文献翻译-材料的处理和特性

机械工程学院毕业设计（论文） i附 录Heat treatment heat treatment term this mean various through heat and cool in order to change metal course of characteristic. Through the appropriate heat treatment. Can make the metal obtain a certain property , for example; Hardness , tensile strength (resist the ability to draw ) and toughness, the heat treatment can be a kind of simple craft that only needs a few tools. Here commercially, the heat treatment is height science , complicated course of demanding to have a lot of apparatus . The machine had no use or not useful to add by a lot of products or products produced in workshop at all until heat-treating. The original meaning only involves the most basic knowledge of the heat treatment about steel. Can heat-treat to a lot of nonferrous metals such as aluminum, copper and brass，but its course of craft is different, omit to mention here. The steel heat treatment method includes quenching , flash back, anneals and the shell is quenched.Quench , quench , heat steel then cool by raising his hardness , tensile strength, reduce its toughness well obtain detailed crystalline grain organize method. This course includes heating to the metal its critical point, i.e. the above critical temperature then cools rapidly. With the heating of the steel , the physical change and chemical change take place between iron and carbon. Critical point , i.e. critical temperature , is that the steel has the most ideal temperature of characteristics. Reach temperature this (circle between 1400600F ) as steel , cool rapidly, to obtain hard high strength material very ideal change this, if metal cooling slowly, it will change and get back to its original state. Throw people water , oil or brine blazing metal (quench), can make the characteristic needed to conform with maintain. In this way the metal becomes very hard , the intensity is very high, and toughness is worse than in the past. Heating to go on in the stove in heat source with gas , oil , electricity. Contain an instrument which is called the pyrometer on the stove. It can record the actual temperature in the stove accurately . Can also decide metal temperature through 机械工程学院毕业设计（论文） iiobserving metal color . Can utilize these colors to simple metal part and tool while heat-treating. But the color is not very accurate. Skilled heat treatment worker temperature with error of real temperature happened to observe can reach 200F more too by this evenQuenching method following :1.Light the stove , make it reach appropriate temperature 2.Put the metal into stove, heat it the critical temperature , as to the tool steel of carbon element, for reach temperature this, take 20-30 minute nearly while being one inch thick while being every. For reach hot under quenching temperature, need , keep warm 10-15 minutes nearly while being one inch thick while being every. 3.Choose the appropriate cooling liquid . Some steel is planted and can be cooled in water, and other steel is planted and must be cooled in the oil or brine. Water whether carbon steel quench cooling liquid that use extensively most. Because water price is cheap, the result is good. The brine usually adds about 9% of ordinary salt to make in water. The brine facilitates making the hardness reached more even , make the whole part cool faster. The oil can make the pace quenched slightly a little slower . It is mineral oil. 4.that most quenching uses the oil. Take out the blazing metal with the clamp, throw people it to cool in the liquid. Stir and cool the liquid it in order to make the metal cool rapidly and evenly . If one thin work piece(look like knife or blade) very, want , cut , cool liquid work piece quench , enable its unlikely warping. If one side afford to cool than another side. 1.Quench steel tool will become hard to become fragile having high tensile strength very normally. It will have internal stress too. If allow , in the state, the internal stress will make the metal the crack take place.The flash back method is as follows:1.To the flash back of the whole, put the whole work piece into the stove. And then heat it to appropriate temperature in order to reach necessary intensity and toughness. Take out the metal and cool rapidly. 1. To the flash back of the small cutting tool:机械工程学院毕业设计（论文） iiia. Cut tool quench , with emery cloth oxidize skin wipeb. entirely. Heat a waste metal to the fervid intensity .c. Put cutting the tool on the metal, the edge department stretches outside this fervid metal d. Observe flash back color , when reaching the tool edge department in appropriate color , make it anxious and cold. It is to soften the steel to enable its eliminations internal stress method to anneal and anneal. This can enable the machine tooling more readily of steel . Heat the steel then the cooling slowly on the critical temperature . It is completely hot that the most frequently used method puts the steel into the stove one. Put out stove , let metal cooling slowly. Another method , is to wrap the metal up with the clay , heat it the critical temperature , take out in stove , let it cooling slowly.Shell harden shell it hardens to be to make outer surface or method that shell hardens of ferrous metal. Through add surface to get low carbon steel a small amount of carbon , can heat-treat , make surface it hard, and the center, i.e. the core department remains the soft one and has toughness. There are a lot of surface hardening methods . In industry , adopt the melted cyanide (this is called the cyanid ). Another kind of industrial method is a carburization law. This is that a a carbon through the following methods adds the surface hardening method from the surface in the steel inwards. These methods are: Solid law , gas law , salt bath law. Hammer head , piston are sold and other and can be dealt with to must stand a large number of vibration and part worn and torn with this law. But this law must not be used in any work piece that must be sharpened.Metal mechanical performance:Mechanical performance is a material characteristics appeared are measured under the circumstances that the extra load acts on . In other words, mechanical performance is the metal under the function of a strength or several pieces of strength , intensity had. If know metal intensity performance , can build a safe and firm structure , so intensity whether metal bear load (external force) but unlikely 机械工程学院毕业设计（论文） ivability that rupture. Intensity characteristic mean tensile strength, bending strength, compression strength, resist intensity of spraining, resist, cut intensity , fatigue strength and bludgeon the intensity into usually.1. The ones that appear within the material in stress resist the ability out of shape, the stress measures 2. by extra load. The emergency is the deformation that is produced by the stress. It expresses 3. with sizes of deformation of each centistere to meet an emergency. The elasticity is the metal after extending or out of shape, the external force is replied to in fact ability of the form when being dismissed from. The rubber band proves what is the elastic best example. After the rubber is elongated , if the handle is unclamped, it will reply to the original form . However, if elongate the rubber to exceed some a little, it will rupture . The flexible metal has the same properties too.4. .Elastic limit material in draw, stress greatest stress of the state still can get back to out of shape , remove , added. 5. The modulus of elasticity compares with pulling force in the internal stress of the range of elastic limit. Put the deformation of the material on certain stress function6. Tensile strength is the ability that the metal resists the external force that will break it. One of the metal more important indexes that it appraises is 7. Compression strength is that the metal resists the ability to crush. As to function direction loaded , compress it just with drawing oppositely. Most metal has very high tensile strength and compression strength. However, the material compression strength of fragility like casting iron is very high, but only have medium-sized tensile strength 8. Bending strength to resist external force cause component along load function direction crooked or property that bend. In fact, the crooked stress is to draw the stress and pigeonhole 9. associations of the stress. It is that the metal resists ability 机械工程学院毕业设计（论文） v10. that the external force causes the component to turn back to resist the intensity of spraining. Shear intensity mean component under two equal in opposite direction function of strength, what strong 11. its ability of resisting is! Fatigue strength is the properties that the material resists the stresses of different fast reversals. For example cylinder rod or what the axle is stood is drawing and pressing the reversal stress. One wire being back and forth crooked until it ruptures to be tired another embodiment. 12. Bludgeon into intensity whether metal resist , add load and high-speed loaded ability often suddenly. The metal impact is the taller in intensity, the greater energy the ones that made its fracture need are. It will influence and assault the intensity seriously to weld, because it is the most sensitive kind of property of structure to assault the intensity. 13. Toughness metal extend , be crooked or turn back but unlikely ability that rupture or destroy. The metal such as copper or wrought iron with very high toughness, with the increase that loads, destroy or rupture and carry on gradually. And the metal such as the casting iron with low toughness, when bearing heavily pay loader, will suddenly rupture and destroy .14. The hardness is the properties that the steel resists the compression or penetrates. Hardness to spend on standard load function purpose-built compression area of steel ball express usually, use in particular load function, a special one keep what hair take shape come , express deeply. 15. Low-temperature property say until low temperature environment very in stress metal performance change that take place under the function. Except that very sensitive to the crystal structure and condition of processing, the metal is very sensitive to low temperature and high temperature. Some very applicable alloy at room temperature, but will be totally destroyed at the low temperature or high temperature. Took place from plasticity to change of destruction of fragility quite suddenly at the low temperature.Stress and meeting an emergency:机械工程学院毕业设计（论文） viThe stress is not the same thing with meeting an emergency, but interrelated, depend on each other. Please see one tow one simple example of car with one white palm rope. The pulling force of the rope produced the stress or internal force in the fiber of the rope . After relaxing in pulling force or stress, this rope has already been produced and extended for ever because of this stress. The increase of the length is out of shape or is called meeting an emergency. Warping that produce often weld, one emergency too, it indicate metal weld , there are stresses obvious. The stress was calculated in poundage (pound / sq.in. ) of each sq.in.s just as pressure. The stress taking pound / sq.in. as unit is equal to loaded P divided by bear this loaded area: S =P/Al. Press the stress ( Push strength ) 2.Draw the stress ( Stretch the stress in the location ) 3.Shearing stress (cut stress), all material can out of shape at the stress of producing promptly load, shorten or extend. Function lay size or change of form can so heavy that can find out with naked eye sometimes in load, such as the situation of the rubber band and metal spring , but to the metal component which bears the design load. This kind of deformation is several little inches. Because rigidity is very big, the metal will only produce very little emergency under very great stress, realize if material produce stress , it can produce , meet an emergency or not out of shape too generally now; But must remember , vice vers, i.e., if metal draw out of shape, it can produce stress too then, essentially, the emergency is a reason for producing the stress.In order to explain the stress and relation while meeting an emergency , lets analyze that weld and try a tensile tests done to one. Welding seam be carried on at 1/2 thick board , melt pair completely in the face of connecting the welding seam totally, try a width of cutting out 2 inches on the board in order to the intensity of testing welding seam. Though not all welding test , have the requirement, we can write down including welding area measurement 2.0000 of length extend degree. These extend degrees of emergency appearance measure testing machine enormous dial demonstrate , add , get weld loaded size of draw to try one. Section to try on piece accumulate , equal 1 promptly for 2 1/2, load to this section, and stress the same, deformation points out that counting can point out that measure extending degree of 20000 inches in length , extending rate of per inch of length is a more useful datum: 机械工程学院毕业设计（论文） viiThis so long as point out deformation reading that count divided by 2 can obtain . This is real unit emergency - The definition that the unit meets an emergency is that in fact each inch of length is extended degree. Try piece insert , at chuck of testing machine , strengthen , add get load to try one gradually while drawing welding. Note these two items of reading of extending rate of the load and 20000 inches at regular intervals, study form the listed result can announce a lot of materials about welding and trying one carefully. First of all, great stress can only cause the small emergency very: Each 15 emergency that produce have 1/10% or 1/1000 / per inch of length only. Secondly , it seems that there are two meeting an emergency areasAs to the low stress, in under 42000 pounds / sq.in., meet an emergency and is directly proportional to stress to higher stress, it is not directly proportional to the stress again to meet an emergency, metal extending is quite big in this area, produce and surrender . Distinguish two emergency stress of characteristic these name stress of surrendering , the surrender to try on piece stress 42000 pound each. The area lower than stress of surrendering is the elastic district, and the elasticity meets an emergency is one such emergency: This disappears by oneself once meeting an emergency after the load is removed. For example steel spring meet an emergency , come , work by elasticity, exceed , surrender stress, the emergency is plasticity, in other words it meets an emergency for ever, still remains after the stress is dispelled . We can make the correct explanation to fragility and plasticity now. Any kind reveals it is a fragility material with very little plasticity emergency or without material of plasticity emergency at calling. And the plasticity material has very long plasticity areas under the function of the stress. Plasticity is an important condition that must possess of the structural material , because plasticity out of shape can send out the warning , explain stress material bear near the limit of it intensity. Because fragility material has no plasticity out of shape, will not send out the warning of the broken ring . The length had increased by 14 to try one before rupturing in welding analyzing above. Play , have 0.14 only , equal to plasticity 1% of emergency meeting an emergency always. Generally speaking, the properties of the soft and low intensity material are plasticity, and the plasticity of hard one and high strength material is very small. Very even 机械工程学院毕业设计（论文） viiimore like this to steel products: The all right plasticity of mild steel extends 25-35%.The surface is dealt with:Various metal and alloy that is nearly usually used, especially iron and steel, it is unless by one layer for oils, paints, medicines or other thingies chemicals can losing bad metal protect stand up, otherwise will all be corrode and corroded by the some materials in the air. A most serious one, though common one corrode most, corrode among being brilliant , in this case the coercivity material plays a corroding role while making up the metal crystal. Purpose that surface punish lie in , prevent the coercivity material from achieve crystal. A layer of oil or oil spread briefly, because they are soft, easy to damage, thus can enable the air in an opponents defence and people. But really very viscous oil, for example the wool oil refined out from the wool, protect the steel products and avoid a very useful method to get rusty during storing temporarily. The large-scale structure usually spreads several layers of paint. If the metal surface is very bright, the paint is difficult to obtain and well seize strength , so, can carry on the chemical disposal for the metal first , i.e. soak the metal in the solution of phosphoric acid and other salt, because they will corrode phosphate crystallization that the metal made its production with thin one story , thus make the surface coarse , helped the paint to glue if the paint was scratched accidentally later, the following coating can prevent the corrosion from expanding and causing serious damage outwards from shaving injury .An important metal and superficial method of protection is electroplating, i.e. adhere to very a layer of thin rustless metal on the metal with the electric current. People a familiar one to plate chromium most, in a bright one or thin first metal chromium very at polishing surface of nickel plate. If surface shiny glossy, usually can also plate with zinc , cadmium , tin , tin zinc alloy. Metal surface must very clean, so that thin metal plate lay