Laptop Hinge Titanium Alloy
Lost wax casting, also known as investment casting, is a precision casting method. The principle is to first use wax to create a wax mold with the same shape as the desired casting, and then apply multiple layers of refractory material on the surface of the wax mold to form a complete shell. Next, heat the shell to melt the wax mold and let it flow out, forming a cavity inside the shell that matches the shape of the wax mold. Finally, pour molten metal into this cavity, and after the metal cools and solidifies, break the mold to obtain the desired casting.
The principle of lost wax casting and its advantages in the application of titanium alloy in laptop shafts
Lost wax casting, also known as investment casting, is a precision casting method. The principle is to first use wax to create a wax mold with the same shape as the desired casting, and then apply multiple layers of refractory material on the surface of the wax mold to form a complete shell. Next, heat the shell to melt the wax mold and let it flow out, forming a cavity inside the shell that matches the shape of the wax mold. Finally, pour molten metal into this cavity, and after the metal cools and solidifies, break the mold to obtain the desired casting.
The use of titanium alloy wax casting for laptop shafts has significant advantages. From the perspective of material properties, titanium alloys have the characteristics of low density, high strength, and good corrosion resistance. Low density can reduce the overall weight of laptops and make them easy to carry; High strength can ensure that the shaft is not easily deformed during frequent opening and closing processes, extending its service life; Good corrosion resistance can prevent the shaft from being oxidized or corroded in different environments, maintaining stable appearance and performance. From the perspective of casting technology, lost wax casting can produce shaft components with complex shapes and high precision. Laptop shafts usually have unique structural designs, such as multiple bends and fine tooth grooves inside. Lost wax casting can accurately replicate these complex shapes, meet design requirements, and ensure the functionality and assembly accuracy of the shaft.
Process flow of wax loss casting of titanium alloy for laptop shaft
Firstly, based on the design drawings of the laptop shaft, high-precision molds are machined using CNC machine tools. The accuracy of the mold directly affects the quality of the wax mold, so strict control of dimensional tolerances and surface roughness is required during the processing. Then, heat the wax material to a molten state. Generally, the melting point of the wax material is between 60-80 ℃, and inject the molten wax material into the mold cavity through an injection machine. The injection pressure and speed need to be adjusted according to the size and complexity of the wax mold to ensure that the wax material can fill the entire cavity without producing defects such as bubbles or shrinkage. After the wax material cools and solidifies, open the mold and remove the wax mold. Conduct a preliminary inspection of the wax mold, remove excess parts such as burrs and burrs, and measure the dimensions to ensure that the wax mold meets the design requirements.
Assemble the pre made wax mold onto the sprue bar to form a module. This can cast multiple shaft components at once, improving production efficiency. Next, the module is degreased to remove oil and impurities from the wax mold surface, ensuring better adhesion of subsequent coatings. Immerse the module in a specially designed coating, which is usually composed of refractory materials (such as silica sol, zircon sand, etc.) and binders. The viscosity and particle size of the coating need to be strictly controlled to ensure the uniformity and thickness of the coating. Then sprinkle a layer of sand on the surface of the module, and the particle size of the sand is selected according to the number of coating layers and requirements. Generally speaking, the first layer of sand particles is finer to ensure the surface accuracy of the shell, and the subsequent layers of sand particles gradually become coarser to increase the strength of the shell. Repeat the process of dipping and sanding until the shell reaches the desired thickness, usually requiring 5-7 layers of coating. Put the coated shell into a hardener for hardening treatment to give the shell sufficient strength and hardness. Finally, the shell is placed in a roasting furnace for roasting, with a roasting temperature generally between 800-1000 ℃ and a time of 2-4 hours. The purpose of roasting is to remove moisture, organic matter, and binders from the shell, making it denser and more stable.
Select appropriate titanium alloy raw materials and determine the alloy composition based on the performance requirements of the shaft. Common titanium alloys include Ti-6Al-4V, which have excellent comprehensive properties. Put the titanium alloy raw materials into a vacuum induction furnace for melting, and the vacuum degree inside the furnace needs to be controlled between 10 ⁻³ -10 ⁻⁴ Pa to prevent the titanium alloy from being oxidized during the melting process. The melting temperature is generally between 1600-1800 ℃. The raw materials are completely melted by electromagnetic induction heating and thoroughly stirred to ensure the uniformity of the alloy composition. After the titanium alloy liquid reaches the appropriate temperature and fluidity, it is poured into the preheated shell. The pouring process needs to be carried out under the protection of inert gas (such as argon) to prevent the titanium alloy liquid from coming into contact with air and being oxidized during the pouring process. The pouring speed and pressure need to be adjusted according to the size and shape of the mold to ensure that the titanium alloy liquid can smoothly fill the mold cavity.
After the titanium alloy liquid cools and solidifies, break the shell and remove the casting. Use mechanical processing methods (such as turning, grinding, etc.) to remove sprues, risers, and excess burrs, burrs, etc. on the surface of castings, in order to achieve the desired smoothness and dimensional accuracy. Heat treat castings to improve their microstructure and properties. Common heat treatment processes include annealing, quenching, tempering, etc. The specific process parameters need to be determined based on the composition of the titanium alloy and the requirements for casting use. Perform non-destructive testing (such as ultrasonic testing, X-ray testing, etc.) on the castings after heat treatment to check for defects such as cracks and porosity inside the castings. Surface treatment such as anodizing, spraying, etc. shall be carried out on castings that have passed the inspection to improve their corrosion resistance and appearance quality.
Quality Control and Testing
Raw material inspection
Perform chemical composition analysis on the purchased titanium alloy raw materials, using spectral analysis and other methods to ensure that the alloy composition meets the design requirements. Test the physical properties of titanium alloy raw materials, such as density, hardness, etc., to ensure the quality stability of the raw materials. Quality testing is also required for auxiliary materials such as wax and coatings to ensure their performance meets the requirements of the casting process.
Process monitoring
During the wax mold production process, the size and surface quality of the wax mold are regularly inspected, and the injection process parameters are adjusted in a timely manner. During the manufacturing process of the shell, the thickness, strength, and breathability of the shell are checked to ensure its quality. During the melting and pouring process of titanium alloys, real-time monitoring of parameters such as furnace temperature, vacuum degree, and pouring speed is carried out to ensure the stability of the casting process.
Finished Product Inspection
Perform dimensional accuracy testing on the cast laptop shaft using equipment such as a coordinate measuring instrument to ensure that all dimensions of the shaft meet the design tolerance requirements. Test the mechanical properties of the shaft, such as strength, toughness, fatigue life, etc., through methods such as tensile testing, bending testing, and fatigue testing. Inspect the surface quality of the rotating shaft to check for defects such as cracks, sand holes, and air holes. Use metallographic microscopes and other equipment to observe the microstructure of the castings to ensure they meet quality standards.
Development Trends and Challenges
Development Trend
With the development of laptops towards slimness and high performance, the requirements for the accuracy and performance of the hinge are becoming increasingly high. The lost wax casting technology will continue to improve, enhancing the dimensional accuracy and surface quality of castings to meet market demand. In order to further improve production efficiency and reduce costs, the lost wax casting process will develop towards automation and intelligence. For example, using robots for wax mold production, shell coating, and other operations can reduce manual intervention and improve production stability and consistency. Develop new titanium alloy materials and wax loss casting processes to meet the usage requirements of laptop shafts in different environments, such as high temperature, high humidity, and other harsh conditions.
Challenge
The melting and casting process of titanium alloys requires special conditions such as high temperature and high vacuum, with large equipment investment and high production costs. How to reduce production costs and improve production efficiency is an important challenge currently faced. Titanium alloys are prone to react with oxygen, nitrogen, and other elements in the air during the melting and pouring process, leading to defects such as porosity and cracks in castings. How to effectively control the melting and pouring process of titanium alloys, prevent oxidation and pollution, is the key to ensuring the quality of castings. With the continuous improvement of environmental protection requirements, the waste generated during the lost wax casting process (such as mold shells, wax materials, etc.) needs to be treated reasonably. How to achieve waste recycling and reduce environmental pollution is also one of the problems that need to be solved.
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