Threaded connection for steel pipe

A set of a first pipe and a second pipe having a threaded connection, wherein:

• the second pipe comprises a box which is an opening end of the second pipe;
• the first pipe comprises a truncated cone shaped pin which is an end of the first pipe and is configured to be inserted into the box;
• the pin includes a male thread portion which is a tapered thread, and a seal portion which includes a tapered surface;
• the box includes a female thread portion which is a tapered thread, and a seal portion which includes a tapered surface;
• a minimum diameter of the tapered surface of the pin is smaller than a maximum diameter of the tapered surface of the box;
• and
• the first pipe and the second pipe have shapes such that a positional relationship between the male thread portion of the first pipe and the female thread of the second pipe shifts from a first state to a second state during make-up by screwing,
• the first state being a state that the seal portion of the pin and the seal portion of the box contact with each other but a root of the male thread portion and a crest of the female thread portion does not contact with each other, and
• the second state being a state that a root of the male thread portion and a crest of the female thread portion contact with each other.