The electromagnetic stirrer (EMS) are widely used in the iron and steel industry both in the continuous casting phases and in the steel refining process in the ladle.
The use of the stirrers allows to increase the quality and the production of steel and, due to the high metallurgical flexibility they will fit perfectly to the production of steels with different carbon content.
The quality of the surface layer and the internal crystalline structure of the steel depend on the chemical composition, the sildification process and the flow of the liquid steel inside the casting line. In the presence of a variable magnetic field inside the liquid steel, volume forces are induced which impress a main rotation motion and secondary motions along the casting line. The mixing induced with the electromagnetic stirrers makes the heat exchange along the casting line more effective, consequently the solidification process is more homogeneous and promotes the formation of equiaxed zones.
Electromagnetic stirrer are user in continuous casting processes, mainly to increase the quality and the production of steel.
A&G stirring plants fit perfectly with existing equipment into the melt shop, as well as new designs.
Here the main technologies and operational precedures:
Browse the map on the side to see details.
After many years of technical and operational experience and the highly specialized know-how, we are able to design and realize stirring systems based on the specific needs of the customer.
For the design phase of new stirring systems we use advanced fluid-dynamic computation software which is able to calculate and display the motions induced in the liquid steel by the variable magnetic field generated by the electric winding of the stirrer.
The multiphysic analysis software allows to solve the complex problems related to conductive fluids immersed in variable magnetic fields in a quick and precise way, thus succeeding in optimizing the design phase of the stirrer. The calculation of the electrical parameters of the stirrer, such as winding resistance and phase inductance, and the thermal behavior of the windings are also analyzed with the finite element simulation software. Computer-aided design is therefore a fundamental tool for developing and testing stirrers using mathematical models before they are put into production.
The power supply terminals of the stirrer are housed in the electrical connection box. The connection box is designed to guarantee perfect electrical insulation from the external environment and the use of special sealing materials prevents any loss of cooling water. A&G offers a quick connection system for power and ground cables that make connection operations more reliable and quicker.
The internal part of the carpentry is made of stainless steel with superior mechanical characteristics that make it particularly resistant to shocks and heat irradiated by the molten steel.
The coils are made of suitably insulated copper conductors to guarantee high thermal and electrical performances. The magnetic core with the electric windings is subjected to a VPI resin coating process which gives it excellent mechanical strength and high electrical insulation between the coil and towards the ground.
The external carpentry is designed and built according to the customer's technical specifications. The use of stainless steel gives it excellent resistance to corrosion.
The magnetic core is composed of superimposed ferromagnetic sheets suitably insulated from each other, which constitute a preferential path for the lines of the magnetic field produced by the electric winding.
The electromagnetic stirrers are used in the continuous casting process, mainly to improve the quality and production of the steel.
They are usually equipped with tri-phase windings that, producing a rotative magnetic field, induce a rotative motion on the steel.
M-EMS (Mould Electromagnetic Stirrer)
S-EMS (Strand Electromagnetic Stirrer)
F-EMS (Final Electromagnetic Stirrer)
The benefits obtained using one or more EMS in combination are listed in the table below.
|Ems type & Combination||M-ems||M+f-ems||M+s+f-ems||M+s-ems||S-ems||S+f-ems|
|Pinhole and blowhole|
|Surface and subsurface cracks|
|Solidification structure and internal cracks|
|Centerline segregration, center porosity|
Our inverter switchboards are equipped with a sliding system that allows easy installation / maintenance of the main IGBT module. They are composed of static converters at impressed voltage with IGBT modules, digital regulation with vector control, capacitor bank, microprocessor control unit and auxiliary circuits (power supplies and transducers). The inverter is specifically designed for critical applications and is designed with the latest and proven technologies, in a modular design for easy installation and maintenance. All Power components are sized to ensure operation of the converter even in the most severe service and load conditions. The power components (diodes and IGBTs) are cooled by forced ventilation. The static converter is available in different sizes up to a maximum power of 4 MW in the case of 8 modules in parallel.
The cooling system with demineralized water it is used to remove the heat produced in the coils for Joule effect and to maintain the winding temperature below the limit value related to the thermal insulation class.
The water system ensures a longer life of the electric insulation of the stirrer and, due to the high efficiency, is able to reduce energy consumption.
Our cooling system is mainly composed of:
1. GAMMA RAY SOURCE
2. GAMMA RAY DETECTOR
3. CONNECTION CABLE
4. HIGH SPEED REGULATOR
The system is designed to monitor the level of liquid steel inside the mold, with the aim of bringing it to the maximum upper level, in order to reduce the effective distance from the exit of the tundish to the level of the mold and consequently minimize turbulence in the liquid metal. The system allows automatic start-up of the line, reducing the possibility of failures due to operator errors.
The system works on the principle of absorption and transmission of radiation. A ray of gamma rays coming from the Source is directed towards the scintillation detector, passing through the liquid steel which partially absorbs the rays. The rays that are not absorbed by the liquid steel will finally reach the detector. The higher the steel level, the greater the absorption. Consequently the measured signal is inversely proportional to the liquid steel level.
The A&G electronic control, together with the New Generation A&G scintillator, can achieve the best performance, eliminating any speed fluctuation (see diagram below). This feature translates into higher billet quality, reduced chance of breakage, perfect lubrication and improved billet surface quality.
Mold level control system
The A&G automatic level control is so precise that it reaches a predetermined level without noticeable fluctuations and is able to keep the level in a fixed position.
Pen type complete with shielded container (lead and steel).
In line with today's trend of minimizing installed radioactivity and exposure in each application, we have adopted a Co60 source, with a counter having an activity of only 20MBq (approximately 0.54mCi).
The A&G scintillator was developed using a new generation of solid state photo multiplier sensors that are more accurate than the photo multiplier tubes normally used by competitors.
Furthermore, our solution is not sensitive to electromagnetic fields so it can also be used in combination with mold stirrers.
The radioactive source is shipped and stored in its lead shielding case which is also used for installation inside the mold.