Basic Knowledge of Metal Materials

Metallic materials refer to metal elements or materials with metal characteristics mainly composed of metal elements. Including pure metals, alloys, intermetallic compounds of metal materials and special metal materials. (Note: Metal oxides (such as aluminum oxide) are not metal materials)

1. Meaning

The development of human civilization and social progress are closely related to metal materials. The Bronze Age and Iron Age, which appeared after the Stone Age, are marked by the application of metal materials. Nowadays, a wide variety of metal materials have become an important material basis for the development of human society.

2. Type

Metal materials are generally divided into ferrous metal, nonferrous metal and special metal materials.

(1) Ferrous metals are also called iron and steel materials, including industrial pure iron containing more than 90 percent iron, cast iron containing 2 to 4 percent carbon, carbon steel containing less than 2 percent carbon, and structural steel, stainless steel, heat-resistant steel, superalloy, stainless steel for various purposes. The broad sense of ferrous metals also includes chromium, manganese and their alloys.

(2) Non ferrous metals refer to all metals and their alloys except iron, chromium and manganese, which are generally divided into light metals, heavy metals, precious metals, semi metals, rare metals and rare earth metals. The strength and hardness of nonferrous alloys are generally higher than that of pure metals, and the resistance is large and the resistance temperature coefficient is small.

(3) Special metal materials include structural metal materials and functional metal materials for different purposes. Among them, amorphous metal materials obtained by rapid condensation process, quasicrystalline, microcrystalline, nanocrystalline metal materials, etc; There are also special functional alloys such as stealth, hydrogen resistance, superconductivity, shape memory, wear resistance, vibration damping and metal matrix composites.

3. Performance

It is generally divided into two categories: process performance and service performance. The so-called technological performance refers to the performance of metal materials under the specified cold and hot working conditions during the processing and manufacturing of mechanical parts. The technological properties of metal materials determine their adaptability to processing and forming in the manufacturing process. Due to different processing conditions, the required process properties are different, such as casting performance, weldability, forgeability, heat treatment performance, and machinability.

The so-called service performance refers to the performance of metal materials under the service conditions of mechanical parts, including mechanical properties, physical properties, chemical properties, etc. The service performance of metal materials determines its scope of use and service life. In the mechanical manufacturing industry, general mechanical parts are used in normal temperature, pressure and very strong corrosive media, and each mechanical part will bear different loads during use. The ability of metal materials to resist damage under load is called mechanical property (also called mechanical property in the past). The mechanical properties of metal materials are the main basis for the design and selection of parts. The mechanical properties required for metal materials will be different due to different properties of applied loads (such as tension, compression, torsion, impact, cyclic load, etc.). Common mechanical properties include: strength, plasticity, hardness, impact toughness, multiple impact resistance, etc.