E级低合金高强度铸钢焊接接头组织与力学性能的研究

对货车车钩结构常用的E级低合金高强度铸钢,采用J857T焊条进行手工电弧焊。通过拉伸、弯曲、冲击、硬度测试以及金相分析等,对E级铸钢焊接接头组织形态和力学性能进行了研究。结果表明:采用J857T焊条焊接E级铸钢时,焊接接头具有良好的拉伸、弯曲和冲击性能;其焊缝组织为铁素体、珠光体以及少量的粒状贝氏体混合组织;熔合区组织为铁素体、珠光体组织;热影响区组织为块状铁素体、粒状贝氏体和珠光体;焊接接头显微硬度在225~390HV之间,热影响区出现轻微软化现象。     

贝氏体巨型台阶和界面结构

使用ＴＥＭ和ＨＲＥＭ分别对贝氏体铁素体和Ｃｕ－Ｚｎ－Ａｌ合金贝氏体台阶形貌和界面结构进行了观察。钢中贝氏体铁素体和Ｃｕ－Ｚｎ－Ａｌ合金贝氏体宽面上存有单台阶、多台阶、系列台阶和三维台阶。贝氏体铁素体台阶高度为６～１６０ｎｍ，相当于｛１１１｝晶面１０００个原子层厚度。Ｃｕ－Ｚｎ－Ａｌ合金台阶高度为几个至几十个纳米。贝氏体铁素体有与马氏体不同的丰富的精细结构。贝氏体铁素体和Ｃｕ－Ｚｎ－Ａｌ合金中有丰富的台阶和巨型台阶。文中讨论了贝氏体的相变机制。     

高强度低合金钢埋弧焊缝成分和显微组织分布特征

进行了X80管线钢埋弧焊接试验,分析了其焊缝的成分、显微组织不均匀性特征.焊缝区的Mn、Ni合金元素的成分不均匀程度较小,Ce、Ti、Al等针状铁素体形核元素在焊缝中心区偏析.熔合区至焊缝中心,焊缝组织变化为:柱状晶形态的先共析铁素体及其分布的粒状贝氏体-大块状的粒状贝氏体→小块状的粒状贝氏体和少量的针状铁素体→针状铁素体.试验分析表明,熔合区附近的焊缝金属难以获得针状铁素体,但可以通过调整合金元素,避免高温铁素体生成,而以粒状贝氏体来提高焊缝区的整体强韧性.     

0.19C-1.53Si-2.54Mn贝氏体钢连续冷却过程中的组织演变

通过Gleeble-3500热模拟试验机,结合热膨胀法、金相法及硬度法,研究了低碳硅锰钢连续冷却过程中组织形貌特征及形成机理。结果表明:在连续冷却过程中,冷速在0.5~10℃/s,出现呈块状或条状的铁素体;在0.5~30℃/s冷速,粒状组织、粒状贝氏体逐渐演变为板条贝氏体铁素体;在30~40℃/s,显微组织主要是板条马氏体及少量贝氏体,板条贝氏体铁素体显深褐色,板条马氏体显浅棕色。随连续冷却速度升高,试验用钢的显微硬度也随之升高。     

贝氏体三维形态及组织演化

在扫描电子显微镜（ＳＥＭ）较高分辨率条件下,用双磨面方法研究了贝氏体亚结构的三维（３－Ｄ）形态,发现上贝氏体及其亚片条的三维形态呈板条状。下贝氏体及其亚片条的三维形态呈片状,下贝氏体亚单元为块状。上,下贝氏体之间在三维形态上无明显界限。在存在过渡型的中间态贝氏体,其形态介于上、下贝氏体之间,这说明上、下贝氏体在本质上是统一的。用激发形核－台阶长大理论分析了上、下贝氏体组织形态演化机理,并提出演化过     

14NiCrM0106V与Q345E焊接接头组织与力学性能的研究

通过室温拉伸、弯曲、冲击、硬度试验及金相分析,对Q345E低合金钢与14NiCrM0 10 6V低合金钢混合气体保护焊焊接接头的力学性能与显微组织进行了研究.结果表明:采用ER50-6实芯焊丝焊接时,可以获得拉伸、弯曲和冲击性能均良好的焊接接头;焊缝区硬度较均匀,焊缝硬度在210～250 HV之间;焊接接头焊缝中心组织为先共析铁素体分布于柱状晶界上,晶内为针状铁素体与珠光体;Q345E侧熔合区组织为沿晶界析出块状先共析铁素体和向晶内生长的条状铁素体以及少量的珠光体和贝氏体;14NiCrMo10 6V侧熔合区和过热区组织为板条状马氏体和粒状贝氏体.     

Fe—Ni合金贝氏体长大原位观察

利用透射电镜观察了Ｆｅ－３０ｗｔ－％Ｎｉ合金贝氏体铁素体／奥氏体界面结构，并利用透射电镜高温样品对贝氏体铁素体台阶长大进行了原位动态观测。结果表明，铁素体呈台阶长大形态，在铁素体／奥氏体宽面上存在Ｂｕｒｇｅｒｓ矢量为［１１１］ｂ型的刃型错配位错，铁素体台阶的增厚速率与按Ｚｅｎｅｒ－Ｈｉｌｌｅｒｔ方程计算结果相符。为关于贝氏体生长台阶长大机制提供实验证据。     

JGR610E大型油罐用钢焊接热影响区的显微结构分析

采用金相显微镜和透射电镜对油罐钢焊接热影响区的显微组织进行了研究。结果表明:粗晶区组织主要由粒状贝氏体和板条贝氏体组成,并存在一定数量的M-A岛;细晶区主要为块状和多边形铁素体组织。     

JW船体钢板热加工后组织和力学性能

研究了热加工温度和冷却方式连铸ＪＷ钢组织和力学性能的影响，结果表明不同温度加热，其冰冷组织的力这性能主要取决于铁素体和马氏体的相对体积分数及马氏体的形态。其空冷组织的力学性能主要取决于铁素体，粒状贝氏体和粒状组织的体积分数以及Ｍ－Ａ岛的性态。偏析形成的条带状组织空冷后有马氏体转变。     

贝氏体巨型台阶和界面结构

使用ＴＥＭ和ＨＲＥＭ分别对贝氏体铁素体和Ｃｕ－Ｚｎ－Ａｌ合金贝氏体台阶形貌和界面结构进行了观察。钢中贝氏体铁素体和Ｃｕ－Ｚｎ－Ａｌ合金贝氏体宽面上存在有单台阶、多台阶、系列台阶和三维台阶。贝氏体铁素台阶高度为６－１６０ｎｍ，相当于（１１１）晶面１０００个原子层厚度。Ｃｕ－Ｚｎ－Ａｌ合金台阶高度为几个至几十个纳米     

15CrMoV钢拘束状态多层焊近缝区M-A组织的精细结构与韧性

本文研究了5CrMoV 钢拘束与非拘束TIG 多层焊近缝区组织,特别是M-A岛状组织精细结构与韧性的对应关系。研究结果证明:拘束接头的韧性高于非拘束接头的韧性。主要原因是拘束接头的M-A 岛状组织数量少,岛内孪晶马氏体少而位错马氏体多,铁素体基体的位错密度高以及有极细的碳化物(直径约200×10~(-10)m)从基体上弥散析出。     

焊接热输入对Q890高强钢热影响区裂纹扩展的影响

采用Gleeble1500热模拟试验机,研究不同热输入对Q890高强钢焊接热影响区粗晶区的微观组织和韧性影响规律. 结果表明,随着热输入的增加,粗晶区的微观组织表现出从马氏体组织向马氏体、贝氏体的混合组织,再向贝氏体、粒状贝氏体的混合组织的转变. 当热输入为19.7 kJ/cm时,冲击吸收功最高为83 J,主要原因是由于先相贝氏体分割后相马氏体,大角度晶界密度最大,改善了冲击韧性. 当热输入较高时,粗晶区脆化的原因是由于M-A组元呈链状分布,造成局部应力集中,成为裂纹起裂和扩展的主要通道.     

Phase field simulation of the carbon redistribution during the quenching and partitioning process in a low-carbon steel

Phase-field modelling is used to simulate the quenching and partitioning process in a low-carbon transformation-induced plasticity (TRIP) steel, in order to understand the carbon redistribution in the microstructure during the heat treatment. The simulations show that, depending on local characteristics of the microstructure, including phase distributions and carbon-concentration gradients, different features in the carbon evolution during the partitioning step occur that are physically and practically relevant, but are not accessible for experimental observation. The overall carbon partitioning from martensite to austenite occurs not only by direct diffusion from martensite to austenite, but also through the bulk ferrite grains. The simulations also show interface migration driven by the free-energy difference between austenite and martensite, which affects the fractions of phases and the dimensions of the austenite grains. The carbon content of individual austenite, martensite and ferrite grains as well as average values are analysed, showing that the carbon concentration within the austenite grains is strongly inhomogeneous at short partitioning times, which contributes to a variable mechanical stability of individual austenite grains, affecting the occurrence of TRIP.     

Influence of cooling conditions on X70 pipeline steel in-service welding HAZ

0 IntroductionWith the development of pipeline transportation, itsmaintenance and recovering are also sharp growth. The in-service welding repairing has the advantages of no stop,speed quick, no pollution and receive the attention by allcountries experts day by day[1 -2]. But two factors makewelding onto in-service pipelines difficult. Firstly, theflowing gas creates a large heat loss through the pipe-wall,resulting in accelerated cooling of the weld. Higher carbonequivalent steels are sensit…     

贝氏体-马氏体钢板的组织与性能

研究了贝氏体-马氏体耐磨钢板的组织及力学性能。结果表明，在低碳贝氏体钢基础上，通过加入一定量的硅元素，利用其在贝氏体组织转变过程中抑制碳化物析出的作用，得到由非等轴铁素体加马氏体和残留奥氏体(M-A)岛或由板条状铁素体及其板条间残留奥氏体(Ar)膜组成的贝氏体一马氏体组织，因此其性能既具有高强度、高硬度，又具有较高的低温冲击韧度。     

冷却时间对Ti微合金钢焊接粗晶区组织及韧性的影响

利用光镜、金属薄膜电子显微分析技术、碳萃取复型电子显微分析技术、系列Ｃｈａｒｐｙ冲击试验等对Ｔｉ微合金钢模拟粗晶区的组织及韧性进行了研究。结果表明,随着８００－５００℃冷却时间的增加,该区域原始奥体（γ）晶粒长大并不严重;二次组织由上贝氏体为主逐渐转变为针状铁素体为主;珠光体的形态由非层片相间变为层片相间;Ｍ－Ａ组元由条状变为块状,且数量减少,因此韧性得以提高,电子衍射及ＥＤＸ分析还表明,该区域中     

Influence of interface mobility on the evolution of austenite–martensite grain assemblies during annealing

The quenching and partitioning (Q&P) process is a new heat treatment for the creation of advanced high-strength steels. This treatment consists of an initial partial or full austenitization, followed by a quench to form a controlled amount of martensite and an annealing step to partition carbon atoms from the martensite to the austenite. In this work, the microstructural evolution during annealing of martensite–austenite grain assemblies has been analyzed by means of a modeling approach that considers the influence of martensite–austenite interface migration on the kinetics of carbon partitioning. Carbide precipitation is precluded in the model, and three different assumptions about interface mobility are considered, ranging from a completely immobile interface to the relatively high mobility of an incoherent ferrite–austenite interface. Simulations indicate that different interface mobilities lead to profound differences in the evolution of microstructure that is predicted during annealing.     

The effect of prior ferrite formation on bainite and martensite transformation kinetics in advanced high-strength steels

Most advanced high-strength steel products contain complex phases, including ferrite, bainite and martensite, which form successively during elaboration. It is essential to understand the effect of prior ferrite transformation on the subsequent bainite and martensite transformation kinetics to achieve precise control of the final microstructure. Nevertheless, the effect of the interface between the prior formed ferrite and the residual austenite (α/γ), together with the related chemical heterogeneity at the interface, on the subsequent phase transformations has been studied only rarely, and remains unclear. This study pays particular attention to the effect of the α/γ interface and its related concentration gradients on bainite and martensite transformation. It is shown that the interface and its related concentration gradients can play a very significant role on the subsequent bainite or martensite transformation kinetics: it retards bainite transformation whereas it accelerates martensite transformation. It is revealed from microprobe wavelength-dispersive spectrometry analysis and model calculations that there are both manganese and carbon gradients in front of the α/γ interface at the end of the ferrite transformation holding. The subsequent bainite transformation kinetics is controlled by the competition between the acceleration effect of the interface boundary itself and the retardation effect of the higher alloying concentration near the interface. Martensite transformation should initiate at the pre-existing dislocations in the center of the residual austenite grains, where the C and Mn contents are the lowest. A simple martensite transformation kinetics model taking into account C heterogeneity is proposed that can describe well the martensite transformation kinetics following the prior ferrite transformation.     

微观组织对X52钢抗H2S腐蚀和开裂性能的影响

通过对X52钢进行热处理获得三种不同组织。SEM观察发现三种组织分别为铁素体/带状珠光体、马氏体/贝氏体和针状铁素体/回火马氏体。通过动电位极化、线性极化电阻、氢致开裂（HIC）实验和硫化物应力腐蚀开裂（SSC）实验,研究了不同热处理对X52钢在H₂S环境中的腐蚀与开裂行为的影响。结果表明马氏体/贝氏体显微组织由于位错密度很高且脆性大,因而腐蚀速率及HIC和SSC敏感性很高。铁素体/带状珠光体组织和针状铁素体/回火马氏体组织腐蚀速率及HIC和SSC敏感性很低。针状铁素体/回火马氏体组织由于不含带状组织且晶粒细小以及碳化物的析出,因此其HIC和SSC抗性优于铁素体/带状珠光体组织。     

Morphology and growth process of bainitic ferrite in steels

The morphologies and the formation mechanisms of isothermally transformed Widmanstatten ferrite and bainite in various steels were investigated. Widmanstatten ferrite often grew from the grain boundary ferrite allotriomorph formed by a diffusional mechanism in the temperature range of the upper C-curve, whereas, bainite grew directly from an austenite grain boundary showing its own C-curve in a TIT diagram at temperatures between Bs (bainite starting temperature) and Ms (martensite starting temperature). Both structures accompanied well-defined surface reliefs of the invariant plane strain-type, and were in the shape of a lath or a plate consisting of several parallel needle-like ferrite subunits with parallelogram cross sc:ctions. The crystallographic properties of Widmanstatten ferrite and upper bainite were similar to those of lath martensite. Therefore, it was concluded that the difference between bainitic ferrite and Widmanstatten ferrite existed only in the nucleation events, where both structures grew by the same mechanism.