A kind of smelting production method of titanium microalloyed low-cost q355b steel plate

Abstract

The invention discloses a smelting production method of a titanium microalloyed low-cost Q355B steel plate. The method comprises the steps of 1, acquiring raw materials, specifically, low-sulfur and low-phosphorus molten iron is slected; 2, smelting through a converter, specifically, deep dephosphorization is carried out by adopting a double slag smelting process; 3, tapping, specifically, any point blowing operations are avoided at the smelting end point, a silicon-manganese alloy is added for deoxidation during the tapping process, and the slag thickness in a molten steel tank is less than or equal to 40 mm after tapping; 4, carrying out argon station treatment, specifically, after molten steel reaches an argon station, argon bottom blowing is kept, an aluminum wire is fed immediately, the Als content in the molten steel is 0.020%-0.040% after the aluminum wire is fed, argon soft blowing is kept for 2-3 minutes, the fine adjustment of the alloy is completed during the period of the argon soft blowing, and then a titanium silicon calcium composite core wire is immediately fed; and 5, continuous casting to carry out protective pouring in the whole process to ensure the Als loss less than or equal to 0.003%. According to the method, titanium microalloying is adopted, and thus, the production cost of Q355B is reduced, and the purity of the molten steel is improved.

Description

technical field [0001] The invention relates to a steel smelting method, in particular to a titanium microalloyed low-cost Q355B steel plate smelting production method, which belongs to the technical field of iron and steel metallurgy. Background technique [0002] Q355B is a low-alloy high-strength structural steel grade upgraded from Q345B to the EU S355 steel grade. It implements the standard GB / T 1591-2018 and is widely used in engineering structures, mining machinery, steel pipes and other fields. It is one of the steel types generally mass-produced by iron and steel enterprises. The national standard has specific restrictions on the weight content of some elements in Q355B steel, in which the C content is not more than 0.24%, Si is not more than 0.55%, Mn is not more than 1.6%, P is not more than 0.035%, S is not more than 0.035%, and Cr is not more than 0.035%. More than 0.3%, Ni not more than 0.3%, Cu not more than 0.4%, N not more than 0.012%. [0003] Whether it ...

AI Technical Summary

Problems solved by technology

[0007] 1) If the process flow of converter smelting-LF refining-continuous casting is used to achieve titanium microalloying, the cost reduction effect is not obvious due to the considerable cost consumption of the LF process

[0008] 2) The temperature of molten steel at the end of smelting is too high, the oxidation of molten steel is too strong, the dephosphorization effect is not good, and it is not conducive to the stability of deoxidation efficiency and alloy yield after the argon station

[0009] 3) Titanium microalloying is realized in the argon station. Due to the strong oxidative properties of molten steel and slag, if aluminum magnesium calcium is added for deoxidation, the consumption will be large, and the deoxidation effect will be unstable. Subsequent blowing of large volume of ladle is required, which will easily cause molten steel secondary. Sub-oxidation has adverse effects on the stability of titanium yield; if the aluminum wire is fed to the deep deoxidation of molten steel, the existence of excess acid-soluble aluminum will inevitably be partially oxidized to form alumina inclusions, resulting in tundish upper nozzles and submerged nozzles. The blockage of the aluminum oxide will affect the smooth flow of production, and the harmfulness can be reduced by special calcium treatment to denature the alumina inclusions, but the silicon-calcium line itself requires a certain cost, and there is loss in the bottom blowing argon mixing process, and the pure mixing It takes more than 8 minutes. The total processing time of the existing technology and practice argon station is more than 20 minutes, which affects the production rhythm and also brings certain temperature fluctuations and cost losses.

[0010] 4) In the process of tapping, large volume bottom blowing of the ladle, etc., the molten steel may contact the outside air and absorb nitrogen, resulting in high nitrogen content in the finished product (≥40ppm)

[0013] 1) The temperature of molten steel at the end of molten steel smelting is too high, the oxidation of molten steel is too strong, and the dephosphorization effect is not good, which is not conducive to the stability of deoxidation efficiency and alloy yield after the argon station. After a series of operations such as blowing, the temperature of molten steel may be lower than the minimum control target, and normal pouring cannot be performed

[0014] 2) Titanium microalloying is realized in the argon station, and there may be problems such as large consumption of deoxidizer, poor deoxidation effect, and seriously low titanium yield in the pre-deoxidation link

[0015] 3) Large volume bottom blowing may cause secondary oxidation of molten steel and lead to high nitrogen content in the finished product. The whole process of soft blowing will take too long to process and reduce production efficiency

[0016] 4) More alumina inclusions in molten steel may cause blockage of the upper nozzle and submerged nozzle during the continuous casting process, and the calcium treatment process will increase the cost and follow-up soft blowing and mixing time

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