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steel pipe and steel plate

A steel plate and steel pipe technology, applied in the direction of furnace type, furnace, heat treatment furnace, etc., can solve the problem of insufficient acid resistance, and achieve the effect of excellent HIC resistance and excellent SSC resistance

Active Publication Date: 2021-09-17
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0013] According to the research of the present inventors, the steel plates of Patent Documents 1 to 4 and the steel plate of Non-Patent Document 2 do not control the structure and hardness throughout the entire range of the surface layer. Acid resistance is not sufficient

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0212] The molten steel having the component compositions shown in Tables 1-1 and 1-2 was continuously cast to produce a steel slab having a thickness of 240 mm. Using this slab, the steel sheets shown in Tables 3-1 to 3-4 were produced under the production conditions shown in Tables 2-1 and 2-2. In Table 2-1, in the column of the water cooling stop temperature of the first cooling, "OK" means that the water cooling stop temperature is 500°C or lower after each water cooling of the multi-stage accelerated cooling, and NG means that the cooling stop temperature exceeds 500°C. example of the situation.

[0213]In addition, in the 1st cooling, about the cooling rate, only the cooling rate of the 1st time is described, but the same cooling rate is set after the 2nd time.

[0214] Nos. 1 to 22 and 54 to 56 are invention steel sheets, and No. 23 to 53 are comparative steel sheets.

[0215] Table 1-1

[0216]

[0217] Underlining means outside the scope of the present invention...

Embodiment 2

[0247] The steel sheets shown in Table 3 were cold-worked into a cylindrical shape, the ends of the cylindrical steel sheets were butted together, and three or four electrodes were used. Submerged arc welding (SAW) is carried out under the conditions to manufacture steel pipes. A heat treatment of heating to 400° C. to Ac1 point was performed on the welded portion of a part of the steel pipe.

[0248] From the obtained steel pipe, a full-thickness tensile specimen was prepared in the circumferential direction according to the API5L standard, and after flattening, the yield strength and tensile strength were measured.

[0249] In addition, as the evaluation of SSC resistance, 4-point bending samples were prepared, and in accordance with NACE TM 0177 standard, various hydrogen sulfide partial pressures shown in Table 4 and pH 3.5 solution environment were subjected to 90% experimentation. A 4-point bending test under the yield stress was carried out to investigate the occurrenc...

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Abstract

A steel pipe comprising a base material portion made of a cylindrical steel plate, and a welded portion provided at an abutting portion of the steel plate and extending in the longitudinal direction of the steel plate; the steel plate has a predetermined chemical composition; the The steel plate satisfies ESSP: 1.5 to 3.0, and Ceq: 0.20 to 0.50; the range from the surface of the base metal part to the depth of 1.0 mm, that is, the metal structure of the surface layer part contains more than 80% of the total area ratio selected from granular shellfish. One or more of tempered bainite, acicular ferrite, tempered bainite, and tempered martensite; the highest hardness Hv in the surface layer of the base metal portion max It is below 250Hv; the yield ratio is above 85%.

Description

technical field [0001] The present invention relates to a steel pipe and a steel sheet suitable as a raw material for the steel pipe. Background technique [0002] In recent years, the drilling depth of oil wells and gas wells (hereinafter collectively referred to as "oil wells") tends to be deeper and deeper. Along with this, high strength is required for oil well steel pipes. In addition, since the steel pipes for oil wells are exposed to an acidic harsh environment (high-pressure hydrogen sulfide environment) containing corrosive gases, sulfide stress cracking (Sulfide Stress Corrosion Cracking: Sulfide Stress Cracking, hereinafter sometimes referred to as "SSC".) , Hydrogen Induced Cracking (Hydrogen Induced Cracking, hereinafter sometimes referred to as "HIC".) becomes a problem. In addition, steel pipes used for oil and gas pipelines are also exposed to corrosive gases produced from oil wells. Therefore, sulfide stress cracking resistance (SSC resistance) and hydrog...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/00C22C38/58C21D8/02
CPCC22C38/001C22C38/002C22C38/005C22C38/02C22C38/04C22C38/06C22C38/08C22C38/12C22C38/14C22C38/16C22C38/18C22C38/22C22C38/24C22C38/26C22C38/28C22C38/40C21D1/19C21D8/0205C21D8/0263C21D8/105C21D9/085C21D2211/002C21D2211/005C21D2211/008C22C38/58C22C38/42B23K31/027
Inventor 原卓也筿原康浩
Owner NIPPON STEEL CORP
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