Deformation behaviors of 21-6-9 stainless steel tube numerical control bending under different friction conditions

For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-plastic finite element(FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die-tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel-tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die-tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die-tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die-tube, mandrel-tube, pressure die-tube and bending die-tube of 21-6-9(0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05-0.15, 0.05-0.15, 0.25-0.35 and 0.25-0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.

Analysis of bending on the front end of sheet during hot rolling

The analysis of bending in finishing rolling was performed. An asymmetrical rolling force model was established, and the upper and lower neutral points were determined. Thc bending which resulted from the asymmetrical rolling force at the roll gap was studied and related flexibility equations were proposed according to elastic mechanics. Moreover, material mechanics was used to analyze the effects of temperature difference and self-weight on the bending out of the roll gap, and the flexibility equations were constructed. The main factors on bending were summed up, and the bending rule in the rolling could be obtained. In addition practical calculation was made with the production data of ribbon steel from Laiwu Iron ＆ Steel Group Co. Ltd.

Bending analysis and control of rolled plate during snake hot rolling

In order to study the bending behavior of aluminum alloy 7050 thick plate during snake hot rolling, several coupled thermo-mechanical finite element(FE) models were established. Effects of different initial thicknesses, pass reductions, speed ratios and offset distances on the bending value of the plate were analyzed. ‘Quasi smooth plate' and optimum offset distance were defined and quasi smooth plate could be acquired by adjusting offset distance, and then bending control equation was fitted. The results show that bending value of the plate as well as the extent of the increase grows with the increase of pass reduction and decrease of initial thickness; the bending value firstly increases and then keeps steady with the ascending speed ratio; the bending value can be reduced by enlarging the offset distance. The optimum offset distance varies for different rolling parameters and it is augmented with the increase of pass reduction and speed ratio and the decrease of initial thickness. A proper offset distance for different rolling parameters can be calculated by the bending control equation and this equation can be a guidance to acquire a quasi smooth plate. The FEM results agree well with experimental results.

Automatic girth welding and performance evaluation of the joints of hot-induction-bend and line pipes with different wall thickness

During the process of laying long-distance oil and gas transmission pipelines, the hot-induction-bend method is extensively used when the direction has to be changed. By considering the pipeline＇ s ongoing processing and loading states during service, the pipeline that is generally used exhibits thicker walls than those that are observed in the line pipe. As such, during pipeline construction, hot-induction-bend and line pipes with different wall thickness are girth-welded. The chemical composition of hot-induction-bend and line pipes differs, with the carbon content being particularly higher in the hot-induction-bend pipe;it also depicts a higher carbon equivalent, which makes it possible to modify the girth of the pipe. In this study, using Baosteel＇ s standard X70M UOE hot- induction-bend and line pipes, solid-wire automatic gas-metal-arc girth welding was performed and the performance of the girth-welded joint was evaluated. Furthermore,the weldability of the pipeline girth and the microstructure of the girth-welded joint were analyzed. The results reveal that Baosteel＇ s standard UOE hot-induction-bend and line pipes exhibit good girth weldability, and their technical quality can be guaranteed in case of consumer field- construction applications.

Experimental and Numerical Study of Dilute Gas-Solid Flow inside a 90°Horizontal Square Pipe Bend

A pneumatic test rig is built to test a curved 90° square bend in an open-circuit horizontal-to-horizontal suction wind tunnel system. Sand particles are used to represent the solid phase with a wide range of particle diameters. Velocity profiles are constructed by measuring the gas velocity using a 3-hole probe. Flow patterns inside the bend duct are introduced using sparks caused by burning sticks of incense with the air flow inside the piping system for flow visualization purpose. Numerical calculations are performed by Lagrangian-particle tracking model for predicting particle trajectories of dispersed phase, and standard k-ε model for predicting the turbulent gas-solid flows in bends. Comparisons made between the theoretical results and experimental data for the velocity vectors and particle trajectories show good agreement.

SNP-9对Aβ_(25-35)导致bEnd.3细胞损伤的作用及其机制

为了研究来源于丝素蛋白水解物的神经保护活性多肽SNP-9对于阿尔茨海默病(Alzheimer′s disease,AD)中血脑屏障损伤的作用,使用Aβ_(25-35)损伤脑微血管内皮细胞bEnd.3建立AD损伤模型,并给药干预。通过MTT实验检测SNP-9和Aβ_(25-35)对细胞活力的影响;RT-qPCR法检测SNP-9和Aβ_(25-35)对细胞紧密连接(tightjunctions,TJs)相关的ZO-1、occludin和claudin-5 mRNA水平的影响;Westernblot检测SNP-9和Aβ_(25-35)对细胞TNF-α、磷酸化NF-κB、NF-κB、IκBα和RAGE蛋白水平的影响。实验结果显示,SNP-9给药减少了Aβ_(25-35)诱导的bEnd.3细胞损伤,改善了模型细胞中ZO-1、occludin和claudin-5 mRNA水平的异常情况,缓解了Aβ_(25-35)导致的TNF-α、磷酸化NF-κB、IκBα和RAGE蛋白水平异常。研究结果表明,SNP-9可能通过影响RAGE/NF-κB通路,调控模型细胞炎症因子TNF-α水平,改善TJs相关指标异常,缓解Aβ_(25-35)诱导的bEnd.3细胞损伤。

Effects of Hot Bending Parameters on Microstructure and Mechanical Properties of Weld Metal for X80 Hot Bends

Mechanical properties of weld metal are the key factors affecting the quality of heavy-wall X80 hot induction bends. The effects of bending parameters on the mechanical properties of weld metal for hot bends were investigated by simulation conducted on a Gleeble 3500 thermal simulator. Continuous cooling transformation （CCT） dia- grams of the weld metal were also constructed. The influences of hot bending parameters （such as reheating temperature, cooling rate, and tempering temperature） on the microstructure and mechanical properties of weld metal were also analyzed. Results show that the strength of all weld metal specimens is higher than the value indicated in the technical specification and increases with the increase of reheating temperature, cooling rate, and tempering tempera ture. The impact toughness is apparently related to the variation of reheating temperature, cooling rate, and tempering temperature.

真空热压制备W-50%Cu复合材料

采用真空热压制备了W-50%Cu复合材料,对其性能进行了测试,并利用SEM对其微观组织和断口形貌进行了观察与分析。结果表明:在30MPa压力下进行950℃×2h烧结,获得了相对密度达99.6%的W-50%Cu复合材料,其显微硬度、电导率和抗弯强度分别达到133HV、68.9%IACS和285MPa;W-50%Cu复合材料的抗弯断裂表现出塑性断裂特征,其断裂方式主要为沿晶断裂,并伴随少量的穿晶断裂。

Al_2O_3加入量对AlN-Al_2O_3复相陶瓷制备及性能的影响

以AlN和Al2O3为原料,Y2O3为烧结助剂,N2气氛下在1650℃下热压烧结制备出了AlN-Al2O3复相陶瓷;采用X射线衍射、扫描电子显微镜和透射电子显微镜等对复相材料的相组成、显微结构进行表征。研究了Al2O3加入量对AlN-Al2O3复相材料的强度、热导率和介电性能的影响。结果表明,Al2O3加入量的增加可促进材料的烧结致密化和抑制AlN基体晶粒的生长。Al2O3含量为20 wt%和30 wt%时可制得致密的AlN-Al2O3复相陶瓷。Al2O3利用其高强度和弥散强化作用对AlN基体起到了明显的增强效果。随着Al2O3加入量的增加,试样的抗弯强度显著提高,热导率和介电性能也得到改善。加入30 wt%Al2O3的复相陶瓷的抗弯强度和热导率达到最大值457 MPa和57 W/(m.K),介电常数和介电损耗达到最低值9.32和2.6×10-4。当Al2O3含量达到40 wt%以后,材料中部分AlN与Al2O3反应生成AlON,从而使材料的抗弯强度、热导率和介电性能又明显下降。

高铝砖高温弯曲应力-应变关系

采用研制的高温弯曲应力-应变测试仪研究了Ⅰ等高铝砖DL-80、Ⅱ等高铝砖GL-75和Ⅲ等高铝砖GL-55在不同温度下的力学性能,包括应力-应变曲线、弹性模量、抗折强度和断裂时的最大变形量。结果表明:高铝砖在不同温度下的应力-应变关系可以分为弹性阶段、塑性阶段和粘滞流动阶段;在低、中温范围内,高铝砖的弹性模量和抗折强度随温度的上升而增加,到达某一转折温度后,随温度的上升而明显下降;3种高铝砖高温力学性能从高到低的排列顺序为:Ⅱ等>Ⅰ等>Ⅲ等。

短纤维增强C-SiC复合材料的制备和性能

将T700或Nicalon-SiC短纤维、碳粉、硅粉和少量碳化硅粉混合,在1900℃热压烧结制备短纤维增强C-SiC复合材料,并对其组织、结构及性能进行了研究。结果表明:SiCf／C-SiC的相对密度和室温强度分别为95.3％和24.38MPa,均高于Cf／C-SiC的相对密度和室温强度,热压烧结过程中Cf的损伤严重。短纤雄增强C-SiC复合材料中,由于C相和SiC相的同时存在,在同一温度下的氧化行为表现为在氧化初期氧化质量损失率较大,C相的氧化起主要作用;随氧化时间的增长,氧化质量损失率逐渐减小;在氧化后期则质量增加,SiC相的惰性氧化起主要作用。SiCf／C-SiC复合材料的抗氧化性能优于Cf／C-SiC复合材料的抗氧化性能。SiCf／C-SiC复合材料在温度为1100℃～1400℃时,温度越高,氧化质量损失率越小,抗氧化性能越强。

ZrB_2含量对LaB_6-ZrB_2复合材料性能的影响

采用碳热还原法合成了不同ZrB2含量的LaB6ZrB2复合粉末。通过热压烧结法制备了相应的复合材料,其性能测试结果表明:随着ZrB2含量的增加,LaB6ZrB2复合材料的硬度和弯曲强度均随之增大,而断裂韧性则先增后减,在ZrB2质量分数为21%时,其断裂韧性达最大值。利用金相显微镜和扫描电镜观察多晶试样的微观组织及断口形貌,初步分析了复合材料的增韧机制。

EAF-CSP工艺生产带钢冷弯裂纹的成因分析

分析了珠钢EAF—CSP工艺生产的热轧带钢冷弯裂纹的形成原因。研究表明:碳、锰含量高的钢中容易形成带状组织,钢中较高的铜含量和带状组织是形成冷弯裂纹的重要原因;生产厚规格带钢时,薄板坯表面微裂纹在轧制过程中难以消除;通过对化学成分和生产工艺的合理控制可以显著提高带钢的冷弯合格率。

Si复合Al_2O_3-SiC材料热机械性能的研究

通过应力-应变关系、高温抗折强度等高温试验,研究了金属硅复合Al2O3-SiC材料的热机械性能,结合SEM和XRD,对金属硅复合Al2O3-SiC材料高温显微结构和物相进行分析。结果表明:金属硅作为一个组元,不仅能缓解Al2O3-SiC材料由于热膨胀系数不匹配产生的内应力,而且使Al2O3-SiC材料兼具有金属塑性的特点,从而改善了Al2O3-SiC无机材料热机械性能。

机械合金化对Fe-Cu-Al热压烧结的影响

本文利用XRD、SEM、DSC等手段研究了Fe-Cu-Al粉末体系机械合金化(MA)过程金属粉体的结构变化及储能情况。将机械合金化处理后的粉末进行热压烧结,并对烧结体进行了金相组织、硬度和抗折强度分析。结果表明,Fe-Cu-Al经MA处理能够形成二元及三元固溶体,粉体粒度和晶粒度明显细化,粉体内储存了大量的表面能和界面能。球磨20 h晶粒度达到稳定值20 nm,粉体储能达到最大值385.1 J/g,球磨30 h粉体粒度达到稳定状态。随着球磨时间的延长,粉末烧结体的成分趋于均匀,组织不断细化。粉末烧结体的硬度在球磨初期显著提高,超过10 h后硬度提高缓慢,而烧结体的抗折强度随着球磨时间的延长几乎成线性增长。球磨50 h粉末烧结体的洛氏硬度和抗折强度分别达到108 HRB和351 MPa。

高强钢/碳纤维增强复合材料热冲压-连接一体化工艺可行性及试样弯曲性能研究

提出一种高强钢/碳纤维增强复合材料(CFRP)的多材料零件连接成形一体化加工工艺,利用热冲压工艺对高强钢和CFRP预浸料进行连接并成形高强钢/CFRP多材料零件。研究热冲压过程中不同的淬火温度下多材料复合板的制备工艺,并对试样中钢板进行微观观测,最后对复合件进行弯曲试验。微观检测结果表明,该工艺下钢板组织为全马氏体组织。三点弯曲试验结果表明,未铺设CFRP试样、铺设2层CFRP试样和铺设4层CFRP试样的弯曲角度分别为130°、110°和104°。对弯曲试验的力位移曲线进行积分,计算试样的能量吸收量,得到如下结论:未铺设CFRP试样、铺设2层CFRP试样和铺设4层CFRP试样的能量吸收量分别为9410 J、9692 J和10050 J;铺设2层CFRP的试样和铺设4层CFRP的试样相比于未铺设CFRP的试样,能量吸收量分别增加2.9%和6.8%。

ZrB_2-SiC层状高强界面复合陶瓷材料高温力学性能研究

强界面硼化锆陶瓷材料是一种性能优异的高温陶瓷材料,在较高的温度下具有较高的强度以及抗氧化性能,广泛应用于可回收式航空航天飞行器领域中。将强界面ZrB_2-SiC材料抛光后置于不同温度下进行高温力学性能测试,在到达测试温度后进行保温30min后对其施加应力直到材料试样完全断裂为止,可以获得材料相应施加的最大力及其对应强度,并通过扫描电镜照片对测试后的试样表面和断口进行分析。结果表明:在平行和垂直两个方向上,材料的弯曲强度不同。首先在平行方向上随着温度的升高而降低;其次在垂直方向上材料的弯曲强度随着温度升高而降低,其强度在1200℃时为396.78MPa和435.90MPa,在1 500℃时强度达到最小值,分别为220.7MPa和195.15MPa。通过分析可知,垂直方向的弯曲强度高于平行方向,随温度升高弯曲强度会下降,但在1 300℃时出现了一个最小值,是因为B_2O_3受热分解和材料本身受高温引起的缺陷共同作用引起的,垂直方向高于平行方向是由于材料的各向异性,垂直时强度比较大。

热压扩散焊接法制备钛-钢复合材料及性能研究

利用热压扩散焊接法法制备钛一钢复合材料。采用用扫描电镜、EDS分析、拉剪试验和三点弯曲试验等方法，研究了扩散焊接温度对钛一钢复合界面附近形貌、成分、界面剪切强度和弯曲性能的影响。结果表明：热压扩散焊接法在压力3MPa，真空度≥10-3Pa，保温时间1h，焊接温度≥820℃的条件下，有Ti、Fe原子相互扩散，可实现冶金结合；在焊接温度≥740℃条件下，钛钢界面的拉伸剪切强度都大于基体强度；在740～840℃的焊接温度下，抗弯曲性能随温度升高而先增大后减小，800℃的抗弯曲性能最强，达到29．71MPa。

铜含量对Al-50%Si_p复合材料显微组织和力学性能的影响

采用热压法制备添加0~6%铜含量(质量分数)的Al-50%Sip(质量分数)复合材料,研究Cu含量对复合材料显微组织和力学性能的影响,对混合粉末进行差示扫描量热分析(DSC),采用扫描电镜(SEM)和X射线衍射仪(XRD)研究试样的显微组织和相组成,并测试复合材料的拉伸和抗弯性能。结果表明:单质Cu粉的加入降低混合粉末的熔点,有利于在相对较低的温度下实现材料的致密化。当Cu含量低于2%时,材料的组织均匀致密,Si颗粒未出现明显粗化;但当Cu含量高于2%时,组织均匀性随Cu含量的增加而逐渐下降;随着Cu含量增加,复合材料的抗拉强度和抗弯强度呈先上升后下降的趋势;在Cu含量为2%时,复合材料的抗拉强度和抗弯强度分别达到最大值(268和423 MPa),较未添加Cu的复合材料分别提高66.5%和46.9%,材料的弹性模量和布氏硬度随Cu含量的增加逐渐上升。

MgO-Y_2O_3对热压烧结Al_2O_3性能的影响

以高纯的硫酸铝氨分解的无定形Al2O3为原料,MgO-Y2O3为烧结助剂,在N2气氛下热压烧结制备Al2O3陶瓷。研究了烧结助剂掺量对Al2O3材料的相组成、显微结构、烧结性能、力学性能、热导率和介电性能的影响。结果表明:所制Al2O3陶瓷具有细晶的显微结构特征和超高的抗弯强度。随着MgO-Y2O3掺量的增加,晶粒尺寸、抗弯强度和热导率先增大后减小,而介电损耗则呈现先减小后增大的变化规律。当MgO和Y2O3掺量均为质量分数2%时,Al2O3陶瓷呈现为较佳的综合性能:抗弯强度达最大值为603 MPa,热导率为36.47 W.m–1.K–1,介电损耗低至6.32×10–4。