Analysis of Metal Flow and Die in Aluminum Profile Extrusion Production
Abstract:
Extrusion forming is a plastic processing method that applies external force to the metal billet inside the extrusion barrel to overcome the friction resistance of the die and the deformation resistance of the metal. This process aims to achieve specific cross-sectional shapes, dimensions, and performance characteristics in the resulting processed products. This study focuses on the critical factors affecting the quality of extruded aluminum profiles, emphasizing the importance of die structure, metal flow uniformity, and the avoidance of defects during the extrusion process.
- Introduction: Extrusion methods vary based on factors such as stress-strain conditions, extrusion direction, lubrication status, temperature, speed, die types, billet shapes, and product shapes. Different classification methods are discussed in Table 2-1.
- Metal Flow Characteristics During Aluminum Profile Filling Extrusion: To facilitate loading the billet into the extrusion barrel, it is common to make the billet diameter smaller than the barrel inner diameter. During aluminum profile extrusion, the billet, being smaller, flows into the gap between the billet and the barrel under axial pressure, filling the barrel and forming a tapered end. This phase is known as the filling extrusion stage.The selection of billet diameter considers deviations, thermal expansion after heating, and the bonding effect of the heated billet on the extrusion barrel’s inner surface. The filling coefficient (K) is typically chosen between 1.06 and 1.10. Adjusting K values based on barrel size ensures successful billet loading without excessive difficulties or defects.
- Metal Flow and Stress Analysis During Aluminum Profile Filling Extrusion: In the filling extrusion stage, axial pressure is applied to the billet, leading to tapering and filling of the barrel and die. The extrusion force increases linearly until reaching the maximum value, marking the end of the filling extrusion stage. The metal flow pattern depends on the extrusion machine type (vertical or horizontal) and the die shape (flat or tapered).
- Main Defects During Aluminum Profile Filling Extrusion: Improper control during the filling extrusion process can result in defects in the final product. Excessive length-to-diameter ratios of billets can lead to double-drum deformation. Additionally, inadequate control may create localized closed spaces, causing gas entrapment and defects like bubbles and skinning on the extruded product.Addressing these issues includes optimizing the filling coefficient, ensuring a smooth billet loading process, and adopting billet temperature gradients to facilitate gas expulsion.
- Metal Flow Characteristics During Aluminum Profile Extrusion: The study of metal flow behavior during extrusion is crucial for understanding its impact on the structure, properties, surface quality, dimensions, accuracy, die design, die lifespan, and production efficiency of extruded products. The extrusion process is roughly divided into three stages: filling extrusion, steady-state extrusion, and turbulent extrusion.
- Varieties, Specifications, and Classification of Aluminum Profiles: The dimensions of aluminum profiles are primarily determined by user requirements. The minimum practical extrusion dimensions for 6063 aluminum alloy profiles under conventional conditions are presented in Figure 1-1. The minimum extrudable wall thickness is influenced by alloy extrudability, production efficiency, die lifespan, and production cost. The maximum achievable section dimensions depend on the extrusion equipment’s capabilities.
In conclusion, a comprehensive understanding of metal flow, die design, and defect prevention is vital for optimizing the extrusion process and ensuring high-quality aluminum profiles. Adjustments in billet dimensions, filling coefficients, and temperature gradients can significantly impact the outcome of the extrusion process.