Aluminum-containing high-boron high-speed steel oil well pump and preparation method thereof

Abstract

The application discloses an oil well pump of high-speed steel containing aluminum and boron and a preparation method thereof, and belongs to the technical field of metal materials. The preparation method comprises the following steps: taking pure iron, micro-carbon chromium iron, tungsten iron, boron iron, pig iron, vanadium iron, titanium iron and aluminum wire as raw materials, and obtaining high-speed steel melt through vacuum induction melting; graphite mold casting is carried out at 1400-1440 DEG C to obtain a cast blank; the cast blank is sequentially subjected to homogenizing annealing, austenitizing, deep undercooling treatment and tempering heat treatment, and finally the product is obtained. The oil well pump comprises the following chemical components in percentage by weight: Al: 1.06%-1.55%, C: 0.11%-0.25%, B: 1.76%-2.47%, and the microstructure is a tempered martensite matrix and (Fe,Cr)2B hard phase. The product has excellent corrosion resistance, wear resistance and service safety, and the cost is lower than that of traditional materials, can effectively resist downhole corrosion and erosion, prolong the service life of the oil well pump, and is suitable for downhole mining scenes in oil fields.

Description

Technical Field

[0001] This invention belongs to the field of metal materials technology, specifically relating to an aluminum-containing high-boron high-speed steel oilfield pump and its preparation method. Background Technology

[0002] As the most important chemical raw material and fuel in modern industry, the exploration and extraction of petroleum is of great strategic significance. In the process of onshore oil extraction, oilfield pumps are important downhole devices that extract crude oil from underground wells to the surface. However, due to the complex liquid environment thousands of meters underground, the pump barrel is susceptible to corrosion from oil-water mixtures and erosion from sediment, eventually leading to damage to the pump barrel sidewalls and affecting pump efficiency and the accuracy of crude oil production calculations.

[0003] Currently, oilfield pump barrels typically use three types of materials: traditional high-speed steel (such as M2 high-speed steel) has good wear resistance, but its cost is high and its corrosion resistance is severely insufficient; stainless steel (such as 316L) has excellent corrosion resistance, but poor wear resistance, resulting in a pump barrel life of less than 6 months; ordinary carbon steel with chromium plating or nitriding surface treatment, although possessing both corrosion resistance and wear resistance, has a brittle coating with a serious risk of peeling off, resulting in poor service safety. High-boron high-speed steel, based on traditional high-speed steel, replaces carbon with boron, reducing the amount of precious metal elements (such as Mo, W, V, Co, etc.) added, lowering production costs. While obtaining higher hardness and toughness in the boride hard phase, it also allows for the control of the metal matrix properties, achieving a wide range of adjustable performance characteristics. Corrosion from oil-water mixtures and erosion of the pump barrel sidewalls by downhole sediment are the main failure modes; therefore, it is necessary to develop new oilfield pump barrel materials that combine strong corrosion resistance, erosion resistance, and good service safety. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing an aluminum-containing high-boron high-speed steel oilfield pumping pump and its preparation method, so as to obtain high-boron high-speed steel with uniform structure and good corrosion resistance and wear resistance, thereby improving its corrosion resistance and wear resistance in oilfield downhole pumping pumps. This invention addresses the technical problems of high cost and insufficient corrosion resistance of traditional high-speed steel (such as M2), poor wear resistance of stainless steel (such as 316L) leading to insufficient pump barrel life, risk of coating peeling and poor service safety of surface-treated carbon steel, and the inability of existing materials to simultaneously achieve excellent corrosion resistance, wear resistance and low cost.

[0005] The present invention adopts the following technical solution:

[0006] A method for preparing an aluminum-containing high-boron high-speed steel oilfield pump includes the following steps:

[0007] S1. High-boron high-speed steel molten steel is obtained by vacuum induction melting using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferroboron, pig iron, ferrovanadium, ferrotitanium, and aluminum wire as raw materials.

[0008] S2. The high-boron high-speed steel molten steel obtained in step S1 is cast in a graphite mold at 1400~1440℃ to obtain a cast billet;

[0009] S3. The as-cast billet obtained in step S2 is subjected to homogenization annealing, austenitization, deep supercooling treatment and tempering heat treatment in sequence to obtain a heat-treated billet of aluminum-containing high-boron high-speed steel, which is then processed to produce an aluminum-containing high-boron high-speed steel oilfield pumping pump.

[0010] Preferably, in step S1, the mass fraction of each raw material is as follows: electrical pure iron 64.619%~70.248%, micro-carbon ferrochrome 10.772%~14.509%, ferrotungsten 3.313%~3.825%, ferroboron 9.239%~12.966%, pig iron 1.067%~4.780%, ferrovanadium 0.399%~1.048%, ferrotitanium 0.189%~0.416%, and aluminum wire 1.060%~1.550%.

[0011] Preferably, in step S1, vacuum induction melting specifically includes:

[0012] Electrically pure iron, micro-carbon ferrochrome, ferrotungsten, pig iron, and ferrovanadium are added to the vacuum induction furnace. After the furnace charge is completely melted, the molten steel is transferred to a ladle for hot ladle pouring.

[0013] Add ferrotitanium and preheated ferroboron to the induction furnace, return the molten steel from the ladle to the furnace for remelting, and heat to 1580~1600℃ and hold for 8~12 minutes.

[0014] Before casting, aluminum wire is placed into the ladle, and then the molten steel in the induction furnace is transferred to the ladle to obtain high-boron high-speed steel.

[0015] Preferably, the preheating treatment of ferroboron involves holding the ferroboron at 380~420℃ for 20~40 minutes.

[0016] Preferably, in step S3, the homogenization annealing conditions are: holding at 1000~1020℃ for 150~240 min, and then cooling to room temperature in the furnace.

[0017] Preferably, in step S3, the austenitizing treatment conditions are: holding at 1025~1075℃ for 90~120min, followed by quenching with vacuum quenching oil to 180~220℃.

[0018] Preferably, in step S3, the deep supercooling treatment involves immersing the workpiece in liquid nitrogen at -200 to -192°C for 90 to 150 minutes and then removing it to allow it to return to room temperature.

[0019] Preferably, in step S3, the heat-treated billet of aluminum-containing high-boron high-speed steel obtained after tempering heat treatment has a tempered martensitic matrix with high density and fine dispersed particles and a (Fe,Cr)2B hard phase.

[0020] Preferably, the tempering heat treatment is performed by holding at 500-600°C for 45-75 minutes and then furnace cooling to room temperature, and this process is repeated at least 3 times.

[0021] Another technical solution of the present invention is an aluminum-containing high-boron high-speed steel oilfield pump.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] A method for preparing an aluminum-boron-containing high-speed steel oilfield pumping unit utilizes vacuum induction melting to prepare high-boron high-speed steel molten steel, avoiding the introduction of impurity elements and raw material loss, and facilitating precise control of the molten steel composition. Casting using a graphite mold significantly increases the solidification rate of the molten steel, resulting in an aluminum-boron-containing high-speed steel billet with a uniform and fine microstructure, thereby improving the alloy's wear resistance. Heat treatment of the aluminum-boron-containing high-speed steel billet using a homogenization annealing + austenitization + deep undercooling + tempering process further improves the microstructure and compositional uniformity of the aluminum-boron-containing high-speed steel, and enhances the alloy's toughness, wear resistance, and service safety. The core of this invention lies in the compositional design of corrosion-resistant and wear-resistant high-boron high-speed steel with synergistic addition of Al and B elements, the induction melting process of the aluminum-boron-containing high-speed steel molten steel, and the hardening and toughening heat treatment technology for the solidified aluminum-boron-containing high-speed steel.

[0024] Furthermore, by precisely controlling the proportions of key raw materials such as electrical pure iron, micro-carbon ferrochrome, ferroboron, and aluminum wire, the alloy composition is optimized. This range is based on the optimal range verified by numerous experiments, ensuring that elements such as Al, B, and Cr fully exert their synergistic effects: Al enhances corrosion resistance and hardenability, B forms a hard phase to enhance wear resistance, and Cr further optimizes corrosion resistance and boride toughness. A reasonable proportion reduces the amount of precious metals used, lowering costs, while avoiding performance defects caused by compositional imbalances, ensuring stable operation of the product in downhole corrosive and erosive environments.

[0025] Furthermore, the process design of melting the basic raw materials first, followed by hot ladle treatment, remelting, and adding aluminum wire ensures the stability of the smelting process and the quality of the molten steel. Melting the basic raw materials first achieves thorough thermal stirring, improving melt uniformity; hot ladle treatment prevents the molten steel from cooling too quickly, affecting casting results; remelting ensures the full integration of ferrotitanium and ferroboron with the molten steel; and the final addition of aluminum wire reduces burn-off. This step-by-step process allows for precise control of the yield of each element, avoiding component segregation and providing uniformly composed molten steel for subsequent casting and heat treatment, ensuring consistent performance of the final product.

[0026] Furthermore, temperatures of 1000–1020℃ and holding times of 150–240 min effectively eliminate compositional segregation and internal stress in the as-cast billet. High-temperature holding allows for sufficient atomic diffusion, resulting in a more homogeneous alloy composition and laying the foundation for subsequent austenitization and deep undercooling treatment. Compared to traditional annealing processes, this parameter range ensures compositional homogenization while avoiding excessive grain growth that could lead to a decrease in toughness, thus improving the microstructural stability and performance reliability of the material after subsequent heat treatment.

[0027] Furthermore, holding at 1025~1075℃ for 90~120 minutes ensures complete dissolution of borides and homogenization of austenite, while vacuum quenching oil quenching to 180~220℃ allows for rapid cooling to form martensite. These process parameters allow for precise control of the martensitic transformation, avoiding coarse microstructure caused by insufficient cooling. Simultaneously, the vacuum quenching oil reduces oxidation and deformation during quenching, ensuring the dimensional accuracy of the billet. Compared to conventional quenching processes, this method improves material hardness and hardenability, providing a favorable microstructure foundation for subsequent deep undercooling and tempering processes.

[0028] Furthermore, placing the workpiece in liquid nitrogen at -200 to -192°C for 90 to 150 minutes promotes the transformation of retained austenite to martensite, refining the grain structure. The extremely low temperature environment accelerates the transformation process, reduces the content of retained austenite, and improves the material's hardness and wear resistance. A suitable holding time ensures a complete transformation, avoiding performance fluctuations caused by incomplete treatment. This process, combined with austenitization and tempering, further optimizes the microstructure and enhances the material's impact resistance and service stability under complex operating conditions.

[0029] Furthermore, holding the material at 500-600℃ for 45-75 minutes, repeated three times, effectively releases internal stress and promotes the precipitation of fine, hard second-phase particles. The tempering process alleviates the brittleness of the martensitic structure and improves the material's toughness. Simultaneously, the precipitated hard phases, such as M7(C,B)3, strengthen the matrix, achieving a balance between hardness and toughness. Multiple tempering processes ensure sufficient release of internal stress and uniform dispersion of the second-phase particles. Compared to single tempering, this significantly improves the material's service safety and performance stability, preventing fractures or damage in complex downhole stress environments.

[0030] Furthermore, the high-density, finely dispersed tempered martensitic matrix and the (Fe,Cr)₂B hard phase are the core components that give the material both corrosion resistance and wear resistance. The tempered martensitic matrix provides good toughness and strength, while the (Fe,Cr)₂B hard phase has high hardness and strong wear resistance. The synergistic effect of the two enables the material to resist downhole mud erosion and corrosion from oil-water mixtures. Compared to the network carbide structure of traditional high-speed steel, this microstructure is more uniform and has better toughness, avoiding early failure caused by microstructural defects in traditional materials and significantly extending the service life of the oil pump.

[0031] Furthermore, the triple tempering process effectively eliminates internal stress, promotes carbide precipitation, and improves the material's toughness and microstructure stability. A tempering temperature of 500-600℃ ensures that the material achieves a good balance of hardness and toughness while maintaining sufficient hardness.

[0032] In summary, this invention utilizes a combination of vacuum melting, graphite casting, and heat treatment processes to prepare an oilfield pump made of aluminum-containing high-boron high-speed steel. This pump possesses a uniform, high-density, dispersed, strengthened tempered martensite-(Fe,Cr)2B hypoeutectic structure, which significantly improves the service life and performance of the oilfield pump body and results in lower operating costs compared to pump bodies made from traditional materials.

[0033] 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

[0034] 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.

[0035] Figure 1 This is a process flow diagram of the present invention;

[0036] Figure 2 This is a SEM image of the aluminum-containing high-boron high-speed steel of Example 3 of the present invention;

[0037] Figure 3 This is a SEM image of the corrosion section of the alloy in Example 3 of the present invention after immersion in a static 3.5 wt.% NaCl aqueous solution at 60°C for 1 year.

[0038] Figure 4 These are comparative photos of Embodiment 3 of the present invention and an M2 high-speed steel oilfield pump after one year of downhole service. (a) is Embodiment 3 of the present invention, and (b) is an M2 high-speed steel oilfield pump. Detailed Implementation

[0039] 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.

[0040] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0041] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0042] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0043] In this invention, unless otherwise specified, the components involved or their preferred components can be combined to form new technical solutions.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] This invention provides an aluminum-containing high-boron high-speed steel oilfield pump and its preparation method. The method combines vacuum induction melting, graphite mold casting, and heat treatment to obtain an oilfield pump material with uniform composition, excellent corrosion and wear resistance, long service life, and stable performance. This improves the corrosion resistance and wear resistance of the pump in oilfield downhole pumps and provides a new approach for the development of high-boron high-speed steel materials in oilfield downhole tools.

[0050] Please see Figure 1 The present invention discloses a method for preparing an aluminum-containing high-boron high-speed steel oilfield pump, comprising the following steps:

[0051] S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferroboron, pig iron, ferrovanadium, ferrotitanium, and aluminum wire as raw materials, clean high-boron high-speed steel molten steel is obtained through vacuum induction melting.

[0052] The mass fraction of electrical pure iron is 64.619%~70.248%, the mass fraction of micro-carbon ferrochrome is 10.772%~14.509%, the mass fraction of ferrotungsten is 3.313%~3.825%, the mass fraction of ferroboron is 9.239%~12.966%, the mass fraction of pig iron is 1.067%~4.780%, the mass fraction of ferrovanadium is 0.399%~1.048%, the mass fraction of ferrotitanium is 0.189%~0.416%, and the mass fraction of aluminum wire is 1.060%~1.550%.

[0053] The alloy contains 1.06%–1.55% Al, which significantly improves the salt water corrosion resistance of the metal matrix while refining the grains and enhancing hardenability, as well as strengthening the tempering precipitation hardening effect. The B content ranges from 1.76% to 2.47%, directly determining the content of the boride hard phase, allowing for direct control of the wear resistance of high-boron high-speed steel based on actual downhole operating conditions. The Cr content ranges from 6.14% to 8.27%, which improves the toughness of the tetragonal (Fe,Cr)₂B boride hard phase in high-boron high-speed steel and synergistically enhances the corrosion resistance of both the boride and the metal matrix. Adding Al to the metal matrix further contributes to this effect. On the basis of further suppressing electrochemical corrosion in oil-water mixtures; the addition of W element is controlled within 4%, which significantly reduces the raw material production cost of high boron high-speed steel. Some elements are dissolved in the hard phase of boride, which further improves the hardness and toughness of boride. Elements dissolved in the metal matrix improve the hardenability of the alloy, which helps to reduce the cost of heat treatment. The content of C element is controlled at 0.11%~0.25%, which can obtain a low-carbon tempered martensitic structure after heat treatment. Its high hardness and toughness improve the service safety under actual working conditions. The addition of small amounts of Ti and V elements can significantly refine the structure and improve the hardenability of the metal matrix, thereby improving the wear resistance of aluminum-containing high boron high-speed steel.

[0054] Vacuum melting specifically refers to:

[0055] First, add electrical pure iron, micro-carbon ferrochrome, ferrotungsten, pig iron, and ferrovanadium to the vacuum induction furnace. After the furnace charge has completely melted, transfer the molten steel to a ladle for hot ladle treatment.

[0056] Then, ferrotitanium and ferroboron held at 400℃ for 20-40 minutes are added to the induction furnace. The molten steel in the ladle is then remelted in the furnace, and the temperature of the molten steel is raised to 1580-1600℃ and held for 10 minutes.

[0057] Just before casting, aluminum wire is placed in the ladle, and the molten steel in the induction furnace is transferred to the ladle again to obtain pure high-boron high-speed steel.

[0058] In the vacuum melting process, ferroboron is first melted before being added to ensure that all raw materials melt quickly and that the molten steel is fully stirred and melted by heat flow, thereby improving the uniformity of the melt. Preheating the ferroboron at 400℃ for 20-40 minutes can improve the yield of boron. Finally, aluminum wire is added to reduce burn-off and improve the yield of Al.

[0059] S2. After the temperature of the molten steel obtained in step S1 drops to 1400~1440℃, a cast billet is obtained by graphite mold casting.

[0060] Using graphite molds for casting can significantly improve the solidification rate of castings, which is beneficial for obtaining aluminum-containing high-boron high-speed steel castings with fine and uniform microstructure, and improving the performance stability of the workpiece.

[0061] S3. The as-cast billet obtained in step S2 is subjected to homogenization annealing, austenitization, cryogenic treatment and tempering heat treatment in sequence to obtain a heat-treated billet of aluminum-containing high-boron high-speed steel for oilfield pumping pumps, and then processed to obtain an aluminum-containing high-boron high-speed steel oilfield pumping pump.

[0062] The heat treatment process involves homogenization annealing, austenitization, cryogenic treatment, and tempering, followed by the following steps:

[0063] First, the castings are homogenized and held at 1000~1020℃ for 150~240 minutes, then cooled to room temperature in the furnace.

[0064] Next, after austenitizing at 1025~1075℃ for 90~120 minutes, quench the material with vacuum quenching oil to 200℃.

[0065] Subsequently, the workpiece at 200°C was immersed in liquid nitrogen at -196°C for 90-150 minutes and then removed to return to room temperature.

[0066] Finally, the workpiece is held at 500~600℃ for 45~75 minutes and then furnace cooled to room temperature. This process is repeated 3 times under the same tempering parameters.

[0067] After homogenization annealing at 1000~1020℃ for 150~240 min, the workpiece is furnace cooled to room temperature. Next, it is austenitized at 1025~1075℃ for 90~120 min and then quenched in vacuum quenching oil to 200℃. Then, it undergoes deep undercooling treatment by immersing the 200℃ workpiece in liquid nitrogen at -196℃ for 90~150 min and then removing it to room temperature. Finally, the workpiece is held at 500~600℃ for 45~75 min and then furnace cooled to room temperature. This process is repeated 3 times under the same tempering parameters. Homogenization degradation can improve the compositional uniformity of the workpiece, which is beneficial to improving the microstructure uniformity after subsequent heat treatment; austenitization + deep undercooling can promote the dissolution of boride sharp corners and increase the proportion of martensite in the metal matrix; the final three tempering treatments can effectively release the internal stress generated in the workpiece during solidification and early heat treatment, significantly promote 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 improve the stability of the alloy microstructure, especially the tempered martensite and the precipitated fine second-phase particles, thereby improving the service performance stability and service safety of the workpiece.

[0068] An aluminum-containing high-boron high-speed steel oilfield pump, prepared by the above method, comprises, by weight percentage: Al: 1.06%~1.55%, C: 0.11%~0.25%, B: 1.76%~2.47%, Cr: 6.14%~8.27%, W: 2.65%~3.06%, V: 0.32%~0.84%, Ti: 0.05%~0.11%, with the remainder being Fe and unavoidable trace impurities.

[0069] The heat-treated aluminum-containing high-boron high-speed steel has a high-density, finely dispersed tempered martensite matrix and a (Fe,Cr)2B hard phase. The addition of Al can significantly improve the corrosion resistance of the alloy, refine the grains, and improve the hardenability of the metal matrix. Cr and W can improve the matrix strength and hardenability, and increase the hardness and toughness of the boride hard phase. The addition of V and Ti can improve the alloy strength. B can form a eutectic boride hard phase and improve the hardenability of the matrix, which determines the wear resistance of high-boron high-speed steel. The addition of C can promote the formation of low-carbon tempered martensite in the matrix, improving the wear resistance and service safety of the material.

[0070] 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.

[0071] Example 1

[0072] Alloy Sample Preparation

[0073] This invention uses electrical pure iron, micro-carbon ferrochrome, ferromolybdenum, ferrotungsten, ferroboron, pig iron, ferrosilicon, and ferromanganese as raw materials. 70.248% electrical pure iron (chemical composition of electrical pure iron: 0.020% C, balance Fe), 10.772% micro-carbon ferrochrome (chemical composition of micro-carbon ferrochrome: 0.060% C, 57.000% Cr, balance Fe), 3.313% ferrotungsten (chemical composition of ferrotungsten: 0.100% C, 80.000% W, balance Fe), and 9.239% ferroboron (chemical composition of ferroboron: 0.380% C, 10.020% Cr, balance Fe) are added respectively. 19.050%B, balance Fe), 4.780% pig iron (pig iron has a chemical composition mass fraction of 4.270%C, balance Fe), 0.399% ferrovanadium (ferrovanadium has a chemical composition mass fraction of 0.25%C, 80.15%V, balance Fe), 0.189% ferrotitanium (ferrotitanium has a chemical composition mass fraction of 0.002%C, 26.46%Ti, balance Fe), 1.060% aluminum wire (aluminum wire has a chemical composition mass fraction of 99.99%Al).

[0074] The specific preparation and smelting process of this invention is as follows:

[0075] S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferroboron, pig iron, ferrovanadium, ferrotitanium, and aluminum wire as raw materials, first, electrical pure iron, micro-carbon ferrochrome, ferrotungsten, pig iron, and ferrovanadium are added to a vacuum induction furnace. After the furnace charge is completely melted, the molten steel is transferred to a ladle for hot ladle treatment. Then, ferrotitanium and ferroboron that has been held at 400℃ for 20 minutes are 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 to 1600℃ and held for 10 minutes. Just before casting, aluminum wire is placed in the ladle. The molten steel in the induction furnace is transferred to the ladle again to obtain pure high-boron high-speed steel.

[0076] S2. After the temperature of the molten steel obtained in step S1 drops to 1440℃, a cast billet is obtained by graphite mold casting.

[0077] S3. The as-cast billet obtained in step S2 is homogenized and annealed at 1020℃ for 240 min, then furnace cooled to room temperature. Next, it is austenitized at 1075℃ and held for 120 min, then quenched in vacuum quenching oil to 200℃. Subsequently, deep undercooling treatment is performed by immersing the 200℃ workpiece in liquid nitrogen at -196℃ for 150 min, then removing it and restoring it to room temperature. Finally, the workpiece is held at 600℃ for 75 min and then furnace cooled to room temperature. This process is repeated 3 times under the same tempering parameters. Aluminum-containing high-boron high-speed steel heat-treated billet for oilfield pumping units is obtained.

[0078] This embodiment prepares aluminum-containing high-boron high-speed steel billets according to the raw material mass ratio, through vacuum induction melting, 1440℃ graphite mold casting, and subsequent heat treatment. In this embodiment, the Al content is 1.06% and the B content is 1.76%. Through optimized melting and heat treatment processes, the material corrosion rate is 0.12 mm / y, and the erosion loss is 2.5 × 10⁻⁴ mm³ / m. The relative production cost is only 55% of that of M2 high-speed steel. The product has a uniform microstructure, with a dispersed (Fe, Cr)₂B hard phase on a tempered martensitic matrix. Its corrosion resistance is superior to that of M2 high-speed steel, and its wear resistance is close to that of M2 high-speed steel. The cost is significantly reduced, making it suitable for cost-sensitive oilfield extraction scenarios with relatively mild corrosion conditions.

[0079] Example 2

[0080] Alloy Sample Preparation

[0081] This invention uses electrical pure iron, micro-carbon ferrochrome, ferromolybdenum, ferrotungsten, ferroboron, pig iron, ferrosilicon, and ferromanganese as raw materials. 64.619% electrical pure iron (chemical composition of electrical pure iron: 0.020% C, balance Fe), 14.509% micro-carbon ferrochrome (chemical composition of micro-carbon ferrochrome: 0.060% C, 57.000% Cr, balance Fe), 3.825% ferrotungsten (chemical composition of ferrotungsten: 0.100% C, 80.000% W, balance Fe), and 12.966% ferroboron (chemical composition of ferroboron: 0.380% C, 14.509% C, 14.509% ferrochrome (chemical composition of micro-carbon ferrochrome: 0.060% C, 57.000% Cr, balance Fe), 3.825% ferrotungsten (chemical composition of ferrotungsten: 0.100% C, 80.000% W, balance Fe), and 12.966% ferroboron (chemical composition of ferroboron: 0.380% C, 14.509% Cr ... 19.050%B, balance Fe), 1.067% pig iron (pig iron has a chemical composition mass fraction of 4.270%C, balance Fe), 1.048% ferrovanadium (ferrovanadium has a chemical composition mass fraction of 0.25%C, 80.15%V, balance Fe), 0.416% ferrotitanium (ferrotitanium has a chemical composition mass fraction of 0.002%C, 26.46%Ti, balance Fe), 1.550% aluminum wire (aluminum wire has a chemical composition mass fraction of 99.99%Al).

[0082] The specific preparation and smelting process of this invention is as follows:

[0083] S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferroboron, pig iron, ferrovanadium, ferrotitanium, and aluminum wire as raw materials, first, electrical pure iron, micro-carbon ferrochrome, ferrotungsten, pig iron, and ferrovanadium are added to a vacuum induction furnace. After the furnace charge is completely melted, the molten steel is transferred to a ladle for hot ladle treatment. Then, ferrotitanium and ferroboron that has been held at 400℃ for 40 minutes are 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 to 1580℃ and held for 10 minutes. Just before casting, aluminum wire is placed in the ladle. The molten steel in the induction furnace is transferred to the ladle again to obtain pure high-boron high-speed steel.

[0084] S2. After the temperature of the molten steel obtained in step S1 drops to 1400℃, a cast billet is obtained by graphite mold casting.

[0085] S3. The as-cast billet obtained in step S2 is homogenized and annealed at 1020℃ for 240 min, then furnace cooled to room temperature. Next, it is austenitized at 1025℃ and held for 90 min, then quenched in vacuum quenching oil to 200℃. Subsequently, deep undercooling treatment is performed by immersing the 200℃ workpiece in liquid nitrogen at -196℃ for 90 min, then removing it and restoring it to room temperature. Finally, the workpiece is held at 500℃ for 45 min and then furnace cooled to room temperature. This process is repeated 3 times under the same tempering parameters. Aluminum-containing high-boron high-speed steel heat-treated billet for oilfield pumping units is obtained.

[0086] This embodiment employs a high Cr, high Al, and high B composition ratio. Through 1400℃ graphite mold casting and low-temperature short-time heat treatment, the material exhibits a corrosion rate of 0.15 mm / y and an erosion loss of 2.0 × 10⁻⁴ mm³ / m. The relative production cost is 65% of that of M2 high-speed steel. The high Cr and B content enhances the material's wear resistance and boride toughness, while the high Al content further strengthens its corrosion resistance. The erosion loss is superior to that of M2 high-speed steel, making it suitable for downhole conditions with high silt content and severe erosion. It can withstand strong erosion for extended periods, with a service life more than three times longer than 316L stainless steel.

[0087] Example 3

[0088] Alloy Sample Preparation

[0089] This invention uses electrical pure iron, micro-carbon ferrochrome, ferromolybdenum, ferrotungsten, ferroboron, pig iron, ferrosilicon, and ferromanganese as raw materials. 67.105% electrical pure iron (chemical composition of electrical pure iron: 0.020% C, balance Fe), 12.941% micro-carbon ferrochrome (chemical composition of micro-carbon ferrochrome: 0.060% C, 57.000% Cr, balance Fe), 3.245% ferrotungsten (chemical composition of ferrotungsten: 0.100% C, 80.000% W, balance Fe), and 11.549% ferroboron (chemical composition of ferroboron: 0.380% C, 12.941% micro-carbon ferrochrome (chemical composition of micro-carbon ferrochrome: 0.060% C, 57.000% Cr, balance Fe) are added respectively. 19.050%B, balance Fe), 2.892% pig iron (pig iron has a chemical composition mass fraction of 4.270%C, balance Fe), 0.642% ferrovanadium (ferrovanadium has a chemical composition mass fraction of 0.25%C, 80.15%V, balance Fe), 0.416% ferrotitanium (ferrotitanium has a chemical composition mass fraction of 0.002%C, 26.46%Ti, balance Fe), 1.210% aluminum wire (aluminum wire has a chemical composition mass fraction of 99.99%Al).

[0090] The specific preparation and smelting process of this invention is as follows:

[0091] S1. Using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferroboron, pig iron, ferrovanadium, ferrotitanium, and aluminum wire as raw materials, first, electrical pure iron, micro-carbon ferrochrome, ferrotungsten, pig iron, and ferrovanadium are added to a vacuum induction furnace. After the furnace charge is completely melted, the molten steel is transferred to a ladle for hot ladle treatment. Then, ferrotitanium and ferroboron that has been held at 400℃ for 30 minutes are 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 to 1590℃ and held for 10 minutes. Just before casting, aluminum wire is placed in the ladle. The molten steel in the induction furnace is transferred to the ladle again to obtain pure high-boron high-speed steel.

[0092] S2. After the temperature of the molten steel obtained in step S1 drops to 1420℃, a cast billet is obtained by graphite mold casting.

[0093] S3. The as-cast billet obtained in step S2 is homogenized and annealed at 1000℃ for 180 min, then furnace cooled to room temperature. Next, it is austenitized at 1050℃ and held for 105 min, then quenched in vacuum quenching oil to 200℃. Subsequently, deep undercooling treatment is performed by immersing the 200℃ workpiece in liquid nitrogen at -196℃ for 120 min, then removing it and restoring it to room temperature. Finally, the workpiece is held at 550℃ for 60 min and then furnace cooled to room temperature. This process is repeated 3 times under the same tempering parameters. Aluminum-containing high-boron high-speed steel heat-treated billet for oilfield pumping units is obtained.

[0094] This embodiment represents the optimal form, with a balanced composition. Through 1420℃ graphite mold casting and intermediate heat treatment, the material exhibits a corrosion rate as low as 0.08 mm / y and an erosion loss of 1.8 × 10⁻⁴ mm³ / m. The relative production cost is 60% of that of M2 high-speed steel. The product forms a continuous Al-rich oxide film, exhibiting corrosion resistance 1.25 times that of 316L stainless steel and erosion resistance 1.17 times that of M2 high-speed steel. The network of eutectic borides in the microstructure exhibits the disappearance of sharp corners, combining excellent corrosion resistance, wear resistance, and toughness. It can still be used normally after one year of downhole service, extending its service life by more than two times compared to M2 high-speed steel pump bodies. It is suitable for complex downhole conditions with severe corrosion and erosion.

[0095] Example 4

[0096] Alloy Sample Preparation

[0097] The following materials were selected: 68.520% electrical pure iron (0.020% C, balance Fe), 11.830% micro-carbon ferrochrome (0.060% C, 57.000% Cr, balance Fe), 3.560% ferrotungsten (0.100% C, 80.000% W, balance Fe), 10.420% ferroboron (0.380% C, 19.050% B, balance Fe), 3.210% pig iron (4.270% C, balance Fe), 0.580% ferrovanadium (0.25% C, 80.15% V, balance Fe), 0.280% ferrotitanium (0.002% C, 26.46% Ti, balance Fe), and 1.190% aluminum wire (99.99% Al).

[0098] The preparation process is as follows:

[0099] S1. Add electrical pure iron, micro-carbon ferrochrome, ferrotungsten, pig iron, and ferrovanadium to the vacuum induction furnace. After the furnace charge is completely melted, transfer it to the ladle for hot casting. Add ferrotitanium and ferroboron that has been held at 400℃ for 25 minutes to the induction furnace. Return the molten steel to the furnace for refining. Raise the temperature to 1585℃ and hold for 9 minutes. Before casting, add aluminum wire and transfer the molten steel to the ladle to obtain high-boron high-speed steel.

[0100] S2. The molten steel is cooled to 1410℃ and cast in a graphite mold to obtain a cast billet;

[0101] S3. The cast billet is homogenized and annealed at 1010℃ for 200 min and then cooled in the furnace; it is austenitized at 1040℃ for 100 min, then vacuum quenched in oil to 190℃; it is held in liquid nitrogen at -198℃ for 110 min and then restored to room temperature; it is held at 520℃ for 55 min and then furnace cooled. The tempering is repeated 3 times to obtain the heat-treated billet.

[0102] The corrosion rate of the material in this embodiment is 0.09 mm / y, the erosion loss is 1.9 × 10⁻⁴ mm³ / m, and the relative production cost is 58% of that of M2 high-speed steel. The composition and process parameters are balanced, taking into account both corrosion resistance and wear resistance. The Al-rich oxide film is continuous and dense, and the borides are evenly distributed. It is suitable for moderate corrosion and erosion conditions, has a moderate production cost, and offers high cost-effectiveness, meeting the batch application needs of large-scale oilfield development.

[0103] Example 5

[0104] Alloy Sample Preparation

[0105] The following materials were selected: 66.310% electrical pure iron (0.020% C, balance Fe), 13.620% micro-carbon ferrochrome (0.060% C, 57.000% Cr, balance Fe), 3.710% ferrotungsten (0.100% C, 80.000% W, balance Fe), 12.150% ferroboron (0.380% C, 19.050% B, balance Fe), 1.980% pig iron (4.270% C, balance Fe), 0.890% ferrovanadium (0.25% C, 80.15% V, balance Fe), 0.350% ferrotitanium (0.002% C, 26.46% Ti, balance Fe), and 1.400% aluminum wire (99.99% Al).

[0106] The preparation process is as follows:

[0107] S1. Add electrical pure iron, micro-carbon ferrochrome, ferrotungsten, pig iron, and ferrovanadium to the vacuum induction furnace. After the furnace charge is completely melted, transfer it to the ladle for hot casting. Add ferrotitanium and ferroboron that has been held at 400℃ for 35 minutes to the induction furnace. Return the molten steel to the furnace for refining. Raise the temperature to 1595℃ and hold for 11 minutes. Before casting, add aluminum wire and transfer the molten steel to the ladle to obtain high-boron high-speed steel.

[0108] S2. The molten steel is cooled to 1430℃ and cast in a graphite mold to obtain a cast billet;

[0109] S3. The as-cast billet is homogenized and annealed at 1015℃ for 220 min and then cooled in the furnace; it is austenitized at 1060℃ for 110 min and then quenched in vacuum oil to 210℃; it is held in liquid nitrogen at -195℃ for 130 min and then restored to room temperature; it is held at 580℃ for 65 min and then furnace cooled. The tempering is repeated 3 times to obtain the heat-treated billet.

[0110] The corrosion rate of the material in this embodiment is 0.11 mm / y, and the erosion loss is 1.85 × 10⁻⁴ mm³ / m, with a relative production cost of 63% of that of M2 high-speed steel. The high Cr and V content further enhances the toughness of the boride and the strength of the matrix, resulting in extremely low erosion loss. It is suitable for harsh downhole conditions with extremely high silt content and severe erosion, while maintaining good corrosion resistance and effectively resisting long-term corrosion from oil-water mixtures. Its service life is extended by more than 15% compared to Example 1.

[0111] Service condition simulation test comparison

[0112] The aluminum-containing high-boron high-speed steel, M2 high-speed steel, and 316L stainless steel from Examples 1, 2, and 3 were subjected to simulated corrosion and wear tests under different service conditions. The corrosion test conditions were: static 3.5 wt.% NaCl aqueous solution at 60℃. The wear test conditions were: impeller driving a pure water slurry containing 10 vol.% quartz sand (40-70 mesh) at a flow rate of 5 m / s.

[0113] Table 1. Comparison of corrosion rates, erosion losses, and relative production costs of pump materials from different oilfields.

[0114]

[0115] The simulation test results are shown in Table 1. The corrosion resistance and erosion resistance of the aluminum-containing high-boron high-speed steel prepared in the embodiments of the present invention are superior to those of M2 high-speed steel and 316L stainless steel. Among them, the corrosion resistance of Example 3 is 1.25 times that of 316L stainless steel and the erosion resistance is 1.17 times that of M2 high-speed steel, but the cost is only 70% and 60% of the two, respectively. The corrosion cross-sectional morphology photograph of the aluminum-containing high-boron high-speed steel in Example 3 is shown in Table 1. Figure 3 A continuous Al-rich oxide film was observed to form on the alloy surface, which significantly inhibited further corrosion of the alloy by the corrosive medium.

[0116] Next, the pump body made of aluminum-containing high-boron high-speed steel in Example 3 and the pump body made of M2 high-speed steel were selected for downhole service testing. The downhole test lasted for 1 year. The pump body made of aluminum-containing high-boron high-speed steel in Example 3 had a less severe corrosion and could continue to be used, while the inner wall of the pump body made of M2 high-speed steel was severely damaged and could not continue to be used.

[0117] Please see Figure 2 The aluminum-containing solidified high-boron high-speed steel prepared according to the process parameters of Example 3 contains a high volume fraction of (Fe,Cr)2B hard phase in its microstructure. The tempered martensitic matrix contains a large number of second-phase precipitated hard particles, and the sharp corners of the network eutectic boride disappear. At this time, the alloy has both corrosion resistance and wear resistance, and has good service safety and long service life.

[0118] Please see Figure 3The cross-sectional photograph of Example 3 after static corrosion with 3.5 wt.% NaCl aqueous solution at 60°C shows that a continuous Al-rich oxide layer was formed on the alloy surface. The formation of this layer protects the alloy and further improves its corrosion resistance.

[0119] Please see Figure 4 A downhole service test was conducted on the pump body made of the material of Example 3 and M2 high-speed steel for one year. The results showed that although the inner wall of the pump body of the aluminum-containing high-boron high-speed steel of Example 3 was corroded, it could still continue to be used. However, the inner wall of the pump body of the M2 high-speed steel was severely damaged and could not continue to be used. This shows that the aluminum-containing high-boron high-speed steel of the present invention has superior service performance and service life compared with traditional materials.

[0120] In summary, this invention provides an aluminum-containing high-boron high-speed steel oilfield pump and its preparation method. The pump is prepared using a combination of vacuum melting, graphite mold casting, and heat treatment processes. This results in the high-boron high-speed steel possessing a tempered martensite matrix containing fine tempered hard particles and a (Fe,Cr)₂B hard phase with a fine eutectic structure. This significantly improves the material's corrosion resistance, wear resistance, and service safety, resulting in superior performance compared to other materials.

[0121] 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 an aluminum-containing high-boron high-speed steel oilfield pump, characterized in that, Includes the following steps: S1. High-boron high-speed steel molten steel is obtained by vacuum induction melting using electrical pure iron, micro-carbon ferrochrome, ferrotungsten, ferroboron, pig iron, ferrovanadium, ferrotitanium, and aluminum wire as raw materials. S2. The high-boron high-speed steel molten steel obtained in step S1 is cast in a graphite mold at 1400~1440℃ to obtain a cast billet; S3. The as-cast billet obtained in step S2 is subjected to homogenization annealing, austenitization, deep supercooling, and tempering heat treatment in sequence. The homogenization annealing conditions are: holding at 1000~1020℃ for 150~240min, followed by furnace cooling to room temperature. The austenitization conditions are: holding at 1025~1075℃ for 90~120min, followed by vacuum quenching oil quenching to 180~220℃. The deep supercooling treatment involves immersing the workpiece in liquid nitrogen at -200~-192℃ for 90~150min, then removing it and restoring it to room temperature. The tempering heat treatment... The process involves holding the steel at 500-600℃ for 45-75 minutes and then furnace cooling to room temperature. This process is repeated at least three times to obtain a heat-treated billet of aluminum-containing high-boron high-speed steel. After processing, an aluminum-containing high-boron high-speed steel oilfield pump is produced. By weight percentage, the billet contains Al: 1.06%-1.55%, C: 0.11%-0.25%, B: 1.76%-2.47%, Cr: 6.14%-8.27%, W: 2.65%-3.06%, V: 0.32%-0.84%, Ti: 0.05%-0.11%, with the remainder being Fe and unavoidable trace impurities.

2. The method for preparing an aluminum-containing high-boron high-speed steel oilfield pump according to claim 1, characterized in that, In step S1, the mass fraction of each raw material is as follows: electrical pure iron 64.619%~70.248%, micro-carbon ferrochrome 10.772%~14.509%, ferrotungsten 3.313%~3.825%, ferroboron 9.239%~12.966%, pig iron 1.067%~4.780%, ferrovanadium 0.399%~1.048%, ferrotitanium 0.189%~0.416%, and aluminum wire 1.060%~1.550%.

3. The method for preparing an aluminum-containing high-boron high-speed steel oilfield pump according to claim 1, characterized in that, In step S1, vacuum induction melting specifically includes: Electrically pure iron, micro-carbon ferrochrome, ferrotungsten, pig iron, and ferrovanadium are added to the vacuum induction furnace. After the furnace charge is completely melted, the molten steel is transferred to a ladle for hot ladle pouring. Add ferrotitanium and preheated ferroboron to the induction furnace, return the molten steel from the ladle to the furnace for remelting, and heat to 1580~1600℃ and hold for 8~12 minutes. Before casting, aluminum wire is placed into the ladle, and then the molten steel in the induction furnace is transferred to the ladle to obtain high-boron high-speed steel.

4. The method for preparing an aluminum-containing high-boron high-speed steel oilfield pump according to claim 3, characterized in that, The preheating treatment of ferroboron involves holding the ferroboron at 380~420℃ for 20~40 minutes.

5. The method for preparing an aluminum-containing high-boron high-speed steel oilfield pump according to claim 1, characterized in that, In step S3, the high-boron aluminum high-speed steel heat-treated billet obtained after tempering heat treatment has a tempered martensitic matrix with high density and fine dispersed particles and a (Fe,Cr)2B hard phase.

6. An aluminum-containing high-boron high-speed steel oilfield pump prepared by the method according to any one of claims 1 to 5.

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