Effect of heat treatment on microstructure and mechanical properties of Ti-containing low alloy martensitic wear-resistant steel

Effects of quenching temperature and cooling conditions(water cooling and 10%NaCl cooling)on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector plate were investigated.The results show that lath martensite can be obtained after austenitizing in the range of 860-980℃and then water cooling.With an increase in austenitizing temperature,the precipitate content gradually decreases.The precipitates are mainly composed of TiC and Ti4C2S2,and their total content is between 1.15wt.%and 1.64wt.%.The precipitate phase concentration by water-cooling is higher than that by10%NaCl cooling due to the lower cooling rate of water cooling.As the austeniting temperature increases,the hardness and tensile strength of both water cooled and 10%NaCl cooled steels firstly increase and then decrease.The experimental steel exhibits the best comprehensive mechanical properties after being austenitized at 900℃,cooled by 10%NaCl,and then tempered at 200℃.Its hardness,ultimate tensile strength,and wear rate reach551.4 HBW,1,438.2 MPa,and 0.48×10^(-2)mg·m^(-1),respectively.

Damage Mechanism of Ultra-thin Asphalt Overlay(UTAO) based on Discrete Element Method

Aiming to analyze the damage mechanism of UTAO from the perspective of meso-mechanical mechanism using discrete element method(DEM),we conducted study of diseases problems of UTAO in several provinces in China,and found that aggregate spalling was one of the main disease types of UTAO.A discrete element model of UTAO pavement structure was constructed to explore the meso-mechanical mechanism of UTAO damage under the influence of layer thickness,gradation,and bonding modulus.The experimental results show that,as the thickness of UTAO decreasing,the maximum value and the mean value of the contact force between all aggregate particles gradually increase,which leads to aggregates more prone to spalling.Compared with OGFC-5 UTAO,AC-5 UTAO presents smaller maximum and average values of all contact forces,and the loading pressure in AC-5 UTAO is fully diffused in the lateral direction.In addition,the increment of pavement modulus strengthens the overall force of aggregate particles inside UTAO,resulting in aggregate particles peeling off more easily.The increase of bonding modulus changes the position where the maximum value of the tangential force appears,whereas has no effect on the normal force.

Microstructures and wear-resistant properties of in-situ TiC_p/ZA-12 composites

TiC_p/ZA-12 composites were fabricated by exothermic disposition method process and stirring-casting techniques. The microstructure and wear-resistant properties were investigated . The results show that TiC particles are formed in-situ and distributed uniformly in matrix. No particles aggregation and macro or micro precipitation are observed. The wear-resistant properties of composites increase with the increase of TiC_p content, but will not increase when the TiC_p content reaches constant value. Finally, the friction and wear mechanism were also discussed.

Effects of air-atomized water spray cooling device structure on the quenching process,microstructure,and properties of wear-resistant steel

With its high strength and hardness, wear-resistant steel has become an important material in the field of construction machinery manufacturing.Given that quenching technology is a crucial component of wear-resistant steel production, the selection of the cooling method to be used during this process is important.In this study, the feasibility of quenching wear-resistant steel by air-atomized water spray cooling was studied, and the cooling rate, microstructure, and hardness of wear-resistant steel under various cooling device structures were analyzed.The results reveal that the air-atomized water spray cooling method is an effective technique in quenching wear-resistant steel.Furthermore, martensite and uniform hardness were obtained by the air-atomized water spray cooling technique.As the space between the nozzles in each row in the device increased, the cooling rate was reduced during quenching.Meanwhile, the martensite content decreased, and more carbides were observed in the martensitic structure.A mixture comprising self-tempered martensite and bainite was formed at a large distance over a longer period of time.All these factors resulted in lower hardness and worse property uniformity.

Numerical simulation of temperature field in laser-arc hybrid welding of wear-resistant steel

Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-flux- attenuation function, a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300TP wear-resistant steel is proposed. The proposed model considers convection, radiation, molten pool flow, and heat conduction effect on temperature. A comparison of the simulation and actual welding test results confirms the reliability of the model. This welding heat-process model can provide the cooling rate at any position in the heat affected zone （HAZ） and can be used as a reference for the analysis of material properties and for process optimization.

Hot cracking susceptibility research in BTW1 austenitic high-manganese wear-resistant steel

Baosteel’s first BTW1 austenitic high-manganese wear-resistant steel exhibits strong deformation-induced hardening characteristics.Compared with common low-alloy martensitic wear-resistant steels in the market, it has improved impact wear resistance, hard abrasive wear, erosion wear performance, and impact toughness.The metallurgical properties of such austenitic wear-resistant steel lead to the risk of failure because of hot cracking defects in the welded structure.In wear-resistant applications, evaluating hot cracking susceptibility is necessary to avoid the effect of welding defects.In this study, the Varestraint test is used to quantitatively analyze and evaluate the hot cracking susceptibility of BTW1 austenitic high-manganese wear-resistant steel.The test results show that by controlling the content of impurity elements and grain refinement, BTW1 austenitic high-manganese wear-resistant steel effectively reduces hot cracking tendency and has a low incidence of hot cracking under small strain conditions.The developed matching welding process can effectively avoid the influence of hot cracking susceptibility.

Developing Maanshan Kuangyou Wear-resistant Materials Group Company

Maanshan KuangyouGroup company is a special largeenterprise making wear-resistantmaterials products,integratingscience,industry and trade.Mainproducts are chromium-contentwear-resistant materials and ship-use anchor chains."Kuangyou"Brand balls have been awardedprizes of Quality Products by theprovince and ministry,and prizeof Scientific Progress by theprovince,and are widely appliedin mining,cement,power andchemicals industries.Ship-useanchor chains have an

大型轴向列管式固定床反应器的设计、制造、运输

通过对大型轴向列管式固定床反应器的列管布置、管板强度计算、支持板结构、管板的焊接及热处理、壳体组装、运输等多方面优化,从设计、制造、运输三方面综合考虑,使大型轴向固定床反应器的本质安全、运行效果达到更高的要求。

超嵌体

Overlay于1992年由刘洪臣翻译为超嵌体,定义为覆盖整个咬合面的嵌体,并收录于2000年由人民军医出版社正式出版发行的《口腔医学专业术语词典》。但在实际应用中的难点是如何与高嵌体区别,其后作者根据临床应用实践和文献,并与国内外同行商榷,修改其定义为修复伴邻面较大缺失空间的牙体缺损、恢复邻接关系的覆盖或不全覆盖咬合面的一种嵌体修复方式。固位方式包括活髓牙的箱式固位或无髓牙的髓腔固位,其修复边缘位于牙颈部之上。超嵌体有利于保护牙体缺损剩余牙体组织,避免了充填窝洞形成的悬突及牙体充填物的折裂,突出了超嵌体的特点和优越性。

水轮机修复堆焊技术研究现状分析

传统能源逐渐枯竭,且对环境影响较大.国家大力推动绿色清洁能源的发展.水力发电占比也逐年提高,对水轮机相关技术的研究有了更高要求.我国河流泥沙含量大,泥沙含量越高,水轮机关键零部件磨损就越大.水轮机零部件修复技术存在成本高、效率低且质量难以保证等问题,因此亟需研究低成本高效率的智能堆焊修复技术.应用于轮机的先进堆焊技术可以促进绿色环保、提高能源利用率,同时也可促进国民经济发展和振兴机械工业.

电弧摆动对管堆焊温度场及微观组织的影响

为掌握电弧摆动对管堆焊过程的影响,采用焊接仿真与工艺试验两种方式对比电弧摆动和不摆动操作的温度场、残余应力及焊接变形并进行了金相分析。首先,基于有限元分析软件Abaqus,采用热弹塑性有限元法建立焊接过程有限元模型,对摆动焊与常规无摆动焊的温度场进行模拟,并分析熔池的演变过程及温度场分布、热循环曲线等特征。结果表明:摆动焊温度分布云图呈拉长状态,其熔池形状相较于不摆动焊的椭圆形更接近波浪形,摆动焊的温度场更均匀、残余应力更低,可提高焊缝等轴晶比例,细化晶粒,改善焊缝显微硬度。其次,通过金相分析对比了摆动焊与不摆动焊的显微组织,结果表明,摆动焊能够提高焊缝等轴晶的比例和焊缝显微硬度。

基于Agent人工智能的异构网络多重覆盖节点入侵检测系统设计

异构网络具有结构复杂、多重覆盖面积大等特征,使得网络入侵检测较为隐蔽,威胁网络运行的安全性;为此,对基于Agent人工智能的异构网络多重覆盖节点入侵检测系统进行了研究;通过检测Agent和通信Agent装设主机Agent,以Cisco Stealthwatch流量传感器作为异构网络传感器检测攻击行为,采用STM32L151RDT664位微控制器传输批量数据,由MAX3232芯片实现系统电平转化,实现硬件系统设计;软件部分设计入侵检测标准,采用传感器设备捕获网络实时数据,通过Agent技术解析异构网络协议并提取数据运行特征,综合考虑协议解析结果及与检测标准匹配度,实现异构网络多重覆盖节点入侵检测;经实验测试表明,基于Agent人工智能的异构网络多重覆盖节点入侵检测系统入侵行为的漏检率和入侵类型误检率的平均值仅为6%和5%,能够有效提高检测精度,减小检测误差。

列举助词“什么的”的历时来源及形成机制

在数量上可以是1至5项不等,可以是各级语法单位,列举项内部的连接形式多种多样。列举助词“什么的”在民国产生,其形成机制是概念叠加和构式整合,即:表列举的构式“什么×”与构式“×的”发生概念叠加,进而构式整合为构式“什么×的”;夹在中间的成分×前移,从而形成“×什么的”,后置的“什么的”发生词汇化形成三音节列举助词。

OVERLAY堆焊技术在核电设备维修中的应用

核电用奥氏体不锈钢和镍基合金的应力腐蚀问题常导致管道等设备产生缺陷和失效。OVERLAY堆焊技术是针对应力腐蚀问题的实用可靠修复手段,通过堆焊一定尺寸的耐应力腐蚀镍基合金材料,形成新的压力边界(密封)焊缝和结构加强。在实际应用过程中,除完成必要的检验和试验项目外,还应进行相应的残余应力和服役寿命等分析评价。

面向vDC的overlay网络关键技术研究

云计算时代,数据中心趋于虚拟化演进。分析了新时期数据中心虚拟化组网演进的需求,对面向虚拟数据中心组网的基于overlay网络架构的多种关键技术进行了对比研究,并提出了电信运营商虚拟数据中心组网仍需关注的问题。

overlay SDN实现异构兼容的关键技术

云计算的规模化发展对数据中心网络提出了新的挑战,要求应用SDN技术对数据中心网络进行虚拟化,以满足多租户环境下灵活调整的动态网络需求,overlay SDN是实现数据中心网络虚拟化的核心技术。研究了overlay SDN网络虚拟化的关键技术,提出了商业overlay SDN存在的兼容性问题,分析了overlay SDN实现异构兼容的主要方法,并提出了基于开源和白盒交换机实现异构兼容的overlay SDN架构。

Overlay组播路由中负载平衡问题的度量

该文改进了半径受限负载平衡组播路由问题模型中的负载平衡策略,同时考虑度约束、最小半径和负载平衡,建立了新的优化模型,并提出了节点的亏度和饱和度等概念,对overlay组播路由中的负载平衡程度从绝对亏度方差和相对亏度方差两个方面进行了精细的度量。最后,通过一个精心设计的算例,进一步阐明了本文所提概念和模型不但是有意义的,而且在计算上也是可行的。

双源CT碘浓度及Overlay值诊断不同分化程度胃癌及转移淋巴结

目的探讨双源CT双能扫描动脉期碘浓度及Overlay值在诊断不同分化程度胃癌及转移淋巴结中的价值。方法回顾性分析46例术前接受双源CT扫描并经术后病理证实的胃癌伴淋巴结转移患者的资料,测量病灶及转移淋巴结碘浓度、Overlay值。根据病理分化程度将胃癌病灶及转移淋巴结分为分化良好组(病理结果为高分化、中高分化、中分化)与分化不良组(病理结果为中低分化、低分化)。采用独立样本t检验比较2组间胃癌及转移淋巴结碘浓度、Overlay值;并绘制ROC曲线,评价其诊断不同分化程度胃癌及转移淋巴结的效能。结果 46例胃癌病灶中分化良好组15例,分化不良组31例;73枚转移淋巴结中分化良好组24枚,分化不良组49枚。分化不良组胃癌、转移淋巴结碘浓度为(2.12±0.72)mg/ml和(1.85±0.67)mg/ml,Overlay值为(37.32±13.18)HU和(32.24±12.10)HU,均高于分化良好组(P均<0.05)。动脉期碘浓度及Overlay值诊断胃癌分化程度的AUC分别为0.799、0.745(P=0.001、0.008),诊断转移淋巴结分化程度的AUC分别为0.787、0.733(P<0.001、P=0.001)。结论动脉期碘浓度及Overlay值对诊断不同分化程度胃癌及转移淋巴结有一定价值,可为术前评估其分化程度提供依据。

高参数垃圾电站锅炉防腐涂层体系的设计策略与评价

随着国家“双碳”战略目标的提出,垃圾发电成为城市垃圾处理的主流方式。针对高参数垃圾电站锅炉管道腐蚀减薄到一定程度时,造成泄漏甚至爆管的严重安全问题,本文在简介了高参数对锅炉腐蚀影响规律的基础上,评述了高参数条件下管道的基材特性及主流涂层防护技术,重点论述了Inconel堆焊、感应熔焊、HVOF等技术及性能。因为涂层系统设计主要是对管道基体和涂层材料与工艺进行选配,同时匹配参数也是对涂层系统的主要评价指标,所以本文对热膨胀系数、导热系数、结合强度、孔隙率、服役寿命以及经济性等参数进行了系统评价,并阐述了涂层结构设计策略,包括防腐涂层的厚度设计、涂层结构设计、涂层材料组分设计等内容。根据涂层防护技术现存的主要问题,提出粉末合成设计-涂层结构设计-服役性能评价一体化研究的重要性;针对目前主要的材料体系设计比较集中于高Cr含量的FeCr系和NiCr系合金的现状,指出应开发以NiCr基辅以W、Mo等元素涂层材料,使其兼具优异的耐腐蚀和抗磨损的综合性能。最后对涂层防护技术的发展前景进行展望。

Overlay服务网络上的服务组合模型

分析了在Overlay服务网络上进行服务组合的必要性,指出了在进行组合时服务次序约束所带来的特定困难,进而给出了服务次序约束的形式化定义以及带OoS组播路由问题的数学优化模型。借助于罚函数的方法,将服务次序约束条件吸收到目标函数中,从而可以用求解一般组播优化模型的算法来求解新模型。