CN113584278A - Process method for improving surface quality of medium carbon manganese boron steel - Google Patents
Process method for improving surface quality of medium carbon manganese boron steel Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 41
- 229910000712 Boron steel Inorganic materials 0.000 title claims abstract description 22
- YHEXKHYQCQBLJR-UHFFFAOYSA-N [B].[Mn].[C] Chemical compound [B].[Mn].[C] YHEXKHYQCQBLJR-UHFFFAOYSA-N 0.000 title claims abstract description 19
- 230000008569 process Effects 0.000 title claims abstract description 19
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 104
- 239000010959 steel Substances 0.000 claims abstract description 104
- 238000010438 heat treatment Methods 0.000 claims abstract description 74
- 238000009749 continuous casting Methods 0.000 claims abstract description 68
- 238000001816 cooling Methods 0.000 claims abstract description 66
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 53
- 238000005096 rolling process Methods 0.000 claims description 39
- 238000005266 casting Methods 0.000 claims description 35
- 238000010583 slow cooling Methods 0.000 claims description 14
- 238000002791 soaking Methods 0.000 claims description 10
- 239000012535 impurity Substances 0.000 claims description 8
- 239000011572 manganese Substances 0.000 claims description 8
- 239000003595 mist Substances 0.000 claims description 8
- 238000005507 spraying Methods 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 238000005272 metallurgy Methods 0.000 abstract description 2
- 230000003313 weakening effect Effects 0.000 abstract description 2
- 238000001514 detection method Methods 0.000 description 19
- 230000007547 defect Effects 0.000 description 14
- 230000004907 flux Effects 0.000 description 12
- 239000010936 titanium Substances 0.000 description 10
- 229910000954 Medium-carbon steel Inorganic materials 0.000 description 8
- 230000035882 stress Effects 0.000 description 8
- 238000012797 qualification Methods 0.000 description 7
- 229910000859 α-Fe Inorganic materials 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 230000003647 oxidation Effects 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- 238000004321 preservation Methods 0.000 description 6
- 239000002893 slag Substances 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 229910052796 boron Inorganic materials 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 3
- PALQHNLJJQMCIQ-UHFFFAOYSA-N boron;manganese Chemical compound [Mn]#B PALQHNLJJQMCIQ-UHFFFAOYSA-N 0.000 description 3
- 230000008646 thermal stress Effects 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000000498 cooling water Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229910052582 BN Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 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
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
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- 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
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
-
- 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
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
-
- 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
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
- B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
-
- 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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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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
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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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
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- 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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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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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
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Continuous Casting (AREA)
- Metal Rolling (AREA)
Abstract
The invention provides a process method for improving the surface quality of medium carbon manganese boron steel, belonging to the technical field of metallurgy and steel manufacturing; in the invention, the surface quality of the continuous casting billet is improved by a mode of combining adjustment of the superheat degree of the molten steel, enhancement of the cooling strength of the crystallizer and weakening of cooling of a secondary cooling zone, and meanwhile, the surface quality of the medium carbon manganese boron steel is improved by matching with a proper heating system.
Description
Technical Field
The invention belongs to the technical field of metallurgy and steel manufacturing, and particularly relates to a process method for improving the surface quality of medium carbon manganese boron steel.
Background
The quality problems of surface cracks and the like possibly exist in the actual production process of the medium carbon steel, and researches show that the existence of the surface cracks is related to boron element and the temperature of a casting blank. The boron has strong binding capacity with free nitrogen in steel, can be preferentially bound in high-temperature austenite to form coarse boron nitride particles, and is aggregated in grain boundaries to effectively prevent the sliding of original austenite grain boundaries to cause the generation of gaps among the grains, so that the thermoplasticity of the steel is reduced, the hot brittleness of the steel is increased, and the surface of medium carbon steel is cracked. In addition, surface cracks caused by the temperature of the casting blank can be generated, two high-temperature brittle intervals of 850-950 ℃ and 1250 ℃ exist during the manganese boron steel continuous casting, and when the manganese boron steel is located in the intervals, the manganese boron steel can obviously reduce the yield strength and improve the brittleness, so that the plastic deformation of the casting blank exceeds the yield strength, and the surface of the casting blank is cracked.
At present, the surface quality of boron-added steel casting blanks is improved mainly by adding titanium to fix nitrogen or increasing the surface temperature of the casting blanks at a straightening position (with maximum plastic deformation). The titanium is added to fix nitrogen, stable TiN is generated before B and N through Ti, the precipitation amount of BN in the solidification process of boron-added steel is reduced, the damage of BN is reduced, and the improvement of the surface quality of a billet is limited. The surface temperature of the casting blank at the straightening position (with the maximum plastic deformation) is improved mainly from the continuous casting process element, and the surface temperature is improved by improving the drawing speed, reducing the water quantity of a crystallizer and reducing the secondary cooling water quantity to be higher than the temperature range of a third brittle zone, so that the generation of casting blank cracks is controlled, but the surface quality of the finished round steel produced by the method is unstable. The reason is that the water quantity of the crystallizer or the water quantity of the secondary cooling area is reduced, but the change of the surface structure of the casting blank is slightly observed, so that the water quantity of the crystallizer is too small, and the skin grains of the casting blank are coarse due to too low crystallization cooling, which is favorable for forming coarse ferrite; after the continuous casting blank exits from the crystallizer, the secondary cooling water quantity and the water quantity distribution of each zone do not consider the structure change of the casting blank, the water quantity of the secondary cooling zone is often too small or is not uniformly distributed, and the formation of a coarse ferrite strip on the surface of the casting blank in a region with weak cooling is further promoted. Since the ferrite strength is about 25% of austenite, stress concentration is likely to occur around a coarse ferrite strip during rolling, and surface cracks are likely to occur.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a process method for improving the surface quality of medium carbon manganese boron steel. In the invention, the surface quality of the continuous casting billet is improved by a mode of combining adjustment of the superheat degree of the molten steel, enhancement of the cooling strength of the crystallizer and weakening of cooling of a secondary cooling zone, and meanwhile, the surface quality of the medium carbon manganese boron steel is improved by matching with a proper heating system.
The present invention achieves the above-described object by the following technical means.
A process method for improving the surface quality of medium carbon manganese boron steel specifically comprises the following steps:
(1) continuous casting:
pouring molten steel, setting parameters of continuous casting automation equipment, uniformly cooling the strength by adopting a water mist spraying combined mode, controlling the temperature of the molten steel, controlling the superheat degree to be 25-30 ℃, and entering a pit for slow cooling to prepare a continuous casting billet;
(2) heating and rolling:
heating a continuous casting billet, wherein the preheating temperature is 780-830 ℃, the heating temperature is 900-1200 ℃, and the soaking temperature is 1050-1150 ℃; and descaling the heated continuous casting billet by using high-pressure water to remove surface oxide skin, then rolling to obtain round steel, feeding the rolled round steel to a cooling bed, and cooling by avoiding wind and stacking the round steel after the round steel is fed into the cooling bed.
Further, in the step (1), the molten steel comprises 0.30-0.48% of C, 0.17-0.37% of Si, 1.00-1.50% of Mn, less than or equal to 0.020% of P, less than or equal to 0.020% of S, 0.010-0.050% of Al, 0.0008-0.0050% of B, less than or equal to 0.10% of V, less than or equal to 0.080% of Ti, 0.10-0.30% of Cr, less than or equal to 0.30% of Ni, less than or equal to 0.25% of Cu, less than or equal to 0.10% of Mo, and [ O ]]≤20×10-6、[N]≤80×10-6And the others are Fe and inevitable impurities.
Further, in the step (1), the parameters of the continuous casting automatic equipment are that the casting speed of the continuous casting billet is 1.2m/min, the water quantity of the crystallizer is 1.40L/kg, and the specific water quantity of the secondary cooling zone is 0.30L/kg.
Further, in the step (1), the superheat degree is 25-27 ℃.
Further, in the step (2), the preheating time is 30-50 min.
Further, in the step (2), the heating is divided into a first heating section and a second heating section; the temperature of the first heating section is 900-1080 ℃, the heating time is 1.5h, the temperature of the second heating section is 1160-1200 ℃, and the heating time is 1.5 h.
Further, in the step (2), the soaking temperature is kept for 1.5 h.
Further, in the step (2), the initial rolling temperature of the rolling is 1060-1070 ℃.
Further, in the step (2), the temperature of the rolled round steel on a cooling bed is 840 ℃.
Further, in the step (2), the cooling time is 36 h.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the cooling strength of the crystallizer is increased, the heat transfer effect of the crystallizer is enhanced, the thickness of the chilled layer on the surface of the casting blank can be obviously increased, and the strength and the grain size of the blank shell are improved, so that the deformation resistance of the blank shell is enhanced, the coarse ferrite formation on the surface of the casting blank is weakened, and the purpose of improving the surface quality of the casting blank is achieved. In addition, the cooling strength of the crystallizer is reasonably adjusted, and the phenomenon that cracks or depressions are formed on the surface of a casting blank due to air gaps between the crystallizer and the blank shell is avoided.
The invention reduces the specific water amount of the secondary cooling area, and overcomes the defects that the casting blank corner obviously blackens, the temperature returns seriously, the thermal stress is increased, and corner cracks and edge cracks are easy to generate when the specific water amount of the secondary cooling area of the continuous casting is larger. The method adopts weak cooling to ensure that the temperature of the casting blank in the tension leveler is 1000-1050 ℃, reduces the thermal stress of the casting blank in the straightening process, is matched with the cooling strength of the crystallizer, and reduces the probability of crack generation
According to the invention, the growth of columnar crystals is controlled by controlling the proper superheat degree of the molten steel, so that the dendritic intercrystalline brittleness is reduced, the generation of cracks is reduced, and the surface quality of a casting blank is improved. In addition, the heating temperature is controlled, the surface quality of the finished round steel is effectively improved, specifically, the preheating section slowly heats and controls the lower temperature, and the phenomenon that the temperature difference between the inside and the outside of the steel is too large, so that the structure stress and the thermal stress are concentrated to induce surface cracks is prevented.
Drawings
FIG. 1 is a surface crack pattern diagram of a casting blank (a) and a round steel (b) prepared by the invention.
FIG. 2 is a surface crack profile of a cast slab (a) and a round steel (b) in the prior art.
Detailed Description
The invention will be further described with reference to the following figures and specific examples, but the scope of the invention is not limited thereto.
Example 1:
(1) continuous casting:
after the continuous ladle is hoisted to the ladle turret, the ladle long nozzle is communicated, so that the molten steel is smoothly poured into the tundish, and the tundish adopts an integral submerged nozzle for whole-process protection pouring, so that the secondary oxidation of the molten steel is prevented. When casting is started, continuous casting automatic equipment is utilized, the casting speed of a continuous casting billet is set to be 1.2m/min, the water quantity of a crystallizer is 1.40L/kg, the specific water quantity of a secondary cooling area is 0.30L/kg, and the temperature of tundish steel water is strictly controlled by adopting a water mist spraying combination mode to uniformly cool the temperature, wherein the superheat degree is 25-30 ℃. Meanwhile, the special covering slag for medium carbon steel is used. After the continuous casting billet is pulled out, the time of entering the pit for slow cooling is controlled to be 36h, and therefore the required continuous casting billet is prepared.
Wherein the composition of the molten steel0.30 to 0.48 percent of C, 0.17 to 0.37 percent of Si, 1.00 to 1.50 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of S, 0.010 to 0.050 percent of Al, 0.0008 to 0.0050 percent of B, less than or equal to 0.10 percent of V, less than or equal to 0.080 percent of Ti, 0.10 to 0.30 percent of Cr, less than or equal to 0.30 percent of Ni, less than or equal to 0.25 percent of Cu, less than or equal to 0.10 percent of Mo and less than or equal to [ O ]]≤20×10-6、[N]≤80×10-6And the others are Fe and inevitable impurities.
(2) Heating and rolling:
conveying the continuous casting billets obtained by pit entering and slow cooling to a steel rolling workshop, and heating by adopting a walking beam type heating furnace, wherein the preheating temperature is 830 ℃ when the continuous casting billets enter the furnace, and the time is 0.5 h; ensuring that the heating temperature is 900-1080 ℃ for 1.5 h; the temperature of the second heating section is 1180-1200 ℃, and the heating time is 1.5 h; the soaking temperature is 1050-1150 ℃, the heat preservation time is about 1.5h, and the total heating time is about 5 h.
After the continuous casting billet is taken out of the heating furnace, surface oxide skin is removed through high-pressure water descaling (water pressure is 19 MPa), round steel is manufactured through rolling, the initial rolling temperature range is controlled to be 1065 ℃, the round steel passes through 12 horizontal and vertical alternative continuous rolling units, and finally the round steel reaches the position of a cooling bed, and the temperature of the cooling bed is 840 ℃.
The round steel is segmented according to the fixed length, is simply packed and collected, is transferred to a wind shielding enclosure area for wind shielding stacking cooling, has the cooling time of 36h, and eliminates the tensile and compressive stress inside and outside the round steel.
(3) Magnetic flux leakage flaw detection:
and performing magnetic flux leakage flaw detection on the surface of the round steel, wherein the detection count is 150, 125 are qualified, 20 are small defects, 5 are large defects, and the qualification rate is 83.3%.
FIG. 1 is a surface crack pattern diagram of a cast slab (a) and a round bar (b) prepared by the present invention, and it can be seen from the diagram that coarse ferrite at the edge of the cast slab disappears, and the round bar has few surface cracks and a shallow depth.
Example 2:
(1) continuous casting:
after the continuous ladle is hoisted to the ladle turret, the ladle long nozzle is communicated, so that the molten steel is smoothly poured into the tundish, and the tundish adopts an integral submerged nozzle for whole-process protection pouring, so that the secondary oxidation of the molten steel is prevented. When casting is started, continuous casting automatic equipment is utilized, the casting speed of a continuous casting billet is set to be 1.2m/min, the water quantity of a crystallizer is 1.40L/kg, the specific water quantity of a secondary cooling area is 0.30L/kg, and the temperature of tundish steel water is strictly controlled by adopting a water mist spraying combination mode with uniform cooling intensity and the superheat degree of 25-27 ℃. Meanwhile, the special covering slag for medium carbon steel is used. After the continuous casting billet is pulled out, the time of entering the pit for slow cooling is controlled to be 36h, and therefore the required continuous casting billet is prepared.
Wherein the molten steel comprises 0.30-0.48% of C, 0.17-0.37% of Si, 1.00-1.50% of Mn, less than or equal to 0.020% of P, less than or equal to 0.020% of S, 0.010-0.050% of Al, 0.0008-0.0050% of B, less than or equal to 0.10% of V, less than or equal to 0.080% of Ti, 0.10-0.30% of Cr, less than or equal to 0.30% of Ni, less than or equal to 0.25% of Cu, less than or equal to 0.10% of Mo, and [ O ]]≤20×10-6、[N]≤80×10-6And the others are Fe and inevitable impurities.
(2) Heating and rolling:
conveying the continuous casting billets obtained by pit entering and slow cooling to a steel rolling workshop, and heating by adopting a walking beam type heating furnace, wherein the preheating temperature is 820 ℃ when the continuous casting billets enter the furnace, and the preheating time is about 0.5 h; ensuring that the heating temperature is 900-1080 ℃ for 1.5 h; the temperature of the second heating section is 1180-1200 ℃, and the heating time is 1.5 h; the soaking temperature is 1050-1150 ℃, the heat preservation time is about 1.5h, and the total heating time is about 5 h.
After the continuous casting billet is taken out of the heating furnace, surface oxide skin is removed through high-pressure water descaling (water pressure is 19 MPa), round steel is manufactured through rolling, the initial rolling temperature range is controlled to be 1065 ℃, the round steel passes through 12 horizontal and vertical alternative continuous rolling units, and finally the round steel reaches the position of a cooling bed, and the temperature of the cooling bed is 840 ℃.
The round steel is segmented according to the fixed length, is simply packed and collected, is transferred to a wind shielding enclosure area for wind shielding stacking cooling, has the cooling time of 36h, and eliminates the tensile and compressive stress inside and outside the round steel.
(3) Magnetic flux leakage flaw detection:
and magnetic flux leakage flaw detection is carried out on the surface of the round steel, the detection count is 150, 131 round steel is qualified, 15 small defects and 4 large defects are detected, and the qualification rate is 87.3%.
Example 3:
(1) continuous casting:
after the continuous ladle is hoisted to the ladle turret, the ladle long nozzle is communicated, so that the molten steel is smoothly poured into the tundish, and the tundish adopts an integral submerged nozzle for whole-process protection pouring, so that the secondary oxidation of the molten steel is prevented. When casting is started, continuous casting automatic equipment is utilized, the casting speed of a continuous casting billet is set to be 1.2m/min, the water quantity of a crystallizer is 1.40L/kg, the specific water quantity of a secondary cooling area is 0.30L/kg, and the temperature of tundish steel water is strictly controlled by adopting a water mist spraying combination mode with uniform cooling intensity and the superheat degree of 25-27 ℃. Meanwhile, the special covering slag for medium carbon steel is used. After the continuous casting billet is pulled out, the time of entering the pit for slow cooling is controlled to be 36h, and therefore the required continuous casting billet is prepared.
Wherein the molten steel comprises 0.30-0.48% of C, 0.17-0.37% of Si, 1.00-1.50% of Mn, less than or equal to 0.020% of P, less than or equal to 0.020% of S, 0.010-0.050% of Al, 0.0008-0.0050% of B, less than or equal to 0.10% of V, less than or equal to 0.080% of Ti, 0.10-0.30% of Cr, less than or equal to 0.30% of Ni, less than or equal to 0.25% of Cu, less than or equal to 0.10% of Mo, and [ O ]]≤20×10-6、[N]≤80×10-6And the others are Fe and inevitable impurities.
(2) Heating and rolling:
conveying the continuous casting billets obtained by pit entering and slow cooling to a steel rolling workshop, and heating by adopting a walking beam type heating furnace, wherein the preheating temperature is 820 ℃ when the continuous casting billets enter the furnace, and the preheating time is about 40 min; ensuring that the heating temperature is 900-1080 ℃ for 1.5 h; the temperature of the second heating section is 1180-1200 ℃, and the heating time is about 1.5 h; the soaking temperature is 1050-1150 ℃, the heat preservation time is about 1.5h, and the total heating time is about 5 h.
After the continuous casting billet is taken out of the heating furnace, surface oxide skin is removed through high-pressure water descaling (water pressure is 19 MPa), round steel is manufactured through rolling, the initial rolling temperature range is controlled to be 1065 ℃, the round steel passes through 12 horizontal and vertical alternative continuous rolling units, and finally the round steel reaches the position of a cooling bed, and the temperature of the cooling bed is 840 ℃.
The round steel is segmented according to the fixed length, is simply packed and collected, is transferred to a wind shielding enclosure area for wind shielding stacking cooling, has the cooling time of 36h, and eliminates the tensile and compressive stress inside and outside the round steel.
(3) Magnetic flux leakage flaw detection:
and performing magnetic flux leakage flaw detection on the surface of the round steel, wherein the detection count is 150, 135 are qualified, 13 are small defects, 2 are large defects, and the qualification rate is 90%.
Example 4:
(1) continuous casting:
after the continuous ladle is hoisted to the ladle turret, the ladle long nozzle is communicated, so that the molten steel is smoothly poured into the tundish, and the tundish adopts an integral submerged nozzle for whole-process protection pouring, so that the secondary oxidation of the molten steel is prevented. When casting is started, continuous casting automatic equipment is utilized, the casting speed of a continuous casting billet is set to be 1.2m/min, the water quantity of a crystallizer is 1.40L/kg, the specific water quantity of a secondary cooling area is 0.30L/kg, and the temperature of tundish steel water is strictly controlled by adopting a water mist spraying combination mode with uniform cooling intensity and the superheat degree of 25-27 ℃. Meanwhile, the special covering slag for medium carbon steel is used. After the continuous casting billet is pulled out, the time of entering the pit for slow cooling is controlled to be 36h, and therefore the required continuous casting billet is prepared.
Wherein the molten steel comprises 0.30-0.48% of C, 0.17-0.37% of Si, 1.00-1.50% of Mn, less than or equal to 0.020% of P, less than or equal to 0.020% of S, 0.010-0.050% of Al, 0.0008-0.0050% of B, less than or equal to 0.10% of V, less than or equal to 0.080% of Ti, 0.10-0.30% of Cr, less than or equal to 0.30% of Ni, less than or equal to 0.25% of Cu, less than or equal to 0.10% of Mo, and [ O ]]≤20×10-6、[N]≤80×10-6And the others are Fe and inevitable impurities.
(2) Heating and rolling:
conveying the continuous casting billets obtained by pit entering and slow cooling to a steel rolling workshop, and heating by adopting a walking beam type heating furnace, wherein the preheating temperature is 820 ℃ when the continuous casting billets enter the furnace, and the preheating time is about 50 min; ensuring that the heating temperature is 900-1080 ℃ for 1.5 h; the temperature of the second heating section is 1180-1200 ℃, and the heating time is about 1.5 h; the soaking temperature is 1050-1150 ℃, the heat preservation time is about 1.5h, and the total heating time is about 5 h.
After the continuous casting billet is taken out of the heating furnace, surface oxide skin is removed through high-pressure water descaling (water pressure is 19 MPa), round steel is manufactured through rolling, the initial rolling temperature range is controlled to be 1065 ℃, the round steel passes through 12 horizontal and vertical alternative continuous rolling units, and finally the round steel reaches the position of a cooling bed, and the temperature of the cooling bed is 840 ℃.
The round steel is segmented according to the fixed length, is simply packed and collected, is transferred to a wind shielding enclosure area for wind shielding stacking cooling, has the cooling time of 36h, and eliminates the tensile and compressive stress inside and outside the round steel.
(3) Magnetic flux leakage flaw detection:
and magnetic flux leakage flaw detection is carried out on the surface of the round steel, the detection count is 150, 139 of the round steel are qualified, 10 of the small defects and 1 of the large defects, and the qualification rate is 92.6%.
Example 5:
(1) continuous casting:
after the continuous ladle is hoisted to the ladle turret, the ladle long nozzle is communicated, so that the molten steel is smoothly poured into the tundish, and the tundish adopts an integral submerged nozzle for whole-process protection pouring, so that the secondary oxidation of the molten steel is prevented. When casting is started, continuous casting automatic equipment is utilized, the casting speed of a continuous casting billet is set to be 1.2m/min, the water quantity of a crystallizer is 1.40L/kg, the specific water quantity of a secondary cooling area is 0.30L/kg, and the temperature of tundish steel water is strictly controlled by adopting a water mist spraying combination mode with uniform cooling intensity and the superheat degree of 25-27 ℃. Meanwhile, the special covering slag for medium carbon steel is used. After the continuous casting billet is pulled out, the time of entering the pit for slow cooling is controlled to be 36h, and therefore the required continuous casting billet is prepared.
Wherein the molten steel comprises 0.30-0.48% of C, 0.17-0.37% of Si, 1.00-1.50% of Mn, less than or equal to 0.020% of P, less than or equal to 0.020% of S, 0.010-0.050% of Al, 0.0008-0.0050% of B, less than or equal to 0.10% of V, less than or equal to 0.080% of Ti, 0.10-0.30% of Cr, less than or equal to 0.30% of Ni, less than or equal to 0.25% of Cu, less than or equal to 0.10% of Mo, and [ O ]]≤20×10-6、[N]≤80×10-6And the others are Fe and inevitable impurities.
(2) Heating and rolling:
conveying the continuous casting billets obtained by pit entering and slow cooling to a steel rolling workshop, and heating by adopting a walking beam type heating furnace, wherein the preheating temperature is 820 ℃ when the continuous casting billets enter the furnace, and the preheating time is about 50 min; ensuring that the heating temperature is 900-1080 ℃ for 1.5 h; the temperature of the second heating section is 1160-1180 ℃, and the heating time is about 1.5 h; the soaking temperature is 1050-1150 ℃, the heat preservation time is about 1.5h, and the total heating time is about 5 h.
After the continuous casting billet is taken out of the heating furnace, surface oxide skin is removed through high-pressure water descaling (water pressure is 19 MPa), round steel is manufactured through rolling, the initial rolling temperature range is controlled to be 1065 ℃, the round steel passes through 12 horizontal and vertical alternative continuous rolling units, and finally the round steel reaches the position of a cooling bed, and the temperature of the cooling bed is 840 ℃.
The round steel is segmented according to the fixed length, is simply packed and collected, is transferred to a wind shielding enclosure area for wind shielding stacking cooling, has the cooling time of 36h, and eliminates the tensile and compressive stress inside and outside the round steel.
(3) Magnetic flux leakage flaw detection:
and performing magnetic flux leakage flaw detection on the surface of the round steel, wherein the detection count is 150, 143 are qualified, 7 are small defects, 0 is large defect, and the qualification rate is 95.3%.
Comparative example 1:
(1) continuous casting:
after the continuous ladle is hoisted to the ladle turret, the ladle long nozzle is communicated, so that the molten steel is smoothly poured into the tundish, and the tundish adopts an integral submerged nozzle for whole-process protection pouring, so that the secondary oxidation of the molten steel is prevented. When the casting is started, continuous casting automatic equipment is utilized, the casting speed of the continuous casting billet is set to be 1.2m/min, the water quantity of a crystallizer is 1.30L/kg, the specific water quantity of a secondary cooling area is 0.45L/kg, and the temperature of the molten steel of the tundish and the superheat degree of 30 ℃ are strictly controlled by adopting a water mist spraying combination mode with uniform cooling intensity. Meanwhile, the special covering slag for medium carbon steel is used. After the continuous casting billet is pulled out, the time of entering the pit for slow cooling is controlled to be 36h, and therefore the required continuous casting billet is prepared.
Wherein the molten steel comprises 0.30-0.48% of C, 0.17-0.37% of Si, 1.00-1.50% of Mn, less than or equal to 0.020% of P, less than or equal to 0.020% of S, 0.010-0.050% of Al, 0.0008-0.0050% of B, less than or equal to 0.10% of V, less than or equal to 0.080% of Ti, 0.10-0.30% of Cr, less than or equal to 0.30% of Ni, less than or equal to 0.25% of Cu, less than or equal to 0.10% of Mo, and [ O ]]≤20×10-6、[N]≤80×10-6And the others are Fe and inevitable impurities.
(2) Heating and rolling:
conveying the continuous casting billets obtained by pit entering and slow cooling to a steel rolling workshop, and heating by adopting a walking beam type heating furnace, wherein the preheating temperature is 830 ℃ when the continuous casting billets enter the furnace, and the heating time is about 30 min; ensuring that the heating temperature is 900-1080 ℃ for 1.5 h; the temperature of the second heating section is 1180-1200 ℃, and the heating time is about 1.5 h; the soaking temperature is 1050-1150 ℃, the heat preservation time is about 1.5h, and the total heating time is about 5 h.
After the continuous casting billet is taken out of the heating furnace, surface oxide skin is removed through high-pressure water descaling (water pressure is 19 MPa), round steel is manufactured through rolling, the initial rolling temperature range is controlled to be 1065 ℃, the round steel passes through 12 horizontal and vertical alternative continuous rolling units, and finally the round steel reaches the position of a cooling bed, and the temperature of the cooling bed is 840 ℃.
The round steel is segmented according to the fixed length, is simply packed and collected, is transferred to a wind shielding enclosure area for wind shielding stacking cooling, has the cooling time of 36h, and eliminates the tensile and compressive stress inside and outside the round steel.
(3) Magnetic flux leakage flaw detection:
and performing magnetic flux leakage flaw detection on the surface of the round steel, wherein the detection count is 150, 72 are qualified, 70 are small defects, 8 are large defects, and the qualification rate is 48.0%.
FIG. 2 is a surface crack pattern diagram of a cast slab (a) and a round steel (b) in the prior art, and it can be seen from the diagram that the edge of the cast slab has a coarse ferrite structure, and the round steel has a large number of surface cracks and a large depth.
Therefore, the water quantity of the crystallizer is increased, the water quantity of a secondary cooling area is reduced, the superheat degree range of molten steel is narrowed, the temperature of a preheating section is reduced, the heating time of the preheating section is prolonged, the temperature range of a heating section is narrowed, the number of cracks on the surface of the obtained medium carbon manganese boron steel round steel is greatly reduced, the depth of the cracks is obviously reduced, the magnetic leakage flaw detection qualification rate of the surface of the round steel is obviously improved, the grinding or tumbling frequency of the surface of the round steel is effectively reduced, the production cost is reduced, and meanwhile, the processing requirements of downstream users are completely met.
The present invention is not limited to the above-described embodiments, and any obvious improvements, substitutions or modifications can be made by those skilled in the art without departing from the spirit of the present invention.
Claims (10)
1. A process method for improving the surface quality of medium carbon manganese boron steel is characterized by comprising the following steps:
(1) continuous casting:
pouring molten steel, setting parameters of continuous casting automation equipment, uniformly cooling the strength by adopting a water mist spraying combined mode, controlling the temperature of the molten steel, controlling the superheat degree to be 25-30 ℃, and entering a pit for slow cooling to prepare a continuous casting billet;
(2) heating and rolling:
heating a continuous casting billet, wherein the preheating temperature is 780-830 ℃, the heating temperature is 900-1200 ℃, and the soaking temperature is 1050-1150 ℃; and descaling the heated continuous casting billet by using high-pressure water to remove surface oxide skin, then rolling to obtain round steel, feeding the rolled round steel to a cooling bed, and cooling by avoiding wind and stacking the round steel after the round steel is fed into the cooling bed.
2. The process for improving the surface quality of medium carbon manganese boron steel according to claim 1, wherein in the step (1), the molten steel comprises 0.30-0.48% of C, 0.17-0.37% of Si, 1.00-1.50% of Mn, 0.020% or less of P, 0.020% or less of S, 0.010-0.050% of Al, 0.0008-0.0050% of B, 0.10% or less of V, 0.080% or less of Ti, 0.10-0.30% of Cr, 0.30% or less of Ni, 0.25% or less of Cu, 0.10% or less of Mo, and [ O ] or less]≤20×10-6、[N]≤80×10-6And the others are Fe and inevitable impurities.
3. The process method for improving the surface quality of the medium carbon manganese boron steel according to claim 1, wherein in the step (1), the parameters of the continuous casting automatic equipment are that the casting speed of the continuous casting billet is 1.2m/min, the water amount of a crystallizer is 1.40L/kg, and the specific water amount of a secondary cooling zone is 0.30L/kg.
4. The process method for improving the surface quality of the medium carbon manganese boron steel according to claim 1, wherein in the step (1), the superheat degree is 25-27 ℃.
5. The process method for improving the surface quality of the medium carbon manganese boron steel according to claim 1, wherein in the step (2), the preheating time is 30-50 min.
6. The process method for improving the surface quality of the medium carbon manganese boron steel according to claim 1, wherein in the step (2), the heating is divided into a first heating section and a second heating section; the temperature of the first heating section is 900-1080 ℃, the heating time is 1.5h, the temperature of the second heating section is 1160-1200 ℃, and the heating time is 1.5 h.
7. The process method for improving the surface quality of the medium carbon manganese boron steel according to claim 1, wherein in the step (2), the soaking temperature is kept for 1.5 hours.
8. The process method for improving the surface quality of the medium carbon manganese boron steel according to claim 1, wherein in the step (2), the rolling temperature at the beginning of rolling is 1060-1070 ℃.
9. The process for improving the surface quality of the medium carbon manganese boron steel according to claim 1, wherein in the step (2), the temperature of the cooling bed on the rolled round steel is 840 ℃.
10. The process method for improving the surface quality of the medium carbon manganese boron steel according to claim 1, wherein in the step (2), the cooling time is 36 h.
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| CN115627409A (en) * | 2022-10-24 | 2023-01-20 | 石钢京诚装备技术有限公司 | Production method for reducing surface crack rate of medium-carbon boron-containing round steel |
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