热处理含英文

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1、Heat treatmentHeat treatment is a method used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or

2、chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering and quenching. It is noteworthy that while the term heat treatment applies only to

3、 processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding.Heat treatment of metals and alloysMetallic materials consist of a microst

4、ructure of small crystals called grains or crystallites. The nature of the grains (i.e. grain size and composition) is one of the most effective factors that can determine the overall mechanical behavior of the metal. Heat treatment provides an efficient way to manipulate the properties of the metal

5、 by controlling rate of diffusion, and the rate of cooling within the microstructure.Complex heat treating schedules are often devised by metallurgists to optimize an alloys mechanical properties. In the aerospace industry, a superalloy may undergo five or more different heat treating operations to

6、develop the desired properties. This can lead to quality problems depending on the accuracy of the furnaces temperature controls and timer.Annealing 退火Annealing is a technique used to recover cold work and relax stresses within a metal. Annealing typically results in a soft, ductile metal. When an a

7、nnealed part is allowed to cool in the furnace, it is called a full anneal heat treatment. When an annealed part is removed from the furnace and allowed to cool in air, it is called a normalizing heat treatment. During annealing, small grains recrystallize to form larger grains. In precipitation har

8、dening alloys, precipitates dissolve into the matrix, solutionizing the alloy.Typical annealing processes include, normalizing, stress relief annealing to recover cold work, and full annealing.Hardening and tempering (quenching and tempering)调质处理(淬火+回火)To harden by quenching, a metal (usually steel

9、or cast iron) must be heated into the austenitic crystal phase and then quickly cooled. Depending on the alloy and other considerations (such as concern for maximum hardness vs. cracking and distortion), cooling may be done with forced air or other gas (such as nitrogen), oil, polymer dissolved in w

10、ater, or brine. Upon being rapidly cooled, a portion of austentite (dependent on alloy composition) will transform to martensite, a hard brittle crystalline structure. The quenched hardness of a metal depends upon its chemical composition and quenching method. Cooling speeds, from fastest to slowest

11、, go from polymer (i.e.silicon), brine, fresh water, oil, and forced air. However, quenching a certain steel too fast can result in cracking, which is why High-tensile steels like AISI 4140 should be quenched in oil, tool steels such as 2767 or H13 hot work tool steel should be quenched in forced ai

12、r, and low alloy or medium-tensile steels such as XK1320 or AISI 1040 should be quenched in brine or water. However, metals such as austenitic stainless steel (304, 316), and copper, produce an opposite effect when these are quenched; they anneal. Austenitic stainless steels must be quench-annealed

13、to become fully corrosion resistant, as they work-harden significantly.Untempered martensite, while very hard and strong, is too brittle to be useful for most applications. A method for alleviating this problem is called tempering. Most applications require that quenched parts be tempered (heat trea

14、ted at a low temperature, often three hundred degree Fahrenheit or one hundred fifty degrees Celsius) to impart some toughness. Higher tempering temperatures (may be up to thirteen hundred degrees Fahrenheit or seven hundred degrees Celsius, depending on alloy and application) are sometimes used to

15、impart further ductility, although some yield strength is lost.Precipitation hardeningSome metals are classified as precipitation hardening metals. When a precipitation hardening alloy is quenched, its alloying elements will be trapped in solution, resulting in a soft metal. Aging a solutionized met

16、al will allow the alloying elements to diffuse through the microstructure and form intermetallic particles. These intermetallic particles will nucleate and fall out of solution and act as a reinforcing phase, thereby increasing the strength of the alloy. Alloys may age naturally meaning that the pre

17、cipitates form at room temperature, or they may age artificially when precipitates only form at elevated temperatures. In some applications, naturally aging alloys may be stored in a freezer to prevent hardening until after further operations - assembly of rivets, for example, may be easier with a s

18、ofter part.Examples of precipitation hardening alloys include 2000 series, 6000 series, and 7000 series aluminium alloy, as well as some superalloys and some stainless steels.Selective hardeningSome techniques allow different areas of a single object to receive different heat treatments. This is cal

19、led differential hardening. It is common in high quality knives and swords. The Chinese jian is one of the earliest known examples of this, and the Japanese katana the most widely known. The Nepalese Khukuri is another example.SpecificationCase hardening 表面淬火Case hardening is specified by hardness a

20、nd case depth. The case depth can be specified in two ways: total case depth or effective case depth. The total case depth is the true depth of the case. The effective case depth is the depth of the case that has a hardness equivalent of HRC50; this is check on a Tukon microhardness tester. This val

21、ue can be roughly approximated as 65% of the total case depth; however the chemical composition and hardenability can affect this approximation. If neither type of case depth is specified the total case depth is assumed.For case hardened parts the specification should have a tolerance of at least 0.

22、005 in (0.13 mm). If the part is to be ground after heat treatment, the case depth is assumed to be after grinding.化学热处理是通过改变工件表层化学成分、组织和性能的金属热处理工艺。化学热处理与表面热处理 不同之处是后者改变了工件表层的化学成分。化学热处理是将工件放在含碳、氮或其它合金元素的介质（气 体、液体、固体）中加热，保温较长时间，从而使工件表层渗入碳、氮、硼和铬等元素。渗入元素后，有时 还要进行其它热处理工艺如淬火及回火。化学热处理的主要方法有渗碳、渗氮、渗金属。回火的种类

23、及应用根据工件性能要求的不同，按其回火温度的不同，可将回火分为以下几种：（一）低温回火（150 250度）低温回火所得组织为回火马氏体。其目的是在保持淬火钢的高硬度和高耐磨性的前提下，降低其淬火 内应力和脆性，以免使用时崩裂或过早损坏。它主要用于各种高碳的切削刃具，量具，冷冲模具，滚动轴 承以及渗碳件等，回火后硬度一般为HRC58 64。（二）中温回火（350 500度）中温回火所得组织为回火屈氏体。其目的是获得高的屈服强度，弹性极限和较高的韧性。因此，它主 要用于各种弹簧和热作模具的处理，回火后硬度一般为HRC35 50。（三）高温回火（500 650度）高温回火所得组织为回火索氏体。习惯上

24、将淬火加高温回火相结合的热处理称为调质处理，其目的是 获得强度，硬度和塑性，韧性都较好的综合机械性能。因此，广泛用于汽车，拖拉机，机床等的重要结构 零件，如连杆，螺栓，齿轮及轴类。回火后硬度一般为HB200 330。热处理（1）:退火：Annealing指金属材料加热到适当的温度，保持一定的时间，然后缓慢冷却的热处理工 艺。常见的退火工艺有：再结晶退火，去应力退火，球化退火，完全退火等。退火的目的：主要是降低金 属材料的硬度，提高塑性，以利切削加工或压力加工，减少残余应力，提高组织和成分的均匀化，或为后 道热处理作好组织准备等。（2） :正火：normalizing指将钢材或钢件加热到或（钢的

25、上临界点温度）以上，3050摄氏度保 持适当时间后，在静止的空气中冷却的热处理的工艺。正火的目的：主要是提高低碳钢的力学性能，改善 切削加工性，细化晶粒，消除组织缺陷，为后道热处理作好组织准备等。（3）:淬火：quenching指将钢件加热到Ac3或Ac1 （钢的下临界点温度）以上某一温度，保持一定 的时间，然后以适当的冷却速度，获得马氏体（或贝氏体）组织的热处理工艺。常见的淬火工艺有盐浴淬 火，马氏体分级淬火，贝氏体等温淬火，表面淬火和局部淬火等。淬火的目的：使钢件获得所需的马氏体 组织，提高工件的硬度，强度和耐磨性，为后道热处理作好组织准备等。（4）:回火：tempering指钢件经淬硬后

26、，再加热到以下的某一温度，保温一定时间，然后冷却到 室温的热处理工艺。常见的回火工艺有：低温回火，中温回火，高温回火和多次回火等。回火的目的：主 要是消除钢件在淬火时所产生的应力，使钢件具有高的硬度和耐磨性外，并具有所需要的塑性和韧性等。（5）:调质：quenching and tempering指将钢材或钢件进行淬火及高温回火的复合热处理工艺。使 用于调质处理的钢称调质钢。它一般是指中碳结构钢和中碳合金结构钢。（6）:渗碳：carburization ,ka:bjuraizei n渗碳是指使碳原子渗入到钢表面层的过程。也是使 低碳钢的工件具有高碳钢的表面层，再经过淬火和低温回火，使工件的表面层具有高硬度和耐磨性，而工 件的中心部分仍然保持着低碳钢的韧性和塑性。是一种化学热处理。