Heat treatment process of machine tool casting:
As a kind of large castings, bed castings must undergo heat treatment to improve their performance and improve the internal quality of cast iron. Metal heat treatment is one of the important processes in mechanical manufacturing. Compared with other processing technologies, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but endowing or improving the working performance of the workpiece by changing the microstructure inside the workpiece or changing the chemical composition on the surface of the workpiece. Its characteristic is to improve the internal quality of the workpiece.
In order to make the metal workpiece have the required mechanical properties, physical properties and chemical properties, in addition to the rational selection of materials and various forming processes, heat treatment process is often essential. Steel is the most widely used material in the mechanical industry. The microstructure of steel is complex and can be controlled by heat treatment. Therefore, heat treatment of steel is the main content of metal heat treatment. In addition, the mechanical, physical and chemical properties of aluminum, copper, magnesium, titanium and their alloys can be changed through heat treatment to obtain different performance.
Integral heat treatment is a metal heat treatment process in which the workpiece is heated as a whole and then cooled at an appropriate rate to change its overall mechanical properties. The overall heat treatment of steel generally includes four basic processes: annealing, normalizing, quenching and tempering.
The common annealing processes include recrystallization annealing, stress relieving annealing, spheroidizing annealing, complete annealing, etc.
The purpose of annealing is to reduce the hardness of metal materials, improve plasticity, facilitate cutting or pressure processing, reduce residual stress, improve the homogenization of structure and composition, or prepare for post-heat treatment.
Total annealing and weighing crystallization annealing, generally referred to as annealing, this annealing is mainly used for various carbon steel and alloy steel casting, forgings and hot rolled profiles of hypoeutectoid composition, and sometimes used for welding structure. It is usually used as the final heat treatment of some non-heavy parts, or as the pre-heat treatment of some workpiece.
Spheroidizing annealing is mainly used for eutectoid carbon steel and alloy tool steel (such as steel used in making cutting tools, measuring tools and molds). Its main purpose is to reduce hardness, improve machinability and prepare for later quenching.
Stress relief annealing, also known as low temperature annealing (or high temperature tempering), is mainly used to eliminate the residual stress in castings, forgings, welding parts, hot rolled parts, cold drawn parts, etc. If these stresses are not eliminated, they will cause deformation or crack in the steel after a certain period of time or in the subsequent cutting process.
Advantages of the ground rail of hebei yuanpeng company: it does not need to be made into a large platform, which not only saves the material cost, but also takes up a small space, which is very cost-effective.
The most commonly used cooling media for quenching are salt water, water and oil. Brine quenching workpiece, easy to get high hardness and smooth surface, not easy to produce soft points not hard quenching, but it is easy to make the workpiece deformation seriously, or even cracking. And oil as quenching medium is only suitable for the quenching of some alloy steel or small size carbon steel workpiece with large stability of supercooled austenite.
Super-audio quenching is a common process to quench the guide rail of machine tools. The quenching layer is generally 2.5-3mm, and the quenching hardness is HT250 material --HRC46 -- 50 material --HRC48 -- 52 material