Yes and no. If you happen to have some Steel bars and some Black Ice, it's not exactly a terrible idea to smelt up a few bars of Hardened Steel, especially if you have a clanmate high enough level to make some of the basic Hardened Steel weapons, it can be very much helpful. However, building up a large stock of these bars before you need them isn't a great idea, in my opinion. There are many things to worry about in the early game, and Hardened Steel only joins that list in the mid to late game. That's not to mention the inevitable frustration if you manage to lose your backstock of Hardened Steel in a PvP raid or a purge. Instead, wait until you need to acquire them. You'll have better tools, armour, and weapons by that time, making it easier to fulfill that need quickly.