A 150mm*150mm square steel rolling method

Abstract

The present invention discloses a 150mm*150mm square steel rolling method, which relates to the technical field of square steel rolling. The square steel rolling method comprises: selecting a 200mm*200mm steel billet, heating and descaling the 200mm*200mm steel billet to obtain a first steel billet; feeding the first steel billet into a first vertical rolling mill for a first vertical rolling pass to obtain a second steel billet; feeding the second steel billet into a flat rolling mill for flat rolling to obtain a third steel billet; feeding the third steel billet into a second vertical rolling mill for a second vertical rolling pass to obtain a finished steel billet of 150mm*150mm. The method can produce 150mm*150mm square steel with good mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of square steel rolling, and in particular to a method for rolling 150mm*150mm square steel. Background Art

[0002] At present, some small-scale rolling production lines for producing steel sections in China use relatively small billets, with the largest size being only 150mm*150mm. When rolling large-section steel sections, the compression ratio is relatively small, and 150mm*150mm square steel with good comprehensive mechanical properties cannot be obtained. Summary of the Invention

[0003] The object of the present invention is to provide a 150mm*150mm square steel rolling method, which can obtain 150mm*150mm square steel with good mechanical properties.

[0004] The present invention provides a 150mm*150mm square steel rolling method, comprising:

[0005] A 200 mm*200 mm steel billet is selected, and the 200 mm*200 mm steel billet is heated and descaled to obtain a first steel billet;

[0006] Feeding the first steel billet into a first vertical rolling mill for a first vertical rolling to obtain a second steel billet;

[0007] feeding the second steel billet into a flat rolling mill for flat rolling to obtain a third steel billet;

[0008] The third steel billet is fed into the second vertical rolling mill for a second vertical rolling to obtain a finished steel billet of 150 mm*150 mm;

[0009] Among them, the reduction of the steel billet during the first vertical rolling is 50-55mm, the reduction of the steel billet during the flat rolling is 70-75mm, and the reduction of the steel billet during the second vertical rolling is 12-16mm; the rolling mill entrance hole type of the first vertical rolling mill and the flat rolling mill is a box-shaped hole, and the rolling mill entrance hole type of the second vertical rolling mill is a square box-shaped hole.

[0010] Optionally, the box-shaped hole of the first vertical rolling mill is 148mm*198mm, the box-shaped hole of the flat rolling mill is 146mm*153mm, and the square box-shaped hole of the second vertical rolling mill is 155mm*151mm.

[0011] Optionally, the groove bottom width b of the box-shaped hole of the first vertical rolling mill is 2-3 mm smaller than the thickness of the first steel billet, the groove bottom width b of the box-shaped hole of the flat rolling mill is 2-3 mm smaller than the thickness of the second steel billet, and the groove bottom width b of the square box-shaped hole of the second vertical rolling mill is 2-3 mm smaller than the thickness of the third steel billet.

[0012] Optionally, the side wall slope y of the box-shaped hole of the first vertical rolling mill is 10-15°, the side wall slope y of the box-shaped hole of the flat rolling mill is 10-15°, and the side wall slope y of the square box-shaped hole of the second vertical rolling mill is 5-7°.

[0013] Optionally, the bottom convexity of the box-shaped hole of the flat rolling mill is 2-3 mm.

[0014] Optionally, the step of heating and descaling a 200 mm*200 mm steel billet to obtain a first steel billet includes:

[0015] The 200mm*200mm steel billet is fed into the heating furnace for preheating, heating and soaking in sequence;

[0016] Among them, the preheating temperature is less than or equal to 850℃, the heating temperature is 1150-1200℃, and the soaking temperature is 1150-1180℃.

[0017] Optionally, the total time for preheating, heating and soaking the steel billet is 150-180 minutes.

[0018] Optionally, the step of heating and descaling a 200 mm*200 mm steel billet to obtain a first steel billet includes:

[0019] Descaling the heated steel billet using a descaling machine;

[0020] The descaling pressure of the descaling machine is greater than or equal to 18 MPa, and the striking distance of the descaling ring on the descaling machine is 30-40 mm.

[0021] Optionally, the inlets of the first vertical rolling mill and the flat rolling mill are both provided with purge nozzles;

[0022] The step of heating and descaling the 200mm*200mm steel billet to obtain the first steel billet further includes: descaling the heated steel billet using the purging nozzle.

[0023] Optionally, before the step of heating and descaling the 200 mm*200 mm steel billet to obtain the first steel billet, the process further includes:

[0024] Evenly coat high-temperature anti-oxidation material on a 200mm*200mm steel billet.

[0025] Compared with the prior art, the beneficial effects provided by the present invention are as follows: a 200mm*200mm steel billet is selected, and the 200mm*200mm steel billet is heated and descaled to obtain a first steel billet; the first steel billet is then sent to a first vertical rolling mill for a first vertical rolling to obtain a second steel billet; the second steel billet is then sent to a flat rolling mill for flat rolling to obtain a third steel billet; finally, the third steel billet is sent to a second vertical rolling mill for a second vertical rolling to obtain a 150mm*150mm finished steel billet; in this process, a 200mm*200mm steel billet is selected as the billet, and by limiting the reduction amount of the steel billet during the first vertical rolling, flat rolling and second vertical rolling, as well as the inlet hole types of the first vertical rolling mill, the second vertical rolling mill and the flat rolling mill, the obtained 150mm*150mm finished steel billet has a relatively flat appearance and an increased compression ratio, which is conducive to obtaining refined grains and a well-uniform structure, thereby improving the comprehensive mechanical properties of the steel, such as strength, plasticity, and impact toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly describes the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope of the present invention. Those skilled in the art can also derive other relevant drawings based on these drawings without inventive effort.

[0027] Figure 1 Flowchart of a method for rolling square steel according to an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of a rolling mill inlet pass of a first vertical rolling mill provided in an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of a rolling mill inlet pass of a flat rolling mill provided in an embodiment of the present invention;

[0030] Figure 4 A schematic diagram of the mill entrance pass profile of the second vertical rolling mill provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the embodiments of the present invention. It should be understood that the described embodiments are only a portion of the embodiments of the present invention, not all of them. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0033] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0034] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0035] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0036] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, terms such as "disposed" and "connected" should be understood in a broad sense. For example, "connected" can mean a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can also mean internal communication between two components. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0037] The inventors of this application have discovered that when rolling large-section steel, the compression ratio is too low, and 150mm*150mm square steel with good comprehensive mechanical properties cannot be obtained. This embodiment provides a 150mm*150mm square steel rolling method, which is used to at least solve the above technical problems.

[0038] See also Figure 1 The 150mm*150mm square steel rolling method provided in this embodiment includes:

[0039] Step S100: Select a 200mm*200mm steel billet, heat and descale the 200mm*200mm steel billet to obtain a first steel billet.

[0040] It should be pointed out that the 200mm*200mm steel billet is a continuous casting billet. During the heating process of the steel billet, iron oxide scale will be produced on the surface of the steel billet. If the iron oxide scale is not removed effectively, it is easy to cause the iron oxide scale to peel off after being pressed in to form pits, and the pressed iron oxide scale is thick and difficult to remove, making it impossible to inspect and handle surface cracks and other defects.

[0041] Descaling the steel billet after heating can remove most of the iron oxide scale on the surface of the steel billet.

[0042] Step S200: feeding the first steel billet into the first vertical rolling mill for the first vertical rolling to obtain the second steel billet.

[0043] Step S300: feeding the second steel billet into a flat rolling mill for flat rolling to obtain a third steel billet.

[0044] Step S400: Send the third steel billet to the second vertical rolling mill for a second vertical rolling to obtain a finished steel billet of 150 mm*150 mm.

[0045] Among them, the steel billet reduction during the first vertical rolling is 50-55mm, the steel billet reduction during flat rolling is 70-75mm, and the steel billet reduction during the second vertical rolling is 12-16mm; the rolling mill entrance hole type of the first vertical rolling mill and the flat rolling mill is a box hole, and the rolling mill entrance hole type of the second vertical rolling mill is a square box hole.

[0046] It should be noted that in the above steps S200-S400, the steel billet is rolled by vertical rolling, flat rolling and then vertical rolling to finally obtain a finished steel billet of 150mm*150mm.

[0047] It is understandable that the size of the finished steel billet allows an upper deviation of +4 mm and a lower deviation of -2 mm. For example, the final finished steel billet is 151 mm*153 mm.

[0048] Considering the flatness of all four sides of the finished billet, a three-pass rolling process is employed: vertical rolling, flat rolling, and then vertical rolling. The second vertical rolling pass uses a small reduction of 12-16mm to control the width and promote straightness on both sides. Based on the size requirements of the finished billet, the reduction in each pass is allocated according to the total amount of deformation. The first vertical and flat mills use box-shaped bores to achieve rolling deformation through a large reduction, while the second vertical mill uses a square box-shaped bore to control the width and ensure smooth edges without bulging. Furthermore, vertical rolling is used as the first rolling pass. The extrusion force of the vertical rolling machine shatters the oxide scale on the billet surface over a large area, which improves descaling and, in turn, facilitates surface quality control.

[0049] In an optional embodiment, the box-shaped hole of the first vertical rolling mill is 148mm*198mm, the box-shaped hole of the flat rolling mill is 146mm*153mm, and the square box-shaped hole of the second vertical rolling mill is 155mm*151mm.

[0050] It should be noted that the cross-sectional shape of the box-shaped hole and the square box-shaped hole is approximately rectangular.

[0051] See also Figure 2-Figure 4 In an optional embodiment, the groove bottom width b of the box-shaped hole of the first vertical rolling mill is 2-3 mm smaller than the thickness of the first steel billet, the groove bottom width b of the box-shaped hole of the flat rolling mill is 2-3 mm smaller than the thickness of the second steel billet, and the groove bottom width b of the square box-shaped hole of the second vertical rolling mill is 2-3 mm smaller than the thickness of the third steel billet.

[0052] For example, the thickness of the first steel billet is 200mm, the groove bottom width b of the box-shaped hole of the first vertical rolling mill is 2mm smaller than the thickness of the first steel billet, and the groove bottom width b of the box-shaped hole of the first vertical rolling mill is 198mm; the thickness of the second steel billet is 148mm, the groove bottom width b of the box-shaped hole of the flat rolling mill is 2mm smaller than the thickness of the second steel billet, and the groove bottom width b of the box-shaped hole of the flat rolling mill is 146mm; the thickness of the third steel billet is 153mm, the groove bottom width b of the square box-shaped hole of the second vertical rolling mill is 2mm smaller than the thickness of the third steel billet, and the groove bottom width b of the square box-shaped hole of the second vertical rolling mill is 151mm.

[0053] By limiting the groove bottom width b to be 2-3mm smaller than the incoming material thickness, the billet can obtain better side and corner quality, reducing the phenomenon of insufficient filling or collapsed corners of the billet.

[0054] In an optional embodiment, the side wall slope y of the box-shaped hole of the first vertical rolling mill is 10-15°, the side wall slope y of the box-shaped hole of the flat rolling mill is 10-15°, and the side wall slope y of the square box-shaped hole of the second vertical rolling mill is 5-7°.

[0055] For example, the side wall slope y of the box-shaped hole of the first vertical rolling mill is 12°, the side wall slope y of the box-shaped hole of the flat rolling mill is 13°, and the side wall slope y of the square box-shaped hole of the second vertical rolling mill is 6°.

[0056] By limiting the side wall inclination y of the box-shaped hole of the first vertical rolling mill and the side wall inclination y of the box-shaped hole of the flat rolling mill to 10-15°, the first vertical rolling mill and the flat rolling mill can better clamp the rolled piece, ensuring that the rolled piece can smoothly enter the next rolling mill; the square box-shaped hole of the second vertical rolling mill is a finished hole type, and by limiting the side wall inclination y of the square box-shaped hole of the second vertical rolling mill to 5-7°, the four corners of the finished steel billet are close to right angles and the difference in diagonal length is less than or equal to 4.5mm.

[0057] In an optional embodiment, the groove bottom convexity of the box-shaped hole of the flat rolling mill is 2-3 mm.

[0058] For example, the bottom convexity f of the box-shaped hole of the flat rolling mill is 2.5 mm. By limiting the bottom convexity f of the box-shaped hole of the flat rolling mill, it is also possible to further ensure that the four sides of the steel billet are straight.

[0059] In addition, step S100 includes:

[0060] Sub-step S110: Place a 200mm*200mm steel billet into a heating furnace for preheating, heating, and soaking. The preheating temperature is less than or equal to 850°C, the heating temperature is 1150-1200°C, and the soaking temperature is 1150-1180°C. The total duration of preheating, heating, and soaking is 150-180 minutes. The air-fuel ratio is 2.0-2.5:1.

[0061] For example, the preheating temperature is 850°C, the heating temperature is 1200°C, and the soaking temperature is 1180°C. The total time for preheating, heating, and soaking the billet is 180 minutes. The air-fuel ratio is 2.0:1.

[0062] By reasonably setting the preheating temperature, heating temperature, soaking temperature, air-fuel ratio and the total time for preheating, heating and soaking the steel billet, the combustion in the heating furnace is effectively controlled and oxidation burning is reduced.

[0063] In addition, step S100 further includes:

[0064] Sub-step S120, descaling the heated steel billet using a descaling machine; wherein the descaling pressure of the descaling machine is greater than or equal to 18 MPa, and the striking distance of the descaling ring on the descaling machine is 30-40 mm.

[0065] For example, the descaling pressure of the descaling machine is limited to 18 MPa, and the striking distance of the descaling ring on the descaling machine is 40 mm.

[0066] By limiting the descaling pressure of the descaling machine and the striking distance of the descaling ring on the descaling machine, the iron oxide scale on the surface of the steel billet can be removed more thoroughly and the descaling effect can be improved.

[0067] In addition, the inlets of the first vertical rolling mill and the flat rolling mill are both provided with purging nozzles. Step S100 also includes:

[0068] Sub-step S140: descaling the heated steel billet using a purge nozzle.

[0069] By arranging purging nozzles at the inlets of the first vertical rolling mill and the flat rolling mill, the purging nozzles can remove the iron oxide scale remaining on the surface of the steel billet during the steel billet rolling process.

[0070] In addition, before step S100, the method further includes:

[0071] Step S500: evenly coating a high-temperature anti-oxidation material on a 200 mm*200 mm steel billet.

[0072] In this step, a high-temperature antioxidant is applied to the outer surface of a 200mm x 200mm steel billet and allowed to stand for a period of time to allow the material to adhere to the billet. While the billet is being heated in the furnace, the coated material effectively reduces surface oxidation and the formation of scale.

[0073] In summary, this embodiment provides a 150mm*150mm square steel rolling method, by selecting a 200mm*200mm steel billet as a billet, the 200mm*200mm steel billet is heated, descaled, and rolled three times to obtain a 150mm*150mm finished steel billet. The finished steel billet meets the square steel size deviation requirements, has a relatively flat appearance, and has an increased compression ratio, which is conducive to obtaining refined grains and a well-uniform structure, thereby improving the comprehensive mechanical properties of the steel, such as strength, plasticity, and impact toughness.

[0074] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for rolling 150mm*150mm square steel, characterized in that: include: A 200 mm*200 mm steel billet is selected, and the 200 mm*200 mm steel billet is heated and descaled to obtain a first steel billet; Feeding the first steel billet into a first vertical rolling mill for a first vertical rolling to obtain a second steel billet; feeding the second steel billet into a flat rolling mill for flat rolling to obtain a third steel billet; The third steel billet is fed into the second vertical rolling mill for a second vertical rolling to obtain a finished steel billet of 150 mm*150 mm; The reduction of the steel billet during the first vertical rolling is 50-55 mm, the reduction of the steel billet during the flat rolling is 70-75 mm, and the reduction of the steel billet during the second vertical rolling is 12-16 mm; the mill entrance pass of the first vertical rolling mill and the flat rolling mill is a box-shaped hole, and the mill entrance pass of the second vertical rolling mill is a square box-shaped hole; The bottom width b of the box-shaped hole of the first vertical rolling mill is 2-3 mm smaller than the thickness of the first steel billet, the bottom width b of the box-shaped hole of the flat rolling mill is 2-3 mm smaller than the thickness of the second steel billet, and the bottom width b of the square box-shaped hole of the second vertical rolling mill is 2-3 mm smaller than the thickness of the third steel billet; The side wall slope y of the box-shaped hole of the first vertical rolling mill is 10-15°, the side wall slope y of the box-shaped hole of the flat rolling mill is 10-15°, and the side wall slope y of the square box-shaped hole of the second vertical rolling mill is 5-7°; the groove bottom convexity f of the box-shaped hole of the flat rolling mill is 2-3mm.

2. The 150mm*150mm square steel rolling method according to claim 1, characterized in that: The box-shaped hole of the first vertical rolling mill is 148mm*198mm, the box-shaped hole of the flat rolling mill is 146mm*153mm, and the square box-shaped hole of the second vertical rolling mill is 155mm*151mm.

3. The 150mm*150mm square steel rolling method according to claim 1, characterized in that: The step of heating and descaling a 200mm*200mm steel billet to obtain a first steel billet comprises: The 200mm*200mm steel billet is fed into the heating furnace for preheating, heating and soaking in sequence; Among them, the preheating temperature is less than or equal to 850℃, the heating temperature is 1150-1200℃, and the soaking temperature is 1150-1180℃.

4. The 150mm*150mm square steel rolling method according to claim 3, characterized in that: The total time for preheating, heating and soaking the steel billet is 150-180 minutes.

5. The 150mm*150mm square steel rolling method according to claim 1, characterized in that: The step of heating and descaling a 200mm*200mm steel billet to obtain a first steel billet comprises: Descaling the heated steel billet using a descaling machine; The descaling pressure of the descaling machine is greater than or equal to 18 MPa, and the striking distance of the descaling ring on the descaling machine is 30-40 mm.

6. The 150mm*150mm square steel rolling method according to claim 1, characterized in that: The inlets of the first vertical rolling mill and the flat rolling mill are both provided with purge nozzles; The step of heating and descaling the 200mm*200mm steel billet to obtain the first steel billet further includes: descaling the heated steel billet using the purging nozzle.

7. The 150mm*150mm square steel rolling method according to claim 1, characterized in that: Before the step of heating and descaling the 200mm*200mm steel billet to obtain the first steel billet, the method further comprises: Evenly coat high-temperature anti-oxidation material on a 200mm*200mm steel billet.

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