Ultralow-carbon bake-hardened steel plate blank and control method of solid solution carbon content thereof

A baking hardening and control method technology, applied in the manufacture of converters, etc., can solve the problems of low solid solution carbon content in one smelting hit rate, shorten the smelting time of vacuum refining furnace, and long smelting time, so as to reduce the vacuum refining time, Improvement of hardening performance and reduction of production cost

Active Publication Date: 2015-09-30
SHOUGANG JINGTANG IRON & STEEL CO LTD
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AI-Extracted Technical Summary

Problems solved by technology

[0004] The embodiment of the present application provides an ultra-low-carbon bake-hardening steel slab and a method for controlling its solid solution carbon content, which solves or partially solves the problem that the production method of ultra-low-carbon bake-hardening steel in the prior art cannot control carbon well. The...
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Abstract

The invention relates to an ultralow-carbon bake-hardened steel plate blank which comprises the following chemical components in percentage by weight: 0.0015-0.0030% of C, at most 0.03% of Si, 0.30-0.60% of Mn, 0.030-0.050% of P, at most 0.015% of S, 0.015-0.060% of Alt, 0.005-0.025% of Nb, at most 0.0050% of N, 0.0005-0.0020% of B and the balance of Fe. The invention also relates to of a control method of the solid solution carbon content of the ultralow-carbon bake-hardened steel, which comprises the following steps: sequentially carrying out pre-desulfurization and slag removal treatment on molten iron to obtain first molten iron with the sulfur content of at most 0.003%; smelting the first molten iron to obtain first molten steel with the carbon content of 0.025-0.050%; refining the first molten steel by a vacuum refining furnace to obtain second molten steel; sending the second molten steel into a continuous casting procedure, injecting into a carbon-free tundish, and casting the molten steel to obtain the ultralow-carbon bake-hardened steel plate blank, wherein the carbon increase amount of the second molten steel in the continuous casting process is at most 0.0003%. The control method shortens the smelting time in the vacuum refining furnace, enhances the production efficiency, and enhances the primary smelting hit rate of the plate blank composition.

Application Domain

Manufacturing converters

Technology Topic

SlagHardened steel +6

Image

  • Ultralow-carbon bake-hardened steel plate blank and control method of solid solution carbon content thereof

Examples

  • Experimental program(2)

Example Embodiment

[0082] Example one
[0083] The method for controlling the solid solution carbon content of ultra-low carbon bake hardening steel provided by the embodiment of the present invention is used to produce bake hardening steel CR180BH. The conditions of molten steel entering the RH furnace are: C content 0.031%; Si content 0.005%; S content 0.007%; P content 0.031%; Mn content 0.02%; temperature 1625°C; oxygen content 650ppm.
[0084] The temperature and oxygen content are appropriate, and there is no need to blow oxygen or add scrap steel. After refining for 3 minutes, ferrophosphorus and ferromanganese were added according to the target P content of 0.036% and the target Mn content of 0.35%. After adjusting the alloy for 4 minutes, sample and analyze the content of P and Mn; obtain P content of 0.037%, Mn content of 0.31%; RH treatment for 15 minutes, fixed oxygen value of 425ppm; after oxygen is fixed, adjust phosphorus iron according to the target value, adjust aluminum particles, and adjust Into the medium carbon ferromanganese 60Kg, the boron-iron alloy 13Kg. 21min when the adjustment is completed.
[0085] After the alloy is adjusted, the vacuum is broken for 7 minutes, and the total processing time is 28 minutes.
[0086] When continuous casting is performed to obtain slabs, the amount of carbon added during continuous casting is controlled by the following method: the carbon content of the working layer of the tundish <1.0% dry material or spread material. Tundish covering agent uses low-carbon high-alkalinity covering agent (C <1.5%), the amount of covering agent added is adjusted accordingly according to the order of the heats: the amount of covering agent added to the topping furnace: 600kg, and the amount of covering agent added to the continuous casting furnace: 30kg.
[0087] The final composition of the slab obtained by the above control method is: C: 0.0023%, Si: 0.01%, Mn: 0.46%, P: 0.04%, S: 0.006%, Alt: 0.043%, Nb: 0.01%, N≤0.0027 %, B: 0.0007%. The solid solution carbon content is 0.001%.

Example Embodiment

[0088] Example two
[0089] The method for controlling the solid solution carbon content of ultra-low carbon bake hardening steel provided by the embodiment of the present invention is used to produce bake hardening steel CR180BH. The conditions of molten steel entering the RH furnace are: C content 0.025%; Si content 0.005%; S content 0.007%; P content 0.031%; Mn content 0.02%; temperature 1646°C; oxygen content 481ppm.
[0090] 30Nm oxygen blowing at the beginning of RH treatment 3 , The deep decarburization process adds 1.9t of low-carbon scrap. After refining for 3 minutes, ferrophosphorus and ferromanganese were added according to the target P content of 0.036% and the target Mn content of 0.35%. After adjusting the alloy for 4 minutes, sample and analyze the content of P and Mn; obtain P content of 0.037%, Mn content of 0.31%; RH treatment for 15 minutes, fixed oxygen value of 425ppm; after oxygen is fixed, adjust phosphorus iron according to the target value, adjust aluminum particles, and adjust Into the medium carbon ferromanganese 60Kg, the boron-iron alloy 13Kg. 21min when the adjustment is completed.
[0091] After the alloy is adjusted, the vacuum is broken for 7 minutes, and the total processing time is 26 minutes.
[0092] When continuous casting is performed to obtain slabs, the amount of carbon added during continuous casting is controlled by the following method: the carbon content of the working layer of the tundish <1.0% dry material or spread material. Tundish covering agent uses low-carbon high-alkalinity covering agent (C <1.5%), the amount of covering agent added is adjusted accordingly according to the order of the heats: the amount of covering agent added to the topping furnace: 600kg, and the amount of covering agent added to the continuous casting furnace: 30kg.
[0093] The final composition of the slab obtained by the above control method is: C: 0.0020%, Si: 0.01%, Mn: 0.47%, P: 0.043%, S: 0.007%, Alt: 0.041%, Nb: 0.009%, N≤0.0018 %, B: 0.0006%. The solid solution carbon content is 0.0009%.
[0094] From the above two embodiments, it can be concluded that the solid solution carbon content of the ultra-low carbon bake hardening steel slab produced by this control method is 0.0009% to 0.0015%. At the same time, through actual production statistics, the ultra-low carbon produced by this method The first hit rate of the solid solution carbon content of the bake hardened steel slab reaches over 80%.
[0095] The method for controlling the solid solution carbon content of the ultra-low-carbon bake-hardened steel slab provided by the present invention firstly adjusts the temperature of the first molten steel, adjusts the micro-carbon ferromanganese, and fixes the decarburization time in the vacuum refining process. Add medium-carbon ferromanganese or high-carbon ferromanganese to increase carbon, and manually weigh to improve the accuracy of the Nb alloy input amount, and obtain a second molten steel with suitable solid solution carbon content and qualified other components. In the continuous casting process, the second molten steel is sent to the continuous casting process and injected into the carbon-free tundish, the composition and amount of the tundish covering agent are controlled, and the second molten steel is cast to obtain an ultra-low carbon baking with a qualified solid solution carbon content Hardened steel slab. Therefore, this control method can improve the control accuracy of solid solution carbon content, increase the one-time smelting hit rate of ultra-low carbon bake hardening steel, and ensure that a large number of ultra-low carbon bake hardening steel slabs produced by this method meet the standard requirements, while reducing Vacuum refining time improves production efficiency and reduces production costs.
[0096] Furthermore, the ultra-low carbon bake hardening steel slab provided by the present invention is obtained by a method for controlling the solid solution carbon content of the ultra-low carbon bake hardening steel slab, and the solid solution carbon content of the slab is in the range of 0.0009 to 0.0015%. The hardening performance of the ultra-low-carbon bake-hardening steel plate made from the steel billet is improved, and it has an ideal yield strength.

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