In terms of processing technology: hot rolling is hot working, and cold drawing is cold working. Hot rolling is rolling above the recrystallization temperature, and cold rolling is rolling below the recrystallization temperature;
Distinguish from appearance: cold-rolled seamless steel pipe has a bright surface, and the diameter is smaller than that of hot-rolled seamless steel pipe. The diameter of hot-rolled seamless steel pipe is larger than that of cold-rolled seamless steel pipe, and the surface has obvious oxide scale or red rust;
In terms of precision: the precision of cold-rolled seamless steel pipe is higher than that of hot-rolled seamless steel pipe, and the price is also higher than that of hot-rolled seamless steel pipe.
In terms of use, hot-rolled steel pipes are used in places where fluid transportation, mechanical structure, etc. do not require high size, and cold-rolled steel pipes are used in places with high requirements such as 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 ingot, refine the grain 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, that the tensile properties of the steel in the thickness direction greatly deteriorate, and there is a possibility of interlaminar tearing when the weld shrinks. The local strain induced by the shrinkage of the weld often reaches several times the yield point strain, which is much larger than the strain caused by the load; 2. Residual stress is 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 → perforation → three-roller skew rolling, continuous rolling or extrusion → de-piping → sizing (or diameter reduction) → cooling → billet tube → straightening → water pressure Test (or flaw detection) → mark → storage.
Cold has drawn (rolled) seamless steel pipe: round tube billet → heating → perforation → heading → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → billet → heat treatment → straightening → Hydraulic test (flaw detection)→marking→warehousing.
Post time: Aug-18-2022