CN105886912B - A kind of low compression ratio think gauge X70 levels steel for gas delivering pipeline and production method - Google Patents

A kind of low compression ratio think gauge X70 levels steel for gas delivering pipeline and production method Download PDF

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CN105886912B
CN105886912B CN201610269204.4A CN201610269204A CN105886912B CN 105886912 B CN105886912 B CN 105886912B CN 201610269204 A CN201610269204 A CN 201610269204A CN 105886912 B CN105886912 B CN 105886912B
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CN105886912A (en
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徐锋
徐进桥
郭斌
孔君华
李利巍
崔雷
邹航
刘小国
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Wuhan Iron and Steel Co Ltd
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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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • 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
    • 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
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
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  • Physics & Mathematics (AREA)
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  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

A kind of low compression ratio think gauge X70 level steel for gas delivering pipeline, its component and wt% are：C：0.03‑0.075%、Si:0.15~0.35%、Mn:1.30~1.90%、P：≤0.015%、S：≤0.002%、N：≤0.006%、Nb：0.035~0.065%、V：0.025~0.05%、Ti:0.015~0.025%、Cr:0.1~0.40%、Ni：0.1~0.2%、Mo：0.10~0.25%.Production stage：To the heating strand that thickness is 225 235mm；Roughing；High-pressure water descaling；Finish rolling；Cooling；Aligning, it is stand-by.It is 30mm and the X70 level pipe line steels of the above that the continuous casting billet that the present invention is 230mm with thickness of strand, which can produce thickness, and the R of productt0.5In 500 ~ 580MPa, RmIn 600 ~ 650MPa, Rt0.5/Rm≤ 0.90, elongation percentage A50≥24%；20 DEG C of ballistic work KV2>=250J, 15 DEG C of DWTT section shearing rate SA >=95%；HV10≤235。

Description

A kind of low compression ratio think gauge X70 levels steel for gas delivering pipeline and production method
Technical field
The present invention relates to a kind of pipe line steel and its production method, and it is defeated to specifically belong to a kind of low compression ratio think gauge X70 levels Gas pipeline steel and production method.
Background technology
The natural gas resource almost all of China concentrates on west area, and the density of population distribution with China is inversely proportional, greatly The burning of the fossil fuels such as the coal of amount, oil brings serious haze problem to Chinese environmental.China's economic must protect Solves energy crisis while holding rapid growth, therefore, the natural gas of the western cleaning of national Devoting Major Efforts To Developing, is completed transfering natural gas from the west to the east First, two wires, three lines are currently built, and has planned four, five, six lines etc..Hi-grade steel, heavy caliber, big wall are thick, high-pressure delivery Into the developing direction of pipe-line construction from now on.But there is more accident in Hi-grade steel X70 ~ X80 of thin wall specification in construction, For security consideration, country is eager to be needed to develop the big wall thickness pipe line steel of X70-X80 ranks to meet that the efficient energy conveys.
From the angle of traditional handicraft control, the compression ratio of pipe line steel must assure that could meet API more than 10 times 5L obdurability matching requires, and grade of steel more high compression ratio requires bigger.At present, continuous casting in China machine strand size mainly has 300mm, 250mm, 230mm, traditionally it is only capable of production thickness and is less than below 30mm pipe line steels.
Through retrieving, before the present patent application, China Patent Publication No. is CN103937950A document, and it discloses " one The production technology of kind low compression ratio think gauge high-grade pipe line steel ", its component and technique are mainly（C：0.03~0.08%；Si： 0.15 ~ 0.35%, Mn:1.5~2.0%；Nb：0.05~0.09%；Ti：0.015~0.025%；Mo≤0.25%；Cu≤0.35%；Ni≤ 0.30%；Cr：≤ 0.030%, using 250mm continuous casting billets by controlling slab reheating temperature, thick, finish rolling rolling total reduction and Rolling temperature and open the technological parameters such as cold, final cooling temperature, cooling velocity and obtain think gauge X80 pipe line steels, mechanical property is （Rt0.5:550 ~ 591MPa, Rm:694~732MPa,-20℃KV2/J≥300J,-15℃,DWTT:>=90%, although it can The Hi-grade steel pipe line steel that wall thickness is 25 ~ 33mm, but its Ni+Cu+Mo >=0.6% are produced, cost of alloy is higher, meanwhile, retouched in patent Last percentage pass reduction >=15% when rough rolling step meets deformation temperature lower limit stated, it is more actually not indicate lowest temperature It is few, meanwhile, because low temperature makes deformation of rolled wire drag excessive in actual production, it is difficult to accomplish.
The another patent document for having China Patent Publication No. to be CN10363919A, disclose " makes under the conditions of a kind of small reduction ratio With the method for continuous casting billet production flow line steel plate ".It uses 300mm continuous casting billets production 40-50mm wide cuts up to 3200-4000mm spy Thick pipe line steel.Its component and technique are mainly（C：0.05~0.10%；Si：0.15~0.30%；Mn：1.0~2.0%;Nb:≤ 0.05%;V: ≤0.05%,Ti:≤ 0.05%, cooled down using 300mm strands by reheating, after two-phase control rolling, power Learning performance is（Rt0.5:511~541MPa；Rm：603 ~ 623MPa, -20 DEG C of KV2/J:≥200~250J,-10℃,DWTT:50~ 60%）Although it can produce the pipe line steel that wall thickness is 40 ~ 50mm, alloy addition level is also seldom.But exist, impact flexibility is not Height, reluctantly higher than 200J, particularly -10 DEG C of DWTT performances only 50 ~ 60%, engineering technology requirement can not be met.
In addition, China Patent Publication No. is CN1927486A document, describe " low compression ratio high grade pipe line steel Production technology ", it is indicated that produce the production technology of 17 ~ 22mmX70 level pipeline pipeline steels through steekle mill with 150mm continuous casting billets.Although Its compression ratio is relatively low, but requires that Molten Steel Cleanliness is excessively strict, and wherein S content is less than 6ppm, and P content is less than 70ppm, right Do not accomplish at all for most of smelting iron and steel enterprises.150mm continuous casting billets country producing line is seldom simultaneously, production equipment and routine Producing line is different, and product thickness is in the range of conventional products, it is impossible to meets pipeline engineering to big wall thickness（≥30mm）Demand.
From the point of view of from the existing document report that think gauge Hi-grade steel pipe line steel is produced by low compression ratio, exist logical Cross a large amount of high alloys of addition and sacrifice the deficiency for the think gauge high-grade pipe line steel that impact and block hammer performance reach；For adopting Rolled with excessively thin continuous casting billet, though having produced high-grade pipe line steel in the case of low-pressure ratio, thickness is maximum Only 22mm, the contradiction of thickness deficiency highlight.
The present invention mainly uses conventional 230mm continuous casting billets, avoids enterprise from separately investing the special think gauge continuous casting billet of enlarging, passes through Composition is smelted in control, reheats, thick, finish rolling rolling and control cold technique reach in the case of compression ratio only 6.0 ~ 7.7 production 30 ~ The purpose of the X70 pipe line steels of 38mm high tenacity.
The content of the invention
It is insufficient existing for above-mentioned technology the invention reside in overcoming, there is provided a kind of to ensure mechanical property and add Cu's Under the premise of, the low compression ratio think gauge X70 levels that thickness up to 30 ~ 38 mm pipe line steels are produced using the most frequently used 230mm continuous casting billets are defeated Gas pipeline steel and production method.
Realize the measure of above-mentioned purpose：
A kind of low compression ratio think gauge X70 level steel for gas delivering pipeline, its component and weight percent content are：C：0.03- 0.075%、Si:0.15~0.35%、Mn:1.30~1.90%、P：≤0.015%、S：≤0.002%、N：≤0.006%、Nb：0.035~ 0.065%、V：0.025~0.05%、Ti:0.015~0.025%、 Cr:0.1~0.40%、Ni：0.1~0.2%、Mo: 0.10~ 0.25%, remaining is Fe and inevitable impurity；Metallographic structure is：Top layer：Acicular ferrite+a small amount of bainite, thickness of slab 1/4 It is with 1/2 tissue:Acicular ferrite+a small amount of granular ferrite.
Produce a kind of method of low compression ratio think gauge X70 level steel for gas delivering pipeline, its step：
1）It is to component and weight percent content：C：0.03-0.075%、Si:0.15~0.35%、Mn:1.30~1.90%、 P：≤0.015%、S：≤0.002%、N：≤0.006%、Nb：0.035~0.065%、V：0.025~0.05%、Ti:0.015~ 0.025%、 Cr:0.1~0.40%、Ni：0.1~0.2%、Mo:0.10 ~ 0.25%, remaining is Fe and inevitable impurity, thickness Heated for 225-235mm strand, its heating and temperature control makes soaking zone soaking time not low at 1120-1180 DEG C In 40 minutes, total heat time was not less than 250 minutes；
2）Roughing is carried out, control recrystallization zone rolling temperature uses maximum rolling force in 1050-1115 DEG C, deformation process Rolling, maximum rolling force are not less than 7500t；Rate of deformation is controlled in 4 ~ 5/s；Passage interval time is no more than 10s, and last three Secondary accumulation reduction ratio >=22%；Warm workpiece thickness is treated in 70-90mm, recrystallization zone total reduction is 60-70%；
3）It is conventional to carry out high-pressure water descaling, start rolling temperature of the control steel billet temperature in finish rolling；
4）Finish rolling is carried out, controlling its start rolling temperature, finishing temperature rolls 6 ~ 9 altogether at 750-850 DEG C at 850-950 DEG C It is secondary, accumulate reduction ratio 55-65%, and make down the 3rd and second passage accumulation reduction ratio >=20%；
5）Being cooled down, control opens cold temperature at 770-830 DEG C, it is cooled to 300 in the case where cooldown rate is 15-35 DEG C/s ~ 400℃；
6）Aligned, it is stand-by.
The effect of each element and main technique and mechanism in the present invention
C：Carbon content is 0.03 ~ 0.075% in the present invention.Carbon be in steel it is indispensable improve steel strength element it One, while microalloy carbide can be formed with effects such as Ti, Nb in steel, precipitation strength effect is played, as its content exceedes 0.075%, then the toughness of steel can be damaged, effect is not had again less than 0.03,
Si：Si contents are 0.15 ~ 0.35% in the present invention.This yuan is known as solution strengthening and deoxidation, and content is less than 0.15% can not work, but can deteriorate modeling, the toughness of pipe line steel if higher than 0.35% simultaneously, especially for welding heat affected The impact in area reduces notable.
Mn：Mn contents are 1.30 ~ 1.90% in the present invention.The element main function expands heat to expand austenite stable region Processing temperature region, be advantageous to fining ferrite grains size, improve the yield strength and tensile strength of steel.In the present invention, it is Ensure material at low temperature impact and DWTT performances, Mn addition, which necessarily be greater than 1.3%, can just play the effect of making up, such as content height Significantly deteriorate steel plate welding performance in 1.9%.
Nb：Nb contents are 0.035 ~ 0.065% in the present invention.Niobium energy significantly crystal grain thinning simultaneously improves tensile strength.Niobium is at this In the During Controlled Rolling of invention, it can be played in the reheating stage and prevent original austenite from growing up rapidly at high temperature, in rough rolling step Recrystallization temperature is significantly improved, mill load is reduced, is grown up by suppressing recrystal grain, can fining austenite grains size. During roller repairing, Nb（C、N）Small particle separates out, and can play precipitation strength, Nb is to crystal grain refinement and separates out work Changed with the change with content, refined crystalline strengthening purpose is unable to reach if less than 0.03%, existed if higher than 0.065% and waste The problem of, cause cost too high.
Ti：Ti content is 0.015 ~ 0.025% in the present invention.Titanium is that a kind of strong carbide and nitride form member Element, steel reheat and high temperature austenite area, rough rolling process in can prevent Austenite Grain Growth, cooling stage separate out Small and dispersed TiC can play significant precipitating reinforcing effect, and so as to effectively improve armor plate strength, content is less than 0.015%, Then to original austenite grain refining effect deficiency, bulky grain TiN is likely to form if higher than 0.025%, is enriched in steel plate center portion, Significantly reduce steel plate toughness.
N：N≤0.006% in the present invention.Belong to normal remaining in converter steel, can be with titanium in steel（Ti）, niobium (Nb) combine Form TiN, NbN to separate out, play and suppress Austenite Grain Growth and precipitation strength effect.Excessive N and Ti forms bulky grain TiN, deteriorate toughness.
Cr：Cr contents are 0.1 ~ 0.40% in the present invention, and the element is that solution strengthening element improves steel plate quenching degree, is promoted Enter the transformation of medium temperature tissue tissue and Second Phase Precipitation, lift armor plate strength.Intensity deficiency caused by making up low-carbon, if being higher than 0.40%, the waste of cost is on the one hand caused, on the other hand causes carbon equivalent to raise, deteriorates weldability.
Ni：Content is 0.1 ~ 0.25% in the present invention, and two kinds of elements are that solution strengthening element improves steel plate quenching degree, Promote the transformation of medium temperature tissue tissue and Second Phase Precipitation, lift armor plate strength.Intensity deficiency caused by making up low-carbon.If it is higher than 0.25% one side causes the waste of cost, on the other hand causes carbon equivalent to raise, and deteriorates welding performance.
Mo：Content is 0.10 ~ 0.25% in the present invention, and the element is among the austenite stabilizing elements and through hardening element, in the present invention In can strongly facilitate medium temperature structural transformation, play that uniformly the histological difference as caused by cooling velocity inequality is excessive along plate thickness direction Effect.Belong to residual elements less than 0.10%, do not have effect, higher than 0.25% strong refinement medium temperature structural transformation product, shape Into MA islands band, cause armor plate strength too high, toughness declines.Mo belongs to noble element simultaneously, and cost is higher.
In process aspect, the present invention takes into account the matching of steel plate obdurability while considering inexpensive, and main innovation point is： 1) 1120 ~ 1180 DEG C of relatively low relation reheating temperature, ensure low C, low Nb, low Cr, Ni, Mo component system under original austenite it is brilliant Grain refinement control.2）The abundant rolling temperature control when recrystallization zone rolls, multiple tracks is used using the method for shortening minor tick The mode of secondary accumulative pressure carries out the crystal grain refinement of austenite.3) allowed in the finish rolling stage equally using accumulative press control mode Steel plate austenite before phase transformation is sufficiently flat, improves strain accumulation energy and defect point, improves nucleation site.4）Using higher cooling rate （15~35℃/s）Realization carries out being quickly cooled to medium temperature structural transformation region " with water cash equivalent ", while is homogenized with Mo along wall thickness The structural homogenity in direction.
The present invention is compared with prior art：The conventional continuous casting billet that thickness of strand can be used to be 230mm produces thickness Reach 30mm and the X70 level pipe line steels of the above so that can also produce think gauge Hi-grade steel without the production line of special thick continuous casting billet Pipe line steel, the development trend in market is adapted to, improved the market competitiveness of pipe line steel.And the yield strength of product of the present invention Rt0.5In 500 ~ 580MPa, tensile strength RmIn 600 ~ 650MPa, yield tensile ratio Rt0.5 /Rm≤ 0.90, elongation percentage A50>=24%,；- 20 DEG C of ballistic work KV2>=250J, -15 DEG C of DWTT section shearing rate SA >=95%；Hardness number HV10≤235。
Brief description of the drawings
Fig. 1 is the top layer metallographic structure figure of 30mm thickness product of the present invention；
Fig. 2 is metallographic structure figure at 1/4 thickness of 30mm thickness product of the present invention；
Fig. 3 is metallographic structure figure at 1/2 thickness of 30mm thickness product of the present invention.
Embodiment
The present invention is described in detail below：
Table 1 is the comparative example of various embodiments of the present invention；
Table 2 is the main technologic parameters list of various embodiments of the present invention；
Table 3 is various embodiments of the present invention transverse direction main performance detection statistics table.
Various embodiments of the present invention produce according to following steps：
1）The strand that thickness is 225-235mm is heated, its heating and temperature control makes at 1120-1180 DEG C Hot arc soaking time is not less than 40 minutes, and total heat time is not less than 250 minutes；
2）Roughing is carried out, control recrystallization zone rolling temperature uses maximum rolling force in 1050-1115 DEG C, deformation process Rolling, maximum rolling force are not less than 7500t；Rate of deformation is controlled in 4 ~ 5/s；Passage interval time is no more than 10s, and last three Secondary accumulation reduction ratio >=22%；Warm workpiece thickness is treated in 70-90mm, recrystallization zone total reduction is 60-70%；
3）It is conventional to carry out high-pressure water descaling, start rolling temperature of the control steel billet temperature in finish rolling；
4）Finish rolling is carried out, controlling its start rolling temperature, finishing temperature rolls 6 ~ 9 altogether at 750-850 DEG C at 850-950 DEG C It is secondary, accumulate reduction ratio 55-65%, and make down the 3rd and second passage accumulation reduction ratio >=20%；
5）Being cooled down, control opens cold temperature at 770-830 DEG C, it is cooled to 300 in the case where cooldown rate is 15-35 DEG C/s ~ 400℃；
6）Aligned, it is stand-by.
The composition value list of the various embodiments of the present invention of table 1 and comparative example（wt%）
The cooling controlling and rolling controlling process of the various embodiments of the present invention of table 2 and comparative example
Explanation：Table 1 is not one-to-one relationship with the data in table 2.
The various embodiments of the present invention of table 3 and comparative example transverse direction main performance detection statistics table
From table 3 it can be seen that the present invention, in the case where compression ratio is only 6.0-7.7, is passed through by 230mm continuous casting billets Low-carbon route is taken, the Cr relatively low by the use of cost of alloy carries out intensity as main intensified element and made up, by controlling thick, finish rolling Total reduction and passage accumulation pressure process and rolling temperature in journey obtain the X70 level pipeline pipeline steels of 30 ~ 38mm think gauges, tool There are excellent intensity and toughness matching, particularly low-temperature impact toughness and low temperature block hammer performance.
Present embodiment is only the best example, not to the restricted implementation of technical solution of the present invention.

Claims (2)

1. a kind of low compression ratio think gauge X70 level steel for gas delivering pipeline, its component and weight percent content are：C：0.03- 0.058%、Si:0.15~0.35%、Mn:1.72~1.90%、P：≤0.015%、S：≤0.002%、N：≤0.006%、Nb：0.055~ 0.065%、V：0.025~0.05%、Ti:0.015~0.025%、 Cr:0.1~0.40%、Ni：0.1~0.2%、Mo: 0.10~ 0.25%, remaining is Fe and inevitable impurity；Metallographic structure is：Top layer：Acicular ferrite+a small amount of bainite, thickness of slab 1/4 It is with 1/2 tissue:Acicular ferrite+a small amount of granular ferrite.
2. a kind of method of low compression ratio think gauge X70 level steel for gas delivering pipeline of production, its step：
1）It is to component and weight percent content：C：0.03-0.058%、Si:0.15~0.35%、Mn:1.72~1.90%、P： ≤0.015%、S：≤0.002%、N：≤0.006%、Nb：0.055~0.065%、V：0.025~0.05%、Ti:0.015~0.025%、 Cr:0.1~0.40%、Ni：0.1~0.2%、Mo:0.10 ~ 0.25%, remaining is Fe and inevitable impurity, thickness 225- 235mm strand is heated, and its heating and temperature control makes soaking zone soaking time be not less than 40 points at 1120-1180 DEG C Clock, total heat time are not less than 250 minutes；
2）Roughing is carried out, control recrystallization zone rolling temperature is rolled in 1050-1115 DEG C, deformation process using maximum rolling force System, maximum rolling force are not less than 7500t；Rate of deformation is controlled in 4 ~ 5/s；Passage interval time is no more than 10s, last three passage Accumulation reduction ratio >=22%；Warm workpiece thickness is treated in 70-90mm, recrystallization zone total reduction is 60-70%；
3）It is conventional to carry out high-pressure water descaling, start rolling temperature of the control steel billet temperature in finish rolling；
4）Finish rolling is carried out, controlling its start rolling temperature, finishing temperature rolls 6 ~ 9 passages altogether at 750-850 DEG C, tires out at 850-950 DEG C Product reduction ratio 55-65%, and make down the 3rd and second passage accumulation reduction ratio >=20%；
5）Cooled down, control opens cold temperature at 770-830 DEG C, and 300 ~ 400 are cooled in the case where cooldown rate is 33-35 DEG C/s ℃；
6）Aligned, it is stand-by.
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CN111748741B (en) * 2020-06-30 2022-01-25 武汉钢铁有限公司 Thick pipeline steel and low compression ratio production process thereof
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