Investment casting is a versatile process, used to manufacture parts ranging from pipe fittings to automotive parts, from food machinery parts to marine hardwares. The industry, though heavily dependent on aerospace and defence outlets, has expanded to meet a widening range of applications. Modern investment casting has its roots in the demands of the Second World War, but it was the adoption of jet propulsion for military and then for civilian aircraft that stimulated the transformation of the ancient craft of lost wax casting into one of the foremost techniques of modern industry.
Investment casting expanded greatly worldwide during the 1980s, in particular to meet growing demands for aircraft engine and airframe parts. Today, investment casting is a leading part of the foundry industry, with investment castings now accounting for 55% by value of all cast metal production in China.
What is Investment Casting?
Investment casting is a metal fabrication process that involves pouring molten metal into moulds. Investment casting allows for the creation of metal parts with accurate dimensions, complex shapes, and smooth surfaces.
A General Breakdown of the Investment Casting Process
Investment casting, famous for its good size accuracy, is always adopted to produce complex metal parts from small to large production runs. Here’s a step-by-step look at the investment casting process:
- A pair of metal mold must be made into two sections, whose cavity is the same shape with the desired casting part.
- Injecting wax into molds to fully fill the cavity of the mold, waiting for solidification.
- Taking the wax models from the mold, and go on next step for shell building.
- After drying the shell, pour liquid metals into the cavity of the shell. The liquid metals will be quickly solid under room temperature.
- Breaking the shell to achieve castings, then remove sprue gate and shot blast the parts for smooth surface.
Investment Casting vs. Sand Casting
Similar process with investment casting, Sand casting is another popular metal fabrication method that involves pouring molten metal into a mold. While these processes share a common goal, their individual machinations drastically differ.
Investment casting is far and away the quickest way to produce precise metal parts, partially because it uses lost wax casting process. When metal solidifies after cooling, it is removed from the mold, possibly sanded or polished, and then it’s done. The mold is then immediately reclosed and prepared for another pour.
Conversely, sand casting requires a new sand mold for each casting and doesn’t utilize any wax, instead with sand. Depending on the complexity of the mold, it can take hours, if not days to make a new mold. While it is lower cost and requires far less equipment to produce a sand mold, this process incurs far more downtime so it’s better suited for casting a lower quantity of parts.
What Metals Are the Most Popular Options for Investment Casting?
When starting an investment casting project, there are a number of metals that can be used. Each of the alloys has unique physical characteristics that have benefits for different applications. After understanding the features of all metals , so it’s always a good idea to speak with an experienced investment casting company. The most commonly used investment-cast metals are as follows:
Stainless Steel
Stainless steel casting is actually silica sol lost wax investment casting process with stainless steel alloys. Most stainless steel parts are not large, due to its complex shapes and high requirement on size accuracy, investment casting is the best option.
Used for many industrial, architectural, chemical and consumer applications for over half a century, stainless steel is essentially a low-carbon steel, which contains chromium at 10.5 percent or more by weight. Isteel coilt is this addition of chromium that gives the steel its unique stainless, corrosion-resisting and enhanced mechanical properties.
The chromium content of the steel allows the formation of a rough, adherent, invisible corrosion-resisting chromium oxide film on the steel surface. If damaged mechanically or chemically, this film is self-healing, providing that oxygen, even in very small amounts, is present. The corrosion resistance and other useful properties of the steel are enhanced by increased chromium content and the addition of other elements such as molybdenum, nickel and nitrogen. Nickel also gives stainless steel a lustrous and brighter appearance which is less gray than steel that has no nickel.
Popular cast stainless steel for investment casting process include: 303, 304(L), 316(L), 17-4 ph, 2205, etc.
Carbon and Alloy Steel
Carbon steel or alloy steel casting is actually water glass investment casting process using carbon steel or alloy steel as the material. This kind of casting method can creat carbon steel parts or alloy steel parts from small to large pieces. But the size accuracy and surface rougness is not as good as silica sol investment casting process. The main advantage is the low cost.
Carbon steel casting: Aside from iron, the main element of this steel is carbon. You probably already figured that much out. The lower the carbon content, the more ductile the part is. The higher the carbon content, the more you can heat treat and harden the metal. Carbon steel casting is comparatively inexpensive, especially with a lower carbon content, it is also easy to work with.
Common applications for carbon steel casting: Agriculture machinery parts, forestry machinery parts, etc.
Alloy steel casting: some of the most common alloying elements are manganese, nickel, chromium, molybdenum, vanadium, silicon, and boron. The improved properties that alloy steel castings have over carbon steel castings are: Strength, Hardness, Toughness, Wear resistance, Corrosion resistance, and hardenability. Alloy steel casting can be more expensive, and ratively more difficult to cast, depending on the alloying elements and ratios.
Common applications for alloy steel casting: Construction and architecture where strength, toughness and corrosion resistance are a pre-requisite for the material.
Starting An Investment Casting Project With CFS China
Investment casting is a good metal forming process. It’s tried, tested, and proven method that is conducive to streamlined, high-quality production. Not only is it a cost-efficient way to produce custom metal parts and components, but also allows you to create complex net shapes and complex internal features. Well understanding the importance of choosing a right investment casting company…
If you’re interested in finding out more about our investment casting services, contact CFS Foundry to speak with one of our experienced sales team today to get a free quote on your project.