Qi Jian

What Hanwei means is that the guard and pommel are part of the same piece of steel as blade and tang. Not just tang and blade forged from the single piece of steel, but also the guard and pommel. (They made their Trondheim viking sword the same way.) The only extra thing, other than that one piece of steel, is the grip covering.

The good side is that the guard and pommel will never loosen. The bad side is that the grip can be heavier than it should be, and it's harder to make changes (like changing guard or pommel, changing the length of the grip).

One piece except for grip wrap is common (but not universal) on bronze jian. An advantage of casting vs forging.

Casting can be quicker (though keep in mind the time taken to make a master and a mold). It lets you make complex shapes that can be very hard to forge.

Forging doesn't need as high temperatures. To cast in steel, you need to be able to melt steel. To make steel stuff by forging, you never need to reach such high temperatures (not even to make the steel in the first place).

If forging bronze, you have problems with work-hardening - you need to keep stopping to anneal it. If you want things, like helmets (or many other things with thin sheet/plate) that are hard to cast, then you forge. But if it's castable, casting is easier.

The Chinese were casting iron (using cast iron as is, and steel and low-carbon iron produced by decarburising cast iron) during the Han dynasty. It is quicker and cheaper than forging, and was common for agricultural tools.

But we don't see cast steel swords (at least, not many) from China. Why? It isn't due to any lack of casting technology, since bronze casting technology was very well developed, and tools were made by casting iron/steel (and weapons, too, such as Ming cannon). I can think of three possible reasons:

1. The standard method for making Chinese swords was sanmei ("three plate"), where a middle layer of high carbon steel is sandwiched between two layers of iron. This gives differential hardening. This would be difficult to do by casting. (The Chinese did cast the equivalent in bronze, using high tin bronze for the edge, and a medium tin bronze for the body.)

2. Iron is harder to cast well than bronze. Since sword blades are wide and thin, this will be more of a problem with swords than with other objects.

3. Very high carbon steels (e.g., about 1.5% carbon, such as seen in many crucible steels and Chinese steels made by decarburising cast iron) need to be worked at red heat to break up cementite (a carbon-iron compound), so that it forms microscopic balls rather than big complexes (which would make the steel very brittle). This needs forging. So forging lets you use higher carbon content steels and avoid excessive brittleness.

In most of the world, for much of the time over which swords were made, furnaces didn't get hot enough to melt iron/steel (. So the casting versus forging was a non-issue. But it should be considered in the Chinese case.

The melting point for iron/steel/cast iron varies from about 1150C for cast iron, through to about 1550C for iron, with steels at about 1400-1500C, depending on carbon content. But you need to have it hotter than that to cast things, so about 1500-1700C is needed to cast steel. About 1000C-1200C is enough for bronze casting.

Hmm. No need to grind up microscopically fine if it gets heated to 2000C. However, if it's heated to 2000F, then it sounds like fairly standard procedure for powder steel (where the powder is sintered - heated to below melting point, and pressed together to fuse the powder into a solid), where high pressure is normal.

If the shape is laser cut, then it isn't a cast sword. That's just stock removal using a laser. The steel that goes into any stock removal sword has been cast (when the steel was made) and forged (when it was rolled into flat stock), but we don't call them cast or forged, because they're not cast to the shape of the final sword or forged to shape.

Any links to stuff on www about this smith?

Normal stock removal by grinding. But does sound like he starts with fancy modern steels. (He's not the only one - Hanwei does powder steel swords, as do others.)

But there's some serious nonsense there: "Each day the swordsmith needs to rub the sword with a cloth. This generates heat, and the molecular structure of the steel changes when it becomes hot after wiping. Two to three years of wiping every day and the structure of the steel becomes stable.
[...]
The only way to get rid of the pores is to rub the steel until it gets hot, forcing the slight amount of aluminum in it to melt. Since aluminum has a low melting point, it will come to the surface and melt, blocking the pores. It takes years to fully achieve this."

No, you won't melt aluminium by rubbing it with a cloth.