Search results

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder metallurgy and composite material processing are briefly discussed. The range of applications of finite elements on these subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE researchers/users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for 1994‐1996, where 1,370 references are listed. This bibliography is an updating of the paper written by Brannberg and Mackerle which has been published in Engineering Computations, Vol. 11 No. 5, 1994, pp. 413‐55.

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming and powder metallurgy are briefly discussed. The range of applications of finite elements on the subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for the last five years, and more than 1100 references are listed.

This paper aims to present the way of modifying surfaces of 316L stainless steel elements that were manufactured in the selected laser melting (SLM) technology and then subjected to mechanical and electrolytic processing (electropolishing [EP]). The surface of the as-generated and commercial produced parts was modified by grinding and EP, and the results were compared. The authors also present an example of the application of EP for the final processing of a sample technological model – an initial prototype of a 316L steel implant manufactured in the SLM technology.

The analyzed properties included surface topography, roughness, resistance to corrosion, microhardness and the chemical composition of the surface before and after EP. The roughness described with the Ra, Rt and Rz was determined before and after EP of samples manufactured from 316L steel with use of traditional methods and additive technologies.

EP provides us with the opportunity to process elements with a complex structure, which would not be possible with use of other methods (such as milling or grinding). Depending on the expected final surface of elements after the SLM process, it is possible to reduce the surface roughness with the use of EP (for t = 20 min, Ra = 3.53 ± 0.37 µm and for t = 40 min, Ra = 3.23 ± 0.22 µm) or mechanical processing and EP (for t = 4 min, Ra = 0.13 ± 0.02 µm). The application of the EP method to elements made from 316L steel, in a bath consisting of sulfuric acid (VI), H2SO4 (35 Vol.%), phosphoric acid (V), H3PO4 (60.5 Vol.%) and triethanolamine 99 per cent (4.5 Vol.%), allows us to improve the surface smoothness and to obtain a value of the Ra parameter ranging from 0.11 to 0.15 µm. The application of a current density of 20 A/dm2 and a bath temperature of 55ºC results in an adequate smoothing of the surface (Ra < 0.16 µm) for both cold rolled and SLM elements after grinding. The application of EP, to both cold rolled elements and those after SLM, considerably improves the resistance to corrosion. The results of potentiodynamic corrosion resistance tests (jkor, EKA and Vp) of the 316L stainless steel samples demonstrate that the values of Vp for elements subjected to EP (commercial material: 1.3·10-4 mm/year, SLM material: 3.5·10-4 mm/year) are lower than for samples that were only ground (commercial material: 4.0·10-4 mm/year, SLM material: 9.6·10-4 mm/year). The microhardness was found to be significantly higher in elements manufactured using SLM technology than in those cold rolled and ground. The ground 316L steel samples were characterized by a microhardness of 318 HV (cold rolled) and 411 HV (SLM material), whereas the microhardness of samples subjected to EP was 230 HV (commercial material) and 375 HV (SLM material).

The 316L samples were built by SLM method. The surface of the SLM samples was modified by EP. Surface morphological changes after EP were studied using optical methods. Potentiodynamic tests enabled to notice changes in the corrosion resistance of 316L. Microhardness results after electropolished 316L stainless steel were shown. The chemical composition of 316L surface samples was presented. The smoothening of the surface amounted to Ra = 0.16 µm.

The steel bars account for a high percentage of material costs for the current construction projects. At the present time, most of the construction projects for the factories of thin‐film transistor liquid crystal display (TFT‐LCD) complete the transactions of steel bars when the suppliers ship the steel bars to the temporary storage/processing sites. This paper applies the buy‐in concept in the Theory of Constraint (TOC) on the supply chain of steel bars. In this study, suppliers are required to establish warehouses at the construction sites and complete the transactions when the formed and processed steel bars are shipped into the factory sites. The aim is to find a win‐win solution to meet with the expectations from constructors as they hope that there is no need to build up inventories but supply is ready at any time. Also, this paper compares and analyzes the traditional supply/inventory model of steel bars and the Demand‐Pull (D‐P) model under the TOC framework. It is proved that Vendor Management Inventory (VMI) in the D‐P model is able to more effectively manage steel bars as a material.

A comprehensive literature review of performance management within the Dutch steel processing industry is presented. The purpose of this paper is to analyse the motives for companies to become excellent performers in their field of expertise. These internal and external motives (refined by quantitative analysis of bibliographic data) sought to reveal the common factors that impact company performance.

Inductive reasoning was adopted using an interpretivist philosophical stance to generate new theoretical insight. A mixed-methods analysis of pertinent extant literature afforded greater synthesis of the research problem domain and generated more valid and reliable findings. The software visualisation of similarities viewer was used to conduct a qualitative bibliographic analysis of extant literature to yield greater clarification on the phenomena under investigation.

Four thematic groups of past research endeavours emerged from the analysis and were assigned appropriate nomenclature, namely: industry internal motives; industry external motives; excellent performer and incremental working method. To further expand upon the continuous improvement process (CIP – embodied within performance management), the paper describes the virtuous cycle of improvement, which consists of the consecutive steps of “planning”, “doing”, “checking” and ultimately of “acting” accordingly to the previous steps. It can be concluded that a high-performing company acts according to its mission, plans in line with the vision do as defined in the strategy and checks by reflection.

This unique study provides invaluable insight into the performance management of Dutch steel processing companies. Although the research context was narrowly defined, the findings presented are equally applicable to clients, contractors and sub-contractors active in other sectors of the construction industry. The research concludes by prescribing factors of mitigation strategies to support chief executive officers to focus on the optimum distribution of their scarce resources.

Friction welding is a solid state bonding process, where the joint between two metals has been established without melting the metal. The relative motion between the faying surfaces (surfaces to be joined) under the application of pressure promotes surface interaction, friction and heat generation which subsequently results in joint formation. Stainless steel is an iron based alloy, contains various combinations of other elements to give desired characteristics, and found a wider range of applications in the areas such as petro‐chemical, fertilizer, automotive, food processing, cryogenic, nuclear and beverage sectors. In order to exploit the complete advantages of stainless steels, suitable joining techniques are highly demanded. The Friction welding is an easily integrated welding method of stainless steel, which considered as non‐weldable through fusion welding. Grain coarsening, creep failure and failure at heat‐affected zone are the major limitations of fusion welding of similar stainless steels. Friction welding eliminates such pitfalls. In the present work an attempt is made to investigate experimentally, the mechanical and metallurgical properties of friction welded joints, namely, austenitic stainless steel (AISI 304) and ferritic stainless steel (AISI 430). Evaluation of the characteristics of welded similar stainless steel joints are carried out through tensile test, hardness measurement and metallurgical investigations.

The objective of this paper is to present the existing state of research relating to the steel industries.

Additive manufacture (AM) such as selective laser melting (SLM) provides significant geometric design freedom in comparison with traditional manufacturing methods. Such freedom enables the construction of injection moulding tools with conformal cooling channels that optimize heat transfer while incorporating efficient internal lattice structures that can ground loads and provide thermal insulation. Despite the opportunities enabled by AM, there remain a number of design and processing uncertainties associated with the application of SLM to injection mould tool manufacture, in particular from H13/DIN 1.2344 steel as commonly used in injection moulds. This paper aims to address several associated uncertainties.

A number of physical and numerical experimental studies are conducted to quantify SLM-manufactured H13 material properties, part manufacturability and part characteristics.

Findings are presented which quantify the effect of SLM processing parameters on the density of H13 steel components; the manufacturability of standard and self-supporting conformal cooling channels, as well as structural lattices in H13; the surface roughness of SLM-manufactured cooling channels; the effect of cooling channel layout on the associated stress concentration factor and cooling uniformity; and the structural and thermal insulating properties of a number of structural lattices.

The contributions of this work with regards to SLM manufacture of H13 of injection mould tooling can be applied in the design of conformal cooling channels and lattice structures for increased thermal performance.

This article aims to focus on implementing Lean Six Sigma (LSS) in steel manufacturing to enhance productivity and quality in the galvanizing process line. In recent trends, manufacturing organizations have expressed strong interest in the LSS since they attempt to enhance its overall operations without imposing significant financial burdens.

This article used lean tools and Six Sigma's DMAIC (Define, Measure, Analyze, Improve and Control) with Yin's case study approach. This study tried to implement the LSS for the steel galvanizing process in order to reduce the number of defects using various LSS tools, including 5S, Value stream map (VSM), Pareto chart, cause and effect diagram, Design of experiments (DoE).

Results revealed a significant reduction in nonvalue-added time in the process, which led to improved productivity and Process cycle efficiency (PCE) attributed to applying lean-Kaizen techniques. By deploying the LSS, the overall PCE improved from 22% to 62%, and lead time was reduced from 1,347 min to 501 min. DoE results showed that the optimum process parameter levels decreased defects per unit steel sheet.

This research demonstrated how successful LSS implementation eliminates waste, improves process performance and accomplishes operational distinction in steel manufacturing.

Since low-cost/high-effect improvement initiatives have not been adequately presented, further research studies on adopting LSS in manufacturing sectors are needed. The cost-effective method of process improvement can be considered as an innovation.

Introduction To the corrosion engineer, the various types of stainless steel are as important as the bible is to a vicar. Corrosion technology never stands still, and developments in both the composition and application of stainless steel are continually being made to keep abreast of the demand to deal with the ever increasing complexity of situations that present themselves.