Selecting Materials for Roll Forming
Ryan Hernden
This blog covers commonly used metals in roll forming, their benefits and drawbacks when used in roll form manufacturing.
This blog covers commonly used metals in roll forming, their benefits and drawbacks when used in roll form manufacturing.
Roll forming is fast and cost-effective, but material selection plays a significant role in the overall economics of the process. Some materials are easier to form than others, some are stronger, and some will almost certainly need secondary finishing or coating operations.
Selecting materials for roll forming takes a deep understanding of both material properties and the roll forming process. It also involves trade-offs between speed, material thickness, and the resulting profile. And, some materials can’t be roll formed at all.
This blog looks at the most widely used roll forming materials and their advantages and disadvantages.
Aluminum is naturally corrosion-resistant, which can avoid the cost of coating. It also has a high specific strength, making it a good choice when weight is a concern.
Aluminum is produced in seven series with widely varying properties. Those most suited to roll forming are the 3xxx series and the 5xxx series. (6xxx series aluminum, while a popular choice in many casting applications, is harder, and, therefore, less readily formed into profiles.)
3xxx series aluminum is alloyed with manganese. This gives it good corrosion resistance and moderate strength. The 5xxx series, produced by alloying with magnesium, is stronger, more corrosion-resistant, and can be readily welded.
The term “steel” covers a wide range of iron-carbon alloys. In general, those with lower carbon content lack the strength and hardness of higher carbon-content alloys but are more formable. They also tend to be less expensive.
The microstructure of steel, and hence its properties, can be changed by heat treatment. Austenitic and ferritic grades of steel can be roll formed. Martensitic grades, which provide high strength and are popular for lightweighting, require tempering to improve formability.
A limitation of steel is that it corrodes quickly. Steel profiles produced by roll forming, therefore, need some form of protection applied after forming, like paint, powder coating, or galvanizing.
Adding a minimum of 10.5% chromium to steel dramatically increases its corrosion resistance and strength. This results in stainless steel, a material with a bright and attractive appearance. Although this material can help reduce costs associated with coating, it’s not an easy metal to roll form. It requires high forces and there is a lot of springback after bending. This is addressed with substantial overbending to arrive at the desired shape. In addition, most grades work harden as they are formed, which can lead to cracking in the bends.
Copper and copper alloys roll form beautifully thanks to their high ductility. They are generally corrosion-resistant but can develop a green patina when used outdoors. As their strength and hardness are relatively low, profiles made by roll forming are used more for decorative and architectural functions than for load-bearing.
The family of copper alloys includes brass (a copper-zinc alloy), bronze(copper alloyed with tin), copper-nickel alloys, and beryllium-copper alloys. Bronze alloys are used extensively in maritime applications. Beryllium-copper combines high strength with light weight, making it an option in some aerospace and space applications. A limitation of copper in all its forms is its relatively high price.
Tin and tin alloys are ductile materials, making them good candidates for roll forming. Tin is non-toxic (hence its use in tin cans) and has a low melting point. Besides food storage and preservation, its other applications are found in the automotive and electronics industries.
Titanium alloys are known for their high strength and low weight, which leads to their use in aerospace and some automotive applications. Though titanium can’t be readily roll formed because it’s prone to work hardening, it can still be rolled formed as long as close attention is paid to forming conditions and the part’s geometry.
Corrosion resistance can be improved, and appearance can be modified by coating or treating strip before roll forming. Typically, carbon steel alloys are coated this way, although other materials can be given various types of coating.
Common coatings and treatments are galvanizing, vinyl laminating, cladding, and painting. When roll forming strip with any of these, close attention is needed to ensure surfaces are unmarked and undamaged.
Material selection is an important consideration when designing parts to be made by roll forming. If you need material selection assistance, turn to MMC Roll Form. We manufacture high-quality roll-formed products in an extensive range of materials. Our substantial inventory of tooling means we can often produce the required profiles without needing to make new rolls. On new orders, this further compresses our already competitive lead times.
Contact us today to learn more about our capabilities or to speak with one of our experts.