Method for producing X70 pipeline steel plate with ultrathin specification of 3-8mm and used under ultralow temperature condition by curling furnace

Abstract

The invention relates to a method for producing an X70 pipeline steel plate with the ultrathin specification of 3-8 mm and used under the ultralow temperature condition by a curling furnace. The method comprises the steps of KR molten iron pretreatment, BOF smelting, LF refining, RH vacuum degassing, 150 mm-thick continuous casting billet continuous casting, continuous casting billet covering andslow cooling, continuous casting billet inspection and cleaning, casting billet heating, high-pressure water descaling, rolling, ACC cooling, straightening, steel plate shearing, inspection and warehousing, and the X70M pipeline steel plate with the ultrathin specification of 3-8 mm and used under the ultra-low temperature condition is manufactured. The yield strength of the steel plate is 500-630MPa, the tensile strength is 580-750 MPa, the elongation is larger than or equal to 30%, the yield ratio Rt0.5 / Rm is smaller than or equal to 0.90, and the product can meet the use requirements of X70M-grade pipeline steel under the ultralow temperature conditions that the Charpy impact energy at -80 DEG C is larger than or equal to 100 J and the drop-weight shearing area at -50 DEG C is larger than or equal to 95%.

Description

technical field [0001] The invention relates to a manufacturing method of X70 pipeline steel, in particular to a manufacturing method of the steel plate with an ultra-thin specification of 3-8 mm and under ultra-low temperature conditions. Background technique [0002] Changes in the relationship between energy supply and supply will lead to the construction of new oil and gas pipeline projects, leading to an increase in the market demand for pipeline steel, and at the same time, the requirements for its comprehensive performance are also getting higher and higher. In order to meet the needs of long-distance transportation and storage, a large number of pipeline steels of different steel grades and specifications are required, especially for pipelines in alpine regions, urban pipeline networks, gas compressor stations, gas transmission and distribution stations, storage depots and other facilities. Pipeline steel that meets the requirements of ultra-low temperature service, ...

AI Technical Summary

Problems solved by technology

At present, the existing pipeline steel research mainly focuses on the research and development of thick-gauge pipeline steel for main lines, and rarely involves research on thin-gauge pipeline steel, especially 10mm and below ultra-thin gauge steel. On the one hand, it is due to the difficulty of producing thin-gauge pipeline steel (Difficulty in plate type control) is extremely high. On the other hand, the low-temperature performance of ultra-thin steel plates is difficult to guarantee, but thin-gauge pipeline steel is just an important material for the construction of urban pipeline networks. For such ultra-thin-gauge and ultra-low temperature pipelines At present, steel still relies on coiling furnaces for production, and has extremely high requirements for blanks, coil rolling, controlled rolling and controlled cooling

[0003] At present, some thin-gauge pipeline steel plates are also produced by the process of low-carbon composition + coil rolling, but it is difficult to guarantee the performance requirements of ultra-low temperature. The main reasons are 1), non-acid-resistant thin-gauge low-carbon type pipeline steel plates generally have high Mn content , prone to center segregation; 2), based on cost considerations, acid-resistant pipeline steel does not have high requirements for the control of P and S content in ironmaking-steelmaking-continuous casting, and it is easy to produce center segregation and banded structure; the above production conditions It will greatly affect the internal structure and ultra-low temperature performance of ultra-thin pipeline steel plates

For example, the patent document of patent announcement number CN102230143A discloses a high-strength toughness pipeline steel and its production process based on the production of the steel-steel rolling mill. The various properties can meet the standard requirements, but the standard impact toughness requirement is only -27 ° C impact energy ≥ 40J and 0 ℃ drop hammer shear area ≥ 85%, can not meet the use requirements under the ultra-low temperature environment; as disclosed in the patent announcement number CN103599928A and CN102266866A, a production method for rolling special pipeline steel in a steckel mill and a single-stand furnace The production process of the hot-rolled pipeline steel of the coil rolling mill, neither of these two patents involves elemental composition, the coil rolling + controlled rolling and controlled cooling process does not match the elemental composition, and it is difficult to predict whether the product can meet the requirements of ultra-low temperature conditions in terms of impact toughness and drop weight. service requirements

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