Method for producing wide alloyed galvanized IF steel at high line speed

Abstract

The invention belongs to the technical field of cold-rolled hot-galvanized steel, and discloses a method for producing wide-width alloyed galvanized IF steel at a high linear speed. The width of the alloyed galvanized IF steel produced through the method is larger than or equal to 1700 mm, the pickling speed is increased to be larger than or equal to 180 m / min, the rolling speed of cold continuous rolling is increased to be larger than or equal to 700 m / min, the galvanizing running speed is increased to be larger than or equal to 100 m / min, through technological control over the procedures of steelmaking, hot rolling, pickling, cold rolling, hot galvanizing and the like, the stability and quality problems of a through plate after the speed of the wide alloyed galvanized IF steel is increased are solved, and the production efficiency is improved. And the production efficiency of a steel mill is greatly improved. The yield strength of the produced wide alloyed galvanized IF steel ranges from 140 MPa to 170 MPa, the tensile strength ranges from 290 MPa to 310 MPa, the elongation ranges from 43% to 47%, the plastic strain ratio r90 ranges from 2.2 to 2.5, the strain hardening index n90 ranges from 0.21% to 0.23%, the surface roughness ranges from 0.7 micrometer to 1.2 micrometers, the plate shape is free of middle waves and edge waves, the pulverization performance is good, and the wide alloyed galvanized IF steel can be widely applied to automobile side panels and top cover parts.

Description

Technical Field

[0001] The invention belongs to the technical field of cold-rolled hot-dip galvanized steel, and in particular relates to a method for producing wide-width alloyed galvanized IF steel at a high line speed. Background Art

[0002] With the in-depth development of the automobile industry, some users need to use cold-rolled plates with larger widths in order to improve the material utilization rate of steel plates, meet the overall forming requirements of parts, and reduce the welding costs of original tailor-welded plates. At the same time, some Japanese automakers still use narrow-specification parts longitudinally, and their order width specifications are usually below 1000mm, which brings production efficiency problems to steel mills.

[0003] Galvanized alloy sheet has excellent corrosion resistance, paintability and easy welding performance, and is widely used in automobile body inner and outer covering parts. Wide-width galvanized alloy sheet can be used for large-sized parts such as front and rear and side inner and outer panels, roof, etc. Compared with conventional width materials, ultra-wide materials can significantly improve the material utilization rate of large-sized parts, reduce the use of laser welded plates, reduce production costs and reduce carbon emissions, and the integral forming of multiple parts can improve the safety performance of the vehicle body. At the same time, for some orders with a width of less than 1000mm, the production efficiency of the steel plant can be greatly improved through the production of double-length materials.

[0004] As the width increases, wide-width alloyed galvanized sheets are prone to deviation during rolling and annealing, causing downtime. At the same time, in order to ensure the forming performance, the annealing temperature of alloyed galvanized IF steel is relatively high. Therefore, as the width increases, the probability of buckling in the annealing furnace also increases, causing adverse effects on the plate shape and surface quality. Therefore, when producing wide-width alloyed galvanized sheets, the production line usually runs at a slow speed to ensure product quality. However, with the downturn in the steel industry, product prices have fallen sharply. In order to survive, steel mills have to begin to pursue extreme efficiency and continuously increase production line speeds to reduce production costs and reduce losses. Therefore, how to ensure the production stability and product quality of wide-width alloyed galvanized IF steel at high line speeds has become a technical problem that needs to be overcome. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for producing wide-width alloyed galvanized IF steel at high line speed in view of the shortcomings of the prior art, which effectively solves the production stability and product quality problems of wide-width alloyed galvanized IF steel after the unit speed is increased, and greatly improves the production efficiency of the steel plant.

[0006] In order to solve the technical problem proposed by the present invention, the present invention provides a method for producing wide-width alloyed galvanized IF steel at high line speed, the steps of which include steelmaking, hot rolling, pickling, cold rolling, hot-dip galvanizing, alloying, and skin-passing.

[0007] In the above scheme, the steelmaking includes smelting and continuous casting.

[0008] Furthermore, the smelting is carried out according to the composition requirements of DC54D+ZF steel or DC56D+ZF steel.

[0009] Furthermore, the continuous casting calming time is ≥30min, and the crystallizer liquid level fluctuation is ≤±3mm.

[0010] In the above scheme, the hot rolling process controls the slab heating time to be 180 to 280 minutes.

[0011] In the above scheme, the thickness of the hot-rolled steel plate is controlled to be 2.8 to 3.0 mm, the convexity value of the hot-rolled steel plate is controlled to be 20 to 60 μm, and the wedge value is controlled to be -20 to 20 μm.

[0012] In the above scheme, the pickling adopts a three-stage pickling tank, the free acid concentration in the first pickling tank is ≥40g / l, the free acid concentration in the second pickling tank is ≥60g / l, and the free acid concentration in the third pickling tank is ≥110g / l.

[0013] Preferably, the free acid concentration in the first pickling tank is 40-60 g / l, the free acid concentration in the second pickling tank is 60-80 g / l, and the free acid concentration in the third pickling tank is 110-130 g / l.

[0014] In the above scheme, the pickling temperature is 75-90°C, and the pickling speed is ≥180m / min.

[0015] Preferably, the pickling speed is 180-200 m / min.

[0016] In the above scheme, the total reduction ratio of the cold rolling is 73-79%.

[0017] In the above scheme, the cold rolling adopts a five-stand cold rolling mill, the crown of the working rolls of each stand F1 to F5 is 5 to 40 μm, the roll diameter of the working roll of the F4 stand is 530 to 560 mm, and the roll diameter of the working roll of the F5 stand is 540 to 560 mm.

[0018] In the above scheme, the rolling speed of the cold rolling is ≥700m / min, and the steady-state rolling is ensured to be as uniform as possible, and the rolling speed fluctuation is controlled within ±20m / min.

[0019] Preferably, the cold rolling speed is 750-900 m / min.

[0020] In the above scheme, the shape of the cold-rolled steel plate is controlled to have no central waves, the height of the side waves is ≤2mm, there are no roller marks, embossing marks, emulsion residues, etc. on the surface, and there is no peak-like morphology on the surface.

[0021] In the above scheme, the cleanliness of the cold-rolled steel plate surface is controlled, and the reflectivity is required to be above 75%.

[0022] In the above scheme, the hot-dip galvanizing is produced by a continuous hot-dip galvanizing unit, and narrow-gauge double-length materials are used as transition materials to transition from wide to narrow. Narrow-gauge IF steel is usually used as inner plates, and the surface requirements are lower than those of outer plates. Therefore, double-length materials are used to confirm the condition of the unit first, and then the wide outer plates are produced after the condition is good.

[0023] In the above scheme, the hot-dip galvanizing includes cleaning, annealing and galvanizing.

[0024] Furthermore, a brush roller is put into use during cleaning, and the brush roller current is controlled to be above 20% of the no-load current.

[0025] Furthermore, during cleaning, the conductivity of the alkaline washing tank is controlled to be 30-40 ms / cm, and the conductivity of the electrolytic tank is controlled to be 45-55 ms / cm.

[0026] Furthermore, after cleaning, the squeezing quality of the squeezing roller must be ensured, and water is prohibited on the surface.

[0027] Furthermore, the annealing temperature is 830-850°C, and the annealing temperature matches the galvanizing running speed. When the line speed is increased, the annealing temperature should be increased accordingly.

[0028] Furthermore, the annealing includes a heating section, a soaking section and a cooling section. The tension of the heating section is controlled at 4-8 KN, the tension of the soaking section is controlled at 3-6 KN, and the tension of the cooling section is controlled at 6-10 KN.

[0029] Furthermore, the running speed during annealing and galvanizing is ≥100m / min and remains stable.

[0030] Preferably, the running speed during annealing and galvanizing is 100-120 m / min.

[0031] Furthermore, when the unit encounters an abnormal condition and needs to slow down, in order to prevent thermal buckling of the strip, the operating speed should be reduced step by step, and the single speed reduction should not exceed 5m / min.

[0032] Furthermore, the temperature of the zinc liquid is 456-458° C., and the aluminum content of the zinc liquid is 0.128-0.132%.

[0033] Furthermore, edge baffles are used during galvanizing to prevent the formation of thick edges of the zinc layer, which would affect subsequent alloying.

[0034] In the above scheme, the alloying temperature is 460-480°C, the online Fe content of the coating is controlled to be 9-10.5%, and the Fe content is detected offline for correction when producing the transition material.

[0035] In the above scheme, the burner-type edge heating device is turned on during the alloying process to heat the edge of the strip.

[0036] In the above scheme, the diameter of the polished working roll is 610-650 mm, the roughness of the working roll is 1.48-1.53 ​​μm, and new working rolls are replaced before producing wide-width alloyed galvanized IF steel.

[0037] In the above scheme, the difference in tension between the inlet and outlet of the finishing process is less than 5KN.

[0038] In the above scheme, for micro-edge waves with wave height ≤ 2mm, tension straightening is carried out, and the tension straightening elongation is controlled at 0.1-0.3%.

[0039] In the above scheme, the width of the wide alloyed galvanized IF steel is ≥1700 mm and the thickness is 0.6-0.8 mm.

[0040] Preferably, the width of the wide alloyed galvanized IF steel is 1750-2050 mm.

[0041] In the above scheme, the yield strength of the wide alloyed galvanized IF steel is 140-170 MPa, the tensile strength is 290-310 MPa, the elongation is 43-47%, and the plastic strain ratio r 90 is 2.2~2.5, strain hardening index n 90 The board has a roughness of 0.21-0.23 and a surface roughness of 0.7-1.2 μm. There are no center waves or side waves on the board.

[0042] In the above scheme, for wide-width alloyed hot-dip galvanized IF steel outer plates, further surface inspection is carried out on the finishing, and defects that affect delivery are cut. For wide-width double-length materials, longitudinal cutting is carried out in the longitudinal cutting unit to ensure the edge quality, and it is forbidden to deliver the edge with burrs.

[0043] The present invention is mainly based on the following design ideas:

[0044] The reason why the present invention requires the continuous casting calming time to be ≥30min and the crystallizer liquid level fluctuation to be ≤±3mm is that when the calming time is short or the crystallizer liquid level fluctuates greatly, small inclusions and slag are easily brought into the steel base. Wide-width plates are more sensitive to small inclusions due to their wider width. After the small inclusion defects cause stamping cracks, it will bring greater losses to users.

[0045] The reason why the present invention requires the slab heating time to be 180 to 280 minutes is that wide-width plates have higher requirements for performance uniformity. When the heating time is less than 180 minutes, the Nb and Ti compounds in the steel base are not fully precipitated, which is easy to cause uneven performance and affect the plate shape and formability in subsequent production; and if the slab heating time is too long, it is easy to over-burn and cause surface decarburization, and affect production efficiency. Therefore, the present invention controls the heating time of the rolled slab to be 180 to 280 minutes.

[0046] The reason why the present invention controls the hot-rolled convexity value to 20 to 60 μm and the wedge value to -20 to 20 μm is because the hot-rolled raw material profile has the most direct influence on the plate shape. In the plate shape control of ultra-wide alloyed galvanized sheets, because the plate width reaches the roller length limit of the rolling mill, conventional plate shape control methods such as bending rolls and stringing rolls cannot achieve the best plate shape control effect. Therefore, appropriate hot-rolled raw material convexity can reduce the intermediate extension degree of strip rolling and improve the strip shape. Through a large number of production results, it is found that when the hot-rolled convexity value of wide-width alloyed galvanized IF steel is 20 to 60 μm and the wedge value is -20 to 20 μm, the cold-rolled plate shape is better controlled. The adjustment of the convexity value and the wedge value can be achieved through CVC roll curve optimization and dynamic adjustment of rolling mill parameters.

[0047] The reason why the present invention controls the acid tank temperature at 75-90° C. and controls the free acid concentration in the three acid tanks, the No. 1 acid tank is not less than 40 g / l, the No. 2 acid tank is not less than 60 g / l, and the No. 3 acid tank is not less than 110 g / l, and the pickling speed is controlled at ≥180 m / min, preferably between 180 and 200 m / min, is to ensure the pickling quality, avoid over-pickling and under-pickling of the steel coil, and improve the product production efficiency.

[0048] The reason why the present invention selects the hot-rolled raw material thickness of 2.8-3.0mm and the rolling reduction rate of 73-79% is that this rolling reduction rate can reduce the rolling force of the rolling mill and better control the shape of the wide plate. The reason why the convexity of the working rolls of the 1-5 frames is controlled, and the convexity range is 5-40μm, is to control the shape of the wide plate by adjusting the convexity. The reason why the roller diameter of the F4 frame working roll is required to be 530-560mm and the roller diameter of the F5 frame working roll is required to be 540-560mm is that the rolling force fluctuation is smaller under this roller diameter, and it is easier to control the plate shape. The reason why there is no middle wave and the side wave height is ≤2mm is that the middle wave cannot be eliminated in the subsequent process. When the side wave height is small, it can be corrected by galvanizing tension control.

[0049] The reason why the present invention requires the rolling speed of wide alloyed galvanized IF steel to be ≥700m / min, and ensures that the steady-state rolling is as uniform as possible, and the rolling speed fluctuation is controlled within ±20m / min, is to improve production efficiency and enhance product profitability while ensuring quality.

[0050] The reason why the present invention requires that the surface after rolling should not be allowed to have roller marks, embossing marks, emulsion and other residues, the reflectivity should be above 75%, and the surface after rolling should be free of peak-like morphology is because the surface residues from acid rolling will hinder the reaction of zinc-iron alloy, resulting in inconsistent alloying degree, thus forming spot defects. Therefore, wide-width alloyed IF steel has higher quality requirements for the acid-rolled surface, requiring a reflectivity of more than 75% and no landscape painting morphology.

[0051] The reason why the invention adopts narrow specification multiple-size material as transition material is to further reduce production costs and reduce non-futures contract output. The reason why the transition is from wide to narrow is that the alloyed coating is relatively hard, and when transitioning from narrow to wide, it is very easy to produce width and narrow marks, affecting the surface quality.

[0052] The present invention requires the brush roller current to be controlled at more than 20%; controls the conductivity, the conductivity of the alkali washing tank is 30-40ms / cm, and the conductivity of the electrolytic tank is 45-55ms / cm, because the cleaning effect is best at this time, avoiding uneven alloying or spot defects caused by surface residues. The reason why the squeezing quality of the squeezing roller is guaranteed and the surface is prohibited from being watery is because the surface water will affect the reaction process of the zinc-iron alloy and cause the online Fe content to be inaccurate, which seriously affects the smooth production.

[0053] The reason why the present invention requires continuous annealing furnace production, annealing temperature of 830 ~ 850 ℃, annealing temperature and galvanizing production line running speed matching, when the line speed is increased, annealing temperature should be increased accordingly, because wide alloyed IF steel, mostly used as car roof and door inner and outer panels, has high requirements for formability, so a higher annealing temperature is required to complete recrystallization, so as to ensure the formability. When the line speed is increased, the heating time of the steel plate in the furnace becomes shorter, so the annealing temperature needs to be increased to ensure the formability.

[0054] The reason why the invention requires the wide plate galvanizing running speed to be ≥100m / min is to adapt to the current development, further improve production efficiency, reduce production costs, and cope with the dilemma of the continuous decline in steel product prices. The reason why the production line speed should be kept stable during galvanizing and the single speed reduction should not exceed 5m / min is that the speed reduction will affect the mechanical properties and coating quality of the product. At the same time, too fast a speed reduction will cause thermal buckling due to uneven stress, causing scratches or even deviation in the furnace.

[0055] The reason why the present invention controls the tension of each process section according to the plate shape, the tension of the heating section is controlled at 4-8KN, the tension of the soaking section is controlled at 3-6KN, and the tension of the cooling section is controlled at 6-10KN, is to control the deviation and warping of ultra-wide strip steel and reduce the fluctuation of the plate, and correct the plate shape of the previous process.

[0056] The present invention requires that the temperature of the zinc liquid be controlled at 456-458°C and the aluminum content of the zinc pot be controlled at 0.128-0.132% before entering the zinc pot, because under such conditions, the zinc-iron alloy reaction and diffusion are more favorable. The edge baffle is used when the wide plate is galvanized to prevent the formation of a thick edge of the zinc layer, which affects the subsequent alloying process and avoids the occurrence of uneven alloying.

[0057] The reason why the alloying temperature is controlled to be 460-480°C in the present invention is that this temperature can ensure that the content of Fe element diffused into the zinc coating is just right, so that the ultra-wide alloyed plate has good anti-powdering performance and welding ability. The reason why the burner-type edge heating device is turned on at the same time to heat the edge of the strip steel and the production of wide alloyed plates is prohibited when the edge burner is abnormal is to ensure the edge alloying temperature and prevent the white edge caused by insufficient edge alloying. The reason why the online Fe content is controlled at 9-10.5% is that within this Fe content range, the coating phase structure is mainly δ phase, which has better anti-powdering performance and forming performance.

[0058] The reason why the present invention requires the working roll diameter to be 610-650mm and the working roll roughness to be 1.48-1.53μm is that wide alloyed IF steel is mostly used as outer plates, which need to be coated later and have requirements for roughness. Low working roll roughness helps to ensure that the steel plate roughness is within the range of 0.7-1.2μm, and the working roll diameter of 610-650mm is easier to ensure the shape of wide plates. The reason why chrome-plated rolls are prohibited is that the surface hardness of chrome-plated rolls is high, the roughness cannot be attenuated, and the surface roughness of the coating cannot be effectively reduced, which easily causes the outer plate roughness to exceed the upper limit. The reason why the difference between the entrance tension and the exit tension of the present invention is less than 5KN is that when the difference between the entrance tension and the exit tension of the finishing is large, it is easy to cause the finishing wave shape. For micro-edge wave products put into tension straightening, the elongation of the tension straightening machine is controlled at 0.1-0.3%, which can effectively correct the plate shape.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] The width of the alloyed galvanized IF steel produced by the present invention is ≥1700mm, the pickling speed is increased to ≥180m / min, the rolling speed of the cold rolling is increased to ≥700m / min, and the galvanizing operation speed is increased to ≥100m / min. Through the process control of steelmaking, hot rolling, pickling, cold rolling, hot-dip galvanizing and the like, the plate passing stability and quality problems of the wide-width alloyed galvanized IF steel after the speed is increased are solved. The yield strength of the wide-width alloyed galvanized IF steel produced is 140-170MPa, the tensile strength is 290-310MPa, the elongation is 43-47%, and the plastic strain ratio r is 0.084mm. 90 is 2.2~2.5, strain hardening index n 90The thickness is 0.21-0.23, the surface roughness is 0.7-1.2μm, the plate has no middle wave and edge wave, and the powdering performance is good. It can be widely used in automobile side panels and roof parts. By speeding up production and using double-size materials to produce some narrow specifications, the production efficiency is greatly improved and the production cost is reduced, making the wide-width alloyed galvanized IF steel have a more obvious market competitive advantage. DETAILED DESCRIPTION

[0061] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0062] Example

[0063] The embodiment of the present invention is produced according to the following steps:

[0064] 1) Steelmaking

[0065] Including smelting and continuous casting, smelting is carried out according to the IF steel composition, continuous casting is controlled to have a calming time of ≥30min, and the crystallizer liquid level fluctuation is ≤±3mm;

[0066] 2) Hot rolling

[0067] The slab heating time is 180 to 280 minutes, the thickness of the hot-rolled steel plate is 2.8 to 3.0 mm, the convexity value of the hot-rolled steel plate is controlled to be 20 to 60 μm, and the wedge value is -20 to 20 μm;

[0068] 3) Pickling

[0069] The pickling temperature is 75-90°C, and the pickling speed is ≥180m / min;

[0070] A three-stage pickling tank is used, the free acid concentration in the first pickling tank is ≥40g / l, the free acid concentration in the second pickling tank is ≥60g / l, and the free acid concentration in the third pickling tank is ≥110g / l;

[0071] 4) Cold rolling

[0072] The total reduction ratio is 73-79%; the rolling speed is ≥700m / min, and the fluctuation is controlled within ±20m / min;

[0073] A five-stand cold rolling mill is used. The crown of the working rolls of each stand F1 to F5 is 5 to 40 μm, the diameter of the working rolls of the F4 stand is 530 to 560 mm, and the diameter of the working rolls of the F5 stand is 540 to 560 mm.

[0074] Control the shape of the cold-rolled steel plate to have no middle waves, the height of the side waves is ≤2mm, there is no roller mark, embossing, emulsion residue on the surface, there is no mountain-like morphology on the surface, and the reflectivity is above 75%;

[0075] 5) Hot dip galvanizing

[0076] The continuous hot-dip galvanizing unit is used for production, and narrow-gauge double-length materials are used as transition materials to transition from wide to narrow. Narrow-gauge IF steel is usually used as inner plates, and the surface requirements are lower than those of outer plates. Therefore, double-length materials are used for production to confirm the condition of the unit, and wide outer plates are produced after the condition is good.

[0077] Enter the cleaning section before galvanizing, put in brush rollers, and control the brush roller current to more than 20% of the no-load current; control the conductivity, the conductivity of the alkali washing tank is 30-40ms / cm, and the conductivity of the electrolytic tank is 45-55ms / cm; after cleaning, ensure the squeeze quality of the squeeze roller, and prohibit the surface from being wet;

[0078] Entering the continuous annealing furnace for production, the annealing temperature is 830-850℃. The annealing temperature matches the running speed of the galvanizing production line. When the line speed is increased, the annealing temperature should be increased accordingly. The running speed during annealing and galvanizing is ≥100m / min and remains stable. When the unit has an abnormal condition and needs to slow down, the running speed is gradually reduced, and the single speed reduction does not exceed 5m / min. The tension of each annealing process section is controlled according to the plate shape. The tension of the heating section is controlled at 4-8KN, the tension of the soaking section is controlled at 3-6KN, and the tension of the cooling section is controlled at 6-10KN.

[0079] When entering the zinc pot, the temperature of the zinc liquid is controlled to be 456-458℃, and the aluminum content of the zinc liquid is 0.128-0.132%. When galvanizing, an edge baffle is put in to prevent the formation of a thick edge of the zinc layer, which affects the subsequent alloying.

[0080] 6) Alloying

[0081] The alloying temperature is 460-480℃, the online Fe content of the coating is controlled at 9-10.5%, and the Fe content is detected offline for correction when producing transition materials; the burner-type edge heating device is turned on to heat the edge of the strip. When the edge burner is abnormal, the production of wide alloyed plates is prohibited;

[0082] 7) Finishing

[0083] Before producing wide alloyed galvanized IF steel, replace the new working rolls with a working roll diameter of 610-650mm and a working roll roughness of 1.48-1.53μm. It is forbidden to use chrome-plated rolls. The difference between the entrance and exit tensions of the skinning process is less than 5KN. For micro-edge wave products, tensile straightening is performed and the elongation of tensile straightening is controlled at 0.1-0.3%.

[0084] 8) Finishing or slitting

[0085] For wide-width alloyed hot-dip galvanized IF steel outer plates, further surface inspection is carried out on the finishing, and defects that affect shipment are cut; for wide-width multiple-size materials, longitudinal cutting is carried out on the longitudinal cutting unit to ensure the quality of the edges, and it is prohibited to ship out with burrs on the edges.

[0086] Table 1 Steelmaking and hot rolling process parameters of various embodiments of the present invention and comparative examples

[0087]

[0088] Note: Examples 3 and 7 are double-sized materials.

[0089] Table 2 Pickling process parameters of various embodiments of the present invention and comparative examples

[0090]

[0091] Table 3 Cold rolling process parameters of various embodiments of the present invention and comparative examples

[0092]

[0093] Table 4 Hot-dip galvanizing process parameters of various embodiments of the present invention and comparative examples

[0094]

[0095]

[0096] Table 5 Hot-dip galvanizing, alloying and skin-finishing process parameters of various embodiments of the present invention and comparative examples

[0097]

[0098] Table 6 Performance test results of wide alloyed galvanized IF steel obtained in various embodiments of the present invention and comparative examples

[0099]

[0100]

[0101] Note: The powdering performance of the material is evaluated through the 60-degree V-bend test. The steel plate is punched on a 60-degree V-shaped die, and then flattened on a flat plate. The coating is adhered with tape to check the coating shedding condition. The coating shedding condition is rated from light to heavy at 1 to 8 levels. Grade 1 has the best powdering performance and grade 8 has the worst powdering performance.

[0102] It can be seen that the wide-width alloyed galvanized IF steel produced at high line speed according to the present invention can not only pass through and produce with high quality, but also, compared with the products at conventional line speed, due to the adjustment of the annealing process according to the line speed, the mechanical properties are better, the powdering performance is good and meets the requirements of the outer plate, and the product is well stamped, welded and painted on the corresponding parts, which is recognized by users. At the same time, by increasing the speed of the production line, using double-sized materials to produce narrow-specification products, and using double-sized materials as transition materials, the production efficiency is greatly improved, the production cost is saved, and the profitability of wide-width alloyed hot-dip galvanized IF steel products is effectively improved.

[0103] The above embodiments are merely examples for clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above descriptions. It is not necessary and impossible to list all the implementation methods here, and the obvious changes or modifications derived therefrom are still within the protection scope of the invention.

Claims

1. A method for producing wide alloyed galvanized IF steel at high line speed, characterized in that: The width of the wide alloyed galvanized IF steel is ≥1700 mm, and the production method thereof comprises the following steps: 1) Steelmaking Smelting and continuous casting are carried out according to the composition of IF steel; 2) Hot rolling The slab heating time is 180 to 280 minutes; the convexity value of the hot-rolled steel plate is controlled to be 20 to 60 μm, and the wedge value is -20 to 20 μm; 3) Pickling The pickling temperature is 75-90°C, and the pickling speed is ≥180m / min; 4) Cold rolling The rolling speed is ≥700m / min, and the fluctuation is controlled within ±20m / min; the shape of the cold-rolled steel plate is controlled to have no middle waves, the height of the side waves is ≤2mm, there is no roller mark, embossing mark, emulsion residue on the surface, there is no mountain-like morphology on the surface, and the reflectivity is above 75%; 5) Hot dip galvanizing Including cleaning, annealing and galvanizing; the running speed during annealing and galvanizing is ≥100m / min and remains stable; the annealing temperature is 830-850℃, the tension of the heating section is controlled to be 4-8KN, the tension of the soaking section is 3-6KN, and the tension of the cooling section is 6-10KN; the temperature of the zinc pot zinc liquid is 456-458℃, and the aluminum content of the zinc liquid is 0.128-0.132%; 6) Alloying The alloying temperature is 460-480°C, and the Fe content of the coating is controlled at 9-10.5%; 7) Finishing The diameter of the working roll is 610-650mm, the roughness of the working roll is 1.48-1.53μm, and the use of chrome-plated rolls is prohibited; the difference between the entrance tension and the exit tension of the finishing is less than 5KN.

2. The method for producing wide-width alloyed galvanized IF steel at high line speed according to claim 1, characterized in that: The width of the wide alloyed galvanized IF steel is 1750-2050 mm; the pickling speed is 180-200 m / min; the cold rolling speed is 750-900 m / min; and the running speed during annealing and galvanizing is 100-120 m / min.

3. The method for producing wide-width alloyed galvanized IF steel at high line speed according to claim 1, characterized in that: The smelting is carried out according to the composition of DC54D+ZF steel or DC56D+ZF steel; the continuous casting is controlled to have a calming time of ≥30min and a crystallizer liquid level fluctuation of ≤±3mm.

4. The method for producing wide-width alloyed galvanized IF steel at high line speed according to claim 1, characterized in that: The pickling adopts a three-stage pickling tank, the free acid concentration in the first stage pickling tank is ≥40g / l, the free acid concentration in the second stage pickling tank is ≥60g / l, and the free acid concentration in the third stage pickling tank is ≥110g / l.

5. The method for producing wide-width alloyed galvanized IF steel at high line speed according to claim 1, characterized in that: The thickness of the hot-rolled steel plate obtained by hot rolling is 2.8-3.0 mm; the total reduction rate of the cold rolling is 73-79%; and the thickness of the wide-width alloyed galvanized IF steel is 0.6-0.8 mm.

6. The method for producing wide-width alloyed galvanized IF steel at high line speed according to claim 1, characterized in that: The cold rolling adopts a five-stand cold rolling mill, the crown of the working rolls of each stand F1-F5 is 5-40 μm, the roll diameter of the working roll of the F4 stand is 530-560 mm, and the roll diameter of the working roll of the F5 stand is 540-560 mm.

7. The method for producing wide-width alloyed galvanized IF steel at high line speed according to claim 1, characterized in that: The cleaning input brush roller has a brush roller current controlled at more than 20% of the no-load current, the conductivity of the alkali washing tank is controlled to be 30-40ms / cm, and the conductivity of the electrolytic tank is controlled to be 45-55ms / cm. After cleaning, the squeezing quality of the squeezing roller is guaranteed and water is prohibited on the surface.

8. The method for producing wide-width alloyed galvanized IF steel at high line speed according to claim 1, characterized in that: The galvanizing input edge baffle prevents the formation of thick zinc layer edges; the alloying opens the burner-type edge heating device to heat the edge of the strip to prevent white edges caused by insufficient edge alloying.

9. The method for producing wide-width alloyed galvanized IF steel at high line speed according to claim 1, characterized in that: After finishing, micro-edge waves with wave height ≤2mm are straightened by tension, and the elongation of tension is controlled at 0.1-0.3%.

10. The method for producing wide-width alloyed galvanized IF steel at high line speed according to claim 1, characterized in that: The yield strength of the wide alloyed galvanized IF steel is 140-170 MPa, the tensile strength is 290-310 MPa, the elongation is 43-47%, and the plastic strain ratio r 90 is 2.2~2.5, strain hardening index n 90 The board has a roughness of 0.21-0.23 and a surface roughness of 0.7-1.2 μm. There are no center waves or side waves on the board.

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