Method for controlling shape of 460MPa-grade wide high-rise building steel plate

Abstract

The invention relates to a method for controlling the shape of a 460MPa-grade wide high-rise building steel plate. The method comprises the steps of casting blank heating, rolling, pre-straightening, ACC cooling process and hot straightening. Particularly, the ACC cooling starting cooling temperature is 720-740 DEG C, the roller speed is 1.0-1.2 m / s, the cooling rate is 10-12 DEG C / s, the self-tempering temperature is 500-540 DEG C, the water convexity valve opening degree is 80%, the head shielding length is 0.5-1.5 m, the tail shielding length is 0.5-1.0 m, and the water ratio of the cooling water lower header flow to the cooling water upper header flow is 1.2-1.3; during hot straightening, the straightening force is ensured to be larger than or equal to 1200 t, the temperature of the steel plate entering a hot straightening machine is 480-520 DEG C, the inlet rolling reduction is 4.5-5.5 mm, the outlet rolling reduction is 0-1.0 mm, the inlet guide roller speed is 0.3 m / s, and the straightening speed is 0.4-0.5 m / s; according to the method, rolling, cooling, straightening and other technological parameters of the Q460GJ steel are redesigned, on the premise that steel components are not changed and cold straightening equipment is not added, the production purpose that the straightness of the steel plate is 3-4 mm / 2 m is achieved, the yield and the contract redemption rate of the steel plate are greatly increased, and the method is suitable for application and popularization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-strength wide-width high-rise building steel processing and production, and particularly relates to a 460MPa-grade wide-width high-rise building steel plate shape control method. BACKGROUND

[0002] With the development of high-rise buildings towards large-scale and super high-rise, higher requirements are put forward for the strength, plate shape precision and resistance to lamellar tearing of building steel. At present, 355MPa, 390MPa and 420MPa grade high-rise building steel are mostly used in the market, and 460MPa grade high-strength steel gradually becomes the core material of high-rise building structure due to its excellent mechanical properties and lightweight advantage. However, for the wide-width building steel plate with a width greater than 3000mm and a thickness of 40-50mm, there is a serious plate shape control problem in production: on the one hand, the steel plate is cooled quickly and the rolled piece is thick during rolling, which leads to uneven metal flow and easily produces defects such as wave shape and transverse under-set, affecting the implementation of welding automation; on the other hand, the existing technology relies on subsequent cold straightening process, which leads to low production efficiency and significant cost increase.

[0003] Previously, the research on thick steel plate shape control mostly focuses on thin gauge products. For example, the patent with publication number CN101069896A proposes a rolling method without final pass reduction to improve the wave shape of steel plates below 30mm, but this method cannot eliminate the warping defects of thick steel plates caused by rolling force sensitivity and temperature gradient, and the accumulation of residual stress caused by insufficient final rolling temperature control. In addition, two-stage controlled rolling combined with normalizing treatment is often used in traditional processes, which can improve the strength, but the carbon equivalent is high (CEV>0.42%), the welding performance is insufficient, and the normalizing process easily causes grain coarsening and aggravates plate shape fluctuation. Another study attempts to optimize the performance by increasing alloying elements (such as Ni), but such design increases the smelting cost, and uneven distribution of cooling water during rolling easily causes temperature difference between the head and tail of the steel plate, further deteriorating flatness.

[0004] Therefore, it is of great significance to develop a 460MPa grade high-rise building steel production process without relying on cold straightening and achieving high-precision plate shape control, to improve the yield of high-rise building steel, contract fulfillment efficiency and economic benefits. SUMMARY

[0005] The purpose of the present application is to solve the problems of the unripe plate shape control process of the 460MPa grade high-rise building steel plate in the prior art, which leads to the easy existence of the buckling defects of the steel plate, the poor plate shape of the steel plate, and the influence on the plate yield and the contract realization rate, and to provide a 460MPa grade wide high-rise building steel plate shape control method. The thickness specification of the steel plate produced by the method is 30-50mm, and the width specification is 2000-4100mm. The method adopts two-stage controlled rolling and combines the MULPIC rapid cooling device to dynamically adjust the water ratio, water quantity and cooling rate, and at the same time, uses a hot straightening machine for slow straightening to achieve the effect of improving the flatness of the steel plate, and achieves the plate shape control purpose of the flatness of the Q460GJ steel plate being 3-4mm / 2m.

[0006] The 460MPa grade wide high-rise building steel plate shape control method of the present application comprises the following steps:

[0007] (1) Casting blank heating: the casting blank discharge temperature is 1160-1200℃, the heating rate is 8-9min / cm, and the section temperature difference is controlled to be ≤25℃; the 200mm section slab is in the furnace for ≥160min, and the 250mm section slab is in the furnace for ≥200min;

[0008] (2) Rolling: two-stage rolling process is adopted, the first stage rolling adopts large reduction strategy, the intermediate blank thickness is 2.5-3 times the finished product thickness, the average reduction rate of each pass in the rolling process is ≥10%, and the snowshoe coefficient value is set to 0-10%; the second stage opening rolling temperature is ≤900℃, the finish rolling temperature is controlled to be 815-835℃, the flattening pass reduction is 2.0-2.5mm, the last pass is empty pass, and the steel throwing speed is ≥6m / s, and the main purpose is to control the opening cooling temperature range to be 720-740℃;

[0009] (3) Pre-straightening: the straightening machine inlet reduction is 4.5-5mm, the outlet reduction is 0-1.0mm, the pre-straightening biting speed is 1.0-1.2m / s, and the pre-straightening force is ≥800 tons;

[0010] (4) ACC cooling process: the steel plate is pre-straightened and then enters the MULPIC rapid cooling device for ACC rapid cooling, the opening cooling temperature is set to 720-740℃, the roller speed is 1.0-1.2m / s, the cooling rate is 10-12℃ / s, the re-red temperature is 500-540℃, the water convexity valve opening degree is 80%, the head shielding length is 0.5-1.5m, the tail shielding length is 0.5-1.0m, and the water ratio of the cooling water lower header flow rate / upper header flow rate is 1.2-1.3;

[0011] (5) Hot straightening: after the ACC fast cooling, the steel plate is subjected to slow straightening, to ensure that the straightening force is greater than or equal to 1200t, the temperature of the steel plate entering the hot straightening machine is 480-520℃, the inlet reduction is 4.5-5.5mm, the outlet reduction is 0-1.0mm, the inlet guide roller speed is 0, and the straightening speed is 0.4-0.5m / s.

[0012] The steel grade model of the wide high-rise building steel plate is Q460GJ steel plate, and the width of the finished steel plate is 2000-4100mm, and the thickness is 30-50mm.

[0013] The MUPLIC rapid cooling device in the application adopts a variable flow water pillow type cooling header with edge shielding and water convexity control, 24 cooling headers are arranged on the upper and lower parts, and are divided into four zones A, B, C and D, each zone is 6m long, the total length is 24m, and each zone has 6 headers on the upper and lower parts, and has an online quenching function.

[0014] The steel grade model of the wide high-rise building steel plate is Q460GJ, and the steel plate is composed of elements with the following mass percentage contents: C: 0.14-0.16%, Si: 0.25-0.35%, Mn: 1.35-1.45%, P≤0.010%, S≤0.005%, Nb: 0.048-0.058%, Ti: 0.010-0.020%, V: 0.038-0.046%, Als: 0.015-0.050%, and the rest is Fe and unavoidable impurities, in addition, the above element contents need to meet CEV: 0.38-0.42%.

[0015] The application is made after in-depth study of the existing high-rise building steel plate shape control difficulties, and the key difficulties in the prior art are that the reduction distribution in the rough rolling stage is unreasonable, resulting in uneven stress distribution in the intermediate billet; the finish rolling temperature is too high (>860℃) or too low (<800℃), which aggravates the deformation stress and forms local warping. In addition, the traditional cooling process is not optimized for the head and tail shielding of the steel plate, resulting in large fluctuation of the re-red temperature range, uneven cooling, significant thickness direction shrinkage difference, and difficult correction of subsequent straightening. Meanwhile, when the straightening temperature of the hot straightening machine is too high (>540℃), the steel plate still undergoes phase transformation during slow cooling, resulting in secondary deformation, and the applicant's enterprise internal 4300mm medium plate production line has no cold straightening machine equipment, and cannot batch process the secondary deformed thick plate.

[0016] In view of the problems existing in the prior art and the existing situation of the applicant's enterprise equipment, the inventors improve the existing process, and through the rolling process and cooling process of the steel plate, the steel plate flatness of 3-4mm / 2m is obtained on the basis of hot straightening. The process parameter setting principle of the application is as follows:

[0017] (1) Casting blank heating

[0018] The casting blank discharge temperature is 1160-1200℃, the heating rate is 8-9 min / cm, and the cross-section temperature difference is controlled to be ≤25℃; the 200mm cross-section slab is in the furnace for ≥160min, and the 250mm cross-section slab is in the furnace for ≥200min; the sufficient heating time can ensure the temperature uniformity in the thickness direction of the slab, the sufficient dissolution of carbide, and the sufficient austenitization.

[0019] (1) Rolling process

[0020] A two-stage rolling process is adopted, a large reduction strategy is adopted in the first-stage rough rolling, the intermediate blank thickness is 2.5-3 times the finished product thickness, the average reduction rate per pass in the rolling process is ≥10%, and the ski coefficient value is set to 0-+10%; the reasonable reduction rate distribution in the rough rolling stage can obtain the intermediate blank with uniform stress distribution;

[0021] The second-stage finish rolling starting temperature is ≤900℃, and the finish rolling temperature is controlled to be 815-835℃, so as to avoid the problem of the local buckling of the steel plate caused by the excessively high or low finish rolling temperature in the finish rolling stage; the flattening pass reduction amount is 2.0-2.5mm, the last pass is an empty pass, and the throw-off speed is ≥6m / s, and the main purpose is to control the open cooling temperature range to be 720-740℃.

[0022] (2) Pre-straightening

[0023] After the rolling is completed, a reasonable pre-straightening process is carried out, the inlet reduction amount is set to 4.5-5mm, the outlet reduction amount is set to 0-1.0mm, the pre-straightening biting speed is 1.0-1.2m / s, and the pre-straightening force is ≥800 tons; the pre-straightening is carried out on the steel plate before cooling, which can play a role in the temperature reduction of the steel plate after rolling, so as to make the open cooling temperature reach the target value, and the pre-straightening is also carried out on the shape of the steel plate;

[0024] (3) ACC cooling process

[0025] After the pre-straightening, the steel plate enters the MULPIC rapid cooling device to carry out the ACC rapid cooling, the open cooling temperature is set to 720-740℃, the roller speed is 1.0-1.2m / s, the cooling rate is 10-12℃ / s, the re-red temperature is 500-540℃, the water convexity valve opening degree is 80%, the head shielding length is 0.5-1.5m, the tail shielding length is 0.5-1.0m, and the cooling water ratio is 1.2-1.3 (lower header water quantity / upper header water quantity); in order to control the cooling uniformity in the width direction of the high-strength steel plate and the problem of the head and tail buckling caused by the excessively low temperature of the head and tail of the steel plate, the reasonable water convexity valve opening degree, the head and tail shielding length, and the lower water quantity adjustment deviation function are set, and the head and tail buckling phenomenon in the cooling process of the 30-50mm thick Q460GJ steel plate is improved.

[0026] (4) the steel plate is slowly straightened after ACC fast cooling, the straightening force is ensured to be greater than or equal to 1200t, the inlet temperature of the steel plate into a hot straightening machine is 480-520 DEG C, the inlet reduction is 4.5-5.5mm, the outlet reduction is 0-1.0mm, the inlet guide roller speed is 0.3m / s, and the straightening speed is 0.4-0.5m / s; the steel plate is slowly straightened after ACC fast cooling in the present application, the straightening force is ensured to be greater than or equal to 1200t, the straightening purpose can be achieved without multiple straightening, the straightening inlet temperature is set to be 480-520 DEG C, and secondary deformation of the steel plate during slow cooling after straightening can be effectively avoided.

[0027] MULPIC water crown control process principle: when the water crown valve opening ratio Water Crown Bias operation side and the transmission side are both 80%, the cooling water ratio is 1.2-1.3 (lower header water quantity / upper header water quantity), and the main role is to split the water flow of the center area of the upper surface of the steel plate, reduce the water of the upper surface of the steel plate, improve the transverse temperature uniformity of the steel plate, and improve the transverse cooling plate shape.

[0028] The method re-designs the rolling, cooling and straightening process parameters of the Q460GJ steel by deeply studying the existing high-rise building steel plate shape control difficulties, realizes the production purpose of the steel plate flatness of 3-4mm / 2m under the premise of not changing the steel composition and not increasing the cold straightening equipment, greatly improves the material yield and contract realization rate of the steel plate, and has very high economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a finished steel plate photo of example 1 of the present application;

[0030] Figure 2 is a flatness measurement photo of the finished steel plate of example 1 of the present application. DETAILED DESCRIPTION

[0031] In order to better explain the technical scheme of the present application, the technical scheme of the present application will be further described below in combination with specific examples, and the following examples are only exemplary descriptions of the technical scheme of the present application and do not limit the present application in any form.

[0032] Table 1 below is a list of chemical composition (wt%) values of the steel plates of each embodiment and the comparative example of the present application;

[0033] Table 2 below is a list of rolling and cooling process parameter values of the steel plates of each embodiment and the comparative example of the present application;

[0034] Table 3 below is a list of ACC function parameters and hot straightening process parameters, flatness detection results of each embodiment and the comparative example of the present application.

[0035] The plate shape control method of the 460MPa wide high-rise building steel plate of the application comprises the following steps:

[0036] (1) Casting blank heating: the casting blank discharge temperature is 1160-1200℃, the heating rate is 8-9min / cm, and the cross-section temperature difference is controlled to be ≤25℃; the 200mm cross-section slab is in the furnace for ≥160min, and the 250mm cross-section slab is in the furnace for ≥200min;

[0037] (2) Rolling: two-stage rolling process is adopted, the first-stage rolling adopts large reduction strategy, the intermediate blank thickness is 2.5-3 times of the finished product thickness, the average reduction rate of each pass in the rolling process is ≥10%, and the ski coefficient value is set to be 0-10%; the second-stage opening rolling temperature is ≤900℃, the finish rolling temperature is controlled to be 815-835℃, the flattening pass reduction is 2.0-2.5mm, the last pass is empty pass, and the steel throwing speed is ≥6m / s, and the main purpose is to control the opening cooling temperature range to be 720-740℃;

[0038] (3) Pre-straightening: the inlet reduction of the straightening machine is 4.5-5mm, the outlet reduction is 0-1.0mm, the pre-straightening biting speed is 1.0-1.2m / s, and the pre-straightening force is ≥800 tons;

[0039] (4) ACC cooling process: the steel plate is cooled after pre-straightening and enters the MULPIC rapid cooling device to perform ACC rapid cooling, the opening cooling temperature is set to be 720-740℃, the roller speed is 1.0-1.2m / s, the cooling rate is 10-12℃ / s, the re-red temperature is 500-540℃, the water convexity valve opening degree is 80%, the head shielding length is 0.5-1.5m, the tail shielding length is 0.5-1.0m, the water ratio of the cooling water lower header flow rate / upper header flow rate is 1.2-1.3;

[0040] (5) Hot straightening: the steel plate is slowly straightened after ACC rapid cooling, the straightening force is ensured to be ≥1200t, the temperature of the steel plate entering the hot straightening machine is 480-520℃, the inlet reduction is 4.5-5.5mm, the outlet reduction is 0-1.0mm, the inlet guide roller speed is 0.3m / s, and the straightening speed is 0.4-0.5m / s.

[0041] The MUPLIC rapid cooling device in the application adopts a variable flow water pillow type cooling header with edge shielding and water convexity control, 24 cooling headers are arranged on the upper and lower parts, and are divided into four zones A, B, C and D, each zone is 6m long, the total length is 24m, and each zone has 6 headers on the upper and lower parts, and has the online quenching function.

[0042] Table 1: Steel plate chemical composition value list of each embodiment and comparative example of the application (wt, %)

[0043]

[0044] Table 2: Rolling and cooling process parameter value list of steel plates of each embodiment and comparative example of the present application

[0045]

[0046] Table 3: ACC function parameters and hot straightening process parameters, unevenness detection list of each embodiment and comparative example of the present application

[0047]

[0048] From Tables 1-3, it can be seen that, with the same content range of chemical composition design, since the embodiments of the present application separately increase the water convexity valve opening in the ACC cooling process, improve the head and tail shielding length, and change the cooling water ratio, etc., the produced steel plate has a flatness of 3-4 mm / 2 m. The five comparative examples do not use the controlled cooling method of the present application under the condition of using the same chemical composition range and the same rolling process as the present application, and the result is that the flatness of the steel plate does not meet the requirement of the flatness of the building steel plate within 6 mm / 2 m.

[0049] Figure 1 is a photograph of the finished steel plate produced by the embodiment 1 of the present application; Figure 2 is a photograph of the unevenness measurement of the finished steel plate produced by the embodiment 1 of the present application; it can be seen from the figure that the flatness of the steel plate produced by the method of the present application is very good, and after unevenness measurement, the flatness is 4 mm / 2 m. Figure 1 Figure 2 Figure 1 is a photograph of the finished steel plate produced by the embodiment 1 of the present application; Figure 2 is a photograph of the unevenness measurement of the finished steel plate produced by the embodiment 1 of the present application; it can be seen from the figure that the flatness of the steel plate produced by the method of the present application is very good, and after unevenness measurement, the flatness is 4 mm / 2 m.

[0050] The main process flow of the method of the present application includes heating, rolling, ACC rapid cooling, and hot straightening. In the rolling and cooling stage, the flatness pass reduction, pre-straightening reduction, fast cooling water convexity valve opening ratio control, fast cooling lower flow deviation, and head and tail shielding are set according to the specifications of the product to improve the cooling uniformity in the length and width directions, reduce internal residual stress, and improve the cooling plate shape. Based on the automatic fast cooling condition, the process is simple and feasible, has high precision, is easy to produce in large quantities, and reduces the cost of heat delivery rescue.

[0051] The above embodiments are merely specific examples of the present application for explaining the present application, and do not limit the present application in any form. Any non-substantial changes made by anyone based on the above content and form without deviating from the protection scope of the claims of the present application should be considered to fall within the protection scope of the claims of the present application.​

Claims

1. A method for controlling the shape of a 460 MPa grade wide high-rise building steel plate, characterized by It comprises the following steps: (1) Casting blank heating: the casting blank discharge temperature is 1160-1200 DEG C, the heating rate is 8-9 min / cm, the cross-section temperature difference is controlled to be ≤25 DEG C; the 200 mm cross-section slab is in the furnace for ≥160 min, and the 250 mm cross-section slab is in the furnace for ≥200 min; (2) Rolling: two-stage rolling process is adopted, the first-stage rolling adopts large reduction strategy, the intermediate blank thickness is 2.5-3 times of the finished product thickness, the average reduction per pass in the rolling process is ≥10%, the ski coefficient value is set to be 0-10%; the second-stage rolling temperature is ≤900 DEG C, the finish rolling temperature is controlled to be 815-835 DEG C, the flattening pass reduction is 2.0-2.5 mm, the last pass is empty pass, and the steel plate is thrown at a speed of ≥6 m / s, so that the open cooling temperature range of the steel plate is controlled to be 720-740 DEG C; (3) Pre-straightening: the inlet reduction of the straightening machine is 4.5-5 mm, the outlet reduction is 0-1.0 mm, the pre-straightening biting speed is 1.0-1.2 m / s, and the pre-straightening force is ≥800 tons; (4) ACC cooling process: the steel plate is subjected to ACC rapid cooling in the MULPIC rapid cooling device after pre-straightening, the open cooling temperature is set to be 720-740 DEG C, the roller speed is 1.0-1.2 m / s, the cooling rate is 10-12 DEG C / s, the re-red temperature is 500-540 DEG C, the water convexity valve opening is 80%, the head shielding length is 0.5-1.5 m, the tail shielding length is 0.5-1.0 m, the water ratio of the cooling water lower header flow rate to the upper header flow rate is 1.2-1.3; (5) Hot straightening: the steel plate is subjected to slow straightening after ACC rapid cooling, the straightening force is ≥1200 t, the temperature of the steel plate entering the hot straightening machine is 480-520 DEG C, the inlet reduction is 4.5-5.5 mm, the outlet reduction is 0-1.0 mm, the inlet guide roller speed is 0.3 m / s, and the straightening speed is 0.4-0.5 m / s.

2. The method according to claim 1, wherein the method is characterized by: The finished product steel plate of the wide-width high-rise building steel plate has a width of 2000-4100 mm and a thickness of 30-50 mm.

3. The method according to claim 1, wherein the method is characterized by: The MUPLIC rapid cooling device adopts a variable flow water pillow type cooling header with edge shielding and water convexity control, 24 cooling headers are arranged on the upper and lower parts and are divided into four zones A, B, C and D, each zone is 6 m long, the total length is 24 m, and each zone has 6 headers on the upper and lower parts, and has the online quenching function.

4. The method according to claim 1, wherein the steel sheet is a 460 MPa grade high-rise building steel sheet having a width of 900 mm or more. The steel plate is composed of the following elements with the mass percentage: C: 0.14-0.16%, Si: 0.25-0.35%, Mn: 1.35-1.45%, P ≤0.010%, S ≤0.005%, Nb: 0.048-0.058%, Ti: 0.010-0.020%, V: 0.038-0.046%, Als: 0.015-0.050%, and the rest is Fe and inevitable impurities, in addition, the above element content needs to meet CEV: 0.38-0.42%.

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