Basic mechanical properties of metal materials

The properties of metal materials are generally divided into two categories: process performance and usage performance. The so-called process performance refers to the performance of metal materials under specified cold and hot processing conditions during the manufacturing process of mechanical parts. The quality of the process performance of metal materials determines its adaptability to processing and forming during the manufacturing process. Due to different processing conditions, the required process properties are also different, such as casting performance, weldability, forgeability, heat treatment performance, cutting processability, etc. The so-called performance refers to the performance of metal materials under the conditions of use of mechanical parts, which includes mechanical properties, physical properties, chemical properties, etc. The performance of metal materials determines its range of use and service life.

In the machinery manufacturing industry, general mechanical parts are used in normal temperature, normal pressure and non-strongly corrosive media, and during use, each mechanical part will bear different loads. The ability of metal materials to resist damage under load is called mechanical properties (or mechanical properties). The mechanical properties of metal materials are the main basis for the design and material selection of parts. Depending on the nature of the applied load (such as tension, compression, torsion, impact, cyclic load, etc.), the mechanical properties required for metal materials will also be different. Commonly used mechanical properties include: strength, plasticity, hardness, toughness, multiple impact resistance and fatigue limit. Each mechanical property is discussed separately below.

1. Strength

Strength refers to the ability of a metal material to resist damage (excessive plastic deformation or fracture) under static load. Since the load acts in the form of tension, compression, bending, shearing, etc., the strength is also divided into tensile strength, compressive strength, flexural strength, shear strength, etc. There is often a certain relationship between various strengths. In use, tensile strength is generally used as the most basic strength index.

2. Plasticity

Plasticity refers to the ability of a metal material to produce plastic deformation (permanent deformation) without destruction under load.

3.Hardness

Hardness is a measure of how hard or soft a metal material is. At present, the most commonly used method for measuring hardness in production is the indentation hardness method, which uses an indenter of a certain geometric shape to press into the surface of the metal material being tested under a certain load, and the hardness value is measured based on the degree of indentation.
Commonly used methods include Brinell hardness (HB), Rockwell hardness (HRA, HRB, HRC) and Vickers hardness (HV).

4. Fatigue

The strength, plasticity, and hardness discussed previously are all mechanical performance indicators of metal under static load. In fact, many machine parts are operated under cyclic loading, and fatigue will occur in the parts under such conditions.

5. Impact toughness

The load acting on the machine part at a very high speed is called impact load, and the ability of metal to resist damage under impact load is called impact toughness.