Material Selection & Specification
The first step of designing a sheet metal component is the selection of material. Over-specifying your material can add significant costs to your component. Using standard materials will help control costs and lead times. Often times it’s far more economical to increase the thickness of the component to achieve a desired strength rather than selecting a more exotic material.
Common Steels
Hot Rolled
Hot-rolled steel is shaped at high temperatures, exceeding 1700 degrees Fahrenheit, to enhance malleability. Large slabs are heated and passed through rollers, resulting in a cost-effective and versatile material used extensively in construction and various industries for its unique mechanical properties.
Considerations:
- Typically available in 16 gage and heavier.
- While cold rolled is marketed as having tighter tolerances you should still expect ± .005″ on thickness.
- Will have a very light coat of oil to prevent rusting.
- Specifying grades will increase costs, however ASTM-A36 is the most common followed by ASTM-A1011 and ASTM-A-1018
Cold Rolled
Cold-rolled steel undergoes a distinct process at room temperature, reducing thickness for a smoother finish. This method enhances strength and precision, making it ideal for applications requiring tight tolerances. Commonly used in automotive parts and appliances, cold-rolled steel offers improved dimensional accuracy and a polished appearance.
Considerations:
- Available in all gages though more common for thinner gages below 16 gage.
- Approximately 15-20% more expensive than hot rolled due to the additional processing.
- Surface finish will be improved over hot rolled in terms of brightness and uniformity
- May have oil to prevent rusting
- Specifying grades increase costs however ASTM-A1008 is the most common.
Galvanized
Galvanized steel undergoes galvanization, a process coating it with a protective layer of zinc. This corrosion-resistant treatment enhances durability, making it resistant to rust and environmental elements. Widely used in construction for roofing, fencing, and structural components, galvanized steel provides a cost-effective solution for materials requiring both strength and long-term protection against corrosion.
Considerations:
- Will be thicker than other steel for the same gage.
- Approximately 30-35% more expensive than hot rolled due to the additional processing.
- If you don’t specify a galvanized thickness you can assume you’re getting “G90” which specifies 0.9 oz/ft2 coating thickness (.45 oz per side) per ASTM-A653 as this is the most common treatment. If you need a thicker treatment be sure to be very clear with your supplier and be prepared for significant cost and lead time increases.
Common Stainless Steels
Martensitic (Good)
ASTM 240 Type 410 (S41000): This stainless steel is heat-treatable and commonly used in applications such as cutlery, surgical instruments, and industrial equipment. The most economical of the stainless steels but shouldn’t be used for outdoor applications or where corrosion resistance id a priority.
Ferritic (Better)
ASTM 240 Type 430 (S43000): This stainless steel is commonly used in appliances, automotive trim, and architectural applications. It provides good corrosion resistance and is less expensive than austenitic stainless steels. Not suited for outdoor use.
Austenitic (Best)
ASTM 240 Type 304 (S30400): This is one of the most widely used stainless steels. It offers good corrosion resistance, formability, and weldability. It is often used in food processing equipment, kitchen appliances, and architectural applications.
ASTM 240 Type 316 (S31600): Known for its increased corrosion resistance, particularly in chloride environments, Type 316 is used in applications such as marine equipment, chemical processing, and medical devices. The most expensive option for when corrosion resistance is a priority.
Aluminum
5052
Best all around choice for formed parts as it offers good corrosion resistance, excellent formability and weldability, and moderate strength. This is also the most economical choice being half the price of 5086 and 1/3 the price of 1100.
5086
5052 and 5086 share similarities as aluminum-magnesium alloys with good formability, the key differences lie in their magnesium content and, consequently, their corrosion resistance. 5086 is favored for applications demanding higher corrosion resistance.
1100
99% Pure aluminum which has excellent corrosion resistance and is very formable. It is however very expensive and much weaker than 5052 and 5086.
What about 6061?
6061 Is a very common alloy used in manufacturing, especially machining and we often see if specified on drawings. While many sites indicate 6061 has good formability this is not our opinion. There are very specific requirements for large bend radii (minimum of 2X material thickness) in order to prevent cracking and even then we see customers surprised at how easily the bends fail, splitting the part along the bend line.