【摘要】：火焰切割是一種常用的鋼鐵粗加工技術,以其成本優(yōu)勢得到了廣泛的使用�；鹧媲懈顣r會產(chǎn)生鐵的浪費,本文以此為出發(fā)點對火焰切割的割縫寬度進行了研究。首先對火焰切割的適用范圍以及火焰切割和其他切割方式的優(yōu)劣對比做了詳細的介紹,解釋了選擇火焰切割的割縫寬度作為研究對象的理由。之后說明了火焰切割過程的基本原理,并以此為基礎,介紹了火焰切割時的工藝參數(shù),以及火焰切割時不同燃氣的特性。在實驗部分,使用數(shù)控火焰切割機對150mm厚的鐵塊進行切割,并研究了丙烷和預熱氧流量對割縫寬度的影響。實驗結(jié)果表明割縫寬度平均為4.8mm。通過調(diào)節(jié)預熱氧流量,令丙烷的當量比為1.2,可使割縫寬度在該丙烷流量下達到最窄,此時若使丙烷、預熱氧流量同時增大,保持丙烷當量比不變,割縫寬度有逐漸降低的趨勢。實驗中還使用了重鉻酸鉀滴定法滴定熔渣樣品,得到熔渣中鐵、二價鐵、三價鐵的含量分別為18.8%、55.53%、25.67%,并結(jié)合切割速度3.5mm/s計算出切割過程中鐵氧燃燒放熱的熱功率為91.1kW。最后,對火焰切割過程進行了數(shù)值模擬,計算達到穩(wěn)態(tài)后鐵塊的溫度場及割縫寬度。模擬中忽略了預熱火焰對鐵塊溫度的影響,并在以割炬位置為中心,割縫寬度為直徑的圓柱形區(qū)域內(nèi)設定了一個均勻分布的熱源項Qt,以模擬切割氧對鐵塊的影響。計算結(jié)果顯示,當Qt取42.4kW時模擬得到的割縫寬度為4.8mm,且Qt每變化1kW,割縫寬度變化0.1mm。另外,割縫處的對流換熱是影響鐵塊冷卻速度的主要因素,但并不影響割縫寬度的大小。
[Abstract]:Flame cutting is a common roughing technology for iron and steel, which is widely used because of its cost advantage. In this paper, the slit width of flame cutting is studied. Firstly, the application scope of flame cutting and the comparison between flame cutting and other cutting methods are introduced in detail, and the reason of choosing the cutting seam width of flame cutting as the object of study is explained. Then the basic principle of flame cutting process is explained, and the technological parameters of flame cutting and the characteristics of different gas in flame cutting are introduced. In the experiment part, the 150mm thick iron block is cut by the numerical control flame cutting machine, and the influence of propane and preheated oxygen flow rate on the slit width is studied. The experimental results show that the average slit width is 4.8 mm. By adjusting the preheated oxygen flow rate, the equivalent ratio of propane to propane is 1.2, and the slit width is the narrowest at the propane flow rate. If propane is made, the preheated oxygen flow rate increases at the same time, keeping the propane equivalent ratio unchanged. The width of slit is decreasing gradually. In the experiment, potassium dichromate titration method was used to titrate the slag samples. The contents of iron, divalent iron and trivalent iron in the slag were 18.855.53 and 25.67, respectively. Combined with cutting speed 3.5mm/s, the heat power of iron oxide combustion is 91.1 kW. Finally, the flame cutting process is numerically simulated, and the temperature field and slit width of the iron block after steady state are calculated. The influence of preheated flame on the temperature of iron block was neglected, and a uniform heat source term (Qt,) was set in the cylindrical region with cutting torch as the center and slit width as the diameter to simulate the effect of cutting oxygen on the iron block. The results show that the slit width is 4.8mm when Qt takes 42.4kW, and the slit width changes 0.1 mm. for each Qt change of 1kW. In addition, the convective heat transfer at the slit is the main factor affecting the cooling rate of the iron block, but it does not affect the size of the slit width.
【學位授予單位】：中國科學技術大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG481

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