The earliest form of iron smelting was devised by the
Hittites of Mesopotamia around 1500 BC.
Damascus Wootz was the first high-quality steel
made by Man. Authentic Damascus steel was used to forge exceptional blades characterized
by prominent surface patterns. The ancient manufacturing secret for those patterned blades
was lost around 1850... For about 140 years.
It turns out that one trace element is essential, namely
vanadium (V).
Traces of vanadium (from 0.005% to 0.01%) are found naturally in
the Indian ores used for most ancient wootz and also in the ores from
Saladin's
caves (the famous historical iron mines at Warda, near
Ajloun Castle).
Lead alloys for bullets (hardness measured with pencils).
Aluminium beverage cans contain about 1% manganese (Mn, 1%-1.5%)
for better resistance to corrosion and 1% magnesium (Mg, 0.8%-1.3%) for thinner can-stock.
3004 alloy
is allowed to contain a number of impurities:
Fe (<0.7%),
Si (<0.3%),
Cu (<0.25%),
Zn (<0.25%),
etc. (<0.15%).
(2021-07-09) Standard silver alloys and fine silver (at least 99.9% Ag)
Coin silver, Sterling, Britannia, Argentium® (935 or 960) and fine silver.
The tradional alloys of silver are rated according to their minimum silver content
(parts per thousand by weight) knowing that the rest is mostly copper.
999 :
Fine silver has a silver content of at least 99.9% by weight.
It doesn't tarnish but is too soft for most uses.
Britannia silver
is an obsolete silver alloy introduced in 1696, with a silver content
of 23/24 (95.833%) per weight (the rest being mostly copper).
It was abandonned for being much softer than sterling silver.
Sterling silver
is usually an alloy of 92.5% silver and 7.5% copper. It does tarnish and requires regular cleaning.
The word goes back to the introduction of the
Norman silver penny (French: esterlin)
late in the eleventh century.
Coin silver is an alloy of 90% silver with base metals.
used for modern coinage. It was used in jewelry when melting used coins was
a popular source of silver alloy.
To achieve a 92.5% silver content, you must mix
1 part fine silver with 3 parts coin silver:
92.5% =
3 × 90% + 1 × 100%
3 + 1
Argentium®
This is the trade name of a silver alloy introduced
at Middlesex University by Peter Johns in 1991.
It comes in two grades, (935 and 960) respectively intended as
replacements for Sterling and Britannia silver.
The main selling point are that Argentium® doesn't tarnish
(without a need for rhodium plating) doesn't produce
firescales
and can be fused.
Germanium lowers the thermal conductivity of the metal,
so it's not as cold to the touch as Sterling silver or fine silver.
Electrical conductivity is also reduced.
"960" : 96% Silver (sometimes called "Argentium Britannia").
"935" : 93.5& Silver, 5.5% Copper and 1% Germanium
(sometimes called "Argentium Sterling").
The 1998 patent also mention the addition of a small amount of boron in Argebntium
(no more than 10 or 20 ppm) as a grain refiner to help fuse the alloy to itself.
The recommended boron content seems to be 2 ppm.
Germanium content could vary from 0.4% to 7% (1% is recommended)
with a silver content as low as 77%. Higher silver contents are used which exceed the
requirements for Sterling or Britannia silver, so the alloy could be
hallmarked as such.
Super Salamander
clay-graphite crucibles can handle temperatures up to 1600°C (2900°F)
which is enough to melt iron and more than enough for other common metals and alloys, in a propane furnace.
Most electric induction furnaces are rated at 1150°C (2102°F)
which isn't reliable enough to melt cast iron.
Green sand is a mixture of sand and clay moistened with
water glass (a solution of sodium silicate).
It can be hardened by gasing it with carbon dioxide.
Unhardened green sand can be reused in successive castings.
If hardening is not required, a better alternative to green sand is
petrobond (oil sand) which allows sand castings reproducing
finer details of a pattern.
A frame for sand casting is called a flask.
The upper part is called the cope.
The lower part is the drag.
(2018-11-30) Sheet metal
Most metals and single-phase alloys can be rolled into thin sheets.
Traditional bell bronze (80% Cu, 20% Sn) is actually a two-phase alloy
(it contains tin grains undissolved in copper) and is too brittle to be rolled.
By contrast, the single-phase alloy called
malleable bronze (92% Cu, 8% Sn) can be rolled into sheets
and has been used to manufacture cymbals and gongs more cheaply than is possible
with traditional bell bronze.
The surface of a file is case-hardened
after the tool has been machined, which makes it
harder than the metals it's intended to cut.
The special brush used to remove debris build-up from a file is called a file card.
The metal bristles in a file card are arranged in a square grid.
For best efficiency, a given file and a given file card should be used
at a specific angle of each other...
When cutting a bolt to length, it's prudent to thread a (steel) nut on it
ahead of time. Unscrewing that nut after cutting will deburr the cut,
usually well enough to make the nut usable again right away.
Otherwise, you have yo file away the burrs by hand or use an external chamfer drill bit
(e.g., Uniburr or Uniburr plus) at crawl speed.
(2018-12-03) Painting and Coating
Protective layers prevent corrosion.
Minium (red lead) paint bonds very well to steel and effectively
prevents it from rusting. In a bygone era it was routinely used
to coat heavy machinery, by itself or as a primer for other paints.
(It's also used in the maritime industry to seal wood and prevent it from rotting.)
(2019-05-22) Electrical Discharge Machining (EDM)
Electric arcs can remove material from anything conductive.
In 1770, Joseph Priestley
(1734-1804)
first noticed the erosion caused by an electrical discharge.
In 1943, B. R. Lazarenko and N. I. Lazarenko
first put this effect to good use in a controlled fashion by
immersing the electrodes in a dielectric fluid.