CN117904534A - Special-shaped blank for weather-resistant hot-rolled H-shaped steel and production process thereof - Google Patents
Special-shaped blank for weather-resistant hot-rolled H-shaped steel and production process thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 75
- 239000010959 steel Substances 0.000 title claims abstract description 75
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 46
- 238000000034 method Methods 0.000 claims abstract description 38
- 238000005266 casting Methods 0.000 claims abstract description 29
- 238000007670 refining Methods 0.000 claims abstract description 26
- 238000009749 continuous casting Methods 0.000 claims abstract description 22
- 239000012535 impurity Substances 0.000 claims abstract description 5
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 54
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 29
- 229910052742 iron Inorganic materials 0.000 claims description 25
- 239000002893 slag Substances 0.000 claims description 22
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 18
- 239000000498 cooling water Substances 0.000 claims description 16
- 238000007664 blowing Methods 0.000 claims description 15
- 230000010287 polarization Effects 0.000 claims description 13
- 229910045601 alloy Inorganic materials 0.000 claims description 11
- 239000000956 alloy Substances 0.000 claims description 11
- 229910052782 aluminium Inorganic materials 0.000 claims description 10
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 9
- 229910052786 argon Inorganic materials 0.000 claims description 9
- 238000003723 Smelting Methods 0.000 claims description 8
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 7
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 7
- 239000004571 lime Substances 0.000 claims description 7
- 229910052799 carbon Inorganic materials 0.000 claims description 6
- 239000008188 pellet Substances 0.000 claims description 5
- 238000003825 pressing Methods 0.000 claims description 5
- 239000005997 Calcium carbide Substances 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 238000005259 measurement Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- 238000005502 peroxidation Methods 0.000 claims description 4
- CLZWAWBPWVRRGI-UHFFFAOYSA-N tert-butyl 2-[2-[2-[2-[bis[2-[(2-methylpropan-2-yl)oxy]-2-oxoethyl]amino]-5-bromophenoxy]ethoxy]-4-methyl-n-[2-[(2-methylpropan-2-yl)oxy]-2-oxoethyl]anilino]acetate Chemical compound CC1=CC=C(N(CC(=O)OC(C)(C)C)CC(=O)OC(C)(C)C)C(OCCOC=2C(=CC=C(Br)C=2)N(CC(=O)OC(C)(C)C)CC(=O)OC(C)(C)C)=C1 CLZWAWBPWVRRGI-UHFFFAOYSA-N 0.000 claims description 4
- 238000005096 rolling process Methods 0.000 abstract description 12
- 229910000870 Weathering steel Inorganic materials 0.000 abstract description 11
- 238000013461 design Methods 0.000 abstract description 7
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- 239000010949 copper Substances 0.000 description 16
- 239000007788 liquid Substances 0.000 description 12
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 12
- 239000007921 spray Substances 0.000 description 9
- 238000009826 distribution Methods 0.000 description 7
- 239000008234 soft water Substances 0.000 description 7
- 239000011575 calcium Substances 0.000 description 6
- 229910052802 copper Inorganic materials 0.000 description 5
- 229910052720 vanadium Inorganic materials 0.000 description 5
- 239000002699 waste material Substances 0.000 description 5
- 230000003111 delayed effect Effects 0.000 description 4
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 3
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
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- 238000004925 denaturation Methods 0.000 description 2
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- 229910052748 manganese Inorganic materials 0.000 description 2
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- 230000008018 melting Effects 0.000 description 2
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- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
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- YOCUPQPZWBBYIX-UHFFFAOYSA-N copper nickel Chemical compound [Ni].[Cu] YOCUPQPZWBBYIX-UHFFFAOYSA-N 0.000 description 1
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- 230000004907 flux Effects 0.000 description 1
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- 229910052758 niobium Inorganic materials 0.000 description 1
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- 238000005204 segregation Methods 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
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- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
- 230000003313 weakening effect Effects 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention provides a special-shaped blank for weather-proof hot-rolled H-shaped steel and a production process thereof, wherein the balance of components ：C0.08～0.14％、Si 0.45～0.65％、Mn1.40～1.55％、P≤0.030％、S≤0.015％、Cu0.20～0.30％、Ni0.20～0.30％、Cr0.20～0.30％、V0.10～0.14％, is Fe and unavoidable impurities. Compared with the prior art, the invention aims at the crack defect generated in the production process of the weathering steel special-shaped blank, combines tracking and process optimization for a plurality of years, adopts fundamental measures from the processes of component design, steelmaking, refining and continuous casting, reduces the generation of transverse cracks of casting blanks and improves the yield of the weathering H-shaped steel after rolling.
Description
Technical Field
The invention belongs to a method for producing special-shaped blanks, in particular to a special-shaped blank for weather-proof hot-rolled H-shaped steel and a production process thereof, and particularly relates to the production of special-shaped blanks for Q420NQR1 weather-proof hot-rolled H-shaped steel.
Background
The weather-proof H-shaped steel for railway vehicles adopts a low-carbon high-manganese microalloying process with the addition of partial Cu, cr and Ni aluminum deoxidization and high vanadium. During production, the casting blank has the characteristics of low high temperature plasticity, complex section of the special-shaped blank and the like, the flange of the special-shaped blank cannot completely avoid the straightening of the third brittle zone, and the defect of transverse crack on the inner side of the flange is easily generated. The defects mainly occur at the groove of the vibration mark at the inner side of the flange, and the defects such as skin warping, cracking and the like of the surface of the rolled material can be caused when the defects are serious, and even batch waste products after rolling are generated.
Patent publication number CN110788293A published in 2 months 14 in 2020 discloses a special-shaped blank continuous casting process for high weather-resistant hot rolled H-shaped steel, wherein the technological parameters of a secondary cooling mode in the continuous casting process comprise: the specific water quantity is 0.5-0.55L/kg, and the water quantity distribution ratio of the first zone A section, the first zone B section and the second zone is 50% -55%:25% -27%:20% -25%, the inner and outer arcs of the section A of a zone are the same, and the water quantity of two side surfaces is 50% of the total water quantity of the inner and outer arcs; the water quantity of the inner arc of the section B of the first zone is 68-72% of the water quantity of the outer arc, and the water quantity of the two side surfaces is 65-69% of the total water quantity of the inner arc and the outer arc; the water quantity of the inner arc of the second area is 60% of the water quantity of the outer arc, and the water quantity of the two side surfaces is the same as the total water quantity of the inner arc and the outer arc. After the method is implemented, the special-shaped blank for the high weather-resistant heavy-load hot-rolled H-shaped steel for the high weather-resistant train is successfully produced on a special-shaped blank continuous casting machine, and the special-shaped blank has good surface quality and internal quality and completely meets the rolling requirement of the H-shaped steel. The method mainly comprises the secondary cooling water ratio and the distribution proportion of each area in the continuous casting process, wherein the components and the content of mold flux for continuous casting are matched with the superheat degree and the drawing speed, and the casting is performed by adopting the center of a web plate of a flat water gap. However, the alloy is applicable to weather-resistant hot-rolled H-shaped steel which does not contain copper and Ni, V and other elements, and cannot solve the problem in the production of weather-resistant hot-rolled H-shaped steel profiled bars.
The patent with publication number CN116900264A published 10/20/2023 discloses a method for producing a special-shaped continuous casting blank of hot-rolled H-shaped steel for a low-alloy high-strength engineering structure, which comprises the following chemical components in percentage by mass: 0.08 to 0.10 percent of C, 0.19 to 0.23 percent of Si, 1.36 to 1.40 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.008 percent of S, 0.038 to 0.040 percent of Nb, 0.06 to 0.08 percent of V, and the balance of Fe and unavoidable impurities; the method comprises the following steps: converter smelting, LF refining, profiled blank continuous casting and casting blank stacking slow cooling; the hot-rolled H-shaped steel special-shaped continuous casting blank for the low-alloy high-strength engineering structure has excellent low-temperature impact toughness. But its weather resistance is poor.
Disclosure of Invention
The invention aims to provide a special-shaped blank for weather-proof hot-rolled H-shaped steel and a production process thereof, which are improved in aspects of component design, steelmaking process, refining process, continuous casting process, equipment precision and the like, so that the special-shaped blank for high-strength weather-proof H-shaped steel is obtained, the generation of transverse cracks of casting blanks is reduced, and the yield of the weather-proof H-shaped steel after rolling is improved.
The invention provides a weather-proof special-shaped blank for hot-rolled H-shaped steel, which comprises the following components in percentage by mass:
C0.08～0.14％、Si 0.45～0.65％、Mn1.40～1.55％、P≤0.030％、S≤0.015％、Cu0.20～0.30％、Ni0.20～0.30％、Cr0.20～0.30％、V0.10～0.14％, The balance being Fe and unavoidable impurities.
The components of the special-shaped blank for the weather-proof hot-rolled H-shaped steel also meet the following conditions: ni/Cu is more than or equal to 1; cu can be precipitated by utilizing the time effect, the strength, the toughness and the welding performance of the steel are enhanced, and in addition, a small amount of Cu, cr and other elements form a compact oxide layer on the surface of the weathering steel to prevent further corrosion; however, during solidification, copper is enriched at the steel matrix interface, weakening the austenite grain boundaries and forming cracks. Therefore, ni is added into the steel to reduce the copper embrittlement risk, and [ Ni ]/[ Cu ] is controlled to be more than or equal to 1.
The invention provides a production process of a special-shaped blank for weather-resistant hot-rolled H-shaped steel, which comprises the following process flows: molten iron pretreatment, converter smelting, argon blowing refining, LF furnace refining and beam blank continuous casting.
In the production, the filling system is as follows: the iron-steel ratio is more than or equal to 0.9, and is mainly used for preventing the iron-steel ratio from being too low and the heat of charging the furnace from being insufficient, so that the molten steel is peroxidized. Specifically preferred are: the total loading amount is 68+/-2 tons, wherein, the molten iron is 60+/-2 tons, and the high-quality scrap steel is 8+/-2 tons.
When the molten iron is pretreated and the special-shaped blank is produced, molten iron with the temperature more than or equal to 1350 ℃ is selected to enter pretreatment, 4-6 kg/t of liquefied lime and 0.45-0.65 kg/t of passivated magnesium are added in the process, the slag skimming bright surface is more than or equal to 70%, and the outlet S is less than or equal to 0.005%.
The converter smelting is carried out, the [ H ] content in steel is controlled, the H content is controlled to be less than or equal to 5.5ppm, and the method specifically comprises the following steps: ore, iron scale pressing balls and pellet ore are added within 8 minutes of converting, and the total amount of the ore, the iron scale pressing balls and the pellet ore added into each furnace is less than or equal to 12.5kg/t; baking the alloy to above 300 ℃ and adding; the final slag alkalinity is controlled at 3.1-3.3.
The converter smelting is carried out, and molten steel peroxidation control is carried out: the end point carbon is controlled to be 0.05-0.07%, and the process adopts a 'high-low' gun position mode, and the method is particularly preferable: the initial spray head is 1150-1250 mm from the liquid level, the middle spray head is 1400-1600 mm from the liquid level, the later spray head is 900-1000 mm from the liquid level, and the gun is pressed before the end point.
And refining in the LF furnace, and controlling inclusions: the refining process adopts low aluminum operation, the Als content is controlled according to 0.006-0.020%, and the added aluminum particles are only used for deoxidizing and white slag making; in order to quickly form white slag, firstly, blowing through the large argon flow with the flow range of 300-500L/min, then adjusting the flow to 80-120L/min, heating the maximum power to the target temperature, and simultaneously adding lime, premelted refining slag and calcium carbide.
And refining in the LF furnace, and carrying out inclusion denaturation and removal: the feeding quantity of the calcium wire is 1.2-1.8 m/t of steel, and the target [ Ca ] is 0.0015-0.0025%; soft blowing with small flow rate of 25-75L/min is more than or equal to 20min, soft blowing is carried out through Cheng Gang, the liquid level is not exposed, and the slag surface slightly fluctuates.
The special-shaped blank is continuously cast, and the flow of soft water of continuous casting is controlled: the total flow of the soft water of the crystallizer is 200+/-10 m 3/h, and the soft water is specifically distributed into 69+/-1 m 3/h of wide flow and 31+/-1 m 3/h of narrow flow.
The special-shaped blank is continuously cast, and the flow of secondary cooling water is controlled: the total specific water content of the secondary cooling water is 0.55L/kg, and the secondary cooling water is specifically divided into three sections, namely: a first zone A section, a first zone B section and a second zone; the water distribution ratio of the first zone A section, the first zone B section and the second zone section is 50% -55%, 25% -27% and 20% -25% in sequence;
the specific water volume of each position of the first zone A section, the first zone B section and the second zone section is as follows:
zone a section: 0.092-0.101L/kg of inner arc, 0.092-0.101L/kg of outer arc and 0.092-0.101L/kg of both sides;
Zone B: 0.034-0.037L/kg of inner arc, 0.049-0.053L/kg of outer arc and 0.054-0.059L/kg of both sides;
Two areas: 0.021-0.026L/kg of inner arc, 0.034-0.043L/kg of outer arc and 0.055-0.069L/kg of both sides;
Preferably, the secondary cooling water is delayed for 40 seconds to be started, and more alloying elements such as Cr, ni, cu, V and the like are added into the steel during component design in order to ensure the high strength and high weather resistance of the rolled material. Production practice and theoretical research show that: the larger the alloy amount in the steel, the more serious the phenomenon of 'warping' of a casting blank during casting. In order to prevent casting blank 'tilting' from causing casting failure, when the secondary cooling water distribution model is arranged, the secondary cooling water is delayed to be started for 40 seconds during the production of the special-shaped blank, and the supercooling phenomenon of the casting blank head is reduced.
The special-shaped blank is continuously cast, the pulling speed is controlled to be matched with the superheat degree, a constant pulling speed casting mode of controlling flow by a stopper rod is adopted, and the specific pulling speed is matched according to the superheat degree of a tundish as follows:
For the casting blank with the width, the height and the thickness of 750 multiplied by 450 multiplied by 120mm of the special-shaped blank, the pulling speed is 0.74/m.min -1 when the tundish temperature is less than 1555 ℃; when 1555 is less than or equal to the temperature of the tundish and less than 1560 ℃, the pulling speed is 0.72/m.min -1; the pulling speed is 0.70/m.min -1 when the temperature of the tundish is less than or equal to 1560 and less than or equal to 1570 ℃; when the temperature of the tundish is more than 1570 ℃, the pulling speed is 0.65/m.min -1;
for the casting blank with the width, the height and the thickness of 500 multiplied by 300 multiplied by 120mm of the special-shaped blank, the pulling speed is 0.92/m.min -1 when the tundish temperature is less than 1555 ℃; when 1555 is less than or equal to the temperature of the tundish and less than 1560 ℃, the pulling speed is 0.90/m.min -1; the pulling speed is 0.88/m.min -1 when the temperature of the tundish is less than or equal to 1560 and less than or equal to 1570 ℃; when the temperature of the tundish is more than 1570 ℃, the pulling speed is 0.86/m.min -1.
Preferably, before the production of the special-shaped blank, the special equipment is used for carrying out polarization measurement on the vibrating table, when no load such as a crystallizer is required, the polarization at the two sides of the vibrating table is less than or equal to 0.2mm, and the inner and outer arcs are less than or equal to 0.3mm.
Q420NQR1 weathering steel belongs to typical high alloy peritectic steel, has strong crack sensitivity, and can be produced with the appearance of concave blank shell, deeper vibration mark and rough surface. In addition, the design of high V content is adopted in the steel grade, so that the ductility is reduced, the third brittle zone moves to a high temperature zone, meanwhile, the Cu melting point is lower, casting blank crack sensitivity is increased by precipitation at a crystal boundary, so that surface longitudinal cracks and transverse cracks are easy to generate in the production of weathering steel, and the waste judgment amount of ton steel after rolling is obviously higher than that of other steel grades. When the composition of molten steel is designed, the Ni content is increased, the Ni/Cu is ensured to be more than or equal to 1, and the influence of Cu segregation on grain boundary cracks is reduced; meanwhile, a low-acid aluminum dissolution process is adopted, nitrogen is increased in the control process, and influence of precipitation on a third brittle zone is reduced; and meanwhile, a tundish temperature and pulling speed matching system is formed, so that the continuous casting pulling speed is ensured, the strain rate during straightening is increased, and the straightening crack expansion of the third brittle zone is reduced.
Compared with the prior art, the invention aims at the crack defect generated in the production process of the weathering steel special-shaped blank, combines tracking and process optimization for a plurality of years, adopts fundamental measures from the processes of component design, steelmaking, refining and continuous casting, reduces the generation of transverse cracks of casting blanks and improves the yield of the weathering H-shaped steel after rolling.
Drawings
FIG. 1 is a schematic diagram of a crack condition in a cast slab produced in comparative example 2;
FIG. 2 shows the production of a cast billet according to the invention without cracks.
Detailed Description
The invention provides a production method of a special-shaped blank for weather-resistant hot-rolled H-shaped steel, which comprises the following process flows:
Molten iron pretreatment, converter smelting, argon blowing refining, LF furnace refining and beam blank continuous casting.
The method comprises the following steps:
and (3) component design: as shown in Table 1, the balance not shown in Table 1 is Fe and unavoidable impurities, and [ Ni ]/[ Cu ]. Gtoreq.1 in the steel.
Table 1 the specific composition of the weathering steel Q420NQR1 of the present invention is as follows (wt%):
And (3) molten iron pretreatment: when the special-shaped blank is produced, molten iron with the temperature more than or equal to 1350 ℃ is selected to enter pretreatment, 5kg/t of molten iron lime and 0.55kg/t of iron passivated magnesium are added in the process, the slag skimming bright surface is more than or equal to 70%, and the outlet [ S ] is less than or equal to 0.005%.
Filling system: the iron-steel ratio is more than or equal to 0.9, and is mainly used for preventing the iron-steel ratio from being too low and the heat of charging the furnace from being insufficient, so that the molten steel is peroxidized. Specifically preferred are: the total loading amount is 68+/-2 tons, wherein, the molten iron is 60+/-2 tons, and the high-quality scrap steel is 8+/-2 tons.
Smelting in a converter:
Control of [ H ] content in steel: ore, iron scale pressing balls and pellets are added within 8 minutes of converting, and the total addition amount of each furnace is not more than or equal to 12.5kg/t; baking the alloy to above 300 ℃ and adding; the final slag alkalinity is controlled at 3.1-3.3.
Controlling molten steel peroxidation: the end point carbon is controlled to be 0.05-0.07%, and the process adopts a 'high-low' gun position mode, and the method is particularly preferable: the initial spray head is 1150-1250 mm from the liquid level, the middle spray head is 1400-1600 mm from the liquid level, the later spray head is 900-1000 mm from the liquid level, and the gun is pressed before the end point.
Refining in an LF furnace:
Inclusion control: the refining process adopts low aluminum operation, and the added aluminum particles are only used for deoxidizing and making white slag; in order to quickly form white slag, firstly, blowing through with high argon flow of 300-500L/min, then adjusting the flow to 80-120L/min, heating the maximum power to the target temperature, and simultaneously adding lime, premelted refining slag and calcium carbide.
Inclusion denaturation and removal: the feeding quantity of the calcium wire is 1.2-1.8 m/t of steel, and the target [ Ca ] is 0.0015-0.0025%; soft blowing with small flow rate of 25-75L/min is more than or equal to 20min, soft blowing is carried out through Cheng Gang, the liquid level is not exposed, and the slag surface slightly fluctuates.
Continuous casting process:
Soft water flow rate: the weather-resistant steel special-shaped blank is produced by the following steps: the total flow of the soft water of the crystallizer is 200+/-10 m 3/h, and the soft water is specifically distributed into 69+/-1 m 3/h of wide flow and 31+/-1 m 3/h of narrow flow.
Second cold water flow: the total specific water content of the secondary cooling water is 0.55L/kg, and the secondary cooling water is specifically divided into three sections, namely: a zone A section, a zone B section and a zone two. The water distribution ratio of each section is 50% -55%, 25% -27% and 20% -25% in sequence, and specific water ratios of each section are shown in table 2.
TABLE 2 second Cold Water flow control
| Position of | Inner arc L/kg | Outer arc L/kg | Two sides L/kg |
| One zone A section | 0.092～0.101 | 0.092～0.101 | 0.092～0.101 |
| One zone B section | 0.034～0.037 | 0.049～0.053 | 0.054～0.059 |
| Two-zone | 0.021～0.026 | 0.034～0.043 | 0.055～0.069 |
On-water control (delay 40 seconds): in order to ensure the high strength and high weather resistance of the rolled material, more alloying elements such as Cr, ni, cu, V and the like are added into the steel during component design. Production practice and theoretical research show that: the larger the alloy amount in the steel, the more serious the phenomenon of 'warping' of a casting blank during casting. In order to prevent casting blank 'tilting' from causing casting failure, when the secondary cooling water distribution model is arranged, the secondary cooling water is delayed to be started for 40 seconds during the production of the special-shaped blank, and the supercooling phenomenon of the casting blank head is reduced.
Pull rate and superheat degree matching: when the special-shaped blank is produced, a constant pull rate pouring mode of stopper rod flow control is adopted, and the specific pull rate is matched according to the superheat degree of the tundish, and the details are shown in the following table 3.
TABLE 3 match pull rate to superheat
Vibrating table polarization: before the production of the special-shaped blank, special equipment is used for carrying out polarization measurement on the vibrating table, when no load such as a crystallizer is required, the polarization at the two sides of the vibrating table is less than or equal to 0.2mm, and the inner arc and the outer arc are less than or equal to 0.3mm.
The following description is made in connection with specific preferred embodiments.
Example 1-example 3
The production method of the special-shaped blank for the weather-resistant hot-rolled H-shaped steel specifically comprises the following process flows:
Molten iron pretreatment, converter smelting, argon blowing refining, LF furnace refining and beam blank continuous casting, wherein the processes are controlled as follows:
The ratio of iron to steel is 0.91, 0.93 and 0.91 when the molten iron and steel scraps are filled, wherein [ Ni ]/[ Cu ] in the steel is more than or equal to 1.
The specific components of examples 1, 2 and 3 are shown in table 4 below.
TABLE 4 Steel composition and content (wt%) of each example
| Alloying element | C | Si | Mn | P | S | Cu | Ni | Cr | V | Iron to steel ratio |
| Example 1 | 0.11 | 0.54 | 1.48 | 0.017 | 0.009 | 0.22 | 0.25 | 0.26 | 0.11 | 0.91 |
| Example 2 | 0.10 | 0.51 | 1.47 | 0.012 | 0.005 | 0.21 | 0.24 | 0.27 | 0.12 | 0.93 |
| Example 3 | 0.10 | 0.50 | 1.48 | 0.014 | 0.008 | 0.22 | 0.24 | 0.27 | 0.11 | 0.91 |
And (3) molten iron pretreatment: molten iron with the temperature of more than or equal to 1350 ℃ is selected to enter pretreatment, 5kg/t of molten iron lime and 0.55kg/t of iron passivated magnesium are added in the process, the slag skimming bright surface is more than or equal to 70%, and the outlet S is less than or equal to 0.005%.
In the production of the embodiment 1, the embodiment 2 and the embodiment 3, ores and iron scales are respectively added in the 6 th, the 7 th and the 6 th minutes of converting, and the total addition amount of each furnace is 618, 594 and 635 kg; baking the alloy to above 410, 401 and 382 ℃ respectively; the final slag alkalinity is controlled at 3.1-3.3. The end point carbon control is respectively 0.061, 0.065 and 0.064 percent so as to prevent the peroxidation of molten steel, and the process adopts a high-low gun position mode, and is particularly preferred: the initial spray head is 1200mm away from the liquid level, the middle spray head is 1400-1600 mm away from the liquid level, the later spray head is 900-1000 mm away from the liquid level, and the gun is pressed before the end point. The specific parameters are shown in Table 5.
TABLE 5 steelmaking parameters for various examples
Refining process of LF furnace: the refining process of each embodiment adopts low-aluminum operation, and the aluminum particles are only used for deoxidizing and making white slag; in order to quickly form white slag, firstly, blowing through with high argon flow of 300-500L/min, then adjusting the flow to 80-120L/min, heating the maximum power to the target temperature, and simultaneously adding lime, premelted refining slag and calcium carbide. The inclusion is denatured and removed: the feeding amount of the calcium wire is according to 1.5m/t steel, and [ Ca ] in the steel is 0.0020 percent, 0.0024 percent and 0.0023 percent respectively; soft blowing is carried out for 22-24min at the low flow rate of 50L/min, the liquid level of steel is not exposed during soft blowing, and the slight fluctuation of the slag surface is kept. The specific parameters of each example are shown in Table 6.
TABLE 6 refining main parameters of LF furnace of each example
And a continuous casting procedure, namely before the production of the special-shaped blank, carrying out polarization measurement on a vibrating table by using professional equipment, wherein when no load such as a crystallizer is required, the polarization of the two sides of the vibrating table is 0.15-0.19 mm, and the inner and outer arcs are 0.22-0.27 mm.
In the production of the special-shaped blank in the embodiment 1-3, the secondary cooling water is delayed to be started for 40 seconds, so that the supercooling phenomenon of the casting head is reduced; the total specific water content of the secondary cooling water is 0.55L/kg, and the secondary cooling water is specifically divided into three sections, namely: a zone A section, a zone B section and a zone two. The water distribution ratio of each section is 50% -55%, 25% -27% and 20% -25% in sequence, and the specific water ratios of each position are shown in Table 7.
TABLE 7 parameters of Soft Water flow, secondary Cold Water flow and Pull Rate during production of examples
The inner arc, the outer arc and the two sides of the special-shaped blank have larger cooling intensity difference, so that during production, the corresponding measures of the inner arc, the outer arc and the two sides of each section are respectively controlled, and the water quantity control range is shown in Table 2.
After the above examples 1 to 3 were slowly cooled, no crack was found near the flange by the rolling test, and the yield after rolling was 96.36 to 96.82%. The special-shaped blank casting blank for the weather-proof hot-rolled H-shaped steel produced by the technical scheme has good quality and high yield after rolling.
Comparative example 1
The special-shaped blank weathering steel Q420NQR1 produced in 7 months of 2021 is produced in small batches under the condition that the polarization of two sides of a vibrating table of a casting machine is 0.57mm and the polarization of inner and outer arcs is 0.74mm due to the tight delivery time and heavy production task. After the batch of casting blanks are cooled, the quality of the casting blanks is checked, and more flange transverse cracks are found, so that the production of a rolling line cannot be met. After the continuous casting machine is overhauled and the functional precision of equipment is recovered, and the technological requirements that the polarization of two sides of a vibrating table is less than or equal to 0.2mm and the internal and external arcs are less than or equal to 0.3mm are met, the yield of the produced Q420NQR1 weathering steel reaches 92.83% after the steel is rolled to 630X 200 specifications in a large H-shaped steel production line. The invention has the technical requirements that the polarization of the two sides of the vibrating table is less than or equal to 0.2mm and the internal and external arcs are less than or equal to 0.3mm, and can obviously reduce the transverse crack of the flange and improve the yield.
Comparative example 2
Ni is introduced by electrolytic nickel during production, and because the alloy has high price (about 16 ten thousand/ton), the on-site Ni/Cu is controlled according to 0.85-0.95 during the production of Q420NQR1 weathering steel before 2021 is 10 months old. Considering that Cu has a lower melting point, the crack sensitivity of a casting blank is increased by precipitation at a crystal boundary, and in order to improve the yield and the production stability of a production line, the inventor starts from 11 months in 2021, and according to the technical scheme of the invention, ni/Cu is more than or equal to 1, the addition of nickel-copper alloy in steel is controlled, and the comprehensive yield after rolling is improved from 93.2% to 96.29%. The invention shows that Ni/Cu is controlled to be more than or equal to 1, and the yield can be obviously improved.
And the production of 3.5 ten thousand tons of weathering steel profiled bars is finished in 2022, the once qualified rate after rolling is steadily improved, the comprehensive yield is 96.29%, the highest record of the same ratio history is 93.2%, and the yield is innovative. According to the method, the yield is improved from 93.2% to 96.29%, the ton steel waste is reduced from 68kg/t to 37.3kg/t, and the ton steel is reduced by 30.7kg/t; 6250 yuan/ton of weather-resistant steel finished products, 2650 yuan/ton of scrap steel, and the gap between ton steel finished products and waste products: 6250-2650=3600 yuan; 3.04, 9.62 and 12.1 ten thousand tons are respectively produced by weathering steel in the last three years, and the annual average yield is 8.25 ten thousand tons; to sum up: the annual waste loss is reduced: 30.7 kg/ton x 3600 yuan/ton x 82500 tons = 911.79 tens of thousands.
Claims (10)
1. The special-shaped blank for the weather-proof hot-rolled H-shaped steel is characterized by comprising the following components in percentage by mass:
C0.08～0.14％、Si 0.45～0.65％、Mn1.40～1.55％、P≤0.030％、S≤0.015％、Cu0.20～0.30％、Ni0.20～0.30％、Cr0.20～0.30％、V0.10～0.14％, The balance being Fe and unavoidable impurities.
2. The weather-resistant hot-rolled H-section steel profiled-stock according to claim 1, wherein the composition of the weather-resistant hot-rolled H-section steel profiled-stock further satisfies: ni/Cu is greater than or equal to 1.
3. A process for producing a profiled bar for weather-resistant hot-rolled H-section steel as claimed in claim 1 or 2, characterized in that the process comprises the following steps: molten iron pretreatment, converter smelting, argon blowing refining, LF furnace refining and beam blank continuous casting.
4. A production process according to claim 3, wherein in the production process, the [ H ] content control in the steel is performed, specifically: ore, iron scale pressing balls and pellet ore are added within 8 minutes of converting, and the total amount of the ore, the iron scale pressing balls and the pellet ore added into each furnace is less than or equal to 12.5kg/t; baking the alloy to above 300 ℃ and adding; the final slag alkalinity is controlled at 3.1-3.3.
5. The production process according to claim 3, wherein the argon blowing refining is performed with molten steel peroxidation control: the endpoint carbon is controlled between 0.05 and 0.07 percent.
6. A production process according to claim 3, wherein the LF furnace is refined to perform inclusion control: the refining process adopts low aluminum operation, the Als content is controlled according to 0.006-0.020%, and the added aluminum particles are only used for deoxidizing and white slag making; in order to quickly form white slag, firstly, blowing through the large argon flow with the flow range of 300-500L/min, then adjusting the flow to 80-120L/min, heating the maximum power to the target temperature, and simultaneously adding lime, premelted refining slag and calcium carbide.
7. A production process according to claim 3, wherein the continuous casting of the profiled blank is carried out, the total specific water content of the secondary cooling water is 0.55L/kg, and the process is divided into three sections, namely: a first zone A section, a first zone B section and a second zone; the specific water volume of each position of the first zone A section, the first zone B section and the second zone section is as follows:
zone a section: 0.092-0.101L/kg of inner arc, 0.092-0.101L/kg of outer arc and 0.092-0.101L/kg of both sides;
Zone B: 0.034-0.037L/kg of inner arc, 0.049-0.053L/kg of outer arc and 0.054-0.059L/kg of both sides;
two areas: inner arc 0.021-0.026L/kg, outer arc 0.034-0.043L/kg, two sides 0.055-0.069L/kg.
8. The production process according to claim 3 or 7, wherein the profiled bar is continuously cast and the second cooling water is turned on with a delay of 40 seconds.
9. The production process according to claim 3 or 7, wherein the continuous casting of the special-shaped blank is performed by controlling the pull rate to match with the superheat degree, and a constant pull rate casting mode of stopper rod flow control is adopted, and the specific pull rate is matched according to the superheat degree of the tundish as follows:
For the casting blank with the width, the height and the thickness of 750 multiplied by 450 multiplied by 120mm of the special-shaped blank, the pulling speed is 0.74/m.min -1 when the tundish temperature is less than 1555 ℃; when 1555 is less than or equal to the temperature of the tundish and less than 1560 ℃, the pulling speed is 0.72/m.min -1; the pulling speed is 0.70/m.min -1 when the temperature of the tundish is less than or equal to 1560 and less than or equal to 1570 ℃; when the temperature of the tundish is more than 1570 ℃, the pulling speed is 0.65/m.min -1;
for the casting blank with the width, the height and the thickness of 500 multiplied by 300 multiplied by 120mm of the special-shaped blank, the pulling speed is 0.92/m.min -1 when the tundish temperature is less than 1555 ℃; when 1555 is less than or equal to the temperature of the tundish and less than 1560 ℃, the pulling speed is 0.90/m.min -1; the pulling speed is 0.88/m.min -1 when the temperature of the tundish is less than or equal to 1560 and less than or equal to 1570 ℃; when the temperature of the tundish is more than 1570 ℃, the pulling speed is 0.86/m.min -1.
10. A production process according to claim 3, wherein before the production of the special-shaped blank, the polarization measurement is carried out on the vibrating table, and when no load such as a crystallizer is required, the polarization of the two sides of the vibrating table is less than or equal to 0.2mm, and the inner arc and the outer arc are less than or equal to 0.3mm.
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