汽车覆盖件表面热处理规范.docx

1、汽车覆盖件表面热处理规范二、Flame Types for Flame Hardening火焰淬火的火焰类型Flame hardening experts favor a slightly carburizing flame in order to avoid the possibility of decarburizing the surface layer of the work piece. This can be accomplished by giving the outer flame tip a very slight feather. Note the flame sketch

2、es below. 火焰淬火专家优选轻微的碳化火避免表面脱碳。火焰外围为轻微羽状火焰。见下图。Four Basic Flame Types 4种基本类型The proportions of oxygen and the type of gas used will determine the characteristics of the resulting flames.氧气和气体的类型将决定生成火焰的特性。 Figuer 8-8 pure fuel gas flame 图8纯燃料气体火焰The pure gas type flame (Figure 8-8) is characterized

3、by a heavilyfeathered tip that burns orange, yellow and blue as it goes back toward the torch tip. It is developed as the gas is ignited and the soot, smoke is adjusted out of the flame. 单一气体类型火焰（图8-8)的特点是有各种的羽毛状的橙色，黄色或蓝色火焰，当火焰返回至焊枪顶端。 再根据要求调整火焰 Figuer 8-9 C arburizing flame碳化火焰Carburizing flame (Fi

4、gure 8-9) contains an excess amount of fuel. Thisflame is used during most flame hardening applications and will yield a work piece surface that is slightly carburized and higher in hardness. Compared to the neutral flame, the inner cone is larger and tends to become feathered. 碳化火焰含有过量的燃油。大部分的火焰淬火都

5、使用这种。能够使轻微碳化和硬度较高的工件表面获得屈服。和中性火焰相比，焰心较大且变为羽毛状。Figuer 8-10 Neutral flame 中性火Neutral flame (Figure 8-10) is developed by using equal amounts of oxygen and fuel mix. It is used for most flame hardening, cutting, and heating applications. This flame will not carburize or decarburize the surface of the w

6、orkpiece. No acetylene feather appears.中性火是由等量的氧气和燃料混合产生的。通常用于大部分的火焰淬火，切割，和加热等，这种火焰将不碳化或脱碳工件表面。没有乙炔羽毛状火焰出现。Figuer 8-11 -Oxidizing flame 氧化焰Oxidizing flame (Figure 8-11) contains an excess amount of oxygen. It isonly used on specific materials where the development of decarburization will not be a pr

7、oblem. Compared to the neutral flame, the inner cone is smaller and slightly tighter.氧化焰含有过量的氧气，只用于脱碳不会有问题的特殊材质，和中性火焰 相比，馅心比较小且更紧凑三、Distortion and Size Change during Hardening淬火过程中的变形和尺寸变化Is Machining of Tools and Dies Too Close to Finished DimensionsBefore Hardening a Gamble worth Taking? 是在淬火前将工具和

8、模具加工接近精加工尺寸吗?There is an increasing trend to machine tools and dies closer and closer to finished dimensions before hardening. This is done in order to minimize the need for finish machining (grinding, EDM) of steels in the hardened condition, thus lowering machining costs. Unfortunately, this is a

9、dangerous practice because dimensional changes that occur during hardening frequently do not work out as planned. If sufficient stock is not left on a tool or die prior to heat treatment, the resultant combination of size change and/or distortion may make it impossible to finish-machine the part to

10、required dimensions. This section provides an overview of the sources of stresses that result in size change and distortion of tools and dies in heat treatment.淬火之前越来越倾向于先将模具等加工的和最终的尺寸越近越好。这么做目的是将硬化状态下精加工(研磨，电火花)的需要最小化，这样加工的费用就较低。但是这非常危险，因为淬火中发生的尺寸变化不会像预计的灵验。如果热处理前，模具等上面的部件没有充分的库存，由于尺寸变化和变形导致的结果可能会使

11、鈑件无法达到精加工的尺寸要求。这部分内容是导致热处理过程中尺寸变化和变形导致的压力源。First, it must be noted that nondeforming or distortion-free tool steels do not exist. All tool steels are subject to problems related to warpage (bending, bowing, twisting),in combination with growth or shrinkage when they are hardened. The degree of disto

12、rtion depends on the amount of residual stresses that develop in the steel. Volume changes not only result in dimensional changes (growth or shrinkage) of the tool or die, but also increase the residual stress level. The following provides an explanation of the causes of size change and distortion:首

13、先，必须指出不会变形的工具钢是不存在的。所有的工具钢都收硬化过程中的弯曲，扭曲有关。变形的程度取决于钢板上的残余应力大小,体积变化不仅仅会导致尺寸变化（变大，变小），也会增加残余应力。以下位大小变化和变形原因解释。1. Mechanically Induced Stresses:机械感应应力These stresses result from cold-working operations (machining, saw cutting, etc.). The magnitude of these stresses is in direct proportion to depth-of-cut

14、, cutting speed, etc. If these stresses are not relieved before a tool or die is heat treated, they will be released during the heating for hardening and may result in distortion(Bending, bowing, and/or twisting).这些应力是由于冷加工导致的（机加，锯切等）导致的。应力大小和切割深度速度等成正比。在热处理之前应力未解除，将在硬化加热过程中释放解除导致变形。（弯曲，顺弯或扭曲。）2. Th

15、ermal Stress Induced From Heating and Cooling: 加热和冷却导致的感应热应力Thermally induced stresses during heating and cooling also increase the residual stress level of a part. When steel is heated to the preheat and hardening temperature, it will expand. The mass and design configuration of the tool or die bei

16、ng heat treated will determine how uniformly the part will expand during heating. Light cross sections expand more rapidly and will reach temperature before heavy sections. The surfaces of heavy cross sections will reach temperature before interior sections. The noted temperature differences result

17、in differential rates of expansion between light and heavy sections, and the surface and interior sections. This differential expansion will result in an increase of the residual stresses until such time as the part is at uniform temperature throughout. 加热和冷却中导致的热感应应力也会使鈑件残余应力增加。当钢板加热到预热和硬化温度就会变大。热处

18、理的设计结构将决定鈑件在加热过程中变大的一致性。较轻的扩快，比重的部分更快达到温度。重的部分比内侧更快达到要求的温度。温差导致膨胀率的不同，从而导致残余应力的增加，直到鈑件完全达到一直温度。When the same part is cooled during the quenching cycle, the reverse happens. Light cross sections and the surfaces of the heavier sections of the tool or die cool faster than either the heavy cross sectio

19、ns or the interior. These temperature differences also result in differential contraction, which in turn results in additional residual stress development.当相同的鈑件在淬火中冷却，会发生相反的情况。较轻的部分和较重的部分表面比较重的横截面和内部冷却的快。温差导致不同程度的收缩，导致额外的残余应力。3. Transformation Stresses From Heating and Cooling:加热和冷却导致的应力转换Transform

20、ation stresses, which develop on heating and cooling, are also responsible for inducing residual stresses. When the steel being heated for hardening reachesits critical temperature on heating, the existing annealed microstructure transformsto austenite. This transformation to austenite results in sh

21、rinkage of the part because austenite is smaller in volume than the annealed structure from which it develops. After all of the annealed microstructure is transformed to austenite on further heating to the hardening temperature, the part begins to expand again.应力转换同样和感应残余应力有关系。当用于硬化的加热的钢板达到关键温度，现有的退

22、火微观结构转变为奥氏体。之后会使鈑件缩水，因为奥氏体的体积比退火结构小。当在硬化温度下，通过进一步加热使所有的微观结构完全转化为奥氏体， 鈑件又会再次扩大。All of the expansion and contraction discussed thus far will occur at different rates in light cross sections as opposed to heavy cross sections, surface locations as opposed to interior locations, etc. In this way, stress

23、 levels are compounded as part geometries expand and contract at different times during heating and cooling. 到目前为止讨论将发生在不同的时间，发生的膨胀和缩水，鈑件的各个部分的变化率是不同的。 这样的话，应力水平也是作为鈑件几何扩张和收缩的一部分。Transformation also occurs on cooling during the quench. The austenite formed on heating to the hardening temperature tra

24、nsforms to martensite during the quench. Martensite is larger in volume per unit of mass than either the austenite from which it transformed or the annealed structure that existed before heat treatment. Again, because the transformation takes place faster in light cross sections as opposed to heavy

25、cross sections and at surface locations as opposedto interior locations, differential stresses will occur in the part being processed. 在淬火过程中也会发生冷却变形。奥氏体变为马氏体，在淬火过程中。马氏体的单位体积比奥氏体以及热处理前的退火结构大。变形的速度和上述情况是一致的，鈑件各个部分会产生不同的应力。4. Stress Combination:应力组合The combination of residual stresses from machining,

26、and ther mal and transformation stresses that occur during hardening, may result in the distortion of a tool or die. Such distortion can be minimized by relieving machining stresses prior to hardening and by heating to the hardening temperature at a rate that will result in minimal temperature diffe

27、rential in the part. While stresses that occur on heating will be relieved when soaking at the hardening temperature is accomplished, the distortion that occurs may not be reversed. Likewise, the combination of thermal and transformation stresses upon cooling (quenching) may also result in distortio

28、n, which will not be removed by subsequent tempering.机加和热镀造成的残余应力和淬火过程产生的变形应力组合在一起，会导致鈑件或模具变形，要想将变形最小化，可以在淬火之前减少加工应力，以及加热至淬火温度以使鈑件的各部分的温差最小化。当淬火温度下可以达到均热处理，加热导致的应力将会被解除。由此导致的变形也不会被取消。这样，淬火的热力和变形应力也会导致变形，后续的回火也不能解除这个变形。5. Volume Changes From Transformation: 变形造成的体积变化On quenching, the overall dimensio

29、ns of the part will change due to the growth in heat treatment described above. The amount of growth has been found to be partly dependent on steel type. The following table shows the expected growth of various types of tool steels in heat treatment. Note that shrinkage may develop ona given dimensi

30、on if full transformation of austenite to martensite is not realized.淬火中，鈑件的整体大小也会变化，如上所述。增大的比例部分取决于钢材类型。以下表格就是不同类型的钢板在热处理过程中的预期增大情况。如果没有达到奥氏体到马氏体的完全转换，在给定的尺寸上也会发生收缩。GROWTH OF VARIOUS TYPES OF TOOL STEELS -增长点的各种工具钢类型Steel Type 钢材类型 Expected Growth 预期增长(In. per In. of Tool Dimensions) Water Hardenin

31、g (W1, W2, etc)水淬火 + 0.002/0.004Oil Hardening (O1, O6, etc) 油淬火 + 0.0015Air Hardening (A2, A6, S7, H13, etc.)气体淬火 +0 .001Air Hardening (D2) 气体淬火 0.0005Caution: The values in the table are not absolute. Experience indicates that part size, mass, geometry, and steel type play roles in dictating that dimensions of the part will grow in heat treatment and which will “shrink.” For example, a long, thin rectangular shape that hardens through completely in heat treatment will grow in all dimensions (i.e., width, thickness, and length). However, a long, thick rectangula