Metal material refers to metal elements or mainly composed of metal elements with metal properties of the material. Including pure metals, alloys, metal materials intermetallic compounds and special metal materials. (Note: Metal oxides (e.g. alumina) are not metallic materials)
The development of human civilization and social progress are closely related to metal materials. The copper Age and Iron Age, which followed the Stone Age, were marked by the application of metal materials. In modern times, various metal materials have become an important material basis for the development of human society.
Metal materials are usually divided into ferrous metal, non-ferrous metal and special metal materials.
1) Ferrous metals are also known as iron and steel materials, including industrial pure iron containing more than 90% iron, cast iron containing 2% ~ 4% carbon, carbon steel containing less than 2% carbon, and various uses of structural steel, stainless steel, heat resistant steel, high temperature alloy, stainless steel, precision alloy and so on. Ferrous metals in 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, usually divided into light metals, heavy metals, precious metals, semi-metals, rare metals and rare earth metals, etc. The strength and hardness of non-ferrous alloy are generally higher than that of pure metal, 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, and quasicrystalline, microcrystalline, nanocrystalline metal materials, etc. There are stealth, hydrogen resistance, superconductivity, shape memory, wear resistance, damping and other special functional alloys and metal matrix composite materials.
It is generally divided into two categories: process performance and service performance. The so-called technological performance refers to the mechanical parts in the process of manufacturing, metal materials in the fixed cold, hot processing conditions of performance. The technological performance of metal material determines its adaptability in manufacturing process. As a result of different processing conditions, the required process performance is also different, such as casting performance, weldability, forging, heat treatment performance, cutting machinability, etc.
Alleged use performance is to point to mechanical part to fall in use condition, the performance that metallic material shows, it includes mechanical performance, physical performance, chemical performance to wait. The performance of metal materials determines its range of use and service life. In the machinery manufacturing industry, the general mechanical parts are used in room temperature, atmospheric pressure and very strong corrosive media, and in the use of the process of mechanical parts will bear different loads. The resistance of metallic materials to damage under load is called mechanical properties (formerly also called mechanical properties). Mechanical properties of metal materials are the main basis of parts design and material selection. Different properties of applied load (such as tensile, compression, torsion, impact, cyclic load, etc.) require different mechanical properties of metal materials. The commonly used mechanical properties include strength, plasticity, hardness, impact toughness, multiple impact resistance and fatigue limit.