So a bit about steel. As you may probably know, steel is deeply affected by which impurities are in the iron prior to the steelmaking process. Swedish iron had very low levels of impurities and thus produced higher quality steel even when identical processes were used to create the steel. As for the temperatures, a variant of coal known as Coke was capable of producing adequate heat for smelting in crucibles and is both naturally occurring and manufacturable as a petroleum product (called pet coke)[1]. Coke was used reportedly as early as 300 bc and could hit 1800 Celsius (3282 F) in proper conditions. India, Africa, Europe, many "nations" were crafting steel for hundreds if not thousands of years.

So the Vikings could get ore, and they could burn the right fuel to melt it, but why couldn't anyone else make their kind of steel?

We need to examine other cultures and how they made steel, mostly their ingredients, as the methods were often similar enough (Melt iron super hot in crucible, add carbon, cool down slowly). European steel often used coal as part of the carbonization ingredient. Compare that to the more Asian/Indian methods which called for pomegranate rinds, seeds, or bits of wood, but more importantly didn't require coal. Additionally, Damascus/Indian steel has trace elements of rare earth metals, which created the carbon nanotubes in the steel (the wavy lines)****. Such unique compositions made Damascus steel much more durable compared to European steel.

Now with that in mind, I think it's safe to say that the durability of the sword in question is probably owed to the metallic composition of the sword and not the methodology itself. There are very few if any references to different forging/smelting techniques, so if we eliminate the manufacturing process, we could surmise that it's the quality and composition of the steel that made it different from English steel, for example. In fact, once the industrial revolution started, England imported Swedish iron, having recognized the nation's ores to have superior properties. Clockmaker Benjamin Huntsman ordered Swedish iron in search of higher quality steels for his springs [3]. He quickly realized the superiority of their iron and set about making the smelting process more efficient. Once again, he used coke and crucibles to produce the high quality steel.

So in summary, from what I've found it looks like the methods were similar globally, but the carbonization element and the make up of the iron heavily influenced the steel's quality. Of course I'm not a weaponsmith so this is just a conclusion drawn from what I've read.

I hope this sheds some insight.

**EDIT: Comments have indicated the folding process in damascus steel also contributed to the nanotubes. As I'd focused more on the material makeup instead of the manufacturing process, I failed to mention this, so grain of salt :)

Source

[1]The Coming of the Ages of Steel. Brill Archive. p. 55. GGKEY:DN6SZTCNQ3G. Retrieved 17 January 2013.

[2]Craddock, P.T, 2003. Cast Iron, Fined Iron, Crucible Steel: Liquid Iron in the Ancient World. In: P.T., Craddock, and J., Lang. (eds) Mining and Metal Production through the ages. London: The British Museum Press,231–257.

[3] Samuel Smiles, Industrial Biography (1879) p99

/u/wee_little_puppetman does a phenomenal job pointing out why the NOVA program is terrible in this thread.

Additionally, the Ulfbehrt swords weren't Scandinavian (viking is a profession - it would be like referring to the English people solely as longbowmen, or the French solely as gendarmes) - they were likely Frankish in origin, as I explain in the Viking Age AMA

Are the Ulfberht swords even proven to exist, and did they play any significant role in history?