A method for producing a large-sized h-shaped steel using a medium-sized profiled blank

Abstract

The application discloses a method for producing large-size H-shaped steel by using medium-size profiled billets, and belongs to the field of steel production, and the production process comprises profiled billet BD rolling, multi-pass continuous rolling and cooling, wherein: (1) the profiled billet BD rolling adopts waist-expanding rolling; (2) the multi-pass continuous rolling adopts X-H rolling method; and (3) the cooling adopts sectional cooling; the first third stage of the total cooling time adopts natural cooling, and the cooling speed is 12-14 DEG C / min; the last two third stages of the total cooling time adopt strong air cooling, and the cooling speed is 25-30 DEG C / min. Compared with the prior art, the process can be used together with medium-size general profiled billets, reduces the difficulty and cost of early-stage operation, and can realize high-size-precision control.

Description

TECHNICAL FIELD

[0001] The application is a divisional application of "A production process of large-specification narrow-flange H-shaped steel" (application number: 2020116069318). It relates to a steel production technology, in particular, a production process of large narrow-flange H-shaped steel based on a production steel simulation extension balancing method. BACKGROUND

[0002] Hot-rolled H-shaped steel is an economic section high-efficiency profile with more optimized cross-sectional area distribution and more reasonable strength-to-weight ratio. Compared with traditional I-shaped steel, it has the characteristics of good mechanical properties and convenient connection. Compared with welded H-shaped steel, it has the advantages of accurate component size, no deformation and residual stress caused by welding, and reduced welding workload. Compared with concrete, it has the advantages of light weight and good anti-seismic performance. Since the various parts of H-shaped steel are arranged at right angles, H-shaped steel has the advantages of strong bending resistance in all directions, simple construction, cost saving, and light structure weight, and has been widely used.

[0003] HN700×300 and above series of H-shaped steel series approaches the equipment limit, with a width of 700-900 mm, which belongs to a large-specification narrow-flange H-shaped steel product. Due to the large cross-section and large width-to-height ratio of this large-specification narrow-flange H-shaped steel, there are the following technical difficulties in the production and rolling process: ① The opening machine is pressed down for rolling, and the web is limited to expand in the width direction by the side wall of the pass. In order to achieve a width of 700-900 mm later, the BD rolling link needs to calculate the special profiled billet according to the final product specification in reverse, for example, to produce HN700×300×13×24 mm (H×B×t×T, H height, B flange width, t web thickness, T flange 1 / 4 thickness) large-specification narrow-flange H-shaped steel, through multiple calculations, a special 1024×420×110×105 mm profiled billet needs to be prepared, which cannot use the general 750×370×100×105 mm profiled billet, increasing the operation link and production difficulty; ② The web occupies a large proportion of the area, and its extension has a significant pulling and shrinking effect on the flange, which easily causes size fluctuations; ③ During the cooling of the rolled piece, the web is not uniformly cooled, causing wave bending and other quality problems; ④ The large size cannot be reduced at the straightening inlet temperature; the above problems seriously restrict the development of large-specification series. SUMMARY

[0004] The technical task of the present application is to overcome the shortcomings of the prior art, and to provide a method for producing large-specification H-shaped steel using medium-specification profiled billets. The process is based on a production steel simulation extension balancing method, which can reasonably allocate the reduction amount of the web and the flange with the general medium-specification profiled billet, so as to stabilize the production of large narrow-flange H-shaped steel, control the high size precision, and achieve the purpose of increasing production and efficiency.

[0005] The technical scheme for solving the technical problems of the present application is: a method for producing large-size H-shaped steel using medium-size profiled billets, characterized in that: the blank size is 750*370*100*105mm profiled billet; the production process comprises profiled billet BD rolling, multi-pass continuous rolling, and cooling, wherein:

[0006] (1) Profiled billet BD rolling: waist expansion rolling is adopted to make the web thin and wide and control the increase of the flange width; the width of the intermediate incoming material obtained after rolling is 1.06-1.08 times the width of the finished product, the flange height of the intermediate incoming material is 1.2-1.5 times the height of the finished product, and the thickness ratio of the flange to the web of the intermediate incoming material is 2.2-2.8;

[0007] (2) Multi-pass continuous rolling: U R EU F X-H rolling method of a reversible continuous rolling mill group, the arrangement form of the reversible continuous rolling mill group is 5 or 7 passes; the reduction coefficient of the flange is in a proportional relationship with the reduction coefficient of the web: the first two passes are 1.04-1.05, the final pass is 1.02-1.03, and the remaining amount is arranged in the intermediate passes; the rollers of the U R X-shaped rack are double-round; heat preservation treatment is required during rolling;

[0008] (3) Cooling: substep cooling is adopted; the first third of the total cooling time adopts natural cooling, and the cooling speed is 12-14℃ / min; the last two thirds of the total cooling time adopts strong wind cooling, and the cooling speed is 25-30℃ / min.

[0009] The above-mentioned double round is that the two straight lines of the roller are connected by arcs with R200 and R36.

[0010] The above-mentioned substep cooling method is that the rolled piece is rotated by 90° to form an I shape at the entrance of the cooling bed, then enters the uniform-speed stepping cooling bed for vertical natural cooling, and when it reaches 1 / 3 of the cooling bed, strong wind cooling is performed.

[0011] The above-mentioned 5-pass web reduction amount data: the deformation amount of 1-2 passes is 10-15%, the deformation amount of 3-4 passes is 10-15%, and the deformation amount of 5 passes is 2-3%.

[0012] The above-mentioned 7-pass rolling, the web deformation amount of the first 4 passes is 6-10%, the deformation amount of 5-6 passes is 6-7%, and the deformation amount of 7 passes is 2-3%.

[0013] Compared with the prior art, the present application has the following outstanding beneficial effects:

[0014] 1. It can use medium-size general profiled billets, reduces the difficulty and cost of early-stage operation, and can realize high-size precision control;

[0015] 2. The product has a high surface quality, overcoming quality problems such as wave bending caused by uneven cooling in the original product;

[0016] 3. It makes full and effective use of existing process equipment and production technology, resulting in significant economic benefits and having great potential for widespread application. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the waist-expanding rolling process of the present invention.

[0018] Figure 2 This is a schematic diagram of the existing technology of roll forming.

[0019] Figure 3 This is a schematic diagram of the reversible continuous rolling mill structure of the present invention.

[0020] Figure 4 This is a schematic diagram of the layout of the reversible continuous rolling mill unit with 5 passes according to the present invention.

[0021] Figure 5 This is a schematic diagram comparing the roll radius of existing technology and the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] This invention provides a method for manufacturing stable, large-diameter, narrow-flange H-beams. Using this method, HN700×300, HN800×300, and HN900×300 series specifications can be produced with high dimensional accuracy, meeting the requirements of stable product performance and high dimensional accuracy.

[0024] The production process of this invention is as follows: irregular billet → BD (brush mill) rolling → multi-pass continuous rolling → cooling.

[0025] 1. BD rolling of irregularly shaped billets

[0026] The rolling of irregularly shaped billets (BD) employs a waist-expanding rolling process. This waist-expanding rolling process, as... Figure 1 As shown, when the web of the shaped billet is pressed down, the web can be freely expanded, and the height (H) of the web of the intermediate material 2 is larger than that of the billet 1. Therefore, the billet can be used with specifications below 700mm. A shaped billet of 750×370×100×105mm (H×B×t×T, H height, B flange width, t web thickness, T flange 1 / 4 thickness) is used.

[0027] Existing traditional technologies involve roll forming, such as... Figure 2 As shown, the web of the shaped billet is pressed down, and the lateral width of the web is restricted by the sidewall of the perforated die. The height of the web of the intermediate feed 2' is smaller than that of the billet 1. A special-sized shaped billet of 1024×420×110×105mm is used; existing general-purpose shaped billets cannot be used.

[0028] In the BD rolling process, the pass system is controlled, the web reduction and the flange applied reduction are adjusted, the web is thinned and widened by large reduction, and the flange width increase is controlled.

[0029] So as to realize that the intermediate material width after BD rolling is 1.06-1.08 times of the finished product width, the intermediate material flange height is 1.2-1.5 times of the finished product height, and the thickness ratio of the intermediate material flange to the web is 2.2-2.8.

[0030] The above proportional relationship can ensure the balance of the web and flange extension during subsequent X-H reversible continuous rolling, overcome the defect of irregular flange shape caused by expanding waist rolling, and play a role in the regulation of the flange shape in the later stage.

[0031] 2. Multi-pass continuous rolling

[0032] The application adopts X-H rolling method to realize the balance of the web and flange extension rate.

[0033] Specifically, a U R EU F reversible continuous rolling mill unit, the U R EU F reversible continuous rolling mill unit Ur rolling mill, E rolling mill and U F rolling mill as Figure 3 indicated.

[0034] The multiple passes are specifically 5 or 7 passes.

[0035] As Figure 4 indicated, the U R EU F reversible continuous rolling mill unit is arranged in 5 passes, each pass participates in rough rolling and ensures the surface quality of the finished product in the finishing pass. The web reduction data of the 5 passes: the deformation amount of 1-2 passes is 10-15%, the deformation amount of 3-4 passes is 10-15%, and the deformation amount of 5 passes is 2-3%.

[0036] U R EU F It can also be reversible 7-pass rolling, the web deformation amount of the first 4 passes is 6-10%, the deformation amount of 5-6 passes is 6-7%, and the deformation amount of 7 passes is 2-3%, and multi-pass small deformation rolling is adopted to ensure the finished product size precision.

[0037] Furthermore, large-size, narrow-flange H-beams have wide webs that occupy a large proportion of the total area. During subsequent XH reversible rolling, the deformation of the web plays a dominant role, and the extension of the web has a significant tensile-contraction effect on the flanges. Therefore, a specific reduction ratio must be allocated between the flanges and the web. Specifically, the reduction coefficient of the flanges should be proportional to the reduction coefficient of the web. For the first two passes, this ratio should be 1.04-1.05, and for the final pass, it should be 1.02-1.03. The remaining reduction should be allocated to intermediate passes. See the reduction parameter table in the example for details.

[0038] Wherein, the flange thickness T is taken as the thickness at the upper middle quarter of the flange. And the compression coefficient is the thickness of the previous pass divided by the thickness of the next pass.

[0039] Utilizing XH technology, the X-shaped frame U R Steel adhesion is more severe at the intersection of the roll radius and the straight section of the side wall, while the H-shaped frame U... F The wear at the rounded corners of the rolls is quite severe. The reduction at the rounded corners is relatively large, and the metal flow is also relatively large, which easily causes wear at the rounded corners.

[0040] This invention transforms the roll from a single rounded corner ( Figure 5 -a) Improved to double rounded corners ( Figure 5 -b) to avoid surface pitting at the R-corner.

[0041] The aforementioned double rounded corner refers to the two straight edges of the roll being connected sequentially by two arcs of different radii. For example, in the prior art, a single rounded corner roll connects the two straight edges of the roll with an arc of R36, while the double rounded corner roll of this invention connects the two straight edges with arcs of R200 and R36. By using different curvature transitions, the X-shaped frame U... R The problem of steel sticking at the intersection of the straight sections of the upper and lower walls. And in the H-shaped frame U... F When the curvatures are different, especially when the upper curvature is greater than the lower curvature, the metal flow is not at the midpoint of a single impact arc, and the wear of the fillet is improved.

[0042] In addition, heat preservation treatment is required during the rolling process, such as adding an insulation cover, to prevent the web from cooling down faster than the flange, causing bending.

[0043] 3. Cooling

[0044] Existing technologies mostly use natural cooling methods. Due to the large size of the components, the temperature at the straightening inlet cannot be lowered, so the cooling time has to be extended, otherwise it will affect the normal production rhythm.

[0045] Some technologies also employ forced air cooling or ultra-cooling techniques for temperature reduction. However, because the web area of ​​the H-beams targeted in this invention is too large, the temperature drop of the web is faster than that of the flanges. This forced cooling mode is prone to causing cooling bending problems.

[0046] In addition, due to air convection, the temperature difference between the upper and lower webs of the H-shaped steel is different, which is more likely to exacerbate deformation.

[0047] Therefore, the present technology adopts the technology of segmented cooling.

[0048] The total cooling time is 32-36 min.

[0049] The first third of the total cooling time is naturally cooled, and the cooling speed is 12-14℃ / min.

[0050] The last two-thirds of the total cooling time is cooled by strong wind, and the cooling speed is 25-30℃ / min.

[0051] Specifically, after the rolled piece is rotated 90° to form an I shape at the entrance of the cooling bed, it enters the uniform speed stepping cooling bed for vertical natural cooling. When the cooling bed is naturally cooled and reaches 1 / 3, it is cooled by strong wind.

[0052] The cooling bed adopts a deep foundation, and air inlets are provided at the entrance and exit thereof, and ventilators are provided above to satisfy good air convection cooling effect.

[0053] The last two-thirds of the cooling bed are provided with a strong cooling fan below, and the strong cooling fan cooling intensity improves the cooling rate, so that the temperature of the rolled piece out of the cooling bed is less than 80℃. After the rolled piece is cooled, it is turned over 90° again at the exit of the cooling bed to restore to an H shape. The above cooling means effectively solves the web cooling wave problem.

[0054] In order to better describe, the rolling process is described taking HN 700×300×13×24mm (H×B×t×T) as an example.

[0055] Practice has proved that: using 750×370×100×105mm special-shaped blank to carry out traditional reduction rolling, the increase of the flange B of the intermediate blank cannot be realized, the reasonable extension cannot be realized in the continuous rolling stage, and HN 700×300×13×24mm specification cannot be produced.

[0056] Comparative example

[0057] Using the prior art, the special-shaped blank is rolled by BD→multi-pass reversible continuous rolling→cooling.

[0058] 1. Special-shaped blank BD rolling

[0059] The comparative example adopts a specific blank 1024×420×110×105mm specification for reduction rolling. The size of the obtained intermediate blank is 850×322×47×107mm.

[0060] 2. Multi-pass reversible continuous rolling

[0061] X-H rolling method, U R EUF Reversing rolling mill train, 5 passes, web reduction data see example continuous rolling parameter table.

[0062] 3. Cooling

[0063] Natural cooling throughout, cooling speed at 12-14℃ / min.

[0064] Example group

[0065] The production process of each example group is: profiled blank→BD expanding waist rolling→multi-pass reversing rolling→combined cooling. The profiled blank size used in each example is 750×370×100×105mm.

[0066] 1. Profiled blank BD expanding waist rolling

[0067] The final obtained intermediate blank specifications are shown in the following table:

[0068]

[0069]

[0070] 2. Multi-pass reversing rolling

[0071] X-H rolling method, U R EU F Reversing rolling mill train, specific pass reduction arrangement see the following table.

[0072]

[0073] 3. Combined cooling

[0074]

[0075] The comparison results of the control example and each example are shown in the following table:

[0076]

[0077]

[0078] From the above results, it can be seen that using the process of the present application to manufacture HN 700×300×13×24 specification narrow edge H-shaped steel, its size can meet the finished product size requirement, the product surface quality is high, and the occurrence of wave bending is significantly reduced compared with the control example, in addition, the double circular arc at the R angle effectively reduces the generation of pits, and improves the shortcomings of the use of X-H technology. The control example using the prior art production method must use a separate blank to implement, and cannot share the blank with HN600×300, HN600×200, HN650×300 series.

[0079] It should be noted that specific embodiments of the application have been described herein for purposes of illustration, but various modifications can be made without deviating from the spirit and scope of the application.

Claims

1. A method of producing a large-sized H-beam using a medium-sized beam blank, characterized by: The blank specification is 750mm in height, 370mm in flange width, 100mm in web thickness and 105mm in flange 1 / 4 thickness; the production process comprises profiled blank BD rolling, multi-pass continuous rolling and cooling, wherein: (1) Profiled blank BD rolling: the flange width is controlled to increase by adopting expanding waist rolling to make the web thin and wide; the width of the obtained intermediate material is 1.06-1.08 times of the product width, the flange height of the intermediate material is 1.2-1.5 times of the product height, and the thickness ratio of the flange to the web is 2.2-2.8; (2) Multi-pass continuous rolling: X-H rolling method of UREUF reversible continuous rolling mill is adopted, the reversible continuous rolling mill is arranged in 5 or 7 passes; the flange reduction coefficient and the web reduction coefficient have a proportional relationship: the first two passes are 1.04-1.05, the final pass is 1.02-1.03, and the remaining amount is arranged in the intermediate passes; the roll of the X-shaped rack UR is double-round; heat preservation treatment is required in the rolling process; (3) Cooling: the rolling piece is rotated by 90° to present I type after entering the cooling bed entrance, then is subjected to vertical natural cooling in the uniform speed stepping type cooling bed, and is subjected to strong wind cooling when reaching 1 / 3 of the cooling bed.

2. The method of producing a large-sized H-shaped steel using a middle-sized profiled blank according to claim 1, characterized in that: The double round is that the two straight lines of the roll are connected by R200 and R36 arcs.

3. The method of producing a large-sized H-shaped steel using a middle-sized profiled blank according to claim 1, characterized in that: The step cooling method is that the rolling piece is rotated by 90° to present I type after entering the cooling bed entrance, then is subjected to vertical natural cooling in the uniform speed stepping type cooling bed, and is subjected to strong wind cooling when reaching 1 / 3 of the cooling bed.

4. The method of producing a large-sized H-shaped steel using a middle-sized profiled blank according to any one of claims 1 to 3, characterized in that: The web reduction data of the 5-pass rolling are that the deformation amount of the first two passes is 10-15%, the deformation amount of the third to fourth passes is 10-15%, and the deformation amount of the fifth pass is 2-3%.

5. The method of producing a large-sized H-shaped steel using a middle-sized profiled blank according to any one of claims 1 to 3, characterized in that: The 7-pass rolling is that the web deformation amount of the first four passes is 6-10%, the deformation amount of the fifth to sixth passes is 6-7%, and the deformation amount of the seventh pass is 2-3%.

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