I highly recommend using JEI for recipes in the crafting table.

Excavate-Ores description :

This mod is based on having in between steps with the already in game gear (iron, diamond, netherite).

THIS MOD ADDS :

New elements
New crafting station
New armors
New tools
New weapons

Steel is an in between element of iron and diamond. It has some property of iron, like the harvest level, and some of diamond, like it's efficiency.

To make steel you need to smelt iron ingot with coal/charcoal in the foundry.

Mythril is the element that is better than diamond but less powerful than netherite.

It can be found in the nether wherever you go ! (It only generates in netherrack and by Y=128>32)

To make mythril ingots, you need to smelt 2 raw mythril with an ingot mold in the foundry.

Titanium is the element to go, it is 1.5x more powerful than the mythril and more powerful than the netherite too.
It is indeed the most powerful ore you can have with this mod. It is almost as rare as the ancient debris, found in the nether and in the same height level as the ancient debris (Y=32>0).

To make titanium ingots, you need to smelt 2 raw titanium with 1 gold ingot in the foundry.

Titanium is the netherite of the mythril, so you just need to upgrade your mythril gear to titanium, with the smithing table, like you do to diamond with netherite !

HAVE FUN ! :D

(PS : Sorry for my bad english i'm french)