Titanium is a higher level material in astroneer. It can be used for important things, such as the crane. It may seem like it takes awhile to get, but once you know where to look, it's just a matter of finding it.
Where to Find Titanium
Titanite, which is the raw form of titanium, can be found on Glacio.
Pack Up and Go
You will want to bring a lot of tethers and other important resources for the journey. Once you are ready, you can launch off and head to Glacio.
Go Into The Caves
Once you are on Glacio, you can only find titanite in the deep caves on the planet.
Mining Titanite
Titanite green and crystallized. Once you find it, I recommend mining all that you can carry.
Once you get all that you need, you can head back to your base.
Smelting Into Titanium
The last step is to place the titanite on your smelter and smelt it into titanium.
Trade Platform
I also want to mention that you can trade scrap for titanite on your trade platform. It cost 2 scrap for 1 titanite.