“So i am seeking guidance here to get exact understanding of 40:46.? Which Fire they will be exposed day and night?”
Try comprehending in the following context:
40:44: You will soon come to remember what I am saying to you now. I commit my affair to God. God is Seer of His servants.'
40:45: And God protected him (the believer) from their evil scheming while surrounding Pharaoh's people WITH SUFFERING OF
40:46: THE FIRE, WHICH THEY HAD BEEN WARNED OF DAY AND NIGHT. On the Day, when the Hour dawns, it will be said, “Cast Pharaoh’s people into the toughest penalty.”
AzaabinNaar = “Suffering of the Fire”. Verses 40:45 and 40:46 are in continuation.
2:126: And Abraham prayed, 'My Lord! Make this Town a haven of peace and security, and provide its residents with plentiful sustenance; those who believe in God and the Last Day.' He answered, 'I will also provide for those who disbelieve and let them enjoy for a while. But then I will commit them to the SUFFERING OF THE FIRE (AzaabinNaar), a miserable destination.'
They argue against God's Revelations, without any basis. This attitude is strongly disapproved in the Sight of God and of those who believe. Thus God sets a seal on every arrogant, brutal heart.' [40:56. According to Divine Laws, when someone sticks to false beliefs and persistently refuses to listen to the truth, one loses the ability to perceive reality. God assigns to Himself all that happens in the Universe. Humans, however, have free will to choose their course. For example, the 'sealing of heart' is a natural consequence of one's own actions.