【作者】 姚成武；

【导师】 张敏；

【作者基本信息】 西安理工大学 ， 材料加工工程， 2006， 硕士

【摘要】 本文从X80管线钢的性能要求出发，确定以贝氏体强化针状铁素体的技术路线，研制出X80管线钢用埋弧焊丝以及高强度管线钢用埋弧焊剂。研制的焊丝与管线钢专用埋弧焊烧结焊剂SJ101-G匹配焊接所得的熔敷金属，不仅具有高的强度（屈服强度σs≥551MPa），而且具有优良的低温韧性(A_KV-20℃≥160J)，满足了X80管线钢埋弧焊缝力学性能要求。研制的碱性烧结焊剂匹配H08C焊丝所得的熔敷金属强度和韧性优于SJ101-G焊剂，其冲击韧性A_KV（0℃）≥170J。 X80管线钢焊接性试验分析表明X80管线钢冷裂倾向小，焊接热影响区的组织和性能发生了较大变化，其中粗晶区（CGHAZ）组织为粗大的先共析铁素体和粒状贝氏体，并伴有少量碳化物和岛状相M-A组元析出，出现硬化脆化现象，并导致韧性下降；在不完全重结晶区（ICHAZ）和回火区（SCHAZ）之间存在一个软化区。 本文在对针状铁素体形核特点的试验分析发现，焊缝熔敷金属中含有Al₂O₃、MnO、Ti₂O₃、α-MnS等相形成的夹杂物，夹杂物周围存在合金元素（如Mn、Ti等）贫乏区，针状铁素体片以夹杂物为核心形核而呈发射状生长。熔敷金属中Mn元素含量过高时，对针状铁素体形核不利，而增加Ni元素含量更易保证焊缝针状铁素体含量和韧性；焊缝熔合区缺少有效的针状铁素体形核质点，针状铁素体含量较少；同其它元素相比，焊缝中Mn、Ni元素的偏析较弱，保证Mn、Ni元素含量有利于熔合区粒状贝氏体而抑制高温先共析铁素体的形成，对焊缝熔合区韧性有利。 X80管线钢焊缝组织强化主要以针状铁素体和粒状贝氏体内的位错强化、以及晶粒细化带来的晶界强化机制为主，而韧化则与焊缝组织中可动位错以及针状铁素体的互锁结构和细小的针状铁素体片束、粒状贝氏体颗粒有关；Mn、Ni元素的固溶强化以及由TiN等质点钉扎位错而形成的沉淀强化也对焊缝金属起到一定强化和韧化作用。更多还原

【Abstract】 According to the requirement for the properties of X80 pipeline steel, The submerged arc welding wire for X80 pipeline steel and a new agglomerated flux for high strength-toughness steels were developed based on the technological route of strengthening acicular ferrite with bainite. The submerged arc welding deposited metals by this welding wire in couple with agglomerated flux SJ101-G possesses quite high yield strength （σ_s≥551MPa） and excellent toughness(A_KV（-20℃）≥160J), which meet the mechanic performance requirement for X80 welding pipe. The submerged arc welding deposited metals by this alkali agglomerated flux in couple with welding wire H08C possesses higher yield strength and toughness than those using SJ101-G,and Charpy impact value is A_KV（0℃）≥170J), which meet the mechanic performance requirement for X80 welding pipe.The analysis of X80 pipeline steel weldability show that X80 pipeline steel has low cold crack sensibility and there are different changes in microstructure and properties at heated affected zone （HAZ）. The toughness of CGHAZ decreases because carbide and martensite-austenite constituents appear in coarse-grained heat affected zone （CGHAZ） which consist of coarse grain proeutectoid ferrite and granular bainite. There is a softened zone between the intercritical heat affected zone （ICHAZ） and the subcritical heat affected zone（SCHAZ）.The nucleation of acicular ferrite is studied in this paper, and the results indicate that the inclusions in welding deposited metals are chemical heterogeneous compound inclusions which includes various phases such as Al₂O₃, MnO, Ti₂O₃, and α-MnS so on. There is alloy elements （such as Mn, Ti, etc.） depletion around inclusion, and multiple acicular ferrite plates nucleate at one inclusion and grow radially. Excessive Mn element content is adverse to the acicular ferrite in the weld, however, the weld containing more Ni element content can obtain more high-strength and toughness for promoting acicular ferrite nucleate effectively. There is a low content of acicular ferrite in the fusion area because of lacking of valid nucleating particles for acicular ferrite. Comparing to alloy elements, there is faintish Mn and Ni elements segregation phenomenon in the weld, so, the weld ensuring Mn and Ni element content can promoting the更多还原