Application of CaCO₃ as Anti-Friction Lubricant Additive to Improve Robustness in Sheet Metal Forming of High-Strength Aluminum

High-strength aluminum is a good candidate for use in light-weighting applications, but forming it is difficult due to its low formability. Elevated temperatures are therefore necessary to improve formability, but this reduces lubricant performance. The use of calcium carbonate (CaCO3) as a lubricant additive in warm- and hot-forming of high-strength aluminum is evaluated by strip-drawing tests at room temperature, 225°C and 425°C. Further, the influence of tool surface roughness on the performance of the particles in reducing friction is evaluated. Lastly, the particle-additivated oil is compared to fully formulated, commercially available warm- and hot forming oils. The results show that CaCO3 particles are suitable for improving tribo-systems in warm- and hot-forming of aluminum, and that they can robustify processes where preparation and maintenance of tool surfaces is difficult as the tribo-system is less sensitive to the tool surface. The performance of the particle-additivated oil was similar to the commercial lubricants at room temperature and 225°C, but was worse at 425°C. However, due to the low cost and effort necessary to prepare the particle-additivated oil, it is a promising alternative to existing lubricant additives

Performance of inert particles as lubricant additives compared to fully formulated industrial forming oils in sheet metal forming

The increasingly restrictive legislation on the use of hazardous chemicals in lubricant formulation necessitates the use of less hazardous lubricant additives in the sheet metal forming industry. The tribological performance of calcium carbonate (CaCO3) as a green lubricant additive was evaluated in comparison to commercially available forming lubricants used in industry, some of which contain hazardous chemicals such as chlorinated paraffins to enable their function. The lubricants were tested by four-ball wear testing, four-ball weld load testing, and bending-under-tension. The ease of cleaning of surfaces formed with the different lubricants was evaluated by methods used in industry and the viscosity was evaluated using standard methods. The CaCO3 mixtures showed a better performance than commercial lubricants in four-ball wear testing, worse performance in four-ball weld load testing, worse cleanability, and a similar development of drawing force in bending-under-tension over 1000 consecutive strokes. When added to fully formed commercial lubricants, the particles degrade the performance of the lubricant in resisting adhesive wear but improve its capacity for resisting abrasive wear. Surfaces of formed parts after bending-under-tension testing with CaCO3 mixtures were scratched, while parts formed using commercial lubricants showed less scratching. The effect of including particles in a commercial lubricant depended on the application, either degrading it or improving it. It is therefore clear that the use of solid particles as lubricant additives should be constrained to selected applications where abrasive wear is a dominant wear mechanism

A review of methods and effects for improving production robustness in industrial micro-deep drawing

Deep-drawing is a method in which flat sheets of metal are formed into complex 3-dimensional geometries. Three main types of challenges arise when transitioning from the macro-scale to micro-deep drawing. These can be summarised as: (1) tribological effects, which mainly stem from the relative difference in surface characteristics between the two size scales, (2) material behaviour effects which arise from the increasing heterogeneity of materials that have a decreasing number of grains that are deformed in forming, and (3) dimensional effects which relate to difficulties in handling and inspection of small components at high rates and challenges in manufacturing and monitoring of tool components for use in micro-deep drawing. Various methods or effects can be applied to micro-deep drawing processes to tackle these challenges. This paper reviews research on methods and effects that can be used to improve the robustness in micro-deep drawing processes. Small changes, such as the choice of lubricant and slight changes to the punch geometry are considered, but so are larger changes such as the use of ultrasonic vibration to improve formability and adjustable tooling. The influence of process monitoring and simulation on process robustness is also considered. A summary of methods and effects is drawn at the end to highlight potential space for innovation

A novel ironing punch concept with adjustable tool diameter

A new tool concept is presented. It reduces galling and tool wear by lowering the interface pressure between workpiece and tool during retraction. The work performed during retraction of a prototype ironing punch is reduced by more than 50% compared to a conventional punch. This is achieved by a hollow punch with an internal mandrel, which provides stiffness during ironing through a conical interface, while the punch contracts during retraction when the mandrel is released. Adjustability of the punch diameter by the mandrel position enables adaptation to variable external factors, e.g. variation of strip thickness in progressive die forming