Having access to an oxyacetylene set-up, I am thinking of brazing up some Jones loop style handlebars. Would 1.5/2mm mild steel tubing be strong enough? Or should I try and get hold of some T45 or similar?

Tensile strength? Impact strength? Fatigue strength? Modulus of rupture? Hardness? Chemical weathering (rust) strength?

Strength means lots of things.

I am aware that strength means a lot of things. With handlebars impact and fatigue strength are going to be important, as well as tensile.
I’ve used T45 for roll cages in the past, but in the amount I need it’s quite expensive. Most suppliers only do 3m lengths minimum.

get a piece of suitably-sized mild steel, support it in a cantilever configuration, extending 500mm

hang 100Kg on it, see if it fails.

better yet, do the maths.

bending Moment = (100*9.81)*0.5

and remember that M/I = s/y

i’d do it myself, but i’m a little busy…

(for mild steel, assume the yield strength is 250N/mm2)

(edit: apologies for mixing metres, and millimetres, that’s just the way my damaged brain works)

I’ll have a go next Monday when I’m back in the workshop 😉
I may be a DT teacher, but I’m better with electronics, wood and computers – metalwork is still something of a dark art to me!