天津職業(yè)技術(shù)師范大學(xué) Tianjin University of Technology and Education 畢 業(yè) 設(shè) 計(jì) 專 業(yè)： 機(jī)械設(shè)計(jì)與制造及其自動(dòng)化 班級(jí)學(xué)號(hào)： XXXXXX 學(xué)生姓名： XXX 指導(dǎo)教師： XXX 副教授 二一二年六月 天津職業(yè)技術(shù)師范大學(xué)本科生畢業(yè)設(shè)計(jì) 尾座體加工工藝及鏜模夾具設(shè)計(jì) Designing lathe tailstock body processing technology and boring fixture design 專業(yè)班級(jí)：機(jī)自 0803 學(xué)生姓名： XXX 指導(dǎo)教師： XXX 副教授 學(xué) 院：機(jī)械工程學(xué)院 2012 年 6 月 摘 要 本課題主要是設(shè)計(jì) CW6163車床尾座體的加工工藝及鏜孔夾具設(shè)計(jì)。本設(shè)計(jì)中包括對(duì)進(jìn)行夾具設(shè)計(jì)必須的毛坯選擇、加工余量的確定、切削刀具和機(jī)床的選擇及機(jī)動(dòng)時(shí)間計(jì)算等方面知識(shí)。本次設(shè)計(jì)內(nèi)容包括兩部分，首先是對(duì)尾座體零件的工藝分析，其次是根據(jù)尾座體鏜孔工序進(jìn)行夾具體設(shè)計(jì)。本設(shè)計(jì)所選用的資料主義到貫徹最 新國家標(biāo)準(zhǔn)及部分標(biāo)準(zhǔn)。 本次設(shè)計(jì)師根據(jù)生產(chǎn)綱領(lǐng)成批量，年產(chǎn)量 1000臺(tái)左右設(shè)計(jì)的。設(shè)計(jì)中考慮大批量生產(chǎn)，在加工過程中，為了保證被加工孔對(duì)其定位基準(zhǔn)和尺寸精度和位置精度的要求，同時(shí)提高效率，對(duì)尾座體的鏜孔工序進(jìn)行夾具設(shè)計(jì)。設(shè)計(jì)采用平面和定位銷組合定位，壓板加緊和螺母鎖緊的設(shè)計(jì)來提高加工效率和減輕工作人員勞動(dòng)強(qiáng)度。 關(guān)鍵詞 ：尾座體 加工工藝 鏜床夾具 ABSTRACT The main task is to design CW6163lathe tailstock body processing technology and boring fixture design. This design including the fixture design to the blank selection, determination of machining allowance, cutting tool and machine tool selection and maneuvering calculation knowledge. This design includes two parts, the first is the tailstock body parts of the process analysis, the second is based on the tailstock body boring process clamp design. The design of the data to carry out the new national standards and standards. The designer according to production plan into the bulk, the annual output of 1000sets of left and right design. Design considerations for mass production, in the process, in order to ensure the hole on the locating datum and dimensional accuracy and position accuracy requirements, while improving the efficiency, the tailstock body bore for fixture design process. The design adopts the plane and positioning pin positioning, plate intensified and nut locking design to improve processing efficiency and reduce the labor intensity of workers. Key Words： The tailstock body Processing technology Jig boring machine I 目 錄 1 緒論 . 1 1.1設(shè)計(jì)的目的 . 1 1.2設(shè)計(jì)任務(wù)及要求 . 1 1.3設(shè)計(jì)的內(nèi)容及步驟 . 1 1.3.1工藝規(guī)程的設(shè)計(jì) . 1 1.3.2專用夾具設(shè)計(jì) . 2 2 零件加工工藝規(guī)程的制定 . 4 2.1 零件的分析 . 4 2.1.1零件的功用 . 4 2.1.2零件的工藝分析 . 4 2.2 零件的工藝規(guī)程 . 4 2.2.1確定零件的生產(chǎn)綱領(lǐng) . 4 2.2.2確定零件毛坯的制造形式 . 5 2.2.3擬定零件機(jī)械加工工藝路線 . 5 3 零件工序設(shè)計(jì) . 7 3.1 零件加工余量的確定 . 7 3.2 確定各工序所用機(jī)床及工藝設(shè)備 . 8 3.3 用量及工時(shí)定額 . 8 4 鏜模夾具設(shè)計(jì) . 11 4.1 設(shè)計(jì)夾具目的 . 11 4.2 鏜模設(shè)計(jì)方案的選擇和確定 . 11 4.2.1定位方案、定位誤 差及定位元件的選擇 . 11 4.2.2 裝置的選擇及夾緊力的布置 . 12 4.2.3 確定刀具的導(dǎo)引方式 . 12 4.2.4 設(shè)計(jì)夾具體 . 13 4.2.5 定夾具其它部分的結(jié)構(gòu)形式 . 13 4.2.6 夾緊力計(jì)算（估算） . 14 結(jié) 論 . 16 翻譯文獻(xiàn) . 19 II 參考文獻(xiàn) . 35 致謝 . 36 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 1 1 緒論 1.1 設(shè)計(jì)的目的 能熟練的運(yùn)用機(jī)械制造工藝學(xué)的基本理論和夾具設(shè)計(jì)原理的知識(shí)，正確的解決一個(gè)零件在加工中的定位、夾緊以及合理制定工藝規(guī)程等問題的方 法，培養(yǎng)分析問題和解決問題的能力。通過對(duì)零件某道工序的夾具的設(shè)計(jì)夾具的訓(xùn)練，提高結(jié)構(gòu)設(shè)計(jì)的能力。本次設(shè)計(jì)也是理論聯(lián)系實(shí)踐的過程，并學(xué)會(huì)使用手冊(cè)、資料 ,增加解決工程實(shí)際問題的獨(dú)立工作能力的過程。 1.2 設(shè)計(jì)任務(wù)及要求 制作成批量生產(chǎn)（ 1000 臺(tái)）中等復(fù)雜程度零件（尾架體）的機(jī)械加工工藝規(guī)程和鏜孔工序中所需要的專用夾具的設(shè)計(jì)。 設(shè)計(jì)任務(wù)要求： 1.零件的工藝性分析及選擇毛坯 2.機(jī)械加工工藝過程卡及鏜孔工序卡 3.夾具裝配圖和零件圖 4.設(shè)計(jì)說明書 1.3 設(shè)計(jì)的內(nèi)容及步驟 1.3.1 工藝規(guī)程的設(shè)計(jì) 1）對(duì)零件進(jìn)行工藝分析。 （ 1）對(duì)零件機(jī)器結(jié)構(gòu)中的作用及零件圖上技術(shù)要求進(jìn)行分析。 （ 2）對(duì)零件主要加工表面尺寸，形狀及相對(duì)位置精度，表面粗糙度及主要技術(shù)條件進(jìn)行分析。 （ 3）對(duì)零件的材質(zhì)、熱處理及工藝性進(jìn)行分析。通過以上分析，以便在工藝過程中切實(shí)加以保證。 2）選擇毛坯的制造方式，繪制零件毛坯綜合示意圖。 選擇毛坯應(yīng)以生產(chǎn)批量的大小來確定，跟據(jù)批量大小的生產(chǎn)規(guī)模決定毛坯形式及制造方法，根據(jù)有關(guān)資料 確定各個(gè)加工表面的總余量，并把各余量加在零件圖各有關(guān)位置上，在毛坯圖上標(biāo)出相關(guān)尺寸。 3）制定零件的機(jī)械加工工藝路線 （ 1）制定工藝路線，在對(duì)零件和毛坯進(jìn)行分析的基礎(chǔ)上制定零件的加工工藝，它包括確定加工方法、確定安排加工順序、確定定位夾緊方法，以及安排天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 2 熱處理、檢驗(yàn)以及其他輔助工序等。 （ 2）選擇定位基準(zhǔn)，合理選定各工序的定位基準(zhǔn)，當(dāng)工序定位基準(zhǔn)與設(shè)計(jì)基準(zhǔn)不重合時(shí)，需要對(duì)它的工序尺寸進(jìn)行換算。 （ 3）選擇機(jī)床及夾具、刀具、量具。機(jī)床設(shè)備及工藝裝備的選用應(yīng)當(dāng)既要保證加工質(zhì)量，還要經(jīng)濟(jì)合理。 （ 4）加工余量 及工序間尺寸與公差的確定。根據(jù)工藝路線的安排，計(jì)算鏜孔相關(guān)工序加工余量。其工序間尺寸公差按經(jīng)濟(jì)精度確定。 （ 5）確定切削用量機(jī)動(dòng)時(shí)間。用公式計(jì)算各工序的切削用量，其余各工序的切削用量可由切削手冊(cè)查到。然后計(jì)算該工序的時(shí)間定額。 （ 6）繪制零件的機(jī)械加工工藝過程卡片，及鏜孔工序的工序卡片。 1.3.2 專用夾具設(shè)計(jì) 在該加工過程中需要設(shè)計(jì)鏜模專用夾具。 夾具結(jié)構(gòu)設(shè)計(jì)的方法和步驟： 1）確定夾具設(shè)計(jì)方案、繪制結(jié)構(gòu)原理圖。 確定夾具設(shè)計(jì)方案應(yīng)遵循幾個(gè)原則： （ 1）保證工序加工精度和技術(shù)要求。 （ 2）結(jié)構(gòu)簡(jiǎn)單、制造 容易。 （ 3）造作方便、省力安全。 （ 4）滿足零件在生產(chǎn)中高效低成本。 確定夾具設(shè)計(jì)方案的主要內(nèi)容為： （ 1）確定工件的定位方案。 （ 2）確定刀具的對(duì)刀或引導(dǎo)方式。 （ 3）確定刀具的夾緊方案。 （ 4）確定夾具其他組成部分的結(jié)構(gòu)形式。 （ 5）確定夾具體。 最后繪制出結(jié)構(gòu)原理示意圖 2）選擇定位原件，計(jì)算定位誤差。 在確定設(shè)計(jì)方案的基礎(chǔ)上，應(yīng)按照加工精度的高低，根據(jù)六點(diǎn)定位原理。約束自由度的數(shù)目以及確定所需的定位元件。選擇好定位原件后，應(yīng)計(jì)算定位誤差。 3）計(jì)算夾緊力，決定夾緊機(jī)構(gòu)及其主要尺寸 夾緊是按照靜力 平衡條件，從具體定位夾緊力方案和切削條件出發(fā)進(jìn)行分析，主要根據(jù)切削力決定理論夾緊力，但由于在加工過程中有沖擊震蕩存在，為了保障安裝穩(wěn)定理論夾緊力還要乘以一個(gè)安全系數(shù) K， K 值可以在相關(guān)手冊(cè)中查到。 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 3 計(jì)算出夾緊力后，根據(jù)所確定的加緊機(jī)構(gòu)決定其主要尺寸。 4）繪制夾具裝配圖： （ 1）要求夾具裝配圖按照比例繪制。 （ 2）要有必要的視圖和剖面圖。 5）在裝配圖上標(biāo)注各部位尺寸、公差配合和技術(shù)條件參考機(jī)床夾具設(shè)計(jì)或其他有關(guān)手冊(cè) 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 4 2 零件加工工藝規(guī)程的制定 2.1 零件的分析 2.1.1 零件的功用 本課題所給零件是 cw6163 車床的尾架體。它的作用主要是。對(duì)工件起到固定支撐，保證定位的作用，減少在加工中因?yàn)楣ぜ灾鼗蚴堑毒咔邢髁σ鸸ぜ巫?，而?dǎo)致的加工誤差。 2.1.2 零件的工藝分析 1） 尺寸精度 加工孔 100H7 30H7 45H7 都是配合尺寸，必須有較高的尺寸精度，尺寸精度均為 IT7 級(jí)公差，精度要求較高，加工中應(yīng)注意保證。 2） 形位精度 孔和右端面的垂直度誤差為 0.08mm， 100H7 孔的內(nèi)表面平行度誤差為0.12mm， 100H7 孔的內(nèi)表面圓柱度誤差為 0.012mm 。 3） 表面粗糙度 配合表面要求較高的表面粗糙度， 100H7 孔的粗糙度為 Ra0.8 m, 30H7 45H7 孔的粗糙度為 Ra1.6 m，下表面粗糙度為 Ra1.6 m，上表面及左右兩端面的粗糙度為 Ra3.2 m。 4） 熱處理 為了消除毛坯鑄件中的殘余應(yīng)力，進(jìn)一步改善切削性能，鑄造后應(yīng)安排去應(yīng)力退火或時(shí)效處理。 2.2 零件的工藝規(guī)程 2.2.1 確定零件的生產(chǎn)綱領(lǐng) 機(jī)器零件的生產(chǎn)綱領(lǐng)按下式計(jì)算： N=Qn（ 1+a%+b%） 式中： N 零件的生產(chǎn)綱領(lǐng)（件 /年） Q 產(chǎn)品的年產(chǎn)量（臺(tái) /年） n 每臺(tái)中該零件的數(shù)量（件 /臺(tái)） a% 備品的百分率 b% 廢品的百分率 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 5 其中：產(chǎn)品的年產(chǎn)量 Q=1000 臺(tái) /年 , 每臺(tái)中該零件的數(shù)量 n=1 件 /臺(tái) , 備品的百分率 a%=4%，平均廢品的百分率 b%=3%， N=1000 1(1+4%+3%)=1070 件 通過計(jì)算可知，生產(chǎn)類型為大批量生產(chǎn)。 2.2.2 確定零件毛坯的制造形式 毛坯種類確定：選用灰口鑄鐵，牌號(hào)為 HT200，灰鑄鐵具有較好的可切削性，鑄造性，耐磨性，而且吸振性好，成本較低。 毛坯制造方法：砂型機(jī)器鑄造，鑄造 精度高，且生產(chǎn)效率較高，鑄件成型后的材質(zhì)比木模穩(wěn)定可靠。在鑄造時(shí)，應(yīng)防止砂眼和氣孔的產(chǎn)生，澆注的位置是大平面朝下，基面朝上。為了減少毛坯制造時(shí)產(chǎn)生的殘余應(yīng)力，其結(jié)構(gòu)，厚度要均勻，澆鑄后應(yīng)安排退火工序。 2.2.3 擬定零件機(jī)械加工工藝路線 1） 工藝路線的制定 : （ 1）先粗后精 加工尾架體頂面和底面時(shí)：先粗刨頂面，粗刨底面；再磨削頂面，磨削底面。粗加工時(shí)切削力較大，產(chǎn)生較多的切削熱。粗加工時(shí)需要較大的夾緊力。粗加工后鑄造毛坯的內(nèi)應(yīng)力重新分配在這些熱和力的周圍。工件會(huì)發(fā)生較大的變形。粗精加工分開，是為了保證這些有 粗加工引起的工件變形，能夠在精加工后被消除掉。 （ 2）先基面后其他 先將精基準(zhǔn)尾架體底面加工出來，然后再加工 100 的孔等。 （ 3）先主后次 尾架體的底面尺寸及 100 孔是主要配合面，它的加工應(yīng)安排在 45 30孔之前。 工藝過程，（參見工藝過程卡） 2） 定位基準(zhǔn)的選擇 （ 1）選擇定位基準(zhǔn)： 工件的加工部位和各表面相對(duì)位置的準(zhǔn)確性，取決于工件在機(jī)床上相對(duì)刀具位置的準(zhǔn)確性，也就是取決于工件在夾具中定位的準(zhǔn)確性，定位的準(zhǔn)確與否，由于定位基準(zhǔn)的選擇正確與否有直接聯(lián)系，所以定位基準(zhǔn)選擇合理與否不僅影響到零件的加 工位置精度，而且決定了工件各表面加工先后順序。 （ 2）選擇粗基準(zhǔn)： 粗基準(zhǔn)的選擇，可以保證重要表面能夠分配到必須且均勻的加工余量，也保證了工件加工表面與不加工表面的相互位置精度。是為了能夠在此基準(zhǔn)的定位下，加工出精基準(zhǔn)，從而對(duì)工件進(jìn)行進(jìn)一步的加工。 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 6 車床尾架體為了保證被加工表面最主要位置要求是 100H7 孔軸線與 B 端面的垂直度為 0.08 （ 3）選擇精基準(zhǔn)： 應(yīng)保證各表面的相互位置精度，使夾具結(jié)構(gòu)簡(jiǎn)單，安裝方便，采用基準(zhǔn)統(tǒng)一原則，即設(shè)計(jì)基準(zhǔn)與定位基準(zhǔn)相互統(tǒng)一。 尾架體零件應(yīng)盡量選擇設(shè)計(jì)基準(zhǔn)為精基準(zhǔn)，以 100H7 孔的軸心線為定位基準(zhǔn)，能保證孔的加工精度。 另外，還應(yīng)考慮到在測(cè)量已加工表面位置時(shí)的測(cè)量基準(zhǔn)。 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 7 3 零件工序設(shè)計(jì) 零件機(jī)械加工工藝路線擬定后還需對(duì)每一工序進(jìn)行設(shè)計(jì)。其主要內(nèi)容包括：確定每一工步的加工余量、計(jì)算各工序的工序尺寸及公差、選擇各工序所使用的機(jī)床及工藝裝備、確定切削用量、計(jì)算工時(shí)定額等 。 3.1 零件加工余量的確定 機(jī)械加工余量對(duì)工藝過程有一定的影響，余量不夠，不能保證零件的加工質(zhì)量，余量過大，不但會(huì)增加機(jī)械加工勞動(dòng)量，而且增加了材料、刀具、能源的 消耗，從而增加了成本，所以必須合理的安排加工余量。 根據(jù)零件毛坯條件：材料灰口鑄鐵 HT200，生產(chǎn)類型為中批生產(chǎn)。采用金屬模型鑄造毛坯。本設(shè)計(jì)采用查表修正和經(jīng)驗(yàn)估計(jì)法相結(jié)合來確定各加工表面的機(jī)械加工余量、工序尺寸及毛坯尺寸。 1）工序尺寸計(jì)算 以加工 035.00100孔為例，設(shè)計(jì)加工方法為： 粗鏜 半精鏜 精擴(kuò) 精鉸 細(xì)鉸 具體計(jì)算值見表 2-1 表 2-1 工序尺寸計(jì)算表 工序名稱 工序余量 mm 工序達(dá)到的公差等級(jí) mm 最小極限尺寸mm 工序尺寸及極限偏差 mm 細(xì)鉸 0.1 )(7 035.00IT 100 035.00100 精鉸 0.6 )(9 054.00IT 100-0.1=99.9 054.009.99 精擴(kuò) 0.8 )(10 14.00IT 99.9-0.6=99.3 14.003.99 半精鏜 1.5 )(11 23.00IT 99.3-0.8=98.5 23.005.98 粗鏜 5 )(13 46.00IT 98.5-1.5=97 46.0097 毛坯孔 )1(16 IT 97-5=92 192 2）工序間尺寸計(jì)算 精鉸孔時(shí)，是以 E 面定位的，而設(shè)計(jì)基準(zhǔn)為軸線，因而定位基準(zhǔn)與設(shè)計(jì)基準(zhǔn)不重合，因而要進(jìn)行尺寸換算。 如下圖所示，在尺寸鏈中，要間接保證的尺 寸為 3.02.0250 ，因此，設(shè)其為封閉環(huán) A ，由豎式法求得： 80.0)0()1(20.0)()()()( 4321 lEslEslEilEi 3.0)0()0(3.0)()()()( 4321 lEilEilEslEs 1968462501 l 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 8 所以，工序尺寸 3.08.0196 3.2 確定各工序所用機(jī)床及工藝設(shè)備 由于該工件生產(chǎn)規(guī)模為中批生產(chǎn)，根據(jù)工件的結(jié)構(gòu)特點(diǎn)和技術(shù)要求，各工序所用機(jī)床及工藝裝備確定如下：工序 030，銑床 X6120、通用夾具；工序 050、055、 060、 065 臥式鏜床 T4680 專用夾具；工序 70，鉆床 Z3063。 3.3 用量及工時(shí)定額 以加工 100H7 孔為例，確定加工中各個(gè)工步的切削用量，機(jī)動(dòng)時(shí)間及工時(shí)定額。 1） 切削用量計(jì)算： （ 1） .粗鏜鑄出孔 毛坯孔 D=92mm，粗鏜加工至 D=97mm，查機(jī)械加工工藝手冊(cè)， P1-132,選擇硬質(zhì)合金刀頭，從表中可以選擇切削速度 v=60m/min,進(jìn)給量 f=0.4mm/r,根據(jù)公式： 1000dnv ， m in/1979714.3 100060 rn 查機(jī)械加工工藝人員手冊(cè)， P1128 確定在粗鏜孔時(shí)的實(shí)際進(jìn)給長度： 加工長度 l =500 mm， 刀具切入長度 1l =2.5 mm,刀具超出長度 2l =2.5 mm, 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 9 m i n409.61974.0 5.25.2500210 nf lllT (2).半精鏜孔 孔徑 D=98.5mm，查機(jī)械加工工藝手冊(cè)， P1-132,選擇硬質(zhì)合金鏜刀頭，從表中可以選擇切削速度 v=80m/min,進(jìn)給量 f=0.3mm/r,根據(jù)公式： 1000dnv ， m in/25 95.9814.3 10 0080 rn 查機(jī)械加工工藝人員手冊(cè)， P1128 確定在半精鏜孔時(shí)的實(shí)際進(jìn)給長度： 加工長度 l =500 mm， 刀具切入長度 1l =2.5 mm,刀具超出長度 2l =2.5 mm m i n499.62593.0 5.25.2500210 nf lllT (3).精擴(kuò)孔 孔徑 D=99.3mm，查實(shí)用機(jī)械 加工工藝手冊(cè)， P1307，選用硬質(zhì)合金擴(kuò)孔刀，從表中可以選擇切削速度 v=120m/min,進(jìn)給量 f=0.2mm/r,根據(jù)公式： 1000dnv m i n/38 53.9914.3 10 0012 0 rn 查金屬機(jī)械加工工藝人員手冊(cè)， P1128 確定在精擴(kuò)孔時(shí)的實(shí)際進(jìn)給長度： 加工長度 l=500 mm，刀具切入長度 1l =2.5 mm,刀具超出長度 2l =2.5 mm m i n558.63852.0 5.25.2500210 nf lllT (4).精鉸孔 孔徑 D=99.9mm，查實(shí)用機(jī)械加工工藝手冊(cè)， P1307，選用硬質(zhì)合金精鉸刀，從表中可以選擇切削速度 v=40m/min,進(jìn)給量 f=4.0mm/r,根據(jù)公式： 1000dnv ， m in/1289.9914.3 100040 rn 查金屬機(jī)械加工工藝人員手冊(cè)， P1132，確定在精鉸孔時(shí)的實(shí)際進(jìn)給長度： 加工長度 l=500 mm，切深 a p=0.3mm,刀具切入長度 1l =0.3 mm,刀具超出長度2l =45 mm m i n650.11280.4 453.0500210 nf lllT (5).細(xì)鉸孔 孔徑 D=100mm，查實(shí)用機(jī)械加工工藝手冊(cè)， P1307，選用硬質(zhì)合金浮動(dòng)天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 10 鏜刀，從表中可以選擇切削速度 v=30m/min,進(jìn)給量 f=2.5mm/r,根據(jù)公式： 1000dnv ， m in/9610 014.3 10 0030 rn 查金屬機(jī)械加工工藝人員手冊(cè)， P1132，確定在細(xì)鉸孔時(shí)的實(shí)際進(jìn)給長度： 加工長度 l=500 mm， 切深pa=0.3mm,刀具切入長度 1l =0.05 mm,刀具超出長度2l =45 mm m i n271.2965.2 4505.0500210 nf lllT 2）單件時(shí)間定額： Tm=Tm1+Tm2+Tm3+Tm4+Tm5 =6.409+6.499+6.558+1.650+2.271 =23.387 min 查手冊(cè)，可以得到以下計(jì)算公式： Ta=2min Te=7% (Tm+Ta)=0.07 25.387=1.78 min Ts=1.5% (Tm+Ta)=0.015 25.387=0.38 min Tr=2% (Tm+Ta)=0.02 25.387=0.51 min 所以： T 定額 =23.387+2+1.78+0.38+0.51=28.057 min Td1 單位時(shí)間 Tm 基本時(shí)間 Ta 輔助時(shí)間 Tr 休息與生理需要 Ts 布置工作的時(shí)間 Te 準(zhǔn)備與終結(jié)時(shí)間 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 11 4 鏜模夾具設(shè)計(jì) 4.1 設(shè)計(jì)夾具目的 機(jī)床夾具是在切削加工中，用以準(zhǔn)確的確定工件位置，并將其牢固的加緊的工藝裝備。它可靠的保證工件的加工精 度，提高加工效率，減輕勞動(dòng)強(qiáng)度。充分發(fā)揮機(jī)床的工藝性能。為了提高生產(chǎn)率，尾架體加工，有必要采用專用夾具來滿足生產(chǎn)率及合理的經(jīng)濟(jì)要求，減輕工人勞動(dòng)強(qiáng)度。 由于孔加工比其它表面要復(fù)雜的多，加工環(huán)境條件差，刀具尺寸受被加工孔的限制，致使刀桿細(xì)長而剛性差，以至于影響孔的加工精度。如果采用劃線找正的方法加工有一定位置精度的孔時(shí)；不僅生產(chǎn)效率低，而且加工質(zhì)量也不高。有必要采用鏜模夾具。設(shè)計(jì)該鏜模夾具，有利于保證加工精度，提高生產(chǎn)率，保證定位準(zhǔn)確，保證夾緊可靠，并盡可能使夾具結(jié)構(gòu)簡(jiǎn)單合理，降低成本。 4.2 鏜模設(shè)計(jì)方 案的選擇和確定 4.2.1 定位方案、定位誤差及定位元件的選擇 工件在機(jī)床相對(duì)刀具占有正確的加工位置，這就是定位。工件在夾具中定位的目的，就是要使同一批工件在夾具中占有一定正確的加工位置。 該方案是以 C 面（底面）作為主要定位面，有 3 個(gè)定位點(diǎn)。 E 面作為導(dǎo)向面。有兩個(gè)定位點(diǎn)，而且 C 面的面積要大于 E 面面積。根據(jù)定位基準(zhǔn)選擇的一般原則：選最大尺寸的表面為安裝面（限制 3 個(gè)自由度），選最長距離的表面為導(dǎo)向面（限制 2 個(gè)自由度）。該定位方案可行。 C 面為主要定位面，限制了三個(gè)自由度。 E 面（側(cè)面）為導(dǎo)向面，限制兩個(gè)自由度。這 樣就確定了工件與刀具間的相對(duì)位置。 由于 C 面為精基面，因此，可在 C 面設(shè)立兩個(gè)支承板，以確保定位穩(wěn)定，而不會(huì)出現(xiàn)過定位。兩個(gè)支承板位置分布在兩側(cè)，比較分散，其形成的受力四邊形面積盡可能大。 E 面兩點(diǎn)定位，為確保質(zhì)量，兩個(gè)支承點(diǎn)間距離應(yīng)盡可能遠(yuǎn)些。 在鏜削加工工序中，是以平面定位的，而這一平面又是精基面，很難保證大平面的平整。因此，不能用大平面作為定位元件來定位。選用支承板作為小平面式定位。在 C 面用兩個(gè)支承板定位。 E 面一側(cè)用兩個(gè)開槽盤頭定位螺釘定位。 定位誤差的計(jì)算： 工件以平面定位，所以 Y=0； 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 12 由于鏜孔的 工序基準(zhǔn)和定位基準(zhǔn)重合，所以 B=0.015+0.1=0.025 定位誤差為 D= B=0.025 4.2.2 裝置的選擇及夾緊力的布置 夾緊裝置選擇的是否合理，對(duì)于確保加工質(zhì)量和提高生產(chǎn)率有很大的關(guān)系，一般來說在不破壞定位精度，保證加工質(zhì)量前提下，應(yīng)盡可能使夾緊裝置的夾緊作用準(zhǔn)確，安全可靠，操作方便省力，夾緊變形小，結(jié)構(gòu)簡(jiǎn)單，制造容易。 鏜削的切削力產(chǎn)生的翻轉(zhuǎn)扭矩不很大，因此，手動(dòng)夾緊已經(jīng)可以滿足。 設(shè)計(jì)和選用夾緊裝置的核心問題是如何正確地施加夾緊力即適當(dāng)布置夾緊力。夾緊力應(yīng)保證定位準(zhǔn)確可靠。 ,而不能 破壞原定位，考慮到中批生產(chǎn)，夾緊力方向應(yīng)便于工人操作。因此，將夾緊螺母設(shè)計(jì)在頂面，減輕勞動(dòng)強(qiáng)度，便于操作。與 C 面兩個(gè)支承板相對(duì)應(yīng)產(chǎn)生夾緊力。 4.2.3 確定刀具的導(dǎo)引方式 鏜模中的導(dǎo)引元件，選用固定式鏜套，這是因?yàn)榧庸ち慵r(shí)，一次性鏜通孔，不用頻繁的更換刀具及鏜套，而且我們?cè)谥贫üに囈?guī)程中，采用的鏜削加工速度也不高。如果用回轉(zhuǎn)式鏜套，則不能滿足上述要求。 鏜桿是依靠鏜套和支架來引導(dǎo)和支承的。鏜套結(jié)構(gòu)對(duì)于被鏜孔的幾何形狀，尺寸精度以及表面粗糙度有很小的影響。因此鏜套的設(shè)計(jì)是鏜模設(shè)計(jì)中的重要環(huán)節(jié)之一。 鏜套的 布置形式是由鏜孔的孔徑 D，以及孔的長度 L 與孔徑之比 L/D 所決定的，鏜桿的長度很長，為了防止鏜桿受切削力而變形，影響其剛度，采用雙面單鏜套的布置形式。由于前后鏜套已經(jīng)確定了鏜桿的位置，因此鏜桿與機(jī)床主軸之間不可用剛性連接，只能是浮動(dòng)連接，以避免鏜套中心與機(jī)床主軸不重合時(shí)發(fā)生孔徑增大，鏜套拉毛等現(xiàn)象。 為了滿足裝配要求和強(qiáng)度要求，在結(jié)構(gòu)上設(shè)置了較大的安裝基面和加強(qiáng)筋，詳見夾具裝配圖。 鏜套的內(nèi)徑是鏜桿的導(dǎo)桿的導(dǎo)引部分直徑?jīng)Q定的，一般來說，為使刀具從鏜套內(nèi)穿過，則其內(nèi)徑應(yīng)大于刀具直徑。 如 100 孔精鏜時(shí)，刀具直徑為 75 。則其鏜套內(nèi)徑應(yīng)大于刀具直徑，選鏜套內(nèi)徑 80 與鏜桿的配合應(yīng)為間隙配合。間隙要適宜，太大，鏜桿導(dǎo)引不好影響加工精度。太小，鏜桿與鏜套磨損嚴(yán)重，產(chǎn)生熱量可能會(huì)使鏜桿與鏜套咬死，這里取56nH。 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 13 鏜套外徑與襯套的配合，襯套與支架內(nèi)徑的配合應(yīng)為過渡配合。為避免個(gè)別出現(xiàn)過盈現(xiàn)象，裝配時(shí)應(yīng)采用修配法，一般配合取66hH。 鏜套長度要選取適宜，太短導(dǎo)引不好，影響鏜桿回轉(zhuǎn)精度，從而影響孔加工質(zhì)量；太長不易散熱，鏜套磨損嚴(yán)重，影響加工精度。一般對(duì)于雙面單鏜套導(dǎo)引，鏜套長度 H 一般取 H=(1.5-2)d。 d 為鏜桿導(dǎo)引部分直徑。 4.2.4 設(shè)計(jì)夾具體 夾具體應(yīng)能保證夾具的整體剛度和強(qiáng)度，在此前提下，要盡量減輕重量。因此，夾具體大部分采用鑄件，以便能根據(jù)需要鑄出各種形狀的筋條和邊框、銑床、磨床等機(jī)床夾具通常是開式或半開式的，以便刀具通過。而鉆床夾具則常設(shè)計(jì)成框架式，以便鉆套的配置。為了提高夾具制造的工藝性，夾具體很少做成整體的，而是分成座底立柱，模板等零件，它們之間用螺釘和銷釘進(jìn)行聯(lián)接定位。 由于粗鏜時(shí)，切削深度較半精鏜時(shí)大，所以粗鏜時(shí)切削力最大。 (1)夾具輪廓（最大）尺寸，之所以需要標(biāo)注輪廓尺寸，是因?yàn)樗绊憴C(jī)床規(guī)格的確定。 (2)配合尺寸及性質(zhì)如定位元件與夾具體的配合，鉆套與襯套、襯套與夾具體的配合等標(biāo)注配合的意義在于給夾具零件設(shè)計(jì)者作出規(guī)定，并給總圖的閱讀提供方便。 有關(guān)配合的選取，通?？蓞⒄諜C(jī)床夾具設(shè)計(jì)手冊(cè)進(jìn)行 (3)裝配位置要求。其中包括定位元件之間，定位元件與對(duì)定元件之間，多個(gè)對(duì)定元件之間以及定位元件與夾具在機(jī)床 工作臺(tái)或主軸上安裝用元件之間等幾方面的位置要求，標(biāo)注這些要求，一方面是作為封閉環(huán)，在規(guī)定夾具零件相關(guān)尺寸位置和公差時(shí)，要予以保證另一方面是用作夾具裝配時(shí)的最終精度檢驗(yàn)指標(biāo)，裝配位置要求通常按被加工工件上相應(yīng)尺寸及位置公差的 1/5 1/3選取，一般當(dāng)工件相應(yīng)尺寸精度要求高應(yīng)取大值，以便于夾具制造。 4.2.5 定夾具其它部分的結(jié)構(gòu)形式 鏜模支架是組成鏜模的重要零件之一，它是安裝鏜套和承受切削力用的。因此，它必須具有足夠的剛性和穩(wěn)定性。因此要防止鏜模支架的受力振動(dòng)和變形，在結(jié)構(gòu)上應(yīng)考慮有較大的安裝基面和設(shè)置必要 的加強(qiáng)筋。 鏜模底座要承受包括工件、鏜桿、鏜套、鏜模支架定位元件和夾緊裝置內(nèi)的全部重量，以及加工過程中的切削力。因此，底座剛性要好，變形要小，通常鏜模底座的壁厚較厚而底座內(nèi)腔設(shè)有十字形加強(qiáng)筋。 為了安裝各元件，鏜模底座上平面，在相應(yīng)位置做出了相配合的凸臺(tái)表面，其凸出高度為 5mm。鏜模材料選用灰鑄鐵 HT200。 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 14 4.2.6 夾緊力計(jì)算（估算） 總切削力的計(jì)算： 由于粗鏜時(shí)，切削深度較半精鏜時(shí)大，所以粗鏜時(shí)切削力最大。切削時(shí)，鏜刀塊一端切深為 3mm，另一端為 2mm。刀具材料 YG6硬質(zhì)合金刀。主偏角 45粗鏜進(jìn)給量 s=0.4mm/r。所以切削力 75.0stCPz PZ 式中： mmKgC PZ /100 ， 75.0)4.0(/1 0 0 tmmkgP Z 當(dāng) t=3mm 時(shí)， mmKgP Z 87.1 5 04.031 0 0 75.01 當(dāng) t=2mm 時(shí)， mmKgP Z 58.1 0 04.021 0 0 75.02 孔加工時(shí)的總切削力 mmKgPPP ZZZ 45.25121 鏜孔時(shí)通常軸向力很小且方向不變，因此它對(duì)夾緊力影響不大。鏜孔關(guān)鍵在于根據(jù)其圓周切削力 ZP 方向的變化，按照可能出現(xiàn)的最壞情況來確定所需夾緊力。 當(dāng)圓周力 ZP 向上時(shí)，是工件繞的支承板右端最遠(yuǎn)的那一端點(diǎn)回轉(zhuǎn)，并有可能抬起工件，此時(shí)，利用公式l LKPW Z進(jìn)行計(jì)算。查機(jī)床夾具設(shè)計(jì)手冊(cè)。 安全系數(shù) K的計(jì)算： 根據(jù)公式6543210 KKKKKKKK 進(jìn)行計(jì)算。其中，工件材料系數(shù) 3.10 K，加工精度系數(shù) 2.11 K ，因?yàn)橛?jì)算工序選擇是粗加工；刀具鈍化程度 0.12 K 切削特點(diǎn)系數(shù) 0.13 K，因?yàn)槭沁B續(xù)切削；夾緊力穩(wěn)定系數(shù) 3.14 K ，因?yàn)槭鞘謩?dòng)夾緊；操作方便系數(shù) 0.15 K因?yàn)榉奖銑A緊；支承面接觸點(diǎn)系數(shù) 0.16 K因?yàn)榻佑|點(diǎn)確定。 所以， 02.20.10.13.10.10.12.13.1 K mmKgl LKPW Z 51.1591150 47045.25102.2 當(dāng)個(gè)圓周力 ZP 方向處于水平方向時(shí)，有使工件產(chǎn)生平移的可能。在不允許定位螺釘承受切削力時(shí)，工件按照靜力平衡方程Zj PffW )( 21 進(jìn)行計(jì)算。查機(jī)床夾具設(shè)計(jì)手冊(cè)。 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 15 mmKgff KPW Z 83.1 2 6 92.02.0 45.2 5 102.221 因?yàn)椋?WW ，所以夾緊力選擇 mmKgW 51.1591 選擇的是 M16 的螺柱，配合壓板，六角螺母一起把工件夾緊。查機(jī)床夾具設(shè)計(jì)手冊(cè)螺母可提供的夾緊力可知，假設(shè)扳手長度為 90mm, 假設(shè)加在扳手上的力為 100 mmKg ，則產(chǎn)生的夾緊力 mmKgQ 523 0 ， WQ 所以能夠完全滿足夾緊需要。 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 16 結(jié) 論 畢業(yè)設(shè)計(jì)不僅僅是一個(gè)綜合性的設(shè)計(jì)，也不只是理論的設(shè)計(jì)，他還包括解決實(shí)際問題的方案設(shè)計(jì)，這就要求我們把理論知識(shí)的應(yīng)用與實(shí)際相結(jié)合，靈活運(yùn)用。 通過本次畢業(yè)設(shè)計(jì)，使我們認(rèn)識(shí)到畢業(yè)設(shè)計(jì)是我們走上工作崗位之前在學(xué)校期間對(duì)所學(xué)基礎(chǔ)知識(shí)、專業(yè)知識(shí)、基 本技能和專業(yè)技能進(jìn)行的一次全面綜合學(xué)習(xí)過程。 畢業(yè)設(shè)計(jì)是一個(gè)綜合性的設(shè)計(jì)，不只是理論的設(shè)計(jì)，而且還用于實(shí)際，這就要求我們把理論知識(shí)的應(yīng)用與實(shí)際相結(jié)合。次畢業(yè)設(shè)計(jì)，是我對(duì)所學(xué)基礎(chǔ)知識(shí)、專業(yè)知識(shí)、基本技能和專業(yè)技能進(jìn)行的一次全面綜合學(xué)習(xí)過程。 在這次畢業(yè)設(shè)計(jì)過程中，對(duì)于計(jì)算機(jī)的操作時(shí)必不可少的，計(jì)算機(jī)的輔助設(shè)計(jì)，文字的輸入、排版的良好的運(yùn)用，極大的提高了設(shè)計(jì)的效率。并且可通過互聯(lián)網(wǎng)在較短的時(shí)間里搜索到自己所需要的資料，從而對(duì)整個(gè)設(shè)計(jì)過程有了很大的幫助。在設(shè)計(jì)過程中，我到圖書館查閱大量的資料，獨(dú)立的分析問題解決問 題。在整個(gè)設(shè)計(jì)過程中發(fā)現(xiàn)自己知識(shí)的漏洞，有問題會(huì)向指導(dǎo)老師學(xué)習(xí)、同學(xué)討論。得到一種解決方案。在和老師、同學(xué)交流的過程中取長豐富自己的知識(shí)面。 設(shè)計(jì)期間，我總結(jié)梳理過去所學(xué)的知識(shí)，綜合應(yīng)用于此次的畢業(yè)設(shè)計(jì)中，通過查閱圖書館的手冊(cè)，一步一步的完成自己的設(shè)計(jì)，有不對(duì)的地方及時(shí)改正，設(shè)計(jì)在六月中旬完成。通過畢業(yè)設(shè)計(jì)我初步體會(huì)到解決工程實(shí)際工作的方法，并學(xué)會(huì)了如何把所學(xué)知識(shí)技能應(yīng)用于工程實(shí)際中，初步掌握了科學(xué)研究的方法與技巧。 總之，通過畢業(yè)設(shè)計(jì)使我們初步體會(huì)到工程實(shí)際工作的經(jīng)歷，并學(xué)會(huì)了如何把所學(xué)知識(shí)技能應(yīng)用于工程 實(shí)際中，了解理論與實(shí)際是否有差別，初步掌握了科學(xué)研究的方法與技巧。對(duì)今后的工作實(shí)踐十分有益。 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 17 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 18 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 19 翻譯文獻(xiàn) Style of materials Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materials. For industrial purposes, materials are divided into engineering materials or nonengineering materials. Engineering materials are those used in manufacture and become parts of products. Nonengineering materials are the chemicals, fuels, lubricants, and other materials used in the manufacturing process, which do not become part of the product. Engineering materials may be further subdivided into: Metal Ceramics Composite Polymers, etc. Metals and Metal Alloys Metals are elements that generally have good electrical and thermal conductivity. Many metals have high strength, high stiffness, and have good ductility. Some metals, such as iron, cobalt and nickel, are magnetic. At low temperatures, some metals and intermetallic compounds become superconductors. What is the difference between an alloy and a pure metal? Pure metals are elements which come from a particular area of the periodic table. Examples of pure metals include copper in electrical wires and aluminum in cooking foil and beverage cans. Alloys contain more than one metallic element. Their properties can be changed by changing the elements present in the alloy. Examples of metal alloys include stainless steel which is an alloy of iron, nickel, and chromium； and gold jewelry which usually contains an alloy of gold and nickel. Why are metals and alloys used? Many metals and alloys have high densities and are used in applications which require a high mass-to-volume ratio. Some metal alloys, such as those based on aluminum, have low densities and are used in aerospace applications for fuel economy. Many alloys also have high fracture toughness, which means they can withstand impact and are durable. What are some important properties of metals? Density is defined as a materials mass divided by its volume. Most metals have relatively high densities, especially compared to polymers. Materials with high densities often contain atoms with high atomic numbers, such as gold or lead. However, some metals such as aluminum or magnesium have low densities, and are used in applications that require other metallic properties but also require low weight. Fracture toughness can be described as a materials ability to avoid fracture, especially when a flaw is introduced. Metals can generally contain nicks and dents without weakening very much, and are impact resistant. A football player counts on 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 20 this when he trusts that his facemask wont shatter. Plastic deformation is the ability of bend or deform before breaking. As engineers, we usuallydesign materials so that they dont deform under normal conditions. You dont want your car to lean to the east after a strong west wind. However, sometimes we can take advantage of plastic deformation. The crumple zones in a car absorb energy by undergoing plastic deformation before they break. The atomic bonding of metals also affects their properties. In metals, the outer valence electrons are shared among all atoms, and are free to travel everywhere. Since electrons conduct heat and electricity, metals make good cooking pans and electrical wires. It is impossible to see through metals, since these valence electrons absorb any photons of light which reach the metal. No photons pass through. Alloys are compounds consisting of more than one metal. Adding other metals can affect the density, strength, fracture toughness, plastic deformation, electrical conductivity and environmental degradation. For example, adding a small amount of iron to aluminum will make it stronger. Also, adding some chromium to steel will slow the rusting process, but will make it more brittle. Ceramics and Glasses A ceramic is often broadly defined as any inorganic nonmetallic material By this definition, ceramic materials would also include glasses； however, many materials scientists add the stipulation that “ ceramic” must also be crystalline. A glass is an inorganic nonmetallic material that does not have a crystalline structure. Such materials are said to be amorphous. Properties of Ceramics and Glasses Some of the useful properties of ceramics and glasses include high melting temperature, low density, high strength, stiffness, hardness, wear resistance, and corrosion resistance. Many ceramics are good electrical and thermal insulators. Some ceramics have special properties: some ceramics are magnetic materials； some are piezoelectric materials； and a few special ceramics are superconductors at very low temperatures. Ceramics and glasses have one major drawback: they are brittle. Ceramics are not typically formed from the melt. This is because most ceramics will crack extensively (i.e. form a powder) upon cooling from the liquid state. Hence, all the simple and efficient manufacturing techniques used for glass production such as casting and blowing, which involve the molten state, cannot be used for the production of crystalline ceramics. Instead, “sintering” or “firing” is the process typically used. In sintering, ceramic powders are processed into compacted shapes and then heated to temperatures just below the melting point. At such temperatures, the powders react internally to remove porosity and fully dense articles can be obtained. An optical fiber contains three layers: a core made of highly pure glass with a high refractive index for the light to travel, a middle layer of glass with a lower refractive index known as the cladding which protects the core glass from scratches 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 21 and other surface imperfections, and an out polymer jacket to protect the fiber from damage. In order for the core glass to have a higher refractive index than the cladding, the core glass is doped with a small, controlled amount of an impurity, or dopant, which causes light to travel slower, but does not absorb the light. Because the refractive index of the core glass is greater than that of the cladding, light traveling in the core glass will remain in the core glass due to total internal reflection as long as the light strikes the core/cladding interface at an angle greater than the critical angle. The total internal reflection phenomenon, as well as the high purity of the core glass, enables light to travel long distances with little loss of intensity. Composites Composites are formed from two or more types of materials. Examples include polymer/ceramic and metal/ceramic composites. Composites are used because overall properties of the composites are superior to those of the individual components. For example: polymer/ceramic composites have a greater modulus than the polymer component, but arent as brittle as ceramics. Two types of composites are: fiber-reinforced composites and particle-reinforced composites. Fiber-reinforced Composites Reinforcing fibers can be made of metals, ceramics, glasses, or polymers that have been turned into graphite and known as carbon fibers. Fibers increase the modulus of the matrix material. The strong covalent bonds along the fibers length give them a very high modulus in this direction because to break or extend the fiber the bonds must also be broken or moved. Fibers are difficult to process into composites, making fiber-reinforced composites relatively expensive. Fiber-reinforced composites are used in some of the most advanced, and therefore most expensive sports equipment, such as a time-trial racing bicycle frame which consists of carbon fibers in a thermoset polymer matrix. Body parts of race cars and some automobiles are composites made of glass fibers (or fiberglass) in a thermoset matrix. Fibers have a very high modulus along their axis, but have a low modulus perpendicular to their axis. Fiber composite manufacturers often rotate layers of fibers to avoid directional variations in the modulus. Particle-reinforced composites Particles used for reinforcing include ceramics and glasses such as small mineral particles, metal particles such as aluminum, and amorphous materials, including polymers and carbon black. Particles are used to increase the modulus of the matrix, to decrease the permeability of the matrix, to decrease the ductility of the matrix. An example of particle-reinforced composites is an automobile tire which has carbon black particles in a matrix of polyisobutylene elastomeric polymer. 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 22 Polymers A polymer has a repeating structure, usually based on a carbon backbone. The repeating structure results in large chainlike molecules. Polymers are useful because they are lightweight, corrosion resistant, easy to process at low temperatures and generally inexpensive. Some important characteristics of polymers include their size (or molecular weight), softening and melting points, crystallinity, and structure. The mechanical properties of polymers generally include low strength and high toughness. Their strength is often improved using reinforced composite structures. Important Characteristics of Polymers Size. Single polymer molecules typically have molecular weights between 10,000 and 1,000,000g/molthat can be more than 2,000 repeating units depending on the polymer structure! The mechanical properties of a polymer are significantly affected by the molecular weight, with better engineering properties at higher molecular weights. Thermal transitions. The softening point (glass transition temperature) and the melting point of a polymer will determine which it will be suitable for applications. These temperatures usually determine the upper limit for which a polymer can be used. For example, many industrially important polymers have glass transition temperatures near the boiling point of water (100 , 212 ), and they are most useful for room temperature applications. Some specially engineered polymers can withstand temperatures as high as 300 (572 ). Crystallinity. Polymers can be crystalline or amorphous, but they usually have a combination of crystalline and amorphous structures (semi-crystalline). Interchain interactions. The polymer chains can be free to slide past one another (thermo-plastic) or they can be connected to each other with crosslinks (thermoset or elastomer). Thermo-plastics can be reformed and recycled, while thermosets and elastomers are not reworkable. Intrachain structure. The chemical structure of the chains also has a tremendous effect on the properties. Depending on the structure the polymer may be hydrophilic or hydrophobic (likes or hates water), stiff or flexible, crystalline or amorphous, reactive or unreactive. The understanding of heat treatment is embraced by the broader study of metallurgy. Metallurgy is the physics, chemistry, and engineering related to metals from ore extraction to the final product. Heat treatment is the operation of heating and cooling a metal in its solid state to change its physical properties. According to the procedure used, steel can be hardened to resist cutting action and abrasion, or it can be softened to permit machining. With the proper heat treatment internal stresses may be removed, grain size reduced, toughness increased, or a hard surface produced on a ductile interior. The analysis of the steel must be known because small percentages of certain elements, notably carbon, greatly affect the physical properties. Alloy steel owe their properties to the presence of one or more elements other 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 23 than carbon, namely nickel, chromium, manganese, molybdenum, tungsten, silicon, vanadium, and copper. Because of their improved physical properties they are used commercially in many ways not possible with carbon steels. The following discussion applies principally to the heat treatment of ordinary commercial steels known as plain carbon steels. With this process the rate of cooling is the controlling factor, rapid cooling from above the critical range results in hard structure, whereas very slow cooling produces the opposite effect. A Simplified Iron-carbon Diagram If we focus only on the materials normally known as steels, a simplified diagram is often used. Those portions of the iron-carbon diagram near the delta region and those above 2% carbon content are of little importance to the engineer and are deleted. A simplified diagram, such as the one in Fig.2.1, focuses on the eutectoid region and is quite useful in understanding the properties and processing of steel. The key transition described in this diagram is the decomposition of single-phase austenite() to the two-phase ferrite plus carbide structure as temperature drops. Control of this reaction, which arises due to the drastically different carbon solubility of austenite and ferrite, enables a wide range of properties to be achieved through heat treatment. To begin to understand these processes, consider a steel of the eutectoid composition, 0.77% carbon, being slow cooled along line x-x in Fig.2.1. At the upper temperatures, only austenite is present, the 0.77% carbon being dissolved in solid solution with the iron. When the steel cools to 727 (1341 ), several changes occur simultaneously. The iron wants to change from the FCC austenite structure to the BCC ferrite structure, but the ferrite can only contain 0.02% carbon in solid solution. The rejected carbon forms the carbon-rich cementite intermetallic with composition Fe3C. In essence, the net reaction at the eutectoid is austenite 0.77%C ferrite 0.02%C+cementite 6.67%C. Since this chemical separation of the carbon component occurs entirely in the solid state, the resulting structure is a fine mechanical mixture of ferrite and cementite. Specimens prepared by polishing and etching in a weak solution of nitric acid and alcohol reveal the lamellar structure of alternating plates that forms on slow cooling. This structure is composed of two distinct phases, but has its own set of characteristic properties and goes by the name pearlite, because oits resemblance to mother- of- pearl at low magnification. Steels having less than the eutectoid amount of carbon (less than 0.77%) are known as hypo-eutectoid steels. Consider now the transformation of such a material represented by cooling along line y-y in Fig.2.1. At high temperatures, the material is entirely austenite, but upon cooling enters a region where the stable phases are ferrite and austenite. Tie-line and level-law calculations show that low-carbon ferrite nucleates and grows, leaving the remaining austenite richer in carbon. At 727 (1341 ), the austenite is of eutectoid composition (0.77% carbon) 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 24 and further cooling transforms the remaining austenite to pearlite. The resulting structure is a mixture of primary or pro-eutectoid ferrite (ferrite that formed above the eutectoid reaction) and regions of pearlite. Hypereutectoid steels are steels that contain greater than the eutectoid amount of carbon. When such steel cools, as shown in z-z of Fig.2.1 the process is similar to the hypo-eutectoid case, except that the primary or pro-eutectoid phase is now cementite instead of ferrite. As the carbon-rich phase forms, the remaining austenite decreases in carbon content, reaching the eutectoid composition at 727 (1341 ). As before, any remaining austenite transforms to pearlite upon slow cooling through this temperature. It should be remembered that the transitions that have been described by the phase diagrams are for equilibrium conditions, which can be approximated by slow cooling. With slow heating, these transitions occur in the reverse manner. However, when alloys are cooled rapidly, entirely different results may be obtained, because sufficient time is not provided for the normal phase reactions to occur, in such cases, the phase diagram is no longer a useful tool for engineering analysis. Hardening Hardening is the process of heating a piece of steel to a temperature within or above its critical range and then cooling it rapidly. If the carbon content of the steel is known, the proper temperature to which the steel should be heated may be obtained by reference to the iron-iron carbide phase diagram. However, if the composition of the steel is unknown, a little preliminary experimentation may be necessary to determine the range. A good procedure to follow is to heat-quench a number of small specimens of the steel at various temperatures and observe the result, either by hardness testing or by microscopic examination. When the correct temperature is obtained, there will be a marked change in hardness and other properties. In any heat-treating operation the rate of heating is important. Heat flows from the exterior to the interior of steel at a definite rate. If the steel is heated too fast, the outside becomes hotter than the interior and uniform structure cannot be obtained. If a piece is irregular in shape, a slow rate is all the more essential to eliminate warping and cracking. The heavier the section, the longer must be the heating time to achieve uniform results. Even after the correct temperature has been reached, the piece should be held at that temperature for a sufficient period of time to permit its thickest section to attain a uniform temperature. The hardness obtained from a given treatment depends on the quenching rate, the carbon content, and the work size. In alloy steels the kind and amount of alloying element influences only the hardenability (the ability of the workpiece to be hardened to depths) of the steel and does not affect the hardness except in unhardened or partially hardened steels. Steel with low carbon content will not respond appreciably to hardening 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 25 treatment. As the carbon content in steel increases up to around 0.60%, the possible hardness obtainable also increases. Above this point the hardness can be increased only slightly, because steels above the eutectoid point are made up entirely of pearlite and cementite in the annealed state. Pearlite responds best to heat-treating operations； and steel composed mostly of pearlite can be transformed into a hard steel. As the size of parts to be hardened increases, the surface hardness decreases somewhat even though all other conditions have remained the same. There is a limit to the rate of heat flow through steel. No matter how cool the quenching medium may be, if the heat inside a large piece cannot escape faster than a certain critical rate, there is a definite limit to the inside hardness. However, brine or water quenching is capable of rapidly bringing the surface of the quenched part to its own temperature and maintaining it at or close to this temperature. Under these circumstances there would always be some finite depth of surface hardening regardless of size. This is not true in oil quenching, when the surface temperature may be high during the critical stages of quenching. Tempering Steel that has been hardened by rapid quenching is brittle and not suitable for most uses. By tempering or drawing, the hardness and brittleness may be reduced to the desired point for service conditions As these properties are reduced there is also a decrease in tensile strength and an increase in the ductility and toughness of the steel. The operation consists of reheating quench-hardened steel to some temperature below the critical range followed by any rate of cooling. Although this process softens steel, it differs considerably from annealing in that the process lends itself to close control of the physical properties and in most cases does not soften the steel to the extent that annealing would. The final structure obtained from tempering a fully hardened steel is called tempered martensite. Tempering is possible because of the instability of the martensite, the principal constituent of hardened steel. Low-temperature draws, from 300 to 400 (150205 ), do not cause much decrease in hardness and are used principally to relieve internal strains. As the tempering temperatures are increased, the breakdown of the martensite takes place at a faster rate, and at about 600 (315 ) the change to a structure called tempered martensite is very rapid. The tempering operation may be described as one of precipitation and agglomeration or coalescence of cementite. A substantial precipitation of cementite begins at 600 (315 ), which produces a decrease in hardness. Increasing the temperature causes coalescence of the carbides with continued decrease in hardness. In the process of tempering, some consideration should be given to time as well as to temperature. Although most of the softening action occurs in the first few minutes after the temperature is reached, there is some additional reduction in hardness if the temperature is maintained for a prolonged time. 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 26 Usual practice is to heat the steel to the desired temperature and hold it there only long enough to have it uniformly heated. Two special processes using interrupted quenching are a form of tempering. In both, the hardened steel is quenched in a salt bath held at a selected lower temperature before being allowed to cool. These processes, known as austempering and martempering, result in products having certain desirable physical properties. Annealing The primary purpose of annealing is to soften hard steel so that it may be machined or cold worked. This is usually accomplished by heating the steel too slightly above the critical temperature, holding it there until the temperature of the piece is uniform throughout, and then cooling at a slowly controlled rate so that the temperature of the surface and that of the center of the piece are approximately the same. This process is known as full annealing because it wipes out all trace of previous structure, refines the crystalline structure, and softens the metal. Annealing also relieves internal stresses previously set up in the metal. The temperature to which a given steel should be heated in annealing depends on its composition； for carbon steels it can be obtained readily from the partial iron-iron carbide equilibrium diagram. When the annealing temperature has been reached, the steel should be held there until it is uniform throughout. This usually takes about 45min for each inch(25mm) of thickness of the largest section. For maximum softness and ductility the cooling rate should be very slow, such as allowing the parts to cool down with the furnace. The higher the carbon content, the slower this rate must be. The heating rate should be consistent with the size and uniformity of sections, so that the entire part is brought up to temperature as uniformly as possible. Normalizing and Spheroidizing The process of normalizing consists of heating the steel about 50 to 100 (10 40 ) above the upper critical range and cooling in still air to room temperature. This process is principally used with low- and medium-carbon steels as well as alloy steels to make the grain structure more uniform, to relieve internal stresses, or to achieve desired results in physical properties. Most commercial steels are normalized after being rolled or cast. Spheroidizing is the process of producing a structure in which the cementite is in a spheroidal distribution. If steel is heated slowly to a temperature just below the critical range and held there for a prolonged period of time, this structure will be obtained. The globular structure obtained gives improved machinability to the steel. This treatment is particularly useful for hypereutectoid steels that must be machined. Surface Hardening Carburizing The oldest known method of producing a hard surface on steel is case hardening or carburizing. Iron at temperatures close to and above its critical temperature has an 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 27 affinity for carbon. The carbon is absorbed into the metal to form a solid solution with iron and converts the outer surface into high-carbon steel. The carbon is gradually diffused to the interior of the part. The depth of the case depends on the time and temperature of the treatment. Pack carburizing consists of placing the parts to be treated in a closed container with some carbonaceous material such as charcoal or coke. It is a long process and used to produce fairly thick cases of from 0.03 to 0.16 in.(0.764.06mm) in depth. Steel for carburizing is usually a low-carbon steel of about 0.15% carbon that would not in itself responds appreciably to heat treatment. In the course of the process the outer layer is converted into high-carbon steel with a content ranging from 0.9% to 1.2% carbon. A steel with varying carbon content and, consequently, different critical temperatures requires a special heat treatment. Because there is some grain growth in the steel during the prolonged carburizing treatment, the work should be heated to the critical temperature of the core and then cooled, thus refining the core structure. The steel should then be reheated to a point above the transformation range of the case and quenched to produce a hard, fine structure. The lower heat-treating temperature of the case results from the fact that hypereutectoid steels are normally austenitized for hardening just above the lower critical point. A third tempering treatment may be used to reduce strains. Carbonitriding Carbonitriding, sometimes known as dry cyaniding or nicarbing, is a case-hardening process in which the steel is held at a temperature above the critical range in a gaseous atmosphere from which it absorbs carbon and nitrogen. Any carbon-rich gas with ammonia can be used. The wear-resistant case produced ranges from 0.003 to 0.030 inch(0.08 0.76mm) in thickness. An advantage of carbonitriding is that the hardenability of the case is significantly increased when nitrogen is added, permitting the use of low-cost steels. 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 28 材料的類型 材料可以按多種方法分類?？茖W(xué)家常根據(jù)狀態(tài)將材料分為：固體、液體或氣體。他們也把材料分為有機(jī)材料 (曾經(jīng)有生命的 )和無機(jī)材料 (從未有生命的 )。 就工業(yè)效用而言，材料被分為工程材料和非工程材料。那些用于加工制造并成為產(chǎn)品組成部分的就是工程材料。 非工 程材料則是化學(xué)品、燃料、潤滑劑以及其它用于加工制造過程但不成為產(chǎn)品組成部分的材料。 工程材料還能進(jìn)一步細(xì)分為：金屬材料陶瓷材料復(fù)合材料 聚合材料，等等。 金屬和金屬合金 金屬就是通常具有良好導(dǎo)電性和導(dǎo)熱性的元素。許多金屬具有高強(qiáng)度、高硬度以及良好的延展性。 某些金屬能被磁化，例如鐵、鈷和鎳。在極低的溫度下，某些金屬和金屬化合物能轉(zhuǎn)變成超導(dǎo)體。 合金與純金屬的區(qū)別是什么？純金屬是在元素周期表中占據(jù)特定位置的元素。例如電線中的銅和制造烹飪箔及飲料罐的鋁。 合金包含不止一種金屬元素。合金的性質(zhì)能通過改變其 中存在的元素而改變。金屬合金的例子有：不銹鋼是一種鐵、鎳、鉻的合金，以及金飾品通常含有金鎳合金。 為什么要使用金屬和合金？許多金屬和合金具有高密度，因此被用在需要較高質(zhì)量體積比的場(chǎng)合。 某些金屬合金，例如鋁基合金，其密度低，可用于航空航天以節(jié)約燃料。許多合金還具有高斷裂韌性，這意味著它們能經(jīng)得起沖擊并且是耐用的。 密度定義為材料的質(zhì)量與其體積之比。大多數(shù)金屬密度相對(duì)較高，尤其是和聚合物相比較而言。 高密度材料通常由較大原子序數(shù)原子構(gòu)成，例如金和鉛。然而，諸如鋁和鎂之類的一些金屬則具有低密度，并被用于 既需要金屬特性又要求重量輕的場(chǎng)合。 斷裂韌性可以描述為材料防止斷裂特別是出現(xiàn)缺陷時(shí)不斷裂的能力。金屬一般能在有缺口和凹痕的情況下不顯著削弱，并且能抵抗沖擊。橄欖球運(yùn)動(dòng)員據(jù)此相信他的面罩不會(huì)裂成碎片。 塑性變形就是在斷裂前彎曲或變形的能力。作為工程師，設(shè)計(jì)時(shí)通常要使材料在正常條件下不變形。沒有人愿意一陣強(qiáng)烈的西風(fēng)過后自己的汽車向東傾斜。 然而，有時(shí)我們也能利用塑性變形。汽車上壓皺的區(qū)域在它們斷裂前通過經(jīng)歷塑性變形來吸收能量。 金屬的原子連結(jié)對(duì)它們的特性也有影響。在金屬內(nèi)部，原子的外層階電子由所有原子共 享并能到處自由移動(dòng)。由于電子能導(dǎo)熱和導(dǎo)電，所以用金屬可以制造好的烹飪鍋和電線。 因?yàn)檫@些階電子吸收到達(dá)金屬的光子，所以透過金屬不可能看得見。沒有光子能通過金屬。 合金是由一種以上金屬組成的混合物。加一些其它金屬能影響密度、強(qiáng)度、斷裂韌性、塑性變形、導(dǎo)電性以及環(huán)境侵蝕。 例如，往鋁里加少量鐵可使其更強(qiáng)。同樣，在鋼里加一些鉻能減緩它的生銹天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 29 過程，但也將使它更脆。 陶瓷和玻璃 陶瓷通常被概括地定義為無機(jī)的非金屬材料。照此定義，陶瓷材料也應(yīng)包括玻璃；然而許多材料科學(xué)家添加了“陶瓷”必須同時(shí)是晶體物組成的約定。 玻 璃是沒有晶體狀結(jié)構(gòu)的無機(jī)非金屬材料。這種材料被稱為非結(jié)晶質(zhì)材料。 陶瓷和玻璃的特性 高熔點(diǎn)、低密度、高強(qiáng)度、高剛度、高硬度、高耐磨性和抗腐蝕性是陶瓷和玻璃的一些有用特性。 許多陶瓷都是電和熱的良絕緣體。某些陶瓷還具有一些特殊性能：有些是磁性材料，有些是壓電材料，還有些特殊陶瓷在極低溫度下是超導(dǎo)體。陶瓷和玻璃都有一個(gè)主要的缺點(diǎn)：它們?nèi)菀灼扑椤?陶瓷一般不是由熔化形成的。因?yàn)榇蠖鄶?shù)陶瓷在從液態(tài)冷卻時(shí)將會(huì)完全破碎(即形成粉末 )。 因此，所有用于玻璃生產(chǎn)的簡(jiǎn)單有效的 諸如澆鑄和吹制這些涉及熔化的技術(shù)都不能用于由晶體 物組成的陶瓷的生產(chǎn)。作為替代，一般采用“燒結(jié)”或“焙燒”工藝。 在燒結(jié)過程中，陶瓷粉末先擠壓成型然后加熱到略低于熔點(diǎn)溫度。在這樣的溫度下，粉末內(nèi)部起反應(yīng)去除孔隙并得到十分致密的物品。 光導(dǎo)纖維有三層：核心由高折射指數(shù)高純光傳輸玻璃制成，中間層為低折射指數(shù)玻璃，是保護(hù)核心玻璃表面不被擦傷和完整性不被破壞的所謂覆層，外層是聚合物護(hù)套，用于保護(hù)光導(dǎo)纖維不受損。 為了使核心玻璃有比覆層大的折射指數(shù)，在其中摻入微小的、可控?cái)?shù)量的能減緩光速而不會(huì)吸收光線的雜質(zhì)或攙雜劑。 由于核心玻璃的折射指數(shù)比覆層大，只要在全內(nèi)反射過 程中光線照射核心 /覆層分界面的角度比臨界角大，在核心玻璃中傳送的光線將仍保留在核心玻璃中。 全內(nèi)反射現(xiàn)象與核心玻璃的高純度一樣，使光線幾乎無強(qiáng)度損耗傳遞長距離成為可能。 復(fù)合材料 復(fù)合材料由兩種或更多材料構(gòu)成。例子有聚合物 /陶瓷和金屬 /陶瓷復(fù)合材料。之所以使用復(fù)合材料是因?yàn)槠淙嫘阅軆?yōu)于組成部分單獨(dú)的性能。 例如：聚合物 /陶瓷復(fù)合材料具有比聚合物成分更大的模量，但又不像陶瓷那樣易碎。 復(fù)合材料有兩種：纖維加強(qiáng)型復(fù)合材料和微粒加強(qiáng)型復(fù)合材料。 纖維加強(qiáng)型復(fù)合材料 加強(qiáng)纖維可以是金屬、陶瓷、玻璃或是已變成石墨的 被稱為碳纖維的聚合物。纖維能加強(qiáng)基材的模量。 沿著纖維長度有很強(qiáng)結(jié)合力的共價(jià)結(jié)合在這個(gè)方向上給予復(fù)合材料很高的模量，因?yàn)橐獡p壞或拉伸纖維就必須破壞或移除這種結(jié)合。 把纖維放入復(fù)合材料較困難，這使得制造纖維加強(qiáng)型復(fù)合材料相對(duì)昂貴。 纖維加強(qiáng)型復(fù)合材料用于某些最先進(jìn)也是最昂貴的運(yùn)動(dòng)設(shè)備，例如計(jì)時(shí)賽競(jìng)賽用自行車骨架就是用含碳纖維的熱固塑料基材制成的。 競(jìng)賽用汽車和某些機(jī)動(dòng)車的車體部件是由含玻璃纖維 (或玻璃絲 )的熱固塑料基材制成的。 天津職業(yè)技術(shù)師范大學(xué) 2012 屆本科生畢業(yè)設(shè)計(jì) 30 纖維在沿著其軸向有很高的模量，但垂直于其軸向的模量卻較低。纖維復(fù)合材料的制造者往往 旋轉(zhuǎn)纖維層以防模量產(chǎn)生方向變化。 微粒加強(qiáng)型復(fù)合材料 用于加強(qiáng)的微粒包含了陶瓷和玻璃之類的礦物微粒，鋁之類的金屬微粒以及包括聚合物和碳黑的非結(jié)晶質(zhì)微粒。 微粒用于增加基材的模量、減少基材的滲透性和延展性。微粒加強(qiáng)型復(fù)合材料的一個(gè)例子是機(jī)動(dòng)車胎，它就是在聚異丁烯人造橡膠聚合物基材中加入了碳黑微粒。 聚合材料 聚合物具有一般是基于碳鏈的重復(fù)結(jié)構(gòu)。這種重復(fù)結(jié)構(gòu)產(chǎn)生鏈狀大分子。由于重量輕、耐腐蝕、容易在較低溫度下加工并且通常較便宜，聚合物是很有用的。 聚合材料具有一些重要特性，包括尺寸 (或分子量 )、軟化及熔化 點(diǎn)、結(jié)晶度和結(jié)構(gòu)。聚合材料的機(jī)械性能一般表現(xiàn)為低強(qiáng)度和高韌性。它們的強(qiáng)度通常可采用加強(qiáng)復(fù)合結(jié)構(gòu)來改善。 聚合材料的重要特性 尺寸：?jiǎn)蝹€(gè)聚合物分子一般分子量為 10,000 到 1,000,000g/mol 之間，具體取決于聚合物的結(jié)構(gòu) 這可以比 2,000 個(gè)重復(fù)單元還多。 聚合物的分子量極大地影響其機(jī)械性能，分子量越大，工程性能也越好。 熱轉(zhuǎn)換性：聚合物的軟化點(diǎn) (玻璃狀轉(zhuǎn)化溫度 )和熔化點(diǎn)決定了它是否適合應(yīng)用。這些溫度通常決定聚合物能否使用的上限。 例如，許多工業(yè)上的重要聚合物其玻璃狀轉(zhuǎn)化溫度接近水的沸點(diǎn) (100 , 212 )，它們被廣泛用于室溫下。而某些特別制造的聚合物能經(jīng)受住高達(dá) 300 (572 )的溫度。 結(jié)晶度：聚合物可以是晶體狀的或非結(jié)晶質(zhì)的，但它們通常是晶體狀和非結(jié)晶質(zhì)結(jié)構(gòu)的結(jié)合物 (半晶體 )。 原子鏈間的相互作用：聚合物的原子鏈可以自由地彼此滑動(dòng) (熱可塑性 )或通過交鍵互相連接 (熱固性或彈性 )。熱可塑性材料可以重新形成和循環(huán)使用，而熱固性與彈性材料則是不能再使用的。 鏈內(nèi)結(jié)構(gòu)：原子鏈的化學(xué)結(jié)構(gòu)對(duì)性能也有很大影響。根據(jù)各自的結(jié)構(gòu)不同，聚合物可以是親水的或憎水的 (喜歡或討厭水 )、硬的或軟的、晶體狀的或非結(jié)晶質(zhì)的、 易起反應(yīng)的或不易起反應(yīng)的。 對(duì)熱處理的理解包含于對(duì)冶金學(xué)較廣泛的研究。冶金學(xué)是物理學(xué)、化學(xué)和涉及金屬從礦石提煉到最后產(chǎn)物的工程學(xué)。 熱處理是將金屬在固態(tài)加熱和冷卻以改變其物理性能的操作。按所采用的步驟，鋼可以通過硬化來抵抗切削和磨損，也可以通過軟化來允許機(jī)加工。 使用合適的熱處理可以去除內(nèi)應(yīng)力、細(xì)化晶粒、增加韌性或在柔軟