In terms of processing technology: hot rolling is hot processing, and cold drawing is cold processing. Hot rolling is rolling above the recrystallization temperature, and cold rolling is rolling below the recrystallization temperature;
Distinguish from the appearance: the surface of the cold-rolled seamless steel pipe is bright, and the diameter is smaller than that of the hot-rolled seamless steel pipe. The caliber of the hot-rolled seamless steel pipe is larger than that of the cold-rolled seamless steel pipe, and the surface has obvious scale or red rust;
In terms of precision: the precision of cold-rolled seamless steel pipes is higher than that of hot-rolled seamless steel pipes, and the price is also higher than that of hot-rolled seamless steel pipes.
Distinguished from the use: hot-rolled steel pipes are used in fluid transportation, mechanical structures, etc. where the size requirements are not high, and cold-rolled steel pipes are used in places with high requirements for precision instruments, hydraulic systems, and pneumatics. In terms of wall thickness, cold-drawn seamless pipes are more uniform than hot-rolled seamless pipes.
Advantages and disadvantages of hot-rolled seamless pipe: The advantage is that hot rolling can destroy the casting structure of the steel ingot, refine the grains of the steel, and eliminate the defects of the microstructure so that the steel structure is dense and the mechanical properties are improved. The disadvantages are 1. The performance of the steel in tension along the thickness direction has greatly deteriorated, and interlaminar tearing may occur when the weld shrinks. The local strain induced by weld shrinkage often reaches several times the yield point strain, which is much larger than the strain caused by the load; 2. Residual stress caused by uneven cooling. It may have adverse effects on deformation, stability, fatigue resistance, etc.
Process flow:
Hot rolling (extruded seamless steel pipe): round tube billet → heating → piercing → three-roll cross rolling, continuous rolling or extrusion → tube removal → sizing (or reducing) → cooling → billet tube → straightening → hydraulic pressure Test (or flaw detection) → mark → storage.
Cold drawn (rolled) seamless steel pipe: round tube blank→heating→perforation→heading→annealing→pickling→oiling (copper plating)→multi-pass cold drawing (cold rolling)→blank tube→heat treatment→straightening→ Hydrostatic test (flaw detection) → marking → storage.
Post time: May-29-2023