Large Diameter and Thin Wall X60 Pipelines

Propelling heat expansion of seamless steel pipes by local induction heating is an effective method for producing large-diameter thin-walled seamless pipes. However, for higher steel grades, subsequent heating and heat treatment in the furnace is required to ensure its good comprehensive mechanical properties, and the heat treatment of large-diameter thin-walled pipes can easily bend and deform the steel pipe, making it impossible to straighten. The article introduces the process of development and production of 406.4mmx7.92mm, X60 pipeline seamless steel pipe by Hongda Company of Henggang Group through local induction heating and thermal expansion . Performance reaches PSL2 level.
Key words : X60 ; large-diameter thin-walled seamless pipe; local induction heating thermal expansion

The role of seamless steel pipes for line pipes as the transportation of oil, gas and other solid substances is increasing. With the improvement of transportation pressure and efficiency, and from the perspective of saving transportation costs and improving pipeline life, large-diameter thin-walled high-grade steel pipelines have no The application of seam pipe is a development direction. It is a low-cost and effective means to produce large-diameter thin-wall seamless pipes by one-time thermal expansion of steel pipes through induction heating and ensuring good comprehensive mechanical properties. This article will introduce the X60 ( API5D pipeline seamless pipe process developed and produced by Hongda Special Steel Company of Henggang Group .
1 X60 pipeline seamless pipe development
406.4mmx 7.92 mm X60 pipeline seamless steel pipe order, the length requirement is 11~12.5m, the standard implements API5L ( 44 .PSL1, but the comprehensive indicators are required to reach PSL2 level.

1 for geometric tolerance requirements ; see Table 2 for performance requirements .
Table 1 Geometric dimension tolerance of seamless steel tubes

serial number	project	tolerance
1	Tube outer diameter	± 0.75%D
2	Pipe end outer diameter	± 1.6mm
3	Tube thickness	-12.5%t ~ +15%t
4	Tube Ovality	W2.0%D
5	Tube end ovality	W1%D
6	Tube Straightness Deviation	Overall length W 0.2% L pipe end W 3 mm/m
7	cut oblique	W 1.6 mm
8	Groove	Pipe end 30 ° ~ 35 ° blunt edge 1.6 ± 0.8mm
9	carbon equivalent	After negotiation W0.50

Table 2 Performance requirements for seamless steel pipes

serial number	project	Required value
1	Yield Strength	415 ~ 565 MPa
2	tensile strength	520 ~ 760 MPa
3	Yield ratio W0.90
4	Elongation (A%	M22%
5	0 Seven horizontal full-scale impact values	Average M40J, individual minimum M30J
6	Hardness W22 HRC
7	Grain size M 6 grade
8	Remanence test	30 Gs max

• Technical Difficulties at present
• The maximum outer diameter of the steel pipe produced by the 340 continuous rolling mill is 368 mm , and the wall thickness is more than 9 mm . For 406.4mmx7.92mm grade X60 seamless pipe. In order to meet the technical indicators required by customers, generally use 325mmx8.8mm hot-rolled capillary tube and then heat-expand to 406.4mmx7.92mm , and then carry out conventional furnace heating, normalizing or quenching and tempering heat treatment to meet the requirements. However, when doing normalizing heat treatment on this kind of large-diameter thin-walled pipe, due to the high heating temperature (the temperature in the furnace is at least 880 ℃ , and the long holding time), the steel pipe is easily deformed and bent seriously, so that the steel pipe cannot be straightened and scrapped. It is guaranteed Good appearance and size control, while ensuring good comprehensive mechanical properties to meet customer requirements for API5L ( 44 X60 pipeline seamless pipe physical performance to PSL2 level , has become a difficult point in development.

1. Table 3 steel composition table

element

C

Si

mn

P

S

Cu

Ni

Cr

M _

Nb

Ti

Al

N

Min

0. 16

0.25

1.45

0.05

0.025

0.01

0.02

<0.02

<0.015

<0.15

<0.10

<0.15

<0.05

<0.01

Max

0.20

0.45

1.55

0.08

0.05

0.06

0.05

Table 4 Statistical Table of Comprehensive Mechanical Properties of Thermal Expansion Finished Tubes

batch number	furnace number	carbon equivalent CE/IIW	tensile strength (MPa)	Yield Strength (MPa)	Yield ratio	(%)	Impact energy ( J )	Hardness ( "#C)
K92L1904)	()3543)-	).44 ).44	5/)	445	o 11	31.5	((42 (25/(22).	().5/9.5/((.)
K92L1902)	((3543) -	).43 ).43	51)	45)	).19	36.5	/5/93/ (4).	1(.)/(2.)/().5
K92L19))	()35432 -	).41 ).46	6))	4/5	)./(	34.5	(34/ (25/22).	().)/((.)/((.5
K92L1903)	()35433 -	).43 ).44	51)	445	).1/	33.)	92/(2)/((2	1.5//.2/6.1
K92L1906)	()35434-	).44 ).44	6()	495	)./(	3/.5	15/15///	().)/((.)/((.)
K94L2112)	()35454-	).45 ).44	6))	45)	).15	33.)	(2)/((6/(()	1.6/6.//1./
K91L2,)/)	()35455-	).46 ).46	53)	42)	).19	4(.5	(14/ (1//(19	5.0/5.5/6.)
K91L2104)	()35456-	).46 ).41	595	415	)./)	33.5	(3)/((1/(25	/.)//.)/9.5
K91L21),)	()35451-	).46 ).41	6))	4/)	)./)	4).)	(5//(12/(14	5.//6.0/6.2
K94L2109)	()3545/-	).45 ).45	515	445	).11	39.5	(2)/(3)/(29	6.)/1.)/6.5
K94L2110)	()35459-	).45 ).45	6))	4/)	)./)	36.)	(13/ (16/(/)	9.)/9.)//.5
K94L2111)	()3546)-	).44 ).44	51)	46)	).11	32.)	()6/()//())	().5/((. 5/((.)
K91L2110)	()3546(-	).43 ).44	59)	45)	).16	39.5	(92/(/)/(14	1.4/1.)/6.9
K91L21)/)	()35462-	).44 ).44	5/)	45)	).11	36.)	(6)/(1)/(64	6.1/6.3/6.5
K91L2109)	()35463-	).43 ).43	5/)	46)	)o 19	31.)	(34/ (36/(14	6.5/6.)/5.5
K9(L25)9)	()35464-	).45 ).45	565	43)	).16	31.5	(5)/(5)/(44	5.0/5.5/6.)
K9(L25)5)	()35465-	).43 ).43	51)	45)	).19	3/.5	9//()4/ ())	9. 5/().5/((.)
K91L2106)	()35466-	).43 ).43	515	43)	).15	34.5	(56/(42/(46	4.1/4.6/4.4
K94L21)/)	()35461-	).43 ).45	51)	445	).1/	4).)	(33/ (36 /(3/	().5/((.)/(2.)
K91L2104)	()3546/-	).44 ).43	6()	49)	)./)	3/.)	9//9)/94	2.1/3.2/3.(
K9(L25)6)	()35415-	).44 ).44	535	43)	)./)	3/.)	(4)/(5//(62	3.1/4.2/3./
K91L2501)	()35416-	).43 ).43	515	455	).19	4).)	2)2/(9)/2()	6.4/5.//6.0
K91L2102)	()3541/C	).43 ).44	59)	46)	).1/	4).)	(2)/((2/((1	1(.5/().)/((.5
K91L2101)	()35419C	).45 ).45	51)	455	)./)	31.5	((//()//(()	().)/((. 5/((.)
K91L2101)	()354/2C	).44 ).45	59)	41)	)./)	36.)	(1)/(3//(52	1.6/1.//1.)
K9(L25)3)	(354/3C).	).45 ).45	59)	465	).19	3/.5	()4/ ()4/ ()6	1(.)/(2.)/(2.)
K9(L25)4)	(354/4C).	).45 ).44	53)	43)	)./(	3/.5	9)/1//16	().3/(). 5/ (). 1
K91L2103)	()35411 -	).44 ).44	515	45)	).1 /	4).)	(44/ (64/(62	5.)/6.)/6.)
K91L2111)	()3546( -	).44 ).44	5/)	465	)./)	3/.5	(5)/(46/(56)	6.0/4.5/6.5

1. 1. Selection of heat expansion mother tube

The parent material of the steel pipe for thermal expansion is L415NB , GB/T9711.2-1997, and complies with the internal control composition index of Henggang Group, and its composition meets API5L ( 44 X60N . The steel composition is based on C-Mn steel, supplemented by See Table 3 for strengthening of microalloying elements and composition control .
actual control of elements in furnace 29 steel is : P < 0.017, S W 0.005, B W 0.0005, £ Sn+Pb+Sb+ As+Bi < 0.050, indicating that the seamless steel pipes of Hengyang Iron and Steel have very good control of harmful elements.

1. 1. Main dimension control of parent pipe

The steel pipe is produced by ① 340 continuous rolling mill, the specification is 325 mm x 8.8 mm x ( 1 400 ~ 1 500 mm (including head and tail), the outer diameter is controlled by ±1% , and the wall thickness is -8% - +10% .
2.3 Blank production process
100 (T Electric Furnace T LF Refining T VD Vacuum T Round Billet Continuous Casting - Cutting - Cooling - Inspection and Storage.

1. Production process of W 34 0 continuous rolling mill

Annular furnace heating — piercing — ① 340MPM continuous rolling T pipe removal T stepping cooling bed T stepping furnace reheating T high pressure water dephosphorization — sizing — cooling bed — straightening.

1. thermal expansion process

Master batch size inspection - head and tail sawing - thermal expansion - straightening - flaw detection - sawing - water pressure - chamfering - final inspection - anti-rust paint - spray labeling, weighing - storage

1. Statistics on comprehensive mechanical properties of thermally expanded finished pipes ( 29 heats of steel)

4 for statistics on comprehensive mechanical properties of thermally expanded finished tubes .
in:

1. Tensile properties According to the standard, take a longitudinal strip sample with a shoulder, with a width of 38.1 mm .
2. Impact test: transverse ( T /0 °C/V8 , like

Dimensions are 10mm x 6.67mm x 55mm .

1. Double samples are taken for each batch of ingredients : CE/IIW=C+Mn/6+ (Cr+Mo+V / 5+ ( Ni+Cu ) /15 .
2. Take the transverse HRC hardness, and the middle interval of the cross section of the steel pipe is 120 . Takes 3 values.

from the statistics in Table 4 that:

1. The yield strength is 420-490 MPa , the tensile strength is 530-610 MPa , the yield strength ratio is 0.75-0.81 , and the elongation after fracture is 33% -40 % , which shows that the finished pipe has good stiffness and strong mixing ratio .
2. 0 C is greater than 100 J in terms of full-scale conversion , indicating that the tube still maintains good toughness after thermal expansion.
3. It can be seen from the table that the maximum hardness ( HRC ) is 12, and the average value does not exceed io ( hrC .
4. The carbon quantity CE/IIWW0.47 meets the requirements of customers and has good welding performance.

In addition, at the site of the final inspection of thermal expansion pipes, two pipe end grooves were randomly drawn in each shift to measure the residual magnetism. The results showed that the maximum value did not exceed 20 Gs . Will increase the magnetic properties of steel.

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