A kind of yield strength 420mpa grade hot-rolled low-temperature resistant H-section steel and preparation method thereof

Abstract

The invention belongs to the technical field of metallurgy, and in particular, the invention relates to a 420MPa-grade hot-rolled low-temperature-resistant H-beam and a preparation method thereof. The chemical composition of the H-beam is as follows by weight percentage: C: 0.08%-0.10%, Si≤0.2%, Mn: 1.25%-1.45%, V: 0.03%-0.045%, Ti: 0.015%-0.025%, Cr : 0.15%~0.30%, A1s: 0.02%~0.04%, N: 0.007%~0.01%, P≤0.008%, S≤0.005%, O≤0.004%, the rest are Fe and inevitable impurities. Combining the characteristics of thin flanges of small and medium-sized H-beams in rectangular billet rolling, the invention adopts the design of low C content suitable for normalizing rolling and V microalloying composition, adds an appropriate amount of Cr element to control the cooling rate, and avoids the appearance of Widmanrite and the like. Abnormal structure, deteriorate the low temperature impact toughness of steel. As a result, high-strength and toughness hot-rolled H-beams above 420 MPa are stably controlled on the hot-rolled H-beam rolling mill.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and in particular, the invention relates to a 420MPa-grade hot-rolled low-temperature-resistant H-beam and a preparation method thereof. Background technique [0002] With the development of energy mining to complex areas such as extreme cold, there is an urgent need for hot-rolled H-beams with higher comprehensive properties to replace the current low-grade H-beams, which can reduce weight and ensure high reliability. At the same time, in order to adapt to the service environment in complex areas such as extreme cold, higher requirements are put forward for the low-temperature impact toughness, welding performance, and laminar tear resistance of steel, and the demand for hot-rolled H steel with higher strength grades is gradually increasing. [0003] At present, my country's hot-rolled H-beam production enterprises have successively developed H-beams of different grades with a yield strength ...

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Problems solved by technology

[0008] At present, the dephosphorization link in the steelmaking process is generally completed in a converter, but the dephosphorization rate of a single converter is low, and it is difficult to stably control the phosphorus content in molten steel below 0.01%. In order to improve the dephosphorization rate, the currently disclosed In the prior art, two converters are mostly used for deep dephosphorization using a dual process, which can stably control the phosphorus content in molten steel below 0.01%. Phosphorus and decarburization requires a new dephosphorization furnace, and the smelting time is more than 40 minutes longer than that of a single converter, which has the disadvantages of large equipment investment and low production efficiency

Some enterprises use converter double slag method for deep dephosphorization, but because the dephosphorization slag cannot be completely drained once in the converter, the deep dephosphorization rate cannot be guaranteed, and it is difficult to stably control the phosphorus content in molten steel below 0.01%

[0009] Some enterprises use the three dephosphorization processes (desiliconization, desulfurization, and dephosphorization) in the pretreatment of molten iron for dephosphorization. However, since the dephosphorization reaction is a reaction at the slag-steel interface, the reaction equation is shown in the following formula ①, phosphorus and oxygen Elemental reaction product P 2 o 5 Very unstable, P 2 o 5 Only enter the slag and react with CaO to form CaO·P 2 o 5 Only the molten steel in contact with steel slag can undergo dephosphorization reaction (the molten steel in the middle and lower part of the ladle hardly undergoes dephosphorization reaction), so only through long-term stirring to promote the contact between steel slag and molten steel can dephosphorization To the required range (the P content in molten iron is less than 0.03%), the pretreatment efficiency of molten iron is low, and the whole three-removal process needs to be carried out for 150-200 minutes, the production efficiency is low and the temperature drop of molten iron is large, which brings serious adverse effects on the benefits of iron and steel enterprises. Fewer and fewer iron and steel enterprises use three strips for pretreatment of molten iron

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