CN102127681B - Production method of hot rolled steel coil - Google Patents

Abstract

The invention relates to a production method of a hot rolled steel coil, comprising the following steps of: (1) designing components, preprocessing molten iron, then smelting in a converter, switching between nitrogen and argon, and tapping to obtain molten steel; (2) continuously casting the molten steel to obtain a plate blank, wherein the molten steel quantity of a tundish when the continuous casting tundish is stopped to be poured is controlled at 8-15t, and the liquid level is controlled at 200-350 mm; protecting the pouring in the whole process, wherein the inserting depth of a long water gap is 300-400 mm; (3) heating the plate blank; and (4) finally, rolling the heated plate blank and curling to obtain the hot rolled steel coil. With the production method, the contents of C and Mnin the components of Q235q-E steel are reduced, in addition, by adopting a proper rolling process and a cooling control process, the combination property of the Q235q-E steel is enhanced, and a Q235q-E hot rolled steel coil with low cost and high performance is produced.

Description

A kind of working method of coils of hot-rolled steel

Technical field

The invention belongs to the coil of strip preparation field, particularly a kind of working method of coils of hot-rolled steel.

Background technology

Existing ys 235MPa level Series Steel of producing is rolled into C height in the branch, and slab surface crack is many, and the intensity surplus capacity is big, and plasticity and toughness are low.When in the special-purpose steel the following existence of Mn being required, its intensity surplus capacity will be bigger, influence cold-forming property; Casting billet surface has the crackle probability can not directly adorn greatly, is unfavorable for energy-saving and emission-reduction; C content is high, and welding property is poor.

The investigation of ys 235MPa level series coil of strip production performance actual achievement

Table 1 ys 235MPa level series coil of strip thickness, performance range cartogram

Can find out from table 1:

Ys 235MPa level series coil of strip is produced thickness below 7.5mm, and ys is at 275～475MPa, and tensile strength is at 405～595MPa, unit elongation 26～45.5%;

Ys 235MPa level series coil of strip is produced thickness more than 7.5mm, and ys is at 245～395MPa, and tensile strength is at 370～520MPa, unit elongation 23～40.5%;

Table 2 ys 235MPa level series coil of strip is less than 7.5mm thickness and performance index frequency table

Table 3 ys 235MPa level series coil of strip is greater than 7.5mm thickness and performance index frequency table

Can find out from table 2, table 3: the ys of ys 235MPa level series coil of strip (less than 7.5mm) mainly be in 310～430MPa, tensile strength mainly at 440～520MPa scope, unit elongation mainly 30～38%, to produce main thickness be 6-3mm;

The ys of ys 235MPa level series coil of strip (greater than 7.5mm) mainly be in 300～360MPa, tensile strength mainly at 450～490MPa scope, unit elongation mainly 29～37%, to produce main thickness be 7.5-14mm;

Ys 235MPa level series coil of strip produces the investigation of branch actual achievement, and 662 stove ys 235MPa level Series Steel are involved in capable C, Si, Mn element statistics.

Table 4 ys 235MPa level series coil of strip C, Si, Mn scope cartogram

Project	C％	Si％	Mn％
				Peak	0.19362	0.24151	0.48282
Minimum value	0.12024	0.00246	0.28643
				MV	0.15	0.15	0.40

Can find out from table 4: ys 235MPa level series coil of strip C average content is 0.15%, the Mn average content is 0.40%;

Table 5C, Si, the Mn composition frequency

C％	The frequency	Si％	The frequency	Mn％	The frequency
						0.12	0	0	0	0.28	0
0.13	39	0.12	88	0.3	1
						0.14	74	0.14	67	0.32	5
0.15	191	0.16	176	0.34	12
						0.16	173	0.18	201	0.36	44
0.17	115	0.2	95	0.38	89
						0.18	44	0.22	32	0.4	166
0.19	19	0.24	2	0.42	200
						0.2	7	0.26	1	0.44	99
				0.46	35

				0.48	8
										0.5	3

Can find out from table 5: ys 235MPa level series coil of strip heat analysis C content is main 0.13～0.18%, Mn content is mainly 0.36～0.46%.

National standard (GB714) is to Q235q-E composition, performance requriements and the contrast of ys 235MPa level series coil of strip production actual achievement, and is as shown in table 6:

Table 6 composition, performance requriements and production actual achievement

Can find out from table 6: the rich amount of ys 235MPa level series coils of hot-rolled steel intensity is big, and plasticity is low.

Summary of the invention

Technical problem to be solved by this invention provides a kind of working method of coils of hot-rolled steel; This method has reduced C in the Q235q-E composition of steel, Mn content; Adopt suitable rolling technology and cooling control technology; Improve the over-all properties of Q235q-E steel, produce low cost, high performance Q235q-E coils of hot-rolled steel, in line with the theory realization energy-saving and emission-reduction of green iron and steel.

The working method of a kind of coils of hot-rolled steel of the present invention comprises:

1) after composition designs, molten iron is carried out pre-treatment, converter smelting then, the nitrogen argon switches, tap molten steel; Re-blow≤1 time tapping time 4.5～8.0min before the tapping; Add alloy before the tapping 4/5; The two pushing off the slag of tapping, the slag that arrives at a station is thick≤80mm; The omnidistance time 17～30min of Argon is handled at the argon station;

2) molten steel after the above-mentioned tapping is carried out continuous casting and gets slab, wherein connect water unwrap when watering in first stove in the water yield 25～30t of Baogang, liquid level 550～580mm; In bag during quick change in the water yield 15～20t of Baogang, liquid level 350～400mm; Normally water the water yield 42～50t of Baogang in time cast maintenance, liquid level 950～1000mm; Change the big Bao Shizhong water yield 35～40t of Baogang, liquid level 800～850mm; Baogang's water yield is controlled at 8～15t, liquid level 200～350mm in when bag stops watering in the continuous casting; The whole process protection cast, long nozzle depth of penetration 300～400mm;

3) with above-mentioned slab heating, 3mm≤slab thickness≤16mm, tapping temperature is controlled at 1200 ± 30 ℃, time inside furnace 150～200min, soaking time 22～30min;

4) with the slab rolling after the above-mentioned heating, curling promptly gets coils of hot-rolled steel; 3mm≤slab thickness≤16mm, finish rolling temperature in are controlled at 1020 ± 30 ℃, and finishing temperature is controlled at 860 ± 30 ℃, and curling temperature is controlled to be 600 ± 30 ℃, and cooling strategy is a leading portion.

Above-mentioned steps 1) in, before finishing, the molten steel processing blows Ar time 5～8min, its bright circle≤200mm a little less than the ladle; Reinforced adjustment composition and temperature in the converter smelting, ladle blows Ar time 5～8min, its bright circle≤200mm; The Argon processing finishes to unwrap the time of watering 10～13min to continuous casting steel in the LF stove.

Above-mentioned steps 1) weight percent of each composition of gained molten steel is seen table 7 in:

Table 7 ingredient standard

Above-mentioned steps 2) in, liquidus temperature is controlled to be 1527 ℃ during continuous casting, and the bag temperature is controlled to be 1552 ± 7 ℃ in the target, and crystallizer protecting residue adopts low-carbon steel protecting slag.

Above-mentioned steps 4) in, the gained coils of hot-rolled steel is the Q235q-E coils of hot-rolled steel.

The low carbon component design of Q235q-E; Guarantee that coil of strip has good plasticity and toughness, its unit elongation improves more than 13%, and-40 ℃ of ballistic works are enhanced about more than once; Good plasticity and toughness; Improve cold-forming property, avoided the bending cracking problem of gross distortion in the use of Q235q-E coil of strip, reduced quality objection; Low carbon component design (C≤0.08%) guarantees surface quality of continuously cast slab good (traditional Q235q-E composition is in inferior peritectoid scope, and casting billet surface produces a large amount of crackles), realizes straight dress simultaneously, energy-saving and emission-reduction; Low carbon component design (C≤0.08%) need not to add Ti, has improved the material welding property; Low Mn design need not to add Ni, reduces the alloy consumption, reduces production costs.

Adopt the TMCP rolling technology, the low finishing temperature and the temperature of curling guarantee that coil of strip organizes tiny, even; Coil of strip has kept the microstructure characteristic of P+F, and coil of strip performance anisotropy is little; The Q235q-E steel of low C, low Mn composition has good combination of strength and toughness.

Beneficial effect

1, the inventive method is simple, adopts the TMCP rolling technology, and low Mn design reduces the alloy consumption, reduces production costs.

2, gained Q235q-E coils of hot-rolled steel of the present invention, low carbon component design guarantees that coil of strip has good plasticity and toughness, has improved the material welding property, guarantees that simultaneously surface quality of continuously cast slab is good, realizes directly dress, energy-saving and emission-reduction.

Description of drawings

Fig. 1 is metallographic structure (500 times of amplifications) behind the Q235q-E steel rolling of sample number into spectrum 1, and grain fineness number is 11 grades.

Fig. 2 is metallographic structure (500 times of amplifications) behind the Q235q-E steel rolling of sample number into spectrum 2, and grain fineness number is 10 grades.

Fig. 3 is metallographic structure (500 times of amplifications) behind the Q235q-E steel rolling of sample number into spectrum 3, and grain fineness number is 10 grades.

Embodiment

Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiment only to be used to the present invention is described and be not used in the restriction scope of the present invention.Should be understood that in addition those skilled in the art can do various changes or modification to the present invention after the content of having read the present invention's instruction, these equivalent form of values fall within the application's appended claims institute restricted portion equally.

Embodiment 1

1) after composition designs, molten iron is carried out pre-treatment, converter smelting then, the nitrogen argon switches, tap molten steel; Re-blow tapping time 4.5min before the tapping 1 time; Add alloy before the tapping 4/5; The two pushing off the slag of tapping, the thick 80mm of the slag that arrives at a station; The omnidistance time 17min of Argon is handled at the argon station;

2) weight percent of each composition of molten steel after the above-mentioned tapping is followed successively by: C 0.05%, and Si 0.12%, and Mn 0.40%, P0.005%, and S 0.004%, and Als 0.020%, and all the other are iron and unavoidable impurities; Said molten steel is carried out continuous casting gets slab, wherein connect water unwrap when watering in first stove in the water yield 25t of Baogang, liquid level 550mm; In bag during quick change in the water yield 15t of Baogang, liquid level 350mm; Normally water time cast keep in the water yield 42t of Baogang, liquid level 950mm changes the big Bao Shizhong water yield 35t of Baogang, liquid level 800mm, when bag stops watering in the continuous casting in Baogang's water yield be controlled at 8t, liquid level 200mm; The whole process protection cast, long nozzle depth of penetration 300mm;

3) with above-mentioned slab heating, time inside furnace 150min, soaking time 22min, during slab thickness 3.05mm, tapping temperature is controlled at 1230 ℃;

4) with the slab rolling after the above-mentioned heating, the finish rolling temperature in is controlled at 1050 ℃, and finishing temperature is controlled at 890 ℃; Curling temperature is controlled to be 630 ℃, and cooling strategy is a leading portion, and curling at last, promptly to get sample number into spectrum be 1 Q235q-E coils of hot-rolled steel.Accompanying drawing 1 is seen in its metallographic structure, impacts assay and sees table 8.

Embodiment 2

1) after composition designs, molten iron is carried out pre-treatment, converter smelting then, the nitrogen argon switches, tap molten steel; Re-blow tapping time 6.0min before the tapping 0 time; Add alloy before the tapping 4/5; The two pushing off the slag of tapping, the thick 60mm of the slag that arrives at a station; The omnidistance time 25min of Argon is handled at the argon station;

2) weight percent of each composition of molten steel after the above-mentioned tapping is followed successively by: C 0.07%, and Si 0.17%, and Mn 0.50%, P0.015%, and S 0.006%, and Als 0.025%, and all the other are iron and unavoidable impurities; Said molten steel is carried out continuous casting gets slab, wherein connect water unwrap when watering in first stove in the water yield 30t of Baogang, liquid level 560mm; In bag during quick change in the water yield 18t of Baogang, liquid level 380mm; Normally water time cast keep in the water yield 45t of Baogang, liquid level 980mm changes the big Bao Shizhong water yield 38t of Baogang, liquid level 830mm, when bag stops watering in the continuous casting in Baogang's water yield be controlled at 10t, liquid level 270mm; The whole process protection cast, long nozzle depth of penetration 350mm;

3) with above-mentioned slab heating, time inside furnace 180min, soaking time 25min, during slab thickness 7.05mm, tapping temperature is controlled at 1200 ℃;

4) with the slab rolling after the above-mentioned heating, the finish rolling temperature in is controlled at 1020 ℃, and finishing temperature is controlled at 860 ℃; Curling temperature is controlled to be 600 ℃, and cooling strategy is a leading portion, and curling at last, promptly to get sample number into spectrum be 2 Q235q-E coils of hot-rolled steel.Accompanying drawing 2 is seen in its metallographic structure.

Embodiment 3

1) after composition designs, molten iron is carried out pre-treatment, converter smelting then, the nitrogen argon switches, tap molten steel; Re-blow tapping time 8.0min before the tapping 1 time; Add alloy before the tapping 4/5; The two pushing off the slag of tapping, the thick 30mm of the slag that arrives at a station; The omnidistance time 30min of Argon is handled at the argon station;

2) weight percent of each composition of molten steel after the above-mentioned tapping is followed successively by: C 0.08%, and Si 0.24%, and Mn 0.60%, P0.018%, and S 0.010%, and Als 0.040%, and all the other are iron and unavoidable impurities; Said molten steel is carried out continuous casting gets slab, wherein connect water unwrap when watering in first stove in the water yield 28t of Baogang, liquid level 580mm; In bag during quick change in the water yield 20t of Baogang, liquid level 400mm; Normally water time cast keep in the water yield 50t of Baogang, liquid level 1000mm changes the big Bao Shizhong water yield 40t of Baogang, liquid level 850mm, when bag stops watering in the continuous casting in Baogang's water yield be controlled at 15t, liquid level 350mm; The whole process protection cast, long nozzle depth of penetration 400mm;

3) with above-mentioned slab heating, time inside furnace 200min, soaking time 30min, during slab thickness 10.55mm, tapping temperature is controlled at 1170 ℃;

4) with the slab rolling after the above-mentioned heating, the finish rolling temperature in is controlled at 990 ℃, and finishing temperature is controlled at 830 ℃; Curling temperature is controlled to be 570 ℃, and cooling strategy is a leading portion, and curling at last, promptly to get sample number into spectrum be 3 Q235q-E coils of hot-rolled steel.Accompanying drawing 3 is seen in its metallographic structure, impacts assay and sees table 8.

The present invention impacts assay and sees table 8.

Table 8 impacts assay

Claims (2)

1. the working method of a coils of hot-rolled steel comprises:

1) after composition designs, molten iron is carried out pre-treatment, converter smelting then, the nitrogen argon switches, tap molten steel, re-blow≤1 time tapping time 4.5～8.0min before the tapping; Add alloy before the tapping 4/5; The two pushing off the slag of tapping, the slag that arrives at a station is thick≤80mm; The omnidistance time 17～30min of Argon is handled at the argon station; Wherein the weight percent of each composition of gained molten steel is followed successively by: C0.05～0.08%, and Si 0.12～0.24%, Mn0.40～0.60%, P≤0.018%, S≤0.010%, Als0.020～0.040%, all the other are iron and unavoidable impurities;

2) molten steel after the above-mentioned tapping is carried out continuous casting and gets slab, wherein connect water unwrap when watering in first stove in the water yield 25～30t of Baogang, liquid level 550～580mm; In bag during quick change in the water yield 15～20t of Baogang, liquid level 350～400mm; Normally water the water yield 42～50t of Baogang in time cast maintenance, liquid level 950～1000mm; Change the big Bao Shizhong water yield 35～40t of Baogang, liquid level 800～850mm; Baogang's water yield is controlled at 8～15t, liquid level 200～350mm in when bag stops watering in the continuous casting; The whole process protection cast, long nozzle depth of penetration 300～400mm;

3) with above-mentioned slab heating, 3mm≤slab thickness≤16mm, tapping temperature is controlled at 1200 ± 30 ℃, time inside furnace 150～200min, soaking time 22～30min;

4) with the slab rolling after the above-mentioned heating, curling promptly gets coils of hot-rolled steel; 3mm≤slab thickness≤16mm, finish rolling temperature in are controlled at 1020 ± 30 ℃, and finishing temperature is controlled at 860 ± 30 ℃, and curling temperature is controlled to be 600 ± 30 ℃, and cooling strategy is a leading portion;

Blow Ar time 5～8min, its bright circle≤200mm a little less than the ladle before the molten steel processing finishes in the said step 1); Reinforced adjustment composition and temperature in the converter smelting, ladle blows Ar time 5～8min, its bright circle≤200mm; The Argon processing finishes to unwrap the time of watering 10～13min to continuous casting steel;

Said step 2) in, liquidus temperature is controlled to be 1527 ℃ during continuous casting, and middle bag temperature is controlled to be 1552 ± 7 ℃, and crystallizer protecting residue adopts low-carbon steel protecting slag.

2. the working method of a kind of coils of hot-rolled steel according to claim 1; It is characterized in that: the weight percent of each composition of tapping gained molten steel is followed successively by in the said step 1): C 0.07%, and Si 0.17%, and Mn 0.50%; P≤0.015%; S≤0.006%, Als 0.025%, and all the other are iron and unavoidable impurities.

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