Production method of seamless pipe or tube, and oxidizing gas supply unit
View Patent ↗A production method of a seamless pipe or tube according to the present invention comprises the steps of applying a lubricant containing carbon to a mandrel bar, producing a material pipe or tube with a mandrel mill using the mandrel bar to which the lubricant is applied, and reheating the material pipe or tube in a reheating furnace, wherein when a temperature of the material pipe or tube is 550° C. or higher and 1000° C. or lower in the reheating step, an oxidizing gas is fed into the material pipe or tube.
1. A production method of a seamless pipe or tube comprising the steps of:
heating a billet in a heating furnace,
subjecting the heated billet to piercing and rolling by a piercer to produce the hollow shell,
applying a lubricant containing carbon to a mandrel bar,
subjecting the hollow shell to drawing and rolling in a mandrel mill using the mandrel bar to which the lubricant is applied, to produce a material pipe or tube, and
reheating the material pipe or tube in a reheating furnace,
wherein when a temperature of the material pipe or tube is 550° C. or higher and 1000° C. or lower in the reheating step, an oxidizing gas is fed into the material pipe or tube, a flow rate of the oxidizing gas being determined so as to satisfy the condition of the following equation (1):
Q
≥
7.7394
×
10
12
·
exp
(
-
22748
(
T
∞
+
T
p
)
×
0.5
+
273
)
·
C
in
T
in
+
273
·
1
ρ
c
D
c
·
A
b
·
π
D
p
L
p
,
(
1
)
wherein
Q represents a flow rate of the oxidizing gas [Nl/sec], T ∞ represents a temperature of atmosphere in the reheating furnace [° C.], T p represents a temperature of the material pipe or tube at the time when the material pipe or tube is introduced into the reheating furnace [° C.], C in represents an oxygen content of the oxidizing gas [vol. %], T in represents a temperature of the oxidizing gas [° C.], ρ c represents a particle density of carbon which the lubricant applied to the mandrel bar contains [kg/m 3 ], D c represents a particle diameter of carbon which the lubricant applied to the mandrel bar contains [μm], A b represents an adhesion density of carbon which the lubricant applied to the mandrel bar contains [g/m 2 ], π represents Ludolphian number, Dp represents an inner diameter of the material pipe or tube [m] and L p represents a length of the material pipe or tube [m].
2. An oxidizing gas supply unit used in a reheating step in the production method of a seamless pipe or tube comprising the steps of heating a billet in a heating furnace, subjecting the heated billet to piercing and rolling by a piercer to produce the hollow shell, applying a lubricant containing carbon to a mandrel bar, subjecting the hollow shell to drawing and rolling in a mandrel mill using the mandrel bar to which the lubricant is applied, to produce a material pipe or tube, and reheating the material pipe or tube in a reheating furnace,
wherein
the oxidizing gas supply unit is installed in a walking beam reheating furnace in which the material pipe or tube is placed on one of pockets provided on a moving beam and a fixed beam and successively shifted to the other pocket alternately between two kinds of beams to be carried, and
the oxidizing gas supply unit includes nozzles which are respectively disposed at the sides of a plurality of successive pockets provided from the side, which is closest to the material pipe or tube introducing inlet of the fixed beam, toward the material pipe ore tube carrying out side of the fixed beam and each of which ejects an oxidizing gas toward the inside of the material pipe or tube placed on each pocket of the fixed beam when a temperature of the material pipe or tube is 550° C. or higher and 1000° C. or lower, a flow rate of the oxidizing gas being determined so as to satisfy the condition of the following equation (1):
Q
≥
7.7394
×
10
12
·
exp
(
-
22748
(
T
∞
+
T
p
)
×
0.5
+
273
)
·
C
in
T
in
+
273
·
1
ρ
c
D
c
·
A
b
·
π
D
p
L
p
,
(
1
)
wherein
Q represents a flow rate of the oxidizing gas [Nl/sec], T ∞ represents a temperature of atmosphere in the reheating furnace [° C.], T p represents a temperature of the material pipe or tube at the time when the material pipe or tube is introduced into the reheating furnace [° C.], C in represents an oxygen content of the oxidizing gas [vol. %], T in represents a temperature of the oxidizing gas [° C.], ρ c represents a particle density of carbon which the lubricant applied to the mandrel bar contains [kg/m 3 ], D c represents a particle diameter of carbon which the lubricant applied to the mandrel bar contains [μm], A b represents an adhesion density of carbon which the lubricant applied to the mandrel bar contains [g/m 2 ], π represents Ludolphian number, Dp represents an inner diameter of the material pipe or tube [m] and L p represents a length of the material pipe or tube [m].