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Investment Casting

Investment casting process refers to making a model with wax, wrapping a layer of clay and other refractory materials on its surface, heating to melt and flow out the wax, so as to obtain the empty shell formed by refractory materials, then melting the metal and pouring it into the empty shell, and crushing the refractory materials to obtain metal modules after the metal cools. This process of processing metal is called precision casting, also known as investment casting or wax loss casting.

The basic feature of Silica Sol precision casting is to use fusible material as the pattern and refractory as the Mold. The pattern is melted out before pouring to form the mold cavity. As early as 3000 years ago, this process has been used to cast handicrafts. During the Second World War, due to the needs of military industry, the static blades of turbojet engine were produced by investment casting in the United States, Britain and other countries, which pushed the process to the industrial field and continuously developed and improved in more than half a century. There are many production processes of silica sol investment casting. It is a close chain from wax mold, shell, pouring to cleaning. Any problem in any link will directly affect the forming and quality of the final casting. It is necessary to strengthen the process control and research.

Top Investment Casting China Company

Pintejin is a manufacturer of precision investment casting components serving the world. Our main service areas include medical equipment (including artificial prosthetic joints), automotive precision parts, door locks, communication equipment, rail transit, 3C electronics, hidden adjustable hinges, sanitary ware and other major industries. We are positioned to be a reliable partner in the mid-to-high-end market, and it is our pursuit and commitment to provide reliable investment casting services to high-quality enterprises in various sub-industries.

We provide customers with overall solutions for metal forming, and help customers integrate supply chain resources with “one-stop” services to achieve “custodial” manufacturing. The manufacturing process covers mold making, lost wax casting, stamping and bending, precision machining, surface treatment and assembly testing. The product range includes the design and manufacture of precision casting parts, stamping and drawing parts, precision machined parts and other components.

“Joint development” is our customer service concept. Committed to participating in the product design at the beginning, working with customers to complete the product design process, and providing the best manufacturing and economic solutions for product development. In order to establish not only meet customer needs, but also meet the manufacturability to the greatest extent, and achieve the optimal cost plan.

We expect to provide customers with professional pre-sales support. In the product inquiry and quotation stage, we “answer questions and solve problems and solve problems” for customers, and provide customers with accurate evaluation plans with the fastest speed and professional perspective. At the same time, relying on the company’s 3D printing equipment and technology, we can provide customers with fast sample delivery services in a 7-day cycle, and provide strong support for process testing and market verification.

It is our development strategy to develop with technology and win the competition with technology. Obtaining high-precision and stable product quality with technical strength is the key to winning market competition. Based on this, the company has established a strong technical research and development team of about 40 people, including 1 doctoral degree, 3 postgraduate degrees, many undergraduate degrees, and many senior industry expert consultants. Not only has the Guangdong Provincial Precision Casting Engineering Technology R&D Center been established, but it has also been rated as a regional “high-tech” enterprise, and has obtained more than 10 invention and utility model patents.

Standardized and efficient management has always been our development idea for many years. It has passed the certification system of ISO 9001 and TS16949 and has always served as the guiding system of company management. At the same time, it is our unswerving belief and goal to strictly follow national policies and industry standards, implement the requirements of environmental protection and occupational health and safety (EHS), and abide by the responsibility of “social people”.

Pintejin’s vision is to become a technology-based high-end lost wax casting manufacturer. Taking technology as the core, carrying forward the spirit of Made in China, and providing reliable services to global customers are our pursuit and mission.

Advantages and disadvantages of investment casting process

Investment casting is also known as investment casting. Compared with other casting methods and parts forming methods, investment casting has the following advantages:

  • 1. The dimensional accuracy of castings is high, the surface roughness value is fine, the dimensional accuracy of castings can reach 4-6 grades, and the surface roughness can reach 0.4-3.2μm, which can greatly reduce the machining allowance of castings, and can achieve no allowance manufacturing, reduce manufacturing cost.
  • 2. Castings with complex shapes and difficult to be processed by other methods can be cast. The outline size of the castings is as small as a few millimeters and as large as thousands of millimeters. The thinnest wall thickness is 0.5mm, and the minimum hole diameter is less than 1.0mm.
  • 3. Unrestricted alloy materials: materials such as carbon steel, stainless steel, alloy steel, copper alloy, aluminum alloy, high-temperature alloy, titanium alloy and precious metal can be produced by precision casting. For alloy materials that are difficult to forge, weld and cut, more It is especially suitable for the production of precision casting methods.
  • 4. High production flexibility and strong adaptability. It can be used for mass production, as well as small batches or even single-piece production.

To sum up, precision casting has the advantages of small investment scale, large production capacity, low production cost, simplified process of complex products, and quick investment effect. Therefore, it is in a favorable position in the competition with other processes and production methods.

Importance of shell making process

in all production processes, wax mold manufacturing and shell manufacturing are two process links reflecting the characteristics of investment casting, which need special attention in process research. In recent years, the worldwide stainless steel investment casting process has made great progress in wax mold manufacturing. Producers can ensure the dimensional accuracy and surface quality of wax mold by selecting appropriate mold materials and adopting modern process equipment. At the same time, compared with the subsequent manufacturing process of investment casting, wax mold manufacturing is relatively independent, and unqualified products can be screened out by means of visual inspection and dimensional measurement, so as to avoid increasing losses due to continuous production. When entering the shell manufacturing process, the surface quality, dimensional accuracy and other information related to the final quality of the casting are hidden. Until the casting is cleaned out, the change of the quality of the inner cavity of the shell can be regarded as a “black box”.

In the manufacturing process, it is impossible to directly observe the change of its size and quality. Only by understanding the relationship between the shell manufacturing process and defects more clearly can we ensure the controllability of the whole production process. More importantly, as the direct cavity of casting, the performance of mold shell ultimately affects the forming quality of liquid metal. Therefore, people pay much attention to the shell making process of aluminum investment casting. At the annual technical conference of American Investment Casting Association ICI, an important international investment casting conference, mold shell research has always been the focus of attention. About 1 / 3 of the papers are related to mold shell, indicating the importance of the development of mold shell manufacturing technology to investment casting.

In the international investment casting shell making process, silica sol shell occupies a dominant position due to the advantages of environmental protection, but it also needs to face the challenges of fierce market competition: on the one hand, it is necessary to meet the quality requirements of larger, thinner and more complex castings put forward in the field of Aerospace and military industry; On the other hand, for a large number of civil products, it is urgent to shorten the production cycle and improve the market response ability.

The development of shell technology puts forward the requirements for the development of new silica sol

1. Meet the requirements of complex investment castings for silica sol shell

In order to manufacture the mold shell of large, thin-walled and complex castings, on the one hand, it is necessary to solve the problem of mold shell manufacturing capacity, such as equipment suitable for large mold shell operation, including shell making manipulator, dewaxing equipment, etc. On the other hand, the final mold shell has higher requirements in strength, deformation resistance and dimensional accuracy, especially the strength and deformation resistance of the mold shell are the basis of casting large investment castings. Only by ensuring the performance requirements of the mold shell and making the casting form correctly can the dimensional accuracy of the casting be further mentioned. The strength of silica sol shell can be divided into normal temperature strength, high temperature strength and residual strength according to its heating effect. Normal temperature strength is to ensure the integrity of medium-sized shell in the process of shell making and dewaxing. High temperature strength is to ensure that the shell will not be damaged during roasting and pouring. High temperature strength is important, but the experimental measurement shows that after high temperature roasting above 950 ℃, the shell strength of silica sol can reach 7 ~ 14MPa, which is more than 6 ~ 8Mpa of ethyl silicate, which can fully meet the requirements of brass investment casting process. On the contrary, with the increase of high temperature strength, the residual strength also increases, resulting in the difficulty of shell cleaning of castings, which needs to be reduced appropriately. Compared with ethyl silicate, the weakness of silica sol shell lies in its relatively low strength at room temperature. Therefore, when the shell becomes larger and more complex, it is easy to cause cracking or deformation of the shell during shell making and dewaxing, affecting the final surface quality and dimensional accuracy of the casting. Therefore, improving the normal temperature strength of silica sol has become an important task to promote and develop silica sol shell process, and it is also an important goal to study new silica sol.

2. Requirements of improving investment casting efficiency for the development of silica sol

Compared with large complex thin-wall castings, civil products have low requirements for casting quality. However, for the latter, the problem of shortening production cycle and improving production efficiency has become more prominent. The gelling process of ordinary silica sol mainly depends on the dehydration and drying of silica sol, which takes longer than that of chemically hardened ethyl silicate. The ethyl silicate shell is dried with ammonia, and the hardening of each layer can be completed in about 2h, while the final hardening of silica sol generally takes more than 12h, and it takes longer for some deep holes and other parts that are difficult to dry. At the same time, because the investment casting shell needs to be manufactured in layers, each layer needs to be fully dried to ensure that the lower layer will not cause the problem of back dissolution and falling off when making the shell and dipping the coating, while the water in the dipping coating itself will immerse in the dried shell, resulting in a long overall drying cycle. It is the schematic diagram of the production cycle of steel casting with silica sol shell under general conditions. It can be seen from the figure that the shell making time accounts for more than 50% of the whole casting production cycle. To shorten the delivery time of products and shorten the shell making cycle is the core of the problem. The key factors to shorten the shell making cycle can be divided into internal and external factors. The internal factor is mainly the characteristics of binder, and the external factor is drying conditions.

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