X65 pipeline steel for use in acid condition and its making process

Abstract

The X65 pipeline steel for use in acid condition consists of C 0.02-0.05 wt%, Mn 1.20-1.50 wt%, Si 0.10-0.50 wt%, S not more than 0.0020 wt%, P 0.004-0.012 wt%, Nb 0.05-0.07 wt%, Ti 0.005-0.025 wt%, Mo 0.050-0.195 wt%, Cu not more than 0.35 wt%, Ni not more than 0.35 wt%, N not more than 0.0080 wt%, Ca 0.0015-0.0045 wt% and Ca/S not less than 2.0 except Fe. Its making process includes the following steps: smelting in a converter or an electric furnace; secondary steel making including LF desulfurizing + RH vacuum deairing and Ca treatment; continuous casting; rolling with initial rolling termination temperature of 940-1020 deg.c and finish rolling termination temperature of 780-840 deg.c; and winding at 500-580 deg.c. The X65 pipeline steel has low manufacture cost, high HIC resistance, high dynamic tear resistance and high impact toughness.

Description

technical field [0001] The invention relates to the field of metal materials and plastic processing, in particular to pipeline steel hot-rolled coils and a manufacturing method thereof. Background technique [0002] At present, steel pipes for oil and natural gas transportation in most countries follow the API 5L specification of the American Petroleum Institute, and based on this, supplementary requirements are put forward according to specific pipeline engineering needs. The hot-rolled coil steel or steel plate used to manufacture such welded pipes is commonly referred to as pipeline steel. Pipeline steel is an important material used in long-distance natural gas pipeline engineering. With the adjustment of energy structure and the increase of demand for natural gas, the development of high-pressure gas transmission pipelines has been greatly promoted. The biggest difference between steel for pipelines for transporting natural gas and steel for pipelines for transporting...

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Problems solved by technology

[0004] There is also the "Excellent HIC-resistant HIC-resistant steel pipe hot-rolled strip manufacturing method" disclosed in Japanese Patent Laid-Open No. 6-81034 (compared to patent 2), the composition of the pipeline steel hot-rolled strip with API X52~X70 HIC resistance Formulas and manufacturing methods, which are aimed at the production and manufacture of HIC-resistant pipeline steel strips of X52-X70 steel grades, adopt low-carbon and low-manganese composition design ideas, and the C content in the examples is 0.05-0.08%. In the example, the composition that meets the strength of X65 steel grade (that is, the yield strength ≥ 65000psi, equivalent to 448MPa) may contain 0.03-0.10% V, and the coiling temperature is less than 500°C; in terms of technology, due to the high content of C, it is necessary to eliminate Composition segregation and heating temperature higher than 1250°C will increase energy consumption, increase manufacturing costs and pressure on environmental protection, and easily cause coarse austenite grains during heating, which will affect the toughness and dynamic tear resistance of pipeline steel unfavorable tearing properties; and, it does not mention toughness and dynamic tear resistance

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