History of metallurgy in China

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Metallurgy in China has a long history. China was the earliest civilization that produced cast iron.^[1]

Archaeologists and historians debate whether bloomery-based ironworking ever spread to China from the Middle East. Around 500 BC, however, metalworkers in the southern state of Wu developed an iron smelting technology that would not be practiced in Europe until late medieval times. In Wu, iron smelters achieved a temperature of 1130°C, hot enough to be considered a blast furnace. At this temperature, iron combines with 4.3% carbon and melts. As a liquid, iron can be cast into molds, a method far less laborious than individually forging each piece of iron from a bloom.

If iron ores are heated with carbon to 1420–1470 K, a molten liquid is formed, an alloy of about 96.5% iron and 3.5% carbon. This product is strong, can be cast into intricate shapes, but is too brittle to be worked, unless the product is decarburized to remove most of the carbon. The vast majority of Chinese iron manufacture, from the Zhou dynasty onward, was of cast iron. Iron, however, remained a pedestrian product, used by farmers for hundreds of years, and did not really affect the nobility of China until the Qin dynasty (ca 221 BCE).

Cast iron is rather brittle and unsuitable for striking implements. It can, however, be decarburized to steel or wrought iron by heating it in air for several days. In China, these ironworking methods spread northward, and by 300 BC, iron was the material of choice throughout China for most tools and weapons. A mass grave in Hebei province, dated to the early third century BC, contains several soldiers buried with their weapons and other equipment. The artifacts recovered from this grave are variously made of wrought iron, cast iron, malleabilized cast iron, and quench-hardened steel, with only a few, probably ornamental, bronze weapons.

During the Han Dynasty (202 BC–AD 220), Chinese ironworking achieved a scale and sophistication not reached in the West until the eighteenth century. In the first century, the Han government established ironworking as a state monopoly and built a series of large blast furnaces in Henan province, each capable of producing several tons of iron per day. By this time, Chinese metallurgists had discovered how to puddle molten pig iron, stirring it in the open air until it lost its carbon and became wrought iron. (In Chinese, the process was called chao, literally, stir frying.) Metal casting was spread westwards to the Dayuan by Han deserters (Shiji, 123).

Also during this time, Chinese metallurgists had found that wrought iron and cast iron could be melted together to yield an alloy of intermediate carbon content, that is, steel. According to legend, the sword of Liu Bang, the first Han emperor, was made in this fashion. Some texts of the era mention "harmonizing the hard and the soft" in the context of ironworking; the phrase may refer to this process.

Cast-iron artifacts are found in China that date as early as the Zhou dynasty of the 6th century BC. An Iron Age culture of the Tibetan Plateau has tentatively been associated with the Zhang Zhung culture described in early Tibetan writings. In 1972, near the city of Gaocheng (藁城) in Shijiazhuang (now Hebei province), an iron-bladed bronze tomahawk (铁刃青铜钺) dating back to the 14th century BC was excavated. After a scientific examination, the iron was shown to be made from aerosiderite.

In the Korean Peninsula, iron objects were introduced through trade just before the Western Han Dynasty began (c. 300 B.C.). Iron ingots became an important mortuary item in Proto-historic Korea. Iron production quickly followed in the 2nd century B.C., and iron implements came to be used by many farmers by the 1st century A.D. in Southern Korea.

[edit] Bronze

Although bronze artifacts were exhumed in historic site of Majiayao culture (3100 BC to 2700 BC), it is commonly accepted that China's bronze age began from around 2100 BC during the Xia dynasty.

In Ban Chiang, Thailand, (Southeast Asia) bronze artifacts have been discovered dating to 2100 BC [4].

The Erlitou culture, Shang Dynasty and Sanxingdui culture of early China used bronze vessels for rituals as well as farming implements and weapons [5].

[edit] Copper

Use of copper in ancient China dates to at least 2000 BC. By 1200 BC excellent bronzes were being made in China. Note that these dates are affected by wars and conquest, as copper is easily melted down and reused.

[edit] Notes

1. ^ In 200 BCE. Srinivasan, Sharda and Srinivasa Rangnathan. 2004. India’s Legendry Wootz Steel. Bangalore: Tata Steel.[1] [2] [3]