Explanation of terms of metal materials (I): Types and properties

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

1. Meaning:

The development of metal materials is closely related to the progress of human civilization. After the stone age, the bronze age and iron age are marked by the application of metal materials. In modern times, a wide variety of metal materials have become an important material basis for the development of human society.

2. Type:

Metal materials are usually divided into ferrous metals, non-ferrous metals and special metal materials.

 (1) Ferrous metals, also known as iron and steel materials, include industrial pure iron containing more than 90% iron, cast iron containing 2% ~ 4% carbon, carbon steel containing less than 2%, as well as structural steel, stainless steel, heat-resistant steel, superalloy, stainless steel and precision alloy for various purposes. Ferrous metals in a broad sense also include chromium, manganese and their alloys.

 (2) Non ferrous metals refer to all metals and their alloys except iron, chromium and manganese. They are usually divided into light metals, heavy metals, precious metals, semi metals, rare metals and rare earth metals. The latest knowledge of metal materials in 2017 is the latest knowledge of metal materials in 2017. The strength and hardness of non-ferrous 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. There are amorphous metal materials obtained by rapid condensation process, quasicrystal, microcrystalline and 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 process performance and service performance. The so-called process performance refers to the performance of metal materials under the set cold and hot working conditions in the processing and manufacturing process of mechanical parts. The process performance of metal materials determines its adaptability to processing and forming in the manufacturing process. Due to different processing conditions, the required process properties are also different, such as casting performance, weldability, malleability, heat treatment performance, machinability and so on. 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 and so on. The service performance of metal materials determines its service range and service life. In the machinery manufacturing industry, general mechanical parts are used in normal temperature, normal pressure and very strongly corrosive media, and each mechanical part will bear different loads in the process of use. The resistance of metal materials to failure under load is called mechanical property (also known as mechanical property in the past). The mechanical properties of metal materials are the main basis for the design and material selection of parts. The mechanical properties of metal materials will be different with different properties of applied load (such as tension, compression, torsion, impact, cyclic load, etc.). Common mechanical properties include strength, plasticity, hardness, impact toughness, multiple impact resistance and fatigue limit.