Hot rolling process for quality carbon structural steel

Abstract

The invention provides a hot rolling process for quality carbon structural steel. Procedures of preheating, heating, soaking, rolling, cooling, finishing and inspection are adopted, the temperature ofa heating section is controlled to be 1060 to 1250 DEG C, and the temperature of a soaking section is controlled to be 1040 to 1240 DEG C, so as to prevent the temperature of the heating section andsoaking section from being too low, resulting in increasing the rolling force and making overload of the rolling mill, and to reduce the risk of equipment damage; the temperature of final rolling is controlled to be 900 to 950 DEG C to make the temperature of final rolling close to a phase transformation point, the transformation rate of undercooled austenite to pearlite with ferrite is accelerated such that the Brinell hardness of the quality carbon structural steel is reduced, and the phenomenon that cracks are prone to occur in the subsequent cold shearing process is improved; and billet composition, cooling method, crimping temperature and other methods are controlled to further reduce the occurrence of edge cracks in the production process of carbon structural steel. The hot rolling process for quality carbon structural steel has low control difficulty, strong operability, simple method, no need for high-cost transformation of controlled cooling process, and low cost, and can be applied to the production of various specifications of quality carbon structural steel.

Description

technical field [0001] The invention relates to the technical field of hot-rolled steel, in particular to a hot-rolled process of high-quality carbon structural steel. Background technique [0002] Carbon steel is an iron-carbon alloy with a mass fraction of carbon between 0.2 and 2.06%, and contains a small amount of Si, Mn, P, S and other impurities. According to its use, carbon steel can be divided into carbon structural steel, carbon Tool steel and carbon cast steel. Carbon structural steel can be divided into ordinary carbon structural steel and high-quality carbon structural steel according to metallurgical quality. Ordinary carbon structural steel has a simple smelting method and contains harmful impurities and non-metallic inclusions. High-quality carbon structural steel refers to carbon steel with a carbon content of less than 0.8%, and contains less sulfur, phosphorus and non-metallic inclusions. The uniformity and surface quality are good, and the mechanical pro...

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Problems solved by technology

In order to give full play to the effect of grain refinement and precipitation strengthening of alloying elements, controlled rolling and controlled cooling technology is widely used in steel mills at present. The cooling bed used in the production line is generally a stepping cooling bed, and the cooling rate is required to be less than 10°C / s to ensure high quality. The transformation of austenite to ferrite + pearlite in carbon structural steel (the microstructure transformation product is ferrite + pearlite above 550°C) is completely completed in the phase transformation zone at this temperature, but the steel billet is required to be rolled in the finish rolling process. After that, it needs to be cooled rapidly to the temperature condition of curling. If the cooling speed is too fast, the supercooled austenite will fail to complete the transformation to ferrite + pearlite, resulting in upper bainite structure. The hardness of the upper bainite structure is high, and the billet Cracks often occur during the subsequent cold shearing, which affects product performance. Therefore, a hot rolling process that can effectively reduce the surface hardness of high-quality carbon structural steel without requiring high-cost modification of the process is suitable for the production of high-quality carbon structural steel of various specifications. very important

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