A method for preparing high-speed bar production nominal diameter 16-20mm HRB400E fine-grain high-toughness anti-seismic steel bar

Abstract

The application discloses a preparation method of high-speed bar production nominal diameter 16-20mm HRB400E fine-grain high-toughness straight bar anti-seismic steel bar, a small amount of Cr is added in the steel, and a higher C content is controlled, so that the hardenability and secondary hardening effect are obviously improved, the pearlite content of a microstructure is further improved, the improvement of the tensile strength of the steel and the improvement of the anti-seismic performance are promoted, and the passivation corrosion resistance of the steel is also improved. The steel bar produced by the preparation method has the advantages of excellent and stable process mechanical properties, fine and uniform microstructure, good plasticity and toughness, excellent anti-seismic performance and corrosion resistance, and the like, and the indexes are all better than GB / T 1499.2-2018, and the production cost is reduced by 60 yuan / t compared with the existing vanadium micro-alloying process 钢 The above significantly improves the market competitiveness of the nominal diameter 16-20mm HRB400E straight bar anti-seismic steel bar, and has remarkable economic and social benefits.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel smelting, and particularly relates to a preparation method of high-speed bar production HRB400E fine-grain high-toughness anti-seismic steel bars with a nominal diameter of 16-20 mm. BACKGROUND

[0002] At present, domestic production of HRB400E straight ribbed steel bars basically adopts vanadium-nitrogen micro-alloying process or niobium micro-alloying process. When HRB400E is produced by using the vanadium micro-alloying process, the V content in the steel is mostly controlled at 0.018-0.030 wt%; when HRB400E is produced by using the niobium micro-alloying process, the Nb content in the steel is mostly controlled at 0.015-0.025 wt%. The straight HRB400E steel bars produced by using the vanadium micro-alloying process or the niobium micro-alloying process through control of rolling temperature and rolling passes meet the requirements of GB / T 1499.2-2018 standard in macroscopic metallography, cross-section Vickers hardness and microstructure. When HRB400E is produced by using the vanadium micro-alloy or the niobium micro-alloy, the production cost is relatively high due to the addition of a certain amount of valuable vanadium alloy or niobium alloy in the steel, which is not conducive to the reduction of production cost of the steel bar enterprise and the improvement of product market competitiveness.

[0003] The application aims to provide a preparation method of HRB400E fine-grain high-toughness anti-seismic steel bars with a nominal diameter of 16-20 mm produced by high-speed bar production at a low cost. SUMMARY

[0004] The application aims to provide a preparation method of HRB400E fine-grain high-toughness anti-seismic steel bars with a nominal diameter of 16-20 mm produced by high-speed bar production.

[0005] The application is achieved in the following manner: a preparation method of HRB400E fine-grain high-toughness anti-seismic steel bars with a nominal diameter of 16-20 mm produced by high-speed bar production is achieved in the following steps:

[0006] A, smelting of molten steel: respectively according to the following mass ratios, the cold charge is loaded in the proportion of 165-175 kg / t 钢 , 10 kg / t 钢 , the following mass ratio of scrap and pig iron is added in the LD converter; then the molten iron is loaded in the LD converter according to the loading ratio of 880 kg / t 钢 , the temperature of the molten iron is greater than or equal to 1310 DEG C; after the scrap, pig iron and molten iron are mixed into the LD converter, the conventional top and bottom combined blowing is carried out, the conventional lime and light-burned dolomite are added for slagging, the lime addition amount is 18-20 kg / t 钢 , the light-burned dolomite addition amount is 17-20 kg / t 钢, control the end point carbon content ≥ 0.07wt%, tapping temperature ≤ 1650℃; before tapping, add active lime to the bottom of the ladle for slag washing, lime addition amount is 1.5kg / t 钢 ; during tapping, adopt full-range bottom blowing nitrogen process, nitrogen flow rate is controlled to be 25-30NL / min;

[0007] B, deoxidation alloying: after tapping the molten steel, when the amount of molten steel in the ladle is greater than 1 / 4, add the following substances to the ladle in the following deoxidation alloying sequence: low-silicon deoxidizer→ferrosilicon→silicon-manganese alloy→high-carbon chromium iron, add the following low-silicon deoxidizer with the mass ratio of CaC2 61.5wt%, Si 4.7wt%, C 4.8wt%, P 0.045wt%, S 0.063wt%, and the rest being unavoidable impurities, in an amount of 1.0kg / t 钢 ; add the following ferrosilicon with the mass ratio of Si 72.3wt% and the rest being Fe and unavoidable impurities, in an amount of 0-2.2kg / t 钢 ; add the following silicon-manganese alloy with the mass ratio of Mn 65.8wt%, Si 17.6wt%, C 1.6wt%, and the rest being Fe and unavoidable impurities, in an amount of 18.2-20.5kg / t 钢 ; add the following high-carbon chromium iron with the mass ratio of Cr 55.7wt%, C 7.5wt%, and the rest being Fe and unavoidable impurities, in an amount of 1.6-2.7kg / t 钢 ; add the above-mentioned alloys when the amount of molten steel in the ladle reaches 4 / 5; after tapping is completed, the molten steel is hoisted to the argon station for refining treatment;

[0008] C, argon station refining of molten steel: the molten steel is hoisted to the argon station and connected to the nitrogen gas belt, nitrogen gas with a flow rate of 30-40NL / min is used to blow nitrogen to the molten steel, the blowing time is 6 minutes, then the molten steel is hoisted to the casting station after adding the molten steel covering agent in an amount of 1.0kg / t 钢 ;

[0009] D, molten steel casting: under the conditions of a tundish temperature of 1530-1540℃, a withdrawal speed of 3.0-3.2m / min, a crystallizer cooling water flow rate of 145-155m 3 / h, and a secondary cooling water amount of 1.8-2.0L / kg, the molten steel of step C is cast into a billet with a section of 165mm x 165mm by using a R12m straight-arc continuous straightening 7-machine 7-stream small square billet caster; the casting billet straightening temperature after leaving the straightening machine is controlled to be ≥980℃;

[0010] E, billet heating: the billet of step D is sent into a heating furnace with a furnace temperature of 1070-1120 DEG C in a soaking section, heated for 60 minutes, and the billet is discharged at a temperature of 970-1000 DEG C, and then pushed to a full continuous bar mill for rolling;

[0011] F, controlled rolling and controlled cooling of the billet: the billet of step E is rolled by a rough rolling mill at a rolling speed of 0.4-1.4 m / s for 6 passes; then the rolled piece is rolled by a medium rolling mill at a rolling speed of 2.0-3.6 m / s for 4 passes; then the rolled piece is rolled by a pre-precision rolling mill at a rolling speed of 4.4-9.2 m / s for 6 passes; then the rolled piece enters a pre-precision rolling control cooling device through 3 groups of water cooling devices with a length of 6 m respectively, and the cooling water flow is 70-90 m 3 / h, and the temperature of the rolled piece entering the first group of precision rolling is controlled at 840-860 DEG C; then the rolled piece is rolled by the first group of precision rolling mill at a rolling speed of 12.0-17.0 m / s for 1-2 passes; before the rolled piece enters the second group of precision rolling mill, it is controlled by 2 groups of water cooling devices with a length of 5 m respectively, and the cooling water flow is 80-90 m 3 / h, and the temperature of the rolled piece entering the second group of precision rolling is controlled at 840-860 DEG C; then the rolled piece is rolled by the second group of precision rolling mill at a rolling speed of 18.0-22.0 m / s for 2 passes; after precision rolling, the rolled piece is controlled by 2 groups of water cooling devices with a length of 7 m respectively, and the cooling water flow is 40-50 m 3 / h; after controlled cooling, the rolled piece is naturally air-cooled to room temperature on a cooling bed, and a nominal diameter of 16-20 mm HRB400E fine-grained high-toughness anti-seismic steel bar is obtained.

[0012] The preparation method of the present application adds a small amount of Cr in the steel and controls a higher C content, and the hardenability and secondary hardening effect are obviously improved, the microstructure of pearlite is further improved, the improvement of the tensile strength of the steel and the improvement of the anti-seismic performance are promoted, and the passivation corrosion resistance of the steel is also improved.

[0013] The steel is rolled at a lower opening rolling temperature; after pre-precision rolling, the rolled piece is controlled at a lower temperature entering the precision rolling by using a longer water cooling device; after the rolled piece enters the precision rolling, the rolled piece is rolled by two groups of precision rolling mills, and a longer water cooling device is used for controlling the cooling between the first group and the second group of precision rolling; after precision rolling, a longer water cooling device is used for controlling the cooling; by using the multiple graded limited cooling process of pre-precision rolling control cooling, precision rolling mill control cooling and post-precision rolling control cooling, the original austenite grains are significantly refined, the nucleation position and nucleation rate of ferrite grains are greatly increased, the ferrite grains are significantly refined, the grain size is above 11.0, the fine-grain strengthening effect is significant, the strength of the steel is greatly improved, and the plasticity and toughness of the steel are improved.

[0014] The preparation method of the nominal diameter 16-20 mm HRB400E fine-grain anti-seismic steel bar has the characteristics of low production cost and strong controllability, and fully plays the role of ferrite grain refinement strengthening through the integrated innovation of chemical composition design, converter smelting, deoxidation alloying structure, continuous casting, rolling heating system, pre-precision rolling, finishing rolling unit and controlled cooling process after finishing rolling. The produced steel bar has excellent and stable process mechanical properties, fine and uniform microstructure, good plasticity and toughness, excellent anti-seismic performance and corrosion resistance, and the like. The various indexes are superior to GB / T 1499.2-2018, and the production cost is reduced by 60 yuan / t compared with the existing vanadium micro-alloying process 钢 The above significantly improves the market competitiveness of the nominal diameter 16-20 mm HRB400E straight bar anti-seismic steel bar, and has significant economic and social benefits. DETAILED DESCRIPTION

[0015] The application will be further described in detail below in combination with examples, but the application is not limited in any way by the examples. Any transformation or improvement based on the teaching of the application falls within the protection scope of the application.

[0016] The application is a preparation method of a nominal diameter 16-20 mm HRB400E fine-grain high-toughness anti-seismic steel bar for high-speed bar production, which is realized according to the following steps:

[0017] A, molten steel smelting: respectively according to 165-175 kg / t 钢 , 10 kg / t 钢 of cold charge loading ratio, the following mass ratio of scrap steel and pig iron is added in the LD converter; then according to the loading ratio of 880 kg / t 钢 , the molten iron is loaded into the LD converter: the temperature of the molten iron is greater than or equal to 1310 DEG C; after the scrap steel, pig iron and molten iron are mixed into the LD converter, the conventional top and bottom combined blowing is carried out, the conventional lime and light-burned dolomite are added for slagging, the lime addition amount is 18-20 kg / t 钢 , the light-burned dolomite addition amount is 17-20 kg / t 钢 , the control end point carbon content is greater than or equal to 0.07wt%, and the tapping temperature is less than or equal to 1650 DEG C; before tapping, active lime is added to the bottom of the ladle for slag washing, and the lime addition amount is 1.5 kg / t 钢 ; the nitrogen blowing process is adopted during the whole tapping process, and the nitrogen flow is controlled to be 25-30 NL / min;

[0018] B, deoxidation alloying: the molten steel is tapped, when the amount of molten steel in the ladle is greater than 1 / 4, the following deoxidation alloying sequence is used: low-silicon deoxidizer→silicon iron→silicon manganese alloy→high-carbon chromium iron, and the following substances are sequentially added into the ladle: according to 1.0 kg / t 钢Add the following low-silicon deoxidizer in the specified mass ratio: CaC₂ 61.5wt%, Si 4.7wt%, C 4.8wt%, P 0.045wt%, S 0.063wt%, with the remainder being unavoidable impurities; at a rate of 0–2.2 kg / t. 钢 Add the following mass ratio of ferrosilicon: Si 72.3 wt%, the remainder being Fe and unavoidable impurities; at a rate of 18.2–20.5 kg / t. 钢 Add the following silicon-manganese alloy in the specified mass ratio: Mn 65.8wt%, Si 17.6wt%, C 1.6wt%, with the remainder being Fe and unavoidable impurities; at a concentration of 1.6–2.7 kg / t. 钢 Add the following high-carbon ferrochrome in the specified mass ratio: Cr 55.7wt%, C 7.5wt%, with the remainder being Fe and unavoidable impurities; add the above alloy when the ladle is 4 / 5 full; after tapping, hoist the molten steel to the argon station for refining.

[0019] C. Steel refining at the argon station: The molten steel is hoisted to the argon station and connected to the nitrogen supply. Nitrogen is then purged at a flow rate of 30–40 NL / min for 6 minutes. Afterward, a covering agent is added at a rate of 1.0 kg / t. 钢 Then the molten steel is hoisted to the casting station;

[0020] D. Steel casting: The tundish temperature is 1530–1540℃, the casting speed is 3.0–3.2 m / min, and the coolant flow rate in the crystallizer is 145–155 m³ / min. 3 Under the conditions of 1.8~2.0L / kg for secondary cooling water, the molten steel from step C is cast into steel billets with a cross section of 165mm×165mm using a 7-strand small square billet casting machine with a 7-machine R12m straight arc continuous straightening machine; the straightening temperature of the billet exiting the straightening machine is controlled at ≥980℃.

[0021] E. Steel billet heating: The steel billet from step D is sent into a heating furnace with a soaking temperature of 1070-1120℃ and heated for 60 minutes. The steel billet exit temperature is 970-1000℃, and then pushed to a fully continuous bar mill for rolling.

[0022] F. Controlled Rolling and Cooling of Steel Billets: The steel billets from step E are rolled for 6 passes on a roughing mill at a speed of 0.4–1.4 m / s; then, the billets are rolled for 4 passes on an intermediate mill at a speed of 2.0–3.6 m / s; finally, the billets are rolled for 6 passes on a pre-finishing mill at a speed of 4.4–9.2 m / s; before entering the finishing mill, the billets are controlled-cooled by three 6-meter-long water-cooling devices with a cooling water volume of 70–90 m³ / s. 3 / h, the temperature of the rolled piece entering the second finishing rolling group is controlled at 840-860°C; then the rolled piece is rolled for 2 passes at a rolling speed of 18.0-22.0 m / s; after the finishing rolling, the rolled piece is cooled by two groups of water cooling devices with a length of 7 m each, and the cooling water flow rate is 40-50 m 3 / h, the temperature of the rolled piece entering the second finishing rolling group is controlled at 840-860°C; then the rolled piece is rolled for 2 passes at a rolling speed of 18.0-22.0 m / s; after the finishing rolling, the rolled piece is cooled by two groups of water cooling devices with a length of 7 m each, and the cooling water flow rate is 40-50 m 3 / h; after the controlled cooling, the rolled piece is naturally air-cooled on the cooling bed to room temperature, and the HRB400E fine-grained high-toughness anti-seismic steel bar with a nominal diameter of 16-20 mm is obtained.

[0023] In step A, the chemical composition of the scrap steel is C 0.07-0.26wt%, Si 0.12-0.55wt%, Mn 0.35-1.55wt%, P 0.020-0.045wt%, S 0.014-0.045wt%, and the rest is Fe and inevitable impurities.

[0024] In step A, the chemical composition of the pig iron is C 3.0-3.2wt%, Si 0.30-0.50wt%, Mn 0.35-0.48wt%, P 0.078-0.110wt%, S 0.020-0.042wt%, and the rest is Fe and inevitable impurities.

[0025] In step A, the chemical composition of the pig iron is C 3.0-3.2wt%, Si 0.30-0.50wt%, Mn 0.35-0.48wt%, P 0.078-0.110wt%, S 0.020-0.042wt%, and the rest is Fe and inevitable impurities.

[0026] The secondary cooling water ratio in step D refers to the ratio of the total water consumption of the secondary cooling zone of the continuous casting machine per unit time to the mass of the casting blank passing through the secondary cooling zone per unit time, in L / kg, which is an index of the secondary cooling water spraying intensity of the continuous casting.

[0027] In step F, the temperature of the steel bar on the cooling bed is controlled at 820-850°C.

[0028] The application further provides the high-speed bar production HRB400E fine-grain high-toughness anti-seismic steel rod with a nominal diameter of 16-20 mm prepared by the preparation method, which has the following chemical components in percentage by weight: C 0.22-0.25wt%, Si 0.25-0.40wt%, Mn 1.20-1.35wt%, Cr 0.12-0.18wt%, S≤0.045wt%, P≤0.045wt%, and the rest is Fe and inevitable impurities; and the process mechanical properties, microstructure and Vickers hardness difference of the steel rod are shown in Table 1 and Table 2.

[0029] Table 1 Process mechanical properties of the HRB400E fine-grain anti-seismic steel rod with a nominal diameter of 16-20 mm produced by the application

[0030]

[0031] Table 2 Metallographic structure and Vickers hardness of the HRB400E fine-grain anti-seismic steel rod with a nominal diameter of 16-20 mm produced by the application

[0032]

[0033] The application is further described below in combination with examples.

[0034] Example 1

[0035] A, smelting of molten steel: respectively according to the cold material loading ratio of 165kg / t 钢 , 10kg / t 钢 , the following mass ratio of scrap steel (chemical components: C 0.07wt%, Si 0.12wt%, Mn 0.35wt%, P 0.020wt%, S 0.014wt%, and the rest is Fe and inevitable impurities) and pig iron (chemical components: C 3.0wt%, Si 0.30wt%, Mn 0.35wt%, P 0.078wt%, S 0.020wt%, and the rest is Fe and inevitable impurities) are added into the LD converter; then according to the hot metal loading ratio of 880kg / t 钢 , the following hot metal with temperature and mass ratio is loaded into the LD converter: hot metal temperature 1310℃, hot metal components C 4.4wt%, Si 0.25wt%, Mn 0.30wt%, P 0.080wt%, S 0.018wt%, and the rest is Fe and inevitable impurities; after the scrap steel, pig iron and hot metal are mixed into the LD converter, the conventional top and bottom combined blowing is carried out, the conventional lime and light-burned dolomite are added for slagging, the lime adding amount is 18kg / t 钢 , and the light-burned dolomite adding amount is 17kg / t 钢, the terminal carbon content is controlled to be 0.07wt%, and the tapping temperature is 1640℃; before tapping, active lime is added to the bottom of the ladle for slag washing, and the lime addition amount is 1.5kg / t 钢 ; during tapping, the whole process is carried out by bottom blowing nitrogen process, and the nitrogen flow is controlled to be 25NL / min.

[0036] B, deoxidation and alloying: after the molten steel in step A is finished, the molten steel is tapped, when the amount of molten steel in the ladle is greater than 1 / 4, the following deoxidation and alloying sequence is used: low-silicon deoxidizer→ferrosilicon→silicon-manganese alloy→high-carbon chromium iron, the following substances are sequentially added to the ladle: 1.0kg / t 钢 of low-silicon deoxidizer with the following mass ratio is added: CaC261.5wt%, Si 4.7wt%, C 4.8wt%, P 0.045wt%, S 0.063wt%, and the rest is unavoidable impurities; 18.2kg / t 钢 of ferrosilicon with the following mass ratio is added: Mn 65.8wt%, Si 17.6wt%, C 1.6wt%, and the rest is Fe and unavoidable impurities; 1.6kg / t 钢 of high-carbon chromium iron with the following mass ratio is added: Cr 55.7wt%, C 7.5wt%, and the rest is Fe and unavoidable impurities; the above-mentioned alloy is added when the amount of molten steel in the ladle reaches 4 / 5; after the tapping is finished, the molten steel is lifted to the argon station for refining treatment.

[0037] C, argon station refining of molten steel: the molten steel is lifted to the argon station and connected to the nitrogen belt, nitrogen with a flow rate of 30NL / min is used to blow nitrogen to the molten steel, the blowing nitrogen time is 6 minutes, then the molten steel is lifted to the casting station after the covering agent is added in an amount of 1.0kg / t 钢 .

[0038] D, molten steel casting: under the conditions of a tundish temperature of 1540℃, a withdrawal speed of 3.0m / min, a crystallizer cooling water flow rate of 145m 3 / h, and a secondary cooling water amount of 2.0L / kg, the molten steel in step C is cast into a billet with a section of 165mm×165mm by using a R12m straight-arc continuous straightening 7-machine 7-stream small billet caster; the casting billet is straightened at a temperature of 980℃.

[0039] E, billet heating: the billet in step D is sent to a heating furnace with a furnace temperature of 1070℃, and heated for 60 minutes, and then pushed to a full continuous bar mill for rolling after the billet temperature is 970℃.

[0040] F, controlled rolling and controlled cooling of the billet: the billet of step E is rolled through a rough rolling mill set under rolling conditions of a speed of 0.6-1.4 m / s for 6 passes; then the rolled piece is rolled through a medium rolling mill set under rolling conditions of a speed of 2.2-3.6 m / s for 4 passes; then the rolled piece is rolled through a pre-precision rolling mill set under rolling conditions of a speed of 4.8-9.2 m / s for 6 passes; then the rolled piece enters a pre-precision cooling through 3 groups of water cooling devices with a length of 6 m respectively before entering the precision rolling, with a cooling water flow of 70 m 3 / h, and the temperature of the rolled piece entering the first group of precision rolling is controlled at 860℃; then the rolled piece is rolled through the first group of precision rolling mill set under rolling conditions of a speed of 12.0-17.0 m / s for 2 passes; the rolled piece enters the second group of precision rolling mill set under rolling conditions of a speed of 22.0 m / s for 2 passes before entering the second group of precision rolling; after the precision rolling, the rolled piece is cooled through 2 groups of water cooling devices with a length of 5 m respectively after the precision rolling, with a cooling water flow of 80 m 3 / h, and the temperature of the rolled piece entering the second group of precision rolling is controlled at 860℃; then the rolled piece is rolled through the second group of precision rolling mill set under rolling conditions of a speed of 22.0 m / s for 2 passes; after the precision rolling, the rolled piece is cooled through 2 groups of water cooling devices with a length of 7 m respectively after the precision rolling, with a cooling water flow of 40 m 3 / h; after the controlled cooling, the temperature of the rebar on the cooling bed is controlled at 850℃, and then the rebar is naturally air-cooled to room temperature on the cooling bed, thereby obtaining the nominal diameter 16 mm HRB400E fine-grained high-toughness anti-seismic rebar, which has the following weight percentage chemical components: C 0.22wt%, Si 0.25wt%, Mn 1.20wt%, Cr 0.12wt%, S 0.022wt%, P 0.021wt%, and the rest is Fe and unavoidable impurities, and the process mechanical properties, microstructure, and Vickers hardness difference thereof are shown in Table 3 and Table 4.

[0041] Table 3 Process mechanical properties of the nominal diameter 16 mm HRB400E straight anti-seismic rebar produced in Example 1

[0042]

[0043] Table 4 Metallographic structure and Vickers hardness of the nominal diameter 16 mm HRB400E straight anti-seismic rebar produced in Example 1

[0044]

[0045] Example 2

[0046] A, smelting of the molten steel: respectively according to 170 kg / t 钢 , 10 kg / t 钢The cold charge is prepared by adding the following mass ratio of scrap steel (chemical composition: C 0.20wt%, Si 0.35wt%, Mn 1.35wt%, P 0.032wt%, S 0.028wt%, the remainder being Fe and unavoidable impurities) and pig iron (chemical composition: C 3.1wt%, Si 0.40wt%, Mn 0.42wt%, P 0.098wt%, S 0.032wt%, the remainder being Fe and unavoidable impurities) and pig iron (chemical composition: C 3.1wt%, Si 0.40wt%, Mn 0.42wt%, P 0.098wt%, S 0.032wt%, the remainder being Fe and unavoidable impurities) to the LD converter; then, at a rate of 880 kg / t 钢 The following iron molten metal was charged into the LD converter at the following temperature and mass ratio: molten metal temperature 1325℃, iron composition C 4.6wt%, Si 0.32wt%, Mn 0.40wt%, P 0.090wt%, S 0.028wt%, with the remainder being Fe and unavoidable impurities; after the scrap steel, pig iron, and molten iron were added to the LD converter, conventional top and bottom combined blowing was carried out, with conventional lime and lightly calcined dolomite added for slag formation, the lime addition amount being 20kg / t. 钢 The amount of lightly calcined dolomite added is 19 kg / t. 钢 The final carbon content was controlled at 0.09 wt%, and the tapping temperature was 1645℃. Before tapping, active lime was added to the bottom of the ladle for slag washing, with an addition rate of 1.5 kg / t. 钢 The steel tapping process adopts a full bottom-blowing nitrogen process, with the nitrogen flow rate controlled at 30 NL / min.

[0047] B. Deoxidation and Alloying: After tapping the molten steel from step A, when the amount of molten steel in the ladle is greater than 1 / 4, add the following substances to the ladle in the following deoxidation and alloying sequence: low-silicon deoxidizer → ferrosilicon → ferrosilicon-manganese alloy → high-carbon ferrochrome, at a rate of 1.0 kg / t. 钢 Add the following low-silicon deoxidizer in the specified mass ratio: CaC2 61.5wt%, Si 4.7wt%, C 4.8wt%, P 0.045wt%, S 0.063wt%, with the remainder being unavoidable impurities; at a rate of 1.2 kg / t. 钢 Add the following mass ratio of ferrosilicon: Si 72.3wt%, the remainder being Fe and unavoidable impurities; at a rate of 19.5 kg / t. 钢 The following mass ratio of silicon-manganese alloy was added: Mn 65.8wt%, Si 17.6wt%, C 1.6wt%, with the remainder being Fe and unavoidable impurities; at a rate of 2.1 kg / t. 钢 Add the following high-carbon ferrochrome in the specified mass ratio: Cr 55.7wt%, C 7.5wt%, with the remainder being Fe and unavoidable impurities; add the above alloy when the ladle is 4 / 5 full; after tapping, hoist the molten steel to the argon station for refining.

[0048] C. Argon station refining: the molten steel is lifted to the argon station and connected to the nitrogen gas pipe. Nitrogen gas with a flow rate of 35 NL / min is used to treat the molten steel. The nitrogen blowing time is 6 minutes. Then, the molten steel cover agent is added, and the amount is controlled to be 1.0 kg / t 钢 Then, the molten steel is lifted to the casting station.

[0049] D. Molten steel casting: under the conditions of a tundish temperature of 1535℃, a casting speed of 3.1 m / min, a crystallizer cooling water flow rate of 150 m 3 / h, and a secondary cooling water amount of 1.9 L / kg, the molten steel of step C is cast into a billet with a section of 165 mm x 165 mm by using a R12m straight arc continuous straightening 7-machine 7-stream small billet caster. The casting billet is straightened at a temperature of 1000℃.

[0050] E. Billet heating: the billet of step D is sent to a heating furnace with a furnace temperature of 1100℃. The billet is heated for 60 minutes, and the billet temperature is 985℃. Then, the billet is pushed to a full continuous bar mill for rolling.

[0051] F. Billet controlled rolling and controlled cooling: the billet of step E is rolled by a rough rolling mill group under the rolling conditions of a speed of 0.4-1.2 m / s for 6 passes. Then, the rolled piece is rolled by a medium rolling mill group under the rolling conditions of a speed of 2.0-3.4 m / s for 4 passes. Then, the rolled piece is rolled by a pre-precision rolling mill group under the rolling conditions of a speed of 4.4-9.0 m / s for 6 passes. Then, the rolled piece enters the pre-precision rolling controlled cooling by 3 groups of water cooling devices with lengths of 6 m respectively. The cooling water amount is 80 m 3 / h. The rolled piece enters the precision rolling group 1 under the rolling conditions of a speed of 12.0-17.0 m / s for 1 pass. The rolled piece enters the precision rolling group 2 controlled cooling by 2 groups of water cooling devices with lengths of 5 m respectively. The cooling water amount is 85 m 3 / h. The rolled piece enters the precision rolling group 2 under the rolling conditions of a speed of 20.0 m / s for 2 passes. The rolled material after precision rolling is controlled cooling by 2 groups of water cooling devices with lengths of 7 m respectively. The cooling water amount is 45 m 3 / h. The temperature of the reinforcing bar on the cooling bed after controlled cooling is controlled to be 835℃. Then, the reinforcing bar is naturally air-cooled to room temperature on the cooling bed. Thus, the HRB400E fine-grained high-toughness anti-seismic reinforcing bar with a nominal diameter of 18 mm is obtained. The chemical composition of the reinforcing bar is as follows: C 0.23wt%, Si 0.34wt%, Mn 1.28wt%, Cr 0.15wt%, S 0.035wt%, P 0.035wt%, and the rest is Fe and unavoidable impurities. The process mechanical properties, microstructure, and Vickers hardness difference of the reinforcing bar are shown in Tables 5 and 6.

[0052] Table 5. Mechanical properties of HRB400E straight seismic-resistant steel bars with a nominal diameter of 18mm produced in Example 2

[0053]

[0054] Table 6. Metallographic structure and Vickers hardness of HRB400E straight seismic-resistant steel bars with a nominal diameter of 18mm produced in Example 2.

[0055]

[0056] Example 3

[0057] A. Steel smelting: 175 kg / t 钢 10kg / t 钢 The cold charge ratio is as follows: In the LD converter, scrap steel (chemical composition: C 0.26wt%, Si 0.55wt%, Mn 1.55wt%, P 0.045wt%, S 0.045wt%, balance being Fe and unavoidable impurities) and pig iron (chemical composition: C 3.2wt%, Si 0.50wt%, Mn 0.48wt%, P 0.110wt%, S 0.042wt%, balance being Fe and unavoidable impurities) are added in the following mass ratio; then, at 880 kg / t... 钢 The following iron molten metal was charged into the LD converter at the specified temperature and mass ratio: molten metal temperature 1335℃, iron composition C 4.7wt%, Si 0.40wt%, Mn 0.50wt%, P 0.100wt%, S 0.040wt%, with the remainder being Fe and unavoidable impurities; after the scrap steel, pig iron, and molten iron were added to the LD converter, conventional top and bottom combined blowing was carried out, with conventional lime and lightly calcined dolomite added for slag formation, at a lime addition rate of 20 kg / t. 钢 The amount of lightly calcined dolomite added is 20 kg / t. 钢 The carbon content at the final stage is controlled at 0.10 wt%, and the tapping temperature is 1650℃. Before tapping, active lime is added to the bottom of the ladle for slag washing, with an addition amount of 1.5 kg / t. 钢 The steel tapping process adopts a full bottom-blowing nitrogen process, with the nitrogen flow rate controlled at 30 NL / min.

[0058] B. Deoxidation and Alloying: After tapping the molten steel from step A, when the amount of molten steel in the ladle is greater than 1 / 4, add the following substances to the ladle in the following deoxidation and alloying sequence: low-silicon deoxidizer → ferrosilicon → ferrosilicon-manganese alloy → high-carbon ferrochrome, at a rate of 1.0 kg / t. 钢Add the following low-silicon deoxidizer in the specified mass ratio: CaC2 61.5wt%, Si 4.7wt%, C 4.8wt%, P 0.045wt%, S 0.063wt%, with the remainder being unavoidable impurities; at a rate of 2.2 kg / t. 钢 Add the following mass ratio of ferrosilicon: Si 72.3wt%, the remainder being Fe and unavoidable impurities; at a rate of 20.5 kg / t. 钢 The following mass ratio of silicon-manganese alloy was added: Mn 65.8wt%, Si 17.6wt%, C 1.6wt%, with the remainder being Fe and unavoidable impurities; at a rate of 2.7 kg / t. 钢 Add the following high-carbon ferrochrome in the specified mass ratio: Cr 55.7wt%, C 7.5wt%, with the remainder being Fe and unavoidable impurities; add the above alloy when the ladle is 4 / 5 full; after tapping, hoist the molten steel to the argon station for refining.

[0059] C. Steel refining at the argon station: The molten steel is hoisted to the argon station and connected to the nitrogen supply. Nitrogen is then applied to the molten steel at a flow rate of 40 NL / min for 6 minutes. Afterward, a covering agent is added at a rate of 1.0 kg / t. 钢 Then the molten steel is hoisted to the casting station.

[0060] D. Steel casting: The tundish temperature is 1530℃, the casting speed is 3.2m / min, and the coolant flow rate in the crystallizer is 155m³ / min. 3 Under the conditions of 1.8 L / kg for secondary cooling water, the molten steel from step C is cast into steel billets with a cross section of 165 mm × 165 mm using a 7-strand small square billet casting machine with an R12 m straight arc continuous straightening machine; the straightening temperature of the billet exiting the straightening machine is controlled at 1010℃.

[0061] E. Billet heating: The billet from step D is sent into a heating furnace with a soaking temperature of 1120℃ and heated for 60 minutes. The billet exits at a temperature of 1000℃ and is then pushed to a fully continuous bar mill for rolling.

[0062] F. Controlled Rolling and Cooling of Steel Billets: The steel billets from step E are rolled for 6 passes on a roughing mill at a speed of 0.4–1.4 m / s; then, the billets are rolled for 4 passes on an intermediate mill at a speed of 2.0–3.6 m / s; finally, the billets are rolled for 6 passes on a pre-finishing mill at a speed of 4.4–9.2 m / s; before entering the finishing mill, the billets are controlled-cooled by three 6-meter-long water-cooling devices with a cooling water volume of 90 m³ / s. 3 / h, the temperature of the rolled piece entering the second finishing rolling group is controlled at 840°C; then the rolled piece is rolled for 2 passes at a rolling speed of 18.0 m / s through the second finishing rolling group; after finishing rolling, the rolled piece is controlled cooled by two groups of water cooling devices with a length of 7 m respectively, the cooling water amount is 50 m 3 / h, the temperature of the rolled piece entering the second finishing rolling group is controlled at 840°C; then the rolled piece is rolled for 2 passes at a rolling speed of 18.0 m / s through the second finishing rolling group; after finishing rolling, the rolled piece is controlled cooled by two groups of water cooling devices with a length of 7 m respectively, the cooling water amount is 50 m 3 / h; after controlled cooling, the temperature of the reinforcing bar on the cooling bed is controlled at 820°C, then the reinforcing bar is naturally air cooled to room temperature on the cooling bed, thus a nominal diameter 20 mm HRB400E fine-grained high-toughness anti-seismic reinforcing bar is obtained, which has the following chemical components in weight percentage: C 0.25wt%, Si 0.40wt%, Mn 1.35wt%, Cr 0.18wt%, S 0.045wt%, P 0.045wt%, the rest is Fe and inevitable impurities, the process mechanical properties, microstructure and Vickers hardness difference of the reinforcing bar are shown in Table 7 and Table 8.

[0063] Table 7 Process mechanical properties of the nominal diameter 20 mm HRB400E straight anti-seismic reinforcing bar produced in Example 3

[0064]

[0065] Table 8 Metallographic structure and Vickers hardness of the nominal diameter 20 mm HRB400E straight anti-seismic reinforcing bar produced in Example 3

[0066]

Claims

1. A method for producing high-speed bar production nominal diameter 16 ~ 20 mm HRB400E fine-grained high-toughness anti-seismic reinforcing steel, characterized in that, The following steps are implemented: A, molten steel smelting: respectively according to 165~175kg / t 钢 , 10kg / t 钢 The cold material is loaded in proportion, and the following mass ratio of scrap steel and pig iron is added in the LD converter; then according to the loading ratio of 880kg / t 钢 , the molten iron is loaded in the LD converter: the temperature of the molten iron is greater than or equal to 1310 DEG C; after the scrap steel, pig iron and molten iron are mixed into the LD converter, the conventional top and bottom combined blowing is carried out, the conventional lime and light-burned dolomite are added for slagging, the lime addition amount is 18~20kg / t 钢 , the light-burned dolomite addition amount is 17~20kg / t 钢 , the control end point carbon content is greater than or equal to 0.07wt%, and the tapping temperature is less than or equal to 1650 DEG C; before tapping, active lime is added to the bottom of the ladle for slag washing, and the lime addition amount is 1.5kg / t 钢 ; the whole process of bottom blowing nitrogen process is adopted in the tapping process, and the nitrogen flow is controlled to be 25~30NL / min; B, deoxidation alloying: the molten steel is tapped, when the amount of molten steel in the ladle is greater than 1 / 4, the following deoxidation alloying sequence is followed: low silicon deoxidizer→ferrosilicon→silicon manganese alloy→high carbon ferrochrome, the following substances are sequentially added to the ladle: 1.0 kg / t 钢 of low silicon deoxidizer with the following mass ratio: CaC2 61.5wt%, Si 4.7wt%, C 4.8wt%, P 0.045wt%, S 0.063wt%, and the rest is inevitable impurities; 0~2.2 kg / t 钢 of ferrosilicon with the following mass ratio: Si 72.3wt%, and the rest is Fe and inevitable impurities; 18.2~20.5 kg / t 钢 of silicon manganese alloy with the following mass ratio: Mn 65.8wt%, Si 17.6wt%, C 1.6wt%, and the rest is Fe and inevitable impurities; 1.6~2.7 kg / t 钢 of high carbon ferrochrome with the following mass ratio: Cr 55.7wt%, C 7.5wt%, and the rest is Fe and inevitable impurities; the above alloys are added when the amount of molten steel in the ladle reaches 4 / 5; after the tapping is completed, the molten steel is hoisted to the argon station for refining treatment; C. Argon station refining: the molten steel is lifted to the argon station and connected to the nitrogen gas pipe, and the nitrogen gas with a flow rate of 30-40 NL / min is turned on to treat the molten steel, the nitrogen blowing time is 6 minutes, then the molten steel covering agent is added, and the addition amount is controlled to be 1.0 kg / t 钢 Then the molten steel is lifted to the casting station; D, steel casting: in the tundish temperature is 1530~1540 ℃, the pulling speed is 3.0~3.2 m / min, the crystallizer cooling water flow is 145~155 m 3 / h, the secondary cooling specific water quantity is 1.8~2.0 L / kg, the steel of C step is cast into the billet with the section of 165 mm x 165 mm by using R12m straight arc continuous straightening 7-machine 7-flow small billet caster; the cast billet exit straightening temperature control is ≥980 ℃; E. Billet heating: the billet of step D is sent into a heating furnace with a furnace temperature of 1070-1120 °C in the soaking section, heated for 60 minutes, and the billet temperature is 970-1000 °C, then pushed to the full continuous bar mill for rolling; F, billet controlled rolling and controlled cooling: the billet of step E is rolled by 6 passes through a rough rolling mill set at a rolling speed of 0.4-1.4 m / s; then the rolled piece is rolled by 4 passes through a medium rolling mill set at a rolling speed of 2.0-3.6 m / s; then the rolled piece is rolled by 6 passes through a pre-precision rolling mill set at a rolling speed of 4.4-9.2 m / s; then the rolled piece enters a pre-precision cooling through 3 groups of water cooling devices with a length of 6 m respectively, and the cooling water amount is 70-90 m 3 / h, and the temperature of the rolled piece entering the first group of precision rolling is controlled at 840-860℃; then the rolled piece is rolled by 1-2 passes through the first group of precision rolling mill set at a rolling speed of 12.0-17.0 m / s; the rolled piece enters the second group of precision rolling mill through 2 groups of water cooling devices with a length of 5 m respectively, and the cooling water amount is 80-90 m 3 / h, and the temperature of the rolled piece entering the second group of precision rolling is controlled at 840-860℃; then the rolled piece is rolled by 2 passes through the second group of precision rolling mill set at a rolling speed of 18.0-22.0 m / s; the rolled piece is cooled through 2 groups of water cooling devices with a length of 7 m respectively after precision rolling, and the cooling water amount is 40-50 m 3 / h; and then the rolled piece is naturally air-cooled to room temperature on a cooling bed, thereby obtaining a HRB400E fine-grained high-toughness anti-seismic steel bar with a nominal diameter of 16-20 mm, which has the following chemical components by weight percentage: C 0.22-0.25 wt%, Si 0.25-0.40 wt%, Mn 1.20-1.35 wt%, Cr 0.12-0.18 wt%, S≤0.045 wt%, P≤0.045 wt%, and the rest is Fe and inevitable impurities.

2. The method for producing high speed rod production nominal diameter 16 ~ 20 mm HRB400E fine-grained high toughness anti-seismic steel bar according to claim 1, characterized in that, In step A, the chemical composition of the scrap steel is C 0.07-0.26wt%, Si 0.12-0.55wt%, Mn 0.35-1.55wt%, P 0.020-0.045wt%, S 0.014-0.045wt%, and the rest is Fe and unavoidable impurities.

3. The method according to claim 1, wherein the high-speed rod production of the nominal diameter 16-20 mm HRB400E fine-grained high-toughness anti-seismic reinforcing steel bar is characterized by, In step A, the chemical composition of the pig iron is C 3.0-3.2wt%, Si 0.30-0.50wt%, Mn 0.35-0.48wt%, P 0.078-0.110wt%, S 0.020-0.042wt%, and the rest is Fe and unavoidable impurities.

4. The method according to claim 1 for producing high speed bar of nominal diameter 16-20 mm HRB400E fine-grained high-toughness anti-seismic reinforcing steel, characterized in that, In step A, the chemical composition of the molten iron is C 4.4-4.7wt%, Si 0.25-0.40wt%, Mn 0.30-0.50wt%, P 0.080-0.100wt%, S≤0.040wt%, and the rest is Fe and unavoidable impurities; the temperature of the molten iron is ≥1310 °C.

5. The method for producing high speed rod production nominal diameter 16 ~ 20 mm HRB400E fine-grained high toughness anti-seismic steel bar according to claim 1, characterized in that, In step F, the temperature of the reinforcing bar on the cooling bed is controlled at 820-850 °C.

6. A high-speed bar production HRB400E fine-grained high-toughness anti-seismic reinforcing bar with a nominal diameter of 16-20 mm prepared by any of the preparation methods of claims 1-5.

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