热镀锌工业设备用钢铁材料耐锌液腐蚀的研究进展

在进行热镀锌工艺生产时,稳定辊、沉没辊、轴套等设备在连续运转过程中与锌液发生强烈腐蚀反应,明显降低设备使用的寿命,是热镀锌行业亟待解决的问题之一。针对热镀锌工业钢铁设备存在的腐蚀问题,从材料和机理角度综述了几类工业设备用钢铁材料的耐锌液研究进展,总结了研究中存在的不足,介绍了对锌液腐蚀产生重要影响的"Sandelin"效应,指出基于"Sandelin"效应研究耐锌液腐蚀性材料将成为今后重要的研究方向。     

钢板热镀锌、铝生产线中辊件涂层的研究现状及发展趋势

钢板热镀锌、铝生产线中辊件常受熔融锌、铝液的腐蚀.概述了钢板热镀锌、铝生产线辊件涂层的研究现状,包括涂层材料、涂层结构、涂层工艺及封孔技术,提出了未来辊件耐熔融锌、铝涂层的发展趋势.     

热镀锌机组沉没辊轴头断裂分析

某厂冷轧带钢热镀锌机组锌锅中的沉没辊轴头发生断裂失效.通过光学、电子等手段分析了沉没辊轴头断裂失效的原因.结果表明,沉没辊轴头失效的主要原因是由于该沉没辊在堆焊修复后,在沉没辊的R角应力集中部位存在一些焊接缺陷,在一定的使用温度环境下,锌液渗入R角的缺陷,液体"锌"引起了轴头材料的脆化,"锌脆"削弱了金属材料的晶界结合力,损伤了其断裂性能,最后在一定的应力作用下,造成轴头的断裂失效.提出了提高沉没辊堆焊修复质量的合理建议.     

耐液锌腐蚀材料的研究进展

实现热镀锌内加热的关键因素是解决材料的耐液锌腐蚀问题.介绍了当前耐液锌腐蚀研究的现状,重点研究了目前常用的几种耐锌蚀材料,分析对比了其优缺点.探讨了用等离子喷涂陶瓷涂层耐液锌腐蚀的可行性,认为等离子喷涂耐液锌腐蚀陶瓷涂层在工业生产应用中有着光明的前景.     

自制铁铬锰合金耐液锌腐蚀性能的研究

针对应用于连续热镀锌生产线上辊类部件用材设计的奥氏体合金,系统研究了自制铁铬锰合金在工业锌液中(Zn-0.2%Al)的腐蚀行为及组织变化规律.研究表明:铁铬锰合金在工业锌液中具有良好的耐锌腐蚀能力,其腐蚀速率为8.11×10-4 g/(cm2.h),而316L的腐蚀速率为1.65×10-3 g/(cm2.h);铁铬锰合金在工业锌液中首先生成Fe2Al5,其稳定性较好,可长时间抑制铁锌反应,12 d后铁锌金属间化合物才开始出现,生成的δ(FeZn7)相中,因固溶了质量分数约为5.14%的Cr,使得δ相稳定性增加,进一提高了铁铬锰合金的耐锌腐蚀能力.以锰代镍来制取低成本的铁铬锰耐锌腐蚀合金具有可行性.     

热镀锌线沉没辊动力学建模与稳定性分析

为弄清热镀锌线锌锅内沉没辊的振动机理,须对其进行动力学建模。对锌锅内组件进行适当简化,分析沉没辊运动和受力情况,建立仅包含部分段带钢、沉没辊和轴承力学模型。在力学模型基础上,利用达朗贝尔原理建立相应的非线性动力学方程。求出系统静平衡位置,得到系统相对于静平衡位置动力学方程。利用李雅普诺夫稳定性理论对沉没辊运动稳定性进行分析,得到稳定性判据。动力学模型建立为以后研究沉没辊振动响应和振动控制奠定了基础。由运动稳定性判据可知适当的初始张力、带速和校正辊上推量有利于沉没辊稳定运行。     

国内外耐熔融锌腐蚀材料研究纵横

针对热镀锌行业中熔融锌液对材料产生强烈腐蚀的问题,综述了耐熔融锌腐蚀材料的发展现状和趋势.     

高温腐蚀工况下滑动轴承摩擦磨损试验机设计

滑动轴承广泛应用于镀锌线沉没辊支撑中,包含轴套和衬套两个部分。轴套和衬套都处于高温、腐蚀以及受载的工况中。所以镀锌线沉没辊滑动轴承很容易因受到腐蚀磨损而失效,滑动轴承副材料的使用寿命决定了整个镀锌线的运行时间。为了保证镀锌生产线的长期运行,目前最理想的方法是选择合适的滑动轴承副材料进行配对。为了筛选出具有良好匹配性能的材料,设计开发了模拟高温锌液环境下滑动轴承副材料的摩擦磨损试验机。试验机分为驱动系统、加载系统和加热系统三部分。驱动系统驱动轴套试样旋转;加载系统驱动衬套式样对轴套试样垂直施加载荷;井式加热炉加热锌锭至480℃模拟锌池环境;解决了驱动系统和加载系统的对中和绝缘问题。在试验机加工前,借助ANSYS分析了试验机在试验条件下的稳定性,确保传感器采集的信号具有较高的参考值。     

锌液对Fe-Al-B合金的腐蚀行为

针对当前热镀锌行业亟待解决的液态锌腐蚀问题,研究了新型耐熔锌腐蚀B合金在液态锌中的腐蚀行为,利用)察了腐蚀界面,并对腐蚀产物进行了能谱分析,初步探讨了Fe-Al-B合金在锌液中的腐蚀机制.结果表明,合金在锌液中的腐蚀是一个反应扩散和溶解的过程,开始时锌原子扩散很快,经过一段时间,在基体与锌液之间形成过渡层,扩散速度将大大减慢.加入Ti元素细化晶粒的Fe-Al-B合金,以其独特的耐液态锌腐蚀的网格状Fe-B共晶组织,阻碍了锌原子在合金基体中的扩散,使合金具有良好的耐蚀性能.     

深度法在Fe基合金耐熔锌腐蚀试验中的应用

熔融的液锌对Fe基合金有很强的腐蚀作用,判断Fe基合金的耐熔锌腐蚀性能对选择Fe基合金材料有重要的作用.近年来普遍采用深度法来测量Fe基合金在熔锌中的腐蚀速率.深度法具有方法简单、测量准确、腐蚀界面能够反映腐蚀过程以及多次测试的优点,已越来越被广泛地应用在Fe基合金耐锌蚀测试中.     

熔融锌液腐蚀的研究现状

对热镀锌连续生产中受熔融金属腐蚀部件的防护现状进行了分析,目前的研究工作可分为两大类:选择整体材料和表面处理.由于采用整体材料生产成本太高,且其耐熔融锌液腐蚀性能提高有限,采用表面处理提高抗锌液腐蚀成为目前研究的重点.表面处理有扩散渗硼、热喷涂层以及表面涂覆、隔离等方法,这些方法各有其特点.最后,对材料在熔融金属的现有腐蚀机理进行了总结,并指出了今后的发展方向.     

Enamel coating for protection of the 316 stainless steel against tribo-corrosion in molten zinc alloy at 460℃

Hot-dip galvanizing provides excellent corrosion and wear resistance for steels.However,the equipment itself,such as the steel roller,immerged in corrosive molten zinc suffers serious material loss during steel's production.Its protection has become the main technique problem in modern galvanizing line.In this study,an enamel coating was designed and prepared.Its tribo-corrosion in molten zinc alloy(Zn-0.2 wt%Al)at 460℃was investigated in comparison with the traditional WC-12 Co composite coating and the 316 stainless steel.Results indicate that the steel suffers serious material damage.Various corrosion products of Fe₂ Al₅ Znx form at the worn surface and the wear scar has reached 200μm deep after merely 5 h tribo-corrosion.Though the two coatings provide an improved tribo-corrosion resistance,for the WC-12 Co coating,its chemical reaction with the molten zinc increases brittleness and promotes cracking.The synergistic wear and corrosion cause its degradation.The enamel coating performs better during tribo-corrosion.It is chemically stable in molten zinc thus able to provide high corrosion resistance.In addition,the amorphous[Si04]network and the self-lubricating CaF₂ crystallite help it to build up an intact amorphous glaze layer readily at surface on sliding,leading to a reduced wear loss.During the whole tribo-corrosion process,the enamel coating is completely free of cracking,and the Zn penetration is inhibited.     

Anodic,polarisation of Nimocast 713 in sulphate melts containing zinc

Abstract

The hot corrosion of superalloys results from deposits of sulphates which form a liquid phase at the operating temperature. The rate of the hot corrosion can be inhibited by the addition of zinc to the sulphates. Anodic polarisation studies were carried out in a ternary eutectic salt mixture (78LiSO₄?13·5K₂S O₄?8·5Na₂S O₄, in mol.-%) at 900°C to ,determine whether the zinc inhibited the corrosion by affecting the electrode kinetics of the alloy, in this case Nimocast 713. The addition of 10 wt-%ZnSO₄ decreased the corrosion current and made the corrosion potential more positive by apparently changing the anode half cell potential. In the presence of zinc in the molten salt electrolyte, the alloy also exhibited some passivation over an anodic potential range of about 0·4 V. Examination of the microstructure of the electrodes at the metal/molten salt interface did not reveal any significant concentration of zinc.

MST/621     

Effect of zinc additions to NaCl-Na2SO4 molten salt mixture on hot corrosion of Nimocast 713

Hot corrosion studies were conducted at 900°C in a simulated combustion gas atmosphere containing sulphur trioxide at a partial pressure of 750 Pa on a nickel-base super alloy (Nimocast 713) partially immersed in various ZnSO₄–10wt-%NaCl–Na₂SO₄ molten salt mixtures. Weight changes were measured thermogravimetrically with time and it was found that the overall effect of the zinc sulphate addition was to reduce the degree of hot corrosion. Quantitative scanning electron microscopy investigations revealed no evidence of zinc in the attacked zone. It is postulated that the zinc reduces the chlorine activity in the system by forming a volatile chloride, thereby reducing the corrosive effect of the gas phase/molten salt mixtures. MST/507     

超音速火焰喷涂制备纳米和微米结构WC-η涂层的耐熔锌腐蚀性能

以钨氧化物、钴氧化物和炭黑为原料, 通过原位还原碳化反应制备纳米WC-η(η为Co₃W₃C、Co₆W₆C等缺碳相)复合粉, 粉末平均粒径为155 nm。该复合粉经团聚造粒制备得到具有高致密性和良好流动性的热喷涂粉末。以此纳米结构和商业化的微米结构低碳WC-12Co粉末作为喂料, 通过超音速火焰喷涂制备硬质合金涂层。结果表明, 纳米结构涂层中生成了一定量等轴状的W₂C相, 裂纹主要沿晶界或相界面扩展, 而微米结构涂层中除W₂C外还含有较多的W相, 主要包裹在WC颗粒表面, 穿晶断裂比例较高, 裂纹扩展路径较平滑。由于纳米结构涂层组织致密、晶粒细小、界面积大, 因此比微米结构涂层具有更高的硬度和断裂韧性。两种涂层在熔融锌液中浸泡200 h后, 微米结构涂层中产生了较多的横向和纵向裂纹, 导致材料的大面积剥落和基材腐蚀; 纳米结构涂层中没有发生锌的浸蚀, 在局部产生了少量纵向裂纹, 裂纹间隙被钨钴氧化物所填充, 反而抑制了熔锌对涂层的腐蚀, 因此纳米结构涂层表现出更高的耐熔锌腐蚀性能。     

不锈钢在熔融NaCl中的电化学-化学-稀释模型

为分析不锈钢在熔融NaCl中的腐蚀机制,通过850℃熔融NaCl完全浸没实验,测量了168 h内3种不锈钢的腐蚀动力学曲线,借助SEM、EPMA、EDS等设备表征了试样横截面形貌、元素分布等特征,研究了Ti元素对合金耐蚀性影响机制,采用X射线衍射仪检测了腐蚀24h后熔融盐成分和168 h后试样表面成分,建立了电化学-化学-稀释联合作用腐蚀模型.结果表明:在熔融NaCl腐蚀介质中,金属材料作为阳极被溶解,吸附氧得到电子变成O2-作为阴极;金属阳离子与O2-在熔融NaCl中发生化学反应,生成易挥发性氯化物逃逸系统;熔融盐作为传质媒介,稀释腐蚀层区域的腐蚀产物浓度,提高腐蚀速度.合金中电极电位最负的微量组元优先溶解后形成微小孔隙,增大了微阳极表面积,加速腐蚀反应过程.     

Theoretical model of the interfacial reactions between solid iron and liquid zinc-aluminium alloy

Steel strip is often coated with a layer of zinc in order to protect it against corrosion. One of the most commonly used coating processes is continuous hot dip galvanizing. In this process, the steel strip is immersed in a molten zinc bath containing small amounts of aluminium (less than 1 wt%). A model has been developed describing the kinetics of the galvanizing reactions that occur at the steel/liquid zinc interface (dissolution of iron, heterogeneous nucleation and growth of the intermetallic phase designated Fe₂Al₅Zn _x ). The model has been validated using experimental data available in the literature for a classical galvanizing treatment that lasts three seconds.     

Surface modification of aluminum alloys in molten salts containing CeCl3

A process for surface modification of A16061-T6 has been carried out in molten salts containing Ce such as a NaCl---SnCl₂---CeCl₃ melt at 200 °C. Samples treated in molten salts for 2 h were subsequently exposed to a NaCl solution for 30 days to evaluate resistance against pitting corrosion. The coating mechanism in molten salts and the pitting corrosion behavior of the coated material have been studied by electrochemical impedance spectroscopy. The results show that this coating technique enhances the pitting corrosion resistance of aluminum alloys in contact with sea water.