Low-yield-ratio structural steel with yield ratio equal to or larger than 550MPa and manufacturing method thereof
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A low-yield-strength ratio and yield-strength technology, applied to low-yield-strength-ratio structural steel with a yield strength of ≥550MPa and its production field, can solve the problems of poor seismic performance, low strength level, and difficult control.
Active Publication Date: 2013-12-04
武汉钢铁有限公司
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[0005] Chinese Patent Application No. 201010599469.3 discloses a 800MPa grade low yield ratio structural steel plate and its production method, the steel whisker contains more Cu , Ni element, the alloy cost is high, and the steel plate must be tempered, which increases the production cost of the process
[0006] Patent No. EP20010930007 discloses "THICK STEEL PLATE BEING EXCELLENT IN CTOD CHARACTERISTIC IN WELDING HEAT AFFECTED ZONE AND HAVING YIELD STRENGTH OF 460MPa OR MORE". Only some of the steel plates produced by direct quenching + tempering have a yield strength above 550MPa, and the yield strength ratio is between 0.84-0.90, which does not have seismic performance and the production process cost is relatively high; the yield strength of steel plates produced by TMCP is all between Below 550MPa, the strength level is low, and its yield ratio is between 0.79-0.88, the seismic performance is poor
The steel plates produced by the above two processes both limit the number of Mg and Al oxide particles per unit area, which is difficult to control and is not conducive to the promotion of production in various metallurgical industries
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[0057] Examples are produced according to the following steps:
[0058] 1) Smelting and continuous casting into billets;
[0059] 2) Heating and keeping the billet warm, the heating temperature is controlled at 1180~1220°C;
[0060] 3) Rough rolling: 1160-1180°C, the total reduction rate is 60-80%, and the end temperature of rough rolling is 1040-1080°C;
[0061] 4) Finish rolling: control the final rolling temperature at 800~860°C, the total reduction rate is 70~80%, and the rolling pass is 6~8;
[0062] 5) Perform relaxation and slow cooling on the steel plate at a cooling rate of 2-5°C / s and a cooling termination temperature of 740-820°C; then perform laminar cooling at a cooling rate of 10-20°C / s and a cooling termination temperature of 300°C -500°C; Finally air cool to room temperature.
[0063] Table 1 The chemical composition of steel in each embodiment of the present invention and comparative examples (wt, %)
[0064]
[0065]Table 1 Comparison of chemical compo...
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Abstract
The invention discloses low-yield-ratio structural steel with a yield ratio equal to or larger than 550MPa. The low-yield-ratio structural steel with the yield ratio equal to or larger than 550MPa comprises, by weight, 0.03-0.10% of C, 0.30-0.60% of Si, 1.40-2.00% of Mn, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 0.10-0.50% of Mo, 0.10-0.40% of Cr, 0.040-0.10% of Nb, 0.008-0.025% of Ti, 0.015-0.055% of Als, 0.0010-0.0080% of Ca, 0.0005-0.0050% of Mg, 10-30*10<-4>% of N, and 5-25*10<-4>% of O. A manufacturing method of the low-yield-ratio structural steel with the yield ratio equal to or larger than 550MPa comprises the steps of carrying out smelting and continuous casting to form a blank, heating the casting blank and carrying out heat insulation on the casting blank, rough rolling, finish rolling, and carrying out relaxation slow cooling on a steel plate. The mechanical properties of the low-yield-ratio structural steel are that RP0.2>=550Mpa, Rm>=700MPa, ductility A>=25%, -20 DEG C KV2>=200J, and RP0.2 / Rm <= 0.80. According to the low-yield-ratio structural steel with the yield ratio equal to or larger than 550MPa and the manufacturing method thereof, preheating is not needed after welding or the preheating temperature is not larger than 50DEG C, heat treatment is not needed after welding, and therefore welding efficiency is greatly improved; the cold and hot machining performance is good, and resistance to large deformation is achieved; cost is low, and the manufacturing processes are simplified.
Description
[0001] technical field [0002] The invention relates to a steel for engineering structure and a production method thereof, in particular to structural steel with a yield strength ≥ 550 MPa and a production method thereof. Background technique [0003] Traditional high-strength steel is generally produced by quenching + tempering. While the strength is increasing, the yield ratio is also increasing. Especially when the tensile strength reaches 600MPa or more, the yield ratio has reached more than 0.90, and the plasticity index is also high. drop to below 20%. Based on safety considerations, bridges, pipelines, and construction steel all have restrictions on the yield strength ratio of steel plates, especially high-rise buildings and public large buildings must have good earthquake resistance, that is, the use of steel The yield ratio (less than 0.85) and plasticity index (above 20%) are strictly limited. Obviously, the higher yield ratio and lower elongation of tradition...
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