One furnace does many jobs! Medium frequency induction heating furnace produces different grades of iron castings in the same furnace

The smelting equipment in a company's foundry workshop is a 10t intermediate frequency furnace. Compared with the cupola furnace, its advantage is that there is no sulfur increase during the smelting process, and the molten iron can be covered with slag during the smelting process, which can prevent the oxidation of silicon, manganese and alloying elements in the molten iron to a certain extent, and reduce the absorption of molten iron. gas, thus making the molten iron relatively pure; the disadvantage is that for the production organization of multi-material products, the flexibility is poor and it is difficult to configure furnaces. There are many types of cast iron parts in production, and most of them are small and medium-sized parts. Therefore, the use of medium frequency induction heating furnaces to smelt and produce cast iron parts has the problems of difficult production organization, low efficiency, and difficulty in successfully completing production tasks. Through practice, the company has realized the production of different grades of iron castings in the same furnace through electric furnace smelting.

1) The method of producing different grades of iron castings in the same furnace. The method of producing different grades of iron castings in the same furnace mainly includes two links, one is the calculation of ingredients, and the other is the selection of furnace temperature and processing method.

① Ingredients calculation, that is, based on the requirements of the chemical composition of the molten iron, taking into account the changes in elements during the smelting process and the actual situation of the charge, calculate the mix ratio requirements of various metal charge, and then analyze the composition differences between different grades, Select the feeding method, and finally determine the feeding amount and feeding method of various raw materials.

②The furnace temperature is mainly determined based on the specific conditions of the molten iron grade, molten iron treatment method and casting structural conditions in different packages. The treatment method mainly selects the type and amount of nodularizing agent and inoculant according to the specific conditions of the molten iron grade and the structural conditions of the castings in different packages.

2) Production example: Taking the production of QT500-7 plum blossom sleeves and HT200 baking plates in the same furnace as an example, the specific implementation method is introduced.

①Ingredients calculation. Since acidic furnace lining is used, damage is not considered during the batching process.

② Instructions for pouring ingredients in front of the furnace. Before determining the batching and pouring order in front of the furnace, it is first necessary to determine which material to produce first based on the production plan and the characteristics of the intermediate frequency furnace. The molten iron volume of this furnace is 9150kg, which can be charged at one time. At the same time, the intermediate frequency furnace cannot blow oxygen for decarburization, so HT200 is produced first and then QT500-7 is produced. In actual production, it can also be achieved by reserving a part of the steel material to produce QT500-7 first. When producing HT200, the reserved steel charge can be added by adjusting the charge ratio according to the composition of the cleared molten iron.

③Return to the adjustment of chemical composition and tapping temperature. It can be seen from the ingredient calculation table and the ingredient pouring instruction sheet in front of the furnace that the main difference between the two materials in terms of composition alone is manganese and carbon. The difference in manganese is that HT200 is adjusted by adding ferromanganese during the modification process, while QT500-7 manganese is adjusted by adding ferromanganese into the furnace after the first package of molten iron is discharged. The carbon adjustment of HT200 is achieved by adjusting the proportion of various metal charges during the batching calculation process; the carbon of QT500-7 is higher than that of HT200. In order to achieve the purpose of adding carbon, it can be adjusted after the first package of molten iron is discharged. Add a certain amount of carburizing agent according to the chemical composition. It should be noted that since there is no steel charge coverage after adding the carburizing agent for the second time, the yield of the carburizing agent is lower and unstable than the first time. It needs to be explored in practice. To be sure. At the same time, from the perspective of tapping temperature, the tapping temperature of HT200 is controlled at (1450±10)℃, and that of QT500-7 is controlled at (1490+20)℃. Usually, carburizing agent and ferromanganese are added after the first package of molten iron is finished. , use the time of sending electricity to melt the carburizer and ferromanganese to achieve the purpose of raising the temperature.

④Incubation treatment. From the perspective of inoculation treatment methods, HT200 only needs to add inoculant, while QT500-7 needs to add nodularizing agent and inoculant, and the type and amount of inoculants added to the two materials are different. The inoculant selected for the production of QT500-7 is a composite of ferrosilicon and rare earth magnesium alloy (also a spheroidizing agent), in which ferrosilicon is added in two times; the inoculant selected for the production of HT200 is a composite of ferrosilicon and ferromanganese. The inoculation treatment of HT200 is to use the flushing method. The inoculant is added into the ladle before tapping, and the impact of the molten iron during the tapping process is used to achieve the purpose of uniformity after tapping. The inoculation treatment of QT500-7 is to use the reverse bag method. First, add spheroidizing agent and ferrosilicon 1 to the spheroidizing bag, and then tap the iron in the spheroidizing bag. The amount of iron to be tapped should not be less than 1/1 of the total amount of iron to be tapped. 2. Then remove the slag and observe the triangular test piece to determine whether it is necessary to add spheroidizing agent and ferrosilicon when pouring the bag. 2. Finally, remove the remaining iron from the teapot bag and pour the molten iron in the spheroidizing bag into the teapot bag. The purpose of uniform composition.

In short, choosing appropriate technological means, such as adding alloys before the furnace and making small adjustments to the ingredients after the furnace, can meet the different requirements of molten iron and produce different grades of cast iron in the same furnace.