CN116694999A - A kind of maglev track steel and its preparation method - Google Patents

Abstract

The application provides a magnetic levitation track profile steel and a preparation method thereof, wherein the profile steel comprises the following chemical components in percentage by mass: c:0.08 to 0.13 percent of Si:0.20 to 0.50 percent of Mn:0.80 to 1.10 percent, less than or equal to 0.015 percent of P, less than or equal to 0.010 percent of S, and Als:0.020 to 0.060 percent, less than or equal to 0.20 percent of Cr, less than or equal to 0.20 percent of Cu, less than or equal to 0.30 percent of Ni, less than or equal to 0.005 percent of Ti, less than or equal to 40ppm of B, less than or equal to 1.5ppm of H, and the balance of iron and unavoidable impurities. The magnetic levitation track is directly rolled by adopting a one-step hot rolling forming process, and has excellent comprehensive properties such as magnetic permeability, strength, elongation, low-temperature impact toughness and the like. The Ti element content in the profile steel, which is unfavorable for the magnetic permeability, is obviously reduced, and the B content is controlled in a smaller fluctuation range. The smaller C element and Mn element are extremely bad, and the toughness of the deformation dead zone of the profile steel is improved.

Description

A kind of maglev track steel and its preparation method

technical field

The invention relates to the technical field of metallurgy, in particular to a magnetic levitation track steel and a preparation method.

Background technique

As an important part of the levitation control of the maglev train, the maglev track must not only have sufficient magnetic permeability, but also meet the structural load-bearing capacity, which brings challenges to material manufacturing.

The Chinese patent with the application number CN02136192.4 discloses a soft magnetic structural steel and a manufacturing method thereof, a soft magnetic structural steel used for a magnetic levitation track and a manufacturing method thereof. The technical solution is: soft magnetic structural steel and its manufacturing method, the constituent elements include: Fe, C, Si, Mn, P, S, Als, Cr, Cu, Ti, N, Ni, Ca, and the characteristic is that the constituent element Ca can be used REM replacement, the weight percentage of constituent elements is: C: 0.010% ~ 0.040%, Si: 1.0% ~ 2.0%, Mn: 0.60% ~ 1.00%, P: ≤0.015%, S: ≤0.005%, Als: 0.005% ~0.020%, Cr: <0.60%, Cu: 0.20%~0.60%, Ti: 0.005%~0.02%, N: ≤0.010%, Ni: ≤1.00%, Ca or REM: ≤0.010%, the rest are iron and Inevitable inclusion. Its rolling process includes: continuous casting process, hot rolling process and normalizing process, and finally obtains a side-guided soft magnetic structural steel plate suitable for use on the track beam of the magnetic levitation train in the north. The steel plate involved in this technology is only used for the side guidance of the maglev train, and is not used as a structural part to bear the weight of the train, and there is no requirement for structural strength and toughness.

The Chinese patent application number CN200410017999.7 discloses a soft magnetic structural steel plate with excellent low-temperature toughness. P≤0.015%, S≤0.005%, Als 0.50%～1.00%, Cr 0.20～0.50%, Cu 0.20%～0.60%, Ti 0.005%～0.02%, N 0.001%～0.008%, Ni0.30～0.80% , Ca 10ppm ~ 60ppm, the rest is iron and unavoidable inclusions, Pcm≤0.20%. Optimize the recrystallization controlled rolling and accelerated cooling process and the subsequent slow cooling process, so that the grain size of the finished soft magnetic structural steel plate is 10-30 μm, and obtain excellent mechanical properties, electromagnetic properties and weldability, especially suitable for magnetic levitation train tracks Side guides that must absorb load-carrying, guiding and driving forces. This patent only provides a soft magnetic steel plate. To make a magnetic levitation track, the steel plate needs to be welded, straightened, machined and other processes. Not only the process is complicated, the cost is high, but also the efficiency is low, which seriously restricts its industrial application.

The Chinese patent with the application number CN201811092935.1 discloses a F-shaped steel for high magnetic flux density maglev track and its production method, including the following components and their weight percentages: C: 0.04-0.07%, Si: 0.08-0.20% , Mn: 0.5-0.8%, P≤0.015%, S≤0.015%, Nb: 0.015-0.030%, Als: 0.03-0.05%, and the rest are Fe and impurity elements. The invention controls the number and size of inclusion particles through steel composition design and steelmaking process, and at the same time, it is equipped with high temperature and fast rolling to achieve solid solution of alloy elements in steel and rapid growth of crystal grains, and obtain high magnetic flux density and F-shaped steel for magnetic levitation track with excellent mechanical properties. This patent adopts a high-temperature fast rolling process to make the crystal grains grow rapidly. Although good magnetic permeability is obtained, the elongation and low-temperature impact properties of the material are poor.

The prior art mainly improves and optimizes the magnetic permeability of section steel materials, but there is no systematic improvement in the comprehensive performance of magnetic permeability and structural load bearing, and there are certain deficiencies. Especially when the material is made into shaped steel, due to the section characteristics of the shaped steel itself and the limitation of cooling conditions, in the dead zone of deformation, the magnetic permeability, strength, elongation and low temperature impact toughness have multiple or single performance parameters that are significantly reduced. , it is difficult to achieve good comprehensive performance.

Therefore, there is a need for a magnetic levitation track steel and a preparation method.

Contents of the invention

The purpose of the present invention is to provide a magnetic levitation track profile steel and its preparation method. The maglev track is directly rolled out by a hot rolling forming process, avoiding the welding and secondary processing of the steel plate, reducing the carbon emission in the track manufacturing process, magnetic permeability, Excellent comprehensive properties such as strength, elongation and low temperature impact toughness.

In order to achieve the above object, the present invention provides the following technical solutions:

A maglev rail profile steel, the profile steel is composed of the following chemical components in terms of mass percentage: C: 0.08% to 0.13%, Si: 0.20% to 0.50%, Mn: 0.80% to 1.10%, P≤0.015%, S≤0.010 %, Als: 0.020% to 0.060%, Cr≤0.20%, Cu≤0.20%, Ni≤0.30%, Ti≤0.005%, B≤40ppm, H≤1.5ppm, and the rest are iron and unavoidable impurities.

Further, in the above-mentioned magnetic levitation track profiled steel, the cross-sectional C range of the profiled steel is ≤0.03%, and the Mn range is ≤0.05%.

On the other hand, a kind of preparation method of above-mentioned magnetic levitation track section steel is provided, comprising the following steps:

Step S1: using converter, LF refining and VD vacuum furnace for smelting,

Step S2: using a continuous casting machine to cast a billet,

Step S3: After the steel billet is heated, rolled and cooled, it is made into a maglev rail profile.

Further, in the above preparation method, in the step S1, the blast furnace molten iron accounts for no less than 90% of the raw materials for converter steelmaking, the blast furnace molten iron is pre-dephosphorized, and sliding slag is used in the process of converter tapping device.

Further, in the above preparation method, in the step S1, the ladle lining, refining slag and alloy of LF refining are all made of low-Ti and low-B materials, wherein the Ti content is ≤0.02% by mass percentage, and the Ti content is ≤0.02% by mass percentage. B content≤0.02%.

Further, in the above preparation method, in the step S1, the Al wire is added first, then the Ca wire, and finally the B wire is added during the LF refining process.

Further, in the above-mentioned preparation method, in the step S2, the continuous casting tundish of the continuous casting machine is equipped with an automatic temperature control device, if the temperature T of the molten steel is within 10°C higher than the liquidus temperature T1, then the cover Put on the cover of the tundish and heat the molten steel; if the temperature T of the molten steel is higher than the liquidus temperature Tl by more than 20°C, open the cover of the tundish to dissipate heat, and stop heating, and the automatic temperature control device makes the middle The temperature fluctuation of molten steel in the ladle is controlled within 20°C.

Further, in the above-mentioned preparation method, the continuous casting machine is equipped with a crystallizer electromagnetic stirring device and an end pressing device to homogenize the molten steel in the solidification process, so that the cross-section C of the slab is less than or equal to 0.04%, and the Mn limit is less than or equal to 0.06%.

Further, in the above-mentioned preparation method, in the step S3, the heating time of the billet is 3 hours to 6 hours, the heating temperature is 1150°C to 1230°C, and the section of the billet before the final rolling is provided with an unbalanced compensation zone , the unbalanced compensation zone brings additional deformation to the deformation dead zone of the final rolling pass, which is more than 2% larger than the deformation in other zones.

Further, in the above-mentioned preparation method, the cooling is air cooling to ambient temperature after rolling, the finished product structure is polygonal ferrite and pearlite, the grain size of the deformation dead zone and the grain size of other areas on the cross section of the steel The difference between them is not more than 1 grade.

It can be seen from the analysis that the present invention discloses a maglev track profile steel and its preparation method. The maglev track is directly rolled out by a hot rolling forming process, avoiding the welding and secondary processing of the steel plate, reducing the carbon emission in the track manufacturing process, magnetic permeability, Excellent comprehensive properties such as strength, elongation and low temperature impact toughness. The ladle lining, refining slag, and alloys are all designed with low Ti and low B content materials, which significantly reduces the content of Ti element in the steel that is unfavorable to magnetic permeability, and keeps the B content within a small fluctuation range, which is the best way to add B in the later stage of LF refining. The B content in the stabilized steel plays an auxiliary role. While obtaining better low-temperature impact properties, it avoids the cracks and fatigue performance reduction of steel caused by excessive addition of B. The automatic temperature control device controls the temperature fluctuation of the molten steel in the tundish within 20°C, which reduces the temperature fluctuation of the molten steel in the tundish, reduces the superheat of the molten steel in the mold, and is beneficial to reduce the segregation of the billet, and the C element and The Mn element is extremely poor, and improves the toughness of the deformation dead zone of the section steel. The control of the H content of the section steel reduces the aggregation of H atoms from the source. The unbalanced compensation area of the billet section before final rolling and the design of the additional reduction greater than 2% increase the deformation amount in the dead zone of deformation, bring about the effect of grain refinement, and change the stress state of the dead zone of deformation to The compressive stress state eliminates the accumulation of H atoms in the deformation dead zone and prevents the toughness reduction caused by hydrogen-induced cracks.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide a further understanding of the present invention, and the schematic embodiments and descriptions of the present invention are used to explain the present invention, and do not constitute an improper limitation of the present invention. in:

Fig. 1 is a schematic cross-sectional structure diagram of a section steel according to an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional structure diagram of a billet before final rolling according to an embodiment of the present invention.

Explanation of reference signs: 1 section steel; 11 side leg; 12 web; 13 middle leg; 14 outer flange; 2 deformation dead zone;

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and examples. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, those skilled in the art will recognize that modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For example, features illustrated or described as part of one embodiment can be used on another embodiment to yield a still further embodiment. Therefore, it is intended that the present invention includes such modifications and variations as come within the scope of the appended claims and their equivalents.

One or more examples of the invention are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or analogous numerals in the drawings and description have been used to refer to like or analogous parts of the present invention.

According to an embodiment of the present invention, a magnetic levitation track profile steel is provided. The profile steel is composed of the following chemical components in terms of mass percentage: C: 0.08% to 0.13%, Si: 0.20% to 0.50%, Mn: 0.80% to 1.10%, P ≤0.015%, S≤0.010%, Als: 0.020%～0.060%, Cr≤0.20%, Cu≤0.20%, Ni≤0.30%, Ti≤0.005%, B≤40ppm, H≤1.5ppm, the rest are iron and Unavoidable impurities, C range ≤ 0.03% and Mn range ≤ 0.05% in the same cross-section of steel.

Extreme difference refers to the variation range of the composition detected in the specified area, which is equal to the difference between the maximum value and the minimum value, for example: on the same cross-section of the section steel (or slab), detect the C of 5 points from the surface to the center content, respectively 0.08%, 0.10%, 0.09%, 0.12%, 0.11%, then the C range of this section is 0.12%-0.08%=0.04%. The lower extreme difference can reduce the composition segregation and improve the comprehensive performance of the deformation dead zone of the maglev track steel.

C: C is the most economical element in steel to increase strength, but as the C content increases, the toughness of steel will deteriorate. For the section steel involved in the present invention, it is necessary to improve the toughness of the deformation dead zone and to avoid the problem of lowering the service life of the ladle caused by the peroxidation of molten steel caused by too low C content, and it is determined to control the C content within the range of 0.08% to 0.13%.

Si: Si is a deoxidizer that must be added in the steelmaking process. After the deoxidation is completed, a small amount will remain in the molten steel. After cooling, it will dissolve in the ferrite to improve the strength, but if the content is too much, it will form inclusions. Reduce plasticity and fatigue properties. The present invention comprehensively considers the needs of deoxidation control and strength improvement, and controls the Si content within the range of 0.20% to 0.50%.

Mn: It has a solid solution strengthening effect. In the present invention, Mn is used to make up for the loss of strength caused by the reduction of C content. The ratio of the Mn content to the S content is greater than 80, which can significantly reduce the slab cracks, but the excessively high Mn content will cause the remanence of the maglev track to increase, increase the coercive force, and improve the energy consumption of the train. Therefore, the present invention controls the Mn content at In the range of 0.80% to 1.10%.

Ti: It is easy to form inclusions with high melting point, which deteriorates the castability of molten steel and affects the magnetic permeability. Under the premise of economical production, controlling the content at a low level (≤0.005%) can improve the magnetic permeability.

B: It has a great influence on the toughness of steel, and a small amount of addition can significantly improve the toughness of steel, but the addition of more than 40ppm will lead to a sharp deterioration of low temperature performance. By adding element B and stably controlling the content, the toughness of steel can be improved at a low cost.

H: For the present invention, since the deformation dead zone of the maglev track steel corresponds to the center of the slab, H atoms are easy to gather. In addition to reducing the aggregation of H atoms at the center of the slab by electromagnetic stirring, the H content in the steel is controlled at Below 1.5ppm can reduce the number of H atoms in the core of the slab as a whole.

Al: It has a deep deoxidation function. On the basis of Si deoxidation, the oxygen content can be further controlled below 30ppm by adding Al. Al also has the effect of refining grains, which can improve the toughness of steel as a whole. Controlling Als in the range of 0.020% to 0.060% can improve the toughness without affecting the castability of molten steel.

Ni: It can reduce the ductile-brittle transition temperature of steel, but it needs a relatively high addition amount (above 6%) to achieve the effect. The Ni element is expensive, and it is not economical to increase the low temperature resistance by adding a large amount of Ni. The present invention can achieve stable improvement of low-temperature impact performance under the condition of low Ni addition (≤0.30%) through the joint action of B element.

Cr: It is an unavoidable residual element in the steel. When the Cr content is high, the cooling structure of the steel will be changed, brittle phases such as bainite and martensite will be formed, and the low-temperature impact performance will be reduced. It is not controlled within the scope of the present invention. have a noticeable effect on toughness.

Cu: an unavoidable residual element in steel, too much content will cause surface cracks to appear after the slab is heated, and will be inherited to the finished product to form surface defects, which will not cause surface crack defects if controlled within the scope of the present invention.

As shown in Figure 1, section steel 1 comprises side leg 11, web 12, middle leg 13 and outer flange 14, and one end of side leg 11 is connected with one end of web 12, and one end of middle leg 13 is connected with the other end of web 12 One end is connected, the other end of the side leg 11 and the other end of the middle leg 13 extend to the same side of the web, one end of the outer flange 14 is connected with the other end of the web 12, and the other end of the outer flange 14 is along the web 12 The axis of the shaft extends away from the web 12.

The present invention also discloses a method for preparing the above-mentioned maglev track steel, comprising the following steps:

Step S1: smelting using converter, LF refining and VD vacuum furnace.

The blast furnace hot metal accounts for no less than 90% of the raw materials for converter steelmaking. The blast furnace hot metal is pre-dephosphorized, and a sliding slag blocking device is used during the converter tapping process. Blast furnace molten iron accounts for no less than 90% of the raw materials for converter steelmaking, which can improve the purity of steel and reduce harmful elements brought about by the addition of scrap steel.

The ladle lining, refining slag and alloy of LF refining are all made of low-Ti and low-B materials, wherein the Ti content is ≤0.02% by mass percentage, and the B content is ≤0.02% by mass percentage. In the LF refining process, the ladle lining, refining slag, and alloys are all designed with low Ti and low B content materials, which significantly reduces the content of Ti element in the section steel that is unfavorable to magnetic permeability, so that the section steel has better magnetic permeability and B. The content is controlled within a small fluctuation range, which plays an auxiliary role in accurately adding B line in the later stage of LF refining and stabilizing the B content. While obtaining a better low-temperature impact value, it avoids steel cracks and fatigue performance reduction caused by adding B. insufficient.

In the LF refining process, the Al line is added first, followed by the Ca line, and finally the B line is added to deoxidize the molten steel through the Al line. The formed Al ₂ O ₃ floats quickly into the steel slag under the action of Ca, which not only reduces content, and does not increase the inclusions in the molten steel, and finally add the B line, which can avoid the oxidation failure of the B element and the formation of B-containing oxide inclusions, and achieve the stable control of the B content.

Step S2: using a continuous casting machine to cast a billet.

As shown in Figure 1, the deformation dead zone 2 of the shaped steel corresponds to the center of the billet, that is, the deformed dead zone 2 of the shaped steel is located at the position where the web 12 and the middle leg 13 are connected, and the magnetic levitation track shaped steel C, Mn, etc. in the prior art Severe element segregation leads to significantly lower toughness in the deformation dead zone of the section steel than in other zones. In an embodiment of the present invention, the continuous casting tundish of the continuous casting machine is provided with an automatic temperature control device, the automatic temperature control device includes an automatic heating device and a heat dissipation device, if the molten steel temperature T is within 10°C higher than the liquidus temperature T1 , then cover the cover of the tundish and use the automatic heating device to heat and supplement the temperature of the molten steel; if the temperature T of the molten steel is higher than the liquidus temperature Tl by more than 20°C, open the cover of the tundish and use the cooling device to For heat dissipation, the automatic heating device stops heating, and the automatic temperature control device controls the temperature fluctuation of the molten steel in the tundish within 20°C. Such setting reduces the temperature fluctuation of the molten steel in the tundish, reduces the superheat of the molten steel in the crystallizer, is beneficial to reduce the segregation of the billet, and improves the toughness of the deformation dead zone 2 of the section steel. The continuous casting machine is equipped with mold electromagnetic stirring and terminal pressing device to homogenize the molten steel in the solidification process, so that the cross-section C of the slab is less than or equal to 0.04%, and the Mn limit is less than or equal to 0.06%. The design of the electromagnetic stirring of the mold and the terminal pressing device reduces the C range and Mn range of the billet, further reduces the segregation of the billet, and improves the toughness of the deformation dead zone 2 of the section steel.

Step S3: After the steel billet is heated, rolled and cooled, it is made into a maglev rail profile.

The heating time of the billet is 3 hours to 6 hours (for example: 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours), and the heating temperature is 1150°C to 1230°C (for example: 1150°C, 1160°C , 1170°C, 1180°C, 1190°C, 1200°C, 1210°C, 1220°C, 1230°C), the section of the billet before the final rolling is provided with an unbalanced compensation zone 4. As shown in Figure 2, on the cross-sectional shape 3 of the billet before final rolling, the unbalanced compensation area 4 of the billet before final rolling is located above the billet, and relative to the finished section steel, the unbalanced compensation area is located above the web 12 and in the middle In the relative position of the legs 13, the unbalance compensation zone 4 brings additional deformation to the deformation dead zone 2 of the final rolling pass, making the deformation dead zone 2 of the section steel more than 2% larger than the deformation in other zones. The design of heating time and heating temperature can diffuse and homogenize the segregated elements in the billet, further improve the composition of the deformation dead zone and the uniformity of the structure, so that the section steel has good magnetic permeability and at the same time improve the overall strength of the section steel. Tensile strength and elongation.

Cooling is air cooling to ambient temperature after rolling, the finished product structure is polygonal ferrite and pearlite, and the difference between the grain size of the deformation dead zone and the grain size of other areas on the cross section of the section steel is not more than 1 grade. In the prior art, the strain in the deformation dead zone rolling process is very small, the grains are more than 2 grades thicker than other areas of the steel section, and the stress is in a state of tensile stress, which causes H atoms to gather, resulting in poor toughness of the steel. In the embodiment of the present invention, the control of the H content of the section steel reduces the aggregation number of H atoms from the source. The unbalanced compensation zone 4 of the billet section before final rolling and the design of the extra reduction greater than 2% increase the deformation amount of the deformation dead zone 2, bring about the effect of grain refinement, and make the stress of the deformation dead zone 2 The state is transformed into a compressive stress state, which eliminates the accumulation of H atoms in the deformation dead zone and prevents the decrease in toughness caused by hydrogen-induced cracks.

The above preparation method adopts a hot rolling forming process to directly roll out the maglev track, which avoids the welding and secondary processing of the steel plate, reduces the carbon emission in the track manufacturing process, has a simple process, reduces the cost, and improves the efficiency. The yield strength of the maglev track is ≥270MPa, the elongation is ≥28%, the saturation magnetic induction intensity B100 is ≥1.78T, and the low temperature impact performance is ≥200J.

It should be noted that the upper and lower limits of the process parameter interval and the interval value of the present invention can realize this method, and the examples are not listed here. The conventional technical knowledge in this field can be used for the contents not described in detail in the present invention.

Example 1:

A maglev rail profile steel, the profile steel is composed of the following chemical components in terms of mass percentage: C: 0.08%, Si: 0.50%, Mn: 0.80%, P: 0.013%, S: 0.010%, Als: 0.024%, Cr: 0.1% , Cu: 0.2%, Ni: 0.30%, Ti: 0.003%, B: 30ppm, H: 1.2ppm, and the rest are iron and unavoidable inclusions. The cross-section C of the section steel is 0.03%, and the Mn is 0.05%.

The method for preparing the above-mentioned magnetic levitation track section steel is as follows: the steel billet is smelted in a converter, LF refining and VD vacuum furnace, and the steel billet is cast by a continuous casting machine, and the steel billet is made into a magnetic levitation track section steel after heating, rolling and cooling. The ladle lining, refining slag and alloy of LF refining are made of low Ti and low B content materials, the Ti content (mass percentage) is 0.02%, and the B content (mass percentage) is 0.01%. During the refining process of LF, the Al line is added first, then the Ca line, and finally the B line.

The raw material for converter steelmaking is 90% blast furnace molten iron, which is pre-dephosphorized.

If the molten steel temperature T is within 10°C higher than the liquidus temperature Tl, lower the tundish cover and heat the molten steel; if the molten steel temperature T is more than 20°C higher than the liquidus temperature Tl, open the tundish The bag lid dissipates heat and turns off the automatic heating mechanism. The automatic control device controls the temperature fluctuation of molten steel in the ladle within 20°C.

The mold electromagnetic stirring and terminal pressing device installed in the continuous casting machine can homogenize the molten steel in the solidification process, so that the cross-section C of the slab is less than or equal to 0.04%, and the Mn limit is less than or equal to 0.06%.

The billet heating time is 6 hours, and the heating temperature is 1150°C. Using the unbalanced compensation zone brings additional deformation to the deformation dead zone in the final rolling pass, which is 3% larger than the deformation in other zones.

Cooling is air cooling to ambient temperature, the finished product structure is polygonal ferrite and pearlite, and the grain size difference between the deformation dead zone and other zones on the section steel section is not more than 1 grade.

Example 2:

A magnetic levitation rail profile steel, the profile steel is composed of the following chemical components in terms of mass percentage: C: 0.10%, Si: 0.20%, Mn: 1.0%, P: 0.010%, S: 0.005%, Als: 0.045%, Cr: 0.2% , Cu: 0.1%, Ni: 0.20%, Ti: 0.001%, B: 20ppm, H: 1.0ppm, and the rest are iron and unavoidable inclusions. The extreme difference of C in the cross section of the section steel is 0.02%, and the extreme difference of Mn is 0.05%.

The method for preparing the above-mentioned magnetic levitation track section steel is as follows: the steel billet is smelted in a converter, LF refining and VD vacuum furnace, and the steel billet is cast by a continuous casting machine, and the steel billet is made into a magnetic levitation track section steel after heating, rolling and cooling. The ladle lining, refining slag and alloy of LF refining are made of low Ti and low B content materials, the Ti content (mass percentage) is 0.01%, and the B content (mass percentage) is 0.02%. During the refining process of LF, the Al line is added first, then the Ca line, and finally the B line.

The raw material for converter steelmaking is 92% blast furnace molten iron, which is pre-dephosphorized.

Continuous casting tundish is equipped with automatic heating and cooling device. If the molten steel temperature T is within 10°C higher than the liquidus temperature Tl, lower the cover of the tundish and heat the molten steel; if the molten steel temperature T is higher than the liquidus temperature Tl by more than 20°C, open it The cover of the tundish dissipates heat and turns off the heating device. The automatic control device controls the temperature fluctuation of molten steel in the ladle within 15°C.

The continuous casting is equipped with mold electromagnetic stirring and terminal pressing device to homogenize the molten steel in the solidification process, so that the cross-section C of the slab is less than or equal to 0.04%, and the Mn limit is less than or equal to 0.06%.

The billet heating time is 3 hours, and the heating temperature is 1230°C. The unbalanced compensation zone brings additional deformation to the deformation dead zone in the final rolling pass, which is 5% larger than the deformation in other zones.

Cooling is air cooling to ambient temperature, the finished product structure is polygonal ferrite and pearlite, and the grain size difference between the deformation dead zone and other zones on the section steel section is not more than 1 grade.

Example 3:

A magnetic levitation rail profile steel, the profile steel is composed of the following chemical components in terms of mass percentage: C: 0.12%, Si: 0.40%, Mn: 0.9%, P: 0.012%, S: 0.007%, Als: 0.055%, Cr: 0.10% , Cu: 0.10%, Ni: 0.20%, Ti: 0.001%, B: 20ppm, H: 1.5ppm, and the rest are iron and unavoidable inclusions. The extreme difference of C in the cross section of the section steel is 0.02%, and the extreme difference of Mn is 0.02%.

The method for preparing the above-mentioned magnetic levitation track section steel is as follows: the steel billet is smelted in a converter, LF refining and VD vacuum furnace, and the steel billet is cast by a continuous casting machine, and the steel billet is made into a magnetic levitation track section steel after heating, rolling and cooling. The ladle lining, refining slag and alloy of LF refining are made of low Ti and low B content materials, the Ti content (mass percentage) is 0.01%, and the B content (mass percentage) is 0.01%. During the refining process of LF, the Al line is added first, then the Ca line, and finally the B line.

The raw material for converter steelmaking is blast furnace molten iron with a ratio of 98%, and pre-dephosphorization is carried out, and a sliding slag blocking device is used in the tapping process.

Continuous casting tundish is equipped with automatic heating and cooling device. If the molten steel temperature T is within 10°C higher than the liquidus temperature Tl, lower the tundish cover and heat the molten steel; if the molten steel temperature T is more than 20°C higher than the liquidus temperature Tl, open the tundish The bag lid dissipates heat and turns off the heating. The automatic control device controls the temperature fluctuation of molten steel in the ladle within 15°C.

The continuous casting is equipped with mold electromagnetic stirring and terminal pressing device to homogenize the molten steel in the solidification process, so that the cross-section C of the slab is less than or equal to 0.04%, and the Mn limit is less than or equal to 0.06%.

The billet heating time is 5 hours, and the heating temperature is 1200°C. The unbalanced compensation zone brings additional deformation to the deformation dead zone in the final rolling pass, which is 5% larger than the deformation in other zones.

Cooling is air cooling to ambient temperature, the finished product structure is polygonal ferrite and pearlite, and the grain size difference between the deformation dead zone and other zones on the section steel section is not more than 1 grade.

Table 1: Properties of the shaped steel prepared in Examples 1-3 of the present invention:

It can be seen from Table 1 that the maglev track-shaped steel prepared in Examples 1-3 has excellent yield strength, elongation and low-temperature impact toughness, and high saturation magnetic induction, which improves the comprehensive performance of the maglev track-shaped steel as a whole.

From the above description, it can be seen that the above-mentioned embodiments of the present invention have achieved the following technical effects:

1) The maglev track is directly rolled out by a hot rolling forming process, which avoids welding and secondary processing of the steel plate, reduces carbon emissions in the track manufacturing process, and has excellent comprehensive properties such as magnetic permeability, strength, elongation, and low-temperature impact toughness.

2) The ladle lining, refining slag, and alloys are all designed with low Ti and low B content materials, which significantly reduces the Ti element content in the section steel that is unfavorable to magnetic permeability, and controls the B content within a small fluctuation range, which is the best choice for the later stage of LF refining. Adding the B line, the B content in the stabilized steel plays an auxiliary role. While obtaining better low-temperature impact performance, it avoids the defects of steel cracks and fatigue performance reduction caused by excessive addition of B.

3) The automatic temperature control device controls the temperature fluctuation of the molten steel in the tundish within 20°C, which reduces the temperature fluctuation of the molten steel in the tundish, reduces the superheat of the molten steel in the mold, and is beneficial to reduce the segregation of the billet, and the smaller C Elements and Mn elements are extremely poor, and improve the toughness of the deformation dead zone 2 of the steel.

4) The control of the H content of the section steel reduces the aggregation of H atoms from the source. The unbalanced compensation area of the billet section before final rolling and the design of the additional reduction greater than 2% increase the deformation amount of the deformation dead zone 2, bring about the effect of grain refinement, and make the stress state of the deformation dead zone 2 Transforming into a compressive stress state eliminates the accumulation of H atoms in the deformation dead zone and prevents the toughness reduction caused by hydrogen-induced cracks.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A magnetic levitation track shaped steel, characterized in that, The section steel is composed of the following chemical components in terms of mass percentage: C: 0.08%-0.13%, Si: 0.20%-0.50%, Mn: 0.80%-1.10%, P≤0.015%, S≤0.010%, Als: 0.020% ~0.060%, Cr≤0.20%, Cu≤0.20%, Ni≤0.30%, Ti≤0.005%, B≤40ppm, H≤1.5ppm, and the rest are iron and unavoidable impurities. 2. The magnetic levitation track section steel according to claim 1, characterized in that, The cross-section C of the profiled steel has a range of ≤0.03%, and a Mn range of ≤0.05%. 3. A preparation method for the magnetic levitation track profiled steel according to any one of claims 1 to 2, characterized in that, comprising the steps of: Step S1: using converter, LF refining and VD vacuum furnace for smelting, Step S2: using a continuous casting machine to cast a billet, Step S3: After the steel billet is heated, rolled and cooled, it is made into a maglev rail profile. 4. preparation method according to claim 3, is characterized in that, In the step S1, the blast furnace molten iron accounts for not less than 90% of the raw materials for converter steelmaking, Pre-dephosphorize the blast furnace molten iron, and use a sliding slag blocking device during the tapping process of the converter. 5. preparation method according to claim 3, is characterized in that, In the step S1, the ladle lining, refining slag and alloys refined by LF are all made of low Ti and low B materials, wherein the Ti content is ≤0.02% by mass percentage, and the B content is ≤0.02% by mass percentage. 6. preparation method according to claim 3, is characterized in that, In the step S1, during the LF refining process, the Al wire is added first, then the Ca wire is added, and finally the B wire is added. 7. preparation method according to claim 3, is characterized in that, In said step S2, the continuous casting tundish of the continuous casting machine is provided with an automatic temperature control device, If the molten steel temperature T is within 10°C higher than the liquidus temperature T1, cover the tundish cover and heat the molten steel; If the temperature T of the molten steel is higher than the liquidus temperature Tl by more than 20°C, open the cover of the tundish to dissipate heat and stop heating. The automatic temperature control device controls the temperature fluctuation of the molten steel in the tundish within 20°C. 8. preparation method according to claim 3, is characterized in that, The continuous casting machine is equipped with mold electromagnetic stirring and terminal pressing device to homogenize the molten steel in the solidification process, so that the cross-section C of the slab is less than or equal to 0.04%, and the Mn limit is less than or equal to 0.06%. 9. preparation method according to claim 3, is characterized in that, In the step S3, the heating time of the billet is 3 hours to 6 hours, and the heating temperature is 1150°C to 1230°C, The section of the billet before the final rolling is provided with an unbalanced compensation area, and the unbalanced compensation area brings additional deformation to the deformation dead zone of the final rolling pass, which is more than 2% larger than the deformation in other areas. 10. preparation method according to claim 3, is characterized in that, Cooling is air cooling to ambient temperature after rolling, the finished product structure is polygonal ferrite and pearlite, and the difference between the grain size of the deformation dead zone and the grain size of other areas on the cross section of the section steel is not more than 1 grade.