Effect of hot stamping parameters on the mechanical properties and microstructure of cold-rolled 22MnB5 steel strips

Thermomechanical experiments were carried out to reproduce the hot stamping process and to investigate the effects of process parameters on the microstructure and mechanical properties of stamped parts. The process parameters, such as austenitizing temperature, soaking time, initial deformation temperature and cooling rate, are studied. The resulting microstructures of specimens were observed and analyzed. To evaluate the mechanical properties of specimens, tensile and hardness tests were also performed at room temperature. The op-timum parameters to achieve the highest tensile strength and the desired microstructure were acquired by comparing and analyzing the results. It is indicated that hot deformation changes the transformation characteristics of 22MnB5 steel. Austenite deformation promotes the austen-ite-to-ferrite transformation and elevates the critical cooling rate to induce a fully martensitic transformation.

Lab experiments on the innovative rapid thick strip casting process

Rapid thick strip casting （RTSC） by Anton Hulek, Inventmetall, is an innovative concept for the production of hot strips with a final as-cast thickness of about 25 mm before rolling. The innovation of the mechanism consists in a vertical mould performing a caterpillar motion. This moving mould has an unconventional parallelogram-shaped cross-section. The conventional rectangular shape is formed in the shaping machine, which is placed straight below the mould. Further elements of the technology are state-of-the-art. For the investigation of this new casting system theoretical calculations were complemented with practical experiments. The investigation focused mainly on two key aspects： the characteristics of the mould and the shaping process. For the practical analysis a static mould with three pairs of elements in laboratory scale was developed and commissioned by the Dept. of Ferrous Metallurgy @ RWTH Aachen University. The shaping experiments were carried out in model scale with two different materials and in variable boundary conditions. The results of these experiments delivered important mechanical as well as thermal informations about the casting system.

Vishay公司汽车级Power Metal Strip电阻WSHP2818

Vishay推出新的功率等级达10W且采用2818外形尺寸的汽车级Power Metal Strip电阻WSHP2818。Vishay Dale WSHP2818在较小的占位面积内具有与尺寸更大电阻相当的高功率,在汽车、工业、消费和计算机产品中能节省空间,减少元器件数量,而且用表面贴装替换引线电阻能大大加快组装速度。新发布的器件采用独有的结构,这种结构改进了热管理设计,使这颗10W电阻在2818封装尺寸内还能保持Power Metal Strip结构的优良电气特性。

Vishay发布新的汽车级Power Metal Strip电池旁路电阻

Vishay宣布,发布新的汽车级Power Metal Strip?电池旁路电阻——WSBS8518...14。该电阻的功率密度达到36W,采用8518外形尺寸,在接头上镀锡。Vishay Dale WSBS8518...14的电阻值低至50μΩ,测量精度比霍尔效应的电流检测方案高,而成本更低,镀锡的接头便于PCB组装,同时也提高了耐腐蚀能力。

Application of multi-scale feature extraction to surface defect classification of hot-rolled steels

Feature extraction is essential to the classification of surface defect images. The defects of hot-rolled steels distribute in different directions. Therefore, the methods of multi-scale geometric analysis （MGA） were employed to decompose the image into several directional subba^ds at several scales. Then, the statistical features of each subband were calculated to produce a high-dimensional feature vector, which was reduced to a lower-dimensional vector by graph embedding algorithms. Finally, support vector machine （SVM） was used for defect classification. The multi-scale feature extraction method was implemented via curvelet transform and kernel locality preserving projections （KLPP）. Experiment results show that the proposed method is effective for classifying the surface defects of hot-rolled steels and the total classification rate is up to 97.33%.

3D stress simulation and parameter design during twin-roll casting of 304 stainless steel based on the Anand model

This study first investigated cracks on the surface of an actual steel strip. Formulating the Anand model in ANSYS software, we then simulated the stress field in the molten pool of type 304 stainless steel during the twin-roll casting process. Parameters affecting the stress distribution in the molten pool were analyzed in detail and optimized. After twin-roll casting, a large number of transgranular and intergranular cracks resided on the surface of the thin steel strip, and followed a tortuous path. In the molten pool, stress was enhanced at the exit and at the roller contact positions. The stress at the exit decreased with increasing casting speed and pouring temperature. To ensure high quality of the fabricated strips, the casting speed and pouring temperature should be controlled above 0.7 m/s and 1520℃, respectively.

Enhanced optical transmission through a nanoslit by coupling light between periodic strips and metal film

Surface plasmon resonance （SPR） is obtained by exciting the surface plasmon （SP） at the metal and dielectric interface, which can greatly enhance the extraordinary optical transmission （EOT） through a nanoslit milled in the metal film. We present a structure with a 50-nm-wide silver nanoslit for EOT by coupling light into the dielectric interlayer between periodic strips and a metal film. When the period of the metallic strips is equal to the wavelength of the SPR, the transmission efficiency of 187.6 through the nanoslit is enhanced. The metallic strip width over the nanoslit is optimized to improve transmission efficiency, and the maximal efficiency of 204.3 is achieved.

REFLECTIVE CHARACTERISTICS OF SAW BY SLANTING METAL STRIP ARRAYS

The reflective characteristics of SAW by slanting metal strips on the surface of YZ - LiNbO3 have been studied. By using both Simple Model and Multi - Reflection Model, the reflective characteristics of SAW by a periodic metal strip array and the SAW distribution in the array have been calculated. Furthermore, by using an improved laser probe, the reflective SAW field by the array has also been measured. By comparing the theoretical results with the experiments, it is shown that the results of Multi - Reflection Model, being more exact than the simple one, are in better agreement with the experiment.

双辊铸轧非晶复合材料条带的微观组织与力学性能

本文设计并制造了一种能够制备高质量非晶复合材料条带的新型配有水冷铜板的双辊铸轧原型机.利用该轧机在不同温度下成功制备了具有三种不同体积分数β-Ti枝晶的非晶复合材料带材(简称BT30,BT48和BT60),并通过一系列三点弯曲试验研究了其力学性能.结果表明,在高温下轧制的带材,高温元素在中间区域富集,导致成分分布不均.此外,由于铸轧过程中热力耦合导致在非晶复合材料中存在较大的内应力,这会显著影响其力学性能.新型铸轧设备为制备非晶复合材料带材提供了新的途径,基于该设备进行的研究深化了对非晶复合材料带材微观组织及力学性能的理解.

A voltammetric sensor for simultaneous determination of lead,cadmium and zinc on an activated carbon fiber rod

In this work, a simple, low cost and sensitive voltammetric sensor was developed for the simultaneous detection of lead （Pb2＋）, cadmium （Cd2＋）, and zinc （Zn2＋） ions based on a disposable carbon fiber rod （CFR）. The important factors to enhance the sensing property were creation of a clean surface by dealing with CFR at a high potential and electrochemical deposition of bismuth （Bi） film to improve the accumulation of heavy metal ions. The morphology and conductivity of such activated CFR was characterized by scanning electron microscopy and electrochemical impedance spectroscopy, respectively. In terms of application, differential pulse anodic stripping voltammetry （DPASV） was employed for the simultaneous detection of Pb2＋, Cd2＋, and Zn2＋ on Bi film-coated activated CFR. Experimental parameters, such as the pH value of buffer solution, stirring speed and enrichment factors were optimized. Under optimal conditions, the DPASV peak currents showed good linear relationships with Pb2＋, Cd2＋ and Zn2＋ concentrations in the range of 0.5-2.25 μg/L, 0.5-4.0 μg/L and 1.0- 4.0 μg/L with detection limits of 0.1, 0.3 and 1.0 μg/L （SIN = 3）, respectively. Finally, the proposed analysis system was successfully utilized for the simultaneous detection of Pb2＋, Cd2＋, and Zn2＋ contents in rice samples. This study indicated that Bi film-coated activated CFR based DPASV sensor can be a promising and reliable tool for rapid analysis of emergency Dollution affairs of heavv metal ions in food.

Finite element beam propagation method for analysis of plasmonic waveguide

The basic idea of the finite element beam propagation method （FE-BPM） is described. It is applied to calculate the fundamental mode of a channel plasmonic polariton （CPP） waveguide to confirm its validity. Both the field distribution and the effective index of the fundamental mode are given by the method. The convergence speed shows the advantage and stability of this method. Then a plasmonic waveguide with a dielectric strip deposited on a metal substrate is investigated, and the group velocity is negative for the fundamental mode of this kind of waveguide. The numerical result shows that the power flow direction is reverse to that of phase velocity.