How to choose and use recarburizer?

The recarburizer is a product of black or gray particles with high carbon content. It is added to the metal smelting furnace to increase the carbon content in the molten iron. On the one hand, it can reduce the oxygen content in the molten iron. On the other hand, it is more important to improve the mechanical properties of smelted metals or castings.

There are many sources and different forms of recarburizers, and the prices vary greatly depending on the processing technology and composition. Traditional smelting methods, such as cupola smelting, use pig iron, recycled materials, scrap titanium alloys, etc. As a metal charge; a new process for the production of synthetic cast iron: use scrap steel as a charge, and use a recarburizer to adjust the carbon equivalent of the molten iron. The latter's production process makes it easier to produce high-quality molten iron, and at the same time, the cost is greatly reduced by using less or replacing pig iron and replacing it with scrap steel. Generally speaking, the use of recarburizers can be smelted (castings) from poor (scrap steel).

Foreign recarburizer technology is becoming more and more mature, while this new technology in my country has only begun to develop in recent years. Many people in the industry do not know enough about the quality of carburetor. Some foundry workers have misunderstandings when choosing a carburetor. For example, the meaning of the fixed carbon content and the carbon content of the recarburizer are confused. The fixed carbon value is calculated based on the moisture, volatile content, ash and sulfur content of the sample, and the carbon content can be obtained through a direct carbon meter. Some recarburizers have high ash content and high carbon content, but their fixed carbon value is not ideal. Some foundry workers unilaterally judge whether the recarburizer is of high quality based on its fixed carbon content and material properties. As a result, they may go astray and lead to improper use of the recarburizer.

1. The choice of recarburizer and its index performance.

In the smelting process, due to improper ingredients or charging, excessive decarburization and other reasons, steel or iron is sometimes mixed together.

When the content does not meet the expected requirements, carbon should be added to the steel or molten iron. Carbon increase generally uses anthracite coal powder, carbon increased pig iron, electric powder, petroleum coke powder, pitch powder, charcoal powder, and coke powder. The requirement of the recarburizer is that the higher the fixed carbon, the better, and the lower the content of harmful impurities such as ash, volatile matter, and sulfur, the better, so as not to pollute the molten iron.

High-quality petroleum coke recarburizer is used for foundry smelting, which has less impurities after high-temperature roasting, which is an important link in the recarburization process. The quality of the recarburizer determines the quality of the molten iron and also determines whether a good graphitization effect can be obtained. In short, the recarburizer plays an important role in reducing the shrinkage of molten iron.

When the scrap steel is smelted in an electric furnace, the graphitized recarburizer is that the carbon atoms of the graphitized recarburizer can change from disorderly arrangement to flake arrangement at high temperature, so that flake graphite becomes graphite nucleation and promotes graphite化. Therefore, we should choose a recarburizer that has been graphitized at high temperatures. The sulfur content is reduced by the overflow of SO2 gas generated during the high-temperature graphitization process. Therefore, the high-quality recarburizer has a low sulfur content, and w(s) is less than 0.05%. At the same time, it is also a concise index to judge whether it is graphitized at high temperature and whether the graphitization is good. If the selected recarburizer is not graphitized at high temperature, the nucleation ability of graphite will be greatly reduced, and the graphitization ability will also be weakened. Even if the same amount of carbon can be achieved, the result is completely different.

The so-called recarburizer means that the carbon content in the molten iron can be effectively increased after being added, so the fixed carbon content of the recarburizer cannot be too low, otherwise, the carbon content to be achieved will require more recarburization than high carbon. This will undoubtedly increase the amount of other unfavorable elements in the recarburizer and make the molten iron less effective. Low sulfur, low nitrogen, and low phosphorus are the key to preventing nitrogen pores in castings, so the lower the nitrogen content of the recarburizer, the better.

The other indicators of the recarburizer such as water, ash, and volatile content are low, and the fixed carbon content is high, so the content of these harmful components will not be very high when the fixed carbon content is high.

According to different smelting methods, furnace types and smelting furnace sizes, it is also important to select the appropriate recarburizer particle size, which can effectively improve the absorption rate and absorption rate of the recarburizer in the molten iron. Since the grain size of the induction furnace is 0.2-5 mm, it is necessary to judge and select according to the details of the specific furnace type and the type of smelting workpiece.

The requirements of converter steelmaking for recarburizers.

When smelting medium and high-carbon steel in a converter, petroleum coke with less impurities is used as a recarburizer. Top-blown converter steelmaking requires high carbon content, low ash content, low volatile content and impurities such as sulfur, phosphorus and nitrogen, dry, clean, and moderate particle size. Fixed carbon WC≥96%, volatile content ≤1.0%, wS≤0.5%, moisture ≤0.5%, particle size 1-5mm; too fine a particle size is easy to burn, too thick will float on the surface of molten steel, not easily absorbed by molten steel.