A multi-directional atmosphere sintering furnace and a multi-directional atmosphere control process

Abstract

The application discloses a multi-directional atmosphere sintering furnace and a multi-directional atmosphere control process, and relates to the technical field of sintering furnaces and sintering processes. The atmosphere sintering furnace comprises a material box, and the front part, rear part, middle part, left part and right part of the material box are respectively provided with atmosphere control mechanisms. The atmosphere control mechanisms comprise air inlet mechanisms and air outlet mechanisms. Air can flow into the material box through the air inlet mechanisms and flow out of the material box through the air outlet mechanisms, so that the flow of air in and out of the material box is formed. The process comprises the following steps. Step one: air is filled into the material box through the atmosphere control mechanisms in at least one direction of the material box as air inlet mechanisms. Step two: air in the material box is discharged through at least one atmosphere control mechanism in other directions of the material box except the atmosphere control mechanisms in step one as air outlet mechanisms. According to the multi-directional atmosphere sintering furnace and the multi-directional atmosphere control process, air can be introduced and discharged in multiple directions of the material box, so that the problems of air flow dead angles and too long air flow distances are avoided.

Description

Technical Field

[0001] This invention relates to the field of sintering furnaces and sintering process technology, and in particular to a multi-directional atmosphere sintering furnace and a multi-directional atmosphere control process. Background Technology

[0002] MIM (Metal Injection Molding) and other powder metallurgy products are used in various fields, such as consumer electronics, medical devices, automotive parts, smart wearables, hardware tools, fiber optic communications, and military supplies, where high requirements are placed on product size and performance. The basic process of MIM and other powder metallurgy is: metal powder + binder → mixing → injection molding → debinding → sintering → (post-processing) → inspection. Each step is crucial to the product's size and performance, and each step also presents challenges. For example, the yield rate of a full-furnace sintering furnace is relatively low, especially for difficult-to-sinter products. Differences in size and performance exist between products sintered from the same furnace, and the product yield needs further improvement. Factors affecting product size and performance include temperature uniformity and atmosphere control, leading to deviations in product dimensions across the top, bottom, left, right, front, middle, and back of the material bin. Atmosphere control, achieved through interlocking sensors and actuators, maintains the required environment within the furnace, including pressure and gas flow, to influence the product's performance. Atmosphere control affects the physical state and chemical reactions of the product preform at high temperatures, volume changes, grain size, pore size, and surface color and quality, ultimately determining the final product's microstructure, mechanical properties, and dimensional control. Atmosphere control is a complex process; selecting appropriate atmosphere control for different materials can achieve optimal product dimensions and performance.

[0003] Current metal injection molding vacuum debinding and sintering furnaces often employ various airflow patterns, such as front and rear air inlets and middle outlets, front air inlet and rear outlet, top air inlet and bottom outlet, left air inlet and right outlet, etc. This unidirectional airflow, with air entering at the inlet and exiting at the outlet during debinding and sintering, creates a specific airflow direction. This directional flow leads to differences in the size and performance of the product in the preceding and following areas. There are three main reasons for this: 1. The influence of gas composition. When the airflow passes over the product, it reacts with the product, affecting it. The impact of the airflow decreasing as it passes through the product, resulting in differences between the preceding and following areas. 2. The influence of volatiles in the product. For example, during the initial debinding process, binders in the product evaporate during heating and enter the outlet with the airflow direction. This causes volatiles from the preceding product to adhere to the surface of the following product, creating differences between the preceding and following areas. 3. The influence of gas flow rate, velocity, and flow state. The gas flow rate and velocity of the product near the inlet are greater than those of the product near the outlet, and the difference becomes more pronounced with increasing distance.

[0004] In their patent application No. 2020800093.9, the inventors employed a bidirectional atmosphere control process where the air inlet and outlet are interchangeable. The airflow paths are the same, but the directions are opposite. Differences in product dimensional performance in certain areas along the flow direction during forward atmosphere control are compensated for by reverse atmosphere control. However, this method has certain limitations: First, there are dead zones in the airflow. During the initial degreasing process, the binder evaporates from the product. Because the side airflow is smaller, more binder remains on the sides. Furthermore, the sintering process further reduces the scouring effect on the side plates, resulting in a higher carbon potential on the sides compared to the center. Second, the airflow path is too long, leading to uneven airflow across the subsequent product. For the bidirectional atmosphere control process, the carbon potential in the center is higher. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-directional atmosphere sintering furnace and a multi-directional atmosphere control process to solve the problems existing in the prior art. The material box can be filled and discharged from multiple directions, thereby avoiding the problems of dead air flow and excessively long air flow path.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] The present invention provides a multi-directional atmosphere sintering furnace, including a material box located inside the sintering furnace. Atmosphere control mechanisms are respectively provided at the front, rear, middle, left and right parts of the material box. The atmosphere control mechanism includes an air inlet mechanism and an air outlet mechanism. Gas can flow into the material box through the air inlet mechanism and flow out of the material box through the air outlet mechanism, thereby forming a gas flow inside and outside the material box.

[0008] Optionally, the air intake mechanism includes an air intake pipe, one end of which is connected to the material box inside the sintering furnace, and the other end is located outside the sintering furnace; the air outlet mechanism includes an air outlet pipe, one end of which is connected to the material box inside the sintering furnace, and the other end is located outside the sintering furnace.

[0009] Optionally, the air intake mechanism includes an air intake pipe, one end of which is connected to the material box inside the sintering furnace, and the other end is located outside the sintering furnace; the air outlet mechanism includes an air outlet pipe, which is a branch pipe of the air intake pipe or an independent air outlet pipe.

[0010] Optionally, the air intake mechanism includes an air intake pipe, one end of which is connected to the material box inside the sintering furnace, and the other end is located outside the sintering furnace; the air outlet mechanism includes an air outlet pipe, which is an independent air outlet pipe; the air intake mechanism and the air outlet mechanism can also exist independently, and neither the air outlet pipe nor the air intake pipe has a branch pipe.

[0011] Optionally, the air intake mechanism includes an air intake pipe, one end of which is connected to the material box inside the sintering furnace, and the other end is located outside the sintering furnace; the air outlet mechanism includes an air outlet pipe, one end of which is connected to the material box inside the sintering furnace, and the other end is located outside the sintering furnace; the multiple air intake pipes and air outlet pipes located at the same end of the material box are all independent pipelines and are arranged sequentially at intervals.

[0012] Optionally, the air intake mechanism includes an air intake valve fixedly installed on the material box, and the air outlet mechanism includes an air outlet pipe, one end of which is connected to the material box located inside the sintering furnace, and the other end is located outside the sintering furnace.

[0013] Optionally, the air outlet mechanism includes an air outlet valve fixedly installed on the material box, and the air inlet mechanism includes an air inlet pipe, one end of which is connected to the material box located inside the sintering furnace, and the other end is located outside the sintering furnace.

[0014] Optionally, the air intake mechanism includes a safety valve, a splicing gap on the material box, or a door panel gap on the material box, wherein the safety valve is fixed on the material box; the air outlet mechanism includes an air outlet pipe, one end of which is connected to the material box located inside the sintering furnace, and the other end is located outside the sintering furnace.

[0015] Optionally, the air outlet mechanism includes a safety valve, a splicing gap on the material box, or a door panel gap on the material box, wherein the safety valve is fixed on the material box; the air inlet mechanism includes an air inlet pipe, one end of which is connected to the material box located inside the sintering furnace, and the other end is located outside the sintering furnace.

[0016] The present invention also provides a multi-directional atmosphere control process, including a pre-process, a sintering process, and a post-process, wherein the sintering process includes the following steps:

[0017] Step 1: Gas is introduced into the material box through an atmosphere control mechanism in at least one direction as an air intake mechanism.

[0018] Step two: The gas in the material box is discharged by at least one atmosphere control mechanism in other directions besides step one.

[0019] Optionally, in step one, the time, temperature, pressure, and gas flow rate during the inflation process can be set as needed.

[0020] The present invention achieves the following technical effects compared to the prior art:

[0021] One type of airflow control can be selected, or multiple airflows can be used in combination. The process settings such as time, temperature, pressure, and airflow are also quite flexible. The airflow path is shortened, the airflow through the product is uniform, and there are no dead zones in the airflow, which makes the airflow more stable and can more efficiently balance the carbon content of the whole furnace product. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1a This is a top view of the bin structure in one embodiment of the present invention;

[0024] Figure 1b For the present invention Figure 1a AA cross-section view;

[0025] Figure 1c For the present invention Figure 1a BB cross-section;

[0026] Figure 1d For the present invention Figure 1a A schematic diagram of one of the material plates;

[0027] Figure 2 This is a schematic diagram of the gas flow state in the atmosphere control method of the present invention;

[0028] Figure 3 This is a schematic diagram of the gas flow state of the atmosphere control system of the present invention.

[0029] Figure 4 This is a schematic diagram of the gas flow state of the atmosphere control system of the present invention (XIV).

[0030] Figure 5 This is a schematic diagram of the gas flow state of the atmosphere control system thirteen of the present invention;

[0031] Figure 6 This is a schematic diagram of the gas flow state of the atmosphere control system of the present invention (Sixteenth).

[0032] Figure 7 This is a schematic diagram of the gas flow state of the atmosphere control system 17 of the present invention;

[0033] Figure 8 This is a schematic diagram of the gas flow state of the atmosphere control system of the present invention.

[0034] Figure 9 This is a schematic diagram of the gas flow state of the atmosphere control system of the present invention.

[0035] Figure 10 This is a schematic diagram of the gas flow state of the atmosphere control system of the present invention.

[0036] Figure 11This is a schematic diagram of the gas flow state of the atmosphere control system of the present invention.

[0037] Figure 12 This is a schematic diagram of the gas flow state of the atmosphere control system of the present invention.

[0038] Figure 13 A schematic diagram showing the process combination of Atmosphere Control 1 and Atmosphere Control 4;

[0039] Figure 14 A schematic diagram showing the process combination for Atmosphere Control 16 and Atmosphere Control 17;

[0040] Figure 15a Schematic diagram of the settings for Atmosphere Control 1, Atmosphere Control 2 and Atmosphere Control 3 when the temperature and pressure remain constant;

[0041] Figure 15b A schematic diagram showing the settings for different flow rates and temperatures in Atmosphere Control 1, Atmosphere Control 2, and Atmosphere Control 3.

[0042] Figure 15c A schematic diagram showing the settings for different times and pressures in Atmosphere Control 1, Atmosphere Control 2, and Atmosphere Control 3.

[0043] Among them, 1 is the material box, 2 is the material plate, 3 is the air inlet mechanism, 301 is the air inlet pipe, 4 is the air outlet mechanism, 401 is the air outlet pipe, and 5 is the control valve. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] The purpose of this invention is to provide a multi-directional atmosphere sintering furnace and a multi-directional atmosphere control process to solve the problems existing in the prior art. The material box can be filled and discharged from multiple directions, thereby avoiding the problems of dead air flow and excessively long air flow path.

[0046] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] This invention provides a multi-directional atmosphere sintering furnace, such as Figure 1a , Figure 1b , Figure 1c and Figure 1dAs shown, the furnace includes a material box 1 located inside the sintering furnace. Multiple material plates 2 are evenly arranged inside the material box 1. Atmosphere control mechanisms are respectively provided at the front, rear, middle, left and right sides of the material box 1. The atmosphere control mechanism includes an unlimited number of air inlet mechanisms 3 and air outlet mechanisms 4. Gas can flow into the material box 1 through the air inlet mechanism 3 and flow out of the material box 1 through the air outlet mechanism 4, thereby forming the flow of gas inside and outside the material box 1.

[0048] The air intake mechanism 3 and air outlet mechanism 4 in this invention can be flexibly configured without specific limitations. In one embodiment, the air intake mechanism 3 includes an air intake pipe 301, one end of which is connected to the material box 1 inside the sintering furnace, and the other end is located outside the sintering furnace. The air outlet mechanism 4 includes an air outlet pipe 401, which is a branch pipe of the air intake pipe 301. Both the branch pipe and the air intake pipe 301 are equipped with control valves 5, which can be flexibly controlled to open and close. The air intake mechanism 3 and the air outlet mechanism 4 can also exist independently, without branch pipes on the air outlet pipe 401 and the air intake pipe 301.

[0049] In different embodiments, multiple air inlet pipes and air outlet pipes located at the same end of the material box are independent pipelines and are arranged sequentially at intervals; or, the air inlet mechanism includes an air inlet valve fixedly installed on the material box, and the air outlet mechanism includes an air outlet pipe, one end of which is connected to the material box located inside the sintering furnace, and the other end is located outside the sintering furnace. Alternatively, the air outlet mechanism includes an air outlet valve fixedly installed on the material box, and the air inlet mechanism includes an air inlet pipe, one end of which is connected to the material box located inside the sintering furnace, and the other end is located outside the sintering furnace.

[0050] More preferably, the air intake mechanism includes a safety valve, a splicing gap on the material box 1, or a door panel gap on the material box, with the safety valve fixed to the material box 1; the air outlet mechanism includes an air outlet pipe, one end of which is connected to the material box 1 located inside the sintering furnace, and the other end located outside the sintering furnace; or, the air outlet mechanism includes a safety valve, a splicing gap on the material box, or a door panel gap on the material box 1, with the safety valve fixed to the material box 1; the air intake mechanism includes an air intake pipe, one end of which is connected to the material box 1 located inside the sintering furnace, and the other end located outside the sintering furnace.

[0051] The present invention also provides a multi-directional atmosphere control process, including a pre-process, a sintering process, and a post-process, wherein the sintering process includes the following steps:

[0052] Step 1: Gas is introduced into the material box 1 through the atmosphere control mechanism in at least one direction as the air inlet mechanism 3. During the inflation process, the time, temperature, pressure and gas flow rate can be set as needed. The mass flow meter controls the gas flow rate to be introduced into the material box 1, and then the flow is distributed to each layer of material plate or to different heights in the material box by the flow distribution device; or the mass flow meter controls the gas flow rate to be directly introduced into the middle of the material box from the bottom.

[0053] Step 2: Gas in the material box 1 is discharged as an exhaust mechanism 4 through at least one atmosphere control mechanism in other directions besides Step 1.

[0054] This invention enables the addition of multiple processes during the operation of the sintering furnace, including multi-directional atmosphere control and arbitrary combinations of inlet and outlet gas ports, such as... Figure 13 He Ru Figure 14 As shown. The air inlets and outlets can be arbitrarily combined according to the specific conditions of the product being sintered, or some air inlets and outlets can be closed and not used (the most suitable combination needs to be explored in actual experiments). Multiple process combinations solve the problem of dead airflow zones, with the main advantages being: reduced adhesive adhesion to the product surface during the degreasing stage; more thorough scouring of every corner by airflow during the sintering stage; and flexible compensation (pressure, airflow, time) for specific areas. Examples of various atmosphere control combinations of this invention are illustrated below: the main combinations include one inlet and one outlet, two inlets and one outlet, one inlet and two outlets, three inlets and one outlet, one inlet and three outlets, and two inlets and two outlets.

[0055] The inlet-outlet atmosphere control includes: Atmosphere control one, air intake at the front of the material plate and air exhaust at the rear of the material plate, such as... Figure 2 The diagram shows gas flow patterns, with arrows indicating the direction of gas flow. Atmosphere control two: rear intake, front exhaust; Atmosphere control three: left intake, right exhaust; Atmosphere control four: right intake, left exhaust, as shown. Figure 3 As shown in the figure, the arrows indicate the direction of gas flow.

[0056] The two-in-one-out atmosphere control includes: Atmosphere control five, left and right air intake, front air exhaust; Atmosphere control six, left and right air intake, rear air exhaust, such as... Figure 12 As shown in the diagram, the arrows indicate the direction of gas flow; atmosphere control seven has front and rear air intakes and left-side air exhaust, as shown... Figure 11 As shown in the diagram, the arrows indicate the direction of gas flow; Atmosphere control eight has front and rear air intakes and right-side air exhaust.

[0057] The three-in-one-out atmosphere control includes: atmosphere control nine, front and left / right air intake, and rear air exhaust, such as... Figure 9 The arrows in the diagram indicate the direction of gas flow; the atmosphere control system has rear and left / right air intakes and front air exhaust. Figure 8 The arrows in the diagram indicate the direction of gas flow; Atmosphere control eleven: air intake at the front, rear, and left, air exhaust at the right; Atmosphere control twelve: air intake at the front, rear, and right, air exhaust at the left, as shown. Figure 10 The arrows in the diagram indicate the direction of gas flow.

[0058] The two-in, two-out atmosphere control includes: atmosphere control thirteen, left and right air intakes, and front and rear air exhausts, such as... Figure 5The arrows in the diagram indicate the direction of gas flow; Atmosphere control fourteen has air intakes at the front and rear, and exhausts to the left and right, as shown. Figure 4 The arrows in the diagram indicate the direction of gas flow; Atmosphere control 15: air intake at the rear and left, air exhaust at the front and right; Atmosphere control 16: air intake at the rear and right, air exhaust at the front and left, as shown. Figure 6 The arrows in the diagram indicate the direction of gas flow; Atmosphere control system 17 has air intake at the front and left, and air exhaust at the rear and right, as shown. Figure 7 The arrows in the diagram indicate the direction of gas flow. Atmosphere control 18 involves air intake at the front and right sides, and exhaust at the rear and left sides. The one-in-three-out path here is similar to the three-in-one-out path, and the one-in-two-out path is similar to the two-in-one-out path.

[0059] Multi-directional atmosphere control can be achieved throughout the entire furnace operation process. For example, in degreasing and sintering processes, multiple atmosphere control techniques can be combined for a single process. A single atmosphere control technique can select one airflow control method or use a combination of multiple airflows. The process is quite flexible and can be adjusted according to the specific requirements of the product materials. For example, if the product has high requirements for size and performance and is sensitive to atmosphere, it can be used in the degreasing process. Figure 9 The process, used in the sintering process Figure 11 and Figure 12 Process configuration (examples provided). Furthermore, the process settings, such as time, temperature, pressure, and gas flow rate, are quite flexible. For example... Figure 15a In the diagram, temperature and pressure remain constant. T represents temperature, P represents pressure, L represents flow rate, and M represents time. m1, m2, and m3 represent the times for atmosphere control one, atmosphere control two, and atmosphere control three, respectively. t1, t2, and t3 represent the holding temperatures for atmosphere control one, atmosphere control two, and atmosphere control three, respectively. p1, p2, and p3 represent the furnace equilibrium pressures for atmosphere control one, atmosphere control two, and atmosphere control three, respectively. L1, L2, and L3 represent the inlet flow rates for atmosphere control one, atmosphere control two, and atmosphere control three, respectively. The temperature and pressure settings in atmosphere control one, atmosphere control two, and atmosphere control three are all the same. If the sintering process reaches a certain temperature and enters the holding state, atmosphere control one is maintained for 2 hours, atmosphere control two for 2 hours, and atmosphere control three for 2 hours, with the pressure remaining the same. This ensures uniform atmospheric conditions for the products within the furnace, maximizing the uniformity of degreasing in the preceding degreasing stage, which helps to achieve uniform sintering dimensions and performance in the subsequent sintering process. If the product dimensions differ significantly, adjustments can be made by setting the flow rate, temperature, or flow rate and time, etc. Figure 15b Different atmosphere control systems (Atmosphere Control 1, Atmosphere Control 2, and Atmosphere Control 3) have different set flow rates and temperatures, and the areas with severe carbon potential distribution are compensated for by increasing or decreasing the temperature and flow rate. For example... Figure 13By altering the flow rate (or flow rate and temperature) of atmosphere control three to differ from that of atmosphere control one, the flow rate (or flow rate and temperature) of the gas passing through areas with severe carbon potential distribution on the side plates is changed, thus more efficiently balancing the carbon content of the entire furnace product. Of course, there are many other methods, such as... Figure 15c Due to variations in time and pressure, the pressure and time of each atmosphere control process (the number of processes is unlimited) differ. Pressure is related to product density and size, and this method can also be used to adjust for differences in density and size between the preceding and following regions. If a certain area of ​​the product in the entire furnace has a larger size, an additional atmosphere process can be added, adjusting the air intake near the larger area. Because the airflow at the intake is relatively large, it has a greater scouring effect on the product. Increasing the atmosphere pressure or lengthening the process time can balance the product size between the preceding and following regions. This process was developed through practical experiments, and this multi-atmosphere control will provide more processes for researching powder metallurgy products.

[0060] In the description of this invention, it should be noted that the terms "center," "top," "bottom," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0061] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A multi-directional atmosphere sintering furnace, comprising a material bin located inside the sintering furnace, characterized in that: Atmosphere control mechanisms are respectively provided at the front, rear, middle, left, and right sides of the material box. Each atmosphere control mechanism includes an inlet mechanism and an outlet mechanism. Gas can flow into the material box through the inlet mechanism and out through the outlet mechanism, thus creating gas flow inside and outside the material box. The inlet mechanism includes an inlet pipe and an inlet valve or safety valve fixedly installed on the material box. One end of the inlet pipe is connected to the material box inside the sintering furnace, and the other end is located outside the sintering furnace. The outlet mechanism includes an outlet pipe and an outlet valve or safety valve fixedly installed on the material box. One end of the outlet pipe is connected to the material box inside the sintering furnace, and the other end is located outside the sintering furnace. Multiple inlet and outlet pipes located at the same end of the material box are independent pipelines and are arranged sequentially at intervals. The material box can inlet and outlet gas from multiple directions. It is possible to select one type of airflow control or use a combination of multiple airflows. The multi-directional atmosphere control process based on the multi-directional atmosphere sintering furnace includes the following steps: Step 1: Gas is introduced into the material box through an atmosphere control mechanism in at least one direction as an air intake mechanism. Step two: The gas in the material box is discharged by at least one atmosphere control mechanism in other directions besides step one.

2. The multi-directional atmosphere sintering furnace according to claim 1, characterized in that: The air intake mechanism includes a safety valve, a splicing gap on the material box, or a door panel gap on the material box, and the safety valve is fixed on the material box; the air outlet mechanism includes an air outlet pipe, one end of which is connected to the material box located inside the sintering furnace, and the other end is located outside the sintering furnace.

3. The multi-directional atmosphere sintering furnace according to claim 1, characterized in that: The air outlet mechanism includes a safety valve, a splicing gap on the material box, or a door panel gap on the material box, with the safety valve fixed to the material box; the air inlet mechanism includes an air inlet pipe, one end of which is connected to the material box located inside the sintering furnace, and the other end is located outside the sintering furnace.

4. The multi-directional atmosphere sintering furnace according to claim 1, characterized in that: In step one, the time, temperature, pressure, and gas flow rate during the inflation process can be set as needed.

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