Flow characteristics and hot workability of a typical low-alloy high-strength steel during multi-pass deformation

Heavy components of low-alloy high-strength(LAHS) steels are generally formed by multi-pass forging. It is necessary to explore the flow characteristics and hot workability of LAHS steels during the multi-pass forging process, which is beneficial to the formulation of actual processing parameters. In the study, the multi-pass hot compression experiments of a typical LAHS steel are carried out at a wide range of deformation temperatures and strain rates. It is found that the work hardening rate of the experimental material depends on deformation parameters and deformation passes, which is ascribed to the impacts of static and dynamic softening behaviors. A new model is established to describe the flow characteristics at various deformation passes. Compared to the classical Arrhenius model and modified Zerilli and Armstrong model, the newly proposed model shows higher prediction accuracy with a confidence level of 0.98565. Furthermore, the connection between power dissipation efficiency(PDE) and deformation parameters is revealed by analyzing the microstructures. The PDE cannot be utilized to reflect the efficiency of energy dissipation for microstructure evolution during the entire deformation process, but only to assess the efficiency of energy dissipation for microstructure evolution in a specific deformation parameter state.As a result, an integrated processing map is proposed to better study the hot workability of the LAHS steel, which considers the effects of instability factor(IF), PDE, and distribution and size of grains. The optimized processing parameters for the multi-pass deformation process are the deformation parameters of 1223–1318 K and 0.01–0.08 s^(-1). Complete dynamic recrystallization occurs within the optimized processing parameters with an average grain size of 18.36–42.3 μm. This study will guide the optimization of the forging process of heavy components.

Recent progress in visualization and digitization of coherent transformation structures and application in high-strength steel

High-strength steels are mainly composed of medium-or low-temperature microstructures,such as bainite or martensite,with coherent transformation characteristics.This type of microstructure has a high density of dislocations and fine crystallographic structural units,which ease the coordinated matching of high strength,toughness,and plasticity.Meanwhile,given its excellent welding perform-ance,high-strength steel has been widely used in major engineering constructions,such as pipelines,ships,and bridges.However,visual-ization and digitization of the effective units of these coherent transformation structures using traditional methods(optical microscopy and scanning electron microscopy)is difficult due to their complex morphology.Moreover,the establishment of quantitative relationships with macroscopic mechanical properties and key process parameters presents additional difficulty.This article reviews the latest progress in microstructural visualization and digitization of high-strength steel,with a focus on the application of crystallographic methods in the development of high-strength steel plates and welding.We obtained the crystallographic data(Euler angle)of the transformed microstruc-tures through electron back-scattering diffraction and combined them with the calculation of inverse transformation from bainite or martensite to austenite to determine the reconstruction of high-temperature parent austenite and orientation relationship(OR)during con-tinuous cooling transformation.Furthermore,visualization of crystallographic packets,blocks,and variants based on actual OR and digit-ization of various grain boundaries can be effectively completed to establish quantitative relationships with alloy composition and key process parameters,thereby providing reverse design guidance for the development of high-strength steel.

Deep decalcification of factory-provided freezing acidolysis solution to achieveα-high-strength gypsum

The freezing acidolysis solution of the nitric acid-phosphate fertilizer process has a high calcium content,which makes it difficult to produce fine phosphate and high water-soluble phosphate fertilizer products.Here,based on the potential crystallization principle of calcium sulfate in NH_(4)NO_(3)-H_(3)PO_(4)-H_(2)O,the deep decalcification(i.e.calcium removal)technology to achieveα-high-strength gypsum originated from freezing acidolysis-solutions has been firstly proposed and investigated.Typically,calcium can be removed from the factory-provided freezing acidolysis-solution by neutralizing it with ammonia,followed by the addition of ammonium sulfate solution.As a result,the formation of calcium sulfate in the reaction system undergoes the nucleation and growth of CaSO_(4)·2H_(2)O(DH),as well as its dissolution and crystallization into short columnarα-CaSO_(4)·0.5H_(2)O(α-HH).Remarkably,with the molar ratio of SO_(4)^(2-)/Ca^(2+)at 1.8,the degree of neutralization(NH_(3)/HNO_(3) molar ratio)at 1.7,the reaction temperature of 94℃,and the reaction time of 300 min,the decalcification rate can reach 86.89%,of which the high-strengthα-CaSO_(4)·0.5H_(2)O(α-HH)will be obtained.Noteworthy,the deep decalcification product meets the standards for the production of fine phosphates and highly water-soluble phosphate fertilizers.Consequently,the 2 h flexural strength ofα-HH is 5.3 MPa and the dry compressive strength is 36.8 MPa,which is up to the standard of commercialα-HH.

Effect of traveling-wave magnetic field on dendrite growth of high-strength steel slab: Industrial trials and numerical simulation

The dendrite growth behavior of high-strength steel during slab continuous casting with a traveling-wave magnetic field was studied in this paper. The morphology of the solidification structure and composition distribution were analyzed. Results showed that the columnar crystals could deflect and break when the traveling-wave magnetic field had low current intensity. With the increase in current intensity, the secondary dendrite arm spacing and solute permeability decreased, and the columnar crystal transformed into an equiaxed crystal. The electromagnetic force caused by the traveling-wave magnetic field changed the temperature gradient and velocity magnitude and promoted the breaking and fusing of dendrites. Dendrite compactness and composition uniformity were arranged in descending order as follows:columnar-toequiaxed transition (high current intensity), columnar crystal zone (low current intensity), columnar-to-equiaxed transition (low current intensity), and equiaxed crystal zone (high current intensity). Verified numerical simulation results combined with the boundary layer theory of solidification front and dendrite breaking–fusing model revealed the dendrite deflection mechanism and growth process. When thermal stress is not considered, and no narrow segment can be found in the dendrite, the velocity magnitude on the solidification front of liquid steel can reach up to 0.041 m/s before the dendrites break.

Hot deformation behavior of novel high-strength Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy

The hot compression behavior of as-extruded Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy was studied on a Gleeble-3500 thermal simulation machine.Experiments were conducted at temperatures ranging from 523 to 673 K and strain rates ranging from 0.001 to 1 s^(-1).Results showed that an increase in the strain rate or a decrease in deformation temperature led to an increase in true stress.The constitutive equation and processing maps of the alloy were obtained and analyzed.The influence of deformation temperatures and strain rates on microstructural evolution and texture was studied with the assistance of electron backscatter diffraction(EBSD).The as-extruded alloy exhibited a bimodal structure that consisted of deformed coarse grains and fine equiaxed recrystallized structures(approximately 1.57μm).The EBSD results of deformed alloy samples revealed that the recrystallization degree and average grain size increased as the deformation temperature increased.By contrast,dislocation density and texture intensity decreased.Compressive texture weakened with the increase in the deformation temperature at the strain rate of 0.01 s-1.Most grains with{0001}planes tilted away from the compression direction(CD)gradually.In addition,when the strain rate decreased,the recrystallization degree and average grain size increased.Meanwhile,the dislocation density decreased.Texture appeared to be insensitive to the strain rate.These findings provide valuable insights into the hot compression behavior,microstructural evolution,and texture changes in the Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy,contributing to the understanding of its processing-microstructure-property relationships.

Development of high-strength magnesium alloys with excellent ignition-proof performance based on the oxidation and ignition mechanisms: A review

High reactivity and ease of ignition are the major obstacles for the application of Mg alloys in aerospace.Thus,the ignition mechanisms of Mg alloys should be investigated systematically,which can guide the ignition-proof alloy design.This article concludes the factors influencing the ignition resistance of Mg alloys from oxide film and substrate microstructure,and also the mechanisms of alloying elements improving the ignition resistance.The low strength is another reason restricting the development of Mg alloys.Therefore,at the last section,Mg alloys with the combination of high strength and good ignition-proof performance are summarized,including Mg-Al-Ca based alloys,SEN(Mg-Al-Zn-Ca-Y)alloys as well as Mg-Y and Mg-Gd based alloys.Besides,the shortages and the future focus of theses alloys are also reviewed.The aim of this article is to promote the understanding of oxidation and ignition mechanisms of Mg alloys and to provide reference for the development of Mg alloys with high strength and excellent ignition-proof performance at the same time.

Microstructure Distribution Characteristics of High-Strength Aluminum Alloy Thin-Walled Tubes during Multi-Passes Hot Power Backward Spinning Process

The microstructure of the thin-walled tubes with high-strength aluminum alloy determines their final forming quality and performance. This type of tube can be manufactured by multi-pass hot power backward spinning process as it can eliminate casting defects, refine microstructure and improve the plasticity of the tube. To analyze the microstructure distribution characteristics of the tube during the spinning process, a 3D coupled thermo-mechanical FE model coupled with the microstructure evolution model of the process was established under the ABAQUS environment. The microstructure evolution characteristics and laws of the tube for the whole spinning process were analyzed. The results show that the dynamic recrystallization is mainly produced in the spinning deformation zone and root area of the tube. In the first pass, the dynamic recrystallization phenomenon is not obvious in the tube. With the pass increasing, the trend of dynamic recrystallization volume percentage gradually increases and extends from the outer surface of the tube to the inner surface. The fine-grained area shows the states of concentration, dispersion, and re-concentration as the pass number increases. .

交通载荷作用下埋地含缺陷玻璃钢管道力学行为研究

为分析含缺陷玻璃钢管道在交通载荷作用下的力学行为,基于ABAQUS有限元软件建立了含不同形状缺陷管道模型和不同埋深管土模型,研究了不同埋深、不同载荷及缺陷深度对管道不同层中截面沿环向应力分布规律的影响。结果表明,无缺陷管道各层应力分布均匀,含缺陷管道内区域层应力沿管材缠绕方向集中于缺陷对称角处;管道仅含轴向缺陷时管体应力峰值与应力突变幅度最大;缺陷相对深度对管道应力峰值影响较大。

Ⅳ型LPG气瓶冲击试验的国内外标准探讨

T/CATSI 02005—2019《液化石油气高密度聚乙烯内胆玻璃纤维全缠绕气瓶》的编制是在理论分析和研究的基础上,修改采用了EN14427:2014《液化石油气设备及配件用于液化石油气的可运输的可充填全封闭复合气瓶设计和施工》有关热塑性非金属内胆全缠绕气瓶部分制定的。通过对冲击试验结果进行分析来探讨T/CATSI 02005—2019和EN14427:2014两个标准的差异性。建议在不影响试验结果的前提下优化试验方法,验证气瓶受外来物体冲击后的抗冲击性能,同时保障试验过程中的生命、财产安全。

玻璃钢撑杆浮球式多功能筏式养殖平台与装备的研究(下)

玻璃钢撑杆浮球式多功能筏式养殖平台由多根横向、纵向玻璃钢撑杆按矩阵排列分布组成,横向及纵向间距均不小于6 m。对紫菜牡蛎养殖设施、混养轮养养殖工艺、防缠绕自伸缩吊绳装置、牡蛎塑型养殖笼、液压驱动生蚝作业平台及养殖物联网系统进行了研究。玻璃钢撑杆浮球式多功能筏式养殖平台的研究可有效提高养殖效益、提升养殖产品品质、实时掌控养殖相关信息并减少养殖户日常出海巡查次数。

玻璃钢锚杆生产工艺介绍与生产线技术改造

文章介绍了玻璃钢锚杆的发展历程,分析了国内外玻璃钢锚杆的生产工艺,介绍了国内玻璃钢锚杆生产线设备发展情况,针对国内某企业玻璃钢锚杆生产线进行了技术改造和关键部件的机械结构设计,提高了产品生产的自动化水平。实践表明,改造后生产效率和生产质量均得到了提升。

船艇用玻璃钢材料的生命周期碳排放分析

玻璃钢(GFRP)因其质轻高强耐腐蚀的特点而广泛应用于船艇壳体材料。在我国船艇行业落实“双碳”发展战略的背景下,“绿色低碳船艇”理念对船艇用玻璃钢材料的碳排放等环境负荷指标提出了新的要求。本文采用面向过程的生命周期分析方法(LCA),构建了船艇用玻璃钢材料从原料生产到废弃过程的分析模型。结果表明:1 t船艇用玻璃钢材料的碳排放为5023.60 kg CO_(2)eq,原辅料生产、生产加工和废弃处置阶段占比分别为70.33%、14.55%和15.12%;原辅料生产阶段碳排放主要来源于树脂产品和玻纤产品,生产加工阶段的碳排放主要来源于电力消费,废弃处置阶段开展废旧玻璃钢材料的综合利用将有助于碳减排。根据上述结果,对船艇用玻璃钢材料生命周期各个阶段的减碳路径提供了建议及成效分析。

Development in oxide metallurgy for improving the weldability of high -strength low-alloy steel-Combined deoxidizers and microalloying elements

The mechanisms of oxide metallurgy include inducing the formation of intragranular acicular ferrite(IAF)using micron-sized inclusions and restricting the growth of prior austenite grains(PAGs)by nanosized particles during welding.The chaotically oriented IAF and refined PAGs inhibit crack initiation and propagation in the steel,resulting in high impact toughness.This work summarizes the com-bined effect of deoxidizers and alloying elements,with the aim to provide a new perspective for the research and practice related to im-proving the impact toughness of the heat affected zone(HAZ)during the high heat input welding.Ti complex deoxidation with other strong deoxidants,such as Mg,Ca,Zr,and rare earth metals(REMs),can improve the toughness of the heat-affected zone(HAZ)by re-fining PAGs or increasing IAF contents.However,it is difficult to identify the specific phase responsible for IAF nucleation because ef-fective inclusions formed by complex deoxidation are usually multiphase.Increasing alloying elements,such as C,Si,Al,Nb,or Cr,con-tents can impair HAZ toughness.A high C content typically increases the number of coarse carbides and decreases the potency of IAF formation.Si,Cr,or Al addition leads to the formation of undesirable microstructures.Nb reduces the high-temperature stability of the precipitates.Mo,V,and B can enhance HAZ toughness.Mo-containing precipitates present good thermal stability.VN or V(C,N)is ef-fective in promoting IAF nucleation due to its good coherent crystallographic relationship with ferrite.The formation of the B-depleted zone around the inclusion promotes IAF formation.The interactions between alloying elements are complex,and the effect of adding dif-ferent alloying elements remains to be evaluated.In the future,the interactions between various alloying elements and their effects on ox-ide metallurgy,as well as the calculation of the nucleation effects of effective inclusions using first principles calculations will become the focus of oxide metallurgy.

纤维复合材料在调水工程长输管道中的应用

调水工程长距离输水管道的材料选择,对工程成本和输水线路的安全有着重要影响。纤维复合材料具有轻质高强、内壁光滑、耐腐蚀性好等特点,正逐步应用在输水管道中。文章分析了影响长距离输水管道材料选择的主要因素,介绍了钢管、球墨铸铁管、混凝土管等传统输水管道的材料特性,阐述了纤维复合材料在输水管道中的应用,重点分析了玻璃钢夹砂管的发展和特点,最后对纤维复合材料输水管道在产品升级、施工技术、安全防护和质量管理四个方面的发展进行了展望。

玻璃纤维板阵列增多层吸波复合结构

本文将电路模拟吸波阵列与玻璃纤维介质板(FEPL)阵列结合,采用真空热压成型工艺制备了一种具有超宽带强吸波性能的多层复合结构。整个FEPL阵列复合结构的表面密度约为2.4 kg/m^(2),厚度约为10.0 mm。仿真和测量结果均表明,FEPL阵列可以明显改善吸波结构的斜入射角的稳定性,提高电磁吸收率,拓宽吸收带宽。在斜入射角40°~60°范围内,FEPL阵列显著提高了吸波复合结构的吸收性能,同时将相对带宽(FBW)拓宽了约9.1%;此外,它还将复合吸波结构正入射角的平均反射系数从−14.4 dB降低到了−25.7 dB,降低了约11.3 dB。本文所提出的玻璃纤维板阵列增多层吸波复合结构性能优异,制备工艺简单,适合实际工程应用。

玻纤生产过程废浇注料回收铂、铑的工艺研究

以玻纤生产过程的废浇注料为原料,采用球磨破碎、碱焙烧、王水溶解、有机相选择沉铑、氯化铵沉铂作为主要工艺回收铂、铑,取得良好的效果。浸出前通过碱焙烧-水溶去除废料中的硅、铝杂质,避免铂、铑在硅、铝元素包裹下难以完全浸出,同时可降低提纯难度。结果表明,碱加入量是废料质量的1.5倍,在750 ℃温度下焙烧40 min时,使用王水浸出,铂、铑的浸出率均在99%以上。使用二乙烯三胺可选择性沉淀浸出液中的铑,完成铂、铑的分离。反应温度为65 ℃,二乙烯三胺加入量为溶液中铑含量的8.5倍时,铑的沉淀率最高,可达到99.98%,同时溶液中的铂不沉淀。铂、铑分离后分别提纯,即可得到所需的海绵铂及铑粉。采用该工艺,铂、铑的回收率可达到99%,生产的海绵铂及铑粉的纯度均大于99.95%。

玻纤耐火砖的加压浸出工艺研究

试验对某玻纤厂产出的废耐火砖进行加压酸浸处理,探索最佳浸出工艺条件。试验结果表明,当耐火砖用量为100 g,液固比为5∶1,盐酸用量为80 mL,硝酸用量为20 mL,反应温度为200℃,压强为1.6 MPa,反应时间为4 h时,铂的浸出率可达99.05%,铑的浸出率可达98.21%,渣中铂含量和铑含量分别降低至0.0016%、0.0003%。在最佳浸出工艺条件下,采用低浓度盐酸+硝酸混酸体系,加压浸出可实现铂和铑的高效浸出,具有较好的应用前景。

剑麻-耐碱玻璃纤维对混凝土的性能影响

剑麻纤维作为一种绿色环保植物纤维,具有成本低廉、韧性和弹性模量高、抗拉抗腐蚀性好等诸多优点,混凝土中掺入剑麻纤维在一定程度上能够提高其劈裂抗拉强度和弹性模量,从而提高混凝土结构的耐久性,延长混凝土的使用寿命。耐碱玻璃纤维具有抗拉强度高、流动性好、与混凝土浆料的包裹黏结性好等特点。该纤维的掺入对于混凝土的抗折和抗拉强度有着明显提高,并且已经成功应用在了隧道工程当中,取得了较为成功的结果。这两种纤维所组成的双掺混合纤维不仅能够保留两者优点,而且能够加强其力学性能。文章主要探讨了两者混合所构成的混合纤维混凝土的特点及其对混凝土力学性能改善的效果。

基于非线性热响应的玻璃纤维/乙烯基酯复合材料拉伸响应预报方法

为探究复合材料结构在火灾条件下的力学响应,建立考虑基体热解和纤维软化效应的复合材料热-拉伸响应模型,通过多维数组运算对非线性方程组进行求解,研究高温下玻璃纤维/乙烯基酯复合材料的拉伸性能变化规律、预测玻璃纤维/乙烯基酯复合材料在不同拉伸载荷和单侧热流工况下的失效时间。结果表明:建立的非线性热-拉伸性响应模型,能够有效预测乙烯基酯及玻璃纤维/乙烯基酯复合材料在单侧恒定热流下的拉伸性能。通过模型预测曲线可知,玻璃纤维/乙烯基酯复合材料拉伸强度随温度的下降主要分为两个阶段:第一阶段为其在玻璃化转变温度附近快速下降;第二阶段为材料基体完全玻璃化转变后,玻璃纤维/乙烯基酯复合材料拉伸强度的缓慢下降。另外,随着拉伸载荷的增加,玻璃纤维/乙烯基酯复合材料失效时间迅速缩短,且失效时间随拉伸载荷变化情况在不同热流密度下具有相同的趋势。在相同拉伸应力下,热流密度的下降可延长材料的失效时间。在80%室温强度的拉伸应力下,层合板在10 kW/m^(2)下的失效时间较75 kW/m^(2)延长了300 s。在10 kW/m^(2)条件下,施加拉伸应力低于50%室温强度时,层合板在长时间内不会发生失效。

酸对玻纤滤纸性能影响的研究

对于玻纤滤纸,加酸分散纤维是其生产过程中的通用工艺。以往研究侧重于分析酸对于纤维分散效果的影响,重点研究了酸的加入对玻纤滤纸力学性能和过滤性能产生的影响。实验结果表明:酸会与玻璃纤维反应导致纤维表面生成了更多的Si-OH;当玻纤滤纸抄造过程中加酸控制浆料pH为2.5时,使用39°SR和49°SR玻璃棉所抄造滤纸的抗张强度比不加酸时分别高了54%和58%,透气度分别下降了11%和14%,平均孔径分别下降了12%和14%。过滤性能测试结果表明,加酸制备滤纸的液体过滤比要明显高于未加酸制备的滤纸。