When the sheet is made its particles become elongated in the direction of rolling.
Grain direction in sheet metal bending.
The raw sheet has a natural micrograin direction that runs parallel to the 144 in.
Bending metal against the grain or perpendicular to the grain is a common way to prevent material failure or cracking.
That has negligible impact on part strength.
Bending with the grain gives a different result than bending against it.
In the example above perhaps were using a certain type of steel and specific bend radius whereby we need to be careful to ensure the sheet metal does not crack due to bending.
The grain direction created in the direction the sheet is rolled at the mill runs the length of the full sheet.
Two rollers compressing the hot metal cause the polycrystalline material to elongate in the direction of rolling.
During sheet metal processing rolling operation material grains are arranged in the direction of rolling.
This can drastically limit the length of parts being formed as most materials grain runs in the long direction but as stated previously reducing the material s grain size may be a solution to this.
The grain direction of the metal also contributes to the amount of springback that occurs in a bending operation.
When sheetmetal is bend perpendicular to rolling direction grain rearranges.
A metal s grain direction is usually only a factor when bending however.
Working with grain direction.
This is because sharper or tighter bends can be made across the grain without cracking.
This micrograin impacts the design in terms of strength and appearance.
Whereas bending parallel to rolling direction can lead to cracks because of destruction in grain structure.
The grain direction is established during the metal rolling process.
Bends that run perpendicular to the material s natural grain require slightly more pressure than those running parallel to the grain.
This occurs because bending along the grain allows for separation of the grain boundaries.
You must pay careful attention to grain or rolling direction when bending high strength metals especially when trying to achieve a small inside bend radius.
You can see it on a new piece of sheet metal by noticing the direction of visible lines running through it.
Once the crystallites are elongated they appear as the grain that we see in cold rolled steel.
In addition the grain direction needs to be considered when the bend radius is less than twice the thickness depending on the material and its hardness.
We can manually control the grain direction of the metal in the flat pattern and subsequently how the bounding box is oriented to address these concerns.
As a general rule the grain line must run perpendicular to the bend to avoid the potential for cracking or fracture.
