Ultrasonic inspection of stainless steel butt welds using horizontally polarized shear waves

Inspection of austenitic stainless steel weldments by conventional ultrasonic means is fundamentally limited by the textured, columnar grain structure of the weld metal. It is shown that, for selected angles of incidence, shear waves normally polarized with respect to the columnar grains can pass through the weld metal-base metal interface without partial reflection. As a consequence, the inspectability of stainless steel weldments can be improved. The operation of a low frequency, ultrasonic system for stainless steel butt weldments is demonstrated.     

铸造奥氏体不锈钢中铁素体与奥氏体位向关系及其对声衰减的影响

研究了铸造奥氏体不锈钢中铁素体与奥氏体位向关系及其对超声散射衰减的影响.利用电子背散射衍射技术表征了两相的晶体取向及其位向关系,基于真实的铁素体形貌建立了二维声传播各向异性模型并利用时域有限差分法进行了计算,分析了不同位向关系、铁素体形貌特征对声衰减系数的影响规律并进行了实验验证.结果表明：铸造奥氏体不锈钢奥氏体晶粒中散布着形状复杂的铁素体,典型铁素体形貌为条状和岛状;铁素体与奥氏体的位向关系以Kurdjumov-Sachs关系为主,少量满足Nishiyama-Wassermann关系.对声传播过程进行计算,发现两相位向关系和铁素体形貌协同作用影响超声波传播,在较高检测频率（15 MHz）下对散射衰减的影响不能忽略.结合“原位”实验对奥氏体<101>柱状晶粒的声衰减影响因素进行了定量分析,发现对于单一铸造奥氏体晶粒,晶粒内部取向不均匀性、奥氏体-铁素体位向关系以及奥氏体晶粒内铁素体形态都是超声散射衰减的主要原因.     

奥氏体不锈钢窄间隙焊缝侧壁未熔合相控阵超声检测*

针对核电站主管道奥氏体不锈钢窄间隙焊缝侧壁未熔合超声检测困难的问题,该文开展基于电子背散射衍射技术的相控阵超声检测研究,并结合全聚焦方法和相位相干成像方法抑制结构噪声。利用电子背散射衍射技术建立壁厚69.5 mm,且同时包含母材和焊缝的奥氏体不锈钢窄间隙焊缝模型。沿焊缝熔合线设置深度26.5 mm、高度3.0 mm的侧壁未熔合,经过仿真优化确定了中心频率2.25 MHz、32阵元以及45°纵波楔块的相控阵超声检测参数。仿真和实验检测结果显示,侧壁未熔合检测信噪比相差不超过0.6 dB,验证了所建模型的有效性。在此基础上,利用全聚焦方法和相位相干成像方法削弱结构噪声,检测信噪比较相控阵扇扫描图像分别提升2.3 dB和4.7 dB,且侧壁未熔合深度与高度定量误差均不超过6.7%。     

Positron beam studies of void swelling in ion irradiated Ti-modified stainless steel

The void swelling behavior of heavy ion irradiated D9 steel has been investigated using variable low energy positron beam. The normalized defect-sensitive S-parameter shows up a large increase in the depth region corresponding to the maximum radiation damage as a function of irradiation temperature. From the variation of S-parameter as a function of irradiation temperature, the peak swelling temperature has been deduced and the results are discussed.     

Initial oxidation of duplex stainless steel

Three different techniques were used to produce thin oxide layers on polished and sputter-cleaned duplex stainless-steel samples. These samples were exposed to 10⁻⁵ mbar of pure oxygen inside the vacuum chamber, exposed to ambient conditions for 24 h, and plasma oxidized. The oxide layers thus produced were analysed using XPS depth profiling in order to determine the oxide layers’ compositions with depth. We found that all the techniques produce oxide layers with different traces of metallic components and with the maximum concentration of chromium oxide shifted towards the oxide-layer-bulk-metal interface. A common characteristic of all the oxide layers investigated is a double-oxide stratification, with regions closer to the surface exhibiting higher concentrations of iron oxide and those more in-depth exhibiting higher concentrations of chromium oxide. A simple non-destructive Thickogram procedure was used to corroborate the thickness estimates for the thinnest oxide layers.     

不锈钢电子束收集极的损伤能量密度阈值

对强磁场相对论返波管系统中电子束收集极损伤的主要影响因素进行了分析,通过设计并使用锥面不锈钢收集极,提高了收集极的耐电子束轰击能力。在单次实验条件下,研究了电子束能量密度对不锈钢收集极表面损伤及系统产生微波的影响,结合对无箔二极管中电子束空间密度分布的研究结果,给出了不锈钢收集极损伤电子束能量密度阈值范围。     

不锈钢电子束收集极的损伤能量密度阈值

对强磁场相对论返波管系统中电子束收集极损伤的主要影响因素进行了分析,通过设计并使用锥面不锈钢收集极,提高了收集极的耐电子束轰击能力。在单次实验条件下,研究了电子束能量密度对不锈钢收集极表面损伤及系统产生微波的影响,结合对无箔二极管中电子束空间密度分布的研究结果,给出了不锈钢收集极损伤电子束能量密度阈值范围。     

充氚不锈钢中氦行为的实验研究

对充氚和未充氚的抗氢-2不锈钢(HR-2)样品进行退火处理,利用正电子湮没寿命谱技术以及金相检验技术探讨不锈钢中氦和微缺陷的相互作用行为.未充氚样品中,影响正电子寿命值的主要因素为杂质元素在晶界的析出.充氚样品实验中,退火温度小于300℃时,正电子寿命值的增加说明了氦泡的形成过程为非热形成,通过“冲出位错环”机制形成及长大;退火温度在300~600℃之间,充氚样品正电子寿命值的降低以及He的跃迁概率的计算结果,说明He原子通过热迁移至晶界;退火温度大于600℃时,热平衡空位浓度的计算结果以及正电子寿命值的增加说明热平衡空位开始发挥作用.     

Magnetic detection of sigma phase in duplex stainless steel UNS S31803

Duplex stainless steels are high strength and corrosion resistant steels extensively used in the chemical and petrochemical industry. The best mechanical properties and corrosion resistance are obtained with a microstructure composed by equal parts of ferrite and austenite and free from tertiary phases. Sigma phase is one of these deleterious tertiary phases. In the present work different amounts of sigma phase were precipitated by heat treatments in a UNS S31803 stainless steel. Some specimens were cold rolled before sigma phase precipitation in order to evaluate the effect of deformation on the magnetic measurements. The amount of sigma phase was precisely determined by microscopy and image analysis for each heat treatment condition. The effects of sigma phase on the steel properties were investigated, confirming the detrimental effects of very small percentages on corrosion resistance and toughness. Two magnetic methods were used to detect sigma phase: magnetization saturation measurements in a Vibrating Sample Magnetometer and ferritoscope testing. Both methods were found to be sensitive to small percentages of sigma phase in the microstructure.     

Effect of silver on antibacterial properties of stainless steel

The microstructural variation and antibacterial properties of the AISI 304 stainless steel containing silver (Ag) element have been investigated by means of optical microscopy (OM), grazing incidence X-ray diffractometry (GIXRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometer (EDS). Furthermore, the antibacterial testing was performed according to JIS Z2801:2000 specification. As the alloy contained Ag elements, the microstructure of the alloys was a mixture of (α + γ + Ag-rich compound)-phases. The amounts of α phase and Ag-rich compound increased as Ag contents increased. The Ag-rich compound has FCC structure with the lattice parameter a = 0.251 nm. No precipitates were found within the matrix and grain boundaries in the present alloys after SHT. Moreover, when the alloy is added to Ag element, antibacterial property was seen obvious against E. coli. It has an AR nearly of 100%.     

Proton-induced grain boundary segregation in stainless steel

Abstract

A technique is developed which addresses the problem of irradiation assisted stress corrosion cracking of stainless steels in light water reactors using high energy protons to induce grain boundary segregation. These results represent the first grain boundary segregation measurements in bulk produced by proton irradiation of stainless steel. The technique allows the study of grain boundary composition with negligible sample activation, short irradiation time, rapid sample turnaround and at minimal cost. Scanning Auger electron microscopy is used to obtain grain boundary composition measurements of irradiated and unirradiated samples of ultra high purity (UHP) type 304L stainless steel and UHP type 304L steels with the additions of phosphorus (UHP + P) and sulphur (UHP + S). Results show that irradiation of all three alloys causes significant Ni segregation to the grain boundary and Cr and Fe away from it. Irradiation of the UHP + P alloy also results in segregation of P at the grain boundary from 5.3 to 8.7 at %, over 80 times the bulk value. No radiation-induced grain boundary segregation of S was measured in the UHP + S alloy. Results also indicate that the presence of P or S may enhance radiation-induced segregation of major alloying elements at the boundary. Comparison of irradiated and unirradiated regions of the UHP + P alloy indicate that while a prior thermal treatment segregates P to the grain boundary to 5.3 at %, the major element concentrations at the grain boundary are completely different from those under irradiation.     

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利用脉冲激光诱导击穿光谱仪(LIBS)结合SEM、EDX和维氏硬度(HV)等分析手段,分析了316L不锈钢在350℃的液态锂中静态腐蚀500h后的腐蚀特性.微观形貌分析表明:样品存在较明显的晶间腐蚀,其腐蚀层厚度约为2.7μm.硬度分析表明:腐蚀后表面硬度值约HV234.72,约是腐蚀前硬度值的0.78倍.LIBS组分分析表明:经液态锂腐蚀后的样品表面Ni、Cr等元素含量相对减少;在被腐蚀区域Li元素含量随激光击打深度的增加而减少,而Ni、Cr等元素含量与之近似呈成正比递增;母材区Li元素的渗透深度约3.5μm,约是焊缝区的0.6倍.     

Evolution of magnetic phase at low aging temperature in a heavily cold-drawn stainless steel fiber

The evolution of the magnetic phase upon aging at 300–520 °C in a heavily cold-drawn AISI 316L austenitic stainless steel fiber was studied using thermomagnetic analysis (TMA) and magnetic force microscopy with a heating stage. An increasing trend of magnetization from 50 °C to around 470 °C in the heating curves of TMA in austenitic stainless steels after a cold-drawing process was observed. No significant M_s temperature signal in the TMA curve at cooling indicated an increase in magnetization upon cooling period without significant phase transformation. A series of in situ magnetic force microscopy observations reveal a growth of the magnetic domain structure after aging at 300 °C for 2.5 h. Results show that the ferromagnetic increase during aging at lower annealing temperature resulted from the growth of martensite.     

316L不锈钢在静态液态锂中的腐蚀行为研究

利用脉冲激光诱导击穿光谱仪(LIBS)结合SEM、EDX和维氏硬度(HV)等分析手段,分析了316L不锈钢在350℃的液态锂中静态腐蚀500h后的腐蚀特性。微观形貌分析表明：样品存在较明显的晶间腐蚀,其腐蚀层厚度约为2.7μm。硬度分析表明：腐蚀后表面硬度值约HV234.72,约是腐蚀前硬度值的0.78倍。LIBS组分分析表明：经液态锂腐蚀后的样品表面Ni、Cr等元素含量相对减少;在被腐蚀区域Li元素含量随激光击打深度的增加而减少,而Ni、Cr等元素含量与之近似呈成正比递增;母材区Li元素的渗透深度约3.5μm,约是焊缝区的0.6倍。     

Double pulse UV laser induced breakdown spectroscopy of stainless steel

Results of experimental investigations of 304 austenitic stainless steel (ASS) ultraviolet spectral range by single and double pulse laser induced breakdown spectroscopy (LIBS) at atmospheric pressure are reported. Various parameters, such as laser energy, placement of the laser beam focus with respect to the surface of illumi-nation, and collinear double laser pulse delay were used as variables. This study contributes to a better under-standing of the LIBS plasma dynamics by observing the temporal evolution of various emission lines. Temperature measurements were made by the Boltzmann diagram method using singly ionized Fe lines, and electron densities were found from Stark broadening. The temporal behaviors of these parameters were also estimated. It was found that the electron temperature for double pulses is higher than that for single pulse of the same total energy. For double pulse LIBS, the iron line emission intensities are enhanced and the analytical performance is improved. For instance, the intensity of iron line Fe I 275.01 nm was a factor of about 300 times higher if a double pulse of 2 × 20 mJ was used instead of a single pulse of 40 mJ when focusing the beam 4.7 mm behind the target surface. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 79, No. 5, pp. 654–660, 2006.     

An ultrasonic testing method for gas pressure welded joints of reinforcing steel bars

Gas pressure welding for jointing of reinforcing steel bars is most commonly used in Japan and the Far Eastern regions, where there are frequent earthquakes. An ultrasonic testing method has been developed for gas pressure welded joints. An intrinsic feature of the ultrasonic testing method is that there is a correlation between the ultrasonic testing results and the mechanical property (tensile strength) of joints. This feature enables non-destructive detection of gas pressure welded joints with tensile strength below a reference value. The theoretical justification for the correlation between the ultrasonic testing results and the tensile strength of the joints is discussed.     

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通过失重法结合SEM、金相分析等手段,研究了含焊缝的316L不锈钢试样在350°C、0.15MPa液态锂中500h的静态腐蚀,并采用LIBS结合台阶仪表征液态锂的渗入深度。结果表明,锂对含焊缝的316L不锈钢样式的平均腐蚀速率为99.8mg·m?2·h?1;腐蚀深度为6.4μm;渗入深度在316L不锈钢焊缝处为8.6μm,在母材处为4.8μm。在焊缝处锂对材料有明显的晶间腐蚀。     

Corrosion behavior of low energy,high temperature nitrogen ion-implanted AISI 304 stainless steel

This work presents the results of a low-energy nitrogen ion implantation of AISI 304 type stainless steel (SS) at a moderate temperature of about 500°C. The nitrogen ions are extracted from a Kauffman-type ion source at an energy of 30 keV, and ion current density of 100 μA cm⁻². Nitrogen ion concentration of 6 × 10¹⁷, 8 × 10¹⁷ and 10¹⁸ ions cm⁻², were selected for our study. The X-ray diffraction results show the formation of CrN polycrystalline phase after nitrogen bombardment and a change of crystallinity due to the change in nitrogen ion concentration. The secondary ion mass spectrometry (SIMS) results show the formation of CrN phases too. Corrosion test has shown that corrosion resistance is enhanced by increasing nitrogen ion concentration.      

液态金属锂对于316L不锈钢焊接件的腐蚀行为研究

通过失重法结合SEM、金相分析等手段,研究了含焊缝的316L 不锈钢试样在350°C、0.15MPa 液态锂中500h 的静态腐蚀,并采用LIBS 结合台阶仪表征液态锂的渗入深度。结果表明,锂对含焊缝的316L 不锈钢样式的平均腐蚀速率为99.8mg·m^-2·h^-1;腐蚀深度为6.4μm;渗入深度在316L 不锈钢焊缝处为8.6μm,在母材处为4.8μm。在焊缝处锂对材料有明显的晶间腐蚀。     

Electron spectroscopic study of passive oxide layer formation on Fe-19Cr-18Ni-1Al-TiC austenitic stainless steel

Surface oxidation of a TiC-enriched austenitic stainless steel alloy was investigated at 50 °C by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). It was found that a passive oxide layer started to form on the alloy surface after 5 L of oxygen exposure. Further oxidation of the alloy was suppressed after 500 L of oxygen exposure when a stable passive layer was formed. It was found also that Ti and Ni did not oxidize and Ti remained in a carbide form during whole oxidation. The oxidation kinetics of different metals were investigated as well.