I spoke to Mufti Yusuf Sacha Saheb (DB) this weekend and he said that there are lots of people who are saying that Hanafi Madhab allows women to expose their face and the evidence is NOT from primary sources, rather the Madhab obligated Niqab later on.
Mufti Yusuf Sacha Saheb (DB) said that this is incorrect and the Niqab is actually present and proven by the primary sources and he quoted the following Hadeeth of Saheeh Bukhari:
حدثنا عبد الله بن يوسف أخبرنا مالك عن ابن شهاب عن عروة عن عائشة رضي الله عنها قالت
كان عتبة عهد إلى أخيه سعد أن ابن وليدة زمعة مني فاقبضه إليك فلما كان عام الفتح أخذه سعد فقال ابن أخي عهد إلي فيه فقام عبد بن زمعة فقال أخي وابن وليدة أبي ولد على فراشه فتساوقا إلى النبي صلى الله عليه وسلم فقال سعد يا رسول الله ابن أخي قد كان عهد إلي فيه فقال عبد بن زمعة أخي وابن وليدة أبي ولد على فراشه فقال النبي صلى الله عليه وسلم هو لك يا عبد بن زمعة الولد للفراش وللعاهر الحجر ثم قال لسودة بنت زمعة احتجبي منه لما رأى من شبهه بعتبة فما رآها حتى لقي الله
XVII. The child belongs to the bed, whether the woman was free or a slave
6368. 'Urwa related that 'A'isha said, "'Utba ibn Abi Waqqas took an undertaking from his brother, Sa'd, 'The son of the slavegirl of Zam'a is my son. Take him into your care.' In the year of the Conquest, Sa'd took him and said, 'He is my nephew, I gave an undertaking about him.' 'Abd ibn Zam'a stood up and said, 'He is my brother, the son of my father's slavegirl. He was born on his bed.' They both went to the Prophet, may Allah bless him and grant him peace, and Sa'd said, 'Messenger of Allah, he is my nephew. I gave an undertaking about him.' 'Abd ibn Zam'a said, 'He is my brother and the son of my father's slave. He was born on his bed.' The Prophet, may Allah bless him and grant him peace, said, 'He is yours, 'Abd ibn Zam'a.' Then the Prophet, may Allah bless him and grant him peace, said, ' The child belongs to the bed and stones belong to the adulterer.' Then he said to Sawda bint Zam'a, 'Veil yourself from him,' because of the resemblance he saw in him to 'Utba. He did not see her until he met Allah [i.e. died]." [Bukhari]