This is an interesting question because the majority view of commentators is that שרפים (Seraphim) and כרבים Cherubim are two different orders of angels.
However, this appears to me to be clearly incorrect. שרף (seraph) in the Hebrew simply means "burning", "a burning one", "a burner".
This is clear from Num 21:6
The LORD sent burning serpents (הנחשים השרפים haNachashim haSeraphim) among the people and they bit the people, so that many people of Israel died.
The "burning" serpent probably called thus because of their fiery red color or because of the burning inflammatory effect of their bite, or both.
and from Num 21:8-9:
Then the LORD said to Moses, "Make a burner (שרף seraph), and set it on a standard; and it shall come about, that everyone who is bitten, when he looks at it, he will live." Num 21:8
And Moses made a bronze serpent (נחש נחשת nachash nachashet) and set it on the standard; and it came about, that if a serpent bit any man, when he looked to the bronze serpent, he lived.
Note that God told Moses to make a Seraph and he made a Nachash--Moses certainly did not think God was asking him to make an angel...
The only use of (שרף seraph) as referring to angels is in Isaiah 6:
Seraphim (שרפים) stood above Him, each having six wings: with two he covered his face, and with two he covered his feet, and with two he flew. Isaiah 6:2
Then one of the seraphim (שרפים) flew to me with a hot coal in his hand, which he had taken from the altar with tongs. Isaiah 6:6
However, these two uses should simply be translated "Burning Ones" or "Burners." They are simply Cherubim, the same as described in Ezekiel chapters 1 and 10.
These Cherubim are "burning" probably in the same sense that the Angel of the Lord was in Exodus 3:2
The angel of the LORD appeared to him in a blazing fire from the midst of a bush; and he looked, and behold, the bush was burning with fire, yet the bush was not consumed.
and in Heb 1:7 (which is a quotation from Psalm 104:4):
And of the angels He says, "WHO MAKES HIS ANGELS WINDS, AND HIS MINISTERS A FLAME OF FIRE."
The connection between a Seraph (burning) Cherub and a Seraph (burning) Serpent is of course Satan, who is both a Cherub ("the annointed covering Cherub" Ezekiel 28:14) and a Serpent ("the Serpent of old who is the Devil and Satan" Rev 12:9)



