CN114480979A - Production method of ultrahigh-strength high-hole-expansion-rate hub steel - Google Patents

Production method of ultrahigh-strength high-hole-expansion-rate hub steel Download PDF

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Publication number
CN114480979A
CN114480979A CN202210117182.5A CN202210117182A CN114480979A CN 114480979 A CN114480979 A CN 114480979A CN 202210117182 A CN202210117182 A CN 202210117182A CN 114480979 A CN114480979 A CN 114480979A
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steel
slag
slab
less
temperature
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吾塔
赵亮
赵晓军
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Xinjiang Bayi Iron and Steel Co Ltd
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Xinjiang Bayi Iron and Steel Co Ltd
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/18—Controlling or regulating processes or operations for pouring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/18—Controlling or regulating processes or operations for pouring
    • B22D11/181—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level
    • B22D11/182—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level by measuring temperature
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C1/00—Refining of pig-iron; Cast iron
    • C21C1/02—Dephosphorising or desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/36—Processes yielding slags of special composition
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/072—Treatment with gases
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips 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 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • 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
    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C21D2211/005—Ferrite
    • 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
    • C21D2211/009—Pearlite

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  • Chemical & Material Sciences (AREA)
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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

The invention discloses a production method of ultrahigh-strength high-hole-expansion-rate hub steel, which comprises the following components in percentage by mass: [C] the method comprises the following steps 0.040-0.055 wt%, [ Mn ]: 1.30-1.40 wt%; si: less than or equal to 0.10wt%, P: less than or equal to 0.012wt%, S: less than or equal to 0.004wt%, Al: 0.025 to 0.050wt%, N: less than or equal to 0.0050wt%, Nb: 0.012-0.020 wt%, Ti: not more than 0.050 to 0.060wt%, Ca: less than 0.005wt%, the balance being iron and unavoidable impurities; the production process flow comprises the steps of molten iron pretreatment, converter smelting, LF refining, slab continuous casting and strip steel hot continuous rolling, wherein the thickness of the produced steel strip or steel plate is 2.5-5 mm; the ultrahigh-strength automobile hub steel produced by the method meets the user requirements (the thickness of the steel plate is mainly 3.5 mm), has the advantages of low cost and high cost performance, and the cost of steel alloy per ton is lower than that of strip steel with the same strength grade by more than 110 yuan.

Description

Production method of ultrahigh-strength high-hole-expansion-rate hub steel
Technical Field
The invention relates to a production method of ultrahigh-strength high-hole-expansion-rate hub steel, belonging to the fields of steel smelting and material processing.
Background
The wheel is an important part of the automobile, and the structure, the performance and the dead weight of the wheel directly influence the technical performance of the whole automobile. In the field of automobile hub steel, the strength of the material is increased, the self weight of the wheel is reduced, the fuel consumption of an automobile is reduced, and the development direction of the automobile hub steel is represented.
The tensile strength of the automobile hub steel with a higher strength level adopted at present is 440MPa, and the thickness of a steel plate for manufacturing the hub is correspondingly increased due to lower strength, so that the self weight of an automobile is increased, and the low-carbon green development of the automobile industry is not facilitated. Therefore, in order to reduce the self weight of the automobile, a new material is adopted or the strength of the steel plate is improved to reduce the self weight of the automobile, which is a necessary trend in the development of automobile hub steel.
Document retrieval
(1) Patent application number ZL201610313707.7 discloses a manufacturing method of high-strength automobile hub steel, which comprises the following components: c: 0.05 to 0.10wt%, Si: less than or equal to 0.010wt%, Mn: 1.10-1.85 wt%, P: less than or equal to 0.025wt%, S: less than or equal to 0.003wt%, Nb: 0.015 to 0.050wt%, Ti: 0.015 to 0.15wt%, Al: 0.015 to 0.060wt%, Ca: less than or equal to 0.0050wt percent. The strengthening mode adopts niobium and titanium composite strengthening. The method has the advantages that the yield strength and the tensile strength of the steel can be improved, the elongation after fracture of the steel is low and is not more than 21%, the plasticity is low, the hole expansibility of the steel is poor, and the cold stamping formability is restricted.
(2) Patent application number ZL 200810201495.9 discloses a hot-rolled rim steel plate with tensile strength of 550MPa and a manufacturing method thereof, and the hot-rolled rim steel plate comprises the following components: c: 0.02 to 0.0.07wt%, Si: 0-0.30 wt%, Mn: 0.80-1.20 wt%, P: less than or equal to 0.035wt%, S: less than or equal to 0.005wt%, Nb: 0-0.10 wt%, Al: 0.025 to 0.060wt%, N: less than or equal to 0.0060wt percent, and the balance of iron and inevitable impurities.
Figure DEST_PATH_IMAGE002
The 550 MPa-grade hot-rolled steel is produced by adopting niobium strengthening or niobium-titanium composite strengthening. The tensile strength is 570-612 MPa, the yield strength is 498-535 MPa, and the elongation after fracture of the steel is 32-35%. The yield ratio is relatively high due to the high yield strength of the material, which is not beneficial to deep drawing forming such as hole expanding and the like.
(3) Patent application number ZL 200710093966.4 discloses a hot-rolled high-hole-expansion steel plate with 440 MPa-level tensile strength and a manufacturing method thereof, and the hot-rolled high-hole-expansion steel plate comprises the following components: c: 0.01 to 0.0.06wt%, Si: 0 to 0.60wt%, Mn: 0.80-1.30 wt%, P: less than or equal to 0.035wt%, S: less than or equal to 0.010wt%, Nb: 0-0.25 wt%, Al: 0.025 to 0.060wt%, N: less than or equal to 0.0060wt%, Ti: less than or equal to 0.03wt%, Ca: less than 0.005wt percent, and the balance of iron and inevitable impurities, the steel plate with high hole expansion rate and 440MPa tensile strength is produced, but the strength of the material is low, the use amount of steel is limited, and the aim of reducing the self weight of the automobile cannot be achieved.
Disclosure of Invention
The invention aims to provide a production method of ultrahigh-strength high-hole-expansion-rate hub steel, which is characterized in that the production process has strong applicability and operability, the steel strength is improved, and meanwhile, the hub steel has excellent hole expansion performance, the production method reduces the alloy usage amount, and realizes alloy reduction production.
A production method of ultrahigh-strength high-hole-expansion-rate hub steel comprises the following steps: the steel adopts a design scheme of low-carbon, high-manganese and high-Ti alloying and adding trace niobium for strengthening, and the steel comprises the following components in percentage by mass.
[C] The method comprises the following steps 0.040 to 0.055, [ Mn ]: 1.30-1.40 wt%; si: less than or equal to 0.10wt%, P: less than or equal to 0.012wt%, S: less than or equal to 0.004wt%, Al: 0.025 to 0.050wt%, N: less than or equal to 0.0050wt%, Nb: 0.012-0.020 wt%, Ti: not more than 0.050 to 0.060wt%, Ca: less than 0.005wt%, and the balance being iron and unavoidable impurities.
The implementation method of the invention comprises the following steps: the production process flow of the invention is as follows: the method comprises the steps of molten iron pretreatment, converter smelting, LF refining, slab continuous casting and strip steel hot continuous rolling, wherein the thickness of the produced steel strip (steel plate) is 2.5-5 mm.
(1) Deep desulfurization treatment is carried out on the molten iron, and the treated molten iron [ S ]]Less than or equal to 0.002 percent, performing KR method desulfurization treatment, adding a desulfurizing agent, stirring for 20-25 min, and adding a slag conglomeration agent into the ladle top slag for modification (the slag conglomeration agent mainly comprises blast furnace water-soaked slag, wherein the main component is SiO2) And then slagging off is carried out.
(2) And (3) smelting in a converter, fully utilizing high-alkalinity slag generated by the previous steel smelting, and quickly and deeply dephosphorizing at the initial stage of smelting (low-temperature stage). Its advantages are short slagging time in low-temp (less than 1400 deg.C) stage, short smelting period and high productivity. The specific method is that high-temperature slag generated by smelting in the previous furnace after tapping is left in the converter (tapping is not carried out). The carbon magnesium balls are used for modifying and thickening the highly-oxidizing slag, nitrogen is blown in to splash the slag for protecting the furnace, and the nitrogen is continuously blown in to cool and solidify the slag, so that the FeO in the slag is reduced, the explosion or environmental protection accident caused by violent reaction of molten iron added into a converter is prevented, and then scrap steel is added and the molten iron is added for oxygen blowing smelting. Slag is discharged after the converter oxygen blowing smelting is carried out for 4.0-4.5 minutes, and in this time, a large amount of silicon in molten iron is oxidized and enters slag, so that the alkalinity of the slag is reduced, the dephosphorization effect is reduced, meanwhile, a dephosphorization product enters the slag at the earlier stage, and dolomite and active lime are added again for slagging after deslagging, thereby being beneficial to deep dephosphorization and inhibiting the resulfurization of the steel slag to the molten steel. The content of the end point [ C ] of the converter is 0.02-0.04%, the content of the [ P ] is not more than 0.007%, and the content of the [ N ] is not more than 0.003%. The tapping temperature of the converter is controlled to be 1640-1680 ℃. The [ S ] of the steel ladle molten steel after tapping is less than or equal to 0.006 percent.
(3) And (3) smelting in a converter, fully utilizing high-alkalinity slag generated by the previous steel smelting, and quickly and deeply dephosphorizing at the initial stage of smelting (low-temperature stage). Its advantages are short slagging time in low-temp (less than 1400 deg.C) stage, short smelting period and high productivity. The specific method is that high-temperature slag generated by smelting in the previous furnace after tapping is left in the converter (tapping is not carried out). The carbon magnesium balls are used for modifying and thickening the highly-oxidizing slag, nitrogen is blown in to splash the slag for protecting the furnace, and the nitrogen is continuously blown in to cool and solidify the slag, so that the FeO in the slag is reduced, the explosion or environmental protection accident caused by violent reaction of molten iron added into a converter is prevented, and then scrap steel is added and the molten iron is added for oxygen blowing smelting. Slag is discharged after the converter oxygen blowing smelting is carried out for 4.0-4.5 minutes, and in this time, a large amount of silicon in molten iron is oxidized and enters slag, so that the alkalinity of the slag is reduced, the dephosphorization effect is reduced, meanwhile, a dephosphorization product enters the slag at the earlier stage, and dolomite and active lime are added again after deslagging to make new slag, thereby being beneficial to deep dephosphorization and inhibiting the steel slag from resulfurizing the molten steel. The content of the converter end point [ C ] is 0.02-0.04%, the content of [ P ] is not more than 0.007%, and the content of [ S ] is not more than 0.007%. [ N ] is less than or equal to 0.003 percent. And controlling the tapping temperature of the converter to be 1640-1680 ℃, and continuously keeping the slag in the converter for modification and solidification, so that the slag is tapped from the 5 th furnace and is poured into the slag after smelting. And continuously producing according to the method for steel tapping, slag remaining, slag pouring and new slag making of the process. And (4) slag stopping and tapping of the converter, wherein the amount of the oxidized slag in the ladle is not more than 100 kg.
(4) The method is characterized in that siliceous deoxidizers are forbidden to be used in LF refining, the key control points of the LF refining are that the initial temperature of the LF refining is higher than 1540, the power transmission time of each steel refining is not more than 15min, the total time of LF refining treatment is controlled to be 42-45 mm, the nitrogen increasing amount of molten steel in the LF refining process is less than 0.0010%, argon is adopted for bottom blowing and stirring, and the flow is 10-25 NL/min. After LF treatment, feeding molten steel into a calcium line (strictly forbidden to use a calcium-silicon line) for treatment, and after LF refining treatment, finishing nitrogen content [ N ] of the molten steel]≤0.0040%、[S]≤0.0040，[Ca]The content is controlled to be 0.0020 to 0.0030 percent, and other elements all meet the control requirements of molten steel of a smelted finished product. And (3) LF refining final slag components: CaO content of 52-55%, SiO2About 10 percent of content, less than or equal to 1.0 percent of FeO and MnO, and Al2O325-30% of MgO, 8-10% of CaF2The content is about 6 percent, the BaO content is about 3 percent, the use of aluminum-containing diffusion deoxidizer or top slag modifier, accelerant and the like is forbidden at the end of LF treatment, the silicon dioxide is prevented from being reduced by aluminum and entering molten steel to cause silicon increase of the molten steel, and ferrotitanium and ferroniobium are added at the same time at the end of LF refining for alloying.
(5) The continuous casting slab specification, slab thickness 250mm, slab width 1100 ~ 1500mm, length 10.5 m. The control method of the center segregation of the continuous casting slab is realized by accurately controlling the temperature of molten steel and keeping the constant drawing speed in the continuous casting process; the method for accurately controlling the temperature of the molten steel is realized by the following method, wherein the baking temperature of an empty ladle is more than 1200 ℃, the time is more than 2 hours, the temperature of the baked ladle is more than 800 ℃, carbon-free high-alkalinity covering agents are added into the ladle and a tundish to preserve the temperature of the molten steel, and the superheat degree of the continuous casting molten steel is 20 +/-5 ℃. The control method is that the pulling speed set according to the width specification of the continuous casting slab is a target value, after the width specification of the slab is set, the slab is accelerated from the pulling speed to a normal pulling speed, then the pulling speed is constant (constant pulling speed continuous casting), and the continuous casting pulling speed is controlled to be 0.95 m/min-1.3 m/min according to different slab widths. And (3) putting the continuous casting process into a slab rolling device, wherein the rolling reduction of the slab is 5-6 mm, the nominal thickness of the outlet slab is 245 mm, the center segregation grade of the low-power slab is less than or equal to 2.5 (Mannesmann standard), and the produced defect-free slab is hot-rolled.
(6) The hot charging temperature of the plate blank is 600 plus or minus 720 ℃, the extraction temperature of the plate blank heating furnace is 1190 +/-15 ℃, water is sprayed to the upper surface and the lower surface of the plate blank discharged from the furnace by using high-pressure water columns with the pressure of 20MPa for descaling, the included angle between the sprayed slit water columns and the surface of the plate blank is 15 degrees, the rough rolling starting temperature is 1160-1190 ℃, the rolling speed is 3.0-4.5 m/s, 5 times of rough rolling is carried out, and meanwhile, cooling water between the passes is started, so that a rough rolling intermediate steel plate is obtained, wherein the thickness is not less than 45 mm; and (3) performing finish rolling on the rough rolled steel plate at the temperature of 920 +/-10 ℃, performing 6-pass continuous finish rolling at the rolling speed of 6-9 m/s, starting inter-pass cooling water, and obtaining the finish rolled steel strip at the finish rolling temperature of 865 +/-10 ℃. After finish rolling, the hot rolled steel strip is subjected to laminar cooling to carry out structure transformation and fine grain strengthening, and the laminar cooling rate is controlled to be 14-15 ℃/s. And (3) coiling the finish rolling steel strip subjected to layer cooling in a coiling machine at the coiling temperature of 600 +/-10 ℃, and naturally air-cooling the steel strip to room temperature to obtain the hot rolled steel strip coil for the high-strength automobile hub. The metallographic structure of the steel plate is acicular ferrite and pearlite, and the grain size is 11-11.5 grade.
(7) The tensile strength of the finished steel plate of the automobile hub steel produced by the method is 618MPa to 6645MPa, and the yield strength is 500MPa to 528 MPa; the elongation after fracture is more than or equal to 29 percent, and the ratio of the yield strength to the tensile strength (yield ratio) is controlled to be 0.81-0.83;
(8) by adopting a low-carbon, low-silicon, titanium and niobium bistable microalloying method, the tensile strength of the material is improved, the over-quick increase of the yield strength of steel is inhibited, and the hole expansion performance of the steel plate is improved. The content of titanium in the finished product is controlled to be 0.050-0.060%, the content of niobium is controlled to be 0.012-0.020%, and the content of nitrogen in the smelted finished product steel is not more than 0.0050%. The composition of the steel and the corresponding properties are shown in Table 1.
Figure DEST_PATH_IMAGE004
Remarking: the gauge length of the tensile property sample is 50 mm.
(9) The ultrahigh-strength automobile hub steel produced by the method meets the user requirements (the thickness of the steel plate is mainly 3.5 mm), has the advantages of low cost and high cost performance, and the cost of steel alloy per ton is lower than that of strip steel with the same strength grade by more than 110 yuan. Compared with 440MPa, the tensile strength of the steel is 178MPa higher, the elongation after fracture is more than 29 percent, and the steel has low yield ratio, high hole expansion rate and excellent cold stamping forming performance.
Detailed Description
A production method of ultrahigh-strength high-hole-expansion-rate hub steel comprises the following steps: the steel adopts a component design scheme of alloying with low carbon, high manganese and high Ti and adding trace niobium for reinforcement, and the components in the steel have the following mass percentage.
[C] The method comprises the following steps 0.040 to 0.055, [ Mn ]: 1.30-1.40 wt%; si: less than or equal to 0.10wt%, P: less than or equal to 0.012wt%, S: less than or equal to 0.004wt%, Al: 0.025 to 0.050wt%, N: less than or equal to 0.0050wt%, Nb: 0.012-0.020 wt%, Ti: not more than 0.050 to 0.060wt%, Ca: less than 0.005wt%, and the balance being iron and unavoidable impurities.
The implementation method of the invention comprises the following steps: the production process flow of the invention is as follows: the method comprises the steps of molten iron pretreatment, converter smelting, LF refining, slab continuous casting and strip steel hot continuous rolling, wherein the thickness of the produced steel strip (steel plate) is 2.5-5 mm.
(1) Carrying out deep desulfurization treatment on molten iron, wherein [ S ] of the treated molten iron is less than or equal to 0.002%, carrying out KR desulfurization treatment, adding a desulfurizing agent, stirring for 20-25 min, adding a slag conglomeration agent into the ladle top slag for modification (the slag conglomeration agent mainly comprises blast furnace blister slag, wherein the main component is SiO 2), and then carrying out slag skimming.
(2) And (3) smelting in a converter, fully utilizing high-alkalinity slag generated by the previous steel smelting, and quickly and deeply dephosphorizing at the initial stage of smelting (low-temperature stage). Its advantages are short slagging time in low-temp (less than 1400 deg.C) stage, short smelting period and high productivity. The specific method is that high-temperature slag generated by smelting in the previous furnace after tapping is left in the converter (tapping is not carried out). The carbon magnesium balls are used for modifying and thickening the highly-oxidizing slag, nitrogen is blown in to splash the slag for protecting the furnace, and the nitrogen is continuously blown in to cool and solidify the slag, so that the FeO in the slag is reduced, the explosion or environmental protection accident caused by violent reaction of molten iron added into a converter is prevented, and then scrap steel is added and the molten iron is added for oxygen blowing smelting. Slag is discharged after the converter oxygen blowing smelting is carried out for 4.0-4.5 minutes, and in this time, a large amount of silicon in molten iron is oxidized and enters slag, so that the alkalinity of the slag is reduced, the dephosphorization effect is reduced, meanwhile, a dephosphorization product enters the slag at the earlier stage, and dolomite and active lime are added again for slagging after deslagging, thereby being beneficial to deep dephosphorization and inhibiting the resulfurization of the steel slag to the molten steel. The content of the converter end point [ C ] is 0.02-0.04%, the content of [ P ] is not more than 0.007%, and the content of [ N ] is not more than 0.003%. The tapping temperature of the converter is controlled to be 1640-1680 ℃. The [ S ] of the steel ladle molten steel after tapping is less than or equal to 0.006 percent.
(3) And (3) smelting in a converter, fully utilizing high-alkalinity slag generated by the previous steel smelting, and quickly and deeply dephosphorizing at the initial stage of smelting (low-temperature stage). Its advantages are short slagging time in low-temp (less than 1400 deg.C) stage, short smelting period and high productivity. The specific method is that high-temperature slag generated by smelting in the previous furnace after tapping is left in the converter (tapping is not carried out). The carbon magnesium balls are used for modifying and thickening the highly-oxidizing slag, nitrogen is blown in to splash the slag for protecting the furnace, and the nitrogen is continuously blown in to cool and solidify the slag, so that the FeO in the slag is reduced, the explosion or environmental protection accident caused by violent reaction of molten iron added into a converter is prevented, and then scrap steel is added and the molten iron is added for oxygen blowing smelting. Slag is discharged after the converter oxygen blowing smelting is carried out for 4.0-4.5 minutes, and in this time, a large amount of silicon in molten iron is oxidized and enters slag, so that the alkalinity of the slag is reduced, the dephosphorization effect is reduced, meanwhile, a dephosphorization product enters the slag at the earlier stage, and dolomite and active lime are added again after deslagging to make new slag, thereby being beneficial to deep dephosphorization and inhibiting the steel slag from resulfurizing the molten steel. The content of the converter end point [ C ] is 0.02-0.04%, the content of the [ P ] is not more than 0.007%, and the content of the [ S ] is not more than 0.007%. [ N ] is less than or equal to 0.003 percent. And controlling the tapping temperature of the converter to be 1640-1680 ℃, and continuously keeping the slag in the converter for modification and solidification, so that the slag is tapped from the 5 th furnace and is poured into the slag after smelting. And continuously carrying out the production by the method for steel tapping, slag remaining, slag pouring and new slag making according to the process. And (4) slag stopping and tapping of the converter, wherein the amount of the oxidized slag in the ladle is not more than 100 kg.
(4) The method is characterized in that siliceous deoxidizers are forbidden to be used in LF refining, the key control points of the LF refining are that the initial temperature of the LF refining is higher than 1540, the power transmission time of each steel refining is not more than 15min, the total time of LF refining treatment is controlled to be 42-45 mm, the nitrogen increasing amount of molten steel in the LF refining process is less than 0.0010%, argon is adopted for bottom blowing and stirring, and the flow is 10-25 NL/min. And after LF treatment, feeding a calcium wire (strictly forbidding to use a silicon-calcium wire) into the molten steel for treatment, wherein the nitrogen content [ N ] of the molten steel is less than or equal to 0.0040%, the nitrogen content [ S ] of the molten steel is less than or equal to 0.0040%, the content of [ Ca ] is controlled to be 0.0020% -0.0030%, and other elements meet the control requirements of smelting finished molten steel. And (3) LF refining final slag components: the method comprises the following steps of adding CaO in 52-55%, SiO2 in about 10%, FeO + MnO in not more than 1.0%, Al2O3 in 25-30%, MgO in 8-10%, CaF2 in about 6%, and BaO in about 3%, prohibiting the use of an aluminum-containing diffusion deoxidizer or top slag modifier, accelerator and the like in the final stage of LF treatment, preventing silicon dioxide from being reduced by aluminum and entering molten steel to cause silicon increase of the molten steel, and simultaneously adding ferrotitanium and ferroniobium in the final stage of LF refining for alloying.
(5) The continuous casting slab specification, slab thickness 250mm, slab width 1100 ~ 1500mm, length 10.5 m. The control method of the center segregation of the continuous casting slab is realized by accurately controlling the temperature of molten steel and keeping the constant drawing speed in the continuous casting process; the method for accurately controlling the temperature of the molten steel is realized by the following method, wherein the baking temperature of an empty ladle is more than 1200 ℃, the time is more than 2 hours, the temperature of the baked ladle is more than 800 ℃, carbon-free high-alkalinity covering agents are added into the ladle and a tundish to preserve the temperature of the molten steel, and the superheat degree of the continuous casting molten steel is 20 +/-5 ℃. The control method is that the pulling speed set according to the width specification of the continuous casting slab is a target value, after the width specification of the slab is set, the slab is accelerated from the pulling speed to a normal pulling speed, then the pulling speed is constant (constant pulling speed continuous casting), and the continuous casting pulling speed is controlled to be 0.95 m/min-1.3 m/min according to different slab widths. And (3) putting the continuous casting process into a slab rolling device, wherein the rolling reduction of the slab is 5-6 mm, the nominal thickness of the outlet slab is 245 mm, the center segregation grade of the low-power slab is less than or equal to 2.5 (Mannesmann standard), and the produced defect-free slab is hot-rolled.
(6) The hot charging temperature of the plate blank is 600-; and (3) performing finish rolling on the rough rolled steel plate at the temperature of 920 +/-10 ℃, performing 6-pass continuous finish rolling at the rolling speed of 6-9 m/s, starting inter-pass cooling water, and obtaining the finish rolled steel strip at the finish rolling temperature of 865 +/-10 ℃. After finish rolling, the hot rolled steel strip is subjected to laminar cooling to carry out structure transformation and fine grain strengthening, and the laminar cooling rate is controlled to be 14-15 ℃/s. And (3) coiling the finish rolling steel strip subjected to layer cooling in a coiling machine at the coiling temperature of 600 +/-10 ℃, and naturally air-cooling the steel strip to room temperature to obtain the hot rolled steel strip coil for the high-strength automobile hub.

Claims (1)

1. A production method of ultrahigh-strength high-hole-expansion-rate hub steel is characterized by comprising the following steps of:
1) the steel comprises the following components in percentage by mass:
[C] the method comprises the following steps 0.040-0.055 wt%, [ Mn ]: 1.30-1.40 wt%; si: less than or equal to 0.10wt%, P: less than or equal to 0.012wt%, S: less than or equal to 0.004wt%, Al: 0.025 to 0.050wt%, N: less than or equal to 0.0050wt%, Nb: 0.012-0.020 wt%, Ti: not more than 0.050 to 0.060wt%, Ca: less than 0.005wt%, the balance being iron and unavoidable impurities;
2) the production process flow comprises the steps of molten iron pretreatment, converter smelting, LF refining, slab continuous casting and strip steel hot continuous rolling, wherein the thickness of the produced steel strip or steel plate is 2.5-5 mm;
(1) deep desulfurization treatment is carried out on the molten iron, and the treated molten iron [ S ]]Less than or equal to 0.002 percent, performing KR method desulfurization treatment, adding a desulfurizing agent, stirring for 20-25 min, adding a slag conglomeration agent into the ladle top slag for modification, wherein the slag conglomeration agent mainly comprises blast furnace water-soaked slag, and the main component is SiO2Carrying out slag skimming;
(2) smelting in a converter, namely, remaining high-temperature molten slag generated in the previous smelting in the converter after tapping, not discharging slag during tapping, modifying and thickening the high-oxidability slag by using carbon magnesium balls, blowing nitrogen to splash the slag for protecting the converter, continuously blowing nitrogen to cool and solidify the slag, then adding waste steel and adding molten iron to perform oxygen blowing smelting, discharging slag after 4.0-4.5 minutes of oxygen blowing smelting in the converter, controlling the content of [ C ] at the end point of the converter to be 0.02-0.04%, the content of [ P ] to be not more than 0.007%, the content of [ N ] to be not more than 0.003%, controlling the tapping temperature of the converter to be 1640-0 ℃, and controlling the content of [ S ] in the molten steel ladle to be not more than 0.006% after tapping; the slag is continuously left in the converter for modification and solidification, so that the slag is smelted until the 5 th furnace taps, is poured, and is continuously produced according to the method for tapping, slag retention, slag pouring and new slag making of the process, the converter blocks slag and taps, and the amount of the oxidized slag in the ladle is not more than 100 kg;
(3) the LF refining prohibits using a siliceous deoxidizer, and has the key control points that the initial temperature of the LF refining is more than 1540, the power transmission time of each steel refining is not more than 15min, the total time of the LF refining treatment is controlled to be 42-45 mm, the nitrogen increasing amount of the molten steel in the LF refining process is less than 0.0010%, argon is adopted for bottom blowing argon stirring, the flow is 10-25 NL/min, the molten steel is fed into a calcium wire for treatment after the LF treatment is finished, and the nitrogen content [ N ] of the molten steel after the LF refining treatment is finished]≤0.0040%、[S]≤0.0040，[Ca]The content is controlled to be 0.0020 to 0.0030 percent, and other elements all meet the control requirement of smelting finished molten steelObtaining the components of LF refining final slag: CaO content of 52-55%, SiO2About 10 percent of content, less than or equal to 1.0 percent of FeO and MnO, and Al2O325-30% of MgO, 8-10% of CaF2Content about 6%, BaO content about 3%;
(4) the method is characterized in that the continuous casting slab specification, slab thickness 250mm, slab width 1100-1500 mm and length 10.5m, and the control method of the continuous casting slab center segregation is realized by accurate control of molten steel temperature and constant drawing speed in the continuous casting process; the method comprises the following steps that the baking temperature of an empty ladle is larger than 1200 ℃, the time is larger than 2 hours, the temperature of the ladle after baking is larger than 800 ℃, carbon-free high-alkalinity covering agents are added into the ladle and a tundish to preserve heat of molten steel, the superheat degree of continuous casting molten steel is 20 +/-5 ℃, the control method is that the pulling speed set according to the width specification of a continuous casting slab is a target value, after the width specification of the slab is set, the pulling speed is accelerated to a normal pulling speed from the pulling speed, then the pulling speed is constant, the pulling speed is controlled to be 0.95-1.3 m/min according to different slab widths, a slab pressing device is put into the continuous casting process, the slab pressing amount is 5-6 mm, the nominal thickness of an outlet slab is 245 mm, the center segregation grade of the slab low-fold is not more than 2.5, and the produced defect-free slab is subjected to hot charging and rolling;
(5) the hot charging temperature of the plate blank is 600-; the rough rolling steel plate is subjected to finish rolling at the temperature of 920 +/-10 ℃, 6-9 m/s of rolling speed for continuous finish rolling for 6 times, cooling water between the times is started, the finish rolling temperature is 865 +/-10 ℃, a finish rolling steel strip is obtained, after finish rolling, hot rolling state steel strip is subjected to structure transformation and fine grain strengthening through laminar cooling, the laminar cooling rate is controlled to be 14-15 ℃/s, the finish rolling steel strip after laminar cooling is fed into a coiling machine for coiling, the coiling temperature is 600 +/-10 ℃, and the steel strip is naturally air-cooled to the room temperature to obtain the hot rolling steel plate coil for the high-strength automobile hub.
CN202210117182.5A 2022-02-08 2022-02-08 Production method of ultrahigh-strength high-hole-expansion-rate hub steel Pending CN114480979A (en)

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CN106399835A (en) * 2016-05-12 2017-02-15 宝钢集团新疆八钢铁有限公司 Production method of high-strength automobile hub steel
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CN112779401A (en) * 2019-11-07 2021-05-11 上海梅山钢铁股份有限公司 High-reaming hot-rolled pickled steel plate with yield strength of 550MPa

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102433501A (en) * 2011-12-02 2012-05-02 山西太钢不锈钢股份有限公司 High strength and toughness strip steel and manufacturing method thereof
CN103469066A (en) * 2013-09-09 2013-12-25 济钢集团有限公司 Method for producing high-formability steel plate by using heavy and medium plate mill and steel plate manufactured by method
CN103602895A (en) * 2013-11-29 2014-02-26 宝山钢铁股份有限公司 High-hole-expansion-ratio steel plate with tensile strength of 780 MPa and manufacturing process thereof
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