One of the more commonly used precision castings is inv […]
One of the more commonly used precision castings is investment casting, also known as lost wax casting: use appropriate investment materials (such as paraffin) to make investment molds; repeat the steps of dipping refractory paint and sprinkling refractory sand on the investment mold, hardening the shell and Dry; melt the inner investment mold to obtain a cavity; roast the mold shell to obtain sufficient strength and burn off the remaining investment material; cast the required metal materials; solidify and cool, and clean the sand after shelling, In order to obtain high-precision finished products. According to product needs or heat treatment, cold processing and surface treatment. For example, in sand casting, mass production factories should create conditions to adopt technologically advanced modeling and core-making methods. The old-fashioned shock-type or shock-type molding machine production line is not high enough in productivity, the labor intensity of the workers is large, the noise is large, and it is not suitable for the requirements of mass production, so it should be gradually reformed. For small castings, a boxless high-pressure moulding machine production line with horizontal or vertical parting can be used. The production efficiency of solid moulding is high and the area is small; for middle parts, various boxed high-pressure moulding machine production lines and gas can be used. Molding line to meet the requirements of fast, high-precision molding production line, core-making methods can be selected: cold core box, hot core box, shell core and other efficient core-making methods.
Medium-volume large castings can consider the application of resin self-setting sand molding and core making.
For heavy castings produced in small batches, manual molding is still an important method. Manual molding can adapt to various complex requirements and is more flexible and does not require a lot of process equipment. Water glass sand molds, VRH water glass sand molds, organic ester water glass self-hardening sand molds, clay dry molds, resin self-hardening sand molds and cement sand molds can be used; for single-piece heavy castings, the pit molding method is used for low cost and put into production fast. It is more suitable for mass-produced or long-term shaped products to adopt multi-box modeling and split-box modeling. Although the initial investment in molds and sand boxes is high, it can be compensated by saving modeling man-hours and improving product quality.
Low pressure casting, die casting, centrifugal casting and other casting methods are only suitable for mass production due to the expensive equipment and molds.
Condition method should be suitable
For example, the same production of large-scale machine bed and other castings generally adopts the core assembly method, instead of making the pattern and sand box, the core is assembled in the pit; while other factories use the sand box method to make the pattern. Different companies have different production conditions (including equipment, site, staff quality, etc.), production habits, and accumulated experience. Based on these conditions, we should consider what products are suitable and what products are not suitable (or not).
Precision requirements and cost
The accuracy of castings obtained by various casting methods is different, the initial investment and productivity are also inconsistent, and the final economic benefits are also different. Therefore, in order to be more, faster, better, and less expensive, all aspects should be considered. A preliminary cost estimate should be made for the selected casting method to determine a casting method that has high economic benefits and can guarantee the requirements of the casting.
Although the development of my country’s foundry industry is in a relatively difficult period, from a long-term perspective, there is still hope for the development of my country’s precision casting industry. The market demand has slowly begun to pick up, and with the addition of my country’s foundry industry We believe that my country’s foundry industry will surely achieve gratifying results with the development of strong strength.
To fundamentally improve the level of casting technology, the following four points must be achieved:
First, develop simulation technology, improve the accuracy of prediction, strengthen process control, and increase yield. The problem of regularity is not well mastered, which affects the yield in mass production.
Second, the integration of production, education and research. In addition to the enhancement of innovation awareness and the enhancement of research and development capabilities, the independent innovation of enterprises also needs to pay attention to and strengthen the integration of "production, learning, and research" with precision casting enterprises as the main body.
Third, attach importance to material research and development. Materials are the foundation of industry, and there is still a lot of work to be done. In the field of aerospace, the research and smelting technology of alloy materials, especially high-temperature alloys, and other new materials still need to be improved, and there is still a big gap with foreign countries.
Fourth, pay attention to the improvement of equipment technology. The process is mainly a problem of equipment. Many key equipment, such as some directional solidification equipment, mainly rely on imports, so the research and development of precision casting equipment is still the focus.