A kind of steel plate for low crack susceptibility pipe fittings used under low temperature conditions and its manufacturing method

Abstract

The invention relates to a low-crack sensitive pipe fitting steel plate used under a low temperature condition. The mechanical component (wt%) of the steel plate comprises 0.03-0.08 of C, 0.2-0.35 of Si, 0.9-1.6 of Mn, 0.02-0.04 of Al, 0.01-0.07 of Nb, 0.01-0.07 of V, 0.01-0.02 of Ti, less than or equal to 0.15% of Nb+V+Ti, less than or equal to 0.5 of Cr, less than or equal to 0.5 of Ni, less than or equal to 0.4 of Mo, less than or equal to 0.3 of Cu, less than or equal to 0.18 of Pcm and the balance Fe and inevitable impurities. The method sequentially comprises the steps of KR molten iron pretreatment, converter smelting, LF refining, RH vacuum degassing, 370-450 mm thickness continuous casting blank continuous casting, continuous casting blank capping slow cooling, continuous casting blank checking and cleaning, casting blank heating, high-pressure water descaling, rolling, cooling, straightening and offline tempering. The steel plate structure is controlled to be a single tempered bainite structure, the grain size is within the range of 3-6 microns, and the steel plate has very excellent low-temperature toughness and can meet the use requirements of X70 pipeline steel underthe low-temperature condition of -60 DEG C.

Description

technical field [0001] The invention belongs to the technical field of metallurgy and relates to a steel plate for low crack sensitivity pipe fittings used under low temperature conditions and a manufacturing method. Background technique [0002] In long-distance pipeline engineering projects, in order to meet the requirements of long-distance transmission, it is necessary to build many compressor stations, gas transmission and distribution stations and other facilities. Therefore, a large amount of steel for station pipe fittings is required. In some alpine regions, especially for station pipe fittings used in low-temperature environments such as the China-Russia East Line, the limit temperature of the station is between -30°C and -50°C. On the basis of conventional pipe fitting steel, more Good low temperature performance. At the same time, during the entire manufacturing process of pipe fittings, the weldability of materials has a great influence on the low-temperature p...

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Problems solved by technology

Traditional steel for pipe fittings is usually designed with medium-high carbon + alloy composition to improve hardenability to ensure the performance requirements after heat treatment. For example, patent announcement number CN102011064 proposes a X80 grade low-temperature pipe fitting steel and its preparation and application, which can meet -46 The use of steel for pipe fittings with a thickness of 30-70mm under the condition of ℃, the range of C is 0.12-0.16%, which does not belong to the easily weldable steel, and the weldability of the material is obviously deteriorated

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