王东坡¹，巴凌志¹，张智²，齐书梅³，李磊³
AuthorsHTML:王东坡¹，巴凌志¹，张智²，齐书梅³，李磊³
AuthorsListE:Wang Dongpo¹，Ba Lingzhi¹，Zhang Zhi²，Qi Shumei³，Li Lei³
AuthorsHTMLE:Wang Dongpo¹，Ba Lingzhi¹，Zhang Zhi²，Qi Shumei³，Li Lei³
Unit:1. 天津大学材料与科学工程学院，天津 300350；
2. 天津大学机械工程学院，天津 300350；
3. 天津冶金集团中兴盛达钢业有限公司，天津 301616
Unit_EngLish:1. School of Materials Science and Engineering，Tianjin University，Tianjin 300350，China；
2. School of Mechanical Engineering，Tianjin University，Tianjin 300350，China；
3. Tianjin Metallurgy Group Flourish Steel Industrial Co.，Ltd.，Tianjin 301616，China
Abstract_Chinese:研究了不同Mn、Ni含量对低合金高强钢(HSLA)焊缝金属组织和冲击韧性的影响，采用6种自制的焊材对低合金高强度钢多道多层埋弧焊焊接，使焊缝金属成分分别达到0.9%、1.2%、1.6%Mn和1.0%、1.5%、2.6%Ni．经过夏比冲击、硬度试验及光学显微镜、扫描电镜分析，对熔敷金属的组织、性能进行研究．结果表明：柱状晶区组织以针状铁素体和先共析铁素体为主，再热区组织主要为多边形铁素体和少量的脆性第2相，如珠光体、马奥组元等；由于大晶界密度的降低，从柱状晶区组织到再热区组织的硬度值逐渐降低；Mn、Ni元素均能通过改变淬透性，降低A1转变温度，促进针状铁素体的生成，且Ni元素对针状铁素体的促进作用大于Mn；过多Mn元素的添加会导致再热区产生大量的脆性第2相如珠光体、马奥组元等，提供裂纹萌生质点，降低起裂吸收功，且脆性第2相网状分布，降低裂纹扩展自由能，恶化冲击韧性；Ni元素抑制大尺寸粒状贝氏体析出，大部分多变形铁素体转变成边界不规则的转多边形铁素体，大角度晶界增加，大大阻碍了裂纹的扩展，并且Ni固溶于铁素体基体中，韧化了基体，从而增加裂纹萌生功；脆性温度转变曲线中，Si-Mn-Ni合金系熔敷金属的脆性转变温度均低于Si-Mn合金系，而上平台冲击韧性低于Si-Mn合金系，Ni的添加大大改善了焊缝金属的低温冲击韧性．
Abstract_English:Effects of Mn and Ni content on the microstructure of weld metal and impact toughness of high-strength， low-alloy (HSLA) steel were studied. Deposited metals containing 0.9%，1.2%，and 1.6% Mn and 1.0%，1.5%，and 2.6% Ni are obtained using six types of welding consumables in multi-pass submerged arc welding. The microstructure and mechanical properties of the deposited metals were investigated by the Charpy impact test，hardness test，optical microscope，and scanning electron microscopy analysis. The result shows that the microstructure of columnar zone is dominantly composed of acicular ferrite and grain boundary by allotriomorphic ferrite. The microstructure of welded zone mainly consists of polygonal ferrite with the small amount of brittle alloys or metals，such as pearlite and martensite-austenite (MA) alloys，formed during the second phase. The hardness tends to decrease from the columnar zone to welded zone because of the presence of high-angle grain boundaries. Both Mn and Ni can change the hardenability，lower the A1 temperature (eutectoid transformation temperature)，initiate the formation of acicular ferrite，but the acicular ferrite formed by Ni element is of higher quality than that of Mn. Excessive Mn results in the formation of a large amount of brittle alloys at the secondary phase such as pearlite and MA alloys and is responsible for crack formation and its propagation，and thereby deteriorates the impact toughness. The presence of Ni inhibits the precipitation of large-sized granular bainite as most of the polygonal ferrites are transformed into quasi-polygonal ferrite. Moreover，the presence of high-angle grain boundary strongly inhibits the crack propagation，and Ni dispersion in the ferrite alloy increases the toughness of the matrix，thereby decreasing the initiation of crack formation and its propagation. In the ductile to brittle temperature transition curve，the brittle transition temperature of the deposited metal of Si-Mn-Ni alloy will be lower than that of Si-Mn alloy，so the impact toughness of the top surface will be lower than that of Si-Mn alloy，and it shows that addition of Ni greatly improves low-temperature impact toughness of weld metal.
Keyword_Chinese:Mn-Ni；低合金高强钢；冲击韧性；针状铁素体
Keywords_English:Mn-Ni；HSLA；impact toughness；acicular ferrite

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