Classifications

• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0226—Hot rolling
• • 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
  • C21D1/84—Controlled slow cooling
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
• • 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
  • B21B45/008—Heat shields
• • 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
  • C21D6/00—Heat treatment of ferrous alloys
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/021—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving particular fabrication steps or treatments of ingots or slabs
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/0006—Details, accessories not peculiar to any of the following furnaces
  • C21D9/0025—Supports; Baskets; Containers; Covers
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
• • 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
  • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
• • 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
  • C21D2211/004—Dispersions; Precipitations

Definitions

• the invention belongs to the technical field of high-strength steel production, and particularly relates to a production method for improving the precipitation strengthening effect of Ti microalloyed hot-rolled high-strength steel on-line.
• microalloyed hot-rolled high-strength steel with a small amount of Ti element (0.01-0.20%) added to the chemical composition of ordinary C-Mn steel or low-alloy steel matrix in automobiles, construction machinery, containers, bridges, buildings, railway vehicles, etc.
• Ti is added as a microalloy in steel and precipitates mainly in the form of TiC or Ti(C,N), which can improve the strength of steel and improve the cold forming properties and weldability of steel.
• China Patent Publication No. CN102703812B discloses "titanium microalloyed 500MPa high strength steel bar and its production method", which emphasizes the principle of using titanium to precipitate and strengthen in steel, and improves the mechanical properties such as yield strength and tensile strength of steel. However, it has not been studied and elaborated on how to improve the effect of precipitation enhancement.
• Chinese Patent Publication No. CN102965574B discloses "a titanium microalloyed low yield ratio high strength hot rolled thick steel plate and a production process thereof", which heats the slab to 1220-1270 ° C, through the austenite recrystallization zone and non-re The crystallization zone is rolled into a steel plate in two stages, cooled to a reddening temperature for hot straightening, and the steel plate is straightened and then stacked to slow down to promote precipitation strengthening.
• the literature "2050 finishing high-strength steel slow cooling process analysis” introduced a slow cooling wall to control the cooling process of BS600MC, BS700MC and other high-strength steel coils in the library to improve the precipitation strengthening effect, internal stress distribution and improve the board The purpose of shape quality.
• the literature “Research and Implementation of 620mm Strip Steel Slow Cooling Pit Construction Scheme” proposes the use of slow cooling pits to control the temperature of the steel coils in a 48-hour slow cooling cycle to make the overall temperature of the coils uniform.
• Chinese Patent Publication No. CN102534141A discloses a "precipitation-strengthened high-strength steel in-line induction heat treatment process", which is characterized by inductive heat treatment of the unrolled steel sheet to precipitate and strengthen the phase, and exhibits a dispersion distribution state to improve the uniformity of the steel sheet.
• this process needs to first flatten the steel coil, and then use induction heating technology to reheat and heat the heat. There are many steps, and it is necessary to increase the induction heating equipment.
• the invention rapidly heats and cools the steel coil by using the micro-alloyed hot-rolled high-strength steel after controlled rolling, controlled cooling and coiling, so as to heat the steel coil and use the residual heat.
• the temperature of the entire coil tends to be uniform, and the TiC is uniformly and sufficiently precipitated, and the size is maintained at the nanometer level, thereby achieving the purpose of improving the precipitation strengthening effect.
• the production method for improving the precipitation strengthening effect of the Ti microalloyed hot-rolled high-strength steel in the present invention comprises: casting the molten steel by adding the microalloying element Ti, and heating, and then rough rolling, finishing rolling, layering
• the flow cooling and the coil are taken to the hot rolled coil, and after unwinding, the heat cover is placed on the wire and moved into the coil store with the transport chain to remove the heat shield after the online heat preservation time, and air cooled to room temperature; wherein the microalloying element Ti
• the content is ⁇ 0.03wt%
• the coiling temperature is 500-700°C
• the insulating cover on the wire cover means that a separate and sealed heat insulating cover device is separately covered within 60 minutes after unwinding each hot rolled coil.
• the online holding time is ⁇ 60 minutes.
• the content of the microalloying element Ti is 0.03-0.10%;
• the slab heating temperature is ⁇ 1200 ° C, and the soaking time is ⁇ 60 minutes;
• the slab heating temperature is 1200-1350 ° C, and the soaking time is 1-2 hours;
• the rough rolling temperature is 1000-1200 ° C, 3-8 passes reciprocating rolling and the cumulative deformation amount ⁇ 50%;
• finish rolling is carried out 6-7 times of continuous rolling and the cumulative deformation amount is ⁇ 80%, and the finishing rolling temperature is 800-900 °C.
• each hot rolled coil is separately covered with a heat insulating cover within 20 minutes after unwinding;
• the cooling speed of the steel coil in the heat preservation cover is ⁇ 15 ° C / hour
• the coil has an on-line holding time of 1-5 hours.
• an exemplary insulative cover is a steel strip manufacturing line in-line thermal insulation slow cooling device disclosed in any of CN 107470377A, which is incorporated herein by reference in its entirety.
• Ti has a strong binding force to C and N atoms in steel. When Ti is added in an appropriate amount, it can meet various requirements at the same time.
• Ti content is ⁇ 0.03%, TiN is mainly formed to prevent austenite grain coarsening; when Ti content is ⁇ 0.03%, Ti which exceeds ⁇ (Ti)/ ⁇ (N) ideal stoichiometric ratio will be solid solution Form or in the form of fine TiC particles significantly inhibits recrystallization and acts as a precipitation strengthening; however, when the amount of Ti added is too high, the embrittlement of the steel is caused by the formation of nitrides and sulfides at the grain boundaries. Therefore, the content of Ti of the present invention is ⁇ 0.03%, preferably 0.03 to 0.10%.
• the heating temperature of the slab must be sufficiently high (eg ⁇ 1200 ° C) to ensure that as many Ti atoms are solid solution in the austenite.
• the upper limit of the heating temperature is limited to the actual achievable or acceptable temperature of the furnace. In principle, the upper limit requirement is not set; however, in order to save energy and reduce consumption, the actual maximum heating temperature is usually controlled at ⁇ 1350 °C.
• the soaking time is ⁇ 60 minutes, and the soaking time is that the slab is heated to a set heating temperature and then kept warm for a period of time.
• Austenite recrystallization rolling and austenite non-recrystallization rolling are performed in the rough rolling and finishing rolling stages, respectively.
• the recrystallization zone is in the high temperature stage (such as rough rolling temperature 1000-1200 °C), and the rolling resistance is small.
• the austenite grains should be sufficiently refined by large deformation; the non-recrystallization zone (such as the finishing temperature of 800-900)
• the purpose of rolling is to cause elongated deformation of the grains, increase dislocations and deformation zones and increase the core of the new phase nucleation.
• the rhythm of the rough rolling and finishing rolling process should be completed as quickly as possible to avoid precipitation of excessive Ti carbonitrides during the rolling stage, and to retain as much Ti atoms as possible to precipitate after rolling.
• the control strategy of one-stage pre-cooling, two-stage cooling, or U-cooling is selected according to the requirements of the phase change structure, but accelerated cooling suppresses the precipitation of nano-sized TiC.
• accelerated cooling suppresses the precipitation of nano-sized TiC.
• the coiling temperature is designed to be 500-700 ° C, which is the temperature range in which TiC can be analyzed; and after each hot rolled coil is unwound, it is quickly covered on line (preferably within 20 minutes).
• Independent, sealed insulation device, holding time is 1-5 hours, the cooling speed of steel coil in the heat preservation cover is ⁇ 15°C/hour, which can make full use of the residual heat after coiling, so that the temperature of the whole steel coil tends to It is homogenized and stays in the temperature range where TiC can be analyzed for a suitable period of time, ensuring that TiC is uniformly and sufficiently precipitated, and the size is maintained at the nanometer level, and the effect of precipitation strengthening is maximized.
• the so-called “online” means that the steel coil is required to be covered with a heat-insulating cover at the first time after unwinding, and compared with the "offline” mode in which the steel coil is placed in the storage and then covered with a heat-insulating cover: 1 to ensure that the steel coil can be charged at the temperature analyzed by TiC
• the section enters the heat preservation cover; in the "offline” mode, the temperature drop of the inner/outer ring and the side part is significantly larger than that of the middle part during the transportation process before the steel coil enters the heat preservation cover, and the temperature uniformity of the whole steel coil is poor; 3" In the off-line mode, the uniformity of the phase change of the coil is poor, and the precipitation of TiC in the local area is insufficient, which is not conducive to uniformly improving the precipitation strengthening effect.
• the invention is designed by a reasonable rolling process, and at the same time, with the innovative "single-volume" thermal insulation slow cooling process, the Ti microalloyed hot-rolled high-strength steel can be improved online, at low cost and with high efficiency. Precipitation enhancement effect, improved strength performance and uniformity.
• the Ti microalloyed hot-rolled high-strength steel produced by the present invention has a yield strength of 10 to 40 MPa and a tensile strength of 10 to 50 MPa as compared with the method of slow cooling using a steel coil stack.
• Table 1 shows the key process parameters of the examples of the present invention
• Table 2 shows the key process parameters of the comparative examples of the present invention
• Table 3 shows the performance of the examples and comparative steel coils of the present invention.
• the process flow of the embodiment of the invention is as follows: the casting blank with the addition amount of Ti ⁇ 0.03% ⁇ the heating of the slab ⁇ the rough rolling ⁇ the finishing rolling ⁇ the laminar cooling ⁇ the coiling ⁇ the thermal cover on the wire cover ⁇ the removal of the heat preservation cover, wherein the key process parameters are as follows. Table 1.
• the comparative process of the invention is as follows: the billet with the addition amount of Ti ⁇ 0.03% ⁇ the heating of the slab ⁇ the rough rolling ⁇ the finishing rolling ⁇ the laminar cooling ⁇ the coiling ⁇ the slow cooling of the steel coil stack, wherein the key process parameters are shown in Table 2.
• Table 1 the key process parameters are shown in Table 2.
• Example Yield strength (MPa) Tensile strength (MPa) Elongation rate (%) 1 792 835 twenty three 2 773 825 twenty two 3 771 813 twenty one 4 636 716 20 5 620 661 26 6 573 672 twenty three Comparative example Yield strength (MPa) Tensile strength (MPa) Elongation rate (%)

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• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Sheet Steel (AREA)
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• 2018
  • 2018-09-20 WO PCT/CN2018/106706 patent/WO2019057115A1/zh not_active Ceased
  • 2018-09-20 KR KR1020207010904A patent/KR102452599B1/ko active Active
  • 2018-09-20 US US16/648,773 patent/US11384406B2/en active Active
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