Rare earth Ce-containing supercritical CO2 corrosion-resistant X52 pipeline steel and production method thereof

Abstract

The invention discloses X52 pipeline steel containing rare earth Ce and resistant to supercritical CO2 corrosion and a production method of the X52 pipeline steel. The steel comprises the following components in percentage by mass: 0.02%-0.04% of C, 0.1%-0.2% of Si, 0.50%-0.80% of Mn, less than or equal to 0.008% of P, less than or equal to 0.001% of S, 0.03%-0.06% of Nb, 0.008%-0.020% of Ti, 0.02%-0.05% of Alt, 0.5%-1.0% of Cr, 0.003%-0.006% of Ce and the balance of Fe and inevitable impurities. The yield strength Rt0.5 of the steel ranges from 416 MPa to 426 MPa, the tensile strength ranges from 526 MPa to 536 MPa, the elongation A is larger than or equal to 29%, the yield ratio is smaller than or equal to 0.82, the Charpy impact energy at the temperature of-60 DEG C is larger than or equal to 412.4 J, the ductile-brittle transition point ranges from-80 DEG C to-90 DEG C, the drop weight shear area at the temperature of-30 DEG C is larger than or equal to 97%, and the hardness HV10 ranges from 163 to 173. Under the conditions that PCO2 is smaller than or equal to 14.5 MPa, the temperature is smaller than or equal to 40 DEG C and the rotating speed is 1 m / s, the uniform corrosion rate is smaller than or equal to 0.26 mm / a, and the corrosion inhibitor has wide application prospects in CO2 capture, utilization and storage systems.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas steel, and relates to a rare earth Ce-containing X52 pipeline steel resistant to supercritical CO2 corrosion and a preparation method thereof. Background Art

[0002] In recent years, in order to reduce the pollution caused by CO2 emissions to the environment, CCUS technology has developed rapidly. At the same time, CO2-EOR technology is also an effective way to reduce CO2. Combining CCUS technology with CO2-EOR technology can not only reduce CO2 in the environment, but also improve oil field recovery. In order to achieve good economic benefits and industrial development requirements, long-distance supercritical CO2 transmission pipelines have gradually become a research focus. However, with the complex service environment during long-distance transportation, higher requirements are placed on the mechanical and corrosion resistance of pipeline steel.

[0003] Oil extraction is gradually developing towards the northern region where the environment is more severe. In order to prevent the pipeline from breaking at extremely low temperatures, higher requirements are placed on the low-temperature toughness and crack arrest of the material. The addition of a small amount of the rare earth element Ce can significantly improve the mechanical properties of the material. When the captured CO2 is compressed to a supercritical state, in the presence of water, CO2 dissolves in water to form H2CO3, which causes corrosion inside the pipeline steel, which can lead to corrosion of the pipeline steel. In severe cases, perforation or even fracture may occur, seriously affecting the safety of pipeline operation. Generally, for supercritical CO2 corrosion environments, stainless steel with a high Cr content should be selected as the material for the transmission pipeline, which has excellent resistance to CO2 corrosion. However, for long-distance transportation, its cost limits its widespread application. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides an X52 pipeline steel containing rare earth Ce and resistant to supercritical CO2 corrosion and a preparation method thereof, and develops a pipeline steel with excellent low-temperature toughness and CO2 corrosion resistance.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A rare earth Ce-containing X52 pipeline steel resistant to supercritical CO2 corrosion, the chemical composition of the steel is C=0.02%~0.04%, Si=0.1%~0.2%, Mn=0.50%~0.80%, P≤0.008%, S≤0.001%, Nb=0.03%~0.06%, Ti=0.008%~0.020%, Al T =0.02%~0.05%, Cr=0.5%~1.0%, Ce=0.003%~0.006%, the rest are Fe and unavoidable impurities, and the carbon equivalent Ceq≤0.35%, the crack sensitivity index Pcm≤0.12%.

[0006] A method for producing X52 pipeline steel containing rare earth Ce and resistant to supercritical CO2 corrosion comprises the following key process steps: 1) Smelting and continuous casting: After batching, smelting and continuous casting according to the chemical composition, the continuous casting billet is obtained; 2) Hot rolling: heat the continuous casting billet to 1200~1250℃, keep it warm for 60~120min, remove the surface iron oxide scale by high-pressure water after heating, and then carry out two-stage controlled rolling by rough rolling and finishing rolling unit. After 5 passes of rough rolling mill, 7 passes of finishing rolling mill are carried out; the starting temperature of rough rolling is ≥1000℃, and the final rolling temperature of rough rolling is ≥880℃; the starting temperature of finishing rolling is ≤870℃, and the final rolling temperature of finishing rolling is 825~850℃; 3) Cooling: ACC laminar cooling is adopted after rolling, the cooling rate is 20~30℃ / s, and the temperature is returned to red at 500~450℃.

[0007] C eq =C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15, P cm =C+Si / 30+(Mn+Cu+Cr) / 20+Ni / 60+Mo / 15+V / 10+5B; Step 2) All rolling temperatures in hot rolling refer to the core temperature of the slab.

[0008] The comprehensive properties of pipeline steel obtained by the above method are: yield strength Rt 0.5 The tensile strength is 416~426MPa, the tensile strength is 526~536MPa, the elongation A≥29%, the yield strength ratio≤0.82, the -60℃ Charpy impact energy≥412.4J, the ductile-brittle transition point is at -80~-90℃, the drop hammer shear area at -30℃ is ≥97%, and the hardness is 163~173. CO2 Under the conditions of water-saturated CO2 of ≤14.5MPa, temperature ≤40℃ and rotation speed of 1m / s, the uniform corrosion rate is ≤0.26mm / a.

[0009] The mechanism of action of each alloy element in the X52 pipeline steel containing rare earth Ce and resistant to supercritical CO2 corrosion of the present invention is as follows: As the most economical and basic strengthening element in steel, C has a significant effect on improving the strength of steel through solid solution strengthening and precipitation strengthening. Low carbon content can avoid central segregation of ingots; however, too high carbon content has an adverse effect on the elongation, toughness and weldability of steel, and easily causes alloy element carbides to precipitate at grain boundaries, thereby reducing the corrosion resistance of the steel. Therefore, the present invention controls the C content to 0.02% to 0.04%.

[0010] Mn can greatly improve the strength and toughness of steel through solid solution strengthening. It is the most important and economical strengthening element to compensate for the strength loss caused by the reduction of C content. It is also an effective deoxidizer and has the effect of removing S. However, too high Mn will promote the formation of carbides, produce segregation, and form large-sized MnS inclusions, reducing the toughness of steel. Therefore, the present invention controls the Mn content to 0.50%~0.80%.

[0011] The main function of Nb is to improve the low temperature toughness of pipeline steel. Its characteristic in steel is to increase the recrystallization temperature of austenite, thereby achieving the purpose of refining austenite grains. A trace amount of Nb is enough to make the steel have excellent comprehensive properties. Too high Nb content will easily cause mixed crystals in the steel. Therefore, the present invention controls the Nb content to 0.03%~0.06%.

[0012] The addition of Cr and the increase of its content have a certain improvement effect on the strength and toughness of the steel pipe body, the strength of the weld and the toughness of the heat-affected zone, but too high Cr content will lead to a decrease in the welding performance of the steel, and the segregation of Cr carbides at the grain boundary will easily lead to a decrease in the sulfur resistance of the steel. Therefore, the present invention controls the Cr content to 0.5%~1.0%.

[0013] Ti can form a small and stable precipitation phase, which can effectively hinder the growth of austenite grains during heating, help to improve the solid solubility of Nb in austenite, and have a significant effect on improving the impact toughness of the welding heat affected zone, thereby improving the welding performance of the material. Too high a Ti content will generate coarse carbonitrides, reduce the toughness of the material, and increase the material cost. Therefore, the present invention controls the Ti content to 0.008% to 0.02%.

[0014] Ce is easy to form compounds such as cerium oxide, cerium sulfide and CeAlO3 with high melting point and low mismatch with the matrix when added to steel. These compounds have high melting points and are easy to be removed from molten steel, thus achieving the effect of purifying molten steel. At the same time, it can serve as an effective starting point for uneven nucleation during the solidification of molten steel, and grain refinement can improve material properties. When the Ce element is added in excessive content, its cost is high. Therefore, the Ce content is controlled at 0.003% to 0.006% in the present invention.

[0015] Al is an indispensable deoxidizer in steelmaking, but excessive Al will increase the number of Al2O3 inclusions and reduce the low-temperature toughness of the material. Therefore, the present invention controls the Alt content to 0.02% to 0.05%.

[0016] P and S are inevitable impurity elements in steel, but too low a content will increase production costs. Therefore, the present invention controls the P and S contents to P≤0.008% and S≤0.001%, respectively.

[0017] The control of the cold crack sensitivity index Pcm is beneficial to ensuring the welding performance of the product. cm Controlled at ≤0.19%.

[0018] The control of Ceq carbon equivalent index is beneficial to ensure the welding performance of the product. eq Controlled at ≤0.32%.

[0019] The beneficial effects of the present invention are as follows: (1) the addition of the rare earth element Ce makes the steel have excellent low-temperature toughness; (2) under water-saturated conditions of a pressure of 14.5 MPa, a temperature of 35° C., and a rotation speed of 1 m / s, the uniform corrosion rate is ≤0.26 mm / a. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a microstructure morphology of the X52 pipeline steel containing rare earth Ce and resistant to supercritical CO2 corrosion prepared in Example 1. The microstructure in the figure is polygonal ferrite and a small amount of pearlite.

[0021] Figure 2 The impact values ​​of the X52 pipeline steel containing rare earth Ce and resistant to supercritical CO2 corrosion prepared in Example 1 at different temperatures. DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention are described in detail below with reference to the diagrams. Example 1

[0023] A rare earth Ce-containing X52 pipeline steel resistant to supercritical CO2 corrosion and a preparation method thereof, the chemical composition of the steel is shown in Table 1. The steel comprises the following steps: 1) Smelting and continuous casting: Smelting and continuous casting are carried out according to the components in Table 1; 2) Rolling: Heat the steel billet to 1220℃ and keep it warm for 90 minutes; the starting temperature of rough rolling is controlled at 1150℃, and the rolling is carried out in 5 passes. The starting temperature of finishing rolling is controlled at 870℃, and the rolling is carried out in 7 passes; 3) Cooling: After finishing rolling, cool to 498°C at a cooling rate of 30°C / s.

[0024] The mechanical properties and corrosion resistance test results of the X52 pipeline steel containing rare earth Ce and resistant to supercritical CO2 corrosion prepared according to the above implementation method are shown in Table 2. Example 2

[0025] A rare earth Ce-containing X52 pipeline steel resistant to supercritical CO2 corrosion and a preparation method thereof, the chemical composition of the steel is shown in Table 1. The steel comprises the following steps: 1) Smelting and continuous casting: Smelting and continuous casting are carried out according to the components in Table 1; 2) Rolling: Heat the steel billet to 1250℃ and keep it warm for 68 minutes; the starting temperature of rough rolling is controlled at 1060℃, and the rolling is carried out in 5 passes. The starting temperature of finishing rolling is controlled at 860℃, and the rolling is carried out in 7 passes; 3) Cooling: After finishing rolling, cool to 465℃ at a cooling rate of 20℃ / s.

[0026] The mechanical properties and corrosion resistance test results of the X52 pipeline steel containing rare earth Ce and resistant to supercritical CO2 corrosion prepared according to the above implementation method are shown in Table 2. Example 3

[0027] A rare earth Ce-containing X52 pipeline steel resistant to supercritical CO2 corrosion and a preparation method thereof, the chemical composition of the steel is shown in Table 1. The steel comprises the following steps: 1) Smelting and continuous casting: Smelting and continuous casting are carried out according to the components in Table 1; 2) Rolling: Heat the steel billet to 1200℃ and keep it warm for 120min; the starting temperature of rough rolling is controlled at 1030℃, and the rolling is divided into 5 passes. The starting temperature of finishing rolling is controlled at 860℃, and the rolling is divided into 7 passes; 3) Cooling: After finishing rolling, cool to 450℃ at a cooling rate of 25℃ / s.

[0028] The mechanical properties and corrosion resistance test results of the X52 pipeline steel containing rare earth Ce and resistant to supercritical CO2 corrosion prepared according to the above implementation method are shown in Table 2.

[0029] Table 1 Element composition of example steel (wt%) .

[0030] Table 2 Mechanical and corrosion resistance properties of the example steels .

Claims

1. A rare earth Ce-containing X52 pipeline steel resistant to supercritical CO2 corrosion, characterized in that: The chemical composition of steel is calculated by mass percentage as follows: C = 0.02% ~ 0.04%, Si = 0.1% ~ 0.2%, Mn = 0.50% ~ 0.80%, P ≤ 0.008%, S ≤ 0.001%, Nb = 0.03% ~ 0.06%, Ti = 0.008% ~ 0.020%, Al T =0.02%~0.05%, Cr=0.5%~1.0%, Ce=0.003%~0.006%, the rest is Fe and unavoidable impurities, and the carbon equivalent Ceq≤0.35%, the crack sensitivity index Pcm≤0.12%; the yield strength of the steel plate Rt 0.5 The tensile strength is 416~426MPa, the tensile strength is 526~536MPa, the elongation A≥29%, the yield strength ratio≤0.82, the -60℃ Charpy impact energy ≥412.4J, the ductile-brittle transition point is at -80~-90℃, the drop hammer shear area at -30℃ is ≥97%, the hardness HV10 is 163~173, and the CO2 The uniform corrosion rate is ≤0.26mm / a under water-saturated CO2 conditions of ≤14.5MPa, temperature ≤40℃ and rotation speed 1m / s.

2. A method for producing X52 pipeline steel containing rare earth Ce and resistant to supercritical CO2 corrosion, comprising the following key process steps: 1) Smelting and continuous casting: After batching, smelting and continuous casting according to the chemical composition, the continuous casting billet is obtained; 2) Hot rolling: heat the continuous casting billet to 1200~1250℃, keep it warm for 60~120min, remove the surface iron oxide scale by high-pressure water after heating, and then carry out two-stage controlled rolling by rough rolling and finishing rolling unit. After 5 passes of rough rolling mill, 7 passes of finishing rolling mill are carried out; the starting temperature of rough rolling is ≥1000℃, and the final rolling temperature of rough rolling is ≥880℃; the starting temperature of finishing rolling is ≤870℃, and the final rolling temperature of finishing rolling is 825~850℃; 3) Cooling: ACC laminar cooling is adopted after rolling, the cooling rate is 20~30℃ / s, and the temperature is returned to red at 500~450℃.

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