What is the closest an asteroid or comet has passed the Sun and survived?
Wikipedia offers some useful info on sungrazers:


  As of October 21, 2017, there are 1495 known comets that come within ~12 solar radii (~0.055 AU).[2] This accounts for nearly one third of all comets.[3] Most of these objects vaporize during their close approach, but a comet with a nucleus radius larger than 2–3 km is likely to survive the perihelion passage with a final radius of ~1 km.


https://en.wikipedia.org/wiki/Sungrazing_comet

There's a bit about pyroxenes sublimating off at 7 solar radii, but no mention of whether any such object made it around the sun. Pyroxenes generally melt at around 1000°C.
An Iron/Nickel body melting at 1538°C/1455°C might well make it through a 7 solar radii passage.