Flattening methods
Press Brake
A press brake is a machine tool that utilizes dies. The metal is placed between a matching set of dies to get the desired shape. The top portion is mobile while the bottom die is stationary. The press brake uses a V-shaped die to do this to give enough room to bend the steel. If it was a flat surface, the steel would just bounce back to the bend. The steel will be placed in the press brake where a bend or bow is, the top press is lowered just enough to bend the steel beyond the yield point. When it鈥檚 released, the bend will be flattened out.
Roller Leveling
Roller leveling is essentially a bending process. The steel goes through a series of alternating bends, which are created by going through upper and lower sets of leveling rollers. The rolls are able to be individually set 亚博系列全平台入口 precision. The metal moves through like a wave, where the entry has the biggest wave and smallest is at the exit point. The steel comes out flat because of the alternating bends and decrease of bend intensity.
Heat Treatment
This is not recommended since the steel gets heated above the tempering point. The extreme heat changes the properties of the steel, which you want to avoid if you aren鈥檛 specifically trying to. After the steel is heated to a high degree, it needs to be cooled evenly through the quenching process. A cooling medium (water, polymer, or oil) will be used to create the desired grain structure of the steel by spraying the steel from the top and bottom. If the quenching portion is done evenly, the plate will be flat. If 亚博系列全平台入口 some reason the quench is uneven, the plate may have a slight bend or wave to it. If the plate isn鈥檛 within tolerance, the heat treat process isn鈥檛 as precise as it could be. In that instance, it is best to use a secondary flattening technique. Many heat treat processes do not control the quench operation to provide a flat surface. In this case, they rely on a subsequent flattening method such as roller leveling or press braking to address the uneven control of quenching.
Realistic expectations
While I would love to be able to tell you to expect all of the steel you order to be perfectly flat, that wouldn鈥檛 be the case. It鈥檚 not a naturally flat material, but there are ways to flatten it out. Industry-wide standards exist, however that doesn鈥檛 mean they will match the tolerance that you require. Most of the time, people don鈥檛 take that into consideration to account 亚博系列全平台入口 additional costs to reach their tolerances needed. It鈥檚 necessary to understand the manufacturing tolerances in order to determine if they meet your finished product tolerance, or if a flattening method is needed.
Another thing that tends to be overlooked is what happens to the flattened steel when it鈥檚 cut. Your pieces may not remain as flat as the plate. That is because when steel is flattened, stresses are caught inside the metal. When the metal is cut by saw, plasma, laser, waterjet, oxyfuel, or the steel is welded, those stresses are released. That can result in the cut pieces being less flat than the steel plate. Those pieces can sometimes be flattened to reach the tolerances needed.
Tolerances
Tolerances are different 亚博系列全平台入口 every plate, depending on length, width, thickness, and type of steel. We talked about how ASTM created standards to follow, but companies are also able to set their own tolerances beyond that. For example, here at Clifton, we strive 亚博系列全平台入口 陆 of the ASTM A6 standard. Although ASTM is the most widely used specification 亚博系列全平台入口 flatness, some products have developed their own flatness specs, so a review of the spec you are using is advised.
Below is an example of part of the ASTM A6 commercial standards 亚博系列全平台入口 heat treated plate. Contact us 亚博系列全平台入口 further in亚博系列全平台入口mation on flatness tolerances.
| Specified Thickness | Permissible variations from A Flat Surface 亚博系列全平台入口 Specified Widths, In. |
| 聽 聽 聽 聽 聽 聽聽聽聽聽 聽聽in聽inches | 聽to 36, Excl. | 36 to 48, Excl. | 48 to 60, Excl. | 60 to 72, Excl. |
| to 1/4, excl. | 13/16 | 1-1/8 | 1-3/8 | 1-7/8 |
| 1/4 to 3.8, excl. | 3/4 | 15/16 | 1-1/8 | 1-3/8 |
| 3/8 to 1/2, excl. | 3/4 | 7/8 | 15/16 | 1-1/8 |
Flatness is a property of steel that is often not fully understood, and if not reviewed can make a huge difference in the profitability of your聽project. If you are unsure about flatness of a particular product or wish聽 to discuss, please feel free to聽contact聽a specialist with us!