CN114959417A - Method for manufacturing large-size low-carbon high-sulfur-content round steel by using large rectangular section blank - Google Patents
Method for manufacturing large-size low-carbon high-sulfur-content round steel by using large rectangular section blank Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 79
- 239000010959 steel Substances 0.000 title claims abstract description 79
- 238000000034 method Methods 0.000 title claims abstract description 42
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 39
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 21
- 238000005096 rolling process Methods 0.000 claims abstract description 93
- 238000010438 heat treatment Methods 0.000 claims abstract description 52
- 238000009749 continuous casting Methods 0.000 claims abstract description 28
- 238000002791 soaking Methods 0.000 claims abstract description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 13
- 238000010583 slow cooling Methods 0.000 claims abstract description 9
- 230000002441 reversible effect Effects 0.000 claims abstract description 6
- 238000003756 stirring Methods 0.000 claims abstract description 5
- 229910052717 sulfur Inorganic materials 0.000 claims description 36
- 239000011593 sulfur Substances 0.000 claims description 36
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 13
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 13
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 11
- 238000007670 refining Methods 0.000 claims description 9
- 238000004513 sizing Methods 0.000 claims description 9
- 238000010008 shearing Methods 0.000 claims description 8
- 239000002893 slag Substances 0.000 claims description 8
- 238000010079 rubber tapping Methods 0.000 claims description 7
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 6
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 5
- 238000003723 Smelting Methods 0.000 claims description 5
- 238000005266 casting Methods 0.000 claims description 5
- 230000007547 defect Effects 0.000 claims description 5
- 229910052698 phosphorus Inorganic materials 0.000 claims description 5
- 239000011574 phosphorus Substances 0.000 claims description 5
- 239000000498 cooling water Substances 0.000 claims description 4
- 238000001514 detection method Methods 0.000 claims description 4
- 238000009792 diffusion process Methods 0.000 claims description 4
- 238000000227 grinding Methods 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 239000002994 raw material Substances 0.000 claims description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 3
- 229910052804 chromium Inorganic materials 0.000 claims description 3
- 239000011651 chromium Substances 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 239000010949 copper Substances 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 229910052710 silicon Inorganic materials 0.000 claims description 3
- 239000010703 silicon Substances 0.000 claims description 3
- 239000002436 steel type Substances 0.000 claims description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims 1
- 229910052748 manganese Inorganic materials 0.000 claims 1
- 239000011572 manganese Substances 0.000 claims 1
- 230000005496 eutectics Effects 0.000 abstract description 13
- 238000002844 melting Methods 0.000 abstract description 13
- 230000008018 melting Effects 0.000 abstract description 13
- 238000005336 cracking Methods 0.000 abstract description 4
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 238000007731 hot pressing Methods 0.000 description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 241001062472 Stokellia anisodon Species 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—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
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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- 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
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The invention relates to a method for manufacturing large-size low-carbon high-sulfur-content round steel by using a large rectangular cross-section blank, wherein in the continuous casting process of the large rectangular blank, a crystallizer is adopted for electromagnetic stirring, and the superheat degree control target is that a first continuous casting furnace is less than or equal to 40 ℃, a continuous casting furnace is less than or equal to 35 ℃, and the round steel is discharged from a pit after slow cooling; s4, feeding the continuous casting billet into a heating furnace for heating, wherein the preheating temperature is less than or equal to 910 ℃, the preheating temperature time is more than or equal to 80 minutes, the first heating temperature is 850-1130 ℃, the first heating temperature time is more than or equal to 40 minutes, the second heating temperature is 1050-1250 ℃, the soaking temperature is 1180-1220 ℃, and the total time of the second heating temperature and the soaking temperature is 95-240 minutes; after descaling the billet by high-pressure water, roughly rolling the billet by using a two-roller reversible rolling mill for 13 passes by adopting a light reduction rolling process, wherein the rolling temperature is more than or equal to 1000 ℃, and the total rolling time is less than or equal to 4 min; and carrying out medium rolling and finish rolling on the cut steel billet. The invention reduces the melting of eutectic of the high-sulfur-content continuous casting billet, and solves the problems of biting and slipping of the high-sulfur-content steel and cracking of the end of the high-sulfur-content steel.
Description
Technical Field
The invention relates to the technical field of special steel processing, in particular to a method for manufacturing large-size low-carbon high-sulfur-content round steel by using a large rectangular section blank.
Background
The large-scale low-carbon high-sulfur steel is one of steel grades which are very challenging in the technical field of steel rolling, and in a solid state, the solubility of sulfur in iron is extremely low, but the sulfur exists in the steel in a FeS form. Due to poor shaping of FeS, the steel containing more sulfur is more brittle. And more seriously, FeS and Fe can form eutectic distribution with low melting point (985 ℃) on the grain boundary of austenite. When the steel is heated to about 1200 ℃ for hot pressure processing, eutectic on a grain boundary is melted, and the bonding between crystal grains is destroyed, so that the billet can slip in the processing process, therefore, the control precision requirement of large-specification (specification being more than or equal to 120 mm) high-sulfur steel is high, and the rolling process is complex. At present, the rolling process of domestic large-specification low-carbon high-sulfur steel is very strict in control of the rolling process, slipping is easy to generate if the temperature is too high in the production process, and the end part cracks and is scrapped if the temperature is slightly low. Therefore, it is necessary to provide a new processing method to solve the above problems.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for manufacturing large-size low-carbon high-sulfur round steel by using a large rectangular section blank, which reduces the eutectic melting of a high-sulfur continuous casting blank, and reduces the reduction of each pass by a soft reduction rolling process, thereby solving the problems of biting and slipping of the high-sulfur steel and cracking of the end of the high-sulfur steel.
The technical purpose of the invention is realized by the following technical scheme:
a method for manufacturing large-size low-carbon high-sulfur-content round steel by using a large rectangular section blank comprises the following specific steps:
s1, casting a steel billet after ladle refining is carried out on the raw materials smelted by the converter, wherein the end point control target of the converter smelting is that the carbon content is less than or equal to 0.04%;
s2, ensuring good slag fluidity in the LF refining process, and simultaneously performing diffusion deoxidation on the slag surface;
s3, in the continuous casting process of the large rectangular billet, a crystallizer is adopted for electromagnetic stirring, and the superheat degree control target is that the continuous casting first furnace is less than or equal to 40 ℃, the continuous casting furnace is less than or equal to 35 ℃, and the large rectangular billet is discharged out of a pit after slow cooling;
s4, feeding the continuous casting billet into a heating furnace for heating, wherein the preheating temperature is less than or equal to 910 ℃, the preheating temperature time is more than or equal to 80 minutes, the first heating temperature is 850-1130 ℃, the first heating temperature time is more than or equal to 40 minutes, the second heating temperature is 1050-1250 ℃, the soaking temperature is 1180-1220 ℃, and the total time of the second heating temperature and the soaking temperature is 95-240 minutes;
s5, descaling the steel billet by high-pressure water, wherein the descaling pressure is more than or equal to 20MP, and removing the scale on the surface of the steel billet by using the high-pressure water;
s6, roughly rolling by using a two-roll reversible rolling mill, and rolling for 13 passes by adopting a light reduction rolling process, wherein the rolling temperature is more than or equal to 1000 ℃, and the total rolling time is less than or equal to 4 min;
s7, performing hydraulic head shearing on the roughly rolled steel billet, wherein the head shearing length is more than or equal to 300mm, and ensuring that the head defects are completely cut off;
s8, carrying out medium rolling and finish rolling on the cut steel billet;
s9, sizing the rolled billet by a sizing machine and then segmenting the billet by a grinding wheel saw;
and S10, finishing the received steel billet to perform chamfering, heat treatment and flaw detection.
In one embodiment, in step S4, the target temperature for the two heating temperatures is 1220 ℃ and the target temperature for the soaking temperature is 1200 ± 10 ℃.
In one embodiment, in step S4, if the heating time of the high temperature zone exceeds the time specified by the process due to production interruption, a cooling process is used, when the temperature of the soaking zone after cooling is greater than or equal to the lower limit temperature, tapping is not needed, and when the temperature of the soaking zone after cooling is less than the lower limit temperature, tapping is performed after the temperature is raised to the lower limit temperature.
In one embodiment, in step S6, the reduction rate of the first 4 passes is less than or equal to 12%, and the reduction rates of the other passes are less than or equal to 16%, wherein the maximum reduction of 13 passes is 46mm, and the average reduction per pass is 36.6 mm.
In one embodiment, in step S6, the rolling speed of the first 4 passes is 2.2-2.5m/S, and the rolling speed of the rest passes is 3.0-3.5 m/S.
In one embodiment, in step S6, after the low-carbon high-sulfur steel slab is rolled for more than or equal to 1000 tons after being replaced by another steel after each 300 tons of rough rolling, the low-carbon high-sulfur steel slab is arranged to continue rolling.
In one embodiment, in step S3, the pit entry temperature is greater than or equal to 600 ℃, the slow cooling time is greater than or equal to 24 hours, and the pit exit temperature is less than or equal to 200 ℃ in the slow cooling process.
In one embodiment, in step S8, the continuous rolling temperature of the billet is controlled to be not less than 960 ℃, the finishing temperature is controlled to be not less than 900 ℃, and the cooling water amount is controlled according to the conventional 60-70%.
In one embodiment, in step S4, the steel slab is a large rectangular cross-section continuous casting slab, and contains, by weight, 0.09% or less of carbon, 0.10% or less of silicon, 1.15% to 1.5% of manganese, 0.04% to 0.09% of phosphorus, 0.3% to 0.4% of sulfur, 0.3% or less of chromium, 0.30% or less of nickel, 0.30% or less of copper, and the balance iron.
In conclusion, the invention has the following beneficial effects:
the invention optimizes the converter and continuous casting process, reduces the heating temperature, reduces the melting of eutectic of the high-sulfur-content continuous casting billet, and reduces the reduction of each pass by the soft reduction rolling process, thereby solving the problem of biting and slipping of the high-sulfur-content steel, and the deformation of each pass can be reduced by the soft reduction rolling process, thereby solving the problem of end cracking of the high-sulfur-content steel.
Detailed Description
The present invention will be described in detail with reference to examples.
In the prior art, the low-carbon high-sulfur steel billet is easy to slip and crack at the end part during hot rolling, which is caused by the overhigh temperature of the steel billet, but the temperature in the heating stage cannot be simply and directly reduced, otherwise, the quality of the steel billet cannot reach the standard.
Aiming at the problems in the prior art, the invention provides a method for manufacturing large-size low-carbon high-sulfur-content round steel by using a large rectangular section blank, which comprises the following specific steps:
s1, casting a steel billet after ladle refining is carried out on the raw materials smelted by the converter, wherein the end point control target of the converter smelting is that the carbon content is less than or equal to 0.04%; wherein, in the process of converter smelting, the first furnace after the converter is greatly supplemented can not smelt low-carbon high-sulfur steel.
S2, ensuring good slag fluidity in the LF refining process, and simultaneously performing diffusion deoxidation on the slag surface; it should be noted that aluminum deoxidation is forbidden in the LF refining process, and the soft argon blowing time is longer than 15 minutes, so that the inclusion can be ensured to float sufficiently.
S3, in the continuous casting process of the large rectangular billet, a crystallizer is adopted for electromagnetic stirring, and the superheat degree control target is that the continuous casting first furnace is less than or equal to 40 ℃, the continuous casting furnace is less than or equal to 35 ℃, and the large rectangular billet is discharged out of a pit after slow cooling; specifically, a rectangular casting blank with the cross section size of 320(mm) × 425(mm) is slowly cooled, wherein the pit entry temperature is more than or equal to 600 ℃, the slow cooling time is more than or equal to 24 hours, and the pit exit temperature is less than or equal to 200 ℃.
In steps S1-S3, the produced rectangular cast slab (i.e., continuous cast billet) is a large rectangular section continuous cast slab, and contains, by weight, not more than 0.09% of carbon, not more than 0.10% of silicon, 1.15% -1.5% of manganese, 0.04% -0.09% of phosphorus, 0.3% -0.4% of sulfur, not more than 0.3% of chromium, not more than 0.30% of nickel, not more than 0.30% of copper, and the balance iron.
S4, feeding the continuous casting billet into a heating furnace for heating, wherein the preheating temperature is less than or equal to 910 ℃, the preheating temperature time is more than or equal to 80 minutes, the first heating temperature is 850-1130 ℃, the first heating temperature time is more than or equal to 40 minutes, the second heating temperature is 1050-1250 ℃, the soaking temperature is 1180-1220 ℃, and the total time of the second heating temperature and the soaking temperature is 95-240 minutes.
Specifically, the target temperature of the second heating temperature is 1220 ℃, the target temperature of the soaking temperature is 1200 +/-10 ℃, the invention controls the highest heating temperature to be about 1200 ℃, and reduces the heating time staying at the highest temperature.
It should be noted that if the heating time of the high-temperature section exceeds the time specified by the process due to production interruption, the cooling process is adopted, when the temperature of the soaking section after cooling is greater than or equal to the lower limit temperature, tapping is not needed, and when the temperature of the soaking section after cooling is less than the lower limit temperature, tapping can be performed after the temperature is raised to the lower limit temperature. Wherein the lower limit temperature means that the target temperature of the soaking temperature is 1990 deg.C (i.e., 1200-10 deg.C).
S5, descaling the steel billet by high-pressure water, wherein the descaling pressure is more than or equal to 20MP, and removing the scale on the surface of the steel billet by using the high-pressure water;
it should be noted that, because of the processing requirements of the low-carbon high-sulfur steel, the temperature in the heating furnace cannot be too low, the invention controls the maximum heating temperature to be about 1200 ℃, and controls the heating time staying at the maximum temperature to relieve the problem of surface slip of the low-carbon high-sulfur steel billet in the hot pressing stage, that is, after descaling with high-pressure water, the temperature of the low-carbon high-sulfur steel billet is no more than 1200 ℃ at most when the low-carbon high-sulfur steel billet enters the hot pressing, and in the hot pressing stage, the temperature of the steel billet will further drop, which is beneficial to solving the problem of surface slip.
Because the eutectic with low melting point formed by FeS and Fe can melt at 1200 ℃, namely, the billet still can slip and crack at the end part when entering a rough rolling mill, the invention mainly solves the technical problems of slip and crack at the end part by improving the process at the hot pressing stage (rough rolling, medium rolling and finish rolling).
S6, roughly rolling by using a two-roll reversible rolling mill, and rolling for 13 passes by adopting a light reduction rolling process, wherein the rolling temperature is more than or equal to 1000 ℃, and the total rolling time is less than or equal to 4 min; wherein, the reduction rate of the first 4 passes is less than or equal to 12 percent, the reduction rate of the rest passes is less than or equal to 16 percent, wherein, the maximum reduction of 13 passes is 46mm, the average reduction of each pass is 36.6mm, the rolling speed of the first 4 passes is 2.2-2.5m/s, and the rolling speed of the rest passes is 3.0-3.5 m/s;
it is easy to understand that, in the rolling of the first 4 passes, the reduction rate is smaller, the speed is slower, the force applied to the surface of the billet by the rolling mill is smaller, the billet is not easy to slip, and because the rolling speed is slower, the stress of the billet is more uniform compared with that of the subsequent passes, the end face of the billet is not easy to crack, after the rolling of the first 4 passes, the billet is also cooled, the phenomenon of melting of the eutectic with low melting point is relieved, therefore, the reduction rate and the rolling speed of the subsequent 9 passes can be improved, and the phenomenon of slipping of the billet is not easy to occur.
Further, after 300 tons of low-carbon and high-sulfur steel billets are roughly rolled, other steel types are replaced and rolled for more than or equal to 1000 tons, and then the low-carbon and high-sulfur steel billets are arranged to be continuously rolled. It is easily understood that when rolling a low-carbon high-sulfur billet, a eutectic with a low melting point formed by FeS and Fe may remain on the surface of the roll, and as the rolling proceeds, the more eutectic with a low melting point remains on the surface of the roll, and since the roll is in direct contact with the high-temperature billet, the eutectic with a low melting point remaining on the surface of the roll may melt, and the friction between the roll and the billet is reduced, resulting in occurrence of slippage. After 300 tons of low-carbon high-sulfur steel billets are roughly rolled, the steel grade is replaced for rough rolling, and eutectic with low melting point on the surface of the roller is consumed.
S7, performing hydraulic head shearing on the roughly rolled steel billet, wherein the head shearing length is more than or equal to 300mm, and ensuring that the head defects are completely cut off;
s8, carrying out medium rolling and finish rolling on the cut steel billet; the temperature of the billet in the continuous rolling is controlled to be more than or equal to 960 ℃, the finishing temperature is controlled to be more than or equal to 900 ℃, and the cooling water amount is controlled according to the conventional 60-70%.
It is easy to understand that the temperature of the billet is reduced to about 960 ℃ at the beginning of the middle rolling, the eutectic with low melting point is not melted any more, so the billet is not easy to slip during the middle rolling and the finish rolling, and in the invention, the temperature of the billet is kept above 900 ℃ from the beginning of the rough rolling to the end of the finish rolling, thereby avoiding the condition that the end part is cracked due to low temperature.
S9, sizing the rolled billet by a sizing machine and then segmenting the billet by a grinding wheel saw;
and S10, finishing the received steel billet to perform chamfering, heat treatment and flaw detection.
The invention optimizes the converter and continuous casting process, reduces the heating temperature, reduces the melting of eutectic of the high-sulfur-content continuous casting billet, and reduces the reduction of each pass by the soft reduction rolling process, thereby solving the problem of biting and slipping of the high-sulfur-content steel, and the deformation of each pass can be reduced by the soft reduction rolling process, thereby solving the problem of end cracking of the high-sulfur-content steel.
The following are specific examples of the present invention.
S1: after ladle refining is carried out on raw materials smelted by the converter, billets are cast, in the smelting process of the converter, the 1 st furnace after the converter is repaired greatly does not smelt the steel grade, a new ladle is not needed, and the end point control target of the converter is as follows: c is less than or equal to 0.04 percent.
S2: in the LF refining process, good slag fluidity is ensured, the slag surface is subjected to diffusion deoxidation, aluminum deoxidation is forbidden, the soft argon blowing time is longer than 15 minutes, and impurities are ensured to float sufficiently;
s3: in the continuous casting process, in the 320 × 425 rectangular billet continuous casting process, electromagnetic stirring is carried out by adopting a crystallizer, and the superheat degree control target is as follows: the continuous casting first furnace is less than or equal to 40 ℃, the continuous casting furnace is less than or equal to 35 ℃, 320 × 425 rectangular casting blanks are slowly cooled, the pit entry temperature is more than or equal to 600 ℃, the slow cooling time is more than or equal to 24 hours, and the pit exit temperature is less than or equal to 200 ℃.
S4: heating in a heating furnace, adjusting a heating process, and feeding the continuous casting billet into the heating furnace for heating, wherein the preheating temperature is less than or equal to 910 ℃, the first heating temperature is as follows: 850 ℃ -1130 ℃, heating temperature: 1050 ℃ -1250 ℃, target temperature: 1220 ℃, soaking temperature: 1180 ℃ to 1220 ℃, target temperature: 1200 +/-10 ℃. Preheating temperature and time: more than or equal to 80 minutes, heating temperature time: more than or equal to 40 minutes, the time of the second heating temperature and the soaking temperature: 95-240 minutes. If the heating time of the high-temperature section exceeds the time specified by the process due to production interruption, a cooling process system is implemented, and when the temperature of the soaking section is more than or equal to the lower limit temperature after cooling, the temperature does not need to be raised during tapping; when the temperature is reduced to be less than the lower line temperature, the steel can be tapped after the temperature is increased to the lower limit temperature.
S5: and removing phosphorus from the steel billet by using high-pressure water, wherein the phosphorus removal pressure is not less than 20MP, and removing the iron oxide scales on the surface of the steel billet by using the high-pressure water.
S6: rough rolling by a two-roll reversible rolling mill (phi 1100 x 2500), rough rolling by a two-roll reversible rolling mill with the model phi 1100 x 2500, rough rolling by a soft reduction rolling process, and rolling reduction of the first 4 passes: less than or equal to 12 percent, and the reduction rate of other passes: less than or equal to 16 percent. The maximum reduction is 46mm, the average reduction per pass is 36.6mm, and the rolling process is carried out for 13 passes to obtain a rolled blank 205 x 205. The rolling temperature is more than or equal to 1000 ℃. Rolling speed of the first 4 passes: 2.2m/s-2.5m/s, and the rolling speed of each pass is 3.0m/s-3.5 m/s. The total rolling time is less than or equal to 4 minutes. When each rolling time is 300 tons, the rolling time of other steel grades is more than or equal to 1000 tons, and then the rolling of the low-carbon high-sulfur round steel is continuously arranged. After the head is bitten into more than or equal to 0.3-0.5/V (S), the cold water is ensured by opening a rolling groove, and the water flow is as follows: 110-130m 3 And h, closing the empty roller way cooling water.
S7: the 1# hydraulic shearing head and the 1# hydraulic shearing head are more than or equal to 300mm in length, and the head defects are completely cut.
S8: all 10 continuous rolling mills for finish rolling are arranged horizontally and vertically in an alternating mode and are short-stress rolling mills of the fifth generation. The composition of the rolling mill is phi 750x6+ phi 550x4, and the whole line realizes the control rolling without torsion, micro tension or tension; the control requirement of the continuous rolling temperature of the rolled piece is more than or equal to 960 ℃, and the control requirement of the finish rolling temperature is as follows: not less than 900 ℃. The water amount is controlled according to 60-70%.
S9: hot sawing, sizing and segmenting, namely segmenting by using a grinding wheel saw after sizing by using a sizing machine;
s10: and (4) carrying out chamfering, heat treatment, flaw detection and other finish machining on the finishing receiving round steel.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.
Claims (9)
1. A method for manufacturing large-size low-carbon high-sulfur-content round steel by using a large rectangular section blank is characterized by comprising the following steps of:
s1, casting a steel billet after ladle refining is carried out on the raw materials smelted by the converter, wherein the end point control target of the converter smelting is that the carbon content is less than or equal to 0.04%;
s2, ensuring good slag fluidity in the LF refining process, and simultaneously performing diffusion deoxidation on the slag surface;
s3, in the continuous casting process of the large rectangular billet, a crystallizer is adopted for electromagnetic stirring, and the superheat degree control target is that the continuous casting first furnace is less than or equal to 40 ℃, the continuous casting furnace is less than or equal to 35 ℃, and the large rectangular billet is discharged out of a pit after slow cooling;
s4, feeding the continuous casting billet into a heating furnace for heating, wherein the preheating temperature is less than or equal to 910 ℃, the preheating temperature time is more than or equal to 80 minutes, the first heating temperature is 850-1130 ℃, the first heating temperature time is more than or equal to 40 minutes, the second heating temperature is 1050-1250 ℃, the soaking temperature is 1180-1220 ℃, and the total time of the second heating temperature and the soaking temperature is 95-240 minutes;
s5, descaling the steel billet by high-pressure water, wherein the descaling pressure is more than or equal to 20MP, and removing the scale on the surface of the steel billet by using the high-pressure water;
s6, roughly rolling by using a two-roller reversible rolling mill, and rolling for 13 passes by adopting a soft reduction rolling process, wherein the rolling temperature is more than or equal to 1000 ℃, and the total rolling time is less than or equal to 4 min;
s7, performing hydraulic head shearing on the roughly rolled steel billet, wherein the head shearing length is more than or equal to 300mm, and ensuring that the head defects are completely cut off;
s8, carrying out medium rolling and finish rolling on the cut steel billet;
s9, sizing the rolled billet by a sizing machine and then segmenting the billet by a grinding wheel saw;
and S10, finishing the received steel billet to perform chamfering, heat treatment and flaw detection.
2. The method for manufacturing large-size round steel with low carbon and high sulfur content by using large rectangular sectional billets as claimed in claim 1, wherein in step S4, the target temperature of the secondary heating temperature is 1220 ℃, and the target temperature of the soaking temperature is 1200 +/-10 ℃.
3. The method for manufacturing large-size round steel with low carbon and high sulfur content by using the large rectangular cross-section billet according to claim 2, wherein in step S4, if the heating time of the high-temperature section exceeds the time specified by the process due to production interruption, a cooling process is adopted, when the temperature of the soaking section after cooling is greater than or equal to the lower limit temperature, the temperature does not need to be raised during tapping, and when the temperature of the soaking section after cooling is less than the lower limit temperature, tapping can be performed after the temperature is raised to the lower limit temperature.
4. The method for manufacturing the large-size low-carbon high-sulfur round steel by using the large rectangular section blank as claimed in claim 1, wherein in step S6, the reduction rate of the first 4 passes is less than or equal to 12%, the reduction rate of the rest passes is less than or equal to 16%, wherein the maximum reduction of 13 passes is 46mm, and the average reduction per pass is 36.6 mm.
5. The method for manufacturing large-size low-carbon high-sulfur round steel by using the large rectangular section blank as claimed in claim 4, wherein in the step S6, the rolling speed of the first 4 passes is 2.2-2.5m/S, and the rolling speed of the rest passes is 3.0-3.5 m/S.
6. The method for manufacturing large-size round steel with low carbon and high sulfur content by using the large rectangular cross-section billet in claim 5, wherein in step S6, after replacing other steel types to roll more than or equal to 1000 tons after each 300 tons of low carbon and high sulfur steel billets are roughly rolled, the low carbon and high sulfur steel billets are arranged to continue rolling.
7. The method for manufacturing large-size low-carbon high-sulfur round steel by using the large rectangular section blank as claimed in claim 1, wherein in the step S3, the pit entry temperature is more than or equal to 600 ℃, the slow cooling time is more than or equal to 24 hours, and the pit exit temperature is less than or equal to 200 ℃.
8. The method for manufacturing large-size round steel with low carbon and high sulfur content by using the large rectangular cross-section billet as claimed in claim 1, wherein in step S8, the temperature of the billet in the continuous rolling is controlled to be more than or equal to 960 ℃, the temperature of the final rolling is controlled to be more than or equal to 900 ℃, and the amount of cooling water is controlled according to the conventional 60-70%.
9. The method for manufacturing large-size round steel with low carbon and high sulfur content by using the large rectangular cross-section billet according to any one of claims 1 to 8, wherein the billet is a large rectangular cross-section continuous billet with the content of carbon being less than or equal to 0.09%, silicon being less than or equal to 0.10%, manganese being 1.15% -1.5%, phosphorus being 0.04% -0.09%, sulfur being 0.3% -0.4%, chromium being less than or equal to 0.3%, nickel being less than or equal to 0.30%, copper being less than or equal to 0.30%, and the balance being iron in step S4.
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| CN1608758A (en) * | 2004-11-22 | 2005-04-27 | 宝钢集团上海五钢有限公司 | Hot continuous rolling process of high-sulfur (sulfur-phosphorus) free cutting structural steel |
| CN101417384A (en) * | 2008-07-29 | 2009-04-29 | 湖南华菱湘潭钢铁有限公司 | Production method of low-carbon free-cutting steel |
| CN110396649A (en) * | 2019-07-17 | 2019-11-01 | 南京钢铁股份有限公司 | A kind of control production method of the low-carbon sulphur automatic steel with hot-rolling edge cracking |
| CN110681696A (en) * | 2019-09-19 | 2020-01-14 | 宝钢特钢韶关有限公司 | Rolling process of high-sulfur steel |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1608758A (en) * | 2004-11-22 | 2005-04-27 | 宝钢集团上海五钢有限公司 | Hot continuous rolling process of high-sulfur (sulfur-phosphorus) free cutting structural steel |
| CN101417384A (en) * | 2008-07-29 | 2009-04-29 | 湖南华菱湘潭钢铁有限公司 | Production method of low-carbon free-cutting steel |
| CN110396649A (en) * | 2019-07-17 | 2019-11-01 | 南京钢铁股份有限公司 | A kind of control production method of the low-carbon sulphur automatic steel with hot-rolling edge cracking |
| CN110681696A (en) * | 2019-09-19 | 2020-01-14 | 宝钢特钢韶关有限公司 | Rolling process of high-sulfur steel |
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