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Steel tube and steel sheet

A technology of steel plates and steel pipes, applied in the 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: 2020-05-01
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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  • Steel tube and steel sheet
  • Steel tube and steel sheet
  • Steel tube and steel sheet

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0212] Continuous casting was performed on molten steel having the composition shown in Tables 1-1 and 1-2 to produce a 240 mm thick steel slab. Using this slab, 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, the so-called OK means that the water cooling stop temperature after each water cooling of the multi-stage accelerated cooling is all below 500°C, and NG means that there are cases where the cooling stop temperature exceeds 500°C example of the situation.

[0213]In addition, in the 1st cooling, only the 1st cooling rate is described about the cooling rate, but the 2nd and subsequent cooling rates are equivalent.

[0214] No.1-22, 54-56 are invention steel plates, and No.23-53 are comparative steel plates.

[0215] Table 1-1

[0216]

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

[0218] ...

Embodiment 2

[0247] The steel plate shown in Table 3 is cold-worked into a cylindrical shape, and the two ends of the cylindrical steel plate are butted, using 3 electrodes or 4 electrodes, and the online energy is in the range of 2.0kJ / mm to 10kJ / mm according to the plate thickness Under the conditions of submerged arc welding (SAW), to manufacture steel pipes. The heat treatment of heating to 400 degreeC - Ac1 point was given to the welded part of some steel pipes.

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

[0249] In addition, as an evaluation of SSC resistance, a 4-point bending sample was prepared, and in accordance with the NACE TM 0177 standard, various hydrogen sulfide partial pressures shown in Table 4 were carried out in a 90% test environment in a solution environment of pH 3.5. 4-point bendi...

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Abstract

This steel tube has: a base material part that comprises a tubular steel sheet; and a weld part that is provided at a joint part of the steel sheet and extends in the longitudinal direction of the steel sheet. The steel sheet has a prescribed chemical composition. The steel sheet satisfies ESSP=1.5 to 3.0 and Ceq=0.20 to 0.50. The metal structure of a surface layer part that goes to a depth of 1.0mm from the surface of the base material part is, by total area ratio, more than 80% granular bainite, acicular ferrite, tempered bainite, and / or tempered martensite. The surface layer part of the base material part has a maximum hardness Hvmax of at least 250 Hv and a yield ratio of at least 85%.

Description

technical field [0001] The present invention relates to a steel pipe and a steel plate suitable as a raw material for the steel pipe. Background technique [0002] In recent years, there is a tendency that oil wells and gas wells (hereinafter, collectively referred to as "oil wells" may be collectively referred to as "oil wells") are drilled deeper and deeper. Along with this, higher strength is required for steel pipes for oil wells. In addition, since steel pipes for oil wells are exposed to acidic and severe environments containing corrosive gases (high-pressure hydrogen sulfide environments), 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 in oil and gas pipelines are also exposed to corrosive gases produced from oil wells. Therefore, sulfid...

Claims

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Application Information

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Patent Type & Authority Applications(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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