Process for improving rare-earth high-strength steel impact toughness
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A technology of impact toughness and high-strength steel, applied in the field of heat treatment of medium and thick plates, to increase the grain boundary area, improve the grain boundary, and reduce the effect of temper brittleness
Inactive Publication Date: 2019-08-16
BAOTOU IRON & STEEL GRP
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[0003] As a characteristic resource in the Baotou area, rare earth elements can also significantly improve the impact toughness of steel. With the promotion of capacity reduction and transformation and upgrading of the steel industry in recent years, it will inevitably become an important issue to give full play to the advantages of rare earth resources and improve the market position of rare earth steel. Current studies are mostly limited to elucidating rare earth metamorphic inclusions or emphasizing the individual role of rare earth elements
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Embodiment 1
[0027] Production process of 690MPa high-strength steel plate, the composition and mass percentage of steel are: C=0.14%, Si=0.32%, Mn=1.5%, P=0.013%, S=0.002%, Als=0.023%, Nb=0.044% , V=0.043%, Ti=0.014%, Cr=0.41%, Mo=0.244%, Ce=0.0005ppm;
[0028] The main process steps and parameters are as follows:
[0029] The molten iron must be pretreated before entering the furnace. After the treatment, the sulfur content of the molten iron is ≤0.010%, and the temperature is ≥1250°C. The slag must be cleaned before the molten iron enters the converter. About 85%, scrap about 15%. Converter end point control C-T coordinated tapping, P≤0.012%, S≤0.015%, strict slag blocking and tapping, tapping time 4-7min, adding alloy at 1 / 5 of tapping, and adding alloy at 2 / 5 of tapping, During the tapping process, depending on the oxygen content at the end point, add an appropriate amount of modifier and lime, the oxygen should not be less than 250m, and make appropriate adjustments depending on th...
Embodiment 2
[0040] Production process of 690MPa high-strength steel plate, the composition and mass percentage of steel are: C=0.13, Si=0.31, Mn=1.51, P=0.013, S=0.002, Al=0.023, Nb=0.042, V=0.044, Ti= 0.013, Cr=0.41, Mo=0.247, Ce=0.0003ppm.
[0041] The main process steps and parameters are as follows:
[0042] The molten iron must be pretreated before entering the furnace. After the treatment, the sulfur content of the molten iron is ≤0.010%, and the temperature is ≥1250°C. The slag must be cleaned before the molten iron enters the converter. About 85%, scrap about 15%. Converter end point control C-T coordinated tapping, P≤0.012%, S≤0.015%, strict slag blocking and tapping, tapping time 4-7min, adding alloy at 1 / 5 of tapping, and adding alloy at 2 / 5 of tapping, During the tapping process, depending on the oxygen content at the end point, add an appropriate amount of modifier and lime, the oxygen should not be less than 250m, and make appropriate adjustments depending on the loading a...
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Abstract
The invention discloses a process for improving rare-earth high-strength steel impact toughness. The process comprises the following steps of KR desulfurization slagging off, converter smelting, LF refining, RH refining and rare-earth treating, continuous casting, heating, rolling, accelerated cooling and heat treating. According to the process, aiming at the influence on the microstructure of low-alloy high-strength steel in the case that rare-earth exists, a research shows that rare-earth cerium Ce can improve the forms of inclusions and purify grain boundaries, so that the strength of the grain boundaries is improved, the possibility that cracks extend due to the through defects is reduced, and the impact toughness is improved; and addition, the impact toughness can be improved throughrefining austenite grain boundaries, and meanwhile, adding the rare-earth cerium Ce can enable the ductile-brittle transition temperature of the steel to reduce by about 10 DEG C.
Description
technical field [0001] The invention relates to the technical field of heat treatment of medium and thick plates, in particular to a process for improving the impact toughness of rare earth high-strength steel. Background technique [0002] High-strength structural steel is widely used in coal mining machinery and construction machinery, such as hydraulic supports, port cranes, flatbed transport vehicles, etc., all of which require high strength and good low-temperature impact toughness. Therefore, in recent years, many researchers have devoted themselves to improving the strength and toughness of high-strength steel, improving its impact toughness on the basis of ensuring high strength, so as to obtain high-strength steel plates with better comprehensive mechanical properties. At present, most iron and steel enterprises adopt the quenching and tempering process of off-line quenching + high temperature tempering, and air cool to room temperature after tempering. [0003] As...
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