What Indicators Should Be Considered For The Stamping Performance Of Steel?

Yield Strength

Yield strength is the stress at which a metallic material resists a small amount of plastic deformation.

Numerous tests have proven that the lower the yield strength, the easier the material yields, the less it will spring back after forming, and the better the moldability and shape freezing properties.

However, during compressive deformation, materials with low yield strength tend to wrinkle.

yield strength ratio

Yield ratio is the ratio of yield strength/tensile strength.

The yield-strength ratio has a great influence on the sheet metal stamping formability.

The smaller the yield ratio, the longer the plastic deformation stage of the sheet from yielding to rupture, that is, the larger the deformation range of the sheet, which is more conducive to stamping.

In general, a smaller yield-to-strength ratio is beneficial for crack resistance in various forming processes of sheet metal.

Elongation

Elongation reflects the ability of the sheet to deform plastically.

In general, the greater the elongation, the better the stamping performance.

r value

The r value is the ratio of the degree of narrowing in the width direction to the degree of thinning in the thickness direction when the sheet is stretched.

The larger the value of r, the easier the deformation in the width direction (in the plane) of the sheet is than the deformation in the thickness direction.

Therefore, the material tends to stretch in the plane, rather than thinning in the thickness direction, which is the fracture during the stamping process. Therefore, the larger the value of r, the lower the probability of rupture.

The r value, also known as the plastic strain ratio, is the most important parameter for evaluating the deep drawing performance of thin plates.

1. How is the r value measured? It is obtained by doing a tensile test (that is, the test that measures yield, tensile and elongation, and is the most basic test for steel). As the specimen is elongated, the width becomes narrower and the thickness becomes thinner.
The ratio of the degree of narrowing in the width direction to the degree of thinning in the thickness direction is the r value.

2. What does the r value indicate? Since the r value is the ratio of the degree of narrowing in the width direction to the degree of thinning in the thickness direction, the larger the r value, the easier the deformation in the width direction (in the plane of the sheet) than the deformation in the thickness direction, so the material tends to stretch in the plane , rather than thinning in the thickness direction, which is the cause of fracture during stamping, so the larger the value of r, the lower the probability of fracture.

When the r value is less than 1, it means that the material is easily deformed and thinned in the thickness direction, resulting in cracking and poor stamping performance.

When the r value is greater than 1, it indicates that the material is easily deformed in the length and width directions during the stamping and forming process, and can resist thinning in the thickness direction. Therefore, the larger the r value, the better the deep drawing performance.

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