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Use of a duplex stainless steel object

a technology of stainless steel and object, applied in the field of objects, can solve problems such as failure, hydrogen induced stress corrosion cracking, impact on the strength and ductility of the duplex,

Inactive Publication Date: 2019-12-12
SANDVIK INTELLECTUAL PROPERTY AB
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present duplex stainless steel has been optimized to have high corrosion resistance, good structure stability, and high strength and toughness. It is easy to manufacture and has good workability. The steel contains no sigma phase which reduces or eliminates problems with corrosion, brittle fracture, and nitride formation during welding. Molybdenum and copper are effective elements in stabilizing the oxide film and improving the stress corrosion cracking-and pitting resistance. The content of molybdenum is between 2.5 to 4.5 wt % and the content of copper is less than or equal to 0.3 wt %。

Problems solved by technology

Even though duplex stainless steels have been a very good choice of material to use in conjunction with cathodic protection, some failures have been encountered over the past years relating to hydrogen induced stress corrosion cracking, also known as HISC.
This failure has an impact on the strength and the ductility of the duplex stainless steels as these materials due to HISC will become more prone to brittle cracking, especially during the application of high loads.

Method used

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  • Use of a duplex stainless steel object

Examples

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examples

[0041]Five different heats with different compositions were melted as 270 kg heats in a high frequency induction furnace and cast to ingots using a 9″ mould. Table 1 shows the compositions of the duplex stainless steels used. Both inventive and comparative examples are shown below. In Table 1, the points E1 and E2 stand for Example 1 and Example 2 of the present disclosure, while the points C1-C3 stands for the comparative examples 1-3.

TABLE 1Chemical composition of different heatsHeatCSPSiMnCrNiMoNCuAlCr + 50NE10.0150.0090.0050.180.4523.796.592.96 0.140.10>0.00330.79E20.0090.0050.0040.230.4223.556.483.960.180.100.00732.55C10.0110.0050.0050.222.1327.027.213.970.230.100.01438.52C20.010.0050.0050.2223.84.733.970.280.100.01737.8C 30.0210.0100.0050.190.427.35.532.92 0.330.10 >0.00343.8

[0042]After casting, the mold was removed and the ingot was held at 1050° C. for 2 hours and then quenched in water. A sample for chemical analysis was taken from each ingot. The chemical analyses were per...

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Abstract

The present disclosure relates to the use of a solution-annealed object comprising a duplex stainless steel, having the following composition in weight % (wt %): C less than or equal to 0.03; Si less than or equal to 0.5; Mn less than or equal to 1.0; Ni 5.0 to 7.0; Cr 22.0 to 26.0; Mo 2.5 to 4.5; N 0.1 to 0.2; P less than or equal to 0.03; S less than or equal to 0.03; Cu less than or equal to 0.3; Al less than or equal to 0.10; the balance being Fe and inevitable impurities; wherein the duplex stainless steel fulfills the equation of Cr+50N≤35; and wherein the duplex stainless steel has a ferrite phase content in the range of from 40% to 60% by volume and an austenite phase content in the range of 40 to 60% by volume; in sea water applications.

Description

TECHNICAL FIELD[0001]The present disclosure relates to a use of an object made of a duplex (ferritic-austenitic) stainless steel in sea water applications wherein this object has a surprisingly good resistance against hydrogen induced stress corrosion (HISC).BACKGROUND ART[0002]Cathodic protection (CP) offshore for prevention of pitting corrosion of duplex and superduplex stainless steels used for subsea components on high temperature wells has been used for more than 20 years. Cathodic protection is defined as an electrochemical protection by decreasing the corrosion potential to a level at which the corrosion rate of the metal is significantly reduced. Thus, it is a technique to reduce corrosion of a metal surface by making that surface the cathode of an electrochemical cell. Hence, the duplex stainless steel will be the cathode and another metal will be the anode (usually Zn).[0003]Even though duplex stainless steels have been a very good choice of material to use in conjunction ...

Claims

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Application Information

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IPC IPC(8): C21D8/02C21D6/00C21D1/26C22C38/44C22C38/42C22C38/06C22C38/04C22C38/02C22C38/00
CPCC21D6/004C22C38/02C21D8/0226C22C38/04C21D8/0236C21D2211/005C21D8/0263C22C38/002C21D2211/001C21D1/26C22C38/001C22C38/44C22C38/42C22C38/06C21D8/0273C21D8/0247C21D9/08C21D9/46C21D9/52C22C38/005C22C38/58
Inventor KIVISÄKK, ULF
Owner SANDVIK INTELLECTUAL PROPERTY AB
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