固溶温度对00Cr26Ni5Mo2Cu3Re超级双相不锈钢显微组织及耐蚀性能的影响

研究了固溶温度对超级双相不锈钢00Cr26Ni5Mo2Cu3Re显微组织及耐蚀性的影响。结果表明:随固溶温度的升高,双相不锈钢中铁素体含量逐渐增多,奥氏体含量逐渐减少,其显微硬度在1000～1050℃时增大明显。在1050～1125℃进行固溶处理,其耐晶间腐蚀性最好,建议2605超级双相不锈钢固溶处理工艺为1100℃保温2h,水冷。     

固溶温度对22Cr双相不锈钢组织与性能的影响

采用金相显微镜、扫描电镜、能谱分析、透射电镜和性能测试等方法,研究了固溶温度对22Cr双相不锈钢显微组织和性能的影响.结果表明:在950～1150 ℃范围,实验钢中α、γ两相含量与固溶温度呈近似直线关系;材料的显微硬度(HV)和强度(σb)先降后升,在1050 ℃时达到最小值;当固溶温度为950 ℃,组织中出现了σ相,σ相是导致22Cr双相不锈钢塑性、韧性下降的主要原因;随着固溶温度的升高,Cr、Mo的分配系数K变小,Ni的分配系数K增大,表明合金元素在α和γ相中浓度差别变小.     

固溶温度对铸造双相不锈钢微观组织及力学性能的影响

研究了不同固溶温度对00Cr22Ni5Mo3N铸造双相不锈钢微观组织和力学性能的影响.结果表明:在1 120～1 200℃温度区内固溶处理后,合金中的铁素体相比例随着固溶温度的升高而升高;冲击性能随着固溶温度的升高而降低;合金的拉伸强度和断面伸长率随固溶温度的升高变化不大;屈服强度在1 120～1 140℃温度阶段有所升高,在1 160～1 200℃屈服强度变化不大.     

固溶温度对2507双相不锈钢力学性能及耐蚀性的影响

利用光学显微镜、扫描电镜、XRD、拉伸试验机和电化学综合测试仪等研究了不同固溶温度对2507超级双相不锈钢组织、力学性能和耐蚀性的影响。采用Thermo-Calc热力学软件计算了2507双相不锈钢的热力学平衡相图,并与测试结果进行了对比。研究结果表明,经1050 ℃及以上温度固溶后,σ相溶解;随着固溶温度的升高,铁素体相含量增加,奥氏体相含量降低,α/γ相体积分数比增加;1050~1100 ℃固溶30 min并水冷时,双相不锈钢具有较好的综合力学性能,屈服强度、抗拉强度和伸长率分别大于600 MPa、840 MPa和35%。1050 ℃固溶30 min时,双相钢可获得较好的耐蚀性能。     

沿海建筑用00Cr25Ni7Mo4N双相不锈钢的热处理与性能

采用光学显微镜、扫描电镜、拉伸试验机和电化学工作站等,研究了固溶温度对00Cr25Ni7Mo4N双相不锈钢显微组织、力学性能和耐腐蚀性能的影响。结果表明,热轧和固溶温度为1025～1200℃时双相钢的显微组织都为铁素体+奥氏体双相组织,随着固溶温度升高,双相钢中α相含量不断增大,γ相含量不断减小,在固溶温度为1175℃时,双相钢中α∶γ相比例接近于1∶1;相较于热轧态双相钢,不同温度固溶处理后,双相钢的抗拉强度、规定塑性延伸强度和洛氏硬度有不同程度减小,而断后伸长率、断面收缩率和冲击吸收能量有不同程度增加;在固溶温度为1175℃时,双相钢的抗拉强度和规定塑性延伸强度较高,而断后伸长率、断面收缩率和冲击吸收能量都达到最大值。当固溶温度为1175℃时,双相钢的腐蚀电位最大、腐蚀电流密度最小,容抗弧半径和钝化膜电阻最大,弥散系数最接近于1,具有最佳的耐蚀性能。     

固溶温度对铸造双相不锈钢Cr25Mn10Mo4Ni2N组织及耐蚀性影响

通过中频感应炉熔炼制备了经济节Ni型铸造双相不锈钢Cr25Mn10Mo4Ni2N,利用OM、XRD、SEM和电化学工作站研究了1000~1150℃温度区间对其显微组织及固溶处理后在人工海水中耐蚀性能的影响。结果表明,固溶温度处于1000~1100℃区间时,材料的组织由α、γ及σ相组成。随着固溶温度升高,σ相的形貌由细小岛状向粗大岛状变化,且数量不断减少。当固溶温度升高至1120℃时,σ相完全消失,组织仅由α和γ两相组成。节Ni型双相不锈钢Cr25Mn10Mo4Ni2N经1120℃固溶时,其腐蚀电流密度最小,电荷转移电阻最大,耐蚀性能最佳;1150℃固溶时,耐蚀性能次之;在1020~1100℃温度区间固溶时,随着温度的升高σ相含量减少,材料耐蚀性能越好。     

固溶温度对ZG0Cr26Ni5Mo2N铸造双相不锈钢组织的影响

针对相比例控制的技术难点,以双相不锈钢OCr26Ni5Mo2N为基础,通过对铸造OCr25Ni5Mo2N双相不锈钢进行系列温度固溶处理,研究了固溶温度对铸造双相不锈钢组织的影响.研究结果表明:1)当固溶温度在980～1120℃时,随着固溶温度的提高,OCr25Ni5Mo2N钢中的铁素体相含量几乎呈直线上升.2)采用980～1120℃进行固溶处理时,铁素体基体上分布的长条状、块状和魏氏组织形态的奥氏体的原有尖角边界逐渐钝化,奥氏体本身分解、球化,弥散分布在铁素体基体上,固溶处理温度越高,奥氏体分解、球化程度越高.     

固溶处理对双相不锈钢组织与性能的影响

研究了固溶处理工艺对双相不锈钢组织及力学性能的影响。对经不同温度固溶处理后的试样进行了性能检测,并借助OM、SEM及电化学等分析手段对2205的显微组组织、析出物及耐腐蚀性能等进行了观察和分析,结果表明:低温固溶时,双相不锈钢中易产生大量的脆性析出相(σ相)是导致其塑性恶化及耐蚀性降低的原因;提高固溶温度可减少σ相的析出,有利于双相不锈钢的塑性和耐蚀性的改善;此外,双相不锈钢中铁素体含量随固溶温度升高而增大,但其所占比例受冷速影响较小。     

短时固溶处理温度对SAF2507超级双相不锈钢点蚀行为的影响

利用恒电位临界点蚀温度测试法和微观形貌观察法研究了短时固溶处理温度对SAF 2507超级双相不锈钢的微观形貌演变和点蚀行为的影响。结果表明,当固溶温度从1020℃提高到1150℃时,样品的铁素体的体积分数明显增加,而铁素体中的铬、钼等元素含量逐渐降低。SAF 2507超级双相不锈钢的临界点蚀温度(CPT)随着短时固溶处理温度的增加先升高后降低,在1100℃达到最大值。     

固溶温度对高导磁双相不锈钢回火组织和性能的影响

研究了固溶温度对1Cr17NilSi2Mn1高强度高导磁双相不锈钢淬火回火后组织和性能的影响.结果表明,在淬火 620℃回火处理之前,先经950～1150℃固溶处理后,抗拉强度和屈服强度随同溶温度升高逐渐升高,1050℃时达到最大值(872 MPa、725 MPa),同溶温度进一步升高,抗拉强度、屈服强度呈下降趋势;硬度随固溶温度升高先下降后升高,950℃固溶时硬度最低(93 HRB),在1100℃达最大(99 HRB).微观组织分析发现,随固溶温度的升高,马氏体含量逐渐增多,在1100℃时马氏体含量最多,相界面最清晰,固溶温度过高时,马氏体含量逐渐下降.分析表明,1050℃固溶,马氏体含量多,且力学性能良好,是该合金的理想固溶温度.     

Evaluation of Microstructure and Mechanical Properties in Dissimilar Austenitic/Super Duplex Stainless Steel Joint

To study the effect of chemical composition on microstructural features and mechanical properties of dissimilar joints between super duplex and austenitic stainless steels, welding was attempted by gas tungsten arc welding process with a super duplex (ER2594) and an austenitic (ER309LMo) stainless steel filler metal. While the austenitic weld metal had vermicular delta ferrite within austenitic matrix, super duplex stainless steel was mainly comprised of allotriomorphic grain boundary and Widmanstätten side plate austenite morphologies in the ferrite matrix. Also the heat-affected zone of austenitic base metal comprised of large austenite grains with little amounts of ferrite, whereas a coarse-grained ferritic region was observed in the heat-affected zone of super duplex base metal. Although both welded joints showed acceptable mechanical properties, the hardness and impact strength of the weld metal produced using super duplex filler metal were found to be better than that obtained by austenitic filler metal.     

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.     

Diffusion of Boron on Superplastic Duplex Stainless Steel

It is well known that duplex stainless steels having refined grain, structure exhibit superplasticity. In this paper, the diffusion of boron in the superplastic duplex stainless steels has been investigated. Boron diffuses through the interior of the grains in superplastic duplex stainless steels. On the other hand, in case of normal duplex stainless steel having the same chemical concentration, boron mainly diffuses along the grain boundaries and does not diffuse through the interior of the grains. Investigations using Auger electron microscopy for super plastic duplex stainless steels revealed, the Cr concentration is much higher than Fe concentration in boron diffused areas. These results indicate that superplasticity activates diffusion into the interiors of grains. Further, it seems that boron preferentially reacts with Cr rather than Fe. Moreover the distribution of Fe and Cr is changed by the diffusion of boron.     

超级双相不锈铸钢电化学极化表面腐蚀产物的XPS分析

采用X射线光电子能谱(XPS)技术研究了超级双相不锈铸钢在人工海水中经电化学极化后表面腐蚀产物。结果表明：双相不锈钢在人工海水中极化后的钝化膜表层主要以CrO₃、CrOOH、Cr(OH)₃和Fe(OH)₃等氢氧型化合物为主,内层主要以CrO₃、Cr₂O₃、FeO和Ni₂O₃等氧化物为主,同时膜内层存在Fe、Cr、Ni和Mo单质。MoO₄^2-和NH₄⁺吸附在钝化膜表面,对钝化膜起到保护作用。     

AOD精炼双相不锈钢00Cr22Ni5Mo3N的工艺实践

介绍了用AOD精炼双相不锈钢的工艺特点，进行了2t的AOD精炼炉精炼00Cr22Ni5Mo3N双相不锈钢的实践，精炼出了合金钢，并浇铸了化工箱体转轮扇面。铸造件的力学性能和金相组织符合技术条件要求。给出了双相不锈钢的精炼和浇注生产中的几点注意事项。     

Passivation Behavior of 2507 Super Duplex Stainless Steel in Hot Concentrated Seawater: Influence of Temperature and Seawater Concentration

The electrochemical behavior and passivation properties of 2507 super duplex stainless steel (SDSS) in the hot concentrated seawater with different concentrations at different temperatures are characterized by electrochemical methods and X-ray photoelectron spectroscopy. The passive film formed on 2507 SDSS belongs to n-type semiconductor and mainly composed of hydroxides and oxides of Fe and Cr under all circumstances. The protectiveness of the passive film decreases with the increase in temperature mainly because of the increase in defect density in the passive film. The corrosion resistance of 2507 decreases with the increase in seawater concentration, and the critical pitting temperature also decreases.     

时效处理对22Gr双相不锈钢机械性能的影响

采用拉伸、疲劳试验,研究了时效处理对22Gr双相不锈钢断裂性能和疲劳性能的影响及其变化规律,并按断口形貌探讨了22Cr双相不锈钢在不同试验条件下的断裂机制,为22Cr双相不锈钢的使用提供参考。     

Wear and corrosion behaviors of duplex surface treated 316L austenitic stainless steel via combination of boriding and chromizing

Surface of low carbon austenitic stainless steel (AISI 316L) was modified by duplex surface treatment to improve its wear behavior, without compromising corrosion resistance of the steel. The duplex surface treating process composed of pack boriding (B) and pack chromizing (Cr) stages. Some specimens were duplex surface treated by boriding followed by chromizing (B–Cr), while some others were treated via chromizing followed by boriding (Cr–B), to evaluate the effect of duplex treatment sequence on wear and corrosion resistances. Microstructural studies, phase identification, wear and corrosion behaviors of the specimens were evaluated by scanning electron microscope (SEM), X-ray diffractometer (XRD), pin-on-disc wear test, and potentiostat electrochemical test. The results show that the precedence of boriding stage to chromizing stage makes significant improvement in wear and corrosion resistances of the duplex coating, whereas B-Cr coating provided superior wear resistances (up to 49%) and reduced corrosion rate (up to 4.5 times) in comparison to Cr-B and boriding coatings. Corrosion resistance of B-Cr coating was comparable to that of the stainless steel.     

Influence of dissolved oxygen content on the bacteria‐induced ennoblement of stainless steels in seawater and its consequence on the localized corrosion risk

The ennoblement of stainless steel (e.g., the increase of open circuit potential [OCP]) is associated with bacterial colonization. This increases the risk of localized corrosion as the critical pitting/crevice potential can be overcome, especially for lower grade stainless steel. In this study, we assessed the influence of dissolved oxygen content (DOC) on the crevice corrosion of duplex and super duplex stainless steels. In addition, we used DNA amplicon sequencing to identify the bacteria most likely associated with the ennoblement. Above approximately 100 parts per billion (ppb) of dissolved oxygen, the ennoblement of OCP was observed leading to an increased risk of localized corrosion. Below approximately 100 ppb of dissolved oxygen, no ennoblement occurred and the risk of localized corrosion was reduced. We identified certain hydrocarbon‐degrading bacteria whose presence correlated with the ennoblement of super duplex stainless steel at saturated DOC. The role of these bacteria is not clear yet, but their distribution indicates a possible involvement in stainless steel ennoblement in seawater.