CN103805850A - Production method of high-strength and high-toughness hot-rolled steel strip - Google Patents
Production method of high-strength and high-toughness hot-rolled steel strip Download PDFInfo
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- CN103805850A CN103805850A CN201210454737.1A CN201210454737A CN103805850A CN 103805850 A CN103805850 A CN 103805850A CN 201210454737 A CN201210454737 A CN 201210454737A CN 103805850 A CN103805850 A CN 103805850A
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Abstract
The invention discloses a production method of a high-strength and high-toughness hot-rolled steel strip. The production method comprises the processes of steel smelting, refining, continuous casting, soaking, hot continuous rolling, laminar cooling and coiling. The production method is characterized in that the narrow face temperature of a plate blank is raised, the corner temperature of a continuous casting blank in a fan-shaped segment straightening area is over 1,000 DEG C, and the soaking temperature of the steel is 1,080-1,130 DEG C; the final rolling temperature is 850-870 DEG C in a hot continuous rolling procedure; and the coiling temperature is 590-610 DEG C. Compared with products produced in the prior art, the high-strength and high-toughness hot-rolled steel strip produced by using a technology adopted in the production method has the advantages that the production cost can be reduced and the structure property of a plate is improved. The production method has the advantages of low cost, stable product quality and excellent strength and impact toughness. The high-strength and high-impact-toughness steel produced by using the method can be applied to manufacturing of automobiles and high-strength structural parts.
Description
Technical field
The invention belongs to metal material field, relate to the production method of a kind of high strength, high-toughness hot strip rolling.
Background technology
At present, what China's manufacture high-strength structure part mainly used is Hi-Stren steel, and the most typical trade mark is Q345B, and wherein one of topmost alloying element is manganese.Manganese has desirable influence to the mechanical property of carbon steel, can improve intensity and the hardness of steel, and for guaranteeing that steel have enough intensity, general manganese content is in 0.9%～1.1% left and right.
Manganese element is at the not high (w of content
mn< 0.8%) time, can improve a little or not reduce plasticity and the toughness of steel, but after manganese content is higher than this value, the performance index such as plasticity, toughness of steel decline thereupon.The problem that adopts the Q345B Hi-Stren steel of existing explained hereafter mainly to exist is exactly the low and poor impact toughness of cold bend cracking, yield tensile ratio.
Summary of the invention
According to above background technology, the object of the present invention is to provide the production method of a kind of high strength, high-toughness hot strip rolling
According to above-mentioned purpose, the technical scheme of entirety of the present invention is:
Find after deliberation, titanium micro-alloyedization hot-rolled sheet coil after treatment can have better strength property, has improved to a great extent toughness and the cold-formed performance of steel plate simultaneously.Adding of titanium can form more stable Ti
4c
2s
2, reduced separating out of MnS, Ti
4c
2s
2compound is harder, not yielding in rolling, and the strip MnS inclusion in steel is just because of Ti
4c
2s
2the formation of nodule and reducing, thus toughness and the cold-bending property of steel plate improved.
Because titanium micro-alloyedization has the effect of highly malleablized, therefore in steel, manganese content can reduce, and has solved the poor problem of impact, cold-bending property of Q345B steel.Titanium micro-alloyedization is favourable to product grains refinement and tissue improvement, and normal temperature and-20 ℃ of shock tests show, compare with the Q345B Hi-Stren steel that prior art is produced, and notched bar impact strength is even more ideal.
Titanium micro-alloyedization steel, in possessing good cold-forming property, also has good weldability energy.Titanium is to stop the optimal element of AUSTENITE GRAIN COARSENING, and adding of titanium can prevent at high temperature excessively alligatoring of austenite crystal in welding process, and the intensity of whole weld and strength of parent are consistent, and improves the welding property of steel.Grain growth when tiny TiN particle can hinder high temperature, can utilize their restraining effect to grain growth, control there is high thermal output and from 800 ℃ to 500 ℃ grain size in the weldment heat affected zone of very long cooling time.
Principle of design of the present invention is by the impact of the performance such as intensity, toughness of element on steel such as Mn, Ti in systems analysis steel in theory, take into account production cost and technique simultaneously, chemical composition to this novel high-strength, high-toughness hot strip rolling designs, and by controlled rolling with control cooling production technology, can obtain thus that a kind of cost is low, constant product quality, intensity and the good hot rolled strip of impelling strength.
The present invention adopts top and bottom combined blown converter+LF refining furnace+continuous casting and rolling technique of sheet bar, and the whole technological process of production is: the technological process such as steel-making, refining, continuous casting, soaking, hot continuous rolling, laminar flow is cooling, batch.
According to above-mentioned purpose and overall technical scheme, the concrete technical scheme of the present invention is:
1, chemical composition
Described high strength of the present invention, the chemical composition (wt%) of high-toughness hot strip rolling are: C:0.20%～0.23%, Si:0.10%～0.20%, Mn:0.25%～0.35%, P :≤0.025%, S :≤0.01%, Ti:0.025%～0.035%, Als:0.015～0.025%, Ca:0.001%～0.002%, remaining is Fe and other inevitable impurity.This steel grades feature is: (1) avoids the peritectoid district 0.08%～0.16% of carbon content; (2) control rational manganese content; (3) refining adopts titanium micro-alloyedization technology; (4) molten steel is processed through Ca; (5) control lower sulphur content.
The design considerations of above-mentioned main chemical compositions is:
C: carbon is the effective element of strengthening steel plate, but carbon content will enter peritectoid district in 0.08%～0.16% scope, process of setting generation Peritectic Reaction is also followed δ → γ phase transformation, produce larger volumetric shrinkage, between strand and crystallizer wall, produce space, derive heat less, base shell attenuate, form depression on surface, depression position is cooling and setting rate is slower than other positions, causes the inhomogeneous of birth shell thickness, and this scope carbon content belongs to crack-sensitivity district, based on these factors, in steel of the present invention, carbon content control is 0.20%～0.23%.
Mn: it is the intensity that solution strengthening improves steel that manganese adds the Main Function in steel, simultaneously, Mn in steel can be combined into MnS with S and be distributed in austenite with wire form, can improve the plasticity of steel, it is the important element that suppresses slab hot cracking tendency, based on these factors, in steel of the present invention, manganese content is controlled at 0.25%～0.35%.
Ti: titanium content and yield strength and transition temperature have substantial connection, when titanium content is lower, the improvement factor of yield strength is refined crystalline strengthening.After titanium content is higher than 0.07%, precipitation strength will significantly improve yield strength, but along with the reinforcement of precipitation strength, sheet material brittle transition temperature improves rapidly, and plate cold bending performance, impact property worsen.The impact of comprehensive two kinds of factors, in the present invention, titanium content is controlled at 0.025%～0.035%.
S: in the process of setting of steel, S has reduced the high-temp plastic of steel billet separating out of austenite grain boundary, has increased the thermal crack susceptibility of strand, therefore requires to reduce S content, and based on these factors, in steel of the present invention, sulphur content should be less than or equal to 0.01%.
Ca: the high strength that the present invention relates to, high-ductility steel are after Ca processes, inclusion in steel effectively sex change is the hard particle take CaS as core, after floating, can from molten steel, remove, Cleanliness of Molten Steel is improved, in steel, Ca content is controlled at 0.001%～0.002%.
2, strand temperature control
Adopt the continuously cast bloom that continuous casting and rolling technique of sheet bar is produced should reach more than 1000 ℃ in the bight temperature in fan-shaped section aligning region, avoid the temperature limit of brittleness district of 850 ℃～950 ℃.According to thermodynamic condition, in this temperature range, TiN will separate out.For slowing down the alligatoring of TiN particle, Heating temperature should be controlled at lower scope; On the other hand, after temperature is lower than 1000 ℃, strand crack sensitivity increases.Therefore, strand soaking temperature should be controlled in the scope of 1080 ℃～1130 ℃.
3, controlled rolling and control cooling technology
According to Ti (C, N) Precipitation Behavior, set rational temperature schedule and cooling system, guarantee that tiny Ti (C, N) particle fully separates out.Guaranteeing device security in the situation that, to formulate rational heating cycle, realize high precision gross distortion load distribution, be conducive to the deformation induced of Ti (C, N) and separate out, suppress growing up of austenite crystal in thermal deformation process, improve precipitation strength effect.
For guaranteeing finished product impelling strength, produce thickness specification in the time of the high strength of 8.0mm～10.0mm, high-ductility steel, finish rolling total reduction must guarantee to be greater than 70%; The product that is less than 8.0mm thickness is being guaranteed under the prerequisite of finish rolling total reduction, R2 draft should be controlled at 48%～52%, is conducive to Austenite Grain Refinement, is conducive on the other hand separate out in the operation of rolling tiny Ti (C, N) particle, suppresses growing up of austenite crystal.
The variation of finishing temperature can change the front austenitic tissue of phase transformation, reduces finishing temperature, can reduce the front austenite grain size of phase transformation, and refinement ferrite crystal grain, increases refined crystalline strengthening component; On the other hand, reduce finishing temperature, will bring out more TiC and separate out at austenite, this precipitation size is larger, less to intensity contribution, has but reduced and has been dissolved in austenitic TiC, weaken the quantity at cold zone precipitation particles, made precipitation strength component decline and reduce with finishing temperature.In addition,, because finishing temperature reduces, deformation energy is raise, deformation energy causes γ → α phase change transition temperature to raise as the motivating force of phase transformation, and the particle of precipitation increases, and has weakened the effect of precipitation strength, therefore, finishing temperature is controlled in the scope of 850 ℃～870 ℃.This steel Main Tissues composition is ferrite+perlite, 10～11 grades of grain fineness numbers.
High strength, the high-toughness hot strip rolling produced for the titanium micro-alloyed metallization processes of low manganese, consider from kinetics angle, and because the diffusion activation energy of titanium is high, TiC precipitation process is the result of titanium long-range diffusion, needs the regular hour fully to separate out.If rate of cooling is too fast, the precipitation process of TiC will be suppressed; Meanwhile, the solid solution capacity of titanium also will improve, unfavorable to precipitation process, and the amount of separating out is reduced.Based on these factors, coiling temperature is controlled at 590 ℃～610 ℃.For reducing the impact of the residual water of rolling belt steel surface in service on product over-all properties, in cooling facility for laminar flow rear design, a set of fixing hair drying device is installed, utilize this device inhibiting band steel remained on surface water, stablize coiling temperature.
The invention has the beneficial effects as follows:
Adopt chemical composition of the present invention, after smelting, LF refining treatment, continuous casting, be cast into strand, be rolling to into 5 passage finish rolling the steel band that 9.5mm is thick through 2 passage roughing.Intercept some samples from steel band middle part and analyze, its chemical composition is as shown in table 1, and mechanical property is as shown in table 2.Wherein table 1 for embodiment of the present invention steel is compared with the prior art routine steel chemical composition contrast table, table 2 is routine steel band mechanical property contrast table for embodiment of the present invention steel band is compared with the prior art, wherein, 1-4# is the embodiment of the present invention, and 5-6# is the Q345B Hi-Stren steel comparative example that prior art is produced.
Table 1 embodiment of the present invention steel is compared with the prior art example---chemical composition contrast table
Table 2 embodiment of the present invention steel band is compared with the prior art example---steel band mechanical property contrast table
These product performance are: yield strength R
elfor 400MPa～470MPa, tensile strength R
mfor 550MPa～630MPa, yield tensile ratio>=0.7, elongation after fracture A is 24%～33%, 20 ℃ of impelling strength KV
2for 80J～130J, 0 ℃ of impelling strength KV
2for 70J～100J ,-20 ℃ of impelling strength KV
2for 50J～80J.High strength, high-ductility steel that in table 2, this employing the technology of the present invention is produced have higher yield strength and yield tensile ratio, also embody desirable impact property simultaneously, especially Q345B steel 30J～40J that the impelling strength under 0 ℃ and-20 ℃ of cold condition is on average produced higher than prior art, low temperature impact properties is very excellent.
Choose prior art produce Q345B Hi-Stren steel and the technology of the present invention produce high strength, high-ductility steel carry out cold bending test, result cold bending test shows, there is cracking situation in the Q345B sample that prior art is produced, the high strength, the high-ductility steel sample clod wash result that adopt the technology of the present invention to produce are good, without cracking phenomena.High strength, high-ductility steel that the technology of the present invention is produced are processed into standard test specimen according to the method for regulation in " the GB/T 13298-1991 metal microstructure method of inspection ", observe mirco structure form, and contrast with the Q345B Hi-Stren steel that existing technique is produced, result shows that the titanium micro-alloyed metallization processes of low manganese of the present invention can crystal grain thinning, make sheet material every mechanical property, especially low-temperature impact toughness be better than the product performance that prior art is produced.Meanwhile, the sample high power of the technology of the present invention detects and does not find banded structure, is more conducive to improve the cold-formed performance of coiled sheet.High strength, the high-toughness hot strip rolling that the technology of the present invention relates to is produced can be applicable to various automobile makings and the manufacture of high-strength structure part.
Embodiment
The chemical composition (wt%) of high strength of the present invention, high-toughness hot strip rolling is: C:0.20%～0.23%, Si:0.10%～0.20%, Mn:0.25%～0.35%, P :≤0.025%, S :≤0.01%, Ti:0.025%～0.035%, Als:0.015～0.025%, Ca:0.001%～0.002%, remaining is Fe and other inevitable impurity.The present invention adopts top and bottom combined blown converter+LF refining furnace+continuous casting and rolling technique of sheet bar, and the whole technological process of production is: the technological process such as steel-making, refining, continuous casting, soaking, hot continuous rolling, laminar flow is cooling, batch.
1, strict control smelted carbon content, and in steel, carbon content control, 0.20%～0.23%, is avoided carbon content in 0.08%～0.16% peritectoid scope, according to the analytical results of carbon content of molten steel in smelting endpoint stove, carbon content of molten steel is adjusted to target value.
2, LF refining procedure, titanium content is controlled at 0.025%～0.035% scope, and manganese content is controlled at 0.25%～0.35% scope.Carry out dark desulfurization operations at LF stove, reach the control target of [S]≤0.008%.
3, in LF stove treating processes, control molten steel nitrogen pick-up.By strengthening bell sealing, arc-covering slag operation, shortening electric-arc heating time, controlling the measures such as argon bottom-blowing stirring intensity, control molten steel nitrogen pick-up.
4, on thinslab casting, by adjusting crystallizer cooling water flow, two cold-zone spray water flows are controlled slab cooling intensity, guarantee that continuously cast bloom reaches more than 1000 ℃ in the bight temperature in fan-shaped section aligning region, avoids the temperature limit of brittleness district of 850 ℃～950 ℃.
5, strand soaking temperature should be controlled in the scope of 1080 ℃～1130 ℃.
6, for guaranteeing finished product over-all properties, the finish rolling total reduction of finished product thickness specification between 8.0mm～10.0mm is greater than 70%; The product that is less than 8.0mm thickness is guaranteeing that, under the prerequisite of finish rolling total reduction, R2 draft should be controlled at 48%～52%, 850 ℃～870 ℃ of finishing temperatures in hot continuous rolling operation.
7, for reducing the impact of the residual water of rolling belt steel surface in service on product over-all properties, in cooling facility for laminar flow rear design, a set of fixing hair drying device is installed, utilize this device inhibiting band steel remained on surface water, coiling temperature is controlled at 590 ℃～610 ℃, stablizes coiling temperature.
Below the production technique of narration is not routine techniques.
Claims (1)
1. the production method of a high strength, high-toughness hot strip rolling, the chemical composition (wt%) of its steel is: C:0.20%～0.23%, Si:0.10%～0.20%, Mn:0.25%～0.35%, P :≤0.025%, S :≤0.01%, Ti:0.025%～0.035%, Als:0.015～0.025%, Ca:0.001%～0.002%, remaining is Fe and other inevitable impurity, comprises that steel-making, refining, continuous casting, soaking, hot continuous rolling, laminar flow are cooling, coiling technique process, it is characterized in that:
(1), when sheet billet continuous casting operation, improve slab leptoprosopy temperature, guarantee that continuously cast bloom reaches more than 1000 ℃ in the bight temperature in fan-shaped section aligning region, avoid the temperature limit of brittleness district of 850 ℃～950 ℃,
(2), the soaking process temperature of this steel is 1080 ℃～1130 ℃,
(3), 850 ℃～870 ℃ of finishing temperatures in hot continuous rolling operation, the finish rolling total reduction of finished product thickness specification between 8.0mm～10.0mm is greater than 70%; The product that is less than 8.0mm thickness is guaranteeing that, under the prerequisite of finish rolling total reduction, R2 draft should be controlled at 48%～52%,
(4), coiling temperature is 590 ℃～610 ℃.
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| CN201210454737.1A CN103805850A (en) | 2012-11-01 | 2012-11-01 | Production method of high-strength and high-toughness hot-rolled steel strip |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104561486A (en) * | 2015-01-22 | 2015-04-29 | 首钢总公司 | Thick-gauge hot continuous rolling steel belt with excellent ultralow temperature CTOD (Crack Tip Opening Displacement) performance and production method of thick-gauge hot continuous rolling steel belt |
| CN107267728A (en) * | 2017-06-09 | 2017-10-20 | 首钢京唐钢铁联合有限责任公司 | A kind of cold-drawn hot rolled strip and its production method |
-
2012
- 2012-11-01 CN CN201210454737.1A patent/CN103805850A/en active Pending
Non-Patent Citations (2)
| Title |
|---|
| 姜锡山: "《连铸钢缺陷分析与对策》", 31 January 2012 * |
| 马占福 等: "热轧工艺对Q345B钢组织和力学性能的影响", 《金属热处理》 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104561486A (en) * | 2015-01-22 | 2015-04-29 | 首钢总公司 | Thick-gauge hot continuous rolling steel belt with excellent ultralow temperature CTOD (Crack Tip Opening Displacement) performance and production method of thick-gauge hot continuous rolling steel belt |
| CN107267728A (en) * | 2017-06-09 | 2017-10-20 | 首钢京唐钢铁联合有限责任公司 | A kind of cold-drawn hot rolled strip and its production method |
| CN107267728B (en) * | 2017-06-09 | 2019-04-12 | 首钢京唐钢铁联合有限责任公司 | A kind of cold-drawn hot rolled strip and its production method |
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Application publication date: 20140521 |