Composite boronizing agent and solid boronizing method for oil pipes

Abstract

The present invention belongs to the field of metal surface treatment and relates to a composite boronizing agent and a solid boronizing method for oil pipes. The composite boronizing agent comprises a boronizing agent and graphite. Calculated on the basis of mass percentage, the graphite is 10-14% of the mass of the boronizing agent. The boronizing agent comprises the following raw materials in mass percentages: boron source: 10-15%, catalyst: 12-20%, activator: 8-10%, dispersant: 4-6%, filler: 50-55%, and flow aid: 8-12%, and the dispersant is triethanolamine borate. In the composite boronizing agent of the present invention, the triethanolamine borate can remove impurities from an inner surface of an oil pipe, improve the boronizing effect and boronized layer quality, and form a protective film to prevent carburization, promote boronizing, and enhance boronized layer bonding strength. In addition, through the combined action of triethanolamine borate and graphite, the boronizing agent can be prevented from agglomerating or adhering to the inner surface of the oil pipe after boronizing treatment, and the uniformity of boronizing can further be improved.

Description

Composite boronizing agent and solid boronizing method for oil pipe TECHNICAL FIELD

[0001] The present application relates to the technical field of metal surface treatment, in particular to a composite boronizing agent and a solid boronizing method for an oil pipe. BACKGROUND

[0002] Oil is an important energy source and strategic material, which is buried deep in the ground or under the sea. The equipment for exploiting oil includes but is not limited to oil pipes made of steel. Oil pipes are used for long-distance transportation of crude oil or refined oil and are easily corroded by pressure, temperature and various corrosive media, so the firmness and durability of the oil pipes need to be improved to reduce the frequency of replacement.

[0003] Boronizing is a chemical heat treatment technology that allows boron to penetrate the surface of a metal under high temperature conditions to obtain a hard layer of boron compound. The inner surface of an oil pipe can be treated by boronizing to improve its hardness, wear resistance and corrosion resistance.

[0004] The prior art can treat oil pipes by boronizing through solid boronizing, gas boronizing, paste boronizing and salt bath boronizing. Solid boronizing has the advantages of convenient operation, simple equipment and easy quality control, and has been widely used in production. However, although solid boronizing has many advantages, it still has some disadvantages, which limit the application of solid boronizing in oil pipes.

[0005] First, the impurities such as metal oxides on the inner surface of the oil pipe are difficult to completely remove, which will affect the quality of the boronized layer.

[0006] Second, as the boronizing process proceeds, the inner surface of the oil pipe will gradually carburize and produce a carburized layer, which will prevent boronizing, form pores, cause the boronizing agent to be unable to use, and cause the boronized layer formed to be not firmly combined with the oil pipe and easily fall off.

[0007] Third, after the existing solid boronizing method is used for boronizing treatment, the boronizing agent will be caked on the inner surface of the oil pipe. The caked boronizing agent needs to be removed by additional manpower and material resources, and for long oil pipes, such as oil pipes with a length of 9.7 m or more, it is difficult to completely remove the caked boronizing agent on the inner surface of the oil pipe.

[0008] Therefore, it is necessary to solve the problems of the prior art that the quality of the boronized layer is easily affected by the impurities on the inner surface of the oil pipe, carburization occurs to cause only carburization but no boronizing, the boronized layer easily falls off, and the caked boronizing agent is difficult to remove after caking on the inner surface of the oil pipe. SUMMARY

[0009] (I) Technical problems to be solved

[0010] In view of the above technical problems, the present application provides a composite boronizing agent and a solid boronizing method for oil pipes, so as to improve the quality of the boronized layer, avoid the phenomenon of only carbon penetration but no boron penetration, improve the bonding strength of the boronized layer and avoid the caking of the boronizing agent.

[0011] (II) Technical solutions

[0012] In order to achieve the above-mentioned purposes, the main technical solutions adopted by the present application include:

[0013] The present application provides a composite boronizing agent, which comprises a boronizing agent and graphite.

[0014] According to the mass percentage, the graphite accounts for 10-14% of the mass of the boronizing agent; the boronizing agent comprises the following raw materials with the mass percentage: boron supply agent: 10-15%, catalyst: 12-20%, activator: 8-10%, dispersing agent: 4-6%, filler: 50-55%, and flow aid: 8-12%; the dispersing agent is triethanolamine borate.

[0015] The composite boronizing agent as described above, preferably, the boron supply agent is boric anhydride or boron carbide.

[0016] The composite boronizing agent as described above, preferably, the catalyst comprises potassium fluoborate, sodium fluoride and potassium fluoride, wherein the potassium fluoborate accounts for 5-10% of the total mass of the boronizing agent, the sodium fluoride accounts for 5-6% of the total mass of the boronizing agent, and the potassium fluoride accounts for 2-4% of the total mass of the boronizing agent.

[0017] The composite boronizing agent as described above, preferably, the activator comprises silicon dioxide and activated carbon, wherein the silicon dioxide accounts for 5-7% of the total mass of the boronizing agent, and the activated carbon accounts for 2-4% of the total mass of the boronizing agent.

[0018] The filler comprises aluminum oxide and / or silicon carbide.

[0019] The composite boronizing agent as described above, preferably, the particle size of the graphite mixed with the boronizing agent is 30-50 mesh.

[0020] The flow aid comprises charcoal powder and graphite powder, wherein the charcoal powder accounts for 3-5% of the total mass of the boronizing agent, and the graphite powder accounts for 4-8% of the total mass of the boronizing agent; the particle size of the graphite powder is 140-160 mesh.

[0021] The present application also provides a solid boronizing method for oil pipes using the above-mentioned composite boronizing agent, which comprises the following steps:

[0022] S1: cleaning the inner surface of the oil pipe;

[0023] S2: mixing the boronizing agent with graphite to obtain a composite boronizing agent, and then loading the composite boronizing agent into the inside of the oil pipe to make the composite boronizing agent contact with the inner surface of the oil pipe;

[0024] S3: sealing treatment is performed on the oil pipe with the composite boronizing agent loaded in the inside;

[0025] S4: heating boronizing treatment is performed on the oil pipe after the sealing treatment, and the oil pipe with a boronizing layer on the inner surface is obtained after cooling.

[0026] The solid boronizing method of the oil pipe as described above, preferably, in step S3, the outer surface of the oil pipe is wrapped with a deoxidizing agent and then metal ceramic balls in sequence, and then the metal ceramic balls are sealed with quartz sand powder.

[0027] The solid boronizing method of the oil pipe as described above, preferably, the thickness of the metal ceramic ball layer is 100-150 mm, the particle size of the metal ceramic balls is 1-2 mm, the particle size of the quartz sand powder is 300-350 mesh, and the thickness of the quartz sand powder layer is 60-100 mm after the sealing treatment of the quartz sand powder.

[0028] The solid boronizing method of the oil pipe as described above, preferably, in step S4, the heating boronizing treatment comprises: heating the oil pipe after the sealing treatment to 660-700 DEG C, keeping for 10-20 min, then heating to 760-800 DEG C, keeping for 5-15 min, continuously heating to 810-840 DEG C, keeping for 15-25 min, then heating to 850-950 DEG C, keeping for 4-6 h, and finally cooling to room temperature to complete the heating treatment.

[0029] The solid boronizing method of the oil pipe as described above, preferably, the oil pipe is prepared by ordinary alloy steel or high alloy steel;

[0030] In the ordinary alloy steel, the total content of alloying elements is ≤5wt%,

[0031] In the high alloy steel, the total content of alloying elements is >5wt%.

[0032] (Three) beneficial effects

[0033] The composite boronizing agent of the present application takes triethanolamine borate as a dispersing agent, and in the solid boronizing process, the triethanolamine borate can wrap the boronizing agent and the catalyst, and then react with the metal oxides on the inner surface of the oil pipe to generate a combination, the combination is further decomposed to generate water and hydrogen fluoride, the water and the hydrogen fluoride form hydrofluoric acid and remove the impurities such as metal oxides on the inner surface of the oil pipe, realize the effect of secondary derusting, and can improve the boronizing effect and the quality of the boronizing layer.

[0034] The triethanolamine borate can form a protective film on the inner surface of the oil pipe in the boronizing process, prevents the workpiece from being oxidized, and helps the boronizing process.

[0035] In addition, the protective film formed by the triethanolamine borate on the inner surface of the oil pipe can prevent carbon atoms from entering the oil pipe, avoid carburization, promote boronizing, solve the problem that only carburization but not boronizing exists in the existing boronizing process, improve the bonding strength of the boronized layer, and avoid the boronized layer from falling off.

[0036] In addition, the composite boronizing agent of the present application further comprises graphite, and under the joint action of the triethanolamine borate and the graphite in the boronizing agent, the boronizing agent can be prevented from caking and adhering to the inner wall of the oil pipe after the boronizing treatment, and the uniformity of the boronizing can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Fig. 1 is a microstructure diagram of the boronized layer on the inner surface of the oil pipe in Example 1;

[0038] Fig. 2 is a microstructure diagram of the boronized layer on the inner surface of the oil pipe in Comparative Example 3;

[0039] Fig. 3 is a microstructure diagram of the boronized layer on the inner surface of the oil pipe in Example 2;

[0040] Fig. 4 is a metallographic structure diagram of the oil pipe alloy steel base body connected with the boronized layer in Example 2;

[0041] Fig. 5 is a microstructure diagram of the boronized layer on the inner surface of the oil pipe in Example 3;

[0042] Fig. 6 is a microstructure diagram of the boronized layer on the inner surface of the oil pipe in Example 4;

[0043] Fig. 7 is a microstructure diagram of the boronized layer on the inner surface of the oil pipe in Example 5 and a metallographic structure diagram of the oil pipe alloy steel base body connected with the boronized layer;

[0044] Fig. 8 is a microstructure diagram of the boronized layer in the control sample;

[0045] Fig. 9 is a metallographic structure diagram of the oil pipe alloy steel base body connected with the boronized layer in the control sample;

[0046] Fig. 10 is a diagram showing the morphological changes of the oil pipe sample prepared in Example 2 observed at different time nodes when the sample is immersed in a 25wt% hydrochloric acid solution;

[0047] Fig. 11 is a diagram showing the morphological changes of the oil pipe sample observed at different time nodes when the sample is immersed in a 25wt% hydrochloric acid solution;

[0048] Fig. 12 is a diagram showing the morphological changes of the oil pipe sample prepared in Example 2 observed at different time nodes when the sample is immersed in a 10wt% NaCl solution;

[0049] Figure 13 is a diagram showing the morphological changes of the control oil pipe sample immersed in 10wt% NaCl solution at different time nodes;

[0050] Figure 14 is a diagram showing the morphological changes of the oil pipe sample prepared in Example 2 immersed in 25wt% HNO3 solution at different time nodes;

[0051] Figure 15 is a diagram showing the morphological changes of the control oil pipe sample immersed in 25wt% HNO3 solution at different time nodes. DETAILED DESCRIPTION

[0052] In order to better explain the present application, the present application is described in detail below in combination with specific embodiments.

[0053] The present application provides a composite boronizing agent, which comprises a boronizing agent and graphite. The graphite accounts for 10-14% of the mass of the boronizing agent. The boronizing agent comprises the following raw materials in the following mass percentages: boron source: 10-15%, catalyst: 12-20%, activator: 8-10%, dispersant: 4-6%, filler: 50-55%, and flow aid: 8-12%. The dispersant used in the present application is triethanolamine borate (TEAB, chemical formula: C6H 12 BNO3).

[0054] In the present application, the boron source is preferably boric anhydride or boron carbide. The boron source in the existing boronizing agent is generally boron carbide, and the addition amount of boron carbide can reach about 50% of the mass of the boronizing agent. The researchers of the present application found through long-term research that the existing boronizing agent adds a high content of boron carbide, but boron carbide can only supply boron at high temperatures. In addition to boron carbide, the present application can also use boric anhydride as a boron source, and the boron supply temperature of boric anhydride is lower than that of boron carbide, which can continuously supply boron during the boronizing process. The boronizing agent of the present application preferentially uses boron carbide when the boronizing treatment temperature in the boronizing process is high, for example, above 900°C, and preferentially uses boric anhydride when the boronizing treatment temperature in the boronizing process is low, for example, 850-900°C.

[0055] The above-mentioned catalyst preferably comprises potassium fluoborate, sodium fluoride and potassium fluoride. The potassium fluoborate accounts for 5-10% of the total mass of the boronizing agent, the sodium fluoride accounts for 5-6% of the total mass of the boronizing agent, and the potassium fluoride accounts for 2-4% of the total mass of the boronizing agent. The addition amount of the catalyst in the present application needs to be strictly controlled within 12-20%. If the addition amount exceeds 20%, the boronizing layer will have too many pores, and the boronizing agent will be caked, affecting the quality of the boronizing layer.

[0056] The activator preferably includes silica and activated carbon. Silica accounts for 5-7% of the total mass of the boronizing agent, and activated carbon accounts for 2-4% of the total mass of the boronizing agent. The activator of this invention has a dual function; it can act as an oxidant and, due to its high melting point, also as a dispersant. Specifically, as a dispersant, it disperses the catalyst, controls the catalyst's reactivity, slows down the decomposition rate of potassium fluoroborate in the catalyst, and improves the boronizing effect.

[0057] The dual-directional effect of the activator in this invention is as follows:

[0058] Potassium fluoroborate in the catalyst undergoes the following decomposition reaction at high temperature:

[0059] KBF4 = BF3 + KF ①

[0060] Taking boron carbide as a boron donor as an example, the boron donor of the present invention will react with BF3 and KF produced by the decomposition of potassium fluoroborate during the boronizing process as follows to achieve boronizing:

[0061] B4C+2KF+SiC+4O2=[B]+BF2↑+B2O3+K2SiO3+2CO↑ ②

[0062] 2B4C+2BF3+5O2=3[B]+3BF2↑+2B2O3+2CO2↑ ③

[0063] 4BF3+3SiC+4O2=2BF2↑+B2O3+2SiF4↑+SiO2+3CO↑ ④

[0064] It should be noted that oxygen is involved in all of the above boronizing reactions ②, ③ and ④, and the oxygen involved in the reactions all comes from the air naturally carried in during the process of wrapping and sealing the oil pipe.

[0065] This invention selects activated carbon and silicon dioxide as activating agents. Under high temperature conditions, silicon dioxide and activated carbon can undergo the following reaction:

[0066] SiO2 + 2C (high temperature) = Si + 2CO↑ ⑤

[0067] The above reaction ⑤ can generate carbon monoxide, which can disperse and regulate the concentration of boron fluoride during the boronizing process, acting as a dispersant to prevent the boron fluoride concentration from being too high, thereby improving the boronizing effect.

[0068] Silica and activated carbon have a lot of pore structure, thus can carry oxygen and play the role of oxidant. In addition, activated carbon can react with excess oxygen to generate carbon monoxide or carbon dioxide gas, which plays the role of reducing agent and disperses the concentration of boron fluoride.

[0069] In the present application, boron can be diffused in the form of gas to realize boronizing after the decomposition of potassium fluoborate at high temperature, and the boron supply agent can also realize boronizing through contact diffusion.

[0070] Preferably, the filler of the present application comprises alumina and / or silicon carbide. Specifically, white and high-purity alumina is required, such as white alumina with a purity of 99.99% or above, and the particle size of the alumina is 0.1-0.2mm. Silicon carbide is selected to be green silicon carbide, and the particle size can be 140-160 mesh.

[0071] Preferably, the above-mentioned flow aid preferably comprises charcoal powder and graphite powder. Among them, the charcoal powder accounts for 3-5% of the total mass of the boronizing agent, the graphite powder accounts for 4-8% of the total mass of the boronizing agent, and the particle size of the graphite powder is 140-160 mesh. In the present application, the addition of flow aid can avoid the caking of boronizing agent before use.

[0072] Further preferably, the particle size of the graphite mixed with the boronizing agent is 30-50 mesh.

[0073] The present application also provides a solid boronizing method for oil pipes, comprising the following steps:

[0074] S1: cleaning the inner surface of the oil pipe.

[0075] S2: mixing the boronizing agent in the above-mentioned composite boronizing agent with graphite to obtain a composite boronizing agent, and then loading the composite boronizing agent into the oil pipe to make the composite boronizing agent contact with the inner surface of the oil pipe.

[0076] S3: sealing treatment of the oil pipe with the composite boronizing agent loaded inside.

[0077] S4: heating and boronizing treatment of the sealed oil pipe, and cooling to obtain an oil pipe with a boronizing layer on the inner surface.

[0078] In the above-mentioned step S1, the inner surface of the oil pipe is specifically treated for rust removal. After completing the rust removal treatment, the oil pipe also needs to be dried to remove the water therein.

[0079] The composite boronizing agent of the present application takes triethanolamine borate as a dispersant, and during the heat treatment process of boronizing, the triethanolamine borate can wrap the boronizing agent and the catalyst, and then reacts with the metal oxides on the inner surface of the oil pipe to generate a combination, the combination is decomposed to generate water and hydrogen fluoride, the water and hydrogen fluoride can form hydrofluoric acid, remove the impurities such as metal oxides on the inner surface of the oil pipe, realize the effect of secondary rust removal, and can improve the quality of the boronized layer.

[0080] The triethanolamine borate can also form a protective film on the inner surface of the oil pipe during the boronizing process, prevent the workpiece from oxidizing, and help the boronizing process.

[0081] Since the ordinary alloy steel workpiece or high alloy steel oil pipe contains carbon elements, the flow aid includes graphite powder, and the boronizing agent is mixed with the graphite, therefore, during the boronizing process, the carbon content will gradually increase, and a large amount of carburized layer will be generated on the inner surface of the oil pipe during the boronizing process, which prevents boron atoms from entering and forms a large number of loose and pores, resulting in that the boronizing agent cannot be used and only carburizing but not boronizing occurs. The protective film formed by the triethanolamine borate on the surface of the workpiece can prevent carbon atoms from entering the workpiece, reduce the carburizing phenomenon, promote boronizing, and thus solve the problem of only carburizing but not boronizing existing in the existing boronizing process, improve the bonding strength of the boronized layer, and can avoid the boronized layer from falling off.

[0082] The present application also mixes the boronizing agent with the graphite and then loads it into the inside of the oil pipe for boronizing treatment. Under the joint action of the triethanolamine borate and the graphite, the boronizing agent can be prevented from caking and adhering to the inner wall of the oil pipe, and the uniformity of boronizing can be improved. If the triethanolamine borate is not added, even if the boronizing agent is dried and then used, there will be a problem of caking to varying degrees. The boronizing agent is prone to moisture, and it is difficult to clean the boronizing agent from the surface of the workpiece after boronizing treatment. If the graphite is not added, for long oil pipes, especially long oil pipes with a length of ≥9.7m, the problem of uneven boronizing of the boronizing agent after boronizing treatment will be more obvious due to the long length of the oil pipe. In addition, if the graphite is not added, for long oil pipes with a length of ≥9.7m, the boronizing agent does not appear obvious caking, but it is still difficult to completely remove from the inner wall of the oil pipe, and the uniformity of boronizing will also be affected.

[0083] Before the composite boronizing agent is loaded into the inside of the oil pipe in the above step S2, in order to avoid boronizing at the oil pipe thread and changing the mechanical properties of the thread, a high-temperature-resistant anti-permeation agent needs to be applied to the oil pipe thread. Moreover, before the composite boronizing agent is loaded into the inside of the oil pipe, the composite boronizing agent can also be subjected to drying treatment to remove the water therein, and the temperature of the drying is ≤120℃, and the drying time is 15-25min.

[0084] In step S3, the outer surface of the oil pipe is wrapped with the deoxidizing agent and the cermet ball in sequence, and then the cermet ball is sealed with quartz sand powder to reduce the influence of air on boronizing. The particle size of the cermet ball is 1-2 mm, the thickness of the cermet ball layer formed after the cermet ball is wrapped is 100-150 mm, preferably 120 mm, the particle size of the quartz sand powder is 300-350 mesh, preferably 325 mesh, and the thickness of the quartz sand powder layer after the sealing treatment of the quartz sand powder is 60-100 mm, preferably 80 mm.

[0085] In addition, the sealing treatment in step S3 can also be achieved by putting the oil pipe with the composite boronizing agent in the sealing device.

[0086] In step S4, the heating boronizing treatment includes: placing the oil pipe after the sealing treatment into a heating device for heating treatment, so that the boron element in the boronizing agent diffuses to the inner surface of the oil pipe to form a boronizing layer. The heating treatment specifically includes: heating the oil pipe to 660-700℃, holding for 10-20 min, then heating to 760-800℃, holding for 5-15 min, continuing to heat to 810-840℃, holding for 15-25 min, then heating to 850-950℃, holding for 4-6 h, and finally cooling to room temperature to complete the heating treatment. After the heating treatment, the oil pipe with the inner surface boronized can be obtained.

[0087] If the boron supply agent in the boronizing agent in step S4 is boric anhydride, the heating treatment in step A5 specifically includes: heating to 660-700℃, holding for 10-20 min, then heating to 760-800℃, holding for 5-15 min, continuing to heat to 810-840℃, holding for 15-25 min, then heating to 850-900℃, holding for 4-6 h, and finally furnace cooling to room temperature to complete the heating treatment.

[0088] If the boron supply agent in the boronizing agent in step S4 is boron carbide, the heating treatment in step A5 specifically includes: heating to 660-700℃, holding for 10-20 min, then heating to 760-800℃, holding for 5-15 min, continuing to heat to 810-840℃, holding for 15-25 min, then heating to greater than 900℃ and less than or equal to 950℃, continuing to hold for 4-6 h, and finally furnace cooling to room temperature to complete the heating treatment.

[0089] It should be noted that the solid boronizing method of the oil pipe of the present application can be applied to various oil pipes or similar tubular articles and other articles, and is not limited to oil pipes with a length of ≥9.7 m. The oil pipe in the present application is prepared from ordinary alloy steel or high alloy steel, wherein the total content of alloying elements in the ordinary alloy steel is ≤5 wt%, and the total content of alloying elements in the high alloy steel is >5 wt%.

[0090] The preparation method of the above-mentioned boronizing agent used in the present application comprises the following steps:

[0091] A1: uniformly mix part of the catalyst and part of the activator to obtain a mixture, then dissolve the triethanolamine borate into an organic solvent to obtain a triethanolamine borate solution. The triethanolamine borate is viscous and gluey, and it is difficult to directly and uniformly mix with other components, so in the present application, the triethanolamine borate is dissolved in an organic solvent, and then mixed with other components.

[0092] A2: uniformly mix the triethanolamine borate solution with the mixture, and then obtain a first powder after drying and crushing.

[0093] A3: add the boron source, the filler, the flow aid, the remaining catalyst and the remaining activator into the first powder and mix uniformly to obtain the boronizing agent.

[0094] Since the content of triethanolamine borate in the boronizing agent of the present application is low, it is difficult to uniformly mix with other components with higher content, therefore, in the process of preparing the boronizing agent, part of the catalyst and part of the activator are mixed with the triethanolamine borate to obtain powder particles containing triethanolamine borate. Mixing these powder particles with the remaining components can improve the uniformity of the mixture, and the powder particles adsorbing triethanolamine borate can wrap the boron source and catalyst in the boronizing agent, which is beneficial to heat and mass transfer during the boronizing heat treatment process, and improves the secondary rust removal and boronizing effect.

[0095] In the boronizing agent, the boron source accounts for 10-15% by mass, the catalyst accounts for 12-20% by mass, the activator accounts for 8-10% by mass, the filler accounts for 50-55% by mass, the flow aid accounts for 8-12% by mass, and the triethanolamine borate accounts for 4-6% by mass.

[0096] Preferably, in step A1, the catalyst in the mixture accounts for 2-4% of the mass of the boronizing agent, and the activator in the mixture accounts for 2-4% of the mass of the boronizing agent.

[0097] Preferably, in step A2, the drying function is to remove the organic solvent and moisture, and the drying temperature is ≤100℃, and the particle size of the first powder is 140-160 mesh.

[0098] In order to further clarify the present application and its technical progress, the following specific examples and technical effects are described.

[0099] Example 1

[0100] The present embodiment provides a solid boronizing method for oil pipes, comprising the following steps:

[0101] S1: rust removal treatment is performed on the inner surface of a high-alloy steel oil pipe with a length of 9.7 m.

[0102] S2: The boronizing agent is subjected to drying treatment, the temperature of drying is 120℃, and the duration of drying is 20min. A high-temperature resistant anti-permeation agent is applied at the threaded part of the oil pipe. The boronizing agent is mixed with graphite to obtain a composite boronizing agent, and then the composite boronizing agent is loaded into the inside of the oil pipe with a length of 9.7m to make the composite boronizing agent contact with the inner surface of the oil pipe. In the composite boronizing agent, the graphite accounts for 12% of the mass of the boronizing agent. The boronizing agent comprises the following raw materials in percentage by mass: boron carbide: 12%, potassium fluoborate: 5.5%, sodium fluoride: 5.5%, potassium fluoride: 3%, silicon dioxide: 5%, activated carbon: 4%, triethanolamine borate: 5%, aluminum oxide: 51%, charcoal powder: 5%, and graphite powder: 4%.

[0103] S3: The deoxidizing agent and the metal ceramic balls with a diameter of 1mm are wrapped outside the oil pipe in sequence, the thickness of the metal ceramic ball layer is 120mm, and then the metal ceramic balls are sealed by using 325-mesh quartz sand powder, and the thickness of the sealing is 80mm.

[0104] S4: The sealed oil pipe is placed into a heating furnace, and the temperature is raised to 680℃, and the temperature is kept for 15min, then the temperature is raised to 780℃, and the temperature is kept for 10min, then the temperature is continuously raised to 820℃, and the temperature is kept for 20min, then the temperature is raised to 950℃, and the temperature is kept for 5h, and finally the furnace is cooled to room temperature.

[0105] S5: The oil pipe after the heating treatment is subjected to post-treatment, and the oil pipe with the inner surface boronized is obtained.

[0106] In this embodiment, the preparation method of the boronizing agent is as follows:

[0107] A1: 5.5% of potassium fluoborate, 5.5% of sodium fluoride and 3% of potassium fluoride are uniformly mixed to obtain a catalyst, and 5% of silicon dioxide and 4% of activated carbon are uniformly mixed to obtain an activator. Part of the catalyst and part of the activator are uniformly mixed to obtain a mixture, and then 5% of triethanolamine borate is dissolved in an organic solvent to obtain a triethanolamine borate solution.

[0108] A2: The triethanolamine borate solution and the mixture are uniformly mixed, and then dried at 80℃, and after crushing, a first powder with a particle size of 150 mesh is obtained.

[0109] A3: 12% of boron carbide, 51% of aluminum oxide, 5% of charcoal powder, 4% of graphite powder, the remaining catalyst and the remaining activator are added into the first powder and uniformly mixed to obtain a boronizing agent.

[0110] In step A1, the catalyst in the mixture accounts for 3% of the mass of the boronizing agent, and the activator in the mixture accounts for 3% of the mass of the boronizing agent.

[0111] The percentages in the examples and comparative examples of the present application are mass percentages.

[0112] Example 2

[0113] The present embodiment provides a solid boronizing method of oil pipe, comprising the following steps:

[0114] S1: rust removal treatment is performed on the inner surface of high alloy steel oil pipe with a length of 10.3 m.

[0115] S2: the boronizing agent is subjected to drying treatment at a temperature of 100℃ for 25 min. A high-temperature-resistant anti-permeation agent is applied at the threaded part of the oil pipe. The boronizing agent is mixed with graphite to obtain a composite boronizing agent, which is then loaded into the inside of the oil pipe with a length of 10.3 m to make the composite boronizing agent contact with the inner surface of the oil pipe. In the composite boronizing agent, the graphite accounts for 10% of the mass of the boronizing agent. The boronizing agent comprises the following raw materials in mass percentages: boron carbide: 10%, potassium fluoborate: 5%, sodium fluoride: 5%, potassium fluoride: 2%, silicon dioxide: 5%, activated carbon: 3%, triethanolamine borate: 6%, aluminum oxide: 55%, charcoal powder: 4%, and graphite powder: 5%.

[0116] S3: the deoxidizing agent and the metal ceramic balls with a diameter of 2 mm are wrapped outside the oil pipe in sequence, the thickness of the metal ceramic ball layer is 100 mm, and then the metal ceramic balls are sealed with 300-mesh quartz sand powder, and the thickness of the sealing is 100 mm.

[0117] S4: the sealed oil pipe is placed in a heating furnace, heated to 660℃, kept for 20 min, then heated to 760℃, kept for 15 min, continuously heated to 840℃, kept for 25 min, then heated to 910℃, kept for 4 h, and finally cooled to room temperature.

[0118] S5: post-treatment is performed on the oil pipe after the heating treatment to obtain the oil pipe with boronized inner surface.

[0119] In the present embodiment, the preparation method of the boronizing agent is as follows:

[0120] A1: 5% of potassium fluoborate, 5% of sodium fluoride, and 2% of potassium fluoride are uniformly mixed to obtain a catalyst, and 5% of silicon dioxide and 3% of activated carbon are uniformly mixed to obtain an activator. Part of the catalyst and part of the activator are uniformly mixed to obtain a mixture, and then 6% of triethanolamine borate is dissolved in an organic solvent to obtain a triethanolamine borate solution.

[0121] A2: the triethanolamine borate solution and the mixture are uniformly mixed, dried at 100℃, and crushed to obtain a first powder with a particle size of 140 mesh.

[0122] A3: 10% boron carbide, 55% alumina, 4% charcoal powder, 5% graphite powder, the rest of the catalyst and the rest of the activator are added to the first powder and mixed uniformly to obtain the boronizing agent.

[0123] In step A1, the catalyst in the mixture accounts for 2% of the mass of the boronizing agent, and the activator in the mixture accounts for 4% of the mass of the boronizing agent.

[0124] Example 3

[0125] The embodiment provides a solid boronizing method of an oil pipe, which comprises the following steps:

[0126] S1: The inner surface of a high-alloy steel oil pipe with a length of 9.7 m is subjected to rust removal treatment.

[0127] S2: The boronizing agent is subjected to drying treatment, the drying temperature is 120℃, and the drying time is 20 min. A high-temperature-resistant anti-permeation agent is applied to the threads of the oil pipe. The boronizing agent is mixed with graphite to obtain a composite boronizing agent, and then the composite boronizing agent is loaded into the inside of the oil pipe with a length of 9.7 m to make the composite boronizing agent contact with the inner surface of the oil pipe. In the composite boronizing agent, the graphite accounts for 14% of the mass of the boronizing agent. The boronizing agent comprises raw materials with the following mass percentages: boron anhydride: 15%, potassium fluoborate: 5%, sodium fluoride: 6%, potassium fluoride: 2%, silicon dioxide: 7%, activated carbon: 3%, triethanolamine borate: 4%, alumina: 25%, silicon carbide: 25%, charcoal powder: 3%, and graphite powder: 5%.

[0128] S3: The deoxidizing agent and the metal ceramic ball with a diameter of 1.5 mm are wrapped outside the oil pipe in sequence, the thickness of the metal ceramic ball layer is 150 mm, and then the metal ceramic ball is subjected to sealing treatment with 350-mesh quartz sand powder, and the thickness of the sealing layer is 60 mm.

[0129] S4: The sealed oil pipe is placed into a heating furnace, the temperature is increased to 700℃, the temperature is maintained for 10 min, then the temperature is increased to 800℃, the temperature is maintained for 5 min, the temperature is continuously increased to 810℃, the temperature is maintained for 15 min, then the temperature is increased to 850℃, the temperature is maintained for 4 h, and finally the furnace is cooled to room temperature.

[0130] S5: The oil pipe after the heating treatment is subjected to post-treatment, and an oil pipe with an inner surface boronized is obtained.

[0131] In the embodiment, the preparation method of the boronizing agent is as follows:

[0132] A1: 5% potassium fluoborate, 6% sodium fluoride and 2% potassium fluoride are uniformly mixed to obtain a catalyst, 7% silicon dioxide and 3% activated carbon are uniformly mixed to obtain an activator. Part of the catalyst and part of the activator are uniformly mixed to obtain a mixture, and then 4% triethanolamine borate is dissolved in an organic solvent to obtain a triethanolamine borate solution.

[0133] A2: The triethanolamine borate solution is mixed with the mixture, and after drying and crushing, a first powder with a particle size of 160 mesh is obtained.

[0134] A3: 15% boron anhydride, 25% aluminum oxide, 25% silicon carbide, 3% charcoal powder, 5% graphite powder, the remaining catalyst, and the remaining activator are added to the first powder and mixed uniformly to obtain a boronizing agent.

[0135] In step A1, the catalyst in the mixture accounts for 4% of the mass of the boronizing agent, and the activator in the mixture accounts for 2% of the mass of the boronizing agent.

[0136] Example 4

[0137] The embodiment provides a solid boronizing method for an oil pipe, and the method comprises the following steps:

[0138] S1: The inner surface of a common alloy steel oil pipe with a length of 11 m is subjected to rust removal treatment.

[0139] S2: The boronizing agent is subjected to drying treatment, the drying temperature is 120°C, and the drying time is 20 min. A high-temperature-resistant anti-permeation agent is applied to the oil pipe thread. The boronizing agent is mixed with graphite to obtain a composite boronizing agent, and then the composite boronizing agent is loaded into the inside of the oil pipe with a length of 11 m, so that the composite boronizing agent is in contact with the inner surface of the oil pipe. In the composite boronizing agent, the graphite accounts for 12% of the mass of the boronizing agent. The boronizing agent comprises the following raw materials in percentage by mass: boron carbide: 10%, potassium fluoborate: 10%, sodium fluoride: 6%, potassium fluoride: 4%, silicon dioxide: 6%, activated carbon: 2%, triethanolamine borate: 4%, silicon carbide: 50%, charcoal powder: 3%, and graphite powder: 5%.

[0140] S3: The deoxidizing agent and the metal ceramic ball with a diameter of 1.2 mm are wrapped outside the oil pipe in sequence, the thickness of the metal ceramic ball layer is 120 mm, and then the metal ceramic ball is subjected to sealing treatment with 325 mesh quartz sand powder, and the thickness of the sealing layer is 80 mm.

[0141] S4: The sealed oil pipe is placed in a heating furnace, and the temperature is increased to 680°C, 780°C, 830°C and 920°C for 15 min, 10 min, 20 min and 5 h respectively, and then the furnace is cooled to room temperature.

[0142] S5: The oil pipe after the heating treatment is subjected to post-treatment, and an oil pipe with a boronized inner surface is obtained.

[0143] In the embodiment, the preparation method of the boronizing agent is as follows:

[0144] A1: 10% potassium fluoborate, 6% sodium fluoride and 4% potassium fluoride are mixed to obtain a catalyst, 6% silicon dioxide and 2% activated carbon are mixed to obtain an activator. Part of the catalyst and part of the activator are mixed to obtain a mixture, then 4% triethanolamine borate is dissolved in an organic solvent to obtain a triethanolamine borate solution.

[0145] A2: The triethanolamine borate solution is mixed with the mixture, and dried at 60°C. After crushing, a first powder with a particle size of 150 mesh is obtained.

[0146] A3: 10% boron carbide, 50% silicon carbide, 3% charcoal powder, 5% graphite powder, the remaining catalyst and the remaining activator are added to the first powder and mixed to obtain a boronizing agent.

[0147] In step A1, the catalyst in the mixture accounts for 3% of the mass of the boronizing agent, and the activator in the mixture accounts for 3% of the mass of the boronizing agent.

[0148] Example 5

[0149] The embodiment provides a solid boronizing method of a tubing, comprising the following steps:

[0150] S1: The inner surface of a common alloy steel tubing with a length of 9.7 m is subjected to rust removal treatment.

[0151] S2: The boronizing agent is subjected to drying treatment, the drying temperature is 120°C, and the drying time is 20 min. A high-temperature-resistant anti-permeation agent is applied to the threading of the tubing. The boronizing agent is mixed with graphite to obtain a composite boronizing agent, and then the composite boronizing agent is loaded into the inside of the tubing with a length of 9.7 m, so that the composite boronizing agent is in contact with the inner surface of the tubing. In the composite boronizing agent, the graphite accounts for 10% of the mass of the boronizing agent. The boronizing agent comprises the following raw materials in percentage by mass: boron anhydride: 10%, potassium fluoborate: 5%, sodium fluoride: 5%, potassium fluoride: 2%, silicon dioxide: 6%, activated carbon: 3%, triethanolamine borate: 5%, silicon carbide: 52%, charcoal powder: 4%, and graphite powder: 8%.

[0152] S3: A deoxidizing agent and a metal ceramic ball with a diameter of 1.8 mm are wrapped outside the tubing in sequence, the thickness of the metal ceramic ball layer is 120 mm, and then the metal ceramic ball is subjected to sealing treatment with 325 mesh quartz sand powder, and the thickness of the sealing is 80 mm.

[0153] S4: The sealed tubing is placed in a heating furnace, heated to 680°C, kept for 15 min, then heated to 780°C, kept for 10 min, continuously heated to 825°C, kept for 20 min, then heated to 900°C, kept for 5 h, and finally cooled to room temperature.

[0154] S5: post-treating the oil pipe after the heating treatment to obtain the oil pipe with boron-permeated inner surface.

[0155] In this embodiment, the preparation method of the boronizing agent is as follows:

[0156] A1: uniformly mixing 5% of potassium fluoborate, 5% of sodium fluoride and 2% of potassium fluoride to obtain a catalyst, uniformly mixing 6% of silicon dioxide and 3% of activated carbon to obtain an activator, uniformly mixing part of the catalyst and part of the activator to obtain a mixture, and then dissolving 5% of triethanolamine borate into an organic solvent to obtain a triethanolamine borate solution.

[0157] A2: uniformly mixing the triethanolamine borate solution and the mixture, drying at 80°C, and crushing to obtain a first powder with a particle size of 150 mesh.

[0158] A3: uniformly mixing 10% of boron anhydride, 51% of silicon carbide, 4% of charcoal powder, 8% of graphite powder, the remaining catalyst and the remaining activator into the first powder to obtain the boronizing agent.

[0159] In step A1, the catalyst in the mixture accounts for 3% of the mass of the boronizing agent, and the activator in the mixture accounts for 3% of the mass of the boronizing agent.

[0160] Comparative Example 1

[0161] The difference between this comparative example and Example 1 is that the content of triethanolamine borate in the boronizing agent is 0. In this comparative example, the preparation method of the boronizing agent is as follows: uniformly mixing the raw components of the boronizing agent with the respective contents, drying and crushing to obtain the boronizing agent.

[0162] Comparative Example 2

[0163] The difference between this comparative example and Example 1 is that the content of the catalyst in the boronizing agent is 25%.

[0164] Comparative Example 3

[0165] The difference between this comparative example and Example 1 is that, in step S2, the content of graphite in the composite boronizing agent is 0.

[0166] Comparative Example 4

[0167] The difference between this comparative example and Example 4 is that the content of triethanolamine borate in the boronizing agent is 0. In this comparative example, the preparation method of the boronizing agent is as follows: uniformly mixing the raw components of the boronizing agent with the respective contents, drying and crushing to obtain the boronizing agent.

[0168] The inner surface boronized oil pipes prepared by the examples 1-5 and the comparative examples 1-4 were tested for performance, and the thickness of the inner surface boronized layer of the oil pipe, the highest microhardness at a certain depth in the boronized layer, the tensile strength, yield strength, ductility, and breaking point shrinkage of the inner surface of the oil pipe were measured, and the results are shown in Table 1.

[0169] Table 1: Performance test results of the inner surface boronized oil pipes of examples 1-5 and comparative examples 1-4

[0170] As can be seen from Table 1, the boronized layers of examples 1-5 have high thickness, hardness, and good mechanical properties, and the hardness and mechanical properties of the boronized layer are much higher than those of the original ordinary alloy steel long oil pipe substrate / high alloy steel long oil pipe substrate. In comparative example 1 and comparative example 4, since triethanolamine borate is not added, the boronized layer prepared has a thin thickness, low hardness, and poor mechanical properties. In comparative example 2, since the catalyst is added in excess, the thickness, hardness, and mechanical properties of the boronized layer prepared are significantly reduced compared to examples 1-3.

[0171] The inner surfaces of the oil pipes of examples 1-5 and comparative examples 1-4 were cut and polished, and the microstructure of the interface between the boronized layer and the substrate was observed using a scanning electron microscope. It was observed that there were almost no cracks and pores between the boronized layer and the substrate of examples 1-5, and there was no delamination, indicating that the boronized layer and the substrate had a high degree of bonding. Some cracks and pores were observed between the boronized layer and the substrate of comparative example 1, comparative example 2, and comparative example 4, and the number of cracks and pores between the boronized layer and the substrate of comparative example 1 and comparative example 4 was greater than that of comparative example 2, indicating that the bonding between the boronized layer and the substrate in comparative example 1 and comparative example 2 was low, and there was a risk of delamination of the boronized layer.

[0172] In addition, after the inner surfaces of the oil pipes of examples 1-5 and comparative examples 1-4 were treated by boronizing, the caking of the boronizing agent in the inner surface of each oil pipe was observed. It was observed that the boronizing agent of examples 1-5 did not caking, and the boronizing agent could be easily separated from the oil pipe. The boronizing agent of comparative examples 1-4 all caked, and since the oil pipe was long, it was difficult to completely remove the residual boronizing agent from the inner wall of the oil pipe, and the uniformity of the boronizing in comparative example 3 was also low.

[0173] Figure 1 and Figure 2 are microstructure diagrams of the inner surface boronizing layer of the oil pipe in Example 1 and Comparative Example 3 respectively, it can be obviously seen from Figure 1 and Figure 2 that the thickness of the boronizing layer of Example 1 is higher, and the thickness of the boronizing layer of Comparative Example 3 is lower. Figure 5 and Figure 6 are microstructure diagrams of the inner surface boronizing layer of the oil pipe in Example 3 and Example 4 respectively, and Figure 7 shows the microstructure of the inner surface boronizing layer of the oil pipe in Example 5 and the metallographic structure of the alloy steel substrate connected with the boronizing layer. It can be known from Figure 5, Figure 6 and Figure 7 that the quality of the boronizing layer of Example 3, Example 4 and Example 5 is better. It can be known from Figure 7 that the boronizing layer does not affect the alloy steel substrate after the boronizing treatment in Example 5.

[0174] The boronizing oil pipe with the best performance at present abroad is taken as a control sample, and the length and material of the control sample oil pipe are the same as those of the high alloy steel oil pipe in Example 2. The boronizing effect and corrosion resistance after boronizing of the boronizing oil pipe in Comparative Example 2 and the control sample are compared.

[0175] ①Boronizing effect:

[0176] Figure 3 is a microstructure diagram of the boronizing layer in Example 2, and Figure 4 is a metallographic structure diagram of the alloy steel substrate connected with the boronizing layer in Example 2. Figure 8 is a microstructure diagram of the boronizing layer in the control sample, and Figure 9 is a metallographic structure diagram of the alloy steel substrate connected with the boronizing layer in the control sample.

[0177] It can be known from the comparison of Figure 3 and Figure 8 that the thickness and uniformity of the boronizing layer of Example 2 are obviously higher than those of the control sample.

[0178] It can be known from the comparison of Figure 4 and Figure 9 that the boronizing layer does not affect the alloy steel substrate after the boronizing treatment in Example 2, the crystal lattice of the alloy steel substrate in Example 2 is refined, the crystal distribution is uniform, and the texture is compact, which indicates that the boronizing method of Example 2 can well maintain the mechanical properties of the alloy steel oil pipe itself. The grains in the control sample are relatively coarse and irregular, which indicates that the boronizing layer of the control sample affects the alloy steel substrate and makes the grain size larger.

[0179] ②Corrosion resistance:

[0180] 1. Hydrochloric acid corrosion resistance:

[0181] A sample with a boronizing layer is cut from the boronizing oil pipe prepared in Example 2, and is recorded as sample 1. Similarly, a sample with a boronizing layer of the same size is cut from the boronizing oil pipe of the control sample, and is recorded as sample 2. The corrosion resistance of sample 1 and sample 2 is tested. Specifically, sample 1 and sample 2 are respectively immersed in a hydrochloric acid solution with a mass concentration of 25% at 30°C, and the morphological changes of sample 1 and sample 2 are recorded respectively at the 1st day, the 1st week, the 2nd week, the 3rd week and the 4th week, and Figure 10 and Figure 11 are obtained.

[0182] As shown in FIG. 10, on the first day, bubbles were generated in the hydrochloric acid solution, and the solution became slightly yellow. On the first week, the hydrochloric acid solution turned light green. On the second week, the corrosion of sample 1 was aggravated, and after weighing, the mass loss of sample 1 at this time was 12.88% compared with the unsoaked mass. On the third week, it was observed that the boronized layer of sample 1 was still good, and after weighing, the mass loss of sample 1 at this time was 16.56% compared with the unsoaked mass. On the fourth week, it was observed that the boronized layer of sample 1 appeared edge damage, and after weighing, the mass loss of sample 1 at this time was 21.29% compared with the unsoaked mass.

[0183] As shown in FIG. 11, on the first day, a large number of bubbles were generated in the hydrochloric acid solution, and the solution turned yellow. On the first week, the hydrochloric acid solution turned green. On the second week, the corrosion of sample 2 was serious, and after weighing, the mass loss of sample 2 at this time was 18.87% compared with the unsoaked mass. On the third week, it was observed that the boronized layer of sample 2 had been damaged, and after weighing, the mass loss of sample 2 at this time was 24.11% compared with the unsoaked mass. On the fourth week, it was observed that the boronized layer of sample 2 had completely fallen off, and after weighing, the mass loss of sample 2 at this time was 31.63% compared with the unsoaked mass.

[0184] 2. Salt solution corrosion resistance:

[0185] A sample with a boronized layer was cut from the boronized oil pipe prepared in Example 2, and was recorded as sample 3. Similarly, a sample 4 with a boronized layer of the same size was cut from the boronized oil pipe of the control, and the corrosion resistance test was performed on sample 3 and sample 4. Specifically, sample 3 and sample 4 were respectively soaked in a NaCl solution with a mass concentration of 10% at 30°C, and the morphological changes of sample 3 and sample 4 were recorded on the first day, the first week, the second week, the third week and the fourth week, respectively, to obtain FIG. 12 and FIG. 13.

[0186] As shown in FIG. 12, on the first day, sample 3 and the NaCl solution were both unchanged. On the first week, the NaCl solution turned light reddish brown. On the second week, sample 3 had no obvious change, and after weighing, the mass loss of sample 3 at this time was 0.06% compared with the unsoaked mass. On the third week, it was observed that the overall body of sample 3 was intact, and after weighing, the mass loss of sample 3 at this time was 0.10% compared with the unsoaked mass. On the fourth week, it was observed that the color of the NaCl solution deepened, but the body of sample 3 was still intact.

[0187] As shown in FIG. 13, at day 1, sample 4 and the NaCl solution were both unchanged. At week 1, the NaCl solution turned reddish-brown. At week 2, sample 4 showed signs of oxidative corrosion, and upon weighing, sample 4 had a mass loss of 0.13% compared to the unsoaked sample. At week 3, sample 4 showed slight damage to the edges, and upon weighing, sample 4 had a mass loss of 0.20% compared to the unsoaked sample. At week 4, the NaCl solution was observed to have darkened, but sample 4 was still in good condition.

[0188] 3. Nitric acid corrosion resistance:

[0189] A sample of the boronized oil pipe prepared in Example 2 was taken, and is referred to as sample 5. Similarly, a sample of the control boronized oil pipe was taken, and is referred to as sample 6. Samples 5 and 6 were subjected to corrosion resistance testing. Specifically, samples 5 and 6 were each immersed in a 25% by mass HNO3solution at 30°C, and the appearance of samples 5 and 6 were recorded at day 1, week 1, week 2, and week 3, to obtain FIG. 14 and FIG. 15.

[0190] As shown in FIG. 14, at day 1, sample 5 showed blackening of the edges, and a small amount of bubbling in the solution. At week 1, the bubbling in the solution increased, and the solution as a whole turned dark brown. At week 2, sample 5 showed significant corrosion, and upon weighing, sample 5 had a mass loss of 28.84% compared to the unsoaked sample. At week 3, sample 5 was observed to have completely lost its boronized layer and was pulverized, and upon weighing, sample 5 had a mass loss of 89.74% compared to the unsoaked sample.

[0191] As shown in FIG. 15, at day 1, sample 6 showed blackening, and a large amount of bubbling in the solution. At week 1, a large amount of bubbling was observed in the solution, and the solution as a whole turned dark brown, and sample 6 showed swelling at the bottom. At week 2, sample 6 showed severe corrosion, and upon weighing, sample 6 had a mass loss of 51.91% compared to the unsoaked sample. At week 3, sample 6 was observed to have completely lost its boronized layer and was pulverized, and upon weighing, sample 6 had a mass loss of 94.80% compared to the unsoaked sample.

[0192] Finally, it should be noted that the above examples are merely used to illustrate the technical solutions of the present application, and are not intended to limit the same; even though the present application has been described in detail with reference to the above examples, those skilled in the art should understand that they can still modify the technical solutions described in the above examples, or make equivalent replacements to some or all of the technical features; and such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the above examples.

Claims

1. A boronizing compound characterized by comprising: The boronizing agent and graphite are mixed. The graphite accounts for 10-14% of the mass of the boronizing agent; the boronizing agent comprises the following raw materials in percentage by mass: boron source 10-15%, catalyst 12-20%, activator 8-10%, dispersant 4-6%, filler 50-55%, and flow aid 8-12%; the dispersant is triethanolamine borate.

2. The boronizing compound of claim 1, wherein The boron source is boric anhydride or boron carbide.

3. The boronizing composition of claim 1, wherein The catalyst comprises potassium fluoborate, sodium fluoride, and potassium fluoride, wherein the potassium fluoborate accounts for 5-10% of the total mass of the boronizing agent, the sodium fluoride accounts for 5-6% of the total mass of the boronizing agent, and the potassium fluoride accounts for 2-4% of the total mass of the boronizing agent.

4. The boronizing composition of claim 1, wherein The activator comprises silicon dioxide and activated carbon, wherein the silicon dioxide accounts for 5-7% of the total mass of the boronizing agent, and the activated carbon accounts for 2-4% of the total mass of the boronizing agent. The filler comprises aluminum oxide and / or silicon carbide.

5. The boronizing composition of claim 1, wherein The particle size of the graphite mixed with the boronizing agent is 30-50 mesh. The flow aid comprises charcoal powder and graphite powder, wherein the charcoal powder accounts for 3-5% of the total mass of the boronizing agent, and the graphite powder accounts for 4-8% of the total mass of the boronizing agent; the particle size of the graphite powder is 140-160 mesh.

6. A method for solid boronizing of a tubular member using the composite boronizing agent according to any one of claims 1 to 5, characterized by, The method comprises the following steps: S1: cleaning the inner surface of the oil pipe; S2: mixing the boronizing agent with graphite to obtain a composite boronizing agent, and then loading the composite boronizing agent into the oil pipe to make the composite boronizing agent contact the inner surface of the oil pipe; S3: sealing the oil pipe with the composite boronizing agent loaded therein; S4: performing heating and boronizing treatment on the sealed oil pipe, and cooling to obtain an oil pipe with a boronized layer on the inner surface.

7. The method of solid boronizing of oil tubes according to claim 6, characterized in that, In step S3, the outer surface of the oil pipe is wrapped with a deoxidizing agent and a metal ceramic ball in sequence, and then the metal ceramic ball is sealed with quartz sand powder.

8. The method of solid boronizing of oil tubes according to claim 6, characterized in that, The thickness of the metal ceramic ball layer is 100-150 mm, the particle size of the metal ceramic ball is 1-2 mm, the particle size of the quartz sand powder is 300-350 mesh, and the thickness of the quartz sand powder layer after sealing is 60-100 mm.

9. The method of solid boronizing of oil tubes according to claim 6, characterized in that, In step S4, the heating and boronizing treatment comprises the following steps: heating the sealed oil pipe to 660-700 ℃, maintaining for 10-20 min, then heating to 760-800 ℃, maintaining for 5-15 min, continuing to heat to 810-840 ℃, maintaining for 15-25 min, then heating to 850-950 ℃, maintaining for 4-6 h, and finally cooling to room temperature to complete the heating treatment.

10. The method of solid boronizing of oil tubes according to claim 6, characterized in that, The oil pipe is prepared from ordinary alloy steel or high alloy steel. In the ordinary alloy steel, the total content of alloying elements is ≤5 wt%, In the high alloy steel, the total content of alloying elements is >5 wt%.

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