hello, I would build an iron staircase to a loft raggiongere, height 2 metr, size scale length scale of 230 cm width 50 cm, 22 cm steps away, how should I do to get a perfect artifact? I use the material?

I'm sorry, the question came out a bit confusing in the translation so you might want to try and rephrase it.

 

One thing you should consider--does this ladder need to be moved or will it be fixed in place?  Many loft ladders like this are made to be removed and stored so if that is the case, I would stick with much lighter materials than iron.

If I were to make the design as shown, I'd probably fabricate (welding) it from rectangular tubing, possibly using inverted channel for the treads.  If I was seeking more of a "blacksmithed" appearance, the design gets a lot more complicated and we'd need to know more about your goals and it's use before commenting.

I would use either stair stringer channel or flatbar like1/4"×6" for stringers.

Treads can be made from capped bar grating and should be bolted with four 3/8" bolts per tread. Stair is then assembled in place.

For this type of Stair angle iron rails look appropriate.

I agree with Kozzy I would use square tube and weld like 2-2 inch 1/8 inch wall square tube between the square tube upright. It's not very blacksmithish but it's steel and will last forever. The down side is it will be heavy and hard to move. If the ladder is moving then some cool looking wood. Hope this helped some.

Just make sure that the treads have some roughness to the surface, so that no-one slips. 

Step ladders seem easy but have their quirkiness. Furthermore they are subject to rules and regulations.

First question is fixed or foldable? (Fissa o pieghevole?)

Second question, is this going to building code or not? (D'accordo con il codice di costruzione o no?) 

THird ... do you know how to weld and what sort of welder do you have? (Sai saldare? Che tipo di saldatrice hai? 

Forth ... no handrail? (Senza corrimano?)

If you can answer this we can suggest a better construction method. (Facci sapere così vediamo che cosa conviene fare) 

 I suggest metal stringers and wooden steps. Hopefully no handrail. (Mi sembra meglio di fare i due montanti di metallo e scalini di legno)