铸铁同质焊材焊接修复工艺研究

发布时间：2018-03-10 19:09

  本文选题：铸铁　切入点：同质焊材　出处：《兰州理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：由于铸铁的组织特点,铸铁自身具有极佳的抗震性能和耐磨性能,并且其生产成本较低,因此在机械领域铸铁是被使用最广泛的合金材料。但是由于在整个铸造过程中涉及的操作环节较多。同时,目前广泛使用的砂型铸造和浇注过程存在很多不确定性,因此铸铁产品的夹砂、夹渣和缩松等问题突出。如果这些缺陷不能被有效修复,必将导致这些铸件报废,将直接导致铸造成本的上升。因此对这些铸件缺陷的修复就显得尤为重要。本文研究了铸铁微合金同质焊条和焊丝的焊接工艺,并分别在灰铁和球铁两种材质的试块上,开展了不同焊接工艺(电弧冷焊、热电弧焊和氧乙炔焊)的试验,通过对电流、焊前预热温度和焊后预热温度的不断调整,最终确定了最理想的焊接参数和工艺流程。并在某大型的船用和燃气轮机铸件上得到应用。在电弧焊中,分别试验了电流为160A、180A、200A和220A时,电流对焊缝热影响区的白口化倾向和焊接缺陷的影响。得出了较为理想的焊接电流为180A。此时可以避免焊接缺陷的产生,又可以尽可能减小焊接区域的白口化倾向。在加热电弧焊中,分别选择了不同的电流(160A、180A、200A和220A)和不同的焊接前预热温度(300℃、400℃、500℃和600℃)进行试验。最终得出较为合适的预热温度为500℃,焊接电流为180A。此时可以避免焊接区域的白口问题,同时又可以使得焊缝加工后的色泽与母材接近。在气焊中,试验了不同的保温温度(300℃、400℃、500℃和600℃)和不同的保温时间(5min、10min、15min和20min)对焊接区域加工形貌、组织和性能的影响,焊接完毕后立即对焊接区域进行加热处理,最终得出较理想的灰铁较为理想的加热温度为500℃,烘烤持续时间为15min。球铁较为理想的加热温度为600℃,烘烤持续时间为15min。此时可以获得良好的焊缝质量。
[Abstract]:Because of the structure characteristics of cast iron, cast iron itself has excellent seismic and wear resistance, and its production cost is relatively low. Therefore, cast iron is the most widely used alloy material in the mechanical field. However, because there are many operating links involved in the whole casting process, there are many uncertainties in the sand mold casting and pouring process, which are widely used at present. Therefore, the problems of sand inclusion, slag inclusion and shrinkage of cast iron products are prominent. If these defects cannot be repaired effectively, they will lead to the scrap of these castings. Therefore, it is very important to repair the defects of these castings. In this paper, the welding process of cast iron microalloyed homogeneous electrode and wire is studied, and it is applied to the test blocks of gray iron and ductile iron, respectively. The experiments of different welding processes (arc cold welding, hot arc welding and oxyacetylene welding) were carried out. By adjusting the current, preheating temperature before welding and preheating temperature after welding, Finally, the optimal welding parameters and technological process are determined and applied to a large marine and gas turbine castings. In arc welding, the electric current is 160 An 180 A 200 A and 220 A, respectively. The effect of current on the whitening tendency and welding defects in HAZ is obtained. The ideal welding current is 180 A. at this time, the welding defects can be avoided. In heating arc welding, the whitening tendency of welding area can be reduced as much as possible. The experiments were carried out with different electric current of 160An 180A 200A and 220A) and different preheating temperatures before welding (300 鈩，

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