Iron is the most prominent element in steel alloys, with carbon coming in second. Additional elements such as manganese, chromium, vanadium, and tungsten may be included in steel investment castings.
The strength and durability of a particular casting is largely dependent upon the specific metallurgical composition. In general, steel and especially stainless steel investment castings are popular in industrial applications as they are stronger than cast iron, wrought iron, and malleable iron. These parts are capable of enduring shocks, wear, and heavy loads.
Though these features can be attributed in large part to the material itself, investment casting allows for the creation of completed precision parts with no flash or parting lines. Because the wax molds are exact replicas of the desired final product, accuracy is easily attained and parts rarely require additional processing.
Because steel investment castings are used in such varied industries as aerospace, automotive, construction, dental, medical, military, mining, food processing, sports, and telecommunications; it is important to consider the design and material used to create a specific component to ensure it is suited to its intended use.
When ordering steel investment castings, the type of steel that will be used to produce the part must be identified. Steel investment castings are usually ordered to ASTM requirements and may be made from carbon steel, low and high alloys steel, low-temperature steel, heat resistant steel, and stainless steel, among others. By specifying the test methods for an order, the requirements of the material can be guaranteed.
Though the material composition of the steel is variable, the investment casting process is relatively straightforward.
First, a wax pattern is carved by hand, machine, or created through injection molding. This model is often a prototype and must meet the exact specifications of the finished part.
The wax master die is then mounted on a wax rod known as a sprue. In some cases several dies are attached to a single sprue creating what is known as a tree.
The assembly is then dipped into a ceramic slurry known as the investment until thoroughly covered. For particularly complex designs, the sprue may be placed in a flask that is then filled with investment and vibrated to remove air pockets and ensure complete adherence to the pattern.
This coating is then dried and hardened using an oven or furnace which also melts the wax. Additional heating may be required to remove moisture or wax residue. As the wax runs out, a hollow shell is left.
Molten steel is poured into it. Once the steel is fully cooled the shell is removed by water-blasting, dissolving agent, or other method to reveal the finished steel product.