CN110904385B - Low-cost cold-rolled steel plate for chain and production method thereof - Google Patents
Low-cost cold-rolled steel plate for chain and production method thereof Download PDFInfo
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- CN110904385B CN110904385B CN201911243395.7A CN201911243395A CN110904385B CN 110904385 B CN110904385 B CN 110904385B CN 201911243395 A CN201911243395 A CN 201911243395A CN 110904385 B CN110904385 B CN 110904385B
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- 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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- 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
- C21D8/0236—Cold rolling
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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
- 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
- C21D8/0273—Final recrystallisation annealing
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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Abstract
The invention discloses a low-cost cold-rolled steel plate for a chain and a production method thereof, and belongs to the technical field of steel rolling. The cold-rolled steel plate for the chain comprises the following components in percentage by weight: 0.15 to 0.30 percent of C; si is less than or equal to 0.40 percent; 0.30 to 0.60 percent of Mn; p is less than or equal to 0.03 percent; s is less than or equal to 0.02 percent; 0.02 to 0.06 percent of Al; the balance of Fe and inevitable impurities. The preparation process flow is as follows: the method comprises the steps of molten steel smelting → continuous casting → hot rolling → coiling → five-stand cold rolling → continuous annealing → leveling. The invention aims to solve the problems of high cost and uneven performance of a chain steel plate in the prior art, and provides a low-cost cold-rolled steel plate for a chain and a production method thereof.
Description
Technical Field
The invention relates to the technical field of steel rolling, in particular to a low-cost cold-rolled steel plate for a chain and a production method thereof.
Background
The chain is used as an important transmission device and is formed by connecting chain pieces through pins and rollers. The chain requires thin thickness of raw materials, and requires light weight of the whole vehicle; the strength is high, and the long-term service of the chain is ensured; the coil passing performance is uniform, and the surface hardness and the material strength are uniform after the quenching and tempering treatment. At present, a lot of shared bicycles are used in the market, and due to the sharing particularity, the manufacturing cost is required to be reduced, the vehicle body is lighter, the load is less, and the chain is different from a chain applied to the existing locomotive or engineering machinery.
The chain steel plate is subjected to quenching and tempering before being stamped, so that the hardness of the steel plate is improved, and the performance of the quenched and tempered steel plate is greatly influenced by a banded structure. Specifically, the banded structure refers to a band-like distribution of pearlite and ferrite, and this structure causes material anisotropy, and also causes uneven smooth zones on the ground surface, coarsening in cutting and surface roughness, and soft spots on the quenched surface, which affects the uniformity of the material. When the banded structure of the steel plate is more than 2 grades, normalizing is difficult to eliminate, so that the punched chain piece has uneven performance and has safety risk. Therefore, it is a constant pursuit goal in the industry to design a cold-rolled steel sheet which can meet the requirements of manufacturing chain pieces, has low cost and good uniformity.
Through search, a large number of patents have been published on steel plates for making chain pieces, such as chinese patent application No.: 2013104663146, the name of invention creation is: the application discloses a heat treatment method of low alloy steel special for vehicle chains, introduces a heat treatment method of low alloy steel special for vehicle chains, and introduces a heat treatment method of low alloy steel special for vehicle chains, which improves the tensile strength, the wear resistance and the corrosion resistance of chain steel by adding alloy elements such as V, Nb, Ti and the like, and comprises the following specific components: 0.16 to 0.18 percent of C; 0.7 to 0.9 percent of Mn; 0.35 to 0.38 percent of Si; 0.030 to 0.035 percent of P; 0.040% -0.042% of S; 0.015 to 0.020 percent of V; 0.015 to 0.020 percent of Nb; 0.02 to 0.08 percent of Ti; the balance being iron. The chain steel plate manufactured by adopting the heat treatment processes of carburizing, quenching, tempering and the like has higher hardness and strength.
Also as in chinese patent application No.: 2013103710262, the name of invention creation is: the application discloses a chain steel material, which is prepared by adding alloy elements and matching with a proper rolling and heat treatment process, and comprises the following specific components: 2.3 to 2.4 percent of C; 2.0 to 2.1 percent of Ni; 0.3 to 0.6 percent of Mg; 0.2 to 0.3 percent of S; 0.3 to 0.5 percent of Na, and the balance of Fe and inevitable impurities. Smelting in a vacuum induction furnace, heating to 1250 ℃, melting, hot rolling, heating to 800 ℃ and air cooling to prepare the high-elongation chain steel material.
The two schemes improve the strength and the elongation after fracture of the chain steel, but have the following problems: (1) a large amount of alloy elements are added, the cost is high, and the difficulty of the smelting process is increased. (2) Elements such as Mn and V have a high segregation coefficient in steel, and a segregation coefficient of Mn is 0.86 and a segregation coefficient of V is 0.62, so that segregation is likely to occur, and a large number of band-shaped structures are formed.
Disclosure of Invention
1. Technical problem to be solved by the invention
The invention aims to solve the problems of high cost and uneven performance of a chain steel plate in the prior art, and provides a low-cost cold-rolled steel plate for a chain and a production method thereof.
2. Technical scheme
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the invention discloses a low-cost cold-rolled steel plate for a chain, which comprises the following chemical components in percentage by weight: 0.15 to 0.30 percent of C; si is less than or equal to 0.40 percent; 0.30 to 0.60 percent of Mn; p is less than or equal to 0.03 percent; s is less than or equal to 0.02 percent; 0.02 to 0.06 percent of Al; the balance of Fe and inevitable impurities.
As a further improvement of the invention, the content of (C +0.1Mn) is more than or equal to 0.20% and less than or equal to 0.35%.
As a further improvement of the invention, the yield strength of the chain steel plate is 260MPa to 350MPa, the tensile strength is 450MPa to 550MPa, and the elongation after fracture is more than or equal to 32 percent.
As a further improvement of the invention, the surface hardness of the chain steel plate is 45-65, and the grade of the banded structure is less than 2.
The components of the low-cost cold-rolled steel sheet for the chain are controlled as follows:
carbon (C): the C element has the function of solid solution strengthening, the content of C is controlled to be 0.15-0.30%, the strength of the steel plate can be improved, and the rolling force of a rolling mill during cold rolling can be ensured not to exceed the load of the cold rolling mill.
Silicon (Si): the content of Si is controlled to be not more than 0.40%, thereby being beneficial to the hardenability and tempering stability of cold-rolled sheets, avoiding the disadvantage of excessively high content of Si on grain refinement, avoiding the steel from becoming coarse grain steel, and further increasing the quenching overheating sensitivity.
Manganese (Mn): the content of Mn is controlled to be 0.30-0.60%, so that the method not only can play a role in strengthening and is beneficial to refining ferrite grains, but also can avoid the phenomenon that a banded structure is easy to generate during the heat treatment when the content of Mn is too high, avoids the occurrence of hardening cracks and is not beneficial to the subsequent heat treatment process of the material.
Phosphorus (P): p is a harmful element in steel, the diffusion coefficient of P in ferrite is small, the content of P is controlled to be not more than 0.030%, and the P can be effectively prevented from being aggregated at a crystal boundary to form Fe3P, thereby avoiding the cold-brittleness phenomenon of the steel plate.
Sulfur (S): s is also a harmful element, and is easily attached to grain boundaries when steel is solidified, thereby causing cracking during hot working. In addition, the content of S in the steel is too high, cracks are easy to generate after quenching, and the quenching and tempering treatment of the chain steel is not facilitated. Therefore, the S content is controlled to be less than 0.02%, and the cracking can be obviously improved.
Aluminum (Al): al is the most common deoxidizer, the content of Al is controlled to be 0.020-0.060%, the effect of refining grains can be achieved, the quenching overheating sensitivity is reduced, and the heat treatment performance is improved.
The invention discloses a preparation method of a low-cost cold-rolled steel plate for a chain, which comprises the following preparation process flows of: the method comprises the steps of molten steel smelting → continuous casting → seven-stand hot continuous rolling → coiling → five-stand cold continuous rolling → continuous annealing → leveling.
As a further improvement of the invention, the molten steel smelting process is characterized in that raw materials are added into a steel-making furnace for smelting, pre-slagging and post-slagging are carried out during desulfurization treatment, so that the target S after molten steel desulfurization is less than or equal to 0.020%, pre-deoxidized carbon powder, medium-carbon ferromanganese, carburant and aluminum iron are added into the molten steel smelting furnace before tapping, the contents of C, Si, Mn and Als in molten steel are adjusted to be within a target range, and the tapping temperature of the molten steel is 15-30 ℃ above the liquidus temperature of the molten steel.
As a further improvement of the invention, in the seven-stand hot continuous rolling procedure, a hot rolling mill is adopted to carry out seven-pass hot continuous rolling on the billet after the continuous casting procedure, and the rolling temperature of the last pass is set to be 870-910 ℃.
As a further improvement of the invention, the coiling temperature of the coiling machine is controlled to be 690-730 ℃ in the coiling process.
As a further improvement of the invention, in the five-stand cold rolling procedure, a cold rolling mill without a frame is adopted to carry out five-pass cold continuous rolling on the steel plate after the steel plate comes out of the coiling machine, and the total reduction rate of the five-pass cold continuous rolling is controlled to be not less than 70%.
As a further improvement of the invention, the continuous annealing process refers to that the steel plate which is cold rolled by five racks is put into a continuous annealing furnace for continuous annealing, wherein the continuous annealing process sequentially comprises five stages of a soaking section, a slow cooling section, a fast cooling section, an overaging section and a final cooling section, the temperature of the soaking section is controlled to be 790-810 ℃, the annealing time is controlled to be 200-250 s, the end point temperature of the slow cooling section is controlled to be 690-700 ℃, the cooling speed is reduced to 350-400 ℃ in the fast cooling section at 120-150 ℃/min, the end point temperature of the overaging section is controlled to be 280-320 ℃, and the end point temperature of the final cooling section is controlled to be 80-120 ℃.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
(1) the low-cost cold-rolled steel sheet for the chain is designed by reasonable chemical components, and is matched with the accurate control of the processes of steel making, continuous casting, hot rolling, five-stand cold rolling, continuous annealing, leveling and the like to obtain the low-cost cold-rolled steel sheet for the chain, which has the strip structure grade less than 2 and uniform performance. The steel plate for the chain produced by the method has the yield strength of 260-350 MPa, the tensile strength of 450-550 MPa, the elongation after fracture of more than or equal to 34 percent and the surface hardness of 45-65 HR, has good wear resistance and uniform mechanical property, and completely meets the use requirements of chain pieces.
(2) According to the low-cost cold-rolled steel plate for the chain, the contents of C and Mn in the components meet the reasonable matching of (C +0.1Mn) and (C + Mn) being more than or equal to 0.20% and less than or equal to 0.35%, C, Mn is favorable for stable mechanical property, the wear resistance of the product meets the requirement, the addition amount of alloy elements is reduced, the steelmaking cost is reduced, the prepared chain has uniform performances, the banded structure is not more than 2-grade, the surface hardness is high, and the wear resistance is good.
(3) According to the preparation method of the low-cost cold-rolled steel plate for the chain, disclosed by the invention, in the five-stand cold rolling process, the cold rolling mill is adopted to carry out five-pass cold continuous rolling on the steel plate after the steel plate is discharged from the coiling machine, and the sum of the total reduction rate of the five-pass cold continuous rolling is controlled to be 71.4%. The five-rack cold rolling process is to further roll the steel plate, and the reduction rate of each cold rolling mill is set according to the thickness of the hot continuous rolled steel plate and the actually required thickness of the chain steel plate, so that the thickness of the steel plate rolled in the last step can meet the actual use requirement. The hot rolling process adopts austenite to roll by adopting a high reduction ratio, so that not only can the refining of crystal grains inside the steel plate be facilitated during the subsequent annealing, but also the internal banded structure can be reduced, the problem of uneven performance of chain pieces punched in the later period is avoided, and the safety risk of the chain steel plate can be effectively avoided.
(4) The invention relates to a preparation method of a low-cost cold-rolled steel plate for a chain, which is characterized in that a hot rolling mill is adopted to carry out seven-pass hot continuous rolling on a billet obtained in a continuous casting process, and the rolling temperature of a last-pass rack is set to be 870-910 ℃. The temperature in the interval is above Ac3 (ferrite-austenite transition temperature), which can ensure that the last rolling of billet hot rolling is austenite rolling, so that the rolled steel plate can obtain uniform grain structure, and the uniformity and the wear resistance of the steel plate are improved. The seven-stand hot continuous rolling is to preliminarily roll steel billets, specifically, the reduction ratios of the hot rolling mills are set according to the thickness of the chain steel plate required actually, and the sum of the total reduction ratios of the hot rolling mills is ensured to meet the thickness requirement before cold rolling
(5) The invention relates to a preparation method of a low-cost cold-rolled steel plate for a chain, wherein the continuous annealing process refers to that a steel plate cold-rolled by five racks is placed into a continuous annealing furnace for continuous annealing, wherein the continuous annealing process sequentially comprises five stages of a soaking section, a slow cooling section, a fast cooling section, an overaging section and a final cooling section, the temperature of the soaking section is controlled to be 790-810 ℃, the annealing time is controlled to be 200-250 s, the end point temperature of the slow cooling section is controlled to be 690-700 ℃, the cooling speed is reduced to 350-400 ℃ at 120-150 ℃/min in the fast cooling section, the end point temperature of the overaging section is controlled to be 280-320 ℃, and the end point temperature of the final cooling section is controlled to be 80-120 ℃. The soaking temperature of 790-810 ℃ is adopted in the annealing process, and the steel plate is cooled at a higher speed in a fast cooling section, the higher cooling rate is favorable for improving the zonal segregation, the pearlite and the ferrite can be prevented from being gathered into strip distribution, the generation of zonal tissues is avoided, the sufficient crystallization in the steel plate can be ensured, the overhigh strength and hardness of the steel plate are avoided, and the processing of the chain steel plate at the later stage is facilitated.
Drawings
FIG. 1 shows metallographic structures (200 times) of steel plates in examples 1 and 2 of the present invention;
FIG. 2 shows metallographic structures (500 times) of steel plates in examples 1 and 2 of the present invention;
FIG. 3 is a scanning electron micrograph (1000 times) of a steel plate in example 1 and example 2 of the present invention;
FIG. 4 is a scanning electron micrograph (5000 times) of a steel plate in example 1 and example 2 of the present invention.
Detailed Description
For a further understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The present invention will be further described with reference to the following examples.
Example 1
The low-cost cold-rolled steel plate for the chain comprises the following components in percentage by weight: 0.15 percent of C; 0.40 percent of Si; 0.30 percent of Mn; 0.03 percent of P; 0.02 percent of S; 0.02 percent of Al; the balance of Fe and inevitable impurities. By adopting a C + Mn strengthening mechanism, the addition of alloy elements is reduced, the steel-making cost is reduced, the prepared chain has uniform performances, the rating of a banded structure is not more than 2, the surface hardness is high, and the wear resistance is good.
The method for manufacturing the low-cost cold-rolled steel sheet for the chain according to the present embodiment is to prepare the molten steel having the above chemical components after the molten steel smelting process → the continuous casting process → the seven-stand hot continuous rolling → the coiling process → the five-stand cold continuous rolling process → the continuous annealing process → the leveling process. According to the embodiment, the cold-rolled steel plate for the chain, which has the banded structure rating less than 2 and uniform performance, is obtained by reasonable chemical composition design and by the accurate control of the processes of steel making, continuous casting, hot continuous rolling, five-stand cold continuous rolling, continuous annealing, leveling and the like. The steel plate for the chain produced by the method has the yield strength of 260-350 MPa, the tensile strength of 450-550 MPa, the elongation after fracture of more than or equal to 34 percent and the surface hardness of 45-65, has good wear resistance and uniform mechanical property, and completely meets the use requirements of chain pieces.
In this embodiment, the molten steel smelting process is to add the raw materials into a steel furnace for smelting, carry out pre-slagging before desulfurization treatment, control the S in the desulfurized molten steel to be not more than 0.010% after desulfurization treatment, carry out post-slagging after desulfurization treatment, so that the target S after desulfurization of the molten steel reaches 0.020%, because the steel slag contains a certain sulfur element, if slagging is not carried out, the S in the steel slag is slowly transferred to the steel slag, so that the content of S in the steel slag is too high, cracks are easily generated after subsequent steel plate quenching, and the quenching and tempering treatment of chain steel are not facilitated. Adding pre-deoxidized carbon powder, medium-carbon ferromanganese, a recarburizer and aluminum iron into a molten steel smelting furnace before tapping, adjusting the contents of C, Si, Mn and Als in molten steel to a target range, modifying impurities in the molten steel by adopting calcium treatment, and ensuring weak stirring time to enable the impurities in the molten steel to fully float upwards, wherein the tapping temperature of the molten steel is 15-30 ℃ above the liquidus temperature of the molten steel. Wherein (C +0.1Mn) is more than or equal to 0.20% and less than or equal to 0.35%, specifically, the weight percentage of (C +0.1Mn) in the embodiment is 0.20%, and the reasonable matching of C, Mn is beneficial to the stability of mechanical properties and ensures that the wear resistance of the product meets the requirements.
In the embodiment, the molten steel discharged from the molten steel smelting furnace is cast into steel billets through continuous casting equipment, the calming time of the continuous casting molten steel is more than or equal to 20min, the continuous casting molten steel is put into the continuous casting equipment under dynamic soft reduction to ensure that the molten steel keeps constant drawing speed for casting, and the surfaces of the steel billets are inspected and cleaned if necessary after the casting is finished. The tapping temperature of the steel billet is controlled to be 1180-1220 ℃, and specifically, the tapping temperature of the steel billet in the embodiment is 1180 ℃. Because the complete austenitizing of the steel billet needs to be over 800 ℃, the full austenitizing of the steel billet can be ensured by keeping higher tapping temperature of the steel billet.
In the seven-stand hot continuous rolling process in this embodiment, a hot rolling mill is used to perform seven-pass hot continuous rolling on the billet obtained in the continuous casting process, and the rolling temperature of the last-pass stand is set to 870 ℃. The temperature in the interval is above Ac3 (ferrite-austenite transition temperature), which can ensure that the billet is rolled and hot-rolled into austenite for the last pass, so that the rolled steel plate can obtain uniform grain structure, and the uniformity and the wear resistance of the steel plate are improved. In the embodiment, the seven-stand hot continuous rolling is the primary rolling of the steel billet, and specifically, the reduction ratios of the hot rolling mills are set according to the thickness of the chain steel plate required actually, so that the sum of the total reduction ratios of the hot rolling mills can meet the thickness requirement before cold rolling.
In this example, the coiling temperature of the coiler was controlled to 690 ℃. The coiling machine can coil the hot continuous rolled steel plate into a circular ring shape, and is convenient to place and transport.
In the five-stand cold rolling process in the embodiment, the cold rolling mill is adopted to perform five-pass cold continuous rolling on the steel plate from the coiling machine, and the total rolling reduction rate sum of the five-pass cold continuous rolling is controlled to be 71.4%. In the five-stand cold rolling process in the embodiment, the steel billet is further rolled, the reduction ratio of each cold rolling mill is set according to the thickness of the hot continuous rolled steel plate and the actually required thickness of the chain steel plate, and the thickness of the steel plate rolled in the last step is ensured to meet the actual use requirement. The austenite region of the steel plate is rolled by adopting a high reduction rate, so that not only can the refining of crystal grains inside the steel plate be facilitated during the subsequent annealing, but also the internal banded structure can be reduced, the problem of uneven performance of chain pieces punched in the later period is avoided, and the safety risk of the chain steel plate can be effectively avoided.
The continuous annealing process in the embodiment refers to that a steel plate which is cold-rolled by five racks is placed into a continuous annealing furnace for continuous annealing, wherein the continuous annealing process sequentially comprises five stages of a soaking section, a slow cooling section, a fast cooling section, an overaging section and a final cooling section, the temperature of the soaking section is controlled to be 790 ℃, the annealing time is controlled to be 200s, the final temperature of the slow cooling section is controlled to be 690 ℃, the cooling speed of the fast cooling section is reduced to 350 ℃ at 120 ℃/min, the final temperature of the overaging section is controlled to be 320 ℃, and the final temperature of the final cooling section is controlled to be 120 ℃. The soaking temperature of 805 ℃ is adopted in the annealing process, and the steel plate is cooled at a high speed in a quick cooling section, so that the high cooling speed is favorable for improving the zonal segregation, the pearlite and the ferrite are prevented from being aggregated into a strip distribution, the generation of a zonal structure is avoided, the sufficient crystallization in the steel plate can be ensured, the overhigh strength and hardness of the steel plate are avoided, and the processing of the chain steel plate at the later stage is facilitated.
The leveling procedure in this embodiment means that the leveling machine is used to level the steel plate after continuous annealing, specifically, the leveling elongation (reduction rate) of the leveling machine in this embodiment is 0.8%, which can effectively eliminate yield platforms, ensure more uniform structure performance of the chain pieces processed in the later period, and further improve the service life of the chain.
The metallographic structure and the high power scanning electron microscope of the chain steel sheet produced by the method of this example are shown in FIGS. 1 to 4. According to the invention, the grain size is grade 10.5 and the band structure is grade 1.5. The evaluation of the band-shaped structure is referred to GB/T34474.1-2017 evaluation part 1 of band-shaped structure in steel: standard rating chart law. Table 1 shows the chemical component contents of the respective examples and comparative examples, table 2 shows the production process control parameters of the respective examples and comparative examples, and table 3 shows the properties of the respective examples and comparative examples.
TABLE 1 examples chemical composition (wt%)
| Categories | C | Si | Mn | P | S | Al |
| Example 1 | 0.15 | 0.40 | 0.30 | 0.030 | 0.020 | 0.020 |
| Example 2 | 0.20 | 0.23 | 0.36 | 0.017 | 0.010 | 0.040 |
| Example 3 | 0.30 | 0.25 | 0.60 | 0.020 | 0.015 | 0.060 |
| Comparative example 1 | 0.08 | 0.23 | 0.38 | 0.018 | 0.009 | 0.041 |
| Comparative example 2 | 0.12 | 0.20 | 0.42 | 0.013 | 0.010 | 0.043 |
| Comparative example 3 | 0.34 | 0.17 | 0.37 | 0.014 | 0.012 | 0.037 |
| Comparative example 4 | 0.37 | 0.25 | 0.77 | 0.015 | 0.015 | 0.041 |
Table 2 example production process
TABLE 3 example Properties
| Categories | Direction | Rp0.2/MPa | Rm/MPa | A50/％ | HR | Strip tissue |
| Example 1 | 0° | 328 | 487 | 36.5 | 63 | 1.5 |
| Example 2 | 0° | 341 | 491 | 35.5 | 62 | 1.5 |
| Example 3 | 0° | 332 | 503 | 36.7 | 64 | 1.5 |
| Comparative example 1 | 0° | 254 | 369 | 41.0 | 38 | 2.5 |
| Comparative example 2 | 0° | 278 | 357 | 34.0 | 43 | 2.0 |
| Comparative example 3 | 0° | 391 | 563 | 32.5 | 70 | 2.5 |
| Comparative example 4 | 0° | 389 | 508 | 30.5 | 74 | 3.0 |
The yield strength of the chain steel plate produced by the embodiment is 328MPa, the tensile strength is 487MPa, the elongation after fracture is 36.5%, the mechanical property is in a reasonable interval, and the requirement of the chain on the strength is met. The surface hardness value of the chain steel plate is 63, so that the chain steel plate is suitable for punching production in subsequent processing. The grade of the banded structure is 1.5, the requirement that the banded structure is less than 2 is met, and the performance is uniform after heat treatment.
Example 2
The low-cost cold-rolled steel sheet for the chain in the embodiment is basically the same as that in the embodiment 1, and is different from the cold-rolled steel sheet in that the low-cost cold-rolled steel sheet comprises the following components in percentage by weight: 0.20 percent of C; 0.23 percent of Si; 0.36 percent of Mn; 0.017 percent of P; 0.01 percent of S; 0.04 percent of Al.
The basic flow of the method for manufacturing a low-cost cold-rolled steel sheet for chains in this example is the same as that in example 1, except that the weight percentage of (C +0.1Mn) in the molten steel smelting process is controlled to be 0.35%.
In this embodiment, the molten steel discharged from the molten steel smelting furnace is cast into a steel billet by a continuous casting device, wherein the discharging temperature of the steel billet is controlled at 1215 ℃.
In the seven-stand hot continuous rolling process in the embodiment, the hot rolling mill is adopted to perform seven-pass hot continuous rolling on the billet obtained in the continuous casting process, the rolling temperature of the last-pass stand is set to be 893 ℃, and the temperature is higher than Ac3 (ferrite-austenite transformation temperature), so that the last-pass rolling of the billet can be ensured to be performed in an austenite region, the rolled steel plate can obtain a uniform grain structure, and the uniformity and the wear resistance of the steel plate are improved.
In this example, the coiling temperature of the coiler was controlled to 718 ℃ in the coiling step. In the five-stand cold rolling procedure in the embodiment, the cold rolling mill is adopted to carry out five-pass cold continuous rolling on the steel plate coming out of the coiler, and the sum of the total rolling reduction rate of the five-pass cold continuous rolling is controlled to be 73 percent
The continuous annealing process in the embodiment refers to that a steel plate which is cold-rolled by five racks is placed into a continuous annealing furnace for continuous annealing, wherein the continuous annealing process sequentially comprises five stages of a soaking section, a slow cooling section, a fast cooling section, an overaging section and a final cooling section, the temperature of the soaking section is controlled to be 800 ℃, the annealing time is controlled to be 225s, the final temperature of the slow cooling section is controlled to be 700 ℃, the cooling speed of the fast cooling section is reduced to 400 ℃ at 150 ℃/min, the final temperature of the overaging section is controlled to be 280 ℃, and the final temperature of the final cooling section is controlled to be 80 ℃.
The yield strength of the chain steel plate produced by the embodiment is 341MPa, the tensile strength is 491MPa, the elongation after fracture is 35.5%, the mechanical property is in a reasonable interval, and the requirement of the chain on the strength is met. The surface hardness value of the chain steel plate is 62, and the chain steel plate is suitable for punching production in subsequent processing. The grade of the banded structure is 1.5, the requirement that the banded structure is less than 2 is met, and the performance is uniform after heat treatment.
Example 3
The low-cost cold-rolled steel sheet for the chain in the embodiment is basically the same as that in the embodiment 1, and is different from the cold-rolled steel sheet in that the low-cost cold-rolled steel sheet comprises the following components in percentage by weight: 0.30 percent of C; 0.25 percent of Si; 0.60 percent of Mn; 0.02 percent of P; 0.015 percent of S; 0.06 percent of Al.
The basic flow of the method for manufacturing a low-cost cold-rolled steel sheet for chains in this example is the same as that in example 1, except that the weight percentage of (C +0.1Mn) in the molten steel smelting process is controlled to be 0.30%.
In this embodiment, the molten steel discharged from the molten steel smelting furnace is cast into steel billets by continuous casting equipment, wherein the discharging temperature of the steel billets is controlled at 1220 ℃.
In the seven-stand hot continuous rolling process in this embodiment, the hot rolling mill is used to perform seven-pass hot continuous rolling on the billet obtained in the continuous casting process, and the rolling temperature of the last-pass stand is set to 910 ℃, which is above Ac3 (ferrite-austenite transition temperature), so that the hot rolling can be guaranteed to be austenite rolling, the rolled steel plate can obtain a uniform grain structure, and the uniformity of the steel plate is improved.
In this example, the coiling temperature of the coiler was controlled to 730 ℃. In the five-stand cold rolling process in the embodiment, the cold rolling mill is adopted to perform five-pass cold continuous rolling on the steel plate from the coiling machine, and the total rolling reduction rate sum of the five-pass cold continuous rolling is controlled to be 75%.
The continuous annealing process in the embodiment refers to that a steel plate which is cold-rolled by five racks is placed into a continuous annealing furnace for continuous annealing, wherein the continuous annealing process sequentially comprises five stages of a soaking section, a slow cooling section, a fast cooling section, an overaging section and a final cooling section, the temperature of the soaking section is controlled at 810 ℃, the annealing time is controlled at 250s, the final temperature of the slow cooling section is controlled at 700 ℃, the cooling speed is reduced to 380 ℃ at 135 ℃/min in the fast cooling section, the final temperature of the overaging section is controlled at 300 ℃, and the final temperature of the final cooling section is controlled at 100 ℃.
The yield strength of the chain steel plate produced by the embodiment is 332MPa, the tensile strength is 503MPa, the elongation after fracture is 36.7%, the mechanical property is in a reasonable interval, and the requirement of the chain on the strength is met. The surface hardness HR30T of the chain steel plate is 64, and the chain steel plate is suitable for punching production in subsequent processing. The grade of the banded structure is 1.5, the requirement that the banded structure is less than 2 is met, and the performance is uniform after heat treatment.
Comparative example 1
The steel plate for the chain of the comparative example comprises the following components in percentage by weight: 0.08 percent of C; 0.23 percent of Si; 0.38 percent of Mn; 0.018% of P; 0.009 percent of S; 0.041 percent of Al.
According to the preparation method of the low-cost cold-rolled steel plate for the chain in the comparative example, the molten steel of the components is subjected to a molten steel smelting process → a continuous casting process → a seven-frame hot continuous rolling → a coiling process → a five-frame cold continuous rolling process → a continuous annealing process → a leveling process, and then the prepared cold-rolled steel plate for the chain is obtained, wherein the yield strength of the steel plate for the chain of the prepared steel plate for the chain is 254MPa, the tensile strength is 369MPa, the elongation after fracture is 41%, and the surface hardness HR30T of the steel plate for the chain is 38, so that the method is not suitable for the production of punching holes in subsequent processing.
Wherein the tapping temperature of the steel blank in the comparative example is controlled at 1209 ℃.
In the comparative example, the rolling temperature of the last stand in the seven-stand hot continuous rolling process was 898 ℃.
In the comparative example, the coiling temperature of the coiler was controlled to 717 ℃.
In the five-stand cold rolling procedure in the comparative example, the cold rolling mill is adopted to carry out five-pass cold continuous rolling on the steel plate coming out of the coiling machine, and the total rolling reduction rate sum of the five-pass cold continuous rolling is controlled to be 61.4%.
The temperature of the soaking section in the continuous annealing of the comparative example was controlled at 792 ℃ and the annealing time was controlled at 202 s.
Comparative example 2
The steel plate for the chain of the comparative example comprises the following components in percentage by weight: 0.12 percent of C; 0.20 percent of Si; 0.42 percent of Mn; 0.013 percent of P; 0.010 percent of S; 0.043 percent of Al.
The preparation method of the low-cost cold-rolled steel plate for the chain in the comparative example is basically the same as that in the comparative example 1, the difference is that the yield strength of the chain steel plate of the prepared chain steel plate is 278MPa, the tensile strength is 357MPa, the elongation after fracture is 43 percent, and the surface hardness value of the chain steel plate is 43, so that the preparation method is not suitable for the production of punched holes in subsequent processing.
Wherein the tapping temperature of the steel blank in the comparative example is controlled to be 1214 ℃.
The rolling temperature of the last secondary stand in the seven-stand hot continuous rolling procedure in the comparative example was 901 ℃.
In the comparative example, the coiling temperature of the coiler was controlled to 714 ℃.
In the five-stand cold rolling procedure in the comparative example, the cold rolling mill is adopted to carry out five-pass cold continuous rolling on the steel plate coming out of the coiling machine, and the total reduction rate sum of the five-pass cold continuous rolling is controlled to be 66.7%.
The temperature of the soaking section in the continuous annealing of the comparative example is controlled at 802 ℃, and the annealing time is controlled at 209 s.
Comparative example 3
The steel plate for the chain of the comparative example comprises the following components in percentage by weight: 0.34 percent of C; 0.17 percent of Si; 0.37 percent of Mn; 0.014% of P; 0.012 percent of S; 0.037 percent of Al.
The method for preparing the low-cost cold-rolled steel plate for the chain in the comparative example is basically the same as the comparative example 1, except that the chain steel plate of the prepared chain steel plate has the yield strength of 391MPa, the tensile strength of 563MPa, the elongation after fracture of 32.5 percent and the surface hardness value of 70 percent.
Wherein the tapping temperature of the steel blank in the comparative example is controlled at 1223 ℃.
The rolling temperature of the last stand in the seven-stand hot continuous rolling procedure in the comparative example was 911 ℃.
In the winding step of this comparative example, the winding temperature of the winder was controlled to 711 ℃.
In the five-stand cold rolling procedure in the comparative example, the cold rolling mill is adopted to carry out five-pass cold continuous rolling on the steel plate coming out of the coiling machine, and the total reduction ratio sum of the five-pass cold continuous rolling is controlled to be 56.0%.
The temperature of the soaking section in the continuous annealing of the comparative example is controlled at 797 ℃, and the annealing time is controlled at 208 s.
Comparative example 4
The steel plate for the chain of the comparative example comprises the following components in percentage by weight: 0.37 percent of C; 0.25 percent of Si; 0.77 percent of Mn; 0.015 percent of P; 0.015 percent of S; 0.041 percent of Al.
The preparation method of the low-cost cold-rolled steel plate for the chain in the comparative example is basically the same as that in the comparative example 1, except that the yield strength of the chain steel plate of the prepared chain steel plate is 389MPa, the tensile strength is 508MPa, the elongation after fracture is 30.5%, and the surface hardness value of the chain steel plate is 74.
Wherein the tapping temperature of the steel billet in the comparative example is controlled to be 1218 ℃.
In the comparative example, the rolling temperature of the last stand in the seven-stand hot continuous rolling procedure was 908 ℃.
In the winding step of this comparative example, the winding temperature of the winder was controlled to 721 ℃.
In the five-stand cold rolling procedure in the comparative example, a cold rolling mill without a stand is adopted for five-pass cold continuous rolling, and the sum of the total reduction ratios of the five-pass cold continuous rolling is controlled to be 66.7%.
The temperature of the soaking section in the continuous annealing of the comparative example is controlled at 804 ℃, and the annealing time is controlled at 217 s.
The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.
Claims (4)
1. A preparation method of a low-cost cold-rolled steel plate for a chain is characterized by comprising the following steps: the chain steel plate comprises the following components in percentage by weight: 0.15 to 0.30 percent of C; si is less than or equal to 0.40 percent; 0.30 to 0.60 percent of Mn; p is less than or equal to 0.03 percent; s is less than or equal to 0.02 percent; 0.02 to 0.06 percent of Al; the balance of Fe and inevitable impurities, the yield strength of the chain steel plate is 260-350 MPa, the tensile strength is 450-550 MPa, the elongation after fracture is more than or equal to 32%, the surface hardness of the chain steel plate is 45-65%, and the grade of a banded structure is less than 2; the preparation process flow of the chain steel plate is as follows: the method comprises the following steps of molten steel smelting process → continuous casting process → seven-stand hot continuous rolling process → coiling process → five-stand cold continuous rolling process → continuous annealing process → leveling process, wherein five-stand cold rolling mill is adopted to carry out five-pass cold continuous rolling on hot-rolled coil in the five-stand cold continuous rolling process, and the total rolling reduction rate of the five-pass cold continuous rolling is controlled to be not lower than 70%; the continuous annealing process refers to that the steel plate which is cold rolled by five racks is continuously annealed in a continuous annealing furnace, wherein the continuous annealing process sequentially comprises five stages of a soaking section, a slow cooling section, a fast cooling section, an overaging section and a final cooling section, the temperature of the soaking section is controlled to be 790-810 ℃, the annealing time is controlled to be 200-250 s, the end point temperature of the slow cooling section is controlled to be 690-700 ℃, the cooling speed of the fast cooling section is reduced to 350-400 ℃ at 120-150 ℃/min, the end point temperature of the overaging section is controlled to be 280-320 ℃, and the end point temperature of the final cooling section is controlled to be 80-120 ℃.
2. The method of manufacturing a cold rolled steel sheet for a low-cost chain according to claim 1, wherein: the molten steel smelting process is to add the raw materials into a steel furnace for smelting, carry out pre-slagging before desulfurization treatment, carry out post-slagging after desulfurization treatment, ensure that the target S after molten steel desulfurization is less than or equal to 0.020%, add pre-deoxidized carbon powder, medium carbon ferromanganese, carburant and aluminum iron into the molten steel smelting furnace before tapping, adjust the contents of C, Si, Mn and Als in molten steel to a target range, and ensure that the tapping temperature of the molten steel is 15-30 ℃ higher than the liquidus temperature of the molten steel.
3. The method of manufacturing a cold rolled steel sheet for a low-cost chain according to claim 1, wherein: in the seven-stand hot continuous rolling procedure, a hot rolling mill is adopted to carry out seven-pass hot continuous rolling on the billet obtained in the continuous casting procedure, and the rolling temperature of the last pass is set to be 870-910 ℃.
4. The method of manufacturing a cold rolled steel sheet for a low-cost chain according to claim 1, wherein: in the coiling procedure, the coiling temperature of the coiling machine is controlled to be 690-730 ℃.
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