It's very much inadvisable to completely remove any screenlock, for your own safety and security, since there's so much sensitive information on a phone.
Open your system settings and search for "lock after screen timeout" (and to find the settings gear, swipe down twice from the top of the phone -- you should see the settings gear icon at the lower right, typically next to a Power button). Set that to something longer, like 2 or 5 minutes. If it's set to something really short, then you find yourself having to reenter the lockscreen PIN frequently -- but I would also be cautious about setting it for too long, like 30 minutes, because if someone were to swipe your phone, they'd have more chance to get into it and wreak havoc.
You can also look for the option "Power button instantly locks" and turn that off.