Steem uses Delegated Proof of Stake (DPOS). The coins are created by the witnesses every time a block is validated (I think it's every 3 seconds). In essence the witnesses are the miners. Currently the POW mining in Steem only generates 1/21 of the blocks but that portion of the algorithm doesn't add any additional security to the network. If you are interested I am including 2 links of Steemit articles about DPOS.

https://steemit.com/bitshares/@testz/bitshares-history-delegated-proof-of-stake-dpos

https://steemit.com/money/@autosmile13/what-is-dpos-delegated-proof-of-stake