Casting ball quenching method and quenching agent

Abstract

The invention provides a casting ball quenching method and a quenching agent. The casting ball quenching method comprises the steps that casting ball surface cleaning, heat treatment, quenching, tempering and natural cooling are conducted, and strength optimization is conducted on a casting ball. According to the method, through the procedures, a controlled heat treatment environment is provided for the cast balls. And particularly, the temperature and time control in the heating stage lays a foundation for obtaining an austenite structure with uniform components, and the accurate matching of subsequent quenching and tempering ensures that the structure is fully transformed to a target martensite and a tempered structure. The whole process control effectively reduces the structure difference caused by process fluctuation, so that the finished cast balls produced in batches show high consistency in key performance indexes such as hardness and wear resistance. According to the method, the water-based quenching liquid is adopted for quenching, so that negative problems caused by quenching of quenching oil can be effectively solved.

Description

TECHNICAL FIELD

[0001] The application relates to a steel piece strength optimization technology, in particular to a cast ball quenching method and a quenching agent. BACKGROUND

[0002] Metal heat treatment is an important part in the mechanical manufacturing process, and the quenching process is an important factor determining the success or failure of heat treatment. Quenching is a process of rapidly cooling the workpiece after heating to a certain temperature. Because steel materials can obtain different organizational structures with the change of heating temperature and cooling speed after heating, and different organizational structures have different mechanical properties, the workpiece can obtain different properties through quenching to meet the use requirements of the workpiece working conditions, so as to achieve the purpose of ensuring product quality.

[0003] The grinding ball for grinding, that is, the cast ball, needs to use the collision and friction of the grinding ball and the material to achieve material crushing in the working process. Such high-strength collision and friction can cause the grinding ball to wear out quickly and the ball adding cycle to be short. Therefore, higher requirements are put forward for the strength of the grinding ball in the grinding crushing process. Quenching is one of the most effective and most widely used strength optimization methods. Because oil quenching can reduce the risk of deformation and cracking, the existing grinding ball adopts the oil quenching mode for strength optimization. However, the oil quenching hardness is low, the hardness of the product core to the surface is uneven, the core hardness is low, the surface hardness is high, the breaking condition is easy to appear, and the oil quenching oil smoke pollution is large and easy to ignite. SUMMARY

[0004] The application provides a cast ball quenching method and a quenching agent to solve the negative problems caused by oil quenching of the cast ball.

[0005] In a first aspect, the application provides a cast ball quenching method, which comprises the following steps: After the surface of the cast ball to be treated is cleaned, the cast ball is sent into a heating furnace for heating to obtain a heat-treated cast ball; The heat-treated cast ball is sent into a quenching tank and quenched by using a quenching liquid prepared by the quenching agent to obtain a quenched cast ball; The quenched cast ball is sent into a tempering furnace, and the quenched cast ball is kept at a tempering temperature for 8-10 hours to obtain a tempered cast ball; The tempered cast ball is naturally cooled to obtain a finished cast ball.

[0006] The scheme of the application has the following beneficial effects: 1) The scheme of the present application provides a controlled heat treatment environment for the cast ball through a standardized sequence of cleaning, heating, quenching, tempering and cooling processes. In particular, the temperature and time control of the heating stage lays the foundation for obtaining a homogeneous austenite structure, and the precise coordination of the subsequent quenching and tempering ensures sufficient transformation of the structure to the target martensite and tempered structure. This whole-process control effectively reduces the differences in the structure caused by process fluctuations, making the finished cast balls in batch production consistent in key performance indicators such as hardness and wear resistance.

[0007] 2) In the scheme of the present application, a tempering process of 8-10 hours is set to specifically eliminate the internal stress generated during the quenching process. This treatment not only significantly reduces the brittleness of the cast ball and improves its impact toughness, but also maintains most of the hardness obtained by quenching. Ultimately, the finished cast ball achieves a good combination of high hardness and high toughness, meeting the requirements for wear resistance and crushing resistance under grinding conditions.

[0008] 3) The gradual heating design in the scheme of the present application avoids the huge thermal stress generated by the instantaneous exposure of the cast ball to high temperature; the limitation of quenching liquid temperature, concentration and other parameters adjusts the cooling intensity. These measures work together to effectively suppress the tendency of cracks and deformation in the cast ball caused by excessive stress during the heat treatment process. The direct effect is to improve the product qualification rate and dimensional stability, and prolong the service life of the cast ball in service.

[0009] Optionally, the surface cleaning includes the following steps: The cast ball to be treated is subjected to ultrasonic cleaning for 20-30 minutes, and then rinsed with clean water after ultrasonic cleaning; The water on the surface of the rinsed cast ball is then blown dry.

[0010] Optionally, the heating temperature in the heating furnace is set to have multiple temperature zones from low to high; the cast ball to be treated is uniformly passed through the multiple temperature zones in the direction of increasing temperature during heating; The heating cycle is 22±2 minutes.

[0011] Optionally, the heating temperature in the heating furnace is set to have 4 temperature zones from low to high; The temperature of the first temperature zone is 530-580°C, the temperature of the second temperature zone is 720-760°C, the temperature of the third temperature zone is 860-900°C, and the temperature of the fourth temperature zone is 960-980°C.

[0012] Optionally, the quenching time is 10-12 minutes; The temperature of the quenching liquid is 45°C±5°C.

[0013] Optionally, the volume concentration of the quenching liquid is 90-98%, and the viscosity is 10-11 mPa·s.

[0014] Optionally, the tempering temperature is 360~400℃.

[0015] Secondly, this application provides a quenching agent for use in the quenching method of cast balls according to any one of the first aspects above, comprising, by weight, 15-25 parts polyether, 3-5 parts corrosion inhibitor, 3-5 parts rust inhibitor, 0.5-1.2 parts defoamer and 70-80 parts purified water.

[0016] Optionally, the polyether has a relative molecular weight of 50,000 to 60,000; The preservative consists of tert-butylhydroquinone and P123 mixed in a 2:3 ratio; Rust inhibitors include isopropanolamine, ethylenediamine, phytic acid, and sodium molybdate; The defoamer is a fluorosilicone defoamer.

[0017] Optionally, the rust inhibitor is formulated with isopropanolamine, ethylenediamine, phytic acid and sodium molybdate in a weight ratio of 1:(1~2):(2.5~4):(2~3).

[0018] The quenching agent provided in this application has the following beneficial effects: 1) In this application, the quenching agent uses polyether in a specific proportion as the main functional component. When the high-temperature cast ball is immersed, the polyether precipitates on the workpiece surface to form a uniform thin film, which can effectively reduce the cooling rate in the high-temperature stage and reduce the risk of thermal stress and deformation cracking. In the low-temperature stage, the thin film dissolves, the cooling rate accelerates, and sufficient hardening depth is ensured. This formulation makes the cooling curve between water quenching and oil quenching, realizing precise control of the cooling process.

[0019] 2) This application contains specific amounts of a corrosion inhibitor and a rust inhibitor. The corrosion inhibitor effectively inhibits microbial growth, prevents the quenching fluid from spoiling and deteriorating, and extends its service life. The rust inhibitor forms a protective film on the surface of the workpiece and the circulating system pipelines, preventing rust from forming during the quenching process and between processes. The addition of an antifoaming agent ensures the smooth flow of the liquid and the efficiency of heat exchange during the quenching process. These components together ensure the long-term stability of the quenching medium itself and the processed workpiece.

[0020] 3) In this application, the quenching agent uses purified water as the main matrix, which has inherent advantages over all-oil quenching agents or certain organic solvents, such as low cost, non-flammability, and no smoke pollution. The specified concentration range of each component ensures the above performance while avoiding the cost increase caused by excessive use. Moreover, the water-based medium is easier to clean and treat later, which helps to reduce the overall production and operation costs and environmental burden. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this application.

[0022] In a first aspect, this application provides a method for quenching cast balls, comprising the following steps: After cleaning the surface of the casting balls to be treated, they are sent into a heating furnace for heating to obtain heat-treated casting balls. The heat-treated cast balls are fed into a quenching tank and quenched with a quenching liquid prepared with a quenching agent to obtain quenched cast balls. The quenched casting balls are fed into a tempering furnace and held at the tempering temperature for 8-10 hours to obtain tempered casting balls. The tempered casting balls are allowed to cool naturally to obtain the finished casting balls.

[0023] In this application, the entire quenching process includes four steps: cleaning, heating, quenching, and tempering. This process is based on metallurgical principles and aims to alter the internal microstructure of the cast balls through systematic heat treatment, thereby endowing them with specific mechanical properties. Each step has a clear technical objective, and the seamless transition between steps is crucial to the quality of the final product.

[0024] Surface cleaning, as an initial step, is necessary to remove casting residues, scale, grease, and other contaminants adhering to the surface of the cast balls. If these contaminants are present in subsequent heating stages, they will lead to uneven heating, causing localized overheating or decarburization. Decarburization will reduce the surface carbon content, severely weakening the surface hardness and wear resistance achievable after quenching. Therefore, thorough surface cleaning is a prerequisite for ensuring heating uniformity and the purity of the base material.

[0025] The core purpose of the heating process is to induce austenitization in the cast balls. This involves heating the balls above the critical temperature to transform their internal structure (such as ferrite and pearlite) entirely into uniform austenite. Austenite, as a solid solution of carbon in γ-Fe, is a prerequisite for obtaining the target microstructure—martensite—through subsequent quenching. Controlling the heating process, including the heating rate and holding time, directly determines the size and compositional uniformity of the austenite grains.

[0026] The quenching process involves rapidly immersing uniformly austenitized cast balls into a quenching medium for rapid cooling. This rapid cooling inhibits the transformation of austenite into an equilibrium structure (ferrite and pearlite), promoting its transformation into martensite at a lower temperature. Martensite is a supersaturated solid solution with a high degree of lattice distortion, which can significantly improve the hardness and strength of the material. However, the quenching process is accompanied by enormous thermal and structural stresses, which, if not properly controlled, can easily lead to workpiece deformation or cracking.

[0027] Tempering is a necessary process to address the high internal stress and brittleness of quenched cast balls. Tempering involves reheating the quenched cast ball to a temperature below its critical point and holding it at that temperature. This causes the unstable martensite to decompose, precipitating fine carbides and effectively eliminating internal stress. This process significantly improves the toughness and dimensional stability of the material while maintaining sufficient hardness.

[0028] The final "natural cooling" is achieved through air cooling, as the cooling rate after tempering has minimal impact on the already stabilized tempered microstructure. Air cooling is a simple process with low energy consumption and avoids the introduction of new internal stresses due to excessively rapid cooling.

[0029] In summary, the complete process consisting of these four steps, through strict control of the thermal effects at each stage, aims to enable the finished cast balls to achieve the best comprehensive mechanical properties, combining high hardness, high wear resistance, and good impact toughness.

[0030] The solution proposed in this application has the following beneficial effects: 1) The solution presented in this application provides a controlled heat treatment environment for the cast balls through a standardized sequence of cleaning, heating, quenching, tempering, and cooling processes. In particular, the temperature and time control during the heating stage lays the foundation for obtaining a uniform austenitic microstructure, while the precise coordination of subsequent quenching and tempering ensures the full transformation of the microstructure into the target martensite and tempered microstructure. This end-to-end control effectively reduces microstructural differences caused by process fluctuations, ensuring consistency in key performance indicators such as hardness and wear resistance in mass-produced cast balls.

[0031] 2) In the scheme of this application, an 8-10 hour tempering process is set up to specifically eliminate the internal stress generated during the quenching process. This treatment not only significantly reduces the brittleness of the cast balls and improves their impact toughness, but also retains most of the hardness obtained from quenching. Ultimately, the finished cast balls achieve a good combination of high hardness and high toughness, meeting the requirements for wear resistance and anti-breakage ability under grinding conditions.

[0032] 3) The gradual heating design in this application avoids the enormous thermal stress generated by the instantaneous exposure of the cast balls to high temperatures; the limitation of parameters such as the temperature and concentration of the quenching fluid regulates the cooling intensity. These measures work together to effectively suppress the tendency for defects such as cracks and deformation in the cast balls due to excessive stress during heat treatment. The direct effect is to improve the product qualification rate and dimensional stability, and extend the service life of the cast balls.

[0033] Optionally, surface cleaning includes the following steps: The casting balls to be treated are ultrasonically cleaned for 20-30 minutes, and then rinsed with clean water. Then blow dry the water on the surface of the cast balls after rinsing.

[0034] In this application, a three-step operation process of "ultrasonic cleaning, rinsing with clean water, and drying" is adopted in the surface cleaning process. This step clarifies the specific implementation method of the cleaning process, and ensures the thoroughness and consistency of the cleaning through the combination of physical and mechanical means.

[0035] Ultrasonic cleaning utilizes the cavitation effect generated by high-frequency sound waves in a liquid medium. The localized high-pressure shock waves produced when cavitation bubbles collapse effectively impact the workpiece surface, peeling off firmly attached contaminants such as molding sand, iron oxide scale, and oil. Limiting the cleaning time to 20 to 30 minutes is based on a comprehensive consideration of cleaning efficiency and energy consumption. Too short a time may result in incomplete removal of stubborn contaminants, especially impurities within the microscopic pits on the surface of cast balls; too long a time leads to increased energy consumption and diminishing returns on cleaning effectiveness. Therefore, this time range achieves stable and efficient cleaning results. To further enhance cleaning performance, cleaning agents can be added to the cleaning water to assist in the cleaning process.

[0036] The water rinsing step follows ultrasonic cleaning and aims to remove any remaining microparticles (or cleaning agent) that have been peeled off but are still suspended on the surface of the cast balls after ultrasonic cleaning. If this step is omitted, these residues will form a film on the surface of the cast balls, becoming a source of contamination or causing surface defects during subsequent heating. Using running water for rinsing ensures that the residues are effectively washed away.

[0037] The drying step, as the final step in the cleaning process, removes moisture from the surface of the cast balls. If the cast balls carry moisture into the heating furnace, the moisture will rapidly vaporize at high temperatures, not only accelerating surface oxidation and forming a scale, but also potentially causing surface decarburization due to the water vapor atmosphere, severely damaging the material properties. Furthermore, the presence of moisture may interfere with the uniformity of the temperature field within the heating furnace. Using compressed air or hot air for drying is an efficient method that ensures the complete drying of the cast ball surface and crevices.

[0038] Therefore, the specific cleaning process, through repeatable and verifiable operational steps, provides technical assurance for obtaining clean and dry casting balls to be treated, laying the foundation for the stable execution of subsequent heat treatment processes.

[0039] Optionally, the heating furnace is equipped with multiple temperature zones with the heating temperature increasing from low to high; the cast balls to be processed pass through the multiple temperature zones at a uniform speed in the direction of increasing temperature during heating. The heating cycle is 22±2 min.

[0040] This application employs a combination of multi-temperature zone progressive heating and a fixed heating cycle. This approach aims to address the problems of deformation, cracking, and uneven microstructure that easily occur in cast balls, especially large-section or high-alloy cast balls, during rapid heating.

[0041] Multi-zone progressive heating refers to dividing the heating furnace along the conveying direction into several independently controlled zones with progressively increasing temperatures. The cast balls pass through these zones sequentially at a constant speed, essentially undergoing a controlled, slow heating process. The primary advantage of this design is a significant reduction in thermal stress. Heating the cast balls from the low-temperature zone maintains a low cross-sectional temperature difference, avoiding the enormous thermal stress generated by rapid temperature increases from the surface inwards, thus effectively suppressing plastic deformation and cracking tendencies in the workpiece. Secondly, this method is beneficial for obtaining a uniform and fine austenitic microstructure. Sufficient holding time in lower temperature zones (such as the preheating zone) allows the transformation of pearlite to austenite and the initial dissolution of carbides to proceed gradually. By the time the cast balls enter the highest temperature zone, the microstructure is already prepared for final homogenization, helping to prevent austenite grain coarsening caused by direct high-temperature heating.

[0042] Uniform feed rate is crucial for ensuring consistency in the heating process. A constant feed rate ensures that each cast ball experiences the exact same temperature-time curve, eliminating batch-to-batch or intra-batch product quality variations caused by speed fluctuations, and improving process stability and repeatability.

[0043] A heating cycle of 22±2 min represents precise control of the total heating time. This time parameter, along with the temperature zone setting, temperature gradient, and feed rate, determines the degree of austenitization. Too short a time may lead to insufficient core transformation or uneven composition; too long a time may result in excessive austenite grain growth and accelerated surface oxidation and decarburization. Experiments have verified that a cycle of 22±2 min can achieve sufficient and uniform austenitization of the cast balls under the specified conditions. The ±2 min tolerance provides the necessary margin for error in equipment control during industrial production.

[0044] Optionally, the heating furnace has four temperature zones with the heating temperature increasing from low to high; The temperature in the first temperature zone is 530~580℃, the temperature in the second temperature zone is 720~760℃, the temperature in the third temperature zone is 860~900℃, and the temperature in the fourth temperature zone is 960~980℃.

[0045] In this application, the specific temperature limits for the temperature zone configuration of the heating furnace are defined above, and the set values ​​for the four temperature zones are specified. This temperature sequence constitutes an optimized heating curve, with each temperature zone undertaking a specific function of heat processing and microstructure transformation.

[0046] The first temperature zone is set at 530~580℃, and its main function is preheating and stress relief. This temperature is below the critical phase transformation point of steel, but it is sufficient to allow the cast balls to heat up slowly and uniformly from room temperature, effectively eliminating residual casting stress and providing a safety guarantee for subsequent heating at higher temperatures, avoiding thermal shock.

[0047] The second temperature zone is set at 720~760℃, which is close to or slightly higher than the lower critical temperature of many steel grades. In this temperature zone, the microstructure of the cast balls begins to transform from pearlite to austenite. Setting this intermediate temperature plateau allows the phase transformation process to start gradually, carbides to begin dissolving, and the microstructure to prepare for complete austenitization, avoiding the severe phase transformation stress caused by jumping directly from the preheating zone to the high-temperature zone.

[0048] The third temperature range is set at 860~900℃, which is significantly higher than the critical point, ensuring that the microstructure of the cast balls completely transforms into austenite. Holding at this temperature allows for the initial diffusion of carbon and alloying elements, achieving preliminary homogenization of the austenite composition. Compared to directly heating to higher temperatures, this temperature range helps control the austenite grain size and prevents grain coarsening.

[0049] The fourth temperature zone is set at 960~980℃. The purpose of this highest temperature zone is to achieve the final homogenization of austenite, especially to promote the full dissolution of alloy carbides (such as chromium and molybdenum carbides). For alloy cast steel, only when the alloying elements are fully dissolved in austenite can they fully exert their effects of improving hardenability and strengthening after quenching. The selection of this temperature ensures the dissolution of alloy carbides, while controlling the residence time in this temperature zone (determined by the total heating cycle) suppresses excessive grain growth.

[0050] The temperature settings of these four temperature zones reflect a progressive, controlled heating process from preheating, phase transformation initialization, complete austenitization to full dissolution of alloying elements, aiming to provide an ideal austenitic structure with uniform composition and moderate grain size for quenching.

[0051] It should also be noted that the lengths of these four temperature zones are equal, but the lengths of each zone can be modified according to individual needs to change the heating time in different zones.

[0052] Optionally, the quenching time is 10~12 min; The temperature of the quenching fluid is 45℃±5℃.

[0053] In this application, the aforementioned features define two key operating parameters for the quenching process: quenching immersion time and the working temperature of the quenching medium. These two parameters together determine the cooling rate curve of the cast ball and are key control factors for achieving a balance between high hardness and low stress / deformation.

[0054] The quenching time is specified as 10 to 12 minutes, determined based on the cross-sectional dimensions of the cast ball and the cooling characteristics of the selected quenching fluid. Quenching cooling must ensure that the cast ball rapidly passes through the most unstable temperature region of austenite (approximately 550-600°C) from the surface to the core, and ultimately cools below the martensitic transformation termination temperature (Mf point). For cast balls with a certain diameter, heat dissipation from the core takes time. If the quenching time is insufficient (less than 10 minutes), the core temperature may still be higher than the martensitic transformation initiation temperature (Ms point), and will transform into a non-martensitic structure (such as bainite or pearlite) during subsequent air cooling, resulting in insufficient core hardness. Setting a quenching time of 10-12 minutes aims to ensure that even large-section cast balls can complete the martensitic transformation in their core, achieving uniform cross-sectional hardness. Simultaneously, this time avoids unnecessary excessive soaking, optimizing the production cycle.

[0055] The quenching fluid temperature is controlled within the range of 45℃±5℃ (i.e., 40 to 50℃) based on the temperature sensitivity of polymer-based quenching fluids to cooling characteristics. The quenching fluid temperature directly affects its cooling capacity. If the temperature is too low (e.g., room temperature 20℃), the cooling rate is too fast, especially in the high-temperature zone, easily generating enormous thermal stress and increasing the risk of cracking and deformation. If the temperature is too high (e.g., exceeding 60℃), the cooling rate is too slow, which may not be able to avoid the "nose" of the austenite transformation curve, causing some of the microstructure to transform into a soft phase, resulting in insufficient hardness. Stable temperature control within the 45℃±5℃ range allows the quenching fluid to provide a relatively mild and controllable cooling rate: a moderate cooling rate in the high-temperature zone to reduce thermal stress, and a sufficiently fast cooling rate in the low-temperature zone to ensure hardenability. Maintaining a constant quenching fluid temperature is a necessary condition for ensuring consistent product quality. The ±5℃ control tolerance provides an allowable range for temperature fluctuations in industrial production.

[0056] In this application, during the quenching process, the quenching tank is continuously circulated and stirred by multiple circulating pumps. The heat-treated cast balls are placed in corresponding cradles, and the cradles are continuously shaken during the quenching process to ensure that the cast balls are quenched evenly. Each cradle contains 380±20 kg of heat-treated cast balls.

[0057] Optionally, the volume concentration of the quenching fluid is 90-98%, and the viscosity is 10-11 mPa·s.

[0058] In this application, the aforementioned features specifically define the physicochemical properties of the quenching fluid, clarifying its volume concentration and viscosity range. These parameters directly determine the cooling characteristics of the quenching medium and are the material basis for achieving the quenching effect.

[0059] The volume concentration is limited to 90% to 98%, which is a relatively high concentration range. A high concentration means a high polymer molecular chain density in the quenching fluid. When the high-temperature cast ball is immersed, a continuous and stable polymer film can quickly form on its surface. This film significantly alters the cooling process: it prolongs and stabilizes the vapor film stage, slows down the cooling rate in the highest temperature range of the cast ball (>600°C), thus effectively reducing thermal shock; it also regulates the cooling intensity of the boiling stage, making the entire cooling process smoother. This high concentration setting aims to achieve an ideal cooling characteristic between water (too fast cooling) and oil (too slow cooling), possessing a sufficiently fast low-temperature cooling rate to ensure hardenability, while also having a relatively slow high-temperature cooling rate to inhibit crack formation. Strictly controlling the concentration within a narrow range of 90-98% is crucial to ensuring batch-to-batch consistency of the quenching fluid's cooling performance.

[0060] Viscosity control is crucial for cooling uniformity. A quenching fluid with appropriate viscosity maintains good fluidity, ensuring that all parts of the cast ball are uniformly surrounded and wetted by the medium, avoiding cooling differences caused by poor flow or uneven adhesion, thus preventing soft spots and deformation. Viscosity and concentration are usually correlated; this viscosity range (10–11 mPa·s) matches high concentrations, indicating that the selected polymer type and molecular weight design are reasonable. Excessively high viscosity leads to poor fluidity and large carry-over losses; excessively low viscosity may affect the integrity of the polymer film, weakening its slow cooling effect. Therefore, a viscosity range of 10–11 mPa·s is necessary to ensure both cooling uniformity and economy.

[0061] Optionally, the tempering temperature is 360~400℃.

[0062] In this application, the aforementioned features specify the temperature parameters for the tempering process. Tempering temperature is the most important variable for adjusting the final mechanical properties of quenched martensite. Setting the tempering temperature in the range of 360°C to 400°C is based on the specific requirements of the service conditions for the cast balls (requiring both high wear resistance and good impact toughness).

[0063] From a metallographic perspective, tempering is a diffusion process that transforms metastable quenched martensite into a stable microstructure. As the tempering temperature increases, the martensite decomposition undergoes different stages. In the temperature range of 360–400°C, martensite undergoes significant decomposition, cementite precipitates in the form of fine spherical particles and begins to aggregate, and internal stress is fully relieved. The transformation product is primarily tempered troostite, which consists of a ferrite matrix and dispersed fine spherical carbides.

[0064] This temperature range was chosen based on the following performance balance considerations: First, tempering at this temperature effectively retains most of the material's hardness. The tempered troostite structure maintains a high hardness level, meeting the core requirement of wear resistance for cast balls. Second, compared to tempered martensite obtained through low-temperature tempering, tempered troostite exhibits significantly improved toughness, plasticity, and impact resistance. This good balance between hardness and toughness allows the cast balls to effectively resist abrasive wear while being less prone to brittle fracture when subjected to severe impacts and wear from grinding media, thus extending their service life.

[0065] Furthermore, the tempering temperature should be chosen to avoid the tempering brittleness temperature range of the material. By controlling the upper limit of this temperature range (400℃) and combining it with a long holding time (8~10 hours), it may help to mitigate the harmful effects of the brittle phase. The long holding time ensures that the heat and diffusion process fully proceed to the core of the cast ball, achieving uniformity of cross-sectional properties.

[0066] Therefore, limiting the tempering temperature to 360~400℃, combined with long-term tempering, aims to obtain cast ball products with a structure characterized by tempered troostite, possessing both high hardness and good toughness, in order to meet their specific service performance requirements.

[0067] Secondly, this application provides a quenching agent for use in the quenching method of cast balls according to any one of the first aspects above, comprising, by weight, 15-25 parts polyether, 3-5 parts corrosion inhibitor, 3-5 parts rust inhibitor, 0.5-1.2 parts defoamer and 70-80 parts purified water.

[0068] In this application, the aforementioned technical features clearly define the basic composition and core proportion range of the quenching agent. This formulation system uses water as the continuous phase, polyether in a specific proportion as the main functional polymer, and is supplemented with necessary additives. The polyether, as the core component, is key to achieving controllable cooling characteristics due to its inverse solubility in water: it precipitates at high temperatures and forms a thin film on the workpiece surface, regulating the cooling rate; it redissolves at low temperatures, restoring solution homogeneity. The addition of corrosion inhibitors aims to prevent the quenching fluid from reacting and deteriorating, extending its service life. Rust inhibitors are used to protect the cast balls from corrosion during the quenching process. Defoamers are used to control foam that may be generated during quenching due to vigorous stirring and polymer action, ensuring cooling uniformity and pumping stability.

[0069] The quenching agent provided in this application has the following beneficial effects: 1) In this application, the quenching agent uses polyether in a specific proportion as the main functional component. When the high-temperature cast ball is immersed, the polyether precipitates on the workpiece surface to form a uniform thin film, which can effectively reduce the cooling rate in the high-temperature stage and reduce the risk of thermal stress and deformation cracking. In the low-temperature stage, the thin film dissolves, the cooling rate accelerates, and sufficient hardening depth is ensured. This formulation makes the cooling curve between water quenching and oil quenching, realizing precise control of the cooling process.

[0070] 2) This application contains specific amounts of a corrosion inhibitor and a rust inhibitor. The corrosion inhibitor effectively inhibits microbial growth, prevents the quenching fluid from spoiling and deteriorating, and extends its service life. The rust inhibitor forms a protective film on the surface of the workpiece and the circulating system pipelines, preventing rust from forming during the quenching process and between processes. The addition of an antifoaming agent ensures the smooth flow of the liquid and the efficiency of heat exchange during the quenching process. These components together ensure the long-term stability of the quenching medium itself and the processed workpiece.

[0071] 3) In this application, the quenching agent uses purified water as the main matrix, which has inherent advantages over all-oil quenching agents or certain organic solvents, such as low cost, non-flammability, and no smoke pollution. The specified concentration range of each component ensures the above performance while avoiding the cost increase caused by excessive use. Moreover, the water-based medium is easier to clean and treat later, which helps to reduce the overall production and operation costs and environmental burden.

[0072] Optionally, the polyether has a relative molecular weight of 50,000 to 60,000; The preservative consists of tert-butylhydroquinone and P123 mixed in a 2:3 ratio; Rust inhibitors include isopropanolamine, ethylenediamine, phytic acid, and sodium molybdate; The defoamer is a fluorosilicone defoamer.

[0073] In this application, the relative molecular weight of the polyether is 50,000 to 60,000 because molecular weight directly affects the viscosity of the polymer solution and the properties and stability of the film formed on the workpiece surface. Polyethers within this molecular weight range can form continuous films with suitable thickness and strength, thereby providing an optimal cooling profile. The corrosion inhibitor is specified to be a 2:3 mixture of tert-butylhydroquinone (antioxidant) and P123 (i.e., polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer), which can produce a synergistic effect, both inhibiting oxidative degradation and enhancing its distribution and effectiveness through surface activity. The rust inhibitor is specifically composed of four substances: isopropanolamine (organic amine), ethylenediamine (organic amine), phytic acid (organophosphonic acid), and sodium molybdate (inorganic passivator). This combination covers multiple rust prevention mechanisms such as vapor phase corrosion inhibition, adsorption film formation, and passivation, providing comprehensive rust protection. The defoamer is a fluorosilicone defoamer because it has extremely high defoaming and foam-suppressing efficiency and chemical stability. It can effectively deal with foam problems in water-based systems, especially those containing surfactants, and can maintain stable chemical properties during long-term use.

[0074] Optionally, the rust inhibitor is formulated with isopropanolamine, ethylenediamine, phytic acid and sodium molybdate in a weight ratio of 1:(1~2):(2.5~4):(2~3).

[0075] In this application, isopropanolamine and ethylenediamine, as organic amines, are in a ratio of approximately 1:(1~2). They synergistically provide an alkaline environment and form a protective layer on the metal surface through adsorption. Phytic acid, as a natural metal chelating agent, can form a dense passivation film by chelating with metal ions. Sodium molybdate, as an anodic corrosion inhibitor, is matched with phytic acid to jointly enhance the passivation film effect. The above ratio ensures that the volatile protection of amines, the strong film-forming ability of phytic acid, and the oxidative passivation effect of sodium molybdate are effectively combined, forming a multi-layered, highly efficient protective system, thus providing excellent rust prevention performance for various metal materials such as cast iron and steel. Specific Implementation Example

[0076] S101. The casting balls to be treated are ultrasonically cleaned for 20 minutes at a frequency of 20-40 kHz. After ultrasonic cleaning, they are rinsed with clean water and the surface of the cast balls is dried. The surface-cleaned casting balls are then sent into a heating furnace and passed through the first, second, third, and fourth temperature zones at a uniform speed in the direction of increasing temperature to obtain heat-treated casting balls. The heating cycle is 22 ± 2 minutes. The temperature in the first temperature zone is 530℃, the temperature in the second temperature zone is 720℃, the temperature in the third temperature zone is 860℃, and the temperature in the fourth temperature zone is 960℃. The time taken for the casting balls to pass through each temperature zone is equal.

[0077] S102. The heat-treated cast balls are fed into a quenching tank and quenched with a quenching liquid with a volume concentration of 90%, a viscosity of 10~11 mPa·s, and a temperature of 45℃±5℃ for 10 minutes to obtain quenched cast balls.

[0078] S103. The quenched casting balls are sent into a tempering furnace and held at a tempering temperature of 360℃ for 10 hours to obtain tempered casting balls.

[0079] S104. Allow the tempered cast balls to cool naturally to room temperature to obtain the finished cast balls. Example

[0080] S201. The casting balls to be treated are ultrasonically cleaned for 30 minutes at a frequency of 20-40 kHz. After ultrasonic cleaning, they are rinsed with clean water and the surface of the cast balls is dried. The surface-cleaned casting balls are then sent into a heating furnace and passed through the first, second, third and fourth temperature zones at a uniform speed in the direction of increasing temperature to obtain heat-treated casting balls. The heating cycle is 22 ± 2 minutes. The temperature in the first temperature zone is 580℃, the temperature in the second temperature zone is 760℃, the temperature in the third temperature zone is 900℃, and the temperature in the fourth temperature zone is 970℃. The time taken for the casting balls to pass through each temperature zone is equal.

[0081] S202. The heat-treated cast balls are fed into a quenching tank and quenched with a quenching liquid with a volume concentration of 98%, a viscosity of 10~11 mPa·s, and a temperature of 45℃±5℃ for 12 minutes to obtain quenched cast balls.

[0082] S203. The quenched casting balls are sent into a tempering furnace and held at a tempering temperature of 400℃ for 8 hours to obtain tempered casting balls.

[0083] S204. Allow the tempered cast balls to cool naturally to room temperature to obtain the finished cast balls. Example

[0084] S301. The casting balls to be treated are ultrasonically cleaned for 25 minutes at a frequency of 20-40 kHz. After ultrasonic cleaning, they are rinsed with clean water and the surface of the cast balls is dried. The surface-cleaned casting balls are then sent into a heating furnace and passed through the first, second, third and fourth temperature zones at a uniform speed in the direction of increasing temperature to obtain heat-treated casting balls. The heating cycle is 22 ± 2 minutes. The temperature in the first temperature zone is 550℃, the temperature in the second temperature zone is 750℃, the temperature in the third temperature zone is 880℃, and the temperature in the fourth temperature zone is 980℃. The time taken for the casting balls to pass through each temperature zone is equal.

[0085] S302. The heat-treated cast balls are fed into a quenching tank and quenched with a quenching liquid with a volume concentration of 95%, a viscosity of 10~11 mPa·s, and a temperature of 45℃±5℃ for 10 minutes to obtain quenched cast balls.

[0086] S303. The quenched casting balls are sent into a tempering furnace and held at a tempering temperature of 380℃ for 8 hours to obtain tempered casting balls.

[0087] S304. Allow the tempered cast balls to cool naturally to room temperature to obtain the finished cast balls.

[0088] Comparative Example 1 The remaining operations are the same as in Example 3, except that commercially available quenching oil is used for quenching.

[0089] Φ80 high-chromium cast balls were selected as the experimental object. The surface hardness of the untreated Φ80 high-chromium cast balls was 55HRC.

[0090] The Φ80 high-chromium cast balls were processed according to the methods of Examples 1 to 3 and Comparative Example 1. Each treatment consisted of 50 Φ80 high-chromium cast balls. After treatment, the hardness and strength after quenching and the hardness after tempering (calculated as average values) as well as the impact resistance and breakage rate were measured using the method of GB / T 17445-2022.

[0091] The casting balls treated using the method of this application have a quenching hardness of more than 65 HRC compared to the traditional oil quenching of 61 HRC, and a tempering hardness of more than 62 HRC compared to the oil quenching of 59 HRC. The average impact resistance can also reach 3.8 J. In the crushing test, the breakage rate is zero. It can be seen that the solution of this application can effectively improve the surface mechanical properties and overall strength of the casting balls.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for quenching cast balls, characterized in that, Includes the following steps: After cleaning the surface of the casting balls to be treated, they are sent into a heating furnace for heating to obtain heat-treated casting balls. The heat-treated cast balls are fed into a quenching tank and quenched with a quenching liquid prepared with a quenching agent to obtain quenched cast balls. The quenched casting balls are fed into a tempering furnace and held at the tempering temperature for 8-10 hours to obtain tempered casting balls. The tempered casting balls are allowed to cool naturally to obtain the finished casting balls.

2. The method for quenching cast balls according to claim 1, characterized in that, The surface cleaning includes the following steps: The casting balls to be treated are ultrasonically cleaned for 20-30 minutes, and then rinsed with clean water. Then blow dry the water on the surface of the cast balls after rinsing.

3. The method for quenching cast balls according to claim 1, characterized in that, The heating furnace has multiple temperature zones with the heating temperature increasing from low to high; the cast balls to be processed pass through the multiple temperature zones at a constant speed in the direction of increasing temperature during heating. The heating cycle is 22±2 min.

4. The method for quenching cast balls according to claim 1, characterized in that, The heating furnace has four temperature zones with the heating temperature increasing from low to high. The temperature in the first temperature zone is 530~580℃, the temperature in the second temperature zone is 720~760℃, the temperature in the third temperature zone is 860~900℃, and the temperature in the fourth temperature zone is 960~980℃.

5. The method for quenching cast balls according to claim 1, characterized in that, The quenching time is 10~12 minutes; The temperature of the quenching fluid is 45℃±5℃.

6. The method for quenching cast balls according to claim 1, characterized in that, The quenching fluid has a volume concentration of 90-98% and a viscosity of 10-11 mPa·s.

7. The method for quenching cast balls according to claim 1, characterized in that, The tempering temperature is 360~400℃.

8. A quenching agent, characterized in that, When applied to the method according to any one of claims 1 to 7, the quenching agent comprises, by weight, 15 to 25 parts polyether, 3 to 5 parts corrosion inhibitor, 3 to 5 parts rust inhibitor, 0.5 to 1.2 parts defoamer, and 70 to 80 parts purified water.

9. The quenching agent according to claim 8, characterized in that, The polyether has a relative molecular weight of 50,000 to 60,000; The preservative comprises tert-butylhydroquinone and P123 mixed in a 2:3 ratio; The rust inhibitor includes isopropanolamine, ethylenediamine, phytic acid, and sodium molybdate; The defoamer is a fluorosilicone defoamer.

10. The quenching agent according to claim 9, characterized in that, The rust inhibitor is formulated with isopropanolamine, ethylenediamine, phytic acid and sodium molybdate in a weight ratio of 1:(1~2):(2.5~4):(2~3).