Investment Casting Glossary
A
Alloy
A metallic material composed of two or more elements, with at least one being a metal. Alloys feature different performance properties, like strength, hardness, corrosion resistance, and machinability. Aero Metals works with a broad range of alloy families including stainless steel, carbon steel, aluminum, nickel-based, cobalt-based, beryllium copper, and copper-based alloys. See: Investment Cast Alloys.
Aluminum Casting
An investment casting produced from an aluminum alloy. Aluminum castings offer an excellent strength-to-weight ratio and are commonly used in aerospace, automotive, and military applications where weight reduction is required. Aero Metals produces aluminum investment castings including the widely specified A356 aluminum alloy. See: Aluminum Castings.
Annealing
A heat treatment process in which a metal is heated to a specific temperature and then cooled slowly to reduce hardness, relieve internal stresses, and improve ductility and machinability. Annealing is a common post-casting operation at Aero Metals, particularly before secondary machining operations.
AS9100
An internationally recognized quality management standard specific to the aviation, space, and defense industries. AS9100 builds on the ISO 9001 framework with additional requirements for safety and reliability. Aero Metals produces castings certified to AS9100 standards for aerospace customers. See: Aerospace Castings.
Austenitic Stainless Steel
A family of stainless steel alloys with a face-centered cubic crystal structure, characterized by high corrosion resistance, good weldability, and non-magnetic properties. Common grades include 304 and 316. Aero Metals produces austenitic stainless steel investment castings for demanding industrial and fluid-handling applications. See: Austenitic Stainless Steel Castings.
Autoclave (De-waxing)
A high-pressure steam vessel used in the investment casting process to rapidly melt and remove the wax pattern from the ceramic shell mold. The autoclave applies heat and pressure quickly to minimize cracking of the ceramic shell, which is essential in maintaining shell integrity before pouring. See: The Investment Casting Process.
B
Beryllium Copper
A copper-based alloy containing beryllium, known for its exceptional combination of high strength, hardness, electrical conductivity, and non-sparking properties. It is commonly used in aerospace connectors, precision instruments, and industrial tooling. Aero Metals is one of the largest investment casters of beryllium copper in North America. See: Beryllium Copper Castings.
Brass
A copper-zinc alloy known for its machinability, corrosion resistance, and acoustic properties. Investment cast brass is used in valves, fittings, hardware, and decorative applications. Aero Metals produces brass castings as part of our copper-based alloy offerings. See: Brass Castings.
Bronze
A copper-tin alloy (or more broadly, a copper alloy with tin, aluminum, or other elements) valued for its wear resistance, corrosion resistance, and strength. Bronze is widely used in pump and valve components, marine hardware, and industrial bearings. See: Bronze Castings.
C
Carbon Steel
A steel alloy in which carbon is the primary alloying element, typically ranging from 0.05% to 2.0% carbon content. Higher carbon content generally increases hardness and tensile strength but reduces ductility. Carbon steel investment castings are used across a wide range of industrial, agricultural, automotive, and defense applications. See: Carbon Steel Castings.
Casting
A metal part produced by pouring molten metal into a mold and allowing it to solidify. Castings can achieve complex geometries that would be difficult or cost-prohibitive to produce through machining or fabrication alone. Investment casting is among the most precise casting methods available.
Ceramic Shell
The refractory mold built up around a wax pattern in the investment casting process through repeated dipping in ceramic slurry and coating with sand. The ceramic shell defines the final geometry of the casting. Once the wax is removed and the shell is fired, molten metal is poured into it. See: The Investment Casting Process.
Cluster (Tree)
An assembly of multiple wax patterns attached to a central wax runner system (the tree) for simultaneous processing through the investment casting cycle. Running multiple parts on a single tree improves production efficiency and reduces per-part cost. See: The Investment Casting Process.
Cobalt-Based Alloy
A family of alloys with cobalt as the primary element, offering superior wear resistance, high-temperature strength, and corrosion resistance. Cobalt alloys including Stellite grades are commonly used in agricultural wear parts, medical devices, and industrial tooling. See: Cobalt-Based Alloy Castings.
Copper-Based Casting
An investment casting produced from a copper-family alloy, including brass, bronze, or beryllium copper. Copper-based alloys offer a range of properties including electrical conductivity, corrosion resistance, and machinability. See: Copper-Based Castings.
Cristobalite
A high-temperature crystalline form of silica that develops in the ceramic shell when it is fired in a furnace prior to pouring. The firing (or curing) of the shell converts the silica binder into cristobalite, giving the mold the strength and thermal stability needed to receive molten metal. See: The Investment Casting Process.
D
Design for Manufacturability (DFM)
An engineering review process conducted at the start of a project to evaluate a part's design in the context of the intended manufacturing method. For investment casting, DFM considers wall thickness, draft angles, parting lines, gate placement, and tolerance expectations to optimize both part quality and production efficiency. Aero Metals performs DFM reviews as the first step of its casting process. See: Investment Casting Engineering.
De-waxing
The process of removing the wax pattern from the ceramic shell mold after the shell has been built up. At Aero Metals, de-waxing is performed using an autoclave, which applies high-pressure steam to quickly melt the wax without cracking the shell. This step gives investment casting its common alternate name: lost wax casting. See: The Investment Casting Process.
Domestic Manufacturing
Production of castings within the United States, as opposed to offshore sourcing. Domestic manufacturing offers advantages in lead time, quality control, supply chain reliability, and compliance with regulations such as ITAR. Aero Metals manufactures all castings at its La Porte, Indiana facility. See: Domestic Manufacturing.
Ductile Iron
Also known as nodular iron or spheroidal graphite iron, ductile iron is a cast iron alloy in which graphite forms as spherical nodules rather than flakes, giving it improved ductility, toughness, and tensile strength compared to gray iron. It is used in industrial, agricultural, and fluid-handling applications. See: Ductile Iron Castings.
E
Engineering Review
The initial consultation between Aero Metals' engineering team and the customer to evaluate print dimensions, tolerances, gate placement, and post-cast requirements before tooling is built. See: Investment Casting Engineering.
F
Ferrous Alloy
A metal alloy in which iron is the primary element. Ferrous alloys include carbon steel, stainless steel, tool steel, and ductile iron. They are distinguished from non-ferrous alloys (such as aluminum, copper, cobalt, and nickel-based alloys) by their iron content and, generally, their magnetic properties.
Finishing
Post-casting operations performed to bring a casting to its final specification. At Aero Metals, finishing can include gate removal by grinding or machining, heat treatment, plating, and final inspection. The extent of finishing required depends on the part's tolerance and surface finish requirements. See: Other Services.
Foundry
A manufacturing facility where metal castings are produced by melting metal and pouring it into molds. Aero Metals is a full-service investment casting foundry operating out of La Porte, Indiana since 1961.
G
Gate / Gating System
The network of channels in a casting mold through which molten metal flows from the pouring cup into the part cavities. Proper gate design is important for controlling metal flow, minimizing turbulence, and reducing defects such as porosity and shrinkage. The gate is removed in the finishing stage after the casting has solidified. See: The Investment Casting Process.
H
Heat Treatment
A controlled process of heating and cooling a metal to alter its mechanical properties (hardness, strength, ductility, or toughness) without changing its shape. Common heat treatment processes for investment castings include annealing, normalizing, quenching, and tempering. Heat treatment is often specified as part of the finishing stage.
High-Volume Casting
Production runs involving large quantities of a given part. Investment casting is well suited to both low- and high-volume production, and the use of multi-part clusters on a single tree makes high-volume runs particularly efficient. Aero Metals accommodates a range of production volumes. See: Investment Casting Overview.
I
Investment Casting
A precision manufacturing process in which a wax pattern is coated with a ceramic shell, the wax is melted out, and molten metal is poured into the resulting cavity. Also known as lost wax casting, it produces net or near-net shaped components with tight tolerances and excellent surface finish, suitable for complex geometries across virtually any metal alloy. See: The Investment Casting Process.
ISO 9001
An internationally recognized quality management system standard published by the International Organization for Standardization. ISO 9001:2015 certification demonstrates that a manufacturer meets consistent quality, process control, and continuous improvement requirements. Aero Metals is certified to ISO 9001:2015. See: ISO 9001 Certification.
ITAR (International Traffic in Arms Regulations)
A set of U.S. government regulations that control the export and import of defense-related articles and services listed on the United States Munitions List. Foundries producing castings for military and defense applications must be ITAR registered. Aero Metals is ITAR registered with a Cage Code and FFL license. See: Military & Defense Castings.
L
Lost Wax Casting
The traditional name for the investment casting process, derived from the step in which the wax pattern is melted out (lost) from the ceramic shell before metal is poured. The process dates back over 5,500 years. See: The Investment Casting Process.
Low-Alloy Steel
A category of steel containing small amounts of alloying elements (typically less than 5% total) such as chromium, molybdenum, nickel, and vanadium, which improve mechanical properties beyond those of plain carbon steel. Common low-alloy investment casting grades include 4130, 4140, 4340, and 8620. See: Carbon Steel Castings.
M
Martensitic Stainless Steel
A category of stainless steel with a body-centered tetragonal crystal structure, known for high hardness and strength when heat treated, and moderate corrosion resistance. Common grades include 410 and 416. Martensitic grades are frequently specified for cutlery, industrial knives, and precision mechanical components. See: Martensitic Stainless Steel Castings.
Metallurgical Testing
Analysis performed to verify the chemical composition, mechanical properties, and microstructure of a metal casting. Aero Metals conducts on-site metallurgical testing using spectrometers to verify alloy chemistry at every stage of production. See: Metallurgical Testing.
Mold (Wax Injection Mold)
A precision-engineered tool used to produce wax patterns in the investment casting process. The wax injection mold defines the geometry of each wax pattern and is built to produce millions of consistent parts over its lifetime. Aero Metals builds all wax injection molds in-house at its mold shop. See: Investment Casting Tooling.
Molten Metal
Metal that has been heated above its melting point to a liquid state for pouring into a casting mold. In investment casting, the ceramic shell mold is preheated before the pour to minimize thermal shock and ensure complete filling of the mold cavity.
N
Near-Net Shape
A casting that closely approximates the final geometry of the finished part, requiring minimal secondary machining or finishing. Near-net shape casting reduces material waste and post-casting labor costs. Investment casting is one of the most effective processes for producing near-net shape components. See: The Investment Casting Process.
Nickel-Based Alloy
A family of alloys with nickel as the primary element, valued for high-temperature strength, oxidation resistance, and corrosion resistance. Nickel-based investment castings are used in aerospace, chemical processing, and industrial applications where performance at elevated temperatures is required. See: Nickel-Based Metal Castings.
Non-Ferrous Alloy
A metal alloy that does not contain iron as the primary element. Non-ferrous alloys cast by Aero Metals include aluminum, beryllium copper, brass, bronze, nickel-based, and cobalt-based alloys. Non-ferrous alloys generally offer superior corrosion resistance and lighter weight compared to ferrous alloys.
P
Pattern (Wax Pattern)
A replica of the final casting, produced by injecting wax into a precision mold. The wax pattern is used to build the ceramic shell that will receive the molten metal. Accurate wax patterns are essential to achieving tight dimensional tolerances in the finished casting. See: The Investment Casting Process.
Porosity
Voids or pores within a casting caused by gas entrapment or shrinkage during solidification. Porosity can reduce a casting's mechanical properties and pressure integrity. Proper gating design, mold temperature control, and alloy selection help minimize porosity in investment castings.
Precision Casting
A casting produced to tight dimensional tolerances and fine surface finish, typically through investment casting or other precision methods. Precision castings reduce or eliminate the need for secondary machining, lowering overall part cost and lead time. See: Investment Casting Overview.
Pump & Valve Casting
Investment castings produced for fluid-handling systems, including pump housings, impellers, valve bodies, and related components. Investment casting's ability to hold tight tolerances in stainless steel, ductile iron, brass, and bronze alloys makes it well suited to pump and valve applications. See: Pump & Valve Castings.
R
Refractory Material
A material capable of withstanding very high temperatures without melting or deforming. In investment casting, refractory ceramic materials are used to build the shell mold that must withstand the heat of molten metal during pouring.
RMS (Root Mean Square) Surface Finish
A measure of surface roughness. Investment casting typically achieves a surface finish of approximately 125 RMS, which is considerably smoother than sand casting and often eliminates the need for additional surface finishing operations.
S
Sand Casting
A casting process in which molten metal is poured into a sand mold. Sand casting is suitable for large, simpler-geometry parts but produces rougher surface finishes and less dimensional accuracy than investment casting. See: Metal Fabrication Method Comparisons.
Shrinkage
The reduction in volume that occurs when molten metal cools and solidifies. Mold and pattern designs must account for shrinkage so that the final casting meets dimensional specifications. Improper shrinkage compensation can result in dimensional inaccuracies or internal voids.
Spectrometer (Optical Emission)
An analytical instrument used to verify the elemental composition of a metal alloy by measuring the light emitted when a sample is excited by an electrical arc or spark. Aero Metals uses on-site spectrometers to verify alloy chemistry at every stage of production. See: Metallurgical Testing.
Stainless Steel
A family of iron-based alloys containing at least 10.5% chromium, which forms a passive oxide layer that gives the material its corrosion-resistant properties. Investment cast stainless steel is used across aerospace, defense, food processing, pump and valve, and industrial applications. Aero Metals produces a wide range of stainless steel grades including 400 series, austenitic, martensitic, and 17-4 PH. See: Stainless Steel Castings.
Steel Casting
An investment casting produced from a carbon or low-alloy steel. Steel castings combine high strength, toughness, and versatility, and are used in a wide range of industrial, agricultural, automotive, and defense applications. See: Carbon Steel Castings.
T
Tolerance
The allowable deviation from a specified dimension in a finished part. Investment casting achieves tighter tolerances than most other casting methods, often eliminating or reducing secondary machining. Typical linear tolerances for investment castings range from ±0.005 to ±0.010 per inch, depending on the alloy and geometry.
Tooling (Wax Injection Tooling)
The precision molds used to produce wax patterns in the investment casting process. Aero Metals designs and builds all tooling in-house, which provides control over quality, lead time, and cost. In-house tooling capability is a key advantage for customers requiring tight dimensional control or rapid production startup. See: Investment Casting Tooling.
Tree
See also: Cluster. The central wax runner assembly onto which individual wax patterns are attached for simultaneous casting. The term "tree" reflects the branching structure of the assembly. See: The Investment Casting Process.
W
Wax Pattern
A replica of the finished part produced by injecting molten wax into a precision mold. The wax pattern is the starting point of the investment casting process and must accurately reflect the final part geometry. See: The Investment Casting Process.
#
17-4 PH Stainless Steel
A precipitation-hardening martensitic stainless steel that combines high strength, hardness, and good corrosion resistance. The 17-4 designation refers to its approximate chromium (17%) and nickel (4%) content. It is widely used in aerospace, defense, and industrial applications requiring a combination of strength and corrosion resistance. See: 17-4 PH Stainless Steel Castings.
