400mpa grade anti-seismic steel bar and preparation method thereof

Abstract

The application provides a 400MPa-grade anti-seismic reinforcing steel bar and a preparation method thereof. The preparation method comprises the following steps: converter smelting, converter tapping, argon blowing, continuous casting and rolling. The anti-seismic reinforcing steel bar comprises the following components in percentage by weight: C: 0.22-0.26%, Si: 0.44-0.51%, Mn: 1.36-1.53%, Ti: 0.012-0.050%, S: 0.015-0.020%, P: 0.020-0.025%, and the rest is Fe and inevitable impurity elements. The structure and performance of the reinforcing steel bar can meet the requirements of HRB400E, the yield strength and tensile strength of the reinforcing steel bar are higher than 400MPa and 600MPa respectively, the mechanical properties are good, the ratio of strength to yield is greater than 1.25, the requirements of anti-seismic reinforcing steel bar are met, and the surface quality is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of metallurgy, and more particularly to a 400MPa grade anti-seismic steel bar and a preparation method thereof. BACKGROUND

[0002] In recent years, natural disasters such as earthquakes have occurred frequently all over the world, and engineering anti-seismicity is an important means to resist natural disasters. Hot-rolled ribbed steel bars are widely used in infrastructure, and their quality directly affects the use effect of buildings and is related to all aspects of people's safe life.

[0003] At present, vanadium and niobium are commonly used in screw steel in China, but the prices of vanadium and niobium are high, which leads to the problem of high cost of HRB400E steel bars. China is rich in titanium resources and the price is stable, which is one of the effective means to reduce the production cost of HRB400E steel bars. However, titanium element has active chemical properties and is easy to chemically react with O, N and S in steel, which will lead to unstable and low titanium yield in the smelting process. At present, titanium is generally added in the refining furnace for alloying, but the demand for ribbed anti-seismic steel bars is large, and the addition of titanium in the refining furnace for alloying will greatly increase the smelting cost and cycle of the steel, therefore, it is of great significance for enterprises to reduce cost and increase efficiency to develop a low-cost Ti micro-alloyed 400MPa grade anti-seismic steel bar production process without refining furnace and stable titanium yield. SUMMARY

[0004] In view of the deficiencies in the prior art, one of the purposes of the present application is to solve one or more problems in the prior art. For example, one of the purposes of the present application is to provide a 400MPa grade anti-seismic steel bar preparation method with low cost, good titanium yield stability and meeting the requirements of new national standard for anti-seismic steel bars.

[0005] One aspect of the present application provides a 400MPa grade anti-seismic steel bar preparation method, which can include the following steps: converter smelting, taking molten iron and scrap steel as raw materials, controlling the end point composition of smelting to be C: 0.05-0.12%, Mn≤0.20%, P≤0.035%, S≤0.03% by mass percentage, and the tapping temperature is 1600-1650℃; converter tapping, deoxidizing alloying and carbonizing during the tapping process; argon blowing, controlling the oxygen content of molten steel after entering the argon station to be 35.0-42.5ppm, adding titanium-containing materials 3-4min before the argon station, controlling the oxygen content after argon blowing to be 15.8-18.5ppm, the temperature of the argon station is 1570-1590℃, and after argon blowing, it is sent to continuous casting for casting; continuous casting, adopting full-process protective casting; rolling, heating the casting blank to 1140-1190℃, controlling the opening rolling temperature to be 1050-1100℃, and the temperature on the cooling bed is 890-1100℃, and the 400MPa grade anti-seismic steel bar is obtained after rolling.

[0006] Further, the 400MPa-grade anti-seismic reinforcing steel bar can include the following ingredients by weight percentage: C: 0.22-0.26%, Si: 0.44-0.51%, Mn: 1.36-1.53%, Ti: 0.012-0.050%, S: 0.015-0.020%, P: 0.020-0.025%, and the rest Fe and inevitable impurity elements.

[0007] Further, the deoxidization and alloying and carbonization can include sequentially adding silicon-calcium-barium alloy, ferrosilicon alloy, silicon-manganese alloy, silicon carbide, and carbonizer to the molten steel for deoxidization and alloying and carbonization.

[0008] Further, the ferrosilicon alloy can be added in an amount of 2 kg / t-2.5 kg / t, the silicon-manganese alloy can be added in an amount of 24 kg / t-25 kg / t, and the carbonizer can be added in an amount of 1-1.5 kg / t; when the content of the C component at the end of smelting is 0.05-0.07%, the silicon carbide can be added in an amount of 0.5-0.7 kg / t, and the silicon-calcium-barium alloy can be added in an amount of 0.9-1.1 kg / t; when the content of the C component at the end of smelting is greater than 0.07%, the silicon carbide can be added in an amount of 0.3-0.5 kg / t, and the silicon-calcium-barium alloy can be added in an amount of 0.9-1.1 kg / t.

[0009] Further, the argon blowing process can include blowing argon at a pressure of 0.8-1.0 MPa for not less than 1 min after the molten steel enters the argon station, adjusting the blowing to a medium gas amount at a pressure of 0.3-0.4 MPa after ensuring that the carbon, alloy, and top slag are well melted, fine-tuning the composition and temperature, and then adjusting to weak blowing at a pressure of 0.1-0.2 MPa, adding low-aluminum titanium-iron wire, and weak blowing for more than 5 min.

[0010] Further, the total argon blowing time can be 13-16 min.

[0011] Further, the titanium-containing material can be low-aluminum titanium-iron wire, the low-aluminum titanium-iron wire can be added in an amount of 1.5-1.6 m / t, the low-aluminum titanium-iron wire core powder can be 390-394 g / m, and the titanium content in the low-aluminum titanium-iron wire can be 67%-70%. For example, the low-aluminum titanium-iron wire can be added in an amount of 95-100 m, and the titanium content in the low-aluminum titanium-iron wire can be 68.3%.

[0012] Further, after adding the low-aluminum titanium-iron wire, 1-1.5 kg / t of carbonized rice husk can be added and the soft blowing time is kept for not less than 3 min.

[0013] Further, the continuous casting can include setting the casting speed to 2.10-2.60 m / min, the water flow in the crystallizer to 150-170 m 3 / h, the overheat degree of molten steel in the continuous casting process is controlled at 25-40 DEG C.

[0014] Further, the scrap steel ratio in the raw material can be 17-20%.

[0015] Another aspect of the present application provides a 400MPa grade anti-seismic reinforcing steel bar, characterized in that it comprises the following components by weight percentage: C: 0.22-0.26%, Si: 0.44-0.51%, Mn: 1.36-1.53%, Ti: 0.012-0.050%, S: 0.015-0.020%, P: 0.020-0.025%, and the rest is Fe and inevitable impurity elements.

[0016] Compared with the prior art, the beneficial effects of the present application at least include at least one of the following:

[0017] (1) The reinforcing steel bar of the present application can achieve the requirements of HRB400E in terms of microstructure and performance, and the yield strength and tensile strength thereof are above 400MPa and 600MPa respectively, the mechanical properties are good, the strength-yield ratio is greater than 1.25 to meet the requirements of anti-seismic reinforcing steel bar, and the surface quality is good.

[0018] (2) The component design of the present application uses the low-cost element Ti to replace Nb and V, thereby reducing the alloy cost, saving valuable alloy resources, and being conducive to sustainable development.

[0019] (3) The preparation method of the present application does not use a refining furnace, and titanium alloying is added at the argon blowing station, thereby greatly reducing the smelting cycle and time, having the advantage of simple process, and improving the market competitiveness of mass production of anti-seismic reinforcing steel bar. BRIEF DESCRIPTION OF DRAWINGS

[0020] The above and other objects and features of the present application will become more apparent from the following description made with reference to the accompanying drawings, in which:

[0021] Figure 1 Microstructure diagram of the reinforcing steel bar prepared in Example 1;

[0022] Figure 2 SEM diagram of the reinforcing steel bar prepared in Example 1;

[0023] Figure 3 Microstructure diagram of the reinforcing steel bar prepared in Example 2;

[0024] Figure 4 SEM diagram of the reinforcing steel bar prepared in Example 2;

[0025] Figure 5 Microstructure diagram of the reinforcing steel bar prepared in Example 3;

[0026] Figure 6SEM image of the reinforcing bar prepared for Example 3;

[0027] Figure 7 Tensile test curve of the reinforcing bar prepared for Example 2. DETAILED DESCRIPTION

[0028] Hereinafter, a 400MPa-grade anti-seismic reinforcing bar and a preparation method thereof according to the present application will be described in detail in conjunction with the accompanying drawings and exemplary embodiments.

[0029] An aspect of the present application provides a 400MPa-grade anti-seismic reinforcing bar preparation method, which may, in some embodiments, include the following steps:

[0030] S01, converter smelting, taking molten iron and scrap steel as raw materials, and controlling the end-point composition of smelting to be C: 0.05-0.12%, Mn≤0.20%, P≤0.035%, and S≤0.03% by mass percentage, and the tapping temperature to be 1600-1650℃.

[0031] S02, converter tapping, performing deoxidization alloying and carbon addition during tapping.

[0032] S03, argon blowing, controlling the oxygen content after the molten steel enters the argon station to be 35.0-42.5ppm, adding titanium-containing materials 3-4min before the argon station, controlling the oxygen content after argon blowing to be 15.8-18.5ppm, the temperature of the argon station to be 1570-1590℃, and sending the molten steel to continuous casting after argon blowing.

[0033] S04, continuous casting, adopting full-process protective casting.

[0034] S05, rolling, heating the casting blank to 1140-1190℃, controlling the opening rolling temperature to be 1050-1100℃, and the upper cooling bed temperature to be 890-1100℃, and obtaining the 400MPa-grade anti-seismic reinforcing bar after rolling.

[0035] In some embodiments, the temperature of the molten iron used as raw material can be controlled at 1340-1406°C, and the components of the molten iron include C: 5.0-5.15%, Si: 0.23-0.30%, Mn: 0.26-0.32%, and P≤0.14%, by mass, for example, C: 5.10-5.12%, Si: 0.25-0.28%, Mn: 0.27-0.30%, and P≤0.12%, by mass. In some embodiments, the mass ratio of scrap steel in the raw material can be 17-20%. For example, when the above molten iron is used as raw material, the mass ratio of scrap steel can be 17.6%, 18.5%, or 19.4%. Of course, the types and mass ratios of molten iron and scrap steel used in the present application can be adjusted according to the requirements of the end-point composition, and the end-point composition can be C: 0.05-0.12%, Mn≤0.20%, P≤0.035%, and S≤0.03%, by mass.

[0036] In some embodiments, limestone and light-burned dolomite can be added after the molten iron and scrap steel are melted into molten steel in the converter smelting process.

[0037] In some embodiments, the end-point composition of the converter smelting process can be C: 0.07-0.10%, Mn≤0.15%, P≤0.030%, and S≤0.025%, by mass, and the tapping temperature can be 1620-1645°C; or the end-point composition of the converter smelting process can be C: 0.08-0.09%, Mn≤0.12%, P≤0.028%, and S≤0.020%, by mass, and the tapping temperature can be 1625-1635°C, or a combination of the above ranges.

[0038] In the above, the control of the end-point carbon in the converter in step S01 can be a one-time hit. If the carbon content is higher than the control value, oxygen is used for supplementary blowing, and if the carbon content is lower than the control value, a carbon additive can be used to increase the carbon content. The converter uses a sub-lance to sample and measure C, S, and P in the molten steel, a total of two times, which are process sample TSC and end-point sample TSO. Generally, whether the composition meets the requirements of the converter process and whether measures are taken to adjust the elements are determined according to TSC.

[0039] According to the reaction equilibrium principle, with the decrease of carbon content in the steel, the oxygen content will inevitably increase, the oxygen content in the molten steel increases, the amount of deoxidizing modifier added in the converter tapping process increases, and the alloy yield is reduced due to alloy oxidation, which increases the alloy consumption; the high oxygen content of the molten steel in the converter is also more serious for the erosion of the converter lining, resulting in high consumption of the converter refractory; the high oxygen content of the molten steel leads to the increase of inclusions in the steel, which not only causes the casting nozzle to be blocked to affect the continuous casting performance, but also reduces the purity of the molten steel, which has an adverse effect on the internal quality of the steel, therefore, the end composition of smelting can be controlled as follows: C: 0.05-0.12%, Mn≤0.20%, P≤0.035%, S≤0.03%, and the tapping temperature is 1600-1650°C.

[0040] In some embodiments, the deoxidizing alloying and carbonizing process in the tapping process includes sequentially adding silicon calcium barium alloy, ferrosilicon alloy, silicon manganese alloy, silicon carbide, and carbonizing agent to the ladle for deoxidizing alloying and carbonizing. By sequentially adding the above-mentioned sequence of deoxidizing alloy and carbonizing agent, the oxygen content of the molten steel is controlled at 35.0-42.5 ppm before entering the argon station by first weak deoxidation. In certain embodiments, the addition amount of ferrosilicon alloy is 2 kg / t-2.5 kg / t, the addition amount of silicon manganese alloy is 24 kg / t-25 kg / t, and the addition amount of carbonizing agent is 1-1.5 kg / t; when the C mass fraction content of the end composition of smelting is 0.05-0.07%, the addition amount of silicon carbide can be 0.5-0.7 kg / t, and the addition amount of silicon calcium barium alloy can be 0.9-1.1 kg / t; when the C mass fraction content of the end composition of smelting is greater than 0.07%, the addition amount of silicon carbide can be 0.3-0.5 kg / t, and the addition amount of silicon calcium barium alloy can be 0.9-1.1 kg / t. The present application greatly controls the oxygen content of the molten steel (35.0-42.5 ppm) by adding the above-mentioned alloy deoxidizer, overcomes the problems of unstable Ti element yield in hot rolled steel bars, casting nozzle blockage, and continuous casting performance, and can ensure product performance. For example, the addition amount of ferrosilicon alloy is 2.1-2.4 kg / t, the addition amount of silicon manganese alloy is 24.2-24.8 kg / t, and the addition amount of carbonizing agent is 1.2-1.4 kg / t; when the C mass fraction content of the end composition of smelting is 0.05-0.07%, the addition amount of silicon carbide is 0.6 kg / t, and the addition amount of silicon calcium barium alloy is 1 kg / t; when the C mass fraction content of the end composition of smelting is greater than 0.07%, the addition amount of silicon carbide is 0.4 kg / t, and the addition amount of silicon calcium barium alloy is 1.05 kg / t. The above unit kg / t refers to the amount added per ton of converter tapping molten steel.

[0041] In some embodiments, after adding ferrosilicon alloy in the tapping process, calcium aluminate cleaner and lime can also be sequentially added to the ladle.

[0042] In some embodiments, the oxygen content after the molten steel enters the argon station can be 35.0-42.5 ppm, the low-aluminum titanium ferroline can be added 3-4 min before the argon station, the oxygen content after argon blowing can be controlled to be 15.8-18.5 ppm, and the temperature at the argon station can be 1570-1590°C. By adding low-aluminum titanium ferroline 3-4 min before the argon station, the Ti oxidation loss can be effectively reduced, and the Ti yield in the steelmaking stage can be significantly improved. For example, the oxygen content after the molten steel enters the argon station can be controlled to be 36.5-41.0 ppm, the low-aluminum titanium ferroline is added 3.5-3.8 min before the argon station, the oxygen content after argon blowing can be controlled to be 16.2-18.1 ppm, and the temperature at the argon station can be 1575-1585°C; or the oxygen content after the molten steel enters the argon station can be controlled to be 37.8-39.5 ppm, the low-aluminum titanium ferroline is added 3.6-3.7 min before the argon station, the oxygen content after argon blowing can be controlled to be 16.9-17.5 ppm, and the temperature at the argon station can be 1578-1582°C; or a combination of the above ranges. By setting the above argon blowing process, the molten steel can be boiled for refining, the chemical composition and temperature of the molten steel can be uniform, the chemical reaction can be accelerated, harmful gases and inclusions can be removed, and the molten steel can be purified.

[0043] In some embodiments, in order to better achieve the purpose of accelerating the chemical reaction, removing harmful gases and inclusions, purifying the molten steel, and achieving the requirement of the predetermined oxygen content of the molten steel, the argon blowing process can include: feeding an appropriate amount of carbon line according to the difference between the carbon content before argon blowing and the target composition, performing bottom strong argon blowing for not less than 1 min under a pressure of 0.8-1.0 mpa after entering the station, for example, strong blowing for 3-5 min, ensuring that the carbon powder, alloy, and top slag are well melted, then adjusting the bottom blowing to medium gas volume with a pressure of 0.3-0.4 mpa, and measuring the temperature and sampling, fine-tuning to the target composition, and keeping the temperature at 1580-1590°C, then adjusting the bottom blowing to weak blowing with a pressure of 0.1-0.2 mpa, feeding low-aluminum titanium ferroline at 1.5-1.6 m / t, wherein the low-aluminum titanium ferroline core powder is 390-394 g / m (for example, 392 g / m), the titanium content of the low-aluminum titanium ferroline is 67%-70% (for example, the content is 68.3%), adding 1-1.5 kg / t of carbonized rice husk, and keeping the soft blowing time for not less than 3 min with a pressure of 0.1-0.15 mpa, then exiting the station after adding carbonized rice husk according to the redness of the slag surface, and strictly prohibiting the liquid surface from being turned over after feeding the titanium ferroline.

[0044] In some embodiments, the total time of argon blowing can be 13-16 min. For example, the total time of argon blowing can be 14-15 min, or a combination of the above ranges.

[0045] In some embodiments, the continuous casting pouring process can include: setting the casting speed to 2.10-2.60 m / min, the water flow of the crystallizer to 150-170 m3 / h, and the superheat of the molten steel in the continuous casting process is controlled at 25-40°C. For example, the casting speed is set at 2.20-2.50 m / min, and the water flow rate of the mold is set at 155-167 m 3 / h, and the superheat of the molten steel in the continuous casting process is controlled at 28-37°C; or the casting speed is set at 2.35-2.45 m / min, and the water flow rate of the mold is set at 158-162 m 3 / h, and the superheat of the molten steel in the continuous casting process is controlled at 31-35°C; or a combination of the above ranges.

[0046] In some embodiments, the continuous casting process can further include: long nozzle protection casting between the ladle and the tundish, connecting the ladle and the tundish by the long nozzle to avoid direct contact of the molten steel with air. Submerged nozzle protection casting between the tundish and the mold, connecting the tundish and the mold by the submerged nozzle to avoid direct contact of the molten steel with air, wherein the insertion depth of the submerged nozzle can be 90-120 mm. A slide plate is arranged between the long nozzle and the bottom of the ladle, and between the submerged nozzle and the bottom of the tundish, and argon is blown at the slide plate surface to prevent air from entering, and the arrangement of the slide plate facilitates replacement of the ladle and the nozzle. Covering agent is added in the tundish after the start of the continuous casting to avoid contact of the molten steel with air and adsorption of inclusions. The argon flow rate in the ladle can be set at 130-180 L / min. For example, the flow rate can be set at 135-170 L / min, 142-162 L / min, 149-158 L / min, or a combination of the above ranges. After the above continuous casting process, the titanium yield is 50-60%, which has a good titanium yield.

[0047] In some embodiments, the rolling process can include heating the casting blank to 1140-1190°C, controlling the opening rolling temperature to be 1050-1100°C, and controlling the upper cooling bed temperature to be 890-1100°C. For example, the casting blank can be heated to 1145-1182°C, the opening rolling temperature can be controlled to be 1060-1090°C, and the upper cooling bed temperature can be controlled to be 895-1080°C; or the casting blank can be heated to 1150-1175°C, the opening rolling temperature can be controlled to be 1070-1080°C, and the upper cooling bed temperature can be controlled to be 950-1030°C; or a combination of the above ranges.

[0048] In some embodiments, the 400MPa grade anti-seismic reinforcing steel bar obtained by the above preparation method comprises the following ingredients by weight percentage: C: 0.22-0.26%, Si: 0.44-0.51%, Mn: 1.36-1.53%, Ti: 0.012-0.050%, S: 0.015-0.020%, P: 0.020-0.025%, and the rest is Fe and inevitable impurity elements. The microstructure of the anti-seismic reinforcing steel bar obtained above is composed of ferrite and pearlite, and no bainite structure is present. Controlling the content of titanium below 0.050% can avoid the appearance of bainite and the appearance of yield platform. For example, the 400MPa grade anti-seismic reinforcing steel bar comprises the following ingredients by weight percentage: C: 0.23-0.25%, Si: 0.47-0.50%, Mn: 1.39-1.48%, Ti: 0.013-0.045%, S: 0.016-0.015%, P: 0.021-0.024%, and the rest is Fe and inevitable impurity elements; or, the 400MPa grade anti-seismic reinforcing steel bar comprises the following ingredients by weight percentage: C: 0.23-0.24%, Si: 0.47-0.49%, Mn: 1.41-1.51%, Ti: 0.020-0.040%, S: 0.016-0.019%, P: 0.021-0.024%, and the rest is Fe and inevitable impurity elements.

[0049] In some embodiments, the size of the continuous casting billet can be 165mm x 165mm.

[0050] In some embodiments, the reinforcing steel bar can have a specification of Φ10-28mm. For example, the reinforcing steel bar can have a specification of Φ15mm, Φ18mm, Φ20mm or Φ25mm.

[0051] Another aspect of the present application provides a 400MPa grade anti-seismic reinforcing steel bar. In some embodiments, it can comprise the following ingredients by weight percentage: C: 0.22%-0.26%, Si: 0.44%-0.51%, Mn: 1.36%-1.53%, Ti: 0.012%-0.050%, S: 0.015%-0.020%, P: 0.020%-0.025%, and the rest is Fe and inevitable impurity elements. The microstructure of the 400MPa grade anti-seismic reinforcing steel bar is composed of ferrite and pearlite, and the yield and tensile strength thereof are above 400MPa and 600MPa respectively, the mechanical properties are good, and the strength-yield ratio is greater than 1.25.

[0052] In order to better understand the present application, the content of the present application is further illustrated below in combination with specific examples, but the content of the present application is not limited to the examples below.

[0053] Example 1

[0054] 400MPa grade anti-seismic steel bar and a preparation method thereof, which can comprise the following steps:

[0055] S1 steelmaking: molten iron and scrap steel are melted into molten steel in a 50-ton converter, lime blocks, light-burned dolomite are added, the smelting endpoint is C: 0.05%, Mn: 0.07%, P≤0.01%, S≤0.02%, and the tapping temperature is 1650℃. During tapping, silicon-calcium-barium alloy 50kg, ferrosilicon alloy 100kg, silicon-manganese alloy 1210kg, composite silicon carbide 30kg, and carbon additive 60kg are sequentially added to the ladle for deoxidation alloying and carbon addition. The ladle temperature is 804℃; after tapping is completed, the ladle is transported to the argon blowing station for argon blowing temperature adjustment and alloy fine adjustment.

[0056] S2 argon blowing: after the molten steel enters the argon station, the temperature is measured, the sample is taken, and the oxygen content is determined to be 36.8ppm; 26m of carbon wire is fed; the strong blowing is adjusted to weak blowing after the carbon powder, alloy, and top slag are well melted, and the temperature is measured and sampled; after the composition and temperature are fine adjusted, the strong blowing is adjusted to weak blowing for ≥1min, then 95m of low-aluminum titanium ferroline is fed 3min before the station is left, the core powder of the low-aluminum titanium ferroline is 392g / m, the titanium content of the low-aluminum titanium ferroline is 68.3%, 5 bags (each bag contains 10kg) of carbonized rice husk are added and the soft blowing time is maintained for 5min, and the carbonized rice husk is added in an appropriate amount according to the red leakage of the slag surface before the station is left, and the liquid surface is strictly prohibited from being turned over after the titanium ferroline is fed. The post-argon oxygen content is 16.8ppm, the total argon blowing time is 13min, and the station temperature is 1576℃.

[0057] S3 continuous casting: full-process protective casting is adopted. Long nozzle protective casting is used to connect the ladle and the tundish to avoid direct contact of the molten steel with air; submerged entry nozzle protective casting is used to connect the tundish and the mold to avoid direct contact of the molten steel with air; sliding plate argon blowing is used to set the sliding plate between the long nozzle and the bottom of the ladle and between the submerged entry nozzle and the bottom of the tundish, which is beneficial to the replacement of the ladle and the nozzle; argon is blown at the sliding plate surface to prevent air from entering; covering agent is added in the tundish after the continuous casting starts to avoid the contact of the molten steel with air and the adsorption of inclusions. The superheat is 32℃, the casting speed is 2.30m / min, and the mold water flow is 160cm 3 / h, and the rolled billet is obtained. The submerged entry nozzle insertion depth is 120mm, and the ladle argon flow rate is set to 130L / min. The titanium recovery rate after continuous casting is 55%.

[0058] S4 steel rolling: the cast billet is heated to 1170℃, the opening rolling temperature is 1075℃, and the upper cooling bed temperature is 894℃, and the Ti micro-alloyed 400MPa grade anti-seismic steel bar is prepared.

[0059] The chemical composition of the 400MPa grade anti-seismic reinforcing steel prepared in the embodiment is as follows in terms of mass percentage: C: 0.22%, Si: 0.47%, Mn: 1.47%, Ti: 0.022%, S: 0.017%, P: 0.021%, and the rest is Fe and inevitable impurity elements. The microstructure diagram is shown in Figure 1 , and the SEM is shown in Figure 2 , indicating that the reinforcing steel structure is ferrite and pearlite. The mechanical properties are shown in Table 1.

[0060] Example 2

[0061] The 400MPa grade anti-seismic reinforcing steel and the preparation method thereof can include the following steps.

[0062] S1 steelmaking: molten iron and scrap steel are melted into molten steel in a 50-ton converter, lime blocks, light-burned dolomite are added, and the smelting end point is C: 0.08%, Mn: 0.07%, P≤0.02%, S≤0.03%, and the tapping temperature is 1670℃. During tapping, silicon-calcium-barium alloy 50kg, ferrosilicon alloy 125kg, silicon-manganese alloy 1230kg, composite silicon carbide 35kg, and carbon additive 75kg are sequentially added to the ladle for deoxidization, alloying, and carbon addition; the ladle temperature is 825℃; after tapping is completed, the ladle is transported to the argon blowing station for argon blowing temperature adjustment and alloy fine adjustment.

[0063] S2 argon blowing: after the molten steel enters the argon station, the temperature is measured, the sample is taken, the oxygen is determined: 37.2ppm, the carbon wire is fed in 76m, the strong blowing is adjusted to≥1min after the carbon powder, alloy, and top slag are well melted, the bottom blowing is adjusted to weak blowing and the temperature is measured and sampled, the composition and temperature are fine adjusted, the strong blowing is≥1min, then the bottom blowing is adjusted to weak blowing, the low-aluminum titanium iron wire 97m is added 4min before the station, the low-aluminum titanium iron wire core powder is 392g / m, the titanium content of the low-aluminum titanium iron wire is 68.3%, 5 bags of carbonized rice husk are added and the soft blowing time is kept for 6min, the carbonized rice husk is added according to the red slag surface and the liquid surface is not allowed to be turned over after the titanium iron wire is fed. The post-argon oxygen is determined to be 17ppm, the total argon blowing time is 15min, the station temperature is 1588℃, and the molten steel is sent to continuous casting for casting.

[0064] S3 continuous casting: the whole process of continuous casting is protected casting. The long nozzle is used to connect the ladle and the tundish to avoid direct contact of the molten steel with air; the submerged entry nozzle is used to connect the tundish and the mold to avoid direct contact of the molten steel with air; the slide plate is used to blow argon gas to protect the long nozzle and the tundish, and the slide plate is used to replace the ladle and the nozzle; the argon gas is blown at the slide plate surface to prevent air from entering; the covering agent is added in the tundish after the continuous casting starts to avoid the molten steel from contacting air and absorbing inclusions. The superheat is 36℃, the casting speed is 2.30m / min, the mold water flow is 165m 3 / h, to obtain a rolling billet. The submerged nozzle insertion depth is 120 mm, and the argon flow rate of the ladle is set to 130 L / min. The titanium yield after continuous casting is 56%.

[0065] S4 Rolling: The billet is heated to 1175℃, the opening rolling temperature is 1078℃, and the upper cooling bed temperature is 894℃, to obtain a Ti micro-alloyed 400 MPa grade anti-vibration steel bar.

[0066] The chemical composition of the 400 MPa grade anti-vibration steel bar prepared in the example is as follows: C: 0.23%, Si: 0.47%, Mn: 1.44%, Ti: 0.028%, S: 0.016%, P: 0.022%, and the rest is Fe and inevitable impurity elements.

[0067] The microstructure diagram of the 400 MPa grade anti-vibration steel bar prepared in the example is shown in Figure 3 , and the SEM is shown in Figure 4 , indicating that the steel bar structure is ferrite and pearlite. The tensile test curve diagram of the 400 MPa grade anti-vibration steel bar prepared in the example is shown in Figure 7 , and the mechanical properties are shown in Table 1.

[0068] Example 3

[0069] The 400 MPa grade anti-vibration steel bar and the preparation method thereof can include the following steps:

[0070] S1 Steelmaking: The molten iron and scrap steel are melted into molten steel in a 50-ton converter, and lime blocks, light-burned dolomite are added. The smelting end point is C: 0.09%, Mn: 0.08%, P: 0.02%, S: 0.03%, and the tapping temperature is 1680℃. During tapping, silicon-calcium-barium alloy 45 kg, ferrosilicon alloy 120 kg, silicon-manganese alloy 1250 kg, composite silicon carbide 28 kg, and carbon additive 70 kg are sequentially added to the ladle for deoxidation alloying and carbon addition. The ladle temperature is 847℃. After tapping is completed, the ladle is transported to the argon blowing station for argon blowing temperature adjustment and alloy fine adjustment.

[0071] S2 Argon blowing: After the molten steel enters the argon station, the temperature is measured, the sample is taken, and the oxygen content is 39.7ppm. The carbon wire 126m is added, the strong blowing is ≥1min, and after ensuring that the carbon powder, alloy, and top slag are well melted, the bottom blowing is adjusted to weak blowing and the temperature is measured and sampled. After the composition and temperature are fine adjusted, the strong blowing is ≥1min, and then the bottom blowing is adjusted to weak blowing. The low-aluminum titanium iron wire 100m is fed 4min before the station is left, the low-aluminum titanium iron wire core powder is 392g / m, the titanium content of the low-aluminum titanium iron wire is 68.3%, 5 bags of carbonized rice husk are added and the soft blowing time is maintained for 7min. After the station is left, the carbonized rice husk is added according to the red appearance of the slag surface, and the liquid surface is strictly prohibited from being turned over after the titanium iron wire is fed. The oxygen content after argon is 17.5ppm, the total argon blowing time is 16min, the station temperature is 1585℃, and it is sent to continuous casting for casting.

[0072] S3 continuous casting: continuous casting is cast with full protection. Long nozzle protection casting, using long nozzle to connect the ladle and tundish, to avoid direct contact of molten steel with air; submerged entry nozzle protection casting, using submerged entry nozzle to connect the tundish and crystallizer, to avoid direct contact of molten steel with air; argon gas protection by slide plate, the slide plate is set between the long nozzle and the bottom of the ladle, and the submerged entry nozzle and the bottom of the tundish, the slide plate is beneficial to replace the ladle and the nozzle; argon protection is blown at the slide plate surface to prevent air from entering; after the start of continuous casting, covering agent is added in the tundish to avoid the contact of molten steel with air and the adsorption of inclusions. The superheat is 39℃, the pulling speed is 2.50m / min, and the crystallizer water flow is 166m 3 / h, to obtain a rolling billet. Among them, the submerged entry nozzle insertion depth is 120mm, and the argon flow of the ladle is set to 130L / min. The titanium recovery rate after continuous casting is 55%.

[0073] S4 rolling: the casting billet is heated to 1180℃, the opening rolling temperature is 1082℃, and the upper cooling bed temperature is 891℃, to obtain a Ti micro-alloyed 400MPa grade anti-vibration steel bar.

[0074] The chemical composition of the 400MPa grade anti-vibration steel bar prepared in the embodiment is as follows in terms of mass percentage: C: 0.26%, Si: 0.50%, Mn: 1.53%, Ti: 0.050%, S: 0.017%, P: 0.022%, and the rest is Fe and inevitable impurity elements. The microstructure diagram is as shown in Figure 5 , and the SEM is as shown in Figure 6 , which shows that the microstructure of the steel bar is ferrite and pearlite, and the mechanical properties are as shown in Table 1.

[0075] Table 1: Mechanical properties of the steel bars prepared in Examples 1-3

[0076]

[0077] As shown in Figures 1-7 and Table 1, the microstructure of the steel bars of Examples 1-3 of the present application is ferrite and pearlite, the yield strength and tensile strength are respectively above 400MPa and 600MPa, and the strength-yield ratio is greater than 1.25. Through the design of titanium micro-alloying composition, combined with the process parameter design of the converter steelmaking, argon blowing station, continuous casting and rolling process, the performance technical requirements can be met.

[0078] Although the present application has been described above by incorporating the exemplary embodiments, it should be clear to those skilled in the art that various modifications and changes can be made to the exemplary embodiments of the present application without departing from the spirit and scope defined by the claims.

Claims

1. A method for producing a 400 MPa grade earthquake resistant reinforcing bar, characterized by, The method comprises the following steps: converter smelting, taking molten iron and scrap steel as raw materials, and controlling the end composition of smelting to be C: 0.05% to 0.12%, Mn ≤ 0.20%, P ≤ 0.035%, and S ≤ 0.03% according to mass percentage, and the tapping temperature is 1600 ℃ to 1650 ℃; converter tapping, deoxidizing and alloying and carbonizing are carried out during the tapping process; argon blowing, controlling the oxygen content of molten steel after entering the argon station to be 35.0 ppm to 42.5 ppm, adding titanium-containing materials before the argon outlet station, controlling the oxygen content after argon blowing to be 15.8 ppm to 18.5 ppm, the temperature of the argon outlet station is 1570 ℃ to 1590 ℃, and after argon blowing, it is sent to continuous casting for casting; continuous casting, adopting full-process protective casting; rolling, heating the casting blank to 1140 ℃ to 1190 ℃, controlling the opening rolling temperature to be 1050 ℃ to 1100 ℃, and the upper cooling bed temperature to be 890 ℃ to 1100 ℃, and after rolling, the 400 MPa anti-seismic steel bar is obtained, wherein the 400 MPa anti-seismic steel bar comprises the following components according to mass percentage: C: 0.22% to 0.26%, Si: 0.44% to 0.51%, Mn: 1.36% to 1.53%, Ti: 0.012% to 0.050%, S: 0.015% to 0.020%, P: 0.020% to 0.025%, and the rest is Fe and inevitable impurity elements; deoxidizing and alloying and carbonizing include sequentially adding silicon calcium barium alloy, ferrosilicon alloy, silicon manganese alloy, silicon carbide, and carbonizer into the molten steel for deoxidizing and alloying and carbonizing; the adding amount of the ferrosilicon alloy is 2 kg / t to 2.5 kg / t, the adding amount of the silicon manganese alloy is 24 kg / t to 25 kg / t, and the adding amount of the carbonizer is 1 kg / t to 1.5 kg / t; when the content of C in the end composition of smelting is 0.05% to 0.07%, the adding amount of the silicon carbide is 0.5 kg / t to 0.7 kg / t, and the adding amount of the silicon calcium barium alloy is 0.9 kg / t to 1.1 kg / t; when the content of C in the end composition of smelting is greater than 0.07%, the adding amount of the silicon carbide is 0.3 kg / t to 0.5 kg / t, and the adding amount of the silicon calcium barium alloy is 0.9 kg / t to 1.1 kg / t.

2. The method of producing a 400 MPa grade earthquake resistant reinforcing steel according to claim 1, characterized by, the argon blowing process includes that after the molten steel enters the argon station, the bottom strong blowing pressure of argon gas is not less than 1 min at 0.8 MPa to 1.0 MPa, after ensuring that carbon, alloy and top slag are well melted, the strong blowing is adjusted to medium gas amount at a pressure of 0.3 MPa to 0.4 MPa, the composition and temperature are finely adjusted, and then the weak blowing is adjusted to a pressure of 0.1 MPa to 0.2 MPa, the low-aluminum titanium iron wire is added, and the weak blowing time is greater than 5 minutes.

3. The method of manufacturing a 400 MPa grade earthquake resistant reinforcing steel according to claim 1 or 2, c h a r a c t e r i z e d b y, the titanium-containing material is a low-aluminum titanium iron wire, the adding amount of the low-aluminum titanium iron wire is 1.5 m / t to 1.6 m / t, wherein the low-aluminum titanium iron wire core powder is 390 g / m to 394 g / m, and the titanium content of the low-aluminum titanium iron wire accounts for 67% to 70% by mass.

4. The method of producing a 400 MPa grade earthquake resistant reinforcing steel according to claim 3, characterized by, after the low-aluminum titanium iron wire is added, 1 kg / t to 1.5 kg / t of carbonized rice husk is further added, and the soft blowing time is kept to be greater than or equal to 3 min.

5. The method of manufacturing a 400 MPa grade earthquake resistant reinforcing steel according to claim 1, 2 or 4, characterised by, The continuous casting includes setting the casting speed to 2.10 m / min~2.60 m / min, the water flow of the crystallizer to 150 m 3 / h~170 m 3 / h, and controlling the superheat of the molten steel in the continuous casting process to 25°C~40°C.

6. The method of manufacturing a 400 MPa grade earthquake resistant reinforcing steel according to claim 1, 2 or 4, wherein, the mass percentage of scrap steel in the raw materials is 17% to 20%.

Images