KR20240013141A - High-toughness hot-rolled H-beam steel for construction and manufacturing method thereof - Google Patents

Abstract

The present invention belongs to the fields of steel smelting technology and rolling forming technology, and specifically, the present invention relates to high-toughness hot-rolled H-beam steel for construction and a method of manufacturing the same. The chemical composition of the hot rolled H-beam steel is C: 0.06~0.10 based on weight percentage (wt%); Si: ≤0.25; Mn: 0.8~1.30; P≤0.015; S≤0.008; Cu: 0.15~0.25; Cr: 0.25~0.60; Ni: 0.10~0.19, V: 0.01~0.03; Al: 0.01~0.03; RE: 0.009~0.019; As+Sn+Zn+Pb+Ca+Mg≤0.035, N≤0.008; T.[O]≤0.002, the remainder is Fe and inevitable impurities. The present invention achieves lightweighting of steel for building structures, while also having comprehensive performances such as excellent corrosion resistance, Z-direction performance, low temperature resistance and toughness, and fully meets the current engineering needs of steel for prefabricated building structures.

Description

High-toughness hot-rolled H-beam steel for construction and manufacturing method thereof

Cross-reference to related applications

This application claims priority of the Chinese patent application filed on July 20, 2022, No. 202210851313.2, the entire contents of which are incorporated herein by reference.

The present invention belongs to the fields of steel smelting technology and rolling forming technology, and specifically, the present invention relates to high-toughness hot-rolled H-beam steel for construction and a method of manufacturing the same.

As the quality requirements of Chinese construction projects gradually increase, the demand for the development of steel for building structures has increased in China. In particular, regarding prefabricated buildings, China has also introduced policies one after another and increased efforts to promote them. Prefabricated buildings have technical advantages such as excellent earthquake resistance, light weight, fast construction speed, high industrialization level, high component prefabrication rate, etc., the use of steel structure meets the unique assembly advantages, and the construction period is longer than the traditional construction period. It has the advantage that most parts in prefabricated steel structures are steel, which is an eco-friendly building material, and has incomparable eco-friendly advantages compared to concrete in terms of recycling and secondary use. The rate of prefabricated buildings in China is much lower than that in developed countries overseas. Therefore, in accordance with the requirements of applicability, economic feasibility, safety, environmental friendliness, and beauty, China promotes innovation in construction methods, develops prefabricated concrete buildings and steel structure buildings on a large scale, and continues to increase the proportion of prefabricated buildings in new buildings. , It will complement the performance and technical measures such as fire prevention and corrosion prevention of steel structure buildings, increase the application of hot rolled H-beam steel, weathering steel, and fireproof steel, and promote the comprehensive development of the core technology and related industries of steel structure buildings. asking for it

Hot-rolled H-beam steel is a major material used in building structures, and depending on working conditions, mechanical properties, corrosion resistance, fire resistance, and structural stability are required. Among them, lamellar tearing resistance has become an important indicator to ensure the safety and structural stability of steel for building structures. Lamellar tearing resistance steel is also called Z-direction steel, and lamellar tearing resistance is mainly evaluated using the cross-sectional shrinkage Z of the tensile test in the thickness direction of the steel plate. For steels with a thickness exceeding 15 mm, the Z-direction lamellar tearing resistance should generally be tested, as long as the structural component generates tensile or fatigue stresses along the plate thickness direction. For architectural structural steel, only the Z-direction performance index of the flange is needed, and for web, there is almost no Z-direction performance index. Therefore, in order to meet the requirements of steel for prefabricated buildings and high-rise construction, the flange and web Z performance, which is an important indicator of excellent comprehensive lamellar tearing resistance, must simultaneously meet the requirements, and as the thickness increases, the difficulty increases accordingly.

Patent application CN113564480A discloses a thick and heavy hot-rolled H-beam with Z-direction performance and a method for producing the same, and the hot-rolled H-beam contains chemical components such as C, Si, Mn, Nb, Ti, N, B, and Als. And the rest is iron and inevitable impurities. The production method includes the steps of molten iron pretreatment → converter smelting → argon blowing refining → RH → beam blank full protection casting → lamination slow cooling → rolling → air cooling after rolling. The present invention adopts a powder rolling + universal rolling + post-rolling air cooling process through reasonable ingredient ratio and process control, and uses a phase change + precipitation + microcrystal combination strengthening method to control the number of secondary particle precipitation, so that it can be used for 10~10 days after rolling. Obtain the granular bainite content between 20%, and ensure that the medium-sized hot rolled H-beam steel with a flange thickness of 80 mm or less has excellent toughness and Z-direction performance, and the Z-direction performance is 65 to 80%. This patent implements strengthening through bainite structure, but since bainite is related to the cooling rate, it is difficult to obtain and control a stable and uniform bainite structure, and at the same time, bainite steel does not have a clear yield phenomenon.

Patent CN103334051B discloses hot-rolled H-beam steel for construction with Z-direction performance and a method for producing the same. The present invention optimizes the smelting process and rolling process, and strictly controls the product quality control means and product production process to obtain steel grades with excellent Z-direction performance and mechanical properties. The chemical components contained in H-beam steel are C: 0.06%~0.18%, Si: 0.10%~0.25%, Mn: 0.90%~1.60%, V≤0.10%, Nb≤0.060%, Ti≤0.030 based on weight percentage. %, and the remainder is iron and inevitable impurities.

Patent CN102418037B discloses hot rolled H-beam steel with lamellar tearing resistance and a method for producing the same. The method for producing H-beam steel according to the present invention is silicon-killed deoxidation by adding Si to the molten steel during the tapping process without using Al deoxidation and controlling the Si in the molten steel to 0.10% to 0.15% of the total weight of the molten steel. After performing, a certain amount of at least one of Ti and Zr is added to the molten steel, and the Si content required for the steel type can be added during refining. The hot-rolled H-beam steel according to the present invention has lamellar tearing resistance and can meet constant Z-direction performance requirements in the thickness direction.

In the above prior art, simple micro-alloying does not help improve the surface quality of the cast piece and seriously limits the improvement of toughness, and at the same time, if the carbon content is too high, welding defects easily occur, which causes a large load to be applied to the rolling mill, causing bending and sagging of the rolled piece. Because this occurs, the size is difficult to control, and the requirements for equipment are high, the overall performance and finished product size compliance rate of H-beam steel are relatively low.

In current section steel production, controlled cooling has always been a serious problem that reduces performance uniformity. Especially for thick specification products, the thickness difference between the flange and the web is large, so using a single cooling mode will have a greater impact on the final performance. At the same time, it will affect the uniformity of Z-direction performance, increasing the gap and affecting the safety of the structure. It's crazy. How to solve this problem and consider both cost and efficiency has always been one of the industry's difficult problems. Some companies use ultra-fast cooling equipment, but it is not economically suitable for large investments and single product varieties with high demand. Therefore, manufacturing structural steel products that require full overall Z-direction performance requires special cooling equipment to be designed to meet the performance requirements.

In order to meet the requirements of structural steel for prefabricated buildings, the cooling system in the present invention is specifically designed to meet these requirements. A hot-rolled H-beam steel for high-toughness building structures with a yield strength reaching the level of 420Mpa and excellent lamellar tearing resistance and a method for manufacturing the same are provided. This section steel product is suitable for use in prefabricated building structural engineering applications, and its web and flange both have high Z-direction performance exceeding Z35 level. In order to achieve excellent Z-direction performance in the flange and web, by combining the steel's composition design and the design of the rolling process and adding a flange and web temperature uniformity control device, excellent impact toughness is achieved under low temperature conditions of -20℃; Because it has features such as excellent corrosion resistance, welding performance, and low yield ratio, it meets the application needs of hot rolled H-beam materials in the field of steel buildings, such as prefabricated building structures in general and cold regions.

In order to achieve the above object, the present invention adopts the following specific technical solutions.

The present invention provides a 420MPa class hot-rolled H-beam steel for construction, and the chemical composition of the H-beam steel is C: 0.06 to 0.10 based on weight percentage (wt%); Si: ≤0.25; Mn: 0.8~1.30; P≤0.015; S≤0.008; Cu: 0.15~0.25; Cr: 0.25~0.60; Ni: 0.10~0.19, V: 0.01~0.03; Al: 0.01~0.03; RE: 0.009~0.019; As+Sn+Zn+Pb+Ca+Mg≤0.035, the remainder is Fe and inevitable impurities. During the smelting process, gases in steel are controlled to N≤0.008 and T.[O]≤0.002 based on weight percentage.

In order to reduce the yield ratio, only a single micro-alloying design of vanadium-nitrogen alloy is used based on the low-carbon component design, and at the same time, the content is strictly controlled to reduce the impact of precipitation strengthening on the yield strength, and the final yield ratio of the above H-beam steel is ≤ It is 0.8. To improve low-temperature resistance and toughness, the number and size of inclusions are strictly controlled, and the content of other residual elements is controlled to As+Sn+Zn+Pb+Ca+Mg≤0.035 based on the addition of RE elements for inclusion modification. desirable.

Each chemical element added to the architectural H-beam for 420MPa steel structures with excellent comprehensive lamellar tearing resistance (Z-direction performance) according to the present invention plays the following role.

Carbon: According to the strength requirement at the level of 420Mpa, low-carbon component design can ensure that the steel for building structures has a certain low temperature resistance, while at the same time ensuring that a certain pearlite structure is created to improve the yield ratio, thereby demanding the use of steel for building structures. suitable for After adding corrosion-resistant elements, lowering the carbon content can prevent the formation of abnormal structures such as Wiedmannstetten structure. In the case of beam blanks, it is easy to control transverse and longitudinal web cracks, so the carbon content is controlled to 0.06% to 0.10% in the present invention, taking organizational performance and smelting costs into consideration.

Silicon: An appropriate amount of Si is beneficial for improving strength, but if the Si content is too high, a bainite-like structure can easily be created, so prevent a large amount of Fe ₂ SiO ₄ from being generated during the reheating process and affecting the surface quality. To this end, the upper limit of Si content is set to 0.25% or less, preferably 0.25% or less, and more preferably 0.20% or less.

Manganese: As an austenite stabilizing element, it can significantly increase the hardenability of steel and at the same time improve the strength of steel in the form of solid solution strengthening. However, if the content is too high, segregation is likely to occur and the difference between parts is large. Since the structure of thick specification building structure section steel is different for each part, it is desirable to set the upper limit of the Mn content at 1.30% in order to ensure strength and at the same time prevent the formation of a large amount of abnormal structure due to a decrease in hardenability. By comprehensively considering various factors, the Mn content in the H-beam steel of the present invention is controlled within the range of 0.8 to 1.30%; To obtain a strength of 420 MPa, the preferred range of VN alloy addition amount is 1.0 to 1.20%.

Phosphorus: The higher the phosphorus content, the easier it is to improve corrosion resistance, but if the phosphorus element content is too high, low-temperature resistance is likely to deteriorate at embrittlement grain boundaries. Therefore, the lower the phosphorus content, the better the effect and the improved low-temperature toughness, so keep P below 0.015%. Control with

Sulfur: If the sulfur element is too high, more sulfides such as MnS will be easily generated, and a large amount of long strip-shaped MnS inclusions will be generated in different parts of the section steel with a complex cross section, which will lower the low-temperature toughness and at the same time will not help improve corrosion resistance; It affects the cross-sectional shrinkage, that is, the lamellar tearing resistance of steel, so it is strictly controlled to S≤0.008%.

Copper: A basic element that improves the corrosion resistance of steel. Cu can promote anodic passivation of steel and reduce the corrosion rate of steel, so it is one of the elements commonly used in corrosion-resistant steel. Its enrichment in the green layer can greatly improve the protection performance of the green layer, and Cu should be more than 0.20% to achieve the effect of Cu enrichment in the green layer. However, if the Cu content is too high, it does not help the welding performance of section steel for building structures and easily causes copper embrittlement. In the process of using continuous casting beam blanks to produce section steel with lamellar tearing resistance, cracks are likely to occur at the corners of the legs due to the concentration of copper, which seriously affects the surface quality of the cast steel and causes a decrease in the plasticity of the steel, which is used for prefabricated building structures. In the present invention, based on meeting the corrosion resistance requirements of section steel, the Cu content is controlled to 0.15 to 0.25%.

Nickel: It improves the strength of steel through solid solution strengthening and is an effective element in improving low-temperature toughness. At the same time, it can improve the high-temperature plasticity of steel and reduce surface defects of cast steel during the continuous casting process. On the one hand, Ni plays a role in expanding the austenite region and improving hardenability, and on the other hand, it can refine pearlite lamellae and refine pearlite, thereby playing a role in strengthening microcrystals. Combined with the Cu content control ratio, the Ni content of the steel is controlled within the range of 0.10 to 0.19%.

Chromium: It is an element that helps improve the strength of steel by improving hardenability and tempering stability, and at the same time, it is an element that helps improve the corrosion resistance of steel materials. When used together with Cu and Ni elements, the corrosion resistance of steel can be greatly improved. When the C content is low, adding an appropriate amount of Cr can improve the hardness and strength of the steel and the corrosion resistance of the section steel. If added in excessive amounts, it reduces the toughness, welding performance and flame cutting performance of the material. In terms of structure control, too much Cr element affects the structure transformation of steel and produces abnormal structures such as bainite. Considering the improvement of strength and corrosion resistance, the Cr content is controlled to 0.25 to 0.60% in the present invention.

Vanadium: Most commonly used in unalloyed steels and one of the most effective strengthening elements. The role of vanadium is to affect the structure and performance of steel by forming VN and V(CN). It mainly precipitates in ferrite at austenite grain boundaries and improves the strength and low-temperature toughness of the material by refining the ferrite grains. Considering that precipitation strengthening has a significant impact on yield strength and improves strength at the same time, V is added at 0.01 to 0.03%.

Rare earths: Rare earths purify steel and change inclusions to reduce pitting and intergranular corrosion. The dissolved rare earth elements in steel increase the polarization resistance and self-corrosion potential of the steel matrix, which is advantageous for improving the corrosion resistance of the steel matrix, changing the tissue structure of the rust layer, and forming a rust layer with good adhesion, denseness, and excellent corrosion resistance, so that it can be used in high-strength weathering steel. Improves corrosion resistance. Considering that an appropriate amount of RE rare earth elements must be added to reform inclusions such as MnS, RE is selected in the range of 0.009 to 0.019%, and RE rare earth elements are a type of complex added element, considering factors such as economic efficiency and cost-effectiveness. , In the present invention, lanthanum-based and cerium-based elements are mainly used to spheroidize inclusions.

Aluminum: Al is added as a strong deoxidizing element during the manufacturing process of low-temperature steel. Reduce the inclusion content to ensure that the oxygen content of the steel is as low as possible, and the excess aluminum after deoxidation can also form AlN precipitates with the nitrogen element in the steel, refining the austenite grains during the heating and hot rolling process. Therefore, the aluminum content as a deoxidizing element and microcrystal strengthening element is controlled within the range of 0.01 to 0.03%.

As, Sn, Zn, Pb, Ca, Mg: These are residual elements in steel that have a significant impact on low-temperature impact toughness and at the same time, also have a significant impact on surface quality. Therefore, since it is an element that cannot be completely removed from steel, its content must be reduced as much as possible. By combining production practices, equipment capabilities and cost control, the total amount of residual elements is controlled within the range of As+Sn+Zn+Pb+Ca+Mg≤0.035.

Nitrogen: If the N content is too high, it is easy to cause quality defects in the cast steel, and at the same time, the VN alloying effect must be guaranteed, so the present invention requires the nitrogen content to be 0.008% or less.

Oxygen: To prevent the formation of large-grained oxide inclusions and a decrease in the toughness and plasticity of steel, the present invention requires the total oxygen content to be T.[O]≤0.0020%.

The H-beam steel product of the present invention has yield strength ≥ 420 MPa, tensile strength ≥ 520 MPa, elongation ≥ 19%; It has excellent overall mechanical properties, such as longitudinal impact energy ≥50J at -20℃, so it is suitable for use in building structures in low-temperature conditions. The Z-direction performance of the web and flange is excellent, and the cross-sectional shrinkage rates are all ≥60%.

The manufacturing method of the above hot rolled H-beam steel, which is suitable for application to building structures in different regions and has excellent lamellar tearing resistance, is mainly molten iron pretreatment - converter smelting - LF refining - RH refining - billet surface defect cleaning - continuous casting beam blank casting - billet It includes the steps of walking beam furnace reheating - high pressure water descaling - temperature controlled rolling + controlled cooling - low temperature straightening - cutting to length - collection and stacking.

In a converter + refining furnace (LF + RH equipment), smelting, refining, and continuous casting processes are performed on molten iron and scrap iron to obtain a continuous casting beam blank, and after surface defect inspection and cleaning, it enters the rolling forming process. The billet is reheated in a walking beam furnace to obtain an austenite structure of an appropriate size, goes through rough rolling and finish rolling, and is then rolled into steel. Control rolling and cooling are performed during the rolling process. It should be noted that precise temperature control is carried out in the last pass of finish rolling, and through the developed special cooling device (see cooling device diagram in Figure 2), the temperatures of the upper and lower legs of the H-beam steel and the upper and lower sides of the flange are basically identical. This ensures consistency of Z-direction performance of flanges and webs under uniform tissue conditions, and ensures structural stability and safety when using the product in prefabricated building structures.

The main processes of controlled rolling and cooling in the rolling process are as follows. The heating temperature is controlled to 1250~1300℃, the final pass temperature of rough rolling is between 1150~1050℃ depending on the size, the cumulative strain is 40%~60%, and the rest is completed in the finishing rolling stage. After rough rolling, three-stage finish rolling is performed, and the final rolling temperature of the finish rolling is precisely controlled between 800°C and 850°C to completely transform the austenite structure into pearlite and ferrite, thereby realizing microcrystal-controlled rolling. Since the temperature difference between the upper leg flange and the lower leg flange of H-beam steel and the temperature difference between the upper and lower surfaces of the web are both 30 to 50℃, cooling control is performed after exiting the rolling mill in the last pass of finishing rolling, and the nozzle of the designed cooling equipment is used. Controlled cooling is achieved by precisely spraying water onto the lower legs and web, controlling the corresponding water flow according to the detected temperature difference. After cooling, the temperature difference in the same area between the upper and lower leg flanges is reduced to within 10℃, and the temperature difference between the upper and lower surfaces of the web is reduced to within 5℃, so that the overall Z-direction performance of the upper and lower leg flanges and web of H-beam steel is basically the same. ensure that it does so. After finish rolling is completed, the rolled pieces pass through a conveyor roller table, and a thermal cover is used to control the cooling rate according to the ambient temperature, preventing large seasonal fluctuations in ambient temperature from affecting the final performance. After leaving the finishing mill, the product is naturally cooled on a cooling bed. After the temperature is reduced to below 100℃, the product enters the straightening machine and is straightened. The flange thickness range of rolled material finished product specification is 15~50mm. Samples are taken from the flange area of the H-beam and the middle area of the web to test the mechanical properties. The Z-direction tensile cross-sectional shrinkage rate deviation of the flange and web of the H-beam produced through the above process is controlled to 5% or less.

Preferably, the 420MPa grade hot rolled H-beam steel for prefabricated construction with excellent lamellar tearing resistance provided in the present invention, its manufacturing method and specific process control specifically include several aspects as follows.

1. Smelting process

1) Converter smelting

The converter is controlled according to the basic operation, and the main process includes strictly stirring the content of sulfur, arsenic and other residual elements in the blast furnace molten iron and processing to optimize the molten iron quality, where arsenic and tin are both less than 0.008%; The alkalinity of the final slag in the converter ranges from 2.1 to 3.9, and slag blocking and steel tapping are used, but aluminum-manganese-iron deoxidation alloying is used during the steel tapping process. During the steel tapping process, when deoxidizer, ferrosilicon, metal manganese, vanadium nitrogen alloy, ferroniobium alloy, nickel plate, etc. are added in batches, the ingredients in the final converter reach the internal control target requirements.

2) Refined LF+RH duplex control

During the refining process, gases and inclusions are controlled through LF+RH duplex. LF uses calcium carbide, silicon-calcium-barium, and aluminum particles to condition the slag, and the top slag must be reduced to white slag or yellow-white slag before leaving the station. After entering the station and taking initial samples, oxygen is determined to be controlled to [O]≤20ppm; RE is added before supplying the calcium wire, nitrogen is blown from the bottom according to process requirements throughout the entire process, the soft blowing time is more than 20 minutes, the refining cycle is more than 30 minutes, and the molten steel temperature at the end of LF refining is controlled to 1600~1620℃, the molten steel temperature is raised to offset the drop in molten steel temperature at the time of RH treatment, and the use of the "method of adding aluminum to generate chemical heat to raise the temperature" at the time of RH treatment is strictly prohibited. do.

RH refining uses this processing mode, the circulation time is longer than 15 minutes, the pure degassing time is longer than 5 minutes, and after the processing is completed, 200-250 meters of calcium-aluminum wire is supplied to each furnace, and the soft blowing time is is more than 10 minutes, and the RH smelting cycle is controlled to 40 to 50 minutes.

Full protection casting means using a long nozzle from the ladle to the tundish and protecting it with an argon seal; Coating the tundish using a coating agent combined with carbonized rice husk; Submerged nozzles are used from the tundish to the crystallizer, protected by argon seals; The crystallizer liquid level uses peritectic steel protection slag; Preferably, on a weight percentage basis, the components of the aerobic steel protection slag are 25%≤SiO≤35%, 35%≤CaO≤45%, 1.90%≤MgO≤3.00%, 3.00%≤Al ₂ O ₃ ≤4.00%. am.

3) Continuous casting

The continuous casting process uses a full protection casting process, controlled by using a long nozzle of the ladle and adding a sealing ring; The tundish casts molten steel using a stopper rod bag; To improve efficiency, the continuous casting beam blank drawing speed is 1.0~1.2m/min; By controlling the degree of superheat to below 20℃~30℃, the nozzle can be prevented from clogging; The smelted molten steel is cast into beam blanks of three sizes that are close to the final cross section. Because the alloy content is large, the beam blanks are cast and formed to prevent surface cracks, and then annealed in an insulating pit or sand pit or using an insulating felt. Slowly cool.

2. Rolling process

1) Heating

The blank is austenitized and heated uniformly in a heating furnace, the heating and cracking stage temperature is controlled to 1250~1300℃, heated for 90~120 minutes, and then discharged from the furnace and rolled. Heating adopts high temperature and short-time heating to control austenite homogenization and refinement.

2) Controlled rolling and controlled cooling

Large-scale production lines use a controlled rolling/controlled cooling process. The rough rolling process implements shape-oriented rolling, and the number of rolling passes is less than 9; Performance control rolling is performed during the finishing rolling process, and the number of rolling passes is less than 7. The final rolling temperature of finish rolling is controlled to 800℃~850℃. The cooling bed cooling track maintains a temperature above 400℃, and the product is intensively cooled in the cooling bed, preventing the cooling rate from being too fast and affecting the final performance. The product is calibrated after the temperature is reduced to 200-300℃, thereby ensuring the integrity of the primary iron oxide scale on the surface.

The present invention provides a cooling device to improve overall performance. During the rolling process, the web and flange are comprehensively cooled using a specially designed cooling device. The cooling device is installed at the rear of the finishing mill, and the cooling devices are distributed at intervals. It includes a plurality of coolant pipes (1) and a plurality of cold pipes (2) distributed at intervals, wherein the coolant pipes (1) are used for cooling the flange and are located on the lower side of the lower flange (6) of the hot rolled H-beam steel. It is installed in and includes a first flange pipe (4) parallel to the web and two sets of second flange pipes vertically communicating with the first flange pipe (4), wherein each set of second flange pipes is one each. corresponds to the flange; Here, each set of second flange tubes includes two parallel lower flange tubes (5), and the lower flange tubes (5) have a plurality of tubes on the surface opposite to the lower flange (6) for cooling the flange. The nozzle (3) is installed, and the lower flange (6) of H-beam is installed between two parallel lower flange pipes (5); The cold pipe (2) is used for cooling the web, has a convex shape, and is installed between the lower flange (6) and the web (8). The cold pipe (2) is parallel to and close to the web (8) and has a plurality of cooling pipes for cooling the web (8). The nozzle (3) is installed. The shape of the cold tube corresponds to the shape formed by the lower flange and web. The cooling rate can be controlled depending on web and flange thickness (see Figure 1). The cooling device is installed behind the finishing mill and operates on the last pass of rolling, and the flange and web are mounted separately for cooling. In Figure 1, the cooling water pipe indicated by symbol 1 is used for cooling the flange; Because the flange is thick, it must be cooled using coolant or another cooling medium depending on the cooling rate. After measuring the temperature difference between the upper flange (7) and lower flange (6) with an online temperature measuring device, the coolant flow rate is adjusted through the nozzle (3). Since the thickness of the web is thinner than that of the flange, the demand can be met with cooling air. The cold pipe marked with symbol 2 is used for cooling the web; Since the temperature difference between the upper and lower surfaces of the web is small, cooling is achieved by appropriately adjusting the flow rate of cooling air from the nozzle (3). Through the above device, the temperature difference between the upper leg flange and the lower leg flange is ensured to be within the range of 5 to 10°C, and the temperature difference of the web is to be within the range of 3 to 6°C. This ensures uniformity of organization and improves the Z-direction performance of webs and flanges of section steel for building structures. Combined with vanadium microalloying design, the equipment can meet the performance requirements of final hot rolled H-beam steel, while ensuring that the Z-direction performance of web and flange both reach a high level.

3) Finishing process

After the product comes off the production line, carry out surface and dimensional finishing treatment; To ensure that the material's performance is true and accurate, samples are taken during the finishing process and product performance is analyzed.

The advantages of the present invention compared to the prior art are as follows.

(1) The low carbon + trace VN alloying + RE composition design is simple and efficient compared to other alloyings and reduces the incidence of defects in cast steel. (2) Controlling the low residual elements and impurity elements in molten steel helps improve the plasticity and low-temperature toughness of steel. (3) Adding a certain amount of RE elements helps to refine the inclusions in the steel and simultaneously improve the lamellar resistance of the flange and web. (4) Beam blank's single-sided casting control technology implements the Al deoxidation process, improves the purity of molten steel, and at the same time prevents the problem of clogging of long nozzles during the casting process. (5) Through the designed special water spray device, the uniform cooling process of the web and flange is realized, the uniformity of the entire web and flange structure is improved, the lamellar tearing resistance is controlled and improved at the same time, and the overall H-beam steel is comprehensively improved. Improves robust performance. (6) The yield strength of the H-beam manufactured through the above process reaches a level of 420 MPa or more, and while realizing lightweight steel for building structures, it has comprehensive performance such as excellent corrosion resistance, Z-direction performance, low temperature resistance and toughness, and is suitable for use in prefabricated buildings. Fully meets the current engineering needs of structural steel.

Figure 1(a) is a plan view of the structure of a cooling device for producing H-beam steel according to the present invention.
Figure 1(b) is a perspective structural diagram of a cooling device for producing H-beam steel according to the present invention.
Figure 2(a) is a microstructure diagram of the H-beam upper leg obtained in Example 1 of the present invention.
Figure 2(b) is a microstructure diagram of the H-beam lower leg obtained in Example 1 of the present invention.
Figure 2(c) is a microstructure diagram of the H-beam steel flange obtained in Example 1 of the present invention.
Figure 3(a) is a microstructure diagram of the H-beam upper leg obtained in Example 6 of the present invention.
Figure 3(b) is a microstructure diagram of the H-beam lower leg obtained in Example 6 of the present invention.
Figure 3(c) is a microstructure diagram of the H-beam flange obtained in Example 6 of the present invention.

The present invention is further explained below with reference to specific examples.

The present invention is described in detail below.

Table 1 is a list of chemical components of each example and comparative example of the present invention.

Table 2 is a list of main process parameters for each example and comparative example of the present invention.

Table 3 is a list of performance tests for each example and comparative example of the present invention.

Each embodiment of the present invention is carried out according to the following steps.

1) Preferably, molten iron with low phosphorus, low sulfur and low residual elements is put into the furnace and then smelted in the converter, and then the components and inclusions are controlled through LF+RH duplex; The molten steel temperature at the end of LF refining is controlled to 1600~1620℃, the molten steel temperature is raised to offset the drop in molten steel temperature at the time of RH treatment, and the temperature is raised by adding aluminum to generate chemical heat at the time of RH treatment. “It is strictly prohibited to use; RH refining uses this treatment mode, the circulation time is longer than 15 minutes, the pure degassing time is longer than 5 minutes, and after the treatment is completed, each furnace is filled with 200-250 m of calcium- Aluminum wire was supplied, the soft blowing time was more than 10 minutes, and the RH smelting cycle was controlled to 40 to 50 minutes.

Finally, it is continuously cast as a beam blank and divided into three blank types according to the flange thickness. The residual elements of molten iron are strictly controlled to As+Sn+Zn+Pb+Ca+Mg≤0.035; During the casting process, the casting superheat is controlled to less than 20℃, and a random value within the blank drawing speed range of 1.0 to 1.18 m/min is selected and used as a constant blank drawing speed, and the calibration temperature is above 850℃.

2) In the rolling process, the blank was reheated in the furnace to control the temperature to 1250-1300°C, heated for 90-120 minutes, and then discharged from the furnace and rolled. A controlled rolling/controlled cooling process was used. The rolling passes of the BD rough rolling process are less than 9 passes; The number of rolling passes in the finishing rolling TM process is less than 7 passes. The final rolling temperature of finish rolling is controlled to 800℃~850℃. The cooling bed cooling track maintains a temperature above 400℃, and the product is intensively cooled in the cooling bed for more than 15 minutes. The product is calibrated after the temperature is reduced to 200-300℃.

3) In the finishing process, surface and dimensional finishing treatment are carried out after the product comes out of the production line; Samples were collected during the finishing process and product performance was analyzed.

Chemical composition (wt.%) of each example and comparative example of the present invention element C Si Mn P S Cu Cr Ni R.E. V Al Nb Ti B Example 1 0.06 0.25 1.25 0.013 0.005 0.18 0.26 0.18 0.012 0.02 0.015 ― ― ― Example 2 0.07 0.24 1.28 0.015 0.007 0.20 0.36 0.17 0.019 0.03 0.022 ― ― ― Example 3 0.09 0.25 1.30 0.012 0.006 0.22 0.32 0.16 0.016 0.025 0.019 ― ― ― Example 4 0.08 0.20 1.22 0.013 0.008 0.25 0.29 0.17 0.009 0.022 0.025 ― ― ― Example 5 0.06 0.23 1.29 0.014 0.005 0.21 0.27 0.19 0.015 0.013 0.017 ― ― ― Example 6 0.10 0.21 1.19 0.015 0.008 0.19 0.33 0.17 0.019 0.026 0.025 ― ― ― Comparative Example 1
CN113564480A 0 .1 0 .22 1 .25 0 .016 0 .0018 ― ― ― ― ― 0.008 0.045 0.015 0.0008 Comparative Example 2
CN102418037B 0.16 0.25 1.40 0.019 0.007 ― ― ― ― 0.013 ― ― ― ― Comparative Example 3CN102418037B 0.15 0.34 1.41 0.015 0.007 ― ― ― ― ― ― 0.032 0.011 ―

The main refining process parameters are listed in Table 2.

Refining main process parameters Example LF refining outlet temperature, ℃ RH refining circulation time, min Pure degassing time of RH refining, min Calcium-aluminum wire (m) RH scouring soft blowing time, min RH refining smelting cycle, min Example 1 1610 18 7 220 12 45 Example 2 1615 17 8 230 12 47 Example 3 1613 16 8 225 12 42 Example 4 1617 17 8 215 11 45 Example 5 1604 16 8 220 12 47 Example 6 1620 18 10 224 11 50

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

Process parameters of continuous casting process Example Liquidus temperature/℃ Top steel temperature/℃ Tundish temperature/℃ Drawing speed/m·min ^-1 Superheat/℃ Example 1 1519 1566 1532 1533 1526 0.76 0.78 0.77 20 Example 2 1521 1567 1535 1539 1531 0.75 0.71 0.71 23 Example 3 1531 1570 1541 1537 1542 0.82 0.88 0.82 21 Example 4 1526 1562 1542 1533 1537 0.79 0.78 0.78 22 Example 4 1523 1564 1545 1538 1531 0.77 0.73 0.70 20 Example 6 1529 1571 1540 1539 1542 0.85 0.86 0.82 23

Table 4 is a list of main process parameters for each example and comparative example of the present invention.

Key process parameters Example Flange thickness/mm Heating temperature, ℃ BD outlet temperature, ℃ Finish rolling outlet temperature, ℃ Temperature difference outside the upper and lower flanges after cooling, ℃ Temperature difference between the upper and lower surfaces of the web, ℃ Rolling Pass BD+TM Example 1 26 1250 1050 820 7 5 16 Example 2 28 1265 1060 830 8 6 16 Example 3 32 1280 1080 825 7 7 16 Example 4 41 1270 1090 840 9 9 14 Example 5 36 1255 1070 835 8 6 14 Example 6 50 1280 1100 850 10 9 12

Table 5 is a list of performance tests for each example and comparative example of the present invention.

Mechanical properties record table of rolled materials ingredient element Flange thickness/mm Examination area Yield strength/MPa Tensile strength/MPa Elongation (%) Longitudinal average impact energy at -20℃/J Z-direction cross-sectional shrinkage, % Example 1 26 upper flange 445 563 31 205 81 lower flange 451 601 28 221 76 web 501 642 27 150 75 Example 2 28 upper flange 456 616 32 211 75 lower flange 448 567 30 199 79 web 498 655 26 166 71 Example 3 32 upper flange 439 556 31 203 78 lower flange 446 595 32 186 79 web 491 638 28 176 73 Example 4 41 upper flange 436 606 29 188 79 lower flange 441 621 30 178 72 web 489 652 26 135 68 Example 5 36 upper flange 431 590 30 168 75 lower flange 439 570 29 189 75 web 491 682 25 163 69 Example 6 50 upper flange 432 576 28 166 78 lower flange 438 608 30 156 75 web 479 630 24 121 67 Comparative Example 1
CN113564480A 50 flange 427 537 ― ― 77 Comparative Example 2CN102418037B 14 flange 360 545 ― ― 40.81 Comparative Example 3CN102418037B 13 flange 420 ― ― ― 39

The performance test was performed by sampling the prototype, and the sampling position of the sample used for mechanical properties was 1/3 from the edge to the center of the H-beam flange, and the sampling position of the web was the central area, in accordance with the standard BS EN ISO 377-1997. Reference was made to “Sampling location and preparation of mechanical properties test samples”; for test methods of yield strength, tensile strength and elongation, reference was made to standard ISO 6892-1-2009 “Room temperature tensile test methods for metallic materials”; The impact energy test method refers to the standard ISO 148-1 "Charpy pendulum impact test of metallic materials", and the test results are shown in Table 5. By comparison, the H-beam flange and web produced using the manufacturing method according to this patent were compared. It was found that the Z-direction performance of is superior to that of the currently patented product. Any content not described in detail in the present invention can be adopted by general technical knowledge in the field.

Lastly, it should be explained that the above embodiments are only for illustrating the technical solution of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art will recognize that any modification or equivalent replacement to the technical solution of the present invention does not depart from the spirit and scope of the technical solution of the present invention, and all are included in the claims of the present invention. You must understand that it must be included.

1: Cooling water pipe, 2: Cold pipe, 3: Nozzle, 4: First flange pipe, 5: Lower flange pipe, 6: Lower flange, 7: Upper flange, 8: Between webs.

Claims (9)

As a hot-rolled H-beam steel for high-toughness construction,
The chemical composition of the hot rolled H-beam steel is C: 0.06-0.10% by weight percentage; Si: ≤0.25%; Mn: 0.8~1.30%; P≤0.015%; S≤0.008%; Cu: 0.15~0.25%; Cr: 0.25~0.60%; Ni: 0.10~0.19%, V: 0.01~0.03%; Al: 0.01~0.03%; RE: 0.009~0.019%; As+Sn+Zn+Pb+Ca+Mg≤0.035%, N≤0.008%; A hot-rolled H-beam steel characterized in that T.[O]≤0.002%, and the remainder is Fe and inevitable impurities. The method of claim 1, wherein the yield ratio of the hot rolled H-beam steel is ≦0.8, the yield strength is ≧420 MPa, the tensile strength is ≧520 MPa, and the elongation is ≧19%; Hot rolled H-beam steel, characterized in that the longitudinal impact energy at -20°C is ≥50J and the cross-sectional shrinkage is both ≥60%. A method of manufacturing hot rolled H-beam steel for high-toughness construction,
1) Smelting process;
2) rolling process; and
3) Including the finishing process,
The smelting process is,
Converter smelting;
LF+RH refining in which the molten steel temperature at the end of LF refining is controlled to 1600-1620°C, the RH refining circulation time is longer than 15 minutes, and the smelting cycle is controlled to 40-50 minutes; and
Contains continuous casting sequentially,
The rolling process is,
Heating and cracking stage The temperature is controlled to 1250-1300℃, heating for 90-120 minutes, then discharged from the furnace and rolling is performed; and
The final rolling temperature of the finish rolling is controlled to 800℃~850℃, and it sequentially includes controlled rolling and controlled cooling in which centralized slow cooling and straightening are performed on the cooling bed;
A manufacturing method characterized in that the web and flange are cooled separately during the rolling process using a cooling device, which is operated in the last pass of rolling. The method of claim 3, wherein in the converter smelting in step 1), the arsenic and tin contents are both less than 0.008%, the alkalinity of the final converter slag is in the range of 2.1 to 3.9, and slag blocking and steel tapping are used, but aluminum-manganese is added during the steel tapping process. - A manufacturing method characterized by using iron deoxidation alloying. According to paragraph 3,
In the LF refining of step 1), RE is added before supplying the calcium wire, the soft blowing time is 20 minutes or more, and the refining cycle is 30 minutes or more;
The pure degassing time of RH refining is longer than 5 minutes, and after the treatment is completed, 200-250 meters of calcium-aluminum wire is supplied to each furnace, and the soft blowing time is not less than 10 minutes;
In full protection casting, a coating material combined with carbonized rice husk is used to coat the tundish; From tundish to crystallizer, submerged nozzles are used and protected by argon seals; For the crystallizer liquid level, aperitoneal steel protection slag is used; By weight percentage, the composition of the perforated steel protection slag is 25%≤SiO≤35%, 35%≤CaO≤45%, 1.90%≤MgO≤3.00%, 3.00%≤Al ₂ O ₃ ≤4.00%. manufacturing method. The method of claim 3, wherein the continuous casting process of step 1) uses a full protection casting process, and the tundish uses a stopper rod bag to cast molten steel; Continuous casting beam blank drawing speed is 1.0~1.2m/min; A manufacturing method characterized in that the degree of superheat is controlled to 20-30°C. According to paragraph 3,
Step 2) further includes a rough rolling process to implement shape-centered rolling, the final pass temperature of rough rolling is between 1150 and 1050°C, the cumulative strain is 40% to 60%, and the rolling pass is Less than 9 passes;
In the finishing rolling process, performance-controlled rolling is performed in the finishing rolling process, and the rolling passes are less than 7 passes; The cooling bed cooling track maintains a temperature above 400°C; The product is intensively cooled in a cooling bed; A manufacturing method characterized in that the temperature of the product is reduced to 200-300℃ and then entered into a calibrator to be calibrated. According to paragraph 3,
After cooling, the temperature difference between the same parts of the upper flange and lower flange is reduced to within 10℃, the temperature difference between the upper and lower surfaces of the web is reduced to within 5℃, and the deviation in the Z-direction tensile cross-sectional shrinkage of the H-beam flange and web is controlled to less than 5%. A manufacturing method characterized by being. A cooling device for overall performance improvement used for cooling according to paragraph 3,
The cooling device is installed behind the finishing mill, and the cooling device includes a plurality of cooling water pipes distributed at intervals and a plurality of cold pipes distributed at intervals;
The cooling water pipe is used for cooling the flange, is installed on the lower side of the lower flange of the hot rolled H-beam steel, and includes a first flange pipe parallel to the web and two sets of second flange pipes communicating perpendicularly to the first flange pipe, , each set of second flange pipes corresponds to one flange;
Each set of second flange pipes includes two parallel lower flange pipes, and a plurality of nozzles for cooling the flange are installed on the lower flange pipe on a surface opposite to the lower flange, and the lower flange of H-beam steel is All are installed between two parallel lower flange pipes;
The cooling pipe is used for cooling the web, has a convex shape, is installed between the lower flange and the web, and a plurality of nozzles for cooling the web are installed in the cold pipe parallel to and close to the web.