Early-stage nucleation of manganese sulfide particle and its processing evolution in Fe—3wt.%Si alloys

Manganese sulfide is often referred to as one of important inhibitors in grain-oriented electrical steels, which is of great importance to yield strong Goss texture. However, the early stage of nucleation for such inhibitors and their evolution during the processing has not been well understood. In present work we selected a Fe--3.12wt.%Si--0.11wt.%Mn--0.021wt.%S model system and used FE-SEM and atom probe tomography (APT) to investigate the precipitation behavior of MnS inhibitors at near atomic scale. It was found that the Si--S enriched clusters with sizes of 5--15 nm were formed close to the MnS particles. The density of inhibitors decreased after large pseudo-plane-strain compression because of the effect of dislocation motion, and then slightly increased again when sample was aged at 200°C for 48 h. The dislocations and grain boundaries can act as fast diffusion paths and assist the reemergence of Si--S enriched clusters.     

管线钢抗氢致裂纹（HIC）性能影响因素浅析

通过工业生产中X60/X65管线钢的抗HIC性能试验,分析了非金属夹杂物、显微组织等对管线钢抗HIC性能的影响,并对出现裂纹的断面进行了扫描电镜分析,结果表明,MnS夹杂物和带状组织是影响抗HIC性能的主要因素。     

超分散纳米MnS的合成与表征

制得表面修饰纳米γ-MnS,表征了其组成和结构,指出产物分子以络合结构形式存在。产物有较好热稳定性和化学稳定性,且粒径小,分布窄,分散性好。其UV-Vis吸收峰有“蓝移”现象,表明其量子尺寸效应,为新型纳米光电化学催化剂的开发奠定了基础。     

保温时间对U75V重轨钢中夹杂物的影响

通过真空感应炉冶炼U75V重轨钢,在箱式电阻炉中将试样加热到1100 ℃,分别保温30、60、90 min,使用扫描电镜对夹杂物进行分析。结果表明,未经热处理的试验钢中,夹杂物类型主要有3种,分别为MnS、Al₂O₃及MnS-Al₂O₃夹杂物。长条状MnS夹杂物随保温时间的延长有分裂趋势,保温90 min时,MnS夹杂物平均圆形度为1.86,与未经热处理的试样相比,圆形度降低了1.52。Al₂O₃夹杂物在保温30、60 min时,形态、大小变化不大,但数量减少,保温90 min时,部分Al₂O₃夹杂物尖锐棱角发生钝化,圆形度略微减小。试样经1100 ℃均热处理后,复合夹杂物增多,随着保温时间的延长,MnS-Al₂O₃夹杂物中MnS和Al₂O₃成分分布发生变化,外层的Al₂O₃有向内部运动的趋势,保温90 min时,夹杂物内部Al₂O₃富集,外包裹层中Al₂O₃含量极低,MnS-Al₂O₃夹杂物逐渐形成以Al₂O₃为核心,MnS外层包裹的复合型夹杂物,从而减小了对钢基体的损伤。     

碲处理对20CrMnTi齿轮钢中MnS夹杂物改性效果

 为了研究碲处理对钢中MnS夹杂物形貌的影响,利用SEM-EDS扫描电镜,研究了20CrMnTi钢中添加高纯碲粉后MnS夹杂物的改性效果。试验结果表明,碲处理使钢中夹杂物的平均长宽比由3.17降至1.83,球化效果较为明显;当碲硫比控制在0.33时,不同硫含量的钢中夹杂物形貌有明显差异,硫质量分数为0.21%的钢中,形成了MnS镶嵌在碲化物中的大型夹杂,而在硫质量分数为0.11%的钢中,形成了碲化物包裹MnS的复合夹杂;当碲硫比为3.21时,发现钢中出现了单独存在的高碲相,MnS外层的碲化物层也较厚,改性率仅为8.75%,这表明高碲硫比并不能提高硫化物改性的数量。     

The influence of lithium on the kinetics and mechanism of manganese sulphidation

The influence of monovalent impurity (lithium) on the kinetics of manganese sulphidation has been studied as a function of temperature (800-1000 °C) and sulphur pressure (1-10⁴ Pa) using microthermogravimetric technique. It has been found that the incorporation of lithium atoms into the growing sulphide scale on manganese decreases the rate of the reaction of about two orders of magnitude. These results are in quantitative agreement with theoretical predictions following from the Hauffe-Wagner theory of alloy oxidation.     

碲处理含硫钢加热过程中MnS-MnTe夹杂物的演变

通过实验室加热试验和热力学计算研究了碲处理含硫钢加热过程中MnS-MnTe夹杂物的演变,得出含硫钢加热过程中MnS-MnTe类夹杂物变化的规律与机理。随着钢中碲含量和Te/S质量比的升高,MnS-MnTe类夹杂物的平均直径增大,平均长径比降低。加热处理后,钢中MnS和MnTe充分生长和析出,碲处理对MnS夹杂物的改性效果相比起热处理前更为明显。随着钢中Te/S质量比的增大,夹杂物的平均直径更大、数密度更低、面积分数更高。随着钢中Te/S质量比的升高,MnS-MnTe类夹杂物中树枝状的Ⅱ类比例降低,球形的I类和块状的Ⅲ类比例升高。在当前试验条件下,当钢中Te/S质量比达到0.33时,钢中MnS开始析出温度低于钢液开始凝固温度,有利于抑制共晶反应中在晶界处Ⅱ类MnS的生成。当Te/S质量比大于1.35后,钢中出现较多球形的纯MnTe夹杂物。     

冷却强度对超高硫中碳钢方坯凝固过程MnS生长的影响

 中碳超高硫易切削钢SAE144是兼具力学性能与切削性能的结构钢,用于制造汽车发动机密封阀件等,产品多采用转炉/电炉→LF精炼→连铸小方坯→线棒材热轧→冷拉及机加工成型流程生产,近年来市场热度稳步提升。若钢中MnS尺寸过大,零件加工使用过程易发生探伤不合、切削性能差、带状组织严重、力学性能各相异性显著,甚至拉拔加工断裂等问题。MnS夹杂物多在铸坯凝固后期形成,随着轧制与钢基体同步变形,控制该类钢种铸坯内MnS原始尺寸成为控制热轧材中MnS夹杂物形态及尺寸的最关键环节。为控制热轧超高硫中碳钢盘条中MnS夹杂物,利用钢坯凝固数值模拟、第二相析出理论、Ostwald熟化理论计算分析了160 mm2钢坯中硫元素偏析及MnS的生成、长大和熟化过程。计算结果表明,当固相分数f_s为0.446、硫微观偏析比达到2.19时,铸坯在凝固末期生成MnS。凝固过程中MnS的生长过程决定了钢坯中MnS颗粒的直径。理论计算表明,当连铸二次冷却水量固定为0.6L/kg时,拉速为1.6、2.1和2.6 m/min时,160 mm2方坯中心的MnS分别增长到30.6、32.2和34.6 μm,与实际测试结果一致。控制该类钢种线材中MnS尺寸的关键是提高二冷区的冷却强度,降低连铸拉速。基于该系列计算方法,提出了160 mm2钢坯中与MnS直径控制目标相匹配的连铸工艺参数控制范围。     

Influence of the dissolution of MnS inclusions under free corrosion and potentiostatic conditions on the composition of passive films and the electrochemical behaviour of stainless steels

The influence of the dissolution of MnS inclusions at the OCP value and 400 mV versus SCE on the chemical composition of passive films and the electrochemical behaviour of resulfurized austenitic stainless steel was studied in 1 M NaClO₄, pH 3, solution using SIMS, XPS, electrochemical impedance spectroscopy and the electrochemical microcell technique. The electrochemical dissolution (at 400 mV versus SCE) of inclusions occurred uniformly along the interface and this process was almost complete after 25 min immersion. A small amount of sulfur was detected on the matrix that exhibited a wide passive range. By contrast, the dissolution process under free corrosion was not uniform along the interface and numerous inclusions were partly dissolved. Grains close to the completely dissolved inclusions showed an active behaviour. This was connected with the adsorption of a large number of sulfur on the surface. In the two cases, the presence of sulfur species on the surface was also found to enhance the kinetics of cathodic reactions.     

车轴钢铸锭中MnS的生成、长大、熟化规律分析

 为降低大尺寸MnS夹杂物引起的车轴磁粉探伤不合格率,利用第二相析出理论以及铸锭凝固数值模拟计算相结合,计算分析了车轴钢铸锭中MnS生成、长大、熟化规律。计算结果显示,MnS形核核心尺寸与熟化过程尺寸增加均为纳米级,凝固过程MnS的长大决定凝固完成时MnS粒子直径,理论计算得到车轴钢铸锭竖直中心线上冒口、中心、底部位置对应的MnS长大后尺寸分别为156.35、107.37和94.96 μm,中心处MnS尺寸为连铸工艺条件下的2倍,与实际检测结果相符。钢锭凝固过程缓慢是MnS易于长大的直接原因,显著区别于连铸过程。在现有工艺条件下,为控制车轴钢模铸钢MnS尺寸,关键在于降低钢液硫质量分数以及控制硫偏析。控制车轴成品中MnS夹杂物不超过1.5级,需降低钢液中w([S])至0.004 3%以下。