Understand the porosity in the casting
1. Reduce the amount of scrap steel to reduce the amount of nitrogen brought in. In addition, increasing the carbon equivalent will also reduce the equilibrium nitrogen content.
2. Electric furnace melting is adopted.
3. Increase pouring temperature. As the temperature of molten iron decreases, the nitrogen contained in the molten iron will precipitate and form bubbles of a certain size after aggregation. At this time, if the pouring temperature is increased, the bubbles will escape from the molten iron under the pressure established by themselves. If it is poured at a lower temperature, the bubbles formed cannot escape and stay in the inspection platform and cast iron plate, forming nitrogen pores.
What level of carburizer is selected, the nitrogen content inside is also different. Low nitrogen carburizers should be selected, and the harmful substances inside will also be reduced. The titanium content in molten iron is very low, and it will not consume a lot of nitrogen, which is easy to cause a large number of pores, gas shrinkage and other defects due to the increase of nitrogen content. It is necessary to find a better graphitization carburizer.