In order to make metal workpieces possess the required mechanical, physical and chemical properties, heat treatment process is essential, in addition to the rational selection of materials and various forming processes. Iron and 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, the heat treatment of steel is the main content of metal heat treatment.

另外，铝、铜、镁、钛等及其合金也都可以通过热处理改变其力学、物理和化学性能，以获得不同的使用性能。

In addition, the mechanical, physical and chemical properties of aluminum, copper, magnesium, titanium and their alloys can also be changed by heat treatment in order to obtain different use properties.

热处理一般不改变工件的形状和整体的化学成分，而是通过改变工件内部的显微组织，或改变工件表面的化学成分，赋予或改善工件的使用性能。其特点是改善工件的内在质量，而这一般不是肉眼所能看到的。

Heat treatment generally does not change the shape and overall chemical composition of the workpiece, but by changing the microstructure of the workpiece or changing the chemical composition of the surface of the workpiece, giving or improving the performance of the workpiece. It is characterized by the improvement of the internal quality of the workpiece, which is generally not seen by the naked eye.

热处理的作用就是提高材料的机械性能、消除残余应力和改善金属的切削加工性。按照热处理不同的目的，热处理工艺可分为两大类：预备热处理和最检查井钢模具 隔离墩模具 隔离墩钢模具 流水槽模具 U型槽模具 螺杆启闭机 卷扬式启闭机 铜雕佛像 终热处理。

The effect of heat treatment is to improve the mechanical properties of the material, eliminate the 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 major categories: preparation heat treatment and final heat treatment.

1.预备热处理

1. preparation heat treatment

预备热处理的目的是改善加工性能、消除内应力和为最终热处理准备良好的金相组织。其热处理工艺有退火、正火、时效、调质等。

The purpose of the preparatory heat treatment is to improve the processing performance, eliminate the internal stress and prepare the fine metallographic organization for the final heat treatment. The heat treatment process is annealed, normalizing, aging, tempering and so on.

（1）退火和正火

(1) annealing and normalizing

退火和正火用于经过热加工的毛坯。含碳量大于0.5%的碳钢和合金钢，为降低其硬度易于切削，常采用退火处理；含碳量低于0.5%的碳钢和合金钢，为避免其硬度过低切削时粘刀，而采用正火处理。退火和正火尚能细化晶粒、均匀组织，为以后的热处理作准备。退火和正火常安排在毛坯制造之后、粗加工之前进行。

Annealing and normalizing are used for hot - processed billets. Carbon and alloy steels with carbon content greater than 0.5% are often annealed for decreasing their hardness and easy cutting. Carbon and alloy steels with carbon content less than 0.5% are treated by normalizing to avoid their low hardness and sticky knives. Annealing and normalizing can still refine grain and uniform tissue, and prepare for heat treatment in the future. Annealing and normalizing are often arranged before and before rough machining.

（2）时效处理

(2) aging treatment

时效处理主要用于消除毛坯制造和机械加工中产生的内应力。

The aging treatment is mainly used to eliminate the internal stress produced in the manufacturing and machining of blanks.

为避免过多运输工作量，对于一般精度的零件，在精加工前安排一次时效处理即可。但精度要求较高的零件（如座标镗床的箱体等），应安排两次或数次时效处理工序。简单零件一般可不进行时效处理。

In order to avoid too much transportation, for parts with general precision, one time treatment can be arranged before finishing. But the parts with high precision, such as the box of the coordinate boring machine, should be arranged two times or several times. Simple parts are generally not treated with aging.

除铸件外，对于一些刚性较差的精密零件（如精密丝杠），为消除加工中产生的内应力，稳定零件加工精度，常在粗加工、半精加工之间安排多次时效处理。有些轴类零件加工，在校直工序后也要安排时效处理。

In addition to castings, for some rigid precision parts, such as precision screw, to eliminate the internal stress generated in the process and stabilize the machining accuracy of parts, many aging treatments are often arranged between rough machining and semi finishing. Some shaft parts are processed, and the aging process should be arranged after the straightening process.

（3）调质

(3) tempering

调质即是在淬火后进行高温回火处理，它能获得均匀细致的回火索氏体组织，为以后的表面淬火和渗氮处理时减少变形作准备，因此调质也可作为预备热处理。

Quenching and tempering is to conduct high temperature tempering treatment after quenching. It can get homogeneous and careful tempering microstructure, prepare for later surface quenching and reduce deformation during nitriding, so conditioning can also be used as a preliminary heat treatment.

由于调质后零件的综合力学性能较好，对某些硬度和耐磨性要求不高的零件，也可作为最终热处理工序。

Because of the good comprehensive mechanical properties of the parts after quenching and tempering, some parts with low requirements for hardness and wear resistance can also be used as the final heat treatment process.

2.最终热处理

2. final heat treatment

最终热处理的目的是提高硬度、耐磨性和强度等力学性能。

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

（1）淬火

(1) quenching

淬火有表面淬火和整体淬火。其中表面淬火因为变形、氧化及脱碳较小而应用较广，而且表面淬火还具有外部强度高、耐磨性好，而内部保持良好的韧性、抗冲击力强的优点。为提高表面淬火零件的机械性能，常需进行调质或正火等热处理作为预备热处理。其一般工艺路线为：下料--锻造--正火（退火）--粗加工--调质--半精加工--表面淬火--精加工。

The quenching has surface quenching and overall quenching. Surface hardening is widely applied because of its small deformation, oxidation and decarbonization. Surface hardening also has the advantages of high external strength and good wear resistance, while the interior maintains good toughness and strong impact resistance. In order to improve the mechanical properties of surface quenched parts, the heat treatment, such as quenching and tempering, is often needed as a preparatory heat treatment. Its general process route is: blanking - forging - normalizing (annealing) - rough processing - tempering - semi finishing - surface quenching - finishing.

（2）渗碳淬火

(2) carburizing and quenching

渗碳淬火适用于低碳钢和低合金钢，先提高零件表层的含碳量，经淬火后使表层获得高的硬度，而心部仍保持一定的强度和较高的韧性和塑性。渗碳分整体渗碳和局部渗碳。局部渗碳时对不渗碳部分要采取防渗措施（镀铜或镀防渗材料）。由于渗碳淬火变形大，且渗碳深度一般在0.5~2mm之间，所以渗碳工序一般安排在半精加工和精加工之间。

Carburizing and quenching are suitable for low carbon steel and low alloy steel. First, increase the carbon content of the surface of the parts. After quenching, the surface layer will obtain high hardness, while the heart will still maintain certain strength and toughness and plasticity. Carburizing is divided into whole carburizing and partial carburizing. For partial carburizing, seepage prevention measures (copper plating or plating impervious material) should be taken for non carburizing parts. Because of the large deformation of carburizing and quenching, and the depth of carburizing is generally between 0.5~2mm, so the carburizing process is usually arranged between semi finishing and finishing.

其工艺路线一般为：下料-锻造-正火-粗、半精加工-渗碳淬火-精加工。

Its process route is generally as follows: forging - forging - normalizing - rough, semi - finishing - carburizing and quenching - finishing.

当局部渗碳零件的不渗碳部分采用加大余量后，切除多余的渗碳层的工艺方案时，切除多余渗碳层的工序应安排在渗碳后，淬火前进行。

When the carburizing part of the carburizing part is used to increase the allowance and remove the excess carburizing process, the process of removing excess carburizing layer should be arranged before carburizing and before quenching.

（3）渗氮处理

(3) nitriding treatment

渗氮是使氮原子渗入金属表面获得一层含氮化合物的处理方法。渗氮层可以提高零件表面的硬度、耐磨性、疲劳强度和抗蚀性。由于渗氮处理温度较低、变形小、且渗氮层较薄（一般不超过0.6~0.7mm），渗氮工序应尽量靠后安排，为减小渗氮时的变形，在切削后一般需进行消除应力的高温回火。

Nitriding is a treatment for nitrogen atoms to be penetrated 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 surface of the parts. Because nitriding treatment temperature is low, deformation is small, and nitriding layer is thin (generally less than 0.6~0.7mm), nitriding process should be arranged as far as possible, in order to reduce the deformation of nitriding, after cutting, we usually need to eliminate stress high tempering.