Cold rolling mill is a new type of steel cold rolling processing equipment. The machine can be hot-rolled wire rods with a diameter of between 6.5mm and 12mm, and hot-rolled into a round-rolled coil to produce finished cold-rolled ribbed steel bars with diameters from 5mm to 12mm. Cold-rolled ribbed steel bars rolled from cold mills are pre-stressed concrete components. They are replacements of cold-drawn low-carbon steel wire. In cast-in-place concrete structures, I-grade rebars can be substituted to save steel. It is a better kind of cold-worked steel of its kind. If no speed regulation is required in the rolling process of the cold rolling mill, an AC motor may be used; if a speed regulation is required during the rolling of the cold rolling mill, a DC motor may be used.