Chemical composition of nodular cast iron
Qt400-18 nodular iron is selected for the study of austenitizing and austempering treatment in this test.
Raw and auxiliary materials for melting
It is very important to master the chemical composition of raw and auxiliary materials for smelting and to calculate the ratio of raw materials and auxiliary materials. The raw and auxiliary materials used in this experiment include metal furnace charge, spheroidizing agent, inoculant and alloy auxiliary materials.
Charge: including high-quality high-purity pig iron; high-quality low-carbon carbon steel (20 ᦇ steel); 75 ᦇ ferrosilicon; red copper; 99% electrolytic nickel plate.
Spheroidizing agent: zt-1df low magnesium and low rare earth nodulizer provided by Shaanxi Zhongyou Special Alloy Co., Ltd.
Inoculant: Si Ba alloy inoculant.
Alloy accessories: Graphite carburizing agent, cryolite particles, etc.
Molten iron melting
The molten iron was melted in 50kg medium frequency induction furnace, and the mass of molten iron was 30kg. The specific adding sequence of raw and auxiliary materials is as follows: firstly, the raw iron block after sand blasting and derusting is put in the furnace for heating. When melting to about 1 / 2, insert the 20 ᦇ steel bar with low carbon content into the molten iron, and add the carburizing agent immediately to effectively absorb the carburizing agent, so as to ensure the sufficient carbon content in the molten iron. After all the raw iron and steel bars are melted and the molten iron temperature rises further, 75 ᦇ ferrosilicon, nickel plate and copper sheet are added successively. Finally, when the furnace charge is completely melted by continuous heating and the temperature of molten iron reaches 1520 ℃ ~ 1550 ℃, slag stripping treatment is started and standing for about 5min, and then the molten iron is ready to be discharged from the furnace.