中梁钢的轧制生产实践

依据中梁钢断面特点,将其划分为腰部、头部、胸椎部及腿部,通过合理的孔型设计,选择斜配孔型系统,轧制9道次,第1～第3孔为切深孔,第4～第9孔为成形孔,实现了用轧制法生产王字钢。切深孔的设计特点是各切深楔子较钝,所切出的头、腿部分厚度小;成形孔设计特点是成形道次少,头、腿、腰各部分延伸系数差值大;胸锥成形设计特点是胸锥单体不按延伸系数设计及局部整合变形系数设计分配法。     

几何模型更新方法在板带热连轧精轧道次中的应用

为了更好的对精轧过程进行数值模拟,提供更为合理的轧制参数,以LS-DYNA软件中的单元更新方法模拟了精轧过程。建立好第1道次轧制模型并数值模拟,对第1道次计算结果进行了分析。以第一道次轧制后的单元形状为基础,进行单元更新,改变边界条件和载荷,对第2道次进行数值模拟,用同样方法对3～7道次进行数值模拟。该方法在准确地模拟了精轧过程中板带变化的同时,为各精轧道次提供准确的轧制参数。     

三种成品孔轧制高精度重轨尺寸和形状精度的研究

对使用两辊成品孔型、半万能成品孔型和万能成品孔型轧制高精度重轨的产品尺寸精度和形状精度进行了研究,在生产条件下进行两辊成品孔型的轧制实验,在实验室进行半万能成品孔型和万能成品孔型轧制高度重轨的实验,三种孔型均可以轧制出满足200km/h2和300km/h标准要求的高精度重轨,成材率和尺寸精度依次为万能孔型和两辊孔型。     

30#工字钢孔型设计

结合攀钢轨梁厂生产特点及断面特点,进行30#工字钢孔型设计,着重阐述了孔型系统的选择和孔型参数的确定,通过孔型系统优化设计,一次性成功轧制出30#工字钢。     

MR first pass imaging: quantitative assessment of transmural perfusion and collateral flow

Recent advances with fast switching gradient coils, and the optimization of magnetic resonance techniques for multislice imaging have made it possible to apply models of contrast agent transit for the quantification of myocardial perfusion, and determination of the transmural distribution of blood flow. This article summarizes some of these recent developments and presents examples of quantitative, multi-slice myocardial perfusion imaging studies in patients and animal models. Multi-slice, true first pass imaging, with high temporal resolution, and T1-weighted, arrhythmia insensitive contrast enhancement is used for the quantification of perfusion changes accompanying mild to severe ischemia. The first pass imaging technique and the modeling approach are sufficiently robust for fitting of tissue residue curves corresponding to a wide, physiologically realistic range of myocardial blood flows. In animals this was validated by comparison to blood flow measurements with radiolabeled microspheres as gold standard. It is demonstrated that with the proposed modeling approach one can determine the myocardial perfusion reserve from two consecutive MR first pass measurements under resting and hyperemic conditions. In patients with microvascular dysfunction the MR studies show for the first time that the myocardial perfusion reserve correlates with Doppler flow measurements (linear regression with slope of 1.02 +/- 0.09; r = 0.80). Since perfusion limitations usually begin in the subendocardium as coronary flow is gradually reduced, first pass imaging with the prerequisitie spatial and temporal resolution allows early detection of a mild coronary stenosis.     

S49钢轨轧制工艺设计

结合攀钢轨梁工厂特点及S49钢轨断面特点，论述了S49钢轨的轧制工艺设计，并着重阐述了孔型系统的选择和孔型参数的测定，同时设计了导卫装置等。通过孔型系统的优化设计，使S49钢轨一次试轧成功。     

单机可逆轧机打滑影响因素分析及防治措施

在冷轧可逆轧机轧制过程中,随着轧制总压下率的增加,由于受轧辊表面粗糙度、辊径、道次压下量、轧制压力以及前后张力差值的影响,易出现打滑现象,造成带钢表面出现热划伤、擦痕等缺陷。通过对影响打滑各因素的分析,制定了增大第1道次前张力、提高轧辊表面初始粗糙度、减小末道次压下量、优化轧制规程等措施,消除了打滑现象。     

The Effect of Cu Powder During Friction Stir Welding on Microstructure and Mechanical Properties of AA3003-H18

Friction stir welding (FSW) was used to join 3003-H18 non-heat-treatable aluminum alloy plates by adding copper powder. The copper powder was first added to the gap (0.1 and 0.2 mm) between two plates and then the FSW was performed. The specimens were joined at various rotational speeds of 800, 1000, and 1200 rpm at traveling speeds of 70 and 100 mm/min. The effects of rotational speed, second pass of FSW, and direction of second pass also were studied on copper particle distribution and formation of Al-Cu intermetallic compounds in the stir zone. The second pass of FSW was carried out in two ways; in line with the first pass direction (2F) and in the reverse direction of the first pass (FB). The microstructure, mechanical properties, and formation of intermetallic compounds type were investigated. In high copper powder compaction into the gap, large clusters were formed in the stir zone, while fine clusters and sound copper particles distribution were obtained in low powder compaction. The copper particle distribution and amount of Al-Cu intermetallic compounds were increased in the stir zone with increasing the rotational speed and applying the second pass. Al₂Cu and AlCu intermetallic phases were formed in the stir zone and consequently the hardness was significantly increased. The copper particles and in situ intermetallic compounds were symmetrically distributed in both advancing and retreating sides of weld zone after FB passes. Thus, the wider area was reinforced by the intermetallic compounds. Also, the tensile test specimens tend to fracture from the coarse copper aggregation at the low rotational speeds. At high rotational speeds, the fracture locations are placed in HAZ and TMAZ.     

Application of Crown-Flatness Vector Analysis in Plate Rolling Schedule

A simple plate crown model was introduced, and the crown-flatness vector analysis method was analyzed. Based on the plate rolling technology, the rolling schedule design of elongation phase is divided into three steps. First step is to calculate the reductions of first pass of elongation making full use of the mill capability to decrease the total pass number. The second step is to calculate the pass reduction for the last three or four passes to control crown and flatness by crown-flatness vector analysis method. In the third step, the maximum rolling force limit and the total pass number are adjusted to make the plate gauge at exit equal to target gauge with satisfactory flatness. The on-line application shows that this method is effective.     

高强韧Ti-451合金的可旋性研究

对高强韧的Tj-451合金进行了可旋性研究,分别研究了旋压温度、道次减壁率、进给率等髓Tj-451合金旋压制品质量的影响规律。研究表明：Ti-451合金开始道次旋压温度应定在800～850℃为宜,随着累计加工率的增加,壁厚变薄,旋压温度逐道次适当下降;道次减壁率对工件的胀缩量及精度有影响,Ti-451合金合适的道次减壁率在13％-27％之间;道次进给率严重影响制品表面质量,Ti-451合金合适的道次进给率范围为0．5～0．65mm／r。     

Endotoxin contamination may be responsible for the unexplained failure of human pancreatic islet transplantation

India ink and radioactive 51Cr-labeled microspheres were used in separate trials to examine the role of the yolk stalk lumen as a distinct pathway between the yolk sac and gut through the first 5 d of posthatch growth in broiler chicks. Throughout this period, India ink was able to pass from the yolk sac through the yolk stalk and into the intestine, but was not able to pass from the intestine into the yolk stalk or yolk sac. Furthermore, labeled microspheres moved from the yolk sac via the yolk stalk into the gut; which caused the total counts per minute of the intestine, yolk stalk, and excreta to progressively increase. It was concluded that India ink and 51Cr-labeled microspheres were useful materials in establishing that the yolk stalk provides a direct one-way passage by which material in the yolk sac may move into the intestine of broiler chicks during the first 5 d after hatching.     

Ø75 mm GCr15圆棒材孔型工艺优化及数值模拟

西宁特钢精品小棒线在生产Ø75 mm的GCr15热轧圆钢时,发现轧后棒材内部存在中心疏松缺陷,导致棒材精整后超声探伤合格率低。通过修改孔型参数,结合数值模拟研究测试棒材芯部应力及等效应变的变化情况,再经现场生产验证,结合成品棒材超声探伤合格率的分析,来验证优化后的孔型参数是否可行,指导现场生产实践,提高轴承钢棒材的产品质量水平。参数的确定中,对各道次压下量的重新分配,主要是增加了第2道次的压下量,从58增加到86 mm,减小了第4道次的压下量,从58减小到30 mm。优化后的工艺直接从11架出Ø75 mm成品,节约了后2架轧机的能源消耗与轧辊磨损消耗。模拟结果显示第1道次的棒材内部应力由之前的拉应力变为压应力,结合轧制速度的降低,有利于提高棒材芯部质量。实际生产证明工艺优化后低倍质量显著提升,探伤合格率为96.37%,较之前提高3.63%。     

The combination of interaural information across frequencies: the effects of number and spacing of components, onset asynchrony, and harmonicity

Threshold interaural delays were measured for a single interaurally delayed low-frequency target component presented against a background of two, four, six, or eight diotic "distractor" components. In the first experiment, a 753-Hz target and the flanking distractor components were gated on and off simultaneously. In subsequent experiments, the distractors were gated on 25-200 ms prior to the target. In addition, the target and distractor components were given various harmonic configurations. In general, threshold interaural delays were higher in all conditions in which distractors were present relative to thresholds obtained for the target component in isolation. Subjects reported that the pitch of the target component was more salient when an onset asynchrony between the target and distractors was present, but the components were perceived as occupying a single intracranial position in spite of the various interaural delays across the frequency domain. These results suggest that binaural processing of stimuli consisting of a small number of low-frequency temporally overlapping components occurs in a spectrally synthetic manner in which interaural information is combined across the spectrum, even in situations in which the segregation of pitch information occurs.     

道次减面率配置对304H不锈钢丝拉拔过程中马氏体相变的影响

设计了两种不同的拉拔工艺(减面率/%:工艺一:34.45,31.67,19.00,20.08;工艺二:20.10,19.28,34.64,31.41),研究了道次减面率配置对304H不锈钢丝拉拔过程中马氏体相变、磁性能及力学性能的影响。结果表明:当钢丝总应变量相同时,大减面率配置在前更有利于马氏体转变,其饱和磁化强度更大,反之则马氏体转变量较少,饱和磁化强度较小。钢丝的强度与拉拔真应变呈线性相关,其大小只与拉拔总应变量相关。本试验中,前两个道次减面率为20.10%和19.28%,后两个道次减面率为34.64%和31.41%时,马氏体转变量较少,钢丝的饱和磁化强度较低。     

Three-dimensional fetal echocardiography: gated versus nongated techniques

The purpose of this study was to compare gated with nongated three-dimensional fetal echocardiography in terms of the ability to demonstrate fetal cardiac anatomy. We examined nine fetuses in utero using conventional two-dimensional sonographic imaging equipment, an electromagnetic position sensor, and a computer-graphics workstation. Free-hand sweeps were performed through the fetal heart and great vessels in either transverse or sagittal orientations with respect to the fetal heart. Seven transverse and five sagittal sweeps were selected for reconstruction and analysis. Cardiac gating was performed by using a temporal Fourier transform to determine the fundamental frequency of cardiac motion. Two-dimensional data from each sweep were reprojected to a series of volume data sets. Each series was then condensed to a single volume, so that each two-dimensional sweep could be compared with its respective gated and nongated volume data sets. The two-dimensional data were reviewed utilizing a display with forward and backward cineloop capability. The gated and nongated volume data sets were displayed interactively as a series of three orthogonal planes, with the ability of the observer to control the location of each image plane within the volume. The gated data were animated with variable display frame rates. Conventional two-dimensional imaging provided a fairly complete evaluation of the fetal heart when scanning included the four-chamber view with a sweep across the outflow tracts. Nongated three-dimensional fetal echocardiography allowed visualization of some structures and views not demonstrated with two-dimensional ultrasonography. Gated three-dimensional fetal echocardiography provided significantly better visualization and comprehension of cardiac anatomy than nongated three-dimensional fetal echocardiography. The superiority of gated over nongated three-dimensional fetal echocardiography appears to come from both improved image quality and the anatomic clues that derive from the ability to view cardiac motion.     

Left ventricular ejection fraction assessed from gated technetium-99m-sestamibi SPECT

By means of ECG gating of tomographic (SPECT) 99mTc-sestamibi (MIBI) images, myocardial perfusion and wall thickening have been evaluated after a single tracer injection. To determine if left ventricular ejection fraction (LVEF) can also be measured from gated MIBI SPECT, 30 patients 1 wk to 6 mo after myocardial infarction (MI) received 22-30 mCi 99mTc-MIBI during treadmill exercise. Eight frame per cardiac cycle gated MIBI 180 degrees SPECT was performed 60 min thereafter. Using 6.4-mm thick mid-ventricular vertical and horizontal long-axis slices from R-wave triggered end-diastolic and end-systolic frames, two independent observers manually drew endocardial borders at a count level of 34% of the maximum. LVEF was computed by the Simpson's rule method, corrected for the average point spread function of the SPECT camera. Results were correlated with LVEF determined from planar gated 99mTc-blood-pool studies performed within 4 days. LVEFs calculated from gated MIBI SPECT ranged from 0.21 to 0.73 and correlated linearly with gated blood-pool values (correlation coefficients ranged from 0.79 to 0.88; interobserver variability r = 0.75; intraobserver reproducibility r = 0.75). We conclude that in patients with MI resting LVEF can be determined from gated MIBI SPECT, thereby considerably augmenting the technique's diagnostic and prognostic value.     

20MnVB钢热处理工艺与其组织和性能之间的关系

由于20MnVB钢的特殊性导致其综合机械性能不稳定，一次合格率较低。此试验应用正交试验设计，对化学成分固定的20MnVB钢的热处理工艺、组织、性能之间关系进行了分析，选择出最佳的热处理工艺，以指导生产检验，提高一次合格率和检验合格率，降低检验成本。     

立辊孔型内倒角半径对轧件变形的影响

采用显式动力学有限元方法,对立辊孔型内倒角半径R为30、50、80、110 mm 4种情况下多道次立-平轧制过程进行了模拟.分析了立辊孔型内倒角半径对轧件切头尾量、轧件稳定段轧件边部变形程度的影响.研究发现:既定条件下,第1道次立-平轧制过程中,随内倒角半径的减小头尾不均匀区域长度减少,第2、3道次立-平轧制过程中,随内倒角半径的增加,头尾不均匀变形区域长度道次增加量减少;对比采用R为30 mm的孔型立辊和R为110 mm的孔型立辊轧后轧件的头尾不均匀长度,前者比后者少5.03%;轧件稳定段轧件变形程度随着孔型立辊内倒角半径的增加而减少.     

冷轧道次变形率对TA18钛合金管材组织与拉伸性能的影响

改变冷轧道次变形率研究其对TA18钛合金管材组织和拉伸性能的影响。用金相显微镜观察了其微观组织形貌,用Instron 1185拉伸试验机测试了拉伸性能。结果表明:冷轧态TA18钛合金管材显微组织为纤维状;冷轧第三、四道次管材的晶粒取向程度弱于第一、二道次,抗拉强度和屈服强度较低,但延伸率大幅提高;经过750℃/90 min再结晶退火后所有TA18管材晶粒为等轴状晶粒,组织取向消失,同时由于细晶强化作用,使第一、二道次退火后的TA18钛合金管材保持了相对较高的强度和延伸率。由于第三、四道次冷加工态性拉伸能指标与第一、二道次退火态较为接近,因此存在通过连轧的方式来简化工艺流程的可能。     

二十辊森吉米尔轧机板形控制方法

介绍了二十辊森吉米尔轧机板形控制方法和各道次板形控制要求。二十辊森吉米尔轧机虽然具有很强的板形控制能力,然而也同样具有可逆冷轧机的一些缺点,如起车轧制和甩尾作业板形变化剧烈,甚至轧制过程中均需要操作工手动控制,二十辊森吉米尔轧机板形调控手段虽多,但有时并不能轻易地消除复杂的不良板形。生产实践表明,预设好第 1 中间辊第 1 道次起车值、控制好带钢板形对称和带钢边部受力情况以及统一规范各道次的轧制板形控制均能有效避免断带,保证二十辊森吉米尔轧机顺稳轧制,提高硅钢产品板形的均一性。