Free-cutting steel wire has good cutting performance and high accuracy has been widely used in machinery parts, precision instruments, standard fittings, and other purposes. This paper introduces the cold drawing process of 12L14 free-cutting steel wire. The main equipment includes drawing die, line setting frame, dephosphorization machine, lubrication device, reducing roll box, drawing machine, mechanical stress removing device, length measuring device, wiring, wire drawing, etc. The dry lubricating powder is placed in the drawing die device to improve the lubrication performance and protect the drawing mold. When producing steel wire, it is still necessary to remove the oxide sheet on the surface of the raw material, so the original dephosphorization wheel is still used. The wireframe and wiring are also essential in wire drawing production. The purpose is to produce free cutting wire with 6.15mm size and high requirements for dimensional accuracy and surface quality, dimensional tolerance of ±0.02mm, the surface without scratches, pits, spots, the design is as follows:
(1) Forging: Forging remelted ingot according to the provisions of ingot forging in medium frequency furnace;
(2) Hot rolling: Heating, hot rolling, coiling, cooling;
(3) Annealing: Industrial energy saving resistance furnace, the heating temperature is 800 ~ 900℃, preferably 850℃, holding for 3 ~ 5h after cooling to 500℃ below furnace cooling;
(4) Straightening, cold rolling sizing and peeling: After annealing, the inclined two-roll straightening and cutting machine is used for straightening, cutting and sizing, and then peeling, butt welding of the straight strip into a large plate weight, and winding;
(5) Cold drawing and bright annealing: cold drawing is carried out on the drawing machine. The diameter after drawing is controlled by the drawing die. The bright annealing temperature is 800 ~ 900℃ (850℃ is the best), and the insulation is 0.5 ~ 2h.
(6) Auxiliary equipment: point rolling machine, butt welding machine, traction chain.
(7) Lubrication and cooling method of drawing die: dry drawing lubricant, water circulation cooling, take away the heat generated in the drawing process, protect the drawing die, water flow 4m³/h, water pressure 0.25Mpa.
Effect of wire tension on accuracy
Taper tension is too small will cause wire jitter, too large to make the size smaller or even broken wire. In the production process, the size is within the range of 6.11mm~6.14mm and the line speed is 7.5m/s, the tension is 35%, and the dimensional accuracy meets the tolerance requirements.
The effect of passes on surfaces
After a single pull, the surface of the free cutting wire has more fish scale spots and poor finish, which is caused by the oxide sheet. Mechanical descaling at the same time process two times drawing, first from 8 mm to 7.5 mm Φ Φ, again from 7.5 mm to 6.15 mm.
Effect of drawing wheel on the surface
The uneven surface of the drawing wheel can cause scratches. Remachining and grinding the surface of the drawing wheel to improve the surface finish, while heat treatment improves the hardness and enhances the wear resistance.