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Basic knowledge of metal heat treatment

QY Precision can complete the whole CNC Process Procedure, including Heat treatment .
Metal heat treatment is a process in which a metal workpiece is heated to an appropriate temperature in a certain medium, and after it is kept at this temperature for a certain period of time, it is cooled at different speeds.
1. Metal structure
Metal: A substance with opaque, metallic luster, good thermal and electrical conductivity, and its electrical conductivity decreases with increasing temperature, and is rich in ductility and malleability. A solid (ie, crystal) in which atoms in a metal are arranged regularly.
Alloy:  A substance with metallic characteristics composed of two or more metals or metals and non-metals.
Phase: the component of the alloy with the same composition, structure and performance.
Solid solution: A solid metal crystal in which the atoms (compounds) of one (or several)elements dissolve into the lattice of another element while still maintaining the lattice type of the other element. The solid solution is divided into interstitial solid solution and replacement Two kinds of solid solution.
Solid solution strengthening: As the solute atoms enter the gaps or nodes of the solvent crystal lattice, the crystal lattice is distorted and the hardness and strength of the solid solution are increased. This phenomenon is called solid solution strengthening.
Compound: The chemical combination between alloy components produces a new crystal solid structure with metallic properties.
Mechanical mixture: An alloy composition composed of two crystal structures. Although it is a two-sided crystal, it is a component and has independent mechanical     properties.
Ferrite: The interstitial solid solution of carbon in a-Fe (iron with body-centered cubic structure).
Austenite: the interstitial solid solution of carbon in g-Fe (face-centered cubic structure iron).
Cementite: a stable compound (Fe3c) formed by carbon and iron.
Pearlite: a mechanical mixture composed of ferrite and cementite (F+Fe3c contains 0.8% carbon)
Leeburite: a mechanical mixture composed of cementite and austenite (4.3% carbon)
Metal heat treatment is one of the important processes in mechanical manufacturing. Compared with other processing processes, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but by changing the internal microstructure of the workpiece, or changing the chemical composition of the surface of the workpiece , To give or improve the performance of the workpiece. Its characteristic is to improve the internal quality of the workpiece, which is generally not visible to the naked eye.
In order to make the metal workpiece have the required mechanical properties, physical properties and chemical properties, in addition to the reasonable selection of materials and various forming processes, heat treatment processes are often indispensable. Steel is the most widely used material in the machinery industry. The microstructure of steel is complex and can be controlled by heat treatment. Therefore, the heat treatment of steel is the main content of metal heat treatment. In addition, aluminum, copper, magnesium, titanium, etc. and their alloys can also be heat treated to change their mechanical, physical and chemical properties to obtain different performance
The performance of metal materials is generally divided into two categories: process performance and use performance. The so-called process performance refers to the performance of metal materials under the specified cold and hot processing conditions in the processing and manufacturing process of mechanical parts. The process performance of metal materials determines its adaptability in the manufacturing process. Due to different processing conditions, the required process performance is also different, such as casting performance, weldability, forgeability, heat treatment performance, machinability, etc. The so-called use performance refers to the performance of the metal material under the conditions of use of the mechanical parts, which includes mechanical properties, physical properties, chemical properties, etc. The performance of a metal material 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 each mechanical part will bear different loads during use. The performance 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. The nature of the applied load is different (such as tension, compression, torsion, impact, cyclic load, etc.), and the required mechanical properties of the metal material will also be different. Commonly used mechanical properties include: strength, plasticity, hardness, impact toughness, multiple impact resistance and fatigue limit.

Post time: Aug-24-2021