The rapid development of modern machinery manufacturing technology and metallurgical technology has put forward high quality, refinement and energy saving requirements for castings. High-performance castings of high-quality ductile iron castings, graphite cast iron and aluminum alloy castings have made the induction melting furnace modern casting. The status in production is increasingly important. In the foundry transformation and new foundry workshops, the transformation or addition of induction melting furnaces is often placed in the first considered location. Therefore, the " selection of induction melting furnace " is a subject worthy of attention. It is also a hot topic in the foundry industry. The electric furnace supplier and the sales staff of the electric furnace factory often use the strengths of their own enterprises as the selling point. This is normal, and the foundry must comprehensively evaluate and evaluate the performance of the equipment. I hope to draw your attention.
The development of efficient, reliable and flexible induction melting furnace manufacturing technology has played an important role in improving and establishing the importance of induction melting furnaces in foundry production. It can be seen from Table 1 that compared with the traditional power frequency induction melting furnace that has been around for nearly a hundred years, the induction melting furnace has an undisputed superiority in terms of technical performance, work performance and investment. This makes it since the last century, 80 since the late years been widely used in Europe, America and other developed countries, basically replacing the traditional frequency induction melting furnace. Since 90 since the mid-years, with the rapid development of electronic technology, high-power solid-state domestic frequency power supply has also been successful in the development, production and application. Therefore, the traditional power frequency induction melting furnace has gradually disappeared from the sales market in China, and the existing power frequency induction melting furnace in the foundry is gradually replaced by the induction melting furnace in the technical transformation.
The induction melting furnace is used as a “ creative ” for the insulation / heating use of the foundry industry and is suitable for large-scale production foundries. Table 1 Comparison of performance of intermediate frequency and power frequency centerless induction melting furnace (taking cast iron as an example)
Comparison indicator | Induction melting furnace | Power frequency induction melting furnace | Comment |
Power density | 600 ~ 1400 kW/t | 300 kW/t | The allowable value of the configured power density per ton of furnace capacity varies with frequency. |
Requirements for adding charge | Small request | High standard | Feeding requirements such as the fast size of the material and the dryness of the charge |
Melting unit consumption | 500-540 kWh/t | 540 -600 kWh/t | Due to the high power density of the induction melting furnace, the heat loss is small, the melting time is short, and the total efficiency is high. |
Power adjustment range | 0~100% stepless adjustment | Level adjustment | The power regulation of the power frequency furnace also involves the adjustment of the three-phase balance, which is more complicated. |
Automatic power adjustment | can | difficult | Power automatic adjustment function is the premise for energy-saving mode operation and constant power output |
Melting effect | variable | Large and fixed | The agitating effect of the induction melting furnace varies inversely with frequency. Therefore, for the melting of aluminum alloy, the stirring of the melt can be reduced by increasing the working frequency, and the oxidation loss of the aluminum liquid during the melting process can be reduced. |
Possibility of implementing energy-saving mode operations | can | Can not | In addition to energy saving, the electric furnace operating in energy-saving mode can avoid overheating of the melt. |
Possibility of achieving constant power output | can | difficult | Achieving constant power output during the melting cycle can increase the productivity of the electric furnace and reduce the unit cost of melting |
Metallurgical operation characteristics | The melt does not have multiple overheating | There are multiple overheating in the melt | This is because the power frequency furnace has to carry out the residual liquid melting operation, and each time the casting is required to retain about 1/3 of the residual molten metal in the crucible. |
Fault diagnosis and protection | Complete, strong | section | Induction melting furnace for self-diagnosis and protection, reducing repair time and effort |
Networking possibilities with computers | can | difficult | Induction melting furnace can be connected to the computer melting process automatic control management system |
High-order harmonic pollution for the power grid | Have | no | The intermediate frequency power supply can take measures to reduce or eliminate the high-order harmonic pollution of the power grid. |
Power consumption ratio | 30 ~ 40% | 100% | |
Total investment ratio | 85 ~ 90% | 100% |
Note 1 . The induction melting furnace operating by the batch melting method can empty the molten metal each time, and the furnace does not need to be frit when the furnace is started, the size and state of the feeding block are small, and the charging time of the charging material is short. These are all advantages that are lacking in the power frequency furnace operating with the residual liquid melting method.
In order to meet the requirements of modern casting production in terms of energy saving, safety, environmental protection, automation and good process adaptability, in recent years, induction melting furnace manufacturing technology has made great efforts in the following aspects, and has achieved success and progress: