Annealing in collapsible aluminium tube production relieves residual stress, restores ductility and removes excess surface lubricant from impact-extruded tube blanks before coating. The annealing oven must be matched with tube size, line speed, cooling, buffering and the following internal-coating process rather than selected as an isolated heating machine.
Why do aluminium tube blanks need annealing?
Impact extrusion forms an aluminium slug into a seamless tube blank, but the forming process also work-hardens the material. Annealing applies controlled heat so the tube regains the plasticity and flexibility required for later handling and finishing. High-temperature evaporation also removes excess lubricant from the inner and outer surfaces, creating a more suitable base for the following internal coating, exterior base coating and tail-coating processes.
Where does annealing sit in the production line?
Annealing is the third main process step in the XUNTANG line. It follows the extrusion press and trimming and threading machine. After the oven, a buffer accumulator cools and temporarily stores the tubes before they enter the internal coating machine.
This sequence matters because the next station needs tubes in a condition that supports stable handling and repeatable coating. The oven outlet, cooling time, buffer capacity and downstream pace should therefore be reviewed as one connected section.
Confirmed XUNTANG annealing oven parameters
| Parameter | Large Line XT-L26 | Small Line XT-S26 |
|---|---|---|
| Tube diameter | Ø19-35 mm | Ø13.5-25 mm |
| Tube length | 110-200 mm | 70-145 mm |
| Production speed | 85 pcs/min | 95 pcs/min |
| Temperature range | 0-500 °C; recommended setting 460 °C | |
| Temperature accuracy | ±2 °C | |
| Heating method | Baking | |
| Curing time (published specification) | 3-4 min | |
| Preheating time | 1 h 20 min | |
| Control | PLC + HMI | |
These are the published equipment parameters for the XUNTANG annealing oven. Final operating settings and acceptance criteria should follow the confirmed tube specification, process materials and approved project documents.
How is temperature controlled?
The oven uses programmed PLC and HMI control with an adjustable-speed chain transmission. Stable temperature across the process is important because the purpose is not simply to make the tube hot; the heat cycle must support stress relief, lubricant removal and repeatable transfer to downstream stations. Operators should use the approved settings for the selected tube and process rather than copying a value from a different product.
Why are cooling and buffering part of the annealing discussion?
A buffer accumulator sits between the annealing furnace and the internal coater. It cools and temporarily stores tubes during continuous operation, helping coordinate differences in pace between heat treatment and coating. Without this process handoff, a short interruption at one station can affect more of the line.
Buffering also has a layout consequence. Buyers should allow for the accumulator, transfer route, operator access and maintenance space when reviewing the factory layout.
What can affect downstream coating preparation?
The annealed tube moves toward internal coating, so the buyer should review the surface condition, cooling and transfer together with the coating requirement. Tube diameter, length, production pace and the selected process materials all influence the final setup. A coating problem should not automatically be attributed to the coating machine before the upstream tube condition and handoff are checked.
The next process is explained in the internal coating and curing guide.
What should buyers confirm before quotation?
| Input | What to provide | Why it matters |
|---|---|---|
| Tube range | All required diameters and lengths | Confirms the applicable line format |
| Output | Target running speed and production plan | Supports whole-line pace review |
| Tube samples | Approved samples or drawings when available | Clarifies the required product condition |
| Coating process | Known internal and external coating requirements | Connects annealing with downstream preparation |
| Factory utilities | Voltage, frequency and installation conditions | Supports electrical and layout planning |
| Acceptance basis | Approved specification and project criteria | Avoids relying on generic assumptions |
Frequently asked questions
What is the purpose of annealing aluminium tubes?
Annealing relieves residual stress, restores ductility and helps remove excess lubricant from impact-extruded tube blanks before coating and later finishing.
When does annealing happen in an aluminium tube line?
It follows extrusion and trimming and threading. The tubes then pass through cooling and buffering before internal coating.
What temperature range does the XUNTANG annealing oven use?
The published oven range is 0-500 °C with a recommended setting of 460 °C and temperature accuracy of ±2 °C. Final settings must follow the confirmed tube and process specification.
Why is a buffer accumulator installed after the oven?
The accumulator cools and temporarily stores tubes, helping coordinate the pace between annealing and internal coating during continuous production.
Can an annealing oven be selected separately from the line?
It can be discussed as an individual machine for a replacement or upgrade project, but its tube range, speed, transfer, cooling and downstream coating requirements still need to match the existing line.
Review annealing as part of the complete process
A good annealing section prepares the tube material and surface for the processes that follow. Buyers should compare the oven together with extrusion, trimming, buffering and coating requirements, then confirm the operating basis against their own products. Review the XUNTANG annealing oven, explore the complete aluminium tube line, or send your tube range for technical discussion.