海水浆体中钢的磨蚀行为

在围海造陆、航道疏浚等作业中,大量泥沙通过管道以浆体的形式输送。管体不仅发生磨损,还承受不同程度的腐蚀,从而使得管体产生严重的磨蚀失效。采用旋转型试验装置对比研究了海水浆体疏浚环境下普碳钢和低合金高强钢的磨蚀行为,测量了磨蚀失重中各磨蚀分量的所占比例,分析了试验钢的磨蚀失效方式及主要影响因素。试验结果表明,钢的磨蚀失重随速度的增加而迅速增加,在海水浆体环境下试验钢的磨蚀失重主要是磨损引起的,同时存在明显的腐蚀与磨损的交互作用。钢中适量的Cr含量有利于降低自然腐蚀电位,起到抑制腐蚀的作用,从而降低了腐蚀失重,提高耐磨蚀性能。普碳钢的磨蚀失效方式主要是犁沟、片层及磨蚀坑的形成;高强钢表面的犁沟较浅且窄,其磨蚀失效方式主要为磨蚀坑和片层的形成。     

300M超高强度钢电化学性能及应力腐蚀开裂

采用动电位扫描技术和慢应变速率拉伸试验研究了超高强度钢300M在3.5%NaCl溶液中的应力腐蚀行为,并利用扫描电镜观察了不同外加电位下的断口形貌.300M钢在3.5%NaCl溶液中开路电位下的应力腐蚀开裂机制为阳极溶解型,Cl-的存在明显地增加了材料的应力腐蚀开裂敏感性.阳极电位-600 mV下300M钢溶解速率加快,表现出较高的应力腐蚀开裂敏感性,断面收缩率损失由开路电路下的52.6%升高至99.5%,裂纹起源于表面点蚀坑处,应力腐蚀开裂为阳极溶解型机制.阴极电位-800 mV下材料处于阴极保护电位范围,表现出较低的应力腐蚀开裂敏感性,强度和韧度与空气中拉伸的数值相近,开裂机制为阳极溶解和氢致开裂协同作用.在更低电位(低于-950 mV)下,300M钢的应力腐蚀开裂机制为氢致开裂,在氢和拉应力的共同作用下表现出很大的应力腐蚀开裂敏感性.      

连退工艺对低合金高强钢HC300LA力学性能的影响

为了研究热处理工艺对低合金高强钢力学性能的影响,在连续退火条件下对HC300LA钢进行了模拟试验和工业试验。采用连续退火模拟试验机模拟连退生产工艺,研究了退火温度对低合金高强钢HC300LA力学性能的影响,获得了不同强度要求的试验钢。在实际生产过程中,分别研究了不同均热时间、快冷冷速条件下低合金高强钢HC300LA的力学性能变化情况。试验结果表明,随着退火温度的提高,低合金高强钢的强度下降,断后伸长率有所提高;随着均热时间的延长,低合金高强钢的强度有缓慢下降的趋势;随着快冷冷速的增加,低合金高强钢的强度增加,断后伸长率逐渐降低。     

溶解氧对X80管线钢腐蚀行为的影响及其机制

通过交流阻抗技术、动电位极化技术以及X射线衍射仪,研究了溶解氧含量对X80管线钢在库尔勒土壤模拟溶液中电化学行为的影响。结果表明:随着溶解氧含量的不断降低,腐蚀电流密度明显减小,金属腐蚀速率显著下降。这是因为溶解氧含量的不同会导致试样腐蚀产物差异,从而造成了试样在库尔勒土壤模拟溶液中腐蚀速率的变化。当溶解氧含量降到0.35mg/L时,金属电极表面生成了一层以FeCO3为主的腐蚀产物膜,FeCO3明显抑制了腐蚀反应的进行,产物膜对X80钢起到保护作用,此时试样腐蚀现象最不明显。     

JT245经济型耐候钢锈层的电化学研究

从电化学的角度出发,采用自然腐蚀电位测定、线性极化、阳极极化、交流阻抗等试验方法对经济型耐大气腐蚀钢JT245的锈层和裸钢的耐大气腐蚀性能进行了实验研究,并与Q235B及Corten A钢进行了对比.试验表明：JT245钢在大气腐蚀过程中生成的锈层,使电化学阳极过程受到显著的阻滞.从热力学上看,JT245钢的自然腐蚀电位正移;从动力学上看,锈层表面趋于钝化,阳极电流降低两个数量级以上.     

浓缩倍率对Q235B钢腐蚀行为的影响

针对中性介质中Q235B钢的腐蚀问题,使用旋转挂片腐蚀试验机进行试验,利用动态腐蚀失重法、动电位极化曲线、交流阻抗等电化学方法研究了Q235B钢在不同浓缩倍率模拟水样中的腐蚀行为。试验结果表明,随着溶液浓缩倍率的增大,Q235B钢的动态腐蚀速率出现增大的趋势。溶液中腐蚀性离子的浓度随着溶液浓缩倍率的增加而增大,同时,电化学试验结果表明,电荷传递电阻和膜电阻均逐渐减小,导致电化学反应过程的阻力变小,加快了Q235B钢的腐蚀,与动态腐蚀失重法腐蚀速率的变化相对应。     

不同脱氧方式对低合金高强钢局部腐蚀性能的影响

采用Al脱氧和Zr-Ti复合脱氧方式对低合金高强钢进行脱氧,利用金相显微镜和扫描电镜观察不同脱氧方式下钢材组织形貌以及夹杂物等方面的差异。根据俄罗斯GOST 9.911—89标准进行室内模拟海水加速腐蚀试验以及电化学试验,探究不同脱氧方式对低合金高强钢局部腐蚀稳定性的影响。研究结果表明,2种脱氧方式形成的夹杂物均为细小氧化物。传统Al脱氧样品中的夹杂物呈球状或呈线性汇集,Zr-Ti复合脱氧样品中的夹杂物则主要呈球状均匀分布。采用Zr-Ti复合脱氧样品的局部耐海水腐蚀性能比常规Al脱氧样品更优异,ZrTi复合脱氧钢平均腐蚀速率比Al脱氧钢减小17.27%。同时,采用Zr-Ti复合脱氧,能有效控制夹杂物的类型、尺寸与分布,尺寸主要分布在1~5μm,Zr-Ti复合氧化物弥散分布于基体中,降低了点蚀诱发敏感性,提高了其耐海水局部腐蚀稳定性。     

浓硫酸中904L不锈钢焊接接头的耐蚀性能

采用动电位极化曲线和电化学阻抗谱研究了904L不锈钢基体和焊接区在浓硫酸溶液中的腐蚀行为,并简要分析其腐蚀机理.实验结果表明:焊接区和基材的阴极极化曲线均为氢还原反应过程,而阳极极化曲线则有较大的差异.焊接区相对于基材,其自腐蚀电位降低且阳极电流增大,焊接对阳极反应起促进作用.904L不锈钢基体和焊接区的腐蚀主要由电化学反应步骤控制,两者的Nyquist图特征相似,均由单一的容抗弧构成,有一个时间常数.基体的耐蚀性能优于焊接区.      

霉菌对超高强钢腐蚀行为的影响

采用扫描Kelvin探针测试技术,研究了300M钢、Aermet100钢与超高强不锈钢在黄曲霉、黑曲霉、球毛壳霉、绳状青霉和杂色曲霉组成的混合霉菌菌种作用下的腐蚀行为.通过扫描电镜结合能谱分析对霉菌在三种超高强钢上的生长进行了观察和分析.300M钢试样上霉菌呈现分散式堆积生长,数量逐渐增加;Aermet100钢试样上霉菌呈现分散式单个生长方式,数量逐渐增加;超高强不锈钢上霉菌呈现放射式网状生长方式,数量急剧增加,在钢表面形成一层生物膜.霉菌实验后,三种超高强钢表面都发生一定的腐蚀.300M钢腐蚀最严重,蚀坑宽而浅;Aermet100钢次之,蚀坑窄而深;超高强不锈钢的耐蚀性最好.扫描Kelvin探针测试结果表明,霉菌一定程度上能促进300M钢和Aermet100钢的腐蚀,而对超高强度不锈钢的腐蚀行为有一定抑制作用.      

HC420LAD+Z低合金高强钢镀锌板腐蚀行为研究

研究了沉降量、腐蚀时间对HC420LAD+Z低合金高强钢镀锌板失重速率和腐蚀行为的影响。试验表明,在不同的沉降量下,镀锌板的腐蚀速率不同,随着沉降量的增加失重也增加;随着腐蚀时间增长,腐蚀产物覆盖在镀锌板表面,阻碍了纯锌层与溶液的接触,减缓了腐蚀的进行。通过显微组织观察,腐蚀产物呈雪花状。     

高强度低合金钢中纳米析出相对腐蚀行为影响的研究进展

高强度低合金钢中Nb、V和Ti等微合金化元素的纳米析出相对于调控钢的组织和性能具有重要作用,它可以确保钢基体同时拥有较高的力学性能和较强的耐蚀性能。本文基于国内外最新研究现状,系统阐述了纳米析出相在高强度低合金钢中的存在形态以及其对钢中氢扩散、均匀腐蚀、应力腐蚀开裂以及各类氢损伤等腐蚀行为的影响规律和机制。研究表明,纳米析出相对钢基体腐蚀行为的影响受其尺寸、数量和分布状态的控制。细小且与基体共格或半共格的纳米析出相不仅可以通过改善钢的微观组织（包括亚结构）提高耐蚀性能,其导致的不可逆氢陷阱及对氢扩散的强烈抑制作用还可以极大提高抗应力腐蚀和各类氢损伤的能力。而大尺寸的非共格析出相则可能恶化钢基体的耐蚀性能和促进氢损伤。最后展望了目前关注较少的纳米析出相对腐蚀疲劳影响的相关研究。明确纳米析出相对高强度低合金钢腐蚀行为的影响规律与机制将有助于更高品质耐蚀钢的开发和应用。      

Influence of Cr on reduction behavior of rust formed on low alloy steels in flowing 3. 5% NaCl solution

The reduction behavior of rust layer formed on carbon steel and on Cr- containing steels was investigated in flowing 3. 5mass% NaCl solution via potentiodynamic polarization curve, EPMA, XRD, and XPS. The results show that the weight loss of Cr- containing steels is lower than that of carbon steel. Fe3+ in the rust layer participated in the cathodic reaction with the corrosion process. Cr concentrated in the inner rust layer formed on the experimental steels, and exited in the form of Cr3+. This concentration behavior of Cr increases the corrosion potential of experimental steels and decreases the amount of Fe3O4 in the inner rust layer. Inhibition of reduction of rust results in a decrease of corrosion of metal. Moreover, inhibition of rust reduction suppresses the reduction reaction of oxygen, owing to the decrease of conductivity of rust layer. Therefore, the corrosion resistance of experimental steels can be improved by suppressing the cathodic reaction in flowing 3. 5 mass% NaCl solution.     

Surface Oxidation of the High-Strength Steels Electrodeposited with Cu or Fe and the Resultant Defect Formation in Their Coating during the Following Galvanizing and Galvannealing Processes

This study examined the surface oxidation of high-strength steels electrodeposited with Cu or Fe and the resultant defect formation in their coating during the following galvanizing and galvannealing processes. The high-strength steels were coated with an Cu or Fe layer by the electroplating method. Then, the coated steels were annealed in a reducing atmosphere, dipped in a molten zinc, and finally transformed into galvannealed steels through the galvannealing process. The formation of Si and Mn oxides on the surface of the high-strength steel was effectively suppressed, and the density of surface defects on the galvanized steel was significantly reduced by the pre-electrodeposition of Cu and Fe. This effect was more prominent for the steels electrodeposited at higher cathodic current densities. The finer electrodeposit layer formed at higher cathodic current density on the steels enabled the suppression of partial surface oxidation by Mn or Si and better wetting of Zn on the surface of the steels in the following galvanizing process. Furthermore, the pre-electrodeposited steels exhibited a smoother surface without surface cracks after the galvannealing process compared with the untreated steel. The diffusion of Fe and Zn in the Zn coating layer in the pre-electrodeposited steels appears to occur more uniformly during the galvannealing process due to the low density of surface defects induced by oxides.     

Ladle deoxidation,desulphurisation and inclusions in steel –Part 2: Observations in practice

Practical observations on the application of oxygen sensors, argon stirring, mould additions for rimstabilized steel. Discussion of ladle desulphurisation. Deformability of oxide inclusions, control of blowhole formation. Suppression of the precipitation of MnS by absorbing the dissolved sulphur with minute calcium aluminate particles entrained in liquid steel containing less than 0.002% S, and by rare earth treatments before casting steel containing 0.002 to 0.006% S. Aspects of steelmaking and casting clean steel, particularly high-strength, low-alloy steels.     

Investigation of stress corrosion cracking of the cast and forged steel in water

The aqueous stress corrosion behavior of cast steel and forged steel of the same heat has been examined. It was shown that the activation energy of crack growth of both cast and forged steels was identical,i.e., Q = 5540 cal/mol, and was comparable with the apparent diffusion activation energy of hydrogen in the steel. Theda/dt for cast and forged steel increased under both cathodic and anodic polarization conditions. Correspondingly, the steady-state hydrogen permeation flux increased steeply with the increase of polarizing current under either cathodic or anodic polarization. The influences of the polarization upon theda/dt and the hydrogen permeation flux were similar. TheK _ISCC of the cast steel was larger than that of the forged steel. This may be due to the observation that the steady-state permeation flux for the forged steel was twice as large as that of the cast steel. For both cast and forged steels the fracture modes were clearly dependent uponK _I at the crack tip, and a transition from dimple to quasi-cleavage or intergranular was observed on the fracture surfaces with decreasingK _I . Formerly Students at Beijing University of Iron and Steel Technology     

汽车用热基镀锌高强钢的研发进展

 日益复杂的服役环境,对汽车底盘及结构内件耐蚀性提出了更高要求,常规酸洗板已无法满足。以低合金高强钢(HSLA)、铁素体贝氏体钢(FB)和复相钢(CP)为代表的热基镀锌高强钢兼具热轧钢板的高成形性及镀层钢板的高耐蚀性,取代酸洗板用于汽车底盘和结构内件制造,不仅可以提高整车防腐性能,还可以降低零件修复、更换和再生产带来的能源消耗与碳排放,为汽车企业选材用材升级、降本增效提供了重要解决方案。汽车用热基镀锌高强钢对组织性能及表面质量的要求极其严格,国内外具备产品开发及稳定供货能力的企业很少。从化学成分、热轧、冷却、卷取和退火等工艺参数对微观组织及析出相的影响方面阐述了热基镀锌高强钢组织性能调控机理,以色差、漏镀和锌流纹等缺陷为例概述了热基镀锌高强钢表面问题产生的原因及相应的攻关方向。重点介绍了锌铝镁镀层在耐腐蚀方面的优势以及热基锌铝镁产品的主要应用途径。综述了国内外汽车用热基镀锌高强钢的生产及应用现状,指出进一步提升综合性能、改善表面质量和拓展极限规格是其发展方向。同时指出,需要持续关注热基镀锌高强钢生产和应用方面的问题,如色差、漏镀和锌流纹等表面问题,焊接飞溅、气孔和LME裂纹问题以及针对底盘特定腐蚀环境的耐蚀性数据积累及评价。     

沉管隧道钢壳在海水中的加速腐蚀

沉管隧道置于不易检查和维护的海泥区域，其钢壳结构受到海水的侵蚀，会缩短其服役周期，腐蚀严重则会影响沉管隧道的安全运行。深中通道（又称“深中大桥”）是国内首个钢壳式沉管隧道，耐久性要求100年，针对深中通道钢壳混凝土沉管的服役环境及超高的耐久性要求等诸多特征，且目前国内外可以借鉴的工程和研究很少，因此需要研究揭示钢壳外壁在海洋环境下的腐蚀机理和腐蚀发展规律。本文采用室内腐蚀模拟加速试验及电化学分析测试等，对深中通道沉管隧道钢壳所用Q390C低合金高强度结构钢在模拟海水条件下的腐蚀发生发展规律进行研究。研究发现Q390C在海水中腐蚀产物主要为Fe₃O₄、α-FeOOH和γ-FeOOH及少量CaCO₃，其均匀腐蚀和局部腐蚀速率都呈指数关系下降，最终趋于稳定。      

Influence of Inclusion on Corrosion Behavior of E36 Grade Low-alloy Steel in Cargo Oil Tank Bottom Plate Environment

Corrosion behavior of low-alloy steel was investigated in simulated cargo oil tank （COT） bottom plate service environment （10% NaCl solution, pH = 0.85）. The corrosion behavior of inclusion was studied by in-situ scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS）. It was found that pitting corrosion was inclined to occur around the place where inclusions exist. After initial corrosion, an area of 10-20μm in diameter was formed as a cireinate cathode around the edge of inclusion. MnS inclusion dissolved in the simulated COT corrosion solution before low-alloy steel matrix, and pitting was formed at the place where MnS dissolved. TiO2 inclusion dissolved in the simulated COT corrosion solution after low alloy steel matrix, and pitting was formed at the place where steel matrix dissolved. The corrosion tended to occur at the area where the curvature radius of inclusion is smaller. The size of round TiO2 inclusions had little influence on corrosion behavior in this certain environment.     

氧化物冶金在高强度低合金钢生产中的试验研究

通过对氧化物冶金技术在高强度低合金钢生产中的试验研究,探索采用氧化物冶金技术冶炼过程中转炉终点及LF精炼过程钢中的氧含量控制、正确的脱氧方式、脱氧合金元素的加入时机等,通过调节钢液成分,确保形核诱导粒子的生成;同时,利用扫描电镜分析了钢中夹杂物的成分、形貌、尺寸及夹杂物周围的组织形貌,并对试验钢板的性能进行了取样检测。结果表明,试验炉次氧化物冶金的效果良好且试验钢板性能很好。     

Effect of Environmental Factors on Electrochemical Behavior of X70 Pipeline Steel in Simulated Solution

 Potentiodynamic polarization measurement was used to investigate effects of temperature, dissolved oxygen concentration and pH on the electrochemical behavior of X70 pipeline steel in simulated solution according to the orthogonal testing method. The results showed that temperature, dissolved oxygen concentration and pH had great influence on corrosion current density (icorr) of X70 steel. Corrosion current density of X70 steel was most influenced by dissolved oxygen concentration in simulated solution. The corrosion degree of X70 steel was least under the environment of low temperature, deficit oxygen and weak acid.