%, and the rest are iron and inevitable trace chemical elements.

[0029] Example 3: The chemical composition percentages of the sucker rod steel are: C: 0.21%, Si: 0.75%, Mn: 1.39%, P: 0.014%, S: 0.008%, V: 0.10%, Nb: 0.006%, Ti: 0.024%, B: 0.0015%, Cr: 0.99%, Mo: 0.20%, and the rest are iron and inevitable trace chemical elements.

[0030] The process parameters for rolling steel for pumping rods in various embodiments are shown in Table 2:

[0031] Table 2: Process parameters of steel for rolling pump rods in various embodiments

[0032]

[0033] The heat treatment test process parameters of steel for rolling pump rods in various embodiments are shown in Table 3:

[0034] Table 3: Process parameters of steel for rolling pump rods in various embodiments

[0035]

[0036] The mechanical properties of steel for rolling pump rods in various embodiments are shown in Table 4:

[0037] Table 4: Mechanical properties of steel for pumping rod after rolling in various embodiments

[0038]

[0039] The impact properties of steel for rolling pump rods in various embodiments are shown in Table 5:

[0040] Table 5: Impact properties of steel for rolling pump rods at room temperature in various embodiments

[0041]

[0042] It can be analyzed from the above mechanical and impact test results that the steel for the pumping rod produced by the present invention has higher tensile and yield strengths and better impact performance.

[0043] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing high-strength steel for sucker rods, characterized in that: The production process specifically includes: molten iron pretreatment - converter smelting - LF furnace refining - billet continuous casting production - heating - bar continuous rolling unit rolling - air cooling; among which: Before smelting, the molten iron is first desulfurized to reduce the sulfur content in the molten steel, reduce the pressure of the refining furnace, and ensure that the tapping w[S] is ≤0.025%; in order to meet the high-drawing re-blowing operation and avoid overoxidation of the molten steel, the w[Si] is required to be 0.46%-0.56% and the temperature is greater than 1250℃; in the converter smelting process, the slag washing process is adopted, lime and refining slag are added, and the good dynamic conditions of the converter steel are used to prepare the pre-slag for the refining furnace smelting; During the LF refining process, lime, refined slag and fluorite are added, and argon is blown from the bottom for stirring throughout the process; the tapping temperature is 1600℃~1610℃ for the first pouring furnace and 1590℃~1600℃ for the continuous pouring furnaces; After LF steel is tapped, the temperature is measured on the continuous casting platform and Ar is blown. The intensity of Ar blowing is based on the condition that the steel surface is not exposed. The Ar blowing time is ≥8min~15min. The existing low-carbon and low-basicity covering agent is still used in the tundish. The covering agent should be added in time and should not be exposed or turn red. The casting machine is used to produce continuous casting billets. The continuous casting process adopts full-process protection casting to prevent secondary oxidation of molten steel. The H content in the billet is less than 2.5ppm, and the composition and gas content of the finished continuous casting billet meet the design requirements. The heating furnace adopts blast furnace gas regenerative combustion technology. The gas pressure and flow rate should be adjusted at any time during the heating process to ensure good heating quality. The heating temperature of the steel billet is between 1100℃ and 1180℃. The furnace temperature of heating stage I is controlled above 900℃, and the furnace temperature of heating stage II is controlled between 1150℃ and 1210℃. The heating time above 950℃ is ≥1.0h. The steelmaking rhythm and heating time are strictly controlled. The heating time of the continuous casting billet above 1100℃ should not exceed 3h. During the steel rolling process, the technical parameters controlled in the high-speed wire rolling process are: Rolling temperature: 1150±20℃; Final rolling temperature 920±20℃; The cooling beds are closely packed and the spacing is less than 10mm; The chemical composition percentage of the steel for sucker rod is: C: 0.18-0.23%, Si: 0.65-0.85%, Mn: 1.30-1.40%, P: ≤0.018%, S: ≤0.015%, V: 0.08-0.10%, Nb: ≤0.006%, Ti: 0.01-0.025%, B: 0.001-0.002%, Cr: 0.90-1.00%, Mo: 0.11-0.21%, and the rest are iron and inevitable trace chemical elements.

2. The method for producing high-strength steel for sucker rods according to claim 1, characterized in that: The chemical composition percentages of the sucker rod steel are: C: 0.21%, Si: 0.71%, Mn: 1.32%, P: 0.012%, S: 0.013%, V: 0.08%, Nb: 0.005%, Ti: 0.02%, B: 0.0017%, Cr: 0.90%, Mo: 0.14%, and the rest are iron and inevitable trace chemical elements.

3. The method for producing high-strength steel for sucker rods according to claim 1, characterized in that: The chemical composition percentages of the sucker rod steel are: C: 0.21%, Si: 0.72%, Mn: 1.37%, P: 0.011%, S: 0.012%, V: 0.09%, Nb: 0.005%, Ti: 0.02%, B: 0.0017%, Cr: 0.94%, Mo: 0.18%, and the rest are iron and inevitable trace chemical elements.

4. The method for producing high-strength steel for sucker rods according to claim 1, characterized in that: The chemical composition percentages of the sucker rod steel are: C: 0.21%, Si: 0.75%, Mn: 1.39%, P: 0.014%, S: 0.008%, V: 0.10%, Nb: 0.006%, Ti: 0.024%, B: 0.0015%, Cr: 0.99%, Mo: 0.20%, and the rest are iron and inevitable trace chemical elements.

5. The method for producing high-strength steel for sucker rods according to claim 1, characterized in that: Its mechanical properties meet the following requirements: tensile strength ≥1000MPa, elongation after fracture ≥13%, and section shrinkage ≥55%.

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