Rational use of recarburizers

The production technology of synthetic cast iron is to change the batching method of using pig iron as the main charge component for a long time in the past, instead of using pig iron, or only using a small amount of pig iron, mainly using scrap steel as the main charge, with recarburizers to increase carbon to achieve the specified chemical composition and new dosing methods. Compared with the old method, the new batching method mainly has the following three advantages:
1. Avoids nascent iron heritability
2. The recarburizer increases the extraneous graphite core
3. It is the nitrogen in the scrap steel and more nitrogen brought in from the recarburizer that promotes pearlite and changes the shape of graphite, but in many literatures introducing synthetic cast iron experience, it is basically recommended to use low nitrogen and low sulfur. The reason for the naive graphite-type recarburizer is that the graphite-type recarburizer can directly dissolve carbon and increase the carbonization block, and the recovery rate is high. Therefore, when using the recarburizer, only the graphite form, carbon content, ash content and particle size are paid attention to. Instead of paying attention to the nitrogen content of the recarburizer, the nitrogen in it is often used as the reason for affecting the pore defects of the casting, and the favorable conditions for the use of nitrogen to increase the strength of the casting are rejected, so that the use of nitrogen in the recarburizer is beneficial. It was affirmed in theory, but denied in practice, but in practice, the manufacturer of recarburizers changed not to analyze the nitrogen content, nor did they analyze the nitrogen content in the technical conditions used, so they were increasing the amount of nitrogen. The nitrogen content of the carbon agent and the nitrogen in the produced gray iron castings are in an out of control state. Therefore, although many foundries have also adopted a high proportion of scrap steel and added about 2% of the recarburizer, the resulting As a result, the nitrogen content in some factories' iron castings is too high, resulting in nitrogen holes and the castings are scrapped. However, the performance of castings produced by most factories is still not high, and the body strength is difficult to stably meet the requirements of HT250. Low carbon is still used. equivalent to increase strength.
Suitable gray iron castings use recarburizers, and the nitrogen content should be controlled within a range that can improve the strength of the cast iron without generating nitrogen pores. We control it under a safe upper limit. If the strength of the cast iron is It is not ideal, and when it has not reached the desired height, we can use this nitrogen-containing enhanced inoculant to increase the nitrogen content to achieve the purpose of improving the strength of cast iron. Sulfur content to ensure good cast iron inoculation effect.
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