Manufacturing method of high-strength carbon dioxide and hydrogen sulfide corrosion resistant rare earth microalloying drill rod

Abstract

The invention discloses a manufacturing method of a high-strength carbon dioxide and hydrogen sulfide corrosion resistant rare earth microalloyed drill rod. The drill rod comprises the following chemical components in percentage by weight: 0.10-0.22% of C; 0.20% to 0.40% of Si; 0.40 to 0.60 percent of Mn; less than or equal to 0.020% of P; s is less than or equal to 0.010%; 0.1 to 0.6 percent of Ni; cr: 12.0 to 14.0%; 0.4 to 0.6 percent of Mo; 0.01 to 0.05 percent of Ti; rE < = 20 ppm; the production process flow comprises the steps of electric arc furnace smelting, LF furnace refining, VD furnace vacuum treatment, pouring, furnace cooling, steel ingot heating, forging, machining, pipe blank heating, perforating, continuous pipe rolling, stretching and reducing, slow cooling, saw cutting, heat treatment, straightening, flaw detection and warehousing. According to the manufacturing method of the high-strength carbon dioxide and hydrogen sulfide corrosion resistant rare earth microalloying drill rod, the toughness and corrosion resistance of steel are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical materials, and in particular relates to a method for manufacturing a high-strength rare earth micro-alloyed drill pipe resistant to carbon dioxide and hydrogen sulfide corrosion. Background Art

[0002] The drill pipe is the main tool for drilling. It is used to connect the surface equipment of the drilling rig and the drilling and grinding equipment at the bottom of the drilling rig. It plays the role of transmitting power and conveying mud, and raises, lowers or rotates the drilling and grinding equipment together with the drill bit. At the same time, high-pressure well washing fluid flows to the bottom of the well through the inner hole of the drill pipe. During drilling, the drill pipe is subjected to various alternating stresses such as tension, compression, torsion, bending, and impact. Its inner hole is also subjected to scouring and corrosion by high-pressure mud, and its outer wall is subjected to wear and corrosion. During the drilling process, failure of the drill pipe at any part will cause serious consequences and even cause the well to be scrapped. Therefore, there are strict requirements on the material, performance, and processing quality of the drill pipe.

[0003] In oil and gas fields containing hydrogen sulfide (H2S), drill pipes are also required to resist H2S corrosion. The working conditions are extremely complex, so the working environment is very harsh. H2S is an inevitable product of the drilling process, and the use of water injection and other technologies in the development of some oil fields will also produce a large amount of S 2- and H + , H2S corrosion is a very serious form of corrosion.

[0004] In actual oil well operation conditions, CO2 often exists in oil and gas as a component of natural gas or associated gas, and carbon dioxide displacement technology also brings CO2 into the crude oil gathering and transportation system, so there is a large amount of CO2 in the oil and gas industry. CO2 is particularly corrosive to drilling tool materials, often causing the materials to have a high corrosion rate and causing severe local corrosion. Under the same pH value conditions, the corrosiveness of CO2 aqueous solution is stronger than that of hydrochloric acid, and accidents caused by CO2 corrosion often occur in oil field exploitation.

[0005] As onshore oil and gas fields gradually enter the middle and late stages of exploitation, oil and gas drilling and production equipment has been transferred to harsh environments such as high temperature and pressure, high CO2-H2S content and deeper waters at home and abroad. In the process of oil and gas drilling and production, high CO2-H2S corrosive media has become the main corrosion factor of oil and gas drill pipes, which will cause different degrees of corrosion of oil and gas drill pipes in the well, and may even cause drill pipe breakage and blowout accidents, resulting in huge economic losses and personal injuries. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a method for manufacturing a rare earth micro-alloyed drill pipe with high strength and resistance to carbon dioxide and hydrogen sulfide corrosion.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The invention discloses a method for manufacturing a high-strength rare earth microalloyed drill pipe resistant to carbon dioxide and hydrogen sulfide corrosion. The chemical composition and content of the drill pipe by mass percentage are designed as follows: C 0.10-0.22%; Si 0.20-0.40%; Mn 0.40-0.60%; P≤0.020%; S≤0.010%; Ni 0.1-0.6%; Cr: 12.0-14.0%; Mo: 0.4-0.6%; Ti: 0.01-0.05%; RE≤20ppm; the rest are Fe and unavoidable impurities, and the mass fraction is 100% in total;

[0009] The specific process of its manufacturing method includes:

[0010] The electric arc furnace is used for smelting. Scrap steel and molten iron are loaded as required. The smelting operations in the melting period, oxidation period and reduction period are carried out according to the process requirements. The arc heat is used to melt the scrap steel at a temperature of up to 4000℃ in the arc action zone, and then dephosphorization and decarburization are carried out. Slag making, deoxidation and alloying are carried out in the reduction period. The temperature of the molten steel is adjusted to the tapping temperature, and ferrochrome, ferromolybdenum and nickel plate are added. Then, refining is carried out. During the refining period, the composition is fine-tuned, rare earth alloys are added to VD, and steel ingots are poured. After demoulding, they enter the slow cooling pit, cool to below 300℃, re-charge the furnace and heat to 1250℃, forge into Φ210mm round bars, and then directly charge the furnace to slow cool to below 300℃ and discharge from the furnace, and then turn them into Φ200mm round bars;

[0011] After the round steel comes off the line, it is sent to the heating furnace for heating, descaling with high-pressure water, and then rolled. The billet rolling temperature is 1150℃-1250℃; the heated billet is pierced-continuously rolled-sizing into a seamless steel pipe, and then slowly cooled to room temperature and then tempered. After tempering, it must be straightened with heat. The straightened steel pipes are subjected to flaw detection and water pressure test one by one, and then checked and put into storage.

[0012] The method for manufacturing a high-strength rare earth microalloyed drill pipe resistant to carbon dioxide and hydrogen sulfide corrosion according to claim 1 is characterized in that the chemical composition and content of the drill pipe by mass percentage are designed as follows: C 0.18%; Si 0.25%; Mn 0.50%; P 0.015%; S 0.005%; Ni 0.13%; Cr: 12.8%; Mo: 0.45%; Ti: 0.02%; RE 0.0002%; the rest are Fe and unavoidable impurities, with a total mass fraction of 100%.

[0013] Further, the billet details: diameter is Φ200mm.

[0014] Furthermore, the specifications of the finished steel pipe are: Φ139.7mm×9.17mm.

[0015] Furthermore, the starting rolling temperature is 1240° C., and the seamless pipe is formed into a seamless pipe with a specification of Φ139.7 mm×9.17 mm through PQF continuous rolling and sizing rolling, and then slowly cooled to room temperature.

[0016] Furthermore, the heat treatment process was set to 960°C for 50 min, air-cooled to room temperature, and then heated to 600°C for 90 min before being taken out of the furnace. The tube straightening temperature was 460°C and air-cooled.

[0017] Furthermore, the drill pipe is manufactured to resist dual corrosion of CO2 and H2S.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are:

[0019] The material of the present invention significantly improves the toughness and corrosion resistance of the steel by adding appropriate rare earth alloys; adding 12.0-14.0% Cr and 0.4-0.6% Mo can significantly improve the steel's CO2 corrosion resistance and H2S corrosion resistance; adding a certain amount of alloying elements Ni and Ti at the same time further refines the grains to improve the toughness and corrosion resistance of the steel; but it is necessary to control the sulfur content in the steel, because sulfur and manganese may combine to form manganese sulfide inclusions in the steel and significantly reduce the corrosion resistance of the drill pipe. Controlling the rolling heating temperature not to exceed 1250°C can ensure the smooth rolling of the seamless pipe and the quality of the inner and outer surfaces of the seamless pipe. In production, slow cooling is performed after hot rolling to prevent cracks from occurring in the seamless pipe after rolling. Through reasonable quenching and tempering treatment and high-temperature straightening, the steel structure is uniform, the toughness is high, the residual stress is small, and the steel has high corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the SSC test specimen. DETAILED DESCRIPTION

[0021] The specific process of the test steel is as follows:

[0022] Billet details: diameter is Φ200mm,

[0023] Finished steel pipe specifications: Φ139.7mm×9.17mm

[0024] The chemical composition and content of the finished product are shown in the following table (Wt%):

[0025] C Si Mn P S Cr Mo Ti Ni Al RE 0.18 0.25 0.50 0.015 0.005 12.8 0.45 0.02 0.13 0.02 0.0002

[0026] 1. Smelting

[0027] The electric arc furnace is loaded with a certain proportion of scrap steel and molten iron as required to adjust the slag composition, basicity, viscosity and reactivity during production.

[0028] According to the process requirements, the smelting operations in the melting period, oxidation period and reduction period are carried out. The power supply should be reasonable in the melting period to melt the solid charge into a uniform liquid. In the oxidation period, dephosphorization and decarburization are carried out through ore oxidation or oxygen blowing operation to reduce and prevent the steel liquid from absorbing air and the volatilization and oxidation loss of the metal. In the reduction period, the reducing slag is quickly made, the steel liquid is deoxidized, desulfurized and alloyed, the steel liquid composition is adjusted to the specified range, and the steel liquid temperature is adjusted to the steel tapping temperature. Add ferrochrome, ferromolybdenum and nickel plate, enter the LF furnace for refining, add ferrotitanium and fine-tune the composition, add rare earth alloys to make the rare earth alloys fully and evenly dissolved, enter the VD furnace for vacuum treatment, and then cast the ingot. The 1.23t steel ingot is slowly cooled to below 300℃ for demolding, and air-cooled to room temperature. .

[0029] The carbon content, phosphorus content and tapping temperature of the molten steel at the end of the electric arc furnace are shown in the following table.

[0030] Steel tapping temperature, ℃ Carbon content of steel, % Phosphorus content of steel, % 1642 0.12 0.011

[0031] 2. Forging

[0032] The steel ingot is re-charged into the furnace and heated to 1250℃, forged into Φ210mm round bars, slowly cooled to below 300℃ and then taken out of the furnace, and then turned into Φ200mm round bars.

[0033] 3. Rolling

[0034] The billet is heated in the heating furnace for more than 3 hours. The billet rolling temperature of the test steel is 1240°C. It is rolled into a seamless pipe with a specification of Φ139.7mm×9.17mm through PQF continuous rolling and sizing, and then slowly cooled to room temperature.

[0035] 4. Heat treatment

[0036] The heat treatment process was set to 960°C for 50 minutes, then air-cooled to room temperature, then heated to 600°C for 90 minutes, and then taken out of the furnace. The straightening temperature of the tube was 460°C and air-cooled.

[0037] The mechanical properties after heat treatment are shown in the following table:

[0038]

[0039] Compared with normal G105, the CO2 corrosion resistance has been greatly improved, and it also has good H2S corrosion resistance.

[0040]

[0041] The material of the present invention is subjected to a H2S corrosion resistance SSC test, and a stress of 580 MPa is loaded in a H2S saturated solution, and the sample does not break after 720 hours.

[0042] The present invention simultaneously adds RE, Cr, Ni, Mo and Ti to the steel pipe, improves the comprehensive performance of the steel pipe, improves the toughness and heat treatment performance, makes the steel pipe resistant to both CO2 and H2S corrosion, improves the corrosion resistance and service life of the steel pipe; slow cooling treatment is performed after casting and rolling to prevent cracks and ensure the internal and surface quality of the steel; timely heat treatment production can speed up the production rhythm and reduce the generation of cracks, so that the steel pipe has uniform organization and high toughness after heat treatment, which is beneficial to the subsequent use performance. It is suitable for a high-strength rare earth micro-alloyed drill pipe resistant to carbon dioxide and hydrogen sulfide corrosion and its manufacturing method, and has broad application prospects.

[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 manufacturing a high-strength rare earth microalloyed drill pipe resistant to carbon dioxide and hydrogen sulfide corrosion, characterized in that: The chemical composition and content of the drill pipe by mass percentage are designed as follows: C 0.10-0.22%; Si 0.20-0.40%; Mn 0.40-0.60%; P ≤ 0.020%; S ≤ 0.010%; Ni 0.1-0.6%; Cr: 12.0-14.0%; Mo: 0.4-0.6%; Ti: 0.01-0.05%; RE≤20ppm; The rest is Fe and unavoidable impurities, with a total mass fraction of 100%; The specific process of its manufacturing method includes: The electric arc furnace is used for smelting. Scrap steel and molten iron are loaded as required. The smelting operations in the melting period, oxidation period and reduction period are carried out according to the process requirements. The arc heat is used to melt the scrap steel at a temperature of up to 4000℃ in the arc action zone, and then dephosphorization and decarburization are carried out. Slag making, deoxidation and alloying are carried out in the reduction period. The temperature of the molten steel is adjusted to the tapping temperature, and ferrochrome, ferromolybdenum and nickel plate are added. Then, refining is carried out. During the refining period, the composition is fine-tuned, rare earth alloys are added to VD, and steel ingots are poured. After demoulding, they enter the slow cooling pit, cool to below 300℃, re-charge the furnace and heat to 1250℃, forge into Φ210mm round bars, and then directly charge the furnace to slow cool to below 300℃ and discharge from the furnace, and then turn them into Φ200mm round bars; After the round steel comes off the line, it is sent to the heating furnace for heating, descaling with high-pressure water, and then rolled. The billet rolling temperature is 1150℃-1250℃; the heated billet is pierced-continuously rolled-sizing into a seamless steel pipe, and then slowly cooled to room temperature and then tempered. After tempering, it must be straightened with heat. The straightened steel pipes are subjected to flaw detection and water pressure test one by one, and then checked and put into storage.

2. The method for manufacturing a high-strength rare earth microalloyed drill pipe resistant to carbon dioxide and hydrogen sulfide corrosion according to claim 1, characterized in that: The chemical composition and content of the drill pipe by mass percentage are designed to be: C 0.18%; Si 0.25%; Mn 0.50%; P 0.015%; S 0.005%; Ni 0.13%; Cr: 12.8%; Mo: 0.45%; Ti: 0.02%; RE 0.0002%; the rest is Fe and inevitable impurities, and the total mass fraction is 100%.

3. The method for manufacturing a high-strength rare earth microalloyed drill pipe resistant to carbon dioxide and hydrogen sulfide corrosion according to claim 1, characterized in that: Billet details: diameter is Φ200mm.

4. The method for manufacturing a high-strength rare earth microalloyed drill pipe resistant to carbon dioxide and hydrogen sulfide corrosion according to claim 3, characterized in that: Finished steel pipe specifications: Φ139.7mm×9.17mm.

5. The method for manufacturing a high-strength rare earth microalloyed drill pipe resistant to carbon dioxide and hydrogen sulfide corrosion according to claim 1, characterized in that: The starting rolling temperature is 1240°C, and the tube is rolled into a seamless tube with a specification of Φ139.7mm×9.17mm through PQF continuous rolling and sizing, and then slowly cooled to room temperature.

6. The method for manufacturing a high-strength rare earth microalloyed drill pipe resistant to carbon dioxide and hydrogen sulfide corrosion according to claim 1, characterized in that: The heat treatment process was set to 960°C for 50 minutes, then air-cooled to room temperature, then heated to 600°C for 90 minutes, and then taken out of the furnace. The straightening temperature of the tube was 460°C and air-cooled.

7. The method for manufacturing a high-strength rare earth microalloyed drill pipe resistant to carbon dioxide and hydrogen sulfide corrosion according to claim 1, characterized in that: The drill pipe is manufactured to resist both CO2 and H2S corrosion.

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