火焰切割割缝宽度的实验与数值模拟研究

发布时间：2018-12-06 21:44

【摘要】：火焰切割是一种常用的钢铁粗加工技术,以其成本优势得到了广泛的使用。火焰切割时会产生铁的浪费,本文以此为出发点对火焰切割的割缝宽度进行了研究。首先对火焰切割的适用范围以及火焰切割和其他切割方式的优劣对比做了详细的介绍,解释了选择火焰切割的割缝宽度作为研究对象的理由。之后说明了火焰切割过程的基本原理,并以此为基础,介绍了火焰切割时的工艺参数,以及火焰切割时不同燃气的特性。在实验部分,使用数控火焰切割机对150mm厚的铁块进行切割,并研究了丙烷和预热氧流量对割缝宽度的影响。实验结果表明割缝宽度平均为4.8mm。通过调节预热氧流量,令丙烷的当量比为1.2,可使割缝宽度在该丙烷流量下达到最窄,此时若使丙烷、预热氧流量同时增大,保持丙烷当量比不变,割缝宽度有逐渐降低的趋势。实验中还使用了重铬酸钾滴定法滴定熔渣样品,得到熔渣中铁、二价铁、三价铁的含量分别为18.8%、55.53%、25.67%,并结合切割速度3.5mm/s计算出切割过程中铁氧燃烧放热的热功率为91.1kW。最后,对火焰切割过程进行了数值模拟,计算达到稳态后铁块的温度场及割缝宽度。模拟中忽略了预热火焰对铁块温度的影响,并在以割炬位置为中心,割缝宽度为直径的圆柱形区域内设定了一个均匀分布的热源项Qt,以模拟切割氧对铁块的影响。计算结果显示,当Qt取42.4kW时模拟得到的割缝宽度为4.8mm,且Qt每变化1kW,割缝宽度变化0.1mm。另外,割缝处的对流换热是影响铁块冷却速度的主要因素,但并不影响割缝宽度的大小。
[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.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG481

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