Why do mechanical processing need heat treatment?

The heat treatment requirement of mechanical machining is actually a technical requirement in the design process. If you are a mechanical structure design engineer, you need to have the cognitive ability in this field. If you don’t have such awareness, then you are not a qualified design engineer, at least not a very comprehensive design engineer.
The cognition of heat treatment design requirements of parts is basically based on the cognition of changes in material use and processing, so this is a very systematic knowledge structure, and it does not exist in isolation.
First of all, we need to know how many ways of heat treatment are included in the so-called mechanical processing of parts? In view of the frequency and importance of various ways in the process of machining, we choose the following to analyze, that is, the key analysis.
In the process of machining, we use four kinds of heat treatment methods most: annealing, normalizing, quenching and tempering. Let’s analyze them one by one.

01 Annealing treatment
Definition of annealing treatment: a metal heat treatment process in which metal parts are heated to a certain high temperature, kept for a period of time, and then naturally cooled.
Its main functions are:
A. Reduce the hardness of parts and improve the cutting performance;
B. Eliminate the residual stress of parts, stabilize the size and reduce the probability of deformation and crack;
C. Refining the crystal grains, adjusting the structure, and eliminating the defects of the material structure;
D. Homogenize the structure and composition of the material, improve the performance of the material or prepare the structure for the subsequent heat treatment process.
02 Normalizing treatment
Definition of normalizing treatment: metal parts are heated to a certain high temperature, kept for a period of time, and then cooled in the air by spraying water, spraying and blowing. Different from annealing treatment, the cooling speed is faster, so the obtained material structure is finer and the mechanical properties are improved.
Its main functions are:
A. Removing the internal stress of the material;
B. Reducing the hardness of the material and improving the plasticity;
03 Quenching treatment
Definition of quenching treatment: metal parts are heated to a temperature above the critical temperature Ac3 or Ac1, and kept for a period of time, so that they are fully or partially austenitized.
And then rapidly cooling to below Ms at a cooling rate greater than the critical cooling rate to carry out a heat treatment process of martensite transformation.
Its main functions are:
A. Greatly improve the rigidity, hardness, wear resistance and fatigue strength of parts;
B. Meet the physical and chemical properties of some special steels such as ferromagnetism and corrosion resistance.
04 Tempering treatment
The definition of tempering treatment: it refers to a kind of heat treatment that the steel after quenching, hardening or normalization is immersed in a temperature lower than the critical temperature for a period of time and then cooled down at a certain speed to increase the toughness of the material.
Its main functions are:
A.  Eliminate the residual stress generated when the workpiece is quenched, and prevent deformation and cracking;
B. Adjust the hardness, strength, plasticity and toughness of the workpiece to achieve better performance requirements;
C. Stabilize the structure and size, and ensure the accuracy;
D. Improve and improve the processing performance.

A. Annealing and normalizing can usually be used instead of each other, especially if the hardness of the parts obtained after treatment is not high (generally, it will not affect the machinability), so we should give priority to normalizing treatment, because its processing cycle is shorter and the cost is correspondingly lower.
B. Empering generally needs to be used in conjunction with quenching or normalizing. Tempering is to “wipe the bottom” for quenching and normalizing, because after quenching and normalizing, the hardness of the parts will be high, so there will be great residual stress, especially after quenching, the parts have great brittleness and hardness, so tempering is usually necessary to “correct the deviation” to better meet our use requirements.
C. The word “quenching” is usually pronounced “zan huo” in factories, especially for the older generation of practitioners. Young people have begun to change, but it is difficult to eliminate it for a while.

When the parts we design need heat treatment, there are only the following requirements:
A. Eliminating the casting stress of materials, aiming at obtaining more stable machining size and accuracy;
B. Improve the cutting performance of parts, with the aim of higher processing efficiency, better processing quality and lower processing cost in the process of processing parts;
C. Improve the rigidity, hardness and wear resistance of parts, this need not be explained.
Our heat treatment requirements for most parts are designed around the above three major aspects, so you only need to use the above four heat treatment methods according to your requirements.

Scroll to Top

Get a Quick Quote!

x

    Get a Quick Quote!

    x