输电线路用新型球铁GMAW接头组织及性能研究
发布时间：2018-12-10 13:39
【摘要】：球墨铸铁属于高强材料,具有接近于钢材的综合性能,且其生产成本较低,已用于制造对强度、韧性和耐磨性要求较高的零部件,在油气管道、交通运输、农机、船舶制造、矿石开采等领域具有广阔的应用前景。近年来,随着社会节能环保意识的不断增强,材料的发展日益倡导轻重量、高效率和低成本,球墨铸铁的优异特性使其有望取代灰铸铁和可锻铸铁等工程材料,表现出巨大的发展潜力。但球墨铸铁的焊接性较差,成为限制其进一步推广应用的首要因素。本课题采用ER50-6低合金钢焊丝作为填充材料,在预热150℃条件下,对新型铁素体基球墨铸铁的CO2气体保护焊(GMAW)展开研究。试验使用金相显微镜(OM)、扫描电子显微镜(SEM)、维氏硬度计和万能拉伸试验机等手段研究接头的组织和力学性能,并分析焊接工艺参数、显微组织、裂纹形态以及力学性能之间的关系。采用双面焊成形和单面焊双面成形两种方式焊接球墨铸铁,获得的接头焊缝中均出现明显的气孔,气孔直径一般小于0.5mm,试验表明,焊接速度是影响气孔产生的重要因素,适当降低焊接速度可以有效的减少气孔数量。接头的宏观裂纹一般出现在双面焊成形的熔合区,裂纹启裂于焊趾部位,并沿着熔合区扩展。裂纹形成的原因主要是接头组织差异较大而产生过大的残余应力,并且熔合区主要为淬硬的莱氏体,对应力的松弛能力较差。针对焊接热输入对焊缝、熔合区组织以及接头显微硬度的影响进行了研究。试验结果表明,淬硬组织一般出现在双面焊接头的后焊焊道,焊缝组织完全由竹叶状的高碳马氏体和少量的残余奥氏体构成,显微硬度达到600～650HV500g。由于热输入较小,接头冷却速度快,在其热影响区还会形成较窄的淬硬区。对于单面焊双面成形接头,焊缝组织主要为细小片层状的托氏体,将热输入由8.6kJ/cm增加到18.2kJ/cm,可以看出托氏体的数量增加,片层间距也逐渐增大,焊缝的硬度由508HV500g降低到444HV500g。熔合区的莱氏体组织对热输入变化并不敏感,但增加热输入会使白口区宽度增大,因而从接头的强韧性考虑要合理的控制焊接热输入。研究球墨铸铁焊接接头的力学性能,结果显示断裂主要出现在熔合区,单面焊双面成形接头的抗拉强度可以达到262MPa。使用扫描电镜(SEM)对断口形貌进行观察,无韧窝产生,断口完全为脆性解理断裂,裂纹沿着熔合区扩展,并形成高低不平的解理台阶。
[Abstract]:Ductile iron is a kind of high strength material, it has close to the comprehensive properties of steel, and its production cost is relatively low. It has been used to manufacture parts which require higher strength, toughness and wear resistance, in oil and gas pipeline, transportation, agricultural machinery, ship manufacture, Ore mining and other fields have broad application prospects. In recent years, with the increasing awareness of energy saving and environmental protection in society, the development of materials increasingly advocates light weight, high efficiency and low cost. The excellent properties of ductile iron make it possible to replace engineering materials such as gray cast iron and malleable cast iron. Show great potential for development. However, the weldability of ductile iron is poor, which is the primary factor restricting its further application. In this paper, ER50-6 low alloy steel wire was used as filling material, and the CO2 gas shielded (GMAW) welding of new ferrite based ductile iron was studied under preheating condition of 150 鈩，
本文编号：2370664
[Abstract]:Ductile iron is a kind of high strength material, it has close to the comprehensive properties of steel, and its production cost is relatively low. It has been used to manufacture parts which require higher strength, toughness and wear resistance, in oil and gas pipeline, transportation, agricultural machinery, ship manufacture, Ore mining and other fields have broad application prospects. In recent years, with the increasing awareness of energy saving and environmental protection in society, the development of materials increasingly advocates light weight, high efficiency and low cost. The excellent properties of ductile iron make it possible to replace engineering materials such as gray cast iron and malleable cast iron. Show great potential for development. However, the weldability of ductile iron is poor, which is the primary factor restricting its further application. In this paper, ER50-6 low alloy steel wire was used as filling material, and the CO2 gas shielded (GMAW) welding of new ferrite based ductile iron was studied under preheating condition of 150 鈩，
本文编号：2370664
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