CN105088068A - Coated steel used for 500 MPa grade automobile girder and ultrafast-cooling production method of coated steel - Google Patents
Coated steel used for 500 MPa grade automobile girder and ultrafast-cooling production method of coated steel Download PDFInfo
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Abstract
Coated steel used for a 500 MPa grade automobile girder comprises, by weight, 0.06-0.09% of C, not more than 0.025% of Si, 1.10%-1.29% of Mn, not more than 0.015% of P, not more than 0.006% of S, 0.020%-0.060% of Als and 0.025%-0.034% of Nb. The production method includes the steps that argon blowing is conducted in an argon station after converter smelting is conducted; casting blanks are heated after tapping is conducted and the blanks are formed through continuous casting; staged hot rolling is conducted; laminar cooling is conducted in a variable-speed cooling manner; reeling is conducted; and finishing and subsequence procedures are conducted. Under the design of low alloy components, ultrafast cooling and staged cooling are adopted, the produced coated steel used for the girder has excellent surface quality and platability, hot galvanizing production can be directly conducted, the denting resistance and coating adhesive force of steel plates are further improved, and good surface quality is achieved.
Description
Technical field
The present invention relates to a kind of automobile steel and production method, belong to a kind of 500MPa level automotive frame coated steel and ultrafast cold production method thereof particularly.
Background technology
Coating hot-rolled steel is used widely at the automotive frame higher for surface quality requirements.Hot-dip galvanizing sheet steel surface has coating light, uniform color, good weather resistance and the feature of aesthetic property; Meanwhile, the parts such as automotive frame also require that steel have good dent resistance, and should have high-yield-ratio.
At present, with regard to its beam steel still at rank steel grades such as Q345, Q235, then at this type of steel grade surface heat zinc coating.Due to the development of automotive industry, it can not meet and has manufactured high-strength vehicle structural part and the zinc-plated requirement of surface heat thereof.For this reason, steel industry manufacturer is all actively developing research and the development of the parties concerned.
In prior art, cooling for steel plate all adopts a lower or conventional stable speed of cooling to be cooled to the temperature required, through a large amount of analysis and research of the applicant, adopt the steel plate that this type of cooling is produced, for reaching intensity and the tissue of regulation, often need to add more alloying element, production cost is higher.
Through preliminary search, Chinese Patent Application No. is the document of CN200910063433.0, disclose a kind of production method of yield strength 460MPa level coating hot-rolled structural steel, it comprises and in turn including the following steps: steel-making, continuous casting, heating of plate blank, hot continuous rolling, section cooling, batch; It is characterized in that at the Chemical Composition of steelmaking process and weight percent be: C:0.05 ~ 0.10%; Si≤0.04; Mn:1.30 ~ 1.65%; P≤0.030%; S≤0.012%; Als:0.01 ~ 0.06%; Nb:0.035 ~ 0.060%; Surplus is Fe and is inevitably mingled with; In hot rolling, adopt controlled rolling, wherein slab heating temperature is 1200 ~ 1260 DEG C; Roughing temperature out is 1020 ~ 1080 DEG C; Hot rolling finishing temperature is 790 ~ 850 DEG C; In coiling process, coiling temperature is 540 ~ 600 DEG C.The technical scheme enumerated is: C:0.075%; Si:0.02%; Mn:1.5%; P:0.02%; S:0.01%; Als:0.03%; Nb:0.050%; Slab heating temperature 1230 DEG C; Finishing temperature 820 DEG C; Coiling temperature 570 DEG C.The document is the conventional laminar flow type of cooling adopted after hot rolling, and its alloy content that there is steel design is high, the problem that cost is higher.
Summary of the invention
The present invention is directed to the deficiency that prior art exists, there is provided a kind of at guarantee yield strength >=500MPa, tensile strength 550-700MPa, unit elongation can reach A >=17%, 180 ° of transverse bending test D=1a are qualified, under yield tensile ratio reaches the prerequisite of more than 0.85, roll rear supper-fast sub-sectional cooling technique, under lower alloying constituent by adopting, improve the dent resistance of steel plate, the 500MPa level automotive frame coated steel that coating adhesion is further enhanced and production method.
Realize the measure of above-mentioned purpose:
A kind of 500MPa level automotive frame coated steel, its chemical composition and weight percent content are: C:0.06 ~ 0.09%, Si≤0.025%, Mn:1.10 ~ 1.29%, P≤0.015%, S≤0.006%, Als:0.020 ~ 0.060%, Nb:0.025 ~ 0.034%, surplus is Fe and inevitable impurity.
Preferably: the weight percent content of Si is no more than 0.018%.
Preferably: the weight percent content of Nb is 0.025 ~ 0.030%.
Produce a kind of method of 500MPa level automotive frame coated steel, its step:
1) after converter smelting, enter argon station Argon, and routine adds aluminum steel deoxidation and composition adjustment; Control argon blowing time: bottom blowing is not less than 4min, and top blast is not less than 5min;
2) through tapping and continuous casting becomes to strand heating after base, its heating and temperature control at 1280 ~ 1310 DEG C, 30 ~ 40min during heating;
3) carry out segmentation hot rolling, and control roughing end temp at 1080 ~ 1110 DEG C, control finish rolling finishing temperature at 860 ~ 890 DEG C;
4) adopt the speed change degree type of cooling to carry out section cooling, that is: first under speed of cooling is 140 ~ 160 DEG C/sec, be cooled to 700 ~ 740 DEG C, then be cooled to coiling temperature according to the speed of cooling of 5 ~ 10 DEG C/sec;
5) batch, control coiling temperature at 550 ~ 580 DEG C;
6) finishing and rear operation is carried out.
The effect of each component and main technique and the reason of control in the present invention:
Carbon: carbon is cheap solution strengthening element.According to the range of application of this steel grade, be mainly used in processing coating crossbeam, send the parts such as transformer tower, need the Pressing Deformation processing carried out to a certain degree, therefore require that material is while meeting requirement of strength, there is good cold shaping performance.If its content is less than 0.06%, then can not meet the requirement of the strength of materials; If its content is greater than 0.09%, then can not meet the favorable forming property of material.So, its content is limited to 0.06 ~ 0.09% scope.
Silicon: silicon is cheap and effective steel liquid deoxidation element, also can play the effect improving steel strength, but be controlled as harmful element in the present invention.Should be more low better.This is because silicon can worsen the surface quality of hot-rolled steel sheet in the present invention, in follow-up galvanizing process, make surface blackening, affecting it can zinc-plated property simultaneously.Therefore strict control has been carried out for silicone content, its content has been limited to less than 0.025%.Preferably: the weight percent content of Si is no more than 0.018%.
Manganese: manganese improves intensity and the most effective element of toughness.If its content is less than 1.10%, then can not meet strength of materials requirement; But add the manganese of volume, the hardening capacity increasing steel can be caused, owing to welding the appearance of hardened layer, crack sensitivity is increased, and increase the cost of alloy of steel.Given this, be defined as 1.29% by it, so, its content is limited to 1.10 ~ 1.29% scopes.
Phosphorus: in order to avoid the welding property of material, stamping formabilily, toughness, suitability for secondary processing worsen, setting its upper content limit is 0.015%.So its content is controlled below 0.015%.
Sulphur: sulphur is the element be harmful to very much.Sulphur in steel often exists with the oxide morphology of manganese, and the impelling strength of this sulfide inclusion to steel is very disadvantageous, and causes the anisotropy of performance, therefore, sulphur content in steel need be controlled more low better.Based on the consideration to Steel Sheet technique and manufacturing cost, plan sulphur content in steel and control below 0.008%.
Aluminium: aluminium adds in order to deoxidation, when Als is containing quantity not sufficient 0.020%, can not play its effect; On the other hand, the aluminium owing to adding volume easily forms aluminum oxide agglomerate, so the regulation Als upper limit is 0.060%.Therefore, Als content is limited to 0.020 ~ 0.060% scope.
Niobium: niobium improves the intensity of steel mainly through crystal grain thinning and precipitation hardening, be strong carbon, nitrogen compound forming element, mainly exist with Nb (C, N) form in steel, stop growing up of austenite crystal, ferrite grain size is finally made to diminish, thinning microstructure.When its content lower than 0.025% time, the requirement of material high strength can not be met; And the niobium added higher than 0.034% time, can meet the requirement of its intensity and processability, if add, cost of alloy can significantly rise again.So, according to the performance objective requirement of steel grade, its content is limited to 0.025 ~ 0.034% scope.Preferably: the weight percent content of Nb is 0.025 ~ 0.030%.
For improving the surface quality of steel, what ensure material can zinc-plated property, and present invention employs strand high temperature rapid firing technique to carry out strand heating, is one of critical process.The present invention takes 1280 ~ 1310 DEG C of Heating temperatures to be ensure the consoluet minimum temperature of alloying element in steel billet, reduce strand heat-up time simultaneously, being controlled at 30 ~ 40min is stove internal oxidition time in order to reduce steel billet, reduces the iron scale of billet surface, improves surface quality.
About carrying out segmentation rolling, and controlling roughing end temp at 1080 ~ 1110 DEG C, controlling finish rolling finishing temperature at 865 ~ 890 DEG C.
Why the present invention adopts cooling speed change cooling to carry out section cooling, namely being first 140 ~ 160 DEG C/sec at ultrafast cold section according to speed of cooling, to carry out front end cold by force, coiling temperature 550 ~ 580 DEG C is cooled to again according to speed of cooling 5 ~ 10 DEG C/sec, after lot of experiments is analyzed, this type of cooling can, under lower design of alloy, make steel plate reach respective strengths requirement.Adopt sub-sectional cooling mode; can not only ensure also not start to cool in time when growing up at the recrystal grain of steel; avoid the generation of thick tissue; to obtain tiny metallographic structure; increase number of grain boundaries, improve the yield tensile ratio of material, and be conducive to obtaining uniform metallographic structure; enable the precipitate even dispersion such as carbide be distributed in base steel, ensure that material possesses good cold shaping performance.
The present invention compared with prior art, under lower design of alloy, adopt ultra-rapid cooling and sub-sectional cooling technique, the coating beam steel produced its there is excellent surface quality and platability, directly can carry out pot galvanize production, meet the requirement of subsequent thermal galvanizer ordered pair plate surface quality, steel plate has yield strength ReL >=460MPa simultaneously, tensile strength 520-670MPa, unit elongation can reach A >=19%, 180 ° of transverse bending test D=1a are qualified, under yield tensile ratio reaches the prerequisite of more than 0.85, improve the dent resistance of steel plate, coating adhesion is further enhanced, there is good surface quality.
Accompanying drawing explanation
Accompanying drawing is metallographic structure figure of the present invention.
Embodiment
Below the present invention is described in detail:
Table 1 is the value list of various embodiments of the present invention;
Table 2 is the main technologic parameters list of various embodiments of the present invention;
Table 3 is the list of various embodiments of the present invention Performance Detection situation.
Various embodiments of the present invention are produced according to following steps:
1) after converter smelting, enter argon station Argon, and routine adds aluminum steel deoxidation and composition adjustment; Control argon blowing time: bottom blowing is not less than 4min, and top blast is not less than 5min;
2) through tapping and continuous casting becomes to strand heating after base, its heating and temperature control at 1280 ~ 1310 DEG C, 30 ~ 40min during heating;
3) carry out segmentation hot rolling, and control roughing end temp at 1080 ~ 1110 DEG C, control finish rolling finishing temperature at 860 ~ 890 DEG C;
4) adopt the speed change degree type of cooling to carry out section cooling, that is: first under speed of cooling is 140 ~ 160 DEG C/sec, be cooled to 700 ~ 740 DEG C, then be cooled to coiling temperature according to the speed of cooling of 5 ~ 10 DEG C/sec;
5) batch, control coiling temperature at 550 ~ 580 DEG C;
6) finishing and rear operation is carried out.
The composition value list (wt%) of table 1 various embodiments of the present invention and comparative example
The main technologic parameters list of table 2 various embodiments of the present invention and comparative example
Table 3 various embodiments of the present invention and comparative example mechanical properties test the results list
Can analyze from table 3, the present invention employing ultra-rapid cooling and sub-sectional cooling technique under, with the design of alloy lower than comparative example, obtain the mechanical property higher than comparative example, production cost is obviously reduced, and the cold shaping performance of product is improved simultaneously, is 2 times of comparative example.
This embodiment is only the best and exemplifies, the restricted enforcement not to technical solution of the present invention.
Claims (4)
1. a 500MPa level automotive frame coated steel, its chemical composition and weight percent content are: C:0.06 ~ 0.09%, Si≤0.025%, Mn:1.10 ~ 1.29%, P≤0.015%, S≤0.006%, Als:0.020 ~ 0.060%, Nb:0.025 ~ 0.034%, surplus is Fe and inevitable impurity.
2. a kind of 500MPa level automotive frame coated steel as claimed in claim 1, is characterized in that: the weight percent content of Si is no more than 0.018%.
3. a kind of 500MPa level automotive frame coated steel as claimed in claim 1, is characterized in that: the weight percent content of Nb is 0.025 ~ 0.030%.
4. produce a kind of method of 500MPa level automotive frame coated steel, its step:
1) after converter smelting, enter argon station Argon, and routine adds aluminum steel deoxidation and composition adjustment; Control argon blowing time: bottom blowing is not less than 4min, and top blast is not less than 5min;
2) through tapping and continuous casting becomes to strand heating after base, its heating and temperature control at 1280 ~ 1310 DEG C, 30 ~ 40min during heating;
3) carry out segmentation hot rolling, and control roughing end temp at 1080 ~ 1110 DEG C, control finish rolling finishing temperature at 860 ~ 890 DEG C;
4) adopt the speed change degree type of cooling to carry out section cooling, that is: first under speed of cooling is 140 ~ 160 DEG C/sec, be cooled to 700 ~ 740 DEG C, then be cooled to coiling temperature according to the speed of cooling of 5 ~ 10 DEG C/sec;
5) batch, control coiling temperature at 550 ~ 580 DEG C;
6) finishing and rear operation is carried out.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105369135A (en) * | 2015-12-22 | 2016-03-02 | 武汉钢铁(集团)公司 | 450 MPa-level zinc-plated dual-phase steel for sedan and production method thereof |
| CN105401071A (en) * | 2015-12-22 | 2016-03-16 | 武汉钢铁(集团)公司 | Galvanized dual-phase steel for 500 MPa class car and production method |
| CN105441805A (en) * | 2015-12-22 | 2016-03-30 | 武汉钢铁(集团)公司 | Galvanized dual-phase steel for 800MPa grade cars and production method |
| CN107675088A (en) * | 2017-11-17 | 2018-02-09 | 武汉钢铁有限公司 | Tensile strength is >=590MPa think gauge wheel rim steel and production method |
| CN107675087A (en) * | 2017-11-17 | 2018-02-09 | 武汉钢铁有限公司 | A kind of good mine wheel-use steel material of low temperature impact properties and production method |
| CN107904501A (en) * | 2017-11-20 | 2018-04-13 | 武汉钢铁有限公司 | A kind of good high intensity Thin Specs wheel of anti-fatigue performance is used and production method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105369135A (en) * | 2015-12-22 | 2016-03-02 | 武汉钢铁(集团)公司 | 450 MPa-level zinc-plated dual-phase steel for sedan and production method thereof |
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| CN105441805B (en) * | 2015-12-22 | 2018-06-26 | 武汉钢铁有限公司 | A kind of 800MPa grades of car Galvanized Dual Phase Steel and production method |
| CN107675088A (en) * | 2017-11-17 | 2018-02-09 | 武汉钢铁有限公司 | Tensile strength is >=590MPa think gauge wheel rim steel and production method |
| CN107675087A (en) * | 2017-11-17 | 2018-02-09 | 武汉钢铁有限公司 | A kind of good mine wheel-use steel material of low temperature impact properties and production method |
| CN107904501A (en) * | 2017-11-20 | 2018-04-13 | 武汉钢铁有限公司 | A kind of good high intensity Thin Specs wheel of anti-fatigue performance is used and production method |
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