In the precision instruments of modern industry, in the common articles of daily life, copper casting plays an indispensable role with its unique performance and charm. From the key mechanical components in the industrial field to the exquisite crafts that decorate life, copper casting is like a low-key hero behind the scenes, silently supporting the operation of our lives. You may not notice it, but it's everywhere. Today, let's walk into the world of copper casting and explore the mystery and story behind it.

First, the production process of copper casting is revealed

(1) Raw material preparation and mold design

The production of copper castings is like a carefully prepared performance, every link is crucial. The first is raw material preparation, which is a key step in laying the foundation of copper casting quality. Copper, as the main raw material, its purity and impurity content directly affect the performance of castings. Common copper raw materials are copper, brass, bronze, etc., each of which has unique physical and chemical properties, suitable for different types of copper casting production. For example, copper has good electrical and thermal conductivity and is often used in the manufacture of electrical components; Brass, with its high strength and corrosion resistance, plays an important role in the field of mechanical manufacturing and decoration; Bronze's excellent wear resistance and casting properties make it an ideal choice for precision instruments and works of art. In addition to copper, other alloying elements, such as zinc, tin, lead, etc. will be added according to actual needs to further improve the performance of copper casting.

After the raw materials are ready, the mold design becomes the core link to determine the shape and dimensional accuracy of the copper casting. The mold is like the "cradle" of copper casting, and its design quality is directly related to the quality of the final product. Mold design needs to consider the shape of the product, size, accuracy requirements and production volume and other factors. For copper castings with complex shapes, design methods such as parting molds and loose blocks may be required to ensure that the copper liquid can fill the mold cavity smoothly and release the mold smoothly after cooling and solidification. At the same time, the machining accuracy of the mold is also crucial, and the high-precision mold can ensure that the dimensional tolerance of the copper casting is controlled within a very small range, so as to meet the needs of various high-precision application scenarios. Nowadays, with the wide application of computer-aided design (CAD) and computer-aided manufacturing (CAM) technology, the efficiency and accuracy of mold design and manufacturing have been greatly improved, which provides a strong guarantee for the high-quality production of copper castings.

(2) The key links of smelting and casting

When the raw materials and molds are ready, they enter the two closely linked key links of smelting and casting. Melting is the process of melting copper and other alloy raw materials into liquid form at high temperatures, which requires precise control of parameters such as temperature, time and atmosphere in the furnace. Excessive temperature may lead to excessive inhalation of copper liquid, resulting in porosity and other defects; If the temperature is too low, the fluidity of the copper liquid will become worse and the molding quality of the casting will be affected. In the melting process, it is also necessary to add an appropriate amount of flux and deoxidizer to remove impurities and oxides in the copper liquid and improve the purity and quality of the copper liquid. For example, commonly used fluxes are borax, cryolite, etc., which can reduce the melting point of impurities and make it easier to separate from copper liquid; Deoxidizer, such as phosphorus copper, magnesium, etc., can effectively remove oxygen in copper liquid to prevent oxidation defects in castings.

Casting is the process of injecting the melted copper liquid into the mold cavity to cool and solidify the copper casting in the desired shape. Common casting methods are sand casting, centrifugal casting, precision casting, continuous casting and low pressure casting, each method has its own unique principle and scope of application. Sand casting is the most traditional and widely used casting method, which takes sand as molding material and forms mold cavity by making sand mold. This method has the advantages of simple process and low cost, and is suitable for the production of copper castings of various shapes and sizes, but the dimensional accuracy and surface quality of castings are relatively low. Centrifugal casting is the use of centrifugal force to evenly distribute copper liquid in the rotating mold cavity, so as to obtain dense tissue, no shrinkage and porosity casting. This method is often used to manufacture copper castings with symmetrical shapes such as tubes and rings, such as copper sleeves and rings. Precision casting, also known as lost wax casting, it is based on a wax mold as a prototype, by coating multiple layers of refractory material on the surface of the wax mold to make a mold shell, and then the wax mold is melted and discharged to obtain a hollow mold shell, and then the copper liquid is injected into the mold shell for casting. Precision casting can obtain copper castings with high dimensional accuracy and good surface quality, which is suitable for manufacturing precision parts with various complex shapes, such as aircraft engine blades and medical equipment parts. Continuous casting is the continuous injection of copper liquid into a specific crystallizer, so that it gradually cools and solidifies during movement to form continuous ingots or castings. This method has high production efficiency and is suitable for large-scale production of copper bars, copper plates and other profiles. Low pressure casting is under the action of low pressure gas, copper liquid is slowly pressed into the mold cavity for casting. It can effectively control the filling speed and pressure of copper liquid, reduce the porosity and inclusions in castings, improve the quality and performance of castings, and is often used in the manufacture of automobile engine cylinder block, cylinder head and other important parts.

(3) Post-treatment process: achieve perfect copper casting

The copper casting after the completion of the casting is only a "semi-finished product", which needs to go through a series of post-processing processes in order to become a perfect product with excellent performance and beautiful appearance. The post-treatment process mainly includes cooling stripping, cleaning, heat treatment, mechanical processing and other links, each link has an important impact on the final quality of copper casting.

Cooling demudding is the first step of copper casting after processing, which is related to the dimensional accuracy of the casting and the stability of the internal structure. Too fast cooling speed may lead to cracks and deformation of castings; If the cooling speed is too slow, the production efficiency will be affected. Therefore, it is necessary to reasonably control the cooling speed according to the shape, size and material of the casting. Generally speaking, for large castings or castings with uneven wall thickness, slow cooling is often used, such as natural cooling in the sand mold or slow cooling in the insulation furnace; For small castings or castings that require high dimensional accuracy, rapid cooling methods can be used, such as cooling in water or spray cooling in air. When releasing the mold, care should be taken to avoid damage to the casting, and appropriate release agents or mechanical auxiliary devices can be used to ensure that the casting is smoothly removed from the mold.

The cleaning process is to remove the sand, oxide, flash and burr and other impurities on the surface of the copper casting, so that the surface of the casting is smooth and smooth. Common cleaning methods include mechanical cleaning, chemical cleaning and electrochemical cleaning. Mechanical cleaning such as shot blasting, sandblasting, grinding, etc., through the high-speed injection of projectiles or abrades impact the surface of the casting to remove impurities; Chemical cleaning is the use of chemical solution and impurities chemical reaction, dissolve or remove it; Electrochemical cleaning is the removal of impurities on the surface of the casting by electrochemical action in the electrolyte. After cleaning, the surface quality of the copper casting has been significantly improved, which has laid a good foundation for subsequent processing and treatment.

Heat treatment is a process of changing the internal structure and performance of copper casting by heating, holding and cooling. Common heat treatment processes are annealing, normalizing, quenching and tempering. Annealing can eliminate the residual stress inside the casting, improve its plasticity and toughness; Normalizing can refine grain and improve the strength and hardness of castings. Quenching can make castings obtain high hardness and high strength, but it will increase its brittleness; Tempering is carried out after quenching, used to eliminate quenching stress, adjust the hardness and toughness of the casting, so that it can achieve the best comprehensive performance. For example, for some copper castings that need to bear a large impact load, such as mechanical parts, tools, etc., a combination of quenching and tempering processes is often used to improve their wear resistance and impact resistance.

Machining is according to the design requirements of the product, cutting, grinding, drilling, boring and other processing operations on the copper casting, so that it can achieve the exact size and surface roughness requirements. Machining can further improve the accuracy and surface quality of copper castings to meet the needs of various high-precision application scenarios. For example, for some copper castings used in precision instruments, electronic equipment and other fields, high-precision machining is required to ensure its matching accuracy and performance requirements with other parts. In the machining process, it is necessary to reasonably select the machining tool, cutting parameters and processing technology to ensure the processing quality and efficiency.