（1） . type of annealing

1．完全退火與等溫退火

1. Complete annealing and isothermal annealing

完全退火又稱重結晶退火，通常稱為退火，這種退火主要用于亞共析成分的各種碳鋼和合金鋼的鑄，鍛件及熱軋型材，有時也會用于焊接結構。一般常用于一些不重要工件的熱處理，或作為某些工件的預先熱處理。

Complete annealing is also called crystallization annealing, which is usually called annealing. This annealing is mainly used for casting, forging and hot-rolled profiles of various carbon and alloy steels with hypoeutectoid composition, and sometimes for welded structures. It is generally used for the final heat treatment of some unimportant workpieces or as the pre heat treatment of some workpieces.

2．球化退火

2. Spheroidizing annealing

球化退火主要用于過共析的碳鋼及合金工具鋼（例如像制造刃具，量具，模具所用的鋼種）。其主要目的在于降低硬度，改善切削加工性，為以后淬火作好準備。

Spheroidizing annealing is mainly used for hypereutectoid carbon steel and alloy tool steel (such as steel used for manufacturing cutting tools, measuring tools and molds). Its main purpose is to reduce hardness, improve machinability and prepare for future quenching.

3．去應力退火

3. Stress relief annealing

去應力退火又稱低溫退火（或高溫回火），這種退火主要用來鑄件，鍛件，焊接件，熱軋件，冷拉件等的殘余應力。如果這些應力不予，將會引起鋼件在一定時間以后，在隨后的切削加工過程中產生變形或裂紋。

Stress relief annealing, also known as low temperature annealing (or high temperature tempering), is mainly used to eliminate the residual stress of castings, forgings, weldments, hot rolled parts, cold drawn parts, etc. If these stresses are not eliminated, deformation or cracks will occur in the subsequent cutting process after a certain time.

(二)．淬火

（2） . quenching

為了提高直線導軌硬度采取的方法，主要形式是通過加熱、保溫、速冷。常用的冷卻介質是鹽水，水和油。鹽水淬火的工件，容易得到較高的硬度與光潔表面，不容易產生淬不硬的軟點，缺點是容易導致工件變形嚴重，甚發生開裂。而用油作淬火介質只適用于過冷，奧氏體的穩定性比一些合金鋼或小尺寸的碳鋼工件淬火效果較好。

In order to improve the hardness of linear guide rail, the main forms are heating, thermal insulation and rapid cooling. The common cooling media are brine, water and oil. The workpiece quenched by brine is easy to obtain high hardness and smooth surface, and it is not easy to produce soft spots that cannot be hardened. The disadvantage is that it is easy to cause serious deformation and even cracking of the workpiece. Using oil as quenching medium is only suitable for undercooling. The stability of austenite is better than that of some alloy steel or small-size carbon steel workpieces.

(三)．回火

（3） . tempering

1．降低脆性，或減少內應力，鋼件淬火后存在很大內應力和脆性，如不及時回火往往會使鋼件發生變形甚是開裂狀態。

1. Reduce brittleness and eliminate or reduce internal stress. Steel parts have great internal stress and brittleness after quenching. If they are not tempered in time, they will often deform or even crack.

2．獲得工件所要求的機械性能，工件經淬火后硬度高而脆性大，為了滿足各種工件的不同性能要求，通過適當回火的配合來調整其硬度，減小脆性，得到所需要的韌性，塑性。

2. Obtain the mechanical properties required by the workpiece. After quenching, the workpiece has high hardness and high brittleness. In order to meet the different performance requirements of various workpieces, adjust its hardness through appropriate tempering to reduce brittleness and obtain the required toughness and plasticity.

3．穩定工件尺寸

3. Stabilize workpiece size

4．對于退火難以軟化的某些合金鋼，在淬火（或正火）后一般采用高溫回火，使鋼中碳化物聚集，將硬度降低，而利于切削加工。

4. For some alloy steels that are difficult to soften after annealing, high temperature tempering is generally adopted after quenching (or normalizing), so as to gather carbides in the steel and reduce the hardness, which is conducive to cutting.