Seamless steel tube has a hollow section, a large number of which are used for conveying fluid, such as crude oil, natural gas, coal gas, water and some solid materials, etc. Compared with solid round steel, when the torsional strength is same, the weight of the seamless steel pipe is relatively light, so it is a kind of economical steel, which is widely used in manufacture oil tubular goods and mechanical parts.
Difference
The cold rolled seamless tube allows local buckling, which can make full use of bending bearing capacity. While, hot rolled steel does not allow local buckling.
The causes of residual stress are different, so the distribution of the cross section is also very different. The distribution of the residual stress on cold rolling thin wall steel is bending. However, the distribution of the residual stress on hot rolled steel is film type.
The free torsional rigidity of hot rolled steel is higher than that of cold rolled steel. In other words, the torsion resistance of hot rolled steel is better than that of cold rolled steel.
Technological process
Hot rolled seamless steel pipe
round billet→heating→perforation→extrusion→sizing→hot rolling→cooling→straightening→hydrostatic test→signing→storage
Cold rolled seamless steel pipe
round billet→heating→perforation→annealing→pickling→annoit→cold rolling→heating→straightening→hydrostatic test→signing→storage