In the manufacturing process of copper capillary assemblies, continuous casting and rolling, an advanced technology combining continuous casting of molten metal with rolling deformation, plays a crucial role in optimizing material uniformity. This process directly pours molten copper into the roll gap, allowing the rolls to simultaneously function as a crystallizer and for rolling deformation, thus reducing the risk of compositional segregation caused by multiple heating and cooling cycles in traditional processes. During solidification, the molten copper contacts the roll surface, and heat is rapidly transferred radially, promoting axial preferential grain growth and forming a strongly oriented columnar crystal structure. This structure lays the foundation for uniform deformation in the subsequent rolling stage.
The core advantage of continuous casting and rolling lies in its continuous process. In traditional processes, the copper billet undergoes multiple steps, including cooling, secondary heating, and extrusion. Each step can introduce temperature gradients or stress concentrations, leading to microstructure inhomogeneity. Continuous casting and rolling, through its integrated "casting-rolling" design, allows the copper billet to undergo initial deformation in the transition zone between the solid and liquid states, avoiding microstructure differences caused by phase transformation. During the rolling process, the synergistic effect of multiple rolls applies progressive pressure to the copper billet, refining the initial columnar crystals and eliminating internal defects through a dynamic recrystallization mechanism, ultimately resulting in metal flow lines with uniform grain size and consistent orientation.
The optimization of material homogeneity is also reflected in the precise control of the temperature field in the continuous casting and rolling process. In the casting stage, the solidification rate of liquid copper can be controlled by adjusting the roll speed and cooling water flow rate, ensuring stable solid-liquid interface progression. This optimized temperature gradient reduces the tendency for dendrite arm coarsening, preventing the formation of coarse grains. Upon entering the rolling stage, the heat treatment design of the soaking furnace homogenizes the temperature of the copper billet, eliminating the temperature difference between the surface and the center, and providing uniform deformation resistance to the rolls. This dual balance of temperature and stress significantly reduces the differences in axial and radial mechanical properties of the copper capillary assembly.
The roll design in the continuous casting and rolling process also directly affects material homogeneity. Modern three-roll or four-roll planetary mills, through unique motion trajectories, subject the copper billet to three-dimensional compressive stress during rolling. This multi-directional stress state promotes the equiaxed transformation of grains, breaking the unidirectional columnar crystal structure and significantly improving the isotropy of the microstructure. Simultaneously, the microtexture on the roll surface guides the formation of fine recrystallized grains on the copper billet surface, further suppressing the propagation of surface defects and ensuring the simultaneous improvement of the quality of the inner and outer walls of the long tube assembly.
The combination of microalloying technology and continuous casting and rolling processes provides a new path for optimizing material uniformity. By adding rare earth elements or specific alloying elements to the copper matrix, grain size can be refined and the distribution of the second phase improved. In the continuous casting stage, microalloying elements slow down the growth rate of columnar crystals by inhibiting grain boundary migration; in the rolling stage, these elements promote the uniform occurrence of dynamic recrystallization by pinning dislocations. Ultimately, the microstructure of the copper capillary assembly exhibits fine, uniform equiaxed crystal characteristics, significantly improving its fatigue resistance and corrosion resistance.
The automated control system of the continuous casting and rolling process is a key support for ensuring material uniformity. By monitoring parameters such as casting speed, rolling force, and temperature field in real time, the system can dynamically adjust process variables to ensure production stability. For example, when a fluctuation in copper billet temperature is detected, the control system can immediately adjust the cooling water flow or roll speed to avoid microstructure inhomogeneity caused by abnormal temperature. This closed-loop control mode significantly reduces batch-to-batch quality fluctuations in copper capillary assembly, meeting the stringent requirements for material consistency in high-end applications.
From macroscopic properties to microstructure, the continuous casting and rolling process comprehensively optimizes the material uniformity of copper capillary assembly through the synergistic effects of process integration, temperature control, roll design, microalloying, and automated control. This process not only improves the mechanical properties and service life of the product but also reduces production costs by minimizing intermediate steps, providing an important technological path for green manufacturing and high-quality development in the copper processing industry.
