AISI 316 is an austenitic stainless steel used for manufacturing parts in food, chemical, marine, and medical industries because of its remarkable corrosion resistance, good ductility, good machinability and bendability. If you are looking for corrosion-resistance parts for your project, read carefully this complete guide of AISI 316 stainless steel for understanding its chemical composition, properties, and applications.
What Is AISI 316 Material?
AISI 316, one of austenitic stainless steels containing Mo element, is known for its excellent corrosion resistance and performs well particularly in chlorides and other industrial chemical environment. It also exhibits good strength and ductility, which makes it suitable for bending parts. Typically, AISI 316 is often used for manufacturing components requiring salt resistance or high-temperature oxidation resistance.
What Is Another Name for AISI 316?
AISI 316 is also called 18/10 stainless steel or hromium-nickel-molybdenum steel based on it chemical composition or alloy elements. It contains 18% Cr and 10% Ni chemical elements. In addition, in practical engineering scenarios, it is called marine-grade stainless steel or 316 stainless steel.
What Is A 316 Material Equivalent to?
In difference nations or industry standard systems, AISI 316 has multiple corresponding designation names. Its equivalent materials include:
- UNS S31600: Unified Numbering System
- EN 1.4401: European Standard
- SUS 316: Japanese Industrial Standard
- X5CrNiMo17-12-2: German/European designation
- 06Cr17Ni12Mo2:Chinese standard
They have similar chemical composition and almost the same features and functions. Therefore, they can be used for the same applications.
AISI 316 Chemical Composition
The chemical composition of AISI 316 stainless steel determines its crack resistance, corrosion resistance, and work hardening behavior during bending processing. The table below has provided its main chemical elements and their content.(According to ASTM A240)
| Element | Weight (%) |
| 탄소(C) | ≤ 0.08 |
| 실리콘(Si) | ≤ 1.00 |
| 망간(Mn) | ≤ 2.00 |
| 인(P) | ≤ 0.045 |
| 황(S) | ≤ 0.030 |
| 크롬(Cr) | 16.0 – 18.0 |
| 니켈(Ni) | 10.0 – 14.0 |
| Molybdenum (Mo) | 2.00 – 3.00 |
| 철(Fe) | Balance |
Molybdenum is the key element that can differ 316 from 403, it can directly enhance the material’s putting corrosion resistance under bending stress. The 10-14% Nickel content ensures 316 stainless steel ‘s stable austenitic microstructure, which can facilitates better plasticity during bending.
내식성
The chromium allows 18/10 stainless steel form a dense passive film in the surface to prevent corrosion. And in chloride ion environments, Mo element can reduce local damage rate of passivation films and increase pitting potential. As for bent 316 stainless steel parts, acid pickling or passivation treatment is recommended to restore the integrity of the passivation film.
Oxidation Resistance
The oxidation resistance of AISI 316 stainless steel is determined by Chromium and nickel. Chromium can form a continuous Cr2O3 oxide layer at elevated temperatures, preventing oxygen diffusion into the material matrix. In some cases, AISI 316 can keep good oxidation resistance in temperature below 870 °C.
Passivation Behavior
AISI 316 stainless steel can from a chromium-rich oxide film with a thickness of 2-5 nanometers. In fabrication, the bending technique can easily destroy original passive film. Therefore, the corrosion-resistance 316 stainless steel parts requires a passivation treatment process, and the pickling time should be controlled to avoid over-corrosion.
AISI 316 Physical Properties
The physical properties determines the thermal conductivity, thermal expansion and magnetic performance of 316 ss during manufacturing. These parameters can directly influence the bending process and dimension of 316 ss parts.
열전도율
At room temperature, AISI 316 exhibits a thermal conductivity of approximately 15 W/(m·K), significantly lower than that of carbon steel. This feature means that 316 ss has poor thermal conductivity. It means that during hot bending, the heat is difficult to dissipate. Therefore, when hot bending 316 ss, the heating speed and heating zone should be controlled to avoid cracking.
Coefficient of Thermal Expansion
The linear expansion coefficient of AISI 316 ss is 16.5 × 10⁻⁶ /°C, which is significantly higher that that of carbon steel and ferritic stainless steel and carbon steel.
Magnetic Properties
AISI 316 stainless steel is non-magnetic. It has stable FCC crystal structure because of the high nickel content. In this structure, the metallic atoms and electrons don’t align in a way that creates a magnetic pull, which makes 316 ss paramagnetic.
AISI 316 Mechanical Properties
Mechanical properties are essential for the manufacturing of AISI 316 parts. Here let us explore its mechanical properties and their impacts.
항복강도
In the annealed state, the typical yield strength of AISI 316 is 205-240 Mpa, which is relatively low. It means that 316 material is prone to enter the plastic deformation stage, which facilitates bending molding. However, in practical manufacturing, bending process may make 316 ss occur work hardening behavior.
인장강도
The tensile strength of AISI 316 is typically 515-620 MPa. During bending, the tensile stress on the outer surface of 316 stainless steel must not exceed its tensile strength, otherwise the material will occur cracking. To avid this risk, you can optimize the design of parts, for example, determine the minimum bend radius.
연신율
In annealed condition, the minimum elongation of 316 ss is about 40%, and common rang is 40-50%. We can easily find that 316 stainless steel has high elongation, which means it can undergo significant deformation prior to fracture. That is why 316 is very suitable for bending, forming and deep drawing.
경도
The typical hardness of the annealed AISI is HB 150-220 HRB. This relatively low hardness facilitates mold forming and reduces mold wear. However, after metal sheet bending, the local work hardening may lead to higher hardness (300-400 HRB). This hardness accelerates tool wear when machining AISI 316. Therefore, as for the parts that require bending and machining, hard alloy tools can be used to reduce cutting speed.
Modulus of Elasticity
The modulus of elasticity of AISI 316 is about 193 GPa, which is very similar to that of carbon steel. Modulus of elasticity is the key parameter for springback calculating.
Why Choose AISI 316 for Manufacturing Parts?
Choose AISI 316 material for bending parts due to its corrosion resistance, mechanical strength and bendability. Compared to 304, the molybdenum content in 316 ss makes it has longer service life in saline and acidic environments. In addition, superior weldability make the connection between 316 ss parts and other parts easier. Therefore, AISI 316 stainless steel is the optimal material for manufacturing chemical equipment, marine components, and medical devices.
Is 316 Stainless Steel Bendable?
Yes, AISI 316 exhibits excellent cold formability. Due to its high elongation, 316 stainless steel can achieve bending of sheets, bars, and tubes at room temperature. It requires greater bending force because its work hardening rate is higher than that of 304 ss.
How to Bend AISI 316 Stainless Steel Parts?
Bending AISI 316 by following this guidelines:
- Calculating minimum bending radius
The bend radius should be 1.5–2.0 times the sheet thickness (t)
- Springback Compensation
Springback should be determined through trial bending based on the yield strength and elastic modulus of 316 stainless steel.
- Tooling Selection
In general, the V-die opening width is 6–8 times the sheet thickness, while the punch radius should match the target internal bend radius.
- Control bending speed
Moderate bending speed (10–30 mm/s) is recommended to avoid high-speed impact loading.
What Is AISI 316 Used for?
AISI 316 is widely used for the manufacturing of components that require exposure to corrosive environments. It can be used to manufacture high-precision and highly corrosion-resistant structural components. Followings are its typical applications.
Food Parts
- Sheet metal housings
- Enclosures
- Tanks & containers
Medical Parts
- Instrument housings
- Trays
- Sterilization containers
Marine Parts
- Panels
- Covers
- Brackets
Chemical Equipment Parts
- Filter plates
- Heat exchanger plates
- Precision baffles
Considerations When Bending AISI 316 Sheet Metal
When bending AISI 316 metal sheet, springback, bend radius, and thickness of plates are needed to consider to ensure the dimension accuracy and reasonable cost.
스프링백
Springback is the most important phenomenon requiring compensation in AISI 316 bending. The yield strength of AISI 316 is 205-240 Mpa, and modulus of elasticity is 193 Gpa, so the theoretical elastic recovery strain ranges from 0.00106-0.00124 mm/mm.
Engineering Compensation methods include:
- Overbending
- Bottoming
- Stretch bending
최소 벤드 반경
Minimum bend radius means the smallest permissible value of the inner bending radius without leading to cracking on the surface. As for AISI 316 metal sheet, the recommended smallest bend radius is:
- When t≤3mm, Rmin ≈ 1.0t;
- When 3mm≤t≤6mm, Rmin≈ 1.5t;
- When t≥6mm, Rmin≈ 2.0t;
If the bend radius is too small, minor cracking or fracture may occur.
Thickness of Sheet
The thickness of 316 ss plates can directly influence the bending force, mold selection and the quality of bending. For example, the bending force required for a 4mm-thick AISI 316 plate is 4 times that of a 2mm-thick plate. In addition, the variations of thickness tolerance can lead to fluctuations in springback during bending.
결론
For engineer, AISI 316 is an austenitic stainless steel famous for its unmatched corrosion resistance because of its Ni and Mo chemical elements, ensuring the reliability of parts in marine, chemical industries, food industries and medical devices. What’s more, it is suitable for bending because of its good bendability. Tuofa bending fabrication service can help you produce stainless steel parts with high precision and smooth surface.
FAQ
Is 304 or 316 easier to bend?
304 ss is easier to bend because its work hardening rate is lower, elongation is higher and yield strength is relatively low. That is why bending 304 stainless steel needs smaller bending force and smaller springback angle.
Which stainless steel is best for bending?
As for cold bending, AISI 304 or 430 is easy to bend. But if you require excellent corrosion resistance, 316 ss is the better choice. As for complex bending, you can choose 316L or 317L. They have lower work hardening rate and better plasticity. Martensitic stainless steel is generally not recommended for bending.
What is a stainless steel bracket?
Stainless steel bracket is a structural component manufactured by bending, stamping or welding processes. It is used to fix, support or connect other machined parts. The specific types of brackets include L-shaped, U-shaped, and Z-shaped bent components. AISI 316 stainless steel brackets are widely used for marine and chemical equipment because of its high strength and corrosion resistance.