STEEL Talk presents to you interesting stories of Science, Technology, Energy, Environment, Life — and of course STEEL!

*Admiral Yi Sun-sin: A navy admiral who led the Joseon Dynasty navy and is still a beloved historical figure by Koreans.
*The Joseon Dynasty: A Korean dynastic kingdom that lasted from 1392 to 1897.

Several invaders of Joseon recorded that the Joseon navy fired arrows, which were as huge as girders. The girder mentioned here is the ‘missile’ of Joseon. Isn’t it amazing that there was a missile even back then? Let’s look into this missile in detail.

The missile of Joseon has the name, Dae-jangun-jeon. ‘Dae-jangun’ in Korean means, ‘the Great Admiral’, and ‘jeon’ means, ‘arrow’, so its name alone shows how frightful this weapon was to the enemy. Admiral Yi Sun-sin — commander of Joseon Navy — reported to the king that he had smashed boats with this weapon after winning the Battle of Dangpo (1592) — the Joseon navy had sunk 21 ships then. Dae-jangun-jeon was the largest and most powerful weapon in Joseon.

▲ A scene from the film, depicting the Great Battle of Myeongnyang (Source: Naver Movie)

When we say cannonballs, we automatically think of round-shaped iron balls because of its name, but “Dae-jangun-jeon” is quite different. It isn’t round but instead stick-shaped, giving it the name — Joseon Dynasty’s missile. According to records of the time, the weight of one Dae-jangun-jeon was around 33.7kg, and its range was 1.14km. Then how could this heavy object fly a long-distance?

The ‘Cheonja Chongtong Gun’ was used to fire the Dae-jangun-jeon. And to get this huge missile to fly, iron was needed. One might think that huge amounts of gunpowder can make missile fly farther. However, gunpowder is just a trigger. Additionally, a missile made with just ‘strong’ iron would crack inside the cannon due to the explosive power of gunpowder. Let’s see the details in the image below.

The main body of Dae-jangun-jeon is made of wood, but it has iron on the head to attack the enemy, on the tail to withstand gunpowder, and also iron wings so that it can fly farther. So for the Dae-jangun-jeon to be strong enough to defeat the enemy and withstand the explosive power in the cannon, it needed iron. According to the records, the iron used to make weapons in the Joseon Dynasty was iron that contained fewer impurities (low-carbon steel).

Just as coke is put into the furnace to melt iron ore at the steel mill these days, iron was made with charcoal during the Joseon Dynasty too. There is a lot of carbon in charcoal, resulting in massive amounts of carbon — impurities — in the molten iron as well. Iron, which contains many impurities, is strong but quite fragile, so it is not suitable for cannonballs. It is also difficult to change its shape into the desired missile shape. By reducing the impurities in the molten iron, iron can be easily straightened and stretched than before.

The secret behind the Dae-jangun-jeon was iron that is hard and strong, yet easily shapable!

Thanks to an interesting question today, we could learn about both history and steel. Don’t forget that Admiral Yi Sun-sin was able to save the country thanks to “iron” and the skills of ancestors to create “iron”!

* This article was written with help from researcher Seung-Hyeon Jo of POSCO Technical Research Laboratories, and curator Kyung-Ju Chae of the POSCO museum.

On October 16^th, on the Yi Sun-sin Bridge of Gwangyang-si of Jeollanamdo Province, the Yi Sun-sin road to national salvation, ‘New Nanjung Camp’ started on a 4-day 3-night journey.

Just as Admiral Yi Sun-sin overcame hardships and adverse circumstances with an undying will, this camp was designed to grow a mind of loyalty, love for the people, and leadership for teenagers who will become leaders of the future in a time of current adverse economic situations and strongly changing society and culture.

Vice President Hwang Eunyeong and Gwangyang Steelworks High School Principal Kim Seongjeong congratulated and encouraged the 282 second year students who are participating in the camp.

The high school students are spending 4 days and 3 nights, starting at the home of Son Gyeongrye in Jinju, Gyeongnam Province, where Admiral Yi Sun-sin received his notice of reappointment as the controller of the naval forces of the three provinces (Chungcheong-do, Jeolla-do, Gyeongsang-do), visiting Gurye where the Joseon naval forces rallied, Gokseong, Suncheon, Boseong, and Jangheung, and on to Wusuyeong where the Myeongryang Naval Battle which played an important role in reclaiming command of the sea took place, visiting the sites where Admiral Yi Sun-sin walked down the path of saving the nation and learning of his mentality of indomitable challenge, venerable mind of sacrifice, and leadership to overcome hardships. Particularly, 37㎞ of the 620㎞including the Jirisan hiking trail, village roads, and oceanside roads is traversed on foot, providing the opportunity to ruminate on the mentality of Admiral Yi Sun-sin, who never lost hope amidst difficult times and rebuilt the naval forces of Joseon.

Vice President Hwang Eungyeon in his commemorative speech said, “The New Nanjung Camp is a long march program that was designed to help you grow a strong will that does not fall to pieces even in adverse situations or under distress, based on the mentality of Admiral Yi Sun-sin who controlled the naval forces of Joseon which had previously fallen apart.  I hope that you can all gain the wisdom and courage to grow a challenging spirit and overcome difficulties as you walk down the same path that Admiral Yi Sun-shin followed with the fate of the country on his shoulders, but grew a flower of hope despite the difficult reality.”

High school students who arrived at the auto-camping site in Gokseong after the first day of the trip said, “I understood Admiral Yi Sun-sin vaguely as a hero who won many naval battles, but this was an opportunity to experience the many difficulties Admiral Yi Sun-sin faced and had to overcome to save the country, displaying great will.”

The second day starts at the site of Neungpajeong to Suncheon Nammun Gate and ends in Nakan Hanggyo and Nakan-Eupseong, while the third day is a march from the site of Joyangchang where the national storehouse of the Joseon Era was located to Hoeryeongjinseong of Jangheung where the ‘resolution of Hoeryeongpo’ took place.  On the 4^th and final day, members will gather at the starting point on the Yi Sun-sin Bridge in Gwangyang for a ceremony of awards and disbanding, closing the long march.

POSCO multiplied the education effect by additionally preparing interesting missions and contest programs to ruminate on the noble mind of Admiral Yi Sun-sin at major footholds of the New Nanjung Camp.