Nippon Steel & Sumikin Stainless Steel Corporation

Nippon Steel Stainless Steel Corporation

Nippon Steel Corporation

Shinji Tsuge

Yukio Nakamura

Kohji Takano

Yuusuke Oikawa

Hiroshige Inoue

Ryo Matsuhashi

Shigeo Fukumoto

Kazuhiro Suetsugu

Takahiro Osuki

Haruhiko Kajimura

Yoichi Yamamoto

Ryuichi Honma

Yuji Mori

Yukihiro Nishida

Masayuki Tendo

Manabu Mizumoto

Hiroshi Urashima

Yusuke Oikawa

Kazuhiko Ishida

Masatomo Kawa

Kenichiro Kusunoki

Junpei Andoh

Harukiho Kajimura

Yoshinori Tada

Yutaka Tadokoro

Toshinori Ohtsubo

An alloy material is provided which contains elements including, in mass %, C: 0.010 to 0.10%, Si: more than 0.10% to 0.50% or less, Mn: 0.05 to 0.50%, Ni: 34.5 to 37.0%, and Nb: 0.001 to 1.0%, and which satisfies [T≤T-2], [C—Nb/7.7-Ta/15≤0.045], [Nb-7.7C≤0.30], and [Ta-15C≤0.30]. Where, each symbol of an element in the above formulas represents a content (mass %) of the corresponding element, Trepresents a Curie temperature (° C.) of the alloy material, and Trepresents a Curie temperature (° C.) of the alloy material after the alloy material is held at 900° C. for one minute and thereafter is cooled under conditions such that an average cooling rate in a temperature range from 600 to 300° C. is 0.2° C./s.

Alloy material and method for producing same

A high-Ni alloy having excellent weld-hot-cracking resistance includes, in mass %, Cr: 16-30%, Ni: 18-50%, Al: 0.01-1.0%, and Ti: 0.01-1.5%. In a first aspect of the invention, a relationship between number density of TiC precipitates having 1.0 μm or more of equivalent circle diameter and Mg content in steel satisfies formula (1) below. In a second aspect of the invention, S average concentration in oxide- and sulfide-inclusions is 0.70 mass % or more. In a third aspect of the invention, mass ratios of CaO, MgO, and AlOin inclusions, where O or S is detected, satisfy formula (2), the mass ratios being respectively calculated from average concentrations of Ca, Mg and Al in the inclusions, (1) number density of TiC (number of pieces/mm)≤463−9.5×Mg concentration in steel (mass ppm) and (2) [CaO−0.6×MgO] (mass %)/[CaO+MgO+AlO] (mass %)≥0.20.

High nickel alloy excellent in high welding temperature cracking resistance

A duplex stainless steel and method of manufacturing the same, said steel having an amount of Cr in an extraction residue [Cr] of 0.005 to 0.050% and an amount of Nb in an extraction residue [Nb] of 0.001 to 0.080%, the [Nb]/[Cr] ratio being 0.2 or more. By slow cooling down to 800&#xb0; C., then fast cooling down to 600&#xb0; C., it is possible to control the precipitation of chromium nitrides and niobium nitrides, and by making the ratio [Nb]/[Cr] 0.2 or more, it is possible to raise the corrosion resistance. Further, by reducing Mn to less than 2.0% and N to 0.25% or less, then adding a trace amount of Nb, the effect of raising the critical pitting temperature CPT is obtained.

Duplex stainless steel and manufacturing method thereof

This alloying element-saving hot rolled duplex stainless steel material contains, by mass %, C: 0.03% or less, Si: 0.05% to 1.0%, Mn: 0.5% to 7.0%, P: 0.05% or less, S: 0.010% or less, Ni: 0.1% to 5.0%, Cr: 18.0% to 25.0%, N: 0.05% to 0.30% and Al: 0.001% to 0.05%, with a remainder being Fe and inevitable impurities, wherein the alloying element-saving hot rolled duplex stainless steel material is produced by hot rolling, a chromium nitride precipitation temperature TN is in a range of 960&#xb0; C. or lower, a yield strength is 50 MPa or more higher than that of a hot rolled steel material which is subjected to a solution heat treatment, and the alloying element-saving hot rolled duplex stainless steel material is as hot rolled state, and is not subjected to a solution heat treatment. This clad steel plate includes a duplex stainless steel as a cladding material, the duplex stainless steel has the above composition, and the chromium nitride precipitation temperature TN is in a range of 800&#xb0; C. to 970&#xb0; C.

Alloying element-saving hot rolled duplex stainless steel material, clad steel plate having duplex stainless steel as cladding material therefor, and production method for same

A nitrogen-rich two-phase stainless steel that has corrosion resistance equal to that of standard type of two-phase stainless steel and is not susceptible to corrosion in a welding heat-affected part, wherein the austenite phase area ratio is 40-70%, the PI value expressed by formula (1) is 30-38, the NI value expressed by formula (2) is 100-140, and the &#x3b3;pre expressed by formula (3) is 1350-1450. (1) PI=Cr+3.3Mo+16N (2) NI=(Cr+Mo)/N.

Duplex stainless steel superior in corrosion resistance of weld

The present invention provides a lean duplex stainless steel able to suppress the drop in corrosion resistance and toughness of a weld heat affected zone comprising, by mass %, C: 0.06% or less, Si: 0.1 to 1.5%, Mn: 2.0 to 4.0%, P: 0.05% or less, S: 0.005% or less, Cr: 19.0 to 23.0%, Ni: 1.0 to 4.0%, Mo: 1.0% or less, Cu: 0.1 to 3.0%, V: 0.05 to 0.5%, Al: 0.003 to 0.050%, O: 0.007% or less, N: 0.10 to 0.25%, and Ti: 0.05% or less, having a balance of Fe and unavoidable impurities. An Md30 value is 80 or less, an Ni-bal is &#x2212;7.1 to 4, an austenite phase area percentage is 40 to 70%, and a 2&#xd7;Ni+Cu is 3.5 or more: Md30=551&#x2212;462&#xd7;(C+N)&#x2212;9.2&#xd7;Si&#x2212;8.1&#xd7;Mn&#x2212;29&#xd7;(Ni+Cu)&#x2212;13.7&#xd7;Cr&#x2212;18.5&#xd7;Mo&#x2212;68&#xd7;Nb; Ni-bal=(Ni+0.5Mn+0.5Cu+30C+30N)&#x2212;1.1(Cr+1.5Si+Mo+W)+8.2 and N(%)&#x2266;0.37+0.03&#xd7;(Ni-bal).

Lean duplex stainless steel excellent in corrosion resistance and toughness of weld heat affected zone

The present invention provides duplex stainless steel superior in corrosion resistance in a chloride environment and impact properties suitable as a material for pumps for seawater desalination plants, facilities and equipment, and materials for chemical tanks, that is, duplex stainless steel characterized by containing, by mass %, C: 0.06% or less, Si: 0.05 to 3.0%, Mn: 0.1 to 6.0%, P: 0.05% or less, S: 0.010% or less, Ni: 1.0 to 10.0%, Cr: 18 to 30%, Mo: 5.0% or less, Cu: 3.0% or less, N: 0.10 to 0.40%, Al: 0.001 to 0.08% or less, Ti: 0.003 to 0.05%, Mg: 0.0001 to 0.0030%, and O: 0.010% or less, having a product of an activity coefficient fof N, Ti content, and N content f&#xd7;Ti&#xd7;N of 0.00004%or more, and having a product of Ti content and N content Ti&#xd7;N of 0.008%or less.

Duplex stainless steel

A welding wire for austenitic stainless steel welding contains, in percent by mass, C: 0.005 through 0.05%, Si: 0.1 through 1.0%, Mn: 1.0 through 3.5%, Cr: 25.0 through 28.0%, Ni: 16.0 through 23.9%, Mo: 1.6 through 3.0%, Cu: 0.1 through 0.5%, Al: 0.001 through 0.02%, and N: more than 0.30 through 0.50%, limiting O to 0.03% or less, P to 0.03% or less, and S to 0.005% or less, and having a ratio of a Cr equivalent to Ni equivalent (Cr equivalent/Ni equivalent) within a range between 0.85 and 1.2 and a PI value of 35 or more, the remainder being iron and unavoidable impurities.

Austenitic stainless steel welding wire and welding structure

An austenitic stainless steel hot-rolled steel material can be provided which has sea-water resistance and strength superior to conventional steel. Low-temperature toughness can be maintained, which is preferable in a structural member of speedy craft. The steel material can include an austenitic stainless steel hot-rolled steel material which excels in the properties of corrosion resistance, proof stress, and low-temperature toughness. In such austenitic stainless steel hot-rolling steel material, e.g., PI [=Cr+3.3(Mo+0.5W)+16N] ranges from 35 to 40, &#x3b4; cal [=2.9 (Cr+0.3Si+Mo+0.5W)&#x2212;2.6 (Ni+0.3Mn+0.25Cu+35C+20N)&#x2212;18] ranges from &#x2212;6 to +2, and a 0.2% proof stress at room temperature is not less than 550 MPa, Charpy impact value measured using a V-notch test piece at &#x2212;40&#xb0; C. is not less than 100 J/cm2, and the pitting potential measured in a deaerated aqueous solution of 10% NaCl at 50&#xb0; C. (Vc'100) is not less than 500 mV (as it relates to saturated Ag/AgCl).

Austenite-type stainless steel hot-rolling steel material with excellent corrosion resistance, proof-stress, and low-temperature toughness and production method thereof

An austenitic stainless steel hot-rolled steel material can be provided which has sea-water resistance and strength superior to conventional steel. Low-temperature toughness can be maintained, which is preferable in a structural member of speedy craft. The steel material can include an austenitic stainless steel hot-rolled steel material which excels in the properties of corrosion resistance, proof stress, and low-temperature toughness. In such austenitic stainless steel hot-rolling steel material, e.g., PI [=Cr+3.3(Mo+0.5W)+16N] ranges from 35 to 40, &#x3b4; cal [=2.9(Cr+0.3Si+Mo+0.5W)&#x2212;2.6(Ni+0.3Mn+0.25Cu+35C+20N)&#x2212;18] ranges from &#x2212;6 to +2, and a 0.2% proof stress at room temperature is not less than 550 MPa, Charpy impact value measured using a V-notch test piece at &#x2212;40&#xb0; C. is not less than 100 J/cm2, and the pitting potential measured in a deaerated aqueous solution of 10% NaCl at 50&#xb0; C. (Vc'100) is not less than 500 mV (as it relates to saturated Ag/AgCl).

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Tokyo, Japan

Shinji Tsuge