超級鋼的基本特徵為超細晶、高潔淨及高均勻性。文獻指出：加入一定體積分率的細小第二相粒子，可有效提高鋼材綜合力學性能並細化晶粒。其中，第二相粒子扮演阻礙晶粒成長的重要角色，因此為了達到晶粒細化的均勻性，第二相粒子須在鋼液裡能均勻分佈。

本研究採用水模物理模型來探討第二相粒子在溶液中的分佈情形。為了得知粒子在溶液中的分佈情況，利用色度濁度儀來量測粒子濃度。藉由水模內各處的粒子濃度分佈隨時間變化的情形，評估粒子達到均勻混合所需的時間。同時也探討將不同粒徑的粒子加入不同濃度的乙醇與丙酮溶液時，粒徑大小和粒子與溶液間的潤濕性對均混時間以及粒子上浮率的影響。

研究結果顯示，粒子在溶液中的均混行為可藉由量測溶液中的濁度來加以判斷。在相同操作條件下，粒子粒徑大小對均混時間並無太大影響；粒子密度和溶液密度越相近時，均混時間越短；粒子與溶液接觸角較小時，均混時間較短且粒子上浮率也較低。顯示溶液和粒子潤濕性較高時，除了粒子較易被溶液帶開、分散較快外，粒子也較不容易上浮。因此，粒子與溶液間的潤濕性對均混時間的影響明顯大於粒子粒徑大小對均混時間的影響。

關鍵字：超級鋼、第二相粒子、水模、濁度、接觸角

Ultra-fine grains, high cleanliness and homogeneity are the basic characteristics of super steel. According to the former researches, adding the second phase fine particles at a specified volume fraction, could efficiently improve the mechanic property of steel and refine its grain. The second phase particles played an important role as the hindrance of grain growth. In order to achieve the homogeneity of grain refinement, the second phase particles should be uniformly distributed in the molten steel

In this study, a physical model was constructed to investigate the distribution of second phase particles in a solution. The concentrations of the second phase particles were measured by using Turbidity Meter to know the distribution of particles in a solution. By analyzing the particle concentration distribution with time in our model, the mixing time could be obtained. In addition, the influences of the different particle sizes and the wettability between particle and solution on the mixing time and the floating ratio for particles were evaluated by compared various particle size and solution concentration.

The results showed that particles distribution in a solution can be decided by measuring the turbidity of the solution. For the same operation conditions, particle size has less influence on the mixing time. Besides, as the density of solution was closed to particle, the mixing time would be decreased. While the contact angle between particle and solution was smaller, the mixing time would be shorten and the floating ratio of particle would also be reduced. From above, the wettability between particles and solution has more influences to the mixing time than particle sizes.

Key words：Super steel, Second-phase particle, Water model, Turbidity, Contact angle

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