14 - 18 October 2018

Bilbao, Spain

A Critical Analysis of the Press & Sintering Technology

Session Chairs

Raquel De Oro Calderon

Alberto Molinari

Dr Raquel de Oro Calderon (TU Wien, Austria)
Prof Alberto Molinari (Trento University, Italy)

Introduction

The drastic technological developments that will presumably take place during the next years may completely shift the automotive sector as we know it today. This represents an enormous challenge for the Press&Sintering technology that needs to be prepared for a change that is already happening.

Where are the future potential applications of P&S? In which directions can the use of P&S components be expanded? And the main question is: Is there a need for scientific/applied research in the P&S sector? Where are the main handicaps of the technology?

Apart from the area of functional materials, the future may offer many chances if someone will develop a powder, a compaction process, a sintering process, a design methodology, a simulation, all these performing better than the current ones. A critical analysis of the P&S technology will allow highlighting possible improvements in the different steps of the process that may open up a potential new application portfolio, and stimulate further efforts in research from the academic and industrial community.

This seminar will host selected speakers from academy and industry that will show their views on how the P&S technology can be improved to bring up significant advances. A round table with academics and industry will bring an opportunity for the P&S community to share ideas on how P&S can be one of the important problem solvers for future advanced products

Presentations

Metal Powder Solutions Designed to Promote Future Growth of the PM Industry

Mr Ulf Engström (Höganäs AB, China)

To further grow the PM market into new high challenging automotive applications cost-effective PM material solutions combining higher precision with increased performance will be required. Development of new cost effective alloy systems enhanced compaction techniques enabling higher densities sintering at higher temperatures in combination with increased cooling rates and carbon control and adoption of secondary heat treatments are all examples of means that either singly or in combination offer opportunities to increase the material performance. The growing awareness of sustainability also makes it important to select both material and manufacturing processes with the least impact on the environment.

The Masteralloy Approach: A Promising Alloying Alternative for PM Steels

Prof Monica Campos (UC3M, Spain)

The increased capacity for adaptation to changes plays a key role in the success of a processing route. By enhancing the flexibility in the selection of the composition it is possible to offer to manufacturers an optimum option to achieve performance in competitive conditions. Considering the alloying methods for modifying the iron base powder it is possible to move from blended mixtures to prediffusion and prealloyed grades. However the design of master alloys can open the door to tailor the final microstructure and thus adjust the requirements that can be fulfilled. Master alloys as liquid phase formers bring the option to introduce high oxygen-sensitive elements controlling the reduction during sintering (by carbothermic or metallothermic reactions) or increasing the densification of the component increasing the infiltration ability of the promoted liquid phase. Once it is determined the compatible composition with the sintered steel and affordable sintering conditions, thermodynamic and kinetics software are initial approach to understand the solid-liquid interactions.

The Knowledge on Powder Compaction and its Modelling

Prof Alberto Molinari (Trento University, Italy)

The objective of cold compaction is to produce a cracks free part with a given density (mean density and its distribution), strength and dimensional and geometrical features, to be further processed by sintering. This goal is achieved by compacting the powder mix through the application of a uniaxial pressure, being the radial and tangential deformation impeded (not completely) by the constrain exerted by the die and the cores. The powder mix is a very complex material, comprising one or more metallic powders, the lubricant, any graphite and additives, and a continuously decreasing content of voids. Powder compaction can be therefore described as an anisotropic multiaxial compression of a complex (unique) and continuously changing material. Further elements of complexity result from the dependence of the stress field on the geometry of the part and the powder, from the unicity of the mechanical properties of the powder that are much different from those of the corresponding solid material (if it exists), and from inhomogeneity introduced by the frictional effects.

The knowledge of the correlations between the stress field and the deformation of the powder is the basis for any attempt to model the compaction process and to predict the density distribution in the green parts. Several authors investigated this subjected in the past, while, based on the literature, only a few are still active in this field. The lecture proposes an analysis of the international literature with the aim of highlight any possible lack of knowledge, and the activities to be implemented by the PM community to improve the results of the modelling of cold compaction, in view of the developments experienced by this technology.

Modelling as a Support to Improve Sintering Control

Prof Didier Bouvard (Grenoble INP, France)

Modelling has played a key role in the study of sintering from the historical two-sphere models to more sophisticated ones based on numerical techniques as discrete element or Monte Carlo methods allowing for the analysis of more complex systems. These approaches produce guides for understanding and controlling the phenomena responsible for powder consolidation and microstructure formation. Another more recent practice mainly using the finite element method consists in simulating the sintering at the scale of the component without describing the details of the microstructure. It mainly provides dimensional changes and internal stresses developing in sintering parts. This practice may bring helpful advises for both designing the components to be sintered and operating the sintering process. The efforts required to implement such a simulation will be explained and examples of practical results obtained with various materials and components will be presented.

Better Mechanical Properties – Key to New Business?

Prof Paul Beiss (RWTH, Germany)

Mechanical properties of porous sintered steels are fairly well understood and, thus, predictable with the reliability of an estimate, if a single data set of property and density is known. This statement pertains to elastic and tensile characteristics, hardness, constant amplitude fatigue strength or unnotched impact energies. In the past many developments aimed at increasing the material strength by higher density, higher alloy contents or alternative alloying concepts, which required processing changes like heated tooling, higher sintering temperatures or rapid cooling after sintering often sacrificing sizeability and in part the proverbial process inherent precision. That can cause tolerance bargains and compromises or additional costly secondary operations. Therefore, the question must be answered, what is the incitement of a design engineer to choose a sintered structural part for a given task instead of a solution from a competing technology. Among the many aspects like precision, mechanical performance, production volume, customer support and service, reliability or price, above a certain minimum strength level better mechanical properties can sometimes be a door opener for new applications. A new solution will, however, only persist if other targets of similar importance are also met, e.g. precision or price and quality criteria.

Innovative Product Solutions – 'PM Technology Makes the Difference'

Dr Gerd Kotthoff (GKN, Germany)

Electrification has already started to have a noticeable impact on the global automotive industry. As a result, the drivetrains of hybrid (HEV) and full electric vehicles (EV) are facing lots of new challenges, like increasing requirements for NVH (Noise Vibration Harshness) for the high speed e-drives and an increased performance need due to recuperation, combined with new demands on system reliability like high cycle fatigue properties etc.. Further trends are the strong drive to weight reduction or smaller packaging, leading to the request for light weight designs/materials and the functional integrated products and systems either in actuation or lubrication systems. As a result, the suppliers are more and more forced to move from a "make to print" to a "system and reliability driven" product design, being able to first understand the product application and collaboratively develop innovative and unique PM taylored products for the system application. Within this speech, the requirements for a holistic product development approach and the strong need of an early collaboration between customer and supplier to drive future innovations will be discussed, considering the PM process expertise beeing the first chain link to deliver products for highly reliable systems.

Round Table

Dr Raquel de Oro Calderon (TU Wien Austria)

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