CN115572891A - Cold-rolled annealed steel strip with yield strength of 420MPa for art designing blade - Google Patents
Cold-rolled annealed steel strip with yield strength of 420MPa for art designing blade Download PDFInfo
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- 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
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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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- 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
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention discloses a cold-rolled annealed steel strip with the yield strength of 420MPa for an art designing blade, which solves the technical problems of low hardness and high manufacturing cost of the existing cold-rolled annealed steel strip for the art designing blade. The technical scheme is that the yield strength 420MPa grade cold rolled annealed steel strip for the art designing blade comprises the following chemical components in percentage by weight: c:0.90% -0.98%, si: 0.10-0.30%, mn: 0.30-0.50%, P is less than or equal to 0.015%, S is less than or equal to 0.003%, cr: 0.10-0.30%, al:0.02% > E0.04 percent of N, less than or equal to 0.0060 percent of N, and the balance of Fe and inevitable impurities; the grade of non-metallic inclusions in the cold-rolled annealed steel strip is 1.5 or less. Yield strength R of cold-rolled annealed steel strip with thickness of 0.30-0.60mm P0.2 420-480 MPa, and is used for manufacturing high-strength art designing blades.
Description
Technical Field
The invention relates to a cold-rolled annealed steel strip for manufacturing a machining cutter, in particular to a cold-rolled annealed steel strip with yield strength of 420MPa for an art designing blade and a manufacturing method thereof, and belongs to the technical field of iron-based alloys.
Background
The art designing knife is commonly called a graver or a wallpaper knife, is a knife for art and handicraft, is mainly used for cutting objects with soft texture, mainly consists of a plastic knife handle and a blade, and is of a drawing structure. There are various sizes, and generally used for cutting paper, cutting tape, sealing box, etc., and the blade is required to have high strength and hardness and a certain brittleness, but is required to have good toughness during forming and to prevent brittle fracture during press forming.
Generally, the hardness and the use durability of the cutter body of the utility knife are different due to different materials of the cutter body, at present, the conventional utility knife blade is generally made of 50 steel or 65Mn, but the hardness of the steel for the utility knife blade after heat treatment is less than or equal to 55HRC, the hardness is low, and the service life is shorter.
The patent application with the application publication number of CN106077087A discloses a strip rolling process method and production equipment special for an art designing blade, discloses a process of rolling strip steel by adopting a 20-roller cold rolling mill, emphasizes the equipment and the flow arrangement of the cold rolling mill, does not describe key process parameters, does not describe the structure control and the requirement of materials, adopts the conventional steel types such as common 50 steel, 65Mn and the like as raw materials, has the hardness of only reaching 52-55HRC after the heat treatment of a cutter, and has lower material hardness and shorter service life.
The patent application with publication number CN 105543646A discloses a production process of medium-high carbon steel in a thin slab, which comprises the following main elements in percentage by weight: 0.5 to 0.88 percent of carbon, 0.15 to 0.68 percent of silicon, 0.65 to 1.55 percent of manganese, 0.09 to 0.22 percent of chromium, 0.08 to 0.12 percent of nickel, 0.02 to 0.035 percent of arsenic, 0.18 to 0.20 percent of copper, less than or equal to 0.2 percent of aluminum, less than or equal to 0.025 percent of phosphorus, 0.002 to 0.0025 percent of sulfur, and the balance of Fe and inevitable impurities; the invention aims to improve the center segregation and the surface crack of the material, adopts the thin slab continuous casting and rolling equipment process, and emphatically discloses the thin slab continuous casting process and parameters.
Disclosure of Invention
The invention aims to provide a 420 MPa-yield-strength cold-rolled annealed steel strip for an art designing blade and a manufacturing method thereof, and solves the technical problems of low hardness and high manufacturing cost of the existing cold-rolled annealed steel strip for the art designing blade.
The technical idea of the invention is that a component design method for improving the matrix content of C element in steel and effectively adding a certain amount of Mn and Cr microalloy elements is adopted, LF + RH double refining is adopted to control harmful elements and inclusions in the steel, and a hot rolling state pearlite structure is regulated and controlled by combining a hot rolling process; and finally, the structure and the performance of the material are improved through multi-pass cold rolling and bell-type annealing furnace spheroidizing annealing, so that the cold-rolled annealed steel strip for the high-strength art designing blade is obtained.
The technical scheme of the invention is that the yield strength 420MPa grade cold rolled annealed steel strip for the art designing blade comprises the following chemical components in percentage by weight: c:0.90% -0.98%, si: 0.10-0.30%, mn: 0.30-0.50%, P is less than or equal to 0.015%, S is less than or equal to 0.003%, cr: 0.10-0.30%, al: 0.02-0.04%, N is less than or equal to 0.0060%, and the balance of Fe and inevitable impurities; the grade of non-metallic inclusions in the cold-rolled annealed steel strip was 1.5 or less.
The metallographic structure of the cold-rolled annealed steel strip is granular pearlite + ferrite, and the nodularity is 90-95%; yield strength R of cold-rolled annealed steel strip with thickness of 0.30-0.60mm P0.2 420-480 MPa, tensile strength R m 560 to 620MPa, elongation after break A 50mm 20 to 25 percent; the Vickers hardness HV0.5 is 175-195.
The cold-rolled annealed steel strip is subjected to heat treatment by adopting a quenching and tempering process, and the Rockwell hardness of the cold-rolled annealed steel strip after the heat treatment is 60-63 HRC.
The reason why the chemical composition of the cold-rolled annealed steel strip for a utility blade having a yield strength of 420MPa level is limited to the above range is as follows:
carbon: carbon is the main alloying element for pearlite formation and affects the hardness of the material after hot rolling, cold rolling, annealing and blade quenching. The C content is too low to meet the final high hardness requirement of the part; if the content of C is too high, the plasticity and toughness are obviously reduced, and the steel coil is brittle and broken. Comprehensively considered, the carbon content is set to be 0.90-0.98 percent.
Silicon: silicon is used as a solid solution strengthening element, has a certain strengthening effect when being dissolved in a steel strip matrix, and also plays a role in deoxidation and desulfurization as a deoxidizer in smelting. However, if the amount of the metal element is large, the ferrite phase is hardened, and the workability is remarkably deteriorated. Si promotes the generation of the rust red iron oxide skin defect on the surface of the steel coil in the hot rolling process, and the appearance of a finished product is influenced; comprehensively considered, the Si content is set to be 0.10-0.30%.
Manganese: manganese is a good deoxidizer and desulfurizer. The steel contains a certain amount of manganese, so that the hot workability of the steel can be eliminated or improved, and the hardenability can be obviously improved. However, when the content is too large, segregation of components occurs, which causes unevenness in structure and drastically lowers moldability of the material. Comprehensively considered, the Mn content is set to be 0.30-0.50%.
Phosphorus: phosphorus is an impurity element, segregates in a grain boundary to reduce the processing performance, and hopefully reduces the content of the phosphorus as much as possible to improve the forming performance; but considering the control capability of process equipment and dephosphorization cost, the invention limits P to be less than or equal to 0.015 percent.
Sulfur: sulfur is an impurity element, and forms inclusions such as MnS in steel, which affects formability. It is desirable to reduce the content thereof as much as possible; considering the practical control capacity and desulfurization cost, the invention limits S to be less than or equal to 0.003 percent.
Chromium: chromium is a carbide forming element and can form various alloy carbides; the grain size of a structure in the cooling process after hot rolling is inhibited, the strength and the hardness of the material are improved, the content is generally required to be more than 0.10 percent, but the alloy cost is increased when the content is too much, and the processing performance is also reduced. Comprehensively considered, the Cr content is set to be 0.10-0.30 percent.
Aluminum: the role of aluminum in the present invention is to perform deoxidation and to bind free nitrogen, aluminum is a strong oxidizing forming element, and oxygen in steel forms Al 2 O 3 Is removed during steel making. Meanwhile, the aluminum also has the functions of refining grains and preventing austenite grains from being coarse, and the effect is obviously reduced along with the increase of the aluminum content; while too high aluminum will form too much Al 2 O 3 And the impurities are easily blocked at a pouring nozzle during continuous casting. Comprehensively considered, the Al content is set to be 0.02-0.04%.
Nitrogen: too high a nitrogen content will seriously deteriorate the plasticity and toughness of the material, increase the brittleness of the steel and cause the cracking of the continuous casting slab. The invention limits N to be less than or equal to 0.0060 percent.
A manufacturing method of a cold-rolled annealed steel strip with the yield strength of 420MPa for a utility knife blade comprises the following steps:
refining the molten steel by an LF refining furnace, carrying out vacuum degassing treatment by an RH furnace, and then carrying out continuous casting to obtain a continuous casting slab, wherein the continuous casting slab comprises the following chemical components in percentage by weight: c:0.90 to 0.98%, si:0.10 to 0.30%, mn: 0.30-0.50%, P is less than or equal to 0.015%, S is less than or equal to 0.003%, cr:0.10 to 0.30%, al:0.02 to 0.04 percent of N, less than or equal to 0.0060 percent of N; the balance of Fe and inevitable impurities; according to the American society for testing and materials' ASTM E45-13 Standard test method for determining the content of inclusions in steel, the method A is adopted for testing, and the grade of non-metallic inclusions in the continuous casting slab is below 1.5;
heating the continuous casting plate blank to 1190-1230 ℃ by a heating furnace, heating for 180-240 min, and then carrying out hot rolling, wherein the hot rolling is a two-section type rolling process, the rough rolling is 5-pass continuous rolling, rolling is carried out at the temperature above the austenite recrystallization temperature, and the finishing temperature of the initial rolling is 1020-1060 ℃; the finish rolling is 7-pass continuous rolling, the finish rolling finishing temperature is 870-910 ℃, and the finish rolling reduction rate is 90-95%; after finish rolling, controlling the thickness of the steel plate to be 2.0-3.0 mm, adopting front-stage cooling for laminar cooling, wherein the cooling speed is 20-30 ℃/S, and the coiling temperature is 620-660 ℃ to coil to obtain a hot-rolled steel coil;
transferring the hot rolled steel coil to a slow cooling area, slowly cooling the hot rolled steel coil by using a slow cooling wall, and after slowly cooling for 48-72 hours, moving the hot rolled steel coil out of the slow cooling area for air cooling;
the hot rolled steel coil is uncoiled again and then is subjected to acid cleaning, strip splitting, cold rolling and annealing by a cover type annealing furnace to obtain a finished cold rolled and annealed steel strip with the thickness of 0.30-0.60mm, and the cold rolling reduction rate is 75-85%; annealing the cold-rolled hard steel strip in the hood-type annealing furnace, wherein the temperature of the steel strip in a soaking section of the hood-type annealing furnace is 700-720 ℃, and the annealing time of the steel strip in the soaking section is 14-16h.
The hot rolling process and the hot rolled steel coil structure control are one of the technical key points for realizing the invention. By calculation, the component system A of the invention cm At 824.8 ℃ A 1 At 733.2 ℃; the adopted hot rolling process is based on the composition system and the calculated phase transformation point.
The reason of the production process system adopted by the invention is as follows:
1. the molten steel adopts LF refining furnace and RH vacuum furnace double refining process and the setting of the level of the inclusion in the continuous casting slab
The control of non-metallic inclusion in molten steel is a key technology for realizing the invention, because the thickness of the art designing blade is very thin and is only 0.3-0.6mm thick, the size and the shape of the non-metallic inclusion in the steel have great influence on the processing of the art designing blade, and the excessive and excessive inclusion can cause the forming processing of the art designing blade to generate micro cracks and even cracking, thus leading to the failure of products. Therefore, in the steelmaking refining process, LF refining furnace and RH vacuum furnace double refining are adopted, the grade of the inclusions in the continuous casting slab is controlled and controlled, the grade of the inclusions in the continuous casting slab is tested by a standard test method for measuring the content of the inclusions in steel according to American society for testing and materials (ASTM E45-13), and the method A is adopted for testing, so that the grade of the non-metallic inclusions in the continuous casting slab is set to be below 1.5, and the forming processing requirement of an art designing blade is met.
2. Setting of heating temperature and heating time of continuous casting slab
The heating temperature and time of the continuous casting slab are set to ensure that alloy elements such as C, si, mn and the like in the continuous casting slab are fully diffused and dissolved, and coarse carbide particles are dissolved and uniformly distributed in steel. Both too low a temperature and too short a heating time do not achieve the above objectives. The method adopts a higher slab heating temperature, the target temperature is 1210 ℃, if the temperature is too high, the heating time is too long, the oxidation and decarburization on the surface of the slab are serious, the final performance and the surface quality of a steel strip are not facilitated, and energy is consumed at the same time. Therefore, the heating temperature of the continuous casting plate blank is set to be 1190-1230 ℃, and the heating time is set to be 180-240 min.
3. Setting of finish Rolling finishing temperature
The finish rolling temperature of the invention is set to have two functions, on one hand, flat austenite grains with deformation zones inside are obtained by rolling the material in an austenite non-recrystallization area and are converted into fine ferrite grains in the subsequent laminar cooling process, thus playing the roles of refining the grains and reducing the zonal segregation; on the other hand, if the finish rolling temperature is too low, the rolling load becomes too large, and the rolling stability is impaired. Therefore, the finish rolling finishing temperature is set to 870 to 910 ℃.
4. Setting of laminar cooling method and cooling rate
The laminar cooling after the finish rolling of the invention adopts a front-stage cooling process, can promote the austenite structure in the material after the finish rolling to quickly generate pearlite transformation, and the structure is uniform and appropriately refined, so the cooling speed is set to be 20-30 ℃/S.
5. Setting of Hot Rolling coiling temperature
The hot rolling coiling temperature mainly influences the structure and the performance of the material and the subsequent spheroidizing annealing effect. The moderate coiling temperature is adopted, so that the crystal grains can be properly refined and uniform, and the subsequent cold rolling is facilitated. If the coiling temperature is too high, the crystal grains become coarse and the structure becomes uneven, and if the coiling temperature is too low, the strength of the hot rolled material is obviously increased, the brittleness of the steel coil is increased, and further uncoiling and splitting and cold rolling processing are not facilitated. Therefore, the hot rolling coiling temperature is set to be 620-660 ℃ in the invention.
6. Setting of slow cooling time of hot-rolled steel coil in slow cooling area
The hot rolled steel coil enters the slow cooling wall after being coiled, and the slow cooling wall is mainly used for preventing the steel coil from being excessively fast cooled after being coiled and generating similar martensite transformation. Because the carbon content of the product is very high, bainite and even martensite transformation can occur in the open stacking air cooling process of the steel coil, so that the brittleness of the material is obviously increased, the problems of local cracking and strip breakage occur, and the subsequent processing is influenced. Therefore, the hot rolled steel coil enters a slow cooling wall for cooling, and the slow cooling time is set to be 48-72 hours.
7. Setting of Cold Rolling reduction
The cold rolling deformation is an important means for improving the hardness and the specification and dimension precision of the steel strip. With the increasing of the cold rolling deformation, the dislocation density in the material is greatly increased, and more energy is provided for spheroidization transformation of lamellar pearlite. However, too high deformation will cause too large load on the cold rolling mill, increase the number of cold rolling passes, and greatly increase the cost of cold rolling. In view of the above, the cold rolling reduction of the present invention is preferably 75 to 85%.
8. Setting of annealing temperature and annealing time
The invention adopts the cover annealing furnace for annealing, and the spheroidization of flaky pearlite is promoted by considering the cold rolling deformation accumulation effect of the previous process, generally at A 1 Annealing is performed below the annealing point temperature. The too high annealing temperature can cause the crystal grains to be coarse, and the too low annealing temperature can hardly achieve the spheroidizing effect, and the annealing temperature of the steel strip in the soaking section of the hood-type annealing furnace is set to be 700-720 ℃.
The heat preservation time of the soaking section is also very critical during annealing; if the heat preservation time is too short, the lamellar pearlite chains cannot be completely fused and disconnected; fine spherical particles cannot be generated, and the dispersion distribution is formed; if the heat preservation time is too long, the granular pearlite can grow up again and agglomerate together to form lamellar segregation, so that the toughness of the material is reduced, and the subsequent processing is not facilitated. In order to improve the spheroidizing annealing effect, the set time of the steel strip in the soaking section is 14-16h.
The metallographic structure of the hot-rolled steel strip is fine lamellar pearlite; yield strength R of hot rolled steel strip with thickness of 2.0-3.0 mm P0.2 600-700 MPa, tensile strength R m 950 to 1100MPa, elongation after break A 50mm Is 12 to 18 percent.
The metallographic structure of the cold-rolled annealed steel strip produced by the method is granular pearlite + ferrite, and the nodularity is 90-95%; yield strength R of cold-rolled annealed steel strip with thickness of 0.30-0.60mm P0.2 420-480 MPa, tensile strength R m 560 to 620MPa, elongation after break A 50mm 20 to 25 percent; the Vickers hardness HV0.5 is 175-195.
The existing conventional quenching and tempering process is used for carrying out heat treatment on the cold-rolled annealed steel strip, and the Rockwell hardness of the cold-rolled annealed steel strip after the heat treatment is 60-63 HRC.
Compared with the prior art, the invention has the following positive effects: 1. the invention adopts high carbon content in the component design to improve the hardness of the material; simultaneously, a certain amount of microalloy elements such as Mn, cr and the like are added to improve the quenching performance of the material, so that the high-hardness cold-rolled annealed steel strip is obtained; the existing conventional quenching and tempering process is used for carrying out heat treatment on the cold-rolled annealed steel strip, and the Rockwell hardness of the cold-rolled annealed steel strip after the heat treatment is 60-63 HRC. 2. In the material manufacturing process, the LF and RH double refining is adopted to control the content of harmful elements and impurities in the steel making process, and the rolling temperature and the cooling mode after rolling are controlled in the hot rolling process to obtain the hot-rolled steel coil with properly refined grains and proper strength and toughness. And through multi-pass cold rolling and reasonable annealing process, lamellar pearlite in the steel is fully spheroidized to obtain the cold-rolled steel strip for the art designing blade with uniformly distributed tissues, which is beneficial to the forming and final heat treatment performance of the blade.
Drawings
FIG. 1 is a photograph of a metallographic structure of a hot-rolled steel strip according to example 3 of the present invention at a magnification of 500.
FIG. 2 is a photograph of a metallographic structure of a cold-rolled and annealed steel strip according to example 3 of the present invention at a magnification of 500.
Detailed Description
The present invention is further illustrated below with reference to examples 1 to 5, which are shown in tables 1 to 5.
Table 1 shows the chemical composition (in weight%) of the steels of the examples of the invention, the balance being Fe and unavoidable impurities.
Table 1 chemical composition of the steel of the examples of the present invention, unit: weight percent.
Smelting in a converter, carrying out desulfurization treatment in an LF ladle refining furnace refining procedure, carrying out alloy component micro-tempering and carrying out vacuum cycle degassing treatment in an RH furnace, wherein the pure degassing time is more than 8 minutes to obtain molten steel meeting the component requirement, and continuously casting the molten steel to obtain a continuous casting slab. The thickness of the continuous casting slab is 210-230 mm, the width is 900-1600 mm, and the length is 8000-11700 mm.
The continuous casting plate blank obtained by the method is detected according to the evaluation method (GB/T10561) of the non-metallic inclusions in the steel, and the grade of the non-metallic inclusions in the continuous casting plate blank is below 1.5.
Directly hot charging and hot conveying the continuous casting plate blank to a heating furnace for heating, and the middle part of the continuous casting plate blank cannot be cooled off-line; and (5) taking out the steel ingot and descaling the steel ingot, and then conveying the steel ingot to a hot continuous rolling unit for rolling. The rolling is controlled by a rough rolling and finish rolling continuous rolling unit, the steel is coiled after laminar cooling, front section cooling is adopted in the laminar cooling, qualified hot rolled steel coils are produced, and the thickness of the hot rolled steel coils is 2.0-3.0 mm.
And transferring the hot rolled steel coil to a slow cooling area, slowly cooling the hot rolled steel coil by using a slow cooling wall, and after slowly cooling for 48-72 hours, removing the hot rolled steel coil out of the slow cooling area for air cooling. The hot rolling process control parameters are shown in table 2.
Referring to fig. 1, the metallographic structure of the hot-rolled steel strip obtained by the above method is fine lamellar pearlite; yield strength R of hot rolled steel strip with thickness of 2.0-3.0 mm P0.2 600-700 MPa, tensile strength R m 950 to 1100MPa, elongation after break A 50mm Is 12 to 18 percent.
The hot rolled steel strip obtained by the invention is subjected to a part 1 of a GB/T228.1-2010 metal material tensile test: room temperature test method, and the microstructure of the steel is detected by a steel microstructure evaluation method (GB/T13299), and the mechanical properties are shown in Table 3.
TABLE 2 Hot Rolling Process parameters of the inventive examples
TABLE 3 mechanical Properties of Hot rolled Steel strips according to examples of the invention
The hot rolled steel coil is uncoiled again and then is pickled, and is cold-rolled for multiple times on a reversible rolling mill or a single-stand cold rolling mill after being stripped according to the width specification, wherein the cold rolling reduction rate is 75-85%; annealing the rolled hard steel coil after cold rolling in a bell-type furnace to obtain a finished cold-rolled steel strip with the thickness of 0.30-0.60mm, wherein the spheroidizing annealing process comprises the following steps: the annealing (soaking section) temperature of the bell-type furnace is 700-720 ℃, and the annealing (soaking section) time is 14-16h. The control parameters of the cold rolling and annealing processes are shown in Table 4.
Table 4 control parameters of the cold rolling and annealing processes according to the embodiments of the present invention
| Cold rolling and annealing parameters | Cold rolling reduction/%) | Annealing temperature/. Degree.C | Annealing time/h | Thickness/mm of cold rolled steel strip |
| The invention | 75-85 | 700-720 | 14-16 | 0.30-0.60 |
| Example 1 | 82.6 | 715 | 15.0 | 0.40 |
| Example 2 | 85.0 | 710 | 14.5 | 0.30 |
| Example 3 | 84.0 | 705 | 15.0 | 0.40 |
| Example 4 | 79.5 | 710 | 16.0 | 0.55 |
| Example 5 | 84.0 | 720 | 14.5 | 0.35 |
Referring to fig. 2, the cold-rolled annealed steel strip obtained by the method has a metallographic structure of granular pearlite + ferrite and a spheroidization rate of 90-95%; yield strength R of cold-rolled annealed steel strip with thickness of 0.30-0.60mm P0.2 420-480 MPa, tensile strength R m 560 to 620MPa, elongation after break A 50mm 20 to 25 percent; the Vickers hardness HV0.5 is 175-195.
The cold-rolled annealed steel strip obtained by the invention is subjected to tensile, microstructure and hardness detection according to a metal material tensile test method (GB/T228.1), a steel microstructure evaluation method (GB/T13299) and a metal material Vickers hardness test method (GB/T4340.1-2009), and the mechanical properties of the cold-rolled annealed steel strip are shown in Table 5.
TABLE 5 Performance index of Cold-rolled annealed Steel strips according to examples of the invention
The cold-rolled annealed steel strip is subjected to heat treatment by the conventional quenching and tempering process, the hardness is detected according to a Rockwell hardness test method (GB/T230.1-2009) of a metal material, and the Rockwell hardness of the cold-rolled annealed steel strip subjected to quenching and tempering heat treatment in examples 1-5 is 61.5HRC, 62.5HRC, 61.0HRC, 60.5HRC and 62.0HRC respectively.
As shown in Table 5, the cold-rolled and annealed steel strip of the invention has good material strength and toughness, and has higher hardness after quenching and tempering heat treatment; meets the requirements of continuous forming processing and high hardness use of the art designing blade.
In addition to the above embodiments, the present invention may have other embodiments; all technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.
Claims (6)
1. A cold-rolled annealed steel strip with yield strength of 420MPa for a utility blade comprises the following chemical components in percentage by weight: c:0.90% -0.98%, si: 0.10-0.30%, mn: 0.30-0.50%, P is less than or equal to 0.015%, S is less than or equal to 0.003%, cr: 0.10-0.30%, al: 0.02-0.04%, N is less than or equal to 0.0060%, and the balance of Fe and inevitable impurities; the grade of non-metallic inclusions in the cold-rolled annealed steel strip is below grade 1.5; yield strength R of cold-rolled annealed steel strip with thickness of 0.30-0.60mm P0.2 420-480 MPa, tensile strength R m 560 to 620MPa, elongation after break A 50mm 20 to 25 percent; the Vickers hardness HV0.5 is 175-195.
2. The cold-rolled and annealed steel strip for a utility blade having a yield strength of 420MPa according to claim 1, wherein the cold-rolled and annealed steel strip has a metallographic structure of granular pearlite + ferrite and a spheroidization ratio of 90 to 95%.
3. The cold-rolled annealed steel strip for a utility blade having a yield strength of 420MPa according to claim 1, wherein the Rockwell hardness of the cold-rolled annealed steel strip after the heat treatment by quenching and tempering is 60 to 63HRC.
4. A manufacturing method of a cold-rolled annealed steel strip with the yield strength of 420MPa for a utility knife blade is characterized by comprising the following steps:
refining the molten steel in an LF refining furnace, carrying out vacuum degassing treatment in an RH furnace, and then carrying out continuous casting to obtain a continuous casting slab, wherein the continuous casting slab comprises the following chemical components in percentage by weight: c:0.90 to 0.98%, si:0.10 to 0.30%, mn: 0.30-0.50%, P is less than or equal to 0.015%, S is less than or equal to 0.003%, cr:0.10 to 0.30%, al: 0.02-0.04 percent of N, less than or equal to 0.0060 percent of N; the balance of Fe and inevitable impurities; according to the Standard test method for measuring the content of the inclusions in the steel by ASTM E45-13 of the American society for testing and materials, the method A is adopted for testing, and the grade of the non-metallic inclusions in the continuous casting slab is below 1.5;
heating the continuous casting plate blank to 1190-1230 ℃ by a heating furnace, heating for 180-240 min, and then carrying out hot rolling, wherein the hot rolling is a two-stage rolling process, the rough rolling is 5-pass continuous rolling, the rolling is carried out above the austenite recrystallization temperature, and the finishing temperature of the initial rolling is 1020-1060 ℃; the finish rolling is 7-pass continuous rolling, the finish rolling finishing temperature is 870-910 ℃, and the finish rolling reduction rate is 90-95%; after finish rolling, controlling the thickness of the steel plate to be 2.0-3.0 mm, adopting front-section cooling for laminar cooling, wherein the cooling speed is 20-30 ℃/S, and the coiling temperature is 620-660 ℃ to coil to obtain a hot-rolled steel coil;
the hot rolled steel coil is transported to a slow cooling area, enters a slow cooling wall to carry out slow cooling on the hot rolled steel coil, and is moved out of the slow cooling area after being slowly cooled for 48-72 hours;
the hot rolled steel coil is uncoiled again and then is subjected to acid cleaning, strip splitting, cold rolling and annealing by a cover type annealing furnace to obtain a finished cold rolled and annealed steel strip with the thickness of 0.30-0.60mm, and the cold rolling reduction rate is 75-85%; annealing the cold-rolled hard steel strip in the hood-type annealing furnace, wherein the temperature of the steel strip in a soaking section of the hood-type annealing furnace is 700-720 ℃, and the annealing time of the steel strip in the soaking section is 14-16h.
5. The method of claim 4The manufacturing method of the cold-rolled annealed steel strip with the yield strength of 420MPa for the art designing blade is characterized in that the metallographic structure of the cold-rolled annealed steel strip is granular pearlite + ferrite, and the nodularity is 90-95%; yield strength R of cold-rolled annealed steel strip with thickness of 0.30-0.60mm P0.2 420-480 MPa, tensile strength R m 560 to 620MPa, elongation after break A 50mm 20 to 25 percent; the Vickers hardness HV0.5 is 175-195.
6. The method for manufacturing a cold-rolled and annealed steel strip for a utility blade having a yield strength of 420MPa according to claim 4, wherein the Rockwell hardness of the cold-rolled and annealed steel strip after the heat treatment by quenching and tempering is 60 to 63HRC.
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