Tinplate Coil
Cold rolled low carbon steel strip tin coated on both sides for can and container making
Specifications
Tinplate Temper and Tin Coating Weight Explained
Tinplate temper controls how stiff and how formable the plate is, and tin coating weight controls how much protection the tin layer gives the contents.
Tinplate temper controls how stiff and how formable the plate is, and tin coating weight controls how much protection the tin layer gives the contents. The tempers held here run T2 T2.5 T3 T3.5 T4 and T5 in the single reduced range and DR7 DR7M and DR8 in the double reduced range, with tin coating from 1.1 to 11.2 g per square meter. Getting both right is what separates a can that runs on the line from one that splits at the flange.
What Tinplate Is
Tinplate, written SPTE or ETP, is cold rolled low carbon steel sheet or strip coated on both sides with commercially pure tin. The tin is there to prevent corrosion and rust, and the combination gives the strength and formability of steel with the corrosion resistance, solderability and appearance of tin.
That is why it dominates packaging. The material seals well, keeps light out, takes print and stands up to handling, so it appears in food packaging, pharmaceutical packaging, commodity packaging, instrument packaging and industrial packaging.
- Substrate is cold rolled low carbon steel in SPCC MR or SPCH
- Commercially pure tin applied to both faces
- Corrosion resistance non toxicity high strength and good ductility
- Solderable and printable for decorated containers
- Supplied as coil strip or cut sheet from the same specification
Reading the Temper Designation
Temper is a hardness and stiffness scale. The single reduced tempers run T2 T2.5 T3 T3.5 T4 and T5, moving from softer and more formable toward harder and stiffer. The double reduced tempers DR7 DR7M and DR8 are rolled again after annealing, which raises stiffness and lets the same rigidity be reached at a thinner gauge.
The rule of thumb on the shop floor is simple. Deep drawn parts and rolled edges want the lower tempers. Flat rigid parts that only need to resist denting can take the higher tempers or a double reduced plate and save material weight.
- T2 and T2.5 for drawn shapes and formed components
- T3 and T3.5 as the general purpose range for can bodies
- T4 and T5 where stiffness matters more than deep forming
- DR7 DR7M and DR8 where a thinner gauge must stay rigid
- Confirm the temper against the part before the gauge is chosen
Batch Annealing Against Continuous Annealing
Tinplate is supplied in both BA and CA condition, meaning batch annealing and continuous annealing. The annealing route is part of the temper specification rather than a separate option, and the tempers listed here are all available in BA and CA.
Name the route on the order when your forming process is sensitive to it. Leaving it blank means the mill decides, and two coils that carry the same temper letter can then behave differently on the same press.
- CA stands for continuous annealing
- BA stands for batch annealing
- Both routes available across the T and DR temper range
- State the route where the press setup is already proven
- Keep the route consistent between trial material and production material
Choosing the Tin Coating Weight
Tin coating is supplied from 1.1 to 11.2 g per square meter. The lower end is for dry contents and printed decorative work where the tin is mostly a base for lacquer and appearance. The upper end is for aggressive contents and long shelf life where the tin layer itself is doing the corrosion work.
This is the specification most often left off an inquiry, and it is the one that decides whether the pack survives its shelf life. Tell us the contents and the intended shelf life and the coating weight can be set against that rather than against a default.
- Coating weight range 1.1 to 11.2 g per square meter
- Lighter coatings for dry contents and lacquered decorative work
- Heavier coatings for acidic contents and longer shelf life
- Coating is applied to both faces of the strip
- Set the coating weight from the contents rather than from habit
Gauge Width and Coil Dimensions
Thickness runs from 0.15 to 0.50mm with a tolerance of plus or minus 0.01mm, and coil width runs from 600 to 1050mm with a tolerance of 0 to 3mm. Coil inside diameter is 420 or 508mm and coil weight is 1 to 5 MT.
Those coil dimensions are not trivia. Your slitter or press feed is built around a specific inside diameter, and the maximum coil weight your crane can lift decides what can be unloaded at your plant. Confirm both before the order is booked.
- Thickness 0.15 to 0.50mm with tolerance plus or minus 0.01mm
- Width 600 to 1050mm with tolerance 0 to 3mm
- Coil inside diameter 420mm or 508mm
- Coil weight 1 to 5 MT
- Cut sheet and slit strip supplied from the same specification
Surface Finish Passivation and Oiling
Surface is supplied in bright, stone or silver finish with passivation treatment, and DOS oil is applied. The finish is a decoration and printing decision, while passivation and oil are what keep the tin surface from staining and sticking between production and use.
If your line degreases before printing, say so. If it does not, the oil film is part of the specification and has to match what your coating shop expects.
- Bright finish for a reflective decorated surface
- Stone finish where a directional texture is wanted
- Silver finish for a matt even appearance
- Passivation treatment applied to the tin surface
- DOS oil applied to protect the surface in transit and storage
Standards to Name on the Order
The standards carried across the tinplate range are GB/T 2520-2008, JIS G3303-2008, DIN EN 10203-1991 and ASTM A623M-2011. Substrate material is quoted as SPCC, MR or SPCH.
Name the standard your customer audits against and the certificate then reads in the same language as your specification. ISO9001, BV, SGS and RoHS documentation is available with the order.
- GB/T 2520-2008 for Chinese practice
- JIS G3303-2008 for Japanese practice
- DIN EN 10203-1991 for European practice
- ASTM A623M-2011 for American practice
- Substrate named as SPCC MR or SPCH
Putting the Specification Together
A complete tinplate line reads as form, standard, substrate, temper with annealing route, tin coating weight, thickness, width, finish and coil dimensions. Written that way it can be quoted in one pass and it can be audited later.
Ask for the mill test certificate with the shipment so the temper and coating weight are on record against the batch that made your cans.
- Form as coil strip or sheet
- Temper with the BA or CA route stated
- Tin coating weight inside the 1.1 to 11.2 g per square meter range
- Thickness and width with the tolerances confirmed
- Finish passivation and oil condition
- Mill test certificate requested with the shipment
Referenced
Products In This Guide
Tinplate Sheet
SPTE sheet supplied in the temper your forming and seaming operation actually needs
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Tinplate Strip
Stocked SPTE strip cut to width for short runs and repeat packaging programs
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Coated Tinplate Coil
Full width electrolytic tinplate coil wound for continuous can and closure lines
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Questions On This Topic
Which temper should I use for a drawn can body?
Drawn and formed parts sit at the softer end of the range, so T2 and T2.5 are the usual starting point, with T3 and T3.5 for general can bodies. Send the part drawing and the draw ratio and the temper can be confirmed before you commit to a coil.
What is the difference between T4 and DR8?
T4 is single reduced and DR8 is double reduced, meaning it is rolled again after annealing. The double reduced plate reaches a higher stiffness, which lets a thinner gauge carry the same rigidity. Both are held here so the choice can be made on part weight.
How much tin coating do I need for food cans?
Coating weight is supplied anywhere from 1.1 to 11.2 g per square meter. Acidic contents and long shelf life push the specification up the range, while dry contents in a lacquered can sit lower. Tell us the product and the shelf life and the coating weight is set against that.
Do you supply tinplate as coil strip and sheet?
Yes. Coil, strip and cut sheet all come from the same specification, including coated and customized sheet, so a press shop and a decoiling line can be served from one order.
What thickness tolerance can I hold my press setup to?
Thickness runs from 0.15 to 0.50mm with a tolerance of plus or minus 0.01mm, and width from 600 to 1050mm with a tolerance of 0 to 3mm.
Which standard will the material be certified to?
GB/T 2520-2008, JIS G3303-2008, DIN EN 10203-1991 and ASTM A623M-2011 are all carried. Name the one your customer audits against on the order and the mill test certificate is issued in that language.
Still Deciding After Reading This
If you are still asking "Which temper should I use for a drawn can body?" send us the sizes and the duty and we will answer it against your actual order.