60Si2Mn spring steel hot-rolled wide coiled plate and preparation method thereof

Abstract

The invention discloses a 60Si2Mn spring steel hot-rolled wide coiled plate and a preparation method thereof. The preparation method comprises the following steps: carrying out heating treatment on a slab subjected to continuous casting; the charging temperature is higher than 500 DEG C; the atmosphere in the heating furnace is a weak reducing atmosphere, the heating treatment time is 120-150 minutes, and the heating treatment temperature is 800-1200 DEG C; carrying out rough descaling treatment on the plate blank subjected to the heating treatment; the pressure of the rough descaling treatment is greater than 200MPa, and the rate of the rough descaling treatment is 1-3m / min; carrying out rough rolling treatment on the plate blank subjected to rough descaling treatment; 5 passes are adopted, and the thickness of the plate blank subjected to rough rolling treatment is 30-40 mm; carrying out finish rolling treatment on the slab subjected to rough rolling treatment; 7 passes are adopted, the finish rolling temperature of finish rolling treatment is 800-860 DEG C, and the thickness of the strip steel subjected to finish rolling treatment is 1.8-6.0 mm; laminar cooling is carried out on the strip steel subjected to finish rolling treatment, and a front-section rapid cooling mode is adopted; coiling the strip steel subjected to laminar cooling; the coiling temperature ranges from 580 DEG C to 650 DEG C, and the coiling tension ranges from 50 MPa to 60 MPa. By means of the preparation method, the 60Si2Mn spring steel hot-rolled wide coiled plate with the excellent structure and performance can be obtained.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of steel rolling, in particular to a 60Si2Mn spring steel hot-rolled wide-width coiled plate and a preparation method thereof. BACKGROUND

[0002] 60Si2Mn is a widely used silicon-manganese spring steel, and the typical feature of the chemical composition is that the contents of Si and C are relatively high. At present, the 60Si2Mn spring steel mainly exists in the forms of bar, wire, flat steel and the like. With the development of the steel industry, the gradually increasing requirement for product quality and the control of the manufacturing cost by the steel enterprises, the steel enterprises need to develop the wide-width coiled plate of the 60Si2Mn spring steel to replace the traditional narrow strip steel. However, compared with the bar, wire and the like and the strip steel product, the production of the 60Si2Mn spring steel hot-rolled wide-width coiled plate has many technical problems. Therefore, how to prepare the 60Si2Mn spring steel hot-rolled wide-width coiled plate with excellent organization and performance becomes a technical problem to be solved urgently. SUMMARY

[0003] The application provides a 60Si2Mn spring steel hot-rolled wide-width coiled plate and a preparation method thereof, and the 60Si2Mn spring steel hot-rolled wide-width coiled plate with excellent organization and performance can be prepared.

[0004] In one aspect, the application provides a preparation method of a 60Si2Mn spring steel hot-rolled wide-width coiled plate, and the preparation method comprises the following steps: performing heating treatment on a continuously cast plate blank to obtain a heated plate blank; the furnace entry temperature of the plate blank is greater than 500 DEG C; the atmosphere in the heating furnace for the heating treatment is a weak reducing atmosphere, the heating treatment time is 120-150 min, and the heating treatment temperature is 800-1200 DEG C; performing rough descaling treatment on the heated plate blank to obtain a rough descaling plate blank; the pressure of the rough descaling treatment is greater than 200 MPa, and the speed of the rough descaling treatment is 1-3 m / min; performing rough rolling treatment on the rough descaling plate blank to obtain a rough rolled plate blank; the rough rolling treatment adopts 5 rough rolling passes, and the thickness of the rough rolled plate blank is 30-40 mm; performing finish rolling treatment on the rough rolled plate blank to obtain a finish rolled plate blank; the finish rolling treatment adopts 7 finish rolling passes, the finish rolling treatment final rolling temperature is 800-860 DEG C, and the thickness of the finish rolled strip steel is 1.8-6.0 mm; performing laminar flow cooling treatment on the finish rolled strip steel to obtain a laminar flow cooled strip steel; the laminar flow cooling treatment adopts a front section rapid cooling mode; and performing coiling treatment on the laminar flow cooled strip steel to obtain a steel coil; the coiling treatment temperature is 580-650 DEG C, and the coiling treatment tension is 50-60 MPa.

[0005] According to one aspect of the application, the furnace entry temperature of the plate blank is 500-700 DEG C.

[0006] According to an aspect of the embodiments of the present application, the heating treatment comprises a preheating section, a first heating section, a second heating section and a soaking section; optionally, the temperature of the preheating section is 800-1000℃, the temperature of the first heating section is 950-1100℃, the temperature of the second heating section is 1050-1200℃, the temperature of the soaking section is 1130-1200℃, and the discharge temperature of the slab is 1150-1180℃.

[0007] According to an aspect of the embodiments of the present application, the pressure of the rough descaling treatment is 200-250MPa.

[0008] According to an aspect of the embodiments of the present application, the cooling rate of the laminar cooling treatment is 30-50℃ / s.

[0009] According to an aspect of the embodiments of the present application, the preparation method further comprises slowly cooling the steel coil to -20℃ to 60℃.

[0010] In another aspect, the embodiments of the present application provide a 60Si2Mn spring steel hot-rolled wide-width coil slab prepared by the preparation method of the first aspect of the present application.

[0011] According to another aspect of the embodiments of the present application, the chemical composition of the 60Si2Mn spring steel hot-rolled wide-width coil slab comprises, based on the total mass of the 60Si2Mn spring steel hot-rolled wide-width coil slab being 100%: C: 0.56%-0.64%, Si: 1.50%-2.00%, Mn: 0.70%-1.00%, Cr≤0.35%, Ni≤0.35%, Cu≤0.25%, P≤0.025%, S≤0.020%; and the balance being Fe and unavoidable impurities.

[0012] According to another aspect of the embodiments of the present application, the thickness of the 60Si2Mn spring steel hot-rolled wide-width coil slab is 1.8-6.0mm, and the width of the 60Si2Mn spring steel hot-rolled wide-width coil slab is 900-1500mm.

[0013] According to another aspect of the embodiments of the present application, the single surface decarburization layer depth of the 60Si2Mn spring steel hot-rolled wide-width coil slab is less than or equal to 1.0% of the nominal thickness, the flatness of the plate is ≤8mm / m, the microstructure is pearlite, and the grain size grade of the pearlite is ≥7 grade.

[0014] The application embodiment adjusts the furnace temperature of the heating treatment to be greater than 500 DEG C, the atmosphere is weak reducing atmosphere, the heating treatment time is 120-150 min, the heating treatment temperature is 800-1200 DEG C, the pressure of the rough descaling treatment is greater than 200 MPa, the rough descaling treatment rate is 1-3 m / min, 5 roughing passes are adopted, the thickness of the slab after the rough descaling treatment is 30-40 mm, the finish rolling temperature is 800-860 DEG C, thereby balancing the relationship between the strip decarburization and the rolling load. The laminar cooling treatment adopts the front section rapid cooling mode, and the coiling tension is adjusted in the range of 50-60 MPa, so that the control of the coil shape of the steel can be realized. By adjusting the finish rolling temperature in the range of 800-860 DEG C, the strip after the finish rolling is subjected to the laminar cooling treatment, and the coiling temperature is adjusted in the range of 580-650 DEG C, the control of the microstructure of the coil can be realized, and the single, uniform and fine full pearlite structure is obtained. Thus, the problems of high rolling load, surface decarburization, poor shape and surface quality of the wide coil in the process of the finish rolling are solved, the production efficiency of the 60Si2Mn spring steel hot-rolled wide coil is improved, and the 60Si2Mn spring steel hot-rolled wide coil with excellent structure and performance is prepared. BRIEF DESCRIPTION OF DRAWINGS

[0015] The features, advantages, and technical effects of the exemplary embodiments of the application will be described below with reference to the accompanying drawings.

[0016] Figure 1 The flowchart of the preparation method of the 60Si2Mn spring steel hot-rolled wide coil of the application embodiment.

[0017] Figure 2 The microstructure diagram of the 60Si2Mn spring steel hot-rolled wide coil prepared in the application embodiment 1. DETAILED DESCRIPTION

[0018] The features and exemplary embodiments of various aspects of the application will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the application. However, it will be apparent to one of ordinary skill in the art that the application can be practiced without some of these specific details. The description of the embodiments is merely to provide a better understanding of the application by showing examples of the application. In the drawings and the following description, at least part of the well-known structures and techniques are not shown in order to avoid unnecessary obscuring of the application; and, for clarity, the size of some structures can be exaggerated. In addition, the features, structures or characteristics described below can be combined in any suitable manner in one or more embodiments.

[0019] It should be noted that in the present application, the terms "first", "second" and the like are used to distinguish similar objects, and are not used to describe a specific order or sequence. Moreover, the term "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or other elements inherent to such a process, method, article or device. Without more limitations, the elements defined by the statement "comprising" do not exclude the presence of other identical elements in the process, method, article or device including the elements. Unless otherwise stated, the test temperature of each parameter mentioned in the present application is 25°C.

[0020] Thermo Mechanical Control Process (TMCP) is a general term for the technology of air cooling or controlled cooling and accelerated cooling after controlling the heating temperature, rolling temperature and reduction in the hot rolling process.

[0021] TMCP technology can well control the microstructure and properties of 60Si2Mn spring steel and control the surface decarburization, so as to produce high-quality 60Si2Mn spring steel products with higher quality and more competitive production cost, and better meet the quality requirements of downstream users such as wave spring, spring pad and butterfly spring.

[0022] 60Si2Mn spring steel hot-rolled wide-width coiled plate is a new type of product form. Because the width-thickness ratio is very large, it faces different technical difficulties from the previous profiles and strip steels. At the same time, the production of 60Si2Mn spring steel hot-rolled wide-width coiled plate has higher technical threshold than bar and wire and strip steel products. For example, the rolling load of wide strip steel is significantly increased compared with narrow strip steel, and there is a great contradiction in increasing slab temperature, reducing rolling load and controlling surface decarburization. For another example, although TMCP technology can well control the microstructure and properties, TMCP technology will increase the reduction rate of a pass or increase the cooling rate after rolling, which leads to difficult control of plate shape, thereby easily causing the problem of poor plate shape of hot-rolled wide-width coiled plate.

[0023] Figure 1 The flowchart of the preparation method of the 60Si2Mn spring steel hot-rolled wide-width coiled plate of the embodiments of the present application is shown as follows. Figure 1 The present application provides a preparation method of 60Si2Mn spring steel hot-rolled wide-width coiled plate, which comprises the following steps:

[0024] S10: performing a heating treatment on the slab after continuous casting to obtain a heated slab; the entry temperature of the slab into the furnace is greater than 500 DEG C; the atmosphere in the heating furnace of the heating treatment is a weak reducing atmosphere, the time of the heating treatment is 120-150 min, and the temperature of the heating treatment is 800-1200 DEG C;

[0025] S20: performing a rough descaling treatment on the heated slab to obtain a rough descaling slab; the pressure of the rough descaling treatment is greater than 200 MPa, and the speed of the rough descaling treatment is 1-3 m / min;

[0026] S30: performing a rough rolling treatment on the rough descaling slab to obtain a rough rolled slab; the rough rolling treatment adopts 5 passes of rough rolling, and the thickness of the rough rolled slab is 30-40 mm;

[0027] S40: performing a finish rolling treatment on the rough rolled slab to obtain a finish rolled slab; the finish rolling treatment adopts 7 passes of finish rolling, the finish rolling temperature is 800-860 DEG C, and the thickness of the finish rolled strip is 1.8-6.0 mm;

[0028] S50: performing a laminar cooling treatment on the finish rolled strip to obtain a laminar cooled strip; the laminar cooling treatment adopts a front section rapid cooling mode;

[0029] S60: performing a coiling treatment on the laminar cooled strip to obtain a steel coil; the coiling temperature is 580-650 DEG C, and the coiling tension is 50-60 MPa.

[0030] 60Si2Mn spring steel material has large elasticity and large rolling load, especially the wide thin gauge 60Si2Mn spring steel coil plate, which is the first problem faced in the production of 60Si2Mn spring steel wide coil plate. Only by solving this problem can stable production be ensured. The most effective means to solve the problem of rolling load is to improve the temperature of the rolled piece during rolling, for example, to increase the heating temperature of the slab and to prolong the heating time, to reduce the temperature drop by adopting rapid rough descaling, and to set a higher temperature for the finish rolling treatment and the coiling treatment. However, because the Si content in the 60Si2Mn spring steel is high, it is very easy to cause decarburization and iron oxide scale pressing, etc. Therefore, how to adjust the preparation process to balance the rolling load, the decarburization of the coil plate, and the excessive surface oxide is one of the core problems of the present application.

[0031] The control principles of the parameters in the heating treatment, the rough descaling treatment, the rough rolling treatment, the finish rolling treatment, the laminar cooling treatment and the coiling treatment in the embodiments of the present application are stated as follows.

[0032] Heating treatment: By setting the heating treatment's entry temperature of the heating furnace to be greater than 500℃, the time for the slab to cool from 500℃ to -20℃ to 60℃ and then to heat from -20℃ to 60℃ to 500℃ can be reduced, so that the decarburization and surface oxidation of the slab during the cooling process can be reduced, and the decarburization layer depth is reduced and the surface quality is improved.

[0033] By controlling the atmosphere in the heating furnace to be weakly reducing, setting the temperature of the heating treatment of the slab to be in the range of 800-1200℃, and setting the time of the heating treatment to be in the range of 120-150min, the temperature of the slab during subsequent rolling can be improved, and the degree of decarburization of the slab can be reduced, while the rolling load can also be considered, and the case of too high subsequent rolling load can be reduced.

[0034] The air excess coefficient in the heating furnace can be 2-3, for example, it can be 2.5.

[0035] Rough descaling treatment: By setting the pressure of the rough descaling treatment to be greater than 200MPa, and setting the speed of the rough descaling treatment to be in the range of 1-3m / min, the speed of the rough descaling treatment can be improved, the temperature drop of the slab can be reduced, and the temperature of the slab during rolling can be improved. At the same time, the thick oxide scale on the surface of the slab can also be removed by high pressure and fast rough descaling.

[0036] Rough rolling treatment: The rough rolling treatment adopts 5 passes of rolling, which can further reduce the temperature drop of the slab, and can reduce the rolling load of the subsequent finishing rolling treatment. The temperature of the rough rolling treatment is high, and the rolling is relatively easy, so the thickness of the slab after the rough rolling treatment is controlled in the range of 30-40mm, that is, the thickness of the slab after the rough rolling treatment is thinned as much as possible, so that the difficulty of the subsequent finishing rolling treatment can be reduced.

[0037] Finishing rolling treatment: By setting the finishing rolling treatment's finishing temperature to be in the range of 800-860℃, the microstructure can be refined, the interlayer spacing between the pearlite lamellas can be reduced, and the microstructure of the strip steel can be controlled and the decarburization of the strip steel can be reduced.

[0038] Laminar cooling treatment: The laminar cooling treatment adopts a front section fast cooling mode, which can suppress the formation of proeutectoid ferrite, obtain single, uniform and fine full pearlite microstructure, and thus the uniformity of the microstructure can be improved. In addition, the internal stress can be released during the subsequent air cooling, and better plate shape can be maintained.

[0039] It should be noted that the front section fast cooling mode in the embodiments of the present application refers to directly cooling the strip steel to the temperature near the coiling treatment.

[0040] The tension of the coiling process is set in the range of 50-60 MPa, so that the tension of the coiling process is in a large range, thereby ensuring that the coiled plate has high flatness.

[0041] In the embodiment, the entry temperature of the heating treatment is greater than 500 DEG C, the atmosphere is weak reducing atmosphere, the heating treatment time is 120-150 min, the heating treatment temperature is 800-1200 DEG C, the pressure of the rough descaling treatment is greater than 200 MPa, the rough descaling treatment rate is 1-3 m / min, 5 roughing passes are adopted, the thickness of the plate after the roughing treatment is 30-40 mm, the finish rolling temperature is 800-860 DEG C, the relationship between the decarburization of the strip and the rolling load is balanced. The laminar cooling treatment adopts the front section rapid cooling mode, and the tension of the coiling process is adjusted in the range of 50-60 MPa, so that the control of the shape of the steel coil is realized. By adjusting the temperature of the finish rolling treatment in the range of 800-860 DEG C, the laminar cooling treatment is performed on the strip after the finish rolling treatment, and the temperature of the coiling treatment is adjusted in the range of 580-650 DEG C, the control of the microstructure of the coiled plate is realized, and single, uniform and fine full pearlite structure is obtained. Thus, the problems of high rolling load, surface decarburization, poor plate shape and surface quality of the wide coiled plate in the hot rolling process are solved, the production efficiency of the 60Si2Mn spring steel hot-rolled wide coiled plate is improved, and the 60Si2Mn spring steel hot-rolled wide coiled plate with excellent structure and performance is prepared.

[0042] In some embodiments, the entry temperature of the plate can be 500-700 DEG C.

[0043] In the embodiment, the entry temperature of the plate is set in the above range, so that the furnace loading time is shortened, and the surface oxidation and decarburization of the plate are reduced.

[0044] In some embodiments, the heating treatment can include a preheating section, a first heating section, a second heating section and a soaking section.

[0045] In some embodiments, the temperature of the preheating section can be 800-1000 DEG C, the temperature of the first heating section can be 950-1100 DEG C, the temperature of the second heating section can be 1050-1200 DEG C, the temperature of the soaking section can be 1130-1200 DEG C, and the exit temperature of the plate can be 1150-1180 DEG C.

[0046] Generally, the rolling load of the hot-rolled wide coil of 60Si2Mn spring steel is high, although the heating temperature of the slab can be increased to reduce the rolling load, but increasing the heating temperature of the slab will cause more obvious decarburization. The temperature of the preheating section, the first heating section, the second heating section and the soaking section and the tapping temperature of the slab in the embodiments of the present application are set in the above range, which can improve the temperature of the slab in the subsequent rolling process, and further reduce the decarburization degree of the slab, and further reduce the case of too high subsequent rolling load.

[0047] The upper limit of the pressure of the rough descaling treatment is determined according to the rough descaling capacity.

[0048] In some embodiments, the pressure of the rough descaling treatment can be 200-250 MPa, for example, can be 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa, 250 MPa.

[0049] The pressure of the rough descaling treatment in the embodiments of the present application is set in the above range, which can quickly rough descaling and remove the thick oxide scale on the surface of the slab, and can reduce the load of the rough descaling treatment.

[0050] In some embodiments, the cooling rate of the laminar cooling treatment can be 30-50℃ / s, for example, can be 30℃ / s, 35℃ / s, 40℃ / s, 45℃ / s, 50℃ / s.

[0051] The specific operation of the laminar cooling treatment includes two groups of side spray water opening the water cooling start position and the water cooling end position.

[0052] By adjusting the cooling rate of the laminar cooling treatment in the above range, the formation of proeutectoid ferrite can be further inhibited, a single, uniform and fine full pearlite microstructure can be obtained, and the internal stress can be released by the later stage air cooling, and better plate shape can be maintained.

[0053] In some embodiments, the preparation method further comprises slowly cooling the steel coil to -20℃ to 60℃, for example, can be -20℃, -10℃, -5℃, 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃.

[0054] In the embodiments of the present application, the cooling rate of the slow cooling is not required, as long as the steel coil enters the slow cooling pit.

[0055] The steel coil in the embodiments of the present application is quickly offline after rolling, and slowly releases stress in the slow cooling pit, thereby being beneficial to the processing and use of the subsequent coil plate.

[0056] The preparation process of the 60Si2Mn spring steel hot-rolled wide coil plate in the embodiment of the present application adopts a wide coil plate rolling mill. The equipment precision of the wide coil plate rolling mill is generally higher than that of the profile and narrow strip steel rolling mill, so that the 60Si2Mn spring steel hot-rolled wide coil plate with higher size precision can be obtained.

[0057] The embodiment of the present application provides a 60Si2Mn spring steel hot-rolled wide coil plate, which is prepared by the preparation method.

[0058] In some embodiments, the chemical composition of the 60Si2Mn spring steel hot-rolled wide coil plate can include, based on the total mass of the 60Si2Mn spring steel hot-rolled wide coil plate being 100%, C: 0.56%-0.64%, Si: 1.50%-2.00%, Mn: 0.70%-1.00%, Cr≤0.35%, Ni≤0.35%, Cu≤0.25%, P≤0.025%, S≤0.020%; and the rest is Fe and inevitable impurities.

[0059] The 60Si2Mn spring steel hot-rolled wide coil plate in the embodiment of the present application has a large width-thickness ratio.

[0060] In some embodiments, the thickness of the 60Si2Mn spring steel hot-rolled wide coil plate can be 1.8-6.0 mm, and the width of the 60Si2Mn spring steel hot-rolled wide coil plate can be 900-1500 mm.

[0061] In some embodiments, the single surface decarburization layer depth of the 60Si2Mn spring steel hot-rolled wide coil plate is less than or equal to 1.0% of the nominal thickness, the flatness of the plate is ≤8 mm / m, the microstructure is pearlite, and the grain size grade of the pearlite is ≥7 levels.

[0062] Embodiments

[0063] The following examples more specifically describe the present disclosure, which are only used for illustrative purposes, because various modifications and changes within the scope of the present disclosure are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the examples are commercially available.

[0064] Example 1

[0065] The continuous casting slab adopts hot charging and hot feeding process, the entry temperature of the slab into the heating furnace is 512-546°C, the atmosphere of the heating furnace is weak reducing atmosphere, the temperature of the preheating section of the heating furnace is 850-980°C, the temperature of the first heating section is 980-1100°C, the temperature of the second heating section is 1100-1190°C, the temperature of the soaking section is 1150-1180°C, the exit temperature is 1178°C, and the time in the furnace is 146 min. The pressure of the rough descaling treatment is set to 220 MPa, and the speed of the rough descaling treatment is set to 2 m / min. Five passes of rough rolling are adopted, and the thickness of the intermediate slab after rough rolling is 32 mm. Seven passes of finish rolling are adopted, the finish rolling temperature is 860°C, and the rolling thickness specification is 1.8 mm steel coil. The laminar cooling is in the front section fast cooling mode, and two groups of side water spray are opened at the water cooling start position and the water cooling end position. The coiling temperature is 640°C, and the coiling tension is 52 MPa. The steel coil is discharged 46 min after rolling and slowly cooled to ambient temperature in the slow cooling pit.

[0066] The 60Si2Mn spring steel hot-rolled wide-width coil produced by the above method has a maximum finish rolling rolling force of 38000 KN and stable production. The single-sided surface decarburization layer depth is 11 μm, the flatness of the plate is 7 mm / m, there is no "leaf edge" and other edge waves, the microstructure is uniform and fine full pearlite structure, and the pearlite grain size level is 8 levels. The thickness tolerance is controlled within ±0.05 mm, and the surface quality is good.

[0067] The microstructure diagram of the 60Si2Mn spring steel hot-rolled wide-width coil prepared in Example 1 is shown in Figure 2 .

[0068] Example 2

[0069] The continuous casting slab adopts hot charging and hot feeding process, the entry temperature of the slab into the heating furnace is 524-557°C, the atmosphere of the heating furnace is weak reducing atmosphere, the temperature of the preheating section of the heating furnace is 880-990°C, the temperature of the first heating section is 990-1080°C, the temperature of the second heating section is 1080-1180°C, the temperature of the soaking section is 1150-1180°C, the exit temperature is 1172°C, and the time in the furnace is 138 min. The pressure of the rough descaling treatment is set to 220 MPa, and the speed of the rough descaling treatment is set to 2 m / min. Five passes of rough rolling are adopted, and the thickness of the intermediate slab after rough rolling is 36 mm. Seven passes of finish rolling are adopted, the finish rolling temperature is 840°C, and the rolling thickness specification is 4.0 mm steel coil. The laminar cooling is in the front section fast cooling mode, and two groups of side water spray are opened at the water cooling start position and the water cooling end position. The coiling temperature is set to 620°C, and the coiling tension is 60 MPa. The steel coil is discharged 52 min after rolling and slowly cooled to ambient temperature in the slow cooling pit.

[0070] The 60Si2Mn spring steel hot-rolled wide coil produced by the above method has a maximum finishing rolling force of 37100KN, and the production is stable. The single surface decarburization layer depth is 24pm, the flatness is 5mm / m, there is no "leaf edge" and other edge waves, the microstructure is uniform and fine full pearlite structure, and the pearlite grain size level is 7. The thickness tolerance is controlled within ±0.07mm, and the surface quality is good.

[0071] Example 3

[0072] The continuous casting slab adopts a hot charging and hot feeding process, the entry temperature of the slab into the heating furnace is 508-541℃, the atmosphere of the heating furnace is weak reducing atmosphere, the temperature of the preheating section of the heating furnace is 860-990℃, the temperature of the first heating section is 990-1100℃, the temperature of the second heating section is 1100-1170℃, the temperature of the soaking section is 1140-1160℃, the exit temperature is 1155℃, and the in-furnace time is 130min. The rough descaling pressure is set to 220MPa, and the rough descaling speed is set to 2m / min. Five passes of rough rolling are adopted, and the intermediate billet thickness after rough rolling is 40mm. Seven passes of finishing rolling are adopted, and the finishing rolling temperature is 820℃. The rolling thickness specification is 6.0mm coil. The laminar cooling is in the front section fast cooling mode, and two groups of side water spray are opened at the water cooling start position and the water cooling end position. The coiling temperature is set to 580℃, and the coiling tension is 60MPa. The coil is discharged after 48min of rolling, and slowly cooled to ambient temperature in the slow cooling pit.

[0073] The 60Si2Mn spring steel hot-rolled wide coil produced by the above method has a maximum finishing rolling force of 36500KN, and the production is stable. The single surface decarburization layer depth is 26pm, the flatness is 5mm / m, there is no "leaf edge" and other edge waves, the microstructure is uniform and fine full pearlite structure, and the pearlite grain size level is 7. The thickness tolerance is controlled within ±0.08mm, and the surface quality is good.

[0074] Comparative Example 1

[0075] The continuous casting slab adopts a hot charging and hot feeding process, the entry temperature of the slab into the heating furnace is 512-546°C, the atmosphere of the heating furnace is weakly reducing, the temperature of the preheating section of the heating furnace is 850-1020°C, the temperature of the first heating section is 1020-1150°C, the temperature of the second heating section is 1150-1250°C, the temperature of the soaking section is 1200-1230°C, the exit temperature is 1220°C, and the time in the furnace is 146 min. The pressure of the rough descaling treatment is set to 220 MPa, and the speed of the rough descaling treatment is set to 2 m / min. Five passes of rough rolling are adopted, and the thickness of the intermediate slab after rough rolling is 32 mm. Seven passes of finish rolling are adopted, the finish rolling temperature is 860°C, and the rolling thickness specification is 1.8 mm steel coil. The laminar flow cooling is in a front section rapid cooling mode, and two groups of side water sprays are opened at the start position and the end position of water cooling. The coiling temperature is 700°C, and the coiling tension is 52 MPa. The steel coil is discharged 46 min after rolling and slowly cooled to ambient temperature in a slow cooling pit.

[0076] The 60Si2Mn spring steel hot-rolled wide-width coil produced by the above method has a maximum finish rolling rolling force of 35800 KN and stable production. The single-sided surface decarburization layer depth is significantly increased to 85 μm, the flatness of the plate is 5 mm / m, there is no "leaf edge" and other edge waste, the microstructure is a small amount of ferrite + coarsened pearlite structure, the pearlite grain size level is 5 levels. The thickness tolerance is within ±0.05 mm, the surface quality is normal, but the surface roughness is increased, and there is dust accumulation.

[0077] Comparative Example 2

[0078] The continuous casting slab adopts a hot charging and hot feeding process, the entry temperature of the slab into the heating furnace is 512-546°C, the atmosphere of the heating furnace is weakly reducing, the temperature of the preheating section of the heating furnace is 850-980°C, the temperature of the first heating section is 980-1100°C, the temperature of the second heating section is 1100-1190°C, the temperature of the soaking section is 1150-1180°C, the exit temperature is 1178°C, and the time in the furnace is 146 min. The pressure of the rough descaling treatment is set to 220 MPa, and the speed of the rough descaling treatment is set to 2 m / min. Seven passes of rough rolling are adopted, and the thickness of the intermediate slab after rough rolling is 32 mm. Seven passes of finish rolling are adopted, the finish rolling temperature is 820°C, and the rolling thickness specification is 1.8 mm steel coil. The laminar flow cooling is in a front section rapid cooling mode, and two groups of side water sprays are opened at the start position and the end position of water cooling. The coiling temperature is 570°C, and the coiling tension is 52 MPa. The steel coil is discharged 46 min after rolling and slowly cooled to ambient temperature in a slow cooling pit.

[0079] The 60Si2Mn spring steel hot-rolled wide-width coiled plate produced by the above method has a maximum finishing rolling force of 45000KN, unstable production, and tail throwing during rolling. The single-sided surface decarburization layer depth is 28μm, the flatness of the plate is 30mm / m, there are obvious "lotus leaf edge" and other edge waves, the microstructure is uniform and fine full pearlite structure, the pearlite grain size level is 8, the thickness tolerance is within ±0.10mm, and there are roll marks and other defects on the surface.

[0080] The specific description parameter of the maximum finishing rolling force, i.e. rolling load, reflects the difficulty of hot rolling.

[0081] The test method of the flatness of the plate refers to GB / T 709-2019 "Size, shape, weight and allowable deviation of hot-rolled steel plate and strip".

[0082] As can be seen from Examples 1-3 and Comparative Examples 1-2 of the present application, the preparation method of the present application can prepare 60Si2Mn spring steel hot-rolled wide-width coiled plate with excellent microstructure and performance.

[0083] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to it and parts thereof can be replaced with equivalents without departing from the scope of the present application. In particular, the technical features mentioned in each embodiment can be combined in any way as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing hot-rolled wide coils of 60Si2Mn spring steel, characterized in that, The preparation method includes: The slab after continuous casting is heated to obtain a heated slab; the furnace temperature of the slab is greater than 500℃; the atmosphere in the heating furnace for the heating treatment is a weakly reducing atmosphere; the heating treatment time is 120-150 min; and the heating treatment temperature is 800-1200℃. The heat-treated slab is subjected to coarse descaling to obtain a coarsely descaled slab; the pressure of the coarse descaling is greater than 200 MPa, and the rate of the coarse descaling is 1-3 m / min. The slab after rough descaling is subjected to rough rolling to obtain a rough rolled slab; the rough rolling process is carried out in 5 passes, and the thickness of the rough rolled slab is 30-40 mm. The rough-rolled slab is then subjected to finish rolling to obtain a finish-rolled slab. The finish rolling process consists of 7 passes, the final rolling temperature is 800-860℃, and the thickness of the finish-rolled strip is 1.8-6.0mm. The strip steel after finishing rolling is subjected to laminar flow cooling treatment to obtain laminar flow cooled strip steel; the laminar flow cooling treatment adopts a front-stage rapid cooling mode. The strip steel after laminar flow cooling is coiled to obtain a steel coil; the coiling temperature is 580-650℃ and the coiling tension is 50-60MPa.

2. The preparation method according to claim 1, characterized in that, The furnace temperature of the slab is 500-700℃.

3. The preparation method according to claim 1, characterized in that, The heating process includes a preheating section, a first heating section, a second heating section, and a homogenization section; Optionally, the temperature of the preheating section is 800-1000℃, the temperature of the first heating section is 950-1100℃, the temperature of the second heating section is 1050-1200℃, the temperature of the soaking section is 1130-1200℃, and the furnace exit temperature of the slab is 1150-1180℃.

4. The preparation method according to claim 1, characterized in that, The pressure for the coarse descaling process is 200-250 MPa.

5. The preparation method according to claim 1, characterized in that, The cooling rate of the laminar flow cooling process is 30-50℃ / s.

6. The preparation method according to claim 1, characterized in that, The preparation method further includes slowly cooling the steel coil to -20°C to 60°C.

7. A hot-rolled wide coil of 60Si2Mn spring steel, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. The 60Si2Mn spring steel hot-rolled wide coil according to claim 7, characterized in that, Based on the total mass of the hot-rolled wide coil of 60Si2Mn spring steel as 100%, the chemical composition of the hot-rolled wide coil of 60Si2Mn spring steel includes: C: 0.56%-0.64%, Si: 1.50%-2.00%, Mn: 0.70%-1.00%, Cr≤0.35%, Ni≤0.35%, Cu≤0.25%, P≤0.025%, S≤0.020%; the remainder is Fe and unavoidable impurities.

9. The 60Si2Mn spring steel hot-rolled wide coil according to claim 7, characterized in that, The thickness of the hot-rolled wide coil of 60Si2Mn spring steel is 1.8-6.0mm, and the width of the hot-rolled wide coil of 60Si2Mn spring steel is 900-1500mm.

10. The 60Si2Mn spring steel hot-rolled wide coil according to claim 7, characterized in that, The decarburized layer depth on one side of the hot-rolled wide coil of 60Si2Mn spring steel is less than or equal to 1.0% of the nominal thickness, the flatness of the plate is ≤8mm / m, the microstructure is pearlite, and the grain size grade of the pearlite is ≥7.

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