CN111636031A - Ultra-low carbon bake-hardening steel and production method thereof - Google Patents
Ultra-low carbon bake-hardening steel and production method thereof Download PDFInfo
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- C21D1/26—Methods of annealing
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- 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
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- 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
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- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- 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
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- C21D2211/005—Ferrite
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Abstract
The invention discloses an ultra-low carbon bake-hardening steel and a production method thereof, wherein the ultra-low carbon bake-hardening steel comprises the following chemical components in percentage by mass: c: 0.0018-0.0029 wt%, Si: 0 to 0.030 wt%, Mn: 0.6-0.7 wt%, P: 0.04-0.05 wt%, S: 0.005-0.015 wt%, Alt: 0.035 to 0.065 wt%, Nb: 0.006-0.010 wt%, Ti: 0.0020-0.0060 wt%, B: 0.0005 to 0.0012 weight percent, and less than or equal to 0.0030 weight percent of N. In the production method, the cold rolling reduction rate is controlled to be 79-82 percent, and the dew point is controlled to be less than or equal to-40 ℃. The ultra-low carbon bake-hardening steel with BH stable at 35-70 is obtained through the synergistic cooperation of the components and the process.
Description
Technical Field
The invention relates to the technical field of steel preparation, in particular to ultra-low carbon bake-hardening steel and a production method thereof.
Background
The ultra-low carbon bake-hardening steel is a high-quality automobile steel plate which has relatively high strength (the yield strength is more than or equal to 220MPa), and the yield strength can be improved to a certain extent after the ultra-low carbon bake-hardening steel is formed by stamping at normal temperature and subjected to baking finish temperature aging treatment. The BH steel sheet is characterized by being soft and easy to form and process before stamping, and the yield strength is increased through the painting and baking process after stamping, so that the BH steel sheet is very suitable for covering parts such as automobile outer plates. The Bake Hardening (BH) steel is characterized by low yield point and excellent formability during stamping, and after stamping, the yield point is increased due to high-temperature short-time heat treatment during coating and drying, so that the stamped part has high strength and dent resistance in a use state. The bake-hardened steel is suitable for producing covering parts such as automobile outer plates, and the dosage of the bake-hardened steel is increased year by year, and becomes an important component of modern automobile steel.
As the prior art generally has the condition that the BH value control is unstable, the surface quality is influenced. Therefore, how to develop an ultra-low carbon bake-hardening steel with stable BH value within a proper range is a technical problem to be solved urgently.
Disclosure of Invention
The invention aims to provide the ultra-low carbon bake-hardening steel and the production method thereof, the BH value is stably controlled to be 35-70, and the surface quality of the ultra-low carbon bake-hardening steel is good.
In order to achieve the purpose, the invention provides an ultra-low carbon bake-hardening steel, which comprises the following chemical components in percentage by mass: c: 0.0018-0.0029 wt%, Si: 0 to 0.030 wt%, Mn: 0.6-0.7 wt%, P: 0.04-0.05 wt%, S: 0.005-0.015 wt%, Alt: 0.035 to 0.065 wt%, Nb: 0.006-0.010 wt%, Ti: 0.0020-0.0060 wt%, B: 0.0005 to 0.0012 weight percent, and less than or equal to 0.0030 weight percent of N; the balance of Fe and inevitable impurities.
Further, the internal microstructure of the ultra-low carbon bake-hardened steel is ferrite.
Further, the size of the ferrite grains is 9-18 um.
The invention also provides a production method of the ultra-low carbon bake-hardening steel, which comprises the following steps:
smelting molten steel to obtain a continuous casting plate blank;
carrying out hot rolling on the continuous casting plate blank to obtain strip steel;
pickling and cold rolling the strip steel to obtain a cold hard coil, wherein the cold rolling reduction rate is set to be 79-82%;
and continuously annealing the chilled coil to obtain the carbon baking hardened steel, wherein the dew point is controlled to be less than or equal to-40 ℃ during continuous annealing.
Further, the continuous casting slab is hot-rolled to obtain a strip steel, including:
discharging, fine rolling and curling, wherein the discharging temperature is 1150-1220 ℃, and the finish rolling temperature of the fine rolling is 890-940 ℃; the coiling temperature is 630-670 ℃.
Further, the cold-hard coil is continuously annealed to obtain the carbon bake-hardened steel, including:
the cold-hard coil is annealed sequentially through a heating section, a soaking section, a slow cooling section and a fast cooling section, wherein the temperature of the heating section is heated to 760-790 ℃ from room temperature, the temperature of the soaking section is kept at 760-790 ℃ and is kept for 45-70 seconds, the temperature of the slow cooling section is 600-660 ℃, and the temperature of the fast cooling section is 340-370 ℃.
Further, the continuous annealing atmosphere is hydrogen and nitrogen.
The invention also provides a packaging product prepared from the ultra-low carbon bake-hardening steel.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
the invention provides an ultra-low carbon bake hardening steel and a production method thereof, wherein (1) on the components, a component system with high excess carbon, Nb and Ti fixed gap atoms and reinforced Si, Mn and P is adopted to control the content of solid solution carbon atoms, so that the bake hardening value is stable; (2) the cold rolling reduction rate is set to be 79-82% in the process; the dew point is controlled to be less than or equal to-40 ℃. In conclusion, the ultralow-carbon bake-hardening steel with BH stable at 35-70 is obtained by the synergistic cooperation of the components and the process.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a metallographic structure diagram of an ultra-low carbon bake-hardened steel prepared in example 1;
FIG. 2 is a flow chart of a method for producing an ultra low carbon bake-hardened steel according to an embodiment of the present invention;
FIG. 3 is a surface quality plot of the parts of example 1 and comparative example 1 after forming;
FIG. 4 is a surface quality plot of the parts of example 2 and comparative example 5 after forming.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
In order to solve the technical problems, the embodiment of the invention provides the following general ideas:
in order to achieve the above object, the present embodiment provides an ultra-low carbon bake-hardening steel, which comprises the following chemical components by mass percent: c: 0.0018-0.0029 wt%, Si: 0 to 0.030 wt%, Mn: 0.6-0.7 wt%, P: 0.04-0.05 wt%, S: 0.005-0.015 wt%, Alt: 0.035 to 0.065 wt%, Nb: 0.006-0.010 wt%, Ti: 0.0020-0.0060 wt%, B: 0.0005 to 0.0012 weight percent, and less than or equal to 0.0030 weight percent of N; the balance of Fe and inevitable impurities. In this example, the internal microstructure of the ultra low carbon bake-hardened steel was ferrite, and the size of ferrite grains was 9 to 18 um. As shown in fig. 1.
The ultra-low carbon bake-hardening steel with the chemical components is formed by optimizing the composition elements, and is based on the following principle:
c: the steel has solid solution strengthening effect, the content of C is controlled to be 0.0018-0.0029 wt%, the yield strength is improved, and the elongation is reduced. Too high will result in a decrease in plasticity, and too low will result in insufficient strength.
N: n in solid solution can improve the strength, N element has the performance of reducing the formability and the anti-aging performance, the nitrogen and aluminum are combined to form a precipitate of AlN, the improvement of the plasticity is facilitated, but the strength of the material with too high N is increased, and the development of the texture of the material is hindered; n is too low to exert a strength-improving effect, so that N is 0.0030 wt%.
Nb and Ti fix interstitial atoms, thereby realizing the steel for ultra-low carbon bake hardening and solving the problem of unstable bake hardening value after the steel is produced by using the prior process technology.
Mn, Si and P: in the invention, Mn-Si-P system composed of Mn, Si and P is used as a strengthening system together, and the Mn element is limited to 0.6-0.7 wt%, the P element is limited to 0.04-0.05 wt%, and the Si element is limited to 0-0.030 wt%, because the Mn-Si-P strengthening system can play a solid solution strengthening role to the maximum extent in the range to improve the yield strength and does not influence the low-temperature toughness and the surface quality of steel.
And Als: als element is used as deoxidizing nitrogen-fixing element, N element precipitation is insufficient due to too little addition, the processing performance is deteriorated, too much addition effect is basically saturated, and the Als element is limited to be 0.035-0.065 wt%.
In the components, a high-excess carbon (2 ppm higher than the conventional excess carbon, namely 10ppm-16ppm), Nb and Ti are used for fixing interstitial atoms, and a component system reinforced by Si, Mn and P is used for controlling the content of solid-solution carbon atoms, so that the bake hardening value is stable.
The embodiment of the present invention further provides a method for producing low carbon bake-hardened steel, please refer to fig. 2, where the method includes:
step 1: smelting molten steel to obtain a continuous casting plate blank;
specifically, molten steel is smelted according to set components and poured into a continuous casting slab in the embodiment of the application. Wherein the continuous casting slab is a product obtained by casting molten steel smelted by a steel smelting furnace by a continuous casting machine.
Step 2: and carrying out hot rolling on the continuous casting slab to obtain strip steel, and cooling and coiling the strip steel after the hot rolling is finished to obtain a strip steel coil.
Further, the tapping temperature of the hot rolling is 1150-1220 ℃, the finishing temperature is 890-940 ℃, and the coiling temperature is controlled at 630-670 ℃.
Process temperature of hot rolling section: if the tapping temperature is less than 1150 ℃, the tapping temperature is too low to be implemented very difficultly; if the finishing temperature is less than 890 ℃, the finishing temperature is too low, the rolling mill cannot roll completely in austenite, and the steel grade is required to be rolled above the austenite temperature, and the austenite temperature of the steel grade is about 880 ℃, so that the finishing temperature is guaranteed to be above 880 ℃. If the heating temperature is higher than 1220 ℃, the finishing temperature is higher than 940 ℃, the coiling temperature is higher than 670 ℃, the energy consumption is high, and the surface quality is poor due to iron scale and the like.
Specifically, the heating temperature of a continuous casting slab is set for hot rolling, wherein the hot rolling adopts the continuous casting slab or a primary rolling slab as a raw material, the raw material is heated by a stepping heating furnace, high-pressure water is used for removing phosphorus and then enters a rough rolling mill, the rough rolling material is cut at the head and the tail and then enters a finish rolling mill for computer-controlled rolling, and after the finish rolling, the rough rolling material is subjected to laminar cooling (the cooling rate of the computer is controlled) and coiling by a coiling machine to form a straight hair coil. The straight hair coil is processed by the finishing lines of head cutting, tail cutting, edge cutting, multi-pass straightening, leveling and the like, and then is cut into plates or rewound to obtain products such as hot rolled steel plates, flat hot rolled steel coils, longitudinal cutting belts and the like. The hot rolling can destroy the casting structure of the steel ingot, refine the crystal grains of the steel and eliminate the defects of the microstructure, thereby leading the steel structure to be compact and improving the mechanical property. The improvement is mainly achieved in the rolling direction, so that the steel is no longer isotropic to some extent; bubbles, cracks and looseness formed during casting can also be welded under the action of high temperature and pressure.
And step 3: and carrying out acid pickling and cold rolling on the strip steel coil to obtain a cold-hard coil, wherein the cold rolling reduction rate of the cold rolling is set to be 79-82%. The inventor finds that the improvement of the cold rolling reduction rate to 79-82% is beneficial to the stability of the BH value, the improvement of the overall performance of the steel and the stability of the BH value. If the cold rolling reduction is less than 79%, the driving force for the annealing step is insufficient. If the cold rolling reduction is higher than 82%, the field equipment capability and stability may be affected.
Specifically, the strip steel coil is subjected to cold rolling, wherein the hot rolled steel coil is adopted as a raw material for the cold rolling, the cold rolling is carried out after removing oxide skin through acid washing, the finished product is a hard rolled coil, and the strength and hardness of the hard rolled coil are increased, the toughness and plasticity indexes are reduced, the stamping performance is deteriorated due to cold work hardening caused by continuous cold deformation, so that the cold rolled coil can only be used for parts with simple deformation. In general, cold continuous rolled plates and cold continuous rolled coils are subjected to annealing removal treatment through a continuous annealing process (CAPL unit) or a bell-type furnace, so that cold hardening and rolling stress are eliminated, and mechanical performance indexes specified by standards are achieved. The surface quality, appearance and dimensional accuracy of the cold-rolled steel sheet are superior to those of a hot-rolled sheet. The cold rolling has the advantages of high forming speed and high yield, does not damage the coating, and can be made into various section forms to meet the requirements of use conditions; and the cold rolling can cause the steel to generate large plastic deformation, thereby improving the yield point of the steel.
And 4, step 4: after cold rolling is finished, the strip steel at room temperature is sent into an annealing furnace for continuous annealing, wherein the cold hard coil is annealed sequentially through a heating section, a soaking section, a slow cooling section and a fast cooling section, the temperature of the heating section is heated from room temperature to 760-790 ℃, the temperature of the soaking section is kept at 760-790 ℃ and kept at 45-70 seconds, the temperature of the slow cooling section is 600-660 ℃, and the temperature of the fast cooling section is 340-370 ℃.
Further, the medium in the annealing furnace consists of hydrogen and nitrogen.
Furthermore, the heating period in the continuous annealing is 120-200S, the soaking period is 45-70S, the slow cooling period is 10-25S, and the fast cooling period is 30-60S.
Continuous annealing adopts the temperature in heating section, soaking section, slow cooling section, four stages of fast cooling section in this application, this is with the composition matched with of this application, can realize that carbide supersaturation rapidly dissolves and heats up the in-process after the rapid cooling fully to separate out, obtains carbide microstructure for graininess evenly distributed on ferrite crystalline grain to shortened low carbon bake hardening steel yield platform length under the not flat condition within 3%, further made the BH value stable between 35-70.
The dew point is controlled to be less than or equal to-40 ℃ during the continuous annealing, because the dew point influences the distribution content of the excessive carbon, the BH value is influenced, and if the dew point is more than-40 ℃, the BH value is unstable.
According to the content, the ultra-low carbon bake-hardening steel and the production method thereof provided by the invention have the advantages that (1) in the components, a component system reinforced by high excess carbon, Nb and Ti fixed interstitial atoms and Si, Mn and P is adopted, the content of solid-dissolved carbon atoms is controlled, and further the bake-hardening value is stable; (2) the cold rolling reduction rate is set to be 79-82% in the process; the dew point is controlled to be less than or equal to-40 ℃. In conclusion, the ultralow-carbon bake-hardening steel with BH stable at 35-70 is obtained by the synergistic cooperation of the components and the process. The yield strength of the finally obtained low-carbon baking hardened steel is 270MPa, the tensile strength reaches 440MPa and the elongation is 29-32%.
An ultra low carbon bake-hardened steel and a method for producing the same according to the present application will be described in detail with reference to examples, comparative examples and experimental data.
Molten iron is smelted in a converter and then enters an LF furnace fire RH furnace for refining treatment, and a slab with chemical components shown as 1 is formed by adopting a conventional continuous casting method. The ultra low carbon bake-hardened steels of example 1 and comparative examples 1-4 were 0.7mm 925mm in gauge and 192203055 in heat number (T1119a10810801, T1119615002201). The ultra low carbon bake hardened steels of examples 2-3 and comparative example 5 were 0.8mm 1340mm gauge with a heat rating of 192205311.
Table 1-main components (mass%, balance Fe and inevitable impurities) of slabs in each group
| Group of | C | Si | Mn | P | S | Alt | Nb | Ti | B | N |
| Example 1 | 0.0019 | 0.0067 | 0.632 | 0.0433 | 0.0079 | 0.0491 | 0.007 | 0.0037 | 0.0009 | 0.001 |
| Comparative example 1 | 0.0019 | 0.0067 | 0.632 | 0.0433 | 0.0079 | 0.0491 | 0.007 | 0.0037 | 0.0009 | 0.001 |
| Comparative example 2 | 0.0019 | 0.0067 | 0.632 | 0.0433 | 0.0079 | 0.0491 | 0.007 | 0.0037 | 0.0009 | 0.001 |
| Comparative example 3 | 0.0019 | 0.0067 | 0.632 | 0.0433 | 0.0079 | 0.0491 | / | / | 0.0009 | 0.001 |
| Comparative example 4 | 0.0019 | 0.0067 | 0.3 | 0.03 | 0.0079 | 0.0491 | 0.007 | 0.0037 | 0.0009 | 0.001 |
| Example 2 | 0.0024 | 0.0065 | 0.66 | 0.0448 | 0.0074 | 0.054 | 0.007 | 0.0039 | 0.0009 | 0.001 |
| Comparative example 5 | 0.0024 | 0.0065 | 0.66 | 0.0448 | 0.0074 | 0.054 | 0.007 | 0.0039 | 0.0009 | 0.001 |
| Example 3 | 0.0029 | 0.03 | 0.70 | 0.05 | 0.015 | 0.065 | 0.01 | 0.006 | 0.0012 | 0.03 |
The carbon bake-hardened steel was obtained by hot rolling, pickling, cold rolling, and continuous annealing of slabs of different compositions shown in table 1, with the main process parameters shown in table 2.
TABLE 2 Process parameters for each group
The properties of the low carbon bake-hardened steels obtained in examples 1 to 3 and comparative examples 1 to 5 were tested and counted as shown in table 3.
TABLE 3
As is clear from tables 1 to 3, comparative example 1 has a different dew point from example 1, and the other conditions are the same. The baking hardening value of the product in example 1 reaches 49, and the product is qualified; while comparative example 1 had a bake hardening value of 19, which was a defective product. Fig. 3 is a surface quality chart of the parts of example 1 and comparative example 1 after forming, and it is understood that the surface quality of the product of example 1 is good, while the surface quality of the product of comparative example 1 is not good, and a tensile strain mark phenomenon occurs.
In comparison with example 1, comparative example 2 differs only in cold rolling reduction, and the other conditions are the same. The baking hardening value of the product in example 1 reaches 49, and the product is qualified; while comparative example 2 had a bake hardening value of 23, which was a defective product.
Comparative example 3 contains no Nb and Ti compared to example 1, and the other conditions are the same. Comparative example 3 had very severe tensile strain marks.
In comparative example 4, the contents of Mn and P were different from those in example 1, and the other conditions were the same. The strength of the steel grade of comparative example 4 was low.
The tapping temperature of comparative example 5 was different from that of example 2, and the other conditions were the same. The baking hardening value of the product in the embodiment 2 reaches 35, and the product is qualified; while comparative example 5 had a bake hardening value of 89, which was a defective product. Fig. 4 is a surface quality chart of the parts of example 2 and comparative example 5 after forming, and it can be seen that the surface quality of the sample of example 2 is normal, and the surface of the sample of comparative example 5 has orange peel defects.
In summary, the ultra-low carbon bake-hardening steel and the production method thereof provided by the invention (1) adopt a component system reinforced by high excess carbon, Nb and Ti fixed interstitial atoms and Si, Mn and P to control the content of solid-dissolved carbon atoms, thereby stabilizing the bake-hardening value; (2) the cold rolling reduction rate is set to be 79-82% in the process; the dew point is controlled to be less than or equal to-40 ℃. In conclusion, the ultralow-carbon bake-hardening steel with BH stable at 35-70 is obtained by the synergistic cooperation of the components and the process.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (8)
1. The ultra-low carbon bake-hardening steel is characterized by comprising the following chemical components in percentage by mass: c: 0.0018-0.0029 wt%, Si: 0 to 0.030 wt%, Mn: 0.6-0.7 wt%, P: 0.04-0.05 wt%, S: 0.005-0.015 wt%, Alt: 0.035 to 0.065 wt%, Nb: 0.006-0.010 wt%, Ti: 0.0020-0.0060 wt%, B: 0.0005 to 0.0012 weight percent, and less than or equal to 0.0030 weight percent of N; the balance of Fe and inevitable impurities.
2. The ultra low carbon bake hardened steel of claim 1, wherein the internal microstructure of the ultra low carbon bake hardened steel is ferrite.
3. The ultra low carbon bake hardened steel of claim 2, wherein said ferrite grains are 9-18um in size.
4. A method for producing the ultra low carbon bake hardened steel of any one of claims 1 to 3, said method comprising:
smelting molten steel to obtain a continuous casting plate blank;
carrying out hot rolling on the continuous casting plate blank to obtain strip steel;
pickling and cold rolling the strip steel to obtain a cold hard coil, wherein the cold rolling reduction rate is set to be 79-82%;
and continuously annealing the chilled coil to obtain the carbon baking hardened steel, wherein the dew point is controlled to be less than or equal to-40 ℃ during continuous annealing.
5. The method for producing an ultra-low carbon bake-hardened steel as claimed in claim 4, wherein said continuously cast slab is hot-rolled to obtain a strip steel comprising:
discharging, fine rolling and curling, wherein the discharging temperature is 1150-1220 ℃, and the finish rolling temperature of the fine rolling is 890-940 ℃; the coiling temperature is 630-670 ℃.
6. The method of producing an ultra-low carbon bake-hardened steel as claimed in claim 4 wherein said cold-hardened coil is continuously annealed to obtain said carbon bake-hardened steel comprising:
the cold-hard coil is annealed sequentially through a heating section, a soaking section, a slow cooling section and a fast cooling section, wherein the temperature of the heating section is heated to 760-790 ℃ from room temperature, the temperature of the soaking section is kept at 760-790 ℃ and is kept for 45-70 seconds, the temperature of the slow cooling section is 600-660 ℃, and the temperature of the fast cooling section is 340-370 ℃.
7. The method for producing the ultra-low carbon bake-hardening steel according to claim 6, wherein the heating period is 120 to 200 seconds, the slow cooling period is 10 to 25 seconds, and the fast cooling period is 30 to 60 seconds.
8. The method for producing ultra-low carbon bake-hardened steel as claimed in claim 4, wherein said atmosphere of continuous annealing is hydrogen and nitrogen.
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| CN113549736A (en) * | 2021-06-22 | 2021-10-26 | 鞍钢蒂森克虏伯（重庆）汽车钢有限公司 | Technological method for stably controlling bake-hardening steel BH2 |
Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1118814A (en) * | 1994-02-17 | 1996-03-20 | 川崎制铁株式会社 | Method for making steel plate with good working performence |
| CN101096034A (en) * | 2006-06-27 | 2008-01-02 | 鞍钢股份有限公司 | Production method of ultra-low-carbon steel for sedan car cortical plate |
| CN103993148A (en) * | 2014-05-19 | 2014-08-20 | 攀钢集团攀枝花钢铁研究院有限公司 | Ultra-low carbon cold-roll steel sheet and preparation method thereof |
| CN104213024A (en) * | 2014-09-10 | 2014-12-17 | 河北钢铁股份有限公司唐山分公司 | Ultra-low carbon high-strength steel produced by cover annealing and production method thereof |
| CN104561789A (en) * | 2015-01-22 | 2015-04-29 | 首钢总公司 | Ultra-low carbon bake-hardened steel having aging index of lower than 20MPa and production method of steel |
| CN104593674A (en) * | 2015-01-21 | 2015-05-06 | 首钢总公司 | Hot-dip galvanized ultra-low carbon bake-hardening steel and production method thereof |
| CN104694817A (en) * | 2015-03-26 | 2015-06-10 | 攀钢集团西昌钢钒有限公司 | Ultralow carbon cold-roll steel sheet production method |
| CN109161814A (en) * | 2018-08-30 | 2019-01-08 | 唐山钢铁集团有限责任公司 | A kind of ultra-low carbon baking hardening steel plate and its production method |
| CN109321839A (en) * | 2018-10-24 | 2019-02-12 | 首钢京唐钢铁联合有限责任公司 | A kind of 240MPa grades of baking hardened steel and its manufacturing method |
| CN110026433A (en) * | 2019-03-20 | 2019-07-19 | 首钢集团有限公司 | A method of improving the continuous annealing of high-strength IF steel containing P plate surface quality |
| CN111850262A (en) * | 2020-06-22 | 2020-10-30 | 鞍钢蒂森克虏伯汽车钢有限公司 | Production method of ultra-low carbon baking hardening continuous hot-dip galvanized steel sheet |
-
2020
- 2020-06-03 CN CN202010493246.2A patent/CN111636031A/en active Pending
Patent Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1118814A (en) * | 1994-02-17 | 1996-03-20 | 川崎制铁株式会社 | Method for making steel plate with good working performence |
| CN101096034A (en) * | 2006-06-27 | 2008-01-02 | 鞍钢股份有限公司 | Production method of ultra-low-carbon steel for sedan car cortical plate |
| CN103993148A (en) * | 2014-05-19 | 2014-08-20 | 攀钢集团攀枝花钢铁研究院有限公司 | Ultra-low carbon cold-roll steel sheet and preparation method thereof |
| CN104213024A (en) * | 2014-09-10 | 2014-12-17 | 河北钢铁股份有限公司唐山分公司 | Ultra-low carbon high-strength steel produced by cover annealing and production method thereof |
| CN104593674A (en) * | 2015-01-21 | 2015-05-06 | 首钢总公司 | Hot-dip galvanized ultra-low carbon bake-hardening steel and production method thereof |
| CN104561789A (en) * | 2015-01-22 | 2015-04-29 | 首钢总公司 | Ultra-low carbon bake-hardened steel having aging index of lower than 20MPa and production method of steel |
| CN104694817A (en) * | 2015-03-26 | 2015-06-10 | 攀钢集团西昌钢钒有限公司 | Ultralow carbon cold-roll steel sheet production method |
| CN109161814A (en) * | 2018-08-30 | 2019-01-08 | 唐山钢铁集团有限责任公司 | A kind of ultra-low carbon baking hardening steel plate and its production method |
| CN109321839A (en) * | 2018-10-24 | 2019-02-12 | 首钢京唐钢铁联合有限责任公司 | A kind of 240MPa grades of baking hardened steel and its manufacturing method |
| CN110026433A (en) * | 2019-03-20 | 2019-07-19 | 首钢集团有限公司 | A method of improving the continuous annealing of high-strength IF steel containing P plate surface quality |
| CN111850262A (en) * | 2020-06-22 | 2020-10-30 | 鞍钢蒂森克虏伯汽车钢有限公司 | Production method of ultra-low carbon baking hardening continuous hot-dip galvanized steel sheet |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113549736A (en) * | 2021-06-22 | 2021-10-26 | 鞍钢蒂森克虏伯（重庆）汽车钢有限公司 | Technological method for stably controlling bake-hardening steel BH2 |
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