1. The strength limit refers to the ability to resist deformation and break under the action of external forces. Common strength restrictions include:

1. Symbol limit: refers to the ratio of the appearance of metal materials under external force to the ratio of its original section.

2. Tensile intensity: refers to the ratio between the larger tensile force between the metal materials and the original cross section.

3. Shear strength: Refers to the relatively large stress of metal material under the action of cutting and force.

2. The ability of metal materials to deform for a long time without causing damage is plastic under the action of external forces. The plastic index commonly used in automatic hardware processing includes:

1. Elm extension: When the metal material is broken under tension, the percentage of the elongation length and the original length is called the elongation.

2. Decreased area: When the metal material is broken under tension, the percentage of the decreased area and the original length is called the area decrease.

3. Cup -shaped test value (stamping depth).

3. Hardness: Metal materials resist more objects that are crushed into it as hardness. Hardware processing hardness is a comprehensive physical quantity of material performance. It represents the ability to resist flexibility deformation, plastic deformation or break in a small volume.