Rolling ultra-low carbon bainitic thin-gauge steel plate by medium and heavy plate rolling mill and production method thereof

Abstract

The invention discloses an ultra-low carbon bainite thin gauge steel plate rolled through a heavy and medium plate mill. The ultra-low carbon bainite thin gauge steel plate comprises, by weight, 0.02%-0.08% of C, 0.10%-0.40% of Si, 0.90%-2.00% of Mn, 0.018% of P or less, 0.005% of S or less, 0.40% of Cu or less, 0.0003% of B or less, 0.10%-0.55% of Ni, 0.10%-0.40% of Mo, 0.12%-0.60% of Cr, 0.030%-0.090% of V, 0.010%-0.035% of Nb, 0.005%-0.035% of Ti, 0.060% of Als or less and the balanced Fe and inevitable impurities. A production method comprises the steps of smelting, casting, heating, rolling, slitting, intermediate material heating, rough rolling, finish rolling and cooling control. The ultra-low carbon bainite thin gauge steel plate is reasonable in process, good in product performance and small in unevenness and can be widely applied to bridge U rib structures.

Description

technical field [0001] The invention relates to the field of low-alloy structural steel manufacturing in iron and steel metallurgical materials, in particular to an ultra-low carbon bainitic thin-gauge steel plate rolled by a medium-thick plate rolling mill and a production method thereof. Background technique [0002] In the field of bridge steel, with the increase of the strength level of the steel, the structure type of the steel gradually changes from ferrite + pearlite to ultra-low carbon bainite. The ultra-low carbon bainite structure belongs to a medium-temperature transformation structure, which has the characteristics of high strength, good toughness, and easy welding, and has been gradually promoted in the field of bridge steel. In some bridge projects, it is hoped to use ultra-low carbon bainitic steel on the U rib of the bridge, and the thickness of the steel plate for the U rib is generally 6mm or 8mm. Ultra-low carbon bainitic thin steel sheets are usually rol...

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Problems solved by technology

[0006] Publication No. CN 104264062 A Chinese invention patent "Manufacturing method of hot-rolled thin-gauge high-strength bridge plate", the application discloses a method for rolling thin-gauge steel plates, and the examples in the examples are all 8mm Thickness steel plate, the structure of the steel plate is not ferrite + pearlite type, but acicular ferrite + granular bainite, but it has strict requirements on the P content, the P content is controlled to be ≤0.013%, and it is required to add 0.02 ~0.04% V element, obviously increases smelting cost

In addition, the patent is not clear about the specifications of the rolled billet, but in the embodiment, the thickness of the billet is 220mm. When rolling a steel plate with a thickness of 8mm, the length of the finished steel plate will be more than 30m, so that the temperature of the steel plate in the length direction is uniform. It is difficult to ensure the uniformity, which will affect the uniformity of the mechanical properties of the steel plate

[0007] In the Chinese invention patent with the publication number CN 102671941A "A production process for thin-gauge pipeline steel in a double-stand medium-thick plate rolling mill", the claims do not specify the structure type of the steel plate, but the examples are all X70 pipeline steel. Although the structure type of the steel is not ferrite+pearlite, it is specified in claim 1 that the thickness of the slab is 180mm, which makes the production of steel limited by the thickness of the slab

Moreover, this technology adopts the method of rolling a thick steel billet to the bottom at one time, which will also make the length of the finished steel plate too long, which will make it difficult to ensure temperature uniformity, and then affect the mechanical properties and shape of the steel plate.

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