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The role of heat treatment in the cutting machinery manufacturing industry

Apr 04, 2018

The purpose of heat treatment of hydraulic cutting machine is to improve mechanical properties of materials, eliminate residual stresses and improve machinability of metals. According to different purposes of heat treatment, heat treatment process can be divided into two main categories: preparatory heat treatment and final heat treatment.


1. Preparatory heat treatment

The purpose of preparatory heat treatment is to improve machinability, eliminate internal stress and prepare good metallurgical structure for final heat treatment. The heat treatment processes include annealing, normalizing, aging, quenching and tempering.


(1) the annealing and normalizing annealing of the cutting machine and normalizing are used for the blanks after hot working. Carbon steel and alloy steel with a carbon content of more than 0.5% are easily cut to reduce their hardness. The carbon steel and alloy steel with less carbon content than 0.5% are used to avoid cutting the knives when the hardness is too low and is treated with normalizing. Annealing and normalizing can still refine grain and uniform structure, and prepare for future heat treatment. Annealing and normalizing are often arranged before rough manufacturing and rough machining.


(2) aging treatment is mainly used to eliminate the internal stress produced in rough manufacturing and machining. In order to avoid excessive transportation workload, a aging treatment can be arranged for precision parts before finishing. However, the parts with high accuracy (such as the box of the boring machine, etc.) should be arranged for two or several aging processes. Simple parts are generally not treated with aging. In addition to the casting, for some precise parts with poor rigidity (such as precision screw), in order to eliminate the internal stress produced in the processing and to stabilize the machining precision of the parts, many times of aging are often arranged between the rough and seminal machining. Some shaft parts are also processed after straightening process.


(3) tempering and quenching and tempering are treated with high temperature tempering after quenching. It can obtain uniform and meticulous microstructure of the tempered Soxhlet, which can reduce deformation for the subsequent surface quenching and nitriding treatment, so the quenching and tempering can also be used as a preparatory heat treatment.


Because the comprehensive mechanical properties of parts are better after quenching and tempering, parts with low hardness and wear resistance can also be used as final heat treatment processes.


2. Final heat treatment

The ultimate heat treatment of the oil cutting machine is to improve hardness, wear resistance and strength.


(1) quenching and quenching has surface quenching and integral quenching. The surface quenching is widely used because of its small deformation, oxidation and decarburization, and the surface hardening has the advantages of high external strength, good wear resistance and good toughness and strong impact resistance. In order to improve mechanical properties of surface quenching parts, conditioning or normalizing is often required as heat treatment. The general process is: blanking -- forging -- normalizing (annealing) -- rough machining -- quenching and tempering -- semi finishing -- surface quenching -- finishing.


(2) carburizing and quenching carburizing and quenching are suitable for low carbon steel and low alloy steel. The carbon content of the surface layer is increased first, and the surface is high hardness after quenching, while the heart still maintains a certain strength and high toughness and plasticity. Carburizing is divided into whole carburizing and partial carburizing. For the carburizing part, impervious measures should be taken for the non carburizing part, such as copper plating or anti seepage material. Because carburizing and quenching are large deformation and carburizing depth is generally between 0.5~ 2mm, the carburizing process is usually arranged between semi finishing and finishing. Its technological route is generally: blanking forging normalizing coarse and semi finish carburizing quenching finish machining.


The process of excision of superfluous carburized layer should be arranged before carburization and before quenching when the non carburizing part of the partial carburizing part is used to increase the residual carburized layer.


(3) nitriding nitriding is a way to make nitrogen atoms infiltrate into the metal surface and get a layer of nitrogen compounds. Nitrided layer can improve the hardness, wear resistance, fatigue strength and corrosion resistance of the parts. Because of low temperature, small deformation, and thinner nitriding layer (generally not more than 0.6~ 0.7mm), the nitriding process should be arranged back as far as possible to reduce the deformation of nitriding, and the high temperature tempering should be carried out after the cutting.


The concept of heat treatment of the cutting machine is very important in order to make the material hardness, the material is heat-treated, the heat treatment includes quenching (increasing the hardness of the material), the quenching and tempering, the actual effect (the stress produced in the mechanical machining), the annealing (making the hardness reduced to be machined), and galvanizing. Surface treatment antirust), chromium plating (surface treatment antirust), carburizing (surface hardening) blue (surface treatment antirust) heat treatment has a very important position on mechanical processing.

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