All these info is a compilation of several of my posts on swordforum... Hope you all like it...
The b&w pics are extracted from Donald B. Wagner's " Iron and Steel in Ancient China", published by E.J. Brill, 2nd Impression (edition), 1996.
In this book on pages 284 and 469, with illustrations from Fig 6.26 to Fig 6.31, Mr Wagner mentions what appears to be a sanmai double-edged sword dated AD 77 with:
1) a cutting edge central plate with 0.7%-0.8% carbon steel (grey zone)
2) sandwiching plates of steel with steel layer zones consisting of 0.4% and 0.6%-0.7% carbon.... (pink and white zones respectively)
The b&w pic showing layers are actually cross-sectional pics of the layers of 0.4% and 0.6%-0.7% carbon steels.
This weapon was unearthed in Tongshan county in Jiangsu province. The book does not describe the specific technical process the researchers used to derive the carbon contents, but they have used the scanning electron microscope to take some micro-magnified photos and a SEM S600 energy spectrum analyser (what's that??) to find out what kind of metals were present in the silicates / impurities.
Mr Wagner's primary sources of info with regards to this weapon were from scientific archaeological/metallurgical publications in China.
In my readings of several books (including Wagner's), I have come to understand that in the beginning, swords were forged and folded (resulting in the creation of multiple layers of steel) during the late Spring and Autumn/early Warring States periods, and then by the early part of the Han Dynasty, were forge-folded and differentially heat-treated by 2nd Century BC, to progressively result in the "hundred refinings" process by the 1st century AD, during the later part of the Han Dynasty, where by then, steel swords were typically of forged and folded stock, with forge-welded laminated construction (sanmai, inserted edge etc), and differentially heat-treated. These key processes were to endure for the next 2 millenia......
As for clay-defined differential heat-treatment, it was developed sometime between 200BC to 500 AD; the ridged-cross-section was most likely developed between 100 to 300 AD, latest 500 AD...
___________________________
The Chinese characters of gold inlay for "50 refinings" on the above jian does not mean it was folded 50 times nor does it mean that the weapon has 50 layers. It was some form of quantitative standard which I am still trying to establish.
In the period just before the Song Dynasty, there were historical records stating that there were several swords made for the respectively kings/emperors which had "10 refinings", and not 30 or 50 or 100 refinings, like the time of the Han Dynasty. Could it be that the Chinese use of this "refinings" terminology has changed over time??
One contemporary method:
Chen Tianyang, the Taiwanese swordsmith ( http://sword.tacomall.com.tw ), says in his book that the refinings process (he says that this knowledge was transmitted to him by his Buddhist monk teacher, i.e. he didn't make it up) was:
See diagram attached, a copy from Chen Tianyang's book:
1st refining:
Prepare 9 bars of cast iron or steel of high-carbon content weighing 30 kg each. Forge-fold all these bars continuously til every bar weighs 10 kg each.
2nd refining:
Take 3 of the refined bars, combine and forge-fold continuously until a single bar results, weighing 10 kg; repeat the process for the remaining 6 bars, you will then have 3 resultant bars at 10kg each.
3rd refining:
Take these 3 resultant bars, combine and go through repeated forging and folding until a single bar results, weighing 10 kg.
4th refining:
Prepare 2 other 10kg bars which had already undergone the 3rd refining; combine the 3 together and forge-fold til you have a 10kg bar that is considered having undergone 4 refinings and so on.
So imagine if this refinings process holds true, how much raw steel is required and the amount of forge-folding work needed to make a sword with steel of 10 refinings. Chen says his teacher had orally elaborated on the process up to 15 refinings...
____________________________________
Description in the Song Dynasty:
Shen Kua, the famous Song Dynasty scientist who observed and wrote down the process of steel-making during that time, has a different opinion (if my translation and interpretation of the classical Chinese text is correct)
"In my work-related travels (he was the Dynasty's Armaments minister), I had actually been to the ironworks at the Ci province. Having seen them make steel, I had understood and known what real steel is.......... To make steel and obtain the purest metal, one must heat the iron a hundred times (I think he meant it figuratively and not literally), hammering repeatedly during the process. A single cycle of heating once, followed by repeated hammering is called one refining and so on. The metal would become lighter in weight each time after a refining. This process is repeated until it finally reaches the stage where the metal would not get any lighter. The end result is pure steel....
This purest form of steel has a colour clear and bright. After polishing, it would then manifest a deep greenish-black colour, totally different from ordinary iron. It is possible to forge until there is absolutely no steel left (in the iron )..........."
Though what Shen Kua describes was steel-making at an ironworks and not swordmaking, I believe the process to make "refined" steel was essentially similar at the time to both industries.
On a side note, 2 National Living Treasure swordsmiths of Japan were once asked for their opinions (in the early 70s) of the Tang Dynasty era swords in the Japanese Imperial collection at the Shosoin Depository, several of whom were of Chinese manufacture. Both of them had expressed the opinion based on the characteristics of the surface grain that the swords were folded about 10 times.
_____________________________
Phillip Tom, the famous Chinese-American scholar of Chinese swords says "The French missionary Joseph-Marie Amiot, SJ, who worked in China during the late Qianlong reign, wrote in the military section of his MEMOIRES CONCERNANT...LES CHINOIS... (1782) that the manufacture of a regulation-pattern saber blade required 4 lb of iron and 9 oz of steel (p 36). I assume from the text that the author is reckoning in Chinese measure, in which a Chinese pound or jin equals about 1.3 English pounds, and is subdivided into 16 oz. or liang) One can see how much of the raw material was consumed (mostly in the forge, some on the grindstone) when you consider that the average finished blade weighed about 1 jin."
In my personal opinion, I believe that the process Joseph-Marie Amiot was describing about, with regards to the manufacture of Qing Imperial regulation-pattern sabers, was essentially similar or not much different from the "refinings" processes mentioned above........
Qing era handpainted colour albums of the extraction of iron ore and the manufacture of cast iron (webapge by Donald Wagner:
http://www.staff.hum.ku.dk/dbwagner/Fate/F...1-28.html#Fig21
Some of these cast iron blocks would be used by steel-making workshops to be forged and folded on the anvil, and repeatedly heated in the furnace, to become decarburized high-carbon and mid-carbon steel, suitable for use as the cutting edges of Chinese sabers...
