Regenerated spherical ceramsite sand, and preparation process and sand blasting process thereof

Abstract

The application discloses a kind of regenerated spherical ceramsite sand and its preparation process, sand blasting process, and relates to the field of metal surface treatment.It includes the following steps: the recyclable abrasive is prepared by sintering process to regenerate spherical ceramsite sand;The recyclable abrasive is obtained by sorting method from sandblasting abrasive.Through multi-stage sand blasting method to workpiece sand blasting treatment, including the following contents: first stage, 0.6~0.8MPa pressure, 60~75° incident angle is carried out rough spraying;Second stage, 0.3~0.5MPa pressure, 75~85° incident angle is carried out fine spraying;Third stage 0.1~0.2MPa pressure, 85~90° incident angle is carried out fine adjustment.The application realizes the efficient resource utilization of waste abrasive by efficient recovery sorting and internal regeneration cycle, solves the environmental pollution problem caused by waste abrasive stockpiling and disposal;Multi-stage sand blasting process avoids excessive treatment and repeated operation, and the optimized abrasive combination and dynamic sand blasting parameters ensure the high uniformity and controllability of workpiece surface cleanliness and roughness.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, specifically to a recycled spherical ceramic aggregate sand and its preparation process and sandblasting process. Background Technology

[0002] Traditional sandblasting is widely used in industrial production, but its inherent technical defects have not been effectively resolved. In practice, this process suffers from significant resource waste, with generally low abrasive utilization. Furthermore, the single and fixed blasting angle leads to uneven workpiece surface treatment, often requiring repeated sandblasting operations to achieve the desired results, further exacerbating the waste of time and resources.

[0003] In terms of process parameter control, traditional methods lack precise control over the particle size distribution of the abrasive, resulting in poor surface quality stability. Furthermore, the energy consumption of this process is unsatisfactory, with insufficient utilization of compressed air. More importantly, the large amount of dust generated during sandblasting causes serious environmental pollution, and operators are exposed to high-dust working environments for extended periods, posing significant occupational health risks.

[0004] In existing technologies, while circulating sandblasting equipment and environmentally friendly sandblasting machines have improved sand recovery and dust control to some extent, and environmentally friendly sandblasting machines achieve a sand separation efficiency of nearly 99% through improved separation systems, these devices are often complex in structure and expensive to implement, limiting their practical application. Furthermore, liquid sandblasting machines or water mist sandblasting technology, by mixing water and abrasive, can significantly suppress dust; for example, water mist sandblasting devices have achieved a 90% dust reduction target. However, these technologies may introduce water pollution problems (requiring additional wastewater treatment) or are unsuitable for working materials sensitive to moisture.

[0005] These existing technologies have failed to systematically and cost-effectively address the comprehensive challenges of traditional sandblasting processes in terms of efficiency, quality, and environmental protection. In particular, they still have significant shortcomings in the dynamic optimization of abrasive material configuration and the convenient adaptive adjustment of process parameters for different workpiece materials. Summary of the Invention

[0006] The purpose of this invention is to provide a recycled spherical ceramsite sand and its preparation process and sandblasting process, so as to improve the problems of low sand utilization and difficulty in balancing sandblasting quality and efficiency in traditional sandblasting technology.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A process for preparing recycled spherical ceramsite sand includes the following: preparing recycled spherical ceramsite sand from recyclable abrasive through a sintering process; wherein the recyclable abrasive is obtained from sandblasting abrasive through a sorting method.

[0009] Traditional sandblasting generates excessively fine abrasive particles that are considered worthless solid waste and are typically disposed of in landfills. This invention constructs a complete, internally circulating sandblasting system, transforming the traditional linear resource-waste model into a closed-loop resource-regeneration-resource model. For the first time, sandblasting operations are tightly integrated with the in-situ regeneration of waste abrasive particles. Through specific formulations and sintering processes, excessively fine abrasive particles, traditionally considered waste, are transformed into reusable recycled spherical ceramsite sand, achieving a high degree of resource recycling within the process system.

[0010] This invention significantly reduces the amount of new abrasive purchased through efficient recycling and sorting, achieving efficient resource utilization of waste abrasive and solving the environmental pollution problems caused by the stockpiling and disposal of waste abrasive.

[0011] Furthermore, spherical sand and irregularly shaped sand are mixed to form a mixed sand material, which is then used to blast the workpiece to obtain a blasting abrasive.

[0012] Furthermore, the mass ratio of spherical sand to irregularly shaped sand is 7~9:1; the mass ratio of Al2O3 to SiO2 in the spherical sand is 2.2~2.4:1, the particle size is 16~30 mesh, and the moisture content is less than 2%.

[0013] This invention employs a mixture of spherical and irregularly shaped abrasive particles in a specific ratio to form a hybrid abrasive. The spherical abrasive ensures good flowability and impact toughness, while the irregularly shaped abrasive particles provide excellent cutting ability. The synergistic effect of these two materials ensures both sandblasting efficiency and quality while reducing waste caused by the insufficient performance of a single abrasive particle. This invention also utilizes a multi-stage sorting process to screen the used abrasive and recycle reusable abrasive.

[0014] Furthermore, the sorting method includes the following: removing metal and metal oxide impurities from the sandblasting abrasive by magnetic separation; followed by three-stage sieving to obtain recyclable abrasive.

[0015] Furthermore, the three-stage screening includes the following:

[0016] First-stage sorting: passing through a 10-15 mesh sieve to remove oversized particles and foreign waste that cannot participate in recycling;

[0017] Second-stage sorting: Useful sand with qualified particle size that can be directly recycled is obtained through a 30-mesh sieve;

[0018] The third stage of sorting involves separating recyclable abrasive particles that are too fine and require a remanufacturing process to restore their performance through a 60-mesh sieve.

[0019] The first stage of sorting specifically removes excessively large particles due to breakage or contamination. If these particles re-enter the sandblasting system, they can easily clog pipes and nozzles, affecting system stability. The second stage of sorting precisely extracts abrasive particles within the optimal working range, recovering usable abrasive and ensuring its direct and efficient return to the sandblasting process, guaranteeing consistent sandblasting quality. The third stage actively separates excessively fine abrasive particles, providing pure and uniformly sized raw materials for preparing high-quality recycled spherical ceramic aggregate. Extremely fine dust passing through a 60-mesh sieve is collected and processed.

[0020] Furthermore, the sintering process includes the following steps:

[0021] Step 1: Ball mill the recyclable abrasive until more than 90% of the particles are smaller than 13μm;

[0022] Step 2: Add bauxite and adjust the mass ratio of Al2O3 to SiO2 to 2.2~2.4;

[0023] Step 3: Add TiO2 and CaO as sintering aids to form a liquid phase that promotes powder spheroidization and densification at the sintering temperature;

[0024] Step 4: Sinter at 1340~1550℃ for 2~3 hours to allow the material to form spherical particles under the action of liquid phase surface tension. Crush and deagglomerate the obtained sintered product and sieve it to obtain particles with a particle size of 16~30 mesh.

[0025] Step 5: When the furnace temperature is 800~1100℃, introduce nitrogen-carrying silane gas with a volume concentration of 1%~5% into the sintering furnace for 15~45 minutes.

[0026] The sintering process of this invention first obtains ultrafine active powder through ball milling, and then adds bauxite to adjust the aluminum-silicon ratio to an optimized range of 2.2-2.4, which lays the chemical foundation for the subsequent formation of a stable mullite crystalline phase. The introduction of TiO2 and CaO as composite sintering aids, at a high temperature of 1340-1550℃, does not simply promote sintering, but reacts with the system to generate a suitable amount of high-temperature liquid phase. This liquid phase, with its surface tension, effectively encapsulates and bridges solid particles, driving the powder agglomerates to automatically shrink, spheroidize, and densify during the heat preservation process, thereby reshaping the irregular fine powder into particles with properties similar to or the same as the original spherical sand.

[0027] First, the aluminum-silicon ratio of the entire system is precisely adjusted to the target range (2.2~2.4) by adding bauxite. This is the fundamental chemical composition that determines the type and content of the main crystalline phase in the final product. The bauxite is then thoroughly mixed with the powder obtained in step 1. After this, sintering aids (TiO2 and CaO) are added to optimize the sintering kinetics and prevent uncontrollable pre-reactions of these aids during the initial mixing process. This ensures that a uniform liquid phase is formed in a timely and appropriate manner at the formal sintering temperature, effectively driving the spheroidization and densification of the particles.

[0028] Deagglomeration refers to using relatively small forces to disperse sintered blocks in order to preserve the integrity of the original spherical particles that have formed within them. Subsequent sieving is for classification to obtain particles within the target particle size range (16-30 mesh).

[0029] Silane gas was introduced into the 800-1100℃ window for chemical vapor deposition. Even with nitrogen as the carrier gas, silane (SiH4) still underwent oxidation deposition; the reaction was not essentially a vigorous combustion with free oxygen. The main role of nitrogen was to create an oxygen-deficient carrier environment, inhibiting premature decomposition of silane in the gas phase to generate soot. The actual reaction occurred on the surface of the incandescent ceramsite sand: silane molecules underwent thermal decomposition at 800-1100℃, and the resulting highly reactive silicon species reacted with trace amounts of water vapor, hydroxyl groups, or trace amounts of oxygen adsorbed on the sand grain surface, resulting in a surface heterogeneous reaction. This process grew a dense, layer-by-layer, amorphous silica (SiO2) protective layer in situ on each sand grain.

[0030] The entire process does not require constant inert protection. The main sintering stages in steps 1-4 can be carried out in air, which is beneficial for the removal of organic matter from the raw materials and the formation of stable oxide phases. However, the surface densification treatment in step 5 must be carried out in an inert atmosphere such as nitrogen. Its core purpose is to strictly control the reaction path to ensure that silane is safely delivered to the material surface and deposited according to the set mechanism.

[0031] The sintering process of this invention produces recycled spherical ceramsite sand that is comparable to virgin sand in terms of core indicators such as sphericity, bulk density, and mechanical strength, fully meeting the requirements for sandblasting reuse and realizing a high-value closed-loop recycling of resources.

[0032] Furthermore, in step 2, the amount of bauxite added accounts for 5% to 30% of the mass of the recyclable abrasive.

[0033] Furthermore, in step 3, the amount of TiO2 added accounts for 0.5% to 2% of the mass of the recyclable abrasive; the amount of CaO added accounts for 3% to 8% of the mass of the recyclable abrasive.

[0034] Further, after step 1, 0.5% to 2% of α-alumina by mass is added to the ball-milled powder as an inert dispersant, and the mixture is stirred evenly.

[0035] The particle size of α-alumina is smaller than that of the final recycled sand, with a particle size of 40~100 mesh. α-Al2O3 has high chemical inertness, exists as intact particles, hardly participates in the reaction, and does not affect the main chemical composition. During the sintering process, it acts as a physical isolation medium to prevent particle adhesion and can be separated and recovered by sieving after sintering.

[0036] A type of recycled spherical ceramsite sand prepared by the aforementioned preparation process.

[0037] A sandblasting process using the aforementioned recycled spherical ceramsite sand for sandblasting, wherein the workpiece is sandblasted using a multi-stage sandblasting method, the multi-stage sandblasting method comprising the following:

[0038] In the first stage, a coarse spraying is performed using a pressure of 0.6~0.8MPa and an incident angle of 60~75° until the thick oxide scale, rust layer or original coating on the surface of the workpiece is completely removed.

[0039] In the second stage, a fine spraying is performed using a pressure of 0.3~0.5MPa and an incident angle of 75~85° until the surface reaches a cleanliness standard of Sa2.5 or higher.

[0040] The third stage involves fine-tuning with a pressure of 0.1~0.2MPa and an incident angle of 85~90° until the surface roughness stabilizes within the preset target range.

[0041] Traditional sandblasting typically uses a fixed set of parameters (pressure, angle) to complete the entire operation, relying on the operator's experience to judge the endpoint, which can easily lead to undertreatment or excessive damage. This invention deconstructs the sandblasting process into three functionally defined stages with progressively optimized parameters, transforming the process from a crude treatment to a controllable and predictable engineering process.

[0042] The first stage is coarse spraying, which uses high pressure (0.6~0.8MPa) and a small incident angle (60~75°) to efficiently peel off thick adhering materials using shear force. The target endpoint is to expose the substrate.

[0043] The second stage is fine spraying, which uses moderate pressure (0.3~0.5MPa) and optimized incident angle (75~85°) to begin building the surface profile while ensuring cleaning power. The target endpoint is to achieve the internationally recognized cleanliness standard (Sa2.5).

[0044] The third stage is fine-tuning, which uses lower pressure (0.1~0.2MPa) and a large incident angle (85~90°) to perform trimming with near-vertical impact. The target endpoint is to obtain a stable and uniform roughness (Ra value).

[0045] The multi-stage sandblasting method of this invention clearly defines the stage endpoints, avoiding human error and ensuring that every workpiece meets the preset cleanliness and roughness standards, significantly improving the first-pass yield. Staged processing avoids excessive damage or deformation to the substrate that might be caused by a single high-pressure mode. The fine-tuning stage achieves an extremely uniform surface profile, providing an optimal adhesion substrate for subsequent coatings. Simultaneously, the targeted coarse blasting stage removes major impurities with maximum efficiency, while the fine blasting and fine-tuning stages quickly achieve the target, greatly reducing the ineffective sandblasting time caused by trying to handle dead corners or achieve high standards under single parameters.

[0046] Compared with the prior art, the beneficial effects of the present invention are:

[0047] This invention achieves efficient resource utilization of waste abrasives through efficient recycling, sorting, and internal regeneration. The multi-stage sandblasting strategy avoids over-processing and repetitive operations, reducing single-piece processing time by more than 25%. Simultaneously, optimized abrasive combinations and dynamic sandblasting parameters ensure highly uniform and controllable surface cleanliness and roughness, with surface roughness consistency (Ra deviation range) optimized to ±0.5μm, significantly improving the first-pass yield. By adjusting the parameters and abrasive ratios at each stage, this process can be flexibly applied to sandblasting of various materials and requirements, from large steel structures to precision parts, and is suitable for workpieces such as ferromagnetic steel and cast iron. Detailed Implementation

[0048] Example 1

[0049] The recyclable abrasive is obtained from sandblasting abrasive through a sorting method.

[0050] Spherical sand and irregularly shaped sand are mixed to form a mixed sand material, which is then used for sandblasting of cast iron workpieces to obtain sandblasting abrasive; the mass ratio of spherical sand to irregularly shaped sand is 8:1; the mass ratio of Al2O3 to SiO2 in the spherical sand is 2.3:1, the particle size is 22 mesh, and the moisture content is 1.8%.

[0051] The sorting method includes the following: removing metal and metal oxide impurities from the abrasive through magnetic separation; followed by three-stage sieving to obtain recyclable abrasive. The three-stage sieving includes the following:

[0052] First-stage sorting: passing through a 12-mesh sieve to remove oversized particles and foreign waste that cannot participate in recycling;

[0053] Second-stage sorting: Useful sand with qualified particle size that can be directly recycled is obtained through a 30-mesh sieve;

[0054] The third stage of sorting involves separating recyclable abrasive particles that are too fine and require a remanufacturing process to restore their performance through a 60-mesh sieve.

[0055] Example 2

[0056] The recyclable abrasive is obtained from sandblasting abrasive through a sorting method.

[0057] Spherical sand and irregularly shaped sand are mixed to form a mixed sand material, which is then used for sandblasting of cast iron workpieces to obtain sandblasting abrasive. The mass ratio of spherical sand to irregularly shaped sand is 7:1. The mass ratio of Al2O3 to SiO2 in the spherical sand is 2.2:1, the particle size is 16 mesh, and the moisture content is less than 1.9%.

[0058] The sorting method includes the following steps: removing metal and metal oxide impurities from the sandblasting abrasive through magnetic separation; followed by three-stage sieving to obtain recyclable abrasive.

[0059] The three-stage screening includes the following:

[0060] First-stage sorting: passing through a 10-mesh sieve to remove oversized particles and foreign waste that cannot participate in recycling;

[0061] Second-stage sorting: Useful sand with qualified particle size that can be directly recycled is obtained through a 30-mesh sieve;

[0062] The third stage of sorting involves separating recyclable abrasive particles that are too fine and require a remanufacturing process to restore their performance through a 60-mesh sieve.

[0063] Example 3

[0064] The recyclable abrasive is obtained from sandblasting abrasive through a sorting method.

[0065] Spherical sand and irregularly shaped sand are mixed to form a mixed sand material, which is then used for sandblasting of cast iron workpieces to obtain sandblasting abrasive. The mass ratio of spherical sand to irregularly shaped sand is 9:1. The mass ratio of Al2O3 to SiO2 in the spherical sand is 2.4:1, the particle size is 30 mesh, and the moisture content is less than 1.7%.

[0066] The sorting method includes the following steps: removing metal and metal oxide impurities from the sandblasting abrasive through magnetic separation; followed by three-stage sieving to obtain recyclable abrasive.

[0067] The three-stage screening includes the following:

[0068] First-stage sorting: passing through a 15-mesh sieve to remove oversized particles and foreign waste that cannot participate in recycling;

[0069] Second-stage sorting: Useful sand with qualified particle size that can be directly recycled is obtained through a 30-mesh sieve;

[0070] The third stage of sorting involves separating recyclable abrasive particles that are too fine and require a remanufacturing process to restore their performance through a 60-mesh sieve.

[0071] The magnetic separation step preferably uses a strong magnetic separator with a background field strength of not less than 8000 Gauss to efficiently separate impurities, including strongly magnetic and weakly magnetic metal oxides.

[0072] Example 4

[0073] The preparation process of recycled spherical ceramsite sand includes the following: recyclable abrasive (obtained by the method in Example 1) is prepared into recycled spherical ceramsite sand through a sintering process;

[0074] The sintering process includes the following steps:

[0075] Step 1: Ball mill the recyclable abrasive for 11 hours until more than 92% of the particles are smaller than 12μm.

[0076] Add 1.2% by mass of α-alumina as an inert dispersant to the ball-milled powder with a particle size of 70 mesh, and mix for 45 minutes.

[0077] Step 2: Add bauxite, adjust the mass ratio of Al2O3 to SiO2 to 2.3:1, and mix with the powder obtained in Step 1 for 1 hour until uniform. The amount of bauxite added accounts for 18% of the mass of the recyclable abrasive.

[0078] Step 3: Add TiO2 and CaO as sintering aids and mix them evenly; so that they form a liquid phase that promotes powder spheroidization and densification at the sintering temperature;

[0079] The amount of TiO2 added accounts for 1.2% of the mass of the recyclable abrasive; the amount of CaO added accounts for 6% of the mass of the recyclable abrasive.

[0080] Step 4: Sinter at 1450℃ for 2.5 hours to form spherical particles under the action of liquid phase surface tension; crush and deagglomerate the obtained sintered product and sieve it to obtain particles with a particle size of 20 mesh.

[0081] Step 5: When the temperature inside the furnace drops to 950℃, introduce nitrogen-carrying silane gas with a volume concentration of 3% into the sintering furnace for 30 minutes.

[0082] Example 5

[0083] The preparation process of recycled spherical ceramsite sand includes the following: recyclable abrasive (obtained by the method in Example 1) is prepared into recycled spherical ceramsite sand through a sintering process;

[0084] The sintering process includes the following steps:

[0085] Step 1: Ball mill the recyclable abrasive for 10 hours until more than 90% of the particles are smaller than 13μm.

[0086] Add 0.5% by mass of α-alumina as an inert dispersant to the ball-milled powder, with a particle size of 40 mesh, and mix for 30 minutes.

[0087] Step 2: Add bauxite and adjust the mass ratio of Al2O3 to SiO2 to 2.2:1; mix with the powder obtained in Step 1 for 40 minutes until uniform. The amount of bauxite added accounts for 5% of the mass of the recyclable abrasive.

[0088] Step 3: Add TiO2 and CaO as sintering aids, mix them evenly, and let them form a liquid phase that promotes powder spheroidization and densification at the sintering temperature;

[0089] The amount of TiO2 added accounts for 0.5% of the mass of the recyclable abrasive; the amount of CaO added accounts for 3% of the mass of the recyclable abrasive.

[0090] Step 4: Sinter at 1340℃ for 2 hours to allow the material to form spherical particles under the action of liquid phase surface tension; crush and deagglomerate the obtained sintered product and sieve it to obtain particles with a particle size of 16 mesh.

[0091] Step 5: When the temperature inside the furnace drops to 800℃, introduce nitrogen-carrying silane gas with a volume concentration of 1% into the sintering furnace for 15 minutes.

[0092] Example 6

[0093] The preparation process of recycled spherical ceramsite sand includes the following: recyclable abrasive (obtained by the method in Example 1) is prepared into recycled spherical ceramsite sand through a sintering process;

[0094] The sintering process includes the following steps:

[0095] Step 1: Ball mill the recyclable abrasive for 12 hours until more than 93% of the particles are smaller than 11μm.

[0096] Add 2% by mass of α-alumina as an inert dispersant to the ball-milled powder with a particle size of 100 mesh, and mix for 30 minutes.

[0097] Step 2: Add bauxite, adjust the mass ratio of Al2O3 to SiO2 to 2.4:1, and mix with the powder obtained in Step 1 for 1.5 hours until uniform; the amount of bauxite added accounts for 30% of the mass of the recyclable abrasive.

[0098] Step 3: Add TiO2 and CaO as sintering aids and mix them evenly; so that they form a liquid phase that promotes powder spheroidization and densification at the sintering temperature;

[0099] The amount of TiO2 added accounts for 2% of the mass of the recyclable abrasive; the amount of CaO added accounts for 8% of the mass of the recyclable abrasive.

[0100] Step 4: Sinter at 1550℃ for 3 hours to allow the material to form spherical particles under the action of liquid phase surface tension; crush and deagglomerate the obtained sintered product and sieve it to obtain particles with a particle size of 30 mesh.

[0101] Step 5: When the temperature inside the furnace drops to 1100℃, introduce nitrogen-carrying silane gas with a volume concentration of 5% into the sintering furnace for 45 minutes.

[0102] Comparative Example 1

[0103] Step 3 is omitted, and bauxite is not added to adjust the mass ratio of Al2O3 to SiO2. Other steps and parameters are the same as in Example 4.

[0104] Comparative Example 2

[0105] Step 3 is omitted, and no sintering aid is added. Other steps and parameters are the same as in Example 4.

[0106] Comparative Example 3

[0107] Step 5 is missing; steps 1 through 4 are the same as in Example 4.

[0108] Comparative Example 4

[0109] After adding the bauxite from step 2 and the sintering aid from step 3 simultaneously, stir until homogeneous. Other steps and parameters are the same as in Example 4.

[0110] The performance parameters of the recycled spherical ceramsite sand prepared by the methods of Examples 4-6 and Comparative Examples 1-4 are compared with those of the initial spherical ceramsite sand (new sand) in Table 1.

[0111] Table 1 Performance parameters of the recycled spherical ceramsite sand prepared by the methods of Examples 4-6 and Comparative Examples 1-4

[0112]

[0113] As shown in Table 1, the spherical ceramsite sand prepared by the methods in Examples 4 to 6 can achieve a sphericity of up to 96%, a bulk density of up to 1.8 g / cm³, a compressive strength of up to 52 MPa, and a mullite phase content of up to 68%. The various performance parameters of the recycled spherical ceramsite sand are close to or even reach the standards of new sand, thus realizing the goal of converting waste into high-performance products.

[0114] Comparative Example 1 omitted the step of "adding bauxite to adjust the aluminum-silicon ratio," which directly resulted in the chemical composition of the material system not being precisely controlled, making it impossible to form a stable structure with mullite (3Al2O3·2SiO2) as the main crystalline phase. The mullite phase is key to providing high strength and high refractoriness; its absence leads to insufficient skeletal strength in the recycled sand, macroscopically manifested as a severe decrease in compressive strength (30MPa) and mullite phase content (35%). At the same time, due to insufficient sintering driving force, the particle densification and spheroidization processes are hindered, resulting in poor sphericity and bulk density.

[0115] Comparative Example 2 omitted the step of "adding TiO2 and CaO as sintering aids". The lack of sintering aids prevented the formation of a sufficient amount of silicate liquid phase at the sintering temperature to reduce interparticle interfacial energy and drive mass migration. The absence of the liquid phase resulted in powder particles primarily relying on solid-phase diffusion bonding, leading to extremely low mass transfer efficiency and hindering the full realization of surface tension-driven spheroidization and densification effects. Consequently, the prepared particles exhibited highly irregular shapes (sphericity only 70%) and numerous internal pores (bulk density only 1.50 g / cm³). 3 The structure is loose, and its compressive strength (25 MPa) is therefore greatly reduced. Although its aluminum-silicon ratio was adjusted and the mullite phase content (55%) was higher than that of Comparative Example 1, the advantages of this phase could not be translated into macroscopic mechanical properties because the sintered body was not dense.

[0116] Although Comparative Example 3 lacks surface treatment, it has composition adjustment and liquid phase sintering. Therefore, its basic properties (sphericity 88%, strength 38MPa) are significantly better than those of Comparative Example 1 and Comparative Example 2, which lack these two core steps, but are clearly lower than all examples.

[0117] In Comparative Example 4, all additives were added simultaneously. Although ball milling was performed, the particles of bauxite (used to adjust the main chemical composition) and sintering aid (used to generate a low-temperature liquid phase) were more prone to agglomeration at the microscale, resulting in less uniform distribution compared to the stepwise method of "adjusting the basic composition first and then precisely introducing the sintering aid." This led to local fluctuations in the location, quantity, and composition of the liquid phase during sintering. The uneven liquid phase caused the surface tension-driven spheroidization and densification processes to be asynchronous in different regions. Excessive liquid phase in some areas could cause particle adhesion, while insufficient liquid phase in others would result in inadequate densification. Strength is a direct reflection of structural uniformity. Microscopic inhomogeneities can become stress concentration points and weak points, leading to a significant decrease in overall strength. Uneven distribution of bauxite caused local deviations in the aluminum-silicon ratio (2.2~2.4), preventing the complete formation of a high-strength mullite network and increasing the amount of impurities.

[0118] The four core steps of this invention—composition adjustment, addition of sintering aid, liquid phase sintering, and surface treatment—form a synergistic organic whole. Without any one of them, it is impossible to prepare high-quality recycled spherical ceramsite sand that simultaneously possesses excellent basic properties and outstanding surface properties.

[0119] Example 7

[0120] A sandblasting process includes the following steps:

[0121] S100. The recycled spherical ceramsite sand (prepared by the method in Example 4) is mixed with irregularly shaped sand at a mass ratio of 8:1 to form a mixed abrasive.

[0122] S200. Using the aforementioned mixed abrasive, a multi-stage sandblasting method is used to perform sandblasting on the cast iron workpiece.

[0123] Multi-stage sandblasting methods include the following:

[0124] In the first stage, coarse spraying is performed using a pressure of 0.7 MPa and an incident angle of 68° until the thick oxide scale, rust layer or original coating on the workpiece surface is completely removed. In the second stage, fine spraying is performed using a pressure of 0.4 MPa and an incident angle of 80° until the surface reaches a cleanliness standard of Sa2.5 or higher. In the third stage, fine adjustment is performed using a pressure of 0.15 MPa and an incident angle of 88° until the surface roughness is stable within the preset target range.

[0125] Example 8

[0126] A sandblasting process includes the following steps:

[0127] S100. The recycled spherical ceramsite sand (prepared by the method in Example 4) is mixed with irregularly shaped sand at a mass ratio of 7:1 to form a mixed abrasive.

[0128] S200. Using the aforementioned mixed abrasive, a multi-stage sandblasting method is used to perform sandblasting on the cast iron workpiece.

[0129] Multi-stage sandblasting methods include the following:

[0130] In the first stage, coarse spraying is performed using a pressure of 0.6 MPa and an incident angle of 60° until the thick oxide scale, rust layer or original coating on the workpiece surface is completely removed. In the second stage, fine spraying is performed using a pressure of 0.3 MPa and an incident angle of 75° until the surface reaches a cleanliness standard of Sa2.5 or higher. In the third stage, fine adjustment is performed using a pressure of 0.1 MPa and an incident angle of 85° until the surface roughness is stable within the preset target range.

[0131] Example 9

[0132] A sandblasting process includes the following steps:

[0133] S100. The recycled spherical ceramsite sand prepared in Example 1 (prepared by the method in Example 4) is mixed with irregularly shaped sand at a mass ratio of 9:1 to form a mixed abrasive.

[0134] S200. Using the aforementioned mixed abrasive, a multi-stage sandblasting method is used to perform sandblasting on the cast iron workpiece.

[0135] Multi-stage sandblasting methods include the following:

[0136] In the first stage, coarse spraying is performed using a pressure of 0.8 MPa and an incident angle of 75° until the thick oxide scale, rust layer or original coating on the workpiece surface is completely removed. In the second stage, fine spraying is performed using a pressure of 0.5 MPa and an incident angle of 85° until the surface reaches a cleanliness standard of Sa2.5 or higher. In the third stage, fine adjustment is performed using a pressure of 0.2 MPa and an incident angle of 90° until the surface roughness is stable within the preset target range.

[0137] Example 10

[0138] A sandblasting process includes the following steps:

[0139] S100. The initial spherical ceramsite sand (new sand) is mixed with irregularly shaped sand at a mass ratio of 8:1 to form a mixed abrasive.

[0140] S200. Using the aforementioned mixed abrasive, a multi-stage sandblasting method is used to perform sandblasting on the cast iron workpiece.

[0141] Multi-stage sandblasting methods include the following:

[0142] In the first stage, coarse spraying is performed using a pressure of 0.7 MPa and an incident angle of 68° until the thick oxide scale, rust layer or original coating on the workpiece surface is completely removed. In the second stage, fine spraying is performed using a pressure of 0.4 MPa and an incident angle of 80° until the surface reaches a cleanliness standard of Sa2.5 or higher. In the third stage, fine adjustment is performed using a pressure of 0.15 MPa and an incident angle of 88° until the surface roughness is stable within the preset target range.

[0143] Example 11

[0144] A sandblasting process includes the following steps:

[0145] S100: Spherical sand and irregularly shaped sand are mixed at a mass ratio of 8:1 to form a mixed abrasive.

[0146] The mass ratio of Al2O3 to SiO2 in the spherical sand is 2.3:1, the particle size is 20 mesh, and the moisture content is 1.8%.

[0147] The spherical sand is a mixture of the initial spherical ceramsite sand (new sand) and the regenerated spherical ceramsite sand prepared in Example 4, with a mass ratio of 1:1; S200~S500 are the same as in Example 7.

[0148] Example 12

[0149] A sandblasting process includes the following steps:

[0150] S100: Spherical sand and irregularly shaped sand are mixed at a mass ratio of 8:1 to form a mixed abrasive.

[0151] The mass ratio of Al2O3 to SiO2 in the spherical sand is 2.3:1, the particle size is 20 mesh, and the moisture content is 1.8%.

[0152] The spherical sand is a mixture of the initial spherical ceramsite sand (new sand) and the regenerated spherical ceramsite sand prepared in Example 4, with a mass ratio of 1:2; S200~S500 are the same as in Example 7.

[0153] Comparative Example 5

[0154] The same recycled spherical ceramsite sand as in Example 7 was used, but a single-stage sandblasting was performed using only the second-stage parameters (0.4 MPa, 80°) of Example 7 until the same cleanliness standard was achieved. The recycling and sorting process was the same as in Example 7.

[0155] Comparative Example 6

[0156] The same initial spherical ceramsite sand (new sand) as in Example 7 was used, but a single-stage sandblasting was performed using only the second-stage parameters (0.4 MPa, 80°) of Example 7 until the same cleanliness standard was achieved. The recycling and sorting process was the same as in Example 7.

[0157] The workpieces were sandblasted using the methods of Examples 7-12 and Comparative Examples 5-6, and the performance parameters are shown in Table 2.

[0158] Table 2 Performance parameters of sandblasting treatment of workpieces using the methods of Examples 7-12 and Comparative Examples 5-6

[0159]

[0160] As shown in Table 2, Examples 7-9, through a closed-loop recycling-sorting-regeneration process, all achieved a sand utilization rate of 92%. Comparing Example 7 (fully recycled sand) and Example 10 (virgin sand), which used the same multi-stage process, it can be found that both performed similarly in key process indicators such as processing time, surface quality consistency, and operating environment (dust concentration), with Example 7 even slightly superior. This indicates that the recycled spherical ceramsite sand prepared by the method of this invention has achieved and slightly exceeded the level of commercial virgin sand in terms of flowability, cutting efficiency, and anti-fracture performance, making it suitable for high-standard sandblasting operations.

[0161] Example 7 (recycled sand, multi-stage) and Comparative Example 5 (recycled sand, single-stage): Despite using the same recycled sand, Example 7 reduced the single-piece processing time from 19.5 minutes to 15.2 minutes with a multi-stage process, resulting in an efficiency improvement of over 28%.

[0162] The consistency of surface roughness (Ra deviation range) was significantly improved from ±2.1 μm in a single-stage process to ±0.5 μm. This is because the multi-stage process is specifically designed to homogenize the surface profile, avoiding the overall over-blasting or poor uniformity issues caused by the single-stage process's focus on cleaning localized stubborn points. Similarly, a completely consistent pattern was observed between Comparative Example 6 (fresh sand, single-stage) and Example 10 (fresh sand, multi-stage), with Example 10 showing shorter time and better quality. This demonstrates that the multi-stage blasting strategy is a universally applicable and efficient method.

[0163] The best overall performance is seen in Example 12, which uses a high proportion of recycled sand (initial sand: recycled sand = 1:2) combined with a multi-stage process, achieving the highest sand utilization rate (94%), the shortest processing time (14.9 min), and the most stable surface quality (Ra deviation ±0.4 μm).

[0164] The recycled spherical ceramsite sand of the present invention uses usable abrasive produced by sandblasting new sand as raw material. Any other usable abrasive obtained by using the method of the present invention and any method for preparing recycled spherical ceramsite sand are within the protection scope of the present invention.

Claims

1. A process for preparing recycled spherical ceramsite sand, characterized in that, This includes the following: preparing recyclable abrasives into recycled spherical ceramic aggregates through a sintering process; The recyclable abrasive is obtained from sandblasting abrasive through a sorting method; The sintering process includes the following steps: Step 1: Ball mill the recyclable abrasive until more than 90% of the particles are smaller than 13μm; Step 2: Add bauxite and adjust the mass ratio of Al2O3 to SiO2 to 2.2~2.4:1; Step 3: Add TiO2 and CaO as sintering aids; Step 4: Sinter at 1340~1550℃ for 2~3 hours, then crush and deagglomerate the sintered product and sieve it to obtain particles with a particle size of 16~30 mesh. Step 5: When the furnace temperature is 800~1100℃, introduce nitrogen-carrying silane gas with a volume concentration of 1%~5% into the sintering furnace for 15~45 minutes.

2. The preparation process according to claim 1, characterized in that, Spherical sand and irregularly shaped sand are mixed to form a mixed sand material, which is then used to blast the workpiece to obtain a blasting abrasive.

3. The preparation process according to claim 2, characterized in that, The mass ratio of spherical sand to irregularly shaped sand is 7~9:1; the mass ratio of Al2O3 to SiO2 in the spherical sand is 2.2~2.4:1, the particle size is 16~30 mesh, and the moisture content is less than 2%.

4. The preparation process according to claim 2, characterized in that, The sorting method includes the following steps: removing metal and metal oxide impurities from the sandblasting abrasive through magnetic separation; followed by three-stage sieving to obtain recyclable abrasive.

5. The preparation process according to claim 4, characterized in that, The three-stage screening includes the following: First-stage sorting: passing through a 10-15 mesh sieve to remove oversized particles and foreign waste that cannot participate in recycling; Second-stage sorting: Useful sand with qualified particle size that can be directly recycled is obtained through a 30-mesh sieve; The third stage of sorting involves separating recyclable abrasive particles that are too fine and require a remanufacturing process to restore their performance through a 60-mesh sieve.

6. The preparation process according to claim 1, characterized in that, In step 2, the amount of bauxite added accounts for 5% to 30% of the mass of the recyclable abrasive; in step 3, the amount of TiO2 added accounts for 0.5% to 2% of the mass of the recyclable abrasive; and the amount of CaO added accounts for 3% to 8% of the mass of the recyclable abrasive.

7. The preparation process according to claim 1, characterized in that, After step 1, 0.5% to 2% of α-alumina by mass is added to the ball-milled powder as an inert dispersant, and the mixture is stirred evenly.

8. A recycled spherical ceramsite sand prepared by the preparation process described in any one of claims 1 to 7.

9. A sandblasting process using recycled spherical ceramsite sand as described in claim 8, characterized in that, The workpiece is sandblasted using a multi-stage sandblasting method, which includes the following: In the first stage, a coarse spraying is performed using a pressure of 0.6~0.8MPa and an incident angle of 60~75° until the thick oxide scale or original coating on the surface of the workpiece is completely removed. In the second stage, a fine spraying is performed using a pressure of 0.3~0.5MPa and an incident angle of 75~85° until the surface reaches a cleanliness standard of Sa2.5 or higher. The third stage involves fine-tuning with a pressure of 0.1~0.2MPa and an incident angle of 85~90° until the surface roughness stabilizes within the preset target range.

Images