Methods of eliminating pollutant emissions from the work environment in welding and related processes

Abstract

The welding and joining of dissimilar metals which have very different properties, such as aluminium and carbon steel, is considered to be a subject for research and development in the welding/joining sector continuing into the 21st century. There are also huge requirements and expectations for this sector.¹ Due to the aforementioned, the research and development of welding and joining of dissimilar materials have been carried out over many years; for instance, eutectic bonding of copper pipe and aluminium pipe was developed 30 years ago and this process is still applied for the heat pipes of refrigerators. Recently it has even progressed for applications in joining of wide plate materials of aluminium alloy and stainless steel by means of the vacuum rolling process² and also for weldments of aluminium alloy and carbon steel joined by means of friction welding and employed as automobile components.³ However, there are problems from aspects of cost and restrictions concerning the configurations for which joining is feasible using conventional welding and joining processes and these techniques have not yet reached the stage where they can be applied in a number of industrial sectors. Accordingly, an extensive programme of research and development has been deployed in recent years using fusion welding processes, such as electron beam and laser welding and brazing, diffusion bonding and also friction stir welding (FSW).⁴     

Assessing the affordability of emerging processes for advanced materials

Quality-cost modeling is a method for obtaining approximate yet quantitative information regarding the potential of emerging manufacturing processes to produce highquality, cost-competitive advanced materials. The modeling method is based on the concept of an affordability space—a set of reachable combinations of cost and performance (quality) unique to a particular process and material. The analysis relies on the development of relatively simple (first order) models intended to capture the essential interactions between the material and its processing environment and their use in calculating the final microstructure (on which a quality index is based) and the associated cost. Both cost and quality are functions of the starting state of the material, process conditions used, and the design of the process. The tool allows numerical experiments to be conducted in which the influence of these variables on cost and quality can be explored. Dana M. Elzey earned his Dr.rer.nat. in materials science at the University of Stuttgart in 1989. He is currently a research assistant professor of materials science and engineering at the University of Virginia. Dr. Elzey is a member of TMS.     

Shell hardening of unalloyed steel cylinders by high speed quenching

Abstract

Kobasko et al. have primarily shown that rapid water quenching can create compressive residual stresses near the surface and thereby a significant increase in the fatigue-limit (Intensive Quenching). Such processes result in an increase in hardness. Depending on steel grade, dimensions of the component and quenching intensity through hardening or only shell hardening will result. In this work, shell hardening processes were investigated in a more detailed manner for cylinders made of two different unalloyed steels. The goal of the work was discovering the general requirements to reach, on the one hand, a sufficient surface hardness paired with a non-through hardened hardening profile. On the other hand, compressive residual stresses in the near surface area should be as high as possible to achieve huge lifetime cycles for the heat treated work pieces. The experiments were carried out with a device that was especially developed for high speed quenching. As a quenching medium only tap water or water with 10% salt were used. It was shown that with this equipment very high heat transfer coefficients up to 50?000 W m^?2 K^?1 can be reached. Within the experimental design, cylinder made out of C35 and C56E2 with diameters between 25 and 43 mm were quenched with heat transfer coefficients in the range of 20?000 to 50?000 W m^?2 K^?1. The quenching results were characterised by measuring the microstructure, the hardness and the residual stresses. The experiments show that compressive stresses in the near surface area of 1200 MPa can be achieved.     

Eigenschaftsprofil des neuentwickelten Stahls X2 CrNiMnMoN 23 1764

Properties of the newly developed steel X 2 CrNiMnMoN 23 17 6 4 A well balanced alloying composition allows to produce the high alloyed stainless steel X 2 CrNiMnMoN 23 17 6 4 containing more than 0.4% nitrogen by conventional processes. Features of this material are a stable fully austenitic microstructure, 0.2% yield strength higher than 420 N/mm², excellent corrosion resistance and good working and welding properties. The critical pitting temperature evaluated in ferric chloride solution according to ASTM G 48–76 standard is higher than 85 deg C and it is only lightly lowered when tested in the as welded condition. By these properties Remanit 4565 S may bridge the gap between high-alloyed stainless steels and non-ferrous materials for applications in the chemical process industries.     

材料硬度试验的虚拟设计与实现

介绍了以VRML为工具，采用交互式多媒体开发三维虚拟试验的关键技术，设计了材料学实验中的硬度试验的操作过程。主要内容包括试验的物理建模、行为建模以及交互性设计等方面。设计达到了较好的真实效果，显示了虚拟现实技术在材料学试验中的广泛应用前景。     

The technology of extrusion‐fusion welding of polythene and polypropylene butt and T joints

Abstract

Laser welding, regarded as one of the welding techniques for use with steel materials and employed in the fabrication of automobiles, has increasing applications in the manufacture of transmission systems and car bodies; however, there are not many examples of application to aluminium alloy components.¹ The reasons for this are thought to be as follows: aluminium alloys have a higher laser reflectivity compared with that of steel materials; consequently an even higher power laser is required to input energy to the material for welding and also, due to the low viscosity of molten aluminium alloy, stable welding is difficult.^2,3     

Methodology for development of welding procedures and empirical weld process models based on principal component analysis techniques

Abstract

With the increased automation of welding processes, there is a necessity for experimental design techniques that will permit rapid and efficient definition of the range of welding process parameters that may be used to produce acceptable welds for each new application. Such techniques are also required during development of empirical weld process models. In the present study, an experimental design technique based on principal component analysis (PCA) has been developed and shown to be more efficient than the traditional fractional factorial approach to experiment design, weld procedure development, and development of weld process models. Gas tungsten arc (GTA) welding of corner joint sheet steel was selected to exemplify the application of the technique. The boundary of a three­dimensional domain of weld process parameters (welding current, speed, and electrode gap) which could be used to produce acceptable welds when using either flush or edge touch corner joint configurations was satisfactorily approximated using only 25 welds. The PCA based technique was able to resolve differences between the procedural domains of these two joint geometries. The procedural field for the edge touch configuration was found to have a larger range of acceptable welding conditions than that for the flush configuration. Empirical weld process models for these joint configurations were developed using standard multivariable regression analysis techniques and only 25 further welds. Finally, an empirical model for weld width prediction in corner joint GTA welding was developed which includes the effect of current, voltage, torch travel speed, and sheet metal fitup. This model had an R ² value of 86%, with all statistical tests yielding acceptable results.     

Mathematical model of welding parameters for rapid prototyping using robot welding

Abstract

Rapid prototyping is a relatively new technology that allows the creation of prototypes in a very short period of time compared with traditional manufacturing techniques. First, a model of the prototype is drawn, using a computer aided design program, which is then mathematically 'sliced' and used to build the prototype layer by layer, using materials such as paper, resins, or thermoplastics, depending on the process. The main disadvantage of these processes is that they do not allow metal as a raw material. Rapid prototyping using robot welding is another approach that overcomes this problem by using a welding robot that deposits metal. As the success of the final component quality depends very much on the welding parameters, it is important to automate their calculation. To automate the task of determining the welding parameters and to generate welded components with consistent quality, a very simple mathematical algorithm was created. The tests carried out to gather the necessary information to generate this model, the mathematical model itself, the limitations of the equations, and the tests to check their feasibility are described.     

Investigation of Wear and Corrosion Protection of AlSi20 Coatings Produced by Plasma Spraying and Laser Cladding on AZ31B

Magnesium and magnesium alloys are the lightest structural materials with an approximate density of 1.7 g/cm² (density of aluminum ~2.7 g/cm²). Due to poor corrosion and wear resistance properties, they need to be coated for usage in service conditions under corrosive and tribological loads. AlSi20 was found to be a suitable coating material to improve the wear and corrosion protection properties of magnesium alloys. Within this work, AlSi20 coatings were applied by plasma spraying, laser cladding, and a combination of both processes. First, the coatings are characterized by their microhardness and residual stresses formed within the coating during the different coating processes. Then, these coatings were investigated regarding corrosion resistance in 3.5% sodium chloride solution in a three-electrode setup to obtain electrochemical corrosion characteristics. Abrasive wear was investigated using a pin-on-disk tribometer and the abrasion rate was calculated. Resistance against shock loads was tested by applying a cyclic load at 50 Hz to investigate the resistance against impact stresses.     

An intelligent approach to welding robot selection

In a shipyard where multiple stationary and mobile workcells are employed in the fabrication of components of complex sub-assemblies,efficient operation requires an intelligent method of scheduling jobs and selecting workcells based on optimum throughput and cost. The achievement of this global solution requires the successful organization of resource availability,process requirements,and process constraints. The Off-line Planner (OLP) of the Programmable Automated Weld Systemd (PAWS) is capable of advanced modeling of weld processes and environments as well as the generation of complete weld procedures. These capabilities involve the integration of advanced Computer Aided Design (CAD), path planning, and obstacle detection and avoidance techniques as well as the synthesis of complex design and process information. These existing capabilities provide the basis of the functionality required for the successful implementation of an intelligent weld robot selector and material flow planner. Current efforts are focused on robot selection via the dynamic routing of components to the appropriate work cells. It is proposed that this problem is a variant of the “Traveling Salesman Problem” (TSP) that has been proven to belong to a larger set of optimization problems termed nondeterministic polynomial complete (NP complete). In this paper, a heuristic approach utilizing recurrent neural networks is explored as a rapid means of producing a near optimal, if not optimal, bdweld robot selection.     

IFHTSE Global 21: heat treatment and surface engineering in the first decades of the twenty-first century: Part 1 – Introduction to ongoing IFHTSE activity

Abstract

Engineering systems and components are the result of a complex chain of actions, starting with a design to match the functional demands: materials science and technology are intimately involved; there are often multiple stages in the manufacturing process, as well as essential quality assurance methods for the component and system. Each step in the process has significance; optimum outcomes and cost effectiveness depend heavily on their being orchestrated and managed as an integrated sequence. Depending on the circumstances, the relative importance of each step may be viewed differently, but the heat treatment and surface engineering manufacturing processes are always likely to be critical. These processes themselves represent a complex balance of materials, technology, energy and environmental factors to achieve an optimum combination of functionality, industrial feasibility and economic and social viability.     

Corrosion of high chrome wear part materials used in vertical roller mills

Abstract

The corrosion resistance of two high chrome wear facings, manganese cold workable steel and heat treated white cast iron, was investigated. The addition of Cl^? to the aqueous solution unexpectedly improves the corrosion resistance. Tribocorrosion experiments show that the current density increases but with magnitudes of no importance in industrial vertical roller mill applications. However, these corrosion magnitudes might show significant material losses in other industrial applications such as marine industries including oil drilling. The investigated wear part materials are not specifically designed to withstand abrasive marine conditions; however, the applied scientific approach might be used on such materials.     

Progress in joining of advanced materials: Part 1: Solid state joining,fusion joining,and joining of intermetallics

Abstract

Advanced materials generally require novel joining techniques. Developments in new materials research should be conducted hand in hand with work on weldability and joining capacity aspects. Sound joint quality for any new material has always been considered a milestone in a research and development scheme for a new material, particularly in terms of widespread applications. Better understanding of the microstructure–mechanical properties relationships of the bonded or welded joints will feed back to the materials development activities both in conventional and new materials areas. The two joining processes diffusion bonding and laser welding are considered in this literature review, since these processes are capable of joining a wide range of materials of interest in the aerospace industry, as well as in many other industrial applications, and offer remarkable advantages over conventional fusion welding processes. Of particular interest is the ability to join the more difficult aerospace alloys with minimal component distortion and high reproducibility of joint quality. The purpose of the review is to outline progress made in this area and to make suggestions for future work. Part 1 deals with solid state joining, fusion joining, and joining of intermetallics, while Part 2 will cover joining of metal matrix composites and joining of other advanced materials.     

模拟废旧锂离子电池湿法冶金浸出液再生铝掺杂LiNi0.5Co0.2Mn0.3O2正极材料

采用共沉淀法制备均相Al掺杂的LiNi0.5Co0.2Mn0.3O2正极材料,以利用Al对再生镍钴锰(NCM)正极材料的正面改性作用,并改善锂离子电池回收过程中繁琐和高成本的除杂过程.当浸出液中的Al3+含量为过渡金属(Ni、Co和Mn)总量的1％(摩尔分数)时,制备的Al掺杂NCM正极材料中晶格氧和Ni2+的浓度增加...     

Progress in joining of advanced materials Part 2: Joining of metal matrix composites and joining of other advanced materials

Abstract

Advanced materials generally require novel joining techniques. Developments in new materials research should be conducted hand in hand with work on weldability and joining capacity aspects. Sound joint quality for any new material has always been considered a milestone in a research and development scheme for a new material, particularly in terms of widespread applications. Better understanding of the microstructure–mechanical properties relationships of the bonded or welded joints will feed back to the materials development activities both in conventional and new materials areas. The two joining processes diffusion bonding and laser welding are considered in this literature review, since these processes are capable of joining a wide range of materials of interest in the aerospace industry, as well as in many other industrial applications, and offer remarkable advantages over conventional fusion welding processes. Of particular interest is the ability to join the more difficult aerospace alloys with minimal component distortion and high reproducibility of joint quality. The purpose of the review is to outline progress made in this area and to make suggestions for future work. Part 1 (STWJ, 1998, 3, (3), 105–126) dealt with solid state joining, fusion joining, and joining of intermetallics, while Part 2 covers joining of metal matrix composites and joining of other advanced materials.     

Improved FE model for simulation of friction stir welding of different materials

Abstract

One of the most relevant aspects of friction stir welding is the possibility to weld different materials. In the present paper, the authors present an improved continuum finite element model for the simulation of friction stir welding processes aimed to obtain T joints, made of a stringer in AA7175-T73511 and of a skin in AA2024-T4. The model, taking into account the thermomechanical behaviours of the two different materials, is utilised to study the occurring material flow and residual stress state. Numerical results are compared with experimental observations: the model is able to predict the material flow, obtaining important information on the joint failure mode.     

Development of base materials for welding

Abstract

The various aspects of weldability, seen as a material property, are introduced. These are illustrated by considering examples, in particular the recent advances in structural C–Mn and microalloyed steels. Important issues for the further development of the weldability of these materials are outlined. In concluding, the growing importance of mathematical modelling as a tool for the design of new weldable materials is emphasised.     

Rapid alloy prototyping: Compositional and thermo-mechanical high throughput bulk combinatorial design of structural materials based on the example of 30Mn–1.2C–xAl triplex steels

We introduce a new experimental approach to the compositional and thermo-mechanical design and rapid maturation of bulk structural materials. This method, termed rapid alloy prototyping (RAP), is based on semi-continuous high throughput bulk casting, rolling, heat treatment and sample preparation techniques. 45 Material conditions, i.e. 5 alloys with systematically varied compositions, each modified by 9 different ageing treatments, were produced and investigated within 35 h. This accelerated screening of the tensile, hardness and microstructural properties as a function of chemical and thermo-mechanical parameters allows the highly efficient and knowledge-based design of bulk structural alloys. The efficiency of the approach was demonstrated on a group of Fe–30Mn–1.2C–xAl steels which exhibit a wide spectrum of structural and mechanical characteristics, depending on the respective Al concentration. High amounts of Al addition (>8 wt.%) resulted in pronounced strengthening, while low concentrations (<2 wt.%) led to embrittlement of the material during ageing.     

Intelligent Control of Consolidation and Solidification Processes

Intelligent processing of materials (IPM) deals with the integration of process models and in situ sensors into an intelligent process controller to achieve desired material properties. IPM-based control systems recently have been developed for both consolidation and solidification processes. This article explores the application of models based on the finite- element method (FEM) to develop process actuation systems, to design process schedules and component shape, and to develop a control model with which to control the process. The results in this article were presented at the AeroMat ’93 Advanced Aerospace Materials/Processes Conference and Exposition, Anaheim, CA, 7–10 June 1993     

Inhibition of Iron Corrosion in Different Acid Media by N-Decyl- Pyridinium Derivatives

Abstract

Some derivatives of the N-Decyl-Pyridinium ion (DP) have been tested as iron corrosion inhibitors in sulphuric and hydrochloric acid solutions at 25°c and 70°c. Theseinhibitors were tested both as bromides (in hydrochloric and in sulphuric acid solutions) and as hydroxides or sulphates (in sulphuric acid solutions). The efficiency of theDP ion can be improved by the introduction of suitable subsituents in the 3-position of the aromatic ring. In all the acid solutions tested, the most efficient ion at 25°c proved to be the N-Decyl-3-hydroxy-Pyridinium (D30P) ion, while at 70°C,. the N-Decyl-3-carboxy-Pyridinium (D3CP) ion was the most efficient.

These derivativesact mainly by physical adsorption between the organic cations and the anions (Cr^? or Br^?) pre-adsorbed at the metal surfaceof the electrode. But in order to explain all the experimental data other types of interactions have to be considered, such as: Van der Waals attractive forces between the aliphatic chains, interaction of Πelectrons with the metal surface, and adsorption on to the metal surface via –COOH and –OH groups. The organic cations studied inhibit mainly the H⁺ ion discharge, but when present in higher concentrations they also inhibit the iron dissolution reaction.