Are you looking for China door factory?

Give me suggestion on dissassemble a steel door frame?

It seems dont get the visible screws on the steel door frame, but there are clips at the top right and left of the door frame.

Answer:

To dissassemble this steel door frame.

Near the floor, using a narrow blade
screwdriver, pry the casing loose either on the opening side or the wall side. As the casing is loosened, work upward with the screwdriver. With about 18″ loose, you can stop using the screwdriver and start rocking the casing back and forth while pulling out.

With the casing removed, remove the door by removing the hinge pins.

You’ll find screws randomly spaced through the flanges under all the casing, remove these and the frame should be able to be lifted slightly so that the floor covering is no longer capturing the door frame on the bottom.

If the door height is 6′8″, when you reverse the swing, the hinge location will also be reversed and will be located where the the latch formerly was.

If the door is a 7′ and has not been undercut, the frame can be flipped, keeping the hinges on the same side as they are presently.

ALSO >> Some have hidden screws beneath the door stop. Some have a nail flange hidden behind the casing trim.

Lastly, It might more practical to tear it out and replace it with a new prehung door in a new jamb.