大型模具利用流體床麻淬火熱處理之微結構與機械性質探討

Study on the Microstructure and Mechanical Properties of Large Molds via Marquenching of Fluidized Bed Heat Treatment

王錦太(Chin-Ta Wang)

指導教授 ： 張世賢

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2012年)

https://doi.org/10.6841/NTUT.2012.00257

摘要

熱作模具鋼廣泛地應用在擠型與壓鑄生產製程，它們最主要的特性是具有高強度與高延展性，較佳之抗回火性與相當適中的成本，工具鋼AISI H13通常是用在鋁壓鑄生產模具，它能提供良好的抗回火性，高熱硬度及強度，與良好的抗熱疲勞強度及抗熱侵蝕與磨耗。流體床是將微細的氧化鋁砂硬粒，利用氣體來產生流體化，當工件浸入流體床後，氧化鋁砂硬粒便會直接與工件表面接觸，提供穩定且均勻的溫度冷卻，流體床的淬火在工件週圍不會形成蒸氣的屏障，能夠提供有效控制殘留應力與變形扭曲的能力。
本研究是針對傳統大型模具鋼AISI H13進行麻淬火熱處理，以流體床氧化鋁砂作為熱處理淬火介質；為探討並改善一般大型模具材料熱處理時淬火時，因冷卻速度過快而產生的變形與淬裂風險之缺點，本實驗採用不同麻淬火溫度(85°C、 165°C、300°C、350°C與400°C)，以及模具表面和心部試片的組織觀察，實驗中，經麻淬火後再立刻進行大氣中氣冷，接著進行回火熱處理至硬度為HRC 44~46。機械性質差異之比較，包括硬度和衝擊值。此外，為進一步探討微結構組織對於AISI H13麻淬火所造成之影響，XRD、SEM和OM顯微組織觀察亦使用之。
實驗結果發現，利用300流體床麻淬因有較快的表面(0.31°C/sec)和心部(0.09°C/sec)冷卻速率，可達到較佳之機械性質；平均硬度可達HRC 45.0~45.6，衝擊韌性為7.3~10.0 J。經由組織觀察，基地的主要析出元素以Cr和V為主，而晶界上之析出物，主要為Mo析出物，造成AISI H13回火後之硬度和強度的增加。

關鍵字

AISI H13 ； 流體床 ； 氧化鋁砂 ； 麻淬火

並列摘要

Hot work tool steels are almost exclusively used on extrusion and die-casting dies. They are characterized by high strength, ductility, good tempering resistance and moderate cost. AISI H13 tool steel is normally used for Al casting dies, given its good temperature resistance, high hot hardness and strength, and good resistance to thermal fatigue, erosion and wear. A fluidized bed consists of a fine hard media that is fluidized by a gas. As a part is immersed in the fluidized bed, the fluidized bed media directly contacts the part, resulting in consistent and even cooling. In fluidized bed quenching, a vapor barrier does not form around the part, thus giving one the ability to control residual stresses and part distortion.
This study focuses on the traditional large molding of AISI H13 steel via various marquenching heat treatments. The experiments utilized the Al2O3 powder as a quenching media for the fluidized bed, the intention being to lessen distortion defects and crack risks in the material of a large mold, which are caused by a fast cooling rate. The experiments were conducted using different marquenching temperatures (85°C, 165°C, 300°C, 350°C and 400°C). The microstructure of the surface and center areas of the mold was analyzed. In the experiments, after the marquenching process, the gas is used to immediately cool the mold to room temperature, and then tempered to a hardness of HRC 44~46. To compare the differences in mechanical properties, the hardness and charpy tests were used. In addition, in order to further study the effect of the microstructure on the marquenching of AISI H13 steel, XRD, SEM and OM microstructure inspections were performed.
The experimental results showed that the optimal marquenching temperature of the fluidized bed is 300°C for AISI H13 steel, due to the fast cooling rate of the surface (0.31

並列關鍵字

AISI H13 ； Fluidized bed ； Alumina Oxide ； Marquenching

參考文獻

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