CN114130842A - Method for removing oxide skin of high Cr-Si alloyed 1000-plus 1800 MPa-level hot forming steel - Google Patents
Method for removing oxide skin of high Cr-Si alloyed 1000-plus 1800 MPa-level hot forming steel Download PDFInfo
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- CN114130842A CN114130842A CN202111428573.0A CN202111428573A CN114130842A CN 114130842 A CN114130842 A CN 114130842A CN 202111428573 A CN202111428573 A CN 202111428573A CN 114130842 A CN114130842 A CN 114130842A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 150
- 239000010959 steel Substances 0.000 title claims abstract description 150
- 238000000034 method Methods 0.000 title claims abstract description 85
- 229910019819 Cr—Si Inorganic materials 0.000 title claims abstract description 17
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 157
- 238000005554 pickling Methods 0.000 claims abstract description 60
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 15
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 14
- 239000002253 acid Substances 0.000 claims description 50
- 238000004140 cleaning Methods 0.000 claims description 36
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 32
- 229910052742 iron Inorganic materials 0.000 claims description 15
- -1 iron ions Chemical class 0.000 claims description 10
- 229910052802 copper Inorganic materials 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- 239000012535 impurity Substances 0.000 claims description 8
- 229910052748 manganese Inorganic materials 0.000 claims description 8
- 229910052758 niobium Inorganic materials 0.000 claims description 8
- 229910052698 phosphorus Inorganic materials 0.000 claims description 8
- 229910052720 vanadium Inorganic materials 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 2
- 238000000576 coating method Methods 0.000 abstract description 16
- 230000003647 oxidation Effects 0.000 abstract description 15
- 238000007254 oxidation reaction Methods 0.000 abstract description 15
- 239000011248 coating agent Substances 0.000 abstract description 14
- 238000005098 hot rolling Methods 0.000 abstract description 14
- 229910018125 Al-Si Inorganic materials 0.000 abstract description 11
- 229910018520 Al—Si Inorganic materials 0.000 abstract description 11
- 239000011159 matrix material Substances 0.000 abstract description 8
- 229910045601 alloy Inorganic materials 0.000 abstract description 7
- 239000000956 alloy Substances 0.000 abstract description 7
- 238000012545 processing Methods 0.000 abstract description 4
- 239000007769 metal material Substances 0.000 abstract description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 21
- 238000005096 rolling process Methods 0.000 description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 7
- 238000004626 scanning electron microscopy Methods 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 238000013461 design Methods 0.000 description 6
- 239000010410 layer Substances 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 238000005406 washing Methods 0.000 description 6
- 239000013556 antirust agent Substances 0.000 description 5
- 235000013980 iron oxide Nutrition 0.000 description 5
- 229910052681 coesite Inorganic materials 0.000 description 4
- 230000007797 corrosion Effects 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 229910052906 cristobalite Inorganic materials 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- 238000005507 spraying Methods 0.000 description 4
- 239000002436 steel type Substances 0.000 description 4
- 229910052682 stishovite Inorganic materials 0.000 description 4
- 229910052905 tridymite Inorganic materials 0.000 description 4
- 229910021577 Iron(II) chloride Inorganic materials 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 description 3
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 3
- 239000003562 lightweight material Substances 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 238000000053 physical method Methods 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
- 229910052596 spinel Inorganic materials 0.000 description 3
- 239000011029 spinel Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 230000003746 surface roughness Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005422 blasting Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000000921 elemental analysis Methods 0.000 description 2
- 229910052840 fayalite Inorganic materials 0.000 description 2
- 238000007667 floating Methods 0.000 description 2
- 239000006260 foam Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229910052909 inorganic silicate Inorganic materials 0.000 description 2
- 230000001050 lubricating effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 229910021556 Chromium(III) chloride Inorganic materials 0.000 description 1
- 229910017060 Fe Cr Inorganic materials 0.000 description 1
- 229910017082 Fe-Si Inorganic materials 0.000 description 1
- 229910017133 Fe—Si Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910003910 SiCl4 Inorganic materials 0.000 description 1
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- QSWDMMVNRMROPK-UHFFFAOYSA-K chromium(3+) trichloride Chemical compound [Cl-].[Cl-].[Cl-].[Cr+3] QSWDMMVNRMROPK-UHFFFAOYSA-K 0.000 description 1
- 239000011636 chromium(III) chloride Substances 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000002068 genetic effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000003550 marker Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- FDNAPBUWERUEDA-UHFFFAOYSA-N silicon tetrachloride Chemical compound Cl[Si](Cl)(Cl)Cl FDNAPBUWERUEDA-UHFFFAOYSA-N 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- RMLPZKRPSQVRAB-UHFFFAOYSA-N tris(3-methylphenyl) phosphate Chemical compound CC1=CC=CC(OP(=O)(OC=2C=C(C)C=CC=2)OC=2C=C(C)C=CC=2)=C1 RMLPZKRPSQVRAB-UHFFFAOYSA-N 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/04—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing
- B21B45/06—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing of strip material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0269—Cleaning
- B21B45/0275—Cleaning devices
-
- 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
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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
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/08—Iron or steel
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Abstract
The invention belongs to the technical field of metal material processing, and particularly relates to a method for removing oxide skin of high Cr-Si alloyed 1000-grade 1800 MPa-grade thermoformed steel. The high Cr-Si alloyed 1000-1800 MPa-level hot-rolling coating-free hot-forming steel has the advantages that because a large amount of alloy elements such as Cr, Si and the like are added to improve the hardenability and the oxidation resistance, the oxide skin on the surface of the steel strip prepared by a hot rolling mode is more compact, the oxide skin is more tightly combined with a matrix, so that the difficulty in removing the oxide skin after hot rolling is higher, and meanwhile, on the premise of avoiding an Al-Si coating, the control requirement of subsequent hot forming on the thickness of the oxide skin is difficult to achieve only by adopting a conventional pickling process. Aiming at the problems, the invention provides the scale removing process combining hydrochloric acid pickling and EPS treatment, which can completely meet the control requirement of subsequent hot forming on the thickness of the scale on the premise of no Al-Si coating.
Description
Technical Field
The invention belongs to the technical field of metal material processing, and particularly relates to a method for removing oxide skin of high Cr-Si alloyed 1000-grade 1800 MPa-grade thermoformed steel.
Background
In order to meet the national requirements for ever-increasing safety performance of automobiles and increasingly stringent environmental regulations, automobile designers must consider reasonable matching of collision safety and fuel economy of automobile bodies, and lightweight design of automobile bodies is the most effective method for solving the problem. The design of the light weight of the automobile mainly comprises 3 aspects of the optimized design of the automobile body structure, the reasonable application of the light weight material and the use of the advanced manufacturing process, wherein the research and the reasonable application of the light weight material are the hot subjects of the current research in the automobile industry, steel and related fields, and are also one of the important measures for realizing the light weight design of the automobile. The high-strength steel is one of the most economical and widely applied materials in a plurality of lightweight materials, and the use of the thin-specification high-strength steel to replace a low-strength-level thick steel plate not only saves the consumption of steel, but also can greatly improve the safety performance while realizing the lightweight of the automobile.
In recent years, hot-formed steels have been increasingly used in key parts of vehicle bodies, such as a-pillars, B-pillars, door impact beams, etc. of vehicle body bumpers and body side structures. Since 2010, most automobile manufacturers have used hot formed parts on body-in-white, and due to the many advantages of hot formed steel, the yield of hot formed parts and the percentage of hot formed parts in body-in-white has increased year by year. In order to avoid the oxidation of the steel plate in the hot stamping process, the metal plate is protected by a coating mode, wherein the Al-Si coating is most widely applied because the Al-Si coating has a series of advantages of low density, high thermal conductivity, wear resistance, small thermal expansion coefficient and the like, but the preparation cost of the coating raw material and the coating process needs to pay extra Annelitar aluminum-silicon coating special fee, so the most direct and effective method for solving the problem is to develop novel low-cost hot forming steel with good high-temperature oxidation resistance, and not only can realize technical breakthrough, but also can greatly improve the economic added value of the product.
The development of the hot forming steel presents two main flow directions, the first direction is to enhance high-temperature oxidation resistance, the steel is driven by the market, in order to cope with the low-cost intense market competition environment and promote the independent innovation capability of enterprises, the limitation of an Al-Si coating patent of Ansailetaer is broken through, the original innovation of component design is established, the low-cost hot forming steel with high-temperature oxidation resistance is researched and developed from the innovative component design angle by referring to the traditional 22MnB5 alloy component system and combining the thought of high-temperature oxidation resistant stainless steel, and the defects of poor surface quality, low yield, poor welding performance, potential safety hazard in the service process and the like of the domestic existing steel for the hot forming bare plate are overcome; and the second direction is to greatly shorten the process flow, improve the production efficiency, remove the existing softening annealing and cold rolling procedures of the hot forming steel, obtain a fine initial structure by optimizing the TMCP process by utilizing the advantages of the thin gauge steel plate rolled by the existing hot rolling equipment, inherit the characteristics of the initial refined structure by utilizing the tissue genetic law in the hot forming process and obtain a product with excellent performance. Meanwhile, the technology of replacing cold with heat can realize energy conservation and consumption reduction of the steel production flow and greatly improve the production efficiency of the ultrahigh-strength automobile steel. Thermoformed products having a thickness of 1.4mm and above make up 90% of the total scale, as estimated by the industry. The hot-rolled oxidation-resistant coating-free thin-specification hot-formed steel has wide market application prospect, and related technical innovation can fill up the international blank.
Based on the above thought, a steel grade which can be made into a steel plate only by hot rolling and can be used for hot forming without an oxidation resistant coating is developed, and the steel grade comprises the following components in percentage by mass: c: 0.15 to 0.35%, Mn: 0.8-3.2%, Si: 0.8-2.8%, S: < 0.01%, P: < 0.015%, Al: 0.01-0.05%, Cr: 1.5-3.9%, Nb: 0.01-0.05%, V: 0.01-0.05%, Ti: 0.01-0.03%, Cu: 0.05-0.15%, and the balance of Fe and other inevitable impurities. The steel is hot-rolled coating-free hot forming steel, breaks through an Al-Si coating patent, and creates a brand-new production mode of hot forming steel, namely compared with an Al-Si coating plate, an Al-Si coating process is omitted, compared with a bare plate, a shot blasting process after hot forming is omitted, so that the requirements of not falling off oxide skin and the like in the hot forming process are met, the production cost is greatly reduced, the requirements of the series of steel on the surface quality of a steel plate for hot forming are very strict, especially the control of the oxide skin is more important, and the requirement of the thickness of the oxide skin after acid washing is not more than 2 mu m for meeting the requirements of subsequent hot forming of the steel is met.
However, in this steel grade, the oxide includes SiO due to the addition of Si element2，FeO，Fe3O4And Fe2O3，SiO2Will form silicate-Fe on the surface2SiO4. In Fe-Si alloys with low Si content, SiO2Nucleation is performed on the surface of the alloy. At the beginning of oxidation, SiO2The iron oxide is spread and grown on the surface of the alloy together with the iron oxide, and the iron oxide is uniformly distributed on the surface of the alloy in a relatively fine shape. At the same time, it reacts with FeO in solid phase to produce fayalite (Fe)2SiO4) As the particle grows, it becomes coated with growing scale. Island-like Fe2SiO4The particles are present in FeO like a marker and are distributed on the metal surface in parallel in strips.
When the Cr content is low, Cr-rich oxides and iron oxides are simultaneously formed on the surface at the initial stage of oxidation. Part of the Cr will be solid soluble in FeO and the solid solubility of Cr is limited due to spinel stability. Fe diffused out with the increase of Cr content in the matrix2+Will be Fe Cr in the Cr-rich layer2O4Hindered by the thickness of the FeO layer being in comparison with Fe3O4The layer is continuously thinned. These stages still have a high oxidation rate, similar to pure iron. With further increase of the Cr content, a mixed spinel containing Fe (Fe, Cr) is formed2O4Scaling of layers is usually accompanied by a lower parabolic rate constant. It is clear that after long-term oxidation, the diffusion of iron ions in the surface scale is much greater than that of Cr3+The oxidation rate is then controlled by the out-diffusion of iron ions through the mixed spinel layer, resulting in relatively pure iron oxide on the outer surface of the oxide scale.
Therefore, because more Cr and Si elements are added into the steel, the oxide skin on the surface of the hot-rolled strip steel (or hot-rolled steel plate) is more compact, and the oxide skin is more tightly combined with a matrix, the difficulty in removing the oxide skin after hot rolling is higher, and meanwhile, on the premise of avoiding an Al-Si coating, the control requirement of subsequent hot forming on the thickness of the oxide skin is difficult to achieve by only adopting a conventional pickling process.
Disclosure of Invention
The high Cr-Si alloyed 1000-1800 MPa-level hot-rolling coating-free hot-forming steel has the advantages that because a large amount of alloy elements such as Cr, Si and the like are added to improve the hardenability and the oxidation resistance, the oxide skin on the surface of the steel strip prepared by a hot rolling mode is more compact, the oxide skin is more tightly combined with a matrix, so that the difficulty in removing the oxide skin after hot rolling is higher, and meanwhile, on the premise of avoiding an Al-Si coating, the control requirement of subsequent hot forming on the thickness of the oxide skin is difficult to achieve only by adopting a conventional pickling process. Aiming at the problems, the invention provides the oxide skin removing process combining the chemical method and the physical method, and the oxide skin removing process can completely meet the control requirement of the subsequent hot forming on the thickness of the oxide skin on the premise of no Al-Si coating.
The technical scheme of the method is as follows:
the steel type aimed by the invention is high Cr-Si alloyed 1000-1800 MPa-grade hot rolling coating-free hot forming steel, and comprises the following chemical components in percentage by weight: c: 0.15 to 0.35%, Mn: 0.8-3.2%, Si: 0.8-2.8%, S: < 0.01%, P: < 0.015%, Al: 0.01-0.05%, Cr: 1.5-3.9%, Nb: 0.01-0.05%, V: 0.01-0.05%, Ti: 0.01-0.03%, Cu: 0.05 to 0.15 percent, and the balance of Fe and other inevitable impurities, and the steel grade can be processed into strip steel with the thickness of 0.6 to 6.0mm through hot rolling.
The strip steel adopts a scale removing process combining a chemical method and a physical method, can completely remove compact scale on the surface of the strip steel after hot rolling, and simultaneously improves the surface roughness of products, and comprises the following process steps:
(1) hydrochloric acid pickling
The steel coil or strip steel with the components after hot rolling and uncoiling flattening is firstly pulled and straightened, and because the steel contains higher Cr and Si contents, oxide skin is more compact and more tightly combined with a matrix than other steel types, aiming at the steel type, a larger pulling and straightening elongation rate is required to be adopted to achieve the scale breaking effect, conditions are provided for effectively removing the oxide skin by subsequent hydrochloric acid pickling, equipment conditions are combined, according to different thicknesses of the strip steel, the pulling and straightening elongation rate is set to be 0.5% -2.0%, the smaller the thickness is, the larger the pulling and straightening elongation rate is; then hydrochloric acid pickling is carried out, the hydrochloric acid pickling is divided into three sections, and the hydrochloric acid pickling process comprises the following steps:
a first stage: the concentration of the hydrochloric acid is 60 g/L-150 g/L, and the temperature of the acid liquor is 60 ℃ to 95 ℃;
and a second stage: the concentration of the hydrochloric acid is 80 g/L-180 g/L, and the temperature of the acid liquor is 60 ℃ to 95 ℃;
a third stage: the concentration of the hydrochloric acid is 100 g/L-200 g/L, and the temperature of the acid liquid is 60 ℃ to 95 ℃.
The concentration of iron ions in the acid tank in the three-stage acid washing is required to be not more than 150 g/L;
the process speed is 15 m/min-120 m/min, and the washing is carried out by hydrochloric acid, rinsing and drying. After the primary acid washing, the surface oxide skin at partial positions of the strip steel is effectively removed, but the thickness of the oxide skin at partial positions is 0.2-6 mu m thicker, namely after the primary acid washing, the thickness of the oxide skin at the surface of the strip steel does not completely meet the requirement of subsequent hot forming on the thickness of the oxide skin not more than 2 mu m. The reaction process for removing the oxide skin on the surface of the strip steel by hydrochloric acid pickling is as follows:
FeO+2HCl=FeCl2+H2O
Fe3O4+8HCl=2FeCl3+FeCl2+4H2O
Fe2O3+6HCl=2FeCl3+3H2O
Fe+2HCl=FeCl2+H2
SiO2 + 4HCl = SiCl4 + 2H2O
Cr2O3+ 6 HCl = 2 CrCl3+ 3 H2O
(2) EPS cleaning
In order to further effectively remove the oxide skin on the Surface of the strip steel, the oxide skin removing process of the steel grade is additionally provided with an EPS (Eco Pickled Surface, environmental-friendly Surface treatment method) cleaning procedure on the basis of the conventional hydrochloric acid pickling process, and the EPS has the working principle that special media (steel grit, water and a water-based antirust agent) are sprayed on the Surface of a steel plate to be treated in an EPS unit, so that the purpose of effectively removing the oxide skin on the Surface of the steel plate is achieved. On one hand, the water-based antirust agent plays a role in lubricating steel sand through a pipeline, can remove floating foam generated in the treatment process, can be attached to the surface of a treated steel plate to form an antirust protective film so as to prevent the steel plate from being rusted, can improve the roughness of the surface of a product and is beneficial to subsequent hot stamping processing.
The EPS cleaning process speed is based on the specific situation of the oxide skin residue on the surface of the strip steel after primary acid cleaning and the actual EPS unit input situation, and the more EPS units are input, the higher the process speed is. In the hydrochloric acid pickling process, the strip steel can be coiled again, so that the strip steel is firstly pulled and straightened again to achieve the effects of further improving the plate shape and breaking the scale, the pulling and straightening elongation rate is 0.2% -2.0%, the elongation rate is according to the residual condition of the scale on the surface of the strip steel before EPS and the thickness of the strip steel, the more the residue is, the thinner the thickness of the strip steel is, the larger the elongation rate is, the EPS process speed is set to be 10-60 m/min, the surface color of the strip steel after EPS treatment is uniform, and the thickness of the scale reaches the requirement of the scale thickness not more than 2 mu m for subsequent hot forming. On the premise of effectively removing the iron scale, the process speed is adjusted to achieve the purpose of controlling the apparent roughness.
The hydrochloric acid has stronger corrosion capability to metal oxides, but has slower speed for dissolving matrix metals such as steel and the like; when pickling with hydrochloric acid, there is less risk of corrosion and hydrogen embrittlement. The surface residues of the workpiece after hydrochloric acid pickling are less, and the rust removal quality is good; the EPS technology (green surface cleaning technology) is a technology for removing oxide skin on the surface of a steel plate by a physical method, and the purpose of removing the oxide skin on the surface of the steel plate is achieved by spraying steel grit, water and a water-based antirust agent on the surface of the steel plate to be treated, and the treated plate surface has no dirt residue and is cleaner and tidier than a shot blasting surface; in addition, the surface quality is stable, the roughness arrangement is uniform, the subsequent spraying process is facilitated, and the paint adhesion is enhanced.
The invention has the following beneficial effects:
1. because the steel contains higher Cr and Si contents, the oxide skin is more compact and more closely combined with a matrix than other steel types, a larger straightening elongation rate mode is needed before pickling, the oxide layer on the surface of the steel can be cracked, the pickling efficiency of the subsequent pickling step is increased, and the effective removal of the oxide skin on the surface of the strip steel can not be achieved only through hydrochloric acid pickling.
2. Because more Cr and Si elements are added into the steel, the oxide skin on the surface of the hot-rolled strip steel is more compact, the oxide skin is more tightly combined with a matrix, the difficulty in removing the oxide skin after hot rolling is higher, and the requirement of subsequent hot forming on the thickness of the oxide skin not more than 2 mu m can not be met only by adopting a single procedure of hydrochloric acid pickling or EPS cleaning. After hydrochloric acid pickling and EPS cleaning treatment, the requirement of subsequent hot forming on oxide skin thickness not more than 2 microns can be met, and after hot forming under the condition of nitrogen/air protective atmosphere, the surface oxide skin thickness is 0.2-2 microns.
3. Through EPS treatment, EPS plate coiled materials with different surface roughness (different Ra values and lower Rz values) can be produced according to customer requirements on the premise of ensuring effective removal of iron scale, and the requirements of subsequent hot stamping processing can be met.
And 4. the EPS treatment can form a stable protective layer on the surface of the steel plate, and can inhibit corrosion, so that the plate coil subjected to the EPS treatment has more excellent corrosion resistance.
5. The oxide skin on the surface of the strip steel is removed by adopting the technological process of hydrochloric acid pickling and EPS cleaning, the production technological process is simple to control and operate, and industrialization is easy to realize.
Drawings
FIG. 1 is an SEM photograph of the surface scale of the steel strip of example 2 after pickling with hydrochloric acid and the results of elemental analysis of the scale.
FIG. 2 is an SEM picture of the surface scale of the steel strip of example 2 after pickling with hydrochloric acid and EPS cleaning and the results of elemental analysis of the scale.
Detailed Description
The embodiment of the invention adopts the steel-cold ultrathin pickling line and EPS cleaning equipment of a certain company.
In the embodiment of the invention, an EVO18 scanning electron microscope of ZEISS company is adopted for observing the microstructure of the oxide scale.
The steel coils in the embodiment of the invention are all prepared from blanks with corresponding components in the following modes: heating the continuous casting blank in a heating furnace to 1150-1300 ℃, preserving heat for 1-2.5 h, removing furnace oxidation skin through primary descaling, and carrying out rough rolling and finish rolling: the initial rolling temperature of rough rolling is 1100-1300 ℃, the rough rolling can be carried out for about 6 passes, the total reduction rate is 80% -90%, and the thickness of the obtained rough rolling intermediate blank is 30-45 mm; removing a secondary oxide skin before finish rolling, carrying out finish rolling for about 7 passes, and obtaining a hot rolled plate with a specified thickness by finish rolling, wherein the start rolling temperature and the finish rolling temperature of the finish rolling are respectively 1000-1090 ℃ and 880-950 ℃; and after finishing the finish rolling, cooling the steel plate to 550-750 ℃ at a cooling rate of 5-30 ℃/s, wherein the temperature range (550-750 ℃) is also used as the initial coiling temperature, coiling the steel plate at the initial coiling temperature, and then cooling the steel plate to room temperature in an air mode to obtain a steel coil or band steel.
In the embodiment of the invention, hydrochloric acid pickling is divided into three sections, the length of each section of acid tank is 25m, the steel coil after hydrochloric acid pickling is subjected to scale breaking and further shape improvement by an 11-roller wet straightener at the inlet of an EPS treatment line, and then enters an EPS unit, the unit is provided with two EPS units, each unit is respectively provided with an upper spraying turbine and a lower spraying turbine, blades of the turbines spray special media (steel grit, water and a water-based antirust agent) onto the surface of a steel plate to be treated at a high speed, and the aims of completely removing the iron scale on the surface of the strip steel and adjusting the surface roughness are achieved by adjusting the process speed. The water-based antirust agent has a lubricating effect on steel grit passing through a pipeline, can remove floating foam generated in the treatment process, and can be attached to the surface of a treated steel plate to form an antirust protective film so as to prevent the steel plate from being rusted.
Example 1
The method comprises the following steps of removing oxide scales of a strip steel of high Cr-Si alloyed hot-rolled coating-free hot forming steel of 1000-1800MPa grade with the specification of 1.2mm (thickness) × 1100mm (width), wherein the steel comprises the following components:
c: 0.18%, Mn: 2.5%, Si: 2.8%, S: 0.005%, P: 0.008%, Al: 0.03%, Cr: 3.5%, Nb: 0.01%, V: 0.05%, Ti: 0.02%, Cu: 0.10%, and the balance of Fe and other unavoidable impurities.
The method adopts the technological process of pickling with hydrochloric acid (100 m/min) + EPS cleaning (15 m/min) to remove the oxide skin on the surface of the strip steel, and comprises the following steps:
(1) hydrochloric acid pickling
Uncoiling and straightening the strip steel, wherein the straightening elongation is as follows: the setting range is less than or equal to 2.0 percent;
hydrochloric acid concentration in the first-stage acid tank: 150 g/L +/-20 g/L, acid liquor temperature of 80 +/-10 ℃,
hydrochloric acid concentration in the second-stage acid tank: 170 g/L +/-20 g/L, acid liquor temperature of 80 +/-10 ℃,
hydrochloric acid concentration in the third stage acid tank: 220 g/L +/-20 g/L, and the temperature of the acid liquor is 80 +/-10 ℃;
the concentration of iron ions is required to be not more than 100 g/L;
the process speed is 100 m/min.
Rinsing and drying after hydrochloric acid pickling, wherein after hydrochloric acid pickling, the oxide skin on the surface of the strip steel is not completely removed through SEM analysis, the thickness of the oxide skin at the edge part is between 1 and 3 mu m, and the thickness of the oxide skin at the middle part is between 2 and 4 mu m.
(2) EPS cleaning
2 EPS units are put into;
and (3) performing withdrawal and straightening on the strip steel again, wherein the withdrawal and straightening elongation is as follows: less than or equal to 1.5 percent;
the process speed is as follows: 15 m/min;
after EPS cleaning, the thickness of the oxide skin on the surface of the strip steel is 0-1.5 mu m, the requirement of subsequent hot forming on the thickness of the oxide skin not more than 2 mu m is met, and the surface color is uniform.
Example 2
The method comprises the following steps of removing oxide scales of a strip steel of hot-rolled plating-free hot-forming steel with a high Cr-Si alloying level of 1000-1800MPa, wherein the specification of the strip steel is 1.5mm (thickness) × 1100mm (width), and the steel comprises the following components:
c: 0.30%, Mn: 0.8%, Si: 1.8%, S: 0.005%, P: 0.008%, Al: 0.01%, Cr: 3.0%, Nb: 0.03%, V: 0.01%, Ti: 0.03%, Cu: 0.05%, and the balance of Fe and other unavoidable impurities.
The method adopts the technological process of pickling with hydrochloric acid (60 m/min) + EPS cleaning (50 m/min) to remove the oxide skin on the surface of the strip steel, and comprises the following steps:
(1) hydrochloric acid pickling
Uncoiling and straightening the strip steel, wherein the straightening elongation is as follows: the setting range is less than or equal to 1.9 percent;
hydrochloric acid concentration in the first-stage acid tank: 120 g/L +/-20 g/L, acid liquor temperature of 80 +/-10 ℃,
hydrochloric acid concentration in the second-stage acid tank: 150 g/L +/-20 g/L, acid liquor temperature of 80 +/-10 ℃,
hydrochloric acid concentration in the third stage acid tank: 190 g/L +/-20 g/L, and the temperature of the acid liquor is 80 +/-10 ℃;
the concentration of iron ions is required to be not more than 100 g/L;
the process speed is 60 m/min.
And after hydrochloric acid pickling, rinsing and drying, and after hydrochloric acid pickling, completely removing oxide scales at the surface parts of the edge parts and the middle parts of the strip steel through SEM analysis as shown in figure 1, wherein the thickness of the oxide scale at the edge parts is 0.7-1 mu m, and the thickness of the oxide scale at the middle parts is 0.7-4 mu m.
(2) EPS cleaning
2 EPS units are put into;
and (3) performing withdrawal and straightening on the strip steel again, wherein the withdrawal and straightening elongation is as follows: less than or equal to 1.2 percent;
the process speed is as follows: 50 m/min;
after EPS cleaning, the thickness of the oxide scale on the surface of the strip steel is 0-1 μm, as shown in figure 2, the requirement of subsequent hot forming on the thickness of the oxide scale not more than 2 μm is met, and the surface color is uniform.
Example 3
The method comprises the following steps of removing oxide scales of a strip steel of hot-rolled plating-free hot forming steel with a high Cr-Si alloying level of 1000-1800MPa, wherein the specification of the strip steel is 1.9mm (thickness) × 1100mm (width), and the steel comprises the following components:
c: 0.20%, Mn: 3.0%, Si: 2.5%, S: 0.005%, P: 0.008%, Al: 0.05%, Cr: 1.8%, Nb: 0.05%, V: 0.03%, Ti: 0.01%, Cu: 0.10%, and the balance of Fe and other unavoidable impurities.
The method adopts the technological process of pickling with hydrochloric acid (40 m/min) + EPS cleaning (30 m/min) to remove the oxide skin on the surface of the strip steel, and comprises the following steps:
(1) hydrochloric acid pickling
Uncoiling and straightening the strip steel, wherein the straightening elongation is as follows: the setting range is less than or equal to 1.8 percent;
hydrochloric acid concentration in the first-stage acid tank: 120 g/L +/-10 g/L, acid liquor temperature of 80 +/-5 ℃,
hydrochloric acid concentration in the second-stage acid tank: 150 g/L +/-10 g/L, acid liquor temperature of 80 +/-5 ℃,
hydrochloric acid concentration in the third stage acid tank: 190 g/L +/-10 g/L, and the temperature of the acid liquor is 80 +/-5 ℃;
the concentration of iron ions is required to be not more than 100 g/L;
the process speed is 40 m/min.
Rinsing and drying after hydrochloric acid pickling, wherein after hydrochloric acid pickling, the oxide scale on the surface of the strip steel is not completely removed through SEM analysis, the thickness of the oxide scale at the edge part is between 5 and 8 mu m, and the thickness of the oxide scale at the middle part is between 9 and 10 mu m.
(2) EPS cleaning
2 EPS units are put into;
and (3) performing withdrawal and straightening on the strip steel again, wherein the withdrawal and straightening elongation is as follows: less than or equal to 1.0 percent;
the process speed is as follows: 30 m/min;
after EPS cleaning, the thickness of the oxide skin on the surface of the strip steel is 0-1.5 mu m, the requirement of subsequent hot forming on the thickness of the oxide skin not more than 2 mu m is met, and the surface color is uniform.
Example 4
The method comprises the following steps of removing oxide scales of strip steel of hot-rolled coating-free hot forming steel of 1000-1800MPa grade alloyed with high Cr-Si with the specification of 3.0mm (thickness) × 1100mm (width), wherein the steel comprises the following components:
c: 0.25%, Mn: 2.0%, Si: 1.0%, S: 0.005%, P: 0.008%, Al: 0.01%, Cr: 2.0%, Nb: 0.02%, V: 0.01%, Ti: 0.03%, Cu: 0.15%, and the balance of Fe and other unavoidable impurities.
The method adopts the technological process of pickling with hydrochloric acid (30 m/min) + EPS cleaning (25 m/min) to remove the oxide skin on the surface of the strip steel, and comprises the following steps:
(1) hydrochloric acid pickling
Uncoiling and straightening the strip steel, wherein the straightening elongation is as follows: the setting range is less than or equal to 1.6 percent;
hydrochloric acid concentration in the first-stage acid tank: 120 g/L +/-10 g/L, acid liquor temperature of 80 +/-5 ℃,
hydrochloric acid concentration in the second-stage acid tank: 150 g/L +/-10 g/L, acid liquor temperature of 80 +/-5 ℃,
hydrochloric acid concentration in the third stage acid tank: 190 g/L +/-10 g/L, and the temperature of the acid liquor is 80 +/-5 ℃;
the concentration of iron ions is required to be not more than 100 g/L;
the process speed is 30 m/min.
Rinsing and drying after hydrochloric acid pickling, wherein after hydrochloric acid pickling, the oxide scale on the surface of the strip steel is not completely removed through SEM analysis, the thickness of the oxide scale at the edge part is between 5 and 8 mu m, and the thickness of the oxide scale at the middle part is between 9 and 10 mu m.
(2) EPS cleaning
2 EPS units are put into;
and (3) performing withdrawal and straightening on the strip steel again, wherein the withdrawal and straightening elongation is as follows: less than or equal to 0.8 percent;
the process speed is as follows: 25 m/min;
after EPS cleaning, the thickness of the oxide skin on the surface of the strip steel is 0-1.85 μm, the requirement of subsequent hot forming on the thickness of the oxide skin not more than 2 μm is met, and the surface color is uniform.
Example 5
The method comprises the following steps of removing oxide scales of strip steel of hot-rolled coating-free hot forming steel of 1000-1800MPa grade alloyed with high Cr-Si with the specification of 5.0mm (thickness) × 1100mm (width), wherein the steel comprises the following components:
c: 0.2%, Mn: 3.0%, Si: 1.8%, S: 0.005%, P: 0.008%, Al: 0.03%, Cr: 1.8%, Nb: 0.02%, V: 0.03%, Ti: 0.02%, Cu: 0.10%, and the balance of Fe and other unavoidable impurities.
The method adopts the technological process of pickling with hydrochloric acid (15 m/min) + EPS cleaning (60 m/min) to remove the oxide skin on the surface of the strip steel, and comprises the following steps:
(1) hydrochloric acid pickling
Uncoiling and straightening the strip steel, wherein the straightening elongation is as follows: the setting range is less than or equal to 1.4 percent;
hydrochloric acid concentration in the first-stage acid tank: 150 g/L +/-20 g/L, acid liquor temperature of 80 +/-10 ℃,
hydrochloric acid concentration in the second-stage acid tank: 170 g/L +/-20 g/L, acid liquor temperature of 80 +/-10 ℃,
hydrochloric acid concentration in the third stage acid tank: 220 g/L +/-20 g/L, and the temperature of the acid liquor is 80 +/-10 ℃;
the concentration of iron ions is required to be not more than 100 g/L;
the process speed is 15m/min (the lowest process speed of the unit).
Rinsing and drying after hydrochloric acid pickling, wherein after hydrochloric acid pickling, the oxide scale on the surface of the strip steel is not completely removed through SEM analysis, the thickness of the oxide scale at the edge part is between 2 and 5 mu m, and the thickness of the oxide scale at the middle part is between 4.5 and 7 mu m.
(2) EPS cleaning
2 EPS units are put into;
and (3) performing withdrawal and straightening on the strip steel again, wherein the withdrawal and straightening elongation is as follows: less than or equal to 0.7 percent;
the process speed is as follows: 60 m/min;
after EPS cleaning, the thickness of the oxide scale on the surface of the strip steel is 0.5-1.2 μm, the requirement of subsequent hot forming on the thickness of the oxide scale not more than 2 μm is met, and the surface color is uniform.
Comparative example 1
The composition and specification of the steel strip were the same as those of example 3, except that the descaling was carried out by washing with hydrochloric acid only in the step (1) of example 1, and the pickling process speed was 15m/min (the lowest process speed of the unit).
Uncoiling and straightening the strip steel, wherein the straightening elongation is as follows: the setting range is less than or equal to 1.8 percent;
hydrochloric acid concentration in the first-stage acid tank: 120 g/L +/-10 g/L, acid liquor temperature of 80 +/-5 ℃,
hydrochloric acid concentration in the second-stage acid tank: 150 g/L +/-10 g/L, acid liquor temperature of 80 +/-5 ℃,
hydrochloric acid concentration in the third stage acid tank: 190 g/L +/-10 g/L, and the temperature of the acid liquor is 80 +/-5 ℃;
the concentration of iron ions is required to be not more than 100 g/L;
rinsing and drying are carried out after hydrochloric acid pickling, after the hydrochloric acid pickling, through SEM analysis, oxide scales on the surface of the strip steel are not completely removed, the thickness of the oxide scales at the edge parts is between 2 and 4 mu m, and the thickness of the oxide scales at the middle parts is between 3.5 and 5 mu m, and according to detection results, the oxide scales are removed only by hydrochloric acid pickling in the comparative example, although the hydrochloric acid pickling process in the comparative example 1 adopts a low speed of 15m/min compared with the embodiment 3, the consumed time is longer than the two steps of hydrochloric acid pickling and EPS cleaning in the embodiment 3, and the requirement of subsequent hot forming on the oxide scales with the thickness of not more than 2 mu m cannot be achieved.
Comparative example 2
The composition and specification of the strip were the same as those of example 3 except that the EPS cleaning of step (2) of example 1 was used only to remove the scale, and the EPS process speed was 10 m/min.
2 EPS units are put into;
and (3) performing withdrawal and straightening on the strip steel again, wherein the withdrawal and straightening elongation is as follows: less than or equal to 1.0 percent;
after EPS cleaning, the thickness of the oxide scale on the surface of the strip steel is 2-2.5 μm through SEM analysis, and the detection result shows that the oxide scale is removed only by EPS cleaning in the comparative example 2, although the EPS cleaning process in the comparative example 1 adopts a low speed of 10m/min compared with the EPS cleaning process in the example 3, the consumed time is longer than the sum of the hydrochloric acid pickling process and the EPS cleaning process in the example 3, but the requirement of subsequent thermal forming on the oxide scale thickness not more than 2 μm cannot be met.
Claims (8)
1. A method for removing oxide skin of 1000-1800 MPa-grade high Cr-Si alloyed hot forming steel is characterized by comprising the following steps:
(1) hydrochloric acid pickling
Uncoiling and straightening the hot-rolled strip steel of the high Cr-Si alloyed 1000-1800MPa grade hot forming steel, then carrying out hydrochloric acid pickling, rinsing and drying the strip steel after pickling;
(2) EPS cleaning
Performing withdrawal and straightening on the strip steel again, and then performing EPS cleaning;
the high Cr-Si alloyed 1000-1800 MPa-grade hot forming steel comprises the following components:
c: 0.15 to 0.35%, Mn: 0.8-3.2%, Si: 0.8-2.8%, S: < 0.01%, P: < 0.015%, Al: 0.01-0.05%, Cr: 1.5-3.9%, Nb: 0.01-0.05%, V: 0.01-0.05%, Ti: 0.01-0.03%, Cu: 0.05-0.15%, and the balance of Fe and other inevitable impurities.
2. The method as claimed in claim 1, wherein the elongation at pulling and straightening in step (1) is 0.5% to 2.0%, and the elongation at pulling and straightening in step (2) is 0.2% to 2.0%.
3. The method for removing the oxide skin of the 1000-1800 MPa-grade hot formed steel alloyed with high Cr-Si according to claim 1, wherein the thickness of the hot rolled strip steel is 0.6-6 mm.
4. The method for removing the oxide skin of the 1000-grade 1800 MPa-grade high Cr-Si alloyed hot formed steel as claimed in claim 1, wherein the hydrochloric acid pickling process is sequentially carried out in three stages:
a first stage: the concentration of the hydrochloric acid is 60 g/L-150 g/L, and the temperature of the acid liquor is 60 ℃ to 95 ℃;
and a second stage: the concentration of the hydrochloric acid is 80 g/L-180 g/L, and the temperature of the acid liquor is 60 ℃ to 95 ℃;
a third stage: the concentration of the hydrochloric acid is 100 g/L-200 g/L, and the temperature of the acid liquid is 60 ℃ to 95 ℃.
5. The method as claimed in claim 4, wherein the concentration of iron ions in the acid bath used in the three-stage hydrochloric acid pickling is not more than 150 g/L.
6. The method as claimed in claim 1, wherein the pickling speed of hydrochloric acid is 15-120 m/min.
7. The method as claimed in claim 1, wherein the EPS cleaning speed is set to 10-60 m/min.
8. The method as claimed in claim 1, wherein the strip steel has uniform surface color and scale after hydrochloric acid pickling and EPS cleaning, and the scale thickness is not greater than 2 μm.
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| PCT/CN2022/109342 WO2023093111A1 (en) | 2021-11-29 | 2022-08-01 | High cr-si alloyed coating-free hot forming steel and hot rolling preparation method therefor |
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| WO2023093111A1 (en) * | 2021-11-29 | 2023-06-01 | 东北大学 | High cr-si alloyed coating-free hot forming steel and hot rolling preparation method therefor |
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