nouns of infix operators

Hello all,

When I enter "factor(6)" in maxima it returns "2*3" (with display2d set 
to false). I am trying to write a function that does the same thing, ie 
it returns a product as a noun. But when I define for example

          f(x,y) := '"*"(x,y)

then f(2,3) returns

          '?mtimes(2,3)

and not 2*3. How does factor do it?

Thanks