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Bob the time traveler has a problem. He went to 75,000,000 BC to get some dinosaur eggs (don't ask) and his time machine re-combobulator broke and a big chunk is missing.

Fortunately he can still make one jump forward in time, but he can't go as far as the XXIV century (his home era). Mostly he could land somewhere before the XX century.

He needs grade 5 titanium alloy to repair the re-combobulator. He just needs to smelt the alloy and his time machine nanites will do the rest.

The further forward he jumps, the biggest the risk of vanishing in the timestream, so he wants to jump the least possible

Consulting his encyclopedia of technology, he tried to figure out when is the earliest in history he can jump to where Titanium alloy grade 5 could be made with the technology available.

He can set his arrival anywhere on Earth. He also has no diplomatic or monetary problems. He can mine the resources or has the raw ores in storage.

P.S.: The story is just to illustrate the case in point. The question's title is all that matters. That is why there is no in this question.

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    $\begingroup$ What does "the technology available" mean? Available to whom? Titanium was not available in metallic form before the 20th century (because titanium oxide cannot be reduced with the smelting processes known before that), and was completely unknown before the very end of the 18th. People who don't know how to make titanium cannot make titanium alloys. So if by "technology available" you mean the technology available without input from the time traveller, then the answer is 1910. If you mean clarketech available to the time traveller... $\endgroup$ – AlexP Sep 17 at 18:08
  • $\begingroup$ Let's confirm, he needs just a chunk of Titanium alloy, not a fully manufactured part? $\endgroup$ – Alexander Sep 17 at 18:44
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    $\begingroup$ It seems... curious that he can go back 99.9995% of the way, but not the last 0.0005% $\endgroup$ – Mark Sep 18 at 5:58
  • $\begingroup$ Maybe it's not a single jump. I picture him cruising along at a few hundred years per second, when he flipped the switch in 1000AD to begin normalizing his time dilation, but something snapped causing him to fall out of time travel very ungracefully a few centuries off course damaging his recombobulator. Now he's got his time machine duct taped back together and is about to do something very brave / stupid / scientifically interesting on a scale where every year matters. $\endgroup$ – Nosajimiki Sep 18 at 15:48
  • $\begingroup$ How good is his first aid kit? Can he maximise his chances by dropping out of the timestream early and doing the last 50 years the slow way? $\endgroup$ – Mike Scott Sep 18 at 18:22
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Depends on how good of a chemist your time traveler is. While the purification methods on many of the needed materials were not discovered until the 1900s a good chemist, craftsman, and historian could go back further to the discovery of the ores he needs.

To make the alloy you will need Iron, Titanium, Vanadium, and Aluminum:

Iron has been around for ~5000 years; so, this is the easy one.

Titanium ore was first discovered in 1791 and could be purified via the Hunter process using chemicals that would be available by 1808 when Sir Humphry Davy learned to isolate pure calcium.

Vanadinite, discovered in 1801 could also be purified by 1808 due to Sir Humphry Davy's discovery.

Bauxite was discovered in 1821. All of the materials you would need for the Bayer process required to turn it into alumina already existed. The Hall-Héroult process required to turn alumina into aluminum requires strong electrical currents, but if you have a time machine, I suspect you've also got one hell of a power source your could tap into to pull electricity from.

[EDIT]

He can set his arrival anywhere on Earth. He also has no diplomatic or monetary problems. He can mine the resources or has the raw ores in storage.

Not sure if I just missed this before or if the question was revised. If the ore is not a problem, then all you are left needing are a good smelting facility and hydrochloric acid

Hydrocloric Acid has been manufactured since about 800AD. It is made from Iron (II) sulfate (which was first used as an ink pigment sometime around 600BCE) and rock salt (which has been used since about 6000BCE). When you consider that these are both commonly minable substances, that means you could just add this to your grocery list of ores. There is also a good chance your timeship will have some extra batteries you could extract it from to save you some time if you are not needing a lot of titanium.

This really just leaves the smelting furnace as your only big obstacle. Simple furnaces that you could probably make by hand and fuel with easily obtainable natural resources can only reach ~1300C, but you would not be able to get your iron pure enough with one. Finery forges are capable of fully melting iron allowing full separation of iron and slag, and could reach the temperatures required to process all of the materials needed to make your small amounts of your titanium alloy. These were first made sometime between 400-200BCE in ancient China. All ancient depictions I've seen of finery forges are pretty large; so, this may be the one thing you really need an existing civilization to be able to acquire.

Incidentally, China is also rich in all of the ores that you need; so, you don't need to go very far for any of your materials.

So, you could in theory go to China (~200BCE), find someone with a finery forge, and offer to exchange some modern metallurgy know how in exchange for use of their equipment.

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There's some ambiguity in the question - the title says "has the feedstock" but doesn't indicate whether that's ore, refined metals, or "can get to places where the ore can be found". Assuming it's the first option, ore:

Probably Around 1900

AlexP's comment is valid, but if your time traveller has Future Wikipedia downloaded into his phone-analogue, all of the necessary precursor chemicals and tools should be available at the turn of the last century - their application would just not have been discovered, so you'd have to Scotty it up a bit.

The biggest hurdle would be vanadium. You'd need the pure metal to get proper grade 5 titanium, and the process for its purification wasn't developed until 1927. The chemicals and lab equipment involved did exist, though, so making a small quantity of the material, given all the necessary discoveries being known ahead of time, should be possible. Aluminum would be available (though expensive), and furnaces would be hot enough to make the alloy.

Edit, Addendum:

I don't know how much a few extra decades matters in a multi-million-year jump, but 1950 would be a much better bet which would make his job near-trivial. I suppose you can make the risk of being lost in the timestream asymptotic as he approaches, say, 2200, if you want to limit him, but assuming that's not the case, there'd be a lot less "explaining metallurgists' jobs to them" by just aiming a half-century further upstream.

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    $\begingroup$ Roscoe was able to isolate vanadium in 1867, and it first saw major industrial usage in 1905 in Ford Automotive steel. I believe 1927 was when the modern method for purifying it was invented; so, depending on the exact tolerance he needs on that titanium will determine if he can do 1905 or have to wait until 1927. $\endgroup$ – Nosajimiki Sep 17 at 18:54
  • $\begingroup$ If he wants Grade 5, it has to be the pure metal. The process is doable using 1900 tech, though, if you already know how to do it. $\endgroup$ – jdunlop Sep 17 at 18:56

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