Colloidal silica:<\/strong> This material is used as a binder in the slurries. It provides good thermal stability and is key to forming the ceramic layer. Ceramic flour:<\/strong> The refractory load of the slurries is composed of zirconium (zirconia), cobalt aluminate, fused silica, and aluminum silicates, materials that offer both mechanical strength and heat resistance.
Refractory sand<\/strong>: Aluminum oxide (alumina) and aluminum silicates are used as “stucco,” or coatings, which are progressively added in layers that evolve from fine to coarse grains, adding strength to the mold\u2019s internal and external layers.
These raw materials, strategic for EIPC\u2019s activities, are supplied by companies that ensure the highest quality worldwide, such as Ransom & Randolph<\/a>, Remet<\/a>, Imerys<\/a>, Arciresa, Chilches, Midegasa<\/a>, CCT, and many others. <\/p>\n
1. Colloidal Silica (Main Binder))<\/strong><\/p>\n Colloidal silica is the most commonly used binder in ceramic slurries. This material has a key function: providing cohesion to the ceramic particles that form the coating and giving structure to the mold. Colloidal silica is a suspension of small silicon dioxide (SiO2) particles in water, with particle sizes typically ranging from 5 to 25 nm. Its main properties are high thermal stability, great crack resistance, and easy handling. <\/p>\n As a suspension, it is easy to apply and has good flow and dispersion properties. Additionally, viscosity can be adjusted depending on the application. <\/p>\n Colloidal Silica Fascote<\/p><\/div>\n The concentration of colloidal silica in the suspension must be carefully controlled to ensure a good balance between strength and flexibility. Temperature and humidity in the production environment can affect the stability of the suspension, so they must be carefully monitored. <\/p>\n 2. Ceramic Flour (Refractory Material)<\/strong><\/p>\n Ceramic flour provides structure and mechanical strength to the ceramic coating. This flour is mainly composed of refractory materials that can withstand high temperatures without degrading. At EIPC, we mainly use three types of ceramic flour: <\/p>\n Particle size of ceramic flour influences the mold’s strength and its ability to capture fine details of the wax model. Finer particles are used in the inner layers to improve the surface finish of the final part, while coarser particles are used in the outer layers to provide structural support. <\/p>\n 3. Refractory Sand (Stucco)<\/strong><\/p>\n Refractory sand, or stucco, is applied over the initial ceramic coating layers and backup layers. This material adds stiffness and strength to each layer of the mold, ensuring it can support the weight of the molten metal without deforming or breaking. Commonly used types of refractory sand include Alumina and Aluminum Silicates. Alumina (Al2O3): <\/strong>Alumina is one of the most widely used refractory materials due to its high temperature resistance and excellent thermal stability. It has a melting point of approximately 2,072 \u00b0C, making it ideal for casting advanced alloys. It provides high wear resistance and is suitable for molds that endure intense thermal cycles. 4. Processing Additives<\/strong><\/p>\n Various additives are also used in ceramic slurries to improve the coating properties and optimize the application process.<\/p>\n Adding different types of resins or polymers to the Colloidal Silica formulations serves multiple purposes:<\/p>\n\n
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\nZirconium is a highly refractory material with an extremely high melting point, close to 2,715 \u00b0C. It offers excellent resistance to thermal shock, which is crucial when pouring very hot metals into the mold. Additionally, its low thermal conductivity helps control the metal\u2019s solidification rate, improving the grain structure of the solidified metal.. <\/li>\n
\nUsed as a nucleating agent, it is added to the primary bath for molds where superalloys will be cast, helping control surface grain size and offering the best nucleation effect.<\/li>\n
\nAlthough silica has a lower melting point (around 1.600 \u00b0C), it remains a key component in ceramic coatings due to its flowability and compatibility with other refractory materials. It is mainly used in the inner layers of the mold, as its thermal stability is sufficient for the early stages of metal pouring.
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Aluminum Silicates<\/strong> with variable Alumina content** (from 42% to 60%, depending on the metal to be cast and the size of the mold and parts). As with ceramic flour, the particle size of refractory sand is crucial. Larger particles are applied in the mold\u2019s backup layers to provide adequate mechanical strength, while finer particles are used in intermediate layers to improve mold density <\/p>\n\n