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Two-phase stainless steel

A duplex stainless steel, quality technology, applied in the field of ferritic and austenitic duplex stainless steel, can solve the problems of insufficient stress corrosion cracking resistance, poor corrosion resistance, and brittle corrosion resistance of welded parts. , to achieve the effect of excellent stress corrosion crack resistance and excellent weldability

Active Publication Date: 2012-05-30
NIPPON STEEL CORP
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  • Claims
  • Application Information

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Problems solved by technology

[0006] However, in the duplex stainless steel described in Patent Document 1, corrosion resistance tends to deteriorate at the welded portion during welding with a large heat input.
In addition, in the duplex stainless steel described in Patent Document 2, intermetallic compounds are precipitated at the welded portion during welding with a large heat input. Insufficient stress corrosion cracking resistance in chloride environments containing corrosive associated gases such as carbon dioxide and hydrogen sulfide when transporting oil and natural gas

Method used

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Examples

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Embodiment

[0082]Duplex stainless steels (inventive examples: test numbers 1 to 11, comparative examples: test numbers 12 to 25) having the chemical compositions shown in Table 1 below were melted in a vacuum melting furnace with a capacity of 150 kg, and cast into steel ingots. Next, each ingot was heated to 1250° C., and forged into a 40-mm-thick plate. Thereafter, each plate material was heated again to 1250° C., and rolled to 15 mm by hot rolling (working temperature 1050° C. or higher). Then, each sheet material after rolling was subjected to a solution heat treatment (treatment of soaking at 1070° C. for 30 minutes, followed by water cooling) to prepare a test steel sheet.

[0083] Table 1

[0084]

[0085] In order to evaluate the weldability of these test steel plates, first, a plate material having a thickness of 12 mm, a width of 100 mm, and a length of 200 mm, with a V-groove of 30 degrees on the long side was prepared by machining. figure 1 A plate 10 produced by mach...

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Abstract

Disclosed is a two-phase stainless steel which has outstanding weldability during high heat input welding and excellent stress corrosion cracking resistance in a chloride environment containing corrosive gas. The two-phase stainless steel satisfies the relationship between formula (1) and formula (2) and has a chemical composition which comprises C: 0.03 mass% or less, Si: 0.2 mass% to 1 mass%, Mn: 5.0 mass% or less, P: 0.040 mass% or less, S: 0.010 mass% or less, sol. Al: 0.040 mass% or less, Ni: 4 mass% to 8 mass%, Cr: 20 mass% to 28 mass%, Mo: 0.5 mass% to 2.0 mass%, Cu: over 2.0 mass% but no more than 4.0 mass%, N: 0.1 mass% to 0.35 mass%, with the remainder being Fe and impurities. In addition, the two-phase stainless steel may contain one or more of V, Ca, Mg, B, and rare earth elements instead of some of the Fe. In formulae (1) and (2), each element symbol represents the content of each element in the steel (unit: mass%). (1) 2.2Cr + 7Mo + 3Cu > 66 (2) Cr + 11Mo + 10Ni < 12 (Cu + 30N).

Description

technical field [0001] The present invention relates to a ferrite-austenite duplex stainless steel with excellent resistance to stress corrosion cracking, and more specifically, to a duplex stainless steel suitable for use as line pipe steel for transporting oil and natural gas. Background technique [0002] In oil and natural gas produced from oil fields and gas fields, carbon dioxide (CO 2 ), hydrogen sulfide (H 2 S) and other corrosive gases. In line pipes that transport such highly corrosive oil and natural gas, general corrosion (general corrosion) that causes stress corrosion cracking (Stress Corrosion Cracking: SCC), sulfide stress cracking (Sulfide Stress Cracking: SSC) and wall thickness reduction ) and so on become a problem. In particular, stress corrosion cracking (SCC) and sulfide stress cracking (SSC) are more serious problems because of their fast growth rate, short time for cracks to penetrate the line pipe, and local occurrence. Therefore, the aforementi...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C22C38/58
CPCC22C38/42C22C38/02C22C38/44C22C38/58C22C38/001C22C1/02
Inventor 天谷尚高部秀树小川和博
Owner NIPPON STEEL CORP
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