Should I need CPU cooler for i5 7600k?
Should I still need a CPU cooler for i5 7600k if I do not want to overclock it?
Yes, you'll need to buy a cooler for it because Intel no longer provide coolers with their overclockable 'K' series processors - - they assume that most 'K' buyers will be overclocking and using a third-party cooler on it.
So even if you don't intend to OC it, you'll still need to buy a cooler for it since it's supplied without one - - and you definitely can't run it without at least a basic cooler.
There's really not much point buying a 'K' if you've no intention of OCing it. You may as well buy a 'non-K' - - they do come with a cooler as standard.
All CPUs will need a CPU cooler or else the PC won't boot. The CPU will simply overheat very quickly and shut down before damage is caused.
A lot of the time, a stock CPU cooler is provided within the CPU package. Since your CPU is unlocked (name contains a 'K' on the end), however, it requires an aftermarket cooler as it doesn't include a stock.
For no overclocking I highly advise the Cryorig M9i for $20 USD. It performs very fine for no overclocking, noise levels are low, and is smaller, better ram clearance and easier to build with unlike the cooler master 212 Evo.