How to detect the quality of carburizer?
Aug 09, 2024
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The quality of the carburizer can be measured by a number of indicators, the following are some of the main criteria for judging:
1. Fixed carbon content
Definition: Fixed carbon is the really useful part of the carburizer, the higher its value, the better the carburizing effect. The fixed carbon content is obtained by calculating the moisture, volatile, ash and sulfur content of the sample.
Standard: In general, the fixed carbon content of high-quality carburizer should be greater than 96%.
2. Ash
Definition: Ash is the residue remaining after the carburizer is burned at high temperatures, and the lower the content, the better.
Impact: The carburizer with high ash content is easy to produce a lot of soot and slag in the smelting process, increase energy consumption, reduce carbon absorption rate, and also extend the operation time, increase power consumption and labor.
Standard: The ash content of graphite carburizer is low, about 0.5% ~ 1.0%; The ash content of calcined anthracite is higher, even if the high quality is not less than 4% to 5%.
3. Sulfur content
Influence: Sulfur is a harmful element that interferes with spheroidization, and the sulfur content should be strictly controlled for the production of the original iron liquid. For gray cast iron, an appropriate amount of sulfur can stabilize pearlite, but too much is harmful.
Standard: The sulfur content of the carburizer for ductile iron should be as low as possible, and the general requirement is S≤0.015%; The sulfur content of gray cast iron carburizer can be slightly higher, but it should also be determined according to specific needs.
4. volatile fractions
Definition: Volatile matter is the gas and water that the carburizer escapes during the heating process, and the lower the content, the better.
Influence: The entry of volatiles into molten steel will increase the gas content in molten steel and increase the risk of porosity defects in castings.
Standard: Properly handled carburizer volatile content should be less than 0.5%.
5. granularity
Influence: The particle size of the carburizer should be selected for different melting methods, furnace types and melting furnace sizes. The carbon absorption rate can be improved by the uniform and moderate particle size carburizer.
Standard: For example, the particle size of the induction furnace is between 0.2 and 6mm; The particle size of steel and other ferrous metals is between 1.4 and 9.5mm; High carbon steel requires low nitrogen and particle size between 0.5 and 5mm.
6. Moisture
Influence: Water brought into the molten steel will increase the amount of hydrogen in the molten steel, which has an adverse effect on the quality of the casting.
Standard: The total moisture index of the carburizer should be as low as possible, the moisture of the carburizer in small bags should be less than 1%, and the moisture of the raw material coke before crushing and packaging should be less than 3%.
7. Nitrogen content
Influence: Nitrogen content has two sides in gray cast iron. The appropriate amount of nitrogen can stabilize pearlite, bend flake graphite and passivate the tip, so as to improve the mechanical properties of gray cast iron. However, excessive nitrogen will cause the casting to produce fissured nitrogen porosity defects.
