Cast Iron

Blast furnaces existed in Scandinavia in the eighth century AD, but cast iron was not widely available in Europe until the 14th century.

The Chinese practiced the technique already in the fourth century BC. Two factors helped greatly.
First, good clay allowed the Chinese to build walls for blast furnaces.
Second, the Chinese used 'black earth', which contained iron phosphate, to reduce the melting temperature of iron from 1130 C to 950 C.

In the third century BC the Chinese were able to hold iron at a high temperature for a week, which made it almost as good as steel, good enough to produce iron plowshares and in the year 1105 to build an iron pagoda 78 feet high.