Strip edge processing for functional applications
“During slitting—that is, when cutting cold-rolled steel strip—the cut is not smooth, because the material first undergoes plastic deformation, then is cut cleanly, and finally is separated by fracture,” explains Dr. Michael Hellmann, operations manager at the Plettenberg facility in Germany, which is one of the Waelzholz Group’s three current centers for strip edge processing. The resulting cut edge exhibits four characteristic zones (see chart); however, it is unsuitable for many further processing steps and end uses, as the fracture zone and burr negatively affect process stability and service life in numerous applications. That is why we offer our customers customized edge finishing optimized for specific materials and applications. Dr. Hellmann outlines the range of services:
With our specialized machinery, which we are currently expanding to include two state-of-the-art lines, we can adjust the edge to be square, square with chamfers, or rounded in various shapes. This is how we create optimal functional edges for our customers.
Slitting cold-rolled steel stripCut edge with four distinct zones
01 Plastic deformation
02 Clean cut
03 Fracture
04 Burr
Existing equipment fleet expanded to include state-of-the-art edge-processing lines
With two state-of-the-art lines, we are expanding our production capacity for strip edge processing at our facility in Germany. In addition to increasing capacity, the new systems also expand the range of dimensions (see table below) and, thanks to an innovative inline cross-sectional measurement system, enable a full inspection of the steel strip. This allows the edge shape specified by the customer to be monitored in real time during the manufacturing process and adjusted immediately if necessary.
In addition, we can now not only produce rounded edges but also right-angled edges with very tight radii of up to 0.1 mm, which, in particular, are required for the manufacture of band saw blades. We have expanded our portfolio of possible shapes for rounded edges. This allows us to offer our customers even wider range of options, combined with our many years of expertise in edge finishing. Dr. Hellmann points out another benefit for customers: “As is typical of our products in general, our customers receive the same high quality in functional edge processing, regardless of whether they purchase the product from our edge processing center in Germany, Italy, or Brazil.” The next steps have already been determined as well. We will also be installing edge-processing lines at our facilities in China and the United States over the next few months.
Possible range of dimensions
We can process cold-rolled steel strip with thicknesses ranging from 0.1 to 3 mm and widths ranging from 5 to 250 mm.
| Location | Thickness | Width | ||||||
| Europa | 0.0039 - 0.118 in | 0.197 - 9.843 in | ||||||
| Brazil | 0.0098 - 0.138 in | 0.197 - 12.401 in | ||||||
| Custom dimensions available upon request. | ||||||||
Functional edges for long service life and precise joining
Two application examples illustrate the functional benefits of machined steel strip edges: Spring steel strip for retractor springs and cold-rolled steel strip for bimetal saw blades.
“Our SORBITEX® textured strip has exceptionally high tensile strength and is therefore used in applications such as springs and tools,” explains Dr. Hellmann. "However, the fracture zone with its notches that forms when the steel strip is cut lengthwise can serve as a starting point for crack formation under cyclic tensile loading, which would shorten its service life. That’s why we round off the edges by machining them, thereby removing the structures that cause notching.” The expert also makes it clear right away that this requires considerable edge finishing expertise: “With high-strength materials such as SORBITEX®, machining generates high temperatures that can have an adverse effect on the material’s microstructure. That is why, in addition to other parameters, we precisely control the temperature range during edge machining.”
André Fleck, Sales at Waelzholz, outlines the benefits that manufacturers of bimetal saw blades gain from edge finishing:
In these products, two types of steel are joined along their edges. For the joining processes—such as laser welding—the edges must be precisely designed and fit together perfectly. We customize the edge geometry for each of our customers’ specific joining processes—even with the tightest radii of up to one-tenth of a millimeter. This is made possible by measurement technology codeveloped by Waelzholz specifically for this application.
Advantages of precisely machined edges
- Improved formability:
Notches and microcracks can increase the susceptibility to cracking during forming. In addition, high notch stresses caused by inhomogeneous stress distribution in the edge region can lead to uneven forming.Rounding specifically removes these notch-inducing structures.
- Longer component life:
Notches and microcracks in components subjected to dynamic loads (e.g., springs) can be the starting point for component failure and thus reduce fatigue strength. Rounded edges prevent these effects and extend the service life.
- Reliable joining performance:
When two materials are joined at their edges, the edges can be optimally adapted to the joining process. This enhances the reliability of the joining process and ensures greater durability of the joint.
- Lower risk of damage:
Compared to sharp edges, machined edges reduce the risk of damaging other components, such as when sliding sleeves onto pipes.
- Increased safety during handling:
Rounded edges without sharp burrs reduce the risk of injury during handling.