CN117324373A - Method for improving performance uniformity of steel for CT 90-level continuous pipe - Google Patents

Method for improving performance uniformity of steel for CT 90-level continuous pipe Download PDF

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CN117324373A
CN117324373A CN202210729144.5A CN202210729144A CN117324373A CN 117324373 A CN117324373 A CN 117324373A CN 202210729144 A CN202210729144 A CN 202210729144A CN 117324373 A CN117324373 A CN 117324373A
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strip steel
thickness
steel
strip
plate blank
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张豪臻
章传国
孙磊磊
李龙
沈建兰
王金涛
庞厚君
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Baoshan Iron and Steel Co Ltd
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Baoshan Iron and Steel Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B21B3/02—Rolling special iron alloys, e.g. stainless steel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/004—Heating the product
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B21B45/0203—Cooling
    • B21B45/0209—Cooling devices, e.g. using gaseous coolants
    • B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
    • B21B45/0218—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for strips, sheets, or plates
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B2001/225—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length by hot-rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2261/00—Product parameters
    • B21B2261/02—Transverse dimensions
    • B21B2261/04—Thickness, gauge
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2261/00—Product parameters
    • B21B2261/20—Temperature

Abstract

The invention discloses a method for improving the uniformity of the performance of steel for a CT 90-level continuous pipe, which comprises the following three aspects: in the first aspect, in the strip steel plate blank heating stage, the plate blank is quickly heated in a heating furnace and is discharged from the furnace at a low temperature; in the second aspect, in the stage of laminar cooling of the strip steel, the proportion of cooling water is dynamically adjusted according to the thickness of the strip steel; in the third aspect, the leveling stage of the strip performs hierarchical control according to the thickness of the strip. The invention can greatly improve the manufacturing stability and effectively improve the performance uniformity of the hot-rolled pickled steel for CT 90-level continuous pipes.

Description

Method for improving performance uniformity of steel for CT 90-level continuous pipe
Technical Field
The invention relates to the technical field of hot-rolled pickled steel production, in particular to a method for improving the performance uniformity of CT 90-grade continuous steel.
Background
The continuous pipe is a jointless continuous pipe which is formed by obliquely connecting a plurality of sections of steel belts together and welding the steel belts through rolling, and is also called a continuous oil pipe, a flexible oil pipe, a coiled pipe or a coil pipe. The coiled tubing has been developed rapidly in recent decades due to its outstanding advantages in oilfield operations, and is widely used in the working processes of oil and gas field workover, drilling, completion, logging, etc., and is known as a "universal working machine".
The CT 90-level coiled tubing is a coiled tubing variety widely applied at home and abroad, and particularly has an increasing application scene along with the development of oil and gas operation, the progress of well drilling and completion and other technologies, and meanwhile, the downhole operation environment is increasingly harsh, so that higher requirements are put on the service life of the coiled tubing. The length of a coiled continuous pipe is several thousands meters to tens of meters, the service life of the coiled continuous pipe depends on the weak point of performance, and the quality uniformity of raw materials is critical because the rolled state structure of the raw materials is basically reserved in the finished pipe. The CT 90-level continuous pipe takes hot-rolled pickled steel strips as raw materials, is divided into 5-8 rolls by longitudinal cutting at a user end, is subjected to head-tail butt joint between the rolls, and finally is manufactured into a continuous pipe with the length of thousands of meters by a forming welding unit, the strips of the same parent roll are also used for producing different pipes, and the performance difference between the heads and the tails of the different strips greatly influences the performance of the pipe making and the finished pipe, so that the performance uniformity of the single-roll full-face and the different rolls is required.
The hot-rolled pickled steel for CT 90-grade continuous pipes has the advantages of thin thickness, high strength, extremely sensitive fluctuation of production process, and larger fluctuation of strength in the head-tail direction, the plate width direction and between different coils of products produced by adopting the conventional process. In the process of controlled rolling and cooling, the residual oxide skin on the surface of the steel strip is easy to adsorb water to cause uneven cooling, so that the local tissue performance is abnormal, meanwhile, the uneven distribution of the cooling water can cause larger temperature difference on the whole plate surface, and an effective improvement means for the strength difference between different positions of a single coil and different coils is lacking.
The existing methods for improving the uniformity of the performance of the hot rolled steel plate are mostly limited to improving the uniformity of cooling through process optimization in a laminar cooling stage, so that the uniformity of the performance is improved. According to the patent CN103599950A, the cooling time of the head-tail low-temperature region and the middle temperature equalizing region of the steel plate is controlled through roller speed transformation so as to realize uniform cooling of the steel plate; the patent CN101979166B utilizes a hot continuous rolling production unit to produce a hot rolled coil with low yield ratio in a water cooling, air cooling and water cooling mode; patent CN106216412a utilizes laminar staged cooling of the steckel mill to control phase change. In the patents, the adjustment is basically carried out from the cooling path of the steel strip by means of roller way speed change or sectional cooling and the like, so that the problem of non-uniformity of cooling water is difficult to solve fundamentally, fine control is not carried out for different thickness specifications, the cooling effect of the thin steel strip caused by the residual oxide skin on the surface is seldom clarified, the control is traced back to the slab heating process, and the technological measures for further improving the performance uniformity by adding flattening in the hot rolling finishing link after controlled rolling and controlled cooling are seldom proposed.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for improving the performance uniformity of the steel for the CT 90-grade continuous pipe, which can greatly improve the manufacturing stability and effectively improve the performance uniformity of the hot-rolled pickled steel for the CT 90-grade continuous pipe.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a method for improving the uniformity of the performance of steel for a CT 90-grade continuous pipe, which comprises the following three aspects:
in the first aspect, in the strip steel plate blank heating stage, the plate blank is quickly heated in a heating furnace and is discharged from the furnace at a low temperature;
in the second aspect, in the stage of laminar cooling of the strip steel, the proportion of cooling water is dynamically adjusted according to the thickness of the strip steel;
in the third aspect, the leveling stage of the strip performs hierarchical control according to the thickness of the strip.
Preferably, the first aspect specifically includes:
the in-furnace time of the strip steel plate blank is adjusted according to the actual thickness of the plate blank, and is controlled to be 0.60-0.95 min/mm;
the tapping temperature of the strip steel plate blank is controlled to be 1000-1200 ℃.
Preferably, the in-furnace time of the strip steel plate blank is adjusted according to the actual thickness of the strip steel, and the adjustment is specifically as follows:
when the thickness of the strip steel plate blank is [2.0,3.4 ] mm, the furnace time is 0.90-0.95 min/mm;
when the thickness of the strip steel plate blank is [3.4,5.1 ] mm, the furnace time is 0.75-0.90 min/mm;
when the thickness of the strip steel plate blank is [5.1,7.0] mm, the furnace time is 0.60-0.75 min/mm.
Preferably, the second aspect specifically includes:
when the thickness of the strip steel is [2.0,3.4 ] mm, the flow ratio between the cooling water on the upper surface of the strip steel and the cooling water on the lower surface of the strip steel is 0.45-0.60;
when the thickness of the strip steel is [3.4,5.1 ] mm, the flow ratio between the cooling water on the upper surface of the strip steel and the cooling water on the lower surface of the strip steel is 0.60-0.75;
when the thickness of the strip steel is [5.1,7.0] mm, the flow ratio between the cooling water on the upper surface of the strip steel and the cooling water on the lower surface of the strip steel is 0.75-0.90.
Preferably, the third aspect specifically includes:
when the thickness of the strip steel is [2.0,3.1 ] mm, the leveling force is less than or equal to 150t;
when the thickness of the strip steel is [3.1,4.3 ] mm, the leveling force is 150-250 t;
when the thickness of the strip steel is [4.3,5.6 ] mm, the leveling force is 250-350 t;
when the thickness of the strip steel is [5.6,7.0] mm, the flattening force is 350-450 t.
Preferably, the yield strength fluctuation of the head and the tail of the same coiled strip steel and the width of the same coiled strip steel is less than or equal to 45MPa, and the tensile strength fluctuation is less than or equal to 55MPa.
The method for improving the uniformity of the performance of the steel for the CT 90-level continuous pipe has the following beneficial effects:
1) The method combines various processes of low-temperature rapid heating of a slab, dynamic adjustment of laminar cooling water ratio and grading leveling, firstly, reduces primary oxide skin generation in a slab furnace from the control of a slab heating path before rolling so as to avoid local rapid cooling caused by water adsorption of residual oxide skin at partial positions of the surface of a steel strip in the process of controlled rolling and cooling, then finely controls the upper cooling water ratio and the lower cooling water ratio to improve cooling uniformity in the laminar flow stage after finish rolling, finally, carries out grading leveling according to the thickness specification of the steel strip in the leveling stage of hot rolling finishing so as to realize further performance homogenization, carries out innovative process design based on key links of the whole-flow production of the steel strip, and adopts a fine control means to greatly improve manufacturing stability;
2) According to the method disclosed by the invention, the performance uniformity of the hot-rolled pickled steel for CT 90-level continuous pipes can be effectively improved, so that the yield strength range of six points in the head-tail and plate width directions (edge-width 1/4-width 1/2) of the same steel belt is less than or equal to 45MPa, the yield strength range among steel belts with different thickness specifications is less than or equal to 60MPa, the whole yield strength range is 528-583 MPa, and the tensile strength range is 660-725 MPa.
Detailed Description
In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below with reference to examples.
The invention provides a method for improving the uniformity of the performance of steel for a CT 90-level continuous pipe, which comprises the following three aspects:
in the first aspect, in the strip steel plate blank heating stage, the plate blank is quickly heated in a heating furnace and is discharged from the furnace at a low temperature;
by adopting a slab heating path with rapid temperature rise and low-temperature tapping, when the heating temperature of a slab in a heating furnace is higher and the heating time is longer, besides higher energy consumption, more importantly, thicker primary oxide skin is generated in the furnace, the subsequent dephosphorization is difficult to remove, the subsequent controlled rolling and cooling process is easy to absorb water with partial residual oxide skin on the surface of steel, rapid cooling is caused, a low-temperature phase change structure of lower bainite even martensite is generated, and the partial strength is obviously abnormal.
Therefore, the method of the invention controls the tapping temperature of the slab to be 1000-1120 ℃ on the basis of ensuring that the slab can be fully austenitized and the load of rough rolling equipment is satisfied, and simultaneously adjusts the tapping temperature of the slab to be 0.60-0.95 min/mm according to the thickness of the slab in the furnace, and reduces the primary oxide skin generated on the surface of the steel billet in the furnace by reducing the heating temperature and the heating time of the strip steel slab, thereby avoiding uneven cooling caused by the adsorption of water by the partial residual oxide skin on the surface of the strip steel in the subsequent controlled rolling and controlled cooling process and influencing the stability of the tissue performance.
The in-furnace time of the strip steel plate blank is regulated according to the actual thickness of the strip steel, and the specific steps are as follows:
when the thickness of the strip steel plate blank is [2.0,3.4 ] mm, the furnace time is 0.90-0.95 min/mm;
when the thickness of the strip steel plate blank is [3.4,5.1 ] mm, the furnace time is 0.75-0.90 min/mm;
when the thickness of the strip steel plate blank is [5.1,7.0] mm, the furnace time is 0.60-0.75 min/mm.
In addition, if the ratio of the time in the furnace to the total time in the furnace when the temperature of the strip steel plate blank is heated to more than 900 ℃ is low, the sufficient dissolution of alloy elements and the homogenization of austenite cannot be ensured, meanwhile, the thickness and the plane direction of the plate blank have larger temperature difference, the final performance uniformity is affected, and if the ratio is high, the load of heating equipment is easily exceeded, and the energy consumption is caused. Therefore, the time ratio in the furnace when the temperature of the strip steel plate blank is heated to be more than 900 ℃ is controlled to be 40-55 percent.
In the second aspect, the cooling water proportion is dynamically adjusted according to the thickness of the strip steel in the strip steel laminar cooling stage;
in the laminar cooling stage, if more water is sprayed on the upper surface of the strip steel, uneven local ponding is easily formed on the surface of the strip steel, so that the strength is obviously increased, and the strength difference in the width direction is increased; if the upper surface cooling water is too small, the cooling is performed by spraying water on the lower surface, and the water sprayed on the lower surface is more likely to be involved in the edge portion of the strip steel, so that the coiling temperature of the width edge portion of the strip steel is lower than that of the middle position.
Therefore, the cooling water proportion of the upper surface and the lower surface of the strip steel in the laminar cooling stage is required to be controlled, so that the cooling water flow of the lower surface is larger than that of the upper surface, the cooling water proportion of the upper surface and the lower surface is limited to be between 0.45 and 0.90 according to the material cooling characteristics, and the cooling water flow proportion of the upper surface and the lower surface is dynamically adjusted according to the rolling thickness specification of the strip steel, so that the fine control is realized, and the optimal cooling uniformity in the width direction is achieved.
The specific dynamic adjustment is as follows:
when the thickness of the strip steel is [2.0,3.4 ] mm, the flow ratio between the cooling water on the upper surface of the strip steel and the cooling water on the lower surface of the strip steel is 0.45-0.60;
when the thickness of the strip steel is [3.4,5.1 ] mm, the flow ratio between the cooling water on the upper surface of the strip steel and the cooling water on the lower surface of the strip steel is 0.60-0.75;
when the thickness of the strip steel is 5.1,7.0 mm, the flow ratio between the cooling water on the upper surface of the strip steel and the cooling water on the lower surface of the strip steel is 0.75-0.90.
In the third aspect, a strip steel flattening stage, wherein grading control is performed according to the thickness of the strip steel and the flattening force;
the strip steel is flattened after hot rolling, so that the yield platform can be shortened or eliminated to a certain extent, the yield strength is improved, and the lifting amplitude is different for strip steel with different thickness specifications after flattening. The lower the yield strength before flattening is, the thinner the thickness is, the larger the flattening rolling force is, and the more the yield strength after flattening is improved, so that different flattening forces are implemented according to thickness specifications, on one hand, the uniformity of the strength in the width and length directions of the plate can be improved, and the strength difference between different strip steels can be reduced, so that the hot-rolled pickled steel for the continuous pipe with stable overall performance is obtained.
The leveling force execution hierarchical control is specifically as follows:
when the thickness of the strip steel is [2.0,3.1 ] mm, the leveling force is less than or equal to 150t;
when the thickness of the strip steel is [3.1,4.3 ] mm, the leveling force is 150-250 t;
when the thickness of the strip steel is [4.3,5.6 ] mm, the leveling force is 250-350 t;
when the thickness of the strip steel is [5.6,7.0] mm, the flattening force is 350-450 t.
Examples
The same strand composition was used in the examples and comparative examples, with the chemical composition (wt%) C:0.08%, si:0.24%, mn:1.9%, P:0.008%, S:0.001%, cu:0.23%, ni:0.14%, cr:0.72%, mo:0.11%, nb:0.09%, V:0.07%, ti:0.012%, ca:0.003%, alt:0.03%.
The thickness specification of the strip steel slabs of each example and comparative example was 250mm, the finish rolling temperature was 850 ℃, the coiling temperature was 560 ℃, the rolled thickness specification and other processes were as follows (see also Table 1):
example 1: the thickness specification of the rolled strip steel is 2.1mm, the tapping temperature of a plate blank is 1080 ℃, the furnace time is 235min (the coefficient is 0.94 min/mm), the furnace time of the plate blank with the temperature exceeding 900 ℃ is 118min (the ratio is 50%), the water-in-water ratio of laminar cooling water is 0.46, and the flattening force of 100t is adopted.
Example 2: the thickness specification of the rolled strip steel is 3.5mm, the tapping temperature of a plate blank is 1120 ℃, the furnace time is 190min (coefficient is 0.76 min/mm), wherein the furnace time of the plate blank temperature exceeding 900 ℃ is 105min (accounting for 55 percent), the water-on-water ratio of laminar cooling water is 0.62, and a 200t leveling force is adopted.
Example 3: the thickness specification of the rolled strip steel is 5.4mm, the tapping temperature of a plate blank is 1005 ℃, the furnace time is 175min (coefficient is 0.70 min/mm), the furnace time of the plate blank with the temperature exceeding 900 ℃ is 79min (accounting for 45 percent), the water-in-water ratio of laminar cooling water is 0.78, and the 300t leveling force is adopted.
Example 4: the thickness specification of the rolled strip steel is 6.7mm, the tapping temperature of a plate blank is 1050 ℃, the furnace time is 158min (coefficient is 0.63 min/mm), the furnace time of the plate blank with the temperature exceeding 900 ℃ is 63min (the ratio is 40%), the water-on-water-off ratio of laminar cooling water is 0.88, and the flattening force of 450t is adopted.
The mechanical properties of examples 1-4 are shown in Table 2, the yield strength at the point of the same tape steel head and tail and the plate width (edge-width 1/4-width 1/2) 6 is extremely poor at 33-45 MPa, the total yield strength is extremely poor at 55MPa, the total yield strength is in the range of 528-583 MPa, and the tensile strength is in the range of 660-725 MPa.
Comparative example 1: the thickness specification of the rolled strip steel is 2.1mm, the tapping temperature of a plate blank is 1200 ℃, the furnace time is 313min (coefficient is 1.25 min/mm), the furnace time of the plate blank with the temperature exceeding 900 ℃ is 109min (accounting for 35 percent), the water-on-water ratio of laminar cooling water is 0.46, and the flattening force of 100t is adopted. Comparative example 1 uses a higher tapping temperature, and the furnace time is longer, while the time in the furnace exceeding 900 ℃ is shorter.
Comparative example 2: the thickness specification of the rolled strip steel is 3.5mm, the tapping temperature of a plate blank is 1118 ℃, the furnace time is 188min (coefficient is 0.74 min/mm), the furnace time of the plate blank with the temperature exceeding 900 ℃ is 101min (the ratio is 54%), the water-on-water ratio of laminar cooling water is 0.82, and the flattening force of 200t is adopted. For this thickness specification, the laminar cooling water ratio in the method of the present invention is 0.60 to 0.75, in contrast to the cooling water ratio of comparative example 2 which is outside of this defined range.
Comparative example 3: the thickness specification of the rolled strip steel is 6.7mm, the tapping temperature of the plate blank is 1047 ℃, the furnace time is 163min (coefficient is 0.65 min/mm), the furnace time of the plate blank with the temperature exceeding 900 ℃ is 68min (the ratio is 42%), and the water-in-water ratio of the laminar cooling water is 0.88. Comparative example 3 was not flattened.
The mechanical properties of comparative examples 1-3 are also shown in Table 2, the yield strength at the 6 point position of the single roll head and tail and the plate width (edge-width 1/4-width 1/2) is extremely poor at 66-73 MPa, the total yield strength is extremely poor at 99MPa, the total yield strength is in the range of 498-597 MPa, and the tensile strength is in the range of 659-725 MPa.
TABLE 1 thickness specification and Process for examples and comparative examples of this patent
TABLE 2 mechanical Properties of examples and comparative examples of this patent
Therefore, according to the method, the low-temperature rapid heating, the dynamic adjustment of the laminar cooling water ratio and the grading leveling process of the plate blank are combined, the yield strength of a single coil is extremely poor from 66-73 MPa to 33-45 MPa, the total yield strength is extremely poor from 99MPa to 55MPa, and the performance uniformity of different positions and among different coils of the single coil of the steel belt is remarkably improved.
It will be appreciated by persons skilled in the art that the above embodiments are provided for illustration only and not for limitation of the invention, and that variations and modifications of the above described embodiments are intended to fall within the scope of the claims of the invention as long as they fall within the true spirit of the invention.

Claims (6)

1. A method for improving the uniformity of the performance of steel for a CT 90-grade continuous pipe, which is characterized by comprising the following three aspects:
in the first aspect, in the strip steel plate blank heating stage, the plate blank is quickly heated in a heating furnace and is discharged from the furnace at a low temperature;
in the second aspect, in the stage of laminar cooling of the strip steel, the proportion of cooling water is dynamically adjusted according to the thickness of the strip steel;
in the third aspect, the leveling stage of the strip performs hierarchical control according to the thickness of the strip.
2. The method for improving uniformity of steel properties for a CT 90-stage coiled tubing according to claim 1, wherein said first aspect specifically comprises:
the in-furnace time of the strip steel plate blank is adjusted according to the actual thickness of the strip steel and is controlled to be 0.60-0.95 min/mm;
the tapping temperature of the strip steel plate blank is controlled to be 1000-1200 ℃.
3. The method for improving the uniformity of steel properties for a CT 90-stage continuous tube according to claim 2, wherein the in-furnace time of the strip slab is adjusted according to the actual thickness of the strip as follows:
when the thickness of the strip steel plate blank is [2.0,3.4 ] mm, the furnace time is 0.90-0.95 min/mm;
when the thickness of the strip steel plate blank is [3.4,5.1 ] mm, the furnace time is 0.75-0.90 min/mm;
when the thickness of the strip steel plate blank is [5.1,7.0] mm, the furnace time is 0.60-0.75 min/mm.
4. The method for improving the uniformity of the performance of steel for a CT 90-stage continuous tube according to claim 1, wherein said second aspect specifically comprises:
when the thickness of the strip steel is [2.0,3.4 ] mm, the flow ratio between the cooling water on the upper surface of the strip steel and the cooling water on the lower surface of the strip steel is 0.45-0.60;
when the thickness of the strip steel is [3.4,5.1 ] mm, the flow ratio between the cooling water on the upper surface of the strip steel and the cooling water on the lower surface of the strip steel is 0.60-0.75;
when the thickness of the strip steel is [5.1,7.0] mm, the flow ratio between the cooling water on the upper surface of the strip steel and the cooling water on the lower surface of the strip steel is 0.75-0.90.
5. The method for improving the uniformity of the performance of steel for a CT 90-stage continuous tube according to claim 1, wherein said third aspect specifically comprises:
when the thickness of the strip steel is [2.0,3.1 ] mm, the leveling force is less than or equal to 150t;
when the thickness of the strip steel is [3.1,4.3 ] mm, the leveling force is 150-250 t;
when the thickness of the strip steel is [4.3,5.6 ] mm, the leveling force is 250-350 t;
when the thickness of the strip steel is [5.6,7.0] mm, the flattening force is 350-450 t.
6. The method for improving the uniformity of steel properties for a CT 90-grade continuous tube according to claim 1, wherein the fluctuation of yield strength of the head and the tail of the same coil of strip steel and the width of the same coil of strip steel is 45MPa or less and the fluctuation of tensile strength is 55MPa or less.
CN202210729144.5A 2022-06-24 2022-06-24 Method for improving performance uniformity of steel for CT 90-level continuous pipe Pending CN117324373A (en)

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