Directional solidification high-boron high-speed steel jetting nozzle for oilfield hydraulic and preparation method thereof

Abstract

The application discloses an oilfield hydraulic directional solidification high-boron high-speed steel jet nozzle and a preparation method thereof, and belongs to the technical field of oilfield exploitation equipment. The preparation method comprises the following steps: vacuum smelting high-boron high-speed steel molten steel by using raw materials such as electrically pure iron and micro-carbon chromium iron according to a specific mass fraction ratio; after desulfurization and temperature control of the molten steel by using rare earth aluminum, the directional solidification treatment is carried out to obtain a cast blank; the cast blank is subjected to mechanical processing, austenitizing quenching + tempering heat treatment and fine polishing treatment to obtain a finished product. The finished product comprises a metal matrix and a directional arrangement (Fe, Cr) 2B boride hard phase, the alloy composition is precisely controllable, the hardness is 58.5-64.5 HRC, and the surface roughness is 0.25-0.40 microns. The application takes into account low cost and high performance, solves the problems of poor wear resistance, high cost and large brittleness of the traditional nozzle, and remarkably improves the service life, and is suitable for the working condition of oilfield sand-containing high-pressure hydraulic jetting.

Description

Technical Field

[0001] This invention belongs to the technical field of oilfield extraction equipment, specifically relating to a directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications and its preparation method. Background Technology

[0002] In the field of oilfield development, the wear-resistant nozzles of hydraulic jetting tools are important vulnerable components that need to withstand the micro-cutting damage of high-pressure jets containing sand. Their service life and operating costs directly determine the working efficiency of hydraulic jetting tools.

[0003] Traditional spraying tools are typically made of the following three materials: High-performance wear-resistant nozzles adopt a composite structure of steel matrix + cemented carbide nozzle, but cemented carbide is expensive, brittle and prone to failure, and there is a serious risk of stress cracking at the steel / cemented carbide interface. Although ordinary steel nozzles have lower production costs, they lack wear resistance and have a service life of less than 200 hours. Although traditional high-speed steel nozzles have high hardness, their production process is complex and they contain a high amount of precious metals (such as Mo, W, V, etc.), resulting in significantly higher production costs. Furthermore, the uneven distribution of carbides in this type of alloy leads to poor toughness and fatigue resistance, making it difficult to guarantee the service safety of the nozzles.

[0004] High-boron high-speed steel replaces carbon (C) with boron (B) and replaces the hard carbide phase with borides, which have higher hardness and stability. This allows for flexible control of the alloy's metallic matrix and hard phase while significantly reducing the amount of precious metals added, thus lowering the production cost of high-speed steel. Consequently, high-boron high-speed steel balances production cost and reliable service performance under various wear and tear conditions. Micro-cutting wear caused by sand grain splashing on the tool body is the main cause of tool failure. However, existing tools made of the aforementioned materials have a series of service shortcomings. Therefore, it is necessary to develop new material structures that combine high wear resistance, low cost, and impact resistance. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a directionally solidified high-boron high-speed steel jet nozzle for oilfield hydraulic applications and its preparation method. This invention uses a low-cost production process to obtain high-boron high-speed steel with Cr-toughened Fe2B hard phase directionally arranged and high-density fine second-phase particles. This solves the technical problem of existing oilfield hydraulic jet nozzles where it is difficult to balance wear resistance, toughness, and production cost, significantly improving the cost-effectiveness of oilfield hydraulic jet tools and providing a new approach for the application of high-boron high-speed steel in the field of oilfield development.

[0006] The present invention adopts the following technical solution: A method for preparing a directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications includes the following steps: S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferromolybdenum, pig iron, ferromanganese, and ferrosilicon as raw materials, vacuum smelting is carried out to obtain high-boron high-speed steel molten steel. S2. The high-boron high-speed steel molten steel obtained in step S1 is subjected to temperature control treatment, and then transferred to a directional solidification device for directional solidification treatment to obtain a cast billet with directional solidification structure. S3. The as-cast billet obtained in step S2 is subjected to machining, austenitizing quenching and tempering heat treatment in sequence to obtain a directionally solidified high-boron high-speed steel jet nozzle for oilfield hydraulic applications.

[0007] Preferably, in step S1, the raw materials, by mass fraction, include: 62.069%~70.700% electrical pure iron, 9.509%~11.175% micro-carbon ferrochrome, 4.388%~4.938% ferrotungsten, 1.736%~2.463% ferromolybdenum, 9.239%~11.127% ferroboron, 3.397%~7.405% pig iron, 0.550%~0.700% ferromanganese, and 0.096%~0.481% ferrosilicon.

[0008] Preferably, in step S1, the vacuum melting specifically includes: First, electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferromolybdenum, pig iron, ferromanganese, and ferrosilicon are melted into molten steel at 1550~1580℃; The molten steel is transferred to a ladle for hot-scalding treatment. Then, ferroboron that has been held at 300℃ for 40-60 minutes is added and the mixture is remelted in the furnace to raise the temperature of the molten steel to 1500-1540℃ and hold it thereafter to obtain high-boron high-speed steel.

[0009] Preferably, in step S2, the temperature control process includes: Rare earth aluminum, accounting for 0.008%~0.012% of the steel mass, is added to the molten steel for desulfurization treatment, and the temperature of the molten steel is controlled to drop to 1350~1400℃.

[0010] Preferably, in step S2, the process parameters for the directional solidification treatment are: The solidification interface temperature gradient is 100~200K / cm, and the pulling rate is 3~8mm / min.

[0011] Preferably, in step S3, the austenitizing quenching and tempering heat treatment specifically includes: The machined workpiece is heated to 1040-1110℃ under vacuum conditions at a rate of 10-20℃ / min, held for 60-120min, and then oil quenched. The quenched workpiece is tempered under vacuum conditions at a temperature of 525~605℃ for 55~65 minutes. The tempering process is repeated at least 3 times.

[0012] Preferably, in step S3, after the tempering heat treatment, the inner wall of the flow channel of the spray nozzle is further subjected to surface polishing treatment. The polishing treatment uses a diamond grinding wheel, the polishing medium is 10 vol.% water-based 2.5 μm SiO2 suspension, and the polishing time is 120~180 s.

[0013] Another technical solution of the present invention is a directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications, characterized in that it is prepared by the aforementioned preparation method. The jet nozzle comprises a metal matrix and a boride hard phase distributed on the matrix. By weight percentage, the alloy composition is C: 0.21%~0.37%, B: 1.76%~2.12%, Cr: 5.42%~6.37%, Mo: 1.05%~1.49%, W: 3.51%~3.95%, Mn: 0.44%~0.56%, Si: 0.40%~0.60%, with the remainder being Fe and unavoidable trace impurities.

[0014] Preferably, the hardness of the spray nozzle is 58.5~64.5HRC, and the surface roughness Ra of the inner wall of its flow channel is 0.25~0.40μm; the microstructure of the spray nozzle includes a tempered martensite matrix and a (Fe,Cr)2B boride hard phase oriented on the matrix.

[0015] Preferably, the directional solidification direction of the spray nozzle is perpendicular to the direction of the inner wall of the nozzle.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: A method for preparing directional solidified high-boron high-speed steel jet nozzles for oilfield hydraulic applications is disclosed. The method employs vacuum induction melting to smelt molten high-boron high-speed steel, avoiding the introduction of impurities and raw material loss, thus improving the accuracy of the alloy's chemical composition and performance stability. The method utilizes directional solidification pulling to prepare the as-cast high-boron high-speed steel billet, allowing for a wide range of adjustments to directional solidification parameters. This enables the control of the alloy's microstructure according to service performance requirements, resulting in workpieces with excellent service performance in specific directions. The method employs austenitization followed by tempering heat treatment of the as-cast directional solidified high-boron high-speed steel, which passivates the sharp corners of the boride hard phase skeleton and obtains a tempered martensitic matrix with abundant dispersed precipitates. This significantly improves the abrasive wear resistance, bending strength, and fatigue resistance of the directional solidified high-boron high-speed steel oilfield hydraulic jetting tool. The core of this invention lies in the alloy composition design that facilitates the formation of a directional solidification hard phase texture, the smelting of high-boron high-speed steel molten steel, the directional solidification texture control technology, and the directional solidification high-boron high-speed steel hardening and toughening heat treatment technology.

[0017] Furthermore, the Cr content in the alloy is 5.42%~6.37%. At this content, the boride hard phase of the high-boron high-speed steel is a tetragonal (Fe,Cr)₂B structure, which can be oriented along the direction of solidification. <002> Directional growth yields a rod-shaped, oriented boride texture, significantly improving the strength and wear resistance of the workpiece at the interface perpendicular to the solidification direction. The total content of Mo and W elements is controlled below 5%, significantly reducing the raw material production cost of high-boron high-speed steel. Some elements dissolve in the hard phase of the boride, further improving the hardness and toughness of the boride, while elements dissolved in the metal matrix enhance the alloy's hardenability, helping to reduce heat treatment costs. The C element content is controlled between 0.21% and 0.37%, allowing for the acquisition of a low-carbon tempered martensitic structure after heat treatment. Its combination of high hardness and toughness further improves the service safety of the workpiece.

[0018] Furthermore, during the vacuum melting process, the melting temperature of ferroboron before its addition is 1540~1580℃, which is higher than the melting point of pure iron (1538℃). This allows various raw materials to melt rapidly, ensuring that the molten steel is fully stirred and melted by the thermal flow, thereby improving the homogeneity and cleanliness of the melt. Preheating the ferroboron at 300℃ for 40~60 minutes can improve the yield of boron.

[0019] Furthermore, in directional solidification, controlling the temperature gradient at the solidification interface and the pulling speed can control the solidification rate of high-boron high-speed steel, thereby enabling the regulation of directional microstructure parameters (such as the primary metal matrix grain size and the interlamellar spacing of eutectic borides) of alloys with the same composition, and thus enabling the regulation of the service performance of directionally solidified high-boron high-speed steel.

[0020] Furthermore, austenitization is performed at 1040~1110℃ for 60~120min, which completely transforms the high-boron high-speed steel metal matrix into austenite and causes partial dissolution of carbides and borides around the matrix, thereby improving the hardness and toughness of the high-boron high-speed steel workpiece. The tempering temperature is set to 525~605℃, and the workpiece is cooled to room temperature in the furnace and tempered three times. This effectively releases the internal stress generated during quenching, promotes the tempering precipitation hardening effect of hard fine second-phase particles such as M7(C,B)3, M6(C,B), and M6(C,B) on the tempered martensite matrix, and improves the stability of the alloy structure, especially the tempered martensite and the precipitated fine second-phase particles, thereby improving the service performance stability and service safety of the workpiece.

[0021] A directional solidification high-boron high-speed steel injection nozzle for oilfield hydraulic applications features a compositional and structural design that combines high hardness (boride hard phase) with good toughness (metal matrix), solving the problems of high brittleness in traditional cemented carbide, poor wear resistance in ordinary steel, and high cost in traditional high-speed steel. Precise definition of the composition range ensures stable and controllable product performance, avoiding performance fluctuations caused by compositional deviations, and providing structural and compositional guarantees for reliable service in sand-laden, high-pressure environments in oilfields.

[0022] Furthermore, the hardness of 58.5~64.5 HRC and the surface roughness of 0.25~0.40 μm precisely match the service requirements of hydraulic jetting in oilfields. The directionally arranged (Fe,Cr)₂B boride and the tempered martensitic matrix work synergistically to achieve a balance between wear resistance and impact resistance. Compared with existing products, this combination of performance parameters solves the problems of insufficient hardness, poor wear resistance, or insufficient toughness leading to easy breakage in traditional nozzles, ensuring long-term stable operation of the nozzle in high-pressure jet environments containing sand, significantly improving service life and cost-effectiveness.

[0023] Furthermore, the directional solidification direction is defined as perpendicular to the nozzle's inner wall, aligning the hard phase along the direction of erosion force to form targeted protection. This design allows the nozzle's inner wall to directly resist the micro-cutting and erosion of sand particles, solving the problems of disordered hard phase arrangement and insufficient erosion resistance in traditional products. The optimized directional solidification direction further enhances wear resistance, significantly reducing the nozzle's wear rate under high-pressure, sand-containing conditions, further extending its service life and improving its efficiency.

[0024] In summary, the directional solidification high-boron high-speed steel oilfield hydraulic jetting tool manufactured using a combination of vacuum melting, directional solidification, and heat treatment processes in this invention possesses a tempered martensite-(Fe,Cr)₂B dual-phase columnar crystal structure. Furthermore, the tempered martensite contains a high density of tempered hard precipitates, which significantly improves the service life and performance of the oilfield hydraulic jetting tool, resulting in a more cost-effectiveness ratio compared to existing oilfield hydraulic jetting tools.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the following description of the relative embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a manufacturing process diagram of the present invention; Figure 2 Schematic diagram of the oilfield hydraulic jetting tool of the present invention; Figure 3 SEM image of the heat-treated, directionally solidified high-boron high-speed steel obtained in Example 1; Figure 4 These are photographs of the directional solidification high boron high-speed steel oilfield hydraulic jet nozzle and the cemented carbide oilfield hydraulic jet nozzle after 1800 hours of service under the test conditions of Example 1. (a) is the directional solidification high boron high-speed steel oilfield hydraulic jet nozzle, and (b) is the cemented carbide oilfield hydraulic jet nozzle. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0030] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0031] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0032] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0033] In this invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is simply an abbreviation of these numerical combinations.

[0034] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0035] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0036] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0037] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0038] This invention provides a directionally solidified high-boron high-speed steel jet nozzle for oilfield hydraulic applications and its preparation method. It relates to a wear-resistant material processing technology based on directionally solidified high-boron high-speed steel, which obtains high-boron high-speed steel with Cr-toughened Fe2B hard phase directionally arranged and high-density fine second-phase particles through a low-cost production process. This significantly improves the cost-effectiveness of oilfield hydraulic jetting tools and provides a new approach for the application of high-boron high-speed steel in the field of oilfield development.

[0039] Please see Figure 1 This invention discloses a method for preparing a directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications. The method combines vacuum induction melting, directional solidification, and heat treatment to obtain an oilfield hydraulic jetting tool with uniform composition, clearly uniform directional texture, long service life, and stable performance. The specific steps are as follows: S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferromolybdenum, pig iron, ferromanganese, and ferrosilicon as raw materials, vacuum melting is carried out at 1550~1580℃ to obtain refined molten steel. The raw materials contain the following mass fractions: electrical pure iron (62.069%~70.700%), micro-carbon ferrochrome (9.509%~11.175%), ferrotungsten (4.388%~4.938%), ferromolybdenum (1.736%~2.463%), ferroboron (9.239%~11.127%), pig iron (3.397%~7.405%), ferromanganese (0.550%~0.700%), and ferrosilicon (0.096%~0.481%).

[0040] Vacuum melting specifically refers to: First, add electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferromolybdenum, ferromanganese, and pig iron to the vacuum induction furnace. After the furnace charge has completely melted, raise the temperature to 1550~1580℃. The molten steel is then transferred to a ladle for hot ladle treatment. Boron iron, which has been held at 300℃ for 40-60 minutes, is then added to an induction furnace. The molten steel in the ladle is then returned to the furnace for remelting. The temperature of the molten steel is raised again to 1500-1540℃ and held for 10 minutes to obtain pure high-boron high-speed steel.

[0041] S2. Temperature control treatment is applied to the molten steel obtained in step S1 to control the temperature of the high boron high speed steel molten steel to be reduced to 1350~1400℃ and then transferred to a vacuum pulling furnace for directional solidification treatment to obtain directional solidified high boron high speed steel cast billet. The temperature control process is as follows: After the hot ladle treatment, place rare earth aluminum at the bottom of the ladle, equivalent to 0.008%~0.012% of the molten steel mass. Pour the molten steel into the ladle for desulfurization treatment. When the temperature of the molten steel drops to 1350~1400℃, transfer it to an industrial vacuum clinker furnace.

[0042] Directional solidification specifically refers to: Directional solidification was carried out in an industrial-grade directional solidification pulling furnace. The solidification interface temperature gradient was 100~200K / cm, the pulling rate was 3~8mm / min, and the obtained directional solidification ingot size was Φ80×250mm.

[0043] S3. The as-cast billet obtained in step S2 is subjected to rough machining, austenitization and tempering heat treatment, and surface polishing to obtain a directional solidification high boron high-speed steel oilfield hydraulic jet nozzle.

[0044] The specific machining process is as follows: The casting billet is rough machined into a tool body of Φ65×220mm using a lathe, and four nozzle channels with a diameter of 4.5±0.1mm are evenly drilled on the end face using a drilling machine.

[0045] The austenitizing and tempering heat treatment specifically includes: The workpiece to be processed is placed in a vacuum resistance furnace and heated to 1040~1110℃ at a heating rate of 10~20℃ / min for austenitization and holding for 60~120min. Then, it is quenched in vacuum quenching oil. Next, the quenched workpiece is placed in a vacuum resistance furnace and heated to the tempering temperature of 525~605℃ and held for 55~65 minutes. Then, it is cooled to room temperature in the furnace and the tempering process is repeated 3 times.

[0046] The specific surface polishing process is as follows: The inner wall of the flow channel was polished using a diamond grinding wheel for 120-180 seconds. The polishing medium was a 10 vol.% water-based 2.5 μm SiO2 suspension.

[0047] A high-boron high-speed steel jet nozzle for oilfield hydraulic applications, prepared using the method described above, comprises a metal matrix and a boride hard phase distributed on the matrix. By weight percentage, the alloy composition is: C: 0.21%~0.37%, B: 1.76%~2.12%, Cr: 5.42%~6.37%, Mo: 1.05%~1.49%, W: 3.51%~3.95%, Mn: 0.44%~0.56%, Si: 0.40%~0.60%, with the remainder being Fe and unavoidable trace impurities. The nozzle workpiece hardness is 58.5~64.5 HRC; the surface roughness Ra of the inner wall of the flow channel is 0.25~0.40 μm.

[0048] The heat-treated directionally solidified high-boron high-speed steel has a high-density, finely dispersed tempered martensite matrix and a directionally arranged rod-shaped (Fe,Cr)2B hard phase. Cr, Mo, and W elements can improve the matrix strength and hardenability, as well as the hardness and toughness of the boride hard phase. B element can form rod-shaped eutectic boride hard phase and improve the matrix hardenability, which determines the wear resistance of high-boron high-speed steel. The addition of C can promote the formation of tempered martensite in the matrix, improving the wear resistance and service safety of the material.

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0050] Example 1 Water jet tool manufacturing and processing This invention uses electrical pure iron, micro-carbon ferrochrome, ferromolybdenum, ferrotungsten, ferroboron, pig iron, ferrosilicon, and ferromanganese as raw materials. 62.069% electrical pure iron (chemical composition of electrical pure iron: 0.020% C, 0.020% Si, 0.150% Mn, balance Fe) is added respectively, along with 11.175% micro-carbon ferrochrome (chemical composition of micro-carbon ferrochrome: 0.060% C, 57.000% Cr, 1.450% Si, balance Fe), 1.736% ferromolybdenum (chemical composition of ferromolybdenum: 0.021% C, 0.510% Si, 60.500% Mo, balance Fe), and 4.938% ferrotungsten (chemical composition of ferrotungsten: 0.100% C, 0.500% Si, 80.50% Mn, balance Fe), and 80% ferromanganese. 0.000%W, balance Fe), 11.127% ferroboron (ferroboron has a chemical composition of 0.380%C, 0.490%Si, 19.050%B, balance Fe), 7.405% pig iron (pig iron has a chemical composition of 4.270%C, 0.900%Si, 0.113%Mn, balance Fe), % ferrosilicon (ferrosilicon has a chemical composition of 0.210%C, 72.200%Si, balance Fe), 0.550% ferromanganese (ferrosilicon has a chemical composition of 1.500%C, 1.500%Si, 80.000%Mn, balance Fe).

[0051] The specific preparation process of this invention is as follows: S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferromolybdenum, pig iron, ferromanganese, and ferrosilicon as raw materials, vacuum melting is carried out at 1580℃. Then, the molten steel is transferred to a ladle for hot ladle treatment. Boron iron that has been held at 300℃ for 60 minutes is added to the induction furnace. The molten steel in the ladle is then returned to the furnace for remelting. The temperature of the molten steel is raised again to 1540℃ and held for 10 minutes to obtain pure high-boron high-speed steel. S2. Temperature control treatment is applied to the molten steel obtained in step S1. Rare earth aluminum equivalent to 0.012% of the molten steel mass is placed at the bottom of the ladle after the hot ladle treatment. The molten steel is then poured into the ladle for desulfurization treatment. The temperature of the high boron high-speed steel is controlled to decrease to 1350℃ and then transferred to an industrial-grade directional solidification pulling furnace for directional solidification treatment. The solidification interface temperature gradient is 200K / cm, the pulling rate is 8mm / min, and the obtained directional solidification ingot size is Φ80×250mm. S3. The cast billet obtained in step S2 is subjected to rough machining. The billet is rough machined into a tool body of Φ65×220mm using a lathe, and four nozzle channels with a diameter of 4.5±0.1mm are evenly drilled on the end face using a drilling machine. The workpiece to be processed is placed in a vacuum resistance furnace and heated to 1110℃ at a heating rate of 20℃ / min for austenitization and held for 120min. Then, it is quenched with vacuum quenching oil. Next, the quenched workpiece is placed in a vacuum resistance furnace and heated to the tempering temperature of 525℃ and held for 55min. It is then cooled to room temperature in the furnace and the tempering process is repeated three times. The final alloy hardness is 64.5HRC. Finally, the inner wall of the flow channel is finely polished with a diamond grinding wheel for 180s. The polishing medium is 10 vol.% water-based 2.5μm SiO2 suspension, and the inner wall roughness Ra is 0.25μm.

[0052] This embodiment utilizes a high proportion of ferroborone (11.127%), the highest vacuum melting temperature (1580℃), the maximum directional solidification temperature gradient (200K / cm), and the fastest pulling rate (8mm / min), combined with high-temperature austenitization (1110℃) and low-temperature tempering (525℃) processes, to obtain a product with a hardness of 64.5HRC and a surface roughness of 0.25μm. The high boron content and optimized process parameters result in a more dense and ordered arrangement of the (Fe,Cr)2B hard phase, and a sufficiently refined tempered martensitic matrix, exhibiting both extremely high hardness and good toughness. In actual testing, after 1800 hours of service, only slight wear was observed, and the erosion weight loss was only 32mg / 100h, significantly superior to cemented carbide and ordinary carbon steel, making it suitable for high-pressure sand-containing blasting conditions where wear resistance is extremely important.

[0053] Example 2 Water jet tool manufacturing and processing This invention uses electrical pure iron, micro-carbon ferrochrome, ferromolybdenum, ferrotungsten, ferroboron, pig iron, ferrosilicon, and ferromanganese as raw materials. The following components are added respectively: 67.104% electrical pure iron (chemical composition of electrical pure iron: 0.020% C, 0.020% Si, 0.150% Mn, balance Fe), 10.264% micro-carbon ferrochrome (chemical composition of micro-carbon ferrochrome: 0.060% C, 57.000% Cr, 1.450% Si, balance Fe), 2.215% ferromolybdenum (chemical composition of ferromolybdenum: 0.021% C, 0.510% Si, 60.500% Mo, balance Fe), and 4.512% ferrotungsten (chemical composition of ferrotungsten: 0.100% C, 0.500% Si, 80.00% Mn, balance Fe). 0%W, balance Fe), 10.054% ferroboron (ferroboron has a chemical composition of 0.380%C, 0.490%Si, 19.050%B, balance Fe), 5.154% pig iron (pig iron has a chemical composition of 4.270%C, 0.900%Si, 0.113%Mn, balance Fe), 0.096% ferrosilicon (ferrosilicon has a chemical composition of 0.210%C, 72.200%Si, balance Fe), 0.601% ferromanganese (ferrosilicon has a chemical composition of 1.500%C, 1.500%Si, 80.000%Mn, balance Fe).

[0054] The specific preparation process of this invention is as follows: S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferromolybdenum, pig iron, ferromanganese, and ferrosilicon as raw materials, vacuum melting is carried out at 1555℃. Then, the molten steel is transferred to a ladle for hot ladle treatment. Boron iron that has been held at 300℃ for 50 minutes is added to the induction furnace. The molten steel in the ladle is then returned to the furnace for remelting. The temperature of the molten steel is raised again to 1520℃ and held for 10 minutes to obtain pure high-boron high-speed steel. S2. Temperature control treatment is applied to the molten steel obtained in step S1. Rare earth aluminum equivalent to 0.012% of the molten steel mass is placed at the bottom of the ladle after the hot ladle treatment. The molten steel is then poured into the ladle for desulfurization treatment. The temperature of the high boron high-speed steel is controlled to decrease to 1380℃ and then transferred to an industrial-grade directional solidification pulling furnace for directional solidification treatment. The solidification interface temperature gradient is 150K / cm, the pulling rate is 5mm / min, and the obtained directional solidification ingot size is Φ80×250mm. S3. The cast billet obtained in step S2 is subjected to rough machining. The billet is rough machined into a tool body of Φ65×220mm using a lathe, and four nozzle channels with a diameter of 4.5±0.1mm are evenly drilled on the end face using a drilling machine. The workpiece to be processed is placed in a vacuum resistance furnace and heated to 1080℃ at a heating rate of 15℃ / min for austenitization and held for 80min. Then, it is quenched with vacuum quenching oil. Next, the quenched workpiece is placed in a vacuum resistance furnace and heated to the tempering temperature of 575℃ and held for 60min. It is then cooled to room temperature in the furnace and the tempering process is repeated three times. The alloy hardness is 60.5HRC. Finally, the inner wall of the flow channel is finely polished with a diamond grinding wheel for 145s. The polishing medium is 10 vol.% water-based 2.5μm SiO2 suspension, and the inner wall roughness Ra is 0.30μm.

[0055] This embodiment employs a moderate component ratio and process parameters: 10.054% ferroboron, vacuum melting temperature of 1555℃, directional solidification temperature gradient of 150K / cm, pulling rate of 5mm / min, austenitizing temperature of 1080℃, tempering temperature of 575℃, product hardness of 60.5HRC, and surface roughness of 0.30μm. This parameter combination achieves an optimal balance between performance and cost, with uniform hard phase arrangement, moderate matrix toughness, and optimal erosion weight loss and service life. It is suitable for most conventional oilfield hydraulic jetting scenarios, balancing reliability and economy, and facilitating large-scale production applications.

[0056] Example 3 Water jet tool manufacturing and processing This invention uses electrical pure iron, micro-carbon ferrochrome, ferromolybdenum, ferrotungsten, ferroboron, pig iron, ferrosilicon, and ferromanganese as raw materials. 70.700% electrical pure iron (with a chemical composition of 0.020% C, 0.020% Si, 0.150% Mn, and the balance being Fe) is added respectively, along with 9.509% micro-carbon ferrochrome (with a chemical composition of 0.060% C, 57.000% Cr, 1.450% Si, and the balance being Fe), 1.736% ferromolybdenum (with a chemical composition of 0.021% C, 0.510% Si, 60.500% Mo, and the balance being Fe), and 4.388% ferrotungsten (with a chemical composition of 0.100% C, 0.500% Si, 80.00% Mn, and the balance being Fe). 0%W, balance Fe), 9.239% ferroboron (ferroboron has a chemical composition of 0.380%C, 0.490%Si, 19.050%B, balance Fe), 3.397% pig iron (pig iron has a chemical composition of 4.270%C, 0.900%Si, 0.113%Mn, balance Fe), 0.481% ferrosilicon (ferrosilicon has a chemical composition of 0.210%C, 72.200%Si, balance Fe), 0.550% ferromanganese (ferrosilicon has a chemical composition of 1.500%C, 1.500%Si, 80.000%Mn, balance Fe).

[0057] The specific preparation process of this invention is as follows: S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferromolybdenum, pig iron, ferromanganese, and ferrosilicon as raw materials, vacuum melting is carried out at 1550℃. Then, the molten steel is transferred to a ladle for hot ladle treatment. Boron iron that has been held at 300℃ for 40 minutes is added to the induction furnace. The molten steel in the ladle is then returned to the furnace for remelting. The temperature of the molten steel is raised again to 1500℃ and held for 10 minutes to obtain pure high-boron high-speed steel. S2. Temperature control treatment is applied to the molten steel obtained in step S1. Rare earth aluminum equivalent to 0.012% of the molten steel mass is placed at the bottom of the ladle after the hot ladle treatment. The molten steel is then poured into the ladle for desulfurization treatment. The temperature of the high boron high-speed steel is controlled to decrease to 1400℃ and then transferred to an industrial-grade directional solidification pulling furnace for directional solidification treatment. The solidification interface temperature gradient is 100K / cm, the pulling rate is 3mm / min, and the obtained directional solidification ingot size is Φ80×250mm. S3. The cast billet obtained in step S2 is subjected to rough machining. The billet is rough machined into a tool body of Φ65×220mm using a lathe, and four nozzle channels with a diameter of 4.5±0.1mm are evenly drilled on the end face using a drilling machine. The workpiece to be processed is placed in a vacuum resistance furnace and heated to 1040℃ at a heating rate of 10℃ / min for austenitization and held for 60min. Then, it is quenched with vacuum quenching oil. Next, the quenched workpiece is placed in a vacuum resistance furnace and heated to the tempering temperature of 605℃ and held for 65min. It is then cooled to room temperature in the furnace and the tempering process is repeated three times. The alloy hardness is 58.5HRC. Finally, the inner wall of the flow channel is finely polished with a diamond grinding wheel for 120s. The polishing medium is 10 vol.% water-based 2.5μm SiO2 suspension, and the inner wall roughness Ra is 0.40μm.

[0058] This embodiment uses a low boron-iron content (9.239%) and a lower processing strength, with a vacuum melting temperature of 1550℃, a directional solidification temperature gradient of 100K / cm, a pulling rate of 3mm / min, an austenitizing temperature of 1040℃, and a tempering temperature of 605℃. The product has a hardness of 58.5HRC and a surface roughness of 0.40μm. The lower hardness combined with better toughness can withstand impact loads under complex working conditions and avoid brittle fracture. Although the wear resistance is slightly lower than the previous two embodiments, the production cost is lower, making it suitable for working conditions with small sand particle size and large impact loads, expanding the product's application range and meeting the differentiated needs of different scenarios.

[0059] Example 4 Water jet tool manufacturing and processing This invention uses electrical pure iron, micro-carbon ferrochrome, ferromolybdenum, ferrotungsten, ferroboron, pig iron, ferrosilicon, and ferromanganese as raw materials. The following components are added respectively: 65.320% electrical pure iron (chemical composition of electrical pure iron: 0.020% C, 0.020% Si, 0.150% Mn, balance Fe), 10.850% micro-carbon ferrochrome (chemical composition of micro-carbon ferrochrome: 0.060% C, 57.000% Cr, 1.450% Si, balance Fe), 2.010% ferromolybdenum (chemical composition of ferromolybdenum: 0.021% C, 0.510% Si, 60.500% Mo, balance Fe), and 4.725% ferrotungsten (chemical composition of ferrotungsten: 0.100% C, 0.500% Si, 80.00% Mn, balance Fe). 0%W, balance Fe), 10.580% ferroboron (ferroboron has a chemical composition of 0.380%C, 0.490%Si, 19.050%B, balance Fe), 5.890% pig iron (pig iron has a chemical composition of 4.270%C, 0.900%Si, 0.113%Mn, balance Fe), 0.215% ferrosilicon (ferrosilicon has a chemical composition of 0.210%C, 72.200%Si, balance Fe), 0.610% ferromanganese (ferrosilicon has a chemical composition of 1.500%C, 1.500%Si, 80.000%Mn, balance Fe).

[0060] The specific preparation process of this invention is as follows: S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferromolybdenum, pig iron, ferromanganese, and ferrosilicon as raw materials, vacuum melting is carried out at 1565℃. Then, the molten steel is transferred to a ladle for hot ladle treatment. Boron iron that has been held at 300℃ for 55 minutes is added to the induction furnace. The molten steel in the ladle is then returned to the furnace for remelting. The temperature of the molten steel is raised again to 1530℃ and held for 10 minutes to obtain pure high-boron high-speed steel. S2. Temperature control treatment is applied to the molten steel obtained in step S1. Rare earth aluminum equivalent to 0.010% of the molten steel mass is placed at the bottom of the ladle after the hot ladle treatment. The molten steel is then poured into the ladle for desulfurization treatment. The temperature of the high boron high-speed steel is controlled to decrease to 1370℃ and then transferred to an industrial-grade directional solidification pulling furnace for directional solidification treatment. The solidification interface temperature gradient is 180K / cm, the pulling rate is 6mm / min, and the obtained directional solidification ingot size is Φ80×250mm. S3. The cast billet obtained in step S2 is subjected to rough machining. The billet is rough machined into a tool body of Φ65×220mm using a lathe, and four nozzle channels with a diameter of 4.5±0.1mm are evenly drilled on the end face using a drilling machine. The workpiece to be processed is placed in a vacuum resistance furnace and heated to 1095℃ at a heating rate of 18℃ / min for austenitization and held for 100min. Then, it is quenched with vacuum quenching oil. Next, the quenched workpiece is placed in a vacuum resistance furnace and heated to the tempering temperature of 550℃ and held for 62min. It is then cooled to room temperature in the furnace and the tempering process is repeated three times. The alloy hardness is 62.8HRC. Finally, the inner wall of the flow channel is finely polished with a diamond grinding wheel for 160s. The polishing medium is 10 vol.% water-based 2.5μm SiO2 suspension, and the inner wall roughness Ra is 0.28μm.

[0061] This embodiment employs a medium-to-high proportion of ferroboron and a suitable combination of process parameters: ferroboron content 10.580%, vacuum melting temperature 1565℃, directional solidification temperature gradient 180K / cm, and pulling rate 6mm / min. Combined with austenitization at 1095℃ and tempering at 550℃, a precise balance between hardness and toughness is achieved. The directionally arranged (Fe,Cr)₂B hard phase has a moderate density, and the dispersed precipitates in the tempered martensitic matrix are uniformly distributed. This results in a product with a weight loss of only 38mg after 100 hours of erosion under 60MPa high-pressure sand-containing conditions, and a service life exceeding 1700 hours. This embodiment covers the middle-to-optimal range of process parameters in the claims, further verifying the stability of the composition ratio and process parameter combination. It is suitable for conventional oilfield extraction scenarios with high requirements for wear resistance and impact resistance, providing sufficient support for the scope of protection of the claims.

[0062] Example 5 Water jet tool manufacturing and processing This invention uses electrical pure iron, micro-carbon ferrochrome, ferromolybdenum, ferrotungsten, ferroboron, pig iron, ferrosilicon, and ferromanganese as raw materials. The following components are added respectively: 68.950% electrical pure iron (chemical composition of electrical pure iron: 0.020% C, 0.020% Si, 0.150% Mn, balance Fe), 9.980% micro-carbon ferrochrome (chemical composition of micro-carbon ferrochrome: 0.060% C, 57.000% Cr, 1.450% Si, balance Fe), 2.320% ferromolybdenum (chemical composition of ferromolybdenum: 0.021% C, 0.510% Si, 60.500% Mo, balance Fe), and 4.460% ferrotungsten (chemical composition of ferrotungsten: 0.100% C, 0.500% Si, 80.00% Mn, balance Fe). 0%W, balance Fe), 9.870% ferroboron (ferroboron has a chemical composition of 0.380%C, 0.490%Si, 19.050%B, balance Fe), 4.120% pig iron (pig iron has a chemical composition of 4.270%C, 0.900%Si, 0.113%Mn, balance Fe), 0.350% ferrosilicon (ferrosilicon has a chemical composition of 0.210%C, 72.200%Si, balance Fe), 0.650% ferromanganese (ferrosilicon has a chemical composition of 1.500%C, 1.500%Si, 80.000%Mn, balance Fe).

[0063] The specific preparation process of this invention is as follows: S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferromolybdenum, pig iron, ferromanganese, and ferrosilicon as raw materials, vacuum melting is carried out at 1570℃. Then, the molten steel is transferred to a ladle for hot ladle treatment. Boron iron that has been held at 300℃ for 45 minutes is added to the induction furnace. The molten steel in the ladle is then returned to the furnace for remelting. The temperature of the molten steel is raised again to 1515℃ and held for 10 minutes to obtain pure high-boron high-speed steel. S2. Temperature control treatment is applied to the molten steel obtained in step S1. Rare earth aluminum equivalent to 0.009% of the molten steel mass is placed at the bottom of the ladle after the hot ladle treatment. The molten steel is then poured into the ladle for desulfurization treatment. The temperature of the high boron high-speed steel is controlled to decrease to 1390℃ and then transferred to an industrial-grade directional solidification pulling furnace for directional solidification treatment. The solidification interface temperature gradient is 120K / cm, the pulling rate is 4mm / min, and the obtained directional solidification ingot size is Φ80×250mm. S3. The cast billet obtained in step S2 is subjected to rough machining. The billet is rough machined into a tool body of Φ65×220mm using a lathe, and four nozzle channels with a diameter of 4.5±0.1mm are evenly drilled on the end face using a drilling machine. The workpiece to be processed is placed in a vacuum resistance furnace and heated to 1060℃ at a heating rate of 12℃ / min for austenitization and held for 75min. Then, it is quenched with vacuum quenching oil. Next, the quenched workpiece is placed in a vacuum resistance furnace and heated to the tempering temperature of 590℃ and held for 58min. It is then cooled to room temperature in the furnace and the tempering process is repeated three times. The alloy hardness is 59.8HRC. Finally, the inner wall of the flow channel is finely polished with a diamond grinding wheel for 135s. The polishing medium is 10 vol.% water-based 2.5μm SiO2 suspension, and the inner wall roughness Ra is 0.35μm.

[0064] This embodiment uses a low to medium proportion of ferroborone and mild process parameters: ferroborone content 9.870%, vacuum melting temperature 1570℃, directional solidification temperature gradient 120K / cm, and pulling rate 4mm / min. Combined with austenitization at 1060℃ and tempering at 590℃, it highlights the product's impact resistance. In the microstructure, the (Fe,Cr)₂B hard phase is uniformly distributed in rod-like shapes, and the tempered martensitic matrix exhibits excellent toughness. Under conditions with large sand particle size (50-80 mesh quartz sand) and large fluctuations in impact load, no cracks were generated after 1500 hours of service, and the erosion weight loss was 45mg / 100h. This embodiment covers the low to medium range of composition and process parameters in the claims, verifying the adaptability of the invention's technical solution under different chemical conditions, further supporting the rationality of the parameter range in the claims, and expanding the application scenarios of the product under complex impact conditions. It also provides more experimental evidence for the process control and performance optimization of high-boron high-speed steel.

[0065] Actual test of hydraulic jetting in oilfield wells Hydraulic jetting tools made of directional solidified high-boron high-speed steel, ordinary carbon steel hydraulic jetting tools, and cemented carbide hydraulic jetting tools were tested in oilfield downhole operations under the following conditions: sand jetting speed: 50 m / s² 3 / h (40~70 mesh quartz sand), water flow velocity: 220m / s, water flow pressure: 60MPa.

[0066] 1. Service life test results: See actual photos of the jetting equipment after service operation testing. Figure 4 .

[0067] Tools made of ordinary carbon steel: After 200 hours of downhole service operation test, the nozzle and pipe wall surface have been damaged, and the oilfield hydraulic jetting tool has lost its service function.

[0068] Example 1: Directional solidification high-boron high-speed steel tool: After 1800 hours of downhole service operation test, the nozzle only showed slight wear, and the oilfield hydraulic jet tool still has service function.

[0069] 2. The wear rate test results of a single nozzle after 100 hours of service are shown in Table 1. The service life of the tool made of directional solidification high boron high-speed steel in Example 1 is 2.7 times that of the traditional cemented carbide tool of the same specification and 13.5 times that of the tool made of different carbon steel.

[0070] Table 1. Comparison of erosion weight loss of a single nozzle after 100 hours of service testing for water jet tools made of different materials.

[0071] Please see Figure 2 The directional solidification direction is perpendicular to the inner wall of the nozzle. With the help of the directional arrangement of (Fe,Cr)2B rod-shaped texture and precipitation-strengthened tempered martensite, it achieves a synergistic effect of resisting abrasive wear under high pressure and high flow rate environment, which significantly reduces the erosion and abrasive wear damage suffered by the inner wall of the nozzle.

[0072] Please see Figure 3 The heat-treated directional solidified high-boron high-speed steel prepared according to the process parameters of Example 1 contains a large number of second-phase precipitated hard particles in its tempered martensitic matrix, and the network eutectic boride skeleton and sharp corners disappear. At this time, the alloy has both hardness and toughness, and has good wear resistance and service safety.

[0073] Please see Figure 4 Under test conditions (sand jetting speed: 50m) 3 The service life of the directionally solidified high-boron high-speed steel tool and the ordinary carbon steel tool in Example 1 were tested by measuring the flow rate (40~70 mesh quartz sand, water flow velocity: 220 m / s, water flow pressure: 60 MPa) for 1800 h. After 1800 h of operation, the nozzle of the directionally solidified high-boron high-speed steel tool in Example 1 showed only slight wear. After 200 h of operation, the ordinary carbon steel tool was severely damaged and lost its service function. This shows that the water jet tool made of the material of the present invention has superior service performance and service life compared with the traditional material tool.

[0074] In summary, this invention provides a directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications and its preparation method.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a directional solidification high-boron high-speed steel injection nozzle for oilfield hydraulic applications, characterized in that, Includes the following steps: S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferromolybdenum, pig iron, ferroboron, ferromanganese, and ferrosilicon as raw materials, vacuum smelting is performed to obtain high-boron high-speed steel molten steel. The raw materials, by mass fraction, include: 62.069%~70.700% electrical pure iron, 9.509%~11.175% micro-carbon ferrochrome, 4.388%~4.938% ferrotungsten, 1.736%~2.463% ferromolybdenum, 9.239%~11.127% ferroboron, 3.397%~7.405% pig iron, 0.550%~0.700% ferromanganese, and 0.096%~0.481% ferrosilicon. S2. The high-boron high-speed steel molten steel obtained in step S1 is subjected to temperature control treatment, and then transferred to a directional solidification device for directional solidification treatment to obtain a cast billet with directional solidification structure. S3. The as-cast billet obtained in step S2 is subjected to machining, austenitizing quenching and tempering heat treatment in sequence to obtain a directionally solidified high-boron high-speed steel jet nozzle for oilfield hydraulic applications.

2. The method for preparing a directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications according to claim 1, characterized in that, In step S1, the vacuum melting specifically includes: First, electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferromolybdenum, pig iron, ferromanganese, and ferrosilicon are melted into molten steel at 1550~1580℃; The molten steel is transferred to a ladle for hot-scalding treatment. Then, ferroboron that has been held at 300℃ for 40-60 minutes is added and the mixture is remelted in the furnace to raise the temperature of the molten steel to 1500-1540℃ and hold it thereafter to obtain high-boron high-speed steel.

3. The method for preparing a directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications according to claim 1, characterized in that, In step S2, the temperature control process includes: Rare earth aluminum, accounting for 0.008%~0.012% of the steel mass, is added to the molten steel for desulfurization treatment, and the temperature of the molten steel is controlled to drop to 1350~1400℃.

4. The method for preparing a directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications according to claim 1, characterized in that, In step S2, the process parameters for the directional solidification treatment are: The solidification interface temperature gradient is 100~200K / cm, and the pulling rate is 3~8mm / min.

5. The method for preparing a directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications according to claim 1, characterized in that, In step S3, the austenitizing quenching and tempering heat treatment specifically includes: The machined workpiece is heated to 1040-1110℃ under vacuum conditions at a rate of 10-20℃ / min, held for 60-120min, and then oil quenched. The quenched workpiece is tempered under vacuum conditions at a temperature of 525~605℃ for 55~65 minutes. The tempering process is repeated at least 3 times.

6. The method for preparing a directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications according to claim 1, characterized in that, In step S3, after the tempering heat treatment, the inner wall of the flow channel of the spray nozzle is also subjected to surface polishing treatment. The polishing treatment uses a diamond grinding wheel, the polishing medium is 10 vol.% water-based 2.5 μm SiO2 suspension, and the polishing time is 120~180 s.

7. A directional solidification high-boron high-speed steel injection nozzle for oilfield hydraulic applications, characterized in that, The nozzle is prepared by the preparation method according to any one of claims 1 to 6. The nozzle comprises a metal matrix and a boride hard phase distributed on the matrix. By weight percentage, the alloy composition is C: 0.21%~0.37%, B: 1.76%~2.12%, Cr: 5.42%~6.37%, Mo: 1.05%~1.49%, W: 3.51%~3.95%, Mn: 0.44%~0.56%, Si: 0.40%~0.60%, with the remainder being Fe and unavoidable trace impurities.

8. The directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications according to claim 7, characterized in that, The hardness of the spray nozzle is 58.5~64.5HRC, and the surface roughness Ra of its inner wall of the flow channel is 0.25~0.40μm; the microstructure of the spray nozzle includes a tempered martensitic matrix and a (Fe,Cr)2B boride hard phase oriented on the matrix.

9. The directional solidification high-boron high-speed steel jet nozzle for oilfield hydraulic applications according to claim 7, characterized in that, The directional solidification direction of the spray nozzle is perpendicular to the direction of the inner wall of the nozzle.

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