CN112981258B - X70M hot-rolled steel plate for thin-specification gas transmission straight welded pipe and manufacturing method - Google Patents
X70M hot-rolled steel plate for thin-specification gas transmission straight welded pipe and manufacturing method Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 141
- 239000010959 steel Substances 0.000 title claims abstract description 141
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 31
- 230000005540 biological transmission Effects 0.000 title claims abstract description 14
- 239000012535 impurity Substances 0.000 claims abstract description 15
- 239000007789 gas Substances 0.000 claims abstract description 14
- 239000000126 substance Substances 0.000 claims abstract description 11
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 10
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 10
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 9
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 7
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 6
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 5
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 4
- 238000005096 rolling process Methods 0.000 claims description 125
- 238000001816 cooling Methods 0.000 claims description 41
- 230000009467 reduction Effects 0.000 claims description 38
- 238000000034 method Methods 0.000 claims description 37
- 238000009749 continuous casting Methods 0.000 claims description 32
- 238000005266 casting Methods 0.000 claims description 25
- 230000008569 process Effects 0.000 claims description 24
- 238000010438 heat treatment Methods 0.000 claims description 21
- 238000003723 Smelting Methods 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 238000007664 blowing Methods 0.000 claims description 14
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 13
- 238000005507 spraying Methods 0.000 claims description 11
- 229910000859 α-Fe Inorganic materials 0.000 claims description 11
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 10
- 238000007670 refining Methods 0.000 claims description 10
- 239000002994 raw material Substances 0.000 claims description 8
- 238000003303 reheating Methods 0.000 claims description 8
- 238000002791 soaking Methods 0.000 claims description 8
- 229910052786 argon Inorganic materials 0.000 claims description 5
- 229910001563 bainite Inorganic materials 0.000 claims description 5
- 229910052742 iron Inorganic materials 0.000 claims description 5
- 238000001953 recrystallisation Methods 0.000 claims description 5
- 239000002893 slag Substances 0.000 claims description 5
- 238000009849 vacuum degassing Methods 0.000 claims description 5
- 238000002425 crystallisation Methods 0.000 claims description 4
- 230000008025 crystallization Effects 0.000 claims description 4
- 238000007872 degassing Methods 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims description 4
- 238000010079 rubber tapping Methods 0.000 claims description 4
- 238000007711 solidification Methods 0.000 claims description 4
- 230000008023 solidification Effects 0.000 claims description 4
- 238000010008 shearing Methods 0.000 claims description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 abstract description 14
- 239000003345 natural gas Substances 0.000 abstract description 7
- 229910045601 alloy Inorganic materials 0.000 description 11
- 239000000956 alloy Substances 0.000 description 11
- 230000001276 controlling effect Effects 0.000 description 10
- 229910001566 austenite Inorganic materials 0.000 description 6
- 238000005728 strengthening Methods 0.000 description 6
- 230000009466 transformation Effects 0.000 description 5
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 238000009628 steelmaking Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
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- 230000006872 improvement Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
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- 239000000203 mixture Substances 0.000 description 3
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- 239000002131 composite material Substances 0.000 description 2
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- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
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- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910000742 Microalloyed steel Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
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- 230000003111 delayed effect Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
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- 238000011089 mechanical engineering Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
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- 238000009966 trimming Methods 0.000 description 1
- RMLPZKRPSQVRAB-UHFFFAOYSA-N tris(3-methylphenyl) phosphate Chemical compound CC1=CC=CC(OP(=O)(OC=2C=C(C)C=CC=2)OC=2C=C(C)C=CC=2)=C1 RMLPZKRPSQVRAB-UHFFFAOYSA-N 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/02—Dephosphorising or desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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Abstract
The invention relates to an X70M hot rolled steel plate for a thin-specification gas transmission straight welded pipe and a manufacturing method thereof, wherein the steel plate comprises the following chemical components in percentage by weight: 0.05 to 0.09 percent of C, 0.10 to 0.35 percent of Si, 1.50 to 1.80 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, 0.04 to 0.09 percent of Nb, 0.008 to 0.0250 percent of Ti, 0.015 to 0.045 percent of Al, less than or equal to 0.4 percent of Cr, 0.020 to 0.06 percent of V, 0.0041 to 0.006 percent of N, and the balance of Fe and inevitable impurities; the steel plate produced by the invention is suitable for manufacturing the steel plate with the pipe diameter of
Description
Technical Field
The invention relates to the technical field of low-carbon microalloyed steel production, in particular to a pipe with a pipe diameter of
A high-strength X70M hot-rolled steel sheet for a natural gas pipeline having a wall thickness of 10 to 18mm and a method for producing the same.
Background
Pipeline transportation is the most economical, convenient and main transportation mode for transporting natural gas in long distance. In order to reduce the construction investment and the operation and maintenance cost of a long-distance natural gas pipeline and improve the conveying efficiency, the long-distance oil and gas conveying pipeline is always developed towards the direction of large pipe diameter and high pressure; meanwhile, in order to ensure the economy and safety of service, the thickness of steel pipes of some branch line projects is gradually reduced, the strength level is gradually increased, and correspondingly, pipeline steel plates must meet the requirements of thickness (10-18 mm), plate width (more than 4000mm) and high steel level (X70M level). The high-grade X70M hot-rolled steel plate is the leading steel for gas transmission lines in the present century and has excellent ductile fracture resistance. To be manufactured
The width of the steel plate of the steel pipe with the caliber is required to be more than 4465mm, namely the width of the steel plate before trimming is not cut is ensured to be at least more than 4610 mm. However, the difficulty of rolling increases greatly as the width of the X70M steel sheet increases and the thickness of the steel sheet decreases. Firstly, the load of a rolling mill, the temperature uniformity of a steel plate, the plate shape control, the surface quality and the like face severe examination, and secondly, the improvement of the performance of the steel plate mainly depends on the contents of impurities such as phosphorus, sulfur and the like in the steel, the contents of alloy elements in the steel and the control of key process parameters in the production processes such as smelting, rolling and the like. Therefore, how to solve the problems existing in the production process of the ultra-wide X70M pipeline steel and reduce the alloy cost of the pipeline steel is a key for developing the thin and wide X70M pipeline steel.
Chinese patent with publication number CN104264069B discloses 'extra-thick X70 pipeline steel and a manufacturing method thereof', wherein the thickness of the pipeline steel is 30-32 mm, and the pipeline steel comprises, by mass, 0.03-0.06% of C, 0.1-0.30% of Si, 1.30-1.60% of Mn, less than or equal to 0.010% of P, less than or equal to 0.0050% of S, 0.030-0.050% of Nb, 0.008-0.020% of Ti, 0.10-0.30% of Ni, 0.10-0.30% of Cr and 0.10-0.30% of Cu. In order to enable the steel plate to be the pipeline steel with high strength, excellent low-temperature toughness and excellent HIC (hydrogen induced cracking) resistance, the technical scheme is that the noble metal elements such as Ni and Cu are added in the component design, the alloy cost is high, and the method only aims at X70 pipeline steel with the thickness specification of 30-32 mm, however, the production process has no characteristics of thin specification and low cost, and the width of the steel plate is not clear.
Chinese patent with publication number CN103882334B discloses an X70 flat plate for gas transmission straight welded pipe and a production method thereof
The caliber gas transmission straight welded pipe comprises the following chemical components in percentage by mass: 0.06 to 0.10 percent of C, 0.10 to 0.35 percent of Si, 1.77 to 1.80 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.005 percent of S, 0.04 to 0.07 percent of Nb, 0.008 to 0.030 percent of Ti, 0.02 to 0.045 percent of Als, less than or equal to 0.20 percent of Ni, less than or equal to 0.20 percent of Cr, less than or equal to 0.20 percent of Cu, 0.020 to 0.048 percent of V. In order to enable the steel plate to be X70 pipeline steel with high strength, high toughness and other performances, the technical scheme adds noble metal elements such as Ni and Cu in component design, so that the alloy cost is high, and the DWTT service temperature is-15 ℃, but the production does not have the characteristic of low cost.
Japanese patent No. JP11080833 discloses a "steel sheet product for high-strength line pipes having excellent HIC resistance", which has strict requirements for the contents of impurity elements such as P and S, has strict requirements for steel making, and increases the steel making cost. Chinese patent with publication number CN101270440A discloses an economical X70 pipeline steel and a production method thereof, which is a coiled plate and contains Mo, and the production does not have the characteristic of low cost.
The production width of X70M mentioned in the journal article rolling process research of ultra-wide pipeline steel X70M (Wide and Thick plate 2010.1) is 3830mm, DWTT performance is not guaranteed, typical chemical components of the steel usually adopt C-Mn-Mo-Nb system, a gamma phase region is enlarged mainly by adding Mo, the transformation temperature of gamma-alpha is reduced, and the formation of acicular ferrite is promoted. However, Mo is relatively expensive, so that the cost of the pipeline steel produced by adopting the alloy series is high, and meanwhile, Mo has high red hardness and high-temperature deformation resistance, thereby bringing serious examination to the load of a rolling mill. Journal article "development of 36.5mm thick X70 steel plate for deep sea and its large-diameter longitudinal submerged arc welded pipe" (mechanical engineering material 2016.12) discloses the composition, structure and performance of X70 steel plate with specification of 36.5mm and longitudinal submerged arc welded pipe with specification of D1016mm × 36.5 mm. The steel contains precious metal elements such as Mo and Ni, the alloy cost is high, and the technical scheme recorded by the paper is not suitable for producing the steel plate with low cost and large thickness-diameter ratio for the steel pipe.
Although the steel grades described in the above prior publications have achieved the high strength requirement and some have excellent HIC resistance, they are either only suitable for producing coil plates or are expensive to produce, and therefore, they do not satisfy the low-cost production of steel plates for thin-gauge, wide-width, high-strength line pipes.
Disclosure of Invention
The invention provides an X70M hot-rolled steel plate for a thin-gauge gas transmission straight welded pipe and a manufacturing method thereof, which are suitable for manufacturing the pipe with the diameter of pipe
The X70M straight welded pipe for the natural gas conveying pipeline with the wall thickness of 10-18 mm. The technical requirements of the X70M steel plate can be met without subsequent off-line heat treatment, the problems of large rolling resistance, large straightening resistance, poor performance uniformity of the steel plate and the like in the production process of the thin-gauge, high-strength and ultra-wide X70M hot rolled steel plate are solved, the produced steel plate has high strength, high toughness and good comprehensive performance, the safety of a natural gas conveying pipeline can be ensured, the production cost is low, and the economical efficiency is good.
In order to achieve the purpose, the invention adopts the following technical scheme:
an X70M hot-rolled steel plate for a thin-specification gas transmission straight welded pipe, wherein the thickness of the steel plate is 10-18 mm; the steel plate comprises the following chemical components in percentage by weight: 0.05 to 0.09 percent of C, 0.10 to 0.35 percent of Si, 1.50 to 1.80 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, 0.04 to 0.09 percent of Nb, 0.008 to 0.0250 percent of Ti, 0.015 to 0.045 percent of Al, less than or equal to 0.4 percent of Cr, 0.020 to 0.06 percent of V, 0.0041 to 0.006 percent of N, and the balance of Fe and inevitable impurities; o in the impurity is less than or equal to 0.0050 percent, and the total amount of other impurity elements is less than 0.05 percent.
A manufacturing method of an X70M hot rolled steel plate for a thin-specification gas transmission straight welded pipe comprises the production process routes of molten steel smelting → external refining, degassing → continuous casting → slab reheating → controlled rolling → controlled cooling → air cooling to room temperature; the method comprises the following specific steps:
1) the molten steel smelting to continuous casting process:
pretreating the raw material by KR molten iron, controlling the content of S to be less than or equal to 0.015 percent, and feeding the raw material into a converter after slagging off; in the smelting process of the converter, a double-slag method is adopted to remove P, and the content of P is controlled to be less than or equal to 0.02 percent; controlling the content of C at the smelting end point of the converter to be 0.05-0.09%, and blowing argon for 10-15 min during tapping; carrying out LF refining and RH vacuum degassing treatment on the molten steel, and keeping RH vacuum for more than 15 min; then carrying out continuous slab casting, wherein the continuous casting superheat degree is 15-25 ℃, and the continuous casting blank drawing speed is 1.1-1.6 m/min; putting the continuous casting billet into a horizontal sector section, namely a solidification tail end under heavy reduction, wherein the reduction of the continuous casting billet is 10-20 mm;
2) slab reheating:
feeding the casting blank into a stepping heating furnace for heating, and discharging the casting blank from the furnace after the casting blank sequentially passes through a preheating section, a heating section and a soaking section; wherein the temperature of the preheating section is 950-1150 ℃, the temperature of the heating section is 1150-1250 ℃, the temperature of the soaking section is 1140-1220 ℃, and the in-furnace time is 3.5-4.5 hours;
3) controlling the rolling and cooling processes:
descaling the cast blank discharged from the furnace for 1-2 min by using high-pressure water before rolling, wherein the pressure of a descaling machine is 30-40 MPa; rolling in two stages: the first stage is recrystallization rolling, namely rough rolling, wherein the initial rolling temperature of the rough rolling is 1010-1190 ℃, the final rolling temperature of the rough rolling is 960-1020 ℃, and the number of rough rolling passes is less than or equal to 8; the second stage is non-crystallization rolling, namely finish rolling, the start rolling temperature of the finish rolling is 800-890 ℃, the finish rolling temperature of the finish rolling is 740-780 ℃, and a finish rolling channelThe frequency is less than or equal to 10; the finish rolling adopts accelerated rolling, and the rolling speed is 3-5 m/s; quickly throwing steel after rolling, wherein the steel throwing speed is 4-6.5 m/s, pre-straightening is not input, then laminar cooling is adopted, the start cooling temperature is 700-740 ℃, the final cooling temperature is 380-450 ℃, and the cooling speed is controlled to be 20-35 ℃/s; after the steel plate is discharged for controlled cooling, side spraying and air blowing are started, the side spraying pressure is 0.5-3 MPa, and the water amount is 50-100 m3The air blowing pressure is 5-10 MPa; then carrying out 3 times of straightening by thermal straightening, wherein the position of a lead-in roller is-1.1 mm to-2.5 mm, and the position of a lead-out roller is-2.6 mm to-4.2 mm;
4) and air-cooling to room temperature.
The thickness of the casting blank is 200-250 mm.
The pass reduction system in the rough rolling process is as follows: the reduction rate of at least 2 passes in the first 4 passes is more than 22%, the reduction rate of at least 1 pass in the last 3 passes is not less than 15%, and the pass reduction system in the finish rolling process is that the reduction rate of at least 1 pass in the first 2 passes is more than 20%, and the reduction rate of at least 1 pass in the last 3 passes is not less than 10%.
The thickness of the intermediate blank obtained after rough rolling is 3-4.5 times of that of the finished steel plate; and (3) spraying scale removal water in each of the last 3 passes of the rough rolling stage, wherein the scale removal time is 0.5-1 min, and the pressure of a descaler is 10-20 MPa.
The metallographic structure of the steel plate is a complex phase structure mainly comprising acicular ferrite and granular bainite.
The steel plate has the following properties: the transverse tensile yield strength is 510-540 MPa, and the tensile strength is 590-630 MPa; the yield ratio is 0.81-0.9, the elongation is more than or equal to 25%, the transverse Charpy impact work at minus 35 ℃ is more than or equal to 350J, and the transverse shearing area SA of DWTT at minus 20 ℃ is not less than 85%.
Compared with the prior art, the invention has the beneficial effects that:
1) the KR molten iron is pretreated for deep desulfurization and then is completely drossed, a converter adopts a double-slag method for removing P, so that the P, S content of a casting blank is lower, the argon blowing time is controlled, and the RH vacuum degassing time is kept, thereby overcoming the defects of casting blank center segregation, inclusion, excessive H, O content and the like caused by higher Mn content, and being beneficial to improving the plastic toughness of pipeline steel; by reasonably controlling the superheat degree and the withdrawal rate of the continuous casting billet and putting into heavy reduction, the method is beneficial to reducing the segregation of the billet, refining austenite grains and reducing the internal structure defects;
2) the steel plate has reasonable chemical component design and low alloy addition, and Cr is used for replacing Mo, and a small amount of microalloy elements Nb and V are added in a matching manner, so that the alloy cost and the high-temperature deformation resistance in the rough rolling and finish rolling stages are greatly reduced, the reduction per pass is favorably improved, and the comprehensive performance of the ultra-wide X70M plate is favorably realized; when a casting blank is heated, the temperature range of a preheating section is 950-1150 ℃, so that carbides and nitrides of Nb and V can be promoted to be rapidly and fully dissolved in a matrix and fully diffused.
3) The two-stage rolling process is adopted, the reduction of rough rolling and finish rolling passes is controlled, the thickness of an intermediate billet is optimized, and the finish rolling starting temperature is increased; by adopting a flexible high-pressure water descaling process, the growth of austenite grains is inhibited, the DWTT performance is improved, the waiting time of the intermediate billet is shortened, and relaxation waiting is not needed after rolling; the grain structure of different stages is refined and has a certain degree of pre-deformation through two-stage rolling so as to reduce the grain size after phase transformation; the final cooling temperature of the steel plate is controlled to be 380-450 ℃ through the technical means of quick steel throwing after rolling, no investment for pre-straightening, laminar cooling and the like, and the investment of side spraying and air blowing is facilitated, so that the uniformity of the performance of the steel plate is improved, the probability of the problems of the shapes of the buckle head and the buckle tail plate is reduced, and the investment cost of subsequent cold straightening equipment is saved.
4) The invention reduces the alloy cost through simple component design, and obtains the alloy suitable for manufacturing the pipe with the wall thickness of 10-18 mm and the pipe diameter through regulating and controlling the steelmaking, continuous casting and controlled rolling and controlled cooling processes
The super-wide steel plate of the natural gas conveying straight welded pipe with the strength level of X70M has the advantages that the metallographic structure is mainly acicular ferrite and bainite, the super-wide steel plate has good low-temperature toughness and DWTT performance, and meanwhile, the shape and the surface quality of the super-wide plate are guaranteed; the steel plate has high strength, narrow strength interval range and moderate elongation.
Detailed Description
The invention provides an X70M hot-rolled steel plate for a thin-specification gas transmission straight welded pipe, wherein the thickness of the steel plate is 10-18 mm; the steel plate comprises the following chemical components in percentage by weight: 0.05 to 0.09 percent of C, 0.10 to 0.35 percent of Si, 1.50 to 1.80 percent of Mn1, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, 0.04 to 0.09 percent of Nb, 0.008 to 0.0250 percent of Ti, 0.015 to 0.045 percent of Al, less than or equal to 0.4 percent of Cr, 0.020 to 0.06 percent of V, 0.0041 to 0.006 percent of N, and the balance of Fe and inevitable impurities; o in the impurity is less than or equal to 0.0050 percent, and the total amount of other impurity elements is less than 0.05 percent.
A manufacturing method of an X70M hot rolled steel plate for a thin-specification gas transmission straight welded pipe comprises the production process routes of molten steel smelting → external refining, degassing → continuous casting → slab reheating → controlled rolling → controlled cooling → air cooling to room temperature; the method comprises the following specific steps:
1) the molten steel smelting to continuous casting process:
pretreating the raw material by KR molten iron, controlling the content of S to be less than or equal to 0.015 percent, and feeding the raw material into a converter after slagging off; in the smelting process of the converter, a double-slag method is adopted to remove P, and the content of P is controlled to be less than or equal to 0.02 percent; controlling the content of C at the smelting end point of the converter to be 0.05-0.09%, and blowing argon for 10-15 min during tapping; carrying out LF refining and RH vacuum degassing treatment on the molten steel, and keeping RH vacuum for more than 15 min; then carrying out continuous slab casting, wherein the continuous casting superheat degree is 15-25 ℃, and the continuous casting blank drawing speed is 1.1-1.6 m/min; putting the continuous casting billet into a horizontal sector section, namely a solidification tail end under heavy reduction, wherein the reduction of the continuous casting billet is 10-20 mm;
2) slab reheating:
feeding the casting blank into a stepping heating furnace for heating, and discharging the casting blank from the furnace after the casting blank sequentially passes through a preheating section, a heating section and a soaking section; wherein the temperature of the preheating section is 950-1150 ℃, the temperature of the heating section is 1150-1250 ℃, the temperature of the soaking section is 1140-1220 ℃, and the in-furnace time is 3.5-4.5 hours;
3) controlling the rolling and cooling processes:
descaling the cast blank discharged from the furnace for 1-2 min by using high-pressure water before rolling, wherein the pressure of a descaling machine is 30-40 MPa; rolling in two stages: the first stage is recrystallization rolling, namely rough rolling, the initial rolling temperature of the rough rolling is 1010-1190 ℃, and the rough rolling is carried outThe finishing temperature is 960-1020 ℃, and the number of rough rolling passes is less than or equal to 8; the second stage is non-crystallization rolling, namely finish rolling, wherein the start rolling temperature of finish rolling is 800-890 ℃, the finish rolling temperature of finish rolling is 740-780 ℃, and the number of finish rolling passes is less than or equal to 10; the finish rolling adopts accelerated rolling, and the rolling speed is 3-5 m/s; quickly throwing steel after rolling, wherein the steel throwing speed is 4-6.5 m/s, pre-straightening is not input, then laminar cooling is adopted, the start cooling temperature is 700-740 ℃, the final cooling temperature is 380-450 ℃, and the cooling speed is controlled to be 20-35 ℃/s; after the steel plate is discharged for controlled cooling, side spraying and air blowing are started, the side spraying pressure is 0.5-3 MPa, and the water amount is 50-100 m3The air blowing pressure is 5-10 MPa; then carrying out 3 times of straightening by thermal straightening, wherein the position of a lead-in roller is-1.1 mm to-2.5 mm, and the position of a lead-out roller is-2.6 mm to-4.2 mm;
4) and air-cooling to room temperature.
The thickness of the casting blank is 200-250 mm.
The pass reduction system in the rough rolling process is as follows: the reduction rate of at least 2 passes in the first 4 passes is more than 22%, the reduction rate of at least 1 pass in the last 3 passes is not less than 15%, and the pass reduction system in the finish rolling process is that the reduction rate of at least 1 pass in the first 2 passes is more than 20%, and the reduction rate of at least 1 pass in the last 3 passes is not less than 10%.
The thickness of the intermediate blank obtained after rough rolling is 3-4.5 times of that of the finished steel plate; and (3) spraying scale removal water in each of the last 3 passes of the rough rolling stage, wherein the scale removal time is 0.5-1 min, and the pressure of a descaler is 10-20 MPa.
The metallographic structure of the steel plate is a complex phase structure mainly comprising acicular ferrite and granular bainite.
The steel plate has the following properties: the transverse tensile yield strength is 510-540 MPa, and the tensile strength is 590-630 MPa; the yield ratio is 0.81-0.9, the elongation is more than or equal to 25%, the transverse Charpy impact work at minus 35 ℃ is more than or equal to 350J, and the transverse shearing area SA of DWTT at minus 20 ℃ is not less than 85%.
The invention discloses an X70M hot rolled steel plate for a thin-specification gas transmission straight welded pipe, which comprises the following main elements in chemical components:
c: the most economical and basic strengthening elements in the steel have obvious effect on improving the strength of the steel through solid solution strengthening and precipitation strengthening, but the improvement of the content of C has negative influence on the plasticity, the toughness and the weldability of the steel. Therefore, the content range of C is set to be 0.05-0.09%.
Mn: the strength of the steel is improved by the solid solution strengthening, and the loss of the strength of the steel sheet caused by the reduction of the C content is compensated. In addition, the gamma-alpha phase transformation temperature can be reduced, so that ferrite grains are refined, a fine low-temperature phase transformation product is obtained, and the toughness of the product is improved. However, increasing the Mn content will aggravate the center segregation of the continuous casting slab, which is not favorable for increasing the low temperature toughness of the steel plate, and the uniformity of the cross section structure of the steel plate cannot be ensured. Therefore, the Mn content range of the present invention is designed to be 1.50% to 1.80%.
Si: has the functions of steelmaking deoxidization and matrix strength improvement. However, excessive Si can reduce the toughness of a welding heat affected zone of the base metal, improve the content of Si, purify ferrite, reduce the content of pearlite and be beneficial to reducing the Bauschinger effect of a base material. Therefore, the Si content is set to 0.10% to 0.35% in the present invention.
Nb: is one of common elements in modern microalloyed pipeline steel, and has good fine grain strengthening and precipitation strengthening effects; austenite recrystallization is also delayed, but excess Nb increases production costs and difficulties in controlling the continuous casting process. The invention selects the Nb content range of 0.04-0.09%, and can obtain a uniform composite phase mainly comprising an acicular ferrite structure by matching with a reasonable TMCP process, so that the composite phase has good toughness.
N: the N element in the steel has no other obvious effect except that fine TiN grains are formed to refine austenite grains, so that the content of the N element needs to be kept at a lower content level, and the N content range selected by the invention is 0.0041-0.006%.
Ti: is a strong solid N element and exists in the form of TiN in the continuous casting billet. The fine TiN particles can effectively inhibit the growth of austenite grains when the continuous casting slab is reheated, and contribute to improving the solid solubility of Nb in austenite and improving the impact toughness of a welding heat affected zone. When the addition amount of Ti exceeds a certain value, the TiN particles will be coarsened, and the stress concentration level of the particle interface and the matrix is improved. Therefore, the Ti content range is 0.008-0.025 percent.
Al: in general, AlN also has a function of refining the structure when it is formed as a deoxidizer in steel. When the content of Al exceeds 0.045%, excessive alumina inclusions may degrade the cleanliness of the steel. If the Al content is too low, deoxidation is not sufficient, and easily-oxidizable elements such as Ti and the like can form oxides, so that the Al content is 0.015-0.045% in the invention.
Cr: can effectively improve hardenability, is a main element for inhibiting ferrite formation and promoting bainite formation, plays an important role in controlling phase transformation structure, can promote acicular ferrite with a large amount of dislocation distribution in crystal in a medium-temperature and low-temperature region, and improves the strength, plasticity and toughness of a steel plate, and the content range of Cr selected by the invention is that Cr is less than or equal to 0.4 percent
V: the vanadium carbonitride is uniformly precipitated in a fine dispersion form in ferrite, so that the yield strength and tensile strength of the material can be obviously improved, but too high vanadium carbonitride is coarse, the toughness is reduced, the alloy cost is also increased, and the proper range is 0.020-0.06%.
P, S: is an inevitable impurity element in steel, and the lower the content, the better. But cannot be lowered without limit due to smelting cost and process. Therefore, the upper limit of the content of P, S is set to 0.020% and 0.015%, respectively.
The following examples are carried out on the premise of the technical scheme of the invention, and detailed embodiments and specific operation processes are given, but the scope of the invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.
[ examples ] A method for producing a compound
As shown in the following tables, Table 1 shows the chemical compositions of the steels in the examples, Table 2 shows the smelting process system of the steels in the examples, and Table 3 shows the casting blank heating system of the steels in the examples and the high-pressure water descaling process parameters before rolling the continuous casting blanks; table 4 shows the heating and rolling process parameters of the steel sheets in each example; table 5 shows the pass reduction of the steel sheets at different rolling stages in each example; table 6 shows the controlled cooling process parameters of the steel plates in the examples; table 7 shows the transverse mechanical properties of the steel sheets in the examples.
TABLE 1 chemical composition of steel (wt%)
Note: the impurity element P in the steels of examples 1 to 6 was not more than 0.02%; s is less than or equal to 0.015 percent; 0 percent or less than 0.0050 percent and the total amount of other impurity elements is less than 0.05 percent.
TABLE 2 smelting process system of steel
TABLE 3 heating System of casting blank and high-pressure water descaling Process parameters before rolling of continuous casting blank
TABLE 4 heating and Rolling Process parameters of the Steel plates
TABLE 5 passage reduction of the steel sheets at different rolling stages
TABLE 6 controlled Cooling Process parameters of Steel plates
TABLE 7 transverse mechanical Properties of the Steel sheets
The embodiment proves that compared with the prior art, the chemical components of the ultra-wide X70M pipeline steel produced by the invention are simple, the strength of the ultra-wide X70M pipeline steel reaches the X70M steel grade, the ultra-wide X70M pipeline steel has excellent comprehensive mechanical property, the steel has excellent formability and welding performance, and the ultra-wide X70M pipeline steel can be used for manufacturing large-caliber steel
X70M pipeline steel pipe.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (2)
1. The X70M hot-rolled steel plate for the thin-specification gas transmission straight welded pipe is characterized in that the thickness of the steel plate is 10-18 mm; the steel plate comprises the following chemical components in percentage by weight: 0.05 to 0.07 percent of C, 0.19 to 0.35 percent of Si, 1.65 to 1.80 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, 0.062 to 0.09 percent of Nb, 0.008 percent of Ti, 0.015 to 0.026 percent of Al, 0.05 to 0.25 percent of Cr, 0.055 to 0.06 percent of V, 0.0051 to 0.006 percent of N, and the balance of Fe and inevitable impurities; o in the impurities is less than or equal to 0.0050 percent, and the total amount of other impurity elements is less than 0.05 percent; the metallographic structure of the steel plate is a complex phase structure mainly comprising acicular ferrite and granular bainite; the steel plate has the following properties: the transverse tensile yield strength is 510-540 MPa, and the tensile strength is 602-630 MPa; the yield ratio is 0.86-0.9, the elongation is more than or equal to 25%, the transverse Charpy impact work at minus 35 ℃ is more than or equal to 350J, and the transverse shearing area SA of the DWTT at minus 20 ℃ is not less than 85%;
the production process route of the steel plate is molten steel smelting → external refining, degassing → continuous casting → slab reheating → controlled rolling → controlled cooling → air cooling to room temperature; the method comprises the following specific steps:
1) the molten steel smelting to continuous casting process:
pretreating the raw material by KR molten iron, controlling the content of S to be less than or equal to 0.015 percent, and feeding the raw material into a converter after slagging off; in the smelting process of the converter, a double-slag method is adopted to remove P, and the content of P is controlled to be less than or equal to 0.02 percent; controlling the content of C to be 0.05-0.07% at the smelting end point of the converter, and blowing argon for 10-15 min during tapping; carrying out LF refining and RH vacuum degassing treatment on the molten steel, and keeping RH vacuum for more than 15 min; then carrying out continuous slab casting, wherein the continuous casting superheat degree is 15-25 ℃, and the continuous casting blank drawing speed is 1.1-1.6 m/min; putting the continuous casting billet into a horizontal sector section, namely a solidification tail end under heavy reduction, wherein the reduction of the continuous casting billet is 10-20 mm; the thickness of the casting blank is 200-250 mm;
2) slab reheating:
feeding the casting blank into a stepping heating furnace for heating, and discharging the casting blank from the furnace after the casting blank sequentially passes through a preheating section, a heating section and a soaking section; wherein the temperature of the preheating section is 950-1150 ℃, the temperature of the heating section is 1150-1250 ℃, the temperature of the soaking section is 1140-1220 ℃, and the in-furnace time is 3.5-4.5 hours;
3) controlling the rolling and cooling processes:
descaling the cast blank discharged from the furnace for 1-2 min by using high-pressure water before rolling, wherein the pressure of a descaling machine is 30-40 MPa; rolling in two stages:
the first stage is recrystallization rolling, namely rough rolling, wherein the initial rolling temperature of the rough rolling is 1010-1085 ℃, the final rolling temperature of the rough rolling is 960-1020 ℃, and the number of rough rolling passes is 4-8; the pass reduction system in the rough rolling process is as follows: the reduction rate of at least 2 passes in the first 4 passes is more than 22%, the reduction rate of at least 1 pass in the last 3 passes is not less than 15%, descaling water is sprayed on each pass in the last 3 passes in the rough rolling stage, the descaling time is 0.5-1 min, and the pressure of a descaler is 10-20 MPa; the thickness of the intermediate blank obtained after rough rolling is 3-4.5 times of that of the finished steel plate;
the second stage is non-crystallization rolling, namely finish rolling, wherein the start rolling temperature of finish rolling is 800-890 ℃, the finish rolling temperature of finish rolling is 740-780 ℃, and the number of finish rolling passes is 6-10; the pass reduction system in the finish rolling process is that the reduction rate of at least 1 pass in the first 2 passes is more than 20 percent, and the reduction rate of at least 1 pass in the last 3 passes is not less than 10 percent; the finish rolling adopts accelerated rolling, and the rolling speed is 3-5 m/s;
quickly throwing steel after rolling, wherein the steel throwing speed is 4-6.5 m/s, pre-straightening is not input, then laminar cooling is adopted, the start cooling temperature is 700-740 ℃, the final cooling temperature is 380-450 ℃, and the cooling speed is controlled to be 20-35 ℃/s; after the steel plate is discharged for controlled cooling, side spraying and air blowing are started, the side spraying pressure is 0.5-3 MPa, and the water amount is 50-100 m3The air blowing pressure is 5-10 MPa; then carrying out 3 times of straightening by thermal straightening, wherein the position of a lead-in roller is-1.1 mm to-2.5 mm, and the position of a lead-out roller is-2.6 mm to-4.2 mm;
4) and air-cooling to room temperature.
2. The manufacturing method of the X70M hot rolled steel sheet for the thin gauge gas transmission longitudinal welded pipe according to claim 1, wherein the production process route is molten steel smelting → external refining, degassing → continuous casting → slab reheating → controlled rolling → controlled cooling → air cooling to room temperature; the method comprises the following specific steps:
1) the molten steel smelting to continuous casting process:
pretreating the raw material by KR molten iron, controlling the content of S to be less than or equal to 0.015 percent, and feeding the raw material into a converter after slagging off; in the smelting process of the converter, a double-slag method is adopted to remove P, and the content of P is controlled to be less than or equal to 0.02 percent; controlling the content of C to be 0.05-0.07% at the smelting end point of the converter, and blowing argon for 10-15 min during tapping; carrying out LF refining and RH vacuum degassing treatment on the molten steel, and keeping RH vacuum for more than 15 min; then carrying out continuous slab casting, wherein the continuous casting superheat degree is 15-25 ℃, and the continuous casting blank drawing speed is 1.1-1.6 m/min; putting the continuous casting billet into a horizontal sector section, namely a solidification tail end under heavy reduction, wherein the reduction of the continuous casting billet is 10-20 mm; the thickness of the casting blank is 200-250 mm;
2) slab reheating:
feeding the casting blank into a stepping heating furnace for heating, and discharging the casting blank from the furnace after the casting blank sequentially passes through a preheating section, a heating section and a soaking section; wherein the temperature of the preheating section is 950-1150 ℃, the temperature of the heating section is 1150-1250 ℃, the temperature of the soaking section is 1140-1220 ℃, and the in-furnace time is 3.5-4.5 hours;
3) controlling the rolling and cooling processes:
descaling the cast blank discharged from the furnace for 1-2 min by using high-pressure water before rolling, wherein the pressure of a descaling machine is 30-40 MPa; rolling in two stages:
the first stage is recrystallization rolling, namely rough rolling, wherein the initial rolling temperature of the rough rolling is 1010-1085 ℃, the final rolling temperature of the rough rolling is 960-1020 ℃, and the number of rough rolling passes is 4-8; the pass reduction system in the rough rolling process is as follows: the reduction rate of at least 2 passes in the first 4 passes is more than 22%, the reduction rate of at least 1 pass in the last 3 passes is not less than 15%, descaling water is sprayed on each pass in the last 3 passes in the rough rolling stage, the descaling time is 0.5-1 min, and the pressure of a descaler is 10-20 MPa; the thickness of the intermediate blank obtained after rough rolling is 3-4.5 times of that of the finished steel plate;
the second stage is non-crystallization rolling, namely finish rolling, wherein the start rolling temperature of finish rolling is 800-890 ℃, the finish rolling temperature of finish rolling is 740-780 ℃, and the number of finish rolling passes is 6-10; the pass reduction system in the finish rolling process is that the reduction rate of at least 1 pass in the first 2 passes is more than 20 percent, and the reduction rate of at least 1 pass in the last 3 passes is not less than 10 percent; the finish rolling adopts accelerated rolling, and the rolling speed is 3-5 m/s;
quickly throwing steel after rolling, wherein the steel throwing speed is 4-6.5 m/s, pre-straightening is not input, then laminar cooling is adopted, the start cooling temperature is 700-740 ℃, the final cooling temperature is 380-450 ℃, and the cooling speed is controlled to be 20-35 ℃/s; after the steel plate is discharged for controlled cooling, side spraying and air blowing are started, the side spraying pressure is 0.5-3 MPa, and the water amount is 50-100 m3The air blowing pressure is 5-10 MPa; then carrying out 3 times of straightening by thermal straightening, wherein the position of a lead-in roller is-1.1 mm to-2.5 mm, and the position of a lead-out roller is-2.6 mm to-4.2 mm;
4) and air-cooling to room temperature.
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