A hot-rolled ribbed steel bar of HRB500E and its processing technology

Abstract

This invention relates to the field of metallurgical technology, and more particularly to an HRB500E hot-rolled ribbed steel bar and its processing technology. The composition of the HRB500E hot-rolled ribbed steel bar is: C: 0.22%~0.25%, Si: 0.65%~0.75%, Mn: 1.45%~1.57%, S: ≤0.045%, P: ≤0.045%, V: 0.045%~0.055%, 0.48≤Ceq≤0.54%. The rolling process includes: The process involves heating in a heating furnace, high-pressure water descaling, rough rolling, first fly shearing of the head and tail, intermediate rolling, controlled rolling, second fly shearing of the head and tail, finish rolling, controlled cooling, multiple-length fly shearing for segmentation, walking beam cooling, cold shearing for fixed length, chain-type collection, counting and bundling, and finished product collection. This invention applies controlled rolling and controlled cooling technology to the production of HRB500E products, ensuring a strength-to-yield ratio greater than 1.25, meeting the requirements for earthquake-resistant steel bars, while effectively reducing alloy costs and improving the overall performance of the product.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to an HRB500E hot-rolled ribbed steel bar and its processing technology. Background Technology

[0002] Due to its high strength, stringent national standards, and difficult production organization, HRB500E products suffer from unsatisfactory performance indicators and energy consumption, resulting in persistently high production costs. Controlled rolling and cooling technology can effectively reduce alloy production costs and energy consumption, representing an advanced steel rolling technology that saves alloys, simplifies production processes, and conserves energy. However, while controlled rolling and cooling technology offers advantages such as improved overall product performance and reduced alloy costs, it significantly impacts the yield strength of the steel, substantially reducing the strength-to-yield ratio. A strength-to-yield ratio greater than 1.25 is a basic requirement for seismic-resistant steel reinforcement. This ratio is already increasingly difficult to maintain as strength increases; the intervention of controlled rolling and cooling further reduces the ratio, making it impossible for HRB500E products to meet the requirements for seismic-resistant steel reinforcement. Therefore, conventional processes have been used to produce HRB500E products, achieving high strength and seismic resistance requirements by increasing alloy costs. Summary of the Invention

[0003] The purpose of this invention is to provide an HRB500E hot-rolled ribbed steel bar and its processing technology to solve the technical problems mentioned in the background.

[0004] A processing technology for HRB500E hot-rolled ribbed steel bars, wherein the composition of HRB500E hot-rolled ribbed steel bars is: C: 0.22%~0.25%, Si: 0.65%~0.75%, Mn: 1.45%~1.57%, S: ≤0.045%, P: ≤0.045%, V: 0.045%~0.055%, 0.48 ≤Ceq≤0.54%;

[0005] The rolling process includes: heating in a heating furnace, high-pressure water descaling, rough rolling, first fly shear head and tail, intermediate rolling, controlled rolling, second fly shear head and tail, finishing rolling, controlled cooling, multiple-length fly shear segmentation, walking beam cooling, cold shear fixed-length shearing, chain-type table collection, counting and bundling, and finished product collection.

[0006] The continuous casting billet has a size of 165mm×165mm×12m and enters the heating furnace for heating. The preheating section temperature (furnace temperature) is 500~1000℃, the heating section temperature is 1170~1210℃ (furnace temperature), and the soaking section temperature is 1210℃ (furnace temperature). The cross-sectional temperature difference of the continuous casting billet is ≤30℃. The furnace pressure is strictly controlled according to the micro-positive pressure control, and the positive pressure is controlled within 8Pa.

[0007] After the steel is tapped from the heating furnace, it enters a high-pressure water descaling process with a water pressure of 18-23 MPa. This process removes the iron oxide scale from the surface of the continuously cast billet, improving the surface quality of the product and facilitating the entry of the rolling mill.

[0008] The initial rolling temperature is controlled at 1030-1060℃. After entering the roughing mill, vertical-horizontal alternating rolling is adopted. After six roughing stands, the first flying shear is used to cut off the head and tail.

[0009] The rough-rolled workpiece has a circular cross-section of 71mm and enters the intermediate rolling mill for alternating vertical and horizontal rolling.

[0010] The intermediate rolling mill uses eight stands (the number of stands is selected according to the specifications), with alternating vertical and horizontal rolling, and pre-cutting rolling in the last pass;

[0011] After pre-cutting, the rolled pieces enter the controlled rolling device with a water pressure of 0.8 to 1.2 MPa. After being cooled by the controlled rolling device, the temperature of the rolled pieces is controlled at 920 to 950°C. After being cooled by controlled rolling, the pre-cut rolled pieces undergo a second flying shear at the head and tail before entering the finishing mill.

[0012] The finishing mill uses four stands (the number of stands is selected according to the specifications), and all rolling is done on a flat mill.

[0013] The first stand of the finishing mill uses slit rolling, while the next two stands use an elliptical-round hole system.

[0014] After the finished product is processed, a controlled cooling device is used for cooling. The controlled cooling device performs compensatory cooling according to the controlled cooling situation.

[0015] This scheme adopts a five-segment design, therefore the cooling line is divided into five segments; the cooling control device adopts segmented cooling with a water pressure of 1.5-1.8MPa and opening degrees of 15%, 25%, 55%, 25%, and 15% respectively, for targeted compensation cooling;

[0016] After being compensated by the cooling control device, the branch line temperatures are 930℃, 920℃, 890℃, 920℃, and 930℃ respectively. The central branch line has a high cooling intensity and a low temperature, while the edge branch line has a low cooling intensity and a high temperature, ensuring that the performance of each branch line fully meets the standards.

[0017] Furthermore, during the smelting process of HRB500E hot-rolled ribbed steel bars, the final carbon content is ≥0.07%, the final phosphorus content is 0.015%~0.008%, the final temperature is ≤1660℃, and the deoxidizer is 0.3kg / t of silicon-aluminum-calcium. The refining nitrogen blowing requirements are: after the composition is adjusted appropriately, soft blowing for 3 minutes, and the soft blowing requirements are: the diameter of the slag surface broken is 10~20cm. The initial temperature of the refining furnace after the furnace is ≥1570℃, the steel tapping temperature of the refining furnace is 1550~1555℃, the continuous casting platform temperature is 1540~1545℃, the tundish temperature is 1513~1525℃, and the average liquidus temperature is 1503℃.

[0018] A type of HRB500E hot-rolled ribbed steel bar, comprising: C: 0.22%~0.25%, Si: 0.65%~0.75%, Mn: 1.45%~1.57%, S: ≤0.045%, P: ≤0.045%, V: 0.045%~0.055%, 0.48 ≤Ceq≤0.54%; and manufactured using the aforementioned processing technology for HRB500E hot-rolled ribbed steel bars.

[0019] The beneficial effects of this invention are:

[0020] By employing this invention, controlled rolling and controlled cooling technology can be applied to the production of HRB500E products, ensuring that the product's strength-to-yield ratio is greater than 1.25, meeting the requirements for earthquake-resistant steel bars, while also effectively reducing alloy costs and improving the overall performance of the product. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] A processing technology for HRB500E hot-rolled ribbed steel bars, wherein the composition of HRB500E hot-rolled ribbed steel bars is: C: 0.22%~0.25%, Si: 0.65%~0.75%, Mn: 1.45%~1.57%, S: ≤0.045%, P: ≤0.045%, V: 0.045%~0.055%, 0.48 ≤Ceq≤0.54%;

[0023] The rolling process includes: heating in a heating furnace, high-pressure water descaling, rough rolling, first fly shear head and tail, intermediate rolling, controlled rolling, second fly shear head and tail, finishing rolling, controlled cooling, multiple-length fly shear segmentation, walking beam cooling, cold shear fixed-length shearing, chain-type table collection, counting and bundling, and finished product collection.

[0024] The continuous casting billet has a size of 165mm×165mm×12m and enters the heating furnace for heating. The preheating section temperature (furnace temperature) is 800℃, the heating section temperature is 1170℃ (furnace temperature), and the soaking section temperature is 1210℃ (furnace temperature). The cross-sectional temperature difference of the continuous casting billet is ≤30℃. The furnace pressure is strictly controlled according to the micro-positive pressure control, and the positive pressure is controlled within 8Pa.

[0025] After the steel is tapped from the heating furnace, it enters a high-pressure water descaling process at a pressure of 18MPa to remove the iron oxide scale from the surface of the continuous casting billet, thereby improving the surface quality of the product and facilitating the entry of the rolling mill.

[0026] The initial rolling temperature is controlled at 1030℃. The mill enters the roughing mill and uses alternating vertical and horizontal rolling. After six roughing stands, the first flying shear is used to cut off the head and tail.

[0027] The rough-rolled workpiece has a circular cross-section of 71mm and enters the intermediate rolling mill for alternating vertical and horizontal rolling.

[0028] The intermediate rolling mill uses eight stands (the number of stands is selected according to the specifications), with alternating vertical and horizontal rolling, and pre-cutting rolling in the last pass;

[0029] After pre-splitting, the rolled piece enters the controlled rolling device with a water pressure of 0.8 MPa. After being cooled by the controlled rolling device, the temperature of the rolled piece is controlled at 920℃. Due to the large width-to-height ratio of the pre-splitting rolled piece, the temperature of the edge of the cooled rolled piece is lower than that of the middle, resulting in a large temperature difference. Taking Φ12×5 five-splitting as an example, the width of the rolled piece reaches 81.29 mm, while the height is only 15.9 mm. Originally, the edges of this type of rolled piece are cooled more than the middle. However, due to the cooling by the controlled rolling device, the temperature difference in the width direction is further aggravated. The temperature difference of the pre-splitting rolled piece in the width direction is as high as about 70℃.

[0030] After being cooled by controlled rolling, the pre-cut rolled pieces undergo a second flying shearing of the head and tail before entering the finishing mill.

[0031] The finishing mill uses four stands (the number of stands is selected according to the specifications), and all rolling is done on a flat mill.

[0032] The first stand of the finishing mill uses slit rolling, while the next two stands use an elliptical-round hole system.

[0033] After the finished product is processed, a controlled cooling device is used for cooling. The controlled cooling device performs compensatory cooling according to the controlled cooling situation.

[0034] The controlled cooling system further exacerbated the temperature difference across the width of the pre-cut rolled piece, resulting in significant performance variations among the different cutting lines. The center line, with its higher temperature, exhibited a lower yield strength, while the edge lines, with their lower temperature, had a higher yield strength. To ensure minimum performance met standards, all cutting lines were cooled simultaneously. While this ensured the center line's yield strength met the standard, the edge lines, already having higher yield strengths due to controlled cooling, resulted in a yield strength-to-strength ratio of less than 1.25 under the same controlled cooling intensity, failing to meet the standard. Consequently, without controlled cooling, the center line's yield strength would be below 500 MPa, also failing to meet the standard; therefore, further controlled cooling is necessary.

[0035] The use of a controlled cooling device resulted in a yield strength ratio of less than 1.25, which does not meet the standard. Therefore, the controlled cooling device adopts a split-line cooling system. This solution uses a five-segment cooling system, so the split-line cooling is divided into five lines. The controlled cooling device uses split-line cooling with a water pressure of 1.5MPa and opening degrees of 15%, 25%, 55%, 25%, and 15% respectively, for targeted compensation cooling.

[0036] After being compensated and cooled by the cooling control device, the branch line temperatures are 930℃, 920℃, 890℃, 920℃, and 930℃ respectively. The central branch line has a high cooling intensity and a low temperature, while the edge branch line has a low cooling intensity and a high temperature, ensuring that the performance of each branch line fully meets the standards.

[0037] After cooling compensation by the controlled cooling device, the yield strength is between 535-570MPa, the yield strength ratio of the edge line is greater than 1.26, and the yield strength ratio of the middle lines is greater than 1.27. The performance meets the standard, and the alloy cost is significantly reduced.

[0038] After cooling compensation by the controlled cooling device, each branch line is cut to length in the third flying shear, and then enters the cooling bed for natural cooling, slowly cooling to below 250°C before being bundled and collected.

[0039] Furthermore, during the smelting process of HRB500E hot-rolled ribbed steel bars, the final carbon content is ≥0.07%, the final phosphorus content is 0.015%~0.008%, the final temperature is ≤1660℃, and the deoxidizer is 0.3kg / t of silicon-aluminum-calcium. The refining nitrogen blowing requirements are: after the composition is adjusted appropriately, soft blowing is carried out for 3 minutes, and the soft blowing requirement is: the diameter of the slag surface is 10cm. The initial temperature of the refining furnace after the furnace is ≥1570℃, the steel tapping temperature of the refining furnace is 1550℃, the continuous casting platform temperature is 1540℃, the tundish temperature is 1513℃, and the average liquidus temperature is 1503℃.

[0040] A type of HRB500E hot-rolled ribbed steel bar, comprising: C: 0.22%~0.25%, Si: 0.65%~0.75%, Mn: 1.45%~1.57%, S: ≤0.045%, P: ≤0.045%, V: 0.045%~0.055%, 0.48 ≤Ceq≤0.54%; and manufactured using the aforementioned processing technology for HRB500E hot-rolled ribbed steel bars.

[0041] By employing this invention, controlled rolling and controlled cooling technology can be applied to the production of HRB500E products, ensuring that the product's strength-to-yield ratio is greater than 1.25, meeting the requirements for earthquake-resistant steel bars, while also effectively reducing alloy costs and improving the overall performance of the product.

[0042] The specific embodiments described herein are merely illustrative examples illustrating the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the scope defined by the spirit of the invention.

Claims

1. A processing technology of HRB500E hot-rolled ribbed steel bars, characterized in that, the composition of the HRB500E hot-rolled ribbed steel bars comprises: C: 0.22% to 0.25%, Si: 0.65% to 0.75%, Mn: 1.45% to 1.57%, S: ≤0.045%, P: ≤0.045%, V: 0.045% to 0.055%, 0.48 ≤ Ceq ≤ 0.54%; the rolling process comprises: heating in a heating furnace, high-pressure water descaling, rough rolling, first flying shear cutting of head and tail, intermediate rolling, controlled rolling, second flying shear cutting of head and tail, finish rolling, controlled cooling, multiple flying shear segmentation, step-by-step cooling bed cooling, cold shear sizing cutting, chain type rack collection, counting and bundling, finished product collection; wherein during the smelting process of the HRB500E hot-rolled ribbed steel bars, the end-point carbon is ≥0.07, the end-point phosphorus is 0.015% to 0.008%, the end-point temperature is ≤1660℃, the deoxidizer is silicon-aluminum-calcium 0.3 kg / t; the nitrogen blowing requirement during the refining process is: after the composition is adjusted to be appropriate, soft blowing for 3 min, the soft blowing requirement is: the diameter of the broken slag surface is 10-20 cm; the initial temperature of the post-furnace refining furnace is ≥1570℃, the tapping temperature of the refining furnace is 1550-1555℃, the continuous casting platform temperature is 1540-1545℃, the tundish temperature is 1513-1525℃, and the average liquidus temperature is 1503℃; in the controlled cooling process, the controlled cooling device adopts split cooling, the water pressure is 1.5-1.8 MPa, and the opening degrees are 15%, 25%, 55%, 25% and 15% respectively for targeted compensation cooling. in the heating process in the heating furnace, the continuous casting billet specification is 165mm×165mm×12m; during the heating process, the furnace pressure is strictly controlled according to the micro-positive pressure, and the positive pressure is controlled within 8 Pa.

2. The processing process of the HRB500E hot-rolled ribbed steel bar according to claim 1, characterized in that, in the high-pressure water descaling step, the water pressure is 18-23 MPa.

3. The processing process of the HRB500E hot-rolled ribbed steel bar according to claim 1, characterized in that, the cross section of the rolled piece after the rough rolling is a 71mm diameter circular cross section.

4. The processing process of the HRB500E hot-rolled ribbed steel bar according to claim 1, characterized in that, the composition comprises: C: 0.22% to 0.25%, Si: 0.65% to 0.75%, Mn: 1.45% to 1.57%, S: ≤0.045%, P: ≤0.045%, V: 0.045% to 0.055%, 0.48 ≤ Ceq ≤ 0.54%; and the HRB500E hot-rolled ribbed steel bars are made by using the processing technology of the HRB500E hot-rolled ribbed steel bars according to any one of claims 1-4.

5. An HRB500E hot-rolled deformed steel bar, characterized in that, ​