CN111411298B - Low-strength iron sheet falling-resistant hot-formed steel coil and preparation method thereof - Google Patents
Low-strength iron sheet falling-resistant hot-formed steel coil and preparation method thereof Download PDFInfo
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- CN111411298B CN111411298B CN202010247607.5A CN202010247607A CN111411298B CN 111411298 B CN111411298 B CN 111411298B CN 202010247607 A CN202010247607 A CN 202010247607A CN 111411298 B CN111411298 B CN 111411298B
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 217
- 239000010959 steel Substances 0.000 title claims abstract description 217
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 175
- 229910052742 iron Inorganic materials 0.000 title claims abstract description 92
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 238000005096 rolling process Methods 0.000 claims abstract description 63
- 238000001816 cooling Methods 0.000 claims abstract description 44
- 238000005097 cold rolling Methods 0.000 claims abstract description 41
- 238000010438 heat treatment Methods 0.000 claims abstract description 28
- 230000003746 surface roughness Effects 0.000 claims abstract description 15
- 238000004140 cleaning Methods 0.000 claims abstract description 12
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 239000011248 coating agent Substances 0.000 claims abstract description 7
- 238000000576 coating method Methods 0.000 claims abstract description 7
- 238000003723 Smelting Methods 0.000 claims abstract description 6
- 238000005266 casting Methods 0.000 claims abstract description 6
- 238000005098 hot rolling Methods 0.000 claims abstract description 5
- 238000000034 method Methods 0.000 claims description 23
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 229910001335 Galvanized steel Inorganic materials 0.000 claims 2
- 239000008397 galvanized steel Substances 0.000 claims 2
- 238000005272 metallurgy Methods 0.000 abstract description 2
- 238000010791 quenching Methods 0.000 description 16
- 230000000171 quenching effect Effects 0.000 description 16
- 239000000463 material Substances 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 238000004080 punching Methods 0.000 description 8
- 238000005406 washing Methods 0.000 description 6
- 238000012216 screening Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- 239000003513 alkali Substances 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 229910001563 bainite Inorganic materials 0.000 description 2
- 239000004519 grease Substances 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229910000797 Ultra-high-strength steel Inorganic materials 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 238000012876 topography Methods 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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Abstract
The invention belongs to the field of metallurgy and steel rolling, and particularly relates to a low-strength hot-formed steel coil resistant to iron sheet shedding, which comprises: 0.20-0.25% of C, 0.20-0.30% of Si, 1.10-1.50% of Mn, 0.02-0.06% of Alt, 0.002-0.004% of B, less than or equal to 0.02% of P, less than or equal to 0.003% of S, less than or equal to 0.005% of N, and the balance of iron and inevitable impurities. The preparation method comprises the following steps: smelting and continuously casting to obtain a steel plate blank, and sequentially heating, hot rolling, cooling and cold rolling the steel plate blank to obtain strip steel; sequentially carrying out cleaning treatment, oil coating treatment and coiling on the strip steel to obtain the low-strength iron sheet shedding resistant thermal-formed steel coil; the cooling mode is back-end laminar flow cooling; the roughness of the roller used in the rolling process is 6.0-6.5 μm; and the surface roughness of the strip steel obtained after the cold rolling is 0.8-1.5 mu m. The product and the preparation method thereof can effectively solve the technical problem that the iron sheet on the surface is easy to fall off during punch forming due to overhigh strength of cold-rolled hot-forming steel.
Description
Technical Field
The invention belongs to the field of metallurgy and steel rolling, and particularly relates to a preparation method of a low-strength iron sheet shedding resistant hot-formed steel coil and a product thereof.
Background
An important approach to achieving weight reduction in automobiles is to apply a large amount of high-strength and ultra-high-strength steel sheets in automobile parts. However, as the strength of the steel plate increases, the stamping forming performance of the steel plate is rapidly reduced, and the steel plate with high strength and ultrahigh strength is easy to crack and rebound seriously when being stamped at normal temperature, and the stamping forming of parts with complex shapes is particularly difficult.
The hot-forming steel plate is an effective way for solving the problems, so that the weight of the vehicle body can be effectively reduced, the oil consumption is reduced, and the safety and the comfort of the vehicle type can be improved.
The hot formed steel is a high strength steel plate which is press-formed and quenched in a die after a steel slab is heated to an austenitizing temperature. The strength of the material can be greatly improved by hot stamping forming, and the maximum strength can reach more than 1500 MPa. At present, the cold-rolled hot-formed steel coil is in a great trend, the cold-rolled hot-formed steel coil needs lower strength, and an annealing type hot-formed steel bare plate is usually used, but when the hot-formed steel bare plate is punched, an iron oxide scale falling off from the surface of the hot-formed steel bare plate easily falls into a die, is difficult to clean, damages the die, greatly reduces the production efficiency by cleaning the die, and is shown in an attached drawing 1.
Disclosure of Invention
In view of the above problems, the invention provides a low-strength hot-formed steel coil resistant to iron sheet falling and a preparation method thereof, and the low-strength hot-formed steel coil resistant to iron sheet falling, which is prepared by adopting the low-strength hot-formed steel coil resistant to iron sheet falling, provided by the invention, can effectively solve the technical problems that the strength of the cold-rolled hot-formed steel is too high and the surface iron sheet is easy to fall off during punch forming in the prior art.
The technical scheme for realizing the purpose is as follows:
the invention provides a low-strength iron sheet shedding resistant hot-formed steel coil, which comprises the following components in percentage by mass: 0.20-0.25% of C, 0.20-0.30% of Si, 1.10-1.50% of Mn, 0.02-0.06% of Alt, 0.002-0.004% of B, less than or equal to 0.02% of P, less than or equal to 0.003% of S, less than or equal to 0.005% of N, and the balance of iron and inevitable impurities.
In one embodiment, in the low-strength and anti-iron sheet shedding thermoformed steel coil of the present invention, the thermoformed steel coil comprises, by mass: 0.22% of C, 0.25% of Si, 1.30% of Mn, 0.035% of Alt0.035%, 0.0025% of B, 0.012% of P, 0.002% of S, 0.004% of N, and the balance of iron and inevitable impurities.
The invention also provides a preparation method of the low-strength iron sheet shedding resistant hot-formed steel coil, which comprises the following steps: smelting and continuously casting to obtain a steel plate blank, and sequentially heating, hot rolling, cooling and cold rolling the steel plate blank to obtain strip steel; sequentially carrying out cleaning treatment, oil coating treatment and coiling on the strip steel to obtain the low-strength iron sheet shedding resistant thermal-formed steel coil;
wherein the steel slab comprises: 0.20-0.25% of C, 0.20-0.30% of Si, 1.10-1.50% of Mn, 0.02-0.06% of Alt, 0.002-0.004% of B, less than or equal to 0.02% of P, less than or equal to 0.003% of S, less than or equal to 0.005% of N, and the balance of iron and inevitable impurities;
the cooling mode is back-end laminar flow cooling;
the cold rolling is carried out by adopting a single frame; the roughness of the roller used in the rolling process is 6.0-6.5 μm; and the surface roughness of the strip steel obtained after the cold rolling is 0.8-1.5 mu m.
In one embodiment, in the method for preparing a low-strength and anti-iron sheet falling hot-formed steel coil, the steel slab comprises: 0.22% of C, 0.25% of Si, 1.30% of Mn, 0.035% of Alt, 0.0025% of B, 0.012% of P, 0.002% of S, 0.004% of N, and the balance of iron and inevitable impurities.
In one embodiment, in the preparation method of the low-strength anti-iron sheet shedding hot-formed steel coil, the heating temperature is 1260-1300 ℃ in the heating process, and preferably 1280 ℃; the heating time is 230-300 min.
In one embodiment, in the method for preparing a low-strength and anti-iron sheet falling hot-formed steel coil, the hot rolling comprises rough rolling and finish rolling; wherein the thickness of the steel plate blank before rough rolling is 237 mm; the thickness of the steel plate blank after rough rolling is 30-40 mm; the thickness of the steel plate blank after the finish rolling is 2.5-3 mm; the finish rolling process is performed by 7 rolling mills.
In the above embodiment, two rolling mills are adopted for the rough rolling process, wherein a "1 + 5" mode or a "3 + 3" mode is respectively adopted for rolling, and the steel slab is rolled from 237mm in thickness to 30-40 mm in thickness; the finish rolling temperature is 850-1100 ℃.
In the above embodiment, the cooling mode is a post laminar cooling mode, that is, laminar cooling is performed at the post laminar cooling stage, that is, the last 25 to 35m of laminar cooling.
In one embodiment, in the preparation method of the low-strength anti-iron sheet shedding hot-formed steel coil, the total rolling reduction rate of the cold rolling is 20-35%. The total rolling reduction rate of the cold rolling limited by the invention can fully reduce the work hardening phenomenon in the cold rolling process on the premise of keeping the grain size more than or equal to 9 grades, thereby reducing the strength of the cold-rolled strip steel.
In one embodiment of the invention, in the process of sequentially performing the cleaning treatment and the oiling treatment on the strip steel, the residual oil amount of the strip steel after the cleaning treatment is less than 50mg/m2(ii) a The residual iron content of the strip steel after the cleaning treatment is less than 100mg/m2(ii) a Preferably, the oil coating amount of the strip steel after the oil coating treatment is 300-1000 mg/m3(ii) a Wherein, the strip steel is cleaned (i.e. degreased) by using alkali liquor and dried;
preferably, the coiling temperature is 680-720 ℃.
The invention also provides the low-strength iron sheet falling-resistant hot-formed steel coil prepared by the preparation method of the low-strength iron sheet falling-resistant hot-formed steel coil.
The invention also provides application of the low-strength iron sheet falling-resistant hot-formed steel coil in preparation of a low-strength iron sheet falling-resistant hot-formed steel plate or a low-strength iron sheet falling-resistant hot-formed steel structural member.
In the invention, the roughness of the roller in the cold rolling process and the surface roughness of the strip steel obtained after the cold rolling are controlled, so that the adhesive force between the surface iron sheet of the low-strength iron sheet falling-resistant hot-formed steel coil and the matrix can be improved, and the phenomenon of iron sheet falling in the subsequent process and the subsequent use can be prevented.
According to the invention, the prepared low-strength iron sheet falling-resistant hot-formed steel coil is uncoiled and blanked to obtain a hot-formed material, then the hot-formed material is punched into a blank through punching equipment (the strip steel is processed into a blank form), and then the blank is sequentially subjected to heat treatment and punching quenching treatment to obtain the low-strength iron sheet falling-resistant formed strip steel. In one embodiment, the step of heat treating comprises: under the protection of nitrogen, heating the blank to 900-910 ℃, and preserving heat for 200-220 seconds; in one embodiment, the process of press quenching includes: and stamping the blank in a stamping and quenching die, and then cooling at a cooling rate of 50-100 ℃/s to a temperature of 100-200 ℃ for 8-12 seconds to obtain the low-strength iron sheet shedding resistant hot formed steel.
According to the preparation method of the low-strength iron sheet falling-resistant hot-formed steel coil, the low-strength iron sheet falling-resistant hot-formed steel coil can be obtained without additionally increasing the alloy cost and is used for preparing the subsequent product hot-formed steel; the preparation method of the low-strength iron sheet shedding resistant hot-formed steel coil is simple and easy to implement, strong in applicability and remarkable in effect.
According to the invention, through a large number of screening tests, the influence of the cooling mode of the steel slab after the rough rolling and the finish rolling on the microstructure of the hot forming steel is determined. The present inventors have found that the grain sizes of the resulting steel sheets are significantly different in the same cooling pattern, as shown in fig. 2(a) and (b). The obtained strip steel is cooled at the later stage of laminar cooling, so that the martensite and bainite structures caused by rapid cooling can be fully avoided. The steel plate blank is coiled at the temperature of 680-720 ℃, and then is subjected to laminar cooling in a later-stage laminar cooling mode, so that the formation of martensite and bainite structures is avoided, and the internal stress and a large amount of dislocation phenomena generated by stamping quenching treatment in the subsequent process are also avoided.
Under the same process and the same performance, the inventor finds that the larger the cold rolling reduction is, the higher the strength (yield strength and tensile strength) of the obtained hot-formed steel coil is when the thickness and the process parameters of the strip steel are the same. In order to obtain the hot-formed steel coil with the tensile strength lower than 850MPa, the cold rolling reduction rate is limited to 20-35%.
Through a large number of screening tests, the following rules are found: in the stamping and quenching process, the surface iron sheet of the hot-formed steel coil can change along with the change of the surface roughness of the strip steel obtained after cold rolling; when the surface roughness of the strip steel obtained after the cold rolling is larger, the iron sheet on the surface of the hot-formed steel coil is more compact and less prone to falling off; the larger the surface roughness of the strip steel is, the stronger the binding force between the iron sheet on the surface layer of the steel plate and the matrix after stamping and quenching is. Furthermore, the roughness of the roller used for cold rolling is controlled within the range of 6.0-6.5 μm, and the roller surface of the roller surface is subjected to chromium plating treatment, so that the surface roughness of the cold-rolled strip steel is not obviously reduced along with the abrasion of the cold rolling roller surface.
In the cold rolling process, some grease of iron powder and emulsion is remained on the strip steel, the iron powder can become a nucleation point for loosening iron scales, and the remained grease can aggravate the oxidation behavior of the strip steel to cause the iron scales on the surface of the strip steel to be more serious and easy to fall off, so the strip steel needs to be oiled and degreased.
In conclusion, the method effectively solves the technical problem that the surface iron sheet is easy to fall off due to the overhigh strength of the hot formed steel in the prior art.
Drawings
Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:
FIG. 1 shows a prior art shedding topography of a hot formed steel surface skin;
FIG. 2 shows a comparison of the grain morphology of the low strength, spall resistant hot formed steel of the present invention with a prior art hot formed steel;
FIG. 3 shows the loose and easy-to-fall appearance of the surface of a prior art hot formed steel;
FIG. 4 shows the appearance of the obtained low-strength anti-iron sheet shedding hot-formed steel with good surface compactness and shedding resistance.
Detailed Description
The present invention is described in further detail below with reference to specific embodiments, which are given for the purpose of illustration only and are not intended to limit the scope of the invention.
The experimental procedures in the following examples are conventional unless otherwise specified. The raw materials and reagent materials used in the following examples are all commercially available products unless otherwise specified.
Example 1
The preparation method of the low-strength iron sheet shedding resistant hot-formed steel coil comprises the following steps:
(1) smelting and continuously casting molten iron or scrap steel to obtain a steel plate blank; wherein, this steel slab contains: 0.20% of C, 0.20% of Si, 1.10% of Mn, 0.02% of Alt, 0.002% of B, 0.02% of P, 0.003% of S, 0.005% of N, and the balance of iron and inevitable impurities;
(2) heating the steel plate blank obtained in the step (1) at 1260 ℃ for 230 min;
(3) carrying out rough rolling on the steel plate blank obtained in the step (2), wherein two rolling mills are adopted for the rough rolling process, and a 1+5 mode or a 3+3 mode is respectively adopted for rolling; the thickness of the steel plate blank before rough rolling is 237 mm; the thickness of the steel plate blank after rough rolling is 30 mm;
(4) performing finish rolling on the strip steel obtained in the step (3), wherein the finish rolling temperature is 850 ℃; the thickness of the steel plate blank after finish rolling is 2.5 mm; the finish rolling process is carried out by 7 rolling mills;
(5) carrying out rear-stage laminar cooling on the strip steel obtained in the step (4) (at the rear stage of the laminar cooling, namely the last 25-35 m stage of the laminar cooling);
(6) cold rolling the strip steel obtained in the step (5), wherein the total reduction rate is 20% in the cold rolling process; the cold rolling is carried out by adopting a single frame, wherein the roughness of a used roller is 6.0 mu m; the surface roughness of the steel coil obtained after cold rolling is 0.8 mu m;
(7) washing the strip steel obtained in the step (6) by using alkali liquor, wherein the residual oil amount of the strip steel after washing treatment is 30mg/m2The residual iron content is 80mg/m2；
(8) Oiling the strip steel obtained in the step (7), wherein the oiling amount of the strip steel is 300mg/m3. If the oiling amount of the strip steel is too low, the requirements of transportation and storage cannot be met, the strip steel is easy to rust, and if the oiling amount of the strip steel is too high, an iron sheet is easy to form;
(9) and (4) coiling the strip steel obtained in the step (8) at the temperature of 680 ℃ to obtain the low-strength iron sheet shedding resistant hot-formed steel coil.
The preparation method of the low-strength anti-iron sheet shedding hot formed steel comprises the following steps:
(1) uncoiling and blanking the obtained low-strength iron sheet shedding resistant hot-formed steel coil to obtain a hot-formed material, and then punching the hot-formed material into a blank through punching equipment (processing the strip steel into a blank form);
(2) sequentially carrying out heat treatment and stamping quenching treatment on the blank obtained in the step (1) to obtain the low-strength iron sheet shedding resistant formed strip steel;
wherein the step of heat treating comprises: under the protection of nitrogen, heating the blank to 900 ℃, and preserving heat for 200 seconds; the process of the stamping quenching treatment comprises the following steps: and stamping the blank in a stamping and quenching die, and then cooling at a cooling rate of 50 ℃/s to 100 ℃ for 8 s.
Example 2
The preparation method of the low-strength iron sheet shedding resistant hot-formed steel coil comprises the following steps:
(1) smelting and continuously casting molten iron or scrap steel to obtain a steel plate blank; wherein, this steel slab contains: 0.25% of C, 0.30% of Si, 1.50% of Mn, 0.06% of Alt, 0.004% of B, 0.01% of P, 0.002% of S, 0.003% of N, and the balance of iron and inevitable impurities;
(2) heating the steel plate blank obtained in the step (1) at 1300 ℃ for 300 min;
(3) carrying out rough rolling on the steel plate blank obtained in the step (2), wherein two rolling mills are adopted for the rough rolling process, and a 1+5 mode or a 3+3 mode is respectively adopted for rolling; the thickness of the steel plate blank before rough rolling is 237 mm; the thickness of the steel plate blank after rough rolling is 40 mm;
(4) performing finish rolling on the strip steel obtained in the step (3), wherein the finish rolling temperature is 1100 ℃; the thickness of the steel plate blank after finish rolling is 3 mm; the finish rolling process is carried out by 7 rolling mills;
(5) carrying out rear-stage laminar cooling on the strip steel obtained in the step (4) (at the rear stage of the laminar cooling, namely the last 25-35 m stage of the laminar cooling);
(6) cold rolling the strip steel obtained in the step (5), wherein in the cold rolling process, the total reduction rate is 35%; the cold rolling is carried out by adopting a single frame, wherein the roughness of a used roller is 6.5 mu m; the surface roughness of the steel coil obtained after cold rolling is 1.5 mu m;
(7) washing the strip steel obtained in the step (6) by using alkali liquor, wherein the residual oil amount of the strip steel after washing treatment is 20mg/m2The residual iron content is 50mg/m2；
(8) Oiling the strip steel obtained in the step (7), wherein the oiling amount of the strip steel is 1000mg/m3. If the oiling amount of the strip steel is too low, the requirements of transportation and storage cannot be met, the strip steel is easy to rust, and if the oiling amount of the strip steel is too high, an iron sheet is easy to form;
(9) and (4) coiling the strip steel obtained in the step (8) at the temperature of 720 ℃ to obtain the low-strength iron sheet shedding resistant hot-formed steel coil.
The preparation method of the low-strength anti-iron sheet shedding hot formed steel comprises the following steps:
(1) uncoiling and blanking the obtained low-strength iron sheet shedding resistant hot-formed steel coil to obtain a hot-formed material, and then punching the hot-formed material into a blank through punching equipment (processing the strip steel into a blank form);
(2) sequentially carrying out heat treatment and stamping quenching treatment on the blank obtained in the step (1) to obtain the low-strength iron sheet shedding resistant formed strip steel;
wherein the step of heat treating comprises: under the protection of nitrogen, heating the blank to 910 ℃, and preserving heat for 220 seconds; the process of the stamping quenching treatment comprises the following steps: and stamping the blank in a stamping and quenching die, and then cooling at a cooling rate of 100 ℃/s to a temperature of 200 ℃ for 12 seconds.
Example 3
The preparation method of the low-strength iron sheet shedding resistant hot-formed steel coil comprises the following steps:
(1) smelting and continuously casting molten iron or scrap steel to obtain a steel plate blank; wherein, this steel slab contains: 0.22% of C, 0.25% of Si, 1.30% of Mn, 0.035% of Alt, 0.0025% of B, 0.012% of P, 0.002% of S, 0.004% of N and the balance of iron and inevitable impurities;
(2) heating the steel plate blank obtained in the step (1) at 1280 ℃ for 300 min;
(3) carrying out rough rolling on the steel plate blank obtained in the step (2), wherein two rolling mills are adopted for the rough rolling process, and a 1+5 mode or a 3+3 mode is respectively adopted for rolling; the thickness of the steel plate blank before rough rolling is 237 mm; the thickness of the steel plate blank after rough rolling is 35 mm;
(4) performing finish rolling on the strip steel obtained in the step (3), wherein the finish rolling temperature is 1100 ℃; the thickness of the steel plate blank after finish rolling is 3 mm; the finish rolling process is carried out by 7 rolling mills;
(5) carrying out rear-stage laminar cooling on the strip steel obtained in the step (4) (at the rear stage of the laminar cooling, namely the last 25-35 m stage of the laminar cooling);
(6) cold rolling the strip steel obtained in the step (5), wherein the total reduction rate is 29% in the cold rolling process; the cold rolling is carried out by adopting a single frame, wherein the roughness of a used roller is 6.5 mu m; the surface roughness of the steel coil obtained after cold rolling is 1.5 mu m;
(7) washing the strip steel obtained in the step (6) by using alkali liquor, wherein the residual oil amount of the strip steel after washing treatment is 40mg/m2The residual iron content is 90mg/m2；
(8) Oiling the strip steel obtained in the step (7), wherein the oiling amount of the strip steel is 600mg/m3. If the oiling amount of the strip steel is too low, the requirements of transportation and storage cannot be met, the strip steel is easy to rust, and if the oiling amount of the strip steel is too high, an iron sheet is easy to form;
(9) and (4) coiling the strip steel obtained in the step (8) at the temperature of 720 ℃ to obtain the low-strength iron sheet shedding resistant hot-formed steel coil.
The preparation method of the low-strength anti-iron sheet shedding hot formed steel comprises the following steps:
(1) uncoiling and blanking the obtained low-strength iron sheet shedding resistant hot-formed steel coil to obtain a hot-formed material, and then punching the hot-formed material into a blank through punching equipment (processing the strip steel into a blank form);
(2) sequentially carrying out heat treatment and stamping quenching treatment on the blank obtained in the step (1) to obtain the low-strength iron sheet shedding resistant formed strip steel;
wherein the step of heat treating comprises: under the protection of nitrogen, heating the blank to 910 ℃, and preserving heat for 220 seconds; the process of the stamping quenching treatment comprises the following steps: and stamping the blank in a stamping and quenching die, and then cooling at a cooling rate of 100 ℃/s to a temperature of 200 ℃ for 12 seconds.
Example 4:
in this example, a screening test was performed to select the optimum heating temperature, heating time, and cooling conditions of the steel slab of the present invention in the case where the cold rolling reduction and the thickness after the finish rolling were determined; therefore, the metallographic structure of the hot-formed steel coil is optimized, and products such as the hot-formed steel coil with low strength and iron sheet shedding resistance are obtained, as shown in table 1; it can be seen that on the premise that the thickness and the cold rolling reduction after finish rolling are kept unchanged, the higher the heating temperature and the longer the heating time of the steel plate blank are, the lower the tensile strength of the hot-formed steel coil is finally; and on the premise that the thickness and the cold rolling reduction rate after the finish rolling are kept unchanged, a laminar flow rear section cooling mode is adopted, wherein the higher the coiling temperature is, the lower the tensile strength of the hot formed steel is finally. In summary, the present invention defines the most suitable parameter range for the optimization of the comprehensive performance, that is: heating at 1260-1300 ℃ for 230-300 min in a laminar flow cooling mode at the rear section, and coiling at 680-720 ℃ to obtain products such as the hot-formed steel coil with optimal comprehensive performance.
TABLE 1
Example 5:
in this example, the following screening test was performed to optimize and select the conditions of the cold rolling reduction and the thickness after the finish rolling according to the present invention in the case where the heating temperature, the heating time, and the cooling condition were determined, as shown in table 2; it can be seen that the smaller the cold rolling reduction, the lower the tensile strength of the hot formed steel; the smaller the finish rolled thickness is, the higher the tensile strength of the hot formed steel is. Thus, the hot formed steel properties obtained are optimal for the parameter ranges defined in the present invention. In summary, the present invention defines the most suitable parameter range for the optimization of the comprehensive performance, that is: the cold rolling reduction rate is 20-35%, the thickness after finish rolling is 2.5-3 mm, and products such as hot-formed steel coils with the optimal comprehensive performance are obtained.
TABLE 2
Example 6:
in this embodiment, the shedding of the scale on the surface of the product such as the hot-formed steel coil is divided into 3 degrees from light to heavy: (1) the scale is seriously peeled off; (2) the iron sheet at the R-angle position obviously falls off, and the iron sheets at the other positions are compact and do not fall off; (3) the iron scale does not drop off obviously. Under the condition that the surface cleanliness of products such as stamping quenching and hot-formed steel coils is kept unchanged, the roughness of the roller used for cold rolling is optimally selected, and the surface roughness of the strip steel obtained after cold rolling is improved, as shown in table 3. It can be seen that if the roughness of the roll is larger, the surface roughness of the strip steel is larger; if the surface roughness of the strip steel is larger, the surface iron sheet of products such as hot-formed steel coils and the like slightly falls off.
TABLE 3
Example 7:
in this example, the following screening test was performed to optimally select the limiting conditions of the present invention for the amount of residual oil and the amount of residual iron after the cleaning treatment of the strip steel in the case where the surface roughness of the strip steel was determined, as shown in table 4. It can be seen that when the residual oil amount and the residual iron amount of the strip steel after the cleaning treatment are less, the scale of the strip steel is less, and the scale is less prone to fall off. The shedding condition of the iron scale is divided into 3 degrees from light to heavy: (1) the shedding of the surface iron oxide scale is serious; (2) the iron sheet at the R-angle position obviously falls off, and the iron sheets at the other positions are compact and do not fall off; (3) the surface iron scale does not drop off obviously.
TABLE 4
In conclusion, the above description of the embodiments of the present invention is not intended to limit the present invention, and those skilled in the art can make various changes or modifications according to the present invention without departing from the spirit of the present invention, which falls within the scope of the appended claims.
Claims (7)
1. A preparation method of a low-strength iron sheet shedding resistant hot-formed steel coil comprises the following steps: smelting and continuously casting to obtain a steel plate blank, and sequentially heating, hot rolling, cooling and cold rolling the steel plate blank to obtain strip steel; sequentially carrying out cleaning treatment, oil coating treatment and coiling on the strip steel to obtain the low-strength iron sheet shedding resistant hot-formed steel coil;
wherein the steel slab comprises: 0.20-0.25% of C, 0.20-0.30% of Si, 1.10-1.50% of Mn, 0.02-0.06% of Alt, 0.002-0.004% of B, less than or equal to 0.02% of P, less than or equal to 0.003% of S, less than or equal to 0.005% of N, and the balance of iron and inevitable impurities;
in the heating process, the heating temperature is 1260-1300 ℃, and the heating time is 230-300 min;
the hot rolling comprises rough rolling and finish rolling, and the thickness of the steel plate blank after the finish rolling is 2.5-3 mm;
the total reduction rate of the cold rolling is 20-35%;
the cooling mode is back-end laminar cooling, and the back-end laminar cooling refers to laminar cooling at the last stage of 25-35 m of laminar cooling;
the cold rolling is carried out by adopting a single frame; the roughness of the roller used in the rolling process is 6.0-6.5 μm; the surface roughness of the strip steel obtained after the cold rolling is 0.8-1.5 mu m;
the method comprises the following steps of sequentially carrying out cleaning treatment and oiling treatment on the strip steel, wherein the residual oil amount of the strip steel after the cleaning treatment is less than 50mg/m2(ii) a The residual iron content of the strip steel after the cleaning treatment is less than 100mg/m2The oil coating amount of the strip steel after the oil coating treatment is 300-1000 mg/m3。
2. The method of making a low strength, iron sheet peel resistant thermoformed steel coil as claimed in claim 1 wherein said steel slab comprises: 0.22% of C, 0.25% of Si, 1.30% of Mn, 0.035% of Alt, 0.0025% of B, 0.012% of P, 0.002% of S, 0.004% of N, and the balance of iron and inevitable impurities.
3. The method of making a low strength, iron sheet peel resistant thermoformed steel coil as claimed in claim 1 wherein the heating is carried out at a temperature of 1280 ℃.
4. The method for preparing a low-strength anti-iron sheet shedding hot formed steel coil as claimed in claim 1, wherein the thickness of the steel slab before the rough rolling is 237 mm; the thickness of the steel plate blank after rough rolling is 30-40 mm.
5. The method for preparing a low-strength and anti-iron sheet falling hot-formed steel coil as claimed in claim 1, wherein the coiling temperature is 680-720 ℃.
6. The low-strength galvanized steel coil prepared by the method for preparing the low-strength galvanized steel coil according to any one of claims 1 to 5.
7. Use of a low strength, spall resistant thermoformed steel coil as in claim 6 in the manufacture of a low strength, spall resistant thermoformed steel sheet or low strength, spall resistant thermoformed steel structure.
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| JP2003183733A (en) * | 2001-12-14 | 2003-07-03 | Sumitomo Metal Ind Ltd | Wire rod manufacturing method |
| CN105543685A (en) * | 2015-12-25 | 2016-05-04 | 本钢板材股份有限公司 | Hot stamping forming steel board for restraining falling off of oxide layer in hot stamping process and production method thereof |
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