How to distinguish the material and hardness of screws?

To distinguish the material and hardness of screws, one can judge from the following aspects:

Material differentiation of screws

Appearance features:

Stainless steel screws: silver white in appearance, smooth in texture, with a layer of oxide film on the surface to prevent rusting.

Carbon steel screws: The appearance is dark gray, slightly less smooth than stainless steel, and there is no oxide film on the surface, which is prone to rust.

Brass screws: have a golden appearance, high smoothness, and a softer texture.

Aluminum screw: It has a silver white appearance, high smoothness, and is relatively light.

Magnetic testing:

Use a magnet to approach the screw. If it is attracted by the magnet, the screw may be made of metals such as iron, nickel, cobalt, etc; If not sucked in, it may be made of non-magnetic metals such as aluminum and brass.

Hardness differentiation of screws

Manufacturing materials:

Screws made of high-strength steel have higher hardness, while stainless steel screws have lower relative hardness.

Surface treatment:

The surface of high hardness screws is often subjected to heat treatment or surface nitriding treatment, and the surface color is mostly dark blue.

The color of screws without surface treatment is usually bright or galvanized.

Hardness value test:

The hardness value refers to the test data corresponding to the local resistance of a material to hard objects pressing into its surface.

The hardness of bolts, screws, and studs should be measured at the head, end, or rod.

The commonly used hardness values include Brinell hardness (HB), Rockwell hardness (HRC), and Vickers hardness (HV).

Hardness testing requires the use of a professional hardness tester and obtaining the corresponding hardness value based on the selected hardness tester.

Summary and induction

When distinguishing the material of screws, it can be determined by observing their appearance characteristics and conducting magnetic tests; When determining the hardness of screws, it is necessary to consider their manufacturing materials, surface treatment, and hardness values obtained through hardness testing. These comprehensive information can help us accurately distinguish the material and hardness of screws.