CN109576592B - Hot-rolled magnetic yoke steel and manufacturing method thereof - Google Patents
Hot-rolled magnetic yoke steel and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses hot-rolled magnetic yoke steel which comprises the following chemical elements in percentage by mass: c: 0.06-0.18%, Si more than 0 and less than or equal to 0.50%, Mn: 1.50-2.20%, Ti: 0.10 to 0.25%, Mo: 0.10-0.50%, V: 0.05-0.22%, 0.05-0.30% of Cu, 0.05-0.30% of Ni, Al: 0.015-0.10% of Fe, less than or equal to 0.010% of N, and the balance of Fe and other inevitable impurities. In addition, the invention also discloses a manufacturing method of the hot-rolled yoke steel, which comprises the following steps: (1) smelting, refining and casting; (2) reheating: the heating temperature is more than or equal to 1230 ℃, and the heat preservation time is more than or equal to 1 h; (3) hot rolling; (4) laminar cooling; (5) coiling: coiling at 520-620 ℃, and then slowly cooling to room temperature. The hot-rolled magnetic yoke steel has high strength, good toughness and good magnetic induction performance.
Description
Technical Field
The invention relates to a yoke steel and a manufacturing method thereof, in particular to a hot-rolled yoke steel and a manufacturing method thereof.
Background
The hydropower resource is renewable clean energy, and the great development of hydropower development has important significance. However, these large hydroelectric projects all require large hydroelectric generating sets with capacity of million kilowatts per machine, which puts more strict requirements on the comprehensive performance of the steel used for the yoke part of the rotor of the hydroelectric generating set.
Conventionally, there have been patent documents disclosing hot-rolled high-strength yoke steel and a method for producing the same. For example: chinese patent publication No. CN101016600, published as 8.15.2007, entitled "C-Mn-Ti-Nb series hot-rolled high-strength high-magnetic induction performance steel and manufacturing method thereof" discloses a C-Mn-Ti-Nb series hot-rolled high-strength yoke steel, which comprises the following components by weight: c: 0.03-0.15%, Si: less than or equal to 0.15 percent, Mn: 1.00-1.80%, P: less than or equal to 0.025 percent, S: less than or equal to 0.015 percent, Ti: 0.08-0.18%, Nb: 0.02-0.07%, Als: 0.02-0.10%, N: less than or equal to 0.010 percent. The production process disclosed in this patent document is: firstly, heating the cast plate blank to 1230-1280 ℃; then rough rolling is carried out, wherein the finish temperature of the rough rolling is more than or equal to 1100 ℃; then, finish rolling is carried out, wherein the finish rolling temperature is 850-930 ℃; and (3) after rolling, adopting laminar flow cooling and then coiling the steel plate, wherein the coiling temperature is 550-620 ℃, and obtaining the hot rolled plate coil. However, the hot-rolled high-strength yoke steel disclosed in this patent document has a low yield strength of only 700MPa, and has a magnetic induction property B50≥1.5T。
The other publication numbers are: CN103451532A, published as 2013, 12 and 18, and entitled "hot-rolled yoke steel with yield strength not less than 750MPa and production method thereof", discloses a hot-rolled yoke steel, which comprises the following components in parts by weight: c: 0.03-0.15%, Si: less than or equal to 0.15 percent, Mn: 1.10-1.90%, P: less than or equal to 0.020%, S: less than or equal to 0.010 percent, Ti: 0.08-0.18%, Nb: 0.075-0.120%, Als: 0.02-0.10%, N: less than or equal to 0.010 percent. The hot-rolled magnetic yoke steel disclosed in the patent document further improves the strength of the steel plate by increasing the Nb content, and adopts a controlled rolling and controlled cooling and heating continuous rolling process, wherein the heating temperature is 1280-1350 ℃, and the rough rolling is carried outThe finishing temperature is more than or equal to 1100 ℃, the finish rolling temperature is 850-930 ℃, and the coiling temperature is 640-700 ℃. The yield strength is more than or equal to 750MPa, the tensile strength is more than or equal to 800MPa, the elongation is more than or equal to 11 percent, and the magnetic induction property B50≥1.5T。
Further, chinese patent publication No. CN103451533A, 12 and 18 in 2013, entitled "hot-rolled yoke steel having a yield strength of 800MPa or more and method for producing the same" discloses a hot-rolled yoke steel having a yield strength of 800MPa or more. In the technique disclosed in this patent document, the strength of the steel is improved to the 800MPa level by further adding Mo (wt%, 0.10 to 0.50%) element. The production process comprises the following steps: heating the plate blank to 1280-1350 ℃; then rough rolling is carried out, wherein the finish temperature of the rough rolling is more than or equal to 1100 ℃; the finish rolling temperature is 850-930 ℃; and (3) after rolling, carrying out laminar cooling on the steel plate, and then coiling at the coiling temperature of 640-700 ℃ to obtain the hot rolled plate coil. The yield strength is more than or equal to 800MPa, the tensile strength is more than or equal to 850MPa, the elongation is more than or equal to 11 percent, and the magnetic induction property B50≥1.5T。
Disclosure of Invention
An object of the present invention is to provide a hot rolled yoke steel having high strength, excellent toughness, and high magnetic induction properties.
In order to achieve the aim of the invention, the invention provides hot-rolled yoke steel which comprises the following chemical elements in percentage by mass:
c: 0.06-0.18%, Si more than 0 and less than or equal to 0.50%, Mn: 1.50-2.20%, Ti: 0.10 to 0.25%, Mo: 0.10-0.50%, V: 0.05-0.22%, 0.05-0.30% of Cu, 0.05-0.30% of Ni, Al: 0.015-0.10% of Fe, less than or equal to 0.010% of N, and the balance of Fe and other inevitable impurities.
In the technical scheme, other inevitable impurities mainly comprise P and S elements, wherein P is controlled to be less than or equal to 0.015 percent, and S is controlled to be less than or equal to 0.005 percent.
In the aspect of component design, the inventor precipitates dispersed fine nano-scale carbide in the process of coiling the strip steel through theoretical analysis and test by adding high Ti content, and plays a strong precipitation strengthening effect; meanwhile, a proper amount of Mo element is added for keeping the high-temperature thermal stability of the Ti carbide and strengthening the duration time of the precipitation strengthening effect of the nano carbide in the slow cooling process after coiling; by adding the V element, the grain refinement is realized, so that the strength is improved; the Si element is designed to improve the strength and the magnetic induction performance; on one hand, the strength of the hot-rolled yoke steel is guaranteed by the design of the content of C, and meanwhile, the content of C is matched with the content of Ti, Mo, V and N, so that the hot-rolled yoke steel finally achieves the required microstructure, and the ferrite and bainite structure with a proper proportion is obtained by the good steel grade performance.
The design principle of each chemical element of the hot-rolled yoke steel is as follows:
c: carbon (C) is one of essential elements in steel, and plays a very important role in improving the strength of steel as interstitial atoms in steel. The carbon content has a great influence on the composition of ferrite and bainite structures in steel. In the technical scheme of the invention, in order to obtain high-strength steel with the tensile strength reaching 900MPa, the mass percent of C is ensured to be more than 0.06 percent so as to form enough bainite structures in the steel and form more carbide precipitates; at the same time, the mass percent of C is not too high, otherwise ferrite transformation is inhibited in the production process, such as hot rolling or high-temperature coiling, the microstructure of ferrite, bainite and nanoscale precipitates is not favorably formed, and the magnetic induction performance and the impact toughness are adversely affected. The addition of C in the hot-rolled magnetic yoke steel is closely related to the addition of Ti, Mo, V and N, and an important principle of the component design of the technical scheme is to ensure that the added C is completely combined with Ti, Mo, V and N atoms to form a large amount of dispersed fine nano precipitates with high thermal stability. The nanoscale precipitates can effectively inhibit ferrite grains from growing in the subsequent process, such as a slow cooling process after high-temperature coiling, and simultaneously play a precipitation strengthening effect. In conclusion, the hot-rolled yoke steel controls the mass percent of carbon to be 0.06-0.18%.
Si: silicon (Si) is one of the basic elements in steel. Si plays a part of deoxidation role in the steel-making process. In addition, the formation range of ferrite can be expanded by Si in steel, which is beneficial to expanding the rolling process window; meanwhile, Si has a strong solid solution strengthening effect. In addition, Si can reduce the anisotropy of crystals, so that the magnetization is easy, the magnetic resistance is reduced, meanwhile, the Si can also reduce the harm of other impurities in steel, the harmful influence on the magnetism is reduced, and the magnetic induction performance of the hot-rolled magnetic yoke steel is obviously improved; however, too high a mass percentage of Si may decrease the thermal conductivity of the steel, for example, causing internal cracking during heating and cooling of the steel strip. Therefore, the hot-rolled yoke steel controls the mass percent of silicon to be more than 0 and less than or equal to 0.50 percent.
Mn: manganese (Mn) is one of the most basic elements in steel, is also an important element for expanding an austenite phase region, can reduce the critical quenching speed of the steel, stabilizes austenite, refines grains and improves the strength and toughness of the steel. In the hot-rolled magnetic yoke steel, in order to ensure the strength and the toughness of the steel plate, the mass percent of Mn is generally controlled to be more than 1.5%; meanwhile, the excessively high mass percentage of Mn can inhibit ferrite phase change in steel, Mn element is easy to segregate in the central component of a continuous casting slab, and hot cracking is easy to occur during slab continuous casting. Therefore, the hot rolled yoke steel according to the present invention is limited to 1.5 to 2.20 mass% of Mn.
Ti: titanium (Ti) is one of important elements in the hot rolled yoke steel according to the present invention. The main purpose of adding Ti with higher mass percent is to form more nano-scale carbide in a ferrite matrix in the transformation process from austenite to ferrite, and simultaneously, a certain amount of Mo element needs to be added to ensure that the nano-scale carbide still has stronger coarsening resistance at high temperature, namely high thermal stability. The mass percentage of Ti is controlled, which is beneficial to fully playing the nanometer precipitation strengthening function of VTi in the steel, so that the hot-rolled magnetic yoke steel has high strength and high magnetic induction performance. Theoretical calculation and experiments prove that the mass percentage of Ti which exerts the optimal precipitation strengthening effect is between 0.10 and 0.25 percent.
Mo: molybdenum (Mo) is also one of the key elements in this case. Mo also has a strong binding force with C, and most of MoC is usually precipitated in ferrite as compared with Ti. Experiments prove that in the high-strength steel with Ti added only, the TiC is coarsened more seriously in the high-temperature coiling process of 600-700 ℃, and the dispersion strengthening effect of the TiC can be greatly weakened after the steel coil is cooled to room temperature slowly. After adding a certain amount of Mo element, not only the diffusion of Ti atoms but also the diffusion of Mo element is required due to the formation of (Ti, Mo) C, and the diffusion process of Mo is very slow. Therefore, the coarsening process of the (Ti, Mo) C is much slower than that of the TiC alone, so that the (Ti, Mo) C has higher thermal stability. Meanwhile, the mass percentages of Ti and Mo are controlled within a certain range, which is beneficial to achieving the best effect. According to the test results, when the mass percent of Mo is controlled to be between 0.10 and 0.50 percent, the Mo has the strongest high-temperature thermal stability with (Ti, Mo) C formed by Ti.
V: vanadium (V) is one of the key elements in the present case. V is generally precipitated in ferrite due to its large solid solubility of carbonitride in austenite, similarly to Ti. V is also a strong carbide forming element, and the excessive C can be fixed by adding a proper amount of V, so that the precipitation strengthening effect is further achieved. According to theoretical analysis and experimental research results, the mass percentage of the hot-rolled yoke steel of the invention to V is limited to V: 0.05 to 0.22 percent.
Cu: copper (Cu) is an element that expands the austenite phase region, and has maximum solubilities of 2% and 8.5% in α iron and γ iron, respectively. The copper element has certain solid solution strengthening effect and aging strengthening effect, and can improve the tensile property of the steel. When the mass percentage of copper is high, a copper-rich layer is formed on the surface due to the selective oxidation of copper, and the copper-rich layer melts at high temperature and erodes the grain boundary of the surface layer of the steel plate, thereby causing the phenomenon of high-temperature copper brittleness during hot deformation processing. Therefore, the mass percent of Cu in the hot-rolled yoke steel is controlled to be more than or equal to 0.05 and less than or equal to 0.30 percent.
Ni: nickel (Ni) is an important element that can improve low-temperature toughness of steel, especially ultra-high strength steel. Meanwhile, Ni has a certain effect of improving the corrosion resistance of the steel plate. In order to match with the precipitation strengthening effect of the Cu element and avoid the copper brittleness phenomenon, Ni is a precious alloy element, so the mass percent of Ni is controlled to be more than or equal to 0.05 and less than or equal to 0.30 percent.
Al: aluminum (Al) is an important alloying element in steel. The basic function of Al in the technical scheme of the invention is mainly deoxidation in the steelmaking process. The mass percent of Al in the steel is generally not lower than 0.015 percent; meanwhile, if the mass percentage of Al is too high, the effect of refining grains is rather weakened. According to the control level of the aluminum content in the actual production process, the mass percent of aluminum in the steel is controlled to be 0.015-0.10%, and preferably, the mass percent of Al is controlled to be 0.02-0.06%.
N: nitrogen (N) is a harmful impurity element in this case, and the lower the content by mass, the better. However, N is an unavoidable element in steel, and these solid-solution or free N elements must be fixed by forming some kind of nitride, otherwise the free nitrogen atoms are very detrimental to the impact toughness of the steel and easily form full-length "tooth-crack" defects during rolling of strip steel. In the scheme, a strong carbide or nitride forming element Ti is added to form stable TiN so as to fix N atoms. Therefore, in the hot-rolled yoke steel, the mass percent of N is controlled within 0.010 percent.
P: phosphorus (P) is a harmful impurity element in steel. P is easy to be partially gathered on the grain boundary, and Fe is formed when the content of P in steel is higher2P is precipitated around the crystal grains to reduce the toughness and the magnetic induction performance of the steel, so the lower the content of the P is, the better the P content is, and the mass percent P of the P in the hot-rolled magnet yoke steel is controlled to be less than or equal to 0.015 percent.
S: sulfur (S) is a harmful impurity element in steel. S in steel is usually combined with Mn to form MnS inclusions, and particularly when the mass percentages of S and Mn are high, the steel forms more MnS, and the MnS has certain plasticity, and the MnS deforms along the rolling direction in the subsequent rolling process, so that the transverse tensile property of the steel plate is reduced. Therefore, the lower the mass percent of S in the steel, the better, the mass percent of S in the hot rolled yoke steel specially for the present invention is controlled to be less than or equal to 0.005%.
Further, in the hot rolled yoke steel according to the present invention, it also satisfies: Ti/Mo is more than or equal to 0.2 and less than or equal to 2.0, wherein both Ti and Mo represent the mass percent of the alloy. In order to further exert the nanometer precipitation strengthening effect of the microalloy elements in the steel, the mass percentages of Ti and Mo are controlled to satisfy the relation: Ti/Mo is more than or equal to 0.2 and less than or equal to 2.0.
Further, in the hot rolled yoke steel according to the present invention, it also satisfies: 0.03 percent to less than or equal to (Ti-3.42N)/4+ Mo/8+ V/4.17 percent to less than or equal to 0.18 percent, wherein Ti, Mo, V and N all represent the mass percent.
Further, in the hot rolled yoke steel according to the present invention, it also satisfies: Ni/Cu is not less than 1/3, wherein Ni and Cu both represent mass percent thereof.
Further, in the hot rolled yoke steel according to the present invention, it also satisfies: v + Ti is more than or equal to 0.18 percent, wherein, Ti and V both represent the mass percent. In order to further ensure the precipitation strengthening effect to obtain ultrahigh yield strength, the mass percentage of V, Ti of the hot-rolled yoke steel is further limited to V + Ti being more than or equal to 0.18%.
Further, in the hot rolled yoke steel according to the present invention, the microstructure thereof is a ferrite + bainite matrix and nano-scale precipitates including precipitates of Ti and precipitates of V.
Further, in the hot rolled yoke steel of the present invention, the phase ratio of bainite is not less than 70%.
Furthermore, the yield strength of the hot-rolled magnet yoke steel is more than or equal to 850MPa, the tensile strength is more than or equal to 900MPa, the elongation is more than or equal to 12 percent, and the longitudinal impact energy KV at the temperature of minus 20 ℃ is higher than2Not less than 40J, magnetic induction property B50≥1.58T，B100≥1.73T，B200≥1.90T，B300≥1.93T。
Accordingly, another object of the present invention is to provide a method for manufacturing the hot rolled yoke steel, which can obtain a hot rolled yoke steel with good properties by designing a composition, such as a composition containing a high content of Ti, in accordance with the composition of the hot rolled yoke steel and using a high heating temperature to ensure that as many Ti atoms as possible are dissolved in a slab.
In order to achieve the above object, the present invention provides a method for manufacturing the above hot rolled yoke steel, comprising the steps of:
(1) smelting, refining and casting;
(2) reheating: the heating temperature is more than or equal to 1230 ℃, and the heat preservation time is more than or equal to 1 h;
(3) hot rolling;
(4) laminar cooling;
(5) coiling: coiling at 520-620 ℃, and then slowly cooling to room temperature.
In the technical scheme of the invention, the heating temperature of the billet is controlled to be more than or equal to 1230 ℃, so as to ensure that Ti atoms are dissolved in the slab as much as possible, because the carbonitride solution temperature of Ti is usually very high (such as more than or equal to 1300 ℃), Ti is precipitated in different stages of steel making, continuous casting and rolling processes, the mass percentage of Ti which can be finally used for precipitation strengthening is reduced, and therefore, high heating temperature is required to ensure that more nano precipitates can be obtained in the final coiling process.
In addition, in the hot rough rolling and the finish rolling, the rhythm of the rolling process should be completed as fast as possible to avoid excessive precipitation of Ti carbonitride in the hot rough rolling and the finish rolling, because the rough rolling, particularly the finish rolling, is in the austenite region in the hot rolling stage, and the carbide or carbonitride of Ti precipitated in the temperature region is mostly tens of micrometers in size, and has little effect on final precipitation strengthening. Therefore, the rough rolling and finish rolling hot rolling stages should be completed as soon as possible to retain more Ti atoms precipitated during the coiling.
Meanwhile, in order to further ensure the low-temperature impact toughness and good magnetic property of the steel, a martensite structure and a lower bainite structure cannot appear in the steel, the grade of various non-metallic inclusions in the steel is less than or equal to 1.5, and the total grade of four types of inclusions is less than or equal to 5.0.
Meanwhile, due to the composition design of the hot-rolled yoke steel, the structure transformation processes which occur in different coiling temperature ranges in the continuous cooling process are different. When the coiling temperature is 520-580 ℃, the finish-rolled deformed austenite has partial ferrite transformation in the cooling process (before coiling), the ferrite content is less than or equal to 20%, and the rest austenite has bainite transformation after coiling into coils, namely the bainite proportion is more than or equal to 80%; when the coiling temperature is more than 580 ℃, the deformation austenite after finish rolling has less ferrite transformation amount (less than or equal to 10 percent) in the cooling process (before coiling), partial ferrite transformation (less than or equal to 20 percent) occurs after coiling, and then the rest deformation austenite has bainite transformation, namely the bainite proportion is more than or equal to 70 percent.
The hot-rolled yoke steel has a large amount of V and Ti precipitation strengthening elements. V and Ti in the steel are re-dissolved in the slab heating process and exist in the steel in a solid solution state; precipitation of nanoscale precipitates such as precipitates including V and precipitates including Ti in the steel will occur during the period from the finish rolling to the coiling slow cooling, and Ti will precipitate to form Ti (CN) -based nanoscale precipitates when the steel is cooled to 550-700 ℃; when the steel is cooled to 650 ℃ of 500 ℃ and 650 ℃, V is precipitated to form V (CN) -like nanoscale precipitates. In the manufacturing method of the invention, the steel contains more Ti and V elements, and the recrystallization temperature of the steel can be increased to more than 920 ℃, so that the finishing rolling temperature of the steel is controlled between 830 ℃ and 920 ℃, fine ferrite and bainite tissues can be obtained, and the grain size of the fine ferrite and bainite tissues is about 12 grades.
Further, in the manufacturing method of the invention, in the step (3), the finish temperature of rough rolling is controlled to be 1000-1100 ℃, the accumulated deformation is more than or equal to 50% after multi-pass large reduction rolling at the temperature of above 1050 ℃, then the intermediate blank is heated to 900-1000 ℃, and then multi-pass rolling is carried out, and the accumulated deformation of the multi-pass rolling is more than or equal to 70%; the finishing temperature is controlled to be 830-920 ℃.
Further, in the manufacturing method of the present invention, the method further includes the step (6) of tempering: the tempering temperature is less than or equal to 600 ℃.
According to different requirements on the shape quality of the steel plate, whether tempering heat treatment is carried out or not can be selected. The tempering heat treatment can eliminate the residual internal stress in the steel, and is beneficial to improving the magnetic property and the plate shape quality of the steel plate. However, the tempering heat treatment has a certain influence on the structure of the steel and also on the coarsening and coarsening of the nano-scale precipitates in the steel, thereby having a certain influence on the tensile properties and low-temperature toughness of the steel sheet. The hot-rolled magnetic yoke steel can effectively prevent the growth of nano-scale precipitates in the tempering heat treatment process through proper component design and process design, so that the hot-rolled magnetic yoke steel can be subjected to hot processing processes such as tempering heat treatment and the like, and in the manufacturing method, the tempering temperature is less than or equal to 600 ℃.
The yield strength of the hot-rolled magnet yoke steel is more than or equal to 850MPa, the tensile strength is more than or equal to 900MPa, the elongation is more than or equal to 12 percent, and the longitudinal impact energy KV at the temperature of minus 20 ℃ is higher than KV2Not less than 40J, magnetic induction property B50≥1.58T，B100≥1.73T，B200≥1.90T，B300≥1.93T。
Drawings
Fig. 1 is a microstructure view of a hot rolled yoke steel of example 1.
Detailed Description
The hot rolled yoke steel according to the present invention will be further described with reference to the following specific examples and the accompanying drawings, but the description should not be construed as unduly limiting the technical solution of the present invention.
Examples 1 to 5
Table 1 shows the mass percentages of the respective chemical elements in the hot rolled yoke steels of examples 1 to 5.
Table 1 (wt%, balance Fe and inevitable impurity elements other than P, S)
The method for manufacturing the hot rolled yoke steel of examples 1 to 5 includes the steps of:
(1) smelting, refining and casting according to the chemical element components listed in Table 1;
(2) reheating: the heating temperature is more than or equal to 1230 ℃, and the heat preservation time is more than or equal to 1 h;
(3) hot rolling: controlling the finish temperature of rough rolling to be 1000-1100 ℃, carrying out multi-pass large reduction rolling at the temperature of above 1050 ℃ and the accumulated deformation of the rough rolling to be more than or equal to 50%, then, allowing the temperature of the intermediate blank to be 900-1000 ℃, and carrying out multi-pass rolling again and the accumulated deformation of the multi-pass rolling to be more than or equal to 70%; the finishing temperature is controlled to be 830-920 ℃;
(4) laminar cooling;
(5) coiling: coiling at 520-620 ℃, and then slowly cooling to room temperature.
It should be noted that examples 2 and 4 further include the step (6) of tempering: the tempering temperature of the embodiment 2 is 500 ℃, and the tempering time is 30 min; the tempering temperature in example 4 was 580 ℃ and the tempering time was 30 min.
Table 2 lists the specific process parameters in the manufacturing method of the hot rolled yoke steel of examples 1 to 5.
Table 2.
The microstructure of the hot-rolled yoke steel of examples 1 to 5 was metallographic observation, and it was found that the microstructure of each example was a ferrite + bainite matrix and nano-scale precipitates including precipitates of Ti and precipitates of V, wherein the phase ratio of bainite in each example was 70% or more.
In addition, the hot rolled yokes of each example of the present application were subjected to the performance measurement and the results thereof are shown in tables 3 and 4.
Table 3 shows the mechanical properties of the hot rolled yoke steels of the examples.
Table 3.
Remarking: impact specimen size: 2.5 x 10 x 55 mm.
As can be seen from Table 3, the yield strength of the hot-rolled yoke steel of each example is not less than 850MPa, the tensile strength is not less than 900MPa, the elongation is not less than 12%, and the longitudinal impact energy KV at-20 ℃ is not less than KV2Not less than 40J (requirement for conversion to full-size sample).
Table 4 shows the magnetic induction properties of the hot rolled yoke steels of the examples.
Table 4.
| Examples | B50(T) | B100(T) | B200(T) | B300(T) |
| 1 | 1.624 | 1.877 | 1.935 | 2.000 |
| 2 | 1.675 | 1.921 | 1.978 | 2.045 |
| 3 | 1.620 | 1.860 | 1.918 | 1.982 |
| 4 | 1.627 | 1.884 | 1.911 | 1.996 |
| 5 | 1.611 | 1.854 | 1.909 | 1.993 |
As can be seen from table 4, the magnetic induction properties of the hot rolled yoke steels of the examples are shown as follows: b is50≥1.58T，B100≥1.73T，B200≥1.90T，B300≥1.93T。
Fig. 1 is a microstructure view of a hot rolled yoke steel of example 1.
As can be seen from fig. 1, the microstructure of the hot rolled yoke steel of example 1 was a ferrite + bainite matrix and nano-scale precipitates including precipitates of Ti and precipitates of V, wherein the phase ratio of bainite was about 90%.
It should be noted that the prior art in the protection scope of the present invention is not limited to the examples given in the present application, and all the prior art which is not inconsistent with the technical scheme of the present invention, including but not limited to the prior patent documents, the prior publications and the like, can be included in the protection scope of the present invention.
In addition, the combination of the features in the present application is not limited to the combination described in the claims of the present application or the combination described in the embodiments, and all the features described in the present application may be freely combined or combined in any manner unless contradictory to each other.
It should also be noted that the above-mentioned embodiments are only specific embodiments of the present invention. It is apparent that the present invention is not limited to the above embodiments and similar changes or modifications can be easily made by those skilled in the art from the disclosure of the present invention and shall fall within the scope of the present invention.
Claims (4)
1. The hot-rolled magnet yoke steel is characterized by comprising the following chemical elements in percentage by mass:
c: 0.06-0.18%, Si more than 0 and less than or equal to 0.50%, Mn: 1.50-2.20%, Ti: 0.10 to 0.25%, Mo: 0.10-0.50%, V: 0.05-0.22%, 0.05-0.30% of Cu, 0.05-0.30% of Ni, Al: 0.015-0.10%, N is less than or equal to 0.010%, and the balance is Fe and other inevitable impurities;
the microstructure of the hot-rolled yoke steel is a ferrite + bainite matrix and a nano-scale precipitate, and the precipitate comprises a Ti precipitate and a V precipitate; wherein the phase proportion of bainite is more than or equal to 70 percent; wherein the steel does not contain martensite structure and lower bainite structure, the grade of various non-metallic inclusions in the steel is less than or equal to 1.5 grade, and the sum of the grades of the four types of inclusions is less than or equal to 5.0;
the yield strength of the hot-rolled magnetic yoke steel is more than or equal to 850MPa, the tensile strength is more than or equal to 900MPa, the elongation is more than or equal to 12 percent, and the longitudinal impact energy KV at the temperature of minus 20 DEG C2Not less than 40J, magnetic induction property B50≥1.58T，B100≥1.73T，B200≥1.90T，B300≥1.93T；
Wherein, the content of each chemical element also satisfies:
0.2≤Ti/Mo≤2.0；
0.03％≤(Ti-3.42N)/4+Mo/8+V/4.17≤0.18％；
Ni/Cu≥1/3；
V+Ti≥0.18％；
wherein Ti, Mo, V, N, Ni and Cu all represent respective mass percentages.
2. A method of manufacturing a hot rolled yoke steel as claimed in claim 1, comprising the steps of:
(1) smelting, refining and casting;
(2) reheating: the heating temperature is more than or equal to 1230 ℃, and the heat preservation time is more than or equal to 1 h;
(3) hot rolling;
(4) laminar cooling;
(5) coiling: coiling at 520-620 ℃, and then slowly cooling to room temperature.
3. The manufacturing method according to claim 2, wherein in the step (3), the rough rolling finishing temperature is controlled to be 1000-1100 ℃, the rolling is carried out at a temperature of more than 1050 ℃ under a plurality of times of large reduction and the accumulated deformation is more than or equal to 50 percent, then the intermediate billet is cooled to 900-1000 ℃, and then the rolling is carried out at a plurality of times and the accumulated deformation of the rolling is more than or equal to 70 percent; the finishing temperature is controlled to be 830-920 ℃.
4. The method of claim 2, further comprising the step (6) of tempering: the tempering temperature is less than or equal to 600 ℃.
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