Method for improving utilization of 180mpa grade phosphorus reinforced steel casting blank

Abstract

The application discloses a method for improving utilization rate of 180MPa phosphor reinforced steel casting blank, which realizes mutual judgment of the casting blank, improves the utilization rate, reduces the company fund occupation, and achieves the purpose of reducing the production cost of the phosphor reinforced steel by optimizing the component design of cold-rolled phosphor reinforced steel HC180Y and galvanized phosphor reinforced steel HX180YD+Z and reasonably adjusting the process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material forming, in particular to a method for improving utilization rate of 180MPa grade phosphorus reinforced steel casting blank. BACKGROUND

[0002] The hot storage length of strip steel is designed differently in the continuous annealing production line and the galvanizing production line of Baotou Steel, and the strip steel length in the furnace area of the continuous annealing production line is much greater than that of the galvanizing line, the strip steel length in the furnace area of the continuous annealing production line is greater than 240 meters, and the strip steel length in the furnace area of the galvanizing production line is less than 150 meters, and there is no overaging section, which results in different temperatures for cold hard strip steel to complete recovery recrystallization, and the performance of the same strength grade brand produced in the continuous annealing and galvanizing production lines has a large difference (the yield strength requirement is 180-240MPa, the yield strength of cold-rolled steel strip is 185-203MPa, and the yield strength of galvanized steel strip is 241-257MPa, which exceeds the standard requirement), and at present, the casting blank of 180MPa grade cold-rolled phosphorus reinforced steel cannot be applied to the galvanizing production line due to the design difference of the production line, and there is no way to change the other steel grades due to the high phosphorus content, so the smelting needs to be carried out separately according to the cold-rolled and galvanized contract, which results in an increase in mixed pouring blank, the utilization rate of the casting blank is only 50%, the inventory is stored for a long time, and the manufacturing cost is obviously increased. The present application optimizes the composition design of cold-rolled phosphorus reinforced steel HC180Y and galvanized phosphorus reinforced steel HX180YD+Z, and reasonably adjusts the process, realizes mutual change of the casting blank, improves the utilization rate, reduces the occupation of company funds, and achieves the purpose of reducing the production cost of phosphorus reinforced steel. SUMMARY

[0003] The purpose of the present application is to provide a method for improving the utilization rate of 180MPa grade phosphorus reinforced steel casting blank, so as to reduce the production cost of phosphorus reinforced steel.

[0004] To solve the above technical problems, the present application adopts the following technical scheme:

[0005] The present application provides a method for improving the utilization rate of 180MPa grade phosphorus reinforced steel casting blank, which comprises the following steps:

[0006] (1) the C content of the 180MPa grade phosphorus reinforced steel is controlled in the range of ≤0.003%, the Si content is controlled in the range of ≤0.04%, the Mn content is controlled in the range of 0.4-0.6%, the P content is controlled in the range of 0.03-0.04%, the S content is controlled in the range of ≤0.015%, the Ti content is controlled in the range of 0.04-0.06%, and the nitrogen content is controlled in the range of ≤0.004%;

[0007] (2) the hot rolling slab heating temperature is ≥1220℃, the finish rolling temperature is ≥900℃, and the coiling temperature is ≤600℃;

[0008] (3) the cold rolling reduction rate is ≥68%;

[0009] (4) After the production of the pickling and rolling process is completed, annealing is carried out in a cold rolling continuous annealing furnace, and the process parameters are as follows: the outlet temperature of the heating and soaking section is 750±10 DEG C, the outlet temperature of the slow cooling section is greater than or equal to 650 DEG C, the outlet temperature of the fast cooling section is less than or equal to 400 DEG C, the overaging section temperature is 200-350 DEG C, the outlet temperature of the final cooling section is less than or equal to 150 DEG C, the furnace zone speed is 120-160 m / min, and the elongation of the skin pass mill is 0.5-0.7%.

[0010] (5) After the production of the pickling and rolling process is completed, annealing and galvanizing are carried out in a galvanizing continuous annealing furnace, and the process parameters of the galvanizing process are as follows: the outlet temperature of the heating and soaking section is 780±10 DEG C, the outlet temperature of the slow cooling section is greater than or equal to 620 DEG C, the outlet temperature of the fast cooling section is less than or equal to 460 DEG C, the zinc pot temperature is 400-450 DEG C, the furnace zone speed is 75-120 m / min, and the elongation of the skin pass mill is 0.8-1.0%.

[0011] Further, the chemical composition of the 180MPa grade phosphorus reinforced steel is as follows: C: 0.0025%; Si: 0.02%; Mn: 0.51%; P: 0.04%; S: 0.008%; Ti: 0.04%; N: 0.0035%, and the rest is Fe and inevitable impurities.

[0012] Further, the chemical composition of the 180MPa grade phosphorus reinforced steel is as follows: C: 0.0020%; Si: 0.02%; Mn: 0.55%; P: 0.030%; S: 0.009%; Ti: 0.06%; N: 0.0020%, and the rest is Fe and inevitable impurities.

[0013] Further, the chemical composition of the 180MPa grade phosphorus reinforced steel is as follows: C: 0.0025%; Si: 0.02%; Mn: 0.59%; P: 0.035%; S: 0.006%; Ti: 0.05%; N: 0.0028%, and the rest is Fe and inevitable impurities.

[0014] Further, the 180MPa grade phosphorus reinforced steel is realized to be mutually judged by the cold rolling HC180Y and the galvanized HX180YD+Z cast billet, the utilization rate of the cast billet is increased from 50% to 90%, and the manufacturing cost of the 180MPa grade phosphorus reinforced steel is significantly reduced.

[0015] Compared with the prior art, the beneficial technical effects of the present application are as follows:

[0016] The present application realizes the mutual judgment of the cast billet by optimizing the composition design of the cold rolling phosphorus reinforced steel HC180Y and the galvanized phosphorus reinforced steel HX180YD+Z, reasonably adjusting the process, improving the utilization rate, reducing the company's capital occupation, and achieving the purpose of reducing the production cost of the phosphorus reinforced steel. DETAILED DESCRIPTION

[0017] A method for improving the utilization rate of 180MPa grade phosphorus reinforced steel casting blank, comprising:

[0018] (1) Steelmaking adopts the process flow of molten iron→ converter steelmaking→ RH refining→ slab continuous casting process. KR molten iron desulfurization technology is adopted, and the terminal sulfur content after deep desulfurization is required to be within 0.002%. After desulfurization is completed, the desulfurization slag is thoroughly removed, and the slag removal area is required to be greater than 95%. The converter turns over and the steel is discharged. In the process of discharging, the top slag modifier is added according to the oxygen content and the amount of slag in the converter to supply the RH with phosphorus content ≤0.06%. According to the composition and temperature of the steel supplied by the converter to the RH, deep decarburization treatment is carried out, and phosphorus iron alloy is added to adjust the composition to the target value. After decarburization is completed, aluminum particles are added according to the oxygen content for deoxidization and alloying, and after circulating for ≥4 minutes, metal manganese and titanium iron alloy are added to adjust the composition to the target value. After the composition is adjusted, the vacuum circulates for ≥6 minutes. The composition of the continuous casting steel is required to be: C content control range ≤0.003%, Si content control range ≤0.04%, Mn content control range 0.4-0.6%, P content control range 0.03-0.04%, S content control range ≤0.015%, Ti content control range 0.04-0.06%, and nitrogen content control range ≤0.004%. The casting machine adopts constant speed control, and protective casting is adopted.

[0019] (2) Hot rolling adopts step-by-step heating furnace to heat the casting blank, and the hot rolling slab heating temperature is ≥1220℃. F1-F7 continuous rolling process is adopted for finishing rolling, and the finishing rolling temperature is ≥900℃ to ensure single-phase austenite rolling. The phosphorus-added high-strength IF steel is prone to form FeTiP precipitated phase during production, which reduces the content of solid solution P element, and the solid solution strengthening effect is also weakened, so the strength and performance of the steel will also be reduced. To avoid the precipitation of the phase, the coiling temperature is ≤600℃.

[0020] (3) Acid pickling and continuous rolling are carried out, and the rolling reduction rate is ≥68%.

[0021] (4) After the acid rolling process is completed, annealing is carried out in the cold rolling continuous annealing furnace, and a reducing atmosphere and a nitrogen-hydrogen mixed protective atmosphere are used for cooling in the furnace. Because the storage capacity of the steel strip in the furnace area of the cold rolling annealing production line is greater than that of the galvanizing annealing production line, the steel strip stays in the furnace area for a longer time. In order to meet the requirements that the phosphorus reinforced steel with the same composition can be applied to each production line, a lower annealing temperature should be used. The outlet temperature of the heating and soaking section is 750±10℃, the outlet temperature of the slow cooling section is ≥650℃, the outlet temperature of the fast cooling section is ≤400℃, the overaging section temperature is 200-350℃, the final cooling section outlet temperature is ≤150℃, the furnace area speed is 120-160m / min, and the elongation rate of the flattening machine is shown in Table 1.

[0022] Table 1 Elongation rate of flattening machine

[0023]

[0024] (5) After the pickling process is completed, annealing and galvanizing are performed in a galvanizing continuous annealing furnace. Since the storage capacity of the steel strip in the furnace area of the cold rolling annealing production line is greater than that of the galvanizing annealing production line, the steel strip stays in the furnace area for a longer time. In order to meet the requirement that the phosphorus reinforced steel and the same composition cast slab can be applied to each production line, a higher annealing temperature should be used for galvanizing. The process parameters of the galvanizing process are as follows: the outlet temperature of the heating and soaking section is 780±10°C, the outlet temperature of the slow cooling section is ≥620°C, the outlet temperature of the fast cooling section is ≤460°C, the temperature entering the zinc pot is 400-450°C, the furnace area speed is 75-120 m / min, and the elongation of the skin pass mill is shown in Table 2.

[0025] Table 2 Elongation of skin pass mill

[0026]

[0027]

[0028] Example 1

[0029] The mass percentage of the components is as follows: [C]: 0.0025%; [Si]: 0.02%; [Mn]: 0.51%; [P]: 0.04%; [S]: 0.008%; [Ti]: 0.04%; [N]: 0.0035%.

[0030] Hot rolling: the hot rolling coil specification is 4.3×1285 mm, the hot rolling slab heating temperature is 1230°C, the finish rolling temperature is 900°C, and the coiling temperature is 540°C.

[0031] Pickling: the pickling reduction rate is 79%.

[0032] Cold rolling continuous annealing: after the pickling process is completed, annealing is performed in a cold rolling continuous annealing furnace. The outlet temperature of the heating and soaking section is 760°C, the outlet temperature of the slow cooling section is 680°C, the outlet temperature of the fast cooling section is 380°C, the overaging section temperature is 300°C, the outlet temperature of the final cooling section is 130°C, the furnace area speed is 155 m / min, and the elongation of the skin pass mill is 0.6%.

[0033] Galvanizing continuous annealing: after the pickling process is completed, annealing and galvanizing are performed in a galvanizing continuous annealing furnace. The outlet temperature of the heating and soaking section is 785°C, the outlet temperature of the slow cooling section is 650°C, the outlet temperature of the fast cooling section is 450°C, the temperature entering the zinc pot is 450°C, the furnace area speed is 85 m / min, and the elongation of the skin pass mill is 0.9%.

[0034] Mechanical properties of the cold rolled steel strip: finished product specification 0.9 x 1250 mm, yield strength 188 MPa, tensile strength 355 MPa, elongation 38.0%, n value 0.22, r value 2.3, performance meets the requirements of EN 10268-2006 standard (yield strength 180-240 MPa, tensile strength 340-400 MPa, elongation ≥ 36.0%, n value ≥ 0.19, r value ≥ 1.7).

[0035] Mechanical properties of the galvanized steel strip: yield strength 203 MPa, tensile strength 362 MPa, elongation 37.5%, n value 0.22, r value 2.2, performance meets the requirements of GB / T 2518-2008 standard (yield strength 180-240 MPa, tensile strength 340-400 MPa, elongation ≥ 34.0%, n value ≥ 0.18, r value ≥ 1.7).

[0036] Example 2

[0037] Mass percentage composition: [C]: 0.0020%; [Si]: 0.02%; [Mn]: 0.55%; [P]: 0.030%; [S]: 0.009%; [Ti]: 0.06%; [N]: 0.0020%.

[0038] Hot rolling: hot rolled coil specification 4.3 x 1285 mm, hot rolled slab heating temperature 1223°C, finish rolling temperature 915°C, coiling temperature 580°C.

[0039] Pickling: pickling reduction rate 79%.

[0040] Cold rolling and continuous annealing: after the pickling process is completed, annealing is carried out in the cold rolling and continuous annealing furnace, the outlet temperature of the heating and soaking section is 740°C, the outlet temperature of the slow cooling section is 660°C, the outlet temperature of the fast cooling section is 400°C, the overaging section temperature is 350°C, the outlet temperature of the final cooling section is 150°C, the furnace zone speed is 160 m / min, and the elongation of the skin pass mill is 0.6%.

[0041] Galvanizing and continuous annealing: after the pickling process is completed, annealing and galvanizing are carried out in the galvanizing and continuous annealing furnace, the outlet temperature of the heating and soaking section is 770°C, the outlet temperature of the slow cooling section is 620°C, the outlet temperature of the fast cooling section is 450°C, the temperature of entering the zinc pot is 420°C, the furnace zone speed is 120 m / min, and the elongation of the skin pass mill is 0.9%.

[0042] Mechanical properties of the cold rolled steel strip: finished product specification 0.9 x 1250 mm, yield strength 182 MPa, tensile strength 351 MPa, elongation 39.5%, n value 0.22, r value 2.4, performance meets the requirements of EN 10268-2006 standard (yield strength 180-240 MPa, tensile strength 340-400 MPa, elongation ≥ 36.0%, n value ≥ 0.19, r value ≥ 1.7).

[0043] Mechanical properties of the galvanized steel strip: yield strength 197 MPa, tensile strength 351 MPa, elongation 38.5%, n value 0.22, r value 2.3, performance meets the requirements of GB / T 2518-2008 standard (yield strength 180-240 MPa, tensile strength 340-400 MPa, elongation ≥ 34.0%, n value ≥ 0.18, r value ≥ 1.7).

[0044] Example 3

[0045] Mass percentage composition: [C]: 0.0025%; [Si]: 0.02%; [Mn]: 0.59%; [P]: 0.035%; [S]: 0.006%; [Ti]: 0.05%; [N]: 0.0028%.

[0046] Hot rolling: hot rolled coil specification 3.7 x 1255 mm, hot rolled slab heating temperature 1233°C, finish rolling temperature 925°C, coiling temperature 600°C.

[0047] Pickling: pickling reduction rate 81%.

[0048] Cold rolling and continuous annealing: annealing in the cold rolling and continuous annealing furnace after the pickling process, heating and soaking segment outlet temperature 753°C, slow cooling segment outlet temperature 660°C, fast cooling segment outlet temperature 370°C, overaging segment temperature 280°C, final cooling segment outlet temperature 140°C, furnace zone speed 120 m / min, skin pass mill elongation 0.5%.

[0049] Galvanizing and continuous annealing: annealing and galvanizing in the galvanizing and continuous annealing furnace after the pickling process, heating and soaking segment outlet temperature 783°C, slow cooling segment outlet temperature 680°C, fast cooling segment outlet temperature 430°C, zinc pot inlet temperature 420°C, furnace zone speed 100 m / min, skin pass mill elongation 0.8%.

[0050] The mechanical properties of the cold-rolled steel strip are as follows: finished product specification 0.7*1230mm, yield strength 197MPa, tensile strength 365MPa, elongation 38.5%, n value 0.22, and r value 2.3, which meet the requirements of the EN10268-2006 standard (yield strength 180-240MPa, tensile strength 340-400MPa, elongation ≥36.0%, n value ≥0.19, and r value ≥1.7).

[0051] The mechanical properties of the galvanized steel strip are as follows: yield strength 202MPa, tensile strength 359MPa, elongation 37.5%, n value 0.22, and r value 2.2, which meet the requirements of the GB / T 2518-2008 standard (yield strength 180-240MPa, tensile strength 340-400MPa, elongation ≥34.0%, n value ≥0.18, and r value ≥1.7).

[0052] In summary, since the cast blanks of the 180MPa grade cold-rolled phosphorus strengthened steel cannot be applied to the galvanizing production line due to the difference in production line design, and there is no way to change the judgment of other steel grades due to the high phosphorus content, the smelting needs to be carried out separately according to the cold-rolled and galvanized contracts during production, which leads to an increase in mixed pouring blanks, a cast blank utilization rate of only 50%, and a long inventory backlog time. The present application provides a method for improving the utilization rate of 180MPa grade phosphorus strengthened steel cast blanks, which includes controlling the smelting chemical composition, hot rolling process, pickling rolling process, cold rolling annealing process, and galvanizing annealing process, realizes the mutual change of the cold-rolled HC180Y and galvanized HX180YD+Z cast blanks, improves the cast blank utilization rate from 50% to 90%, and significantly reduces the manufacturing cost of the 180MPa grade phosphorus strengthened steel.

[0053] The above-described embodiments are only used to describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for improving the utilization of a 180 MPa grade phosphorus strengthened steel casting characterized in that, It comprises: (1) the 180MPa phosphorus reinforced steel smelting C content control range ≤0.003%, Si content control range ≤0.04%, Mn content control range 0.4-0.6%, P content control range 0.03-0.04%, S content control range ≤0.015%, Ti content control range 0.04-0.06%, nitrogen content control range ≤0.004%; (2) the hot rolling slab heating temperature is ≥1220℃, the finish rolling temperature is ≥900℃, and the coiling temperature is ≤600℃; (3) the pickling rolling reduction rate is ≥68%; (4) after the pickling rolling process is completed, annealing is carried out in the cold rolling continuous annealing furnace, and the process parameters are: the heating and soaking section outlet temperature is 750±10℃, the slow cooling section outlet temperature is ≥650℃, the fast cooling section outlet temperature is ≤400℃, the overaging section temperature is 200-350℃, the final cooling section outlet temperature is ≤150℃, the furnace zone speed is 120-160m / min, and the skin pass mill elongation is 0.5-0.7%; (5) after the pickling rolling process is completed, annealing and galvanizing are carried out in the galvanizing continuous annealing furnace, and the galvanizing process parameters are: the heating and soaking section outlet temperature is 780±10℃, the slow cooling section outlet temperature is ≥620℃, the fast cooling section outlet temperature is ≤460℃, the zinc pot temperature is 400-450℃, the furnace zone speed is 75-120m / min, and the skin pass mill elongation is 0.8-1.0%.

2. The method of improving the utilization of a 180 MPa grade phosphorus-added reinforced steel casting blank according to claim 1, characterized by, The 180MPa phosphorus reinforced steel quality percentage chemical composition is: C: 0.0025%; Si: 0.02%; Mn: 0.51%; P：0.04％； S: 0.008%; Ti: 0.04%; N: 0.0035%, the rest is Fe and inevitable impurities.

3. The method of improving the utilization of a 180 MPa grade phosphorus-added reinforced steel casting blank according to claim 1, characterized in that, The 180MPa phosphorus reinforced steel quality percentage chemical composition is: C: 0.0020%; Si: 0.02%; Mn: 0.55%; P：0.030％； S：0.009％； Ti: 0.06%; N: 0.0020%, the rest is Fe and inevitable impurities.

4. The method of improving the utilization of a 180 MPa grade phosphorus-added high-strength steel casting blank according to claim 1, characterized in that, The 180MPa phosphorus reinforced steel quality percentage chemical composition is: C: 0.0025%; Si: 0.02%; Mn: 0.59%; P：0.035％； S：0.006％； Ti: 0.05%; N: 0.0028%, the rest is Fe and inevitable impurities.

5. The method of improving the utilization of a 180 MPa grade phosphorus-added reinforced steel casting blank according to claim 1, characterized by, The 180MPa phosphorus reinforced steel quality percentage chemical composition is: C: 0.0025%; Si: 0.02%; Mn: 0.59%; Ti: 0.05%; N: 0.0028%, the rest is Fe and inevitable impurities. The cold rolling HC180Y and galvanized HX180YD+Z billets are realized to be mutually judged, the billet utilization rate is increased from 50% to 90%, and the manufacturing cost of the 180MPa phosphorus reinforced steel is significantly reduced.

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