Yes-ish… String players will naturally interpret 90% of this by context, only computers need you to be explicit. If you insist, a simple legato (or perhaps sempre legato) once at the start of a passage would suffice irrespective of any slurs. Please don’t do legato… slur… legato… etc.
Remember there are only half a dozen articulation marks, but hundreds of practical interpretations of them.
“Détaché” would generally work to indicate separate bows for the full value of the note. You could probably even write “legato détaché” to get your point across. There is also some precedent for double slurs (a long one for the phrase plus short ones for bowing) which you can find in Brahms, but some players might find that confusing at first.
Like the other responders, I don’t write legato, détaché, etc. as those are understood by the player. But for NotePerformer playback, sometimes I use the playing technique “legato” and hide it, if the playback is too separated (which is rare in my experience).
The simplest example that comes to mind is if there are two analogous figures/phrases, one which should be slurred and the other which should not. String players, especially in a section, have a tendency to write in their own bowing and might reasonably assume that the composer forgot to write in the slurs for the second phrase. Adding a parenthetical détaché in the music would avoid this and save time in rehearsal.
There are a million examples in which you shouldn’t write anything, and there are fewer examples where some indication is beneficial. If OP is asking this question, I’m assuming (without seeing the music) that there is some reason they think their intention might be misunderstood. That’s up to OP’s judgement, unless they want to share their score to give more context.
It’s two separate passage that are not immediately next to each other. I’m thinking specifically about the second one, which is quite a bit slower.
If I indicate the slur, I’m concerned the resulting sound will be less full so as to fit it in a single bow or otherwise minimize the amount of bow change. But if I indicate nothing, I’ll end up with a grand detache with accents, edges and less cohesion.
I’ve also thought about cantabile instead, but wouldn’t that be more confusing and imply a softer tone? Sempre legato so far sounds like the clearest approach.
What is the dynamic of the passage? From your description, it sounds like you want a full but not aggressive forte.
I don’t think cantabile would imply a softer tone — in fact, I think it would signify the opposite, especially if the passage in question is a melody. You could also use espressivo if you think cantabile doesn’t fit. “Sempre legato e cantabile/espressivo” should work wonderfully. I would be reluctant to use either cantabile or espressivo if it is not a melodic line.
It also sounds like tenuto marks might be helpful on longer notes, again depending on the passage.