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History of Casting
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24 pound cannon for Nirayama Reverberatory Furnace

History of Casting

"Casting" the Forming Technology that Fascinates the World -5600 years of casting history-
Human being has first encountered with metals back in 5,000-6,000 B.C. when people were processing natural gold/silver/copper by hand beating. Thus, the very first processing method of metals was forging. The prideful Japanese sword could be said as the most advanced forging technology in the world.
The start of casting technology which forms casting by pouring melted metal into a mold and solidifying it, origins back to around 3,600 B.C. at Mesopotamia. It was approximately 5600 years before from today. Back then, bronze was melted and poured into a mold.
On a papyrus from about 1500 B.C. of Egypt, we can see a drawing of people using their legs on bellows to send air. By inventing “bellows”, human being has achieved to obtain higher heating technology. This was how the Bronze Age arrived. By the way, the melting point of bronze is approximately 800℃ with Cu-25%Sn. Considering casting, it could be assumed that the melting temperature could have been exceeded 1000 deg C.
It is a mystery of bronze ware of how people came up with an idea of adding tins. It is considered that tins were transported from East Iran (Caucasus district or Turkmen). Whoever it was, it was surely a great discovery.
It is thought that people's first encountering with iron was realized by meteorite. Meteorite can be forged since it contains lots of nickel. A pattern called Widmannstatten structure which was formed by solidifying at extraordinarily slow speed (few degrees in a million years) could be observed on meteorite. In Egypt, an iron necklace made from meteorite of around 3000 B.C. was found.
Since iron is oxidized on earth, it would not function as iron if not been deoxidized. It is believed that in 1700 B.C., the Hittite empire has first obtained iron by deoxidizing iron ore. It is assumed that they were producing iron products by using a batch method furnace which deoxidizes iron sand by charcoal and extracting iron, which is close to spongy pure iron that could be collected at the bottom of furnace, to heat forge it. It is indicated in one of the epic poetries of Homeros of around 800 B.C. that iron was very much valuable. Probably, its value was way higher than gold.
Additionally, since it is also noted about a blacksmith, it could also be imagined that the hardening technology was already established by the era when Homeros lived. An odd fact is that in Europe, iron production by forging continued till 14th century while casting to pour in melted metal in a mould did not come into practice until after 14th century. The fact that weapons used in then Europe were knives and sables was maybe due to this difference in history of iron.
The casting technology, which produces product by pouring melted metal into a mould, was first developed in China, approximately 7th century B.C. It is generally thought that the Chinese bronze ware technology achieved an extremely high temperature by utilizing bellows and from this line of technology, it is assumed that pig iron was developed by melting iron with high carbon content.
An iron with high carbon content has low melting temperature of about 1150 deg C as well as good flow property and these have enabled the casting of iron. The components of cast iron of around 4th century B.C. in China were about: C2.5-4.3%、Si0.1-0.2%、Mn0.01-0.2%、P0.1-0.5% 、S0.01-0.1%. Due to the low Si, this sort of structure is called as chill which does not have graphite and has hard and brittle characteristics. This brittle characteristic probably led to a factor for iron casting technology not being introduced to Europe until 14th century. It was not until 1779, when the Iron Bridge was constructed in England, that cast iron with non-chill structure and high Si content was found.
From 7th century B.C. to 18th century at the time of Industrial Revolution, cast iron was made hard and brittle. Thus, no wonder iron with stickiness which could be hardened by hardening used for forging products was more valued. However, by increasing Si content, the property of cast iron has shifted largely. This non-chill cast iron came to become an important material to support the industry. All sorts of casting products as bridge and cannon begun to appear on manufacturing line.
Casting of bronze door (BC1500)
Casting of bronze door (BC1500)
Widmannstatten which could be seen on section of meteorite
Widmannstatten which could be seen on section of meteorite
6th century B.C. Iron manufacture furnace drawn on Greek vase
6th century B.C. Iron manufacture furnace drawn on Greek vase
Chill structure of cast iron
Chill structure of cast iron
A bridge made of cast iron (Iron Bridge) England
A bridge made of cast iron
(Iron Bridge) /England
High strength flake graphite
High strength flake graphite
Spheroidal Graphite Cast Iron
Spheroidal Graphite Cast Iron
For modern cast iron, there are two significant developments.One of it is the manufacturing method of spheroidal graphite cast iron based on inoculation technology which was developed by G. F. Meehan and O. Smalley in 1940s. By this technology, it became possible to produce high strength cast iron with tensile strength more than 300N/mm2 stably.The second is spheroidal graphite cast iron which was discovered by Morrogh in England back in 1947. By this discovery, the manufacturing of cast iron with even higher strength of more than 800N/mm2 realized.
By 1945 when Japan was about to experience the end of war, its cast iron technology was already greatly advanced. Japan took in the technology of postwar foreign countries, improved it and established the highest level of casting technology in the world. Furthermore, from here on, the Japanese casting technology grew in tandem with the rapid progress of automobile industry.

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