tions among the shell components and phase transfor- mation within the a morphous silica take place at high temperature, the amount and rate of these reactions will significantly affect the specific heat capacity values used in modeling. In the inverse method, the shell is heated rapidly when metal is poured and cooled down at a relatively slower cooling rate as the metal solidifies. Tese processes associate with more instantaneous measure- ment of a property which includes latent heat effects from phase changes. However, a small mass specimen is equilibrated at an environmental test temperature in the laser flash. Consequently, the transformation occurring in the inverse method may have already taken place prior to the measurement by the laser flash method. Similarly, when comparing the total enthalpy change


from room temperature (68F [20C]) to 2,885F (1,420C) among the values from theoretical calculation of the inverse method and the laser flash method, the laser flash method shows similar values, because the thin speci- men used in the laser flash method was under partially thermally stabilized condition which is closer to thermal equilibrium. Te shell in reality is hardly in thermal equilibrium conditions, thus the inverse method provided more realistic effective heat capacity values for modeling the pouring and solidification processes. Termal property data measured by laser flash could be used as the starting point in the automatic optimi- zation process, which greatly reduces the number of simulation cases needed to approach a well fitted case and reduces the potential extrapolation error in itera- tion step estimates. Te theoretical thermal conductivity of pure silica with 33% porosity was plotted in Fig. 5 as well as ther- mal conductivity values of shell #1 and shell #3. Tose industrial shells had similar measured and theoretical values of thermal conductivity at a lower temperature but were more heat conductive at a higher temperature. Tis could result from different particle and porosity size distributions, since smaller particle size with higher grain boundary to volume ratio will lower thermal conductiv- ity. Tis theoretical model may not consider the photon conductivity of the pore phase at higher temperature. Obtaining the data from laser flash and then applying the data in the inverse method can be time consuming and costly. Te researchers recommend that industries developing their own investment casting shells pick the thermal property data of shells from given investment casting facilities in the study with the closest composition and utilize those estimates in their simulations. Whoever uses the data must measure the bulk density and poros- ity of their shells, because bulk density is used in most simulations and porosity is needed to adjust the value of thermal conductivity. ■


Tis article was based on the paper, “Termal Property Database for Investment Casting Shells,” (Paper No. 14-020, presented at the 118th Metalcasting Congress.


қђ室温（ ℉ A ℃C）ӱ ℉（ ℃） 激֨О֜，ङѷब是қङ法ذ照Ұ激，化Պ焓总ङ 常非，Јў条定६热֨ה片薄ङ用҅，И法ذ照Ұ 状੫平热йה难很ד型，Иф生际实。੫平热近接 д供提३过֡凝չ注浇ङ型铸О法方է逆此֜，ہ 更О现实ङ有效热容қ。 ਘОҁљՕ，据数ਈ性热ङ定测法ذ照Ұ激过通


并理ה拟模要需дѺ降םם这，点起ङਫ工化ѩ动 ङ֨潜ङઋѳ骤步ї迭дصӗ，量数ङ本样ङ合适 。差ન推י љ，率حѮ热ખ理ङ硅化氧иষङ％ 孔隙率О


Џ工п这。ॐ۱ ֣ײ率ح热ङד型 ＃չד型 Ճ＃ ，ѷबқખ理չқ量测ङ率ح热，境环温Ѻ֨ד型 چটਚحਈՕ这。强更Јچ温ङ高较֨性حѮ热Ѹ 高较Њت尺ট颗ङش较О֜，գЉ٢ӣت尺隙孔չ य़这，Јچ温高更֨。性热حѺ降ر比॥ѽउ晶ङ 。率حѮ子Ұङ隙孔й用ਈЉਈՕ型模ખ理 ҅И法方է逆֨ե然据数ङ得ੂ法数صҰ激用 用，৴时并昂贵。ू९ыմ建ઑ，熔模铸造੧Џ应 选挑И据数ਈ性热ד型ङЏѣ造铸模熔ङ定োђથ ד型造铸模熔ङ己ਘՇ开，९ू੧进ङ近接最ӣ成 谁ખ无。И拟模֨用қѳп这把并，库据数ਈ性热 ֜，率隙孔չچإ॥ׄङד型量测须必，据数用҅ 用Օ率隙孔৲，用҅И拟模数ӣ部ם֨چإ॥ׄО ■ 。қ数ङ率ح热ਭલй


ȕ库据数ਈ性热ङד型造铸模熔Ȕ文ખਘ编改章文ক这 （ખ文编՚


。ѫם造铸ه ，Շ੮й


March 2016 FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION | 55


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