A boronizing process based on 00Cr special alloy steel and its products

Abstract

This invention relates to the field of boronizing technology, and more specifically, to a boronizing process based on 00Cr special alloy steel and its products. The process steps are as follows: heat treatment before boronizing; boronizing treatment: (1) fill the cleaned and dried boronizing cylinder with boronizing agent, then place it in the boronizing box, sprinkle boronizing agent on its surface to balance the boronizing atmosphere in the workpiece box, cover it with a cover plate and seal it with refractory slurry; (2) after the refractory slurry has dried, lift the boronizing box and stack it on the trolley resistance furnace, turn on the power to preheat and keep it warm, and then raise the temperature to the boronizing temperature for boronizing; (3) after boronizing is completed, take it out and air cool it down. It can achieve a high matrix hardness, has good mechanical properties, obtains a good boronizing layer depth and hardness, has excellent wear resistance and corrosion resistance, and optimizes the performance of 00Cr special alloy steel cylinder.

Description

Technical Field

[0001] This invention relates to the field of boronizing technology, particularly to the field of IPC C23, and more specifically, to a boronizing process based on 00Cr special alloy steel and its products. Background Technology

[0002] OOCr special alloy steel possesses excellent mechanical properties and corrosion resistance. Due to its superior performance and high weldability, it has seen widespread application in petroleum development, marine equipment, and the construction industry in recent years. With rapid economic and industrial development, the intensity of oil well extraction is continuously increasing, leading to increasingly stringent quality requirements for oil pumps. An oil pump is a downhole device driven by a pumping unit to lift crude oil from the well to the surface. Depending on the depth of the well and the quality of the crude oil, the required performance and structure of the oil pump vary. To ensure the safe operation of the oil pump system, the materials used must be treated to ensure that the pump meets the requirements for excellent strength, corrosion resistance, and wear resistance. Boronizing, as a chemical heat treatment process, involves the penetration, diffusion, and reaction of boron atoms with the matrix on the metal surface to form a boride layer composed of one or more intermetallic compound phases. Surface boronizing treatment of oil pump materials allows boron to exist on the material surface in the form of borides. The boronized layer has high hardness, good wear resistance, and excellent corrosion resistance in sulfuric acid, dilute hydrochloric acid, acetic acid, alkalis, and seawater, making it suitable for use in oil wells and extending their service life.

[0003] CN102071384A discloses a boronizing agent process, including process conditions (1) boronizing temperature: 800℃-950℃; (2) holding time: 3-5 hours; (3) amount of boronizing agent: generally enough to fill the boronizing box; the process flow is as follows: the workpiece is degreased with gasoline or alcohol and then dried, a 5 mm thick layer of boronizing agent is sprinkled at the bottom of the boronizing box, the workpiece is placed vertically to reduce bending deformation, then the boronizing agent is filled, and the box is sealed with clay mixed with water glass. After the workpiece is removed from the furnace or cooled to room temperature with the furnace, it can be quenched directly after boronizing. It can reach the advanced level at home and abroad, such as the boronizing sheet machine pressure plate, the service life is 6 times longer than the nitriding pressure plate and 1 time longer than the sprayed hard alloy.

[0004] CN102517542B discloses a boronizing agent for boronizing the surface of metallic titanium and its preparation method. The boronizing agent is composed of the following components by mass percentage: Na₂B₄O₇ 20-35%; H₃BO₃ 10-20%; B₄C 10-20%; KCl 15-25%; NaCl 15-25%; KBF₄ 1-5%. The boronizing process of this invention first places a metallic titanium sample in a molten boronizing agent of a specific composition, holds it at a certain temperature for a certain time to form a boronized layer on the surface of the metallic titanium sample, and then solidifies the boronized layer through a quenching operation to obtain a thick, uniform, high-hardness, and well-bonded boronized layer on the surface of the metallic titanium sample. Furthermore, the molten salt on the surface of the metallic titanium sample is easily treated. The boronizing process of this invention is simple and easy to control, with minimal loss of boronizing agent; the operation time is short, energy consumption is low, and it is suitable for industrial production.

[0005] CN104911535B discloses a boronizing agent and process for solid boronizing on titanium surfaces. The boronizing agent consists of 5–93.9 wt.% boron source, 5–25 wt.% low-melting-point compound, 1–10 wt.% oxide fixative, and 0.1–89 wt.% diluent. During boronizing, the prepared boronizing agent is first ball-milled and mixed evenly, then placed in a boronizing tank. Simultaneously, a titanium workpiece is immersed in the boronizing agent. The temperature is raised to 750–1300°C and held for 0.5–24 hours. The workpiece is then removed, cooled appropriately, and the boronizing agent adhering to its surface is cleaned. The boronizing agent described in this invention can increase the rate of boron migration to the workpiece surface while preventing the reduction in boronizing rate due to oxidation of the titanium matrix. The aforementioned prior art focuses on improving boronizing efficiency, obtaining a thick and uniform boronized layer, and improving the mechanical properties of the boronized layer surface. However, the problem that the impact toughness significantly decreases while increasing the thickness and hardness of the boronized layer has not been effectively solved. Summary of the Invention

[0006] To address the aforementioned problems, the first aspect of this invention provides a boronizing process based on 00Cr special alloy steel, comprising the following steps:

[0007] S1 pre-boronizing heat treatment: The 00Cr special alloy steel cylinder is placed in an electric resistance furnace and held at 890-920℃ for 45-60 min, then air-cooled for quenching, and then held at 620-660℃ for 75-90 min, and then air-cooled for tempering.

[0008] S2 boronizing treatment:

[0009] (1) After cleaning and drying the 00Cr special alloy steel cylinder, fill the 00Cr special alloy steel cylinder with boronizing agent and place the 00Cr special alloy steel cylinders filled with boronizing agent neatly in the boronizing box. Sprinkle boronizing agent on the inner and outer surfaces of the cylinder to balance the boronizing atmosphere in the workpiece box. After covering the cover plate, seal it with refractory mud.

[0010] (2) After the refractory slurry has dried, the boronizing box is lifted and stacked on the bogie furnace. After the bogie furnace is preheated and kept warm, the temperature is raised to the boronizing temperature and boronizing is carried out.

[0011] (3) After boronizing is completed, the boronizing box is lowered, the cover plate is pried open, and the 00Cr special alloy steel cylinder is taken out using tooling fixtures. The boronizing agent inside the cylinder is poured out, and the cylinder is neatly arranged and directly cooled by air cooling. The hardness of the matrix is ​​greater than 36HRC.

[0012] Preferably, in the S1 boronizing pretreatment step, the temperature for heat preservation and air cooling quenching is 900°C, the time is 55 min, and the temperature for heat preservation and air cooling tempering is 660°C.

[0013] Pre-heat treatment of the 00Cr special alloy steel cylinder before boronizing can improve the machinability of the cylinder material. Tempering the boronized part eliminates internal stress and prevents thermal deformation caused by uneven internal microstructure distribution. To prevent thermal deformation and improve the mechanical properties of the 00Cr special alloy steel cylinder, quenching and tempering at appropriate temperatures are crucial. This application employs an overall heat treatment of the 00Cr special alloy steel cylinder before boronizing, using a method of holding at 900℃ for 55 minutes followed by air quenching, and then continuing to hold at 660℃ for air tempering. This yields a uniform and fine sorbite microstructure, giving the material excellent mechanical properties and effectively reducing thermal deformation during boronizing, thus effectively achieving the desired quality of the boronized 00Cr special alloy steel cylinder.

[0014] Preferably, the filler is at least one of alumina and silicon carbide.

[0015] Preferably, the filler is alumina.

[0016] Preferably, the penetration enhancer is at least one of potassium borofluoride and ammonium bicarbonate.

[0017] Preferably, the penetration enhancer is a mixture of potassium borofluoride and ammonium bicarbonate, wherein the mass ratio of potassium borofluoride to ammonium bicarbonate is (5-10):(2-10).

[0018] Preferably, the boronizing agent in step S2 comprises, by mass percentage: 30%–40% powdered ferroborone, 50%–60% filler, and 10% penetration enhancer.

[0019] Preferably, the penetration enhancer is potassium borofluoride and ammonium bicarbonate in a mass ratio of 3:2.

[0020] Preferably, the boronizing agent in step S2 comprises, by mass percentage: 34% powdered ferroborone, 56% alumina, 6% potassium borofluoride, and 4% ammonium bicarbonate.

[0021] This application, through the formulation of a boronizing agent comprising 34% powdered ferroborone, 56% alumina, 6% potassium borofluoride, and 4% ammonium bicarbonate, can adjust the carbon and boron content entering the 00Cr steel alloy cylinder during the boronizing process. This controls the hardness of the 00Cr special alloy steel cylinder while improving its impact toughness, resulting in a thicker boronized layer and effectively improving the morphology and properties of the 00Cr steel alloy matrix. Using this formulation, a high activity of the boronizing agent can form a two-phase boronizing layer of FeB and Fe2B; appropriately reducing the activity yields a single-phase Fe2B layer. For alloy steels containing elements such as chromium, molybdenum, nickel, and vanadium, alloyed borides are formed, with the interdental phase of boron in sorbite beneath the compound layer. The hardness of the boron-dipped layer is as high as 1290-2340 HV, compared with the surface hardness of hard chrome plating ≤825 HV. The hardness and wear resistance of the boron-dipped layer are more than twice that of the hard chrome plating layer. In sulfuric acid, dilute hydrochloric acid, acetic acid, alkali and seawater, the corrosion resistance of the boron-dipped layer is similar to that of stainless steel.

[0022] In the solid boronizing process, the filler acts as a carrier for boronizing, ensuring the uniform distribution of the boronizing agent and the boronizing catalyst. This allows for uniform contact between the workpiece and the boronizing agent, guaranteeing the uniformity of the boronized layer. Additionally, it keeps the boronizing agent loose and prevents sintering, ensuring that the boronized layer and boronizing agent remain loose when the boronizing process cools to room temperature. The treated 00Cr special alloy steel cylinder has a smooth surface without scaling, requiring no special cleaning. The addition of 56% alumina is used to adjust the boron potential of the boronizing agent.

[0023] In the solid boronizing process, a penetration catalyst is needed to improve the boronizing effect. At the same time, 6% potassium borofluoride and 4% ammonium bicarbonate are added together as a penetration catalyst to increase the penetration rate and the thickness of the boronized layer, so as to achieve the best penetration effect.

[0024] Preferably, the boronizing agent is prepared by weighing each component according to the mass ratio, mixing them evenly, and drying them to obtain the boronizing agent.

[0025] Preferably, the ferroboron has a carbon content of ≤0.05% and a boron content of 22-25%.

[0026] Preferably, the alumina has a particle size range of 60 to 100 mesh.

[0027] Preferably, the alumina has a particle size of 80 mesh.

[0028] Preferably, the hardness of the 00Cr special alloy steel cylinder after the pre-boroning heat treatment in step S1 is 207-240 HBW.

[0029] Preferably, in step (2), the preheating temperature of the trolley furnace is 480-510℃ and the holding time is 2.5-3h.

[0030] Preferably, the boronizing temperature in step (2) is 880-1000℃ and the holding time is 5.5-12h.

[0031] Preferably, the boronizing temperature in step (2) is 900°C and the holding time is 10h.

[0032] Preferably, the mass percentage content of each component in the 00Cr special alloy steel cylinder is as follows: C: ≤0.065%, Si: ≤0.35%, Mn: 0.80-1.20%, P: ≤0.035%, S: ≤0.010%, Cr: 9.00-12.50%, Ni: 0.60-1.00%, Mo: 0.15-0.90%, Cu: 0.30-0.60%, V: 0.05-0.15%, with Fe as the balance.

[0033] A second aspect of the present invention provides an article based on the boronizing process of 00Cr special alloy steel as described above, the article being an oil pump cylinder.

[0034] Beneficial effects:

[0035] In this application, by controlling the process flow and parameters of the pre-boronizing tempering heat treatment and the boronizing treatment of the 00Cr special alloy steel cylinder, a uniform and fine 00Cr special alloy steel cylinder structure can be obtained by using a 900℃ holding temperature for 55 min followed by air cooling quenching, and then a continuous 660℃ holding temperature followed by air cooling tempering. This maintains good toughness within the material, improves its mechanical properties, and effectively reduces thermal deformation during boronizing, thus ensuring the quality of the 00Cr special alloy steel cylinder after boronizing. Furthermore, by controlling the temperature and time of the boronizing process and using a boronizing agent with appropriate composition and proportion, the carbon and boron content in the boronized layer entering the 00Cr special alloy steel cylinder during the boronizing process can be controlled, thereby effectively improving the performance of the 00Cr special alloy steel cylinder. The boronizing process of this application significantly improves the wear resistance and corrosion resistance of the 00Cr special alloy steel cylinder, and its service life is increased by 2-3 times compared to the hard chrome plating of J55 medium carbon alloy steel cylinders. Detailed Implementation

[0036] Example

[0037] Example 1 provides a boronizing process based on 00Cr special alloy steel and its products. The steps of the boronizing process for 00Cr special alloy steel cylinders include:

[0038] S1 pre-boronizing heat treatment: The 00Cr special alloy steel cylinder is placed in an electric resistance furnace and held at 900℃ for 55 min, then air-cooled for quenching, and then held at 660℃ for 80 min, and then air-cooled for tempering.

[0039] S2 boronizing treatment:

[0040] (1) After cleaning and drying the 00Cr special alloy steel cylinder, fill the 00Cr special alloy steel cylinder with boronizing agent and place the 00Cr special alloy steel cylinders filled with boronizing agent neatly in the boronizing box. Sprinkle boronizing agent on the inner and outer surfaces of the cylinder to balance the boronizing atmosphere in the workpiece box. After covering the cover plate, seal it with refractory mud.

[0041] (2) After the refractory slurry has dried, the boronizing box is lifted and stacked on the bogie furnace. The power supply of the bogie furnace is turned on and the temperature is raised to 500℃ for preheating and heat preservation for 3 hours. Then, the temperature is raised to the boronizing temperature of 900℃ and boronizing and heat preservation is carried out for 10 hours.

[0042] (3) After boronizing is completed, the boronizing box is lowered, the cover plate is pried open, and the 00Cr special alloy steel cylinder is taken out using tooling fixtures. The boronizing agent inside the cylinder is poured out, and the cylinder is neatly arranged and directly cooled by air. The hardness of the matrix is ​​greater than 36HRC.

[0043] The 00Cr special alloy steel cylinder body is sourced from Zhejiang Ruizhi Steel Industry Co., Ltd.

[0044] The weight percentage of each component in the 00Cr special alloy steel cylinder is as follows: C: 0.06%, Si: 0.3%, Mn: 0.8%, P: 0.035%, S: 0.004%, Cr: 12.5%, Ni: 0.65%, Mo: 0.35%, Cu: 0.56%, V: 0.15%, with the balance being Fe.

[0045] The 00Cr special alloy steel cylinder has a hardness of 228 HBW after heat treatment before boronizing.

[0046] The boronizing agent comprises, by mass percentage: 34% powdered ferroborone, 56% alumina, 6% potassium borofluoride, and 4% ammonium bicarbonate.

[0047] The carbon content of the ferroboron is 0.05%, the boron content is 21-25%, and the particle size is 150μm.

[0048] The particle size of the filler alumina is 80 mesh.

[0049] The boronizing agent is prepared by weighing each component according to the mass ratio, mixing them evenly, and drying them to obtain the boronizing agent.

[0050] The resistance furnace used for the heat treatment before boronizing is a non-standard energy-saving periodic resistance furnace with dimensions of 5000×1300mm×800mm.

[0051] The boronizing chamber measures 4600mm × 600mm × 55mm.

[0052] The product manufactured using the above boronizing process is an oil pump barrel.

[0053] Comparative Example 1

[0054] The specific implementation method of this comparative example is the same as that of Example 1, except that the boronizing temperature is 900℃ and the boronizing holding time is 2h.

[0055] Comparative Example 2

[0056] The specific implementation method of this comparative example is the same as that of Example 1, except that the boronizing temperature is 850℃ and the boronizing holding time is 6h.

[0057] Comparative Example 3

[0058] The specific implementation method of this embodiment is the same as that of embodiment 1, except that the boronizing agent comprises, by mass percentage: 30% powdered ferroborone, 65% alumina, 3% potassium borofluoride, and 2% ammonium bicarbonate.

[0059] Performance testing methods:

[0060] Referring to JB / T 4214 "Boronizing" and JB / T 7709 "Methods for Testing the Microstructure, Hardness and Depth of Boronized Layer", the diffusion depth, microstructure and surface hardness of the 00Cr special alloy steel cylinder after boronizing treatment were tested, and the test results are recorded in Table 1.

[0061] Performance test data:

[0062] Table 1

[0063]

Claims

1. A boronizing process based on 00Cr special alloy steel, characterized in that, It comprises the following steps: S1: heat treatment before boronizing: the 00Cr special alloy steel cylinder is placed in a resistance furnace for 45-60 min at 890-920 ℃, then air-cooled, and then air-cooled tempering at 620-660 ℃ for 75-90 min; S2: boronizing treatment: (1) the 00Cr special alloy steel cylinder is cleaned and dried, then the boronizing agent is filled into the cylinder, the cylinder is arranged neatly in the boronizing box, the boronizing agent is scattered on the inner and outer surfaces of the cylinder to balance the boronizing atmosphere in the box, and the box is sealed with refractory mud; (2) after the refractory mud is dried, the box is lifted and stacked on the trolley furnace, the trolley furnace is preheated, then heated to the boronizing temperature, and then boronizing is carried out; (3) after the boronizing is completed, the box is lifted down, the cover is pried open, the 00Cr special alloy steel cylinder is taken out with a fixture, the boronizing agent in the cylinder is poured out, and the cylinder is arranged neatly and directly air-cooled to a hardness greater than 36HRC; The boronizing agent comprises, by mass percentage: 30-40% of powdered ferroboron, 50-60% of filler, and 10% of boronizing agent; The filler is alumina with a particle size of 60-100 mesh; The hardness of the 00Cr special alloy steel cylinder after the step S1 is 207-240 HBW; The boronizing agent is a mixture of potassium fluoroborate and ammonium bicarbonate, and the mass ratio of the two is (5-10):(2-10); The content of each component in the 00Cr special alloy steel cylinder is as follows: C: ≤0.065%, Si: ≤0.35%, Mn: 0.80-1.20%, P: ≤0.035%, S: ≤0.010%, Cr: 9.00-12.50%, Ni: 0.60-1.00%, Mo: 0.15-0.90%, Cu: 0.30-0.60%, V: 0.05-0.15%, and Fe makes up the balance.

2. The boronizing process based on 00Cr special alloy steel according to claim 1, characterized in that, The preparation method of the boronizing agent comprises the following steps: each component is weighed according to the mass ratio, mixed uniformly, and dried to obtain the boronizing agent.

3. The boronizing process based on 00Cr special alloy steel according to claim 1, characterized in that, The carbon content of the ferroboron is ≤0.05%, and the boron content is 22-25%.

4. The boronizing process based on 00Cr special alloy steel according to claim 1, characterized in that, In the step (2), the preheating temperature of the trolley furnace is 480-510 ℃, and the holding time is 2.5-3 h.

5. The boronizing process based on 00Cr special alloy steel according to claim 1, characterized in that, In the step (2), the boronizing temperature is 880-1000 ℃, and the holding time is 5.5-12 h.

6. An article made by the process of boronizing 00Cr special alloy steel according to any one of claims 1 to 5, characterized in that, The product is an oil pump cylinder.

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