WO2018126502A1

WO2018126502A1 - Shell mold sintering device and method

Info

Publication number: WO2018126502A1
Application number: PCT/CN2017/072411
Authority: WO
Inventors: 蔡欲期; 蔡政达; 蔡耀明
Original assignee: 蔡欲期
Priority date: 2017-01-03
Filing date: 2017-01-24
Publication date: 2018-07-12
Also published as: TW201825209A; CN106734883B; CN106734883A

Abstract

A shell mold sintering device and method are provided, belonging to the technical field of precision casting. The shell mold sintering device comprises a sintering cavity (1). A shell mold holding platform (2) is disposed in the sintering cavity (1). The shell mold sintering device is an electric furnace. An upper surface of the shell mold holding platform (2) is provided with multiple grooves (21). The grooves (21) extend in a lengthwise direction of the sintering cavity (1). A first air intake tube (6) used to supply air is disposed in the sintering cavity (1). The first air intake tube (6) is connected to a blower and is provided with a first nozzle (61) facing the grooves (21). A second nozzle (71) used to supply a combustible gas or liquid is further disposed in the sintering cavity (1). A flue gas outlet (4) is positioned higher than the shell mold holding platform (2). The device of the invention can greatly shorten a wax melting period and enable the environment in the sintering furnace to change from high to low oxygen, or to be oxygen-free, as soon as possible after wax melting is completed, and carbon powder added into a shell mold is not burned up, ensuring shell mold quality and thus improving casting quality.

Description

Shell mold sintering device and method

Technical field

The present invention relates to a precision casting process, and more particularly to a shell mold sintering apparatus and method.

Background technique

Precision casting is a casting method relative to conventional casting processes that achieves relatively accurate shape and high casting accuracy. The process of precision casting is: first, a wax mold is produced, which is consistent with the size and shape of the product to be cast; then, a ceramic shell is formed on the surface of the prepared wax mold; and then, the ceramic shell is dewaxed. Treatment (after melting the wax mold inside thereof); after that, the ceramic shell is sintered at a high temperature; finally, the metal material is cast into the sintered ceramic shell, and after the metal material is cooled and solidified, the ceramic shell is crushed and removed to obtain The casting is the desired product.

In the above process, the production of ceramic shell is very important, and its quality determines the pros and cons of the casting. At present, the commonly used method for making ceramic shells is: shell moulding method, in particular, water-soluble silica sol shelling method is often used. In the method of making ceramic shell, refractory material is used to prepare different slurry and sand, one layer of pulp A layer of sand is gradually layered on the surface of the wax mold to form a ceramic shell of the required thickness. Then, the obtained ceramic shell is dried, dewaxed, and placed in a sintering furnace at a high temperature sintering at 900 to 1400 °C. Since sintering is an indispensable step in the fabrication of shell molds, the quality of the shell directly affects the quality of the shell mold and the quality of the final casting.

The inventor's prior application CN 105903898 A discloses a shell mold sintering method and a sintering apparatus using the same, which adopts a segmented heating method to divide the shell mold sintering process into a wax burning stage and a sintering stage, and the wax burning stage ensures sintering. There is sufficient oxygen and wax in the environment for full combustion reaction, so that there is almost no residual carbon formed in the shell mold due to the carbonization of the residual wax, which avoids the problem of molten steel splashing during casting and the penetration of the casting. The problem of stomata. At the same time, the oxygen concentration in the sintering environment is reduced as much as possible in the sintering stage, and the carbon powder in the shell mold is completely burned out in the sintering stage, so that the mold wall reaction phenomenon occurs when the shell mold is poured into the molten steel.

The inventor found in the course of further research that the prior application still exists to some extent. In the following questions:

1. In the wax burning stage (requiring high oxygen low temperature), it maintains sufficient oxygen content (ie high oxygen) in the sintering furnace, and the furnace temperature is 600 ° C ~ 800 ° C (low temperature relative to the sintering temperature), maintaining The time is 5-20 min. Under this condition, due to sufficient oxygen content, high furnace temperature and long maintenance time, the carbon powder added in the shell mold may still be partially consumed by combustion, thereby weakening the toner. The mold wall reaction will still occur to some extent to the protection of the shell mold;

2. In the sintering stage (requiring low oxygen and high temperature), it is to control the low-oxygen or oxygen-free environment in the sintering furnace by closing the air blowing device and the exhaust flue, but at the end of the wax burning stage, due to the sintering furnace The oxygen content inside is still at a high level, and these residual oxygen will continue to consume the carbon powder added in the shell mold during the sintering stage, further weakening the protective effect of the carbon powder on the shell mold and increasing the probability of occurrence of the mold wall reaction. .

In addition, in the continuous production of the shell mold, after the first shell mold is taken out from the sintering furnace, the temperature in the furnace is about 900 ° C. When the second shell mold is placed, the temperature in the furnace is still high. When the second shell mold is waxed, once the temperature of the shell mold increases, in the high oxygen environment, the carbon powder added in the shell mold may start to be burned successively, so it is necessary to shorten the wax burning stage. Time (shortening the time of high oxygen), and as far as possible, the high-oxygen to low-oxygen or oxygen-free environment in the sintering furnace after the end of the wax-burning stage is used to reduce the consumption of the carbon powder added in the shell mold.

Summary of the invention

The technical problem to be solved by the present invention is to provide a shell mold sintering apparatus and method which can greatly shorten the time of the wax burning stage and make the high-oxygen to low-oxygen or anaerobic in the sintering furnace as soon as possible after the end of the wax-burning stage. Environment, reducing the consumption of toner added to the shell mold.

In order to solve the above technical problem, the present invention provides the following technical solutions:

In one aspect, a shell mold sintering apparatus is provided, including a sintered inner chamber in which a shell mold placement platform and a heating device are disposed, one end of the sintered inner chamber is provided with a closed door, and the sintered inner chamber is The other end is provided with a flue gas outlet, and the flue gas outlet is connected with an exhaust flue, wherein:

The shell mold sintering device is an electric heating furnace, and the upper surface of the shell mold placing platform is provided with a plurality of rows of grooves, the grooves extending along the length direction of the sintering inner cavity, and the width of the groove is smaller than The diameter of the gate cup of the sintered shell mold;

The sintered inner cavity is provided with an inner side of one end of the flue gas outlet at a position corresponding to the shell mold placement platform, and a first intake pipe for supplying air, and the first intake pipe is connected with a blower device. a first nozzle having a direction toward the groove is disposed on the first intake pipe;

a second nozzle for providing a flammable gas or liquid is further disposed in the sintering inner cavity;

The height of the flue gas outlet is higher than the height of the shell mold placement platform.

Further, the sintering inner cavity is provided with one end inner side of the flue gas outlet at a position corresponding to the shell mold placing platform, and a second air inlet pipe for supplying a flammable gas or liquid, the second nozzle Located on the second intake pipe and oriented toward the groove.

Further, a plurality of windshields are uniformly disposed in a middle portion of at least one sidewall of the groove, and lengths of the windshields are sequentially lengthened from the inside to the outside along the sintering cavity.

Further, the end of the wind deflector is an arc-shaped air guiding portion.

Further, the windshield portion is inclined rearward along the direction from the inside to the outside of the sintering inner cavity, and the angle of inclination is 1-10.

Further, the sintering inner cavity is provided with an inner side of one end of the closing door at a position corresponding to the shell mold placing platform, and a falling sand collecting groove is arranged along the width direction of the sintering inner cavity. extend.

Further, a secondary combustion furnace is disposed between the flue gas outlet and the exhaust flue, and the secondary combustion furnace is provided with a third nozzle for supplying air and a fourth for providing a flammable gas or liquid. a nozzle, the flue gas outlet being a contraction structure toward the secondary combustion furnace.

Further, the temperature in the secondary combustion furnace is 1200 ° C or higher, and the oxygen content of the secondary combustion furnace is 25% or more.

Further, a ceramic sponge filter is disposed in the secondary combustion furnace at a connection with the exhaust flue.

Further, the first intake pipe is connected with a metal preheating pipeline, and the metal preheating pipeline is disposed in the secondary combustion furnace.

Further, a temperature sensing module and an oxygen concentration monitoring module are disposed in the sintering inner cavity.

On the other hand, there is provided a method for performing shell mold sintering using the above-described shell mold sintering apparatus, include:

Step 1: placing the shell mold to be sintered under the shell mold placement platform in the sintered inner cavity, and closing the closed door;

Step 2: Turn on the heating device, the air blowing device and the exhaust flue, so that there is sufficient oxygen content in the sintering cavity, the temperature is raised to the burning temperature of the shell mold wax, and the temperature in the sintered inner cavity is maintained until the residual in the shell mold The wax is completely burned out;

Step 3: The nozzle is opened to make the sintered inner cavity a low-oxygen or oxygen-free environment, and the temperature is raised to the sintering temperature of the shell mold and the temperature in the sintered inner cavity is maintained as the sintering temperature of the shell mold until the shell mold is sintered.

Further, in the step 2, when it is detected that the oxygen content in the sintering inner cavity does not decrease within a certain time, the process proceeds to step 3.

Further, in the step 2, the heating device, the air blowing device and the air exhausting device are turned on, so that the oxygen content of the sintering inner cavity is 16 to 20%; in the step 3, the nozzle is opened to make the sintering inner The oxygen content of the chamber is below 5%.

Further, in the step 2, the combustion temperature of the shell mold wax is 600 ° C to 800 ° C, and the maintenance time of the temperature in the sintering furnace is maintained within 3 min; in the step 3, the shell mold is The sintering temperature is 1150 to 1400 ° C, and the maintenance time for maintaining the temperature in the sintering furnace is 10 to 30 minutes.

The invention has the following beneficial effects:

The invention adjusts the direction of the groove on the shell mold placing platform, and reasonably arranges the position of the first nozzle for providing air, so that a circulating air flow can be formed in the sintering inner cavity, the heating efficiency is improved, and the position of the first nozzle is The design can drive the airflow inside the shell mold, and can bring enough oxygen to the wax burning during the wax burning stage, so that the wax can be burned more quickly, thereby greatly shortening the time of the wax burning stage; the invention is also in the sintering cavity A nozzle is arranged in the nozzle, and after the wax burning stage is finished, the nozzle can spray a flammable gas or a liquid, and consumes oxygen in the sintered inner cavity by combustion, thereby achieving the purpose of rapidly reducing the oxygen content in the sintered inner cavity, so that the burning After the wax stage is over, the sintering furnace changes from high oxygen to low oxygen or oxygen-free environment as soon as possible. Even in the continuous production of the shell mold, the present invention ensures that the carbon powder added in the shell mold is not consumed by combustion, ensuring the quality of the shell mold, thereby improving the quality of the casting. The invention can produce castings with high precision, The subsequent casting precision can be achieved without or with less finishing, which reduces the defective product and the scrap rate, improves the production efficiency, and greatly reduces the production cost.

DRAWINGS

1 is a schematic structural view of an embodiment of a shell mold sintering apparatus of the present invention;

2 is a schematic cross-sectional view of the shell mold placement platform A-A of FIG. 1;

3 is a top plan view showing a structure of a groove of the shell mold placement platform of FIG. 1;

4 is a top plan view showing another structure of a groove of the shell mold placement platform of FIG. 1;

Figure 5 is a front structural view of the side wall of the groove shown in Figure 3 with a wind deflector;

Figure 6 is a schematic view showing the structure of another embodiment of the shell mold sintering apparatus of the present invention;

Fig. 7 is a schematic flow chart showing a method of sintering a shell mold of the present invention.

detailed description

The technical problems, the technical solutions, and the advantages of the present invention will be more clearly described in the following description.

In one aspect, the present invention provides a shell mold sintering apparatus, as shown in FIGS. 1-5, including a sintered inner chamber 1 in which a shell mold placing platform 2 and a heating device (not shown) are disposed, and sintered One end of the chamber 1 is provided with a closing door 3, the other end of the sintering chamber 1 is provided with a flue gas outlet 4, and the flue gas outlet 4 is connected with an exhaust flue 5, wherein:

The shell mold sintering device is an electric heating furnace, and the upper surface of the shell mold placing platform 2 is provided with a plurality of rows of grooves 21 extending along the longitudinal direction of the sintering inner chamber 1 (ie, the left-right direction in FIG. 1). a width smaller than a diameter of the gate cup 8 of the shell mold to be sintered;

The sintered inner chamber 1 is provided with an inner side of one end of the flue gas outlet 4 at a position corresponding to the shell mold placing platform 2, and a first intake pipe 6 for supplying air is provided, and the first intake pipe 6 is connected with an air blowing device (not shown). a first nozzle 61 having a direction toward the groove 21 is disposed on the first intake pipe 6;

The sintering chamber 1 is also provided with a flammable gas or liquid (such as gas, alcohol, etc.). Second nozzle 71;

The height of the flue gas outlet 4 is higher than the height of the shell mold placement platform 2. Generally, the height difference may be 5-20 cm, and those skilled in the art may flexibly adjust according to actual conditions.

The inventors found in the research process that the sintering furnaces in the prior art are mainly divided into two types. The first one is an electric heating furnace, and the disadvantages are as follows: 1. Heating by the electric heating pipes arranged on three sides in the furnace, only heat radiation heating, The heat is not uniform and the efficiency is not good. 2. The electric furnace is mostly closed, no ventilation and no convection, the oxygen content is not enough, it is difficult to provide the high oxygen environment required for the wax burning stage; the second is the gas/oil burner, its disadvantages It is: 1. Although there is ventilation and convection, but it relies on gas/fuel to heat and consume most of the oxygen, so there are often defects in the oxygen content in the wax burning stage; 2. If the oxygen supply is increased, then The sintering stage is liable to cause the carbon powder added to the shell mold to be consumed by combustion.

The beneficial effects of the invention are:

1. On the basis of the existing electric furnace, and in combination with the inventor's prior application, the direction of the groove 21 on the shell mold placement platform 2 is adjusted, and the position of the first nozzle 61 for providing air is reasonably arranged. The circulating gas flow can be formed in the sintering inner cavity 1 to improve the heating efficiency, and the specific description is as follows:

An electric air blower is introduced on the electric furnace to stir the air in the furnace, which solves the disadvantage that the electric furnace only has heat radiation and has poor efficiency. The air in the furnace stirs the air, creating the most heat convection, heat conduction and heat radiation. Good heat transfer conditions, fully transfer the heat of the electric heating tube to the shell mold quickly, increase the heating efficiency, save energy, shorten the time required for sintering, and increase production efficiency;

The arrows in each figure indicate the direction of flow of the airflow. The direction of the circulating gas flow formed in the present invention is as shown in Fig. 1. According to the prior application of the present invention, the direction of the gas flow is more reasonable and the heating efficiency is higher.

Moreover, the groove 21 extends along the length of the sintering cavity 1, and this arrangement is advantageous for cleaning out the falling sand generated during the sintering process (both for artificial sand cleaning and for automatic sand cleaning by the inlet air flow).

2. In the present invention, the first intake pipe 6 for supplying air is provided with a first nozzle 61 oriented in the direction of the groove 21, and the shell mold to be sintered is placed on the shell mold placing platform 2 due to the inverted manner. It is located above the groove 21, so that the flow of the intake airflow of the first nozzle 61 will drive the airflow inside the shell mold, and the advantage is that: in the wax burning stage, sufficient oxygen can be brought to the wax combustion. The wax can be burned more quickly, and the internal and external temperature difference of the shell mold can be reduced in the sintering stage (the inner and outer temperature difference of the shell mold can be as low as 5 ° C in the present invention), thereby avoiding the shell during the sintering process due to the temperature difference between the inside and the outside. The difference in the amount of expansion inside and outside the mold may cause a problem of fine cracks on the shell mold, thereby avoiding the problem that the surface of the casting has an outwardly protruding burr or a convex water/concave water pattern;

3. The width of the groove 21 is smaller than the diameter of the gate cup 8 of the shell mold to be sintered, so that the shell mold can be smoothly placed on the shell mold placing platform 2 without slipping/falling in the groove 21, so that Adhere to the falling sand falling during the sintering process to ensure that the casting does not produce sand holes;

4. The sintering inner chamber 1 is provided with a second nozzle 71 for supplying a flammable gas or liquid. After the wax burning phase is finished, the second nozzle 71 can eject a flammable gas or liquid, and consumes the sintered inner cavity by combustion. In the oxygen, the purpose of rapidly reducing the oxygen content in the sintered cavity 1 is achieved.

In summary, the present invention adjusts the direction of the groove on the shell mold placement platform, and rationally arranges the position of the first nozzle for providing air, so that a circulating air flow can be formed in the sintered inner cavity, the heating efficiency is improved, and the first The position of the nozzle can be designed to form a gas flow inside the shell mold, which can bring enough oxygen to the wax burning during the wax burning stage, so that the wax can be burned more quickly, thereby greatly shortening the time of the wax burning stage; A nozzle is arranged in the sintering cavity, and after the wax burning phase is finished, the nozzle can spray a flammable gas or liquid, and consumes oxygen in the sintering cavity by combustion, thereby achieving the purpose of rapidly reducing the oxygen content in the sintering cavity. After the end of the wax burning stage, the sintering furnace is changed from high oxygen to low oxygen or oxygen-free environment as soon as possible. Even in the continuous production of the shell mold, the present invention ensures that the carbon powder added in the shell mold is not consumed by combustion, ensuring the quality of the shell mold, thereby improving the quality of the casting. The invention can produce castings with high precision enough, so that the required casting precision can be achieved without or with less finishing, the defective product and the scrap rate are reduced, the production efficiency is improved, and the production cost is greatly reduced.

As shown in FIG. 1 , preferably, the sintered inner chamber 1 is provided with an inner side of one end of the flue gas outlet 4 at a position corresponding to the shell mold placing platform 2, and a second intake pipe 7 for supplying a combustible gas or liquid is further provided. The two nozzles 71 are located on the second intake pipe 7 and face in the direction of the groove 21.

The positional design of the second nozzle 71 (direction toward the groove 21) enables the groove 21 to become a fire The road can make the oxygen outside the shell mold be quickly consumed, and the oxygen inside the shell mold can be quickly consumed, thereby further increasing the speed of oxygen removal. Moreover, if the residual carbon formed by carbonization of the wax which is not completely removed in the high temperature and low oxygen environment remains in the shell mold, the position design of the second nozzle 71 can also blow away the residual carbon, thereby improving the shell mold. quality.

In the present invention, the groove 21 on the shell mold placing platform 2 may have various shapes such as a U shape, a trapezoid shape, a triangle shape, etc., and the embodiment shown in FIG. 2 is a triangular groove. In this embodiment, in order to increase the falling sand. The capacity is increased, and a semicircular recess 24 is added to the bottom of the groove.

As shown in FIG. 2-3, the middle portion of at least one side wall of the recess 21 is preferably evenly disposed with a plurality of wind deflectors 22, and the length of each wind deflector 22 is lengthened along the direction from the inside to the outside of the sintered inner chamber 1. As can be seen in Fig. 3, the closer to the left side (the direction of the closed door 3 of the sintered inner chamber 1), the longer the length of the wind deflector. This has the advantage that when the intake air flow passes, the wind deflector can block a portion of the wind and lead it into the pouring cup of the upper shell mold, increasing the air flow in the shell mold. In order to improve the air intake effect, as shown in FIG. 3, the end of the wind deflector 22 may be an arc-shaped air guiding portion 221.

It should be noted that the wind deflector 22 is disposed at the middle of the side wall of the groove 21, and the lower end does not extend downward, so that the intake air flow can still flow under the entire groove, so that the falling sand falling during the sintering process can be blown out. To the side of the closed door. As shown in FIG. 2, the heights of the windshields may be the same, and only the lengths may be different. Alternatively, the wind deflector can be designed either on one side wall of the recess (as shown in Figure 3) or on both side walls of the recess (as shown in Figure 4). It can be understood that the specific parameters, such as the size and the number of the groove and the wind deflector, can be flexibly set according to actual needs, and will not be further described herein.

As shown in FIG. 5, preferably, the upper portion of the windshield 22 is inclined rearward from the inside to the outside of the sintering inner cavity 1, and the angle of inclination (that is, the angle between the wind deflector and the vertical direction) α may be 1- 10°. In this way, more wind will be drawn into the interior of the shell mold, further increasing the air flow within the shell mold.

In the present invention, the sintered inner chamber 1 is provided with an inner side of one end of the closing door 3 at a position corresponding to the shell mold placing platform 2, preferably provided with a falling sand collecting groove 9, which extends in the width direction of the sintering inner chamber 1, In order to collect the falling sand regularly. When the sintering device is stopped, the air can be blown through the first air inlet pipe and the first nozzle by means of the air blowing device, and the sand falling in the groove can be blown into the falling sand collecting groove to facilitate centralized cleaning.

As a further improvement of the present invention, as shown in FIG. 6, a secondary combustion furnace 10 is disposed between the flue gas outlet 4 and the exhaust flue 5, and a third nozzle 11 for supplying air is disposed in the secondary combustion furnace 10 and A fourth nozzle 12 for supplying a flammable gas or liquid, the flue gas outlet 4 being a contraction structure toward the secondary combustion furnace 10.

In the process of burning wax, black smoke is easily generated, which is caused by insufficient combustion and mixed with charcoal powder in the flue gas. The secondary combustion furnace can provide a high-temperature and oxygen-rich environment to burn and consume the carbon in the inclusion. Powder, avoiding black smoke, so that the last exhausted flue gas meets environmental protection requirements. The flue gas outlet is a shrinking structure facing the secondary combustion furnace, so that the backflow of the oxygen gas in the secondary combustion furnace to the sintered inner cavity can be effectively prevented from affecting the quality of the shell mold.

Preferably, the secondary combustion furnace 10 is in a high temperature and high oxygen environment, and preferably has an internal temperature of 1200 ° C or higher and an oxygen content of 25% or more. Further, a ceramic sponge filter 13 is disposed in the secondary combustion furnace 10 at the junction with the exhaust flue 5 to adsorb the char powder that has not been burned, since the ceramic sponge filter 13 is located in the secondary combustion furnace 10 However, the adsorbed char powder can be later burned into a gas discharge in the high-temperature and high-oxygen environment of the secondary combustion furnace 10.

In the present invention, since the first intake pipe 6 introduces outside air into the sintering inner cavity 1, in order to avoid the adverse effect of the outdoor air cooling, it is preferable that the first intake pipe 6 is connected with a metal preheating pipe (not shown). The metal preheating line may be a metal coil, and the metal preheating line may be disposed in the secondary combustion furnace 10 to make full use of the residual heat in the furnace. In addition, a temperature sensing module and an oxygen concentration monitoring module are preferably disposed in the sintering inner chamber 1 to monitor the condition in the furnace in real time and perform corresponding control in time.

In another aspect, the present invention also provides a method for performing shell mold sintering using the above-described shell mold sintering apparatus, as shown in FIG. 7, comprising:

Step S1: placing the shell mold to be sintered under the shell mold placement platform in the sintered inner cavity, and closing the closed door;

Step S2: Turn on the heating device, the air blowing device and the exhaust flue, so that there is sufficient oxygen content in the sintering inner cavity, the temperature is raised to the burning temperature of the shell mold wax, and the temperature in the sintering inner cavity is maintained until the residual in the shell mold The wax is completely burned out;

Since the carbon can be relatively fully burned at an oxygen content of 16.5%, it is preferred to pass here. Control the air blowing device and the exhaust flue so that the oxygen content of the sintering cavity is 16-20%; the burning temperature of the shell mold wax is preferably 600 ° C to 800 ° C, and the maintenance time of the sintering furnace is maintained within 3 min. can.

Step S3: The nozzle is turned on to make the sintered inner cavity a low-oxygen or oxygen-free environment, and the temperature is raised to the sintering temperature of the shell mold and the temperature in the sintered inner cavity is maintained as the sintering temperature of the shell mold until the shell mold is sintered.

In this step, after the nozzle is opened, the nozzle sprays a flammable gas or liquid, and consumes oxygen in the sintered inner cavity by combustion, thereby achieving the purpose of rapidly reducing the oxygen content in the sintered inner cavity, thereby realizing a low-oxygen or oxygen-free environment; The temperature of the sintering to the shell mold is achieved by the electric heating tube of the electric furnace itself. Compared with the prior application, the present invention does not close the air blowing device and the exhaust flue (only the opening and the size of the air blowing device and the exhaust flue are properly adjusted according to the high temperature and low oxygen environment required in the sintering stage), thereby A circulating gas flow is still formed in the sintered inner cavity, which can agitate the air in the furnace and maintain a high heating efficiency.

In this step, low oxygen means that the oxygen content of the sintered inner cavity is 5% or less. The sintering temperature of the shell mold may be 1150 to 1400 ° C, and the maintenance time of the temperature in the sintering furnace may be 10 to 30 min.

Since the circulating gas flow in the sintering inner cavity of the present invention forms a gas flow in the pouring cup, the present invention can completely burn the wax in a short time (within 3 minutes), and can make the sintered inner cavity in 1 minute. The oxygen content is reduced from 16-20% to less than 5%, and the shell mold can be sintered in a short period of time (10-30 min). For a typical shell mold, the prior art typically requires more than 45 minutes to complete the entire sintering process, and there are many drawbacks as mentioned in the prior application and the background of the present application; while the present invention can complete sintering in 20 minutes. And ensure the quality of the shell mold and improve the quality of the casting.

The inventor further discovered in the research process that since the sintering process is divided into a wax burning stage and a sintering stage, the wax burning stage maintains low temperature and high oxygen, and the sintering stage maintains high temperature and low oxygen. The accurate and rapid switching of the two stages can ensure the quality of the final shell mold. , so the timing of switching is very important. In this regard, the inventors have found that, in step 2, when it is detected that the oxygen content in the sintered inner cavity does not decrease within a certain period of time (for example, within 3-5 s), it is indicated that the residual wax in the shell mold has burned. After completion, the oxygen in the sintered inner cavity is no longer consumed, and the process proceeds to step 3 to start the sintering phase. The switching is accurate and there is no misjudgment.

The above is a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It should be considered as the scope of protection of the present invention.

Claims

A shell mold sintering device comprises a sintering inner cavity, a shell mold placing platform and a heating device are arranged in the sintering inner cavity, one end of the sintering inner cavity is provided with a closing door, and the other end of the sintering inner cavity is provided with a flue gas outlet connected to the exhaust flue, characterized in that

The shell mold sintering device is an electric heating furnace, and the upper surface of the shell mold placing platform is provided with a plurality of rows of grooves, the grooves extending along the length direction of the sintering inner cavity, the width of the grooves being smaller than to be sintered The diameter of the gate cup of the shell mold;

The sintered inner cavity is provided with an inner side of one end of the flue gas outlet at a position corresponding to the shell mold placement platform, and a first intake pipe for supplying air, and the first intake pipe is connected with a blower device. a first nozzle having a direction toward the groove is disposed on the first intake pipe;

a second nozzle for providing a flammable gas or liquid is further disposed in the sintering inner cavity;

The height of the flue gas outlet is higher than the height of the shell mold placement platform.
The shell mold sintering apparatus according to claim 1, wherein an inner side of the one end of the sintering chamber where the flue gas outlet is provided is further provided with a flammable gas at a position corresponding to the shell mold placing platform. Or a second intake pipe of liquid, the second nozzle being located on the second intake pipe and oriented toward the groove.
The shell mold sintering apparatus according to claim 1, wherein a middle portion of at least one side wall of the groove is uniformly provided with a plurality of wind deflectors, and the length of each wind shield is along the sintering inner cavity from inside to The outer direction becomes longer in turn.
The shell mold sintering apparatus according to claim 3, wherein the end of the wind deflector is an arc-shaped air guiding portion.
The shell mold sintering apparatus according to claim 4, wherein said windshield portion is inclined rearward from the inside to the outside of said sintering inner cavity at an angle of 1-10.
The shell mold sintering apparatus according to claim 1, wherein the sintering inner chamber is provided with an inner side of one end of the closing door at a position corresponding to the shell mold placing platform, and a sand collecting collecting groove is provided. The falling sand collecting groove extends in the width direction of the sintering inner cavity.
A shell mold sintering apparatus according to claim 1, wherein said flue gas A secondary combustion furnace is disposed between the outlet and the exhaust flue, and the secondary combustion furnace is provided with a third nozzle for supplying air and a fourth nozzle for supplying a flammable gas or liquid, the flue gas outlet It is a contraction structure facing the secondary combustion furnace.
The shell mold sintering apparatus according to claim 7, wherein the temperature in the secondary combustion furnace is 1200 ° C or higher, and the oxygen content in the secondary combustion furnace is 25% or more.
The shell mold sintering apparatus according to claim 7, wherein a ceramic sponge filter is disposed in the secondary combustion furnace at a junction with the exhaust flue.
The shell mold sintering apparatus according to claim 7, wherein the first intake pipe is connected to a metal preheating pipe, and the metal preheating pipe is disposed in the secondary combustion furnace.
A method for performing shell mold sintering using the shell mold sintering apparatus of claim 1, comprising:

Step 1: placing the shell mold to be sintered under the shell mold placement platform in the sintered inner cavity, and closing the closed door;

Step 2: Turn on the heating device, the air blowing device and the exhaust flue, so that there is sufficient oxygen content in the sintering cavity, the temperature is raised to the burning temperature of the shell mold wax, and the temperature in the sintered inner cavity is maintained until the residual in the shell mold The wax is completely burned out;

Step 3: The nozzle is opened to make the sintered inner cavity a low-oxygen or oxygen-free environment, and the temperature is raised to the sintering temperature of the shell mold and the temperature in the sintered inner cavity is maintained as the sintering temperature of the shell mold until the shell mold is sintered.
The method according to claim 11, wherein in the step 2, when it is detected that the oxygen content in the sintering inner cavity does not decrease within a certain period of time, the step 3 is performed.
The method according to claim 11, wherein in the step 2, the heating device, the air blowing device and the air exhausting device are turned on, so that the oxygen content of the sintering cavity is 16 to 20%; The nozzle is opened such that the sintered inner cavity has an oxygen content of 5% or less.
The method according to claim 11, wherein in the step 2, the combustion temperature of the shell mold wax is 600 ° C to 800 ° C, and the maintenance time of the temperature in the sintering furnace is maintained within 3 min; In the step 3, the sintering temperature of the shell mold is 1150 to 1400 ° C, and the maintenance time of the temperature in the sintering furnace is maintained at 10 to 30 min.