The majority of steel manufacturers create coils because they are easier to handle. This provides benefits for the end users too. However, it does mean they need to look at uncoiling and addressing potential issues before making products. Levelling is absolutely crucial to reduce the chance of part distortion. We know all about it from our work to offer the finest ERW steel tubes in the West Midlands. So, let’s have a closer look.
Stress
The main thing to keep in mind is coiling steel applies tension to the material. It is necessary to ensure that the coils won’t collapse. However, it means you leave tensile and compressive stress in the material. You need to think carefully about this or distortion could become a major problem and ruin parts.
It is also important to remember that the degree of stress differs in different parts of a coil. The outer laps have a much bigger diameter, so it reduces the stresses. On the other hand, inner laps, especially close to the centre of the coil, have a much smaller diameter. Therefore, the stress tends to be much higher.
Two issues
The coiling can lead to two different problems when you uncoil the steel to create strips. Firstly is coil set. What happens here is there is more stretching on the top surface of the steel than on the bottom. So, it can bow downwards, parallel to the direction it was rolled.
The second issue is known as crossbow. Again it has the problem that there has been more stretching on the top than the bottom. This time though, the bow is perpendicular to the direction of rolling. It curves downward and can mean there is a significantly raised section in the centre.
Levelling
The solution to the issues is to level the strips carefully. It can massively increase the quality of the products. This is crucial, and one of the reasons why we are the top provider of ERW steel tubes in the West Midlands.
There are two options for equipment for levelling the steel. They both work similarly, using a series of rollers to adapt the upper and lower surface, carefully flattening the material. Some manufacturers favour using a precision leveller here because they can apply tension to increase deformation.
Setting up the equipment properly is vital if you want to level the steel efficiently. Typically, you begin with smaller gaps between the rollers at first. It provides a higher level of initial deformation. Then, as you progress, the spacing between the rollers increases. Ultimately, the final rollers should have a gap to match the material thickness.
Crucially, you need to ensure you adapt the levelling to address the type of distortion. With coil set, you need to target around 20% of the outer surfaces; the inner core doesn’t need adapting. On the other hand, with crossbow you need to adapt more of the outer material (only 20% of the core material won’t need adapting).
Choose exceptional ERW steel tubes in the West Midlands
Levelling is important to get coil close to flat. However, you also need to keep in mind that the process does have an impact on formability. You must be careful to ensure you can still do additional operations like tube rolling.
Union Steel Tubes has been providing high quality tubing for a long time. As a result, we know how to address all kinds of potential flaws to deliver reliable products. We use the best equipment and rely on the expertise of our team.
So, if you want to order ERW steel tubes in the West Midlands, make us your first call. We can go over everything with you, including your application and specifications. We’ll then help you to select tube.
