Nb-ti microalloyed hydrogen embrittlement resistant pipeline steel and method of making

Abstract

The application discloses a kind of Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel and preparation method, including heating furnace, cooling furnace being arranged at the right side of heating furnace, feeding mechanism being arranged above heating furnace and cooling furnace;Heating furnace includes the heating furnace body of upper end opening, left furnace door and right furnace door being arranged on the heating furnace body, several heaters being arranged on the inner wall of heating furnace body, heating cover plate being arranged on the upper end of heating furnace body, and first temperature pressure sensor being arranged on the heating furnace body;Cooling furnace includes the cooling furnace body of upper end opening, cooling furnace door being arranged at the left end of cooling furnace body, cooling cover plate being arranged on the upper end of cooling furnace body, second temperature pressure sensor being arranged on the cooling furnace body;The application has the characteristics of improving the mechanical properties and hydrogen embrittlement resistance of X52 pipeline steel.

Description

Technical Field

[0001] This invention relates to the field of hydrogen pipeline technology, and in particular to an Nb-Ti microalloyed anti-hydrogen embrittlement pipeline steel and its preparation method. Background Technology

[0002] Storage and transportation are among the bottlenecks currently hindering the development of hydrogen energy in my country. Safe and efficient hydrogen transportation technology is a prerequisite for the large-scale commercialization of hydrogen energy. Among all hydrogen transportation options, pipeline transportation is the most economical.

[0003] With the rapid development of hydrogen energy, the pressure and flow rate of hydrogen pipeline transportation are increasing. Currently, the strength of X52 pipeline steel used for hydrogen transportation is relatively low. In addition, in a high-pressure hydrogen environment, hydrogen atoms will rapidly diffuse and accumulate in large quantities in X52 pipeline steel, which reduces the hydrogen embrittlement resistance, decreases ductility, increases the fatigue crack propagation rate, and reduces fracture toughness, seriously restricting the safe and efficient transportation of hydrogen.

[0004] Austenitic stainless steel, as a pipeline steel material, can slow down the diffusion of hydrogen atoms and reduce their accumulation in high-pressure hydrogen environments, thus improving the pipeline steel's resistance to hydrogen embrittlement. However, austenitic stainless steel is too expensive to be used in practice. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing X52 pipeline steel in meeting the requirements for safe and efficient transportation of hydrogen, and to provide an Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel, X52 pipeline steel, is composed of carbon (C), manganese (Mn), phosphorus (P), sulfur (S), copper (Cu), nickel (Ni), chromium (Cr), molybdenum (Mo), hafnium (Hf), lanthanum (La), niobium (Nb), thallium (Ti), and iron (Fe). The mass percentages of each component in X52 pipeline steel are: 0.08% ≤ C ≤ 0.28%, 1.20% ≤ Mn ≤ 1.40%, 0.01% ≤ P ≤ 0.03%, 0.02% ≤ S≤0.03%, 0.20%≤Cu≤0.50%, 0.12%≤Ni≤0.50%, 0.10%≤Cr≤0.30%, 0.08%≤Mo≤0.15%, 0.0001%≤Hf≤0.0003%, 0.0001%≤La≤0.0003%, 0.018%≤Nb≤0.036%, 0.035%≤Ti≤0.05%, balance Fe.

[0008] The microalloying and tempering heat treatment process of this invention can produce X52 pipeline steel with high strength and toughness, excellent resistance to hydrogen embrittlement, and low cost. The Nb and Ti added in this invention can refine the grain structure of the pipeline steel, increasing its strength and toughness. The formed (Nb,Ti)C particles can hinder dislocation slip and promote precipitation strengthening, significantly improving the strength of the pipeline steel. Furthermore, in a hydrogen environment, tempering forms uniformly distributed (Nb,Ti)C particles with a diameter of 5-10 nm. The C particles maintain a semi-coherent orientation with the matrix, forming irreversible deep traps for hydrogen atoms, significantly reducing the amount of diffusible hydrogen in the pipeline steel, thereby reducing its hydrogen embrittlement sensitivity. After process and equipment optimization and improvement, this invention not only significantly improves the strength of the pipeline steel but also greatly enhances its resistance to hydrogen embrittlement.

[0009] Therefore, this invention effectively improves the strength and hydrogen embrittlement resistance of X52 pipeline steel (the tensile, fatigue crack propagation and fracture toughness of the material in a hydrogen environment are greatly improved).

[0010] A method for preparing Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel includes a heating furnace, a cooling furnace located to the right of the heating furnace, and a feeding mechanism located above the heating furnace and the cooling furnace.

[0011] The heating furnace includes a heating furnace body with an opening at the top, a left furnace door and a right furnace door on the heating furnace body, several heaters on the inner wall of the heating furnace body, a heating cover plate at the top of the heating furnace body, and a first temperature and pressure sensor on the heating furnace body; the cooling furnace includes a cooling furnace body with an opening at the top, a cooling furnace door at the left end of the cooling furnace body, a cooling cover plate at the top of the cooling furnace body, and a second temperature and pressure sensor on the cooling furnace body; the lower end of the cooling furnace is connected to an external gas cylinder, and a first solenoid valve is provided on the external gas cylinder;

[0012] It also includes a cooling circulation mechanism, which includes a gas pipeline connected to the cooling furnace at both ends, and several booster pumps in the gas pipeline for pressurizing the cooling gas; the cooling furnace is provided with several gas nozzles connected to the gas pipeline, and the gas pipeline is connected to an air-cooled motor, which is connected to the right side of the cooling furnace body through a connecting pipe.

[0013] The feeding mechanism includes a fixed frame, two rollers on the fixed frame, a conveyor belt on the two rollers, a drive motor connected to the shaft of one of the rollers, an up-down adjuster on the conveyor belt, and a hook at the lower end of the up-down adjuster; it also includes a controller, which is electrically connected to the first solenoid valve, the air-cooled motor, the drive motor, the first temperature and pressure sensor, the second temperature and pressure sensor, each heater, and each booster pump.

[0014] Preferably, the connecting pipe is replaced by a helium purification mechanism, which includes a vacuum pump, an adsorption filter, a compressor, a gas separator, a heat exchanger, and a recovery gas cylinder connected sequentially through a gas guide pipe; the vacuum pump is connected to the right side wall of the cooling furnace, the recovery gas cylinder is connected to the right side wall of the cooling furnace, and a second solenoid valve is provided on the gas guide pipe between the recovery gas cylinder and the cooling furnace; a third solenoid valve is provided on the gas guide pipe between the heat exchanger and the recovery gas cylinder, the heat exchanger is connected to the air-cooled motor housing of the air-cooled motor through the gas guide pipe, and a fourth solenoid valve is provided on the gas guide pipe between the heat exchanger and the air-cooled motor housing; the controller is electrically connected to the vacuum pump, the adsorption filter, the compressor, the gas separator, the heat exchanger, the second solenoid valve, the third solenoid valve, and the fourth solenoid valve respectively.

[0015] Preferably, the cooling furnace body is provided with a circular vertical cylinder, which includes four arc-shaped plates with a central angle of 90°. The bottom plate of the cooling furnace body is provided with four radially distributed slide rails. Each of the four arc-shaped plates is provided with a supporting vertical rod at its lower end. The four supporting vertical rods are slidably connected to the four slide rails by sliders. The circular vertical cylinder is provided with evenly distributed mounting holes. Each gas nozzle is installed in each mounting hole. The rear of each gas nozzle is connected to a gas pipeline through a flexible hose.

[0016] Each gas nozzle can surround the pipeline steel to spray gas, enabling the pipeline steel to cool rapidly and evenly, ensuring the uniformity of the pipeline steel's structure, preventing local cracking, and enhancing the comprehensive mechanical properties and resistance to hydrogen embrittlement of the pipeline steel.

[0017] As a preferred option, the following steps are included:

[0018] Step 1, Smelting:

[0019] Workers add carbon (C), manganese (Mn), phosphorus (P), sulfur (S), copper (Cu), nickel (Ni), chromium (Cr), molybdenum (Mo), hafnium (Hf), lanthanum (La), niobium (Nb), thallium (Ti), and iron (Fe) in a vacuum induction melting furnace according to the mass percentage for melting. Argon gas is blown throughout the melting process to prevent oxidation of the molten steel. After melting, the steel billet is cast into a steel billet.

[0020] Step 2, heating:

[0021] Workers place the steel billet into the heating furnace, control the heating of each heater, and observe the temperature data detected by the first temperature sensor. The temperature inside the heating furnace is raised to 1100℃-1150℃ and held for more than 40 minutes before the steel billet is removed from the heating furnace. This process improves the uniformity and ductility of the steel billet, facilitating subsequent piercing and hot rolling.

[0022] Step 3, perforation:

[0023] Workers use a piercing machine to pierce holes in steel billets to obtain steel pipes;

[0024] Step 4, Rolling:

[0025] Workers use a hot rolling mill to continuously hot roll the wall of the steel pipe;

[0026] Step 5: The workers water-cool the steel pipe twice to obtain pipeline steel; the first water cooling temperature is 810℃-850℃, the second water cooling temperature is 500℃-540℃, and then the steel pipe is air-cooled to room temperature.

[0027] Step 6: The workers use a drilling machine to drill hook holes in the pipe wall at one end of the pipeline steel. The pipeline steel with the hook holes is then hung on the hooks. The height of the pipeline steel is changed by adjusting the up and down adjusters. The heating cover plate is removed, the left furnace door is opened, and the active motor is controlled by the controller. The conveyor belt drives the hooks to move to the right, transporting the pipeline steel into the heating furnace. The active motor is then stopped, the left furnace door is closed, and the heating cover plate is closed.

[0028] Step 7, perform the first conditioning treatment:

[0029] Step 7-1: The staff controls each heater to heat at a rate of 6℃ / min-8℃ / min through the controller, observes the temperature data detected by the first temperature sensor, and makes the temperature inside the heating furnace reach 900℃-930℃, holds the temperature for 50min-70min, and then stops each heater in the heating furnace.

[0030] Step 7-2: The staff removes the heating cover plate and cooling cover plate, opens the right furnace door and cooling furnace door, adjusts the height of the hook using the up and down adjuster, controls the active motor to work, and the conveyor belt drives the hook to move to the right. The conveyor belt transports the pipeline steel to the center of the cooling furnace, stops the active motor, closes the right furnace door and cooling furnace door, and covers the heating cover plate and cooling cover plate.

[0031] The controller opens the first solenoid valve, allowing helium to be introduced into the cooling furnace from an external gas cylinder. The pressure data detected by the second temperature and pressure sensor is observed to maintain the pressure inside the cooling furnace within the range of 1.2MPa-1.8MPa.

[0032] The controller controls the operation of the air-cooled motor and the pressurization of each booster pump. The cooled helium gas is sprayed onto the pipeline steel through each gas nozzle to cool the pipeline steel until the temperature data detected by the second temperature and pressure sensor drops to room temperature, at which point the air-cooled motor and each booster pump are turned off.

[0033] In this invention, helium is used for cooling. Helium has an outstanding cooling effect, requires less cooling time, is stable, has low reactivity, and is not prone to reacting with metals at high temperatures.

[0034] This invention employs a suspended heat treatment method for pipeline steel samples, which allows for more uniform heating and cooling of the samples; ensures the uniformity of the sample microstructure, prevents local cracking, and enhances the overall mechanical properties and resistance to hydrogen embrittlement of the samples.

[0035] Step 7-3: The staff opens the cooling furnace door and the right furnace door, removes the heating cover and the cooling cover, controls the active motor to work, and the conveyor belt drives the hook to move to the left, transporting the pipeline steel to the middle position of the heating furnace, so that the active motor stops working and the right furnace door and the heating cover are closed.

[0036] The controller controls each heater to heat at a rate of 5℃ / min. The temperature data detected by the first temperature sensor is observed, and the temperature inside the heating furnace is brought to 590℃-610℃. The temperature is held for 100min-140min, and then each heater is stopped. The right furnace door is opened, the heating cover is removed, the drive motor is started, and the conveyor belt drives the hook to move to the right, transporting the pipeline steel to the space between the heating furnace and the cooling furnace. The drive motor is stopped, the right furnace door is closed, the heating cover is closed, and the pipeline steel is cooled to room temperature.

[0037] Step 8, perform the second conditioning process:

[0038] Step 8-1: The operator opens the right furnace door, removes the heating cover, and starts the drive motor. The conveyor belt moves the hook to the left, transporting the pipeline steel to the middle position of the heating furnace. The drive motor then stops, the right furnace door is closed, and the heating cover is replaced. The controller controls each heater to heat at a rate of 6℃ / min-8℃ / min. The temperature data detected by the first temperature sensor is observed, and the temperature inside the heating furnace is brought to 900℃-930℃. The temperature is maintained for 50min-70min, and then each heater in the heating furnace stops working.

[0039] Step 8-2: The staff removes the heating cover plate and cooling cover plate, opens the right furnace door and cooling furnace door, starts the drive motor, and the conveyor belt transports the pipeline steel to the center of the cooling furnace. The drive motor stops working, the right furnace door and cooling furnace door are closed, and the heating cover plate and cooling cover plate are put back on.

[0040] The controller controls the operation of the air-cooled motor and the pressurization of each booster pump. The cooled helium gas is sprayed onto the pipeline steel through each gas nozzle to cool the pipeline steel until the temperature data detected by the second temperature and pressure sensor drops to room temperature, causing the active motor to stop working and shutting down the air-cooled motor and each booster pump.

[0041] Step 8-3, repeat step 7-3 once, the pipeline steel preparation process is complete.

[0042] The cyclic tempering heat treatment process is adopted, which utilizes the cyclic recrystallization of austenite and martensite to refine the grain size of X52 pipeline steel, thereby further improving the material's strength, toughness, and resistance to hydrogen embrittlement.

[0043] Helium cooling offers excellent cooling performance, requires less cooling time, is stable, has low reactivity, and is unlikely to react with metals at high temperatures. Helium can also be recovered, purified, and recycled, significantly reducing production costs and ensuring quenching quality.

[0044] Preferably, the connecting pipe is replaced with a helium purification mechanism, which includes a vacuum pump, an adsorption filter, a compressor, a gas separator, a heat exchanger, and a recovery gas cylinder connected sequentially via a gas guide pipe. The vacuum pump is connected to the right side wall of the cooling furnace, and the recovery gas cylinder is connected to the right side wall of the cooling furnace. A second solenoid valve is installed on the gas guide pipe between the recovery gas cylinder and the cooling furnace. A third solenoid valve is installed on the gas guide pipe between the heat exchanger and the recovery gas cylinder. The heat exchanger is connected to the air-cooled motor housing of the air-cooled motor via the gas guide pipe. A fourth solenoid valve is installed on the gas guide pipe between the heat exchanger and the air-cooled motor housing. The controller is electrically connected to the vacuum pump, adsorption filter, compressor, gas separator, heat exchanger, second solenoid valve, third solenoid valve, and fourth solenoid valve, respectively. The process also includes the following steps: Step 7-2, where the controller controls the air-cooled motor and each booster pump to pressurize, and the cooled helium is sprayed onto the pipeline steel through each gas nozzle to cool the pipeline steel until the temperature data detected by the second temperature and pressure sensor drops to room temperature, at which point the air-cooled motor and each booster pump are shut down. This is replaced by the following steps:

[0045] The operator controls the vacuum pump via a controller, causing the gas in the cooling furnace to pass through an adsorption filter to remove impurities. The compressor increases the gas pressure, allowing helium to pass through a gas separator. The purified helium is then cooled by a heat exchanger. The fourth solenoid valve opens, allowing the helium to be purified by the recovery and purification mechanism before entering the gas-cooled motor housing. The controller then operates the gas-cooled motor, which in turn pressurizes the various booster pumps, spraying the cooled helium through nozzles onto the pipeline steel for gas cooling until the temperature detected by the second temperature and pressure sensor drops to room temperature. At this point, the gas-cooled motor and booster pumps are shut down, and the fourth solenoid valve is closed. The third solenoid valve opens, controlling the vacuum pump to operate for 30-60 minutes, drawing the cooled and purified helium into a recovery gas cylinder. Finally, the third solenoid valve closes.

[0046] In step 8-2, the controller operates the air-cooled motor and pressurizes each booster pump. The cooled helium gas is then sprayed onto the pipeline steel through various gas nozzles to cool the pipeline steel until the temperature detected by the second temperature and pressure sensor drops to room temperature. The air-cooled motor and each booster pump are then shut down. This process is replaced by the following steps:

[0047] The staff controlled the second solenoid valve to open, allowing helium from the recovered gas cylinder to fill the cooling furnace. They observed the gas pressure data detected by the second temperature and pressure sensor, maintained the gas pressure in the cooling furnace within the range of 1.2MPa-1.8MPa, and then closed the second solenoid valve.

[0048] The vacuum pump is started, and the controller opens the fourth solenoid valve, allowing helium gas to enter the gas-cooled motor housing after purification by the purification unit. The controller then controls the gas-cooled motor to operate, pressurizing each booster pump. The cooled helium gas is sprayed onto the pipeline steel through various gas nozzles to cool the pipeline steel until the temperature data detected by the second temperature and pressure sensor drops to room temperature. At this point, the gas-cooled motor and each booster pump are turned off, and the fourth solenoid valve is closed. The third solenoid valve is then opened, controlling the vacuum pump to operate for 30-60 minutes. After the cooled helium gas is drawn into the recovery gas cylinder, the third solenoid valve is closed.

[0049] Helium is expensive, but this invention can recover, purify and recycle helium, significantly reducing production costs and ensuring the quenching quality of pipeline steel.

[0050] Preferably, the cooling furnace body is provided with a circular vertical cylinder, which includes four arc-shaped plates with a central angle of 90°. The bottom plate of the cooling furnace body is provided with four radially distributed slide rails. Each of the four arc-shaped plates is provided with a supporting vertical rod at its lower end. The four supporting vertical rods are slidably connected to the four slide rails by sliders. The circular vertical cylinder is provided with evenly distributed mounting holes. Each gas nozzle is installed in each mounting hole. The rear of each gas nozzle is connected to a gas pipeline through a hose.

[0051] After the conveyor belts in steps 7-2 and 8-2 transport the pipeline steel to the center of the cooling furnace, the following steps are included:

[0052] The initial positions of the four arc-shaped plates are close to the inner wall of the cooling furnace. The workers push each arc-shaped plate towards the pipeline steel, so that the supporting vertical rod of each arc-shaped plate slides along the corresponding slide rail through the slider, so that the four arc-shaped plates move together to form a circular vertical cylinder structure, so that the gas outlets of each gas nozzle are evenly surrounded and face the outside of the pipeline steel.

[0053] After removing the heating and cooling covers in step 7-3, the following steps are included:

[0054] Workers pushed each curved plate along the track, gradually bringing each plate closer to the inner wall of the furnace.

[0055] Preferably, step 3 includes the following detailed steps:

[0056] The steel pipe is obtained by passing a mandrel through the center of the billet at a rotation speed of 50-60 r / min, a piercing rate of 0.6-0.8 m / min, an initial piercing temperature of 1050-1110℃, and a final piercing temperature of 980-1020℃.

[0057] Preferably, the initial rolling temperature in step 4 is 870℃-910℃, the final rolling temperature is 830℃-860℃, the cumulative reduction rate in the hot rolling stage is 62%-67%, and the number of rolling passes is 3-5.

[0058] By controlling the quenching temperature to around 910℃, the grain size is relatively small when Nb, Ti, and other microalloys are completely dissolved. The tempering temperature is around 600℃, which causes a large number of uniformly dispersed (Nb,Ti)C particles with a diameter of 5-10nm to precipitate from the martensite. These particles can pin dislocations, thereby improving the strength of the material. Furthermore, the precipitates form a semi-coherent interface with the matrix, which can irreversibly capture a large number of hydrogen atoms, thus improving the hydrogen embrittlement resistance of pipeline steel.

[0059] The cumulative reduction rate in the hot rolling stage of this invention is 62% to 67%, which increases the phase transformation nucleation rate in the non-recrystallized austenite region during the hot rolling stage, ultimately resulting in a fine phase transformation structure.

[0060] Therefore, the present invention has the following beneficial effects:

[0061] The addition of trace amounts of rare earth elements Hf and La modifies non-metallic inclusions, refines the grains of pipeline steel, improves the pinning effect and resistance to lamellar tearing of oxides, and enhances the strength and toughness of pipeline steel.

[0062] This increases the phase transformation nucleation rate in the non-recrystallized austenite region during hot rolling, resulting in fine phase transformation microstructure in pipeline steel.

[0063] The cyclic tempering heat treatment process is adopted, which utilizes the cyclic recrystallization of austenite and martensite to refine the grain size of X52 pipeline steel, thereby further improving the material's strength, toughness, and resistance to hydrogen embrittlement.

[0064] By controlling the quenching temperature to around 910℃, the grain size is relatively small when Nb, Ti, and other microalloys are completely dissolved. The tempering temperature is around 600℃, which causes a large number of uniformly dispersed (Nb,Ti)C particles with a diameter of 5-10nm to precipitate from the martensite. These particles can pin dislocations, thereby improving the strength of the material. Furthermore, the precipitates form a semi-coherent interface with the matrix, which can irreversibly capture a large number of hydrogen atoms, thus improving the hydrogen embrittlement resistance of pipeline steel.

[0065] Helium cooling offers excellent cooling performance, requires less cooling time, is stable, has low reactivity, and is unlikely to react with metals at high temperatures. Helium can also be recovered, purified, and recycled, significantly reducing production costs and ensuring quenching quality.

[0066] Suspended heat treatment of pipeline steel ensures more uniform heating and cooling, enabling rapid and even cooling of the pipeline steel, guaranteeing a uniform microstructure and preventing localized cracking.

[0067] By altering the precipitates and microstructure, the mechanical properties and hydrogen embrittlement resistance of X52 pipeline steel were significantly improved, extending its service life. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of the structure of the present invention;

[0069] Figure 2 This is a top view of the circular vertical cylinder and slide rail of the present invention;

[0070] Figure 3 This is a metallographic image of Embodiment 1 of the present invention;

[0071] Figure 4 This is a TEM image of Embodiment 1 of the present invention;

[0072] Figure 5 This is an HRTEM image of Embodiment 1 of the present invention;

[0073] Figure 6 These are stress-strain curves of Embodiment 1 and the comparative example of the present invention under environments of 6.3 MPa N2 and H2, respectively.

[0074] Figure 7 These are ΔK-da / dN curves of Embodiment 1 and the comparative example of the present invention under 6.3 MPa N2 and H2 environments, respectively;

[0075] Figure 8 This is a Δa-Jintegral curve of Embodiment 1 and the comparative example of the present invention under 6.3MPa N2 and H2 environments, respectively. Detailed Implementation

[0076] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0077] Example 1

[0078] like Figure 1 , Figure 2 The illustrated embodiment is an Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel. The X52 pipeline steel is composed of carbon (C), manganese (Mn), phosphorus (P), sulfur (S), copper (Cu), nickel (Ni), chromium (Cr), molybdenum (Mo), hafnium (Hf), lanthanum (La), niobium (Nb), thallium (Ti), and iron (Fe). The mass percentages of each component in the X52 pipeline steel are as follows:

[0079] C: 0.1%, Mn: 1.33%, P: 0.015%, S: 0.025%, Cu: 0.25%, Ni: 0.18%, Cr: 0.14%, Mo: 0.1%, Hf: 0.0002%, La: 0.0003%, Nb: 0.02%, Ti: 0.038%, balance Fe.

[0080] A method for preparing Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel includes a laboratory heating furnace 1, a laboratory cooling furnace 2 located to the right of the heating furnace, and a laboratory feeding mechanism located above the heating furnace and the cooling furnace.

[0081] The heating furnace includes a heating furnace body 10 with an opening at the top, a left furnace door 11 and a right furnace door 12 on the heating furnace body, multiple heaters 15 on the inner wall of the heating furnace body, a heating cover plate 13 at the top of the heating furnace body, and a first temperature and pressure sensor 14 on the heating furnace body; the cooling furnace includes a cooling furnace body 20 with an opening at the top, a cooling furnace door 21 at the left end of the cooling furnace body, a cooling cover plate 22 at the top of the cooling furnace body, and a second temperature and pressure sensor 23 on the cooling furnace body; the lower end of the cooling furnace is connected to an external gas cylinder 5, and a first solenoid valve 50 is provided on the external gas cylinder;

[0082] It also includes a cooling circulation mechanism, which includes a gas pipe 41 connected to the cooling furnace at both ends, and several booster pumps 42 installed in the gas pipe for pressurizing the cooling gas; the cooling furnace is provided with several gas nozzles connected to the gas pipe, and an air-cooled motor 44 is connected to the gas pipe, and the air-cooled motor is connected to the right side of the cooling furnace body through a connecting pipe.

[0083] The feeding mechanism includes a fixed frame 30, two rollers 31 on the fixed frame, a conveyor belt 32 on the two rollers, a drive motor connected to the shaft of one of the rollers, an up-down adjuster 33 on the conveyor belt, and a hook 34 at the lower end of the up-down adjuster; it also includes a controller, which is electrically connected to the first solenoid valve, the air-cooled motor, the drive motor, the first temperature and pressure sensor, the second temperature and pressure sensor, each heater, and each booster pump.

[0084] The connecting pipe is replaced with a helium purification mechanism, which includes a vacuum pump 61, an adsorption filter 62, a compressor 63, a gas separator 64, a heat exchanger 65, and a recovery gas cylinder 66 connected sequentially through a gas guide pipe 60. The vacuum pump is connected to the right side wall of the cooling furnace, and the recovery gas cylinder is connected to the right side wall of the cooling furnace. A second solenoid valve 300 is installed on the gas guide pipe between the recovery gas cylinder and the cooling furnace. A third solenoid valve 301 is installed on the gas guide pipe between the heat exchanger and the recovery gas cylinder. The heat exchanger is connected to the air-cooled motor housing 303 of the air-cooled motor through the gas guide pipe. A fourth solenoid valve 302 is installed on the gas guide pipe between the heat exchanger and the air-cooled motor housing. The controller is electrically connected to the vacuum pump, the adsorption filter, the compressor, the gas separator, the heat exchanger, the second solenoid valve, the third solenoid valve, and the fourth solenoid valve, respectively.

[0085] The cooling furnace body is equipped with a circular vertical cylinder 7, which includes four arc-shaped plates 71 with a central angle of 90°. The bottom plate of the cooling furnace body is provided with four radially distributed slide rails 72. Each of the four arc-shaped plates is provided with a supporting vertical rod 73 at its lower end. The four supporting vertical rods are slidably connected to the four slide rails by sliders. The circular vertical cylinder is provided with evenly distributed mounting holes. Each gas nozzle is installed in each mounting hole. The rear of each gas nozzle is connected to a gas pipeline through a flexible hose.

[0086] The preparation method includes the following steps:

[0087] Step 1, Smelting:

[0088] Workers add carbon (C), manganese (Mn), phosphorus (P), sulfur (S), copper (Cu), nickel (Ni), chromium (Cr), molybdenum (Mo), hafnium (Hf), lanthanum (La), niobium (Nb), thallium (Ti), and iron (Fe) in a vacuum induction melting furnace according to the mass percentage for melting. Argon gas is blown throughout the melting process to prevent oxidation of the molten steel. After melting, the steel billet is cast into a steel billet.

[0089] Step 2, heating:

[0090] Workers put the steel billet into the heating furnace, control the heating of each heater, observe the temperature data detected by the first temperature sensor, and make the temperature in the heating furnace reach 1100℃-1150℃. They hold the temperature for more than 40 minutes and then take the steel billet out of the heating furnace.

[0091] Step 3, perforation:

[0092] Workers use a piercing machine to pierce holes in steel billets to obtain steel pipes;

[0093] The steel pipe is obtained by passing a mandrel through the center of the steel billet at a rotation speed of 55 r / min, a piercing rate of 0.7 m / min, an initial piercing temperature of 1100℃, and a final piercing temperature of 1000℃.

[0094] Step 4, Rolling:

[0095] Workers use a hot rolling mill to continuously hot roll the wall of the steel pipe;

[0096] The initial rolling temperature is 900℃, the final rolling temperature is 850℃, the cumulative reduction rate during the hot rolling stage is 65%, and the number of rolling passes is 4.

[0097] Step 5: The workers water-cool the steel pipe twice to obtain pipeline steel 8; the first water cooling temperature is 840℃, the second water cooling temperature is 520℃, and then the steel pipe is air-cooled to room temperature.

[0098] Step 6: The workers use a drilling machine to drill hook holes in the pipe wall at one end of the pipeline steel. The pipeline steel with the hook holes is then hung on the hooks. The height of the pipeline steel is changed by adjusting the up and down adjusters. The heating cover plate is removed, the left furnace door is opened, and the active motor is controlled by the controller. The conveyor belt drives the hooks to move to the right, transporting the pipeline steel into the heating furnace. The active motor is then stopped, the left furnace door is closed, and the heating cover plate is closed.

[0099] Step 7, perform the first conditioning treatment:

[0100] Step 7-1: The staff controls each heater to heat at a rate of 7℃ / min using the controller, observes the temperature data detected by the first temperature sensor, and makes the temperature inside the heating furnace reach 920℃, holds it at that temperature for 60 minutes, and then stops each heater in the heating furnace from working.

[0101] Step 7-2: The operator removes the heating and cooling covers, opens the right furnace door and the cooling furnace door, adjusts the height of the hook using the up-and-down adjuster, controls the drive motor to work, and the conveyor belt moves the hook to the right. The conveyor belt transports the pipeline steel to the center of the cooling furnace. The initial positions of the four arc-shaped plates are close to the inner wall of the cooling furnace. The operator pushes each arc-shaped plate towards the pipeline steel, so that the supporting vertical rod of each arc-shaped plate slides along the corresponding slide rail via the slider, so that the four arc-shaped plates move together to form a circular vertical cylinder structure, so that the gas outlets of each gas nozzle are evenly surrounding and facing the outside of the pipeline steel; the drive motor stops working, the right furnace door and the cooling furnace door are closed, and the heating and cooling covers are put on.

[0102] The controller opens the first solenoid valve, allowing helium to be introduced into the cooling furnace from an external gas cylinder. The pressure data detected by the second temperature and pressure sensor is observed to maintain the pressure inside the cooling furnace within the range of 1.5 MPa.

[0103] The operator controls the vacuum pump via a controller, causing the gas in the cooling furnace to pass through an adsorption filter to remove impurities. The compressor increases the gas pressure, allowing helium to pass through a gas separator. The purified helium is then cooled by a heat exchanger. The fourth solenoid valve opens, allowing the helium to be purified by the recovery and purification mechanism before entering the gas-cooled motor housing. The controller then operates the gas-cooled motor, which in turn pressurizes the various booster pumps, spraying the cooled helium through nozzles onto the pipeline steel for gas cooling until the temperature detected by the second temperature and pressure sensor drops to room temperature. At this point, the gas-cooled motor and booster pumps are shut down, and the fourth solenoid valve is closed. The third solenoid valve opens, controlling the vacuum pump to operate for 50 minutes, drawing the cooled and purified helium into the recovery gas cylinder before closing the third solenoid valve.

[0104] Step 7-3: The staff opens the cooling furnace door and the right furnace door, removes the heating cover and the cooling cover, pushes each arc plate along the track to slide each arc plate closer to the inner wall of the furnace, controls the active motor to work, and the conveyor belt drives the hook to move to the left to transport the pipeline steel to the middle position of the heating furnace, so that the active motor stops working and the right furnace door and heating cover are closed.

[0105] The controller controls each heater to heat at a rate of 5℃ / min. The temperature data detected by the first temperature sensor is observed. The temperature inside the heating furnace reaches 600℃ and is held for 120 minutes. Then, each heater stops working. The right furnace door is opened, the heating cover is removed, the drive motor is started, and the conveyor belt drives the hook to move to the right, transporting the pipeline steel to the space between the heating furnace and the cooling furnace. The right furnace door is closed, the heating cover is closed, and the pipeline steel is cooled to room temperature.

[0106] Step 8, perform the second conditioning process:

[0107] Step 8-1: The operator opens the right furnace door, removes the heating cover, and starts the drive motor. The conveyor belt moves the hook to the left, transporting the pipeline steel to the middle position of the heating furnace. The drive motor then stops, the right furnace door is closed, and the heating cover is replaced. The controller controls each heater to heat at a rate of 7℃ / min. The temperature data detected by the first temperature sensor is observed. The temperature inside the heating furnace reaches 910℃ and is held for 60 minutes. Then, all heaters in the heating furnace stop working.

[0108] Step 8-2: The worker removes the heating cover and cooling cover, opens the right furnace door and cooling furnace door, and starts the drive motor. The conveyor belt transports the pipeline steel to the center of the cooling furnace. The worker pushes each arc plate towards the pipeline steel, so that the supporting vertical rod of each arc plate slides along the corresponding slide rail via the slider. The four arc plates move together to form a circular vertical cylinder structure, so that the gas outlets of each gas nozzle are evenly surrounding and facing the outside of the pipeline steel. The drive motor stops working, the right furnace door and cooling furnace door are closed, and the heating cover and cooling cover are put back on.

[0109] The staff controlled the second solenoid valve to open, allowing helium from the recovered gas cylinder to fill the cooling furnace. They observed the gas pressure data detected by the second temperature and pressure sensor, maintained the gas pressure in the cooling furnace within the range of 1.5 MPa, and then closed the second solenoid valve.

[0110] The vacuum pump is started, and the controller opens the fourth solenoid valve, allowing helium gas to enter the gas-cooled motor housing after purification by the purification unit. The controller then controls the gas-cooled motor to operate, pressurizing each booster pump. The cooled helium gas is sprayed onto the pipeline steel through various gas nozzles to cool the pipeline steel until the temperature data detected by the second temperature and pressure sensor drops to room temperature. At this point, the gas-cooled motor and each booster pump are turned off, and the fourth solenoid valve is closed. The third solenoid valve is then opened, controlling the vacuum pump to operate for 50 minutes. After the cooled helium gas is drawn into the recovery gas cylinder, the third solenoid valve is closed.

[0111] Step 8-3, repeat step 7-3 once, the pipeline steel preparation process is complete.

[0112] Comparative example:

[0113] X52 pipeline steel is a steel for hydrogen-blended natural gas pipelines produced by a steel plant. Its chemical composition and mass percentage are the same as those in Example 1, except that rare earth elements Hf and La are not added. The performance tests are also the same as those in Example 1.

[0114] Slow strain rate tensile test (SSRT), fatigue crack propagation test (FCG), and fracture toughness test (J1C) were conducted on the Instron 8801 testing machine for Example 1 and the comparative example. The stress-strain curves of the X52 pipeline steel samples under 6.3 MPa H2 and 6.3 MPa N2 conditions were obtained, and the performance test results are shown in Tables 1 and 2; the ΔK-da / dN curves and their performance test results are shown in Table 3; and the Δa-J integral curves and their performance test results are shown in Table 4.

[0115] Table 1. Performance test results of Example 1 and Comparative Example under N2 environment.

[0116] Experimental materials Yield strength / MPa Tensile strength / MPa Elongation / % Example 528 616 19.6 Comparative Example 461 552 20.1

[0117] Table 2. Performance test results of Example 1 and Comparative Example in H2 environment

[0118] Experimental materials Yield strength / MPa Tensile strength / MPa Elongation / % Example 532 610 18.7 Comparative Example 456 551 18.0

[0119] Table 3 shows the fatigue crack propagation rate and acceleration factor of the comparative example and Example 1 under N2 and H2 environments at ΔK45 (da / dN value in H2 environment compared to da / dN value in N2 environment).

[0120] Example Comparative Example <![CDATA[6.3MpaN2]]> <![CDATA[4.6*10 -4 ]]> <![CDATA[4.1*10 -4 ]]> <![CDATA[6.3MpaH2]]> <![CDATA[4.3*10 -3 ]]> <![CDATA[5.4*10 -3 ]]> Accelerator 9.3 13.2

[0121] Table 4. Fracture toughness values ​​of Example 1 and the comparative example under N2 and H2 environments.

[0122] Example Comparative Example <![CDATA[6.3MpaN2]]> <![CDATA[216.8KJ / m 2 ]]> <![CDATA[226.7KJ / m 2 ]]> <![CDATA[6.3MpaH2]]> <![CDATA[72.8KJ / m 2 ]]> <![CDATA[63.0KJ / m 2 ]]>

[0123] The metallographic structure of the pipeline steel prepared in Example 1 was observed using an optical microscope. The results are as follows: the grain size was reduced to a certain extent, and the grain size remained at about 20 μm.

[0124] The reason for the reduction in grain size is: large deformation during rolling, continuous tempering, and alloying elements hindering grain boundary migration.

[0125] Transmission electron microscopy (TEM) revealed the following characteristics of the precipitated phases: a large number of uniformly dispersed (Nb,Ti)C particles with a diameter of 5-10 nm precipitated in the martensitic matrix. These precipitates pin dislocations, increasing the resistance to dislocation slip and thus enhancing the strength of the pipeline steel. Furthermore, the interface between the precipitates and the matrix exhibits a semi-coherent state.

[0126] Previous studies have shown that fully coherent precipitates have a hydrogen capture energy of only 1.7-4.0 kJ / mol, which is insufficient to capture hydrogen atoms; non-coherent precipitates have a hydrogen capture energy (>90 kJ / mol), and due to their high potential barriers, they are almost impossible to fill with hydrogen at room temperature. The semi-coherent precipitate in Example 1 of this invention has a hydrogen capture energy of 30-70 kJ / mol, which can irreversibly capture a large number of hydrogen atoms at room temperature, exhibiting excellent resistance to hydrogen embrittlement.

[0127] A comparison of the test results of Example 1 and the comparative example under slow strain rate tensile tests, fatigue crack propagation tests, and fracture toughness tests in 6.3 MPa H2 and 6.3 MPa N2 environments shows that:

[0128] The pipeline steel produced in Example 1 exhibits significantly higher strength than the comparative steel, without a noticeable decrease in ductility or toughness. Furthermore, while the pipeline steel of Example 1 shows increased strength, its hydrogen embrittlement sensitivity is significantly reduced. Therefore, it can be concluded that the X52 pipeline steel of the present invention, while increasing strength, significantly reduces hydrogen embrittlement sensitivity, demonstrating excellent comprehensive mechanical properties.

[0129] Tissue observation and performance testing:

[0130] The pipeline steel sample was mechanically ground with #400-#2000 silicon carbide sandpaper, followed by polishing with 1μm diamond suspension. Subsequently, the sample was etched in 5% nitric acid ethanol solution for 10 seconds, rinsed with anhydrous ethanol, and dried with a hair dryer. Its metallographic structure was then observed under an optical microscope. Figure 3 As shown.

[0131] from Figure 3 As can be seen, the grain size of the X52 pipeline steel of this invention is reduced to a certain extent, remaining at around 20 μm. This is mainly due to the large deformation during rolling, continuous tempering, and the hindering of grain boundary migration by alloying elements.

[0132] Target finished samples of 10mm × 10mm were prepared by wire cutting. The samples were progressively ground to 50μm–55μm using different grades of sandpaper, and then punched into 3mm diameter discs using a punching machine. These discs were then further ground to 40μm–45μm using 3000# sandpaper. Thinning and perforation were performed using an electrolytic double-jet method with a mixed solution of 5% perchloric acid and 95% glacial acetic acid. Finally, transmission electron microscopy was used to analyze the distribution and size of (Nb,Ti)C precipitates on the heat-treated samples. Figure 4 As shown;

[0133] from Figure 4 It can be seen that a large number of uniformly dispersed (Nb,Ti)C particles with a diameter of 5-10 nm are precipitated in the martensitic matrix. The nanoprecipitates can pin dislocations, which increases the resistance to dislocation slip and thus increases the strength of the steel.

[0134] HRTEM is used to observe and analyze the orientation relationship between the precipitated phase and the matrix at the atomic scale, such as Figure 5 As shown.

[0135] from Figure 5 As can be seen, the interface between the (Nb,Ti)C particle precipitates with a diameter of 5-10 nm and the matrix is ​​semi-coherent. The hydrogen capture energy of the semi-coherent precipitates is 30-70 kJ / mol, which can irreversibly capture a large number of hydrogen atoms at room temperature, resulting in slower diffusion and less aggregation of hydrogen atoms in the pipeline steel, thus giving the pipeline steel excellent resistance to hydrogen embrittlement.

[0136] Slow strain rate tensile tests (SSRT) were conducted on Example 1 and the comparative example on an Instron 8801 (100KN) testing machine. The results are as follows: Figure 6 As shown;

[0137] from Figure 6As can be seen, in N2, the strength of Example 1 is significantly higher than that of the comparative example, while the elongation decreases very little; in H2, the elongation of Example 1 is significantly higher than that of the comparative example, that is, the hydrogen embrittlement sensitivity of Example 1 is significantly less than that of the comparative example.

[0138] Fatigue crack propagation test (FCG), results as follows Figure 7 As shown;

[0139] from Figure 7 As can be seen from the data: In N2, because the elongation of Example 1 is slightly less than that of the comparative example, the crack passivation degree of the Example 1 sample is less than that of the comparative example, so the crack propagation rate is greater than that of the comparative example. In H2, however, the crack propagation rate of Example 1 is less than that of the comparative example, indicating that the degree of continuous propagation of hydrogen-induced cracks in Example 1 is less than that in the comparative example, and the hydrogen embrittlement sensitivity of Example 1 is significantly less than that in the comparative example.

[0140] Fracture toughness test (J1C), results are as follows Figure 8 As shown;

[0141] from Figure 8 As can be seen from the data: In N2, because the elongation of Example 1 is less than that of the comparative example, the energy absorbed by Example 1 during the fracture process is lower than that of the comparative example, and the fracture toughness value of Example 1 is lower than that of the comparative example. In H2, however, the fracture toughness of Example 1 is higher than that of the comparative example, meaning that the fracture of the sample of Example 1 requires the absorption of more energy than that of the comparative example, and the hydrogen embrittlement sensitivity of Example 1 is significantly lower than that of the comparative example.

[0142] Before the experiment, the environmental chamber was first evacuated to a vacuum level of approximately 0.1 Pa. Then, argon gas was introduced for purging, followed by evacuation to a final vacuum level of 0.1 Pa, and then 6.3 MPa H2 or N2 was introduced. The experiment was conducted only after the chamber pressure stabilized. The tensile rate for the slow strain rate tensile test was 10... -5 s -1 The fatigue crack propagation was tested using a constant ΔP test with a ΔP value of 6.5 kN; the fracture toughness test was conducted using displacement control with a displacement loading rate of 0.12 mm / min.

[0143] The above test results show that the X52 pipeline of the present invention exhibits excellent resistance to hydrogen embrittlement in a hydrogen environment. In a hydrogen environment, the elongation of the X52 pipeline steel of the present invention can reach 18.7%, and the tensile strength reaches 610 MPa, meeting the requirements for high strength and excellent resistance to hydrogen embrittlement. This indicates that the present invention, while improving resistance to hydrogen embrittlement, also meets the mechanical performance requirements.

[0144] Example 2

[0145] In Example 2, the mass percentages of each component in the X52 pipeline steel are as follows: C: 0.08%, Mn: 1.20%, P: 0.01%, S: 0.02%, Cu: 0.20%, Ni: 0.12%, Cr: 0.10%, Mo: 0.08%, Hf: 0.0001%, La: 0.0001%, Nb: 0.018%, Ti: 0.035%, with the balance being Fe.

[0146] The other structural and methodological parts in Example 2 are the same as those in Example 1.

[0147] Example 3

[0148] In Example 3, the mass percentages of each component in the X52 pipeline steel are as follows: C: 0.28%, Mn: 1.4%, P: 0.03%, S: 0.03%, Cu: 0.50%, Ni: 0.50%, Cr: 0.30%, Mo: 0.15%, Hf: 0.0003%, La: 0.0003%, Nb: 0.036%, Ti: 0.05%, with the balance being Fe.

[0149] The other structural and methodological parts in Example 3 are the same as those in Example 1.

[0150] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel, characterized in that, The mass percentages of each component in X52 pipeline steel are as follows: 0.08%≤C≤0.28%, 1.20%≤Mn≤1.40%, 0.01%≤P≤0.03%, 0.02%≤S≤0.03%, 0.20%≤Cu≤0.50%, 0.12%≤Ni≤0.50%, 0.10%≤Cr≤0.30%, 0.08%≤Mo≤0.15%, 0.0001%≤Hf≤0.0003%, 0.0001%≤La≤0.0003%, 0.018%≤Nb≤0.036%, 0. 0.35%≤Ti≤0.05%, with the balance being Fe; also includes a heating furnace (1), a cooling furnace (2) located on the right side of the heating furnace, and a feeding mechanism located above the heating furnace and the cooling furnace; the heating furnace includes a heating furnace body (10) with an opening at the top, a left furnace door (11) and a right furnace door (12) located on the heating furnace body, several heaters (15) located on the inner wall of the heating furnace body, a heating cover plate (13) located at the top of the heating furnace body, and a first temperature and pressure sensor (14) located on the heating furnace body; the cooling furnace includes a cooling furnace body (20) with an opening at the top, and a feeding mechanism located above the heating furnace and the cooling furnace. The furnace body includes a cooling furnace door (21) at the left end, a cooling cover plate (22) at the upper end of the cooling furnace body, and a second temperature and pressure sensor (23) on the cooling furnace body. The lower end of the cooling furnace is connected to an external gas cylinder (5), and the external gas cylinder is equipped with a first solenoid valve (50). The furnace body also includes a cooling circulation mechanism, which includes a gas pipe (41) connected to the cooling furnace at both ends, and several booster pumps (42) in the gas pipe for pressurizing the cooling gas. The cooling furnace is equipped with several gas nozzles connected to the gas pipe, and the gas pipe is equipped with an air-cooled motor (44). The air-cooled motor is connected to the right side of the cooling furnace body via a connecting pipe; the feeding mechanism includes a fixed frame (30), two rollers (31) on the fixed frame, a conveyor belt (32) on the two rollers, an active motor connected to the shaft of one roller, an up-and-down adjuster (33) on the conveyor belt, and a hook (34) at the lower end of the up-and-down adjuster; it also includes a controller, which is electrically connected to the first solenoid valve, the air-cooled motor, the active motor, the first temperature and pressure sensor, the second temperature and pressure sensor, each heater, and each booster pump; the preparation method includes the following steps: Step 1, Smelting: Workers add carbon (C), manganese (Mn), phosphorus (P), sulfur (S), copper (Cu), nickel (Ni), chromium (Cr), molybdenum (Mo), hafnium (Hf), lanthanum (La), niobium (Nb), thallium (Ti), and iron (Fe) in a vacuum induction melting furnace according to the mass percentage for melting. Argon gas is blown throughout the melting process to prevent oxidation of the molten steel. After melting, the steel billet is cast into a steel billet. Step 2, heating: Workers put the steel billet into the heating furnace, control the heating of each heater, observe the temperature data detected by the first temperature sensor, and make the temperature in the heating furnace reach 1100℃-1150℃. They hold the temperature for more than 40 minutes and then take the steel billet out of the heating furnace. Step 3, perforation: Workers use a piercing machine to pierce holes in steel billets to obtain steel pipes; Step 4, Rolling: Workers use a hot rolling mill to continuously hot roll the wall of the steel pipe; Step 5: The workers water-cool the steel pipe twice to obtain pipeline steel (8); the first water cooling temperature is 810℃-850℃, the second water cooling temperature is 500℃-540℃, and then the steel pipe is air-cooled to room temperature; Step 6: The workers use a drilling machine to drill hook holes in the pipe wall at one end of the pipeline steel. The pipeline steel with the hook holes is then hung on the hooks. The height of the pipeline steel is changed by adjusting the up and down adjusters. The heating cover plate is removed, the left furnace door is opened, and the active motor is controlled by the controller. The conveyor belt drives the hooks to move to the right, transporting the pipeline steel into the heating furnace. The active motor is then stopped, the left furnace door is closed, and the heating cover plate is closed. Step 7, perform the first conditioning treatment: Step 7-1: The staff controls each heater to heat at a rate of 6℃ / min-8℃ / min through the controller, observes the temperature data detected by the first temperature sensor, and makes the temperature inside the heating furnace reach 900℃-930℃, holds the temperature for 50min-70min, and then stops each heater in the heating furnace. Step 7-2: The staff removes the heating cover plate and cooling cover plate, opens the right furnace door and cooling furnace door, adjusts the height of the hook using the up and down adjuster, controls the active motor to work, and the conveyor belt drives the hook to move to the right. The conveyor belt transports the pipeline steel to the center of the cooling furnace, stops the active motor, closes the right furnace door and cooling furnace door, and covers the heating cover plate and cooling cover plate. The controller opens the first solenoid valve, allowing helium to be introduced into the cooling furnace from an external gas cylinder. The pressure data detected by the second temperature and pressure sensor is observed to maintain the pressure inside the cooling furnace within the range of 1.2 MPa - 1.8 MPa. The controller controls the operation of the air-cooled motor and the pressurization of each booster pump. The cooled helium gas is sprayed onto the pipeline steel through each gas nozzle to cool the pipeline steel until the temperature data detected by the second temperature and pressure sensor drops to room temperature, at which point the air-cooled motor and each booster pump are turned off. Step 7-3: The staff opens the cooling furnace door and the right furnace door, removes the heating cover and the cooling cover, controls the active motor to work, and the conveyor belt drives the hook to move to the left, transporting the pipeline steel to the middle position of the heating furnace, so that the active motor stops working and the right furnace door and the heating cover are closed. The controller controls each heater to heat at a rate of 5℃ / min. The temperature data detected by the first temperature sensor is observed, and the temperature inside the heating furnace is brought to 590℃-610℃. The temperature is held for 100min-140min, and then each heater is stopped. The right furnace door is opened, the heating cover is removed, the drive motor is started, and the conveyor belt drives the hook to move to the right, transporting the pipeline steel to the space between the heating furnace and the cooling furnace. The drive motor is stopped, the right furnace door is closed, the heating cover is closed, and the pipeline steel is cooled to room temperature. Step 8, perform the second conditioning process: Step 8-1: The operator opens the right furnace door, removes the heating cover, and starts the drive motor. The conveyor belt moves the hook to the left, transporting the pipeline steel to the middle position of the heating furnace. The drive motor then stops, the right furnace door is closed, and the heating cover is replaced. The controller controls each heater to heat at a rate of 6℃ / min-8℃ / min. The temperature data detected by the first temperature sensor is observed, and the temperature inside the heating furnace is brought to 900℃-930℃. The temperature is maintained for 50min-70min, and then each heater in the heating furnace stops working. Step 8-2: The staff removes the heating cover plate and cooling cover plate, opens the right furnace door and cooling furnace door, starts the drive motor, and the conveyor belt transports the pipeline steel to the center of the cooling furnace. The drive motor stops working, the right furnace door and cooling furnace door are closed, and the heating cover plate and cooling cover plate are put back on. The controller controls the operation of the air-cooled motor and the pressurization of each booster pump. The cooled helium gas is sprayed onto the pipeline steel through each gas nozzle to cool the pipeline steel until the temperature data detected by the second temperature and pressure sensor drops to room temperature, causing the active motor to stop working and shutting down the air-cooled motor and each booster pump. Step 8-3, repeat step 7-3 once, the pipeline steel preparation process is complete.

2. The method for preparing Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel according to claim 1, characterized in that, The connecting pipe is replaced by a helium purification mechanism, which includes a vacuum pump (61), an adsorption filter (62), a compressor (63), a gas separator (64), a heat exchanger (65), and a recovery gas cylinder (66) connected in sequence through a gas guide pipe (60). The vacuum pump is connected to the right side wall of the cooling furnace, and the recovery gas cylinder is connected to the right side wall of the cooling furnace. A second solenoid valve (300) is provided on the gas guide pipe between the recovery gas cylinder and the cooling furnace. A third solenoid valve (301) is provided on the gas guide pipe between the heat exchanger and the recovery gas cylinder. The heat exchanger is connected to the air-cooled motor housing (303) of the air-cooled motor through the gas guide pipe. A fourth solenoid valve (302) is provided on the gas guide pipe between the heat exchanger and the air-cooled motor housing. The controller is electrically connected to the vacuum pump, the adsorption filter, the compressor, the gas separator, the heat exchanger, the second solenoid valve, the third solenoid valve, and the fourth solenoid valve, respectively.

3. The method for preparing Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel according to claim 1 or 2, characterized in that, The cooling furnace body is provided with a circular vertical cylinder (7), which includes four arc-shaped plates (71) with a central angle of 90°. The bottom plate of the cooling furnace body is provided with four radially distributed slide rails (72). The lower end of each of the four arc-shaped plates is provided with a supporting vertical rod (73). The four supporting vertical rods are slidably connected to the four slide rails by sliders. The circular vertical cylinder is provided with evenly distributed mounting holes. Each gas nozzle is installed on each mounting hole. The rear of each gas nozzle is connected to a gas pipeline through a hose.

4. The method for preparing Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel according to claim 1, characterized in that, The connecting pipe is replaced with a helium purification mechanism, which includes a vacuum pump, an adsorption filter, a compressor, a gas separator, a heat exchanger, and a recovery gas cylinder connected sequentially via a gas guide pipe. The vacuum pump is connected to the right side wall of the cooling furnace, and the recovery gas cylinder is connected to the right side wall of the cooling furnace. A second solenoid valve is installed on the gas guide pipe between the recovery gas cylinder and the cooling furnace. A third solenoid valve is installed on the gas guide pipe between the heat exchanger and the recovery gas cylinder. The heat exchanger is connected to the air-cooled motor housing of the air-cooled motor via a gas guide pipe. A fourth solenoid valve is installed on the gas guide pipe between the heat exchanger and the air-cooled motor housing. The controller is electrically connected to the vacuum pump, adsorption filter, compressor, gas separator, heat exchanger, second solenoid valve, third solenoid valve, and fourth solenoid valve, respectively. The process also includes the following steps: In step 7-2, the controller controls the air-cooled motor to operate and each booster pump to pressurize. Cooled helium is sprayed onto the pipeline steel through each gas nozzle to cool the pipeline steel until the temperature data detected by the second temperature and pressure sensor drops to room temperature. The air-cooled motor and each booster pump are then shut down. The following steps replace the previous steps: The operator controls the vacuum pump via a controller, causing the gas in the cooling furnace to pass through an adsorption filter to remove impurities. The compressor increases the gas pressure, allowing helium to pass through a gas separator. The purified helium is then cooled by a heat exchanger. The fourth solenoid valve opens, allowing the helium to be purified by the recovery and purification mechanism before entering the gas-cooled motor housing. The controller then operates the gas-cooled motor, which in turn pressurizes the various booster pumps, spraying the cooled helium through nozzles onto the pipeline steel for gas cooling until the temperature detected by the second temperature and pressure sensor drops to room temperature. At this point, the gas-cooled motor and booster pumps are shut down, and the fourth solenoid valve is closed. The third solenoid valve opens, controlling the vacuum pump to operate for 30-60 minutes, drawing the cooled and purified helium into a recovery gas cylinder. Finally, the third solenoid valve closes. In step 8-2, the controller controls the operation of the air-cooled motor and the pressurization of each booster pump. The cooled helium gas is sprayed onto the pipeline steel through each gas nozzle to cool the pipeline steel until the temperature data detected by the second temperature and pressure sensor drops to room temperature. Then, the air-cooled motor and each booster pump are turned off and replaced by the following step: The staff controlled the second solenoid valve to open, allowing helium from the recovered gas cylinder to fill the cooling furnace. They observed the gas pressure data detected by the second temperature and pressure sensor, maintained the gas pressure in the cooling furnace within the range of 1.2 MPa - 1.8 MPa, and then closed the second solenoid valve. The vacuum pump is started, and the controller opens the fourth solenoid valve, allowing helium gas to enter the gas-cooled motor housing after purification by the purification unit. The controller then controls the gas-cooled motor to operate, pressurizing each booster pump. The cooled helium gas is sprayed onto the pipeline steel through various gas nozzles to cool the pipeline steel until the temperature data detected by the second temperature and pressure sensor drops to room temperature. At this point, the gas-cooled motor and each booster pump are turned off, and the fourth solenoid valve is closed. The third solenoid valve is then opened, controlling the vacuum pump to operate for 30-60 minutes. After the cooled helium gas is drawn into the recovery gas cylinder, the third solenoid valve is closed.

5. The method for preparing Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel according to claim 1, characterized in that, The cooling furnace body has a circular vertical cylinder, which includes four arc-shaped plates with a central angle of 90°. The bottom plate of the cooling furnace body has four radially distributed slide rails. The lower end of each of the four arc-shaped plates is provided with a supporting vertical rod. The four supporting vertical rods are slidably connected to the four slide rails by sliders. The circular vertical cylinder has evenly distributed mounting holes. Each gas nozzle is installed in each mounting hole. The rear of each gas nozzle is connected to a gas pipeline through a hose. After the conveyor belts in steps 7-2 and 8-2 transport the pipeline steel to the center of the cooling furnace, the following steps are included: The initial positions of the four arc-shaped plates are close to the inner wall of the cooling furnace. The workers push each arc-shaped plate towards the pipeline steel, so that the supporting vertical rod of each arc-shaped plate slides along the corresponding slide rail through the slider, so that the four arc-shaped plates move together to form a circular vertical cylinder structure, so that the gas outlets of each gas nozzle are evenly surrounded and face the outside of the pipeline steel. After removing the heating and cooling covers in step 7-3, the following steps are included: Workers pushed each curved plate along the track, gradually bringing each plate closer to the inner wall of the furnace.

6. The method for preparing Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel according to claim 1, characterized in that, Step 3 includes the following detailed steps: The steel pipe is obtained by passing a mandrel through the center of the billet at a rotation speed of 50-60 r / min, a piercing rate of 0.6-0.8 m / min, an initial piercing temperature of 1050-1110℃, and a final piercing temperature of 980-1020℃.

7. The method for preparing Nb-Ti microalloyed hydrogen embrittlement resistant pipeline steel according to claim 1, 4, 5, or 6, characterized in that, In step 4, the initial rolling temperature is 870℃-910℃, the final rolling temperature is 830℃-860℃, the cumulative reduction rate during the hot rolling stage is 62%-67%, and the number of rolling passes is 3-5.

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