CN115418559A

CN115418559A - High-strength and high-toughness hot-rolled H-shaped steel for buildings and preparation method thereof

Info

Publication number: CN115418559A
Application number: CN202210851313.2A
Authority: CN
Inventors: 赵培林; 王建军; 张佩; 路峰; 武文健; 马佐仓; 孔令坤; 李超; 刘洪银; 李栋
Original assignee: Shandong Iron and Steel Co Ltd
Current assignee: Shandong Iron and Steel Co Ltd
Priority date: 2022-07-20
Filing date: 2022-07-20
Publication date: 2022-12-02
Anticipated expiration: 2042-07-20
Also published as: WO2024016543A1; KR20240013141A; CN115418559B

Abstract

The invention belongs to the technical field of steel smelting technology and roll forming, and particularly relates to high-strength and high-toughness hot-rolled H-shaped steel for buildings and a preparation method thereof. The hot-rolled H-shaped steel comprises the following chemical components in percentage by weight: c:0.06 to 0.10; si: less than or equal to 0.25; mn:0.8 to 1.30; p is less than or equal to 0.015; s is less than or equal to 0.008; cu:0.15 to 0.25; cr:0.25 to 0.60; ni:0.10 to 0.19, V:0.01 to 0.03; al:0.01 to 0.03; RE the method comprises the following steps: 0.009-0.019; as + Sn + Zn + Pb + Ca + Mg is less than or equal to 0.035, and N is less than or equal to 0.008; t, O is less than or equal to 0.002, and the balance of Fe and inevitable impurities. The invention realizes the weight reduction of the building structural steel, has good comprehensive properties such as corrosion resistance, Z-direction property, low-temperature toughness resistance and the like, and completely meets the engineering requirements of the existing fabricated building structural steel.

Description

High-strength and high-toughness hot-rolled H-shaped steel for buildings and preparation method thereof

Technical Field

The invention belongs to the technical field of steel smelting technology and roll forming, and particularly relates to high-strength and high-toughness hot-rolled H-shaped steel for buildings and a preparation method thereof.

Background

With the gradual improvement of the requirements of the quality of domestic construction engineering, the state puts forward higher requirements on the development of the building structural steel. Particularly, in the aspect of assembly type buildings, the country continues to make a policy, and the force is increased to popularize. The prefabricated building has the technical advantages of good anti-seismic performance, light dead weight, high construction speed, high industrialization degree, high component prefabrication rate and the like, the steel structure meets the inherent assembly advantages in use, the construction period has great advantages compared with the traditional construction period, the components in the prefabricated steel structure are mostly steel, the prefabricated steel structure belongs to green and environment-friendly building materials, and compared with concrete, the prefabricated steel structure has incomparable green and environment-friendly advantages in the aspects of recycling and reutilization. The assembly type building of China occupies a lot of lower than that of developed countries abroad. Therefore, the national requirements promote the innovation of construction modes according to the requirements of applicability, economy, safety, greenness and beauty, vigorously develop the fabricated concrete building and the steel structure building, continuously improve the proportion of the fabricated building in the newly-built building, perfect the performances and technical measures of fire prevention, corrosion prevention and the like of the steel structure building, increase the application of hot-rolled H-shaped steel, weather-resistant steel and fire-resistant steel, and promote the comprehensive development of key technologies and related industries of the steel structure building.

The hot-rolled H-shaped steel is used as a main material for building structures, and different working conditions put higher requirements on mechanical properties, corrosion resistance, fire resistance, structural stability and the like of the hot-rolled H-shaped steel. The lamellar tearing resistance becomes an important index to ensure the safety and the structural stability of the building structural steel. The lamellar tearing resistance steel is also called Z-direction steel, and the lamellar tearing resistance is evaluated by mainly adopting the reduction of area Z of a tensile test in the thickness direction of the steel plate. For steel materials having a thickness of more than 15mm, it is generally necessary to examine the Z-direction laminar tearing resistance as long as the structural member generates tensile force or fatigue stress in the plate thickness direction. For common building structure section steel, only the Z-direction performance index of the flange needs to be carried out, and the Z-direction performance index is less provided for the web. Therefore, in order to meet the requirements of the steel for the assembly type building and the high-rise building, the Z performance of the flange and the web which are important marks with excellent comprehensive lamellar tearing resistance can meet the requirements at the same time, and the difficulty is correspondingly improved along with the increase of the thickness.

Patent application CN113564480A discloses a thick and heavy hot-rolled H-shaped steel with Z-direction performance and a production method thereof, wherein the hot-rolled H-shaped steel comprises the following chemical components: C. si, mn, nb, ti, N, B, als, and the balance of Fe and unavoidable impurities; the production method comprises the following steps: molten iron pretreatment → converter smelting → argon blowing refining → RH → shaped blank full protection pouring → stacking slow cooling → rolling → air cooling after rolling; according to the invention, through reasonable component proportion and process control, through the processes of cogging rolling, universal rolling and air cooling after rolling, and by utilizing the mode of phase change, precipitation and fine grain combined reinforcement, the precipitation quantity of second-direction particles is regulated and controlled, and the content of the rolled granular bainite is 10-20%, so that the heavy hot-rolled H-shaped steel with the flange thickness of below 80mm has excellent strength and toughness and Z-direction performance, and the Z-direction performance is 65-80%. The patent realizes strengthening through a bainite structure, but bainite is related to cooling rate, so that the stable and uniform bainite structure is obtained with great control difficulty, and meanwhile, bainite steel has no obvious yield phenomenon.

Patent CN103334051B discloses hot-rolled H-shaped steel with Z-direction performance for buildings and a production method thereof. According to the invention, the steel grade with excellent Z-direction performance and mechanical property is obtained by optimizing the smelting process and the rolling process, and strictly controlling the product quality control means and the product production process. The H-shaped steel comprises the following chemical components in percentage by weight: c:0.06% -0.18%, si: 0.10-0.25%, mn:0.90 to 1.60%, 0.10% or less of V, 0.060% or less of Nb, 0.030% or less of Ti, and the balance of iron and unavoidable impurities.

Patent No. CN102418037B provides a hot-rolled H-shaped steel with lamellar tearing resistance and a production method thereof. According to the method of manufacturing H-shaped steel of the present invention, instead of Al deoxidation, si is added to molten steel during tapping to adjust the Si in the molten steel to 0.10 to 0.15% by total weight of the molten steel for silicon-killed deoxidation, and then a predetermined amount of at least one of Ti and Zr is added to the molten steel, wherein the required Si content of the steel may be supplemented during refining. The hot-rolled H-shaped steel has lamellar tearing resistance and can meet the Z-direction performance requirement in a certain thickness direction.

In the prior art, simple microalloying is not beneficial to improving the surface quality of a casting blank, and the toughness is severely restricted; meanwhile, the excessive carbon content easily causes welding defects, causes large load of a rolling mill, is difficult to control the bending, head deviation and size of a rolled piece, has high requirements on equipment, and causes lower comprehensive performance of the H-shaped steel and lower qualified rate of finished product size.

In the prior production of section steel, the problem of uniform performance is always troubled by the control cooling. Especially for thick products, the difference between the thickness sizes of flanges and webs is large, the influence on the final performance is large by adopting a single cooling mode, and meanwhile, the uniformity of Z-direction performance is influenced, so that the difference is large, and the safety of the structure is influenced. How to solve the problem and consider the cost and the efficiency is one of the problems in the industry. Some enterprises adopt super block cooling equipment, but the investment is large, and meanwhile, the economic aspect is not suitable for a single product variety with requirements. Therefore, for structural and architectural steel products that require overall Z-direction performance, special cooling equipment needs to be designed to meet the performance requirements.

Disclosure of Invention

In order to meet the requirements of the steel for the fabricated building structure, the cooling system is specially designed according to the requirements. Provides the hot-rolled H-shaped steel with high strength and toughness and excellent lamellar tearing resistance with the yield strength reaching 420MPa and the preparation method thereof. The section steel product is suitable for the field of assembly type building structure engineering, and the web and the flange of the section steel product have high Z-direction performance and exceed the Z35 level. In order to realize excellent Z-direction performance of flanges and webs, a flange and web temperature uniformity control device is added in combination with the component design of steel in the rolling process, so that the high-impact toughness at the low temperature of-20 ℃ is realized, and the high-impact toughness hot-rolled H-shaped steel has the characteristics of excellent corrosion resistance, welding performance, low yield ratio and the like, and meets the application requirements of hot-rolled H-shaped steel materials in the steel building field of assembly type building structures and the like in common areas and cold areas.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides 420 MPa-grade hot-rolled H-shaped steel for buildings, which comprises the following chemical components in percentage by weight: c:0.06 to 0.10; si: less than or equal to 0.25; mn:0.8 to 1.30; p is less than or equal to 0.015; s is less than or equal to 0.008; cu:0.15 to 0.25; cr:0.25 to 0.60; ni:0.10 to 0.19, V:0.01 to 0.03; al:0.01 to 0.03; RE: 0.009-0.019; as + Sn + Zn + Pb + Ca + Mg is less than or equal to 0.035. The balance of Fe and inevitable impurities. Controlling the gas in the steel in the smelting process to be less than or equal to 0.008 percent by weight; t. O is less than or equal to 0.002.

In order to reduce the yield ratio, only a single microalloying design of vanadium-nitrogen alloy is adopted on the basis of low-carbon component design, the content is strictly controlled, the influence of precipitation strengthening on the yield strength is reduced, and finally the yield ratio of the H-shaped steel is less than or equal to 0.8. In order to improve the low temperature resistance and strictly control the quantity and the size of the inclusions, on the basis of adding RE elements to modify the inclusions, the content of other residual elements is preferably controlled to be less than or equal to 0.035 percent.

The H-shaped steel for the building with the excellent comprehensive lamellar tearing resistance (Z-direction performance) 420MPa level steel structure is added with various chemical elements to play a role as follows:

carbon: according to the requirement of 420MPa level of strength, the low-carbon component design can ensure that the building structural steel has certain low-temperature resistance, and meanwhile, a certain pearlite structure is generated to improve the yield ratio, so that the steel is suitable for the use requirement of the building structural steel. After the corrosion-resistant elements are added, the lower carbon content can avoid the generation of weishi body and other abnormal structures. For the special-shaped blank, the transverse and longitudinal web cracks are easy to control, so the carbon content is controlled to be 0.06-0.10% in the invention in consideration of the structure property and the smelting cost.

Silicon: proper amount of Si is beneficial to improving the strength; bainite and other structures are easily generated when the Si content is too high; to avoid large amounts of Fe produced during reheating ₂ SiO ₄ Thus affecting the surface quality, the upper limit of the Si content is set to 0.25% or less, preferably 0.25% or less, and more preferably 0.20% or less.

Manganese: the austenite stabilizing element can significantly increase the hardenability of the steel and improve the strength of the steel in a solid solution strengthening mode, but segregation is easily caused when the austenite stabilizing element is too high, and the difference between different positions is large. Since the thick structural section steel has a difference in structure between different portions, it is preferable to set the upper limit of the Mn content to 1.30% in order to secure strength and reduce hardenability while preventing occurrence of a large amount of abnormal structure. By combining various factors, the content of Mn in the H-shaped steel is controlled within the range of 0.8-1.30%; in order to obtain a strength of 420MPa grade, the interval of 1.0-1.20% is preferred according to the addition of VN alloy.

Phosphorus: although high phosphorus content tends to improve corrosion resistance, too high phosphorus content tends to deteriorate low temperature resistance at embrittlement grain boundaries, so that lower efficiency and better effect of phosphorus control increase low temperature toughness; p is controlled below 0.015 percent;

sulfur: the sulfur element is too high, so that more sulfides such as MnS and the like are easily generated, a large amount of strip-shaped MnS inclusions are generated at different parts of the section steel with a complex section, the low-temperature toughness is reduced, the corrosion resistance is not improved, the reduction of section area is influenced, namely the lamellar tearing resistance of the steel is influenced, and therefore, the S is strictly controlled to be less than or equal to 0.008%;

copper: the Cu can promote the steel to generate anodic passivation, thereby reducing the corrosion rate of the steel, and the Cu is one of common elements of the corrosion-resistant steel. The enrichment of the rust in the rust layer can greatly improve the protective performance of the rust layer; in order to achieve the effect of enriching Cu in the rust layer, cu is required to be more than 0.20%. However, too high Cu content is not favorable for the welding performance of structural steel for buildings, and is also easy to cause copper brittleness. In the process of producing the anti-layer tearing performance section steel by adopting the special-shaped continuous casting billet, the corner part of the leg part is easy to crack due to the enrichment of copper, the surface quality of the casting billet is seriously influenced, the plasticity of the steel is deteriorated, and the Cu content is controlled to be 0.15-0.25 percent on the basis of meeting the corrosion resistance requirement of the fabricated building structure section steel.

Nickel: the strength of the steel is improved through solid solution strengthening, the steel is also an effective element for improving low-temperature toughness, and meanwhile, the high-temperature plasticity of the steel in the continuous casting process can be improved, and the generation of surface defects of a casting blank is reduced. On one hand, ni plays a role in expanding an austenite region and improving hardenability, and on the other hand, ni can refine pearlite lamella to refine pearlite and play a role in fine grain strengthening. The steel controls the Ni content within the range of 0.10-0.19% in combination with the control proportion of the Cu content.

Chromium: the elements which contribute to the improvement of the strength of steel by improving the hardenability and the tempering stability and which contribute to the improvement of the corrosion resistance of steel. It can be used with Cu and Ni elements to obviously improve the corrosion resistance of steel. Under the condition of low C content, proper amount of Cr is added to improve the hardness and strength of the steel and the corrosion resistance of the steel. Excessive addition will reduce the toughness, weldability and flame cutting properties of the material. In the structure control, an excessive amount of Cr element affects the structure transformation of steel, and an abnormal structure such as bainite is generated. In the aspects of strength and corrosion resistance improvement, the content of the alloy is controlled to be Cr:0.25 to 0.60 percent.

Vanadium: is one of the most common and effective strengthening elements of microalloyed steel. The vanadium has the function of influencing the structure and the performance of steel by forming VN and V (CN), and is mainly precipitated in ferrite of an austenite crystal boundary to refine ferrite grains, so that the strength and the low-temperature toughness of the material are improved. Since the precipitation strengthening has a large influence on the yield strength and the strength is improved, the amount of V added is 0.01 to 0.03%.

Rare earth: rare earth purifies steel, and is modified and mixed, so that pitting corrosion and intergranular corrosion are reduced. The rare earth is dissolved in the steel in a solid solution manner to improve the polarization resistance and the self-corrosion potential of a steel matrix, so that the corrosion resistance of the steel matrix is improved, the tissue structure of a rust layer is changed, the rust layer with good adhesion and good compact corrosion resistance is formed, and the corrosion resistance of the high-strength weathering steel is improved. Considering that the RE rare earth element needs to be added in a proper amount for modifying inclusions such as MnS, the selection range is as follows: 0.009-0.019 percent, RE rare earth element is a compound added element, and the lanthanum and cerium series elements are mainly used in the application to play a role in spheroidizing inclusions in consideration of factors such as economy, cost performance and the like.

Aluminum: al is added as a strong deoxidizing element in the preparation process of low-temperature steel. In order to ensure that the oxygen content in the steel is as low as possible, the inclusion content is reduced, and the excessive aluminum after deoxidation can form AlN precipitates with nitrogen elements in the steel, thereby refining austenite grains during heating and hot rolling. Therefore, the content of aluminum as a deoxidizing element and a fine grain strengthening element is controlled within a range of 0.01 to 0.03%.

As, sn, zn, pb, ca, mg: the residual elements in the steel have a great influence on the low-temperature impact toughness and also on the surface quality. Therefore, as an element that cannot be completely removed from the steel, the content thereof should be minimized. The total amount of residual elements is controlled within the range of less than or equal to 0.035 percent by combining with production practice, equipment capability and cost control.

Nitrogen: the N content is too high, so that quality defects of a casting blank are easily induced; meanwhile, the VN alloying effect is ensured, so the nitrogen content is required to be less than 0.008 percent.

Oxygen: in order to avoid the formation of large-particle oxide inclusions and the deterioration of the toughness and plasticity of the steel, the total oxygen content T [ O ] is required to be less than or equal to 0.0020%.

The H-shaped steel product has excellent comprehensive mechanical properties, the yield strength is more than or equal to 420MPa, the tensile strength is more than or equal to 520MPa, and the elongation is more than or equal to 19 percent; longitudinal impact energy at minus 20 ℃ is more than or equal to 50J, and the material is suitable for building structures in low-temperature areas. The Z-direction performance of the web and the flange is excellent, and the reduction of area is more than or equal to 60 percent.

The preparation method of the hot-rolled H-shaped steel with excellent lamellar tearing resistance suitable for building structures in different areas mainly comprises the following steps: the method comprises the following steps of molten iron pretreatment, converter smelting, LF refining, RH refining, billet surface defect cleaning, casting of a special-shaped continuous casting billet, reheating of a billet walking-type heating furnace, high-pressure water descaling, temperature control rolling, cooling control, low-temperature straightening, sizing saw cutting, collecting and stacking.

Molten iron and scrap steel are smelted, refined and continuously cast in a converter and a refining furnace (LF and RH equipment) to obtain a special-shaped continuous casting billet, and the surface of the special-shaped continuous casting billet is subjected to defect detection and cleaning and then enters a rolling forming procedure. The billet steel firstly enters a stepping heating furnace to be reheated to obtain an austenite structure with a proper size, and is rolled into a material after rough rolling and finish rolling, and the rolling process is controlled to be rolled and cooled. It should be noted that the precise temperature control is performed in the last finish rolling pass, and the developed special cooling device (see the cooling device diagram in fig. 2) meets the requirement that the temperatures of the upper and lower legs of the H-shaped steel and the upper and lower sides of the flange are basically consistent, so that the consistency of the Z-direction performance of the flange and the web under the condition of uniform tissue is ensured, and the structural stability and the safety of the assembled building structure when the product is used are ensured.

The main process for controlling rolling and cooling in the rolling process comprises the following steps: the heating temperature is controlled to be 1250-1300 ℃, the temperature of the last pass of rough rolling is 1150-1050 ℃ according to different sizes, the accumulated deformation rate is 40-60%, and the rest is finished in the finish rolling stage. And (3) carrying out three-stand finish rolling after rough rolling, and accurately controlling the finish rolling temperature to be between 800 and 850 ℃ so that the austenite structure is completely converted into pearlite and ferrite, thereby realizing fine grain controlled rolling. Because the upper and lower sides of the flange and the web of the upper and lower legs of the H-shaped steel have the temperature difference of 30-50 ℃, cooling control is carried out after the final pass of finish rolling is finished and is discharged from a rolling mill, the lower legs and the web are accurately controlled and cooled by adopting nozzle water spraying by using designed cooling equipment, and corresponding water flow control is carried out according to the detected temperature difference. After cooling, the temperature difference of the same parts of the flanges of the upper leg and the lower leg is reduced to be within 10 ℃, and the temperature difference of the upper surface and the lower surface of the web plate is reduced to be within 5 ℃, so that the Z-direction performance of the flanges of the upper leg and the lower leg of the H-shaped steel and the overall Z-direction performance of the web plate are basically consistent. After finish rolling, the rolled piece passes through the conveying roller way, and the cooling rate is controlled by adopting the heat-insulating cover according to the environmental temperature, so that the influence on the final performance caused by the large fluctuation of the environmental temperature in different seasons is avoided. And naturally cooling the product after the product is taken out of the finishing mill on a cooling bed, and straightening the product after the temperature of the product is reduced to be below 100 ℃. The thickness range of the flanges of the specification of the rolled product is 15-50mm. And sampling at the flange part and the middle part of the web plate of the H-shaped steel to detect the mechanical property. The Z-direction stretching reduction rate deviation of the flange and the web of the H-shaped steel produced by the process is controlled to be less than 5 percent.

Preferably, the 420 MPa-level hot-rolled H-shaped steel with excellent lamellar tearing resistance for the fabricated building, the preparation method and the specific process control thereof provided by the invention specifically comprise the following aspects:

1 smelting step

1) Smelting in a converter

The converter is controlled according to basic operation, and the main procedures comprise strictly controlling the content of residual elements such as sulfur, arsenic and the like in molten iron of the blast furnace and carrying out the quality optimization treatment on the molten iron, wherein both arsenic and tin are less than 0.008%; the alkalinity of the converter final slag is in the range of 2.1-3.9, slag blocking and tapping are adopted, and aluminum, manganese and iron are adopted for deoxidation and alloying in the tapping process. In the tapping process, a deoxidizer, ferrosilicon, metal manganese, vanadium-nitrogen alloy, ferroniobium alloy, a nickel plate and the like are added in batches, and finally the components of the converter meet the requirements of internal control targets.

2) Refining LF + RH duplex control

And LF and RH are adopted in the refining process to control gas and impurities in a duplex manner. And (3) adjusting slag of the LF by adopting calcium carbide, silicon, calcium, barium and aluminum particles, and performing slag jacking to obtain white slag or yellow white slag before leaving the station. Oxygen is determined and controlled to be less than or equal to 20ppm after the initial sample is taken in the station; RE is added before the calcium wire is fed, bottom blowing nitrogen is carried out in the whole process according to the process requirement, the soft blowing time is not less than 20 minutes, the refining period is not less than 30 minutes, the temperature of the molten steel is controlled to be 1600-1620 ℃ at the end of LF refining, the temperature of the molten steel is increased to offset the temperature drop of the molten steel at the RH processing time, and the RH processing time is strictly forbidden to adopt the method of heating by adding aluminum to generate chemical heat.

The RH refining adopts the treatment mode, the circulation time is more than 15min, the pure degassing time is more than 5min, 200-250 m calcium-aluminum wires are fed into each furnace after the treatment is finished, the soft blowing time is not less than 10 min, and the RH smelting period is controlled within 40-50 min.

The whole-process protective casting means that a long nozzle is adopted from a large ladle to a middle ladle and argon sealing protection is carried out; the tundish is covered by a covering agent combined with the carbonized rice hulls; the tundish to the crystallizer adopts an immersion type water gap and adopts argon seal protection; the liquid level of the crystallizer adopts peritectic steel covering slag; preferably, the peritectic steel casting powder comprises, by weight, 25% to 35% of SiO, 35% to 45% of CaO, 1.90% to 3.00% of MgO, and 3.00% to Al ₂ O ₃ ≤4.00％。

3) Continuous casting

The continuous casting process adopts a full-protection pouring process, a ladle long nozzle is used, and the control of a sealing ring is increased; pouring molten steel in a tundish by adopting a stopper rod ladle; in order to improve the efficiency, the pulling speed of the special-shaped continuous casting billet is 1.0-1.2 m/min; the superheat degree is controlled below 20-30 ℃, so that the water gap can be prevented from being blocked; and (3) casting the smelted molten steel into a profiled blank with a near-net-shaped section in 3 size specifications, wherein the profiled blank is subjected to slow cooling treatment in a heat insulation pit or a sand pit or by using a heat insulation felt after casting and forming in order to avoid surface cracks due to more alloy amount.

2 Rolling Process

1) Heating of

The blank is austenitized and uniformly heated in a heating furnace, the temperature of the heating and soaking stages is controlled at 1250-1300 ℃, the heating time is 90-120 min, and then the blank is discharged from the furnace for rolling. The heating adopts high-temperature short-time heating, and austenite homogenization and refinement are controlled.

2) Controlled rolling and controlled cooling

The controlled rolling/controlled cooling process is adopted in a large production line. The rough rolling procedure realizes pass rolling mainly in shape, and the rolling pass is less than 9; and performing performance control rolling in the finish rolling process, wherein the rolling pass is less than 7. The finishing temperature is controlled between 800 ℃ and 850 ℃. The cooling track of the cooling bed keeps the temperature above 400 ℃, and products are intensively and slowly cooled in the cooling bed, so that the final performance is prevented from being influenced by too fast cooling speed. The temperature of the product is reduced to 200-300 ℃ and the product enters a straightening machine for straightening, so that the integrity of the primary oxide scale on the surface is ensured.

The invention provides a cooling device for improving comprehensive performance, which is characterized in that a specially designed cooling device is adopted to carry out comprehensive cooling on a web and a flange in the rolling process, and the cooling device is arranged behind a finishing mill, wherein the cooling device comprises a plurality of cooling liquid pipelines 1 distributed at intervals and a plurality of cold air pipelines 2 distributed at intervals, the cooling liquid pipelines 1 are used for cooling the flange and are arranged below a lower flange 6 of hot-rolled H-shaped steel, the cooling device comprises a first flange pipeline 4 parallel to the web and two groups of second flange pipelines which are perpendicular to and communicated with the first flange pipeline 4, and each group of second flange pipelines respectively corresponds to one flange; each group of second flange pipelines comprises two parallel lower flange pipelines 5, a plurality of nozzles 3 are arranged on the surfaces of the lower flange pipelines 5 opposite to the lower flanges 6 and used for cooling the flanges, and the lower flanges 6 of the H-shaped steel are arranged between the two parallel lower flange pipelines 5; the cold air pipeline 2 is used for cooling the web plate, is convex, is arranged between the lower flange 6 and the web plate 8, and is provided with a plurality of nozzles 3 which are parallel to the web plate 8 and close to the cold air pipeline and used for cooling the web plate 8. The shape of the cold air duct matches the shape formed by the lower flange and the web. The cooling rate can be controlled according to the web and flange thickness (see fig. 1). The cooling device is arranged behind the finishing mill, and is opened at the last rolling pass, and the flange and the web are separately arranged for cooling. In fig. 1, the coolant line numbered 1 is used for flange cooling; because the flange thickness is big, adopt cooling water or other cooling medium to cool down according to the cooling rate needs. The flow rate of the cooling liquid is adjusted through the nozzle 3 after the temperature difference measurement is carried out by the online temperature measuring device for the upper flange 7 and the lower flange 6. Because the thickness of the web plate is thinner than that of the flange, the requirement can be met by adopting cooling air. The cold air pipeline with the number 2 is used for cooling the web; the temperature difference between the upper part and the lower part of the web is small, so that the flow of cooling air of the nozzle 3 is properly adjusted according to the requirement to realize cooling. By the device, the temperature difference between the flange of the upper leg and the flange of the lower leg is within the range of 5-10 ℃, and the temperature difference between the web plates is within the range of 3-6 ℃. Thereby guaranteed the homogeneity of tissue, promoted the Z of the web and the edge of a wing of building structure shaped steel and moved to the performance. The equipment is matched with a vanadium microalloying design, so that the performance requirement of final hot rolling of the H-shaped steel can be met, and the Z-direction performance of a web and a flange can reach a higher level.

3) Finishing procedure

Finishing the surface and the size of the product after the product is off-line; in order to ensure the real and accurate performance of the material, sampling is carried out in the finishing process to analyze the performance of the product.

Compared with the prior art, the invention has the advantages that:

(1) The low-carbon alloying with trace VN and RE are simple and efficient compared with other alloying, and the occurrence rate of casting blank defects is reduced; (2) The molten steel is low in residual elements and impurity elements, so that the plasticity and low-temperature toughness of the steel are improved; (3) A certain amount of RE elements are added, so that inclusions in steel are fine, and the anti-stratification performance of flanges and webs is improved; (4) The Al deoxidation process is realized by adopting the profiled blank single-side casting control technology, the purity of molten steel is improved, and the problem of blockage in the long nozzle casting process is avoided. (5) The uniform cooling process of the web flange is realized through the designed special water spraying device, the integral structure uniformity of the web flange is improved, the lamellar tearing resistance is synchronously controlled and improved, and the comprehensive toughness of the H-shaped steel is integrally improved. (6) Through the process, the yield strength of the prepared H-shaped steel reaches the level of more than 420MPa, the weight reduction of the building structural steel is realized, and meanwhile, the composite steel has good corrosion resistance, Z-direction performance, low-temperature toughness resistance and other comprehensive performances, and completely meets the engineering requirements of the existing assembly type building structural steel.

Drawings

FIG. 1 (a) is a plan view of a cooling arrangement for H-beam steel production according to the present invention;

FIG. 1 (b) is a perspective view of a cooling arrangement for H-beam production according to the present invention;

FIG. 2 (a) is a microstructure diagram of an upper leg of an H-shaped steel obtained in example 1 of the present invention;

FIG. 2 (b) is a microstructure of a lower leg of the H-shaped steel obtained in example 1 of the present invention;

FIG. 2 (c) is a view showing the flange microstructure of the H-section steel obtained in example 1 of the present invention;

FIG. 3 (a) is a microstructure of an upper leg of an H-shaped steel obtained in example 6 of the present invention;

FIG. 3 (b) is a microstructure of a lower leg of an H-shaped steel obtained in example 6 of the present invention;

FIG. 3 (c) is a view showing the flange microstructure of the H-section steel obtained in example 6 of the present invention;

reference numerals:

1. the cooling liquid pipeline 2, the cold air pipeline 3, the nozzle 4, the first flange pipeline 5, the lower flange pipeline 6, the lower flange 7, the upper flange 8 and the web plate.

Detailed Description

The present invention will be further described with reference to the following specific examples.

The present invention is described in detail below:

table 1 is a list of chemical compositions of examples of the present invention and comparative examples;

table 2 is a table of the main process parameters of each example of the present invention and comparative example;

table 3 is a table of performance tests of each example of the present invention and comparative example.

The preparation method comprises the following steps:

1) Preferably, low-phosphorus, low-sulfur and low-residual element molten iron enters an LF + RH duplex for component and inclusion control after being smelted in a converter; controlling the temperature of the molten steel to be 1600-1620 ℃ at the LF refining finishing moment, increasing the temperature of the molten steel to offset the temperature drop of the molten steel at the RH processing moment, and strictly forbidding the RH processing moment to adopt a method of adding aluminum to generate chemical heat to increase the temperature; the RH refining adopts the treatment mode, the circulation time is more than 15min, the pure degassing time is more than 5min, after the treatment is finished, a calcium-aluminum wire of 200-250 m is fed into each furnace, the soft blowing time is not less than 10 min, and the RH smelting period is controlled to be 40-50 min.

Finally, continuously casting into a special-shaped blank, and dividing into three blank types according to different flange thicknesses. The residual elements of the molten iron are strictly controlled to be less than or equal to 0.035 of As + Sn + Zn + Pb + Ca + Mg; in the casting process, the casting superheat degree is controlled to be less than 20 ℃, any one value is selected as a constant throwing speed within the throwing speed of 1.0-1.18 m/min, and the straightening temperature is not lower than 850 ℃.

2) Rolling, wherein the blank is reheated in a heating furnace at 1250-1300 ℃, heated for 90-120 min, and then discharged for rolling. A controlled rolling/controlled cooling process is employed. The rolling pass of the BD rough rolling procedure is less than 9 passes; and (3) rolling passes in the finish rolling TM process are less than 7. The finish rolling temperature is controlled at 800-850 ℃. The cooling track of the cooling bed keeps the temperature above 400 ℃, and the product is intensively and slowly cooled in the cooling bed for more than 15 min. The temperature of the product is reduced to 200-300 ℃ and the product enters a straightening machine for straightening.

3) Finishing, namely finishing the surface and the size of the product after the product is off-line; and sampling samples in a finishing process to analyze the product performance.

Table 1 chemical composition (wt.%) of each example of the present invention and comparative example

The main process parameters of refining are shown in Table 2

TABLE 2 refining of the main Process parameters

The specific process parameters of the continuous casting process are shown in Table 3.

TABLE 3 Process parameters of the continuous casting Process

Table 3 is a table of the main process parameters of each example of the present invention and comparative example;

TABLE 4 Main Process parameters

Table 5 is a table listing the performance tests of the examples of the present invention and the comparative examples.

Table 5: mechanical property recording table for rolled material

Sampling a trial-made product, and carrying out performance inspection, wherein the sampling position of a sample for mechanical performance is 1/3 of the flange of the H-shaped steel from the edge to the center, and the sampling position of a web plate is in the middle, and the reference standard is BS EN ISO 377-1997 for sampling position and preparation of mechanical performance test samples; the yield strength, tensile strength and elongation are tested according to the standard ISO 6892-1-2009 Metal Material tensile test method at Room temperature; the method for the impact test is referred to ISO Standard 148-1 "Charpy pendulum impact test for metallic materials", the results of which are given in Table 5. Through comparison, the Z-direction performance of the flange and the web of the H-shaped steel produced by the preparation method is superior to that of products in the current patent products.

Conventional technical knowledge in the art can be used for the details which are not described in the present invention.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or substituted with equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered by the scope of the claims of the present invention.

Claims

1. The hot-rolled H-shaped steel for the high-strength and high-toughness building is characterized by comprising the following chemical components in percentage by weight: c:0.06 to 0.10 percent; si: less than or equal to 0.25 percent; mn:0.8 to 1.30 percent; p is less than or equal to 0.015 percent; s is less than or equal to 0.008 percent; cu:0.15 to 0.25 percent; cr:0.25 to 0.60 percent; ni:0.10 to 0.19%, V:0.01 to 0.03 percent; al:0.01 to 0.03 percent; RE: 0.009-0.019%; as + Sn + Zn + Pb + Ca + Mg is less than or equal to 0.035%, and N is less than or equal to 0.008%; t, O is less than or equal to 0.002%, and the balance of Fe and inevitable impurities.

2. The hot-rolled H-shaped steel according to claim 1, wherein the yield ratio of the hot-rolled H-shaped steel is less than or equal to 0.8, the yield strength is greater than or equal to 420MPa, the tensile strength is greater than or equal to 520MPa, and the elongation is greater than or equal to 19%; the longitudinal impact energy is more than or equal to 50J at the temperature of minus 20 ℃, and the reduction of area is more than or equal to 60 percent.

3. A preparation method of hot-rolled H-shaped steel for high-strength and high-toughness buildings comprises the following steps:

1) Smelting process, which comprises the following steps in sequence:

smelting in a converter;

LF + RH refining: controlling the temperature of molten steel to be 1600-1620 ℃ at the moment of finishing LF refining; the RH refining circulation time is more than 15min, and the smelting period is controlled to be 40-50 min;

continuous casting;

2) The rolling process sequentially comprises the following steps:

heating: controlling the temperature in the heating and soaking stage at 1250-1300 ℃, heating for 90-120 min, and then discharging for rolling;

controlling rolling and cooling: the finish rolling temperature is controlled to be 800-850 ℃, and the cold bed is intensively and slowly cooled and straightened;

the method comprises the following steps that a cooling device is adopted in the rolling process to separately cool a web plate and a flange, and the cooling device is started at the last rolling pass;

3) And (5) finishing.

4. The preparation method of claim 3, wherein in the step 1), the content of arsenic and tin in the converter smelting is less than 0.008%, the alkalinity of the converter final slag is in the range of 2.1-3.9, slag stopping and tapping are adopted, and aluminum, manganese and iron are adopted for deoxidation alloying in the tapping process.

5. The preparation method according to claim 3, wherein in the step 1) LF refining, RE is added before a calcium feeding line, the soft blowing time is not less than 20 minutes, and the refining period is not less than 30 minutes;

the RH refining pure degassing time is more than 5 minutes, after the treatment is finished, 200-250 m calcium-aluminum wires are fed into each furnace, and the soft blowing time is not less than 10 minutes;

protecting the casting in the whole process, and covering the tundish by using a covering agent combined with carbonized rice hulls; the tundish to the crystallizer adopts an immersion type water gap and adopts argon seal protection; the liquid level of the crystallizer adopts peritectic steel covering slag; wherein, the peritectic steel casting powder comprises the components of, by weight, 25% to 35% of SiO, 35% to 45% of CaO, 1.90% to 3.00% of MgO and 3.00% to Al ₂ O ₃ ≤4.00％。

6. The preparation method according to claim 3, wherein the continuous casting process in the step 1) adopts a full-protection pouring process, and the tundish adopts a stopper ladle to cast molten steel; the pulling speed of the special-shaped continuous casting billet is 1.0-1.2 m/min; the degree of superheat is controlled between 20 and 30 ℃.

7. The preparation method according to claim 3, characterized in that the step 2) further comprises a rough rolling process, which realizes pass rolling mainly in shape, wherein the last pass temperature of the rough rolling is 1150-1050 ℃, the accumulated deformation rate is 40-60%, and the number of rolling passes is less than 9;

in the finish rolling procedure, the performance control rolling is carried out in the finish rolling process, and the rolling pass is less than 7; the cooling track of the cooling bed keeps the temperature above 400 ℃, and the products are intensively and slowly cooled in the cooling bed; the temperature of the product is reduced to 200-300 ℃ and the product enters a straightening machine for straightening.

8. The manufacturing method according to claim 3, wherein the temperature difference between the same portions of the upper and lower flanges is reduced to within 10 ℃ after cooling, the upper and lower surfaces of the web are reduced to within 5 ℃, and the Z-direction tensile reduction of area deviation between the flange of the H-beam and the web is controlled to be less than 5%.

9. A cooling apparatus for improving overall performance for the cooling of claim 3, wherein said cooling apparatus is mounted behind a finishing mill, wherein said cooling apparatus comprises a plurality of spaced coolant lines and a plurality of spaced cold air lines;

the cooling liquid pipeline is used for cooling flanges, is arranged below the lower flange of the hot-rolled H-shaped steel, and comprises a first flange pipeline parallel to the web and two groups of second flange pipelines which are perpendicular to and communicated with the first flange pipeline, and each group of second flange pipelines respectively corresponds to one flange;

each group of second flange pipelines comprises two parallel lower flange pipelines, a plurality of nozzles are arranged on the surfaces of the lower flange pipelines, which are opposite to the lower flanges, and are used for cooling the flanges, and the lower flanges of the H-shaped steel are arranged between the two parallel lower flange pipelines;

the cold air pipeline is used for cooling the web plate, is convex, is arranged between the lower flange and the web plate, and is provided with a plurality of nozzles parallel to the web plate and close to the cold air pipeline for cooling the web plate.