Method for producing high-strength HRB600E deformed steel bar

Abstract

According to the method for producing the high-strength HRB600E deformed steel bar, through V-N microalloying, grain refinement and strengthened precipitation, the yield strength of the deformed steel bar with the diameter phi being 50 mm is larger than or equal to 600 MPa, the tensile strength is larger than or equal to 800 MPa, and the deformed steel bar is free of cracks during cold bending; the continuous casting superheat degree is controlled to be 10-25 DEG C, the throwing speed is smaller than or equal to 4.0 m / min, generation of columnar crystals and dendritic structures is greatly inhibited, and the risk of cold-bending cracks is reduced; rolling mill load is stabilized, and equipment abrasion is reduced; by adopting the hole pattern sharing and optimal design that the first six flat rollers in the 12 passes are shared, 7-10 existing hole patterns and 11-12 flat elliptical new hole patterns are shared, spare parts such as roller guides and guards are saved, and the consistency and excellent cold bending crack resistance of material patterns are ensured; through an empty guide groove driven by 20 input rollers, double-length stable separation and continuous conveying are achieved, and it is guaranteed that feeding of the cooling bed is uniform; the whole process abandons a through-water cooling process, the system is simplified, and the system is more environment-friendly and efficient.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of metallurgy, and in particular to a method for producing high-strength HRB600E threaded steel. BACKGROUND

[0002] With the continuous improvement of the performance requirements of steel bars, 600MPa (HRB600) threaded steel has a wide application prospect due to its high strength and excellent mechanical properties. At present, most domestic hot-rolled steel bar production lines are only approved to produce φ50mm HRB500E steel, while the national standard "GB 1499.2-2024 Steel Reinforced Concrete Part 2 Hot Rolled Ribbed Steel Bar" has explicitly allowed the production of φ50mm HRB600 grade steel bar. 600MPa grade steel bar has good mechanical properties, and can reduce the use amount of steel bar, save direct cost and labor input of the project, meet the specification and design requirements while ensuring the quality of the project, and the market demand is increasing. In order to meet the market demand, enrich the product variety structure of the enterprise, and improve the market competitiveness of the enterprise, it is particularly important to develop larger size and higher strength threaded steel.

[0003] However, there are still many technical problems in the existing production practice: the section size of the used billet is 155mmx155mm, φ50mm threaded steel is single-line rolled, and considering the small compression ratio, large finished product section size and other factors, the mechanical properties are difficult to guarantee. The high superheat of molten steel. The maximum superheat of the tundish is more than 30℃, accounting for more than 60%; the drawing speed is fast, the average drawing speed of 155mm square billet is 4.2m / min, and the fastest is more than 4.5m / min. High superheat and high casting speed lead to the development of columnar crystal of the casting billet, increase the proportion of dendritic structure of the threaded steel after rolling, and easily lead to cold bending cracking. In the rolling process, the soaking temperature is an important factor affecting the homogenization degree of austenite grain, mainly considering two aspects, one is that the soaking temperature has an important influence on the size and homogenization of austenite grain, that is, the higher the soaking temperature, the larger the austenite grain, and the uneven distribution; the second is that the soaking temperature also has a great influence on the solid solubility of micro-alloying elements, and the soaking temperature needs to be set considering the relationship between the solid solubility product of micro-alloying elements and temperature. The existing rolling mill has poor compatibility, and the pass system needs to be redesigned for φ50mm specification to consider the rolling life, guide compatibility and threaded forming quality. SUMMARY

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a method for producing high-strength HRB600E threaded steel.

[0005] The technical scheme adopted by the present application to solve its technical problems is: a method for producing high-strength HRB600E threaded steel, the method for producing high-strength HRB600E threaded steel comprises:

[0006] The following steps are sequentially performed:

[0007] Continuous casting and rough rolling: the temperature of molten steel is 1503℃±5℃, and the drawing speed is ≤4.0m / min;

[0008] Heating and soaking: the cast blank is heated to 1120℃-1180℃, and the soaking time is ≥120min, and the temperature difference of the out-of-furnace is ≤30℃;

[0009] Rolling: the base circle diameter is 48.5mm, the height of the cross rib is the standard size+0.1mm-0.3mm, and the α angle and the β angle are both 50°;

[0010] Cold bed unloading: the final rolling temperature is 1070℃±10℃, the rolling speed is 4.0m / s-5.0m / s, and after being divided by the air passing guide groove, the product is sent to the cold bed;

[0011] The components of the HRB600E threaded steel bar are as follows in percentage by weight: C: 0.25%-0.28%, Si: 0.55%-0.75%, Mn: 1.5%-1.6%, P, S≤0.04%, V: 0.11%-0.13%, and Ceq: 0.52%-0.57%.

[0012] As a further improvement of the application, the continuous casting and rough rolling step is that the continuous casting overheat degree is in the range of 10-25℃.

[0013] As a further improvement of the application, it further includes that the argon blowing time is ≥12min during the converter tapping to the refining station, and the molten steel is poured after being covered and kept in the ladle.

[0014] As a further improvement of the application, the rolling step includes rough rolling and medium rolling, the rough rolling of 6 passes is flat roller design, and the 6 passes adopt existing pass, and the 11-12 racks are redesigned.

[0015] As a further improvement of the application, the finishing rolling in the rolling step uses the air passing guide groove, and the air passing guide groove is driven by 20 input rollers.

[0016] As a further improvement of the application, it further includes that 95-105 tons of hot metal is added, and the hot metal temperature is >1280℃, and 20-25 tons of scrap steel is added.

[0017] As a further improvement of the application, it further includes that the converter smelting adopts the high-lifting complementary blowing process, and the molten steel composition at the smelting endpoint is: C≤0.015%, Si≤0.003%, Mn≤0.12%, P≤0.025%, S≤0.025%, and the endpoint temperature is ≤1675℃.

[0018] As a further improvement of the present application: also including converter tapping using vanadium-nitrogen micro-alloying, adding finished before tapping to 3 / 4, silicon calcium barium deoxidizer 20 kg, silicon aluminum barium deoxidizer 20 kg, adding carbon powder, silicon manganese alloy, silicon iron alloy, vanadium-nitrogen alloy.

[0019] As a further improvement of the present application: also including converter tapping into the refining station for component fine-tuning, refining argon blowing time > 12 minutes, before the steel ladle is lifted, cover is added and then poured on the platform.

[0020] As a further improvement of the present application: the temperature of the end of the cold bed feeding into the cold bed is kept at 650-700℃ in the cold bed discharging step.

[0021] Compared with the prior art, the present application has the beneficial effects that:

[0022] 1. By precisely adding V-N micro-alloying elements in the converter tapping stage and strictly controlling the chemical composition range, double precipitation strengthening and grain refinement are realized; the process significantly improves the yield strength and tensile strength of the deformed steel bar, while ensuring the elongation and cold bending performance, and the mechanical performance index of the finished product meets or exceeds the requirements of the HRB600 standard;

[0023] 2. The continuous casting steel overheat degree is strictly controlled within the range of 10-25℃, and the drawing speed is limited to 3.5-4.0m / min, which can effectively inhibit the excessive development of the columnar crystal of the casting blank. The reduction of the columnar crystal content helps to reduce the proportion of dendritic structure after rolling, significantly improves the internal organizational uniformity and compactness of the casting blank, thereby greatly reducing the risk of crack generation during subsequent cold bending forming, and ensuring the cold bending reliability of the large-size deformed steel bar;

[0024] 3. The heating-soaking combined process with heating temperature of 1120-1180℃, soaking time ≥120min and discharge temperature difference ≤30℃ makes the temperature distribution of the casting blank more uniform, which is beneficial to the dissolution of the subsequent micro-alloying elements, and also can avoid the peak value of rolling resistance caused by local overheating or excessive temperature gradient, thereby reducing the rolling mill power fluctuation and equipment wear, meeting the needs of high-strength steel high-efficiency and stable production;

[0025] 4. In the 12-rolling pass, the pass is reasonably arranged to be shared, the first 6 passes of rough rolling use general flat rollers, the 7-10 passes of medium rolling use existing passes, and the 11-12 passes are redesigned to be flat elliptical screw passes; at the same time, the key geometric parameters such as base circle diameter, transverse rib height and α / β angle are optimized to the best value;

[0026] 5. No water cooling equipment and process is used in the whole process, only relying on the optimization of heating, soaking and rolling parameters, the organization control and performance standard can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions, the drawings required to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art without creative effort based on these drawings belong to the protection scope of the present application.

[0028] Figure 1 The structure schematic diagram of 11-arch hole type in the present application.

[0029] Figure 2 The structure schematic diagram of 12-arch hole type in the present application. DETAILED DESCRIPTION

[0030] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions will be described clearly and completely in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0031] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to include all the steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0032] The relative arrangement of parts and steps, numerical expressions, and numerical values set forth in the Examples herein are not intended to limit the scope of the present application unless specifically stated otherwise. At the same time, it should be understood that the dimensions of the various parts shown in the drawings are not drawn to actual scale for the sake of convenience in description. Techniques, methods, and equipment known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered part of the enabling description where appropriate. In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limiting. Thus, other examples of the exemplary embodiments can have different values. It should be noted that like reference numerals and letters refer to like items throughout the drawings, and thus, once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

[0033] With The dual demands of strength and economy of HRB600 grade threaded steel in high-rise and large-span buildings are increasing, and the existing production line is facing multiple technical bottlenecks: when a 155mmx155mm square billet is rolled into a large-sized threaded steel, it is difficult to meet the mechanical properties of 600MPa grade steel due to small compression ratio and large finished section; the superheat of continuous casting molten steel is usually >30℃ and the billet drawing speed is above 4.2m / min, resulting in a large amount of columnar crystal and dendritic structure, which is prone to cracking during cold bending; if the heating-soaking temperature is too high, it is beneficial to uniform grain, but it will weaken the solid solution of V, N and other micro-alloy elements, thereby affecting the precipitation strengthening; on the contrary, the temperature is too low and it is also difficult to eliminate dendrites; in addition, the existing rolling pass compatibility is poor, not only the types of rolling mill and guide are numerous and the cost is high, but also it is difficult to balance the forming quality and equipment life, which seriously restricts the efficient and stable production of 600MPa grade large-sized threaded steel.

[0034] In order to solve the above problems, the present application provides a method for producing high-strength HRB600E threaded steel, which is further illustrated by combining the drawings and examples with the present application: the method for producing high-strength HRB600E threaded steel comprises:

[0035] The following steps are carried out in sequence:

[0036] Continuous casting and blooming: the temperature of molten steel is 1503℃±5℃, and the billet drawing speed is ≤4.0m / min;

[0037] Heating and soaking: the billet is heated to 1120℃-1180℃, and the soaking temperature is ≥120min, and the furnace temperature difference is ≤30℃;

[0038] Rolling: the base circle diameter is 48.5mm, the transverse rib height is the standard size+0.1mm-0.3mm, and the α angle and the β angle are both 50°;

[0039] Cold bed blanking: finish rolling temperature 1070℃±10℃, rolling speed 4.0m / s-5.0m / s, after being divided by air passing guide groove, it is sent to the cold bed;

[0040] The component of the HRB600E threaded steel bar is as follows in percentage by weight: C: 0.25%-0.28%, Si: 0.55%-0.75%, Mn: 1.5%-1.6%, P, S≤0.04%, V: 0.11%-0.13%, Ceq: 0.52%-0.57%.

[0041] As an embodiment of the present application, the billet section size used by the two-bar production line is 155mmx155mm, and the φ50mm large-size threaded steel is rolled by single line. Considering the factors such as small compression ratio and large finished product section size, the vanadium micro-alloying technology is used to ensure the mechanical property indexes of the finished steel. The vanadium added into the micro-alloyed steel forms VC and VN, which has a large contribution to the precipitation strengthening. Through the strengthening mechanism of vanadium, the purpose of improving the billet strength and refining the grain can be achieved. The alloy element V has a strong precipitation strengthening effect and a strong grain refining effect, and can accelerate the γ-α transformation, reduce the probability of appearance of bainite and martensite, and form stable F+P organization. The threaded steel produced by the present application currently uses the V micro-alloying process, and the production control points of the process have been mastered to a certain extent, so that the addition amount of V alloy element can be accurately controlled, the mechanical property indexes are ensured, and the production cost is saved to the maximum. Since the compression amount of the large-size threaded steel is small, when designing the chemical composition of the billet, the influence of the chemical composition on the performance of the threaded steel should be fully considered. If the composition fluctuates greatly, the performance of the threaded steel below the size limit may be unqualified. Compared with small-size threaded steel, the contents of alloy elements such as V, Si and Mn should be appropriately increased. Based on the experience data of φ40mm threaded steel, the corresponding chemical composition of φ50mm threaded steel HRB600 is formulated through regression analysis. C: 0.25%-0.28%, Si: 0.55%-0.75%, Mn: 1.5%-1.6%, P, S≤0.04%, V: 0.11%-0.13%, Ceq: 0.52%-0.57%.

[0042] Vanadium element precipitates fine and uniform VC, VN precipitates in the austenite matrix, enhances the dislocation pinning effect of the grain boundary and the matrix, greatly improves the yield strength (≥600 MPa) and tensile strength, while maintaining good elongation (≥11%); the fine-grain strengthening effect of vanadium can effectively inhibit the austenite grain growth, and accelerate the γ→α phase transition, reduce the tendency of bainite and martensite formation, realize the stable microstructure mainly of ferrite + pearlite (F+P), reduce the dendritic and banded segregation. The fine and uniform precipitates and the optimized F+P structure greatly improve the toughness and plasticity of the matrix, reduce the risk of brittle fracture at the stress concentration site, and ensure that the φ50mm large size threaded steel does not produce cracks in the cold bending test (5D bending). Through the accurate regression analysis and proportioning of the contents of V, Si, Mn and other elements (C0.25%-0.28%, Si0.55%-0.75%, Mn1.5%-1.6%, V0.11%-0.13%), the performance fluctuation caused by low compression ratio is effectively offset, and the lower limit size steel bar can also be stabilized to meet the standard; at the same time, with the mature control experience of V micro-alloying process, the minimum alloying amount is realized, so as to reduce the alloy cost.

[0043] As an embodiment of the present application, it is specified that the continuous casting and pouring (155mm square billet) superheat is in the range of 10-25℃, the ladle cover heat preservation is used in cooperation with the continuous casting and pouring with low superheat, the casting speed is controlled to be not more than 4.0m / min, and the development of columnar crystal of the casting billet is avoided.

[0044] The superheat of molten steel is strictly controlled in the range of 10-25℃ and the ladle top cover heat preservation is used in cooperation, which can reduce the shell-steel interface temperature difference, make the primary grain of the casting billet more equiaxed, and reduce the formation of long columnar crystal structure; the moderate superheat and the casting speed of ≤4.0m / min can slow down the solidification speed gradient, reduce the dendritic segregation, and obtain more dense and uniform solidification structure, which improves the subsequent rolling performance; the refined and uniform microstructure of the casting billet reduces the existence of dendritic segregation and fragile structure zone, and the matrix toughness is better during cold bending forming, so that the crack generation rate is greatly reduced. Controlling the superheat and casting speed can stabilize the casting billet temperature field and the movement of the solidification front, reduce the casting billet cracking, shrinkage and other defects, and improve the consistency and qualification rate of the continuous casting-rolling process. Improving the internal quality of the casting billet makes the subsequent hot rolling process more smooth, reduces the rolling resistance fluctuation and product rejection rate caused by poor structure, and saves material and energy cost.

[0045] As an embodiment of the present application, in the rolling process, the soaking temperature is an important factor affecting the homogenization degree of austenite grains, and there are mainly two aspects to be considered, one is that the soaking temperature has an important influence on the austenite grain size and homogenization, that is, the higher the soaking temperature, the larger the austenite grain, and the uneven distribution; the second is that the soaking temperature also has a greater influence on the solid solubility of micro-alloying elements, and the relationship between the solid solubility product of micro-alloying elements and temperature needs to be considered to set the soaking temperature. Therefore, the soaking temperature needs to be considered in combination with the solid solubility of micro-alloying elements and the austenite homogenization, so as to obtain uniformly distributed austenite grains, and then rolling. In addition, when the heating temperature is low and the holding time is short, the uniform diffusion of the structure is not sufficient, and it is easy to retain developed dendritic structure. Therefore, the reasonable heating temperature and holding time are the key factors to eliminate the dendritic structure of the steel bar. After comprehensive consideration, the temperature of the φ50mm specification billet soaking section is controlled at 1120-1180℃, the billet discharge temperature is uniform, the temperature difference along the length direction of the billet is not more than 30℃, and the furnace time is not less than 120 minutes.

[0046] The soaking temperature is controlled in the range of 1120-1180℃, and the holding time of ≥120min is ensured, so that the grains are fully recrystallized and grown at high temperature, but excessive coarsening is avoided within a controllable range, so that fine and uniformly distributed austenite structure is obtained. Within this temperature-time window, the solid solubility product of micro-alloying elements such as V and N is effectively utilized to promote the full dissolution of micro-alloying elements in the austenite matrix; sufficient holding time and uniform temperature field can eliminate the primary dendrite and banded segregation structure, so that the chemical composition and structure inside the billet are more homogeneous, laying a foundation for the mechanical properties of the finished product after rolling; the billet discharge temperature difference ≤30℃ ensures the consistency of the temperature of each part, the rolling resistance is stable, the power peak value and equipment impact are reduced, the service life of the rolling mill is prolonged and the rolling stability is improved. Uniform austenite grains and micro-alloy distribution ensure that the strength, plasticity and cold bending performance of the rolled thread steel are uniform and stable, and the performance fluctuation and finished product rejection rate are significantly reduced.

[0047] As an embodiment of the present application, the groove system design is carried out on the basis of considering the groove commonality, the rolling passes are 12, the rough rolling 6 passes are flat roll design. The middle rolling 6 passes, the 7-10 frames use the existing groove, the 11-12 frames redesign the groove. In this way, not only the investment of process spare parts such as rollers and guides is saved, but also the material shape is stable, and the smooth development and production is ensured. In order to increase the relative area of the bottom circle in the steel bar and improve the engineering ability index of the performance of the steel bar, the base circle diameter D is 48.5 mm. The cross rib height: not only the service life of the groove is considered, but also the factors such as milling slot processing, roller consumption, steel weight deviation and cross rib fullness are considered. Therefore, the cross rib height is h = standard size + (0.1-0.3 mm). In the cold bending process, the steel bar is subjected to bending stress due to the action of bending moment, so that the external surface tension of the bending part of the bent steel bar is greatly increased. The existence of this tensile stress makes the plasticity and toughness of the cross rib root part far less than that of the base circle part, and the anti-fracture ability is greatly reduced, and the cold bending is prone to cracking. Therefore, the α angle value needs to be appropriately reduced to 50°, with the reduction of the α angle, the positive pressure value is also reduced, the bending stress value is reduced; the shear stress is also reduced, so the stress concentration is alleviated, which can effectively reduce the cold bending cracking phenomenon. For the same specification steel bar, the front slip value increases with the increase of the base circle, and with the reduction of the angle β between the cross rib and the axis, the influence of the front slip on the metal wear of the cross rib is also reduced, so the β angle value needs to be appropriately reduced to 50°. The K2 before the finished product adopts a flat oval groove, which can force the metal to flow transversely, so as to increase the cross rib width of the finished product, and ensure that the cross rib is full and the size is qualified. In addition, the flat oval groove can also increase the stability of the elliptical rolled piece in the groove, reduce the impact of the head of the rolled piece on the finished product groove, and reduce the process waste in rolling as much as possible.

[0048] In the 12 passes, the first 6 passes adopt general flat rolls, the 7-10 frames use existing grooves, and the 11-12 frames are only redesigned for large specification threads, so that the types and inventory of spare parts such as rollers and guides are significantly reduced, saving equipment procurement and maintenance costs; considering the arrangement of general and special grooves, not only the consistency of the material shape in different rolling stages is ensured, but also the process interruption and correction caused by frequent roller replacement are avoided, ensuring the smooth switching between development and mass production stages; the base circle diameter is optimized to 48.5 mm, increasing the relative area of the bottom circle in the cross section and improving the effective working cross section of the steel bar, so that it exhibits higher bearing capacity and yield strength under stress; the cross rib height is controlled within the standard size + 0.1 mm ~ 0.3 mm, the α and β angle values are reduced to 50°, the normal pressure and shear stress concentration are reduced, the bending stress distribution is optimized, the risk of cross rib root cracking is greatly reduced, and the threaded steel is crack-free in the 5D cold bending test; the last two frames use flat oval grooves to force the transverse metal flow, which not only can increase the cross rib width and fullness, ensure the size qualification, but also can disperse the impact load, reduce the head erosion, prolong the service life of the groove and reduce the process waste rate.

[0049] Further, the 11-arch pass is as shown in Figure 1 The 12-arch pass is as shown in Figure 2

[0050] As an embodiment of the present application, the finishing rolling uses an emptying guide groove driven by 20 input rollers, which ensures that the roller bed has sufficient power and speed to separate the front and rear double lengths and transport the double lengths normally to the cooling bed.

[0051] The emptying guide groove driven synchronously by the 20 input rollers ensures that the rolled double lengths have sufficient traction and speed in the guide groove, so that the separated steel bars are not jammed and are smoothly transported to the cooling bed; the emptying guide groove is designed to effectively separate the front and rear double lengths, so as to avoid mutual entanglement or overlapping and reduce the risk of congestion and accumulation of the rolled material during the transportation process. The stable transportation rhythm and speed ensure the continuity of the cooling bed material receiving, so that the cooling process is more uniform and the temperature fluctuation caused by unstable material flow of the cooling bed is reduced.

[0052] The mechanical property test results of the steel produced by the method for producing high-strength HRB600E threaded steel according to the present application are as follows: the yield strength, tensile strength, maximum total elongation rate, etc. all meet the requirements. The finished product is not cracked after cold bending.

[0053]

[0054] The main functions of the present application are as follows:

[0055] By accurately adding V-N micro-alloy (V: 0.11%-0.13%), fine and uniform VC and VN precipitates are formed in the austenite matrix; the yield strength of the finished threaded steel is greater than or equal to 600 MPa, the tensile strength is greater than or equal to 800 MPa, the elongation rate is greater than or equal to 11%, the cold bending is not cracked, and the mechanical properties are stable to meet the requirements of HRB600 grade. The superheat degree of the molten steel is controlled at 10-25℃, the blank drawing speed is less than or equal to 4.0 m / min, the generation of columnar crystal and dendritic structure is inhibited; the soaking temperature is 1120-1180℃, the holding time is greater than or equal to 120 min, and the discharge temperature difference is less than or equal to 30℃, which not only ensures the refinement and uniformity of the austenite grains, but also promotes the full solid solution of the micro-alloy elements; the first 6 passes of the 12 passes share the flat roller, the existing passes 7-10, and the new flat oval pass 11-12, which greatly reduces the types and inventory of spare parts such as rollers and guides; the base circle diameter is 48.5 mm, the transverse rib height is equal to the standard plus 0.1-0.3 mm, and the alpha / beta angle is both 50°, which improves the engineering capability index and cold bending crack resistance, ensures the stability of the material shape and the forming quality; the emptying guide groove driven synchronously by the 20 input rollers ensures the stable separation and continuous transportation of the front and rear double lengths, avoiding entanglement, accumulation and friction scratches.

[0056] ​In summary, the person skilled in the art can make other corresponding transformation schemes according to the technical scheme and technical concept of the present application without creative mental labor after reading the present application file, and all of them belong to the protection scope of the present application.

Claims

1. A method for producing high-strength HRB600E threaded steel, characterized in that: The method for producing high-strength HRB600E threaded steel comprises: Follow these steps in order: Continuous casting and initial rolling: molten steel temperature 1503℃±5℃, casting speed ≤4.0m / min; Heating and soaking: heat the billet to 1120℃~1180℃, soak and keep warm for ≥120min, and the temperature difference out of the furnace is ≤30℃; Rolling: base diameter 48.5mm, transverse rib height = standard size + 0.1mm~0.3mm, α angle and β angle are both 50°; Cooling bed unloading: final rolling temperature 1070℃±10℃, rolling speed 4.0m / s~5.0m / s, after passing through the guide groove and being divided into strips, it is sent to the cooling bed; The components of HRB600E threaded steel bars are as follows by weight: C: 0.25%-0.28%, Si: 0.55%-0.75%, Mn: 1.5%-1.6%, P, S≤0.04%, V: 0.11%-0.13%, Ceq: 0.52%-0.57%.

2. The method for producing high-strength HRB600E threaded steel according to claim 1, characterized in that: The overheat degree of the continuously cast steel in the continuous casting and initial rolling steps is within the range of 10-25°C.

3. The method for producing high-strength HRB600E threaded steel according to claim 1, characterized in that: It also includes the argon blowing time ≥12 minutes during the process of steel tapping from the converter to the refining station, and the steel ladle is covered and kept warm before pouring.

4. The method for producing high-strength HRB600E threaded steel according to claim 1, characterized in that: The rolling steps include rough rolling and intermediate rolling. The six passes of rough rolling are designed with flat rolls. In the six passes, the 7th to 10th stands adopt the existing pass type, and the 11th to 12th stands adopt a redesigned pass type.

5. The method for producing high-strength HRB600E threaded steel according to claim 4, characterized in that: The finishing rolling in the rolling step uses an idle guide trough driven by 20 input rollers.

6. The method for producing high-strength HRB600E threaded steel according to claim 1, characterized in that: It also includes adding 95-105 tons of molten iron, the molten iron temperature is greater than 1280℃, and adding 20-25 tons of scrap steel.

7. The method for producing high-strength HRB600E threaded steel according to claim 6, characterized in that: It also includes the use of a high-drawing supplementary blowing process in converter smelting, with the final smelting molten steel composition being: C ≤ 0.015%; Si ≤ 0.003%; Mn ≤ 0.12%; P ≤ 0.025%; S ≤ 0.025%; and the final temperature being ≤ 1675°C.

8. The method for producing high-strength HRB600E threaded steel according to claim 1, characterized in that: It also includes the use of vanadium-nitrogen microalloying in converter steelmaking, which is added before 3 / 4 of the steel is tapped, 20 kg of silicon-calcium-barium deoxidizer, 20 kg of silicon-aluminum-barium deoxidizer, carbon powder, silicon-manganese alloy, silicon-ferroalloy, and vanadium-nitrogen alloy.

9. The method for producing high-strength HRB600E threaded steel according to claim 8, characterized in that: It also includes the steel being taken out of the converter and sent to the refining station for fine-tuning of the composition, the refining argon blowing time being greater than 12 minutes, and the covering of the molten steel ladle before being hoisted and then put on the platform for pouring.

10. The method for producing high-strength HRB600E threaded steel according to claim 1, characterized in that: In the cooling bed unloading step, the temperature of the terminal before being fed into the cooling bed is maintained at 650° C. to 700° C.

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