CN111850396B - Economical bainite weathering steel for container and CSP (cast steel plate) line production method - Google Patents
Economical bainite weathering steel for container and CSP (cast steel plate) line production method 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
- 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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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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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
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
Abstract
An economical bainite weathering steel for containers comprises the following components in percentage by weight: c: 0.051-0.065%, and Si: 0.61-0.85%, Mn: 0.81-1.02%, P: 0.08-0.15%, S: less than or equal to 0.005 percent, Al: 0.015-0.055%, Cu: 0.46-0.61%, Cr: 0.61-0.72%, Ti: 0.026-0.061%, N: less than or equal to 0.006 percent; the CSP production method comprises the following steps: smelting; casting into a blank; heating in three stages; descaling; rolling; cooling; coiling; pit cooling; leveling; and (5) directly coating after slitting. The invention not only improves the corrosion resistance by not less than 13 percent compared with the prior art, but also can be directly coated without surface treatment, does not contain Ni, and can improve the elongation by more than 50 percent, and the thickness of the steel plate is less than or equal to 2.0 mm.
Description
Technical Field
The invention relates to container steel and a production method thereof, in particular to bainite weathering steel for an economical container and a production method thereof.
Background
China is the largest container production base, the yield accounts for more than 90% of the whole world, and the annual demand of weather-resistant steel for containers reaches 350-. To improve the transportation efficiency and reduce the transportation cost, light weight has become the main development trend of the container industry. The low-cost reduction of the thickness of the steel plate is one of the important characteristics of the new generation of weathering steel for containers.
In the consumed weathering steel for the container, the proportion of the extremely thin steel plate with the thickness of less than or equal to 2.0mm is the largest, and the occupied specific weight is about 50 percent, because the hot rolling production difficulty is high, the coating treatment is needed when the steel plate is used, when the hot rolling plate is used as a raw material, the surface treatment such as shot blasting or acid pickling treatment is needed, the process cost and the environmental pollution are increased, and the thickness is not less than 4 mm. At present, cold rolled products are generally taken as main products, but the production cost of the cold rolled sheet is high. The development trend in the field is that the manufacturing process can be effectively shortened by replacing a cold-rolled sheet with a thin hot-rolled sheet, and the manufacturing cost is reduced.
After retrieval:
the chinese patent publication No. CN103103458A discloses a method for manufacturing a high-strength cold-rolled weather-resistant steel sheet and a high-strength cold-rolled weather-resistant steel sheet, which is considered as cold-rolled steel, and solves the technical problem that the conventional hot continuous annealing production line is difficult to realize the stable batch production of the high-strength cold-rolled weather-resistant steel sheet, and the production process flow thereof is continuous cast slab heating → rough descaling → fixed width press → rough rolling → flying shear → fine descaling → finish rolling → laminar cooling → coiling → acid washing → cold rolling → continuous annealing → leveling, and the like. The production process is long, and the finished product of the document cannot be directly coated without surface treatment.
Chinese patent publication No. CN103103458A discloses a high-strength weathering steel and a preparation method thereof, wherein the surface of the weathering steel is covered with an iron oxide layer, and Fe in the iron oxide layer3O4The content is more than 80%, the thickness is 7-10 μm, and the weathering steel comprises the following components in percentage by weight: c: 0.01-0.05%, Si is less than or equal to 0.2%, Mn: 1.5-2.0%, P is less than or equal to 0.02%, S is less than or equal to 0.008%, Cu: 0.2 to 0.4%, Ni: 0.2-0.4%, Cr: 0.4 to 0.7%, Mo: 0.15 to 0.50%, Nb: 0.02 to 0.04%, Ti: 0.015-0.025%, less than or equal to 0.03% of Als, and the balance of Fe and inevitable impurities. The weathering steel has good comprehensive properties of mechanics, weather resistance, welding and the like. The steel is added with more noble metal elements such as Ni and the like in order to ensure the weather resistance and the formability of the steel, the alloy cost is higher, the product thickness of the steel is more than 6mm, the steel belongs to the traditional weather-resistant steel with thick specification, and the purpose of replacing cold with heat cannot be realized.
The Chinese patent publication No. CN 105603320A discloses a method for producing container plates by continuous casting and rolling of thin slabs, the production flow comprises the procedures of converter smelting, LF refining, continuous casting of thin slabs, heating by a heating furnace and hot continuous rolling, and in the LF refining procedure, the mass percentage of the components of the molten steel during tapping is controlled as follows: 0.05-0.09% of C, 0.30-0.50% of Si, 0.40-0.60% of Mn, 0.070-0.120% of P, 0.001-0.015% of S, 0.30-0.50% of Cr, 0.03-0.10% of Ni, 0.25-0.40% of Cu, and the balance of Fe and inevitable impurities. Although the document can eliminate the internal segregation of the continuous casting billet, reduce the addition amount of alloy and reduce the energy consumption of the whole process, the coating treatment is required when the continuous casting billet is used, namely when a hot rolled plate is used as a raw material, the surface treatment such as shot blasting or acid pickling is required, and the process cost and the environmental pollution are increased.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the bainite weathering steel for the economical container, which not only improves the corrosion resistance by not less than 13 percent, but also can be directly coated without surface treatment, does not contain Ni, improves the elongation by more than 50 percent on the basis of not reducing the strength and ensures that the thickness of a steel plate is less than or equal to 2.0mm, and the production method of the bainite weathering steel by a CSP line.
The measures for realizing the aim are as follows:
an economical bainite weathering steel for containers comprises the following components by weight percent: c: 0.051-0.065%, and Si: 0.61-0.85%, Mn: 0.81-1.02%, P: 0.08-0.15%, S: less than or equal to 0.005 percent, Al: 0.015-0.055%, Cu: 0.46-0.61%, Cr: 0.61-0.72%, Ti: 0.026-0.061%, N: less than or equal to 0.006 percent, the balance of Fe and inevitable impurities, and a metallographic structure of not less than 95 percent bainite by volume; mechanical properties: yield strength: 351-396 MPa, tensile strength: 483-532 MPa, elongation: 36-47%.
Preferably: the Mn content is 0.84-0.96% by weight.
Preferably: the Cr content is 0.61-0.69 wt%.
Preferably: the weight percentage content of Si is 0.61-0.81%.
Preferably: the Cu content is 0.46-0.58 wt%.
Preferably: the weight percentage content of P is 0.08-0.12%.
A method for producing an economical bainite weathering steel for containers by a CSP line comprises the following steps:
1) smelting by adopting the covering slag according to required components;
2) continuously casting into a blank, controlling the thickness of the blank to be 71-89 mm, and controlling the continuous casting drawing speed to be 5.2-6.1 m/min;
3) directly placing the casting blank into a tunnel furnace for three-section heating, and controlling the feeding temperature of the casting blank to be 769-987 ℃; the sections are separated by a lifting furnace door; controlling the front section of the tunnel furnace: the heating temperature is 1251-1287 ℃, the heating time is 5-12 min, and O2The content is 4.16-7.89%; the temperature of the middle section of the tunnel furnace is controlled to be 1007-1089 ℃, the heating time is 10-21 min, and O2The content is 1.56-4.11%; the temperature of the rear section of the tunnel furnace is controlled to be 1231-1249 ℃, the heating time is 10-21 min, and O2The content is 0.89-1.48%;
4) descaling by adopting high-pressure water, wherein the pressure of the descaling water is 428-497 bar;
5) rolling with 7 stands:
in this process, the following are provided: the thickness of the steel plate entering the 1 st frame is H, and the thickness of the steel plate at the outlet of the 1 st to the 7 th frames is H respectively1~ H7(ii) a The total accumulated rolling reduction in the rolling process is H-H7Cumulative reduction h of No. 1 to No. 2 frames1~2=（H-H2）/ (H-H7) Cumulative rolling reduction h of No. 3 to No. 5 stands3~5=（H2-H5）/ (H-H7) Cumulative reduction h of the 6 th to 7 th frames6~7=（H5-H7）/ (H-H7) (ii) a And satisfies the following conditions: h is3~5＞h1~2＞h6~7And satisfy h1~2+ h3~5+ h6~7= 100%; meanwhile, high-pressure water is adopted for descaling between the No. 2 and No. 3 frames and between the No. 5 and No. 6 frames, and the descaling water pressure is 311-386 bar; controlling the rolling finishing temperature to be 758-799 ℃;
6) carrying out laminar cooling, adopting a front-section cooling mode, and controlling the cooling speed to be 53-95 ℃/s to be cooled to the coiling temperature;
7) coiling at 418-511 ℃;
8) performing pit cooling, and cooling to room temperature in a natural cooling mode when the steel coil is cooled to 61-73 ℃;
9) flattening the strip steel coil, wherein the flattening temperature does not exceed 40 ℃; the roll shape convexity of the leveling working roll is 22-53 mu m, and the leveling rolling force is 652-807 KN;
10) and directly performing coating treatment after slitting.
It is characterized in that: during rolling: h is3~5＞h1~2Not less than 10%, h1~2＞h6~7Not less than 2%.
It is characterized in that: the physical and chemical performance indexes of the covering slag are as follows: the melting point of the hemisphere is 902-1042 ℃, the alkalinity is 0.82-1.22, the viscosity is 0.93-1.53 poise at 1290-1310 ℃, and the volume density is 0.65 +/-0.1 Kg/L.
It is characterized in that: the requirements during rolling are as follows: the surface roughness Ra of the working roll of the 1 st and the 2 nd frames is 8.7-10.3 μm, the surface roughness Ra of the working roll of the 3 rd to the 5 th frames is 3.2-6.6 μm, and the surface roughness Ra of the working roll of the 6 th and the 7 th frames is 0.1-0.8 μm.
Mechanism and action of each element and main process in the invention
C: the steel is a main strengthening element in steel, the carbon content is too low, the hardness of the steel is too low, and the steel quality is too soft; the carbon content is too high, the hardness of steel is too high, the problems of cracking and the like easily occur in the machining process, and the machining performance is poor, so that the C content is 0.051-0.065%.
Si: the steel plays a role in solid solution strengthening, and the formation of an inner rust layer is promoted due to the excessively high Si content, so that the descaling is difficult during rolling, and the surface quality of a steel strip is deteriorated; when the Si content is too low, the solid solution strengthening effect is difficult to be obtained. Therefore, the Si content is controlled to be 0.61-0.85%, preferably 0.61-0.81%.
Mn: the Mn can reduce the phase transformation temperature, thereby avoiding the phase transformation at higher temperature at a lower cooling rate and obtaining more bainite. Therefore, the minimum Mn content is 0.81%, and the excessive Mn content easily causes slab center segregation in the continuous casting process and reduces the usability of the material, so the maximum Mn content is 1.02%, and preferably the Mn content is 0.84-0.96%.
P: the addition of a certain amount of P in the steel can play a role in solid solution strengthening, improve the strength and atmospheric corrosion resistance of the steel, easily cause segregation due to too high content of P, reduce the strength and hardness of the steel and have adverse effects on welding performance. Therefore, the content of P is controlled to be 0.08-0.15%, preferably 0.08-0.12%.
S: the Mn-S-containing steel is an impurity element in steel, is easy to generate segregation at a crystal boundary, reduces the toughness of steel, is fully removed during steel making, and is ensured to be lower than 0.005%, and in addition, in order to reduce MnS inclusion of steel, the contents of Mn and S in the steel are met: [ Mn ]/[ S ] > 162.
Al: the Al can be used as a deoxidizing and nitrogen-fixing agent in the steelmaking process, can refine grains, improve the low-temperature toughness of steel, and can also increase the driving force of bainite phase transformation and obviously accelerate the bainite phase transformation. However, when the Al content is too high, a nozzle is easy to block, and casting is difficult, so that the Al content is controlled to be 0.015-0.055%.
Cu: the Cu is a main weather-resistant element in the weather-resistant steel, can effectively improve the weather-resistant performance of the steel, and has solid solution and precipitation strengthening functions when being added into the steel as an alloy element. However, if the Cu content is too high, cracks are likely to occur during heating or hot rolling, and the surface properties of the steel are deteriorated. Therefore, the Cu content is controlled to be 0.46 to 0.61%, preferably 0.46 to 0.58%.
Cr: the Cr element can be matched with Cu and other elements in the steel to obviously improve the atmospheric corrosion resistance of the steel, and in addition, the Cr element can effectively improve the hardenability of the steel, so the Cr content is controlled to be 0.61-0.72 percent, and the preferable content is 0.61-0.69 percent.
Ti: the titanium-based austenite grain growth inhibitor is a strong carbonitride forming element, the carbonitride of the element can effectively pin austenite grain boundaries and is beneficial to controlling the growth of austenite grains, and the content of Ti is controlled to be 0.026-0.061%.
N: the content of impurity elements in steel is controlled to 0.006% or less because the content is too high, the impurity elements tend to form bubbles and porosity in steel, and form brittle inclusions with edges and corners with elements such as aluminum in steel, which affect the formability of products.
According to the invention, the thickness of the cast blank after casting is controlled to be 71-89 mm, the continuous casting pulling speed is controlled to be 5.2-6.1 m/min, and the phenomenon that the total compression ratio in the subsequent rolling process is small due to the fact that the thickness of the cast blank is too thin, the recrystallization of the finished product is insufficient, and the mixed crystal phenomenon of the finished product is caused, so that the quality of the finished product is seriously influenced; too thick casting blank thickness can lead to insufficient subsequent rolling capability and can not be rolled to obtain a finished product within the target thickness range. And controlling the continuous casting drawing speed within the drawing speed range in order to keep the thickness of the liquid slag layer stable and the proper consumption of the casting powder.
According to the invention, the casting blank is controlled to directly enter the tunnel furnace for heating without cooling, and the charging temperature of the casting blank is controlled to be 769-987 ℃; the separation of the sections by adopting lifting furnace doors is used for ensuring the independence of the temperature and atmosphere of the hearth of each section; controlling the front section of the tunnel furnace: the heating temperature is 1251-1287 ℃, the heating time is 5-12 min, and O2The content is 4.16-7.89%; the temperature of the middle section of the tunnel furnace is controlled to be 1007-1089 ℃, the heating time is 10-21 min, and O2The content is 1.56-4.11%; the temperature of the rear section of the tunnel furnace is controlled to be 1231-1249 ℃, the heating time is 10-21 min, and O2The content is 0.89-1.48%; the method is characterized in that a casting blank enters a front section of a tunnel furnace to be heated after entering the furnace, and at the moment, the casting blank is heated under the high-temperature strong-oxidizing atmosphere condition, so that an oxide layer is rapidly generated on the surface of the casting blank, surface defects existing on the surface layer of the casting blank are oxidized, and the oxidized surface defects are effectively removed along with the oxidized iron sheet formed on the surface in the subsequent descaling process. Excessive heating temperature and O at the front section of the tunnel furnace2Too high content and too long heating time can cause serious surface oxidation of the casting blank and reduction of yield. The heating temperature of the front section of the tunnel furnace is too low, O2The content is too low, the heating time is too short, the surface of the casting blank cannot be fully oxidized, and the surface defects are difficult to remove. The casting blank enters the tunnel furnace middle section for heating after leaving the tunnel furnace front section, and the temperature of the middle section and the front section ensures a certain temperature difference, so that the adhesive force of the surface iron sheet layer is reduced, and the surface iron sheet is conveniently removed in the subsequent descaling process. The temperature of the middle section of the tunnel furnace is too low, so that the temperature difference between the surface and the core of the slab is too large, the casting blank cracks are caused, and the quality of the casting blank is influenced. Too high temperature of the middle section of the tunnel furnace can cause the temperature difference between the middle section and the front section to be too small, and the surfaceThe scale is difficult to be stripped. Middle section O2Too high a content results in severe oxidation of the surface of the cast slab and a reduction in yield. Middle section O2Too low a content may result in insufficient oxidation of the surface of the cast slab and difficulty in removing surface defects. The casting blank enters the rear section of the tunnel furnace for heating after leaving the middle section of the tunnel furnace, the temperature of the rear section is overhigh, the heating time is overlong, and O2Too high content can result in too thick iron sheet on the subsurface layer, severe burning loss and reduced yield. Over-low temperature of the rear section of the tunnel furnace, over-short heating time and O2If the content is too low, a compact oxide layer is difficult to form on the subsurface layer, so that the surface of a rolled steel coil cannot be directly coated, and if the temperature of the rear section is too low and the heating time is too short, the casting blank is difficult to be completely soaked, so that the deformation resistance in the subsequent rolling process is large, and the required thin-specification product is difficult to roll.
According to the invention, after the ingot is taken out of the soaking furnace, high-pressure water is adopted to remove the scale on the surface of the ingot, and the descaling water pressure is 428-497 bar. The scale removing water pressure is too low, so that iron sheets are difficult to remove, the scale removing water pressure is too high, the temperature of the strip steel is too fast, and the performance of a finished product is difficult to guarantee.
The invention controls the surface roughness Ra of the working roll of the 1 st frame and the 2 nd frame to be 8.7-10.3 mu m, the surface roughness Ra of the working roll of the 3 rd frame to the 5 th frame to be 3.2-6.6 mu m, and the surface roughness Ra of the working roll of the 6 th frame and the 7 th frame to be 0.1-0.8 mu m, and is matched with the screw-down system, and aims to obtain a steel coil meeting the performance and the target thickness, and to crush secondary iron sheets generated in the rolling process and reduce the adhesive force through the rolling of the large-roughness roller of the 1 st frame and the 2 nd frame so as to remove the steel coil in the subsequent process. The scale of the strip steel has proper roughness by rolling the rollers with certain roughness of the No. 3 to No. 5 frames, and the scale of the strip steel has certain density after rolling the rollers with smaller roughness of the No. 6 and No. 7 frames, so that the direct coating in the subsequent process is convenient.
According to the invention, high-pressure water is adopted between the No. 2 and No. 3 racks and between the No. 5 and No. 6 racks for descaling, and the descaling water pressure is controlled to be 311-386 bar, so that the scale for 2 times formed in the rolling process is effectively removed, and the influence on the surface quality of the strip steel caused by the press-in of the scale in the rolling process is avoided. The scale removing water pressure is too low, so that iron sheets are difficult to remove, the scale removing water pressure is too high, the temperature of the strip steel is too fast, and the performance of a finished product is difficult to guarantee.
The rolling finishing temperature is controlled to be 758-799 ℃, because the finishing temperature is too low, the strip steel enters an austenite and ferrite two-phase region for rolling, and the final finished product is mixed with crystals, so that the performance is uneven; the secondary oxidation of the surface of the strip steel is serious due to the overhigh finishing temperature.
The invention carries out laminar cooling after rolling, adopts a front-section cooling mode, and requires a cooling speed of 53-95 ℃/s, because the rapid cooling speed can cause the iron scale layer on the surface of the strip steel to generate micro cracks to influence the subsequent coating quality, and the slow cooling speed can cause the iron scale to have thicker thickness and be difficult to directly coat.
The coiling temperature is controlled to be 418-511 ℃, because the bainite structure meeting the performance requirement is difficult to obtain under the condition of over high or over low coiling temperature.
The invention cools the steel coil pit to 61-73 ℃, and then naturally cools the steel coil pit to room temperature, because the purpose of slowly cooling the steel coil is to react iron scales on the surface with oxygen components to form a compact oxide layer. If the temperature is too low, the steel coil is cooled too fast, the iron scale reaction is insufficient, a compact oxide layer is difficult to form, and the subsequent coating effect is influenced; if the temperature is too high, the retention time of the steel coil in a high-temperature section is long, so that the surface oxidation of the strip steel is serious, the thickness of the iron sheet on the surface is difficult to be uniform, and the subsequent coating effect is also influenced.
The invention controls the roll shape convexity of the leveling working roll to be 22-53 um and the leveling rolling force to be 652-807 KN, because the surface iron scale structure is damaged due to the overlarge roll convexity and the rolling force, and the thickness uniformity of the iron scale layer is reduced. The working roll convexity and the rolling force are too small, so that the strip shape of the strip steel is difficult to improve and the strip steel is difficult to use.
Compared with the prior art, the invention not only improves the corrosion resistance by not less than 13 percent compared with the prior art, but also can be directly coated without surface treatment, does not contain Ni, and can improve the elongation by more than 50 percent, and the thickness of the steel plate is less than or equal to 2.0 mm.
Description of the drawings:
FIG. 1 is a metallographic structure of the present invention;
FIG. 2 is a drawing of a coated steel sheet according to the present invention.
Detailed Description
The present invention is described in detail below:
table 1 is a list of values of chemical components of each example and comparative example of the present invention;
table 2 is a table of the main process parameters of each example of the present invention and comparative example;
table 3 is a list of the performance test cases of the examples and comparative examples of the present invention;
table 4 is a list of the corrosion resistance tests of the examples of the present invention and the comparative examples.
The preparation method comprises the following steps:
1) smelting by adopting the covering slag according to required components;
2) continuously casting into a blank, controlling the thickness of the blank to be 71-89 mm, and controlling the continuous casting drawing speed to be 5.2-6.1 m/min;
3) directly placing the casting blank into a tunnel furnace for three-section heating, and controlling the feeding temperature of the casting blank to be 769-987 ℃; the sections are separated by a lifting furnace door; controlling the front section of the tunnel furnace: the heating temperature is 1251-1287 ℃, the heating time is 5-12 min, and O2The content is 4.16-7.89%; the temperature of the middle section of the tunnel furnace is controlled to be 1007-1089 ℃, the heating time is 10-21 min, and O2The content is 1.56-4.11%; the temperature of the rear section of the tunnel furnace is controlled to be 1231-1249 ℃, the heating time is 10-21 min, and O2The content is 0.89-1.48%;
4) descaling by adopting high-pressure water, wherein the pressure of the descaling water is 428-497 bar;
5) rolling with 7 stands:
in this process, the following are provided: the thickness of the steel plate entering the 1 st frame is H, and the thickness of the steel plate at the outlet of the 1 st to the 7 th frames is H respectively1~ H7(ii) a The total accumulated rolling reduction in the rolling process is H-H7Cumulative reduction h of No. 1 to No. 2 frames1~2=（H-H2）/ (H-H7)，Cumulative reduction h of No. 3 to No. 5 stands3~5=（H2-H5）/ (H-H7) Cumulative reduction h of the 6 th to 7 th frames6~7=（H5-H7）/ (H-H7) (ii) a And satisfies the following conditions: h is3~5＞h1~2＞h6~7And satisfy h1~2+ h3~5+ h6~7= 100%; meanwhile, high-pressure water is adopted for descaling between the No. 2 and No. 3 frames and between the No. 5 and No. 6 frames, and the descaling water pressure is 311-386 bar; controlling the rolling finishing temperature to be 758-799 ℃;
6) carrying out laminar cooling, adopting a front-section cooling mode, and controlling the cooling speed to be 53-95 ℃/s to be cooled to the coiling temperature;
7) coiling at 418-511 ℃;
8) performing pit cooling, and cooling to room temperature in a natural cooling mode when the steel coil is cooled to 61-73 ℃;
9) flattening the strip steel coil, wherein the flattening temperature does not exceed 40 ℃; the roll shape convexity of the leveling working roll is 22-53 mu m, and the leveling rolling force is 652-807 KN;
10) and directly performing coating treatment after slitting.
TABLE 1 list of chemical compositions (wt%) of inventive and comparative examples
Table 2 list of main process parameter controls for various embodiments of the present invention
TABLE 3 Table of mechanical Properties of each example and comparative example of the present invention
Table 4 shows the corrosion resistance test conditions of the examples of the present invention and the comparative examples
Description of the drawings: corrosion resistance test conditions: and measuring the corrosion resistance of the sample by adopting a periodic infiltration test. The experiments were carried out in a Fl-65 type dry-wet cycle immersion corrosion tester using the TB/T2375 + 1993 standard. The test conditions were as follows: test solutions: 1.0X 10-2mol/l NaHSO3And (3) supplying solution: 2.0X 10-2mol/l NaHSO3The test temperature: 45 ± 2 ℃, relative humidity: 70 +/-5 RH, rotation speed of the soaking wheel: 1 cycle/60 min, test time: and 72 h. And (5) measuring the mass of the sample before and after corrosion, and calculating the corrosion weight loss and the corrosion rate. The sample size of the periodic infiltration test is 60mm multiplied by 40mm multiplied by the thickness, 4 samples are used for each steel sample, 3 samples are used for the periodic corrosion test, and 1 blank is used. All the samples were planed and ground to a surface finish accuracy of 0.7 μm. Punching and marking before testing, cleaning by using an oil removal agent, dehydrating by using absolute ethyl alcohol, removing oil by using acetone, and weighing. The mass was accurate to 0.0001 g. Corrosion weight loss sample treatment: the outer layer of the rust is mechanically removed, and then the sample is immersed in the rust removing solution and is continuously brushed by a brush to remove corrosion products.
As can be seen from tables 3 and 4, the steel of the invention not only improves the corrosion resistance by not less than 13% on the basis of the existing container steel (SPA-H), but also improves the elongation by more than 50% on the basis of the existing container steel on the basis of not reducing the strength, and obviously improves the comprehensive performance.
The above examples are merely preferred examples and are not intended to limit the embodiments of the present invention.
Claims (3)
1. A method for producing an economical bainite weathering steel for containers by a CSP production line comprises the following steps:
1) smelting by adopting the covering slag according to required components;
2) continuously casting into a blank, controlling the thickness of the blank to be 71-89 mm, and controlling the continuous casting drawing speed to be 5.2-6.1 m/min;
3) directly placing the casting blank into a tunnel furnace for three-section heating, and controlling the feeding temperature of the casting blank to be 769-987 ℃; the sections are separated by a lifting furnace door; controlling the front section of the tunnel furnace: the heating temperature is 1251-1287 ℃, the heating time is 5-12 min, and O2The content is 4.16-7.89%; the temperature of the middle section of the tunnel furnace is controlled to be 1007-1089 ℃, the heating time is 10-21 min, and O2The content is 1.56-4.11%; the temperature of the rear section of the tunnel furnace is controlled to be 1231-1249 ℃, the heating time is 10-21 min, and O2The content is 0.89-1.48%;
4) descaling by adopting high-pressure water, wherein the pressure of the descaling water is 428-497 bar;
5) rolling with 7 stands:
in this process, the following are provided: the thickness of the steel plate entering the 1 st frame is H, and the thickness of the steel plate at the outlet of the 1 st to the 7 th frames is H respectively1~ H7(ii) a The total accumulated rolling reduction in the rolling process is H-H7Cumulative reduction h of No. 1 to No. 2 frames1~2=（H-H2）/ (H-H7) Cumulative rolling reduction h of No. 3 to No. 5 stands3~5=（H2-H5）/ (H-H7) Cumulative reduction h of the 6 th to 7 th frames6~7=（H5-H7）/ (H-H7) (ii) a And satisfies the following conditions: h is3~5＞h1~2＞h6~7And satisfy h1~2+ h3~5+ h6~7= 100%; meanwhile, high-pressure water is adopted for descaling between the No. 2 and No. 3 frames and between the No. 5 and No. 6 frames, and the descaling water pressure is 311-386 bar; controlling the rolling finishing temperature to be 758-799 ℃;
6) carrying out laminar cooling, adopting a front-section cooling mode, and controlling the cooling speed to be 53-95 ℃/s to be cooled to the coiling temperature;
7) coiling at 418-511 ℃;
8) performing pit cooling, and cooling to room temperature in a natural cooling mode when the steel coil is cooled to 61-73 ℃;
9) flattening the strip steel coil, wherein the flattening temperature does not exceed 40 ℃; the roll shape convexity of the leveling working roll is 22-53 mu m, and the leveling rolling force is 652-807 KN;
10) directly carrying out coating treatment after slitting;
the bainite weathering steel for the economical container comprises the following components in percentage by weight: c: 0.051-0.065%, and Si: 0.61-0.85%, Mn: 0.81-1.02%, P: 0.08-0.15%, S: less than or equal to 0.005 percent, Al: 0.015-0.055%, Cu: 0.46-0.61%, Cr: 0.61-0.72%, Ti: 0.026-0.061%, N: less than or equal to 0.006 percent, the balance of Fe and inevitable impurities, and a metallographic structure of not less than 95 percent bainite by volume; mechanical properties: yield strength: 351-396 MPa, tensile strength: 483-532 MPa, elongation: 36-47%.
2. The method for producing a bainite weathering steel for economical containers as claimed in claim 1, wherein: the physical and chemical performance indexes of the covering slag are as follows: the melting point of the hemisphere is 902-1042 ℃, the alkalinity is 0.82-1.22, the viscosity is 0.93-1.53 poise at 1290-1310 ℃, and the volume density is 0.65 +/-0.1 Kg/L.
3. The method for producing a bainite weathering steel for economical containers as claimed in claim 1, wherein: the requirements during rolling are as follows: the surface roughness Ra of the working roll of the 1 st and the 2 nd frames is 8.7-10.3 μm, the surface roughness Ra of the working roll of the 3 rd to the 5 th frames is 3.2-6.6 μm, and the surface roughness Ra of the working roll of the 6 th and the 7 th frames is 0.1-0.8 μm.
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