Our company produces a wide variety of stainless steel pipe fittings, among which cast pipe fittings account for a large proportion. At present, our casting products adopt the investment process commonly used in China. After strict review and control by relevant parties, coupled with our strict processing methods, the precision castings produced have won unanimous praise from customer service. In simple terms, the so-called investment casting process is to use a fusible material (such as wax or plastic) to make a fusible model (called an investment pattern or pattern), and then apply several layers of special fire-resistant paint on it . . After hardening to form a whole shell, the model is melted out of the shell with steam or hot water, then the shell is placed in a sandbox, dry sand is filled around it and shaped, and finally the mold is made. Put it in a roasting furnace, after high-temperature roasting (if a high-strength shell is used, the die-cut shell can be directly roasted without molding), after the mold or shell is baked, pour molten metal into it to obtain a casting.
It wasn’t until the 1940s that modern steel investment casting methods were truly used in industrial production. At that time, the development of jet engines required the manufacture of heat-resistant alloy parts with complex shapes, precise dimensions, and smooth surfaces, such as blades, impellers, and nozzles. Due to the difficulty in processing heat-resistant alloy materials and the complex shape of parts, it is impossible or difficult to manufacture by other methods, so it is necessary to find a new precision forming process, so it is necessary to learn from lost wax casting. . The improvement of modern investment casting methods has achieved important developments on the basis of ancient techniques. Therefore, the development of the aviation industry has promoted the application of investment casting, and the continuous improvement and perfection of investment casting has also created favorable conditions for the aviation industry to further improve its performance. my country began to apply investment casting to industrial production in the 1950s and 1960s. Since then, this advanced casting process has been greatly developed and widely used in aviation, automobiles, machine tools, ships, internal combustion engines, gas turbines, communication equipment, weapons, medical equipment, cutting tools and other manufacturing industries.
The dimensional accuracy of investment casting is relatively high, generally reaching CT4-6 (CT10-13 for sand casting and CT5-7 for die casting). The die-casting process is complex, and there are many factors that affect the dimensional accuracy of castings, such as shrinkage of mold materials, deformation of investment molds, changes in shell dosage during heating and cooling, etc. Ordinary investment castings have high dimensional accuracy, and the consistency needs to be further improved.
When pressing the investment mold, a mold with a high surface finish of the cavity is used, so the surface finish of the investment mold is relatively high. In addition, the shell is made of heat-resistant special adhesives and refractory coatings prepared from refractory materials, coated on the investment mold and suspended, and the inner surface of the cavity that directly contacts the molten metal has high smoothness. Therefore, the surface finish of stainless steel investment casting is higher than that of ordinary castings, generally reaching Ra.1.6~3.2μm.
The biggest advantage of investment casting is high dimensional accuracy and surface finish. Therefore, processing work can be reduced. For parts with higher requirements, only a small machining allowance is left. Some castings are ground and polished only with allowances. Ready to use without treatment. Facts have proved that using the investment casting method saves a lot of machine tool equipment and processing time, and saves a lot of metal raw materials.
Another advantage of investment casting is the ability to cast complex castings of various alloys, especially superalloy castings. Jet engine blades, for example, have streamlined profiles and internal cooling cavities that are nearly impossible to machine. The investment casting process can not only achieve mass production and ensure the consistency of castings, but also avoid the stress concentration of residual knife lines after machining. As a result, the jewelry investment casting process is now widely used in foundries around the world. However, with the emergence of new materials and rising labor costs, the foundry process is facing new challenges. For example, the new material precision casting corundum unanimously recommended by the Chinese foundry organization China Foundry Association and the International Foundry Consulting Network, and Taiwan’s casting manual robot will be the next development direction of precision casting.