I agree that is most likely to have been the procedure. On the other hand what we don't really know is if the porosity was a problem for them.
I suspect you are using modern ideas as a guide, knowing of other techniques etc. Back then in learning about melting copper, they must observe it melt. Learning annealing they again need to observe the effects, thereby also learning to heat to just below melting point and lend itself to the "hammer welding" you refer to below.
....and it would also eliminate porosity, would it not? So the small bit could well be melted and cast into a small ingot - to later "hammer weld" the porosity out of it.
I'm aware of the difficulty - as well as the evidence it provides of casting. As such evidence does exist, even if not widely, it indicates the ability to melt copper.
Try the old 3 cent piece - it was silver + copper alloy. Nor does it need to be "fit for casting" in the modern sense, as all I see it used for is to generate a larger lump of material to work with as a smith would.
A copper alloy is in general called "bronze" irrespective of the mix (eg arsenic + copper) except when it is called "brass" (nickle + copper?).
No, it has been done a lot of the time. In Sweden (damn I lost the info tag..) they have something they call "malm" (ore) that is a bronze, but a far redder colour than normal bronze. I can't tell you the mix of it as I lost the info. However there is a lot of arsenic + copper bronze around in Asia Minor. It was mined in the Ural mountains as a ready mixed ore.
It does if you heat it to the melting point of copper.
Tin is indeed the most common, but not the sole mix.
It is still called "bronze" as the "bronze age" term itself says.
Ahhh.... but irrespective of the fact that artisans may get their nose out of joint, melting/smelting metals IS called a "technology". So having that technology under ones belt in addition to the smithing, is indeed one up on the smithing alone :-)
Not suggesting modern people do cast copper - I am saying ancient people did.
While there is/was almost pure copper available at the time, much of it had impurities embedded within it. Large hunks of pure copper were relatively rare. The vast amounts that are indicated to have been mined must include copper with much impurities or copper embedded in other material. This had to be refined somehow, melting is the simplest way of refining it - unless you know of another technique available to the ancients.
Nobody is suggesting that smithing isn't an extremely skilled occupation..... but then so is flint knapping in my view. The casting was not used to manufacture anything much apparently. I see it as a refining process to later be hammered at near melting temperatures, thereby producing fine artefacts.
As I said mastering one technology, is less than mastering TWO technologies.... if you want to call smithing a "technology" in favour of Art :-)
I don't know what if any testing of composition of artefacts has been done. Some bronzes only contain 3 -> 5% tin elsewhere. If none are done then a claim that bronze doesn't exist can't be made. Testing the metals would also finger print them for origin, which hasn't been done either to my knowledge.