The difference between ASTM A105 flange and ASTM A105N flange

When we produce the carbon steel flange,some customer request the ASTM A105 steel material,and some request the ASTM A105N steel material.What is the difference between the ASTM A105 flange and ASTM A105N flange?

ASTM A105 steel flanges  and ASTM A105N steel flanges are not same,they have same raw materials,same steel grades,but the heat treatment requirement are different.N means Normalization heat treatment,and A105 flange haves no heat treatment requirement.

That means the A105N flange is one kind of A105 flange.But A105N flange have a better mechanical properties than regular A105 flange,better strength and better performance in low temperature service.
In a word,the ASTM A105 flange and ASTM A105N flange have a same chemical composition,but the A105N have a better mechanical property and usually used in critical situation.