The above phrases are somewhat similar in meaning as they both give reference to the internal weld bead of a round, square or rectangular steel tube.
When cold forming steel tubes the weld bead can be controlled by a scarfing tool. This is done inline during the cold forming process and is done right after the weld on the tube has been completed.
The customer has the option to take the weld bead out completely by internally scarfing the steel tube. This is usually done for steel tubes used in an application where another tube has to fit inside the internally scarfed steel section. Conveyor tubes and steel tubes that is bent by using a mandrel also requires to be scarfed internally.
A fin controlled steel tube will have a weld bead which is controlled leaving a constant size weld bead on the inside of the tube. Tough the weld bead is kept to a minimum it would not be flat with the surface of the tube as is done when internally scarfing the welded steel section.
Round, square and rectangular tubes that are rolled from cold rolled material is commonly taken as either internally scarfed or fin controlled depending on the purpose of the tube.