Below, a case of steel used to rebuild a legendary power sword:
More selections referring to the power sword:Crucible of War
This is an excerpt from CRUCIBLE OF WAR, a collection of Warhammer 40,000 short stories
edited by Marc Gascoigne & Christian Dunn, published by The Black Library in 2003.
LEVIATHAN
An Ultramarines story Graham McNeill
THE FORGE ECHOED to the sound of iron on steel. Sweltering heat rippled the air and Uriel sweated as he worked the narrow, flat-headed hammer along a length of orange-red metal, rounding off the edges to prevent them from folding when it came time to draw out the blade of his new sword.
He worked the hammer up and down the blade, keeping the temperature of the steel as constant as possible. Working it too hot could cause it to burn, resulting in impurities within the metal rising to the surface of the blade and making the weapon brittle. Conversely, working the metal too cold would 'work-harden' the steel, resulting in fine cracks that would greatly weaken the blade.
Satisfied the metal was ready for drawing, Uriel placed it at the correct angle on the anvil and began hammering one edge. He flattened and straightened the resulting twist in the metal, turning the blade over and repeating the process. His muscles ached from the long day and hot steam burned in his lungs with every breath. The stars glittered through the open roof and a warm breeze sighed in from across the mountains, carrying the scent of evergreen highland pines.
He had not slept in six days, his time on Macragge as full as he could ever remember it being. The majority of this time had been spent reorganizing the Fourth Company after the Pavonis expedition and inducting its newest members from the reserve companies, but he had made sure to set aside time for this work in the Artificers' forge chambers. Uriel had until morning to finish the blade. The Fourth Company had been called to action once more, this time in the far-away system of Tarsis Ultra, and he was determined to finish the weapon before departing.
...
With the Nightbringer's icon secured, Uriel had then taken the broken blade of Captain Idaeus's sword and placed it in the Chapter's most sacred reliquary. He thought back to his former captain and though he still mourned his friend and mentor's passing, he had now grown into his role as captain of the Fourth Company.
Shaking himself from such weighty thoughts, Uriel lifted the glowing blade, checking that the sword was the correct length and that it was accurately balanced. He nodded to himself and selected a smaller hammer from a table beanng all manner of tongs, fullers, punches, hammers files and grindstones. He began the relatively simple, but time-consuming, task of hammering the edges of the blade. Moisture dropped from his brow, hissing on the heated metal of the blade, and Uriel thought it appropriate that a measure of his own sweat be part of its forging. He worked the hammer backwards along the length of me blade, periodically turning the metal to keep it straight.
The Artificers had metriculators for measuring the exact line of a blade, but Uriel preferred the honest feel of a blade worked by hand and eye. Finally, he lifted the sword from the anvil and held it before him, checking for any bends or twists in the metal. Finding none, he turned to the roaring forge coals and thrust the blade deep within. Uriel left the sword to heat and wiped his brow, walking back to the entrance of the forge and lifting a day jug of mountain water from a battered workbench. He raised the jug to his lips and drank deeply. The water was a day old and had warmed in the forge's heat, but was gloriously refreshing nonetheless. Uriel drained the jug in one long draught and set it back on the workbench. He stared up into the star-filled sky, shutting out the ring of hammers and ritual chants of the Artificers in other parts of the forge.
Working in the forge, with the heat of toil burning in his muscles and the scent of the wilds of Macragge in his nostrils, he was as close to content as he had been following his confrontation with the Nightbringer.
He shivered and tried to push all memory of the ancient star-god from his mind as he returned to the forge coals and lifted the sword from the fires.
The blade glowed a fierce red-orange and Uriel knew it was ready. He plunged it into a trough of water and oil, steam hissing angrily from the cooling metal. He pulled the sword from the water and smiled as he turned his gaze to a velvet wrapped object on his workbench. As the sword blade cooled, he unwrapped the bundle, revealing the golden sword hilt that had once held the blade of Captain Idaeus's power sword. As he began the tempering process, he nodded to himself as he felt his former captain's silent approval. The hilt had remained in the Chapter's reliquary until Marneus Calgar, lord of the Ultramarines, had presented it to him as a mark of respect for his success on Pavonis. Uriel no longer needed the sword of his former captain to symbolize his authority over the Fourth Company, but Calgar had understood that Uriel well deserved to carry such a precious relic of the Ultramarines.
By morning he would have the weapon finished, its blade polished and sharp. Then he would take it to the chapel of the venerable Chaplain Cassius and have it anointed with clear water he had collected from the pool at the base of Hera's Falls, at the end of the Valley of Laponis. The Chaplain would sanctify the blade and entreat the spirits of war and battle to impart a measure of their wrath within the weapon. Uriel could feel the sword's weight in his hand and it felt good, it felt natural.
I selected the sections only relevant to the sword and its (re)smithing.He gripped the hilt of his new power sword. The weapon was yet to be blooded and, despite his belief that the hulk they were to board was lifeless, he hoped that there might be enemies as yet undiscovered aboard that might satisfy his blade.
Uriel gripped the hilt of his power sword and offered a prayer to Roboute Guilliman that he would prove worthy of his Chapter. He had not failed in his duty before this and vowed that he would not do so now. For this present duty was entrusted to him by no less a person than the primarch himself. The defence of the Tarsis Ultra system was a sacred task to the Ultramarines, the result of an ancient oath sworn by Roboute Guilliman during the days of the Great Crusade. It had been a time of heroes, when the Emperor's own progeny, the primarchs, had stood shoulder to shoulder and carved His realm from the flesh of the galaxy, wresting His worlds back from the domination of vile aliens and heretics.
Tarsis III had been one such world, liberated from the lies of heretic secessionists by Roboute Guilliman at the head of the Ultramarines Legion. The battles fought to reclaim this world of the Emperor were the stuff of fireside legend on Macragge, taught at every one of the many training barracks throughout Ultramar, as was the courage and discipline shown by the inhabitants in rising to fight alongside the Ultramarines. It was said that a lowly trooper of Tarsis III had saved the life of Guilliman in the last battle and such was the primarch's gratitude that, at its end, he had dropped to one knee and sworn to a mighty oath of brotherhood with the soldier, declaring that should Tarsis III ever be threatened, the Ultramarines would return to fight by their side.
The victory was commemorated in a legendary work that adorned the walls of a giant room in the heart of the Imperial governor's palace. Named the Tarsis Fresco, it was said to be a gargantuan mosaic that covered the walls and ceiling of the palace's inner sanctum. Tales spoke of a work of unsurpassed majesty and Uriel greatly looked forward to seeing this spectacular mosaic.
Instead of the wastelands many of his brother primarchs left in the wake of their victories, Guilliman left those who could help rebuild the world in the image of his home-world. The grateful populace eagerly took up the challenges laid before them by the primarch and renamed their world Tarsis Ultra, that they might always remember their liberators. Once more entrusted with the honour of the Chapter, Uriel knew that his victory on Pavonis had earned him this sacred duty and, though the oath sworn by the primarch was almost ten thousand years past, it was no less binding. He would see that the ancient debt was fulfilled. This he swore by the spirit of the weapon he now held.
This is a good description of the kind steel that's used. Make that conventional, or not. If not, then it has little reason to be inferior to conventional steel, whatever conventional means in 40K: Uriel would never allow crap metal be used for the sword of Idaeus. All the quotes prove the importance of the mission, of the legacy, of the symbolism of the sword itself to the eyes of Uriel and its role in the coming battle. Finally, add that to the prestige of the Ultramarines, and it becomes clear that the steel used there will be considered perfectly good for the task.
Uriel is of course not your baseline human, but there's plenty of information about the steel, the smithing of the sword and the effects of heat on Uriel's body, to get an idea of its properties.
Here's a summary of the working on the blade and the observed thermal effects:
- A mere iron tool is plain sufficient to smith the steel blade, meaning that the excess of heat from the luminous blade doesn't reach a point where the tools themselves suffer. This may sound absurd to point out, but you never know, considering the degree of insanity observed in Wankhammer fans (talking of the rabbid ones there).
- The steel blade is first described as glowing "orange-red".
- Uriel sweats. He's also close to the furnace.
- Hitting the blade up and down its length helps spreading the temperature. Another obvious point and nothing new for those who understand how smithing works, but then it puts a strong limit on the thermal properties of the metal.
- The working is quite intensive as Uriel breathes steam that is quite uncomfortable, burning his lungs (although it's not necessarily literal, it could just mean that it was simply too hot to be bearable while working on the blade).
- Uriel's muscles ache, and he's been up for six days.
- Sweat that drips on the glowing metal hisses, which puts a limit on the steel's temperature : too hot, the water droplets would literally blast into vapour.
- Coals are used to heat the blade. Pulling the blade out of the forge coals after having plunged it into them some undetermined time before, the steel then glows "a fierce red-orange".
- While glowing "a fierce red-orange", Uriel quenches the steel blade by putting it into a trough of water and oil, and "steam hisses angrily from the cooling metal." No boiling, no explosion of vapour.
- All the leveling and sharpening of the blade is done manually, by gauging straightness through Uriel's naked eye; which might be enhanced but the description seems to imply that Uriel preferred using his own sight rather than the Artificers' metriculators. That said, it's possible the Artificers have augmented sight.
- The power sword's advanced mechanism is located in the hilt, most obviously.
Forge coal (soft bituminous coal) has a heat content inferior to 35,380 kJ/kg, and as a whole, in terms of heating value, coal has an energy density of 24 MJ/kg. It has an average density of 1346 kg/m³ (Marks' Standard Handbook for Mechanical Engineers 11e).
Soft bituminous coal has a medium ignition temperature of between 750°F and 850ºF. Then, working steel should not require pushing steel temperature beyond 1600°F, tops.
The observed colours of the steel in question would suggest a temperature around 850°C to 875°C. Same here with a likely temp at 870°c. This source may allow for temperatures closer to 900°C or higher.
One can also take a look at chapter 4 of the following document.