GALf - Galling in Aluminium forming

Raufoss Technology and Steertec Raufoss are important industries in Norway that form and shape aluminium to light weight components demanded by international automotive industry. The formed parts produced by these two companies are represented in almost 30% of the total European and 5 % of the worldwide produced cars, such as Mercedes Benz, Audi and BMW. Forming of aluminium to the desired geometry is accomplished by pressing the material by using a set of forming tools. The force required to form the material into a complex geometry can be high, and the forming processes are therefore often carried out in several steps. The friction between forming tools and aluminum has a great effect on the arising forming forces. Here, it is a fact that the friction mechanisms, together with a large surface pressure, increases the risk of aluminum adhering to the forming tools, eventually forming a layer on the surface of the forming tool. This phenomenon is called galling. Galling is today a limiting factor in production, and cause of production and maintenance stops, wreck production and defects in parts and tools produced. Since galling depends on forming speed, galling also limits productivity. The most important goal of the GALF project is to develop an innovative coating - lubricant system that is interlinked to tool geometry and knowledge of processing parameters. The goal is to achieve cost-effective processes through reduced galling. The question is which underlying mechanisms determine the Al layer's origin and build on the tool in the complex interaction between different surfaces, and how the understanding of the mechanism can contribute to solutions that reduce galling. To achieve the project goal, GALF evaluated the most used physical test methods used nationally and internationally to measure and describe galling. Numerical methods were also evaluated with the aim to predict galling and galling tendencies through virtual testing. Typical industrial challenges for the participating forming industries are discussed and related to the test methods that were described. Some forming tools from partners, used in different temperature ranges, and used with and without lubricant, were analysed. Results were compared with results from lab-scale tests (Raman, PinOnPlate) to determine which chemical surface layers form, before and after a galling process. All input was used to define which friction and galling tests are used on a laboratory and industrial scale, and how these tests are evaluated using SEM and TEM microscopy. As a result, a collaboration with Uppsala University was established for a type of lab scale test (LoadScanner). Test series were discussed and conducted in Uppsala, and afterwards a seminar was performed in Uppsala where scientific and industrial topics were reviewed. Related to the questions about shaping tool steel, an open seminar was held on tool steel at Raufoss. The issues around coating technology and coating effect were discussed in an open seminar for coating technology at NTNU Gjøvik. Lessons learned from ongoing SFI -Phd work on cold welding of steel and aluminum were included in project meetings. Based on all knowledge, it was concluded that there is a need for a test method that reflects technologically high temperature forming. Therefore, a new industrial scale test was developed (SPIKE) and used in the project. That test method uses a special tool geometry that is iteratively developed through practical testing and simulation in a FEM program. In several test series, hot forming parameters were used, and in other test series cold forming was in focus. As an important source of mechanism understanding, some lab-scale tests were performed on hot-formed temperatures. More insight into mechanisms that control galling in dry, and lubricated hot-mold temperature ranges are given. Industrial tests were carried out, and findings from the project have already led to new solutions in production. Some test results provided direct input to calibrate numerical tools that are available after the project is completed. Numerical models for varying surface roughness were built, and the analysis results presented. The models predict and explain tendencies for parameter changes by shaping interaction, which in turn will reduce the need for testing. If this is further developed, it may be possible to analyse the effect of surface treatments of tools, possibly recommending certain tool geometries and materials. The project focused on hot forming with and without lubricant towards the end. Generic, so-called "pin on plate tests" were carried out to compare results to Industrial experiments, were also galling tendencies in dependence on lubricants were studied. A tool made by a partner enables temperature measurement during forming also after GALF, as well as a new coating solution will be tested after the project is finished.

Resultatene planlegges utnyttet i bedriftene gjennom anvendelse av de nye smøremiddel-belegg kombinasjoner som ble definert i produksjon. Industrien bruker resultatene til å forbedre tilbudet sitt i de relevante markeder de betjener. Resultatene som førte til en forståelse av at mer RnD kreves blir brukt i videregående prosjekter. Resultatene blir fulgt opp gjennom interne prosesser i industriene. En statistisk kartlegging av resultat ventes. Aktivitet i industrien fortsetter utover prosjektperioden, der resultatene blir testet og industrialisert. Den antatte fremtidige verdiskapingen som følge av prosjektet er uendret.

Many industries in Norway process and shape aluminium to any required form, among them Raufoss Technology and Steertec Raufoss. The Al forming parts produced by these two companies are represented in almost 30% of the total European and 5 % of the worldwide produced cars, such as Daimler, Audi and BMW. Shaping of Al is performed through a forming process in which a layer of Al is transferred to the forming tool surface due to the friction-induced contact. The build-up and location of this Al transfer layer at the workpiece-tool interface depends on both the process conditions and the tool geometry. This phenomena is called galling and may lead to failure of the tool or the product. Today, galling is the main cause for process scrap during production and part/tool failure. Due to its sensitivity to the forming speed, galling limits the productivity. The overall idea of this project is to optimise coating and lubrication solutions under consideration of tool geometry and process parameters, towards an innovative tool design for a more cost effective production, allowing higher productivity by a reduction of galling. To achieve the new surface solutions will be studied in lab scale reproducing the relevant mechanisms for different temperatures under fully controlled boundary conditions to learn more about galling initiation and influence for different coatings and lubricants. This will be combined with high-resolution microscopic analysis to reveal underlying mechanisms. However, the innovation in coating and lubrication will reduce galling, but not suppress it. Therefore, another important innovation element in this project will be the use of numerical tools to predict galling on short time scales. The second part of the project will focus on the process itself and the possibility of manipulative methods, such as the superposition of vibrations to the forming.