beat up vs welt

beat up is not a noun while welt is a noun.

Word	Noun	Adjective	Verb	Adverb
beat up	No	No	Yes	No
welt	Yes	No	Yes	No

As verbs, welt is a hyponym of beat up; that is, welt is a word with a more specific, narrower meaning than beat up:

beat up: give a beating to; subject to a beating, either as a punishment or as an act of aggression
welt: beat severely with a whip or rod

beat up (noun)	welt (noun)
	a raised or strengthened seam
	a raised mark on the skin (as produced by the blow of a whip); characteristic of many allergic reactions

beat up (verb)	welt (verb)
gather	put a welt on
give a beating to; subject to a beating, either as a punishment or as an act of aggression	beat severely with a whip or rod