Properties Of Final Component Research Articles

Experimental and Numerical Evaluation of the Heat Transfer Coefficient in Press Hardening

When producing thin ultra high strength steel components with the press hardening process, it is essential that the final component achieves desirable material properties. This applies in particular to passive automotive safety components where it is of great importance to accurately predict the final component properties early in the product development process. The transfer of heat is a key process that affects the evolution of the mechanical properties in the product and it is essential that the thermal contact conditions between the blank and tool are properly described in the forming simulations. In this study an experimental setup is developed combined with an elementary inverse simulation approach to predict the interfacial heat transfer coefficient (IHTC) when the hot blank and cold tool are in mechanical contact. Different process conditions such as contact pressure and blank material (22MnB5 and Usibor 1500P) are investigated. In the inverse simulation, a thermo-mechanical coupled simulation model is used with a thermo-elastic-plastic constitutive model including effects from changes in the microstructure during quenching. The results from simulations give the variations of the heat transfer coefficient in time for best match to experimental results. It is found that the pressure dependence for the two materials is different and the heat transfer coefficient is varying during quenching. This information together with further testing will be used as a base in a future model of the heat transfer coefficient influence at different conditions in press hardening process.

The printing and firing process of A1 paste in PTC ohmic contact electrodes

Al electrodes are well known as ohmic contact electrodes for the PTC component, the influence of their thickness on final component properties was investigated by comparing their ohmic characteristics with the ones of InGa electrodes. After observing the Al paste physical and chemical behaviors during rising temperature by thermal analysis (DTA), the firing operation of Al electrodes could be divided into three main subsections: the temperature rising time (tr), the peak firing temperature (Tp) and the hold time at peak firing temperature (th). The effects of these three parameters on final component properties were discussed in detail.

Experimental and numerical analysis of the effects of process parameters on the properties of components in metal injection molding

*The paper mainly concerns the effects of process parameters on the final properties of components obtained by injection molding of metallic powders loaded by thermoplastic binders. The two main stages of the process are investigated. The injection stage is studied both from experiments and numerical modeling. The biphasic flow approach developed reveals well the effects of mould design and injection parameters on the final powder volume fraction distribution. The sintering stage is also investigated both from experiments and modeling. The viscoplastic like sintering model accounts well for the effect of initial powder volume fraction and sintering cycle on the final density and shrinkage of the component. Furthermore the final mechanical properties of the components obtained by metal injection molding are also investigated.

Some current development trends in metal-forming technology

Various trends in metal-forming technology which will change future plant construction and production technology are already becoming apparent. The report describes the shortening, flexibilization and integration of a number of processes. Moreover hollow structure technologies become more and more interesting for innovative production. Furthermore FEM-simulation and optimization, also reported on in the paper, are increasingly important tools for the development of new or improved processes and plants. In view of the need to minimize production costs, to increase environmental compatibility and to manufacture products to a defined quality standard, long, complex processes should be shortened as far as is possible or necessary. In the field of strip production, mention should be made of the development of thin slab technology and thin strip casting, in which certain manufacturing steps are eliminated completely. For formed parts, possible methods for shortening the process include forming in the solidus-liquidus range (thixoforming). Another possibility is a combination of forming with heat treatment. Shorter process chains often mean more favourable mechanical properties for the products and hence new applications. Against a background in which forming processes are becoming more flexible in order to enlarge the spectrum of products, it is necessary to use flexible forming units with adaptable links to preceding and succeeding steps as well as universal dies and intelligent controls. For example, robot-manipulated open die forging allows reproducible manufacture of complex forgings with relatively small allowances. A variable rolling gap in the rolling process means that sheet metals can be produced with a defined longitudinal thickness profile matching the load case for the subsequent component. The integration of different production processes also paves the way for new approaches. Existing process limits can be extended and the final properties of components optimized by using partial heating methods during or directly after forming and by coupling forming processes with parting or joining techniques. A promising approach in the field of innovative lightweight construction is the systematic use of hollow structures; new processes for generating cavities and production techniques for processing the new hollow structures are being developed. Apart from suitable tests, physical and numerical simulation can be used to optimize existing or develop new methods of manufacture. Physical simulation may be especially successful in solving questions of material flow. A new material flow simulator is presented. Numerical simulation is used especially for quantitative analysis of local process variables; methods have recently been developed for taking the modification of structure during the forming process into account.

Liquid Phase Sintering of AISI 316L Stainless Steel

Abstract The sintering behaviour of AISI 316L powders alloyed with 20%Cu has been studied as a function of various sintering parameters. Copper additions are known to improve compressibility, sinterability, and dimensional control of the final component, as well as improving the corrosion resistance of the sintered material. Specimens have been sintered in an industrial furnace using various N2–H2 atmospheres and sintering times. Microstructural and structural examination of the specimens revealed that: (i) copper additions can reduce nitride precipitation during sintering, thus preventing sensitisation; (ii) copper diffusion into the austenitic particles is promoted by hydrogen rich (i.e. reducing) atmospheres; and (iii) the chosen copper addition of 20% is excessive. The results confirm that copper can have a beneficial effect on the sintering process and in improving the final properties of components; however, its content must be optimised to obtain a homogeneous sintered material. Atmosphere composit...