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CN112077165B - Rolling method of 50Mn thin high-carbon cold-rolled steel sheet - Google Patents

Rolling method of 50Mn thin high-carbon cold-rolled steel sheet Download PDF

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Publication number
CN112077165B
CN112077165B CN202010901367.6A CN202010901367A CN112077165B CN 112077165 B CN112077165 B CN 112077165B CN 202010901367 A CN202010901367 A CN 202010901367A CN 112077165 B CN112077165 B CN 112077165B
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rolling
welding
less
annealing
equal
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CN112077165A (en
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王野
郭久明
齐林雷
李远旭
郑茂刚
包红军
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Rizhao Baohua New Material Co Ltd
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Rizhao Baohua New Material Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
    • B21C37/02—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of sheets
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
    • 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
    • C22C38/002—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
    • C22C38/04—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
    • C22C38/06—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
    • 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
    • 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
    • C21D2211/009—Pearlite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Abstract

The invention discloses a rolling method of a 50Mn thin high-carbon cold-rolled steel plate, belonging to the field of cold-rolled steel plate rolling, and the production process comprises the following steps: heating a plate blank → rough rolling → finish rolling → cooling → coiling the hot rolled material → uncoiling → welding → crushing the scale → acid washing and rinsing → rolling of five racks → coiling → coil unloading → annealing → leveling → shearing → cold rolling of the finished product. Compared with the prior art, the stable production of the 50Mn high-carbon steel on an acid rolling line can be realized, frequent strip breakage of a welding line is avoided, the quality of a 50Mn cold-rolled sheet final product is guaranteed, and the use requirement of a user is met.

Description

Rolling method of 50Mn thin high-carbon cold-rolled steel sheet
Technical Field
The invention relates to a production process of 50Mn high-carbon steel, in particular to a rolling method suitable for a thin 50Mn high-carbon cold-rolled steel plate with the thickness less than or equal to 2.5 mm.
Background
A 50Mn high carbon steel is a high carbon steel product which is widely used, and is generally an intermediate product of a so-called hot rolled steel sheet which is produced from a slab through a continuous hot rolling process, and is cold rolled after a pickling and spheroidizing annealing process to produce a cold rolled steel sheet. The cold-rolled steel sheet is then subjected to an annealing process and a cold-rolling process in this order, and a cold-rolled steel sheet having a desired thickness is produced.
With the progress of the technological process of the hot rolling production line, the production of hot rolled steel plates with the thickness of below 2.5mm is feasible. Because the 50Mn high-carbon steel has high content of C, Si and Mn and high strength, the strength of the high-carbon steel is higher than that of the high-carbon steel of the traditional hot rolling process by more than 60MPa under the same specification through the production of a continuous rolling, continuous casting and hot rolling production line. However, since the strength is too high, the thermal conductivity is poor for high carbon steel with a carbon content of more than 0.5% and a thickness of less than or equal to 2.5mm, a significant temperature difference is generated between a welding zone and an unheated part when the high-strength 50Mn high carbon steel is produced through a continuous pickling line, and cracks are easily formed due to internal stress caused in a weld when a molten pool is rapidly cooled; the weld and the heat affected zone are more likely to generate hard and brittle high carbon martensite, so the hardenability tendency and the crack sensitivity are greater, and the weldability is poor. Due to the influence of high welding temperature, crystal grains grow fast, carbides are easy to accumulate and grow on crystal boundaries, welding seams are weak, the strength of welding joints is reduced, rolling is difficult in a cold rolling stage, and particularly high-carbon steel with the thickness of less than or equal to 1.5mm is produced, and frequent strip breakage of the welding seams is caused. Therefore, at present, domestic medium-high carbon strip steel is basically produced on a single-stand rolling mill, and the production efficiency is low.
In order to overcome the technical defects of weak welding seams and cold rolling cracking, the invention of China applies for a high-carbon steel thin strip and a production method thereof (CN201910777534.8) to directly replace a cold rolling annealing product by producing hot-rolled thin strip steel with the thickness of less than 2.5mm at one time. However, since the annealing and cold rolling processes are processes necessary for forming fine spheroidized cementite in the pearlite structure of the hot-rolled high carbon steel sheet, this method has a thin gauge and stability, but the yield strength is not large because of the pearlite contained therein, the fatigue life is reduced, and the quality of the final product is not satisfactory.
Disclosure of Invention
The technical task of the invention is to provide a rolling method of a 50Mn thin high-carbon cold-rolled steel sheet aiming at the defects of the prior art.
The technical scheme for solving the technical problem is as follows: a rolling method of a 50Mn thin high-carbon cold-rolled steel plate is characterized by comprising the following production process steps: heating a plate blank → rough rolling → finish rolling → cooling → coiling to obtain a hot rolled material → uncoiling → welding → crushing scale → acid washing and rinsing → rolling of a five-rack → coiling → coil unloading → annealing → flattening → shearing → cold rolling to obtain a finished product; wherein:
s1, heating of the plate blank: the 50Mn high-carbon steel hot rolled material comprises the following components: 0.5 to 0.56 percent of C; 0.2 to 0.3 percent of Si; mn: 0.6% -0.7%, P: less than or equal to 0.025 percent; s: less than or equal to 0.005 percent; and Als: less than or equal to 0.02 percent; cr: less than or equal to 0.02 percent; ni is less than or equal to 0.02 percent; cu is less than or equal to 0.02 percent, and the balance is Fe and inevitable impurities;
s2, rough rolling;
s3, finish rolling;
s4, cooling;
s5, coiling to obtain a hot rolled material;
s6, uncoiling the hot rolled material;
s7, welding: welding by using a wire filling welding machine, adopting 1-time preheating and 2-time annealing process, wherein the thickness of the raw material is less than or equal to 1.50mm and less than 2mm, the welding speed is 7.2-7.8 m/min, the preheating power is 10-12KW, and the annealing power is 18-20 KW; the thickness of the raw material is less than or equal to 2mm and less than or equal to 2.5mm, the welding speed is 7.8m/min, the preheating power is 14KW, and the annealing power is 22 KW;
s8, breaking scales;
s9, acid washing and rinsing: the speed of the pickling process section is less than or equal to 120 m/min;
s10, cold rolling: adopting a five-frame continuous rolling process, wherein the compression ratio is 36-50%;
s11, coiling;
s12, coil stripping;
s13, annealing: the annealing temperature is heated from 400 ℃ to 720 ℃, and the heating time is 12-13 hours; keeping the temperature for 10-11 hours at the annealing temperature of 720 ℃;
s15, leveling;
and S16, shearing to obtain a cold-rolled finished product.
The annealing process of 1 time of preheating and 2 times of annealing comprises the following specific operations: after the welding seam is preheated for 1 time and annealed for 1 time, the laser welding function of the welding machine is closed by adopting manual control, the annealing power is kept, and the welding wheel of the welding machine moves away from the welding seam again.
The annealing adopts a hood annealing process.
Parameters in the leveling step are as follows: the thickness is less than or equal to 1.5mm, and the leveling elongation is 1.0%; the thickness is more than 1.5mm, and the flat elongation is 1.2%.
Compared with the prior art, the invention has the following outstanding beneficial effects:
1. the high-strength 50Mn high-carbon steel is welded under the control of an acid rolling welding machine, so that the rolling stability in the cold rolling stage is ensured, frequent strip breakage of a welding line is avoided, and the stable production of the 50Mn high-carbon steel on an acid rolling line is realized;
2. the compatibility of thin specification and stability is realized, the strength is ensured, the yield strength is high, the fatigue life is not influenced, the quality of a 50Mn cold-rolled sheet end product is ensured, and the use requirement of a user is met;
3. the existing equipment and facilities are utilized, the components are simple, the production cost is not increased, and the popularization is convenient.
Detailed Description
The present invention will be further described with reference to the following specific embodiments. Unless defined otherwise, technical or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The invention relates to a rolling method suitable for a thin 50Mn high-carbon cold-rolled steel plate with the thickness less than or equal to 2.5 mm.
The production process comprises the following steps: heating a plate blank → rough rolling → finish rolling → cooling → coiling to obtain a hot rolled material → uncoiling → welding → crushing scale → acid washing and rinsing → rolling of a five-rack → coiling → coil unloading → annealing → flattening → shearing → cold rolling to obtain a finished product.
S1, heating the plate blank
The 50Mn high-carbon steel hot rolled material comprises the following components: 0.5 to 0.56 percent of C; 0.2 to 0.3 percent of Si; mn: 0.6% -0.7%, P: less than or equal to 0.025 percent; s: less than or equal to 0.005 percent; and Als: less than or equal to 0.02 percent; cr: less than or equal to 0.02 percent; ni is less than or equal to 0.02 percent; cu is less than or equal to 0.02 percent, and the balance is Fe and inevitable impurities.
S2 rough rolling
Outlet temperature: 1160-1180 ℃. The temperature difference between the inlet of R1 and the plate is less than or equal to 30 ℃, and the outlet of R3 is more than 950 ℃.
S3 finish rolling
The descaling pressure is more than or equal to 340bar, and the finishing temperature is 820-860 ℃.
S4, cooling
Laminar cooling, back cooling and water spraying cooling of the upper and lower surface nozzles are adopted to maintain the opening degree of the nozzle valve at 50%.
S5, coiling to obtain the hot-rolled material
The coiling temperature is 675-705 ℃.
The hot rolled product is offline and intensively cooled slowly, air blowing and forced cooling are not needed, the slow cooling requires 48 hours or the temperature of a hot rolled coil is less than or equal to 200 ℃.
The properties of the hot rolled material obtained by the above steps are shown in the following table:
thickness mm Yield strength MPa Tensile strength MPa Elongation percentage%
1.50 597 870 17.6
1.80 578 865 18.5
2.00 540 846 19.3
2.20 530 843 19.4
2.50 527 840 20.2
S6 uncoiling of hot rolled material
The feeding temperature is less than or equal to 60 ℃.
S7, welding
As the 50Mn high-carbon steel has high contents of C, Si and Mn and high strength, hard and brittle high-carbon martensite is more easily generated in a welding seam and a heat affected zone, and the welding performance is poor.
In order to ensure the welding stability and the stable production, the steel grade requirement of lap welding is carried out on the 50Mn high-carbon steel welding requirement and the 50Mn steel grade, the yield strength difference of the two steel grades is less than or equal to 150MPa, and the thickness difference of the two steel coils is less than 10 percent or less than 0.1 mm; the difference in width must not exceed 200 mm.
The welding machine of the acid rolling combined unit is a Mibach wire filling welding machine. The basic parameters are: the maximum welding speed is 12 m/min; the welding power is 12KW at maximum; the maximum pressure of the leveling wheel is 100 Bar; the maximum preheating power is 40KW, the maximum annealing power is 40KW, and the maximum laser head pressure is 100 Bar; the wire feeding speed of the wire filling is 15 m/min.
The lap welding parameters of the 50Mn high-carbon steel and the 50Mn high-carbon steel are shown in the following table, wherein the process parameters are percentages of the welding machine parameters.
Wherein,
the thickness of the raw material is more than or equal to 1.50mm and less than 2mm, the welding speed is 60-65% (7.2-7.8 m/min) of the maximum parameter of the welding machine, the welding power is 75% (9KW) of the maximum parameter of the welding machine, the pressure of the leveling wheel is 10% (10Bar) of the maximum parameter of the welding machine, the preheating power is 25-30% (10-12KW) of the maximum parameter of the welding machine, the annealing power is 45-50% (18-20KW) of the maximum parameter of the welding machine, the pressure of the laser head is 25% (25Bar) of the maximum parameter of the welding machine, and the wire feeding speed is 75% (11.25m/min) of the maximum parameter of the welding machine.
The thickness of the raw material is not less than 2mm and not more than 2.5mm, the welding speed is 7.8m/min, the welding power is 9.6-10.2 KW, the pressure of a leveling wheel is 15-20 Bar, the preheating power is 14KW, the annealing power is 22KW, the pressure of a laser head is 30Bar, and the wire feeding speed is 12 m/min.
Figure BDA0002659869280000061
The lap welding parameters of the 50Mn high-carbon steel and the low-carbon steel are shown in the following table, wherein the process parameters are percentages of the parameters of the welding machine.
Wherein,
the thickness of the raw material is more than or equal to 1.50mm and less than 2mm, the welding speed is 65-70% (7.8-8.4 m/min) of the maximum parameter of the welding machine, the welding power is 75-80% (9-9.6 KW) of the maximum parameter of the welding machine, the pressure of the leveling wheel is 10% (10Bar) of the maximum parameter of the welding machine, the preheating power is 25-30% (10-12KW) of the maximum parameter of the welding machine, the annealing power is 30-45% (12-18 KW) of the maximum parameter of the welding machine, the pressure of the laser head is 25% (25Bar) of the maximum parameter of the welding machine, and the wire feeding speed is 75% (11.25m/min) of the maximum parameter of the welding machine.
The thickness of the raw material is not less than 2mm and not more than 2.5mm, the welding speed is 7.8m/min, the welding power is 9.6-10.2 KW, the pressure of a leveling wheel is 15Bar, the preheating power is 14KW, the annealing power is 22KW, the pressure of a laser head is 30Bar, and the wire feeding speed is 12 m/min.
Figure BDA0002659869280000071
The welding process of the wire filling welding machine comprises three steps of preheating, welding and annealing: the preheating temperature for welding the high-carbon steel is 250-350 ℃, the temperature for stress relief heat treatment is 600-650 ℃, and the selection of proper preheating power and annealing power in the welding process is crucial. The strength of the hot-rolled 50Mn raw material is higher than the yield strength and tensile strength of the traditional hot-rolled 50 MN. Therefore, the preheating power and the annealing power are increased during welding, and the welding speed is slower. The welding speed is slow, the preheating function and the annealing power are high, and the welding of two welded steels can be better ensured.
In order to ensure that the structure of a heat affected zone of a high-carbon steel weld joint is sorbite and ferrite and ensure the stability of the weld joint, the invention has the most important welding process characteristic of adopting 1-time preheating and 2-time annealing process, and the specific operation is as follows: after the welding seam is preheated for 1 time and annealed for 1 time, the laser welding function of the welding machine is closed by manual control, the annealing power is kept, the welding wheel of the welding machine moves away from the welding seam again, and the secondary annealing power plays a role in heating and insulating the welding seam. The traditional high-carbon steel welding is generally 1 time of preheating and 1 time of annealing, because the carbon content of 50Mn is high, the laser welding annealing belongs to air cooling, the cooling speed is high, when the 1 time of annealing is adopted, the weld structure can not completely convert ferrite and pearlite, bainite and sorbite exist, and the toughness of the weld structure is poor. Meanwhile, the heat affected zone on one side of 50Mn is martensite and sorbite, the brittleness is high, the cup bulge experiment is directly cracked, and the welding seam does not meet the production requirement. When 2 times of annealing is adopted, the effect of heat preservation on the weld joint structure is equivalent to that bainite and sorbite in the weld joint structure are completely replaced by ferrite and pearlite, martensite in the weld joint of the heat affected zone on one side of 50Mn is completely converted into ferrite and sorbite, the structure has good toughness and high strength, the vertical weld joint is cracked during the cup-convex test of the weld joint, and the weld joint meets the production requirement.
S8 scale breaking
Because the high-carbon steel has high strength and relatively poor welding quality, the welding seam is easy to break in the repeated bending process of the phosphorus breaking machine. In order to ensure the stability of the high-carbon steel welding seam over-breaking phosphorus machine, the welding seam over-breaking phosphorus machine, a bending roller and a straightening roller of the phosphorus machine are opened.
S9 acid washing and rinsing
The welding line is broken when the strip steel is repeatedly bent by a tension roller or a phosphorus breaker roller, and the speed of the pickling section needs to be controlled in order to ensure the stable production of high-carbon steel. The speed of the pickling process section is less than or equal to 120 m/min.
S10, cold rolling
The five-stand continuous rolling process is adopted, and the following parameters are controlled:
(1) compression ratio:
because the 50Mn alloy has high components, high raw material strength and large rolling force in the production process, in order to avoid the abnormal conditions of uneven thick plates, poor plate shapes or broken welding seams in the production process of a rolling mill, the rolling is usually carried out by adopting a proper compression ratio, so that the rolling force of each frame of the rolling mill can be reduced, and therefore, the design of the 50Mn compression ratio adopts a small compression ratio design idea, and the compression ratio is 36-50%.
Thickness of raw material (mm) Finished product thickness (mm) Compression ratio Finished product thickness (mm) Compression ratio
1.5 0.8 46.6％ 0.85 43.3
1.8 0.9 50％ 1 44％
2.0 1.05 48％ 1.2 40％
2.2 1.25 43％ 1.4 36％
2.5 1.45 42％ 1.6 36％
(2) Load distribution for racks
The 50Mn high-carbon steel is produced in a five-stand acid rolling combined unit, and the 50Mn high-carbon steel has higher strength, so that strip steel can stably enter a rolling mill, and the situations of slipping and weld breakage are prevented.
The load distribution of each rack is as follows:
a frame: 18 to 22 percent of the total weight of the mixture,
II, two frames: 20 to 25 percent.
Three frames: 18 to 22 percent
Four frames: 12-15%, mainly adopting tension adjustment and inclination adjustment to ensure the plate shape, and simultaneously rolling the thickness to the target thickness.
Five frames: 5-6%, and has the effects of leveling and further improving the plate shape.
The tension among the first, second, third and fourth frames is 2-5 percent, and the strip steel is prevented from slipping.
(3) The speed of the outlet of the rolling mill is controlled to be less than or equal to 600M/min; when the welding seam passes through each frame of the rolling mill, the positive bending roll is manually reduced. And recovering the roller after the welding seam.
(4) Control of roll profile
After the working roll and the supporting roll are rolled for a long time, the roll shape is greatly changed due to thermal expansion, the roll curve is abraded into an irregular shape at the last stage of the roll, the effect of the positive bending roll is reduced, and the condition that the thickness of the strip steel is not consistent or the strip shape is poor is easy to occur. Therefore, to ensure smooth rolling, 50Mn high carbon steel was arranged to be rolled early on the work rolls. The working roll period is within 2500 tons of rolling quantity, and one working roll adopts a 0.05mm roll curve; the second, third and fourth frames adopt 0.06mm roller curves. Five rolls used 0mm roll curves. The cycle of the first, second and third support rolls is in the production scheduling of 60000 tons of rolling quantity. Four and five support rollers can be used for production ranging within 35000 tons. Meanwhile, the material of the front 5 coils of the working roll is not allowed to discharge 50Mn high-carbon steel.
(5) Emulsion parameters of rolling mill
The temperature of the rolling liquid is controlled to be 50 ℃, and the cooling effect is enhanced; the concentration is controlled according to the upper limit, the target concentration of the emulsion A system of the rolling mill is 3.0 percent, the control concentration range of the emulsion L system is 0.3 to 1.0 percent, the optimization target is 0.7 percent, the lubricating effect of the rolling liquid is enhanced, and the rolling force is reduced. The flow rate of the first, second and third emulsion is controlled to be more than 5600L/min.
S11, winding
S12, coil stripping
S13 annealing
The 50Mn high-carbon steel treated by the process is not suitable for production in a continuous annealing unit and is suitable for production in a traditional bell-type furnace. Therefore, the invention adopts the cover annealing process, the annealing temperature is heated from 400 ℃ to 720 ℃, and the heating time is 12-13 hours; the temperature is kept for 10 to 11 hours at the annealing temperature of 720 ℃.
S15, leveling
Leveling parameters: the thickness is less than or equal to 1.5mm, and the leveling elongation is 1.0%; the thickness is more than 1.5mm, and the flat elongation is 1.2%.
S16, shearing to obtain cold-rolled finished product
To better compare the process of the present application with the prior art, comparative tests were performed.
The process steps adopted by the control group comprise: heating a plate blank → rough rolling → finish rolling → cooling → coiling to obtain a hot rolled material → uncoiling → welding → crushing scale → acid washing and rinsing → rolling of a five-rack → coiling → coil unloading → annealing → flattening → shearing → cold rolling to obtain a finished product.
The part of the 'slab heating → rough rolling → finish rolling → cooling → coiling to obtain the hot rolled material' is consistent with the method of the embodiment, so the raw material hot rolled material is the same as the embodiment, at the moment, the hot rolled material with the thickness of 1.8mm is selected, and other process parameters are the same as those in the embodiment with the thickness of 1.8mm except the following table.
In the welding procedure, the traditional technological parameters are adopted, and 1 preheating and 1 annealing process are adopted. In the same thickness specification, the preheating power and the annealing power are respectively adjusted down by 5 percent in a maximum parameter table of a welding machine, and the welding speed is 7.2 m/min. The speed of the pickling process section is 120 m/min. Other process parameters are the same as those of the raw material thickness in the same specification embodiment.
The comparison result shows that the thickness specification of the raw material of 1.5-2.5 mm in the embodiment has no broken welding line condition in the process production, the specification of 1.5mm in the comparison group cannot be produced due to frequent broken welding line, and the broken welding line frequency in the specifications of 1.8mm, 2mm, 2.25mm and 2.5mm is respectively 5%, 3%, 4% and 6%. From the results, the process for producing the high-strength 50Mn high-carbon steel realizes good rolling stability in the cold rolling stage and avoids frequent strip breakage of welding seams by controlling welding and pickling in the acid rolling welding machine.
In the embodiment, the yield strength of the raw material with the thickness of 1.5-2.5 mm is 590-525MPa, the compatibility of the thin specification and the stability is realized, the fatigue life is not influenced, the quality of the 50Mn cold-rolled sheet end product is guaranteed, and the use requirement of a user is met.
It should be noted that while the invention has been described in detail with respect to specific embodiments thereof, it will be apparent to those skilled in the art that various obvious changes can be made therein without departing from the spirit and scope of the invention.

Claims (4)

1. A rolling method of a 50Mn thin high-carbon cold-rolled steel plate is characterized by comprising the following production process steps: heating a plate blank → rough rolling → finish rolling → cooling → coiling to obtain a hot rolled material → uncoiling → welding → crushing scale → acid washing and rinsing → rolling of a five-rack → coiling → coil unloading → annealing → flattening → shearing → cold rolling to obtain a finished product; wherein:
s1, heating of the plate blank: the 50Mn high-carbon steel hot rolled material comprises the following components: 0.5 to 0.56 percent of C; 0.2 to 0.3 percent of Si; mn: 0.6% -0.7%, P: less than or equal to 0.025 percent; s: less than or equal to 0.005 percent; and Als: less than or equal to 0.02 percent; cr: less than or equal to 0.02 percent; ni is less than or equal to 0.02 percent; cu is less than or equal to 0.02 percent, and the balance is Fe and inevitable impurities;
s2, rough rolling;
s3, finish rolling;
s4, cooling;
s5, coiling to obtain a hot rolled material; the thickness specification of the hot rolled material is 1.5-2.5 mm;
s6, uncoiling the hot rolled material;
s7, welding: welding by using a wire filling welding machine, adopting 1-time preheating and 2-time annealing process, wherein the thickness of the raw material is less than or equal to 1.50mm and less than 2mm, the welding speed is 7.2-7.8 m/min, the preheating power is 10-12KW, and the annealing power is 18-20 KW; the thickness of the raw material is less than or equal to 2mm and less than or equal to 2.5mm, the welding speed is 7.8m/min, the preheating power is 14KW, and the annealing power is 22 KW; the 1-time preheating and 2-time annealing process comprises the following specific operations: after the welding seam is preheated for 1 time and annealed for 1 time, the laser welding function of the welding machine is closed, the annealing power is kept, and a welding wheel of the welding machine moves away from the welding seam again;
s8, breaking scales;
s9, acid washing and rinsing: the speed of the pickling process section is less than or equal to 120 m/min;
s10, cold rolling: adopting a five-frame continuous rolling process, wherein the compression ratio is 36-50%;
s11, coiling;
s12, coil stripping;
s13, annealing: the annealing temperature is heated from 400 ℃ to 720 ℃, and the heating time is 12-13 hours; keeping the temperature for 10-11 hours at the annealing temperature of 720 ℃;
s15, leveling;
and S16, shearing to obtain a cold-rolled finished product.
2. The method of rolling a 50Mn thin gauge high carbon cold rolled steel sheet according to claim 1, wherein: in step S7, the operation is manual control.
3. The method of rolling a 50Mn thin gauge high carbon cold rolled steel sheet according to claim 1, wherein: in step S13, a hood annealing process is used for the annealing.
4. The method of rolling a 50Mn thin gauge high carbon cold rolled steel sheet according to claim 1, wherein: parameters in the leveling step are as follows: the thickness is less than or equal to 1.5mm, and the leveling elongation is 1.0%; the thickness is more than 1.5mm, and the flat elongation is 1.2%.
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CN115555719A (en) * 2022-09-26 2023-01-03 武汉钢铁有限公司 Laser welding method for continuous pickling of 65Mn high-carbon steel
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