The performance of the silicon steel sheet in the transformer not only affects the loss of electric energy, but also relates to the performance, volume, weight and the saving of various materials of the motor and transformer. Therefore, the shearing process of the silicon steel sheet is very important. Importantly, the silicon steel sheet is cut by laser cutting.
However, the burrs of the silicon steel sheet produced during the cutting process will affect the electromagnetic characteristics, motor output power, and generator life. When laminating the sheets, the burrs will cause the lap short circuit between the sheets to increase the vortex loss. We must improve the laser cutting process. Reduce silicon steel sheet burrs and reduce losses.
1. The development of transformer core material
Early transformer core
s were made of low-carbon steel. Now there are two specifications of silicon steel sheets, one is 0.35 mm silicon steel sheet and the other is 0.5 mm silicon steel sheet, which is the same as mild steel. In contrast, the resistance of silicon steel sheet is almost unchanged.
Only the whole iron core is divided into many metal flakes, and the flakes are insulated, so that the utilization rate of magnetic materials is improved, the AC resistance is increased, and the eddy current loss of the iron core is reduced. The development of silicon steel sheets has gone through three stages. The early ones are hot-rolled silicon steel sheets, which have low silicon content and high loss.
The cold-rolled non-oriented silicon steel sheet appeared in the 1940s. This kind of silicon steel sheet has high silicon content and low loss. It has been widely used as soon as it is launched. With the continuous deepening of research, the scientific community has discovered that iron The crystal orientation is easy to magnetize.
In 1934, the United States adopted a method of combining cold rolling and high-temperature heat treatment to make the crystals in silicon steel sheets order in a regular manner along the direction, which made it have excellent magnetic properties and gradually moved to industrial production, although the iron loss of silicon steel sheets has been large so far. , The iron core is easy to saturate, but because its production process is relatively simple and the cost is not high, silicon steel sheet is still a common iron core material for power transformers.
Second, the cutting requirements of silicon steel sheet
The burrs of the silicon steel sheets used in generators, transformers, and motors have an impact on its electromagnetic properties. The burrs of silicon steel sheets will affect the electromagnetic characteristics, motor output power, and generator life. The burrs will cause inter-chip laps when laminated The short circuit causes an increase in eddy losses.
At the same time, it is necessary to reduce the lamination filling factor, so it is necessary to ensure that the cut silicon steel sheet is basically free of burrs. After the silicon steel sheet is punched and cut, internal stress will be generated, resulting in a decrease in the permeability of grain deformation and an increase in specific iron loss. Therefore, it is necessary to ensure the elimination of internal stress and ensure the originality.
Silicon steel sheet is not allowed to have insulation damage on the surface with material within the shear range, and the edge of the sheet material must not be damaged, because it will affect the quality of the iron core. The silicon steel sheet after shearing must have no obvious waves, otherwise the silicon steel sheet will be severely deformed, the magnetic domain structure will be destroyed, and the loss will increase.
Silicon steel blanking work is generally carried out on a mechanical press using stamping abrasive tools. The stamping abrasive tool of silicon steel sheet is composed of concave and convex abrasive tools. It is installed on the punching machine to stamp the silicon wafer into the iron chips of the stator and rotor of the motor or transformer. The cutting edge part has to withstand the impact force, shearing force, bending force, while being squeezed and rubbed by the silicon steel sheet. The surface of the silicon steel sheet has a special coating, which strengthens the friction and abrasion of the cutting edge, resulting in a gap in the manufacture of abrasive tools. Too large, when the grinding tool manufacturing gap is too large.
The silicon steel sheet will be squeezed and deformed during punching, and burrs will be formed on the edge of the punching sheet. The main reason for the normal failure of the die of silicon steel sheet is the wear of the cutting edge, the high cost of manufacturing the abrasive tool and the long development cycle, which led to a new cutting technology, that is, laser cutting.