本文選題：平面流鑄法 + 氣流邊界層��； 參考：《鋼鐵研究總院》2017年碩士論文

【摘要】：在平面流鑄法制備非晶帶材過程中,由于冷卻輥的高速旋轉(zhuǎn),在冷卻輥輥面會形成一層具有高速度梯度的氣流邊界層。氣流邊界層會對非晶熔潭中非晶熔體的流動、傳熱和凝固行為(簡稱熔潭行為)產(chǎn)生影響,進而影響非晶帶材的厚度、邊部質(zhì)量、表面質(zhì)量和使用性能。本課題以計算流體力學為理論基礎,通過建立數(shù)學模型,研究平面流鑄法制備非晶帶材過程中氣流邊界層對熔潭行為的影響。在此基礎上,分析氣體物性參數(shù)、環(huán)境壓力和平面流鑄過程工藝參數(shù)對氣流邊界層及熔潭行為的影響,以期闡明氣流邊界層對熔潭行為及非晶帶材質(zhì)量影響的機理,以期為現(xiàn)場生產(chǎn)過程中控制氣流邊界層提供理論參考。得出以下結(jié)論:(1)在非晶熔潭形成過程中,氣流邊界層均對熔潭行為產(chǎn)生影響。非晶熔潭尚未形成時,氣流邊界層會在非晶熔體-氣體界面帶走非晶熔體的熱量。非晶熔潭形成后,氣流邊界層沖擊熔潭上彎月面,會導致氣體卷入非晶熔潭,并對非晶熔體的溫度分布產(chǎn)生影響。氣流邊界層會在熔潭邊部形成繞流熔潭現(xiàn)象,不利于非晶帶材邊部質(zhì)量。(2)采用負壓吸氣時,吸氣位置及吸氣壓力十分關(guān)鍵。當在熔潭上彎月面?zhèn)冗M行側(cè)部吸氣時,較低的吸氣負壓(5000Pa和8000Pa)對氣流邊界層的破壞較小。當在熔潭上彎月面?zhèn)冗M行頂部吸氣時,吸氣負壓(5000Pa)能夠減弱繞流熔潭現(xiàn)象,從而有利于提高非晶帶材邊部質(zhì)量。當吸氣負壓提高至80000Pa時,在熔潭邊部會產(chǎn)生高速逆制帶方向氣流,不利于非晶帶材邊部質(zhì)量。(3)噴吹速度和噴吹方向?qū)姶挡煌瑲怏w的效果有很大影響,當逆制帶方向噴吹不同氣體(Ar、He、CO2)時,噴吹速度的提高有助于破壞氣流邊界層。當沿制帶方向噴吹低密度氣體(高溫CO2)時,有助于減少氣流卷入現(xiàn)象的發(fā)生。(4)工藝參數(shù)(非晶熔體噴注速度、冷卻輥旋轉(zhuǎn)速和噴嘴-冷卻輥間距)的調(diào)整均會影響熔潭行為。非晶熔體的噴注速度主要影響非晶熔潭與冷卻輥輥面的夾角。調(diào)整冷卻輥旋轉(zhuǎn)速度會改變?nèi)厶秲?nèi)的溫度分布。噴嘴-冷卻輥間距會改變?nèi)厶渡蠌澰旅娓浇鼩饬鬟吔鐚铀俣确植?從而對氣體卷入產(chǎn)生影響。增大制帶寬度會增大繞流熔潭的最大速度,從而對非晶帶材邊部質(zhì)量產(chǎn)生影響。
[Abstract]:In the process of preparing amorphous strip by plane flow casting, due to the high speed rotation of cooling roll, a layer of air flow boundary layer with high velocity gradient will be formed on the surface of cooling roll. The gas flow boundary layer will affect the flow, heat transfer and solidification behavior of amorphous melt, and then affect the thickness, edge mass, surface quality and performance of amorphous strip. On the basis of computational fluid dynamics (CFD), a mathematical model was established to study the effect of gas flow boundary layer on the fluid-pool behavior in the process of preparing amorphous strip by plane flow casting. On this basis, the effects of gas physical parameters, environmental pressure and process parameters of plane flow casting on the behavior of gas flow boundary layer and molten pool are analyzed in order to elucidate the mechanism of the influence of gas flow boundary layer on the fluid-pool behavior and the quality of amorphous strip. In order to provide a theoretical reference for the control of air flow boundary layer in the field production process. The following conclusion is drawn: (1) during the formation of amorphous molten pool, the gas flow boundary layer has an effect on the molten pool behavior. When the amorphous melt pool is not formed, the gas flow boundary layer will take the heat of the amorphous melt at the interface between the amorphous melt and the gas. After the formation of amorphous melt pool, the air flow boundary layer impinges on the meniscus of the molten pool, which results in the gas sucking into the amorphous melt pool and affects the temperature distribution of the amorphous melt. The flow around the pool is formed in the boundary layer of the gas flow, which is unfavorable to the mass of the edge part of the amorphous strip. The suction position and suction pressure are very important when negative pressure is used to inhale the boundary layer. When the lateral suction is carried out on the meniscus side of the pool, the lower suction negative pressure of 5 000 Pa and 8 000 Pa) does little damage to the boundary layer of the gas flow. When the top suction is carried out on the meniscus side of the molten pool, the suction negative pressure of 5 000 Pa) can reduce the flow around the pool and thus improve the quality of the edge part of the amorphous strip. When the suction negative pressure is increased to 80000Pa, a high speed reverse zone flow will occur at the edge of the melt pool, which is unfavorable to the injection speed and the direction of injection on the effect of injection of different gases, which is not conducive to the quality of the edge part of the amorphous strip. When different gases are injected in the reverse direction of the belt, the higher the injection velocity is, the more the boundary layer will be destroyed. When the low density gas (high temperature CO _ 2) is injected along the belt direction, the adjustment of the process parameters such as the injection rate of amorphous melt, the rotation rate of the cooling roll and the distance between the nozzle and the cooling roll will affect the melt behavior. The injection rate of amorphous melt mainly affects the angle between amorphous melt pool and cooling roll surface. Adjusting the rotation speed of the cooling roll will change the temperature distribution in the melt pool. The distance between nozzle and cooling roll will change the velocity distribution of the gas flow boundary layer near the meniscus of the molten pool, which will have an effect on the gas entrainment. The maximum velocity of the flow pool will be increased by increasing the width of the strip, which will have an effect on the quality of the edge of the amorphous strip.
【學位授予單位】：鋼鐵研究總院
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG24

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