A method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment

Abstract

This application belongs to the field of cemented carbide manufacturing technology, specifically relating to a method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment, including the following steps: S1, obtaining cemented carbide extruded billets, including billets exempt from inspection and billets to be inspected; drying the cemented carbide extruded billets, and placing the billets to be inspected in the detection area of ​​the drying equipment; S2, after the cemented carbide extruded billets have completed drying, removing the billets to be inspected; S3, performing a rapid heat treatment weight loss test on the billets to be inspected to obtain their average weight loss rate N; S4, setting the maximum value of the average weight loss rate that meets production requirements to M; if N≤M, then the drying quality is deemed qualified; if N>M, then repeating steps S1-S4 on the cemented carbide extruded billets until N≤M. This application combines specific drying process parameters with objective and quantifiable end-quality criteria to form a complete process control and quality evaluation system.

Description

Technical Field

[0001] This application relates to the field of cemented carbide manufacturing technology, specifically, to a method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment. Background Technology

[0002] The drying process of cemented carbide extruded bars aims to remove organic binders (such as paraffin) and solvents from the formed blank, which is a key pretreatment step to ensure the quality of subsequent sintering.

[0003] Currently, the industry commonly uses a combination of water bath heating and vacuum drying. This technology has the following inherent drawbacks: the water bath has limited heat capacity and slow heat transfer, resulting in a drying cycle that typically exceeds 72 hours, leading to low production efficiency. After a long period of low-temperature drying, organic components may still remain inside the green body. These residues will rapidly vaporize during the subsequent high-temperature dewaxing stage, easily causing irreversible defects such as blistering and cracking of the green body.

[0004] The current drying process is a "black box," meaning that after drying, it's impossible to quickly ascertain whether the drying uniformity and organic matter removal of the entire batch of products meet the standards. Traditional destructive sampling inspections of the entire furnace are time-consuming and costly, and the sampling points may not represent the slowest-drying and highest-risk areas within the furnace. Therefore, the inherent quality risks of the drying process are implicitly transmitted to the high-temperature dewaxing and sintering processes, often only being discovered after a batch of products has been scrapped, leading to significant economic losses and production fluctuations.

[0005] To address the problems of low drying efficiency, long drying cycle, uneven heat transfer leading to uneven removal of organic matter inside the billet and resulting in bubbling and cracking defects in subsequent processes, as well as the lack of a rapid, accurate, and representative quality assessment method at the drying endpoint that can represent the worst quality state of the entire furnace, and the hidden transmission of quality risks to subsequent processes, it is urgent to propose a method to improve the drying quality of cemented carbide extruded billets based on drying quality assessment. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment, comprising the following steps: S1, obtaining cemented carbide extruded billets, the cemented carbide extruded billets including non-inspection billets and inspection billets; drying the cemented carbide extruded billets, wherein the inspection billet is placed in the detection area of ​​the drying equipment, the detection area being determined based on the structure of the drying equipment, the detection area being the area with the worst heat flow and material diffusion conditions during the drying process; S2, after the cemented carbide extruded billets have completed drying, removing the inspection billet; S3, performing a rapid heat treatment weight loss test on the inspection billet to obtain its average weight loss rate, setting the average weight loss rate of the inspection billet to N; S4, setting the maximum value of the weight loss rate of the cemented carbide extruded billet that meets production requirements to be M, wherein if N≤M, the drying quality of the cemented carbide extruded billet is deemed qualified; if N>M, repeating steps S1-S4 on the cemented carbide extruded billet until N≤M.

[0007] As a preferred embodiment of the method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment described in this application, in step S1, the billets exempt from inspection and the billets to be inspected are prepared by the same batch formula and the same forming process, and the number of billets to be inspected is ≥1.

[0008] As a preferred embodiment of the method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment described in this application, step S2 further includes performing a visual inspection on the billet to be inspected. If macroscopic cracks are found, it is directly determined to be unqualified and the subsequent steps are terminated. If no macroscopic cracks are found, step S3 is performed. Step S4 further includes that after the drying quality of the cemented carbide extruded billet is determined to be qualified, it is transferred to the sintering process to obtain cemented carbide products, and the qualification rate of the cemented carbide products is ≥99%.

[0009] As a preferred embodiment of the method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment described in this application, the rapid heat treatment weight loss test in step S3 is specifically performed as follows: under nitrogen protection, the billet to be tested is heated from room temperature to 180-200℃ at a rate of 30-50℃ / min, held at that temperature for 3-5min, and then the N is measured after cooling.

[0010] As a preferred embodiment of the method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment described in this application, in step S4, M is related to the bursting defect rate of the cemented carbide extruded billet in the standard dewaxing sintering process, wherein M=0.05%.

[0011] As a preferred embodiment of the method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment described in this application, in step S1, the drying method is heat transfer medium bath heating, and the drying equipment is a vacuum drying furnace.

[0012] As a preferred embodiment of the method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment described in this application, the heating method of the heat medium bath is specifically as follows: In a vacuum environment, the cemented carbide extrusion billet is heated by a heat transfer medium bath using the following multi-stage heating and holding process: First stage: Increase the temperature from room temperature to 30-40℃ at a rate of 0.2-0.5℃ / min, and hold at that temperature for 300-500min; Second stage: Increase the temperature to 50-60℃ at a rate of 0.2-0.5℃ / min and hold for 300-500min; The third stage: Increase the temperature to 90-110℃ at a rate of 0.5℃-0.8℃ / min and hold for 500-700min; Fourth stage: Increase the temperature to 130-150℃ at a rate of 1-2℃ / min and hold for 800-1200min; After the program is completed, heating is stopped and the furnace is allowed to cool. The absolute pressure of the vacuum environment is maintained at 50-150 Pa.

[0013] As a preferred embodiment of the method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment described in this application, the heat medium bath heating is oil bath heating.

[0014] As a preferred embodiment of the method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment described in this application, the detection area is located in a space within the vacuum drying furnace with a height of 100-400 mm and a horizontal distance of 100-400 mm from the vacuum pipe interface.

[0015] As a preferred embodiment of the method for improving the drying quality of cemented carbide extrusion billets based on drying quality assessment described in this application, the furnace cooling includes: natural cooling in the furnace under vacuum to below 25°C.

[0016] The beneficial effects of this application are as follows: This application proposes a method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment. This method replaces water baths with high-boiling-point, high-heat-capacity oil baths, combined with a precisely controlled stepped heating-holding process, achieving more efficient and uniform heat transfer. This promotes the migration and removal of organic matter (such as paraffin wax) in a smoother, more gradient manner, effectively avoiding localized stress concentration and the risk of residual "boiling," thus reducing the incidence of drying defects to an extremely low level from the process source.

[0017] This application defines the region within the furnace with the worst heat flow and material diffusion conditions during the drying process as the detection area, and establishes a rapid appearance and average weight loss rate of representative blanks in this region as criteria. After drying, the condition of the entire batch of products, especially the weakest links in quality, can be determined within tens of minutes, enabling timely interception of unqualified batches and preventing them from flowing into subsequent sintering processes and causing greater losses.

[0018] This application combines specific drying process parameters (temperature, time, rate) with objective and quantifiable end-quality criteria (state of the preform in the inspection area) to form a complete process control and quality evaluation system. This makes the development and optimization of drying processes for products with different formulations and specifications more scientific and directional, significantly improving the adaptability of the production process and the stability of product quality between different batches. Detailed Implementation

[0019] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] This application provides a method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment, including the following steps: S1. Obtain a cemented carbide extrusion billet, the cemented carbide extrusion billet including an inspection-free billet and an inspection-to-be-inspected billet; dry the cemented carbide extrusion billet, wherein the inspection-to-be-inspected billet is placed in the inspection area of ​​the drying equipment, the inspection area is determined based on the structure of the drying equipment, and the inspection area is the area with the worst heat flow and material diffusion conditions during the drying process; The inspection-exempt blank and the inspection blank are prepared by the same batch formula and the same molding process, and the number of the inspection blank is ≥1; The drying method is heating with a heat transfer medium bath, and the drying equipment is a vacuum drying oven; The heating method of the heat medium bath is specifically as follows: In a vacuum environment, the cemented carbide extrusion billet is heated by a heat transfer medium bath using the following multi-stage heating and holding process: First stage: Increase the temperature from room temperature to 30-40℃ at a rate of 0.2-0.5℃ / min, and hold at that temperature for 300-500min; Second stage: Increase the temperature to 50-60℃ at a rate of 0.2-0.5℃ / min and hold for 300-500min; The third stage: Increase the temperature to 90-110℃ at a rate of 0.5℃-0.8℃ / min and hold for 500-700min; Fourth stage: Increase the temperature to 130-150℃ at a rate of 1-2℃ / min and hold for 800-1200min; After the program is completed, heating is stopped and the furnace is allowed to cool. The absolute pressure of the vacuum environment is maintained at 50-150 Pa. The heat transfer medium bath is an oil bath; the detection area is located in the vacuum drying oven at a height of 100-400mm and at a horizontal distance of 100-400mm from the vacuum pipe interface; the furnace cooling includes: natural cooling under vacuum to below 25°C.

[0021] S2. After the cemented carbide extrusion billet has been dried, the billet to be inspected is taken out. The blank to be inspected is visually inspected. If macroscopic cracks are found, it is directly judged as unqualified and the subsequent steps are terminated. If no macroscopic cracks are found, step S3 is performed. S3. Perform a rapid heat treatment weight loss test on the blank to be inspected to obtain its average weight loss rate, and set the average weight loss rate of the blank to be inspected to be N. The rapid heat treatment weight loss test method is as follows: under nitrogen protection, the blank to be tested is heated from room temperature to 180-200℃ at a rate of 30-50℃ / min, held at that temperature for 3-5min, and then the N is measured after cooling. S4. Set the maximum value of the weight loss rate of the cemented carbide extrusion billet that meets the production requirements to be M. If N≤M, the drying quality of the cemented carbide extrusion billet is deemed to be qualified. If N>M, repeat steps S1-S4 on the cemented carbide extrusion billet until N≤M. M is related to the bursting defect rate of the cemented carbide extruded billet in the standard dewaxing and sintering process, wherein M=0.05%. Step S4 further includes that after the drying quality of the cemented carbide extruded billet is determined to be qualified, it is transferred to the sintering process to obtain cemented carbide products, and the qualification rate of the cemented carbide products is ≥99%.

[0022] The technical solution of this application will be further described below with reference to specific embodiments.

[0023] Example 1 A cylindrical cemented carbide extrusion billet with a diameter of 3.0 mm and a length of 330.0 mm was obtained and placed in a vacuum drying furnace. The cemented carbide extrusion billet included a billet exempt from inspection and a billet to be inspected. The billets exempt from inspection and the billets to be inspected were prepared by the same batch formula and the same forming process. The number of billets to be inspected was 3. According to the structure of the vacuum drying furnace, the inspection area was determined to be a space area with a height of 260 mm in the furnace and a horizontal distance of 240 mm from the vacuum pipe interface. This area was the area with the slowest drying rate determined by airflow simulation. Four billets to be inspected were placed in this area. Start the vacuum system to maintain the absolute pressure inside the furnace at 100 Pa; Start the oil bath heating system and execute the following multi-stage heating and heat preservation program: First stage: Increase the temperature from room temperature (approximately 25°C) to 35°C at a rate of 0.45°C / min, and hold at 35°C for 350 min; Second stage: Increase the temperature to 55℃ at a rate of 0.50℃ / min, and hold at 55℃ for 300min; The third stage: the temperature is increased to 95℃ at a rate of 0.60℃ / min, and held at 95℃ for 500min; Fourth stage: Increase the temperature to 130℃ at a rate of 1.50℃ / min, and hold at 130℃ for 850min; After the program is completed, heating is stopped, and the billet is allowed to cool naturally under vacuum to below 25°C before being removed for inspection. The three blanks to be inspected were examined one by one under a 100x optical microscope, and no macroscopic cracks were observed on the surface of any of the blanks. The average weight loss rate of the blank to be tested was obtained by rapid heat treatment weight loss test. The test method is as follows: under nitrogen protection, the blank to be tested was heated from room temperature to 185℃ at a rate of 35℃ / min and held for 5min. After cooling, the average weight loss rate was measured. N=0.016%, M=0.05%. If N≤M, the drying quality of the cemented carbide extruded blank is deemed to be qualified.

[0024] Once the drying quality of the cemented carbide extruded billet is deemed acceptable, it is transferred to the sintering process to obtain the cemented carbide product. The pass rate of the cemented carbide product is 99.89%, which indicates that this drying method can effectively and uniformly remove organic matter with an extremely low defect rate.

[0025] Example 2 A cylindrical cemented carbide extrusion billet with a diameter of 6.0 mm and a length of 310.0 mm was obtained and placed in a vacuum drying furnace. The cemented carbide extrusion billet included a billet exempt from inspection and a billet to be inspected. The billets exempt from inspection and the billets to be inspected were prepared by the same batch formula and the same forming process. The number of billets to be inspected was 4. According to the structure of the vacuum drying furnace, the inspection area was determined to be a space area with a height of 280 mm in the furnace and a horizontal distance of 220 mm from the vacuum pipe interface. This area was the area with the slowest drying rate determined by airflow simulation. The 4 billets to be inspected were placed in this area. Start the vacuum system to maintain the absolute pressure inside the furnace at 80 Pa; Start the oil bath heating system and execute the following multi-stage heating and heat preservation program: First stage: Increase the temperature from room temperature (approximately 25°C) to 35°C at a rate of 0.40°C / min, and hold at 35°C for 360 min; Second stage: Increase the temperature to 55℃ at a rate of 0.35℃ / min, and hold at 55℃ for 420min; The third stage: the temperature is increased to 95℃ at a rate of 0.65℃ / min, and held at 95℃ for 600min; Fourth stage: Increase the temperature to 140℃ at a rate of 1.25℃ / min, and hold at 140℃ for 920min; After the program is completed, heating is stopped, and the billet is allowed to cool naturally under vacuum to below 25°C before being removed for inspection. Each of the four blanks to be inspected was examined under a 100x optical microscope, and no macroscopic cracks were observed on the surface of any of the blanks. The average weight loss rate of the blank to be tested was obtained by rapid heat treatment weight loss test. The test method is as follows: under nitrogen protection, the blank to be tested is heated from room temperature to 200℃ at a rate of 40℃ / min and held at that temperature for 5min. After cooling, the average weight loss rate is measured as N=0.041% and M=0.05%. If N≤M, the drying quality of the cemented carbide extruded blank is deemed to be qualified.

[0026] Once the drying quality of the cemented carbide extruded billet is deemed acceptable, it is transferred to the sintering process to obtain the cemented carbide product. The pass rate of the cemented carbide product is 99.83%, which indicates that this drying method can effectively and uniformly remove organic matter with an extremely low defect rate.

[0027] Example 3 A cylindrical cemented carbide extrusion billet with a diameter of 18.0 mm and a length of 350.0 mm was obtained and placed in a vacuum drying furnace. The cemented carbide extrusion billet included a billet exempt from inspection and a billet to be inspected. The billets exempt from inspection and the billets to be inspected were prepared by the same batch formula and the same forming process. The number of billets to be inspected was 5. According to the structure of the vacuum drying furnace, the inspection area was determined to be a space area with a height of 250 mm in the furnace and a horizontal distance of 250 mm from the vacuum pipe interface. This area was the area with the slowest drying rate determined by airflow simulation. The 5 billets to be inspected were placed in this area. Start the vacuum system to maintain the absolute pressure inside the furnace at 120 Pa; Start the oil bath heating system and execute the following multi-stage heating and heat preservation program: First stage: Increase the temperature from room temperature (approximately 25°C) to 35°C at a rate of 0.45°C / min, and hold at 35°C for 350 min; Second stage: Increase the temperature to 55℃ at a rate of 0.50℃ / min, and hold at 55℃ for 300min; The third stage: the temperature is increased to 95℃ at a rate of 0.60℃ / min, and held at 95℃ for 500min; Fourth stage: Increase the temperature to 130℃ at a rate of 1.50℃ / min, and hold at 130℃ for 850min; After the program is completed, heating is stopped, and the billet is allowed to cool naturally under vacuum to below 25°C before being removed for inspection. Five blanks were inspected one by one under a 100x optical microscope, and no macroscopic cracks were observed on the surface of any of the blanks. The average weight loss rate of the blank to be tested was obtained by rapid heat treatment weight loss test. The test method is as follows: under nitrogen protection, the blank to be tested was heated from room temperature to 185°C at a rate of 35°C / min and held at that temperature for 5min. After cooling, the average weight loss rate was measured as N=0.062% and M=0.05%. Since N>M, the above steps were repeated for the cemented carbide extrusion blank. The average weight loss rate was measured as N=0.018%. Since N≤M, the drying quality of the cemented carbide extrusion blank was deemed to be qualified.

[0028] Once the drying quality of the cemented carbide extruded billet is deemed acceptable, it is transferred to the sintering process to obtain the cemented carbide product. The pass rate of the cemented carbide product is 99.86%, which indicates that this drying method can effectively and uniformly remove organic matter with an extremely low defect rate.

[0029] Comparative Example 1 The difference between this comparative example and Example 3 is that after the first drying, when the average weight loss rate N of the blank to be tested is greater than M, the drying step is not repeated, and it is directly transferred to the sintering process to obtain the cemented carbide product. The pass rate of the cemented carbide product is 49.40%.

[0030] Comparative Example 2 The difference between this comparative example and Example 1 is that, instead of using a multi-stage heating and holding process, the temperature is directly raised to 130°C at a rate of 1.50°C / min and held at 130°C for 2000 min. The blank is then naturally cooled to below 25°C under vacuum and then removed for inspection. The three blanks to be inspected were examined one by one under a 100x optical microscope. If macroscopic cracks were observed on the surface of all the blanks to be inspected, they were directly judged as unqualified and the subsequent steps were terminated.

[0031] As can be seen from the above embodiments and comparative examples: Example 3, combined with Comparative Example 1, shows that insufficient drying of the billet and insufficient pressing strength, leading directly to the sintering process, results in cracks forming on the billet surface during the subsequent dewaxing and sintering stage due to the rapid removal of the forming agent, affecting product surface quality and yield. Example 1, combined with Comparative Example 2, shows that billet drying is a slow and gradual process. Excessive drying temperature rise causes violent volatilization of the forming agent, resulting in concentrated stress release in the billet and the initiation of numerous surface cracks, affecting product surface quality. Examples 1-3, combined with Comparative Examples 1-2, demonstrate that this application, by combining specific drying process parameters (temperature, time, rate) with objective and quantifiable final quality criteria (the state of the billet to be inspected in the testing area), forms a complete process control and quality evaluation system. This makes the development and optimization of drying processes for products with different formulations and specifications more scientific and directional, significantly improving the adaptability of the production process and the stability of product quality between different batches.

[0032] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment, characterized in that, Includes the following steps: S1. Obtain a cemented carbide extrusion billet, the cemented carbide extrusion billet including an inspection-free billet and an inspection-to-be-inspected billet; dry the cemented carbide extrusion billet, wherein the inspection-to-be-inspected billet is placed in the inspection area of ​​the drying equipment, the inspection area is determined based on the structure of the drying equipment, and the inspection area is the area with the worst heat flow and material diffusion conditions during the drying process; S2. After the cemented carbide extrusion billet has been dried, the billet to be inspected is taken out. S3. Perform a rapid heat treatment weight loss test on the blank to be inspected to obtain its average weight loss rate, and set the average weight loss rate of the blank to be inspected to be N. S4. Set the maximum value of the weight loss rate of the cemented carbide extrusion billet that meets the production requirements to be M. If N≤M, the drying quality of the cemented carbide extrusion billet is deemed to be qualified. If N>M, repeat steps S1-S4 on the cemented carbide extrusion billet until N≤M.

2. The method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment according to claim 1, characterized in that, In step S1, the inspection-exempt blank and the blank to be inspected are prepared by the same batch formula and the same molding process, and the number of blanks to be inspected is ≥1.

3. The method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment according to claim 1, characterized in that, Step S2 further includes performing an appearance inspection on the blank to be inspected. If macroscopic cracks are found, it is directly determined to be unqualified and the subsequent steps are terminated. If no macroscopic cracks are found, step S3 is performed. Step S4 further includes that after the drying quality of the cemented carbide extrusion blank is determined to be qualified, it is transferred to the sintering process to sinter and obtain cemented carbide products. The qualification rate of the cemented carbide products is ≥99%.

4. The method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment according to claim 1, characterized in that, In step S3, the rapid heat treatment weight loss test is specifically performed as follows: under nitrogen protection, the blank to be tested is heated from room temperature to 180-200℃ at a rate of 30-50℃ / min, held at that temperature for 3-5min, and then the nitrogen is measured after cooling.

5. The method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment according to claim 1, characterized in that, In step S4, M is related to the bursting defect rate of the cemented carbide extruded billet in the standard dewaxing sintering process, wherein M = 0.05%.

6. The method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment according to claim 1, characterized in that, In step S1, the drying method is heating with a heat transfer medium bath, and the drying equipment is a vacuum drying oven.

7. The method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment according to claim 6, characterized in that, The heating method of the heat medium bath is specifically as follows: In a vacuum environment, the cemented carbide extrusion billet is heated by a heat transfer medium bath and subjected to the following multi-stage heating and holding process: First stage: Increase the temperature from room temperature to 30-40℃ at a rate of 0.2-0.5℃ / min, and hold at that temperature for 300-500min; Second stage: Increase the temperature to 50-60℃ at a rate of 0.2-0.5℃ / min and hold for 300-500min; The third stage: Increase the temperature to 90-110℃ at a rate of 0.5℃-0.8℃ / min and hold for 500-700min; Fourth stage: Increase the temperature to 130-150℃ at a rate of 1-2℃ / min and hold for 800-1200min; After the program is completed, heating is stopped and the furnace is allowed to cool. The absolute pressure of the vacuum environment is maintained at 50-150 Pa.

8. A method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment according to claim 6, characterized in that, The heat transfer medium bath heating is an oil bath heating.

9. A method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment according to claim 6, characterized in that, The detection area is located in the space inside the vacuum drying oven, with a height of 100-400mm and a horizontal distance of 100-400mm from the vacuum pipe interface.

10. A method for improving the drying quality of cemented carbide extruded billets based on drying quality assessment according to claim 7, characterized in that, The furnace cooling includes: natural cooling under vacuum to below 25°C.