Nb对09CuPRe耐候钢在模拟工业大气腐蚀环境下耐蚀性的影响

Nb元素能细化钢的晶粒进而可影响其耐大气腐蚀性能。目前,关于Nb对耐候钢耐腐蚀性能影响的报道较少。在09CuPRe耐候钢中添加Nb元素,冶炼了4种不同Nb含量的耐候钢,于实验室作周期浸润加速腐蚀,以模拟耐候钢在工业大气干湿交替环境中的腐蚀。通过动电位极化曲线、电化学阻抗谱(EIS)和扫描电镜(SEM)等对不同Nb含量耐候钢的耐腐蚀性能进行了研究。结果表明,增大09CuPRe钢中Nb含量可以细化钢的晶粒,提高其耐蚀性能,显著降低其腐蚀速率,提高其自腐蚀电位,使其阳极电流密度减小,腐蚀锈层等效电阻与电荷传输电阻均随Nb含量增大呈上升趋势。     

稀土(Ce/La)对碳素钢耐海洋性大气腐蚀影响的电化学研究

稀土元素提高钢铁材料耐大气腐蚀性能的机理已有多种解释,但它本身所具有的缓蚀特性对提高钢铁材料耐候性的机理没有深入研究报道.为此,使用极化曲线、交流阻抗测试、锈层微观分析等方法研究了Ce/La混合稀土对碳素结构钢耐海洋性大气腐蚀性能的影响.结果表明:在中性氯化钠溶液中,钢中加入稀土后自腐蚀电位负移,阴极反应受到阻碍;随着稀土含量的增加,试验钢的锈层变得较为致密,厚度减薄,裂纹和空洞也明显减少,锈层中的电荷传递电阻呈上升趋势,而锈层电阻成下降趋势.对稀土提高钢铁材料耐候性的缓蚀机理进行了讨论.     

6061-T6铝合金多道搭接FSP腐蚀性能

将6061-T6铝合金进行空冷、水冷的多道搭接搅拌摩擦加工(multi-pass FSP),用金相显微镜、扫描电镜、透射电镜、浸泡腐蚀试验和电化学腐蚀等手段表征了核区材料的腐蚀性能。结果表明:母材经这两种冷却方式的FSP改性后,核区的晶粒明显细化,腐蚀性能有显著的提高;与母材相比,核区的腐蚀电压较高,腐蚀电流密度较小,阻抗较大;空冷FSP的核区材料比水冷的腐蚀性能更好。     

经济型耐大气腐蚀钢大气曝晒腐蚀性能研究

随着耐大气腐蚀钢的应用越来越广泛,掌握其耐大气腐蚀性能显得十分重要.采用电化学方法、电子探针等手段对JT345经济型耐大气腐蚀钢在北京、青岛、沈阳3地1年大气曝晒的试样进行分析研究,并采用Q235B和Corten A钢作为对比钢.电化学试验表明,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.电子探针与电子能谱分析结果表明,JT345钢的内锈层存在有效合金元素的富集,使内锈层结实、致密、牢固,抑制了腐蚀性物质的侵入,保护了基体金属.结果表明JT345经济型耐候钢具有优良的耐蚀性能,腐蚀率接近CortenA的水平,随着曝晒时间的延长,腐蚀率还将显著地下降,JT345钢的耐大气腐蚀的优越性将会更加充分体现出来.     

海洋大气环境下稀土及铌微合金钢的腐蚀行为研究

为给微合金钢的设计开发理论提供数据支撑,通过显微组织表征、干湿交替循环试验、中性盐雾试验和电化学分析等测试手段研究了稀土微合金钢和铌微合金钢在海洋大气环境中的腐蚀行为,对比分析了其耐腐蚀性能.结果表明:微合金钢的显微组织由铁素体和珠光体组成,并且铌微合金化有助于细化晶粒并能阻碍珠光体组织的形成.在腐蚀初期锈层的主要成分为γ-Fe2O3,γ-FeOOH,对于基体的保护性并不明显.随着暴露周期的延长,γ-FeOOH逐渐转化为α-FeOOH,提高了锈层对基体的保护作用,从而使腐蚀电流密度下降,提升了 2种钢的耐腐蚀性能.经过较长周期腐蚀后,铌微合金钢中晶粒的细化有利于增加表面锈层的致密性,α-FeOOH的含量相对较高,从而减慢了腐蚀速率.因此,相对于稀土微合金钢,铌微合金钢显示出更好的耐大气腐蚀性能.     

Q345qNHY跨海桥梁用钢的耐候性能研究

针对南钢开发的Q345qNHY新型跨海桥梁用钢,选用普通Q345qE钢作为对比材料,在模拟海洋大气环境的盐溶液中,进行了极化曲线测试和干湿交替加速腐蚀试验,比较了两种钢的动电位极化曲线和模拟干湿交替条件下的腐蚀速率。结果表明,Q345qNHY钢的耐海洋大气腐蚀性能显著优于普通桥梁钢。     

Si对碳钢耐大气腐蚀性能的影响

通过周浸加速腐蚀试验,采用SEM观察腐蚀试样表面和截面形貌,X射线能潽(EDAX)对锈层截面进行分析,X射线衍射(XRD)测定腐蚀产物的物相组成,在利用废钢中残Cu、P的基础上,研究Si对碳钢耐大气腐蚀性能的影响.结果表明,Cu、P能明显提高钢的耐腐蚀性能,而在模拟工业大气条件下Si的加入一定程度上减弱了钢的耐蚀性.     

超细晶粒高碳钢的研究现状及展望

晶粒超细化能同时提高材料的强度和韧性,是新一代钢铁材料研究与开发所追求的重要目标,而超细晶粒高碳钢则是新一代钢铁材料中具有重要发展前景的高性能结构材料.综述了超细晶粒高碳钢细化技术的主要研究成果,简述了高碳钢组织超细化的具体工艺、适用条件及应用情况等,并从工业应用角度分析了现有超细晶粒高碳钢制备技术的主要问题和研究方向.     

脱硫泵叶轮用新型不锈钢组织与性能研究

研究了固溶状态下新型不锈钢SRTZ1材料显微组织、力学及耐腐蚀性能,试验结果表明:固溶状态下,STRZ1试验钢为典型的由铁素体α和奥氏体γ组成的双相不锈钢材料,具有优异的力学性能。在具备良好的耐点蚀、均匀腐蚀性能的前提下,试验钢的耐冲刷腐蚀及空泡腐蚀性能明显优于对比材料1.4470的。试验钢可代替双相不锈钢材料1.4470作为脱硫泵叶轮用材料,提高叶轮使用寿命。     

钢铁晶粒超细化方法及其研究进展

综述了目前钢铁材料的各种晶粒细化方法、原理及其研究动态,展望了钢铁材料晶粒细化技术的研究前景,以期对新一代钢铁材料的研究和开发提供理论指导。分析认为今后钢铁晶粒超细化技术的研究方向主要有2个方面:一是继续深入讨论和探索晶粒超细化机理以及超细晶粒材料结构与性能的关系;二是开发适宜于工业化生产的钢铁晶粒超细化技术。     

A Model of Dynamic Recrystallization in Alloys during High Strain Plastic Deformation

1.IntroductionVerysmallrecrystallizedgrainswereobservedintheadiabaticshearbandsinmetalswhentheywereheavilydeformedathighstrainrates,whichwerezonesofhighlylocalizedplasticdeformation[1~5].Pak[1]foundthatshearbandsinacommerciallypuretitaniumwereconsistedofsmallgrainsof5o~3Oonmindiameterwithwell-definedboundaries.Chokshi[2],And.ade[3jandHinesI4Jalsoobservedtherecrystal-lizedgrainswith1oO~2Oonmdiameterswithintheshearbandsofcopper.Cho151showedthattherewereequiaxedcellswiththesizesof2oo~5oonminth…     

Study of the effect of grain size on the dynamic mechanical properties of microalloyed steels

In the present paper the effect of grain refinement on the dynamic response of ultra fine-grained (UFG) structures for C–Mn and HSLA steels is investigated. A physically based flow stress model (Khan-Huang-Liang, KHL) was used to predict the mechanical response of steel structures over a wide range of strain rates and grain sizes. However, the comparison was restricted to the bcc ferrite structures. In previous work [K. Muszka, P.D. Hodgson, J. Majta, A physical based modeling approach for the dynamic behavior of ultra fine-grained structures, J. Mater. Process. Technol. 177 (2006) 456–460] it was shown that the KHL model has better accuracy for structures with a higher level of refinement (below 1 μm) compared to other flow stress models (e.g. Zerrili-Armstrong model). In the present paper, simulation results using the KHL model were compared with experiments. To provide a wide range of the experimental data, a complex thermomechanical processing was applied. The mechanical behavior of the steels was examined utilizing quasi-static tension and dynamic compression tests. The application of the different deformation histories enabled to obtain complex microstructure evolution that was reflected in the level of ferrite refinement.     

Achievements of New Generation Steel Project in China

Major achievements of the national project, Fundamental Research on New Generation of Iron and Steel Materials in China (NG Steel). are reviewed in the paper. Uhrafine grained steel technology, based on deformarion induced ferrite trartsformation (DIFT)and successivechanges, is illustrated tor grain refinement in both plain low carbon steel and mieroalloyed steel. Delayed fracture resistance of alloy structure steel can be improved through prior austenite grain refinement. It is shown by results that nano scale precipitates play an important role to grain refinement in thin slab casting and rolling (TSCR)process. Progresses on super cleanliness, high homogeneity, welding and metallurgical process simulation are also briefly introduced.     

Achievements of New Generation Steel Project in China

Major achievements of the national project, Fundamental Research on New Generation of Iron and Steel Materials in China (NG Steel), are reviewed in the paper. Ultrafine grained steel technology, based on deformation induced ferrite transformation (DIFT)and successive microstructure changes, is illustrated for grain refinement in both plain low carbon steel and microalloyed steel. Delayed fracture resistance of alloy structure steel can be improved through prior austenite grain refinement. It is shown by results that nano scale precipitates play an important role to grain refinement in thin slab casting and rolling (TSCR)process. Progresses on super cleanliness, high homogeneity, welding and metallurgical process simulation are also briefly introduced.     

Mechanisms of Solidification Structure Improvement of Ultra Pure 17 wt% Cr Ferritic Stainless Steel by Ti,Nb Addition

The grain structures and the precipitates in the solidification microstructure of the ultra pure 17 wt% Cr ferritic stainless steels with different Ti and/or Nb micro-alloying were investigated both experimentally and theoretically.It was found by the grain structure observation that the addition of Ti or Nb to the steel reduced the grain size (D) and elongation factor (E),and improved the equiaxed grain proportion (P) and globularity factor (ξ).Among the four steels studied,the minimum grain size and maximum equiaxed grain proportion were obtained by jointly adding both Ti and Nb to the steel.The SEM observation indicated that several kinds of precipitations,such as TiN,MC (rich in Nb),Laves phase (Fe2Nb) and so on,formed in the corresponding steels.In addition,the results calculated using the Thermo-Calc software illustrated that TiN precipitates in the liquid at proper Ti and N contents.Meanwhile,the solidification interval (△T) was enlarged by the addition of Ti or Nb,and the effectiveness of Nb was stronger than Ti.Based on the experimental and calculation results,the mechanisms of grain refinement and increment in equiaxed grain proportion were discussed.     

Electron-beam rapid quenching of an ultra high-strength alloy steel

Rapid quenching using electron beams has been used to treat the surface layers of an ultra high-strength alloy steel. The microstructure of the treated surface layers has been investigated by optical, scanning and electron microscopy and by X-ray diffractometry. The microstructure produced by conventional solid state quenching of the same steel has also been examined for comparison. This microstructural study shows that the rapid quenching process leads to a high degree of grain refinement and an increase in solid solubility which, in turn, increases the amount of retained austenite. The lowering ofM _s temperature due to the high cooling rate and the increased solid solubility favour the formation of twinned martensite. These interlinked phenomena have increased the microhardness of the rapidly quenched layer considerably, with respect to that of the solid state quenched steel.     

超高强度船体结构钢的开发现状与趋势

为了给超超高强度船体结构钢的开发提供理论指导,从性能要求、强韧化机制和焊接性几个方面综述了超高强度船体结构钢的特征,结合国内外超高强度船体结构钢的开发现状,阐述了强化机制的调整是超高强度船体结构钢总体的发展趋势,其中以析出强化的增加为主要特点.通过分析各种析出强化粒子的引入在高强钢中的作用特点,认为综合考虑析出粒子的引入带来的细晶优化效果、组织转变优化效果与析出强化效果对韧性的影响是超高强度船体结构钢开发的技术难点之一,同时保持良好的焊接性是超高强度船体结构钢开发的另一技术难点.     

Suppression of Type IV fracture in welded joints of advanced ferritic power plant steels – effect of boron and nitrogen

Abstract

The effect of boron and nitrogen on the grain refinement in HAZ during heating and on the Type IV fracture in welded joints has been investigated for P92 and 9Cr–3W–3Co–VNb steel containing boron and or nitrogen. Creep tests were carried out at 650°C (923 K) for up to about 3 × 10⁴ h for base metals, simulated HAZ specimens and welded joints. The addition of boron of 47 to 139 ppm to 9Cr – 3W–3Co–VNb steel containing minimized nitrogen as low as 10–20 ppm suppresses the grain refinement in HAZ and hence suppresses the Type IV fracture in welded joints at low stresses. The addition of excess nitrogen of 0.06% causes the grain refinement during heating at around Ac3 temperature, in both conditions of no boron and high boron of 130 ppm. A combination of high boron of 130 ppm and low nitrogen of 80 ppm causes no grain refinement in HAZ during heating at around Ac3 temperature as well as significant improvement of creep rupture strength of base metal by fine MX nitrides without any formation of boron nitrides.     

数值模拟在超级钢焊接中的应用

本文综述了超级钢焊接温度场的数值模拟方法及研究现状,以及超级钢焊接热影响区微观组织的预测方法及研究现状,论述了超级钢的强化机制及细晶原理。超级钢作为一种性能好、成本低的新型材料,有着广阔的应用前景,但其焊接工艺尚不完善。数值模拟方法能够准确的模拟超级钢焊接温度场,预测超级钢焊接热影响区微观组织,这对了解超级钢焊接机理有很大帮助,并为优化焊接工艺提供指导和依据。