A water glass shell hardening droplet reaction device and a water glass shell hardening process

Abstract

The present invention discloses a water glass mold shell hardening droplet reaction device and a water glass mold shell hardening process, the reaction device includes an atomizer, a liquid storage tank, a reaction chamber and a residual liquid collecting tank; the hardener solution outlet end of the liquid storage tank is fluidly connected with the hardener solution inlet end of the atomizer through a liquid supply pipe, the hardener solution atomized droplet outlet end of the atomizer is fluidly connected with the hardener solution atomized droplet inlet end of the reaction chamber through a droplet delivery pipe; the hardener solution residual liquid outlet end of the reaction chamber is fluidly connected with the hardener solution residual liquid inlet end of the residual liquid collecting tank; the hardening process uses the above reaction device to harden the water glass mold shell. The present invention can effectively avoid the problems of large consumption of hardener solution, easy pollution, changes in physical and chemical properties with frequency of use, large fluctuations in mold shell hardening characteristics, and large discharge of hardener waste liquid in the existing immersion process.

Description

Technical Field

[0001] The invention relates to the technical field of water glass mold shell hardening, in particular to a water glass mold shell hardening droplet reaction device and a water glass mold shell hardening process. Background Art

[0002] Due to the advantages of low cost and non-toxicity, water glass is often used as a binder in the production of investment casting shells and is widely used. At present, the hardening of water glass shells adopts the immersion method, that is, after the wax model is coated with a coating, it is immersed in a hardener solution for a certain period of time, and the binder in the coating reacts chemically with the hardener solution to obtain strength. Since the strength of a single coating shell is low, multi-layer coatings and refractory powders are used in industrial production to form a shell with a certain thickness. Each shell layer must be immersed in a hardener solution and hardened to obtain the corresponding strength and meet its mechanical and process performance requirements. However, when the same shell or multiple batches of shells are immersed in the hardener solution for many times, the shell material absorbs a large amount of solvent water, which will cause the concentration of the hardener solution to change; the shedding of some shell materials (such as binders, refractory powders, etc.) will contaminate the hardener solution; these will cause the physical and chemical properties of the hardener solution to change significantly with the frequency of use, making it difficult to control the performance and quality of the hardened water glass shell. In addition, after the hardening solution is used for a certain period of time, the waste liquid cannot be reused, the discharge volume is large, and it is very easy to cause environmental pollution.

[0003] As the room temperature strength of the water glass shell increases, its firing strength and residual strength also increase to varying degrees, but the growth ranges (rates) of the three are different (this is closely related to the phase transition under high temperature conditions). However, as long as the growth rates of the room temperature strength and firing strength exceed the growth rate of the residual strength, the residual strength can be relatively reduced under the condition that the room temperature strength value and the firing strength value are required to be certain. For example, in the production of a certain medium-sized structural casting, the room temperature strength of the shell is required to be not less than 10.0MPa, the firing strength is not less than 7.0MPa, and the residual strength is not greater than 3.0MPa. The traditional shell making process (immersion hardening) is used. Usually, the room temperature strength and firing strength are easy to meet the requirements, but the residual strength often exceeds the standard. If the residual strength is reduced by reducing the thickness, the room temperature strength and firing strength will not meet the requirements. Therefore, it is difficult for the traditional shell making process (immersion hardening) to take into account both "room temperature strength and firing strength" and residual strength at the same time. In order to ensure that the room temperature strength and roasting strength meet the requirements, the mold shell prepared by the traditional shell making process usually has a large thickness. The large thickness of the mold shell not only increases the discharge of solid waste, but also has poor heat dissipation, which is not conducive to the rapid solidification of metal castings, resulting in unsatisfactory grain structure of the castings, which is not conducive to the improvement of casting performance. In addition, in actual casting production, the temperature of some southern enterprises' production workshops without heating in winter is generally -5 to 10°C. Under this temperature condition, when the mold shell is prepared by the immersion method, if the concentration of the hardener is low, the mold shell hardening reaction is slow or even cannot be hardened. Therefore, it is necessary to use a high-concentration hardener solution for production. However, the mold shell produced by the high-concentration hardener solution has a fast hardening reaction during the immersion hardening method, resulting in severe cracking. The prepared mold shell usually has extremely low roasting strength and cannot meet the application requirements, resulting in a high scrap rate. Summary of the invention

[0004] To this end, the technical problem to be solved by the present invention is to provide a water glass mold shell hardening droplet reaction device and a water glass mold shell hardening process with good adaptability to low temperature environment, so as to solve the problem of high mold shell scrap rate produced by high concentration hardener solution when hardening the water glass mold shell by immersion method, and solve the problems that the effective concentration of the hardener solution changes with the increase of the number of uses during the shell making process, the hardener solution is easily contaminated by the shell making material, resulting in low strength of the water glass mold shell, difficult to control performance and quality, and low utilization rate of the hardener solution, large emission, and serious environmental pollution; at the same time, the process of the present invention can effectively improve the room temperature strength and baking strength of the water glass mold shell, reduce the residual strength, so that the mold shell can meet the requirements of high "room temperature strength and baking strength" and low "residual strength" at a thinner thickness, thereby realizing the "enhancement and thinning" of the mold shell.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A water glass shell hardening droplet reaction device comprises an atomizer, a liquid storage tank, a reaction chamber and a residual liquid collecting tank; the hardener solution outlet end of the liquid storage tank is fluidly connected with the hardener solution inlet end of the atomizer through a liquid supply pipe, the hardener solution atomized droplet outlet end of the atomizer is fluidly connected with the hardener solution atomized droplet inlet end of the reaction chamber through a droplet delivery pipe; the hardener solution residual liquid outlet end of the reaction chamber is fluidly connected with the hardener solution residual liquid inlet end of the residual liquid collecting tank; the liquid storage tank can be connected with the atomizer in a direct or indirect form.

[0007] The above-mentioned water glass mold shell hardening droplet reaction device, the reaction chamber is provided with a droplet distributor and a sample holder; the sample holder is fixedly installed in the reaction chamber, and the wax mold sample is placed on the sample holder; the hardener solution atomized droplet inlet end of the droplet distributor is fluidly connected with the hardener solution atomized droplet outlet end of the droplet delivery pipe, and the hardener solution atomized droplet outlet end of the droplet distributor faces the wax mold sample; a residual liquid discharge hole is opened on the bottom wall of the reaction chamber, and the reaction chamber is fluidly connected with the residual liquid collection tank through the residual liquid discharge hole; the reaction chamber in the present invention is a cube, a cylinder or a cuboid, as well as reaction chambers of other shapes composed of a cube, a cylinder and a cuboid.

[0008] In the above-mentioned water glass shell hardening droplet reaction device, the droplet distributor is bell-mouth-shaped, that is, the inner diameter of the droplet distributor gradually increases from its hardener solution atomized droplet inlet end to its hardener solution atomized droplet outlet end.

[0009] The above-mentioned water glass mold shell hardening droplet reaction device has a liquid filling hole on the liquid storage tank, and the atomizer is electrically connected to the power supply through a power supply cable; the particle size of the droplets formed by the hardener solution after being atomized by the atomizer is 0.5-500 μm, and the larger the droplet particle size, the larger the contact area with the water glass coating on the mold shell surface per unit time, so that the hardening rate of the water glass film is accelerated, but when the atomized particle size is too large, the hardening rate is too fast, and it is easy to crack due to the fast dehydration shrinkage rate of the water glass film, forming large-sized cracks, thereby reducing the strength of the mold shell, and the smaller the droplet, the higher the hardening strength, but the mold shell hardening rate is slow and requires hardening time The time is prolonged, resulting in low productivity; the atomized droplet flow rate of the atomized droplet outlet of the hardener solution of the atomizer is 0.2-2.0L / min, and the carrier gas pressure of the atomizer is 0.2-1.5MPa; the atomizer is various devices that use high frequency, hydraulic or jet principles to drive the liquid to achieve atomization of the hardener solution, such as the atomizer is an ultrasonic atomizer, a liquid atomizer, a sprayer or a Venturi ejector, or it can be other forms of atomizers that can achieve the atomization function; the liquid atomizer can be a single-liquid head atomizer or a double-liquid head atomizer, and the Venturi ejector refers to various ejectors prepared using the Venturi principle.

[0010] The water glass shell hardened droplet reaction device further comprises a reaction chamber support; the reaction chamber is fixedly mounted on the reaction chamber support.

[0011] A water glass shell hardening process, using the water glass shell hardening droplet reaction device to harden the water glass shell, specifically comprises the following steps:

[0012] Step A: filling the liquid storage tank with a hardener solution; coating the wax model with water glass paint and performing sanding treatment, and obtaining a wax model sample after the sanding treatment; placing or hanging the wax model sample directly in the reaction chamber; the hardener solution can be an unsaturated solution, a saturated solution or a supersaturated solution; in the present invention, coating and sanding treatment include any type of coating and refractory aggregate used in the construction of each shell layer such as the surface layer, the transition layer, the reinforcement layer, the back layer and the sealing layer; the coating is applied to the surface of the wax model or the wax model group by brushing, dipping, spraying and the like; the sanding is applied in a boiling sand bed, a rain-type sanding machine or by hand;

[0013] Step B: starting the atomizer, wherein the atomizer pumps the hardener solution in the liquid storage tank into the atomizer through the liquid supply pipe for atomization;

[0014] Step C: the hardener solution is converted into atomized droplets of the hardener solution by the atomizer, and the atomized droplets of the hardener solution are transported to the reaction chamber through the droplet transport pipe, and undergo a hardening reaction with the water glass coating on the surface of the wax mold sample placed in the reaction chamber, so that the water glass coating on the surface of the wax mold sample is hardened into a water glass shell; the atomized droplets of the hardener solution remaining after the reaction are deposited and collected at the bottom of the reaction chamber, and flow into the residual liquid collection tank; the time of the hardening reaction can be selected according to the shape, size, structure and layer thickness of the water glass shell; the hardening time can be controlled by opening and closing the atomized droplet generator; the hardening rate of the water glass shell can be controlled by the atomized droplet flow rate (power adjustment) and the carrier gas pressure ( Pressure valve adjustment) is realized, and the carrier gas can be air or CO2 and other gases; when the flow rate of atomized droplets increases, the amount of atomized droplets deposited on the mold shell surface per unit time is large, the coverage area of ​​atomized droplets on the mold shell surface increases, and the hardening reaction rate is accelerated; when the carrier gas pressure increases, the atomized droplet deposition rate is fast, and the amount of atomized droplets deposited on the mold shell surface is large; the high-speed atomized droplets impacting the mold shell surface are easy to spread, the contact area between the atomized droplets and the mold shell increases, and the hardening reaction rate is accelerated; but too fast a reaction rate will cause the performance of the water glass mold shell generated after the atomized droplets of the present invention are hardened to gradually approach the traditional immersion hardening method, and the advantages are weakened or even disappear; when the flow rate of atomized droplets is small and the carrier gas pressure is low, it is conducive to obtaining high mold shell performance, but the mold shell productivity is low. Therefore, the appropriate atomized droplet flow rate is 0.2-2.0L / min, and the carrier gas pressure range is 0.2-1.5MPa.

[0015] Step D: taking out the wax mold sample with the water glass mold shell, repeating steps A to C, completing the hardening of all the mold shell layers on the wax mold sample to obtain a wax mold with a water glass mold shell layer, cutting off the power supply, and taking out the wax mold with the water glass mold shell layer from the reaction chamber; repeating steps A to C as appropriate, constructing a water glass mold shell composed of multiple layers of the same or different coatings and refractory aggregate shell layers on the surface of the wax mold or mold group;

[0016] Step E: drying the wax mold with the water glass shell layer, and dewaxing the shell by a hot water bath method, and obtaining a water glass shell after dewaxing; baking the water glass shell in a resistance furnace and cooling it to room temperature with the furnace to obtain a baked water glass shell. The shell obtained by the water glass shell hardening droplet reaction device and process of the present invention can be a single-layer / multi-layer shell or a composite shell formed by different binders.

[0017] In the above-mentioned water glass shell hardening process, the hardener solution is a salt solution of one or two or more metals and / or non-metals, or the hardener solution is a solution of one or two or more organic acids and / or inorganic acids; the particle size of droplets formed by the hardener solution after being atomized by the atomizer is 0.5 to 500 μm, the atomized droplet flow rate of the hardener solution atomized droplet outlet of the atomizer is 0.2 to 2.0 L / min, and the carrier gas pressure of the atomizer is 0.2 to 1.5 MPa.

[0018] In the above water glass shell hardening process, in step C, the hardening reaction time is 6 to 18 minutes;

[0019] In step A: the hardener solution is an ammonium chloride solution with a concentration of 5 to 25wt%; the preparation method of the water glass coating is: mixing refractory powder and water glass in a mass ratio of 1.2:1, then adding a wetting agent and a defoaming agent, stirring for 1 hour, and then standing for 8 hours to ensure that the binder and the refractory powder are fully wetted; the water glass coating is stirred for 20 minutes before use and then stood for 5 minutes before use; the coating application and sanding method is: immersing the wax model or wax model group in the water glass coating and standing for 30 to 50 seconds; then taking out the wax model or wax model group coated with the water glass coating, and placing it in a boiling sand bed or a rain-type sand spreader for sanding treatment. After the sanding treatment is completed, it is naturally dried for 50 to 60 minutes to obtain the wax model sample;

[0020] In step D: prepare the water glass coating again: mix the refractory powder and water glass in a mass ratio of 1.1:1, and then stir continuously for at least 4.0 hours and store for standby; the water glass coating is stirred for 20 minutes before use and then allowed to stand for 5 minutes before use; the method of coating and sanding is: immerse the wax mold or wax mold group that has already constructed a layer of water glass shell layer in the water glass coating, and let it stand for 30 to 50 seconds; then take out the wax mold or wax mold group that has already constructed a layer of water glass shell layer coated with the water glass coating, and put it into a boiling sand bed and a rain-type sand spreader for sanding treatment. After the sanding treatment is completed, it is naturally dried for 40 to 50 minutes to obtain the wax mold sample, and then the operation method of step BC is repeated to form a second layer of water glass shell on the surface of the wax mold sample; then a third layer of water glass shell is constructed on the surface of the wax mold or wax mold group according to the construction method of the second layer of water glass shell.

[0021] In the above-mentioned water glass shell hardening process, in step C, the hardening reaction time is 9 minutes; the hardener solution is an ammonium chloride solution with a concentration of 5wt%; in step A, the refractory powder is 270-mesh quartz powder, and the sand and gravel used in the sand spreading treatment is 50-mesh and / or 70-mesh quartz sand; in step D, the refractory powder is a mixture of 270-mesh quartz powder and 200-mesh mullite powder in a mass ratio of 7:3, and the sand and gravel used in the sand spreading treatment is 20-mesh and / or 40-mesh quartz sand.

[0022] In the above-mentioned water glass shell hardening process, in step E, the drying temperature is 5-30°C, and the drying time is 12-24h; the temperature of the hot water bath is 90-98°C, and the hot water bath time is 10-15min; during roasting, the temperature is first raised to 750°C at a rate of 5°C / min, then kept warm for 2.0h, and finally cooled to room temperature with the furnace.

[0023] The technical solution of the present invention achieves the following beneficial technical effects:

[0024] 1. The water glass mold shell hardening droplet reaction device of the present invention uses an atomizer to atomize the hardener solution. The atomized droplets of the hardener solution are transported and deposited on the surface of the water glass mold shell coating under the impetus of the air flow, and gradually penetrate into the water glass mold shell coating, and chemically react with the water glass in the water glass mold shell coating to build the shell strength; since during the hardening process of the water glass mold shell, the hardener solution is always stored in the liquid storage tank and does not contact the water glass mold shell, its concentration will not change, and its physical and chemical properties are stable, so that the hardening characteristics of the water glass mold shell hardened under the same process parameters have high consistency. The water glass mold shell hardening droplet reaction device of the present invention can be used to transport the hardener droplets to any shell layer such as the surface layer, transition layer and sealing layer of the water glass mold shell, and the shell hardening rate can be controlled by the droplet concentration and the transport amount (atomization time); compared with the immersion method, the strength of the water glass mold shell prepared by the device and process is significantly improved, and the performance of different batches of water glass mold shells prepared under the same process parameters is stable, and the consumption of the hardener solution is also significantly reduced.

[0025] 2. The water glass shell hardening process of the present invention can effectively avoid the problems existing in the existing immersion method hardening water glass shell hardening process, such as large consumption of hardener solution, easy pollution, change of physical and chemical properties with the frequency of use, large fluctuation of shell hardening characteristics, large discharge of hardener waste liquid, etc., and achieves near-zero discharge of hardener residual liquid; at the same time, due to the stable properties of the hardener and controllable hardening rate, it can improve the room temperature strength and baking strength of the water glass shell, reduce its residual strength, etc. At the same time, the process can improve the utilization rate of the hardener solution, reduce the discharge of waste liquid, and is conducive to protecting the environment. Compared with the traditional immersion method, the water glass shell hardened by the water glass shell hardening droplet reaction device and method of the present invention can improve the peak value of the room temperature strength of the water glass shell prepared by 47.01% and the peak value of the roasting strength by 42.58% under certain hardening process conditions (the concentration of the hardener solution is 5% to 25%, and the hardening time is 6 to 18 minutes); while the peak value of the residual strength can be reduced by 8.42%; in addition, since the room temperature strength of the semi-enclosed droplet hardening process is much higher than that of the shell prepared by the immersion method, the shell thickness can be appropriately reduced under the condition that the shell strength meets the requirements, which will be beneficial to further reduce the residual strength of the shell. The peak value of the room-temperature strength of the mold shell obtained by the present invention is 21.42MPa, and the corresponding roasting strength and residual strength are 8.22MPa and 6.31MPa respectively; the ratios of the residual strength to the room-temperature strength and roasting strength are 29.46% and 76.76% respectively; while the peak value of the room-temperature strength of the mold shell hardened by the immersion method is only 14.57MPa, and the corresponding roasting strength and residual strength are 6.52MPa and 5.20MPa respectively; the ratios of the residual strength to the room-temperature strength and roasting strength are 35.69% and 79.75% respectively; it indicates that the growth rate of the residual strength of the mold shell prepared by the present invention is lower than the growth rate of the room-temperature strength and roasting strength, that is, the room-temperature strength and roasting strength equivalent to those of the immersion method can be obtained under the condition of a thinner shell thickness, and the residual strength is correspondingly reduced after the thickness of the mold shell is thinned, which is beneficial to shelling after the casting is solidified. In addition, during the shell hardening process, the content of hardener droplets in the liquid-gas two-phase flow is low, the delivery volume can be accurately controlled, the residual waste liquid after the hardening reaction is small, and the utilization rate is increased to more than 96%.

[0026] 3. The present invention prepares water glass mold shells for investment casting through a simple and easy-to-use water glass mold shell hardening droplet reactor device and method. Each shell layer is hardened under the action of hardener droplets at a constant concentration. The hardener is not contaminated, the consumption is small, the hardening reaction process is easy to control, and the controllability of the water glass mold shell performance is achieved by adjusting very few process parameters. The process of the present invention can prepare a mold shell with high room temperature strength and roasting strength under the condition of high hardener solution concentration, and can produce mold shells that meet application requirements in a production environment with low production temperature, thereby reducing the scrap rate of the mold shell in a low-temperature production environment.

[0027] 4. The water glass mold shell prepared by the process of the present invention has higher room temperature strength and roasting strength, and a relatively lower residual strength ratio than the water glass mold shell prepared by the traditional immersion method; this means that when the room temperature strength and roasting strength requirements are certain, the process of the present invention can be used to prepare a thinner water glass mold shell while appropriately reducing the thickness of the water glass mold shell, that is, a thinner water glass mold shell wall thickness (thin shell) can achieve sufficient room temperature strength and roasting strength requirements; and the thin-walled water glass mold shell can not only further reduce the residual strength, but also reduce the emission of solid waste, and is conducive to the rapid solidification of the metal and the improvement of the casting performance (because the thin shell has strong heat dissipation capacity, fast cooling, fine metal grains, and good mechanical properties), and is also conducive to the shelling of the shell after the casting solidifies. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic structural diagram of a water glass shell hardening droplet reaction device according to Example 1 of the present invention;

[0029] Figure 2 The firing strength bar graph of the fired water glass shell prepared in Example 2 of the present invention (compared with the immersion method);

[0030] Figure 3 The normal temperature strength bar graph of the water glass shell prepared in Example 2 of the present invention (compared with the immersion method);

[0031] Figure 4 The firing strength bar graph of the fired water glass shell prepared in Example 4 of the present invention (compared with the immersion method);

[0032] Figure 5 The normal temperature strength bar graph of the water glass shell prepared in Example 4 of the present invention (compared with the immersion method);

[0033] Figure 6 The firing strength bar graph of the fired water glass shell prepared in Example 6 of the present invention (compared with the immersion method);

[0034] Figure 7 Room temperature strength bar graph of the water glass shell prepared in Example 6 of the present invention (compared with the immersion method).

[0035] The reference numerals in the figure are as follows: 1-atomizer; 2-liquid storage tank; 3-droplet delivery pipe; 4-droplet distributor; 5-reaction chamber; 6-wax mold sample; 7-sample holder; 8-residual liquid discharge hole; 9-residual liquid collecting tank; 10-power supply cable; 11-liquid adding hole; 12-liquid supply pipe; 13-reaction chamber holder. DETAILED DESCRIPTION

[0036] Example 1

[0037] The schematic diagram of the water glass shell hardening droplet reaction device in this embodiment is as follows: Figure 1 As shown, it includes an atomizer 1, a liquid storage tank 2, a droplet distributor 4, a reaction chamber 5, a sample holder 7, a residual liquid collecting tank 9 and a reaction chamber holder 13; the sample holder 7 is fixedly installed in the reaction chamber 5, and the wax mold sample 6 is placed on the sample holder 7; the hardener solution outlet end of the liquid storage tank 2 is fluidly connected with the hardener solution inlet end of the atomizer 1 through a liquid supply pipe 12, and the atomized droplet outlet end of the hardener solution of the atomizer 1 is fluidly connected with the atomized droplet inlet end of the hardener solution of the droplet distributor 4 located in the reaction chamber 5 through a droplet delivery pipe 3; The atomized droplet outlet of the hardener solution of the droplet distributor 4 faces the wax mold sample 6, and the droplet distributor 4 is in a trumpet shape, that is, the inner diameter of the droplet distributor 4 gradually increases from its atomized droplet inlet end to the atomized droplet outlet end of the hardener solution (in some other embodiments, the droplet distributor 4 can be in other shapes, such as a rectangular, disc-shaped or linear shape); the residual liquid outlet of the hardener solution of the reaction chamber 5 is fluidly connected with the residual liquid inlet end of the hardener solution of the residual liquid collecting tank 9 through the residual liquid discharge hole 8 opened on the bottom wall of the reaction chamber 5.

[0038] A liquid filling hole 11 is provided on the liquid storage tank 2, and the atomizer 1 is electrically connected to the power supply through a power supply cable 10; the atomizer 1 in this embodiment is an ultrasonic atomizer, and in some other embodiments, a liquid atomizer, a sprayer or a Venturi ejector can also be selected to replace the ultrasonic atomizer in this embodiment. The liquid atomizer can be a single-liquid head atomizer or a double-liquid head atomizer. The Venturi ejector refers to various ejectors prepared using the Venturi principle; the reaction chamber in this embodiment is a cube, and in some other embodiments, a cylinder, a cuboid, and reaction chambers of other shapes composed of a cube, a cylinder and a cuboid can also be used.

[0039] Example 2

[0040] In this embodiment, the water glass mold shell hardening process is to use the water glass mold shell hardening droplet reaction device of Example 1 to harden the water glass mold shell; the wax film sample is a rectangular groove wax mold of 40×20×6 mm prepared by injection molding using a wax injection machine, and the water glass mold shell layer is constructed by coating and sanding on the surface of the groove wax mold, which specifically includes the following steps:

[0041] Step A: filling a hardener solution into a liquid storage tank; coating the wax model with water glass paint and performing sanding treatment; after the sanding treatment is completed, a surface wax model sample is obtained, and the surface wax model sample is placed in a reaction chamber;

[0042] In this step, 270 mesh refined quartz powder is selected as 1.2 kg of refractory powder, and a mixture is prepared according to a powder-liquid ratio (refractory powder mass: water glass mass) of 1.2:1. After stirring evenly, 1.0 mL of wetting agent and defoaming agent are added respectively. After continuous stirring for 1.0 h, the mixture is allowed to stand for 8.0 h to obtain a surface water glass coating, which is stored for standby use. The surface water glass coating is stirred again before use for 20 min, and then the coating is applied after standing for 5 min. After the injection-molded wax mold is cleaned with a cleaning agent and dried naturally, the wax mold or wax mold group is immersed in the prepared surface water glass coating, and the mixture is allowed to stand for 30 to 50 s. Then, the wax mold coated with the surface water glass coating is taken out, and placed in a boiling sand bed and a rain-type sand spreader for sanding (50 / 70 mesh quartz sand), and then dried naturally for 50 to 60 min to obtain a surface wax mold sample. The wetting agent, defoaming agent and cleaning agent used in this step are all commonly used by those skilled in the art, and will not be described in detail in this example. The hardener solution used in this step is a 5.0wt% NH4Cl solution.

[0043] Step B: starting the atomizer, and pumping the hardener solution in the liquid storage tank into the atomizer through the liquid supply pipe for atomization; the particle size of the droplets formed by the hardener solution after atomization by the atomizer is 0.5-500 μm; the atomized droplet flow rate of the hardener solution atomized droplet outlet of the atomizer is 1.0 L / min, and the carrier gas pressure of the atomizer is 0.5 MPa;

[0044] Step C: The hardener solution is converted into atomized droplets of the hardener solution through an atomizer, and the atomized droplets of the hardener solution are transported to the reaction chamber through a droplet transport pipe, and react with the surface water glass coating on the surface of the surface wax mold sample placed in the reaction chamber, and the reaction time is 6 to 18 minutes, so that the surface water glass coating on the surface of the surface wax mold sample is hardened to form a water glass mold shell surface layer; the residual atomized droplets of the hardener solution after the reaction are deposited and collected at the bottom of the reaction chamber, and flow into the residual liquid collection tank;

[0045] Step D: taking out the wax mold sample with the water glass mold shell, repeating steps A to C to continue to sequentially construct the water glass mold shell transition layer and the water glass mold shell sealing slurry layer on the wax mold sample, and when all the mold shell layers on the wax mold sample are hardened, a wax mold with a water glass mold shell layer is obtained, cutting off the power supply, and taking out the wax mold with the water glass mold shell layer from the reaction chamber, the hardening of the water glass mold shell is completed;

[0046] In this step, the construction method of the water glass shell transition layer is as follows: 270 mesh quartz powder and 200 mesh mullite powder are prepared into a mixed powder according to a mass ratio of 7:3, and the mixture is prepared according to a powder-liquid ratio (refractory powder mass: water glass mass) of 1.1:1, and the mixture is continuously stirred for at least 4.0 hours and then stored for standby use to obtain a transition layer water glass coating; the transition layer water glass coating is stirred again before use, and the stirring time is 20 minutes, and then it is allowed to stand for 5 minutes before coating; the wax mold or module with the water glass shell surface layer constructed is immersed in the prepared transition layer water glass coating, and it is allowed to stand for 30 to 50 seconds, and then the wax mold coated with the transition layer water glass coating is taken out and placed in a rain-type sand spreader to sprinkle sand (20 / 40 mesh quartz sand), and then naturally dried for 40 to 50 minutes to obtain a transition layer wax mold sample; then the transition layer wax mold sample is placed in a reaction chamber, and the operation method of step BC is used to form a water glass shell transition layer on the surface of the wax mold sample;

[0047] In this step, the construction method of the water glass shell sealing layer and the raw materials used are exactly the same as the construction method of the water glass shell transition layer mentioned above, and will not be repeated here.

[0048] Step E: drying the wax mold with the water glass shell layer at 20° C. for 12 to 24 hours, and dewaxing the shell by a hot water bath method, i.e. immersing the wax mold sample with the water glass shell layer in hot water at about 95° C., taking out the water glass shell after the water bath for about 10 to 15 minutes, and obtaining the water glass shell after the dewaxing is completed; placing the water glass shell in an XD-1400S box-type resistance furnace, heating to 750° C. at a rate of 5° C. / min, and then keeping the temperature for 2.0 hours, and cooling to room temperature with the furnace, to prepare a baked water glass shell;

[0049] The water glass shell and the fired water glass shell are prepared by the traditional immersion method. Compared with the present embodiment, except that the hardening reaction of the water glass coating is the immersion method (i.e., the wax film sample is immersed in the hardener solution), the other operation methods and process parameters are completely consistent with those of the present embodiment, and the reagents, coatings, raw material ratios, etc. used are also exactly the same.

[0050] The water glass shell and the fired water glass shell prepared in this embodiment are compared with the water glass shell and the fired water glass shell prepared by the traditional immersion method respectively; the firing strength of the water glass shell prepared by the two different hardening methods of this embodiment and the traditional immersion method can be compared by comparing the bending strength test of the fired water glass shell. Figure 2 The bending strength test of the water glass shell can be compared to compare the room temperature strength of the water glass shell prepared by the two different hardening methods of this embodiment and the traditional immersion method. Figure 3 .

[0051] The conventional immersion process of this embodiment is referred to as "immersion process", and the preparation process of this embodiment is referred to as "atomization process". The room temperature strength, firing strength and residual strength of the water glass shell prepared by the two processes with different hardening times are shown in Table 1.

[0052] Table 1

[0053]

[0054] It can be seen from Table 1 that the firing strength of the water glass shell prepared by the hardening process of this example reaches the highest when the hardening time is 9 minutes, which is 9.7 MPa, while the firing strength of the water glass shell prepared by the traditional intrusion process does not change much within the hardening time range of 6 to 18 minutes, both between 6.38 and 6.71 MPa; under the two hardening process conditions, when the hardening time is 6 to 15 minutes, the firing strength of the water glass shell prepared by the traditional immersion process is significantly lower than that of the water glass shell prepared by the hardening process of this embodiment.

[0055] At the same time, it can be seen from Table 1 that the water glass shell prepared by the hardening process of this example has a maximum room temperature strength of 21.42 MPa when the hardening time is 6 min; while the water glass shell prepared by the traditional intrusion process has a maximum room temperature strength of 14.57 MPa when the hardening time is 12 min; under the two hardening process conditions, when the hardening time is in the range of 6 to 18 min, the room temperature hardening strength shows a trend of first decreasing, then increasing, and then decreasing.

[0056] Compared with the traditional immersion method, the peak strength of the water glass shell prepared in this embodiment at room temperature is increased by 47.01%, and the peak strength at firing is increased by 44.56%. When the water glass shell reaches the peak strength at room temperature, the residual strength ratio (residual strength / peak strength at room temperature) is reduced by 6.23%; when the water glass shell reaches the peak strength at firing, the residual strength ratio (residual strength / peak strength at firing) is reduced by 44.26%; the utilization rate of the hardener solution is increased to 98.0%.

[0057] Example 3

[0058] In this embodiment, the water glass mold shell hardening process also uses the water glass mold shell hardening droplet reaction device of Example 1 to harden the water glass mold shell; except that the hardener solution used is an NH4Cl solution with a concentration of 10.0wt%, other specific operating steps, reagent raw materials used, process parameters, etc. are exactly the same as those of Example 2.

[0059] The water glass shell and the fired water glass shell are prepared by the traditional immersion method. Compared with the present embodiment, except that the hardening reaction of the water glass coating is the immersion method (i.e., the wax film sample is immersed in the hardener solution), the other operation methods and process parameters are completely consistent with those of the present embodiment, and the reagents, coatings, raw material ratios, etc. used are also exactly the same.

[0060] The water glass mold shell and the fired water glass mold shell prepared in this embodiment are compared with the water glass mold shell and the fired water glass mold shell prepared by the traditional immersion method respectively; the firing strength of the water glass mold shell prepared by the two different hardening methods of the present embodiment and the traditional immersion method can be compared through the bending strength test comparison of the fired water glass mold shell; the room temperature strength of the water glass mold shell prepared by the two different hardening methods of the present embodiment and the traditional immersion method can be compared through the bending strength test comparison of the water glass mold shell.

[0061] The conventional immersion process of this embodiment is referred to as "immersion process", and the preparation process of this embodiment is referred to as "atomization process". The room temperature strength, firing strength and residual strength of the water glass shell prepared by the two processes with different hardening times are shown in Table 2.

[0062] Table 2

[0063]

[0064] Compared with the traditional immersion method, the peak strength of the water glass shell prepared in this embodiment at room temperature is increased by 27.33%, and the peak strength at firing is increased by 3.24%. When the water glass shell reaches the peak strength at room temperature, the residual strength ratio (residual strength / peak strength at room temperature) is reduced by 2.95%; when the water glass shell reaches the peak strength at firing, the residual strength ratio (residual strength / peak strength at firing) is reduced by 8.25%; the utilization rate of the hardener solution is increased to 97.5%.

[0065] Example 4

[0066] In this embodiment, the water glass shell hardening process also uses the water glass shell hardening droplet reaction device of Example 1 to harden the water glass shell; except that the hardener solution used is an NH4Cl solution with a concentration of 15.0wt%, other specific operating steps, reagent raw materials used, process parameters, etc. are exactly the same as those of Example 2.

[0067] The water glass shell and the fired water glass shell are prepared by the traditional immersion method. Compared with the present embodiment, except that the hardening reaction of the water glass coating is the immersion method (i.e., the wax film sample is immersed in the hardener solution), the other operation methods and process parameters are completely consistent with those of the present embodiment, and the reagents, coatings, raw material ratios, etc. used are also exactly the same.

[0068] The water glass shell and the fired water glass shell prepared in this embodiment are compared with the water glass shell and the fired water glass shell prepared by the traditional immersion method respectively; the firing strength of the water glass shell prepared by the two different hardening methods of this embodiment and the traditional immersion method can be compared by comparing the bending strength test of the fired water glass shell. Figure 4 The bending strength test of the water glass shell can be compared to compare the room temperature strength of the water glass shell prepared by the two different hardening methods of this embodiment and the traditional immersion method. Figure 5 .from Figure 4 and Figure 5 It can be seen from the figure that when the hardener concentration increases to 15.0wt%, under the two hardening process conditions, after the hardening time exceeds 9min, the room temperature strength and the strength after calcination will no longer increase, and will even gradually decrease. Therefore, the hardening time is generally controlled not to exceed 9min.

[0069] The conventional immersion process of this embodiment is referred to as "immersion process", and the preparation process of this embodiment is referred to as "atomization process". The room temperature strength, firing strength and residual strength of the water glass shell prepared by the two processes with different hardening times are shown in Table 3.

[0070] Table 3

[0071]

[0072]

[0073] Compared with the traditional immersion method, the peak strength of the water glass shell prepared in this embodiment at room temperature is increased by 26.23%, and the peak strength at firing is increased by 90.91%. When the water glass shell reaches the peak strength at room temperature, the residual strength ratio (residual strength / peak strength at room temperature) is reduced by 3.09%; when the water glass shell reaches the peak strength at firing, the residual strength ratio (residual strength / peak strength at firing) is reduced by 6.45%; the utilization rate of the hardener solution is increased to 96.0%.

[0074] Example 5

[0075] In this embodiment, the water glass mold shell hardening process also uses the water glass mold shell hardening droplet reaction device of Example 1 to harden the water glass mold shell; except that the hardener solution used is an NH4Cl solution with a concentration of 20.0wt%, other specific operating steps, reagent raw materials used, process parameters, etc. are exactly the same as those of Example 2.

[0076] The water glass shell and the fired water glass shell are prepared by the traditional immersion method. Compared with the present embodiment, except that the hardening reaction of the water glass coating is the immersion method (i.e., the wax film sample is immersed in the hardener solution), the other operation methods and process parameters are completely consistent with those of the present embodiment, and the reagents, coatings, raw material ratios, etc. used are also exactly the same.

[0077] The water glass mold shell and the fired water glass mold shell prepared in this embodiment are compared with the water glass mold shell and the fired water glass mold shell prepared by the traditional immersion method respectively; the firing strength of the water glass mold shell prepared by the two different hardening methods of the present embodiment and the traditional immersion method can be compared through the bending strength test comparison of the fired water glass mold shell; the room temperature strength of the water glass mold shell prepared by the two different hardening methods of the present embodiment and the traditional immersion method can be compared through the bending strength test comparison of the water glass mold shell.

[0078] The conventional immersion process of this embodiment is referred to as "immersion process", and the preparation process of this embodiment is referred to as "atomization process". The room temperature strength, firing strength and residual strength of the water glass shell prepared by the two processes with different hardening times are shown in Table 4.

[0079] Table 4

[0080]

[0081] Compared with the traditional immersion method, the peak strength of the water glass shell prepared in this embodiment at room temperature is increased by 69.60%, and the peak strength at firing is increased by 83.84%. When the water glass shell reaches the peak strength at room temperature, the residual strength ratio (residual strength / peak strength at room temperature) increases by 12.15%; when the water glass shell reaches the peak strength at firing, the residual strength ratio (residual strength / peak strength at firing) decreases by 4.93%; the utilization rate of the hardener solution is increased to 96.3%.

[0082] Example 6

[0083] In this embodiment, the water glass mold shell hardening process also uses the water glass mold shell hardening droplet reaction device of Example 1 to harden the water glass mold shell; except that the hardener solution used is an NH4Cl solution with a concentration of 25.0wt%, other specific operating steps, reagent raw materials used, process parameters, etc. are exactly the same as those of Example 2.

[0084] The water glass shell and the fired water glass shell are prepared by the traditional immersion method. Compared with the present embodiment, except that the hardening reaction of the water glass coating is the immersion method (i.e., the wax film sample is immersed in the hardener solution), the other operation methods and process parameters are completely consistent with those of the present embodiment, and the reagents, coatings, raw material ratios, etc. used are also exactly the same.

[0085] The water glass shell and the fired water glass shell prepared in this embodiment are compared with the water glass shell and the fired water glass shell prepared by the traditional immersion method respectively; the firing strength of the water glass shell prepared by the two different hardening methods of this embodiment and the traditional immersion method can be compared by comparing the bending strength test of the fired water glass shell. Figure 6 The bending strength test of the water glass shell can be compared to compare the room temperature strength of the water glass shell prepared by the two different hardening methods of this embodiment and the traditional immersion method. Figure 7 .from Figure 6 and Figure 7 It can be seen that when the hardener concentration is 25.0wt% and the hardening time does not exceed 12min, the shell strength at room temperature and the firing strength of the shell of this embodiment are better than the shell prepared by the traditional immersion method. When the hardening time exceeds 12min, the strength advantage of the shell prepared by the hardening method of this embodiment weakens.

[0086] The conventional immersion process of this embodiment is referred to as "immersion process" and the preparation process of this embodiment is referred to as "atomization process". The room temperature strength, firing strength and residual strength of the water glass shell prepared by the two processes with different hardening times are shown in Table 5.

[0087] Table 5

[0088]

[0089] For precision casting production, the performance of the shell must first meet the requirements of normal temperature and roasting strength. Only under this premise, whether the residual strength is low enough is considered. It is meaningless to only compare the residual strength of the two hardening processes. As can be seen from Table 5, when the hardener concentration reaches 25.0wt%, the roasting strength of all immersion hardened shells is lower than 3.0MPa, which does not meet the roasting strength requirements of general shells (not less than 3.0MPa). Therefore, although the residual strength of the shell obtained under this hardening condition is extremely low, it cannot be used in actual production due to the low roasting strength. When the atomization method is used, even if the hardener concentration reaches a high concentration of 25.0wt%, a shell with a roasting strength that meets the application requirements can be prepared.

[0090] Compared with the conventional immersion method, when the water glass shell prepared in this embodiment reaches the peak strength at room temperature, the residual strength ratio (residual strength / peak strength at room temperature) increases by 10.95%, but the peak strength at room temperature of the water glass shell increases by 67.04%, the peak strength at firing increases by 483.44%, and when the water glass shell reaches the peak strength at firing, the residual strength ratio (residual strength / peak strength at firing) decreases by 74.03%; the utilization rate of the hardener solution increases to 97.0%. The results of this embodiment show that under the condition of high concentration of hardener solution, the firing strength loss of the shell prepared by the conventional immersion method is much higher than that of the hardening process of the present invention, especially its firing strength is lower than 2.0MPa, which is far from meeting the requirements of industrial production.

[0091] It should be pointed out that in actual casting production, the hardening reaction of the mold shell is slow under low temperature environment (generally <10°C), the shell making cycle is extended, and the productivity is low. For example, under the production conditions of southern enterprises without heating in winter, the temperature of the production workshop is generally -5 to 10°C. When the concentration of the hardener is low, the mold shell cannot be hardened, and a high concentration hardener must be used. Although the use of a high concentration hardener solution to produce the mold shell by immersion method can accelerate hardening, the consequence is that the produced mold shell has a low residual strength, but due to the extremely low roasting strength, it cannot be used, resulting in a high scrap rate. This example further highlights the advantages of the present invention. Even if a high concentration solution of 25.0wt% is used as a hardener (close to the saturated concentration value of 27.11% at 20°C), the strength performance of the atomization hardened mold shell can still meet the requirements, that is, it has a strong adaptability to low temperature environments for changes in the hardener solution.

[0092] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

[0093] In summary, the water glass mold shell hardening droplet reaction device of the present invention can be used to harden the water glass mold shell in an atomized droplet impact manner, thereby realizing controllable preparation of the water glass mold shell; compared with the traditional immersion hardening process, the water glass mold shell hardening droplet reaction device used in the process of the present invention has a simple structure; and the type, concentration, droplet input amount, and carrier gas of the hardener can be selected according to actual needs; the hardening reaction rate, reaction degree, and the performance of each shell layer can be conveniently regulated. Since the hardener solution in the liquid storage tank of the device never contacts the mold shell and will not be contaminated, its composition and physical and chemical properties are stable, and the hardening characteristics of the water glass mold shell obtained after atomization remain unchanged; the hardener solution contacts the mold shell surface in the form of atomized droplets to produce a hardening reaction, so the hardener dosage consumed by the mold shell hardening is small; it can avoid the problems of large consumption of hardener solution, easy contamination, change of physical and chemical properties with the frequency of use, fluctuation of mold shell hardening characteristics, and large discharge of hardener waste liquid in the existing immersion method hardening water glass mold shell process; since the hardener has stable properties and controllable hardening rate, it can improve the room temperature strength and baking strength of the water glass mold shell and reduce the residual strength; so that the performance of the prepared water glass mold shell is much higher than that of the general and traditional immersion method mold shell. At the same time, it can improve the utilization rate of the hardener solution, reduce the discharge of waste liquid, and is beneficial to environmental protection. In addition, the process preparation cycle of the present invention is short, and the mold shell hardening can be completed in the shortest few minutes. The process is simple, fast and easy to operate; the hardening process is carried out in a closed reactor, without volatilization, and the operating environment is good; it is suitable for the controllable preparation of various precision casting mold shells hardened with various water glass binders such as sodium and potassium and other acidic liquid hardeners, and can also provide a fast and simple fast hardening method for the preparation of other types of composite mold shells and the material processing of cementitious materials, and has extremely high universality.

Claims

1. A water glass shell hardening process, characterized in that: The water glass shell hardening droplet reaction device is used to harden the water glass shell. A water glass shell hardening droplet reaction device comprises an atomizer (1), a liquid storage tank (2), a reaction chamber (5) and a residual liquid collection tank (9); the hardener solution outlet end of the liquid storage tank (2) is fluidly connected to the hardener solution inlet end of the atomizer (1) through a liquid supply pipe (12); the hardener solution atomized droplet outlet end of the atomizer (1) is fluidly connected to the hardener solution atomized droplet inlet end of the reaction chamber (5) through a droplet delivery pipe (3); the hardener solution residual liquid outlet end of the reaction chamber (5) is fluidly connected to the hardener solution residual liquid inlet end of the residual liquid collection tank (9); a liquid storage tank (1) is provided in the reaction chamber (5); A droplet distributor (4) and a sample holder (7) are provided; the sample holder (7) is fixedly installed in the reaction chamber (5), and the wax model sample (6) is placed on the sample holder (7); the atomized droplet inlet end of the hardener solution of the droplet distributor (4) is fluidly connected to the atomized droplet outlet end of the hardener solution of the droplet delivery pipe (3), and the atomized droplet outlet end of the hardener solution of the droplet distributor (4) faces the wax model sample (6); a residual liquid discharge hole (8) is provided on the bottom wall of the reaction chamber (5), and the reaction chamber (5) is fluidly connected to the residual liquid collection tank (9) through the residual liquid discharge hole (8); The specific steps include: Step A: filling the hardener solution into the liquid storage tank (2); coating the wax model with water glass coating and performing sanding treatment, and obtaining a wax model sample (6) after the sanding treatment; placing the wax model sample (6) in the reaction chamber (5); Step B: starting the atomizer (1), wherein the atomizer (1) pumps the hardener solution in the liquid storage tank (2) into the atomizer (1) through the liquid supply pipe (12) for atomization; Step C: the hardener solution is converted into atomized droplets of the hardener solution through the atomizer (1), and the atomized droplets of the hardener solution are transported to the reaction chamber (5) through the droplet transport pipe (3), and undergo a hardening reaction with the water glass coating on the surface of the wax model sample (6) placed in the reaction chamber (5), so that the water glass coating on the surface of the wax model sample (6) is hardened into a water glass mold shell; the atomized droplets of the hardener solution remaining after the reaction are deposited and collected at the bottom of the reaction chamber (5), and flow into the residual liquid collection tank (9); Step D: taking out the wax model sample (6) with the water glass mold shell, repeating steps A to C, completing the hardening of all mold shell layers on the wax model sample (6) to obtain a wax model with a water glass mold shell layer, cutting off the power supply, and taking out the wax model with the water glass mold shell layer from the reaction chamber (5); Step E: drying the wax mold with the water glass shell layer, and dewaxing the shell by a hot water bath method, to obtain a water glass shell after dewaxing; baking the water glass shell in a resistance furnace and cooling it to room temperature with the furnace to obtain a baked water glass shell; The hardener solution is a salt solution of one or two or more metals and / or non-metals, or the hardener solution is a solution of one or two or more organic acids and / or inorganic acids; the particle size of the droplets formed by the hardener solution after being atomized by the atomizer (1) is 0.5 to 500 μm, the atomized droplet flow rate at the atomized droplet outlet of the hardener solution of the atomizer (1) is 0.2 to 2.0 L / min, and the carrier gas pressure of the atomizer (1) is 0.2 to 1.5 MPa.

2. The water glass shell hardening process according to claim 1, characterized in that: The droplet distributor (4) is in a bell-mouth shape, that is, the inner diameter of the droplet distributor (4) gradually increases from the hardener solution atomized droplet inlet end to the hardener solution atomized droplet outlet end.

3. The water glass shell hardening process according to claim 1, characterized in that: The liquid storage tank (2) is provided with a liquid filling hole (11), and the atomizer (1) is electrically connected to a power source via a power supply cable (10).

4. The water glass shell hardening process according to claim 1, characterized in that: It also comprises a reaction chamber support (13); the reaction chamber (5) is fixedly mounted on the reaction chamber support (13).

5. The water glass shell hardening process according to claim 1, characterized in that: In step C, the hardening reaction time is 6 to 18 minutes; In step A, the hardener solution is an ammonium chloride solution with a concentration of 5 to 25 wt %; the preparation method of the water glass coating is: mixing refractory powder and water glass in a mass ratio of 1.2:1, then adding a wetting agent and a defoaming agent, stirring for 1 hour, and then standing for 8 hours; the water glass coating is stirred for 20 minutes before use and then standing for 5 minutes before use; the coating application and sanding method is: immersing a wax model or a wax model group in the water glass coating and standing for 30 to 50 seconds; then taking out the wax model or wax model group coated with the water glass coating, and placing it in a boiling sand bed or a rain-type sand spreader for sanding treatment. After the sanding treatment is completed, it is naturally dried for 50 to 60 minutes to obtain the wax model sample (6); In step D: prepare the water glass coating again: mix the refractory powder and water glass in a mass ratio of 1.1:1, and then stir continuously for at least 4.0 hours and store for use; the water glass coating is stirred for 20 minutes before use and then left to stand for 5 minutes before use; the coating coating and sanding method are: immerse the wax mold or wax mold group that has already constructed a layer of water glass mold shell into the water glass coating, and let it stand for 30 to 50 seconds; then take out the wax mold or wax mold group that has already constructed a layer of water glass mold shell and coated with the water glass coating, and put it into a boiling sand bed and a rain shower sand spreader for sanding treatment. After the sanding treatment is completed, it is naturally dried for 40 to 50 minutes to obtain the wax mold sample (6), and then repeat the operation method of step BC to form a second layer of water glass mold shell on the surface of the wax mold sample (6); then construct a third layer of water glass mold shell on the surface of the wax mold or wax mold group according to the construction method of the second layer of water glass mold shell.

6. The water glass shell hardening process according to claim 5, characterized in that: In step C, the hardening reaction time is 9 minutes; the hardener solution is an ammonium chloride solution with a concentration of 5wt%; in step A, the refractory powder is 270-mesh quartz powder, and the sand and gravel used in the sand spreading treatment is 50-mesh and / or 70-mesh quartz sand; in step D, the refractory powder is a mixture of 270-mesh quartz powder and 200-mesh mullite powder in a mass ratio of 7:3, and the sand and gravel used in the sand spreading treatment is 20-mesh and / or 40-mesh quartz sand.

7. The water glass shell hardening process according to claim 1, characterized in that: In step E, the drying temperature is 5-30°C, and the drying time is 12-24h; the temperature of the hot water bath is 90-98°C, and the hot water bath time is 10-15min; during roasting, the temperature is first raised to 750°C at a rate of 5°C / min, then kept warm for 2.0h, and finally cooled to room temperature with the furnace.

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