熱物性系數(shù)的設計研究

材料構(gòu)造、成分和使用溫度含有親密而敏感的關系、由此可解決研究中碰到的許多難題。率、溫度、壓力等。數(shù)值上導熱系數(shù)等于單位溫度下熱流的密度矢量的模。

λ熱擴散率也密度和熱擴散率三者的乘積存在一定關系。熱常數(shù)的測量辦法分為兩大類，一為穩(wěn)態(tài)法，另一為非穩(wěn)態(tài)法，穩(wěn)態(tài)法重要特點為：在測試過程中，被測樣品的溫度場不隨時間變化，直接測得導熱系數(shù)；非穩(wěn)態(tài)法為測量過程中樣品溫度場隨時間變化，直接測得熱擴散率。1高碳鋼的比熱容在溫度<750℃750℃左右會出1000℃750℃100℃250℃出現(xiàn)一種極大值。750℃750℃之間，導溫250℃出現(xiàn)一種極大值。2J/(kg.℃)。由于固體在沒有物態(tài)變化的狀況下，外界供應的熱量幾乎全部用來不需加以區(qū)別。普通采用德國耐馳公司生產(chǎn)的高溫型差示掃描量熱計DSC(DifferentialScanningCalorimetry)，通過間接法進行各相試樣的比熱測試。1m1m21℃時，單位時間(小時)內(nèi)通過的傳熱量W/(m.℃)比熱容。熱擴散系數(shù)(thermaldiffusioncoefficient)，又稱為導溫系數(shù)，表征物體熱αm2/s，是材料傳輸溫度變料，非穩(wěn)態(tài)法的合用范疇比較廣泛。閃光法(FlashMethod)就是現(xiàn)在最為慣用的非穩(wěn)態(tài)法90~3000Kλρ

π π

1/t1/2

參數(shù)。根據(jù)測量時應變速率不同，將測量辦法分為靜態(tài)法和動態(tài)法兩種:應變速率趨近于(1)PA=1/(0.1212+0.0033x0.23)=8.1995Pf=1/0.1271=7.8678珠光體密度Pp=1/(0.1271+0.0005×0.23)=7.8607貝氏體密度Pb=1/(0.1271+0.0015×0.23)=7.8465馬氏體密度Pm=1/(0.1271+0.0025×0.23)=7.8324對于混合相的組織，其混合相密度為各相密度和比例的乘積之和，因此采用700~800oCα-Feγ-Fe658~800oC1400~1500oC（E36NE36-E36-

DensityDensityDensity

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- 2004006008001000120014001600 DensityDensity(g.m-DensityDensity(g.m- - 2004006008001000120014001600

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80010001200

1600

DensityDensity- 2004006008001000120014001600鋼 Y=-3.376×10-4t+7.839(35oC Y=-3.453×10-4t+7.845(35oCY=2.557×10-6t2-3.7×10-3t+8.941(658oC<T≤803oCY=2.859×10-6t2-4.18×10-3t+9.134(700oC Y=-5.394×10-4t+8.066(803oC<T≤1471oC) Y=-8.203×10-4t+8.212(1515oC<T≤1600oC)鋼

Y=-5.40×10-4t+8.076(824oC<T≤1483oC)Y=-6.64×10-3t+17.07(1483C<T≤1492oC)NM30-擬 Y=-3.462×10-4t+7.823(35oC成 Y=9.627×10-4t+6.876(700oC<T≤771

Y=-3.487×10-4t+7.825(35oC<T≤710oC)Y=1.17×10-3t+6.729(710oC<T≤771Y=-5.262×10-4t+8.024(771oC<T≤1424oC)Y=-8.078×10-4t+8.18(1490oC<T≤1600oC)

Y=-5.262×10-4t+8.022(771oC<T≤1420oC)Y=-5.31×10-3t+14.919(1420oC<T≤1491oC)鋼 Y=-3.546×10-4t+7.853(35oCY=4.154×10-6t2-6.12×10-3t+9.86(694oCY=-5.354×10-4t+8.069(810oC<T≤1470Y=-6.93×10-3t+17.483(1470oC<T≤1509Y=-8.12×10-4t+8.211(1509oC<T≤1600(2).膨脹時，在一維方向上的伸長，在一定溫度范疇內(nèi),材料的長度普通隨溫度的升高而增加。在某一溫度區(qū)間內(nèi),當溫度的變化量為ΔTl。的試樣受熱后的長度變化量用l表達(Δl/ΔT)0oC(1/°C,公式是中國國家軍用原則[113]定義的線膨脹系數(shù),表達材料在溫度t(2-10)改寫成公式(2-11)i—jaiitα1tLTα

(ljli l l(TT ai為第i時刻的熱膨脹系數(shù),即溫度為Ti時的熱膨脹系數(shù)li和Ti分別為第i時刻的試樣長度和溫度，ljTjj時刻的試樣長度和溫度.數(shù)增加，當溫度升高至700oC，實驗的延伸系數(shù)隨溫度的增加而減小，這是由于發(fā)生體心的致密度減小，延伸系數(shù)急劇增加，γAverageAverageexpansioncoeff.(10-6 2004006008001000120014001600

AverageAverageexpansioncoeff.(10e-6 2004006008001000120014001600expansionexpansioncoefficient(10-6K- 2004006008001000120014001600

AverageAverageexpansioncoeff.(10e-6 2004006008001000120014001600expansionexpansioncoeff.(10e-6 2004006008001000120014001600鋼 Y=3.73×10-3t+12.48(30oCY=-1.615×10-4t2+0.216t-57.687(653oC<T≤807oC) Y=-7.346×10-6t2+0.026×10-2t-5.339(807oC<T≤146 Y=0.179t-244.194(1470oC<T≤1514oC)Y=0.0109t+10.967(1514oC<T≤1600

Y=3.71×10-3t+12.48(30oCY=-1.81×10-4t2+0.246t-69.298(653oCY=-8.366×10-6t2+0.029×10-2t-7.205(807oC<T≤1472oC)Y=0.247t-348.923(1472oC<T≤1514oC)Y=0.0106t+11.285(1514oC<T≤1600oCY=3.83×10-3t+12.371(30oCNM30-Y=3.97×10-3t+12.387(30oCY=-0.0835t+75.256(710oCY=-0.0805t+72.798(711oCY=-7.615×10-6t2+0.026×10-2t-4.303(807oCY=8.982×10-9t3-3.74×10-5t20+5.848×10-2t-15.727(711Y=0.224t-307.626(1472oC<T≤1489Y=0.0106t+11.407(1489oC<T≤1600Y=0.2385t-328.451(1470oC<T≤1483Y=0.0105t+11.685(1516oC<T≤1600Y=3.546×10-4t+7.853(35oCY=-2.115×10-6t3+4.65×10-3t2-3.431×10-oCY=7.36×10-7t3-3.317×10-5t2+5.594×10-2t-oC<T≤1471Y=0.252t-354.71(1470oC<T≤1516oC)Y=0.0105t+11.518(1516oC<T≤1600oC)（3）鑄坯液相區(qū)的鋼液存在強制對流運動，加緊了鋼水過熱度的消除,因此對液相區(qū)經(jīng)常采用等效導熱系數(shù)，其值比靜止鋼液導熱系數(shù)放大了3~7keff 間。介于固相和液相之間，采用關系 (t)[1(n1)(1f)2]k

式中n辦法倍數(shù)。導熱系數(shù)隨溫度的變化如圖所示。從圖能夠看出，低溫區(qū)域(t<800oC)導熱系數(shù)隨著溫度升高而減少,在高溫區(qū)域(t>800oC)隨著溫度的升高導熱系數(shù)逐步升高,ThermalconductivityThermalconductivity - 2004006008001000120014001600

- 2004006008001000120014001600ThermalconductivityThermalconductivity - 2004006008001000120014001600T

- 2004006008001000120014001600- 2004006008001000120014001600鋼 擬 Y=-0.042t+59.75(30oC成 Y=0.012t+16.74(815oC

Y=-0.039t+58.643(30oC<T≤815oC)Y=0.012t+16.81(815oC<T≤1479oC)鋼 NM30-Y=-0.037t+56.67(30oCY=-0.102t+103.834(721oCY=0.012t+16.845(773oC

Y=-0.042t+59.75(30oCY=0.114t+112.198(712oC<T≤767oC)Y=0.012t+16.808(767oC鋼 Y=-0.044t+61.187(30oCY=0.012+16.81(814oC急劇減小至靠近0。鑄坯在鋼水靜壓力和溫度梯度作用下,會發(fā)生彈性和塑性變形;外載溫度每升高100oC,彈性模量下降3%~5%,這正是鋼在高溫下容易進入塑性狀態(tài)的因素。另外,凝固早期的鑄態(tài)金屬組織存在一種零強度溫度,當溫度減少到零強度溫度下列時鑄坯才體現(xiàn)出一定的強度.因此,零強度溫度以上的兩相區(qū)以及液相區(qū)的彈性模量為零.然而在具體的計算過程中,彈性模量不能取精確的零值,否則將會出現(xiàn)奇異性,模擬就 Young'smodulusYoung'smodulusYoung'smodulus

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- 2004006008001000120014001600Young'sYoung'smodulus

Young'sYoung'smodulus

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2004006008001000120014001600Young'sYoung'smodulus0- 2004006008001000120014001600鋼 擬 Y=-9.784×10-5t2-0.0311t+211.831(30oC<T≤751oCY=-9.404×10-5t2-0.0338t+212.141(30oC成 Y=-0.103t+210.095(751oC Y=0.103t+208.725(787oC鋼 NM30-擬 Y=-8.489×10-5t2-0.0402t+214.838(30oC<T≤751oC)Y=-9.284×10-5t2-0.0327t+212.957(30oC成 Y=-0.0995t+207.58(751oC Y=-0.0995t+207.48(751oC鋼 擬 Y=-9.653×10-5t2-0.0319t+212.118(30oC成 Y=-0.102t+208.704(705C泊松比是垂直于加載方向的線應變與平行加載方向線應變之比,表征材料拉伸或壓縮

Poisson'sPoisson's

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- 2004006008001000120014001600

Poisson'sPoisson's

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- 2004006008001000120014001600- 2004006008001000120014001600Y=3.937×10-5t+0.288(30oCY=3.923×10-5t+0.288(30oCY=5.644×10-7t2-6.882×10-4t+5.664(621Y=8.551×10-7t2-1.12×10-3t+0.687(641oCY=5.897×10-5t+0.292(803oCY=5.908×10-5t+0.292(815oCNM30-Y=3.795×10-5t+0.287(30oCY=3.818×10-5t+0.286(30oCY=4.094×10-4t+2.04×10-2(722oCY=6.76×10-3t+4.49×10-4(722oCY=5.734×10-5t+0.292(776oCY=5.742×10-5t+0.292(775oCY=3.96×10-5t+0.288(30oCY=1.095×10-7t2-1.5×10-3t+8.31×10-1(702oCY=5.903×10-5t+0.292(814oC容 考慮凝固潛熱的釋