The selection of carburizer is mainly based on the following key factors:
Chemical composition and performance:
Fixed carbon content: Fixed carbon is the truly useful part of the carburizer. The higher its content, the higher the carburizing efficiency.
Ash content: Ash is the ineffective component in the carburizer. The higher its content, the lower the carburizing efficiency, and it will increase the amount of slag, extend the operation time, and increase power consumption.
Sulfur and nitrogen content: Sulfur is a harmful element that interferes with spheroidization. For the production of ductile iron, the sulfur content should be as low as possible; nitrogen content has two sides in gray cast iron. A moderate amount of nitrogen can stabilize pearlite and improve mechanical properties, but excessive nitrogen will cause nitrogen pore defects in castings.
Volatile matter and moisture: Volatile matter and moisture will increase the gas content in molten iron and increase the risk of pore defects in castings.
Particle size and shape:
Particle size: The appropriate particle size should be selected according to the specific smelting method, furnace type and size of the smelting furnace to increase the absorption speed and absorption rate of the recarburizer by the molten iron.
Shape: Recarburizers with uniform particles and regular shapes are more easily absorbed by the molten iron.
Production process and cost:
Production process: Recarburizers that have been treated with high-temperature graphitization are preferred, because high-temperature graphitization treatment can increase the absorption rate and dissolution rate of recarburizers.
Cost: On the premise of meeting the chemical composition and performance requirements, the cost of the recarburizer should be considered, and products with high cost performance should be selected.
Environmental protection and sustainability:
Environmental performance: Selecting environmentally friendly recarburizers can reduce waste gas emissions and environmental pollution.
Sustainability: Consider whether the production process of the recarburizer has a negative impact on the environment and whether a sustainable production method is adopted.
Specific type selection:
High temperature fully graphitized low sulfur recarburizer: low in S and N, can effectively prevent the generation of nitrogen pores, suitable for high-end castings, absorption rate can reach about 95%.
Medium temperature graphitized recarburizer: cost-effective, suitable for ordinary ductile iron and gray iron smelting process, absorption rate ≥90%.
Semi-graphitized recarburizer: mainly used for gray iron castings, absorption rate ≥90%, suitable for ordinary ductile iron products with less recarburizer added in the smelting ingredients.
High sulfur recarburizer: non-graphitized recarburizer, suitable for gray iron products, absorption rate between 85%-90%, but not suitable for adding to the later stage of molten iron melting.