Upcasting, Horizontal Casting or Vertical Semi-Continuous Casting: Which Process Is Better for Copper Rod?
Release time:
2026-08-28
Which copper rod casting process is more suitable for wire production? This article compares upcasting, horizontal continuous casting, and vertical semi-continuous casting, focusing on their structural characteristics, advantages, limitations, and impact on downstream wire drawing and annealing.
Copper rod is the starting material for a wide range of electrical products, including power cable conductors, magnet wire, electronic wire and fine copper wire.
When selecting a copper casting process, production capacity and rod diameter are often the first factors considered. However, the casting method also has a significant influence on the internal structure of the copper, including grain size, grain orientation, impurity distribution and oxygen content.
These characteristics can directly affect subsequent rolling, drawing and annealing performance.
Among the commonly used processes, upward continuous casting, horizontal continuous casting and vertical semi-continuous casting each have their own characteristics. There is no single process that is best for every application.
1. Upward Continuous Casting
Upward continuous casting, commonly known as upcasting, is widely used for the production of oxygen-free copper rod.
In this process, molten copper is held in a furnace under a controlled atmosphere. A graphite die is immersed in the molten copper, and the metal solidifies inside a water-cooled crystallizer before being continuously withdrawn upward.
One of the main advantages of upcasting is its ability to produce copper rod with very low oxygen content and high electrical conductivity. The process is relatively compact and can produce rod directly for subsequent wire drawing, reducing the need for additional hot-rolling operations.
Main Advantages
- Suitable for oxygen-free copper rod production;
- High electrical conductivity;
- Relatively clean and smooth rod surface;
- Compact production line;
- Flexible production capacity through multi-strand casting;
- Rod can be directly supplied to downstream drawing processes.
However, upcasting involves strong directional solidification. As a result, the copper rod normally develops relatively pronounced columnar grains along the casting direction.
For ordinary conductor production, this structure is generally acceptable. But when the rod is further drawn into very fine or ultra-fine wire, excessive grain size or strong grain orientation may result in uneven deformation.
Therefore, melt cleanliness, cooling conditions and casting speed must be carefully controlled when the final product requires intensive wire drawing.
2. Horizontal Continuous Casting
Horizontal continuous casting uses a horizontally arranged graphite mold. Molten copper flows into the mold and is continuously withdrawn in the horizontal direction while solidifying.
The process can be used for copper as well as various copper alloys and is suitable for producing rods, bars, billets and other sections.
Main Advantages
- Continuous and relatively efficient production;
- Good dimensional control;
- Flexible product sizes and cross-sections;
- Suitable for copper and a wide range of copper alloys;
- Easy integration with downstream production equipment.
The main metallurgical challenge of horizontal casting comes from the asymmetric thermal conditions created by gravity and horizontal solidification.
The upper and lower parts of the casting may experience slightly different cooling and solidification conditions. If the process is not properly controlled, this can result in differences in grain structure, segregation or local defects across the section.
For products that will later undergo substantial rolling or drawing, these structural differences may influence deformation uniformity.
For this reason, temperature control, melt cleanliness, mold condition and cooling stability are particularly important when horizontal-cast material is intended for demanding electrical applications.
3. Vertical Semi-Continuous Casting
In vertical semi-continuous casting, molten copper or copper alloy solidifies inside a vertically arranged water-cooled mold, while the billet or ingot is gradually withdrawn downward.
Unlike continuous rod casting, the casting length is limited, which is why the process is generally described as semi-continuous casting.
The resulting billet normally undergoes further processing such as rolling, extrusion or drawing before becoming a finished wire or conductor product.
Main Advantages
- Suitable for large-section billets and rods;
- Applicable to many copper alloy grades;
- Relatively symmetrical solidification conditions;
- Suitable for products requiring extensive downstream deformation;
- Good flexibility for billet-based production routes.
Because of the larger casting section, the solidification rate is generally lower than that of small-diameter continuously cast rod.
This may result in a relatively coarse as-cast grain structure. However, subsequent rolling or extrusion can significantly refine and modify the material structure.
For large billets and alloy products, vertical semi-continuous casting therefore remains an important industrial process.
4. Why Does the Casting Structure Matter for Wire Drawing?
A copper rod may look completely normal from the outside while still having a very different internal structure.
For wire manufacturers, several factors are particularly important.
Grain size and orientation
Fine and relatively uniform grains generally provide more uniform deformation during wire drawing. Very coarse or strongly oriented grains may increase deformation differences between adjacent regions.
Oxygen and impurity content
Oxygen, inclusions and other impurities can influence conductivity, ductility and wire-break performance, especially when copper is drawn to very small diameters.
Segregation and porosity
Local chemical segregation, shrinkage cavities or internal porosity can become potential failure points during heavy drawing.
Surface quality
Surface cracks, oxide particles or casting marks may become more serious after repeated drawing passes.
This is why copper rod quality should not be evaluated only by conductivity or chemical composition. Casting structure and process stability are equally important for downstream processing.
For wire and cable manufacturers, however, copper rod casting is only the first step. The stability of the subsequent drawing and annealing process is equally important in determining final wire quality.
CABMAC provides copper wire processing equipment including rod breakdown machines, intermediate and fine wire drawing machines, annealing systems, take-up equipment and related auxiliary equipment. Matching the downstream processing route to the characteristics of the incoming copper rod can help improve production stability, wire surface quality and drawing performance.
5. Comparison of the Three Casting Processes
Item | Upward Continuous Casting | Horizontal Continuous Casting | Vertical Semi-Continuous Casting |
|---|---|---|---|
Typical product | Copper rod | Rod, bar, billet, profile | Billet, large rod |
Production mode | Continuous | Continuous | Semi-continuous |
Typical materials | Mainly oxygen-free copper | Copper and copper alloys | Copper and copper alloys |
Main structural feature | Strong directional solidification | Possible upper/lower structural differences | Relatively symmetrical large-section solidification |
Oxygen control | Excellent for OF copper | Depends on melt protection and process control | Depends on melting and atmosphere control |
Downstream processing | Often direct wire drawing | Drawing, rolling or extrusion | Usually rolling or extrusion before drawing |
Main advantage | High conductivity and compact production | High flexibility and continuous production | Suitable for large sections and alloy billets |
Main concern | Coarse or directional grains | Uneven solidification and segregation | Larger grains and additional downstream processing |
6. Which Process Should You Choose?
The answer depends on the final product rather than on the casting equipment alone.
For oxygen-free electrical copper rod intended for conductor and wire production, upward continuous casting is often an efficient and practical choice because of its low oxygen level, high conductivity and direct connection with wire drawing.
For continuous production of copper or copper-alloy rods, bars and profiles, horizontal continuous casting offers greater flexibility in product form and alloy selection.
For large billets, special copper alloys or products requiring significant rolling or extrusion, vertical semi-continuous casting is often more appropriate.
When the final copper wire diameter becomes smaller, the requirements on the original rod become increasingly strict. Grain structure, impurities, surface condition and casting consistency all become more important.
Therefore, especially for fine and ultra-fine wire production, the casting process should be considered together with the complete downstream route, including rod breakdown, intermediate drawing, fine drawing and annealing.
At CABMAC, we consider these processes as part of an integrated production chain rather than as isolated machines. The characteristics of the incoming copper rod, target wire diameter, required conductivity and production capacity should all be considered when selecting suitable wire drawing and annealing equipment.
Conclusion
Upcasting, horizontal continuous casting and vertical semi-continuous casting are not simply competing technologies. Each process has its own advantages and is suitable for different materials, product sizes and downstream applications.
For wire and cable manufacturers, the key is not only how the copper rod is produced, but also how well its metallurgical characteristics match the subsequent drawing, annealing and take-up process.
A stable combination of raw material quality and properly selected processing equipment can help achieve more consistent wire diameter, improved surface quality, fewer wire breaks and higher production efficiency.
CABMAC offers wire drawing and cable manufacturing equipment for different production requirements, from copper rod breakdown and fine wire processing to downstream cable production. If you are planning a new copper wire production line or upgrading an existing line, our team can help evaluate the process according to your raw material, final wire size and required production capacity.
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