1.Why is it technically feasible?
Cold-rolled coils (usually cold-rolled stainless steel coils, such as 304 and 316) possess the basic requirements for manufacturing the outer shell of a thermos flask:
Material properties: Good strength, formability (easy to stretch and bend), and corrosion resistance.
Hygiene and safety: Food-grade stainless steel (such as 304) itself meets the requirements for food contact.
2.What are the processing steps for cold-rolled coils?
Unwinding and Leveling: Unwind and level the rolled material.
Cutting: Cut into round or square sheets.
Stretching and Forming: On a large press, the flat sheet is stretched multiple times through a die to form a cup-shaped cylinder. This is a crucial plastic deformation process.
Edge Trimming/Trimming: Trim the irregular edges of the stretched cup rim neatly.
Threading/Bottom Machining: Thread the rim of the cup and machine a smooth bottom.
Surface Treatment (The Most Critical and Expensive Step): The original cold-rolled stainless steel surface is an industrial "white board" (matte, with rolling texture). A thermos cup requires:
Mirror Finish/Brushed Polishing: Requires multiple grinding and polishing processes, resulting in extremely high costs.
Painting/Baking: Requires surface treatment (such as cleaning and phosphating) before spraying and baking.
Electroplating: For colors such as titanium gold and rose gold, the process is even more complex.
Assembly: Assemble with the inner liner, bottom lid, and other components.
3.What are the steps involved in using "pre-processed materials"?
To improve efficiency, reduce costs, and ensure consistent appearance, large-scale insulated cup manufacturers typically don't start with raw cold-rolled coils. They instead source:
Pre-polished stainless steel sheets/coils: Material suppliers already provide materials with specific surface finishes (such as brushed or glossy finishes), allowing the factory to simply cut and shape them, greatly simplifying the most tedious surface treatment process.
Clad sheets: Steel sheets with a pre-applied colored PVC or PET film, which, after stretching and forming, already possess the final color and texture, eliminating the need for painting.
Specifically sized cup-body materials: Narrow strip steel with performance optimized for the stretching process.
4.How does the performance of using raw cold-rolled coils work?
Surface Quality: Starting from scratch makes it difficult to guarantee consistency across large batches, resulting in low yield.
Production Process: Long process, requiring a dedicated, high-investment polishing/spraying workshop.
Production Cost: Very high. Surface treatment is the main cost, and environmental protection investments are substantial.
Suitable Scenarios: Small-batch customization, experimental products, and products with special, non-standard surface requirements.
5.What are the conclusions and recommendations?
Yes, but it's uneconomical: If you're a small workshop or DIY enthusiast wanting to try making a few thermos cup shells from readily available cold-rolled stainless steel sheets, it's technically feasible, requiring complex processes such as leveling, cutting, multiple stretching, and polishing.
However, this isn't used in industry: For large-scale industrial production, starting with raw cold-rolled coils to make thermos cup shells is a costly and outdated method. The industry generally uses pre-processed materials to improve efficiency and quality control.
The key is the surface: What determines the appearance and quality of a thermos cup isn't the starting point-the cold-rolled coil-but the final finishing surface treatment technology (polishing, spraying, coating, etc.).