Steel material for graphitization and graphite steel with excellent machinability and cold forging characteristic

Abstract

The invention relates to a steel material for graphitization and a graphite steel with excellent machinability and cold forging characteristic. The steel material for graphitization includes, by weight, 0.30-0.80% of carbon (C), 2.0-3.0% of silicon (Si), 0.01-1.00% of manganese, 0.001-0.020% of aluminum (Al), 0.01-0.02% of magnesium (Mg), 0.01-0.50% of copper (Cu), less than 0.030% of phosphorus (P), less than 0.030% of sulphur (S), 0.002-0.006% of boron (B), 0.006-0.012% of nitrogen (N), less than 0.005% of oxygen, and the balance Fe and unavoidable impurities.

Description

Technical field [0001] The invention relates to a steel material for graphitization heat treatment and graphite steel with excellent machinability and cold forgeability. Background technique [0002] Generally speaking, mechanical parts such as industrial machinery or automobiles are usually processed into parts with complex shapes through one of the cutting process or cold forging process. However, in order to process the raw material into the final shape, the cutting process has the problem of an increase in the amount of processing, resulting in large parts loss and excessive production costs. On the contrary, compared with the cutting process, the cold forging process has the advantages of less material loss and can be implemented through a simple process. However, when the final shape of the part is complicated, it is difficult to complete a complex shape only through the forging process. Therefore, the cold forging process is processed into a shape close to the final shape...

AI Technical Summary

Problems solved by technology

[0007] However, despite having the above-mentioned advantages, this graphite steel has not been popularized yet.

The main reason is that although the addition of carbon in steel will make the properties of graphite more stable, due to the precipitation of metastable iron carbide, it is difficult to precipitate graphite without additional long-term heat treatment. Decarburization occurs, negatively impacting the performance of the finished product

Moreover, even if graphite particles are precipitated by graphitization heat treatment, if the graphite is roughly precipitated in the steel matrix, the possibility of cracking will be high, resulting in low cold forgeability. When cutting, due to uneven distribution of physical properties during cutting, chip handleability or surface roughness will become poor, and tool life will be shortened, making it difficult to obtain the advantages of graphite steel

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