奥氏体不锈钢平均晶粒尺寸的超声评价技术

采用超声纵波声速评价奥氏体不锈钢昌粒尺寸,建立了超声纵波声速与平均晶粒尺寸的关系式,其平均晶粒尺寸与超声速线性相关,并分析了声速测量误差。     

超声声速无损评定304不锈钢晶粒尺寸

用A型脉冲超声纵波对不同晶粒尺寸的304不锈钢进行超声声速测量,建立纵波声速和晶粒尺寸之间的关系.结果表明,奥氏体不锈钢晶粒尺寸随着保温时间的延长或固溶温度的提高而长大,水冷条件下的纵波声速呈指数衰减趋势,空冷条件下的纵波声速呈线性衰减趋势.     

超声无损评价2219铝合金晶粒尺寸

为了研究铸态2219铝合金平均晶粒尺寸与超声声速和超声衰减系数的关系,在铸锭不同径向位置取样,获得不同晶粒尺寸的试块。采用RITEC RAM-5000 SNAP非线性高能超声测试系统进行超声参数测量。研究结果表明,纵波声速和平均晶粒尺寸呈线性减小趋势,衰减系数和平均晶粒尺寸呈三次多项式增长趋势。     

固溶温度对GH4169微观组织形貌及超声特性的影响

对不同固溶温度的GH4169合金试样,进行了微观组织形貌观察,提取了晶粒尺寸、形状特征参数。采用纵波回波法和共线穿透法进行超声检测和非线性超声检测,计算合金的超声特性参数。提取的超声特性参数包括:衰减系数、声速、相对非线性系数、背散射信号(位于一次底波和二次底波之间)经验模态分解后固有模态函数的平均功率和波形指数。超声-微观结构参数对比分析的结果表明,通过衰减系数、声速、非线性系数可有效识别相变,衰减系数对晶粒尺寸波动敏感,随晶粒粗化而增大;所提取的固有模态函数平均功率和波形维数都可以对晶粒尺寸进行评价,但尚难以用于表征晶粒纵横比。     

LA103Z镁锂合金锻件超声评价技术

针对镁锂合金锻件检测时存在超声波能量的严重衰减,导致无法实施有效的内部质量检测难题,通过对不同锻造变形量下的LA103Z镁锂合金锻件进行金相观察,分析了不同变形量对材料微观结构造成的影响;同时还分析了不同变形量对超声波衰减系数及材料纵波声速的影响,最后研究了探头晶片尺寸对超声波衰减系数的影响。结果发现,对于LA103Z镁锂合金锻件,锻造变形量越大,镁锂合金α相微观组织越细密;超声衰减系数随锻造变形量增大而减小;材料的超声波纵波声速随锻造变形量增大而增大;随着超声检测探头晶片尺寸增大,超声波衰减系数减小;相同变形量的镁铝合金材料,随着使用的探头频率的提高,材料的声波衰减系数和声速都变大。     

厚壁CCASS材料特性及其对超声检测的影响

对壁厚98 mm的离心铸造奥氏体不锈钢(Centrifugally Cast Austenitic Stainless Steel,CCASS)试样的纵波声速、衰减系数和幅度谱等声学特性进行了测试分析,并采用TRL相控阵探头进行扇形扫描和B扫描检测。结合试样的宏观、微观组织对实验结果进行了分析讨论。研究表明:试样晶粒粗大,内部组织存在分层,介质的非均质性明显,导致超声检测信号噪声水平高、幅度谱波动大,纵波声速和衰减系数在一定范围内变化,相控阵扇形扫查和B扫查成像效果较差。利用CIVA软件得到的模拟结果为解释上述实验现象提供了依据。     

支柱瓷绝缘子及瓷套超声波检测工艺方法研究

在研制超声波系列探头和与瓷声速相近试决的基础上完成的工艺方法，其中爬波探头可以在距缺陷50mm时检测出深度西1mm当量缺陷，小角度纵波斜探头可以发现支柱瓷绝缘子内部≤Ф1mm当量缺陷，双晶横波探头则可以发现瓷套内部和内壁≤Ф1mm当量缺陷。这意味着根据检测部位和指示长度分析，支柱瓷绝缘子及瓷套超声探伤可以做到定位、定性和定量。     

超级钢与低碳钢焊接热影响区晶粒尺寸对比

利用数值模拟方法对超级钢和低碳钢的焊接温度场进行了模拟，在此基础上，对其热影响区晶粒尺寸进行了预测，并将结果进行了对比分析。结果定量地表明，超级钢热影响区的晶粒尺寸比低碳钢热影响区的晶粒尺寸小，超级钢焊缝比低碳钢焊缝性能优良。     

正确选择和使用纵波双晶探头

介绍了如何正确选择和使用纵波双晶探头。对纵波双晶探头的结构、声束交区作了详细的介绍。对纵波双晶探头的选择，从探测厚度、频率、晶片尺寸作了具体的阐述，通过对比试块、探测灵敏度、扫查方向的选择，对纵波双晶探头的探伤方法进行了系统的讨论。     

反射横波筑底衍射纵波检测焊缝下表面开口缺陷的研究

介绍了利用横波和纵波的声速差,使底面反射横波信号和底面开口缺陷上端点衍射纵波信号产生位置差的方法,将两个实际位置差极小(即底面开口缺陷自身高度)的两个回波信号在显示屏上有效分开、清晰识别,从而实现对下表面开口缺陷的有效检测。试验测试使用普通横波斜探头和纵波斜探头及常规A型脉冲反射式超声检测仪,测试结果证明该方法对下表面表面开口缺陷可有效识别并准确定位。     

表面纳米化低碳钢电化学行为尺寸效应

利用超声喷丸技术制备了表面纳米化低碳钢.结构分析表明,最表层低碳钢的晶粒尺 度在20nm左右,随着向基体方向靠近,纳米层晶粒尺度逐渐增加.对纳米低碳钢在0.05 mol /L H2SO4+0.05 mol/L Na2SO4腐蚀介质中腐蚀速度测试结果表明,纳米化后低碳钢 的腐蚀增加; 纳米低碳钢的电化学腐蚀行为存在尺寸效应.在晶粒尺度小于35 nm时,纳米 低碳钢的电化学腐蚀速度随晶粒尺度的增加而降低,当晶粒尺度高于35 nm后,晶粒尺寸对 腐蚀速度影响不大.纳米化后低碳钢的阳极反应历程不变,阳极交换电流密度提高;而阴极 反应历程改变,析氢反应容易,并由电化学步骤控制转变为由扩散步骤控制.纳米化后低碳 钢阴阳极反应同时得到促进,腐蚀速度增加.     

用超声波速度无损表征38CrMOAl钢热处理转变产物的研究

研究了淬火、正火、淬火＋低温回火及淬火＋高温回火状态下38CrMoAl钢的超声纵波速度以及150－600℃范围内回火温度与超声波速度之间的关系，实验表明，超声波速度按照淬火、淬火＋低温回火、正火、淬火＋高温回火的顺序由低到高变化，超声波速度与回火温度之间有很好的线性相关性，随着回火温度的升高，超声波的速度增加。     

Ultrasonic velocity measurements for estimation of grain size in austenitic stainless steel

Ultrasonic velocity measurements have been used to estimate average grain size in an AISI type 316 stainless steel. For precise ultrasonic transit time measurements, the pulse-echo-overlap technique has been used. Master graphs relating ultrasonic velocity with metallographically obtained grain size have been generated. Using these graphs, grain sizes in new specimen have been obtained. The results indicate that grain size can be predicted with good confidence level using ultrasonic velocity measurements. Shear waves are found to be more sensitive for grain size measurement, as compared to longitudinal waves. The grain size estimated by velocity measurements is found to be more accurate when compared to that obtained by attenuation measurements.     

水平连铸圆钢的混合波检测及缺陷信号的提取

采用由超声纵波和横波组成的混合波检测水平连铸圆钢中埋藏较深的径向缺陷,得到的缺陷回波信号很弱,且完全“湮没”在强烈且复杂的材料组织散射噪声之中。分析了检测信号的特征,并采用截止频率法成功地提取了微弱的缺陷回波信号。     

圆柱件斜入射水浸探伤中线聚焦探头焦线的计算

建立了水浸探伤中线聚焦探头倾斜入射圆柱体工件时工件中实际焦线计算的数学模型,并计算了不同折射角时的折射横波和折射纵波形成的焦线。     

An ultrasound method for the acoustoelastic evaluation of simple bending stresses

Ultrasonic waves constitute a privileged tool for investigation in the analysis and characterisation of mechanical stress states. Ultrasonic wave velocities depend on many physical properties of the propagation medium such as the second-, third- and higher-order elastic constants, the volume density and the strain. They also depend on whether the wave is longitudinal or transversal. In this last case, they also depend on the wave polarisation direction.

The present paper deals with the classical acoustoelasticity in stressed and elastically deformed media when they are submitted to bending stresses. A numerical and an experimental evaluation of the resulting change in the ultrasound velocities as a function of bending loads are described. Some results have been obtained on the variation of propagation velocities of the longitudinal and transversal polarised waves as a function of mechanical bending loads applied on samples made of S 185 steel. The acoustoelastic evaluations have been achieved in three zones under bending stress (compressed, central and extended fibres) in the case where the path of probing, longitudinal and linearly polarised shear waves are parallel to the sample axis. As additional investigation on acoustoelastic behaviour on bending load, we propose some acoustoelastic responses simulated numerically on materials of known macroscopic properties.

The experimental study was achieved by means of a measurement set-up composed of an ultrasound bench and a mechanical test machine. In order to measure the variations of the propagation velocity, a correlation technique has been used to obtain an accurate estimation of the propagation time. The velocity measurements have taken into account the elastic deformation of the samples made of carbon steel (C 35).     

304不锈钢晶粒散射特性的超声检测分析

研究了304不锈钢不同热处理状态下晶粒尺寸对超声声速的影响。对同厚度钢和不锈钢的一次回波、二次回波和两者间的信号进行了频谱特性分析。结果表明,超声波在不锈钢中传播时,晶粒越大,声速越高;不锈钢的一次回波、二次回波及两者间的信号均在回波信号频带范围内,随晶粒度增加频率降低,散射作用增强。     

晶粒尺寸对超低碳IF钢耐大气腐蚀性能的影响

采用不同轧制及热处理工艺制备了化学成分相同而晶粒尺寸不同的3种超低碳IF钢试样.采用浸泡腐蚀、周浸腐蚀、原子力显微镜(AFM)及扫描电镜(SEM)微观分析、电化学阻抗测试等手段对晶粒尺寸与IF钢耐大气腐蚀性能之间的规律进行了研究.AFM及SEM微观分析结果表明,随着晶粒尺寸从15μm增加到220μm,超低碳IF钢浸泡腐蚀后晶界处的局部腐蚀更加严重,腐蚀裂纹处的深度加深,裂纹宽度变宽.超低碳IF钢晶粒尺寸从15μm增加到46μm,周浸腐蚀实验后锈层中空洞和裂纹增多,锈层电阻下降,耐候性下降;晶粒尺寸进一步增大到220μm后,锈层整体致密性得到增加,锈层电阻上升,耐候性得到增加.对晶粒尺寸影响耐大气腐蚀性能的机理进行了讨论.晶粒尺寸增大后晶界能的减少使得腐蚀表面的宏观总体缺陷数量有所减少,耐候性有所提高;但是晶粒尺寸增大后晶界处因局部腐蚀电流密度增大将会在局部造成更深的腐蚀坑槽并降低耐候性;晶粒尺寸的变化对钢铁材料耐大气腐蚀性能的影响不仅要考虑其对晶界局部腐蚀电流密度的影响,而且还必须考虑对基体整体晶界能所造成的影响.     

Plastic flow characteristics of ultrafine grained low carbon steel during tensile deformation

In order to explain steady-state plastic deformation, i.e. the absence of strain hardening in ultrafine grained low carbon steel during tensile deformation, steel of different ferrite grain sizes was prepared by intense plastic straining followed by static annealing and then tensile-tested at room temperature. A comparison between the ferrite grain size of ultrafine grained steel and the dislocation cell size of coarse grained steel formed during tensile deformation revealed that uniform dislocation distribution with high density and cell formation were unlikely to occur in this ultrafine grained steel. This is ascribed to the fact that the ultrafine grain size is comparable to or smaller than the cell size at the corresponding stress level. In addition, from a consideration of dynamic recovery, it was found that the characteristic time for trapped lattice dislocations to spread into the grain boundaries was so fast that the accumulation of lattice dislocation causing strain hardening could not occur under this ultrafine grain size condition. Therefore, the extremely low strain hardening rate of ultrafine grained low carbon steel during tensile deformation is attributed to the combined effects of the two main factors described above.