CN113102499A - 50Mn hot-rolled narrow strip steel and preparation method thereof - Google Patents

50Mn hot-rolled narrow strip steel and preparation method thereof Download PDF

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Publication number
CN113102499A
CN113102499A CN202110409954.8A CN202110409954A CN113102499A CN 113102499 A CN113102499 A CN 113102499A CN 202110409954 A CN202110409954 A CN 202110409954A CN 113102499 A CN113102499 A CN 113102499A
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steel
hot
cooling
rolled
narrow strip
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徐灯亮
梁鹏
马啸晨
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Tangshan City Delong Iron and Steel Co Ltd
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Tangshan City Delong 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
    • B21B15/00—Arrangements for performing additional metal-working operations specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/74—Temperature control, e.g. by cooling or heating the rolls or 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
    • 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
    • B21B45/04—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 de-scaling, e.g. by brushing
    • B21B45/06—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 de-scaling, e.g. by brushing of strip material
    • 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
    • B21B45/04—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 de-scaling, e.g. by brushing
    • B21B45/08—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 de-scaling, e.g. by brushing hydraulically
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • 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
    • B21B15/00—Arrangements for performing additional metal-working operations specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B2015/0057—Coiling the rolled product

Abstract

The invention provides 50Mn hot-rolled narrow strip steel and a preparation method thereof, belonging to the technical field of metallurgy. According to the invention, the thickness of the iron scale on the surface of the 50Mn hot-rolled narrow strip steel can be effectively reduced by controlling the heating temperature and matching with two descaling processes; the rough rolling and the finish rolling are carried out in sequence, so that crystal grains can be effectively refined, the band spacing in a band-shaped structure is improved, and the level of the band-shaped structure is reduced; through carrying out ultrafast cooling, link joint cooling, batch water-cooling and batching to the finish rolling base in proper order, compensatied the ribbon steel production line and not possessed laminar flow cooling's not enough, further reduced the banded structure rank of 50Mn steel, improved the tensile strength of 50Mn steel. The results of the examples show that the 50Mn hot-rolled narrow strip steel prepared by the preparation method provided by the invention has the banded structure grade of less than or equal to 0.5 grade, the thickness of the iron scale of less than or equal to 10 mu m and the tensile strength of more than or equal to 720 MPa.

Description

50Mn hot-rolled narrow strip steel and preparation method thereof
Technical Field
The invention relates to the technical field of metallurgy, in particular to 50Mn hot-rolled narrow strip steel and a preparation method thereof.
Background
The 50Mn steel is high-quality carbon structural steel, has high strength, elasticity and hardness, and is widely applied to manufacturing stress bearing parts, high wear-resisting parts and high stress parts. 50Mn steel is high in Mn content, a ferrite/pearlite banded structure is easy to appear in the rolling process, the existence of the banded structure causes uneven structure of the steel, influences the performance of the steel, forms anisotropy, reduces the plasticity, impact toughness and section shrinkage rate of the steel, and is not beneficial to deep processing treatment. Meanwhile, the Si content in 50Mn steel is generally more than or equal to 0.20%, and the steel rolled by the conventional hot rolling process is easy to generate red rust, so that the pickling of iron scales is difficult, the pickling consumption in the cold rolling process is increased, and the method is in contradistinction with the national strategy of energy conservation, emission reduction and sustainable development.
At present, manufacturers with 50Mn steel production capacity are all medium-wide strip steel production lines, 50Mn hot-rolled narrow strip steel production lines cannot effectively control the temperature after rolling because the 50Mn hot-rolled narrow strip steel production lines do not have laminar cooling systems, the produced 50Mn hot-rolled narrow strip steel generally has the defects of high level of strip structure, unclean strip steel pickling and the like, large-scale stable production cannot be realized, the mode of reducing Mn content in 50Mn steel can reduce the level of strip structure, but the reduction of Mn content can cause the reduction of tensile strength of the rolled strip steel, and mechanical property indexes cannot meet the use requirements. Therefore, it is desired to provide a method for producing a 50Mn hot-rolled narrow strip steel having a low band structure grade and excellent mechanical properties.
Disclosure of Invention
The invention aims to provide 50Mn hot-rolled narrow strip steel and a preparation method thereof, and the preparation method provided by the invention can reduce the level of a banded structure and improve the pickling effect on the premise of ensuring the mechanical property of the 50Mn hot-rolled narrow strip steel.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of 50Mn hot-rolled narrow strip steel, which comprises the following steps:
(1) heating a 50Mn steel billet to obtain a steel billet to be rolled; the heating comprises a first-stage heating section, a second-stage heating section and a soaking section which are sequentially carried out; the temperature of the first-stage heating is 1000-1030 ℃; the temperature of the second section heating is 1140-1160 ℃, and the temperature of the soaking section is 1200-1220 ℃;
(2) sequentially carrying out first pass descaling, rough rolling, second pass descaling and finish rolling on the steel blank to be rolled in the step (1) to obtain a finish rolling blank;
(3) and (3) sequentially carrying out ultra-fast cooling, chain plate cooling, coiling water cooling and coiling on the finish rolling blank in the step (2) to obtain the 50Mn hot rolled narrow strip steel.
Preferably, the 50Mn hot-rolled narrow strip steel comprises the following components in percentage by weight: c: 0.48 to 0.53%, Si: 0.20 to 0.26%, Mn: 0.73-0.80%, P: less than or equal to 0.035%, S: less than or equal to 0.025 percent, Cr: less than or equal to 0.10 percent, Ni: less than or equal to 0.10 percent, Cu: less than or equal to 0.10 percent and the balance of iron.
Preferably, the first heating time in the step (1) is 32-36 min, the second heating time is 43-50 min, and the soaking time is 20-24 min.
Preferably, the first-pass descaling and the second-pass descaling in the step (2) are high-pressure water descaling, and the water pressure of the first-pass descaling and the water pressure of the second-pass descaling are 17-19 MPa independently.
Preferably, the inlet temperature of rough rolling in the step (2) is 1185-1205 ℃, and the outlet temperature is 1180-1195 ℃.
Preferably, the inlet temperature of the finish rolling in the step (2) is 1130-1160 ℃, and the outlet temperature is 910-930 ℃.
Preferably, the cooling rate of the ultra-fast cooling in the step (3) is 80-120 ℃/s, and the water pressure of the ultra-fast cooling is 0.7-0.9 MPa.
Preferably, the water pressure for coiling water cooling in the step (3) is 0.20-0.21 MPa.
Preferably, the coiling speed in the step (3) is 1.9-2.1 m/s, and the coiling temperature is 640-660 ℃.
The invention provides 50Mn hot-rolled narrow strip steel prepared by the preparation method in the technical scheme, wherein the grade of a banded structure of the 50Mn hot-rolled narrow strip steel is less than or equal to 0.5 grade, and the thickness of an iron scale is less than or equal to 10 mu m.
The invention provides a preparation method of 50Mn hot-rolled narrow strip steel, which comprises the following steps: (1) heating a 50Mn steel billet to obtain a steel billet to be rolled; the heating comprises a first-stage heating section, a second-stage heating section and a soaking section which are sequentially carried out; the temperature of the first-stage heating is 1000-1030 ℃; the temperature of the second section heating is 1140-1160 ℃, and the temperature of the soaking section is 1200-1220 ℃; (2) sequentially carrying out first pass descaling, rough rolling, second pass descaling and finish rolling on the steel blank to be rolled in the step (1) to obtain a finish rolling blank; (3) and (3) sequentially carrying out ultra-fast cooling, chain plate cooling, coiling water cooling and coiling on the finish rolling blank in the step (2) to obtain the 50Mn hot rolled narrow strip steel. According to the invention, the thickness of the iron scale on the surface of the 50Mn hot-rolled narrow strip steel can be effectively reduced by controlling the heating temperature and matching with two descaling processes; the rough rolling and the finish rolling are carried out in sequence, so that crystal grains can be effectively refined, the band spacing in a band-shaped structure is improved, and the level of the band-shaped structure is reduced; through carrying out ultrafast cooling, link joint cooling, batch water-cooling and batching to the finish rolling base in proper order, compensatied the ribbon steel production line and not possessed laminar flow cooling's not enough, further reduced the banded structure rank of 50Mn steel, improved the tensile strength of 50Mn steel. The results of the examples show that the 50Mn hot-rolled narrow strip steel prepared by the preparation method provided by the invention has the banded structure grade of less than or equal to 0.5 grade, the thickness of the iron scale of less than or equal to 10 mu m and the tensile strength of more than or equal to 720 MPa.
The preparation method disclosed by the invention is low in implementation difficulty, is suitable for industrial production, and overcomes the technical bottleneck that a narrow strip steel production line cannot stably produce 50Mn steel with excellent mechanical properties in a large scale.
Drawings
FIG. 1 is a metallographic structure morphology of a 50Mn hot-rolled narrow strip in example 1;
FIG. 2 is a plot of scale thickness morphology for a 50Mn hot rolled ribbon of example 1;
FIG. 3 is a metallographic structure morphology of a 50Mn hot-rolled narrow strip in example 2;
FIG. 4 is a plot of scale thickness morphology for a 50Mn hot rolled ribbon of example 2;
FIG. 5 is a metallographic structure morphology of a 50Mn hot-rolled narrow strip in example 3;
FIG. 6 is a plot of scale thickness morphology for a 50Mn hot rolled ribbon of example 3;
FIG. 7 is a metallographic structure morphology chart of 50Mn steel in comparative example 1;
FIG. 8 is a scale thickness morphology of 50Mn steel in comparative example 1.
Detailed Description
The invention provides a preparation method of 50Mn hot-rolled narrow strip steel, which comprises the following steps:
(1) heating a 50Mn steel billet to obtain a steel billet to be rolled; the heating comprises a first-stage heating section, a second-stage heating section and a soaking section which are sequentially carried out; the temperature of the first-stage heating is 1000-1030 ℃; the temperature of the second section heating is 1140-1160 ℃, and the temperature of the soaking section is 1200-1220 ℃;
(2) sequentially carrying out first pass descaling, rough rolling, second pass descaling and finish rolling on the steel blank to be rolled in the step (1) to obtain a finish rolling blank;
(3) and (3) sequentially carrying out ultra-fast cooling, chain plate cooling, coiling water cooling and coiling on the finish rolling blank in the step (2) to obtain the 50Mn hot rolled narrow strip steel.
The method heats the 50Mn steel billet to obtain the steel billet to be rolled.
In the present invention, the composition of the 50Mn hot-rolled narrow strip preferably includes, in weight percent: c: 0.48 to 0.53%, Si: 0.20 to 0.26%, Mn: 0.73-0.80%, P: less than or equal to 0.035%, S: less than or equal to 0.025 percent, Cr: less than or equal to 0.10 percent, Ni: less than or equal to 0.10 percent, Cu: 0.10% or less and the balance iron, more preferably C: 0.50%, Si: 0.23%, Mn: 0.75%, P: less than or equal to 0.030 percent, S: less than or equal to 0.020%, Cr: less than or equal to 0.10 percent, Ni: less than or equal to 0.10 percent, Cu: less than or equal to 0.10 percent and the balance of iron. The invention further improves the mechanical property of the 50Mn hot-rolled narrow strip by optimizing the components and the content of the 50Mn hot-rolled narrow strip.
In the present invention, the 50Mn steel slab is preferably an as-cast billet. In the present invention, the shape of the 50Mn steel billet is preferably rectangular; the length of the rectangle is preferably 8000-9000 mm, and more preferably 8550 mm; the width of the rectangle is preferably 300-350 mm, and more preferably 330 mm; the thickness of the rectangle is preferably 150 mm. The invention adopts the rectangular blank for processing, thereby facilitating the subsequent rolling.
In the invention, the heating comprises a first-stage heating, a second-stage heating and a soaking stage which are sequentially carried out. In the invention, the temperature of the first-stage heating is 1000-1030 ℃, and 1020 ℃ is preferred; the time for the first heating is preferably 32-36 min, and more preferably 35 min; the temperature of the two-stage heating is 1140-1160 ℃, and preferably 1150 ℃; the time for the second-stage heating is preferably 43-50 min, and more preferably 45 min; the temperature of the soaking section is 1200-1220 ℃, and 1210 ℃ is preferred; the time of the soaking section is preferably 20-24 min, and more preferably 22 min. In the invention, the total heating time is preferably 95-110 min, and more preferably 100-105 min. The invention adopts a three-stage heating mode, and can avoid Fe in the alloy2SiO4And (4) solidifying.
After a steel blank to be rolled is obtained, the steel blank to be rolled is sequentially subjected to first-pass descaling, rough rolling, second-pass descaling and finish rolling to obtain a finish-rolled blank.
In the invention, the first-pass descaling and the second-pass descaling are preferably high-pressure water descaling; the water pressure of the first-pass descaling and the water pressure of the second-pass descaling are respectively and preferably 17-19 MPa, and more preferably 18 MPa. The time for the first-pass descaling and the second-pass descaling is not particularly limited, and can be determined according to the technical common knowledge of the skilled in the art. According to the invention, through two descaling processes, the stripping property of the iron scale can be effectively improved, and the thickness of the iron scale on the surface of the 50Mn hot-rolled narrow strip steel can be reduced.
In the invention, the inlet temperature of rough rolling is preferably 1185-1205 ℃, and more preferably 1190 ℃; the outlet temperature of the rough rolling is preferably 1180-1195 ℃, and more preferably 1180-1190 ℃. In the present invention, the number of passes of the rough rolling is preferably 4 to 6, and more preferably 5. In the present invention, the single-pass deformation amount of the rough rolling is not particularly limited, and may be determined according to the technical common knowledge of those skilled in the art. The rough rolling of the billet can lead the rough grains in the billet to be crushed preliminarily and improve the surface quality of the billet.
In the invention, the inlet temperature of the finish rolling is preferably 1130-1160 ℃, and more preferably 1150 ℃; the outlet temperature of the finish rolling is preferably 910-930 ℃, and more preferably 920 ℃. In the present invention, the pass of the finish rolling is preferably 8 to 10 passes, and more preferably 9 passes. In the present invention, the total deformation of the billet to be rolled after rough rolling and finish rolling is preferably not less than 83%, more preferably not less than 85%. In the present invention, the single-pass deformation amount of the finish rolling is not particularly limited, and may be determined according to the technical common knowledge of those skilled in the art. According to the invention, the fine rolling is carried out on the blank body, so that the crystal grains in the blank body can be further crushed, the tissue structure is refined, the band spacing in the band-shaped tissue is improved, and the level of the band-shaped tissue is reduced.
After a finish rolling blank is obtained, the finish rolling blank is sequentially subjected to ultrafast cooling, chain plate cooling, coiling water cooling and coiling to obtain the 50Mn hot rolled narrow strip steel.
In the invention, the cooling rate of the ultra-fast cooling is preferably 80-120 ℃/s, more preferably 90-110 ℃, and most preferably 100 ℃; the water pressure of the ultra-fast cooling is preferably 0.7-0.9 MPa, and more preferably 0.8 MPa. The method adopts an ultra-fast cooling mode to avoid the growth of crystal grains in the blank body and obtain the 50Mn steel with fine crystal grains.
In the invention, the temperature of the steel plate after the ultra-fast cooling is preferably 800-820 ℃, and more preferably 810-815 ℃.
In the invention, the running speed of the chain plate in the chain plate cooling is preferably 0.6-1 m/s, and more preferably 0.8 m/s; the chain plate is preferably cooled by water mist, and the water pressure of the water mist cooling is preferably 0.13-0.15 MPa, and more preferably 0.14 MPa. According to the invention, the water mist cooling arranged on the chain plate can make up the defect of no laminar cooling, and the strip steel is cooled.
In the invention, the temperature of the steel plate before the chain plate is cooled is preferably 750-770 ℃, and more preferably 760-765 ℃; the temperature of the steel plate after the chain plate is cooled is preferably 720-740 ℃, and more preferably 730-735 ℃.
In the present invention, the water pressure of the coiling water cooling is preferably 0.20 to 0.21 MPa. The invention can avoid the generation of abnormal structures such as martensite and the like caused by over-high cooling speed by controlling the water pressure of the coiling water cooling.
In the invention, the coiling speed is preferably 1.9-2.1 m/s, and more preferably 2.0 m/s; the coiling temperature is preferably 640-660 ℃, and more preferably 650 ℃.
According to the invention, the finish rolling billet is sequentially subjected to ultra-fast cooling, chain plate cooling, coiling water cooling and coiling, so that the defect that a narrow strip steel production line does not have laminar cooling is overcome, the banded structure grade of 50Mn steel is further reduced, and the tensile strength of the 50Mn steel is improved.
The preparation process is simple, does not need to purchase special equipment, and is suitable for industrial large-scale production.
The invention also provides the 50Mn hot-rolled narrow strip steel prepared by the preparation method in the technical scheme, wherein the banded structure grade of the 50Mn hot-rolled narrow strip steel is less than or equal to 0.5 grade, and the thickness of an iron scale is less than or equal to 10 mu m.
The 50Mn hot-rolled narrow strip steel provided by the invention has the advantages of low banded structure level, thin iron scale thickness and higher tensile strength, and can be used for manufacturing stress-bearing parts, high-wear-resistant parts and high-stress parts.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The preparation method of the 50Mn hot-rolled narrow strip steel comprises the following steps:
(1) heating a 50Mn rectangular billet with the length of 8550mm, the width of 330mm and the thickness of 150mm to obtain a billet to be rolled; the heating is a first-stage heating, a second-stage heating and a soaking section which are sequentially carried out; the temperature of the first heating stage is 1025 ℃, and the heating time is 34 min; the temperature of the second-stage heating is 1157 ℃, and the heating time is 50 min; the temperature of the soaking section is 1212 ℃, the heating time is 24min, and the total heating time is 108 min;
(2) sequentially carrying out first pass descaling, rough rolling, second pass descaling and finish rolling on the steel blank to be rolled in the step (1) to obtain a finish rolling blank; the water pressure of the first-time descaling is 18.2 MPa; the inlet temperature of rough rolling is 1196 ℃, the outlet temperature of the rough rolling is 1190 ℃, the pass is 5, and the thickness of the rough-rolled blank is 26.2 mm; the water pressure for descaling in the second pass is 18.5 MPa; the inlet temperature of the finish rolling is 1157 ℃, the outlet temperature of the finish rolling is 920 ℃, and the pass is 9; after the steel blank to be rolled is subjected to rough rolling and finish rolling, the total deformation is 83%;
(3) sequentially carrying out ultra-fast cooling, chain plate cooling, coiling water cooling and coiling on the finish rolling blank in the step (2) to obtain 50Mn hot-rolled narrow strip steel; the water pressure of the ultrafast cooling is 0.90MPa, the cooling rate is 100 ℃/s, and the temperature of the steel plate after the ultrafast cooling is 810 ℃; the temperature of a steel plate before chain plate cooling is 762 ℃, the running speed of the chain plate in the chain plate cooling process is 0.8m/s, the water mist pressure in the chain plate cooling process is 0.15MPa, and the temperature of the steel plate after the chain plate cooling is 731 ℃; the water pressure for coiling and cooling is 0.20 MPa; the winding speed was 1.9m/s and the winding temperature was 658 ℃.
The 50Mn hot-rolled narrow strip steel obtained in the embodiment comprises the following components in percentage by mass: c: 0.48%, Si: 0.23%, Mn: 0.80%, P: 0.020%, S: 0.018%, Cr: 0.03%, Ni: 0.03%, Cu: 0.06% and balance iron.
The 50Mn hot-rolled narrow strip obtained in this example had a band structure grade of 0.5, an iron scale thickness of 8.29 μm and a tensile strength of 754 MPa.
Example 2
The preparation method of the 50Mn hot-rolled narrow strip steel comprises the following steps:
(1) heating a 50Mn rectangular billet with the length of 8550mm, the width of 330mm and the thickness of 150mm to obtain a billet to be rolled; the heating is a first-stage heating, a second-stage heating and a soaking section which are sequentially carried out; the temperature of the first heating stage is 1002 ℃, and the heating time is 36 min; the temperature of the second-stage heating is 1141 ℃, and the heating time is 50 min; the temperature of the soaking section is 1205 ℃, the heating time is 24min, and the total heating time is 110 min;
(2) sequentially carrying out first pass descaling, rough rolling, second pass descaling and finish rolling on the steel blank to be rolled in the step (1) to obtain a finish rolling blank; the water pressure of the first-time descaling is 17.9 MPa; the inlet temperature of rough rolling is 1188 ℃, the outlet temperature of rough rolling is 1182 ℃, the pass is 5, and the thickness of the rough-rolled blank is 25.6 mm; the water pressure for descaling in the second pass is 18.9 MPa; the inlet temperature and the outlet temperature of the finish rolling are 1134 ℃ and 911 ℃ respectively, and the pass is 9; after the steel blank to be rolled is subjected to rough rolling and finish rolling, the total deformation is 83%;
(3) sequentially carrying out ultra-fast cooling, chain plate cooling, coiling water cooling and coiling on the finish rolling blank in the step (2) to obtain 50Mn hot-rolled narrow strip steel; the water pressure of the ultrafast cooling is 0.71MPa, the cooling rate is 100 ℃/s, and the temperature of the steel plate after the ultrafast cooling is 802 ℃; the temperature of the steel plate before the chain plate is cooled is 751 ℃, the running speed of the chain plate in the cooling process of the chain plate is 0.8m/s, the water mist pressure in the cooling process of the chain plate is 0.15MPa, and the temperature of the steel plate after the chain plate is cooled is 722 ℃; the water pressure for coiling and cooling is 0.21 MPa; the coiling speed was 2.1m/s and the coiling temperature was 652 ℃.
The 50Mn hot-rolled narrow strip steel obtained in the embodiment comprises the following components in percentage by mass: c: 0.53%, Si: 0.20%, Mn: 0.73%, P: 0.015%, S: 0.010%, Cr: 0.07%, Ni: 0.04%, Cu: 0.02% and balance iron.
The 50Mn hot-rolled narrow strip obtained in this example had a non-strip structure, an iron scale thickness of 7.95 μm, and a tensile strength of 778 MPa.
Example 3
The preparation method of the 50Mn hot-rolled narrow strip steel comprises the following steps:
(1) heating a 50Mn rectangular billet with the length of 8550mm, the width of 330mm and the thickness of 150mm to obtain a billet to be rolled; the heating is a first-stage heating, a second-stage heating and a soaking section which are sequentially carried out; the temperature of the first heating is 1017 ℃, and the heating time is 32 min; the temperature of the second-stage heating is 1150 ℃, and the heating time is 44 min; the temperature of the soaking section is 1220 ℃, the heating time is 20min, and the total heating time is 96 min;
(2) sequentially carrying out first pass descaling, rough rolling, second pass descaling and finish rolling on the steel blank to be rolled in the step (1) to obtain a finish rolling blank; the water pressure of the first-time descaling is 17.2 MPa; the inlet temperature of rough rolling is 1195 ℃, the outlet temperature of the rough rolling is 1187 ℃, the pass is 5, and the thickness of the rough-rolled blank is 26.5 mm; the water pressure of the second-pass descaling is 18.8 MPa; the inlet temperature of finish rolling is 1145 ℃, the outlet temperature of finish rolling is 927 ℃, and the pass is 9; after the steel blank to be rolled is subjected to rough rolling and finish rolling, the total deformation is 83%;
(3) sequentially carrying out ultra-fast cooling, chain plate cooling, coiling water cooling and coiling on the finish rolling blank in the step (2) to obtain 50Mn hot-rolled narrow strip steel; the water pressure of the ultra-fast cooling is 0.90MPa, the cooling rate is 100 ℃/s, and the temperature of the ultra-fast cooled steel plate is 819 ℃; the temperature of the steel plate before the chain plate is cooled is 767 ℃, the running speed of the chain plate in the cooling process of the chain plate is 0.8m/s, the water mist pressure in the cooling process of the chain plate is 0.15MPa, and the temperature of the steel plate after the chain plate is cooled is 738 ℃; the water pressure for coiling and cooling is 0.20 MPa; the winding speed was 1.9m/s and the winding temperature was 658 ℃.
The 50Mn hot-rolled narrow strip steel obtained in the embodiment comprises the following components in percentage by mass: c: 0.52%, Si: 0.26%, Mn: 0.77%, P: 0.032%, S: 0.007%, Cr: 0.01%, Ni: 0.08%, Cu: 0.02% and balance iron.
The 50Mn hot-rolled narrow strip obtained in this example had an banded structure, an iron scale thickness of 7.83 μm and a tensile strength of 762 MPa.
Comparative example 1
The preparation method of the 50Mn steel comprises the following steps:
(1) heating a 50Mn rectangular billet with the length of 8550mm, the width of 330mm and the thickness of 150mm to obtain a billet to be rolled; the heating is a first-stage heating, a second-stage heating and a soaking section which are sequentially carried out; the temperature of the first heating section is 1120 ℃, and the heating time is 35 min; the temperature of the two-stage heating is 1250 ℃, and the heating time is 55 min; the temperature of the soaking section is 1230 ℃, the heating time is 30min, and the total heating time is 120 min;
(2) sequentially carrying out first pass descaling, rough rolling, second pass descaling and finish rolling on the steel blank to be rolled in the step (1) to obtain a finish rolling blank; the water pressure of the first-time descaling is 15.2 MPa; the inlet temperature of rough rolling is 1225 ℃, the outlet temperature of rough rolling is 1180 ℃, the pass is 5, and the thickness of the rough-rolled blank is 36 mm; the water pressure for the second-pass descaling is 15.8 MPa; the inlet temperature of the finish rolling is 1180 ℃, the outlet temperature of the finish rolling is 975 ℃, and the pass is 9; after the steel blank to be rolled is subjected to rough rolling and finish rolling, the total deformation is 83%;
(3) sequentially carrying out ultra-fast cooling, chain plate operation and coiling on the finish rolling blank in the step (2) to obtain 50Mn steel; the water pressure of the ultra-fast cooling is 0.50MPa, the cooling rate is 70 ℃/s, and the temperature of the ultra-fast cooled steel plate is 885 ℃; carrying out water mist cooling without a chain plate, wherein the running speed of the chain plate is 1.5m/s, and no cooling water is coiled; the coiling speed is 4m/s, and the coiling temperature is 820 ℃.
The 50Mn steel obtained in comparative example 1 comprises the following components in percentage by mass: c: 0.52%, Si: 0.30%, Mn: 0.90%, P: 0.025%, S: 0.020%, Cr: 0.01%, Ni: 0.02%, Cu: 0.02% and balance iron.
The 50Mn steel obtained in comparative example 1 had a band structure of grade 3, an iron scale thickness of 19.20 μm, and a tensile strength of 695 MPa.
It can be seen through the performance comparison of the 50Mn steel prepared in the embodiments 1-3 and the comparative example 1 that the defect that a narrow strip steel production line does not have laminar cooling is overcome by sequentially carrying out ultra-fast cooling, chain plate cooling, coiling water cooling and coiling on a finish rolled blank, the banded structure level and the oxide scale thickness of the 50Mn steel are further reduced, and the tensile strength of the 50Mn steel is improved.
FIG. 1 is a metallographic structure morphology of a 50Mn hot-rolled narrow strip in example 1. As can be seen from FIG. 1, the 50Mn hot-rolled narrow strip prepared in example 1 of the present invention has fine internal crystal grains, uniform structure distribution and low level of banded structure.
FIG. 2 is a graph showing the scale thickness profile of a 50Mn hot-rolled narrow strip in example 1. As can be seen from FIG. 2, the 50Mn hot-rolled narrow strip produced in example 1 of the present invention has a small scale thickness.
FIG. 3 is a metallographic structure morphology of the 50Mn hot-rolled narrow strip in example 2. As can be seen from FIG. 3, the 50Mn hot-rolled narrow strip steel prepared in example 2 of the present invention has fine internal crystal grains, uniform structure distribution and no strip structure.
FIG. 4 is a graph of scale thickness morphology for 50Mn hot rolled ribbon steel of example 2. As can be seen from FIG. 4, the 50Mn hot-rolled narrow strip produced in example 2 of the present invention has a small scale thickness.
FIG. 5 is a metallographic structure morphology of the 50Mn hot-rolled narrow strip in example 3. As can be seen from FIG. 5, the 50Mn hot-rolled narrow strip steel prepared in example 3 of the present invention has fine internal crystal grains, uniform structure distribution and no strip structure.
FIG. 6 is a plot of scale thickness morphology for the 50Mn hot rolled ribbon of example 3. As can be seen from FIG. 6, the 50Mn hot-rolled narrow strip produced in example 3 of the present invention has a small scale thickness.
FIG. 7 is a metallographic structure morphology chart of 50Mn steel in comparative example 1. As can be seen from fig. 7, the 50Mn steel prepared in comparative example 1 has large internal crystal grains and a high band structure grade.
FIG. 8 is a scale thickness morphology of 50Mn steel in comparative example 1. As can be seen from fig. 8, the 50Mn steel prepared in comparative example 1 has a thick scale thickness.
As can be seen from the comparison of the performances of the 50Mn steels prepared in the embodiments 1-3 and the comparative example 1, the finish rolling blank is sequentially subjected to ultra-fast cooling, chain plate cooling, coiling water cooling and coiling, so that the laminar cooling effect can be achieved, the banded structure grade and the oxide scale thickness of the 50Mn steel are reduced, and the tensile strength is improved.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A preparation method of 50Mn hot-rolled narrow strip steel comprises the following steps:
(1) heating a 50Mn steel billet to obtain a steel billet to be rolled; the heating comprises a first-stage heating section, a second-stage heating section and a soaking section which are sequentially carried out; the temperature of the first-stage heating is 1000-1030 ℃; the temperature of the second section heating is 1140-1160 ℃, and the temperature of the soaking section is 1200-1220 ℃;
(2) sequentially carrying out first pass descaling, rough rolling, second pass descaling and finish rolling on the steel blank to be rolled in the step (1) to obtain a finish rolling blank;
(3) and (3) sequentially carrying out ultra-fast cooling, chain plate cooling, coiling water cooling and coiling on the finish rolling blank in the step (2) to obtain the 50Mn hot rolled narrow strip steel.
2. The method of manufacturing of claim 1 wherein said 50Mn hot rolled narrow strip comprises, in weight percent: c: 0.48 to 0.53%, Si: 0.20 to 0.26%, Mn: 0.73-0.80%, P: less than or equal to 0.035%, S: less than or equal to 0.025 percent, Cr: less than or equal to 0.10 percent, Ni: less than or equal to 0.10 percent, Cu: less than or equal to 0.10 percent and the balance of iron.
3. The preparation method according to claim 1, wherein the first heating period in the step (1) is 32-36 min, the second heating period is 43-50 min, and the soaking period is 20-24 min.
4. The preparation method according to claim 1, wherein the first-pass descaling and the second-pass descaling in the step (2) are high-pressure water descaling, and the water pressure of the first-pass descaling and the water pressure of the second-pass descaling are 17-19 MPa independently.
5. The preparation method according to claim 1, wherein the rough rolling in the step (2) has an inlet temperature of 1185-1205 ℃ and an outlet temperature of 1180-1195 ℃.
6. The production method according to claim 1, wherein the finish rolling in the step (2) has an inlet temperature of 1130 to 1160 ℃ and an outlet temperature of 910 to 930 ℃.
7. The preparation method according to claim 1, wherein the cooling rate of the ultra-fast cooling in the step (3) is 80-120 ℃/s, and the water pressure of the ultra-fast cooling is 0.7-0.9 MPa.
8. The production method according to claim 1, wherein the water pressure for the coiling water cooling in the step (3) is 0.20 to 0.21 MPa.
9. The method according to claim 1, wherein the coiling speed in the step (3) is 1.9-2.1 m/s, and the coiling temperature is 640-660 ℃.
10. The 50Mn hot-rolled narrow strip prepared by the preparation method of any one of claims 1 to 9, wherein the 50Mn hot-rolled narrow strip has a band structure grade of less than or equal to 0.5 grade and an oxide scale thickness of less than or equal to 10 μm.
CN202110409954.8A 2021-04-16 2021-04-16 50Mn hot-rolled narrow strip steel and preparation method thereof Withdrawn CN113102499A (en)

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