Britannia metal
Britannia metal , also called "Britannium" is a group of pewter - alloys with prone to bluish, silver white coloring. The tin is alloyed with antimony , usually together with copper , but also with nickel , lead and bismuth .
Depending on the definition, Britanniametall is sometimes differentiated from Pewter ( pewter ), sometimes Britanniametall is viewed as a special case of Pewter (with Britanniametall as the harder alloy with more antimony, little or no lead). In German-speaking countries (according to Richter) Pewter was even assigned to the Britanniametall (as pewter from Great Britain).
definition
All alloys containing between 65 and 97% tin, 1 to 24% antimony and 1 to 5% copper and bismuth can be called Britannia metal in the broadest sense. An alloy of 93% tin, 5% antimony and 2% copper is described as Britanniametall or Vickers White Metal (Encyclopedia Britannica). An alloy of 90% tin and 10% antimony has proven to be suitable for casting in many cases, as it fills the casting mold well even when it cools down. This is also referred to in sources as Britannia metal.
There are various alloys that (according to Richter) are assigned to the Britannia metal, including:
- Spoon metal, English: tin 82%, antimony 16%, copper 2%.
- Spoon metal, German: tin 72%, antimony 24%, copper 4%.
- Pewter for pitchers: tin 81%, antimony 6%, copper 6%, lead 7%.
- Queens metal for jugs: tin 89%, antimony 7%, copper 2%, bismuth 2%.
- Tutania metal: tin 86%, antimony 10%, copper 3%, lead 1%.
Properties and use
Due to its alloy with antimony, the Britannia metal is much more brittle and harder than tin, which allows mechanical processing and polishing . However, it is not much more solid. The break is fine-grained.
The alloy is mainly used for castings, including u. a. Tin utensils , ornaments, buttons, bearing metal , printing plates. She is z. B. used to make the famous statuette, the Oscar or Academy Award of Merit.
Because of their brittleness, only alloys with a higher tin concentration are suitable for rolling . The addition of lead increases strength without reducing ductility to the same extent as antimony . The casting properties are also better. However, objects with lead in the alloy lose their luster quickly, are grayer and, because of the toxicity of the lead, cannot be used for food.
Production of the melt
First melt the copper (as provided) because of the high melting point, then add tin, antimony and reduce the heat, as the alloy has a significantly lower melting point.
to water
Brass molds were preferably used , these were previously sooty or flushed with blood stone and preheated, for lintel casting up to melting temperature.
Slow cooling is useful if z. B. a good sound is desired for bells. To cool down, it should stay in the paraffin bath for an hour at approx. 230 ° C.
After casting, the surface is gray-white and only becomes shiny after polishing. Another refinement option is to silver-plate the castings (electroplating).
Britannia metal is solderable .
Similar alloys
- Ashberrium (like English spoon metal plus 1% zinc, 1% nickel, 1% aluminum).
- Metal argentine (94–97% tin, 5–2% copper, 0.5% antimony, or 2/3% bismuth)
- Minofor metal (≈66% tin, 17–20% antimony, 3–4% copper, ≈9% zinc, up to 1% iron)
Solder alloy (4 parts tin, 3 parts lead) is also used for pewter figures and ornaments (often with approx. 3% antimony for more hardness).
literature
- Karl Richter (Ed.): Zinc, tin and lead. A detailed description of the properties of these metals, their alloys with each other and with other metals, as well as their processing in physical and chemical ways. For metal workers and art industrialists . (= Chemical-technical library ; volume 109). 3. Edition. A. Hartleben Verlag, Vienna / Leipzig 1927.
Individual evidence
- ↑ a b Karl Richter (Ed.): Zinc, tin and lead. A detailed description of the properties of these metals, their alloys with each other and with other metals, as well as their processing in physical and chemical ways. For metal workers and art industrialists. ( Chemical-technical library , volume 109). 3. Edition. A. Hartleben Verlag, Vienna / Leipzig 1927.