CN112962025A - Production method of low-cost flaw-detection-guaranteed low-alloy structural steel medium plate - Google Patents
Production method of low-cost flaw-detection-guaranteed low-alloy structural steel medium plate Download PDFInfo
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/02—Dephosphorising or desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/30—Regulating or controlling the blowing
- C21C5/35—Blowing from above and through the bath
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/36—Processes yielding slags of special composition
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- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- 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
- C22C33/06—Making ferrous alloys by melting using master alloys
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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
Abstract
The invention relates to the technical field of steel making-steel rolling, in particular to a production method of a low-alloy structural steel medium plate with low cost and flaw detection. The invention adopts the design idea of substituting chromium for manganese on the aspect of component design, and adopts a converter and an argon station on the aspect of production process. The 12-60mm low-alloy Q345B/C, Q355B/C/D medium and thick plate obtained by the method has excellent performance indexes, yield, tensile strength and elongation completely meet the national standard, impact power is stable, and the flaw detection qualification rate and the comprehensive qualification rate are obviously improved compared with the prior art; meanwhile, as the process of directly installing the argon station is adopted, the whole production flow is shortened, the LF refining cost is saved, the cost per ton of steel is reduced by 50-100 yuan/ton comprehensively, the economic benefit is remarkable, and the method has good market popularization prospect.
Description
Technical Field
The invention relates to the technical field of steel making-steel rolling, in particular to a production method of a low-alloy structural steel medium plate with low cost and flaw detection.
Background
The low-alloy Q345 and Q355B/C/D steel is a common low-alloy steel, has huge actual production capacity, and is widely applied to the fields of steel structures, bridges, buildings and the like. No matter the steel grade Q345B/C before upgrading or the steel grade Q355B/C/D which is a new national standard and begins to be executed in 2019 from 2 months, a C-Mn-based component system is basically adopted in design. Mn is mainly solid solution strengthened in steel grades, and the high manganese content is adopted, and the Mn content is generally controlled to be 1.2-1.6%. However, when the manganese content is high, the production cost is high, the solid-liquid two-phase region of the high manganese steel is large, the continuous casting billet is coarse in grains, the center segregation of the Mn element is relatively serious, the core of the rolled steel plate is easy to form super-cooled austenite, if the cooling speed after controlled rolling is too high, bainite tissue is easy to generate in the local region of the core, and in addition, factors such as the segregation of inclusions in the core and the like are easy to generate in the center of the steel plate, so that the defects such as internal cracks, delamination and the like are easy to generate, and the problems of strict pile cooling.
The Chinese invention patent, application number 201810908403.4, discloses a manufacturing method for producing a guaranteed flaw detection Q345B medium plate by adopting a low-manganese high-titanium component, the flaw detection qualification rate is obviously improved while the Mn content is reduced, and the effect on improving the flaw detection qualification rate is obvious after the Mn content is fully reduced. Industrial practical experience also shows that the flaw detection qualification rate of the common carbon structural steel designed by adopting the low manganese component is far higher than that of the low alloy structural steel designed by adopting the high manganese component. However, the method has certain problems in the implementation process, and the LF refining process is adopted for production at first, so that the LF production process has higher cost; in addition, if the argon station direct-upward process is adopted for production, the yield of the added Ti element is unstable, the Ti content is difficult to accurately control, the problems of water gap blockage and the like are easily caused, the performance fluctuation range of the rolled steel plate is large, the low-temperature impact power is low and the like, and the method can only be used for producing the steel plate with the thickness of below 30mm and below C level generally.
Disclosure of Invention
The invention aims to provide a medium plate manufacturing method which adopts a design idea of replacing manganese with chromium in component design, adopts a converter and an argon station in a production process, can meet the performance requirement of a low-alloy Q345B/C, Q355B/C/D medium plate, can obviously improve the flaw detection quality of a low-alloy steel plate and has lower production cost.
The method comprises the following specific steps:
a low-cost flaw detection method for producing medium and thick low-alloy structural steel plates adopts a method of substituting chromium for manganese in the component design of the steel plates, reduces the Mn content of low-alloy steel within the common Mn content range of plain carbon steel, cancels the addition of Ti element, adds 0.20-0.30% of Cr element, and comprises the following chemical components in percentage by mass: 0.16 to 0.24 percent of C, 0.20 to 0.50 percent of Si, 0.60 to 1.10 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.015 percent of S, 0.20 to 0.30 percent of Cr, 0.003 to 0.040 percent of Als, and the balance of Fe and inevitable impurity elements.
The method is characterized in that LF refining is cancelled in the molten steel smelting process of the steel plate, a short flow mode of an argon station is adopted, and the method specifically comprises the steps of carrying out converter-argon station-continuous casting-rolling on molten iron, and obtaining a finished steel plate.
Further, the method is suitable for the production of 12-60mm low alloy Q345B/C, Q355B/C/D medium and heavy plates.
Furthermore, the production flow of the steel plate also comprises KR desulfurization, wherein P in blast furnace molten iron is less than or equal to 0.15 percent, S is less than or equal to 0.050 percent, the temperature T of the KR desulfurization station is greater than or equal to 1280 ℃, S in the molten iron after KR desulfurization is less than or equal to 0.015 percent, and the desulfurized slag is removed from the molten iron tank by more than 2/3 percent before the molten iron is added into the converter; preferably, if the B-grade steel plate is produced and S in the arriving molten iron is less than 0.020%, KR desulfurization may not be performed.
Further, the desulfurized molten iron is added into a top-bottom combined blown converter for smelting, dephosphorizing agents such as lime, magnesium balls and the like are added for oxygen blowing and blowing, the alkalinity of the final slag of the converter is controlled to be 3.0-3.5, calcium carbide and fluorite powder are added into a steel ladle before the steel is discharged from the converter, the adding amount is respectively 1.0-1.2kg/t and 0.5-0.7kg/t, the content of C in the steel discharged from the converter is controlled to be 0.06-0.12%, the content of P is less than or equal to 0.030%, the content of N is less than or equal to 30ppm, and the steel discharging temperature is controlled to be 1640-plus 1680.
Further, lime is added into the molten steel in the converter tapping process, the adding amount is 3-5kg per ton of the molten steel, alloy ferrosilicon, silicomanganese, high-carbon ferromanganese and high-carbon ferrochromium are added into the molten steel after 1/3 steel is tapped, the components in the molten steel are controlled to reach the middle and lower limits of target components, argon is blown in the whole tapping process, the tapping time is controlled within 5 minutes, argon is blown in a forced mode (based on the violent rolling of the surface of the molten steel) for 1-2 minutes after the tapping is finished, the lime and the alloy are made to melt as soon as possible, and then a covering agent is added and the molten steel is transferred to an argon station for treatment.
Further, after the molten steel arrives at an argon station, sampling and testing components, measuring the temperature, then adding 100-300Kg of lime and 20-50Kg of fluorite to melt slag, continuously blowing argon strongly for 1-2 minutes until the lime is completely melted, and after the fluidity of a slag layer becomes good, converting the slag layer into soft argon blowing (the soft blowing standard is that no naked eye with the diameter exceeding 10cm is formed on the surface of the molten steel), and during the soft blowing, adding various alloys and aluminum wires to finely adjust chemical components so as to ensure that the components reach design target components; adding a calcium silicon wire according to the standard of 1.5-2m/t before steel feeding and pouring in an argon station, carrying out soft blowing for 5-10min, and then carrying out steel feeding, wherein the steel feeding temperature is controlled between 1555 and 1570 ℃.
Further, the ladle casting adopts long nozzle argon seal protection casting, the superheat degree of the tundish is controlled between 1530 and 1545 ℃, a steel billet is obtained through continuous casting, and the steel billet is sent to a rolling link when the surface temperature of the steel billet is reduced to be below 500 ℃.
Further, the heating temperature of the steel billet is 1200-1240 ℃, a two-stage rolling process is adopted, the thickness of the intermediate blank airing steel of the steel plate with the thickness of 12-30mm is controlled according to 50-70mm, the thickness of the intermediate blank airing steel of the steel plate with the thickness of more than 30-60mm is controlled according to 1.8-2.2 times of the thickness of the finished product, the finish rolling temperature is 780-850 ℃, the ACC cooling finish cooling temperature is 580-630 ℃, and the cooling speed after rolling is 3-20 ℃/s.
Further, after the hot rolled steel plate is straightened, the steel plate with the thickness less than or equal to 20mm is not subjected to off-line stacking cooling, and is subjected to slow cooling on a cooling bed with a heat preservation cover for 1-2 hours and then is directly subjected to off-line cooling; and (3) performing off-line finishing after the steel plate with the diameter of 20-60mm is cooled in a heaped mode for 12-24 hours to obtain a finished steel plate.
The beneficial effects of the invention include:
(1) the alloy composition design adopts a method of replacing manganese with chromium, the Mn content of the low alloy steel is reduced to the common Mn content range of plain carbon steel, the addition of Ti element is cancelled, 0.2-0.3% of Cr element is added, the Cr content is higher than the Ti content by one order of magnitude, and when the argon standing process is adopted, the Cr content is easier to control, the molten steel has good fluidity, and a water gap is not easy to block. The carbon equivalent of the new components is not increased, and the welding performance of the rolled steel plate can be ensured. The alloy adopts high-carbon ferrochrome, the metal yield is more than 99.5 percent, and the residual chromium element of the converter molten iron is added, so that only about 0.10 to 0.20 percent of Cr is actually added, the actual dosage of the Mn alloy is greatly reduced, and the alloy cost is not high.
(2) In the steelmaking link, a converter argon station direct technology is adopted, LF refining treatment is not carried out, LF refining cost per ton of steel can be reduced by 30-70 yuan/ton, and smelting process cost is low. Meanwhile, the problems of H increase, N increase and the like in the refining process are avoided because the LF refining process is not carried out, the content of N in molten steel is low (below 40 ppm), the crack rate of the steel billet is extremely low, the steel billet cleaning process is omitted, the steel billet cleaning cost is reduced, and the surface quality of the steel plate is favorably ensured. Furthermore, the molten steel is not subjected to an LF refining process, the refining H increase problem is avoided, the hydrogen content in the steel plate is reduced, the heap cooling time is greatly shortened, the steel plate with the thickness of less than 20mm is subjected to offline heap cooling, the steel plate is directly subjected to heap cooling on a cooling bed with a heat-insulating cover, and the heap cooling time is only 1-2 hours; the cold storage time of the steel plate with the thickness of 20-60mm is also greatly shortened from the original 24-48 hours to 6-24 hours, the cold storage of the steel plate and the occupation of funds are reduced, and the flaw detection qualification rate is not reduced, but also greatly improved.
(3) The flaw detection qualification rate of the rolled steel plate is greatly improved, the qualification rate of a flaw detection third-level product reaches more than 98.2%, the flaw detection quality rate reaches more than 99.8%, and the qualification rate is improved by more than 3% compared with the traditional process; the performance stability of the rolled steel plate is improved, the one-time qualified rate of the performance reaches more than 99.5%, the problem that the impact of the steel plate is abnormally low is avoided, and the stable production of the Q355B/C/D grade steel plate is realized; the surface quality of the rolled steel plate is obviously improved, the rust resistance of the steel plate is improved, the burning loss rate of the steel billet is also reduced, and the unplanned proportion of the cracks of the steel plate is below 0.1 percent.
(4) The production process flow is shortened, the comprehensive production cost is obviously reduced, the comprehensive cost of each ton of steel is reduced to 50-100 yuan/ton, the delivery period is accelerated, and the economic benefit is obvious.
Detailed Description
The component design adopts a method of replacing manganese with chromium, the Mn content of the low alloy steel is reduced within the common Mn content range of plain carbon steel, the addition of Ti element is cancelled, 0.20-0.30% of Cr element is added, the chromium content is higher than Ti by one order of magnitude, the process control on the stand of argon station is convenient, and the specific chemical components and the mass percentage content are as follows:
TABLE 1 chemical composition combinations for various steel grades according to the invention
The production process route of the steel plate is as follows: (KR desulfurization), converter, argon station, continuous casting, billet quick cooling, heating, rolling, controlled cooling, straightening, steel plate stacking and cooling, offline finishing and detection warehousing, wherein the specific manufacturing method comprises the following steps:
p in blast furnace molten iron is less than or equal to 0.15 percent, S is less than or equal to 0.050 percent, the temperature T of the molten iron reaching a KR desulfurization station is more than or equal to 1280 ℃, S in the molten iron after KR desulfurization is less than or equal to 0.015 percent, and the desulfurization slag is removed from the molten iron tank by more than 2/3 percent before the molten iron is added into a converter; if the B-grade steel plate is produced and the S content in the arriving molten iron is less than 0.020%, KR desulfurization can not be carried out.
The converter is added with high-quality scrap steel which is not more than 15 percent in advance, the desulfurized molten iron is added into a top-bottom combined blown converter for smelting, dephosphorization agents such as lime, magnesium balls and the like are added for oxygen blowing and blowing, the alkalinity of the final slag of the converter is controlled to be 3.0-3.5, the carbon is successfully drawn for one time in the smelting process of the converter as far as possible, and the problems of additional blowing and point blowing are avoided, and the molten steel is strictly prohibited from being oxidized. Adding calcium carbide and fluorite powder into a steel ladle before tapping of the converter, wherein the adding amount is respectively 1.0-1.2kg of calcium carbide and 0.5-0.7kg of fluorite powder per ton of molten steel, the content of C in the tapping of the converter is controlled to be 0.06-0.12%, the content of P is less than or equal to 0.030%, the content of N is less than or equal to 30ppm, and the temperature before tapping is controlled to be 1640-1680 ℃.
Adding lime into molten steel in the tapping process, wherein the adding amount is 3-5kg per ton of molten steel, adding alloy ferrosilicon, silicomanganese, high-carbon ferromanganese and high-carbon ferrochromium into the molten steel after 1/3 steel is tapped by a converter, controlling the components in the molten steel to reach the middle-lower limit of target components, blowing argon in the whole process of the tapping process of the converter, strictly controlling the slag amount, and controlling the tapping time within 5 minutes. And (3) strongly blowing argon for 1-2 minutes (based on the violent rolling of the surface of molten steel) after tapping is finished, promoting lime and alloy to melt as soon as possible, then adding a covering agent and transferring to an argon station for treatment.
After the molten steel arrives at an argon station, sampling and testing components, measuring the temperature, then adding 100-300Kg lime and 20-50Kg fluorite slag, continuously blowing argon strongly for 1-2 minutes until the lime is completely melted and the fluidity of a slag layer becomes good, and then converting into soft blowing (the soft blowing standard is that no naked eye with the diameter of more than 10cm is required on the surface of the molten steel). During the soft blowing period, various alloys and aluminum wires are added according to the components of the test, the chemical components are finely adjusted, and the components are ensured to reach the designed target components. Adding a calcium-silicon wire according to the standard of 1.5-2m/t before steel pouring in an argon station, and carrying out steel pouring after soft blowing for 5-10 min. During the soft blowing, the soft blowing flow is adjusted according to the temperature of the molten steel, so that the continuous casting temperature of the upper steel is ensured to be between 1555 and 1570 ℃.
The ladle casting adopts long nozzle argon seal protection casting to ensure that the Als loss is less than 0.003 percent, the N content increase is controlled within 5ppm, the N content of a finished product is controlled within 40ppm, the tundish temperature is controlled within 1530-1545 ℃, and the continuous casting and billet heating are carried out according to a normal process.
The heating temperature of the steel billet is 1200-1240 ℃, two-stage rolling is adopted, the rough rolling temperature is 950-1050 ℃, the steel airing thickness of the steel plate with the thickness of 12-30mm is controlled according to 50-70mm, and the steel airing thickness of the steel plate with the thickness more than 30-60mm is controlled according to the thickness of the finished product which is 1.8-2.2 times; the finish rolling temperature is 780-850 ℃, the ACC finish cooling temperature is controlled at 580-630 ℃, and the cooling speed after rolling is 3-20 ℃/s.
After the steel plate is straightened and off-line, the steel plate with the thickness of 20mm or less is not cooled down and piled up, the steel plate is directly finished off after being subjected to heat preservation on a cooling bed with a heat preservation cover (namely, a fireproof heat preservation cover is added on the cooling bed to reduce the cooling rate of the steel plate on the cooling bed) for 1 to 2 hours, and the steel plate with the thickness of 20 to 60mm is finished off after being cooled down for 6 to 24 hours.
The following table shows the chemical composition combinations and the resulting steel sheet properties of a typical example of the invention in practice:
table 2 chemical composition of a typical example of the practice of the invention
| Examples of the invention | Steel brand | Thickness (mm) | C | Si | Mn | P | S | Als | Ti | Cr | Ceq |
| 1 | Q345B | 14 | 0.19 | 0.27 | 0.70 | 0.024 | 0.01 | 0.002 | 0.002 | 0.27 | 0.36 |
| 2 | Q345B | 20 | 0.19 | 0.22 | 0.79 | 0.016 | 0.012 | 0.002 | 0.002 | 0.281 | 0.38 |
| 3 | Q345B | 30 | 0.18 | 0.28 | 0.95 | 0.021 | 0.009 | 0.002 | 0.003 | 0.254 | 0.39 |
| 4 | Q345B | 40 | 0.20 | 0.22 | 1.10 | 0.016 | 0.005 | 0.004 | 0.004 | 0.227 | 0.43 |
| 5 | Q355B | 16 | 0.23 | 0.39 | 0.75 | 0.020 | 0.012 | 0.003 | 0.004 | 0.277 | 0.41 |
| 6 | Q355B | 20 | 0.23 | 0.34 | 0.85 | 0.023 | 0.006 | 0.003 | 0.003 | 0.29 | 0.43 |
| 7 | Q355B | 30 | 0.22 | 0.31 | 0.90 | 0.018 | 0.007 | 0.002 | 0.003 | 0.265 | 0.42 |
| 8 | Q355B | 60 | 0.21 | 0.32 | 1.10 | 0.013 | 0.007 | 0.015 | 0.002 | 0.24 | 0.44 |
| 9 | Q345C | 18 | 0.18 | 0.24 | 1.02 | 0.018 | 0.008 | 0.017 | 0.002 | 0.255 | 0.40 |
| 10 | Q355C | 20 | 0.18 | 0.26 | 1.08 | 0.018 | 0.008 | 0.019 | 0.002 | 0.235 | 0.41 |
| 11 | Q355D | 30 | 0.17 | 0.28 | 1.10 | 0.018 | 0.008 | 0.020 | 0.003 | 0.265 | 0.42 |
TABLE 3 Properties of the steel sheets obtained in the above examples according to the invention
It can be seen from tables 2 and 3 that the actual smelting component Mn content is greatly reduced, the C, Cr content is improved, the carbon equivalent is kept stable and unchanged, the welding performance is ensured, and all the components meet the national standard requirements.
The rolled steel plate in each example has excellent performance, yield, tensile strength and elongation completely meet the national standard, impact energy is stable, the problem of low single value is solved, and the flaw detection qualification rate and the comprehensive qualification rate are obviously improved. The alloy is produced by adopting an argon station direct-loading continuous casting process without LF refining, the content of Mn is obviously reduced although the content of Cr is increased, the alloy cost is kept unchanged or slightly increased, the LF refining cost is saved, the production process flow is shortened, the cost per ton of steel is comprehensively reduced by 50-100 yuan/ton, the delivery period is accelerated, the economic benefit is obvious, and the market popularization prospect is good.
Claims (9)
1. A production method of a low-cost flaw detection-protecting low-alloy structural steel medium plate is characterized by comprising the following steps: the steel plate is designed by adopting a method of substituting chromium for manganese, the Mn content of the low alloy steel is reduced to be within the common Mn content range of plain carbon steel, the addition of Ti element is cancelled, and 0.2-0.3% of Cr element is added; the steel plate comprises the following chemical components in percentage by mass: 0.16 to 0.24 percent of C, 0.20 to 0.50 percent of Si, 0.60 to 1.10 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.015 percent of S, 0.20 to 0.30 percent of Cr, 0.003 to 0.040 percent of Als, and the balance of Fe and inevitable impurity elements;
the production of the steel plate adopts a short flow mode, and specifically comprises the steps of carrying out converter-argon station-continuous casting-rolling on molten iron to obtain a finished steel plate.
2. The method for producing a low-cost flaw detection low-alloy structural steel medium plate according to claim 1, characterized by comprising: the method is suitable for the production of low-alloy Q345B/C, Q355B/C/D medium and heavy plates of 12-60 mm.
3. The method for producing a low-cost flaw detection low-alloy structural steel medium plate according to claim 1, characterized by comprising: the production flow of the steel plate also comprises KR desulfurization, wherein P in blast furnace molten iron is less than or equal to 0.15 percent, S is less than or equal to 0.050 percent, the temperature T to a KR desulfurization station is greater than or equal to 1280 ℃, S in the molten iron after KR desulfurization is less than or equal to 0.015 percent, and the desulfurized slag is removed from the molten iron tank by more than 2/3 percent before the molten iron is added into a converter; preferably, if the B-grade steel plate is produced and S in the arriving molten iron is less than 0.020%, KR desulfurization may not be performed.
4. The method for producing a low-cost flaw detection low-alloy structural steel medium plate according to claim 1, characterized by comprising: adding desulfurized molten iron into a top-bottom combined blowing converter for smelting, adding dephosphorizing agents such as lime, magnesium balls and the like for oxygen blowing and converting, controlling the alkalinity of final slag of the converter to be 3.0-3.5, adding calcium carbide and fluorite powder into a steel ladle before tapping of the converter, wherein the adding amount is 1.0-1.2kg/t and 0.5-0.7kg/t respectively, controlling the content of C in the converter to be 0.06-0.12%, the content of P to be less than or equal to 0.030%, the content of N to be less than or equal to 30ppm, and controlling the tapping temperature to be 1620 plus 1680 ℃.
5. The method for producing a low-cost flaw detection low-alloy structural steel medium plate according to claim 1, characterized by comprising: adding lime into molten steel in the tapping process of a converter, wherein the adding amount is 3-5kg per ton of molten steel, adding alloy ferrosilicon, silicomanganese, high-carbon ferromanganese and high-carbon ferrochromium into the molten steel after 1/3 tapping, controlling the components in the molten steel to reach the middle and lower limits of target components, blowing argon in the whole tapping process, controlling the tapping time within 5 minutes, blowing argon forcibly (based on the violent rolling of the surface of the molten steel) for 1-2 minutes after the tapping is finished, promoting the lime and the alloy to melt as soon as possible, then adding a covering agent, and transferring into an argon station for treatment.
6. The method for producing a low-cost flaw detection low-alloy structural steel medium plate according to claim 1, characterized by comprising: after the molten steel arrives at an argon station, sampling and testing components, measuring the temperature, then adding 100-plus 300Kg lime and 20-50Kg fluorite slag, continuously blowing argon strongly for 1-2 minutes until the lime is completely melted, and after the fluidity of a slag layer becomes good, converting into soft blowing argon (the soft blowing standard is that the surface of the molten steel cannot have naked eyes with the diameter exceeding 10 cm), and during the soft blowing period, adding various alloys and aluminum wires to finely adjust chemical components to ensure that all the components reach design target components; adding a calcium-silicon wire according to the standard of 1.5-2m/t molten steel before steel feeding and pouring in an argon station, carrying out soft blowing for 5-10min, and then carrying out steel feeding, wherein the steel feeding temperature is controlled between 1555 and 1570 ℃.
7. The method for producing a low-cost flaw detection low-alloy structural steel medium plate according to claim 1, characterized by comprising: the ladle casting adopts long nozzle argon seal protection casting, the temperature of the tundish is controlled between 1530 ℃ and 1545 ℃, a billet is obtained through continuous casting, and the billet is sent to a rolling link when the surface temperature of the billet is reduced to be below 500 ℃.
8. The method for producing a low-cost flaw detection low-alloy structural steel medium plate according to claim 1, characterized by comprising: the heating temperature of the steel billet is 1200-1240 ℃, a two-stage rolling process is adopted, the thickness of the intermediate billet dried steel of the steel plate with the thickness of 12-30mm is controlled according to 50-70mm, the thickness of the intermediate billet dried steel of the steel plate with the thickness of more than 30-60mm is controlled according to the thickness of a finished product which is 1.8-2.2 times, the finish rolling temperature is 780-850 ℃, the ACC cooling finish cooling temperature is 580-630 ℃, and the cooling speed after rolling is 3-20 ℃/s.
9. The method for producing a low-cost flaw detection low-alloy structural steel medium plate according to claim 1, wherein after the hot rolled steel plate is straightened, the steel plate with the thickness of less than or equal to 20mm is not subjected to off-line cooling and piling, and is subjected to slow cooling on a cooling bed with a heat-insulating cover for 1-2 hours and then directly subjected to off-line cooling; and (3) performing off-line finishing after the steel plate with the diameter of 20-60mm is cooled in a heaped mode for 12-24 hours to obtain a finished steel plate.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113406291A (en) * | 2021-06-29 | 2021-09-17 | 西安热工研究院有限公司 | Quality verification method of structural steel plate for wind power tower |
| CN115074486A (en) * | 2022-07-11 | 2022-09-20 | 河北普阳钢铁有限公司 | External refining and slagging method for converter steelmaking |
| CN115807149A (en) * | 2022-12-09 | 2023-03-17 | 日照钢铁控股集团有限公司 | Preparation process of high-aluminum steel ladle slag modifier for converter straight-up process |
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