Thin-specification low-yield-ratio high-strength bridge steel and production method thereof

A technology with low yield strength ratio and production method, which is applied in the field of metallurgy, can solve the problems of large influence of thin-gauge steel plate shape, grain recovery and growth, and reduced production efficiency, so as to avoid grain recovery and growth, yield strength, etc. Easier to control and improve production efficiency

Active Publication Date: 2020-11-24
ZHANGJIAGANG HONGCHANG STEEL PLATE CO LTD +2
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Problems solved by technology

Patent CN106811704A discloses a bridge steel with a yield strength of 500 MPa and a low yield ratio bridge steel and its manufacturing method. The invention adopts three-stage controlled rolling, the final rolling temperature of the third stage is 700-830°C, accelerated cooling after rolling, and the start-cooling temperature is 650-800°C. 770°C, the termination temperature of the accelerated cooling of the steel plate is 200-550°C, and then air-cooled, the finishing temperature of the invention is lower, the waiting time is longer, and the production efficiency is reduced; Big
Patent CN107130191A discloses a low yield ratio air-cooled ferritic bainite dual-phase steel plate and its production method. The invention adopts a lower final rolling temperature, reduces the finishing rolling reduction and reduction passes, and rolling The post-air cooling method to obtain ferritic bainite dual-phase steel plate, first of all, a large reduction is adopted at a lower final rolling temperature, which will cause a large loss of equipment, and secondly, the chemical composition Mn 2.02 used in the steel plate above 500MPa grade in the embodiment %, Mo0.37%, V 0.021%, the alloy cost is high, and the impact toughness is poor
Patent CN108624744A discloses a Q500qE bridge steel plate and its production method. In this invention, the steel plate relaxes for 10 to 160 seconds after rolling, and then enters the laminar flow cooling area. This cooling method has a high temperature area after the hot rolling During the heating process, it is easy to cause the crystal grains to grow back, and the production efficiency is low
Patent CN108914007A discloses a low-carbon, low-alloy, low-yield-ratio, high-performance steel plate for bridges and its manufacturing method. The invention adopts a one-stage air cooling plus one-stage water cooling method for cooling. First, this method also has a high-temperature zone waiting process , and the lower yield strength of steel plates in the examples are all lower than 450MPa

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  • Thin-specification low-yield-ratio high-strength bridge steel and production method thereof
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  • Thin-specification low-yield-ratio high-strength bridge steel and production method thereof

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Embodiment 1

[0037] The chemical composition of the steel plate includes by weight percentage: C 0.06%, Si 0.18%, Mn 1.5%, Cr 0.40%, Mo 0.15%, Ni 0.30%, Nb 0.035%, Ti 0.015%, Alt 0.030%, P 0.009% , S0.002%, the rest is Fe and unavoidable impurities.

[0038] In the continuous casting slab heating process, the ingot heating temperature is 1200°C; the rolling process is two-stage controlled rolling, the rough rolling start temperature is 1050°C, the finish rolling start temperature is 910°C, and the finish rolling temperature is 860°C.

[0039] The hot-rolled steel plate is subjected to variable-speed cooling, and the cooling steps are as follows: first, the hot-rolled plate is rapidly cooled to 730° C., and the cooling rate is 18° C. / s. Second, the steel plate is slowly cooled to 670°C at a cooling rate of 2°C / s. Finally, the steel plate is cooled to 300°C at a cooling rate of about 15°C / s.

[0040] The mechanical properties of the steel plate prepared by this composition and process are ...

Embodiment 2

[0042] The chemical composition of the steel plate includes by weight percentage: C 0.06%, Si 0.20%, Mn 1.55%, Cr 0.45%, Mo 0.10%, Ni 0.20%, Nb 0.025%, Ti 0.015%, Alt 0.030%, P 0.010% , S0.001%, the rest is Fe and unavoidable impurities.

[0043] In the continuous casting slab heating process, the ingot heating temperature is 1200°C; the rolling process is two-stage controlled rolling, the rough rolling start temperature is 1060°C, the finish rolling start temperature is 890°C, and the finish rolling temperature is 830°C.

[0044] The hot-rolled steel plate is subjected to variable-speed cooling, and the cooling steps are as follows: first, the hot-rolled plate is rapidly cooled to 700° C., and the cooling rate is 15° C. / s. Second, the steel plate is slowly cooled to 645°C at a cooling rate of 3°C / s. Finally, the steel plate is cooled to 290°C at a cooling rate of about 20°C / s.

[0045] The mechanical properties of the steel plate prepared by this composition and process are...

Embodiment 3

[0047] The chemical composition of the steel plate includes by weight percentage: C 0.07%, Si 0.20%, Mn 1.65%, Cr 0.55%, Mo 0.10%, Ni 0.20%, Nb 0.020%, Ti 0.015%, Alt 0.030%, P 0.008% , S0.002%, the rest is Fe and unavoidable impurities.

[0048] In the continuous casting slab heating process, the steel ingot heating temperature is 1200°C; the rolling process is two-stage controlled rolling, the rough rolling start temperature is 1060°C, the finish rolling start temperature is 930°C, and the finish rolling temperature is 850°C.

[0049] The hot-rolled steel plate is subjected to variable-speed cooling, and the cooling steps are as follows: first, the hot-rolled plate is rapidly cooled to 680° C., and the cooling rate is 18° C. / s. Second, the steel plate is slowly cooled to 620°C at a cooling rate of 4°C / s. Finally, the steel plate is cooled to 250°C at a cooling rate of about 25°C / s.

[0050] The mechanical properties of the steel plate prepared by this composition and proce...

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Abstract

The invention discloses thin-specification low-yield-ratio high-strength bridge steel and a production method thereof. A steel plate adopts a component design of increasing Mn and Cr and reducing Nb and Ti, and chemical components include, by mass, C: 0.06-0.08%, Si: 0.15-0.25%, P: less than or equal to 0.015%, S: less than or equal to 0.008%, Ni: 0.2-0.4%, Mo: 0.1-0.2%, Al: 0.01-0.045%, Mn+Cr: 1.90-2.20%, Nb+Ti: 0.035-0.05% and the balance Fe and other inevitable impurities. By means of a rolling and cooling process of high-temperature finish rolling and after-rolling variable-speed cooling,a ferrite+bainite bidirectional tissue is acquired, and the steel plate has a yield strength 520-570 MPa, a tensile strength 670-760 MPa and a yield ratio 0.69-0.79, and realizes a good balance of a thickness 8-16 mm, a bridge steel strength 500-550 MPa and a yield ratio.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and relates to a thin-gauge, low-yield-ratio, high-strength bridge steel and a production method thereof. Background technique [0002] With the development and construction of long-span bridges. In recent years, high-strength grade Q500qE bridge steel has been successfully applied. In the production of Q500qE steel, one of the difficulties is to control the yield ratio. The microstructure of 235-355MPa grade products is mainly ferrite + pearlite. By controlling the grain size, a suitable yield strength ratio and toughness matching can be achieved. The yield strength ratio is generally relatively low and easy to control; The low-carbon bainite structure is obtained by using the cooling and cooling process. While ensuring the strength, plasticity and toughness, the yield ratio is greatly improved, and it is more difficult to control the lower yield ratio. Especially for thin steel plates (su...

Claims

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Application Information

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IPC IPC(8): C22C38/02C22C38/04C22C38/06C22C38/44C22C38/48C22C38/50C21D8/02C22C33/04
CPCC21D8/0205C21D8/0221C21D8/0247C22C33/04C22C38/02C22C38/04C22C38/06C22C38/44C22C38/48C22C38/50
Inventor 武凤娟杨浩曲锦波
Owner ZHANGJIAGANG HONGCHANG STEEL PLATE CO LTD
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