Process of producing a duplex stainless steel tube
AssigneeSandvik Intellectual Property AB
InventorsErik Könberg, Daniel Svedberg
Life of this patent
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Abstract
A process of producing a duplex stainless steel tube comprises the steps of: a) producing an ingot or a continuous casted billet of said duplex stainless steel; b) hot extruding the ingot or the billet obtained from step a) into a tube; and c) cold rolling the tube obtained from step b) to a final dimension thereof. The outer diameter D and the wall thickness t of the cold rolled tube is 50-250 mm respectively is 5-25 mm, and, for the cold rolling step, R and Q are set such that the following formula is satisfied: Rp0.2target=416.53+113.26·log Q+4.0479·R+2694.9·C %−82.750·(log Q)2−0.04279·R2−2.2601·log Q·R+16.9·Cr %+26.1·Mo %+83.6·N %+Z (1) wherein Rp0.2target is targeted yield strength and is 800-1100 MPa and 0<Q<3.6.
Claims10
A process of producing a duplex stainless steel tube, the process comprising:
- producing an ingot or a continuous casted billet of the duplex stainless steel;
- hot extruding the produced ingot or the produced billet into a tube;
- selecting a cold reduction (R) and a Q-value (Q) to be used in cold rolling so as to obtain a value for targeted yield strength (Rp0.2target) that is 1000-1100 MPa and a value for Q-value (Q) is 0<Q<3.6;
- and
- cold rolling the hot extruded tube to a final dimension using the selected cold reduction (R) and Q-value (Q),
- wherein the cold reduction (R) is defined as:
- R
- =
- 1
- -
- A
-
-
- 1
- A
-
-
- 0
- where A1 is tube cross section area before cold rolling and A0 is tube cross section area after cold rolling,
- wherein the Q-value (Q) is calculated using the following formula:
- Q=(W0−W1)×(OD0−W0)/W0((OD0−W0)−(OD1−W1))
- where
- W1 is tube wall thickness before cold rolling,
- W0 is tube wall thickness after cold rolling,
- OD1 is outer diameter of tube before cold rolling, and
- OD0 is outer diameter of tube after cold rolling,
- wherein the value for targeted yield strength (Rp0.2target) is calculated using the following formula:
- Rp
-
-
- 0.2
-
-
- target
- =
- 416.53
- +
- 113.26
- ·
- log
-
-
- Q
- +
- 4.0479
- ·
- R
- +
- 2694.9
- ·
- C
-
-
- %
- -
- 82.750
- ·
- (
- log
-
-
- Q
- )
- 2
- -
- 0.04279
- ·
- R
- 2
- -
- 2.2601
- ·
- log
-
-
- Q
- ·
- R
- +
- 16.9
- ·
- Cr
-
-
- %
- +
- 26.1
- ·
- Mo
-
-
- %
- +
- 83.6
- ·
- N
-
-
- %
- ±
- Z
- ,
- wherein Z=65, 50, 20 or 0, and
- wherein the duplex stainless steel has a composition including (in weight %):
- C
- 0-0.3,
- Cr
- 22-26,
- Cu
- 0-0.5,
- Mn
- 0-1.2,
- Mo
- 3.0-4.0,
- N
- 0-0.35,
- Ni
- 5.0-7.0,
- Si
- 0.2-0.8,
- and
- balance Fe and unavoidable impurities.
Dependencies are inferred from the claim text.