Plasma derating for clad steels

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Hi there,Can anyone tell me the exact reason you need to derate a plasma by 1/2 when cutting clad steels?Thanks
Reply:I'm not sure where you got that information! Clad steels are cut all the time...and while (depending on the materials) you may have to change speeds and settings somewhat....there should be no reason so have less thickness capability. What particular types of materials are you referring to...and what type of plasma are you planning on using?Jim Colt
Reply:what is meant by "clad "? galv or other coating?
Reply:I agree with Jim on this. Our shop cuts thru all kind of Clad? cover steel and we have never had a problem. True cutting thru Glav covered metals tend to make the arc bend or spread out sometimes making it harder to make your intial pierce! But once the cutting starts it shouldn't limit your torch capacity.Co-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.&  2 Hypertherm HPR260's Plasma CutterSorry I had a bad stroke but now I am back.
Reply:There are a lot of different types of "clad" metals.......I guess the term means a layer of one type of material bonded to the base material. Often steel will be bonded to a material such as hardox that will have a wear resistant surface. In the shipbuilding (military) business I have seen 1/2" aluminum that was bonded (explosion bonded) to 1" carbon steel......As Spector says.....once you get through the cladding....the cutting process works almost normally!Jim
Reply:In the ITP welding notes we have here in Alberta it stated that when cutting clad steels up to 30% of the composite you have to derate your plasma machine by 1/2.  They were referring to vessel clads generally 1/2" composite or thicker.No one I have talked to can give me a reason as to why they say this.  I don't see why it would matter to a plasma and that is why I asked.
Reply:A lot of the old plasma technology is reflected in technical manuals and "best practice" manuals today. Plasma has come a long way in the last 20 years.As an example....may states DOT (transportation department) rules forbid the use of plasma on metals used in bridge construction...due to weldability issues with the raw cut edge. When these technical articles were writeen in the 60's, 70's and 80's....all plasma torches used nitrogen as the plasma gas and c02 as the shield gas.....this caused an approx .005" hardened, nitrided cut face...and in some cases some embrittlement and micro-cracking. It was suggested back then to use oxy-fuel to cut bridge steels! Todays oxygen plasma's can cut these materials at 6 times the speed of oxy-fuel...and with no nitriding...and 100% weldability....and this is backed up by a great study by the Edison Welding Institute "The Weldability of Bridge Steels" which compared nitrogen plasma, oxygen plasma and oxy-fuel cut processes on a variety of steels...and the resulting weldability....oxygen plasma was clearly the winner.....with oxy fuel second and nitrogen plasma third!I would like to get a copy of the ITP welding notes you mention for review....can you contact me at [email protected]  ?Best regards, Jim