On a General Parameterization for Inverse Analysis of Heat Deposition Processes

A general parameterization for inverse analysis of heat deposition processes using incomplete or minimal experimental data is presented. This parameterization is considered general in the sense that it can be applied, in principle, to the inverse analysis of a wide range of different types of heat deposition processes, including welding. The structure of this parameterization follows from the concepts of model and data spaces that imply the existence of an optimal parametric representation for a given class of inverse problems. Accordingly, the corresponding optimal parametric representation lies in the model space and is determined by the characteristics of the available data sets spanning the data space and the nature of the data sampling for purposes of parameter determination via appropriate optimization techniques. The elements of the proof presented here provide an elucidation of certain aspects of inverse heat-deposition analysis that are important for practical application.     

A Physically Consistent Path-Weighted Diffusivity Function for Modeling of Drop-by-Drop Liquid Metal Deposition

A physically consistent path-weighted diffusivity function is derived for parametric representation of heat diffusion patterns occurring within a volume of material where in there exists inhomogeneous or anisotropic thermal diffusivity. A physically consistent parametric representation of energy deposition processes, where there exists spatially dependent thermal diffusivity, provides for more optimal inverse analysis of such processes. The path-weighted diffusivity function presented here further extends an inverse analysis approach presented previously. The general functional characteristics of the path-weighted diffusivity function derived are examined via a prototype simulation of drop-by-drop liquid metal deposition upon a material characterized by anisotropic thermal diffusivity. The results of this simulation are compared with previous simulations concerning path-weighted thermal diffusivity. The parametric representations presented, which are constructed using path-weighted sums of analytic basis functions, are examined from the perspective of discrete numerical methods. This perspective provides a foundation for the development of control algorithms for process optimization with respect to achieving specific microstructures within a fabricated structure.     

General Basis Functions for Parametric Representation of Energy Deposition Processes

General basis functions for parametric representation of energy deposition processes are constructed according to the general physical characteristics of energy deposition within a volume of material from a beam energy source. These basis functions include previously constructed source functions as special cases. The construction of a general parameterization of energy deposition processes, e.g., welding and rapid prototyping, is necessary for inverse analysis of such processes. The structure of such a parameterization follows from the concepts of model and data spaces that imply the existence of an optimal parametric representation for a given class of inverse problems. Accordingly, the optimal parametric representation lying within the model space is determined by the characteristics of the available data, i.e., data space, which contain both experimental measurements and numerical simulation data. Experimental measurements include solidification cross-sections, thermocouple measurements, and microstructural changes. Numerical simulation data include general temperature field trend characteristics, response characteristics of materials to volumetric energy deposition, and the relative sensitivity of temperature field characteristics to phenomena occurring on different space and time scales. A general procedure is described for using basis functions with the available experimental and numerical data to construct a multidimensional field representation of a large class of energy deposition processes.     

An Algorithm for Inverse Modeling of Layer-by-Layer Deposition Processes

Metallic parts can be made by deposition of liquid metal in a layer-by-layer fashion. By this means, layered structures can be produced that are made up of overlapping reinforced droplets. In particular, prototypes, i.e., customized parts and tooling, can be produced in this way. In order that layer-by-layer fabrication techniques transition from prototyping to manufacturing, however, the processes must be made reliable and consistent. Accordingly, detailed microstructural and thermal characterizations of the product are needed to advance manufacturing goals based on layer-by-layer deposition processes. The inherent complexity of layer-by-layer deposition processes, characteristic of energy and mass deposition processes in general, is such that process modeling based on theory, or the direct-problem approach, is extremely difficult. A general approach to overcoming difficulties associated with this inherent complexity is the inverse-problem approach. Presented here is an algorithm for inverse modeling of heat transfer occurring during layer-by-layer deposition, which is potentially adaptable for prediction of temperature histories in samples that are made by layer-by-layer deposition processes.     

钢热处理的新工艺

钢经热处理后保存残余奥氏体可以改善钢件的塑性和韧性。在20世纪,我们在热处理中应用奥氏体热稳定化,有效地减小淬火（高速钢回火）时钢件的畸变。本文介绍Speer等近年来发展的钢热处理新工艺-淬火和分配（Q＆P）处理,即含Si或Al的Q—P钢经淬火至Ms—Mf间一定的温度（QT）后,再在一定温度（PT,在淬火温度或者高于Ms）停留,使碳由马氏体扩散（分配）至残余奥氏体,使其稳定化．增加最后淬至室温的奥氏体含量,改善钢件的强、韧混合性质。示例说明,钢经Q—P处理后显示良好的力学性质。实验表明,Q—P热力学模型“限制条件碳准平衡”（CPE,CCE）的限制假设奈件常不存在。认为：在Q—P处理,尤其在较高温度、作较长时间分配处理时,宜以稳态平衡为理论基准,并计算各类可能相变的△G值,以预测可能发生的相变,包括碳化物的析出,γ→α,以及M（α）→γ。碳原子可能按扩散动力学在马氏体和奥氏体两相间分配。以Q—P处理为基础,本文作者提出淬火-分配-回火（Q—P—T）工艺,钢件局域的渗碳,以及高强度钢经碳分配等热处理新工艺。     

电火花沉积工艺对点焊电极TiC沉积层厚度的影响

为了改善镀锌钢板点焊电极的寿命,选用铬锆铜球型点焊电极,以TiC作为熔敷材料,进行了点焊电极表面电火花沉积TiC工艺试验。通过正交试验考察了沉积工艺参数(电容、基体电极转速、振动频率、沉积时间)以及前处理与后处理对沉积层厚度的影响。结果表明,电容是影响电火花沉积层厚度的主要因素;振动频率对沉积层厚度有一定的影响;基体电极转速、沉积时间对沉积层厚度影响较小。试验条件下最佳的工艺参数是:电容量30000μF,基体电极转速1320r/min,振动频率50Hz,沉积时间120s。前处理(沉积前清洗)对其厚度影响很小。后处理(沉积后700℃×30min退火)促进元素扩散并减小沉积层厚度。     

激光沉积及热处理工艺对TC11钛合金组织和性能的影响

采用激光沉积工艺制备了TC11钛合金,研究了激光功率及固溶温度对其组织和力学性能的影响.结果 表明:随着激光功率的提高,合金的强度增加,塑性降低;随着固溶温度的升高,从950℃提高到970℃,固溶时效后合金横纵向的组织和性能逐渐趋于均匀一致,固溶温度提高至990℃时,合金的各向异性加大;采用970℃保温1h空冷+530...     

Solid Oxide Fuel Cells: A Challenge for Plasma Deposition Processes

Fuel cells directly convert chemical energy into electrical energy with the potential of very high-efficiency values, because they are not subjected to the Carnot relationship. Of the different fuel cell types in particular Solid Oxide Fuel Cells (SOFC) meet a high interest for different applications due to their specific advantageous properties. They operate in the high temperature range around and above 800 °C and consist in the electrochemical active part mainly of ceramic material. Their economic and technical breakthrough depends still on the success to realize them with high quality, reliability, and efficiency and in particular with acceptable and attractive costs. Different manufacturing methods are in application or under development for the production of the cell components. Beneath these methods are also plasma spray technologies. This review will show the specific demands, the performed and ongoing work, the state of development and especially the required R + D goals to render this type of methods successful.     

套筒裂纹分析及热处理工艺改进

图1所示为某厂生产的WQ202产品套筒零件,热处理后对632件零件探伤检验时发现其中有54件存在裂纹,裂纹比例为8．5％。随后,发现每批零件热处理后都出现裂纹,个别批次裂纹比例高达10％以上,严重影响了正常生产。为此,对产生裂纹的零件进行了失效分析,以查明裂纹原因,提出改进措施。     

New Sensor Concepts for Enhancing Heat Treatment Processes and Analysis

The need for developing accurate quenching models requires an extensive experimental database that includes surface heat flux characterization. Quantification of the quenching process permits i) the development of high-quality heat treated products, ii) the evaluation of new quenchants and quenchant systems, and iii) the evaluation of quenchant quality over usage time. The surface heat transfer coefficient (or heat flux) is rarely measured, calculated or modeled in sufficient detail for real scientific use. Many single-thermocouple based probes are designed for the purpose of measuring the cooling power of a liquid quenchant or for monitoring quenchant quality. Lumped based probes are sufficient for these types of applications. However, the lack of sufficient distributed detail impedes the development of future high-quality heat-treated products. Frankel and his coworkers are developing a new family of transient thermal-rate sensors that will improve both diagnostic and real-time analyzes in heat transfer studies. Analyzes have been performed indicating that there exists a novel,thermal-rate sensor hierarchy that stabilizes predictions when used with analysis. This concept can be used for investigating both (i) direct surface heat transfer effects, and (ii) projective surface analysis based on embedded sensors. This new sensor family includes the ability to measure temperature, T; heat flux, q“; and their temporal derivatives, i.e., dT/dt, d^2F/dt^2 and dq“/dt.     

Spatial Modulation and Filtering of Diffusion Patterns for Inverse Analysis of Heat Deposition

General parameterizations are constructed for spatial modulation and filtering of heat diffusion patterns according to general energy deposition characteristics occurring within a volume of material resulting from a volumetrically coupled energy source. These parameterizations include previously constructed models of energy deposition as special cases. The construction of a general parameterization of energy deposition processes is necessary for their inverse analysis. The structure of such a parameterization follows from the concepts of model and data spaces that imply the existence of an optimal parametric representation for a given class of inverse problems. Accordingly, the optimal parametric representation is determined by the characteristics of the available data, which in principle can contain both experimental measurements and numerical simulation data. Parameterizations for spatial modulation and filtering of heat diffusion follow from the observation that many different types of energy deposition processes can be represented by weighted sums of basis functions whose general forms are that of spatially modulated or filtered diffusion. A significant aspect of the parameterizations presented is that the definition of the inverse heat deposition problem, which is adopted for their construction, provides a rigorous foundation for a highly flexible and general parameterization of energy deposition processes, which is essential for their inverse analysis. A preliminary proof is presented that shows the significance of these parameterizations for the application of similarity transformations to the inverse analysis of energy deposition processes. The applicability of similarity transforms to the inverse analysis of heat deposition is another property that follows from the specific definition of the inverse heat deposition problem considered here.     

5GPa压力处理后CuCrSeTeFe合金的热容与热扩散系数

利用热常数测试仪测试了CuCrSeTeFe合金经5GPa压力处理后在25～600℃的热容和热扩散系数,并分析了温度对CuCrSeTeFe合金热扩散系数和热容的影响.结果表明:在25～600℃内,CuCrSeTeFe合金的热扩散系数随温度的升高而逐渐增大,而热容在200～300℃内较高.     

低压导叶锻造及热处理工艺探讨

对某汽轮机组低压隔板导叶片X5CrMoAl12材料的锻造及热处理工艺进行了研究,提出该叶片的始锻温度为1 000℃,终锻温度为850℃。热处理工艺参数为960～990℃淬火,670℃×6 h回火。为指导低压导叶片毛坯生产提供了技术支持。     

SiCp/ZL109复合材料热处理工艺优化

利用正交试验和极差分析法优化了SiCp增强铝基复合材料热处理工艺,结果表明当固溶温度为500℃、固溶时间为2 h、时效温度为175℃、时效时间为12 h,经热处理后的复合材料的硬度最佳,其中时效温度起主要作用,其次是固溶温度.     

阀片钢3Cr13的热处理工艺研究

研究了阀片钢３Ｃｒ１３经两种热处理后组织和性能的变化规律。试验结果表明,要求高硬度（５２ＨＲＣ）的阀片可采用１０５０℃油淬、２５０℃×２ｈ回火,或采用１０００℃加热、于２４０℃等温１５ｍｉｎ、３００℃×２ｈ回火;要求较低硬度（４０ＨＲＣ）的阀片,则可采用１０５０℃油淬、５５０℃×２ｈ回火的调质处理,或１０００℃加热、于２４０℃等温１５ｍｉｎ、５５０℃×２ｈ回火。弯曲疲劳模拟试验表明,高硬度的等温处理具有最长疲劳裂纹萌生期Ｎｏ和最高的疲劳强度,较低硬度的调质工艺也同样获得很高的Ｎｏ和良好的疲劳性能。     

GH690合金管材热处理工艺优化

以国外Inconel 690成品管的显微组织为参照对象,对国产GH690合金管材在不同工艺条件下的固溶处理与TT处理工艺进行了研究;采用OM、SEM和TEM等表征手段分析了工艺参数对其晶粒度、晶界碳化物形貌和贫Cr区的影响。结果表明:国产GH690合金管在固溶处理过程中,随着固溶温度的提高,尺寸较大晶粒所占比例逐渐升高,长大激活能为265 kJ/mol。当固溶温度超过1100℃时,保温时间对晶粒尺寸影响显著。国产GH690合金管析出细小半连续晶界碳化物的TT处理工艺参数为680℃/10~20 h,715℃/10~20 h,750℃/5~15 h。经1090~1110℃/5 min固溶处理以及715℃/10 h或15 h的TT处理后,国产GH690合金管晶粒尺寸分布、晶界碳化物形貌特征和贫Cr区演化特征与国外Inconel 690成品管非常相似;而其TiN颗粒数量和尺寸明显少于和小于后者,贫Cr区的最低Cr浓度高于后者。通过对显微组织特征的综合评价,表明国产GH690合金管的显微组织总体优于国外Inconel 690成品管。同时,兼顾实际生产中的成本问题,提出国产GH690合金管热处理工艺优化的建议。     

ZG15Cr2Mo1钢的热处理工艺研究

为了确保含017%C、1.93%Cr、0.97%Mo、0.43%Si和0.68%Mn(质量分数)的ZG15Cr2Mo1钢的室温和高温力学性能满足要求,对其进行了不同温度和冷却方式的正火及不同温度的回火工艺试验。经不同工艺热处理的钢的室温和高温力学性能确定的ZG15Cr2Mo1钢的最佳热处理工艺为:920~970℃保温8~12h空冷正火,随后720~760℃回火8~12h。     

CRONIDUR30高氮不锈钢的热处理工艺及组织和性能

CRONIDUR30钢是一种新型高氮、高韧性和高强度马氏体不锈轴承用钢。研究用高氮CRONIDUR30不锈钢的主要成分为0.316%C、14.89%Cr、0.986%Mo、0.425%Mn、0.697%Si、0.207%Ni和0.435%N(质量分数)。对14mm×5mm的CRONIDUR30钢试样进行了1010℃、1020℃、1030℃、1040℃和1050℃油淬、-150℃深冷处理和-85℃冷处理以及160℃、180℃、200℃、250℃、300℃、350℃、400℃、450℃、500℃、600℃回火,检测了经不同工艺热处理的钢的硬度和显微组织。结果表明:经1025℃油淬、-85℃冷处理和470℃回火的CRONIDUR30钢的硬度高于60HRC,组织为回火马氏体、细小均匀的氮化物和碳化物及小于5%的残留奥氏体,能满足高端轴承的性能要求。     

双丝焊温度场仿真的热源模型研究

分别以高斯热源模型及双椭球形热源模型为基础，推导出两种模型用于双丝焊的计算公式，建立了合适的有限元模型。在充分考虑各种边界条件下，对两种模型所建立的温度场进行了计算，得到25钢的双丝焊接瞬态温度场的分布规律。两种模型的仿真结果与工艺试验结果比较表明，双椭球形热源模型比高斯热源模型更适合双丝焊的三维有限元分析。     

氮气喷射沉积镁合金传热过程分析

针对氮气喷射沉积镁合金雾化过程中的快速散热阻燃行为,采用数学模型模拟了镁合金喷射沉积过程中雾化气体与液滴之间的传热情况.结果表明,雾化气体速度随着喷射距离的增加呈单调递减趋势;雾化液滴先加速飞行,在液滴和气体速度相等后开始减速,随着粒径增大,液滴的最大速度减小;传热系数先减小再增加,且随着液滴粒径减小而增大,其平均值均在l000W· m-2·K-1以上;液滴的温度持续降低;在雾化阶段,液滴与气体之间传热的最小速率远远大于反应放热的最大速率,避免了喷射沉积过程中热量的蓄积,从而保障了氮气喷射沉积制备镁合金过程的生产安全.