A kind of preparation method of graphitized hot-rolled steel plate

Abstract

The invention discloses a preparation method of a graphitizing hot rolled steel plate, which belongs to the technical field of metallurgy. The method mainly comprises the steps of steelmaking, refining, continuous casting, heating, hot continuous rolling, laminar cooling, coiling, steel coil spreading and air cooling, leveling and rolling, graphitizing annealing and the like. In order to increase the graphitizing rate and promote a graphitizing process, a pulsed magnet field is applied in a graphitizing annealing process, the magnetic field intensity is 10000 to 30000 A / m, and the magnetic field frequency is 20 to 100 Hz. Within the graphitizing time of 3 to 6 hours, the graphitizing rate can reach more than 90%, the diameter of graphite is 3 to 6 mum, the graphite is spherical or nearly spherical and is uniformly distributed, and the diameter range of ferrite grains is 20 to 30 mum. According to the structural features, the steel plate, especially the steel plate with high carbon content, has low hardness and high plasticity, therefore, the steel plate has good stamping and forming performance, and the preparation method is favorable for enlarging the application range of medium and high carbon steel plates in a stamping and forming process of components and parts in complex shapes.

Description

technical field [0001] The invention belongs to the technical field of metallurgy and relates to a method for preparing a graphitized hot-rolled steel plate. Background technique [0002] Due to their high strength and hardness, medium and high carbon steel plates are widely used in the fields of machinery manufacturing and automobiles, and the market demand is relatively large. However, due to its poor plasticity, it is generally difficult to form directly, thus limiting its application in the stamping of parts with complex shapes. [0003] In order to improve the formability of medium and high-carbon steel plates, the main method currently used is spheroidizing annealing, such as Chen Jinrong’s paper "40Z steel plate isothermal The spheroidizing annealing process of 40Z medium carbon steel is studied in "Spheroidizing annealing process", and it is pointed out that when the medium carbon steel requires low hardness and high toughness (for cold stamping blanks), isothermal ...

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Problems solved by technology

[0006] Comparing patent 1 and patent 2, there is a large difference in their Si content. Although an excessively high Si content is helpful for graphitization, Si hardens ferrite and it is difficult to have good forming performance. Therefore, the Si content of patent 1 The content is controlled below 0.10%

In order to obtain a good graphitization effect, the graphitization annealing time of patents 1 and 2 is more than tens of hours (according to the embodiment), and the slow graphitization process restricts the precision of medium and high carbon steel plates in the stamping and forming of parts with complex shapes. application, therefore, it is necessary to propose a method to promote the graphitization process

In addition, the graphite rate in patent 1 is not high, the highest is 77% (according to the embodiment); the graphitization rate in patent 2 is relatively high, but the graphitization time is more than 20 hours

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