Metal pipe having upset ends

A metal pipe having a central portion of uniform inner and outer peripheral surfaces and an internal upset end portion adjacent said central portion at an end of said pipe, said internal upset end portion comprising:

• an end section of an increased outer diameter and wall thickness at the end of said upset end portion and defining inner and outer peripheral surfaces;
• and
• an inner transition section of a varying wall thickness between said central portion and said end section;
• said inner transition section having an inner peripheral surface extending between said inner peripheral surface of said central portion and said inner peripheral surface of said end section, said inner transition section having an axial length which is greater than one-half the inside diameter of said central portion of said pipe, and said inner peripheral surface of said transition section being of an inner concave curvature formed from a radius having a length which is at least three times the axial length of said transition section.