Heat Treatment In Cutting Machinery Manufacturing

- Aug 12, 2020-

What are the functions of heat treatment in cutting machinery manufacturing?

The purpose of the heat treatment of the cutting machine is to improve the mechanical properties of the material, eliminate residual stress and improve the machinability of the metal. According to the different purposes of heat treatment, the heat treatment process can be divided into two categories: preliminary heat treatment and final heat treatment.

1. Preparatory heat treatment

The purpose of the preliminary heat treatment is to improve processing performance, eliminate internal stress and prepare a good metallographic structure for the final heat treatment. The heat treatment process includes annealing, normalizing, aging, quenching and tempering.

(1) Annealing and normalizing of cutting machine Annealing and normalizing are used for hot processed blanks. Carbon steel and alloy steel with a carbon content of more than 0.5% are often annealed to reduce their hardness and easy to cut; carbon steel and alloy steel with a carbon content of less than 0.5% are often used to avoid sticking to the cutting tool when the hardness is too low. Instead, normalizing is used. Annealing and normalizing can still refine the grains and uniform structure, preparing for the subsequent heat treatment. Annealing and normalizing are often arranged after the blank is manufactured and before the rough machining.

(2) Aging treatment The aging treatment is mainly used to eliminate the internal stress generated in the blank manufacturing and machining. In order to avoid excessive transportation workload, for parts with general precision, an aging treatment can be arranged before finishing. However, for parts with higher precision requirements (such as the box of a coordinate boring machine, etc.), two or several aging treatment procedures should be arranged. Simple parts are generally not subject to aging treatment. In addition to castings, for some precision parts with poor rigidity (such as precision lead screws), in order to eliminate the internal stress generated during machining and stabilize the machining accuracy of the parts, multiple aging treatments are often arranged between rough machining and semi-finish machining. Some shaft parts are processed with aging treatment after the straightening process.

(3) Quenching and tempering is the high temperature tempering treatment after quenching, it can obtain uniform and fine tempered sorbite structure, and prepare for the reduction of deformation during the subsequent surface quenching and nitriding treatment, so the quenching and tempering is also Can be used as a preliminary heat treatment.

Due to the better comprehensive mechanical properties of the parts after quenching and tempering, some parts that do not require high hardness and wear resistance can also be used as the final heat treatment process.

2. Final heat treatment

The purpose of the final heat treatment of the hydraulic cutting machine is to improve the mechanical properties such as hardness, wear resistance and strength.

(1) Quenching There are surface quenching and overall quenching for quenching. Among them, surface quenching is widely used because of small deformation, oxidation and decarburization, and surface quenching also has the advantages of high external strength and good wear resistance, while maintaining good internal toughness and strong impact resistance. In order to improve the mechanical properties of surface hardened parts, heat treatment such as quenching and tempering or normalizing is often required as a preliminary heat treatment. The general process route is: blanking-forging-normalizing (annealing)-rough machining-quenching and tempering-semi-finishing-surface quenching-finishing.

(2) Carburizing and quenching. Carburizing and quenching is suitable for low-carbon steel and low-alloy steel. First, increase the carbon content of the surface layer of the part. After quenching, the surface layer can obtain high hardness, while the core part still maintains a certain strength and high Toughness and plasticity. Carburizing is divided into overall carburizing and partial carburizing. In the case of partial carburization, anti-seepage measures (copper plating or anti-seepage material plating) should be taken for the non-carburized part. Due to the large deformation of carburizing and quenching, and the carburizing depth is generally between 0.5~2mm, the carburizing process is generally arranged between semi-finishing and finishing. The process route is generally: blanking-forging-normalizing-rough and semi-finishing-carburizing and quenching-finishing.

When the non-carburized part of the local carburized parts adopts the process plan of removing the excess carburized layer after increasing the margin, the process of removing the excess carburized layer should be arranged after carburizing and before quenching.

(3) Nitriding treatment Nitriding is a treatment method that allows nitrogen atoms to penetrate into the metal surface to obtain a layer of nitrogen-containing compounds. The nitriding layer can improve the hardness, wear resistance, fatigue strength and corrosion resistance of the part surface. Because the nitriding treatment temperature is low, the deformation is small, and the nitriding layer is thin (generally no more than 0.6~0.7mm), the nitriding process should be arranged as far back as possible. In order to reduce the deformation during nitriding, it is generally required after cutting. Perform stress-relieving high-temperature tempering.

The concept of cutting machine heat treatment is very large. In order to make the hardness of the material and the material meet the processing requirements, the material must be heat treated. The heat treatment includes quenching (to increase the hardness of the material), quenching and tempering, actual effect (to relieve the stress generated in machining), and annealing (To reduce the hardness so that it can be machined), galvanizing (surface treatment to prevent rust), chrome plating (surface treatment to prevent rust), carburizing (surface hardening) blue (surface treatment to prevent rust) heat treatment is very important for machining status.