To get a general estimate of power, start with energy conservation: Calculate the energy needed to melt/evaporate 1 mm³ of the material you want to cut. Then calculate the volumn you cut in a second: cutting kerfs area *  cutting speed. This gives you the abvsolute minimum of energy you need. Include losses by reflection and you know the power the laser has to deliver. to be on the save side, doble this value to account for losses by thermal conductivity and you have a good estimate for the power you need. these calculations for many materials are listed in the book Solid-State Lasers for Materials Processing by Reinhard Iffländer , Springer, Berlin ISBN-10: 3540669809

@Yiğit Ozan Aydın: Thank you for the quick answer! I found the links very informative.

@Gerhard Heise: Thank you very much! Your answer reminded me of this saying:

"Give a man a fish, and you feed him for a day. Teach a man to fish, and you feed him for a lifetime."

Your answers helped me learn more, yet I'm still hunting for some experimental results for cutting 30 millimeter thick steel (or thicker) using different lasers especially the CO2 laser. 

La Rete , il PC , i vari files e Papers on -line sono una cosa bella e una conquista ma, molti - non tutti - hanno perso il bello ed il gusto dello STUDIO del PROBLEMA che è posto a noi in quel momento . Ormai si spera di trovare sempre QUALCUNO che, prima di NOI, ha studiato lo stesso Problema, lo ha sperimentato, lo ha pubblicato e ha messo in rete anche delle TABELLE complete, ricche di dati ed esaustive . NON E' QUESTO IL MODO DI FARE RICERCA !!!!!!! Prendere uno spunto, vedere ciò che già si è fatto E' UMANO ed ACCETTABILE ed UTILE ............... il PIATTO SEMPRE PRONTO, SERVITO A TAVOLA e A DOMICILIO, non mi troverà MAI DACCORDO .

Sorry Collega, io la penso così, dopo aver dato 45 anni della mia Vita alla Ricerca e per la Ricerca . STUDIARE, STUDIARE et STUDIARE !!!!!!!!!!!

Infine, ti dico, per mia esperienza che, tagliare a Laser ( CO2 o altro) 30mm di acciaio, NON E' CONVENIENTE, date le grandi Potenze laser da impiegare ed il Costo di investimento, per l'acquisto del Laser, da sostenere .

Buona Fortuna !!!!!!!!!

*****************

The Web, the PC, the various files and papers on -line is a beautiful thing and a conquest, but many - not all - have lost the beauty and taste of the STUDIO PROBLEM that is placed to us at that time. Now we hope to find more and SOMEONE that before us, studied the same problem, has experienced, has published and placed online also complete TABLES, data-rich and comprehensive.  'THIS IS NOT THE WAY TO DO SEARCH !!!!!!! Take a cue, see what has already been done and 'HUMAN and ACCEPTABLE and PROFIT ............... PLATE ALWAYS READY, SERVED ON THE TABLE AT HOME, and  this will not find me NEVER agree .

Colleague sorry, I think so, having given 45 years of my life to Research and for the Research. STUDY, STUDY et STUDY !!!!!!!!!!!

Finally, I tell you, in my experience it, cut Laser (CO2 or other) 30mm steel, NOT 'AFFORDABLE, given the large laser powers to be used and the investment cost for the purchase of the laser, to sustain.

Good luck !!!!!!!!!

@G. Daurelio: Thanks for your concerned answer.

Hello Mr Pedram,

I got some journals that maybe could help you to understand the interaction between laser power requirement and material thickness.

1. Parameterization of hybrid laser-assisted oxygen cutting of thick steel plates

2. Laser cutting of thick sheet metals: Effects of cutting parameters on kerf size variations

3. Laser power requirement for cutting thick-section steel and effects of processing parameters on mild steel cut

quality

Hope this can would help you

Thank.