国产桥梁缆索用热镀锌钢丝的质量及应用状况

介绍了桥梁缆索用镀锌钢丝的种类及主要质量要求,重点叙述了国产钢丝与国际标准及进口实物质量的比较,认为目前国产斜拉索用镀锌钢丝的标准水平和实物水平已进入国际先进领域,1995年全国14座斜拉桥使用国产钢丝建造。     

大跨度桥梁索缆模拟酸雨加速腐蚀行为研究

采用RH402定氢仪和盐雾腐蚀试验方法研究了索缆用镀锌钢丝在模拟酸雨腐蚀介质中的腐蚀行为,并用XRD表征腐蚀产物.结果表明,经2.5个月腐蚀后,位于索缆外层钢丝的镀锌层发生局部耗尽,而钢丝的氢含量随暴露时间延长呈增加趋势;经2个月和3个月腐蚀的索缆镀锌钢丝的主要腐蚀产物分别为3Zn(OH)_2·ZnSO_4·5H_2O和ZnSO_3·2H_2O与Fe_6(OH)_(12)CO_3.提出三个腐蚀阶段以描述索缆镀锌钢丝在模拟酸雨中的腐蚀过程.     

镀锌时间对桥梁缆索用钢丝组织及扭转性能的影响

采用扫描电镜(SEM)、透射电镜(TEM)观察并研究了镀锌时间对桥梁缆索用钢丝组织和扭转性能的影响。结果表明:当镀锌时间从0 s逐步增加至30、150、240 s时,钢丝扭转性能急剧下降,组织退化逐渐严重;随镀锌时间的增加,镀层厚度逐渐增加,Zn-Fe合金层中ζ相(脆性相)的厚度也随之增加,钢丝铁基体表面的微裂纹数量逐渐增加、分布更广、长度增加,钢丝内部索氏体结构被破坏越发严重,渗碳体球化现象逐渐严重,大颗粒状渗碳体周围伴随着微观缺陷的出现。因此,在保证镀锌层厚度足够的前提下,镀锌时间应尽可能短。     

缆索用高强热浸镀锌及锌铝合金钢丝的性能

采用SEM、EDS、间歇式中性盐雾加速试验和电化学测试等对热镀锌和热镀锌铝合金高强度钢丝的镀层结构和耐蚀性能进行了对比研究.结果表明:镀锌层由疏松且耐腐蚀性较差的纯Zn相和Fe-Zn相组成,而锌铝合金镀层组织主要由均匀致密且耐蚀性较好的Zn-Al相和Fe-Zn-Al相组成;镀锌铝合金钢丝的耐蚀能力是镀锌钢丝的2～3倍,...     

热处理对高强度冷拉钢丝塑性影响的研究

桥梁缆索钢丝通过高碳索氏体盘条冷拉拔生产,但镀锌和稳定化处理常导致钢丝扭转值显著降低,无法满足缆索指标要求.主要模拟镀锌和稳定化热处理过程对冷拉钢丝塑性的影响并开展研究,结果显示,在420 ～500℃温度范围内进行27s短时间热处理对钢丝塑性影响不明显,随460℃保温时间的延长钢丝扭转值先缓慢上升,后迅速降低,由27 s时的35次下降到72s的13次,钢丝塑性显著降低.保温初期扭转值缓慢上升主要与钢丝拉拔应力释放有关,进一步延长保温时间钢丝硬度不断提高,塑性降低,导致钢丝扭转值显著降低,继续增加保温时间将导致钢丝纤维状组织的渗碳体片层发生球化,硬度下降.     

模拟酸雨溶液中温度对桥梁索缆镀锌钢丝腐蚀行为影响

采用Tafel直线外推法、交流阻抗和加速腐蚀试验,研究了拉伸应力作用下高强度镀锌钢丝在不同温度的模拟酸雨溶液中的腐蚀行为,表征其腐蚀前后形貌.结果表明:1100 MPa拉伸应力作用下镀锌钢丝于60℃模拟酸雨溶液中的腐蚀速率为27.6μA/cm2,较室温下腐蚀速率增加31%;腐蚀产物由多孔膜状变为颗粒状堆积于微孔处;1100 MPa拉伸应力作用下镀锌钢丝于50℃盐雾腐蚀试验环境中的腐蚀速率为4.3 mg/dm2.d,较35℃时增加19%.     

宝钢超高强度镀锌钢丝中标世博轴工程

日前，宝钢二钢公司与浦江缆索厂签订了上海世博会标志性建筑——世博轴工程用600吨超高强度镀锌钢丝供货合同。标志着宝钢历时7年艰苦攻关，在国内独家掌握的超高强度镀锌钢丝制造技术已日臻成熟，除应用于国内外20余座大型桥梁外，又成功打入高级别大型建筑应用领域。     

铝包钢丝制品的工艺特点及市场展望

用连续挤压包覆和拉拔方法生产铝包钢丝是目前工艺最先进、生产效率高和产品质量最好的先进技术。对铝包钢丝与镀锌钢丝的性能进行了对比,分析并指出铝包钢丝制品在电力输送、电气化铁路建设、信息通讯及交通、建筑等领域都有广阔的市场。     

缆索用镀锌钢丝缠绕断裂分析

采用金相检验、扫描电镜观察以及化学成分分析等方法,对镀锌钢丝缠绕断裂试样进行全面检验。结果表明:钢丝表面擦伤是导致缠绕断裂的主要原因;同时,本文梳理造成表面伤损的各因素,进而提出了改进措施。     

热镀锌法提高B82 MnQL材料的抗拉强度研究

目的增强B82Mn QL材料的抗拉强度。方法以B82Mn QL盘条作为热镀锌的试验材料,利用拉伸试验机、反复弯曲试验机对其力学性能进行测试,借助金相显微镜、扫描电镜分析几种镀锌工艺下的横截面和轴向截面以及拉拔断口的组织形貌,同时测试显微硬度。结果 B82Mn QL盘条拉拔后钢丝的抗拉强度由原来的1250 MPa提高至1670 MPa。断面收缩率由32.5%下降至7%。采用新镀锌工艺和助镀配方,B82Mn QL钢丝镀锌后抗拉强度下降幅度为8%,低于传统的10%~15%。稳定化后B82Mn QL的扭转次数为20次左右,反复弯曲次数为6次左右,强度由1650 MPa提高至1710 MPa,硬度值比镀锌后有较大提高,由镀锌后的430HV升高至450HV,而且分布均匀。结论通过优化镀锌工艺,能大幅提高B82Mn QL盘条的抗拉强度。     

高硅铝铸件镀前浸锌溶液的研究

为了提高高硅铝铸件表面电镀层与基体的结合强度,对镀前浸锌溶液进行了改进和优化,并用电化学测试技术探讨了浸锌时间对电位的影响,结果表明,经过二次浸锌能保证镀层与高硅铝铸件基体之间良好的结合强度.     

AFM STUDY ON THE MORPHOLOGICAL CHANGE OF Zn ELECTRODEPOSIT

Nano-sized growth of zinc electrodeposit on the ferrite substrate has been studied by means of in situ scanning tunnel microscopy (STM) and atomic force micoscopy (AFM). It is found that the morphology of zinc electrodeposit varies from initial about 30nm granular crystals to layered platelet crystals with increasing deposition time by using in situ STM. With AFM, the results show that the platelet crystals are hexagonal in shape and the hexagonal platelet crystals form steps perpendicular to the growth direction by side-by-side stacking along the (0001)η surface. The mechanism of morphological change is discussed in details. It is proposed that these steps grow laterally as a result of the embedment of zinc ion clusters.     

ELECTROCHEMICAL NOISE ANALYSIS OF THE INFLUENCE OF THE Zn^2＋ IONS CONCENTRATION ON ZINC ELECTROPLATING

The influence of the concentration of Zn^2 ions on zinc electroplating process was investigated by means of electrochemical noise (EN) and cyclic voltammetry methods in conjunction with the scanning electron microscopy (SEM) technique. It was found that the EN generated during the electroplating of dentritic or large polymeric zinc deposit has large potential oscillation amplitude and positive potential drift while the compact zinc deposit possesses small noise amplitude and little potential drift. With the change of rate determining step from diffusion-control through mixed-contro! to activation-control, the maximum relative energy obtained from wavelet analysis defined from the region with larger scales to those with smaller scales, and the EDP (relative energy distribution plot) can be us, as “fingerprints” of EN to characterize the electroplating process and the deposit structure. The results also showed that electrochemical noise technique can give more information about the electrodeposit structure than other normal electrochemical measurements, such as linear potential sweep method and cyclic voltammetry, technique.     

Electrochemical deposition of nanocrystalline zinc on steel substrate from acid zincate bath

Nanocrystalline zinc coatings were deposited from acid zincate bath containing newly synthesized condensation product. The effect of bath constituents, pH, temperature and current density on the deposit nature were investigated through Hull cell experiments. Current efficiency, throwing power, cathodic polarization and corrosion behavior in 3.5 wt.% NaCl were studied under optimum concentration of additives. Salt spray test and electrochemical measurements showed that nanocrystalline zinc coatings have better corrosion resistance than the zinc coatings deposited from a simple acid zincate bath without additive. The surface morphology and thickness (cross section) of the zinc deposits were studied by scanning electron microscopy (SEM). The preferred orientation and average grain size of the zinc electrodeposit were obtained by X-ray diffraction analysis. The particle size was also characterized by TEM analysis. Energy X-ray diffraction (EDX) and FT-IR spectral analysis were carried out to determine the inclusion of addition agent in the deposit. The experimental results indicated that the addition of condensation product of thiamine hydrochloride (THC) and furfural (FFL) leads to a more uniform nanocrystalline deposition with the grain sizes varying from 20-22 nm.     

Electrodeposition of dixanthogen on surface of pyrrhotite electrode

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Relationship between corrosion resistance,microstructure and cobalt content in a Zn–Co alloy electroplated from alkaline electrolyte

Abstract

Various protective methods may be used to improve the corrosion resistance of steel, and the application of coatings of zinc and its alloys is one of them. The efficiency of zinc in corrosion protection is due to its behaviour as a sacrificial anode. To enhance the corrosion protection, zinc has been alloyed with more noble metals such as cobalt, nickel and iron. In this work zinc-cobalt alloys were electrodeposited onto steel from an alkaline electrolyte. The investigation was carried out on electrodeposits with low and high cobalt contents. An in situ study was performed using a TEM equipped with a hot stage to relate the heat treatment with changes in structure and, consequently, corrosion behaviour. The images of the specimens as deposited and after heat treatment showed the presence of a phase that was identified as Co₅Zn₂₁. However only the diffraction pattern of the heat treated specimen fitted the strongest lines for this compound. The corrosion tests showed differences in the corrosion resistance before and after heat treatment, for alloys with low and high cobalt. The heat treated specimens displayed more active behaviour.     

Material characteristics of Ni-P-B electrodeposits obtained from a sulfamate solution

Material properties of Ni-P-B alloy electrodeposits obtained from a Ni sulfamate bath were investigated as a function of the contents of the P and B sources (H₃PO₃ and the dimethyl amine borane complex (DMAB), respectively) with/without additives of 35 mg/L and the duty cycle by analyzing the chemical composition, microstructure, microhardness results, residual stress and stress-strain curves. SCC (stress corrosion cracking) resistance for a Ni-P-B electrodeposit was assessed by using the C-ring test. It was found that P and B are incorporated competitively during an electrodeposition and the sulfur from an additive is codeposited into the electrodeposit. As the contents of the alloying element sources of P and B increased, the crystallinity and the grain size of the electrodeposit decreased. The effect of boron on the crystallinity and grain size was also relatively larger than the phosphorus. It was explained by a restraining force against a grain growth and an adsorption of DMAB. Introduction of an additive into the bath retarded the crystallization and grain growth, which may be attributed to a change of the grain growth kinetics by the additive adsorbed on the substrate and electrodeposit surfaces during an electrodeposition. Hardness change with the heat treatment temperature was explained by a NiP_x and NiB_y precipitation which effectively impeded a grain growth and a precipitate coarsening leading to a recrystallization and grain growth. Moreover it was found that grain size was refined leading to a hardness increase with an increase of the P and B contents, which is in good agreement with the Hall-Petch relation. With an increase of the duty cycle, the grain size increased leading to a decrease in the yield strength and tensile strength. This could be described by the relatively faster kinetics of the hydrogen reduction reaction. A Ni-P-B electrodeposit formed inside a tube by using an anode assembly showed an excellent SCC resistance suggesting that an electrodeposition inside a tube can be used as a SCC mitigation method.     

复杂铜波导的内腔镀银工艺

铜波导作为功率传输器件,其内腔镀银质量的优劣将直接影响其传输性能的高低,但按照传统的电镀工艺很难保证复杂铜波导内腔获得均匀的银镀层。从产品的结构设计、加工工艺等方面,分析了影响复杂铜波导内腔镀银质量的主要因素,并结合表面处理过程控制、添加辅助阳极、改进电镀工艺等方面,提出了提高复杂铜波导内腔镀银质量的方案。     

Characterization of Zinc-Cobalt Electrodeposits

The structure and morphology of electrodeposits depend on many factors including temperature, current density, time of deposition and composition of the bath. The properties of an electrodeposit depend on its micro structure. For example corrosion and wear resistance, hardness, internal stress, strength, brightness, electrical conductivity, magnetic properties and leveling are all affected by structure.

The relationships between electroplating parameters such as current density, temperature, bath agitation and electrolyte composition have been investigated for the zinc-cobalt system. It was found that electrolyte composition and temperature affect both deposit composition and morphology. The cathodic current efficiency decreased with current density and hardness was raised with increasing cobalt content in the deposit.

Three powerful techniques were used to access the microstructure of zinc-cobalt deposits: scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that the alloy is constituted of a single phase of a solid solution of cobalt dissolved in zinc within an hexagonal crystal system. The deposit is porous and changes from dendritic to nodular with increasing cobalt content.     

Oxidation of Cr–C electroplating between 400 and 900 °C in air

The high temperature oxidation of Cr–C electroplated on a steel substrate was studied at 400–900 °C in air. Before oxidation, the deposit consisted primarily of C‐supersaturated, amorphous Cr grains. During oxidation, oxygen diffused inward, while Cr and the substrate elements such as Fe diffused outward. Carbon tended to escape, but some of it remained and existed mainly as graphite throughout the oxide layer and the Cr–C electrodeposit. A Cr₂O₃ oxide layer having dissolved Fe ions formed on the unoxidized, crystalline Cr layer. The Cr–C electrodeposit oxidized approximately parabolically, with a faster oxidation rate than bulk Cr.