Analysis of six surface heat treatment
Date of release:2018-07-06 Author: Click:
Surface heat treatment is a metal thermal processing technology, which changes the chemical composition and microstructure on the surface of the material by means of heating, heat preservation and cooling. The following are six methods of surface heat treatment.
The workpiece is rapidly heated by different heat sources. When the surface temperature of the part reaches the critical point above the critical point (at this time the temperature of the workpiece is below the critical point), the workpiece is cooled quickly so that the surface of the workpiece is hardened and the core remains the original structure. The most widely used industries are induction heating and flame hardening.
Chemical heat treatment
The workpiece is heated and insulated in the medium containing active elements, so that the active atoms in the medium are penetrated into the surface of the workpiece or form a covering layer of a certain compound to change the structure and chemical composition of the surface, so that the surface of the part has special mechanical or physical and chemical properties. Nitriding and nitriding, for example, refer to a chemical heat treatment process that allows nitrogen atoms to infiltrate into the surface of the workpiece under certain temperature. Nitriding products have excellent wear resistance, fatigue resistance, corrosion resistance and high temperature resistance.
Contact resistance heating quenching
The voltage of less than 5 volts is added to the workpiece by the electrode. A large amount of electric current flows through the contact between the electrode and the workpiece, and a large amount of resistance heat is produced to heat the workpiece surface to the quenching temperature, and then the electrode is removed. The heat is introduced into the workpiece and the surface is cooled quickly, that is, to the quenching purpose.
Electrolytic heating and quenching
The workpiece is placed in the electrolyte of acid, alkali or salt aqueous solution, the workpiece is connected to the cathode, and the electrolytic cell is connected with the anode. After the direct current is switched on, the electrolyte is electrolyzed, oxygen is released on the anode, and hydrogen is released on the workpiece. Hydrogen is formed by forming a gas film around the workpiece, becoming a resistor and producing heat, which quickly heat the workpiece surface to the quenching temperature, then cut off electricity, disappear immediately, and the electrolyte becomes quenching medium, so that the surface of the workpiece is cooled and hardened quickly.
Laser heat treatment
The application of laser in heat treatment began in the early 70s, and then entered the stage of production and application from the laboratory research stage. When a focused high energy density (10W/cm) laser is used to irradiate the metal surface, the metal surface rises to the quenching temperature in a few seconds or even a few seconds in a few seconds.
Electron beam heat treatment
The electron beam surface quenching should be carried out in vacuum, and the other characteristics are the same as that of the laser. When the electron beam strikes the metal surface, the bombardment point is heated rapidly. The depth of electron beam penetrating the material depends on the acceleration voltage and material density.