Micro Alloying VS Normal Alloy

I do not know the specifics for tubing, but generally speaking in bar products and forgings, microalloy steels are able to develop higher mechanical properties (yield strengths greater than say 60,000 psi) or higher toughness as forged by just cooling in air or with a mist water spray; normal alloys require a full austenitize, quench and temper to develop properties greater than as rolled or cold worked.

So the advantage is higher mechanical properties (Yield strength or toughness) for lower cost because you don't have to fully heat treat and temper.

Metallurgical microstructure developed depends on the grade and type, but normal alloy steels require a transformation to martensite in order to achieve higher properties.

Microalloy steel precipitate out various nitirides or carbides and may have either a very fine ferrite pearlite microstructure or may transform to bainite.

Microalloy steel is manufactured likwe any other, but the chemical ingredients at the melt include microalloying elements like vanadium columbium (sorry Niobium for you IUPAC folks) titanium and higher amounts of Manganese and perhaps moly or nickel.

Vanadium, Columbium Niobium, and titanium are also grain refiners and agressive oxygen scavengers, so these steels tend to be very fine austenitic grain size.

Milo