【作者】 刘炜；

【导师】 严铿；

【作者基本信息】 江苏科技大学 ， 材料加工工程， 2013， 硕士

【摘要】 随着海洋资源开采向深海发展，海洋平台建设用钢级别越来越高，钢材的厚度也越来越大。本文选用埋弧焊焊接方法来焊接海洋平台用钢F550Z，通过研制高碱低氢焊剂，配合合金焊丝，采用不同的焊接热输入，研究不同的热输入对焊接接头力学性能的影响。分析了不同的焊接热输入对F550Z焊接接头的强度、韧性、微观组织及硬度的影响，为合理选择焊接工艺参数和生产实践提供了试验和理论依据。通过研究不同的原材料对焊接工艺性能的影响，确定了配方中不同原料的加入量，并检测配方的脱渣性、成型能力等性能。经过大量的调试，确定焊剂的配方，并通过检测焊剂成分计算焊剂碱度，为3.39达到设计要求。配合焊丝，研究了全焊缝金属力学性能，检测了焊缝金属的扩散氢含量，并研究了低的含氢量的原因。采用CHW-SEM2NP型焊丝和所研制氟碱型烧结焊剂，当热输入分别为输入分别为15kJ·cm^-1、27kJ·cm^-1、38kJ·cm^-1、50kJ·cm^-1时，焊接接头力学性能呈现出一定的变化趋势。研究结果表明：随着焊接热输入量的增大，接头抗拉强度都超过CCS要求的最低值670MPa，并且没有随热输入出现明显的变化，接头强度对热输入不敏感；焊接接头的硬度分布均匀，焊缝中心较母材处略低，没有出现较大的波动。焊接热输入对F550Z钢焊接接头不同部位的组织与-60℃低温韧性有较大的影响。试验结果表明，焊缝中心的韧性随着热输入增加，呈现先降低后升高的趋势，当热输入为15kJ·cm^-1时冲击吸收功平均值为65J，热输入增加到38kJ·cm^-1时已经达不到CCS的要求最低值34J，但热输入增加到50kJ·cm^-1时，冲击吸收功平均值为110J，是其他热输入的2到4倍。通过金相与能谱分析，发现热输入为15kJ·cm^-1和50kJ·cm^-1时，对焊缝中心有热处理作用，组织为针状铁素体加细小弥散的碳化物，其中50kJ热处理作用较明显。熔合线及熔合外2mm处冲击韧性随热输入增加而减小，当热输入超过27kJ·cm^-1时，熔合线及熔合线外2mm处冲击韧性已经达不到使用要求。分析发现熔合线及熔合线2mm处组织为板条贝氏体加粒状贝氏体。小热输入时，粒状贝氏体含量少并且打乱了板条贝氏体方向，对韧性有利；随着热输入增加，粒状贝氏体逐渐增多且晶粒粗大，低温韧性较差。熔合线外5mm受焊接热输入影响不大，冲击吸收功与母材没有明显差异。综上所述，15kJ·cm^-11和27kJ·cm^-1时，焊接接头各个区域的性能都能满足CCS标准的要求。考虑到接头性能与生产效率，建议埋弧焊焊接F550Z钢时焊接热输入为27kJ·cm^-1左右为宜。更多还原

【Abstract】 As the exploitation of marine resources from shallow sea to deep sea, the offshoreplatform steel’s grade and thickness are higher and higher. In this paper, used submerged arcwelding for jointing the offshore platform steel F550Z, developed high basicity and lowhydrogen flux, combined with alloy wire, and researched the effects of heat-inputs on thewelding joints’ mechanical properties by using different heat-inputs. Analysising heat-inputseffects on the welding joints’ tensile strength and low temperature toughness andmicrostructure and hardness, affording experimental and theoretical basis for weldingproduction and selecting welding parameter reasonably.Study the effects of different raw materials on the welding operability; confirm theamount of different raw materials in the formulation, and check the flux properties of slagremoval and welding performance. After lots of trails, the flux formulation is established,and tset the flux components for calculating the basicity, which is3.39and meets the designrequirements. Combining with solid wire, study the mechanical properties, check thediffusible hydrogen of deposit metal and research the reason of low levels of diffusiblehydrogen.The welding material is the combination of developed flux and CHW-SEM2NP cordwire. When the heat-inputs is designed as15kJ·cm^-1and27kJ·cm^-1and38kJ·cm^-1and50kJ·cm^-1, the mechanical properties show certain trends. The research results indicate thatwhen the heat-inputs increased, the joints’ tensile strength exceed the minimum value ofCCS requirement which is670MPa, and no significant changes with the heat-inputs changes,the tensile strength is not sensitive to the heat-inputs. The hardness of welded jointsdistribute evenly, the hardness in the welding center is lower than that in base metal, nosignificant fluctuations.The heat-inputs affect heavily the microstructure in different parts of joints andtoughness at-60℃. The experimental results indicate that toughness decrease firstly andincrease then with heat-inputs increase. When the heat-input is15kJ·cm^-1, the average ofimpact value is65J, as the heat-input reaches38kJ·cm^-1, it can’t meet the minimum value ofCCS requirement which is34J, but the heat-input reaches50kJ·cm^-1, it is110J, which is2to4times than others. By analysing microstructure and SED, the welding metal get theeffect of heat treatment when heat-inputs is15kJ·cm^-1or50kJ·cm^-1, the microstructure areacicular ferrite and fine granular dispersed carbides, especially the heat-input is50kJ·cm^-1.The microstructure in the fusion line and2mm from fusion line are lath bainite and granular bainite. When the heat input is small, a spot of granular bainite disrupt the direction of lathbainite, which is good for toughness. But granular bainite increase and get coarse withheat-input increase, which leads to bad toughness. The impact values in these zonesdecrease with heat-inputs increase. The microstructure and toughness in5mm from fusionline are almost the same with those in base metal.In summary, when the heat-inputs are15kJ·cm^-1and27kJ·cm^-1, all the properties ofjoints meet the CCS requirements, considering the mechanical properties and efficiency ofproduction, Using SAW for F550Z steel, the heat-inputs should be27kJ·cm^-1.更多还原