本研究是針對不銹鋼(AISI 420與AISI 630)、熱作工具鋼(AISI H10與AISI H13)與空冷工具鋼(AISI A2與AISI A6)在700K、800K與900K時，其放射率的實驗分析與利用多光譜輻射測溫法(MRT)去推測溫度的結果之探討。而所使用的放射率模型為HHR、IST、IST*(IST的另一種型式)、IWS、WLT與WLT*(WLT的另一種型式)等形式。目的在找出各種不同情況下都適用的多光譜放射率模型。
放射率分析上，(1)在研究範圍內(2.91μm ~ 4.13μm)大多呈現隨波長增加而下降的趨勢；(2)並且在3小時前有較大的變動，3小時之後隨時間的變化則趨於穩定；(3)受到表面氧化與表面顏色變化的影響，在700K與800K之間放射率多為上升，而900K因為表面顏色由灰黑色轉成暗紅色，導致整體放射率下降或上升幅度較小；(4)而對高鉻含量的材料而言，因為鉻氧化層的保護作用，放射率多為偏低。
溫度推測上，(1)整體來看誤差多在10%以內，其中以IWS與WLT兩個放射率模型表現最佳，並且面對不同外在條件變化時，穩定度較其他模型為高。(2)在最小平方法的曲線迴歸上，推論的輻射強度結果若能越貼近原始資料點的分布情形時，將有更準確的推論溫度結果，進一步從推論出的放射率來觀察，只要推論出的放射率分布行為越接近真實情況，所得到的溫度也將越準確。 (3)MRT所使用的波長數之多寡，在本研究中區分為最少所需的波長數n與最多可用的波長數N，從結果發現其影響溫度推測的準確性並不明顯，但若將n波長數之MRT與單波長輻射測溫法(SRT)相比，則能清楚發現增加波長數的確有效改善推測的溫度誤差。(4)放射率在3小時後趨於穩定，也因此放射率隨時間變動較小的情況下，多光譜輻射測溫法的準確性將會有所提高，此亦說明氧化層在三小時時已經接近完全發展。(5)當放射率大於0.6時，各種放射率模型多能有不錯表現，尤其IWS、WLT與IST*都很適用。(6)在700K到800K時，因為氧化效應和表面變黑使得放射率提高，推論的效果變得更好；而在800K到900K時，卻因為熔融狀態的開始而表面變暗紅色使得放射率較不規律，甚至某些試件較800K時為低，因此誤差反而比800K時要大。

This study includes experimental investigation of surface emissivity and analysis of inferred temperature by multispectral radiation thermometry (MRT) for stainless steel (AISI 420 and AISI 630), hot work tool steel (AISI H10 and AISI H13) and cold work tool steel (AISI A2 and AISI A6) at 700K, 800K and 900K. Six emissivity models, HHR, IST, IST* (another form of IST), IWS, WLT and WLT* (another form of WLT) are used to examine the MRT on steel surface temperature determination. The goal of this study is to find the best MRT emissivity model which can well compensate the steel emissivity variations and accurately infer the surface temperature.
For steel emissivity behaviors, (1) overall, emissivity decreases with increasing wavelength in the wavelength range from 2.91 to 4.13 μm; (2) due to surface oxidation and discoloration, emissivity increases between 700 and 800 K. However, between 800 and 900 K, the onset of melt is observed and causes the decrease in emissivity; (3) for steel with high chromium, emissivity is usually lower than others because of the chromium oxide protection layer; (4) emissivity becomes fairly constant after the 3rd hour, which points to the surface oxidation becoming fully developed.
For the examination of MRT emissivity models on steel, (1) most models provide the percent error of inferred temperature under 10%. IWS and WLT emissivity models show the best overall stability and accuracy for different alloys and temperatures; (2) for least-squares technique, the closer the generated intensity and measured one, the more accurate inferred temperature. Also, if the emissivity model can well represent the real emissivity behaviors, the more accurate inferred temperature can be achieved; (3) increasing number of wavelength does not significantly improve measurement accuracy while applying MRT. However, MRT indeed provides better performance than SRT; (4) constant emissivity enhances temperature prediction by MRT following the initial 3 hours period; (5) when steel emissivity value is higher than 0.6, all emissivity models examined in this study provide good results, especially IWS, WLT and IST*; (6) additionally, the emissivity change due to aforementioned temperature effects results in the temperature measurement accuracy improving between 700 and 800 K and deteriorating between 800 and 900 K.

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