压水堆一回路主管道热老化现象研究现状

压水堆核电站一回路主管道材料最初为低合金管，经过不断发展，到如今二代核电站使用的双相不锈钢以及第三代核电站使用的316LN奥氏体不锈钢。这两个钢种都具有优异的力学性能、耐腐蚀性能以及抗辐照性能。但是长期在280～320℃下服役，双相不锈钢中的铁素体相会发生调幅分解，生成富Cr的α′相、富Fe的α相以及富Ni和Si的析出相G相；316LN在长期服役后在晶界附近位错塞积与杂质原子偏聚，并导致材料的晶间腐蚀敏感性增加。本文综述了目前两种材料的热老化性能研究现状，为二代核电站的延寿以及第三代核电站一回路主管道热老化研究方向提供参考。     

TDS2101经济型双相不锈钢焊接接头性能研究

近年来,节镍经济型双相不锈钢发展很快,不少国家都在进行研制,结合国内资源情况,经济型双相不锈钢具有很好的开发价值.氮是一种强烈的形成并扩大奥氏体的元素,对双相不锈钢的力学性能具有强化作用,同时能够提高焊缝的耐点蚀性能.研究了TDS 2101经济型双相不锈钢中N合金元素、焊接工艺、焊接热输入等对焊接热影响区的力学性能和抗...     

铸造双相不锈钢时效过程组织演变

借助光学显微镜（OM）、扫描电子显微镜（SEM）研究了铸造双相不锈钢在800 ℃时效不同时间的组织演变规律,并结合电子布氏硬度计（HBE-3000 A）研究时效过程组织转变对材料力学性能的影响。结果表明：时效过程中,双相不锈钢中铁素体相的比例随时效时间延长而逐渐减少,铁素体在时效处理过程中分解析出富Cr相和γ2相,富Cr相主要存在铁素体与奥氏体的晶界处,而γ2相则分布在铁素体基体上,并随着时效时间增加不断生成并长大。结合硬度测试结果发现,富Cr相的析出对材料硬度的提高起到了主要作用。     

时效时间对隔板材料SAF 2507性能和组织的影响

为了分析时效处理时间对SAF 2507双相不锈钢力学性能和显微组织的影响,研究了SAF2507双相不锈钢经不同热处理(固溶处理、固溶处理+350℃时效处理)后的力学性能和显微组织。结果表明:1070℃固溶处理的不锈钢具有良好的力学性能,冲击功平均值在230 J以上,组织为典型α相和γ相相间分布的条状组织;SAF 2507双相不锈钢经固溶处理后进行350℃时效处理时,随着时效时间的延长,不锈钢的组织由两相组织逐渐转变为多相组织,并且析出相逐渐增多、冲击功下降。     

热加工对Z3CN20-09M双相不锈钢组织及热老化冲击断裂行为的影响

铸态Z3CN20-09M双相不锈钢经1200℃热锻后,采用400℃热老化100、1000、3000 h处理。利用SEM和EBSD分析了铸态及锻态Z3CN20-09M双相不锈钢的显微组织和热老化1000、3000 h的冲击断口,采用纳米力学探针和冲击试验机测试了铸态及锻态Z3CN20-09M双相不锈钢热老化0、100、1000、3000 h微区力学性能和冲击性能。研究表明,经热加工后铁素体晶粒的取向呈现无序态,奥氏体晶粒由粗大的柱状晶经再结晶后变成细小的等轴晶。随热老化时间延长,铸态和锻态材料的冲击功都呈现下降趋势。热老化1000 h,铸态和锻态材料均呈现微孔聚集型断裂,断口出现大量韧窝花样。热老化3000 h,铸态和锻态材料均呈现韧窝/解理混合型断裂特征,铁素体发生脆性解理断裂,奥氏体以撕裂或呈微孔聚集型断裂。铁素体区域内取向不同导致锻态材料冲击断口解理特征明显少于铸态材料。     

TC4-DT合金不同热处理后的组织与性能

研究了热处理对TC4-DT合金棒材的显微组织、力学性能的影响。结果表明，经过（α＋β）区固溶处理后的TC4-DT合金显微组织为等轴状α相＋晶间β相构成的双相组织；在β区和α＋β）区双重处理后的显微组织为网篮组织。两相区固溶时效处理能明显提高材料的强度和塑性，可以得到比较好的综合力学性能。     

双相不锈钢及其焊接接头腐蚀研究进展

双相不锈钢耐点蚀、耐晶间腐蚀和耐氯化物应力腐蚀性能优良,是优良的海洋用金属材料,但其焊接接头常成为薄弱区而发生腐蚀问题.从材料因素综述了双相不锈钢腐蚀研究的进展.首先,总结了合金元素和热处理对双相不锈钢耐腐蚀性能的影响.合金元素分配及其引起的二次相析出及产生的元素贫化区、铁素体/奥氏体相比例的变化决定双相不锈钢的耐腐蚀...     

不锈钢高温组织与高温力学性能研究进展

主要综述了奥氏体不锈钢中δ相、铁素体不锈钢中σ相、马氏体不锈钢中Ms、双相不锈钢中γ相与α相的相对含量和沉淀硬化不锈钢中ε-Cu对不锈钢高温组织的影响;还综述了变形温度、应变速率和应变量对不锈钢高温力学性能的影响.     

基于相场法的Cr浓度对Fe-Cr合金中α′相析出的影响

基于Cahn-Hilliard扩散方程,采用时间和空间函数定义场变量描述成分随时间演变,通过相场模型对Fe-35Cr、Fe-40Cr和Fe-45Cr合金的失稳分解行为进行模拟研究,分析沉淀相体积分数、平均粒径和粒度分布变化。结果表明,随着时效时间增加,Fe-Cr合金中α′相由最初的蠕虫状,逐渐长大并向椭球状或棒状转变。随着Cr含量升高,α′相的平均半径逐渐增大,平衡体积分数逐渐增大,形核、长大及粗化速率加快。模拟结果有助于理解Fe-Cr合金的相分解和高温双相不锈钢的设计。     

模拟工况热老化对核电管道用Z3CN20-09M奥氏体不锈钢力学性能的影响

采用纳米压入法和微型杯突试验法对400℃模拟工况环境下热老化不同时长的Z3CN20-09M奥氏体不锈钢的力学性能进行研究,并用扫描电子显微镜对微型杯突断口形貌进行观察。结果表明,随着热老化时间的延长,铁素体相的纳米硬度值明显增大,奥氏体相纳米硬度值总体变化不明显,奥氏体不锈钢的微型杯突最大强度和屈服强度都有不同程度的增加,而比断裂能一直呈降低的规律,微型杯突断裂机理从以韧窝为主的微孔聚集型断裂变为微孔聚集型+准解理型断裂,这些变化都与热老化不同时长后两相亚结构的变化以及热老化3000 h以后铁素体发生调幅分解和调幅结构的粗化有关,材料出现脆化倾向。     

Corrosion behavior of a superduplex stainless steel in chloride aqueous solution

Super duplex stainless steels (SDSS) have been widely used as structural materials for chemical plants (especially in those engaged in phosphoric acid production), in the hydrometallurgy industries, and as materials for offshore applications due to their excellent corrosion resistance in chloride environments, compared with other commercial types of ferritic stainless steels. These alloys also possess superior weldability and better mechanical properties than austenitic stainless steels. However, due to their two-phase structure, the nature of which is very dependent on their composition and thermal history, the behavior of SDSS regarding localized corrosion appears difficult to predict, especially in chloride environments. To improve their final properties, the effect of the partition of the alloying elements between the two phases, and the composition and microstructure of each phase are the key to understanding the localized corrosion phenomena of SDSS. This paper concerns the effects of the SDSS microstructure and heat treatment on the SDSS corrosion resistance in aqueous solutions, containing different amounts of NaCl at room temperature.     

Effects of Rare Earth Metals addition and aging treatment on the corrosion resistance and mechanical properties of super duplex stainless steels

Effects of rare earth metals addition and aging treatment on corrosion resistance and mechanical properties of super duplex stainless steels were investigated using optical/SEM/TEM metallographic examination, an X-ray diffraction test, a potentiodynamic anodic polarization test and a tensile test. The performance of the experimental alloy with 0.32% REM addition was compared with commercial super duplex stainless steel such as SAF 2507 when they were exposed to solution annealing heat treatment and aging treatment. The corrosion resistance in Cl⁻ environments and mechanical properties of the experimental alloy were found superior to those of the commercial duplex stainless steel. The REM with larger atomic radii than those of Cr, Mo and W may fill vacancies inside the matrix and around the grain boundaries, retarding formation of harmful intermetallic σ and η phases. In addition, fine REM oxides/oxy-sulfides (1–3 μm) seemed to enhance the retardation effects. With REM additions, strength and ductility increased due to the phase and grain refinement caused by fine REM oxides and oxy-sulfides.     

Selektive Korrosion von Duplexstahl. Teil 2: Lokale Korrosionserscheinungen an Duplexstahl X2CrNiMoN22‐5‐3 unter Einwirkung von Chloriden und mechanisches Verhalten in Abhängigkeit vom Gefügezustand

Selective corrosion of duplex stainless steel. Part 2: Localized corrosion manifestations under exposure of chlorides on duplex stainless steel X2CrNiMoN22‐5‐3 and mechanical behavior in dependence of the microstructure In completion to part 1 of this paper this part deals with interrelations between localized corrosion manifestations, mechanical properties and the microstructure of duplex stainless steel X2CrNiMoN22‐5‐3. The pit formation on duplex stainless steels is substantially determined by the distribution of the alloying elements within single phases and by defects in the oxide layer. The positive properties of molybdenum become ineffective at thicker oxide layers due to the fact, that molybdate, which is responsible for inhibition of pitting, can not be formed. Depletion areas caused by precipitations are preferential attack places for corrosion. The influence of chlorides for duplex stainless steels in rolled and welded conditions is characterized by a logarithmic dependence.     

Complex magnetic and microstructural investigation of duplex stainless steel

Heat treatment induced microstructural processes were studied by different non-destructive magnetic methods in the present work. A commercial SAF 2507 type superduplex stainless steel was investigated. This alloy contains about 40% ferrite and 60% austenite phases in its initial condition. The ferrite phase is not stable, therefore it can decompose to sigma phase and secondary austenite due to heat treatment. All the mechanical, corrosion resistance and magnetic properties are strongly influenced by the microstructural changes. This study had two aims: to understand better the kinetics of the ferrite decomposition process and to study the application possibilities of the applied magnetic measurements. The results, which were supported by electronmicroscopic method (electron back scattered diffraction, EBSD), help us to understand better the microstructural changes in duplex stainless steels caused by heat treatment.     

Influence of sigma-phase formation on the localized corrosion behavior of a duplex stainless steel

Because of their austenitic-ferritic microstructures, duplex stainless steels offer a good combination of mechanical and corrosion resistance properties. However, heat treatments can lower the mechanical strength of these stainless steels as well as render them susceptible to intergranular corrosion (IGC) and pitting corrosion. In this study, a low-carbon (0.02%) duplex stainless steel is subjected to various heat treatments at 450 to 950 °C for 30 min to 10 h. The heat-treated samples then undergo ASTM IGC and pitting corrosion tests, and the results are correlated with the microstructures obtained after each heat treatment. In the absence of Cr₂₃C₆ precipitation, σ-phase precipitates render this duplex stainless steel susceptible to IGC and pitting corrosion. Even submicroscopic σ-phase precipitates are deleterious for IGC resistance. Longer-duration heat treatments (at 750 to 850 °C) induce chromium diffusion to replenish the chromium-depleted regions around the σ-phase precipitates and improve IGC resistance; pitting resistance, however, is not fully restored. Various mechanisms of σ-phase formation are discussed to show that regions adjacent to σ-phase are depleted of chromium and molybdenum. The effect of chemical composition (pitting resistance equivalent) on the pitting resistance of various stainless steels is also noted.     

Characterization of Impact Deformation Behavior of a Thermally Aged Duplex Stainless Steel by EBSD

The effect of thermal aging on phase transformation and impact toughness of an as-cast duplex stainless steel was investigated at room temperature. After long-term thermal aging, the impact toughness decreases significantly and the cracks initiate and propagate more easily. The plastic deformation ability of the ferrite phase decreases after thermal aging,which leads to the degradation of impact toughness. High stress concentration occurs on the grain boundaries of the austenite phase in the aged materials. Meanwhile, high-stress concentration areas are also observed in the austenite phase near the grain boundaries. After long-term thermal aging, pinned dislocations in ferrite and along phase boundaries lead to the high stress concentration. Micro-cracks preferentially initiate in the ferrite phase and propagate via separation of phase boundaries. The blocking influences of spinodal decomposition precipitates and G-phase precipitates are stronger than the effect of grain boundaries and phase boundaries on the dislocation movement.     

双相不锈钢特性及热轧中板生产要点

双相不锈钢兼有奥氏体不锈钢和铁素体不锈钢的优点,即具有优良的力学性能、耐蚀性,以及良好的焊接性而得到迅速发展。本文介绍了双相不锈钢的发展情况,其优良的耐腐蚀性能和力学性能,以及生产中钢板边裂和热处理σ相的控制要点。     

铌和钛微合金化超级马氏体不锈钢在海水中点蚀机制的研究(英文)

超级马氏体不锈钢(SMSS)在较高温度下具有良好的力学性能,并具有高的应力腐蚀断裂抗力和良好的可焊性,因此其在苛刻环境下的应用正日趋广泛。用于石油勘探的材料要求其具有优良的综合性能,双相不锈钢和超级双相不锈钢尽管价格昂贵,但仍在该领域得到了广泛应用,而具有技术和经济优势的SMSS能取代上述两种钢在石油勘探领域获得应用。通常,SMSS在许多加工行业也有望得到应用。本文研究了添加与未添加Nb或Ti的SMSS的点蚀机制和形貌。添加Nb和Ti是为了使敏化的影响减至最小,促进晶粒细化,并研究其对钢在海水中点蚀的影响,重点在于点蚀的形貌和腐蚀电位。添加与未添加Nb和Ti的钢具有相近的显微硬度和类似的回火马氏体组织。阳极极化曲线表明,用Nb微合金化的钢的腐蚀电位高于其他钢。对不同电位下点蚀的形成和扩展进行了重复试验,并采用光学显微镜进行观察。在工业用钢中,添加Ti的钢显示出了最佳的耐蚀性能——具有最高的腐蚀电位和较低的点蚀电位。添加Nb的钢尽管腐蚀电位较高,但其点蚀电位比未添加Nb的钢低。     

1Cr21Ni5Ti双相不锈钢不同温度时效脆化倾向研究

对1Cr21Ni5Ti双相不锈钢在400~600 ℃之间进行时效处理,测试其冲击韧性和力学性能,结合断口形貌和金相组织观察,研究1Cr21Ni5Ti 双相不锈钢不同温度时效脆化规律,提出抑制缓解脆化的工艺措施。结果表明:1Cr21Ni5Ti双相不锈钢在550 ℃时效的脆化倾向较小,脆化倾向最敏感的时效温度区间为450~500 ℃,在此区间时效时,铁素体脆化而发生解理或准解理断裂;同时,高的Ti/C比值增大450~500 ℃之间的脆化倾向,但高的Ti/C提高奥氏体的稳定性,显著降低600 ℃时效脆化倾向。在上述基础上,研究证明增加锻造比使奥氏体相产生足够变形并使其均匀分布,能有效阻止铁素体脆性裂纹的扩展,可以较大程度地降低脆化倾向。     

Corrosive-wear resistance of stainless steels for the impeller of slurry pump used in zinc hydrometallurgy process

1. IntroductionA number of pumps have been widely used in thefollowing fields: water power, electric power, smelting,coal mine, oil field, chemical plant, papermaking and soon. The wet parts of pump (mainly consists of impellerand pump shell etc.) can easily be damaged due to theerosion and corrosion of the slurry, namely the combinedcorrosion wear (C-W) or erosion-corrosion (E-C) [1-3]. Ithas been reported that C-W is responsible for more than5 % of the total wear encountered in industrial …