CN102181796A - Production method of X70 hot-rolled medium plate for submerged pipeline - Google Patents

Abstract

The invention provides a production method of an X70 hot-rolled medium plate for a submerged pipeline. The medium plate comprises the following components in percentage by weight: 0.035 to 0.07 percent of C, 0.10 to 0.35 percent of Si, 1.40 to 1.85 percent of Mn, less than or equal to 0.010 percent of P, less than or equal to 0.0035 percent of S, 0.01 to 0.06 percent of Alt, 0.035 to 0.07 percent of Nb, 0.008 to 0.020 percent of Ti, 0.10 to 0.30 percent of Mo, 0.10 to 0.25 percent of Ni, 0.10 to 0.25 percent of Cr, 0.10 to 0.25 percent of Cu and the balance of Fe and inevitable impurity elements. In the steel plate manufacturing process, the effects of the alloy elements and the potential of an excavation thermo-mechanical control process are fully exerted through an optimized blank type design, a strict heating schedule and a reinforced thermo-mechanical control process in coordination with an appropriate amount of Ni, Cr and Cu alloy elements, so that an organization form based on a uniform fine acicular ferrite is obtained on a steel plate with the whole wall thickness, and the medium plate has relatively high horizontal and longitudinal tensile strength and high low-temperature toughness, and completely meets the requirements of high performance of steel for a deepwater submerged pipeline.

Description

A kind of subsea pipeline production method of X70 hot rolled steel plate

Technical field

The invention belongs to the low-carbon micro steel-alloy production technical field, particularly relate to a kind of subsea pipeline production method, be applicable to the production of subsea pipeline engineering that transverse and longitudinal tensile strength and low-temperature flexibility are had relatively high expectations with 25～35mmX70 hot rolled steel plate with the X70 hot rolled steel plate.

Background technology

Along with the high speed development of global economy, the oil and gas demand has occurred for the situation that need not ask, and this has greatly promoted the exploitation of limit and offshore oil and gas resource and the construction of subsea pipeline, and subsea pipeline shows especially day by day with the importance of steel.

Subsea pipeline is on active service in deep-sea part and abominable ocean environment, and pipeline bears deep-sea high pressure and serious marine corrosion; And because the complicacy of seabed physical features and the polytropy of seabed ocean current, pipeline beard and hair in process of deployment is given birth to the flexural deformation of various different angles, require subsea pipeline to have higher cleanliness factor, higher low-temperature flexibility, higher transverse and longitudinal intensity and lower steel plate anisotropy, so subsea pipeline has been proposed than terrestrial pipeline with the tighter higher specification of quality of steel with steel with steel.Require very high with big wall thickness X70 pipe line steel to transverse and longitudinal strength property and low-temperature flexibility as South China Sea subsea pipeline engineering, and the steel plate specification is thick, so development difficulty is very big, high-strong toughness index qualification rate is on the low side, therefore bring bigger financial loss to manufacturer, brought huge hidden danger for equally the security of pipe laying engineering and pipeline operation.

At present, high-grade subsea pipeline becomes the focus in metallurgical and investigation of materials field gradually with steel, from the patented technology of being applied for and the document delivered, product has essential difference at aspects such as thickness specification, transverse and longitudinal tensile strength, the toughness reguirements of dropping hammer, composition design and rolling methods with this patent.Patent 200710052601.7 discloses " a kind of steel plate and rolling method thereof that is used to make subsea pipeline ", has proposed the production method of subsea pipeline with the X65 hot-rolled sheet coil, with the big wall thickness X70 of this patent hot rolled steel plate production method essential difference is arranged; The pertinent literature exploitation and the application of steel " subsea pipeline with " (welded tube .2006,29 (5): 36-39), only introduced the physicochemical property of Baosteel subsea pipeline, but do not carried out fully open in addition to the chemical ingredients and the production method thereof of steel plate with the X65 grade steel plate.

The present invention relates to subsea pipeline with 25～35mmX70 hot rolled steel plate, steel plate should satisfy the high-intensity high-tenacity requirement, also will guarantee lower carbon content and carbon equivalent, and good welding adaptability will be arranged.Take all factors into consideration the requirement of each side, the present invention adopts low C composition, utilizes Nb, Ti element crystal grain thinning, adopts alloying elements such as Mo, Cr, Cu to cooperate, and improves the hardening capacity of steel plate, guarantees transverse and longitudinal intensity, and adding the Ni element simultaneously improves the steel plate low-temperature flexibility; And adopt the cooling controlling and rolling controlling process technology, improve the comprehensive mechanical property of steel plate.

Summary of the invention

The object of the present invention is to provide the production method of a kind of subsea pipeline with the X70 hot rolled steel plate, by rational alloying element coupling, the base type design of optimizing, the strict heating cycle and the cooling controlling and rolling controlling process of reinforcement, solved big wall thickness X70 subsea pipeline has good obdurability coupling with steel a difficult problem effectively, guaranteed that steel plate transverse and longitudinal intensity index and low-temperature flexibility index satisfy standard-required simultaneously, thereby reduced the financial loss of manufacturer, improved the security of pipe laying engineering and pipeline operation, the development of China's subsea pipeline engineering project has been significant.

Subsea pipeline provided by the invention with the chemical ingredients (weight %) of X70 hot rolled steel plate is: C:0.035～0.07%, Si:0.10～0.35%, Mn:1.40～1.85%, P :≤0.010%, S :≤0.0030%, Alt:0.01～0.06%, Nb:0.035～0.070%, Ti:0.008～0.020%, Mo:0.10～0.30%, Ni:0.10～0.25%, Cr:0.10～0.25%, Cu:0.10～0.25%, surplus are Fe and inevitable impurity element; Its production technique is specific as follows:

(1) base type design: require to produce steel plate compression ratio 〉=10, select the thick steel billet of 400mm for use;

(2) heating cycle: steel billet is heated to 1120～1210 ℃, guarantees steel billet soaking time 1.5～2.5 hours, improve the homogeneity that heats on the steel billet thickness direction;

(3) rolling technology: rolling rolling in two stages, i.e. austenite recrystallization district rolling (roughing) and austenite non-recrystallization rolling (finish rolling); At rough rolling step, the rolling temperature interval is 980～1070 ℃, behind the control steel billet broadening before treat temperature total deformation rate between 60%～75%, need guarantee simultaneously behind the broadening to treating that the axial rolling pass deformation rate before the temperature rises gradually, and the single pass deformation rate is controlled between 15.5%～30%, will guarantee that especially last 3 pass deformation rates all 〉=23%; Intermediate blank is treated temperature thickness/finished product thickness 〉=3.3; In the finish rolling stage, start rolling temperature is 850～920 ℃, and stopping rolling temperature is 760～840 ℃, and control steel billet total deformation rate is between 70%～80%;

(4) water-cooling process: with the speed cooling of 12～28 ℃/s, cooling termination temperature is 455～570 ℃ after the hot rolling.

Adopt above-mentioned chemical ingredients steel billet and production technique, producing steel plate thickness specification is 25～35mm, and the steel plate microtexture is based on even tiny acicular ferrite, and grain fineness number is 12～13 grades.

The invention has the advantages that: the present invention is at lower C content 0.035～0.07%, on the composition system basis of an amount of Nb and Mo microalloying, be aided with an amount of Ni, Cr, the Cu alloying element cooperates, by the base molded dimension design of optimizing, the strict heating cycle and the cooling controlling and rolling controlling process of reinforcement, give full play to the potentiality of alloy element action and excavation cooling controlling and rolling controlling process, making and obtaining even tiny acicular ferrite on the steel plate total wall thickness is main tissue morphology, improve steel plate transverse and longitudinal intensity and low-temperature flexibility, the steel plate of producing significantly improves than the comprehensive mechanical property of ad eundem terrestrial pipeline with steel, has improved the security of subsea pipeline laying project and pipeline operation widely.Produce big wall thickness X70 subsea pipeline according to the described technical scheme of this patent and can reach following level with rigidity:

(1) tensile property

A) horizontal: yield strength is more than 515MPa, and tensile strength is more than 605MPa, and yield tensile ratio is below 0.88;

B) vertical: yield strength is more than 500MPa, and tensile strength is more than 620MPa, and yield tensile ratio is below 0.83;

(2) low-temperature flexibility

A) impact property: 10 * 10 * 55mm sample transverse and longitudinal v-notch Charpy-V impact power is all more than 370J in the time of-20 ℃, the transverse and longitudinal Charpy-V impact power is all more than 325J in the time of-40 ℃, the transverse and longitudinal Charpy-V impact power is all more than 240J in the time of-60 ℃, 50%FATT＜-60 ℃;

B) block hammer performance: DWTT monodrome 〉=60% during DWTT monodrome during-10 ℃ of transverse and longitudinal Drop-Weight Tear Test (DWTT) (DWTT) shear area monodrome 〉=87% ,-20 ℃ 〉=82% ,-40 ℃, 50%FATT＜-50 ℃;

(3) cold-bending property: horizontal clod wash d=2a (d is a bending diameter, and a is a steel plate thickness), 180 °, stretching face is intact.

Specific implementation method

Embodiment 1

Subsea pipeline utilizes the thick steel billet of 400mm to produce thickness on 4300mm two-shipper frame Wide and Thick Slab production line and is the 25mm steel plate with the production method of X70 hot rolled steel plate according to the present invention.Its steel billet chemical ingredients is as shown in table 1, and cooling controlling and rolling controlling process is as shown in table 2, and strength property is as shown in table 3, and the impelling strength of series of temperatures lower steel plate is as shown in table 4.

The chemical ingredients of table 1 embodiment 1 (weight, %)

C	Si	Mn	P	S	Alt	Nb	Ti	Mo	Ni	Cr	Cu
												0.062	0.19	1.53	0.009	0.0020	0.042	0.046	0.018	0.17	0.18	0.18	0.23

Table 2 process system

The strength property of table 3 steel plate

The toughness of table 4 series of temperatures lower steel plate

Embodiment 2

Subsea pipeline utilizes the thick steel billet of 400mm to produce thickness on 4300mm two-shipper frame Wide and Thick Slab production line and is the 30mm steel plate with the production method of X70 hot rolled steel plate according to the present invention.Its steel billet chemical ingredients is as shown in table 5, and cooling controlling and rolling controlling process is as shown in table 6, and strength property is as shown in table 7, and the impelling strength of series of temperatures lower steel plate is as shown in table 8.

The chemical ingredients of table 5 embodiment 2 (weight, %)

C	Si	Mn	P	S	Alt	Nb	Ti	Mo	Ni	Cr	Cu
												0.054	0.22	1.65	0.008	0.0018	0.037	0.053	0.012	0.23	0.21	0.20	0.22

Table 6 process system

The strength property of table 7 steel plate

The toughness of table 8 series of temperatures lower steel plate

Embodiment 3

Subsea pipeline utilizes the thick steel billet of 400mm to produce thickness on 4300mm two-shipper frame Wide and Thick Slab production line and is the 35mm steel plate with the production method of X70 hot rolled steel plate according to the present invention.Its steel billet chemical ingredients is as shown in table 9, and cooling controlling and rolling controlling process is as shown in table 10, and strength property is as shown in table 11, and the impelling strength of series of temperatures lower steel plate is as shown in table 12.

The chemical ingredients of table 9 embodiment 3 (weight, %)

C	Si	Mn	P	S	Alt	Nb	Ti	Mo	Ni	Cr	Cu
												0.05	0.23	1.70	0.006	0.0013	0.03	0.065	0.015	0.28	0.23	0.20	0.20

Table 10 process system

The strength property of table 11 steel plate

The toughness of table 12 series of temperatures lower steel plate

Claims (2)

1. a subsea pipeline is with the production method of X70 hot rolled steel plate, the chemical ingredients of this steel (weight %) is: C:0.035～0.07%, Si:0.10～0.35%, Mn:1.40～1.85%, P :≤0.010%, S :≤0.0030%, Alt:0.01～0.06%, Nb:0.035～0.070%, Ti:0.008～0.020%, Mo:0.10～0.30%, Ni:0.10～0.25%, Cr:0.10～0.25%, Cu:0.10～0.25%, surplus is Fe and inevitable impurity element, it is characterized in that production technique is as follows:

(1) base type design: require to produce steel plate compression ratio 〉=10, select the thick steel billet of 400mm for use;

(2) heating cycle: steel billet is heated to 1120～1210 ℃, guarantees steel billet soaking time 1.5～2.5 hours, improve the homogeneity that heats on the steel billet thickness direction;

(3) rolling technology: rolling rolling in two stages, i.e. austenite recrystallization district rolling (roughing) and austenite non-recrystallization rolling (finish rolling); At rough rolling step, the rolling temperature interval is 980～1070 ℃, behind the control steel billet broadening before treat temperature total deformation rate between 60%～75%, need guarantee simultaneously behind the broadening to treating that the axial rolling pass deformation rate before the temperature rises gradually, and the single pass deformation rate is controlled between 15.5%～30%, will guarantee that especially last 3 pass deformation rates all 〉=23%; Intermediate blank is treated temperature thickness/finished product thickness 〉=3.3; In the finish rolling stage, start rolling temperature is 850～920 ℃, and stopping rolling temperature is 760～840 ℃, and control steel billet total deformation rate is between 70%～80%;

(4) water-cooling process: with the speed cooling of 12～28 ℃/s, cooling termination temperature is 455～570 ℃ after the hot rolling.

2. in accordance with the method for claim 1, it is characterized in that producing steel plate thickness specification is 25～35mm, the steel plate microtexture is even tiny acicular ferrite, and grain fineness number is 12～13 grades.