镀锌钢丝干式拉拔工艺参数探讨

对镀锌钢丝干式拉拔时采用不同总压缩率和拉丝模工作锥角度生产的产品力学性能和锌层质量进行试验研究,获得最佳工艺参数:总压缩率应小于52%,拉丝模工作锥角度应使钢丝与模具的实际接触长度大于4.00 mm.     

热镀5%铝-锌钢板在青岛不同海水区带的腐蚀行为

开展了热镀5%铝-锌钢板在青岛不同海水区带的实海腐蚀测试,并利用电化学测试、失重腐蚀测试和扫描电镜首次研究了镀层的海水腐蚀行为.结果表明,由于腐蚀电流密度小,腐蚀产物具有保护性,镀层在全浸区表现出较好的耐蚀性能;镀层在潮差区出现不同程度的生物污损,而比较充分的充气条件又促进了镀层的氧化,其腐蚀速度比全浸区明显降低;镀层在飞溅区未出现生物污损,耐蚀性能最好,可能与良好的充气条件和腐蚀产物层的阻挡作用有关.镀层在飞溅区和潮差区的耐蚀性比全浸区分别提高197%和183%;但在全浸区和潮差区,镀层有局部腐蚀倾向.     

热镀55%铝-锌钢板在青岛不同海水区带的腐蚀行为

开展了热镀55%铝-锌钢板在青岛不同海水区带的实海腐蚀测试,并利用电化学测试、失重腐蚀测试和扫描电镜首次研究了镀层的海水腐蚀行为.结果表明,由于腐蚀电流密度小,腐蚀产物具有保护性,55%铝-锌镀层在全浸区的耐蚀性能比镀锌层和5%铝-锌镀层好;由于保护性锌的腐蚀产物被滞留在富铝的枝晶网络中,充分的充气条件又促进了镀层富铝相的钝化,镀层腐蚀的传质过程受到明显抑制,所以55%铝-锌镀层在潮差区和飞溅区的耐蚀性能显著优于全浸区,是全浸区的2到3倍;值得注意的是,镀层在全浸区出现较严重的局部腐蚀.     

球墨铸铁热浸镀铝的抗氧化性

为了延长铸铁工件的使用寿命,采用熔剂法将墨铸铁热浸镀铝,对镀层截面进行了形貌观察(SEM)、能谱分析(EDS)和衍射分析(XRD),测试了镀层的抗氧化性.结果表明,镀层由表面富铝层及扩散层构成,富铝层包含降温形成的针状FeAl3相,扩散层由FeAl3,Fe2Al5 物相组成,其形态呈舌状,并嵌入基体;氧化时镀层全部转变为扩散层,并能保持非常缓慢的退化速度,使球墨铸铁的抗氧化性显著提高.     

Development of phosphate inter layered hydroxyapatite coating for stainless steel implants

As zinc phosphate acts as a versatile material for potential biomedical applications, it was modified into a thin layer coating for orthopaedic applications in the present study. A unique layering system consisting of pure substrate (316L SS), thick Fe-Zn alloy layers, thin ZnP layer on which a hydroxyapatite (HA) layer, was developed and studied. The composition, surface morphology and corrosion resistance characteristics of the layering system was evaluated. The stability of the multi-layered coating system consisting of ZnP inter layer, was evaluated by subjecting to different extent of dissolution in aggressive physiological media followed by allowing for re-growth in simulated body fluid (SBF). The coating system revealed good stability.     

热镀锌钢卷力学性能GBDT预报模型

针对热镀锌钢卷力学性能预报建模条件属性选取难、预报精度不足的问题,研究了热镀锌钢卷力学性能梯度提升树(gradient boosting decision tree,GBDT)预报模型。利用互信息差算法综合评估工艺参数、化学成分和钢卷尺寸参数等条件属性的相对重要性以及属性之间冗余性,进行模型条件属性筛选;采用同分布原理进行样本划分,结合网格搜索法和交叉验证法优化模型参数,建立力学性能GBDT预报模型。将GBDT模型预报结果与随机森林(random forest,RF)、AdaBoost算法和BP神经网络的预报结果进行比较,比较表明GBDT模型优于其他模型,90%的数据样本预测的绝对误差小于14.24 MPa,94.6%的数据样本相对误差在6%范围内,具有更高的预测精度。     

热镀锌钢在模拟混凝土孔隙液中电化学腐蚀行为

采用电化学阻抗法研究了不同pH值、不同氯离子浓度条件下热镀锌钢在模拟混凝土孔隙液中的电化学腐蚀行为,建立了两种腐蚀等效电路模型,分析了腐蚀参数的变化规律.结果表明:当饱和Ca(OH)2溶液受到严重碳化(pH<11)时,热镀锌钢在该体系中会发生析氢反应,耐腐蚀性能降低;当饱和Ca(OH)2溶液受到较小程度的碳化(11.5≤pH<12.5)反而更有利于热镀锌钢的进一步钝化,耐腐蚀性能提高,pH=12.0时的年腐蚀率最小,仅为0.59μm/a,而pH=12.5时的年腐蚀速率约为1.21μm/a;当饱和Ca(OH)2溶液未碳化(pH=12.5)且NaC l浓度不超过0.5%时,热镀锌钢在该体系中所形成的钝化膜的耐蚀性能较好,不会发生析氢反应;随着碳化程度的增大,氯离子对热镀锌钢腐蚀作用加剧.     

热镀锌板上γ-APT硅烷自组装膜的制备及相容性

采用交流阻抗谱和接触角的方法研究了γ-APT硅烷的单分子自组装膜在热镀锌钢板表面的成膜过程,以及γ-APT硅烷自组装膜和γ-GPT硅烷的相容性.实验成功制备硅烷单分子自组装膜.组装开始时硅烷分子水解生成硅醇键的一端快速吸附在锌的表面并形成了Si—O—Zn键,硅烷分子之间的硅醇键随即脱水形成Si—O—Si键,从而自组装成为有序、规律排布的单分子自组装膜,组装10 h后膜的完整性最好,随后形成连续性较差的混杂膜.经过10 h组装后的γ-APT硅烷自组装膜与γ-GPT硅烷具有良好的相容性.     

Effect of hot-dip galvanizing processes on the microstructure and mechanical properties of 600-MPa hot-dip galvanized dual-phase steel

A C-Mn dual-phase steel was soaked at 800℃ for 90 s and then either rapidly cooled to 450℃ and held for 30 s (process A) or rapidly cooled to 350℃ and then reheated to 450℃ (process B) to simulate the hot-dip galvanizing process. The influence of the hot-dip galvanizing process on the microstructure and mechanical properties of 600-MPa hot-dip galvanized dual-phase steel (DP600) was investigated using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tensile tests. The results showed that, in the case of process A, the microstructure of DP600 was composed of ferrite, martensite, and a small amount of bainite. The granular bainite was formed in the hot-dip galvanizing stage, and martensite islands were formed in the final cooling stage after hot-dip galvanizing. By contrast, in the case of process B, the microstructure of the DP600 was composed of ferrite, martensite, bainite, and cementite. In addition, compared with the yield strength (YS) of the DP600 annealed by process A, that for the DP600 annealed by process B increased by approximately 50 MPa because of the tempering of the martensite formed during rapid cooling. The work-hardening coefficient (n value) of the DP600 steel annealed by process B clearly decreased because the increase of the YS affected the computation result for the n value. However, the ultimate tensile strength (UTS) and elongation (A₈₀) of the DP600 annealed by process B exhibited less variation compared with those of the DP600 annealed by process A. Therefore, DP600 with excellent comprehensive mechanical properties (YS=362 MPa, UTS=638 MPa, A₈₀=24.3%, n=0.17) was obtained via process A.     

组合材料芯片技术在Zn-Al合金镀层组分优选中的应用

组合材料芯片技术是材料研究的一种全新方法,能够高效、快速地筛选、优化新材料.按照组合材料芯片技术筛选结果,具有良好力学和耐蚀性能的Zn-Al合金中Al含量应控制在50%～75％,其中Al含量为72.6%时性能最佳.选择纯锌、55Al-Zn和72Al-Zn三种组分进行热浸镀和耐蚀性比较及机理研究.结果表明,72Al-Zn合金的耐蚀性稍优于55Al-Zn,都明显优于纯锌.这与组合材料芯片技术筛选结果一致,表明该组合材料芯片技术在优选Zn-Al耐蚀合金镀层组分方面是可靠的.