Thin-strip continuous casting high-hole-expansion steel and manufacturing method thereof

Abstract

The invention discloses thin-strip continuous casting high-hole-expansion steel and a manufacturing method thereof. The thin-strip continuous casting high-hole-expansion steel comprises, by weight, 0.01-0.05% of C, 0.2-0.6% of Si, 0.8-1.5% of Mn, less than or equal to 0.02% of P, less than or equal to 0.005% of S, less than or equal to 0.008% of N, less than 0.001% of Als, less than or equal to 0.0050% of Ca, 0.001-0.006% of B, 0.007-0.020% of total oxygen [O]T and the balance Fe and inevitable impurities, and also contains one or two of 0.1-0.6% of Cu and 0.005-0.04% of Sn, wherein the Mn / S ratio is greater than 250. According to the method, residual elements such as Sn and Cu in scrap steel are used for smelting, and microalloy elements such as B are selectively added; the alkalinity ofslag, the type and melting point of inclusions in the steel, the content of free oxygen in molten steel and the content of acid-soluble aluminum Als are controlled in the smelting process; and a caststrip is cast through double-roller thin-strip continuous casting, the cast strip directly enters a lower closed chamber after being discharged out of crystallization rollers and then enters an onlinerolling mill under the closed condition to be subjected to hot rolling, and strip steel obtained after rolling is cooled in a gas atomization cooling mode and is finally coiled.

Description

technical field [0001] 本发明涉及高扩孔钢制造技术,特别涉及一种薄带连铸高扩孔钢及其制造方法。 Background technique [0002] 在传统钢铁生产流程中,锡(Sn)、铜(Cu)是钢中典型的残余元素或有害元素,炼钢过程中要充分地去除Sn、Cu非常困难而且也是非常昂贵,一旦钢中含有Sn、Cu,基本是无法彻底消除的,只能通过稀释钢水来降低Sn、Cu的含量,这些都造成钢铁产品冶炼成本的升高。 [0003] 近年来,由于废钢的连续循环利用,废钢资源越来越多,电价也持续降低,国内基于废钢的短流程电炉炼钢日益兴起,导致钢中的Sn、Cu等残余元素的含量逐渐升高,钢中的Sn、Cu是易偏析元素,容易富集在晶界导致裂纹等缺陷发生,因此在传统的工艺中Sn、Cu元素的含量是被严格控制的,在普通结构用钢中,对Sn、Cu的含量均有明确的要求:Sn(wt%)≤0.005%;Cu(wt%)≤0.2%。 [0004] 因此,如果能对钢(特别是废钢)中Sn、Cu等残余元素做到合理利用,“化害为利”,将对整个冶金界产生积极的影响;可以实现对现有废钢或低品质劣质矿资源(高锡矿、高铜矿)的有效利用,促进钢的循环利用,降低生产成本,实现钢铁业可持续发展。 [0005] 传统的薄带钢大都是由厚达70-200mm的铸坯经过多道次连续轧制生产出来的,传统热轧工艺流程是:连铸+铸坯再加热保温+粗轧+精轧+冷却+卷取,即首先通过连铸得到厚度为200mm左右的铸坯,对铸坯进行再加热并保温后,再进行粗轧和精轧,得到厚度一般大于2mm的钢带,最后对钢带进行层流冷却和卷取,完成整个热轧生产过程。如果要生产厚度小于1.5mm(含)的钢带,则难度相对较大,通常要对热轧钢带进行后续冷轧以及退火来完成。且工艺流程长、能耗高、机组设备多、基建成本高,导致生产成本较高。 [0006] 薄板坯连铸连轧工艺流程是:连铸+铸坯保温均热+热连轧+冷却+卷取。该工艺与传统工艺的主要区别是:薄板坯工艺的铸坯厚度大大减薄,为50-90mm,由于铸坯薄,铸坯只要经过1~2道次粗轧(铸坯厚度为70-90mm时)或者不需要经过粗轧(铸坯厚度为50mm时),而传统工艺的连铸坯要经过反复多道次轧制,才能减薄到精轧前所需规格;而且薄板坯工艺的铸坯不经冷却,直接进入均热炉进行均热保...

AI Technical Summary

Problems solved by technology

[0011] With the increasing requirements of automobile design on the chassis structure, the forming of parts is more complex, and the requirements for flanging and hole reaming performance of steel plates are further improved. The strength and rigidity of parts can be improved through the shape design of flanging and local reaming of automobile parts, which can To achieve the purpose of reducing the thickness and weight of automobile steel plates, traditional carbon-manganese solid-solution strengthened steel and low-alloy precipitation-strengthened steel structural steel plates are difficult to meet the forming requirements of automobile chassis and cantilever parts, such as traditional 440MPa steel plate carbon-manganese solid-solution strengthened steel and low-alloy The hole expansion rate of precipitation strengthened steel is only between 50% and 70%, thus the high hole expansion steel was born

In the 1990s, the United States and Japan successively developed hot-rolled steel sheets with high hole expansion performance of 440-780MPa, and the hole expansion rate was 70%-131%. They are mainly used in formability, especially those that require good flanging performance. For automobile chassis, wheels and other parts, the hole expansion performance of the steel plate is related to the composition, strength and structure uniformity of the steel plate. Because it contains more precious alloy elements Cr, Nb, Ti, V and Mo, etc. Ferrite / bainite dual phase structure can be obtained under the same conditions, but its cost is higher

At the same time, the contact of high-temperature strip steel with cooling water will cause many problems: first, water spots (rust spots) will be formed on the surface of the strip steel, which will affect the surface quality; second, the cooling water used for laminar flow cooling or spray cooling It is easy to cause uneven local cooling on the surface of the strip, resulting in uneven microstructure inside the strip, resulting in uneven performance of the strip, affecting product quality and hole reaming performance; third, uneven local cooling on the surface of the strip will cause The deterioration of the shape affects the quality of the shape

[0020] Chinese patents CN105154769 and CN106119702 respectively disclose a kind of 780MPa and 980MPa grade hot-rolled high-strength high-reaming steel and its manufacturing method, both of which are in the category of high-strength steel. Multi-microalloying elements are used to strengthen the steel type, and the alloy cost is relatively high; at the same time, its production method adopts traditional continuous casting + traditional hot rolling process to produce

[0021] International patent WO200928515 uses C, Si, Mn to add a small amount of Nb, Ti alloy elements, and can produce reaming steel with a tensile strength above 490MPa. Hot rolling must adopt a two-stage laminar flow cooling method, which can be more accurately simulated in the laboratory. However, in hot rolling production, the strip speed changes greatly during hot rolling, and the temperature of the steel plate in the air cooling section cannot be measured. A two-stage cooling model is used to control laminar cooling, and the steel plate The actual temperature fluctuates greatly, which will easily lead to large fluctuations in the performance of the steel coil head, middle and tail

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