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The hot processing of metals is to put the metals work piece in certainly lie quality to heat the feat temperature, and after this keep certain time in the temperature, again with a kind of craft method that the different speed cool off.
The hot processing of metals is one of the important craft within the machine manufacturings, processing the craft to compare with the other, the hot processing does not change the shape and whole chemistry compositions of the work piece generally, but pass to change the work piece inner part of show minute details the organization, or change the chemistry composition of a surface, giving or improving the usage function of the work piece.Its characteristics is an inside quantity that improves the work piece, but this is not the naked eye generally to can see of. For make the metals work piece have need of mechanics function, the physics function and the chemistry function, in addition to reasonable choosing to use the material and variously taking shape the craft, the hot processing craft is usually essential to have of.The steel is an applied most wide material in the machine industry, the steel shows minute details the organization complications, can pass hot the processing gives the control, so the hot processing of the steel is a metals hot processing of main contents.Moreover, aluminum, copper, magnesium ...etc. and its metal alloys can also change the different from the chemistry function, to acquire usage function of its mechanics, physics through a hot processing.
In 1863, the British gold learned the different from the geologist displayed the steel under the microscope of six kinds ofly gold of house mutually to organize mutually, proving the steel while heating and cooling off, the inner part will take place the organization change, hour of heat in steel of mutually at nasty and cold change into a kind of harder mutually.Frenchman the Aositing receives the together plain and different theories of the iron of the virtuous establishment, and British the carbon of iron that the Aositing draw up at the earliest stage mutually diagram, lay the theories foundation for the modern hot processing craft first step.At the same time, the people still studied in the metals heating process of the hot processing to the protection method of the metals, to avoid to heat the process in the metals of oxidize and take off carbon etc..
1850-1880 years, carry on the protection heating to once have a series of patent for applied various air( such as hydrogen, coal gas, carbon monoxide...etc.).The British gram of 1889-1890 years acquires various metalses the patent of the shining hot processing. Since 20 centuries, the new technical transplantation of the development and others of the metals physics is applied, making the hot processing craft of metals get the larger development.A progress that shows the is 1901-1925 years, the application turns the tube stove to carry on the air carbon in industry produce;The 30's appears the dewdrop potential difference to account, making the carbon of the atmosphere inside the stove attained certainly can control, hereafter again study to use the red and outside instrument, oxygen of carbon dioxide to stretch forward etc. the further control stove inside the atmosphere carbon power of method;60's, the hot processing technique made use of etc. the function of the ion field, developped the ion nitrogen, carbon craft of ;Technical application of laser, electron beam, and then make the metals acquire the hot processing method of the new surface heat processing and chemistries.
The hot processing craft includes the heating, heat preservation and cools off three processes generally, sometimes only heating and cooling off two processes.These processes connect up properly with each other, can't interrupted.
The heating is one of the important steps of the hot processing.The metals heating method of the hot processing is a lot of, at the earliest stage is to adopted the charcoal and coals to be the hot source, then applied the liquid and gaseous fuels.The application of the electricity makes heat to be easy to the control, and have no pollution of the environment.Make use of these hot sources can heat directly, can also pass the salt or metalses of the meltdown, to go to float a son to carry on the indirect heating. When the metals heat, the work piece expose up in the air, usually take place to oxidize, take off the carbon( namely the steel spare parts surface carbon content lower), this to the hot processing behind spare parts of surface function have the very disadvantageous influence.As a result metals usually should in can control atmosphere or protect atmosphere, the meltdown salt moderates the vacuum in the heating, also can use the coating or packing the method carries on the protection heating.
Heat the temperature is one of the important craft parameters of the hot processing craft, choosing and controling the heating temperature, is a key problem that guarantees the hot processing quantity.Heat the temperature with the metals material and hot processings that is handles of purpose be different, but generally is all to heat to change the temperature mutually above, to acquire the organization of demand.Change to need certain time moreover, so when a surface of the metals work attains the heating temperature of request, return must keep certain time in this temperature, make is consistent inside the outside temperature, making show minute details the organization the change completely, this time is called heat preservation time.Adoption high ability density heat and hot processing of surface, very heat the speed quickly, general have no heat preservation time or the heat preservation time very short, but chemistry hot processing of heat preservation time is usually longer.
The cooling also is indispensable in the hot processing craft process of step, cool off method dissimilarity because of craft dissimilarity, mainly is a control cooling speed.Back the cooling speed of the fire generally the slowest, positive fire of cooling speed compare quickly, fire of cooling speed sooner.But return to have the different request because the steel grows the dissimilarity, for example the empty hard steel can use the similar cooling speed of positive fire to carry on the hard.
The hot big body of craft of processing of metals can is divided into whole hot processing, surface hot processing, part hot processing and chemistry hot processing etc..Lie the quality and heat the temperature and cool off the dissimilarity of method according to the heating, each a major type can classified into some hot processing crafts of dissimilarity again.The same kind of metals adopts the different hot processing craft, can acquire the different organization, thus having the different function.The steel is an industry up the applied most wide metals, and the steel show minute details organization also the most complicated, therefore steel hot processing the craft category numerous.
Whole and hot processing is to a whole heating of work, then cool off with the appropriate speed, to change the metals heat processing craft of its whole mechanics function.The whole hot processing of steel mostly backs the fire, positive fire, fire of and returns to four kinds of basic crafts of fire.
Back the fire is to heat the work piece to the appropriate temperature, according to different from work piece size adoption heat preservation time of material, then carry on slow-moving cool off, the purpose is to make the metals internal organization attain or near to the equilibrium, acquiring the good craft function and using the function, or make the organization preparation for the further fire of .The positive fire is to heat the work piece to the feat temperature behind up in the air cooling, positive fire of result together back the fire likeness, the organization that just get is thinner, in common use in improvement the material slices to pare the function, also sometimes useding for being the end hot processing to the not high spare parts of some requests.
Fire of is heat the work piece heat preservation after, in water, oil or others have no machine salt, organic aqueous solution wait coldly lie quality fast cooling.The steel piece becomes after the fire of hard, but change the frailty at the same time.For lowering the brittleness of the steel piece, carry on fire of behind of the steel piece at high in indoor temperature but low in 710 some appropriate temperatures of the ℃s long-playing heat preservation, then carry on the cooling, this kind of craft is called to return to fire.It is" four fires"s within whole and hot processings to back the fire, positive fire, fire of and return to fire, the fire of that is among them with return to the fire relation close, usually match with the usage, lack a can't.
" Four fires" along with heat the temperature and cool off the dissimilarity of way, and then turn into a different and hot processing craft.For acquiring the certain strength and tenacities, the craft that the fire of and heat returns to the fire knot to put together, be called to adjust the quality.Some metal alloys fire formation supersaturation after is solid dissolve the body place it in indoor temperature or slightly high and appropriate temperature descend keep to compare the long time, to raise degree of hardness, strength or electricity magnetism etc.s of the metal alloy.The hot processing craft that is thus is called the time limited efficacy processing.Process the form to the pressure to change is valid with hot processing but closely the knot puts together to carry on, making the work piece method that acquires the good strength, tenacity to match with be called the form to become the hot processing;Carry on hot in take press atmosphere or vacuums the processing is called the vacuum hot processing, it not only can make the work piece does not oxidize, don't take off the carbon, a surface of work is clean after keep processing, raise the function of the work piece, but also can open into the of to carry on the hot processing of chemistry.
The hot processing of surface heats a surface layer of work only, to change the metals heat processing craft of its surface layer mechanics function.For heating a surface layer of work but don'ting make the excessive calories stream into an inner part of work only, the hot source beard of the usage has the high energy density, giving on the work piece of the unit area bigger thermal energy, make a surface layer of work or part ability short time or attain the heat in a moment.Surface hot processing of main method, have the laser hot processing, the flames fire and respond the hot processing of heating, the in common use and hot source contain the oxygen B or oxygen propane etc. flameses, respond the electric current, laser and electron beam etc..
The hot processing of chemistry is the metals heat processing craft that passes to change a surface layer chemistry composition, organization of work and functions.The chemistry hot processing and the surface heats handle the different place is the chemistry composition that the latter changed a surface layer of work.Hot processing of chemistry is put the work piece in contain carbon, nitrogen or other metal alloy chemical elements lie quality( air, liquid, solid) heating, the heat preservation compare with long hours, thus make the chemical elements, such as a surface layer infiltration carbon, nitrogen, of work and chrome...etc..After seeping into the chemical element, sometimes still need to carry on other hot processing crafts,such as fire of 淬 , and return to fire.Chemistry the main method of the hot processing contain carbon, nitrogen, metals, the compound ...etc.
The hot processing is one of the machine spare parts and important work preface within the work molding tool manufacturing processes.Big body to say, it can guarantee and raise various function of the work piece, if bear to whet, bear corrosion etc..Can also improve the organization of the semi-finished product and should the dint appearance, for the convenience of in carry on various cold, the heat process.
For example an iron casting pass by to back with long hours the fire processing and can acquire can iron casting, exaltation;The wheel gear adoption the hot processing of the exactitude craft, the service life can compare not through hot processing of wheel gear become doubly or several decuples ground exaltation;Moreover, the carbon steel of the low price passes to seep into the metal alloy steel function that some metal alloy chemical elements have some prices, can replace the some and heat-proof steel, stainless steel;The work molding tool then almost all demands can use through hot processing square.
外文資料翻譯
金屬熱處理是將金屬工件放在一定的介質(zhì)中加熱到適宜的溫度,并在此溫度中保持一定時(shí)間后,又以不同速度冷卻的一種工藝方法。
金屬熱處理是機(jī)械制造中的重要工藝之一,與其它加工工藝相比,熱處理一般不改變工件的形狀和整體的化學(xué)成分,而是通過(guò)改變工件內(nèi)部的顯微組織,或改變工件表面的化學(xué)成分,賦予或改善工件的使用性能。其特點(diǎn)是改善工件的內(nèi)在質(zhì)量,而這一般不是肉眼所能看到的。 為使金屬工件具有所需要的力學(xué)性能、物理性能和化學(xué)性能,除合理選用材料和各種成形工藝外,熱處理工藝往往是必不可少的。鋼鐵是機(jī)械工業(yè)中應(yīng)用最廣的材料,鋼鐵顯微組織復(fù)雜,可以通過(guò)熱處理予以控制,所以鋼鐵的熱處理是金屬熱處理的主要內(nèi)容。另外,鋁、銅、鎂、鈦等及其合金也都可以通過(guò)熱處理改變其力學(xué)、物理和化學(xué)性能,以獲得不同的使用性能。
1863年,英國(guó)金相學(xué)家和地質(zhì)學(xué)家展示了鋼鐵在顯微鏡下的六種不同的金相組織,證明了鋼在加熱和冷卻時(shí),內(nèi)部會(huì)發(fā)生組織改變,鋼中高溫時(shí)的相在急冷時(shí)轉(zhuǎn)變?yōu)橐环N較硬的相。法國(guó)人奧斯蒙德確立的鐵的同素異構(gòu)理論,以及英國(guó)人奧斯汀最早制定的鐵碳相圖,為現(xiàn)代熱處理工藝初步奠定了理論基礎(chǔ)。與此同時(shí),人們還研究了在金屬熱處理的加熱過(guò)程中對(duì)金屬的保護(hù)方法,以避免加熱過(guò)程中金屬的氧化和脫碳等。
1850~1880年,對(duì)于應(yīng)用各種氣體(如氫氣、煤氣、一氧化碳等)進(jìn)行保護(hù)加熱曾有一系列專利。1889~1890年英國(guó)人萊克獲得多種金屬光亮熱處理的專利。二十世紀(jì)以來(lái),金屬物理的發(fā)展和其它新技術(shù)的移植應(yīng)用,使金屬熱處理工藝得到更大發(fā)展。一個(gè)顯著的進(jìn)展是1901~1925年,在工業(yè)生產(chǎn)中應(yīng)用轉(zhuǎn)筒爐進(jìn)行氣體滲碳 ;30年代出現(xiàn)露點(diǎn)電位差計(jì),使?fàn)t內(nèi)氣氛的碳勢(shì)達(dá)到可控,以后又研究出用二氧化碳紅外儀、氧探頭等進(jìn)一步控制爐內(nèi)氣氛碳勢(shì)的方法;60年代,熱處理技術(shù)運(yùn)用了等離子場(chǎng)的作用,發(fā)展了離子滲氮、滲碳工藝;激光、電子束技術(shù)的應(yīng)用,又使金屬獲得了新的表面熱處理和化學(xué)熱處理方法。
熱處理工藝一般包括加熱、保溫、冷卻三個(gè)過(guò)程,有時(shí)只有加熱和冷卻兩個(gè)過(guò)程。這些過(guò)程互相銜接,不可間斷。
加熱是熱處理的重要步驟之一。金屬熱處理的加熱方法很多,最早是采用木炭和煤作為熱源,進(jìn)而應(yīng)用液體和氣體燃料。電的應(yīng)用使加熱易于控制,且無(wú)環(huán)境污染。利用這些熱源可以直接加熱,也可以通過(guò)熔融的鹽或金屬,以至浮動(dòng)粒子進(jìn)行間接加熱。 金屬加熱時(shí),工件暴露在空氣中,常常發(fā)生氧化、脫碳(即鋼鐵零件表面碳含量降低),這對(duì)于熱處理后零件的表面性能有很不利的影響。因而金屬通常應(yīng)在可控氣氛或保護(hù)氣氛中、熔融鹽中和真空中加熱,也可用涂料或包裝方法進(jìn)行保護(hù)加熱。
加熱溫度是熱處理工藝的重要工藝參數(shù)之一,選擇和控制加熱溫度 ,是保證熱處理質(zhì)量的主要問(wèn)題。加熱溫度隨被處理的金屬材料和熱處理的目的不同而異,但一般都是加熱到相變溫度以上,以獲得需要的組織。另外轉(zhuǎn)變需要一定的時(shí)間,因此當(dāng)金屬工件表面達(dá)到要求的加熱溫度時(shí),還須在此溫度保持一定時(shí)間,使內(nèi)外溫度一致,使顯微組織轉(zhuǎn)變完全,這段時(shí)間稱為保溫時(shí)間。采用高能密度加熱和表面熱處理時(shí),加熱速度極快,一般就沒(méi)有保溫時(shí)間或保溫時(shí)間很短,而化學(xué)熱處理的保溫時(shí)間往往較長(zhǎng)。
冷卻也是熱處理工藝過(guò)程中不可缺少的步驟,冷卻方法因工藝不同而不同,主要是控制冷卻速度。一般退火的冷卻速度最慢,正火的冷卻速度較快,淬火的冷卻速度更快。但還因鋼種不同而有不同的要求,例如空硬鋼就可以用正火一樣的冷卻速度進(jìn)行淬硬。
金屬熱處理工藝大體可分為整體熱處理、表面熱處理、局部熱處理和化學(xué)熱處理等。根據(jù)加熱介質(zhì)、加熱溫度和冷卻方法的不同,每一大類(lèi)又可區(qū)分為若干不同的熱處理工藝。同一種金屬采用不同的熱處理工藝,可獲得不同的組織,從而具有不同的性能。鋼鐵是工業(yè)上應(yīng)用最廣的金屬,而且鋼鐵顯微組織也最為復(fù)雜,因此鋼鐵熱處理工藝種類(lèi)繁多。
整體熱處理是對(duì)工件整體加熱,然后以適當(dāng)?shù)乃俣壤鋮s,以改變其整體力學(xué)性能的金屬熱處理工藝。鋼鐵整體熱處理大致有退火、正火、淬火和回火四種基本工藝。
退火是將工件加熱到適當(dāng)溫度,根據(jù)材料和工件尺寸采用不同的保溫時(shí)間,然后進(jìn)行緩慢冷卻,目的是使金屬內(nèi)部組織達(dá)到或接近平衡狀態(tài),獲得良好的工藝性能和使用性能,或者為進(jìn)一步淬火作組織準(zhǔn)備。正火是將工件加熱到適宜的溫度后在空氣中冷卻,正火的效果同退火相似,只是得到的組織更細(xì),常用于改善材料的切削性能,也有時(shí)用于對(duì)一些要求不高的零件作為最終熱處理。
淬火是將工件加熱保溫后,在水、油或其它無(wú)機(jī)鹽、有機(jī)水溶液等淬冷介質(zhì)中快速冷卻。淬火后鋼件變硬,但同時(shí)變脆。為了降低鋼件的脆性,將淬火后的鋼件在高于室溫而低于710℃的某一適當(dāng)溫度進(jìn)行長(zhǎng)時(shí)間的保溫,再進(jìn)行冷卻,這種工藝稱為回火。退火、正火、淬火、回火是整體熱處理中的“四把火”,其中的淬火與回火關(guān)系密切,常常配合使用,缺一不可。
“四把火”隨著加熱溫度和冷卻方式的不同,又演變出不同的熱處理工藝 。為了獲得一定的強(qiáng)度和韌性,把淬火和高溫回火結(jié)合起來(lái)的工藝,稱為調(diào)質(zhì)。某些合金淬火形成過(guò)飽和固溶體后,將其置于室溫或稍高的適當(dāng)溫度下保持較長(zhǎng)時(shí)間,以提高合金的硬度、強(qiáng)度或電性磁性等。這樣的熱處理工藝稱為時(shí)效處理。把壓力加工形變與熱處理有效而緊密地結(jié)合起來(lái)進(jìn)行,使工件獲得很好的強(qiáng)度、韌性配合的方法稱為形變熱處理;在負(fù)壓氣氛或真空中進(jìn)行的熱處理稱為真空熱處理,它不僅能使工件不氧化,不脫碳,保持處理后工件表面光潔,提高工件的性能,還可以通入滲劑進(jìn)行化學(xué)熱處理。
表面熱處理是只加熱工件表層,以改變其表層力學(xué)性能的金屬熱處理工藝。為了只加熱工件表層而不使過(guò)多的熱量傳入工件內(nèi)部,使用的熱源須具有高的能量密度,即在單位面積的工件上給予較大的熱能,使工件表層或局部能短時(shí)或瞬時(shí)達(dá)到高溫。表面熱處理的主要方法,有激光熱處理、火焰淬火和感應(yīng)加熱熱處理,常用的熱源有氧乙炔或氧丙烷等火焰、感應(yīng)電流、激光和電子束等。
化學(xué)熱處理是通過(guò)改變工件表層化學(xué)成分、組織和性能的金屬熱處理工藝?;瘜W(xué)熱處理與表面熱處理不同之處是后者改變了工件表層的化學(xué)成分?;瘜W(xué)熱處理是將工件放在含碳、氮或其它合金元素的介質(zhì)(氣體、液體、固體)中加熱,保溫較長(zhǎng)時(shí)間,從而使工件表層滲入碳、氮、硼和鉻等元素。滲入元素后,有時(shí)還要進(jìn)行其它熱處理工藝如淬火及回火?;瘜W(xué)熱處理的主要方法有滲碳、滲氮、滲金屬、復(fù)合滲等。
熱處理是機(jī)械零件和工模具制造過(guò)程中的重要工序之一。大體來(lái)說(shuō),它可以保證和提高工件的各種性能 ,如耐磨、耐腐蝕等。還可以改善毛坯的組織和應(yīng)力狀態(tài),以利于進(jìn)行各種冷、熱加工。
例如白口鑄鐵經(jīng)過(guò)長(zhǎng)時(shí)間退火處理可以獲得可鍛鑄鐵,提高塑性 ;齒輪采用正確的熱處理工藝,使用壽命可以比不經(jīng)熱處理的齒輪成倍或幾十倍地提高;另外,價(jià)廉的碳鋼通過(guò)滲入某些合金元素就具有某些價(jià)昂的合金鋼性能,可以代替某些耐熱鋼、不銹鋼;工模具則幾乎全部需要經(jīng)過(guò)熱處理方可使用。
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