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Ni-reduced austenite stainless steel

a technology of stainless steel and austenite, which is applied in the field of austenite stainless steel, can solve the problems of confusion in the scrap market, difficulty in fractionation of mn scraps, and inability to use ni content of at least 8% in some applications, and achieve good recyclability, good corrosion resistance, and workability.

Inactive Publication Date: 2009-02-12
NISSHIN STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0019]According to the invention, there is provided an Ni-reduced austenite stainless steel which has a reduced Mn content of at most 2.5% by mass and has good recyclability with no problem of producibility depression to be caused by the surface property thereof, and which has good corrosion resistance, worka

Problems solved by technology

However, as Ni raw material prices are rising up these days, SUS301 having an Ni content of more than 6% and SUS304 having an Ni content of at least 8% could not be used in some applications owing to their costs.
In producing a high-Mn austenite stainless steel having an Mn content of more than 2.5% by mass, harmful Mn oxide fine particles are formed during its steelmaking and refining, and therefore some measures may be often needed from the viewpoint of the environmental protection.
In recycling stainless steel, non-magnetic ones have heretofore been processed as 300-series scraps; however, since high-Mn steel is also non-magnetic, expensive high-Ni scraps and low-Ni and high-Mn scraps are difficult to fractionate, therefore causing some confusion in the scrap market.
Further, the high Mn content may cause surface quality dep

Method used

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  • Ni-reduced austenite stainless steel

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0037]A molten austenite stainless steel having the composition shown in Table 1 was prepared, then continuously cast into a slab, and thereafter hot-rolled at a slab extrusion temperature of 1230° C. to produce a hot-rolled steel strip having a thickness of 3 mm. The hot-rolled steel strip was annealed at 1100° C. for 1 minute for soaking, then cold-rolled to be a cold-rolled steel strip having a thickness of 1 mm, and annealed at 1050° C. for 1 minute for soaking, and pickled to produce an annealed pickled steel strip.

TABLE 1SteelChemical Ingredients (mass %)GroupCodeCSiMnNiCrCuNC + NMd30 *1SFE *2Samples ofA0.0600.551.505.0218.102.500.1010.161 −6.6 29.2theB0.0550.431.625.9217.932.610.0970.152−29.3 33.4InventionC0.0510.611.985.8418.332.650.1230.174−48.4 30.3D0.0520.561.545.0818.211.950.1000.152 9.8 25.7ComparativeE0.0570.563.654.8117.971.480.0980.155 16.1 20.0SamplesF0.0510.562.485.3018.902.900.0950.146−38.4 30.0Sample ofG0.0520.622.325.4918.203.200.0990.151−44.6 32.4theInventionCo...

example 2

[0040]From the annealed pickled steel strips A to E and M produced in Example 1, circular discs were blanked out, having a different outer diameter φ within a range of from 76 to 84 mm at regular intervals of 2 mm, and these were deep-drawn into cups, using a deep-drawing machine. Concretely, using a dice having an inner diameter Dd φ of 43 mm and a corner curvature rd of 4 mm and using a punch having an outer diameter Dp φ of 40 mm and a corner curvature rp of 3 mm, the disc blank was completely deep-drawn under a condition of blank holding pressure of 5 tons, with applying a lubricant oil having a viscosity of 60 mm2 / sec onto the surface of the blank kept in contact with the dice.

[0041]The shaped article was left in air at room temperature for 24 hours, and then this was checked for the presence or absence of cracking at the edge of the shaped cup. The season cracking susceptibility limit drawing ratio of each steel was determined according to the following formula (4):

[Season Cra...

example 3

[0045]The pitting potential of the steels B, H and I produced in Example 1 was measured according to JIS G0577. Concretely, the test solution was aqueous 3.5% NaCl solution and the temperature was 30° C. Using a potentiostat, the potential of each sample was increased from the natural potential at a sweep rate of 0.33 mV / sec, and the potential (mV vs S.C.E) at which the corrosion current in the passive region became at least 100 mA / cm2 was read as the pitting potential. For substituting them for conventional ordinary austenite stainless steel sheets with no Ni reduction therein, the steels are desired to have good corrosion resistance, concretely having the pitting potential of at least 200 mV. The results are shown in Table 4.

TABLE 4PittingSteelCrC + NPotentialGroupCode(mass %)(mass %)Md30(mV vs. SCE)Sample of theB17.930.152−29.3235InventionComparativeH15.820.159−24.1185SampleSample of theI16.030.156−22.9201InventionUnderline: outside the defined scope of the invention.

[0046]As kno...

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Abstract

Provided is an Ni-reduced austenite stainless steel having excellent recyclability with no problem of producibility depression to be caused by the surface property thereof and having good workability, season cracking resistance, corrosion resistance and stress corrosion cracking resistance in point of the material characteristics thereof. The steel comprises C in an amount of more than 0.05% (by mass) and within a range of from 0.15 to 0.3% as (C+N), Si in an amount of at most 1%, Mn in an amount of from 0.5 to 2.5%, Ni in an amount of from 3 to 6%, Cr in an amount of from more than 16 to 25% and Cu in an amount of from 0.8 to 4%, and has Md30 of the following formula (1) of from −50 to 10 and SFE of the following formula (2) of at least 5:
Md30=551−462(C+N)−9.2Si−8.1Mn−29(Ni+Cu)−13.7Cr   (1),
SFE=2.2Ni+6Cu−1.1Cr−13Si−1.2Mn+32   (2).

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to austenite stainless steel in which the content of Ni indispensable to austenite stainless steel is reduced to the minimum quantity thereof and which is excellent in the workability, the season cracking resistance, the corrosion resistance and the stress corrosion cracking resistance, not detracting from the surface quality thereof.[0003]2. Background Art[0004]Austenite stainless steel such as typically SUS304 has been much used in various fields of western tableware and pans, kitchen utensils, building materials, household electrical appliances and others, as having excellent workability and corrosion resistance. In these applications, not only workability and corrosion resistance but also designability is often required; and the nickel silver color peculiar to stainless steel is essential for industrial product materials in point of both interior and exterior aspects.[0005]However, as N...

Claims

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Application Information

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IPC IPC(8): C22C38/42C22C38/02C22C38/58
CPCC22C38/001C22C38/58C22C38/42C22C38/02
Inventor SUZUKI, SATOSHIHIDESHIMA, YASUTOSHISUETUGU, TERUHIKOWATANABE, TOMOHISA
Owner NISSHIN STEEL CO LTD
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