Optimization Method for Red Scale Defects on the Surface of High-Silicon Hot-Rolled Strip Steel

Abstract

The present application discloses an optimization method for the red scale defect on the surface of high-silicon hot-rolled strip steel. The method includes: sequentially performing a heating process, a rough rolling process, a coiling process in a coil box, and a finish rolling process on the high-silicon hot-rolled strip steel to obtain the high-silicon hot-rolled strip steel; wherein, in the heating process with a tensile strength less than 590 MPa, controlling the tapping temperature of the high-silicon hot-rolled strip steel to be 1150 °C to 1180 °C, and controlling the time of the high-silicon hot-rolled strip steel in the heating furnace to be 110 min to 140 min. The technical solution provided by the present application can reduce the red scale defect on the surface of the high-silicon hot-rolled strip steel.

Description

Technical Field

[0001] This application belongs to the technical field of the surface quality of high-silicon hot-rolled strip steel, and particularly relates to an optimization method for the red scale defect on the surface of high-silicon hot-rolled strip steel. Background Art

[0002] At present, when alloying design is carried out for high-strength automotive steel sheets, in order to enhance the hardenability of the steel and improve the finished product strength, a certain amount of Si element will be added. The addition of Si element, especially when the Si content is higher than 0.1%, will cause the surface of high-silicon hot-rolled strip steel to be extremely prone to red scale defects. Therefore, a method capable of reducing the red scale defects on the surface of high-silicon hot-rolled strip steel is needed. Summary of the Invention

[0003] The embodiment of this application provides an optimization method for the red scale defect on the surface of high-silicon hot-rolled strip steel, and the method can reduce the red scale defect on the surface of high-silicon hot-rolled strip steel.

[0004] Other characteristics and advantages of this application will become obvious through the following detailed description, or be learned partially through the practice of this application.

[0005] According to the first aspect of the embodiment of this application, an optimization method for the red scale defect on the surface of high-silicon hot-rolled strip steel is provided, characterized in that the method includes: sequentially performing a heating process, a rough rolling process, a coiling process in a coil box, and a finish rolling process on the high-silicon hot-rolled strip steel to obtain the high-silicon hot-rolled strip steel; wherein, in the heating process with a tensile strength less than 590 MPa, controlling the tapping temperature of the high-silicon hot-rolled strip steel to be 1150°C to 1180°C, and controlling the time of the high-silicon hot-rolled strip steel in the heating furnace to be 110 min to 140 min.

[0006] In some embodiments of this application, based on the foregoing solution, the method further includes: in the heating process with a tensile strength greater than 590 MPa, controlling the tapping temperature of the high-silicon hot-rolled strip steel to be 1270°C to 1280°C, and controlling the time of the high-silicon hot-rolled strip steel in the heating furnace to be 140 min to 200 min.

[0007] In some embodiments of this application, based on the foregoing solution, the method further includes: in the rough rolling process, controlling the descaling pressure to be greater than or equal to 17 MPa.

[0008] In some embodiments of this application, based on the foregoing solution, the method further includes: in the rough rolling process, controlling the rough rolling mill R2 to start 5 passes of descaling.

[0009] In some embodiments of the present application, based on the foregoing solutions, the method further includes: in the rough rolling process, controlling the reduction of the vertical roll mill E2, wherein the reduction of the first pass of the vertical roll mill E2 is 46 mm to 52 mm, the reduction of the third pass of the vertical roll mill E2 is 46 mm to 50 mm, and the reduction of the fifth pass of the vertical roll mill E2 is 16 mm to 20 mm.

[0010] In some embodiments of the present application, based on the foregoing solutions, the method further includes: in the coiling process of the coil box, controlling the thickness of the intermediate billet of the high-silicon hot-rolled strip to be 30 mm to 34 mm.

[0011] In some embodiments of the present application, based on the foregoing solutions, the method further includes: in the finish rolling process, controlling the descaling pressure to be greater than or equal to 24 MPa.

[0012] In some embodiments of the present application, based on the foregoing solutions, the method further includes: in the finish rolling process, opening the outlet nozzle and the inlet nozzle of the finish descaling.

[0013] In some embodiments of the present application, based on the foregoing solutions, the method further includes: in the finish rolling process, controlling the height of the finish descaling header to be 130 mm.

[0014] The beneficial effects produced by the present application: During the implementation of the present application, when the high-silicon hot-rolled strip performs the heating process, and in the heating process with a tensile strength less than 590 MPa and / or in the heating process with a tensile strength greater than 590 MPa, controlling the tapping temperature of the high-silicon hot-rolled strip and the time of the high-silicon hot-rolled strip in the heating furnace, thereby reducing the red scale defect of the high-silicon hot-rolled strip.

[0015] When the high-silicon hot-rolled strip performs the rough rolling process, before the rough rolling mill performs rolling, controlling the descaling pressure to be greater than or equal to 17 MPa. At the same time, in the rough rolling process, it is possible to control the rough rolling mill R2 to start descaling for 5 passes. At the same time, in the rough rolling process, controlling the reduction of the vertical roll mill E2, thereby increasing the reduction of the vertical roll mill E2, and further improving the plasticity of the edge scale of the high-silicon hot-rolled strip and reducing the red scale defect of the high-silicon hot-rolled strip.

[0016] When the high-silicon hot-rolled strip performs the coiling process of the coil box, controlling the thickness of the intermediate billet of the high-silicon hot-rolled strip to be 30 mm to 34 mm, thereby effectively increasing the surface temperature of the intermediate billet and improving the red scale defect through the coil box.

[0017] When performing the finish rolling process on high-silicon hot-rolled strip steel, before rolling on the finishing mill, control the descaling pressure to be greater than or equal to 24 MPa. At the same time, in the finish rolling process, turn on the nozzles at the outlet and inlet of the finish descaling. At the same time, in the finish rolling process, control the height of the finish descaling header to be 130 mm. According to the various controls in the finish rolling process, the descaling effect of the high-silicon hot-rolled strip steel can be improved, and the red scale defect of the high-silicon hot-rolled strip steel can be reduced.

[0018] Based on this, the optimization method for the red scale defect on the surface of high-silicon hot-rolled strip steel proposed in this application can reduce the red scale defect on the surface of high-silicon hot-rolled strip steel.

[0019] According to the second aspect of the embodiments of the present application, there is provided a high-silicon hot-rolled strip steel, characterized in that the high-silicon hot-rolled strip steel is manufactured by applying the method as described above.

[0020] For the beneficial effects of the embodiments in the above second aspect, reference may be made to the beneficial effects of the above first aspect and each embodiment of the first aspect, which will not be elaborated here.

[0021] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings here are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. In the drawings:

[0023] Figure 1 Shows the generation diagram of the red scale defect on the surface of the high-silicon hot-rolled strip steel in the embodiments of the present application;

[0024] Figure 2 Shows the flowchart of the optimization method for the red scale defect on the surface of the high-silicon hot-rolled strip steel in the embodiments of the present application;

[0025] Figure 3 Shows the surface quality comparison diagram of the high-silicon hot-rolled strip steel in the embodiments of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0027] In addition, the described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present application. However, those skilled in the art will realize that the technical solutions of the present application can be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, well-known methods, devices, implementations, or operations are not shown or described in detail to avoid obscuring aspects of the present application.

[0028] The block diagrams shown in the drawings are only functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0029] The flowcharts shown in the drawings are only illustrative and not necessarily include all the contents and operations / steps, nor are they necessarily executed in the described order. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined, so the actual execution order may change according to the actual situation.

[0030] Referring to Figure 1 , a diagram showing the generation of red scale defects on the surface of high-silicon hot-rolled strip steel in an embodiment of the present application is shown. As Figure 1 can be seen, in order to enhance the hardenability of steel and improve the finished product strength, a certain amount of Si element (i.e., silicon element) is added to high-silicon hot-rolled strip steel. When the content of the Si element is higher than 0.1%, it will cause red scale defects to easily occur on the strip steel surface. Because at high temperatures, the Si element will form fayalite phase (i.e., Fe2SiO4) between the strip steel matrix and the oxide scale layer. After the fayalite phase solidifies, it will form an anchor-like morphology to pin FeO. The pinned FeO is difficult to be completely removed during descaling. The remaining FeO breaks during the subsequent hot rolling process and increases the contact area with oxygen in the air, thus resulting in the formation of red Fe2O3, that is, red scale defects.

[0031] Next, the present application will be elaborated in detail:

[0032] Figure 2 A flowchart showing an optimization method for red scale defects on the surface of high-silicon hot-rolled strip steel in an embodiment of the present application is shown. Referring to Figure 2 shown, the optimization method for red scale defects on the surface of the high-silicon hot-rolled strip steel includes at least steps 210 to 230, which are introduced in detail as follows:

[0033] In step 210, a heating process, a rough rolling process, a coiling process in a coil box, and a finish rolling process are sequentially performed on the high-silicon hot-rolled strip to obtain the high-silicon hot-rolled strip.

[0034] In this application, by performing different treatments on the high-silicon hot-rolled strip during the heating process, rough rolling process, coiling process in a coil box, and finish rolling process, the red scale defect on the surface of the high-silicon hot-rolled strip can be optimized.

[0035] Continue to refer to Figure 2 , in step 230, among them, in the heating process where the tensile strength is less than 590 MPa, control the tapping temperature of the high-silicon hot-rolled strip to be 1150°C to 1180°C, and control the time of the high-silicon hot-rolled strip in the heating furnace to be 110 min to 140 min.

[0036] In this application, since the melting point temperature of the fayalite phase (i.e., Fe2SiO4) is about 1173°C, and when tapping at 1150°C to 1180°C, the liquid fayalite has not yet formed, and at this time, descaling is easy to remove. By rapid firing at a low temperature, the development of the high-temperature fayalite phase network structure can be inhibited, and the anchoring of the liquid fayalite phase to the matrix can be inhibited. At the same time, by maintaining a high temperature in the furnace for a long time, it can be ensured that after the slab is tapped, the fayalite phase between the matrix and the oxide scale layer during primary descaling is still in a liquid phase and no solidification occurs, and all the liquid fayalite phase is also easy to remove during descaling.

[0037] Further, in some embodiments of this application, the method further includes: in the heating process where the tensile strength is greater than 590 MPa, control the tapping temperature of the high-silicon hot-rolled strip to be 1270°C to 1280°C, and control the time of the high-silicon hot-rolled strip in the heating furnace to be 140 min to 200 min.

[0038] Further, in some embodiments of this application, the method further includes: in the rough rolling process, control the descaling pressure to be greater than or equal to 17 MPa.

[0039] Further, in some embodiments of this application, the method further includes: in the rough rolling process, control the roughing mill R2 to start 5-pass descaling.

[0040] Further, in some embodiments of this application, the method further includes: in the rough rolling process, control the reduction of the vertical roll mill E2, where the reduction of the first pass of the vertical roll mill E2 is 46 mm to 52 mm, the reduction of the third pass of the vertical roll mill E2 is 46 mm to 50 mm, and the reduction of the fifth pass of the vertical roll mill E2 is 16 mm to 20 mm.

[0041] In this embodiment, since the increase in the rolling force in each pass of the vertical rolls is beneficial to increasing the deformation heat and improving the low temperature point at the edge. Therefore, when controlling the increase in the reduction of the vertical roll mill E2, the edge temperature of the high-silicon hot-rolled strip can be increased by 10°C to 20°C, thereby improving the plasticity of the edge scale and reducing the red scale defect.

[0042] Further, in some embodiments of the present application, the method further includes: in the coiling process of the coil box, controlling the thickness of the intermediate billet of the high-silicon hot-rolled strip to be 30 mm to 34 mm.

[0043] In this embodiment, in the coiling process of the coil box, since the contact between the vertical rolls and the high-silicon hot-rolled strip has a good descaling effect, after descaling, the intermediate billet forms a coiled structure, thereby avoiding the re-generation of scale when the high-temperature intermediate billet contacts the air. At the same time, the coil box has a good heat preservation effect, which can effectively increase the surface temperature of the intermediate billet, improve the plasticity of the scale and avoid the scale being broken and oxidized to generate Fe2O3 during the finish rolling. Based on this, the coil box has a good improvement effect on the red scale defect.

[0044] Further, in some embodiments of the present application, the method further includes: in the finish rolling process, controlling the descaling pressure to be greater than or equal to 24 MPa.

[0045] Further, in some embodiments of the present application, the method further includes: in the finish rolling process, opening the outlet nozzle and the inlet nozzle of the finish descaling.

[0046] Further, in some embodiments of the present application, the method further includes: in the finish rolling process, controlling the height of the finish descaling header to be 130 mm.

[0047] In this embodiment, by adjusting the distance between the finish descaling nozzle and the surface of the high-silicon hot-rolled strip, the optimal descaling water impact force and the overlapping amount of the fan-shaped surface can be achieved, thereby improving the descaling effect.

[0048] By integrating the above methods, when the high-silicon hot-rolled strip is subjected to the heating process, and in the heating process with a tensile strength less than 590 MPa and / or in the heating process with a tensile strength greater than 590 MPa, controlling the outgoing furnace temperature of the high-silicon hot-rolled strip and the time of the high-silicon hot-rolled strip in the heating furnace, thereby reducing the red scale defect of the high-silicon hot-rolled strip.

[0049] When the high-silicon hot-rolled strip is subjected to the rough rolling process, before the rough rolling mill is rolled, controlling the descaling pressure to be greater than or equal to 17 MPa. At the same time, in the rough rolling process, it is possible to control the rough rolling mill R2 to start descaling for 5 passes. At the same time, in the rough rolling process, controlling the reduction of the vertical roll mill E2, thereby increasing the reduction of the vertical roll mill E2, and further improving the plasticity of the edge scale of the high-silicon hot-rolled strip and reducing the red scale defect of the high-silicon hot-rolled strip.

[0050] When the coiling process of the coiler is carried out for the high-silicon hot-rolled strip steel, control the thickness of the intermediate billet of the high-silicon hot-rolled strip steel to be 30 mm to 34 mm, so as to effectively increase the surface temperature of the intermediate billet and improve the red scale defect through the coiler.

[0051] When the finishing rolling process is carried out for the high-silicon hot-rolled strip steel, before the rolling of the finishing mill, control the descaling pressure to be greater than or equal to 24 MPa. At the same time, in the finishing rolling process, open the finishing descaling outlet nozzle and the finishing descaling inlet nozzle. At the same time, in the finishing rolling process, control the height of the finishing descaling header to be 130 mm. According to the various controls in the finishing rolling process, the descaling effect of the high-silicon hot-rolled strip steel can be improved, and the red scale defect of the high-silicon hot-rolled strip steel can be reduced.

[0052] Specifically, refer to Table 1 and Figure 3 . Table 1 shows the probability of the occurrence of defects of the high-silicon hot-rolled strip steel below 590 MPa and above 590 MPa. Figure 3 Shows the surface quality comparison diagram of the high-silicon hot-rolled strip steel in the embodiment of the present application.

[0053]

[0054] Table 1

[0055] In the heating process, and when it is below 590 MPa, control the range of the tapping temperature to be 1166 °C - 1192 °C, the time in the furnace to be 126 min, and the range of the time in the furnace to be 114 min - 135 min. When it is above 590 MPa, control the range of the tapping temperature to be 1274 °C - 1278 °C, and the range of the time in the furnace to be 150 min - 189 min.

[0056] In the rough rolling process, control the range of the rough descaling pressure to be 17.2 MPa - 17.9 MPa, and control the roughing mill R2 to start 5 passes of descaling. At the same time, increase the reduction of the vertical roll mill E2. The reduction of the first pass is 47 mm - 52 mm, the reduction of the third pass of the vertical roll mill E2 is 46 mm - 49 mm, and the reduction of the fifth pass of the vertical roll mill E2 is 16 mm - 19 mm.

[0057] In the coiling process of the coiler, control the thickness of the intermediate billet to be 34 mm.

[0058] In the finishing rolling process, control the finishing descaling pressure to be above 24 MPa, open the finishing descaling outlet nozzle and the finishing descaling inlet nozzle, and control the height of the finishing descaling header to be 130 mm.

[0059] Using the above method, 1000 rolls of high-silicon hot-rolled strip steel were tested, including 500 rolls with a tensile strength below 590 MPa and 500 rolls with a tensile strength above 590 MPa. From Figure 1 it can be seen that when the tensile strength is below 590 MPa, the defect rate is 0.8%. When the tensile strength is above 590 MPa, the defect rate is 0.6%. At the same time, from Figure 3 it can be seen that after the above method, the surface quality of the high-silicon hot-rolled strip steel has been improved.

[0060] Based on this, the optimization method for the red scale defect on the surface of the high-silicon hot-rolled strip steel proposed in this application can reduce the red scale defect on the surface of the high-silicon hot-rolled strip steel.

[0061] Based on the same inventive concept, this application also provides a high-silicon hot-rolled strip steel, characterized in that the high-silicon hot-rolled strip steel is manufactured by applying the method as described above.

[0062] The above are only the embodiments of this application and are not used to limit this application. For those skilled in the art, this application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the scope of the claims of this application.

Claims

1. An optimization method for the red scale defect on the surface of high-silicon hot-rolled strip steel, characterized in that, The method includes: Performing a heating process, a rough rolling process, a coiling process in a coil box, and a finish rolling process on the high-silicon hot-rolled strip in sequence to obtain the high-silicon hot-rolled strip; Among them, in the heating process with a tensile strength less than 590 MPa, controlling the tapping temperature of the high-silicon hot-rolled strip to be 1150°C to 1180°C, and controlling the time of the high-silicon hot-rolled strip in the heating furnace to be 110 min to 140 min; In the heating process with a tensile strength greater than 590 MPa, controlling the tapping temperature of the high-silicon hot-rolled strip to be 1270°C to 1280°C, and controlling the time of the high-silicon hot-rolled strip in the heating furnace to be 140 min to 200 min; In the coiling process in the coil box, controlling the thickness of the intermediate billet of the high-silicon hot-rolled strip to be 30 mm to 34 mm; In the finish rolling process, controlling the height of the finish descaling header to be 130 mm.

2. The method according to claim 1, wherein The method further includes: In the rough rolling process, controlling the descaling pressure to be greater than or equal to 17 MPa.

3. The method according to claim 1, characterized in that The method further includes: In the rough rolling process, controlling the roughing mill R2 to start 5 passes of descaling.

4. The method according to claim 1, characterized in that, The method further includes: In the rough rolling process, controlling the reduction of the vertical roll mill E2, wherein the reduction of the first pass of the vertical roll mill E2 is 46 mm to 52 mm, the reduction of the third pass of the vertical roll mill E2 is 46 mm to 50 mm, and the reduction of the fifth pass of the vertical roll mill E2 is 16 mm to 20 mm.

5. The method according to claim 1, characterized in that, The method further includes: In the finish rolling process, controlling the descaling pressure to be greater than or equal to 24 MPa.

6. The method according to claim 1, wherein The method further includes: In the finish rolling process, opening the finish descaling outlet nozzle and the finish descaling inlet nozzle.

7. A high-silicon hot-rolled strip steel, characterized in that The high-silicon hot-rolled strip is manufactured by using the method according to any one of claims 1-6.

Images