【作者】 袁轩一；

【导师】 王晓慧； 陈克新；

【作者基本信息】 清华大学 ， 材料科学与工程， 2011， 博士

【摘要】 在自然灾害当中，在战场上，人们都要在无电的情况下进行应急焊接作业。然而，目前已有的焊接方法很难满足抢修作业简便、高效的需求。本文正是针对上述需求，将自蔓延技术结合手工焊接方法，创新出一种新型热剂焊接方法。该焊接方法无需借助任何外部能源和辅助设备，焊接人员可随身携带，随时随地进行焊接作业。文章采用自创的自蔓延反应造渣技术，成功实现了热剂反应后金属与氧化铝的迅速分离。通过研究不同原料粒径以及球磨混料工艺对热剂反应的影响，获得了可控的热剂反应，实现了将分离出的熔融金属产物向待焊母材上铺展，并形成焊缝。文章分别选择Al/Fe₂O₃，Al/CuO作为主要的热剂反应体系进行焊接实验，并采用合金化的方法对焊缝进行强化。研究了上述两热剂体系的焊缝成型性能及组织情况，并分析了合金元素对焊缝显微组织以及性能产生的影响。研究表明：Al/Fe₂O₃体系的焊缝成型性能较差，合金元素C的添加将导致焊缝焊接性能的急剧恶化，Al/CuO体系的焊缝成型性能较好，Al/NiO体系的加入将有效改善焊缝的显微组织结构以及提高焊缝强度，实现与母材强度的相互匹配。在Al/CuO、NiO反应体系的基础上，通过添加惰性稀释剂的办法对热剂反应进行调控，研究不同燃烧速度和温度对焊缝成型、显微组织以及力学性能的影响；对热剂焊接过程中裂纹产生的原因进行了详细分析，研究了不同Ni含量以及Fe含量对焊缝产生结晶裂纹的影响。研究表明：添加4wt.%硅灰石，即在燃烧速度为0.37cm/s，温度为1918℃条件下获得的焊接接头组织较好，未有缩松和气孔存在。焊缝中Ni和Fe的含量将对结晶裂纹的产生起到至关重要的作用，当二者含量均控制在10wt.%以下时，便能消除结晶裂纹。经严格调控后所得焊接接头的抗拉强度为424MPa，延伸率为10.4%，完全可以满足应急焊接的需要。将热剂焊接成果应用于热剂堆焊，实现了一种新颖的原位合成金属基复合材料堆焊层的简单方法。实验结果表明：原位合成的TiC颗粒尺寸细小，大部分均小于10μm，且弥散分布于堆焊层当中。更多还原

【Abstract】 People have to operate an emergency welding without electric power in naturedisaster or battle fields. However, all the existed welding method hardly meet thesimple、efficient requirements for emergency repair. This paper presents a novel methodof thermite welding, which combined SHS technology with manual welding. Ahand-operated portable welding can be conveniently realized by using thermite weldingwithout any outside power and auxiliary equipment.Rapid separation of aluminum oxide and molten metal production could berealized by Self-propagating slagging reaction technology. The influence of rawmaterials particle size and milling process were discussed. Finally a controlled thermitereaction and weld formation were achieved.Al/Fe₂O₃and Al/CuO system were selected as the main exothermic reaction inthermite welding. The formability and microstructure of weld bead were studied. Theinfluence of alloying elements on weld microstructure and property were discussed aswell. Results showed the weld performance for Al/Fe₂O₃system is bad and weldabilitywas deteriorated sharply when adding alloying elements C. While Al/CuO system has abetter weld performance and the microstructure and property of weld was improved byadding Al/NiO system.Effect of thermite burning rate and temperature on microstructure and mechanicalproperties of weld joints was studied in Al/CuO、NiO system. The thermite reaction wasadjusted by varying addition of diluent. The causes of solidification cracking duringthermite weld process were discussed and the effect of Ni and Fe content on formingsolidification cracking was studied. Results showed a fine microstructure with fewshrinkage pore or micro-crack was obtained at0.37cm/s burning rate,1918℃with4wt.%wollastonite addition. The Ni and Fe contents were key reasons in formingsolidification cracking, when their levels were controlled by less then10wt.%, it couldbe able to eliminate the solidification cracking. The tensile properties with424MPaultimate tensile strength and10.4%uniform elongation were obtained after strictcontrolling the welding process. The properties of weld fully meet the needs ofemergency welding. A simple and novel method to prepare ceramic particulate reinforced MMCcoatings were realized via thermite welding technology. Results showed in situsynthesized TiC particles were fine with an average size of <10μm and uniformlydistributed in the metal matrix.更多还原