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Material grain size matters in sheet metal bending

Grain Size Image - (C) The Fabricator

8 ways material grain size affects how metal parts form

The Fabricator recently ventured to put together a comprehensive list on the ways that material grain size can affect the process of metal forming.

Eight Factors

During forming, sheet metal expands on the outside of the bend and compresses on the inside of the bend. How well the metal responds to the expansion and compression during bending determines the amount of unexpected deformation.

There are eight main factors that affect deformation during sheet metal forming related to material grain. A deeper understanding of these factors allows manufacturers to make corrective action that reduce variations during a part run. Analysis and insight into these eight factors, operators should see errors diminish and product quality improve.

The eight factors identified by The Fabricator article include:

1. Work Hardening. Plastic deformation causes dislocations within the metal’s structure, which in turn generates additional dislocations. 

2. Hardness Variation. Steelmakers make sheet metal within a tolerance zone for hardness. 

3. Thickness Variation. The same thing goes for material thickness, specified within a tolerance zone that corresponds to a given material gauge.

4. Bend Line Location. A feature near a bend changes the way that the metal expands, compresses, and deforms. 

5. Forming Method. The common bending methods on the press brake are air forming (or air bending), bottoming (or bottom bending), and coining.

6. Bend Length. The length of the bend is proportional to the tonnage required to make the bend. 

7. Grain Direction. During the process of turning ingots of metal into sheet at the mill, the metal is forced between a set of rollers. 

8. Grain Size. Grain within the material influences its strength. The borders between grains act like a barrier to dislocation movement. 

Further details about these eight factors and information on identifying grain is available in the full article available on The Fabricator: https://www.thefabricator.com/thefabricator/article/bending/grain-size-part-i-material-grain-size-matters-in-sheet-metal-bending

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