Medium-large thin-gauge hot-rolled h-shaped steel and production method thereof

Abstract

The application provides a medium-large thin-gauge hot-rolled H-shaped steel and a production method thereof, wherein the heating temperature of the special-shaped blank is 1260-1310 DEG C, the heating time is 160-250 min; the rolling temperature of the breakdown section is 1240-1290 DEG C, the rolling temperature of the universal section is 1200-1250 DEG C, the total reduction rate of the first three passes before the universal pass rolling is controlled to be 40-60%, the reduction rate difference between the flange and the web is gradually reduced with the increase of the pass number in the intermediate pass, and the total reduction rate in this stage is controlled to be 20-40%; the elongation rate of the flange and the web is kept consistent in the last five passes, and the total reduction rate is controlled to be 15-20%; and 3) the H-shaped steel is hot straightened before the cooling bed. Compared with the prior art, the application solves the problem that the tensile stress and the compressive stress are sufficient to cause the web or the flange to produce a wave shape through the above method, and successfully produces the medium-large thin-gauge hot-rolled H-shaped steel.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hot-rolled steel product production, more specifically, it is a production method of medium and large thin-gauge hot-rolled H-shaped steel. BACKGROUND

[0002] H-shaped steel is composed of a web and two flanges. When producing hot-rolled H-shaped steel from a contoured billet, there is usually a certain gap between the elongation rates of the flanges and the web, that is, the elongation rate of the flange of some specifications of hot-rolled H-shaped steel is greater than that of the web, and the elongation rate of the flange of some specifications of hot-rolled H-shaped steel is less than that of the web. This difference in elongation rate between the web and the flange usually results in tensile stress or compressive stress between the web and the flange, especially for thin-gauge hot-rolled H-shaped steel, which is sufficient to cause the web or flange to produce a wave shape. Due to the problem of web or flange wave defects, the research and development of thin-gauge hot-rolled H-shaped steel products has been stagnant. Currently, the minimum thickness of the flange of hot-rolled H-shaped steel with an H value less than 400 mm is 6 mm to 9 mm, and the minimum thickness of the web is 8 mm to 13 mm. For medium and large specifications of hot-rolled H-shaped steel with an H value greater than 400 mm, the thickness of the web and the flange is basically more than 10 mm, especially for large hot-rolled H-shaped steel with an H value greater than 900 mm, the minimum thickness of the flange and the web is 23 mm and 15 mm, respectively. The H value refers to the sum of the web height value and the thickness value of the two flanges of the H-shaped steel. In addition, as the thickness of the hot-rolled H-shaped steel becomes thinner and the H value increases, the rolling pressure will significantly increase, causing the rolling equipment to be overloaded or even unable to produce. For some medium and large thin-gauge H-shaped steel that exceeds the standard thickness range, it is mainly made by welding.

[0003] The patent document with publication number CN112246880A, published on January 22, 2021, discloses a twenty-roll mill plate shape optimization control method based on feed-forward intermediate roll shifting compensation. By collecting data and real-time feed-forward, the intermediate roll shifting compensation amount and other parameters are automatically adjusted to improve the plate shape wave of the steel plate. This method effectively reduces the operation difficulty and labor intensity of the operator, improves the quality of the steel strip product, and ensures the stability of the production of new steel grades. However, the production equipment and method mentioned in this invention are not suitable for the production of thin-gauge hot-rolled H-shaped steel, because the number of horizontal rollers of the hot-rolled H-shaped steel universal mill is limited and roll shifting cannot be achieved.

[0004] The patent document with publication number CN112157139A, published on January 1, 2021, discloses a method for automatically adjusting the plate shape of a skin pass mill based on the parameters of a plate shape instrument. By adjusting the bending amount of the work roll and the support roll and combining CVC roll shifting, the plate shape wave of the strip steel is controlled. However, the number of horizontal rollers of the hot-rolled H-shaped steel universal mill is limited and roll bending and shifting cannot be achieved, so the production equipment and method mentioned in this invention are not suitable for the production of thin-gauge hot-rolled H-shaped steel.

[0005] Patent document CN111036674A published on April 21, 2020 discloses a kind of high-strength ultra-thin H-shaped steel and preparation method.The invention patent proposes using specific pass design technology, at roughing stage, it is preformed to rectangular blank with large reduction, small spread, and the intermediate blank that flange and web are more coordinated is rolled to rectangular blank in roughing section as far as possible, so that the extension difference of flange and web is reduced in the process of finish rolling, thereby improving or eliminating the H-shaped steel appearance wave brought by the extension difference of flange and web.The method is suitable for rectangular blank, and rectangular blank can only be used for the production of some small size hot-rolled H-shaped steel at present, which is not suitable for the production of medium and large size thin specification hot-rolled H-shaped steel using special-shaped blank, because special-shaped blank is usually limited in size to consider the production feasibility, it is difficult to achieve one-to-one correspondence between blank type and finished product specification, and only the thickness of web and H value of special-shaped blank are processed at roughing section, the flange thickness of special-shaped blank cannot be processed, resulting in that the difference between the elongation rates of web and flange during universal rolling is difficult to eliminate.

[0006] Patent document CN103831295A published on June 4, 2014 discloses a rolling equipment and production method of ribbed H-shaped steel.By discontinuously grooving at the round corner of horizontal roll of universal mill set, the carrying capacity of H-shaped steel is improved, and the gripping force of H-shaped steel and concrete is also improved.The method has no actual effect on the web or flange wave of medium and large size thin specification hot-rolled H-shaped steel.Therefore, the method cannot be used to solve the wave of medium and large size thin specification hot-rolled H-shaped steel.

[0007] Patent document CN107035074A published on August 11, 2017 discloses a hot-rolled patterned H-shaped steel, its roller and production method.The pattern of the invention patent is mainly to increase the friction force, which is used for floor, step or combined with concrete, and the pattern shape has a certain effect on the flange or web wave of thin specification hot-rolled H-shaped steel, but the longitudinal strength provided by the pattern is very small.Therefore, the method cannot be used to improve the wave defect of medium and large size thin specification hot-rolled H-shaped steel.

[0008] Therefore, it is necessary to provide a production method of medium and large size thin specification hot-rolled H-shaped steel. SUMMARY

[0009] The purpose of the present application is to provide a medium and large size thin specification hot-rolled H-shaped steel and a production method thereof, which successfully produces a medium and large size thin specification hot-rolled H-shaped steel by controlling heating, rolling and cooling processes.

[0010] The specific technical scheme of the present application is as follows:

[0011] A production method of medium and large size thin specification hot-rolled H-shaped steel, comprising the following steps:

[0012] 1) The heating temperature of the profiled blank in the heating furnace is controlled at 1260-1310℃, and the heating time is controlled at 160-250min;

[0013] 2) The rolling temperature of the breakdown mill is controlled at 1240-1290℃, and the rolling temperature of the universal mill is controlled at 1200-1250℃;

[0014] 3) The H-shaped steel is hot straightened before the cooling bed.

[0015] In step 1), the heating temperature and time are controlled to ensure that the temperature of the rolled piece meets the requirements in the subsequent rolling process; the heating temperature and time are controlled to improve the rolling speed, and the purpose is to facilitate the subsequent universal rolling, mainly to ensure that the rolling temperature during the universal rolling can be controlled at 1200-1250℃, so as to reduce the deformation resistance, facilitate the rolling process, promote the uniformity of metal flow, reduce the uneven deformation between the web and the flange, and improve the shape and size precision of the H-shaped steel.

[0016] In step 2), the rolling temperature of the breakdown mill is controlled at 1240-1290℃, and the rolling temperature of the universal mill is controlled at 1200-1250℃, so as to reduce the tensile and compressive stress caused by the incoordination of the web and flange deformation; at the same time, the metal deformation resistance is smaller when rolling in this temperature range, which is beneficial to reduce the rolling load.

[0017] In step 2), the reduction rates of the flange and the web in the universal pass rolling process are reasonably distributed, and the deformation with a larger difference in reduction rate is arranged in the first 3 passes as far as possible, that is, the total reduction rate of the flange in the first 3 passes is controlled to be 40%-60%; the reduction rates of the flange and the web are gradually reduced according to the principle that the difference between the reduction rates of the flange and the web gradually decreases with the increase of the pass number in the middle pass, and the difference between the reduction rates of the flange and the web gradually decreases from 5% to 2% according to the linearity with the increase of the pass number, that is, the difference between the reduction rates of the flange and the web in the first pass of the middle pass rolling (which is the fourth pass of the universal pass rolling) is 5%, and the difference between the reduction rates of the flange and the web in the last pass of the middle pass rolling is 2%; the difference between the reduction rates of the flange and the web in the middle pass rolling is linearly reduced according to y=ax+b, wherein y is the difference between the reduction rates of the flange and the web, and the unit is %, and x is the number of the x pass in the middle pass rolling; generally, the middle pass rolling is 5-15 passes; taking the middle pass rolling of 10 passes as an example, the calculation is as follows: when the first pass of the middle pass rolling is rolled, x=1, y is the difference between the reduction rates of the flange and the web, and the value is 5%; when the tenth pass is rolled, x=10, and y is 2% here; the values of a and b are calculated according to the above data; the difference y between the reduction rates of the flange and the web in the second to ninth passes of the middle pass rolling can be determined according to the value of x and the calculated values of a and b. And the total reduction rate in the middle pass rolling stage is controlled to be 20%-40%; the elongation rates of the flange and the web in the last 5 passes are kept consistent, and the total reduction rate of the flange and the web is controlled to be 15%-20%. This method mainly ensures that the rolled piece is deformed under the condition of higher temperature, that is, the larger difference between the elongation rates of the web and the flange is completed in the first 3 passes, and the recovery and recrystallization processes are promoted under the condition of high temperature to eliminate the internal stress of the rolled piece. In the passes with relatively low temperature, that is, the last 5 passes, the elongation rates of the flange and the web are basically equal, and the deformation coordination of the flange and the web is better.

[0018] In step 2), according to the elongation relationship between the flange and the web of the rolled piece in the universal mill rolling, the vertical roll and the horizontal roll with a suitable diameter are selected. That is, for the rolled piece with the web elongation rate greater than the flange elongation rate, the vertical roll with a diameter of 800mm-900mm and the horizontal roll with a diameter of 1400mm-1600mm are adopted; for the rolled piece with the web elongation rate less than the flange elongation rate, the vertical roll with a diameter of 1000mm-1100mm and the horizontal roll with a diameter of 1000mm-1300mm are adopted. This method can effectively change the elongation and spread of the flange metal of the rolled piece, and further reduce the difference between the elongation rates of the flange and the web.

[0019] In step 3), before the cooling bed, the H-shaped steel is hot straightened by using a hot straightening machine, and the straightening temperature is controlled at 850-950 DEG C, so as to reduce the tensile and compressive stress between the flange and the web of the H-shaped steel by using the advantages of good plasticity and small deformation resistance of the metal at high temperature, and to improve or eliminate the wave defect of the H-shaped steel. Then the H-shaped steel is naturally cooled on the cooling bed, and is cold straightened at a temperature not higher than 100 DEG C after cooling according to the normal process.

[0020] The application provides a medium-large thin-gauge hot-rolled H-shaped steel produced by the method.

[0021] The H-shaped steel has an H value of 400-700 mm and a flange thickness less than 20 mm, or an H value of 900-1100 mm and a flange thickness less than 30 mm.

[0022] Compared with the prior art, the application solves the problem that the tensile and compressive stress is sufficient to cause the wave shape of the web or the flange by controlling the heating, rolling and cooling processes, and successfully produces the medium-large thin-gauge hot-rolled H-shaped steel. DETAILED DESCRIPTION

[0023] Example 1

[0024] A production method of a medium-large thin-gauge hot-rolled H-shaped steel, which produces a hot-rolled H-shaped steel with a height of 900 mm x a width of 300 mm x a web thickness of 9 mm x a flange thickness of 14 mm, and a weight of 1200 tons. When the product is rolled, the method of the application is used, which comprises the following steps:

[0025] 1) The heating temperature of the profiled billet in the heating furnace is controlled at 180 min, and the heating temperature is 1260-1290 DEG C.

[0026] 2) the breakdown rolling temperature is between 1250℃-1285℃, the universal rolling temperature is between 1210℃-1230℃. The total reduction of the first three passes of the universal rolling section is 48%, the difference between the flange elongation and the web elongation is 0.50%; the total reduction of the last 5 passes is 15%, the flange and web elongation is consistent; the intermediate pass rolling is 9 passes in total, the difference between the flange and web reduction gradually decreases from 5% to 2% according to a linear, that is, the difference between the flange and web reduction of the first pass of the intermediate pass rolling (which is the fourth pass of the universal pass rolling) is 5%, the difference between the flange and web reduction of the last pass, the ninth pass of the intermediate pass rolling is 2%; the difference between the flange and web reduction decreases according to y=ax+b, a is the coefficient of x, b is the constant term; the calculation is as follows: when the first pass of the intermediate pass rolling is rolled, x=1, y is the difference between the flange and web reduction, which is 5%; when the ninth pass is rolled, x=9, y is 2% here; according to the above data, a=-0.375 and b=5.375 are calculated; the difference between the flange and web reduction y of the second to ninth passes of the intermediate pass rolling can be determined according to the value of x and the calculated values of a and b, the difference between the flange and web reduction of the second pass is (-0.375*2)+5.375=4.625%, and the others are calculated in turn; when the method is used, the difference between the web elongation and the flange elongation of the intermediate 9 passes gradually decreases from 0.30% to 0.02%; the straight roll diameter used is 850mm, and the horizontal roll diameter is 1500mm.

[0027] 3) hot straightening is performed using a hot straightening machine before the upper cooling bed, the straightening temperature is 860℃-920℃, and the cold straightening temperature is 70℃. After inspection in the finished product warehouse, it is found that no flange wave or web wave defects are produced.

[0028] Example 2

[0029] A production method of a medium-large thin-gauge hot-rolled H-shaped steel, producing a 1000*300*14*16 gauge hot-rolled H-shaped steel, 1600 tons, when rolling the product of this specification, the method of the application is enabled, comprising the following steps:

[0030] 1) the special-shaped billet is heated in the heating furnace for 190-240min, and the heating temperature is 1270℃-1300℃.

[0031] 2) the breakdown rolling temperature is between 1243℃-1276℃, the universal rolling temperature is between 1210℃-1240℃. The total reduction of the first three passes before the universal section is 55%, the difference between the flange elongation and the web elongation is 0.40%; the total reduction of the last 5 passes is 19%, the flange elongation and the web elongation are consistent; the intermediate pass rolling is 7 passes in total, the difference between the flange reduction and the web reduction gradually decreases from 5% to 2% according to a linear, that is, the difference between the flange reduction and the web reduction of the first pass of the intermediate pass rolling (the fourth pass of the universal pass rolling) is 5%, the difference between the flange reduction and the web reduction of the last pass of the intermediate pass rolling (the seventh pass) is 2%; the difference between the flange reduction and the web reduction decreases according to y=ax+b linearly; the calculation is as follows: when the first pass of the intermediate pass rolling is rolled, x=1, y is the difference between the flange reduction and the web reduction, which is 5%; when the seventh pass is rolled, x=7, y is 2% here; according to the above data, a=-0.5 and b=5.5 are calculated; the difference between the flange reduction and the web reduction y of the second to sixth passes of the intermediate pass rolling can be determined according to the value of x and the calculated values of a and b, which is calculated as 4.5% for the second pass, and the others are calculated in turn. When the method is used, the difference between the flange elongation and the web elongation of the intermediate 7 passes gradually decreases from 0.23% to 0.01%. The diameter of the edger roller is 1050mm, and the diameter of the horizontal roller is 1150mm.

[0032] 3) hot straightening is performed before the upper cooling bed using a hot straightening machine, and the straightening temperature is 880℃-940℃. The cold straightening temperature is 90℃. After inspection in the finished product warehouse, it is found that no flange wave or web wave defects are generated.

[0033] Comparative Example 1

[0034] A production method of a medium-large thin hot-rolled H-shaped steel, producing a 900×300×10×14 size hot-rolled H-shaped steel, 300 tons, without using the method of the present application when rolling the product of this size, as follows:

[0035] 1) the special-shaped billet is heated in the heating furnace for 165-180min, and the heating temperature is 1220℃-1240℃.

[0036] 2) the breakdown rolling temperature is between 1160℃-1180℃, and the universal rolling temperature is between 1060℃-1080℃. The total reduction of the first three passes before the universal section is 30%; the total reduction of the last 5 passes is 25%, the flange elongation and the web elongation are consistent; the total reduction of the intermediate 7 passes is 45%, and the reduction of 4 passes is >5%. The diameter of the edger roller is 1050mm, and the diameter of the horizontal roller is 1150mm.

[0037] 3) No hot straightening machine was used before the upper cooling bed, and cold straightening was carried out after cooling to 90℃. After inspection in the finished product warehouse, it was found that the flange produced a wave-shaped defect.

Claims

1. A method for producing a medium-large thin-gauge hot-rolled H-beam, characterized by, The production method comprises the following steps: 1) the heating temperature of the profiled blank in the heating furnace is controlled at 1260-1310 DEG C, and the heating time is controlled at 160-250 min; 2) the rolling temperature of the breakdown mill is controlled at 1240-1290 DEG C, and the rolling temperature of the universal mill is controlled at 1200-1250 DEG C; 3) the H-shaped steel is hot straightened before the cooling bed; In step 2), the total reduction rate of the first three passes of the universal pass rolling is controlled at 40-60%; the reduction rate difference between the flange and the web is gradually reduced according to the principle that the pass number increases in the intermediate passes of the universal pass rolling, and the reduction rate difference between the flange and the web is gradually reduced from 5% to 2% according to the linearity with the increase of the pass number; the total reduction rate of the intermediate passes of the universal pass rolling is controlled at 20-40%; the elongation rate of the flange and the web is kept consistent in the last five passes of the universal pass rolling; the total reduction rate of the last five passes of the universal pass rolling is controlled at 15-20%; In step 3), the H-shaped steel is hot straightened before the cooling bed, and the straightening temperature is controlled at 850-950 DEG C.

2. The production method according to claim 1, characterized in that, characterized in that, In step 2), for the rolled piece with the web elongation rate greater than the flange elongation rate, a vertical roll with a diameter of 800-900 mm and a horizontal roll with a diameter of 1400-1600 mm are adopted.

3. The production method according to claim 1, characterized in that, characterized in that, In step 2), for the rolled piece with the web elongation rate less than the flange elongation rate, a vertical roll with a diameter of 1000-1100 mm and a horizontal roll with a diameter of 1000-1300 mm are adopted.

4. A medium-large thin-gauge hot-rolled H-beam steel produced by the production method according to any one of claims 1 to 3, characterized by, The H-shaped steel is a hot-rolled H-shaped steel with an H value of 400-700 mm and a flange thickness less than 20 mm, or an H value of 900-1100 mm and a flange thickness less than 30 mm.