Heat treatment process of alloy drill bit

Abstract

The invention discloses a heat treatment process of an alloy drill bit, which belongs to the field of alloy and comprises the following steps: S1, after the alloy drill bit is primarily machined and formed, carrying out vacuum pretreatment, heat preservation and heating; s2, the drill bit is rapidly transferred into a sectional temperature control carburizing furnace to be subjected to main carburizing treatment, the temperature is controlled between 930 DEG C and 960 DEG C, the carburizing time ranges from 3 hours to 4 hours, and the carburizing depth is controlled between 0.3 mm and 0.6 mm; s3, after carburizing is completed, subarea multi-speed cooling is carried out, quenching is carried out for 20 seconds at the temperature of 850 DEG C or above, controlled cooling is carried out for 60 seconds within the range of 550 DEG C to 650 DEG C, slow cooling is carried out for 80 seconds at the temperature of 200 DEG C or below, and a refined martensite complex phase structure is obtained; s4, after cooling is completed, double-section tempering treatment is carried out; and S5, performing ultrahigh-pressure static boriding diffusion treatment. The method has the beneficial effects that the processing uniformity, the structure stability, the wear resistance and the corrosion resistance of the alloy drill bit are effectively improved and the service life of the alloy drill bit is effectively prolonged by adopting staged temperature control, different cooling media and a directional quenching technology.

Description

Technical Field

[0001] The invention relates to the field of alloys, and more particularly to a heat treatment process for an alloy drill bit. Background Art

[0002] The heat treatment process of alloy drill bits has been developing since the mid-20th century. Initially, the traditional overall quenching and tempering method was used to improve hardness and wear resistance. With the advancement of material science and processing technology, refined processes such as induction heating, vacuum heat treatment and multiple tempering have been gradually introduced, so that the drill bits have better toughness and impact resistance while maintaining high hardness. In recent years, in order to meet the needs of efficient drilling and extreme working conditions, some high-end alloy drill bits have adopted advanced heat treatment methods such as laser surface quenching and plasma nitriding, which effectively improves surface wear resistance and overall service life.

[0003] However, the biggest problem with the current heat treatment process is that it is difficult to strike a balance between processing uniformity and organizational stability, especially in complex geometric structures or multi-material composite drill bits. Uneven hardness distribution or unstable phase change organization may occur, leading to local early wear or fracture in actual applications, restricting the application reliability of alloy drill bits under high-precision and high-strength working conditions. Summary of the invention

[0004] The purpose of the present invention is to provide a heat treatment process for an alloy drill bit to solve the problems raised in the above-mentioned background technology: However, the biggest problem with the current heat treatment process is that it is difficult to balance processing uniformity and organizational stability, especially in complex geometric structures or multi-material composite drill bits. It is easy to have uneven hardness distribution or unstable phase change organization, resulting in local early wear or fracture in actual applications, which restricts the application reliability of the alloy drill bit under high-precision and high-strength working conditions.

[0005] Technical solution: A heat treatment process for an alloy drill bit includes the following steps:

[0006] S1. After the alloy drill bit is initially processed and formed, vacuum pretreatment and heat preservation are performed, and the temperature is controlled between 580°C and 620°C, and the time is controlled between 1.5 hours and 2.5 hours;

[0007] S2. After the insulation is completed, the drill bit is quickly transferred to a segmented temperature-controlled carburizing furnace for main carburizing treatment, the temperature is controlled between 930°C and 960°C, the carburizing time is 3 hours to 4 hours, and the carburizing depth is controlled between 0.3mm and 0.6mm;

[0008] S3. After carburizing is completed, multi-speed cooling is performed in different zones, including rapid cooling in a high temperature section, controlled cooling in a medium temperature section, and slow cooling in a low temperature section, wherein the temperature is controlled to be above 850°C for 20 seconds, controlled cooling in the range of 550°C to 650°C for 60 seconds, and then slow cooling at a temperature below 200°C for 80 seconds, to obtain a refined martensite multiphase structure;

[0009] S4. After cooling, a double-stage tempering treatment is implemented, the first tempering temperature is controlled at 560 ℃ to 580 ℃, the holding time is 1 hour, the second tempering temperature is controlled at 300 ℃ to 320 ℃, the holding time is 45 minutes;

[0010] S5. After the heat treatment, ultra-high pressure static boronizing diffusion treatment is performed at a temperature of 920°C to 940°C for 1 hour.

[0011] Preferably, the vacuum pretreatment heat preservation heating is performed in a high vacuum environment, and the air pressure of the high vacuum environment is less than one thousandth of a square Pascal.

[0012] Preferably, the staged temperature-controlled carburizing step precisely controls the atmosphere components at different time points, and the carburizing gas adopts a combination of hydrocarbon, CO and nitrogen, and the ratios are adjusted to: 40:40:20 in the initial stage, 50:30:20 in the middle stage, and 30:50:20 in the final stage.

[0013] Preferably, the multi-speed cooling adopts a three-stage temperature-controlled liquid medium cooling method, and each stage adopts salt water, polymer solution and oil cooling medium of different concentrations.

[0014] Preferably, an intermediate heat preservation delay process is implemented during the double-stage tempering process, and the first and second stages of tempering are naturally cooled to room temperature and left to stand for more than 6 hours.

[0015] Preferably, the static boronizing treatment is performed in an inert atmosphere to protect the diffusion cavity, the diffusion medium is a mixture of boron powder and a diffusion aid, the molar ratio is 5:1, and the applied axial load is not less than 10 MPa.

[0016] Preferably, the boronizing treatment further includes a high temperature low oxygen nitriding passivation treatment after the diffusion, with the temperature ranging from 780° C. to 800° C. and keeping the temperature for 45 minutes.

[0017] Preferably, in the atmosphere-controlled carburizing step, an atmosphere pressure pulse disturbance is performed every 30 minutes during carburizing, the pulse peak is 1.5 times the normal pressure, and the duration is 15 seconds.

[0018] Preferably, in the three-stage liquid medium cooling method, the first stage salt water concentration is 10wt%, the second stage polymer solution is a polyacrylamide solution with a mass fraction of 15wt%, and the third stage oil is a high boiling point mineral oil. The switching time between each stage does not exceed 10 seconds.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] (1) Through the vacuum pretreatment stage, the impurities at the grain boundaries of the drill bit are effectively removed, the purity of the structure is improved, and a stable foundation is provided for subsequent heat treatment.

[0021] (2) The two-stage temperature-controlled austenitization method is adopted to make the distribution of alloy elements more uniform, which is conducive to the formation of stable and fine austenite structure and reduces the structural unevenness during the phase transformation process.

[0022] (3) The multi-stage liquid medium cooling process realizes gradient cooling in high temperature, medium temperature and low temperature stages, effectively regulates the microstructure transformation rate, and significantly reduces the risk of thermal stress accumulation and cracking.

[0023] (4) The first stage uses low-temperature brine for rapid cooling to prevent grain coarsening; the second stage uses polymer solution for controlled cooling to promote the formation of bainite phase; the third stage uses high-boiling point oil for slow cooling, which helps stabilize the martensitic structure and significantly improves the matching of hardness and toughness of the finished product.

[0024] (5) Rapid conversion between cooling media, precise control of cooling time and temperature, effectively improving tissue uniformity and batch stability.

[0025] (6) It overcomes the problem of balancing processing uniformity and organizational stability in the prior art, and significantly improves the service life and reliability of the alloy drill bit.

[0026] (7) The process flow is suitable for automated control and can be widely used in the heat treatment of complex structure cemented carbide tools, with good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is an overall schematic diagram of a heat treatment process of an alloy drill bit of the present invention; DETAILED DESCRIPTION

[0028] Example

[0029] Examples 1-4

[0030] Embodiment 1: A heat treatment process for an alloy drill bit, comprising the following steps:

[0031] S1. Place the processed alloy drill bit in a vacuum furnace, pre-treat it at a gas pressure of 0.001 Pa, heat it to 600°C, and keep it warm for 30 minutes to remove grain boundary impurities and inhibit oxidation.

[0032] S2. A two-stage temperature-controlled austenitizing process is used, first raising the temperature to 850°C and keeping it for 20 minutes, then raising the temperature to 1050°C and keeping it for 15 minutes, so that the alloy elements are distributed more evenly and stable austenite is obtained.

[0033] S3. Use three-stage temperature-controlled liquid cooling for multi-speed cooling:

[0034] The first stage cooling medium is 10% sodium chloride aqueous solution, the temperature is 8°C, and the cooling time is 20 seconds;

[0035] The second cooling medium is 15% polyacrylamide solution, the temperature is 60°C, and the cooling time is 60 seconds;

[0036] The third stage cooling medium is high boiling point mineral oil (initial temperature 25°C), and the cooling time is 80 seconds; the three-stage conversion time is controlled within 10 seconds.

[0037] S4. The cooled workpiece is tempered at 200°C, kept at this temperature for 2 hours, and then air-cooled.

[0038] After testing, the obtained alloy drill bit has a hardness of HRC64.2 and an impact toughness of 15.8J / cm 2 , the organization is evenly distributed and there are no crack defects.

[0039] Example 2: The difference from Example 1 is that the vacuum pretreatment temperature is 650°C and the temperature is kept for 20 minutes;

[0040] The temperature of the first stage of austenitization is 870°C, which is kept for 25 minutes, and the temperature of the second stage is 1020°C, which is kept for 10 minutes;

[0041] The first stage cooling medium temperature is 5°C, and the cooling time is 25 seconds;

[0042] The second stage polymer solution temperature was 65°C and the cooling time was 55 seconds;

[0043] The third stage oil cooling temperature is 30℃ and the cooling time is 90 seconds.

[0044] The obtained alloy drill bit has a hardness of HRC63.7 and an impact toughness of 16.1 J / cm 2 .

[0045] Example 3: The difference from Example 1 is that the first cooling stage uses 12% sodium chloride solution, the temperature is 6°C, and the cooling time is 18 seconds;

[0046] The second cooling stage uses 18% polyacrylamide solution, the temperature is 55°C, and the cooling time is 70 seconds;

[0047] The third stage of cooling uses high boiling point mineral oil with an initial temperature of 20°C and a cooling time of 100 seconds.

[0048] After testing, the drill bit drilled holes in cemented carbide material 300 times continuously without any cutting edge cracking.

[0049] Example 4: The difference from Example 1 is that the vacuum pretreatment holding time is extended to 40 minutes;

[0050] The austenitizing temperature was 900℃ for 15 minutes and 1080℃ for 10 minutes respectively;

[0051] The three cooling time stages are set to 20 seconds, 60 seconds, and 70 seconds, corresponding to medium temperatures of 6°C, 70°C, and 28°C, respectively.

[0052] The results of microstructure observation show that the martensite is fine and dense, the bainite is evenly distributed, the hardness is HRC64.5, and the wear resistance is excellent.

[0053] Comparative Example

[0054] Comparative Example 1: The vacuum pretreatment step was omitted, and austenitization was directly performed by heating to 1050°C and keeping the temperature for 30 minutes, followed by oil cooling.

[0055] The surface of the product has oxidation and decarburization, uneven microstructure, hardness HRC is only 60.2, and impact toughness is less than 12J / cm 2 .

[0056] Comparative Example 2: Single-stage austenitizing treatment: directly heating to 1050°C and keeping warm for 25 minutes without staged treatment; cooling using a single oil.

[0057] The results show that the grains are obviously coarsened, the local hardness fluctuates greatly, the structure is mixed, and the wear resistance is significantly reduced.

[0058] Comparative Example 3: The cooling process did not adopt the three-stage cooling method, but only used 10% salt water to quickly cool to room temperature without temperature zone transition.

[0059] This leads to thermal stress concentration, micro cracks easily appear on the drill bit during use, and the average service life is reduced by 35%.

[0060] In order to measure the comparative experiment on the machining uniformity and organizational stability of the alloy drill bit between the embodiment and the comparative example, the following experiment was designed, and the experimental steps are as follows:

[0061] All alloy drill bit samples used in this experiment are alloy steel drill bit blanks from the same batch, totaling 70 pieces. The cemented carbide matrix composition of all samples is the same to ensure experimental comparability.

[0062] The equipment used is as follows:

[0063] Vacuum heat treatment furnace: used for vacuum pretreatment and two-stage austenitization;

[0064] Box-type resistance furnace: used for austenitizing treatment of some experimental groups;

[0065] Oil tank, polymer cooling tank, brine cooling tank: used to implement the liquid cooling medium in the three-stage cooling process;

[0066] Microhardness tester: used to measure the hardness of drill bits;

[0067] Metallographic microscope: used to analyze the metallographic structure of samples;

[0068] Scanning electron microscope (SEM): used for more detailed tissue observation;

[0069] Impact testing machine: used to measure the impact toughness of the drill bit.

[0070] The test environment of the experiment is a normal temperature of 25℃ and a humidity of 50%±5%. In order to ensure the accuracy of the experimental results, the experimental area should be kept free of strong wind interference.

[0071] 2. Experimental Grouping and Heat Treatment Conditions: The experiment is divided into seven groups, including four embodiment groups and three comparison groups. The specific groups are as follows:

[0072] Group A: Example 1 (vacuum + two-stage austenitization + three-stage cooling)

[0073] Group B: Example 2 (Differences from Example 1: vacuum pretreatment temperature is 650°C, heat preservation for 20 minutes, etc.)

[0074] Group C: Example 3 (differences from Example 1: different cooling medium, cooling time, etc.)

[0075] Group D: Example 4 (Difference from Example 1: Process parameter changes)

[0076] Group E: Comparative Example 1 (no vacuum, single oil cooling)

[0077] Group F: Comparative Example 2 (single-stage austenitizing, oil cooling)

[0078] Group G: Comparative Example 3 (Single-stage brine rapid cooling)

[0079] Each group contains 10 samples to ensure the reliability of the data.

[0080] 3. The specific experimental steps are as follows:

[0081] Select 70 alloy drill bit blanks from the same batch and number them according to the grouping requirements to ensure that the number of samples in each group is consistent and independent of each other.

[0082] Label each sample to avoid cross contamination.

[0083] Heat treatment operation: different heat treatment steps are performed according to the group. The heat treatment process of the embodiment group includes: vacuum pretreatment, two-stage austenitization, three-stage cooling and other steps. The comparative group is carried out according to the conventional single treatment method, such as comparative example 1 adopts single oil cooling, comparative example 2 adopts single stage austenitization, etc.

[0084] The specific heat treatment steps are as follows:

[0085] Vacuum pretreatment (applicable to the embodiment group): the alloy drill bit is placed in a vacuum furnace, heated to 600° C. under a gas pressure of 0.001 Pa, and kept warm for 30 minutes to remove grain boundary impurities and inhibit oxidation.

[0086] Two-stage austenitizing treatment (applicable to the embodiment group): in the first stage, the sample is heated to 850°C and kept at this temperature for 20 minutes; in the second stage, the temperature is raised to 1050°C and kept at this temperature for 15 minutes.

[0087] Multi-stage cooling process (applicable to the embodiment group): a three-stage liquid cooling method is adopted. The first stage uses a 10% sodium chloride aqueous solution, the cooling medium temperature is 8°C, and the cooling time is 20 seconds; the second stage uses a 15% polyacrylamide solution, the cooling medium temperature is 60°C, and the cooling time is 60 seconds; the third stage uses a high boiling point mineral oil with an initial temperature of 25°C, and the cooling time is 80 seconds. The three-stage conversion time is controlled within 10 seconds.

[0088] Tempering treatment (applicable to all groups): The cooled drill bit is tempered at 200℃, kept at this temperature for 2 hours and then air-cooled.

[0089] Processing uniformity test: Hardness measurements were performed on each drill bit at three locations along the axial direction (head, middle, and tail), and the Vickers hardness value of the drill bit was measured using a microhardness tester.

[0090] Calculate the hardness fluctuation value (ΔHV) of each drill bit using the formula: maximum hardness value - minimum hardness value to evaluate processing uniformity.

[0091] Organization stability test: Take samples, slice them and polish them, and use a metallographic microscope to observe the metallographic structure of the samples. Use a scanning electron microscope (SEM) to observe the samples more closely, focusing on whether there are problems such as martensitic cracks, decarburization areas, and grain coarsening.

[0092] An impact testing machine was used to measure the impact toughness of each drill bit and to evaluate the wear resistance of the drill bit.

[0093] The experimental data are shown in Table 1:

[0094]

[0095] Table 1

[0096] IV. Experimental data and analysis: Hardness fluctuation value: used to evaluate processing uniformity. The hardness fluctuation of the embodiment group is small, and the uniformity is good, while the hardness fluctuation value of the comparative example group is large, indicating that the structure is uneven.

[0097] Grain size and organizational morphology: Microstructural analysis will show that the grains of the embodiment group are relatively fine and uniform without obvious defects; while the grains of the comparative example group are relatively coarse and have organizational abnormalities such as decarburization or cracks.

[0098] Impact toughness: The impact test will reveal that the drill bits in the embodiment group have higher toughness and better wear resistance, while the drill bits in the comparative group show lower impact toughness and are prone to breakage.

[0099] Through comparative experiments, the following conclusions can be drawn: the heat treatment process of Examples 1-4 significantly improves the processing uniformity of the alloy drill bit, with smaller hardness fluctuations, showing better organizational stability.

[0100] The drill bits of the embodiment group exhibit higher impact toughness and stronger wear resistance, while the drill bits of the comparative group are prone to problems such as cracks, decarburization or grain coarsening during use.

[0101] In summary, the heat treatment process of the embodiment group effectively improves the performance of the drill bit and has strong market competitiveness.

[0102] In order to measure the comparative experiment on the wear resistance, corrosion resistance and service life of the alloy drill bit of the embodiment and the comparative example, the following experiment was designed, and the experimental steps are as follows:

[0103] Experimental article: Alloy drill bit sample: Alloy drill bits were prepared according to the heat treatment processes of the embodiment and the comparative example.

[0104] Wear tester: used to test the wear resistance of drill bits under standard loads.

[0105] Corrosion test box: used to simulate the corrosion resistance of the drill bit in different corrosive environments (acidic, alkaline, salt water).

[0106] Temperature and humidity control box: used to simulate the drill usage conditions in different working environments.

[0107] Standard abrasives: such as sand or ceramic particles, used in wear testing.

[0108] Saline solutions (NaCl, concentrations of 3%, 5%, and 7%) were used for corrosion testing.

[0109] Acidic solution (HCl, concentration of 10%) and alkaline solution (NaOH, concentration of 10%) were used to simulate different working environments.

[0110] Specifically, the wear resistance test experimental steps are as follows:

[0111] Sample preparation: According to the heat treatment process in the embodiment and comparative example, the alloy drill bit samples were prepared.

[0112] Wear test: Fix the drill sample on the wear tester and load a standard load (e.g. 50N). Use standard abrasive (sand or ceramic particles) to rub on the drill surface and perform a wear test for 20 hours. Record the wear amount of each sample.

[0113] Specifically, the corrosion resistance test experimental steps are as follows:

[0114] Corrosion simulation: The drill bit samples were immersed in saline solutions of different concentrations (3%, 5%, 7%), acidic solution (10% HCl) and alkaline solution (10% NaOH) to test the corrosion resistance under different environments.

[0115] Corrosion cycle: The sample immersion time is 72 hours, the corrosive medium is replaced every 12 hours, and the surface corrosion of each sample is recorded.

[0116] Surface damage assessment: Use a scanning electron microscope (SEM) to observe the corrosion condition of the sample surface and record the corrosion rate and surface damage area.

[0117] Specifically, the service life test is as follows:

[0118] Equipment preparation: Install the drill bit on a standard drilling machine, perform drilling operations in a simulated working environment, and record the usage time and drill bit wear.

[0119] Service life record: Continue the drilling operation until the drill bit efficiency drops below 20% (i.e. the drilling efficiency drops significantly or there is obvious wear), and record the service life.

[0120] The experimental data are shown in Table 2:

[0121]

[0122] Table 2

[0123] The above shows and describes the basic principles, main features and advantages of the present invention; those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected; the scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A heat treatment process for an alloy drill bit, characterized in that: The heat treatment process of the alloy drill bit comprises the following steps: S1. After the alloy drill bit is initially processed and formed, vacuum pretreatment and heat preservation are performed, and the temperature is controlled between 580°C and 620°C, and the time is controlled between 1.5 hours and 2.5 hours; S2. After the insulation is completed, the drill bit is quickly transferred to a segmented temperature-controlled carburizing furnace for main carburizing treatment, the temperature is controlled between 930°C and 960°C, the carburizing time is 3 hours to 4 hours, and the carburizing depth is controlled between 0.3mm and 0.6mm; S3. After carburizing is completed, multi-speed cooling is performed in different zones, including rapid cooling in a high temperature section, controlled cooling in a medium temperature section, and slow cooling in a low temperature section, wherein the temperature is controlled to be above 850°C for 20 seconds, controlled cooling in the range of 550°C to 650°C for 60 seconds, and then slow cooling at a temperature below 200°C for 80 seconds, to obtain a refined martensite multiphase structure; S4. After cooling, a double-stage tempering treatment is implemented, the first tempering temperature is controlled at 560 ℃ to 580 ℃, the holding time is 1 hour, the second tempering temperature is controlled at 300 ℃ to 320 ℃, the holding time is 45 minutes; S5. After the heat treatment, ultra-high pressure static boronizing diffusion treatment is performed at a temperature of 920°C to 940°C for 1 hour.

2. The heat treatment process of an alloy drill bit according to claim 1, characterized in that: The vacuum pretreatment heat preservation heating is performed in a high vacuum environment, and the air pressure of the high vacuum environment is less than one thousandth of a square Pascal.

3. The heat treatment process of an alloy drill bit according to claim 1, characterized in that: The step of temperature-controlled carburizing precisely controls the atmosphere components at different time points. The carburizing gas uses a combination of hydrocarbon, CO and nitrogen, and the ratios are adjusted to 40:40:20 in the initial stage, 50:30:20 in the middle stage and 30:50:20 in the final stage.

4. The heat treatment process of an alloy drill bit according to claim 1, characterized in that: The multi-speed cooling adopts a three-stage temperature-controlled liquid medium cooling method, and each stage adopts salt water, polymer solution and oil cooling medium of different concentrations.

5. The heat treatment process of an alloy drill bit according to claim 1, characterized in that: During the double-stage tempering process, an intermediate heat preservation delay process is implemented, and the first and second stages of tempering are naturally cooled to room temperature and left to stand for more than 6 hours.

6. The heat treatment process of an alloy drill bit according to claim 1, characterized in that: The static boronizing treatment is performed in an inert atmosphere to protect the diffusion cavity. The diffusion medium is a mixture of boron powder and a diffusion aid in a molar ratio of 5:

1. The applied axial load is not less than 10 MPa.

7. The heat treatment process of an alloy drill bit according to claim 6, characterized in that: The boronizing treatment further includes a high temperature low oxygen nitriding passivation treatment after the diffusion, with the temperature ranging from 780° C. to 800° C. and keeping the temperature for 45 minutes.

8. The heat treatment process of an alloy drill bit according to claim 3, characterized in that: In the atmosphere-controlled carburizing step, an atmosphere pressure pulse disturbance is performed every 30 minutes during carburizing, with a pulse peak value of 1.5 times the normal pressure and a duration of 15 seconds.

9. The heat treatment process of an alloy drill bit according to claim 4, characterized in that: In the three-stage liquid medium cooling method, the first stage has a brine concentration of 10wt%, the second stage has a polymer solution of 15wt% polyacrylamide solution, and the third stage has a high-boiling point mineral oil. The switching time between the stages does not exceed 10 seconds.

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