310 stainless steel castings are a type of austenitic stainless steel alloy known for its ability to perform in high-temperature environments. This alloy contains a high level of chromium and nickel, which contributes to its strength and resistance to oxidation and corrosion at elevated temperatures. Because of these characteristics, 310 stainless steel is used to produce cast parts for a variety of industrial applications. This article will provide you with a detailed analysis of 310 stainless steel castings, including their properties, the investment casting process used for their production, and their applications in different industries.

International Equivalents of 310 Stainless Steel

Many countries and regions have their own standards for materials. The standards for 310 stainless steel castings may be found under different designations depending on the country. Here are some common international equivalents for aisi 310 stainless steel:

UNS (Unified Numbering System): S31000 is the designation for the standard 310 grade. For the low-carbon version, it’s S31008 (310S), which is often used for investment casting.
EN (European Norm): The designation is 1.4845, with the common name X8CrNi25-21. This grade is also known as 310S.
JIS (Japanese Industrial Standards): The standard is SUS310S.
DIN (Deutsches Institut für Normung): The designation is X15CrNiSi25-20 or 1.4841.
GB (China National Standard): The equivalent is 2Cr25Ni20, which is part of the Chinese standards for heat-resisting steels.

Understanding these international designations is helpful when specifying or sourcing 310 stainless steel cast parts from different global markets. Below is a table summarizing the international equivalents of 310 stainless steel:

Standard	Designation	Common Name
UNS	S31000	310
UNS	S31008	310S (low carbon)
EN	1.4845	X8CrNi25-21
JIS	SUS310S	N/A
DIN	1.4841	X15CrNiSi25-20
GB	2Cr25Ni20	N/A

Chemical Composition of 310 Stainless Steel

Grade 310 is a type of austenitic stainless steel, the chemical makeup of 310 stainless steel casting is what gives it its unique properties, particularly its high-temperature strength and corrosion resistance. The material is a high-alloyed austenitic steel with significant amounts of chromium and nickel. The balance of these elements, along with other trace elements, helps the alloy perform well in demanding applications.

The below table shows the typical chemical composition of AISI 310 stainless steel:

Element	Weight Percentage (%)
Carbon (C)	0.25 max
Chromium (Cr)	24.00 – 26.00
Nickel (Ni)	19.00 – 22.00
Manganese (Mn)	2.00 max
Silicon (Si)	1.50 max
Phosphorus (P)	0.045 max
Sulfur (S)	0.030 max

Each element in the alloy contributes to its overall performance:

Chromium (Cr): This is the main alloying element that provides corrosion resistance. At high temperatures, chromium forms a stable, protective chromium oxide layer on the surface, which prevents further oxidation and scaling.
Nickel (Ni): Nickel helps stabilize the austenitic structure of the steel. This structure gives the material good strength, ductility, and toughness, even at high temperatures. Nickel also contributes to the alloy’s resistance to corrosion in certain environments.
Carbon (C): Carbon adds strength to the alloy. However, in higher amounts, it can lead to the formation of chromium carbides, which may reduce corrosion resistance. The low-carbon variant, 310S, is used to limit this effect, especially in welded 310 stainless steel cast parts.
Silicon (Si): Silicon helps improve the alloy’s resistance to oxidation and also promotes the formation of a protective oxide layer.
Manganese (Mn): Manganese is added for its role in steelmaking. It helps in deoxidation and aids in hot workability.
Phosphorus (P) and Sulfur (S): These elements are considered impurities and are kept at low levels. They can have a negative effect on the material’s properties, particularly its weldability and ductility, if their concentrations are too high.

Mechanical Properties of 310 Stainless Steel Castings

The mechanical properties of 310 stainless steel castings relate to how the material reacts to applied forces. The high chromium and nickel content gives the alloy a good balance of strength and ductility at both room and elevated temperatures. Below is a table of typical mechanical properties for 310 stainless steel cast parts.

Property	Value (Metric)	Value (Imperial)
Tensile Strength	515-750 MPa min	75-109 ksi min
Yield Strength	205-310 MPa min	30-45 ksi min
Elongation	40% min	40% min
Hardness (Rockwell B)	70-90 HRB	70-90 HRB
Hardness (Brinell)	180-220 HB	180-220 HB
Shear Strength	420-470 MPa	61-68 ksi
Modulus of Elasticity	200 GPa	29 x 10⁶ psi

Physical Properties of 310 Stainless Steel

The physical properties of 310 stainless steel casting are key to its performance, especially in high-temperature settings. These properties dictate how the material interacts with heat and other forms of energy. Below table indicates typical physical properties for AISI 310 stainless steel, for an intuitive view.

Property	Value
Melting Point	1400 – 1450 °C (2552 – 2642 °F)
Density	7.9 g/cm³ (0.285 lb/in³)
Thermal Conductivity	14.2 W/m·K at 20 °C (9.8 BTU/h·ft·°F at 68 °F)
Coefficient of Thermal Expansion	16.5 x 10⁻⁶ /°C (9.2 x 10⁻⁶ /°F) at 20-100 °C
Electrical Resistivity	0.78 µΩ·m at 20 °C

Melting Point: The high melting point of 310 stainless steel is a direct benefit for casting. It means the material remains solid and stable at temperatures where many other metals would melt or lose their structural integrity. This allows for the production of 310 stainless steel cast parts that can operate in furnaces, heat exchangers, and other extremely hot environments without failure.
Thermal Conductivity: This property measures how well a material transfers heat. 310 stainless steel has a lower thermal conductivity compared to carbon steel. This characteristic can be an advantage in some applications where heat transfer needs to be controlled or limited, such as in furnace components where the goal is to contain heat rather than conduct it.
Coefficient of Thermal Expansion: This describes how much a material expands or contracts with changes in temperature. 310 stainless steel has a relatively high coefficient of thermal expansion. In applications with significant temperature cycling, like those in a heat treatment furnace, this property must be considered in the design of the 310 stainless steel investment casting part to manage stress and prevent warping or cracking. Proper design with expansion joints or other allowances helps mitigate these effects.
Density: The density of AISI 310 stainless steel is similar to that of other austenitic stainless steels. It’s a fundamental physical property used in calculations for weight and mass of the final cast part.

These properties collectively make 310 stainless steel suitable for environments that require resistance to heat, thermal cycling, and high-temperature corrosion. The alloy’s ability to maintain its structure and strength while withstanding high heat loads is a main reason for its use.

Manufacturing Properties of 310 Stainless Steel

The manufacturing properties of 310 stainless steel are important for how the material is processed into finished 310 stainless steel cast parts. These properties relate to its behavior during various manufacturing operations, including casting, forming, welding, and machining.

Property	Description
Castability	Good, often used for investment casting due to its ability to fill complex mold cavities and produce fine details.
Machinability	Poor to fair. It is a tough material and tends to work harden, which can cause tool wear.
Weldability	Good. It can be welded using common methods without preheating. The low-carbon 310S grade is often used to avoid carbide precipitation.
Forgeability	Good. It can be forged and hot-worked, typically at temperatures between 982°C and 1232°C (1800°F and 2250°F).
Cold Workability	Limited. It work hardens quickly, which can make cold forming difficult. This is why it is not typically cold-formed into complex shapes.

Castability: The ability of a material to be formed into a useful shape by casting is called castability. 310 stainless steel has good castability, which is a key reason for its widespread use in the investment casting process. The alloy’s fluidity when molten allows it to flow into intricate and thin sections of a mold. This enables the production of detailed 310 stainless steel investment casting parts with complex geometries. The casting process is a common and effective way to produce components from this alloy, especially for shapes that would be difficult or expensive to create through other methods like forging or machining.
Machinability: This refers to the ease with which a material can be cut by a cutting tool. AISI 310 stainless steel is known for being difficult to machine. Its high strength and tendency to work harden—meaning it becomes harder and stronger as it is machined—can lead to rapid tool wear. For this reason, a slow speed, a heavy feed, and a rigid machine setup are recommended when machining 310 stainless steel cast parts.
Weldability: This is the capacity of a material to be welded without any problems. 310 stainless steel has good weldability. It can be joined using a variety of welding processes, and preheating is not typically necessary. Post-weld heat treatment is also not usually required. For applications where the part will be exposed to temperatures between 427°C and 816°C (800°F and 1500°F), the low-carbon version, 310S, is often used. This helps to prevent the formation of chromium carbides at the grain boundaries during welding, a phenomenon known as sensitization, which can reduce corrosion resistance.
Forgeability and Cold Workability: Forgeability relates to the material’s ability to be formed when hot. 310 stainless steel has good forgeability, allowing it to be shaped through forging. Its high work hardening rate, however, limits its cold workability. This is why cold forming is generally not the preferred method for making complex shapes from this alloy. The investment casting process is often used instead for producing detailed geometries for 310 stainless steel casting parts.

The Investment Casting Process for 310 Stainless Steel Castings

The investment casting process is a precision method used to produce intricate and detailed 310 stainless steel cast parts. This process is particularly useful for complex geometries that are difficult to achieve with other manufacturing methods. It is also known as the “lost wax” process because it uses a wax pattern that is melted away. The investment casting process for 310 stainless steel investment casting involves these steps.

Pattern Making: A wax pattern of the final part is created. This can be done by injecting molten wax into a metal die. For more complex or one-off parts, 3D printing or machining the wax pattern is an alternative. A separate pattern is needed for each part to be cast.
Assembly: Multiple wax patterns are assembled onto a central wax “sprue” to form a tree-like structure. This sprue acts as a channel for the molten metal to flow into the molds. This assembly allows for the production of many 310 stainless steel cast parts in a single pour.
Shell Building (Investing): The wax assembly is dipped into a ceramic slurry and then coated with a fine sand or stucco. This process is repeated several times, with the shell drying between each coat, until a thick, rigid shell is formed around the wax patterns. This shell will become the mold for the 310 stainless steel casting.
Dewaxing: Once the ceramic shell is hard and dry, it is heated in a furnace or an autoclave. The wax melts and drains out of the shell, leaving a hollow cavity that is an exact negative of the original wax pattern. The wax is often reclaimed and reused.
Melting and Pouring: AISI 310 stainless steel is melted in a high-temperature furnace. The molten metal is then poured into the preheated ceramic shell. The high temperature of the shell helps the metal flow evenly into all parts of the mold, creating a precise 310 stainless steel cast part.
Cooling and Solidification: The molten metal cools and solidifies inside the shell. This can take anywhere from minutes to hours, depending on the size and complexity of the cast part.
Knockout: Once the metal has solidified and cooled, the ceramic shell is broken away from the metal casting using hammers, vibration, or other mechanical means.
Finishing: The individual 310 stainless steel castings are cut away from the central sprue. Any remaining sprue material is ground off. The parts may then undergo further finishing processes, such as sandblasting, heat treatment, or machining, to meet the final specifications.

Benefits of 310 Stainless Steel Investment Castings

Investment casting offers a way to produce 310 stainless steel cast parts with several advantages. The process is well-suited to the properties of this specific alloy.

310 stainless steel spiral nozzle — 310 stainless steel investment casting spiral nozzle

High-Temperature Corrosion and Oxidation Resistance

One of the main benefits of using 310 stainless steel for investment casting is the material’s ability to resist corrosion and oxidation at high temperatures. The high chromium and nickel content of the alloy allows it to form a stable, passive oxide layer on its surface when heated. This layer protects the underlying metal from corrosive gases and scaling, which is a common problem in hot industrial environments. Because of this, 310 stainless steel investment casting is used for parts that are directly exposed to flames or hot exhaust gases.

Excellent Strength at High Temperatures

Unlike many other metals that lose significant strength as temperature increases, AISI 310 stainless steel maintains its mechanical properties at elevated temperatures. The stable austenitic microstructure provides good tensile and creep strength, even when the part is under continuous load in a hot environment. This property makes 310 stainless steel casting a reliable choice for components like furnace fixtures, heat exchangers, and boiler parts that must operate under both heat and mechanical stress.

Design Freedom and Part Consolidation

The investment casting process allows for the production of highly complex geometries with fine details and thin walls. This design freedom means that several smaller parts that would typically be welded or assembled can be combined into a single, monolithic 310 stainless steel cast part. This part consolidation reduces manufacturing steps, lowers the risk of failure at welded joints, and often results in a stronger, more durable component. This is a significant advantage for producing intricate parts for high-temperature applications.

Surface Finish and Dimensional Accuracy

Investment casting is known for producing castings with a good surface finish and tight dimensional tolerances. This means that 310 stainless steel investment casting parts often require little to no additional machining, which is particularly beneficial given the alloy’s poor machinability. The near-net-shape production capability of this process saves time and reduces material waste, which is a consideration given the cost of the alloy.

Applications of 310 Stainless Steel Castings

The properties of 310 stainless steel casting make it a material for many industries, particularly where high heat, thermal cycling, and corrosive atmospheres are present.

Furnace and Heat Treatment Industry

The furnace and heat treatment industry is a primary user of AISI 310 stainless steel cast parts. The alloy’s ability to resist oxidation and maintain strength at temperatures up to 1093°C (2000°F) is highly useful here. 310 stainless steel castings are used to make parts like furnace rollers, fixtures for heat-treating operations, radiant tubes, and conveyor parts that move materials through hot zones. Its stability at high temperatures reduces the need for frequent replacement of components.

Petrochemical Industry

In the petrochemical industry, 310 stainless steel is used for parts that must operate in environments with both high temperatures and corrosive chemicals. 310 stainless steel investment casting parts are used for tube hangers, burner nozzles, and other components in refinery and cracking furnaces. The alloy’s resistance to high-temperature sulfidation and other forms of corrosion makes it a good choice for these demanding environments.

Power Generation

The power generation sector uses 310 stainless steel castings for boiler components and other parts that are exposed to high temperatures and pressures. 310 stainless steel cast parts are used in components like boiler baffles, steam nozzles, and gas turbine parts. The material’s creep resistance is important in these applications, where parts must withstand constant stress over a long period.

HVAC and Heat Exchanger Components

While often associated with high temperatures, 310 stainless steel casting also serves in heating, ventilation, and air conditioning (HVAC) systems. It is used in specialized heat exchangers and recuperators where corrosive flue gases are present. The material’s resistance to corrosion and its ability to handle temperature changes make it useful for parts that facilitate heat transfer from hot gas to cooler air or fluid.

General Engineering

Beyond specific industries, 310 stainless steel casting is used in various general engineering applications where parts are exposed to high heat. This includes components for food processing equipment, kilns, and chemical processing plants. The versatility of the 310 stainless steel alloy allows for its use in a wide range of custom 310 stainless steel cast parts that must operate reliably in hot and corrosive settings.

310 stainless steel casting boiler parts & components

Conclusion

310 stainless steel castings are a specific type of austenitic stainless steel. The alloy’s unique chemical composition, particularly its high levels of chromium and nickel, gives it properties like high-temperature strength and resistance to corrosion and oxidation. The investment casting process is a good manufacturing method for this material because it allows for the production of complex and detailed 310 stainless steel cast parts with a good surface finish and dimensional accuracy.

The combination of the material’s properties and the precision of the 310 stainless steel investment casting process makes these components useful across many industries. From furnace parts to boiler components and petrochemical equipment, AISI 310 stainless steel parts are used in applications that require reliability in demanding, high-heat environments.

Taiyuan SIMIS Investment Casting Co., Ltd. is a professional foundry in China, offering industry-leading investment casting services. Our capabilities include stainless steel casting, carbon steel casting, alloy steel casting, and manganese steel casting. Besides, we offer comprehensive post-casting services such as tooling, machining, and various types of treatments. Contact us to start your project with us today!

Benefits and Applications of 310 stainless steel castings