Method for manufacturing round billet of Ni-containing high alloy having improved internal quality

Patent metadata

Field	Value
Publication number	US-10144058-B2
Application number	US-201314364334-A
Country	US
Kind code	B2
Filing date	Aug 8, 2013
Priority date	Aug 9, 2012
Publication date	Dec 4, 2018
Grant date	Dec 4, 2018

Abstract

Provided is a method for manufacturing a round billet of Ni-containing high alloy including steps of continuously casting a molten steel by using a casting mold, thereby obtaining a rectangular billet, and shaping the rectangular billet into round billet by forging/rolling, wherein the casting mold has a shape such that a w/h ratio between long side length (w) and short side length (h) of a cross section of the rectangular billet perpendicular to the casting direction of rectangular billet is 1.0 to 2.0, the chemical composition of molten steel is, by mass %: C: 0.005 to 0.250%, Si: 0.05 to 2.00%, Mn: 0.05 to 3.00%, P: 0.04% or less, S: 0.004% or less, Cu: 0.01 to 3.00%, Cr: 10 to 35%, Ni: 10 to 80%, Mo: 1.5 to 10.0%, Al: 0.001 to 0.300%, N: 0.001 to 0.300%, W: 0.00 to 6.00%, Ti: 0.00 to 2.00%, and the balance: Fe and impurities.

First claim

The invention claimed is:

1. A method for manufacturing a round billet of Ni-containing high alloy, the method consisting essentially of:
continuously casting a molten steel by means of a casting mold, thereby obtaining a rectangular billet;
subjecting the rectangular billet to a soaking prior to any shaping of the rectangular billet, the rectangular billet soaked at 1200 to 1300° C. for a period of time; and
shaping the rectangular billet subjected to the soaking into a round billet with a circular cross section by forging or rolling,
wherein the casting mold has a shape such that a w/h ratio between long side length (w) and short side length (h) of a cross section of the rectangular billet is 1.1 to 2.0, and the cross section is perpendicular to the casting direction of the rectangular billet;
a ratio (A/B) of the cross section of the rectangular billet before the shaping step (A) to the cross section of the round billet with the circular cross section after the shaping step (B) is 2.5 to 12.0;
the period of time the rectangular billet is soaked is no less than 9 hours where the shaping is carried out by forging, and is no less than 24 hours where the shaping is carried out by rolling; and
the chemical composition of the molten steel is:

C: 0.005 to 0.250% by mass,
Si: 0.05 to 2.00% by mass,
Mn: 0.05 to 3.00% by mass,
P: no more than 0.04% by mass,
S: no more than 0.004% by mass,
Cu: 0.01 to 3.00% by mass,
Cr: 10 to 35% by mass,
Ni: 30 to 80% by mass,
Mo: 1.5 to 10.0% by mass,
Al: 0.001 to 0.300% by mass,
N: 0.001 to 0.300% by mass,
W: 0.00 to 6.00% by mass,
Ti: 0.00 to 2.00% by mass, and
the balance: Fe and impurities;
a Mo segregation degree of the round billet is no more than 0.20; and
the Mo segregation degree is a ratio ((c Mo ′−c Mo )/c Mo ) of a difference (c Mo ′−c Mo ) between Mo concentration at the axial center of the round billet (c Mo ′) and Mo concentration in the molten steel (c Mo ) to Mo concentration in the molten steel (c Mo ).

2. The method for manufacturing a round billet of Ni-containing high alloy according to claim 1 ,
wherein the w/h ratio is 1.1 to 1.7.

3. The method for manufacturing a round billet of Ni-containing high alloy according to claim 1 ,
wherein the chemical composition of the molten steel contains:

W: 0.01 to 6.00% by mass.

4. The method for manufacturing a round billet of Ni-containing high alloy according to claim 1 ,
wherein the chemical composition of the molten steel contains:

Ti: 0.05 to 2.00% by mass.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Miyamoto Seiji
• Kagari Takayoshi

Classifications

• B22D11/1213

  for heating or insulating strands · CPC title

• B22D11/002 Primary

  Stainless steels · CPC title

• C21D7/13

  by hot working · CPC title

• C22C19/055

  with the maximum Cr content being at least 20% but less than 30% · CPC title

• C22C30/00

  Alloys containing less than 50% by weight of each constituent · CPC title