Method of manufacturing sheet steel for thick-walled sour-resistant line pipe of excellent toughness

A manufacturing method and excellent technology, applied in the direction of manufacturing tools, metal rolling, furnace types, etc., can solve problems such as acid resistance deterioration, and achieve the effect of excellent acid resistance

Inactive Publication Date: 2012-01-18
NIPPON STEEL CORP
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] It is known that acid resistance deteriorates due to the formation of MnS extending in the rolling direction or the formation of cluster-like inclusions

Method used

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  • Method of manufacturing sheet steel for thick-walled sour-resistant line pipe of excellent toughness
  • Method of manufacturing sheet steel for thick-walled sour-resistant line pipe of excellent toughness

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Experimental program
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Effect test

Embodiment

[0122] Steel having the chemical composition shown in Table 1 was smelted by secondary refining in a converter, and a 250 mm thick billet was produced by continuous casting. The obtained slabs were hot-rolled under the conditions shown in Table 2 to form steel sheets. The HIC properties of the manufactured steel sheets were evaluated by the NACE test.

[0123] As the conditions of the NACE test, hydrogen sulfide gas is saturated in a solution of 5% NaCl solution + 0.5% acetic acid, pH 2.7, and the immersion time is specified as 96 hours, the presence or absence of cracks is observed, and the HIC fracture rate (CAR) is measured.

[0124] Toughness was evaluated by DWTT test. From the steel plate, according to API, 5L3, ASTM, E436, the plate width direction is taken as the longitudinal direction, and the pressed notch test piece provided with the notch parallel to the plate thickness direction is produced. DWTT was performed at -35°C, and the ductile fracture ratio (SA) was ob...

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Abstract

Sheet steel for line pipe with a wall thickness of not less than 25 mm, and with excellent toughness and sour resistance is manufactured using steel billets that contain C, Si, Mn, Nb, and Ti, while Al, P, and N content is limited. The billets further contain Ca: 0.001-0.004%, there are limitations such that S: not more than 0.0008% and O: not more than 0.0030%, and the Ca, O, and S content meets the condition [Ca](1 - 124[O])/1.25[S] > 3.0. The billets are heated to a heating temperature (T1) in the range of 1000-1150 DEG C that meets the condition T1 >= -7970/(log([Nb] [C]) - 3.31) - 170, and are then rough milled, finish rolled, and subjected to accelerated cooling. The finish rolling therein is performed at a finishing temperature of not less than 800 DEG C and at a 950 DEG C or less reduction ratio of not less than 3 so that the plate thickness is not less than 25 mm, the cooling rate of the accelerated cooling is 10-30 DEG C/s and the stop temperature is 200-500 DEG C. Thus, it is possible to have both sour-resistance properties and drop weight tear properties.

Description

technical field [0001] The present invention relates to hydrogen sulfide (H 2 S) A method of manufacturing a steel plate for line pipes that is excellent in hydrogen-induced cracking resistance, ie, acid resistance, and toughness in an environment. Background technique [0002] Acid resistance is required for steel pipes used in main line pipes for transporting acid oil containing hydrogen sulfide and acid gas, and for steel plates used in piping ancillary equipment. It should be noted that the so-called acid resistance refers to hydrogen-induced cracking resistance (HIC property) in a corrosive environment containing hydrogen sulfide. [0003] It is known that acid resistance is deteriorated by formation of MnS extending in the rolling direction or formation of cluster-like inclusions. In addition, in order to improve the acid resistance in a very severe corrosive environment, a method of controlling the form of MnS by reducing the content of P, S, O, and N and adding Ca ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21D8/02B21B1/38B21B3/00C22C38/00C22C38/14C22C38/54
CPCC21D8/0263C22C38/002C21D9/08C21D8/0226C21D2211/002C22C38/001C22C38/14C22C38/06C21D9/14C22C38/04C22C38/12C22C38/02
Inventor 朝日均村木太郎泽村充原卓也
Owner NIPPON STEEL CORP
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