Different mythologies and fictional universes have their own magical metals. For example, Marvel’s Asgardians have Uru and the elves of Middle-earth have Mithril. The great Chinese classic Journey to the West (Xiyouji, 西遊記, 1592 CE) hosts a long list of magical weapons, armor, and objects made from all kinds of metal (steel, iron, brass, gold, silver, etc.). A specific type is called Bin iron or Bin steel (bin tie, 鑌鐵) and it is mentioned several times in the narrative.
This is divine ice steel greatly refined,
Polished so highly that it glows and shines.
Laozi wielded the large hammer and tong;
Mars himself added charcoals piece by piece.
Five Kings of Five Quarters applied their schemes;
Twelve Gods of Time expended all their skills.
They made nine prongs like dangling teeth of jade,
And brass rings were cast with dropping gold leaves.
[…] (Wu & Yu, 2012, vol. 1, p. 382)
The “divine ice steel” (shen bing tie, 神冰鐵) is likely an error for “divine Bin steel” (shen bin tie, 神鑌鐵) as bing (冰) and bin (鑌) sound similar. This may also have something to do with the snowflake-like grain pattern of Bin steel (see sections one and two below). Take note that the metal is associated with Laozi and his furnace. We will see this association again.
Fig. 1 – A modern action figure of Zhu Bajie with his battle rake (larger version).
On the cusp of his battle with the Monkey King, the demon King Silverhorn (Yinjiao wang, 銀角王) is described as wearing polished armor made from the material.
He wears a phoenix helmet white than snow
And armor made of bright [Bin] steel. 
The belt on his waist is dragon’s tendon.
Plum-flower shaped gaiters top his goat-skin boots.
He seems the living Lord of Libation Stream;
He looks no different from Mighty Spirit.
He holds in his hands the sword of seven stars,
Stern and imposing in a towering rage (Wu & Yu, 2012, vol. 1, p. 127).
The monster is later revealed to be one of two young attendants of Laozi’s furnace sent by heaven to test the resolve of the pilgrims (Wu & Yu, 2012, vol. 2, p. 145).
The Monkey King recites a poem about his divine staff (fig. 2) prior to battling a lion demon.
The rod of [Bin] steel nine cyclic times refined
Was forged in the stove by Laozi himself.
King Yu took it, named it “Treasure Divine,”
To fix the Eight Rivers and Four Seas’ depth.
In it were spread out tracks of planets and stars,
Its two ends were clamped in pieces of gold.
Its dense patterns would frighten gods and ghosts;
On it dragon and phoenix scripts were drawn.
Its name was one Rod of Numinous Yang,
Stored deep in the sea, hardly seen by men.
Well-formed and transformed it wanted to fly,
Emitting bright strands of five-colored most.
[…] (Wu & Yu, 2012, vol. 3, p. 375)
Here again we see Laozi is associated with the material.
Fig. 2 – A modern action figure of Sun Wukong with his magic staff (larger version).
I. The metal of heroes
I want to reiterate the fact that Zhu Bajie and Sun Wukong, two of Tripitaka’s three main disciples and bodyguards, have weapons made from Bin steel (Sha Wujing’s staff is made from a heavenly tree). Each is the product of Laozi refining Bin steel in his magic furnace and smelting the polearms by hand. Just like dwarves imbued Thor’s uru-metal hammer with magical abilities, so too did the high god of Daoism for Zhu and Sun’s weapons. Each has supernatural durability and the power of transformation. In fact, the Monkey King’s staff is one of the strongest weapons in the entire novel, making its association with Bin steel very important. After all, a great hero requires a great weapon.
Another example of a hero wielding a Bin steel weapon is Wu Song (武松) from the classic Chinese novel the Water Margin (Shuihu zhuan, 水滸傳, c. 1400). The former constable-turned-outlaw comes into possession of a pair of Buddhist sabers (fig. 3) made from “snowflake [pattern] Bin steel” (xuehua bintie jiedao, 雪花鑌鐵戒刀) and housed in a sharkskin sheath.  They are described as being made from the “finest steel, and obviously hadn’t been made in a day” (Shi, Luo, & Shapiro, 2015, p. 317). In addition, the blades are said to “often groan in the night” (Shi, Luo, & Shapiro, 2015, p. 350), suggesting a magical, sentient longing for combat. Wu later sates this desire by using the sabers in a prolonged skirmish with an evil Daoist priest, eventually beheading the brigand with a single strike (Shi, Luo, & Shapiro, 2015, pp. 352-353).
Fig. 3 – A modern drawing of Wu Song with his Buddhist sabers (larger version).
II. Real world history
Wagner (2008) suggests the name Bin (鑌) is a transliteration of a foreign term, possibly the Sanskrit word Piṇḍa, meaning “steel” or “lump” (p. 270). The material is mentioned in Chinese records of the 6th and 7th-centuries as being imported from Persia (Bosi, 波斯) and Jaguda (Cao, 漕, modern day Ghazni) in Afghanistan. Mentions of the metal strangely disappear for centuries, only to reappear in early 10th-century records. This is possibly due to the disruption of Persian trade wrought by the Islamic conquest of Persia and the subsequent rise of Muslim trade with the east. Bin steel is believed to have originally been transported in a raw “lump” state prior to smelting in China. But the secret of its manufacture eventually reached the Middle Kingdom, for a 12th-century report shows the metal was produced in Inner Mongolia. The early Yuan government is known in 1275 to have established the “Office for Bin iron” (Bintie ju, 鑌鐵局), which possibly catered to elite blacksmiths (Wagner, 2008, pp. 268-272).
Fig. 4 – Persian-made Damascus steel blades of the 13th-century (larger version). Take note of the intricate grain pattern. Bin steel was known to have various patterns (see below).
The best description of the material comes from Cao Zhao’s (曹昭) The Essential Criteria of Antiquities (Ge gu yao lun, 格古要論, 1368), an early guide for connoisseurs.
Bin iron: It is produced by the Western Barbarians. Some [types] have a spiral self-patterning, while others have a sesame-seed or snowflake patterning. When a knife or sword is wiped clean and treated with ‘gold thread’ alum, [the pattern] appears. Its value is greater than silver.
An ancient saying holds that “knowing the strength of iron is like knowing gold” [i.e., the ability to judge the properties of steel is as valuable as the ability to assay the purity of gold]. Forgeries have a black patterning. One should examine [a steel object] very carefully.
There are three rules for knives. The first is that in the blade there should be perfect control of fire, metal, and water [i.e., the blade should be correctly quench-hardened and tempered]. The second is that the haft should be of xichi wood from the Western Barbarians, and the third is that the sheath should be of Tatar birchbark.
I once had a pair of scissors of bin iron, of exquisite workmanship. It had a raised gilt pattern on the inside, and on the outside a silver-inlaid inscription in Islamic characters (Wagner, 2008, p. 271).
So we see Bin steel is comparable to Damascus steel (fig. 4), as both require quench-hardening and produce a number of intricate grain patterns visible after an acid treatment. One such pattern is the snowflake pattern associated with Wu Song’s sabers (and possibly Zhu Bajie’s rake). Most importantly, the metal was considered an exceptionally fine steel. One general is described as boasting that rebels would “have to nick (chi, 齒) his sword of bin iron” if they wished to rise up (Wagner, 2008, p. 269).  I take this statement to be symbolic of his unbreakable resolve. At the same time, it shows Bin steel was considered exceptionally durable.
Highly durable Bin steel weapons could have seemed like magic in comparison to those made from lesser quality metal. Therefore, it’s interesting that Journey to the West presents the metal being smelted by a god in his magic furnace. It seems only natural that a magical forge would produce the finest steel. In fact, after the 10th-century, the very name Bin steel came to be used as a term for any type of exquisite steel (Wagner, 2008, p. 271). So the author-compiler of Journey to the West may have been using it in that sense instead of referring to imported Persian steel.
1) Anthony Yu’s original translation says “…bright Persian steel.” The historical origin is discussed in the second section of the article.
2) While the Water Margin presents them as sabers, Buddhist knives (jiedao, 戒刀, lit: “precept knife”) were historically small, unadorned, curved, finger-length blades used for cutting robes, trimming fingernails, opening wounds, or slicing food (Yifa, 2009, p. 250, n. 37).
3) Wagner (2008) states the story is listed as coming from the 9th-century but the housing source is from the 11th-century (p. 269, n. 103). Therefore, it likely originates after the reappearance of Bin steel in Chinese records during the early 10th-century.
Shi, N., Luo, G., & Shapiro, S. (2015). Outlaws of the marsh. California: CreateSpace Independent Publishing Platform.
Wagner, D. (2008). Science and civilisation in China: volume 5, chemistry and chemical technology, part 11, ferrous metallurgy. Cambridge: Cambridge Univ. Press.
Wu, C., & Yu, A. C. (2012). The journey to the west: vol. 1-4. Chicago, Ill: University of Chicago Press.
Yifa. (2009). The Origins of Buddhist monastic codes in China: An annotated translation and study of the Chanyuan Qinggui. Honolulu: University of Hawai’i press.