A method for producing fine lamellar eutectoid iron oxide scale steel plate

Abstract

The present invention discloses a method for producing a fine lamellar eutectoid iron oxide scale steel plate, comprising the following steps: (1) finishing rolling an intermediate billet after rough rolling and descaling to obtain a finished rolled plate; (2) cooling the finished rolled plate to obtain a plate strip; (3) coiling the plate strip to obtain a hot-rolled steel coil; (4) cooling the hot-rolled steel coil to room temperature; wherein the inlet temperature of the finishing rolling is ≤1030°C, the finishing rolling temperature is 850°C to 900°C; and the coiling temperature is 540°C to 570°C. The present invention controls parameters such as the finishing rolling inlet temperature, the finishing rolling temperature, and the coiling temperature to generate a lamellar eutectoid Fe3O4 / α-Fe structure in the surface iron oxide scale of the hot-rolled steel plate, accounting for more than 50% of the total iron oxide scale. The lamellar spacing of the lamellar eutectoid Fe3O4 / α-Fe structure is 80nm to 200nm, and the total iron oxide scale thickness is less than 10um.

Description

Technical Field

[0001] The invention belongs to the technical field of steel rolling technology in the field of metallurgy, and relates to a method for producing a fine lamellar eutectoid iron oxide scale steel plate. Background Art

[0002] As industrial energy conservation, emission reduction, and green manufacturing become increasingly important for the development of the steel industry, extensive research has been conducted both domestically and internationally on pickling-free steel production technologies. A representative example is pickling-free technology focused on scale control. Pickling-free steel exhibits a strong bond between the scale and the substrate, allowing it to withstand deformation without breaking off, allowing the steel to be used directly without undergoing a pickling process.

[0003] Iron oxide scale is composed of layers of Fe2O3, Fe3O4, eutectoid Fe3O4 / α-Fe, and FeO. Fe3O4 and eutectoid Fe3O4 / α-Fe have higher tensile strength than Fe2O3 and FeO, are more resistant to deformation, and are less susceptible to shedding during processing. Current research on pickling-free steels focuses on controlling rolling and cooling schedules to increase the Fe3O4 content and reduce the overall thickness of the oxide scale. Because eutectoid Fe3O4 / α-Fe is a lamellar structure composed of alternating α-Fe and Fe3O4, the spacing between these lamellar structures determines the toughness of the oxide scale. Smaller lamellar spacing results in greater toughness and less resistance to shedding during deformation. Currently, no research specifically addresses the generation of eutectoid Fe3O4 / α-Fe oxide scale with fine lamellar spacing. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for producing fine lamellar eutectoid iron oxide scale steel plate, in which the generated lamellar eutectoid Fe3O4 / α-Fe structure accounts for more than 50% of the total iron oxide scale, the lamellar spacing is 80nm to 200nm, and the total iron oxide scale thickness is less than 10um.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for producing a fine lamellar eutectoid iron oxide scale steel plate comprises the following steps:

[0007] (1) Finish rolling the intermediate billet after rough rolling and descaling to obtain finished rolled plate;

[0008] (2) cooling the finished rolled plate to obtain a plate strip;

[0009] (3) coiling the strip to obtain a hot-rolled steel coil;

[0010] (4) Cooling the hot-rolled steel coil to room temperature.

[0011] Furthermore, the inlet temperature of the finishing rolling in step (1) of the present invention is ≤1030°C.

[0012] Furthermore, the final rolling temperature of the finishing rolling in step (1) of the present invention is 850°C to 900°C.

[0013] Furthermore, the cooling in step (2) of the present invention adopts front-stage concentrated laminar cooling, and the cooling rate is 30°C / s to 50°C / s.

[0014] Furthermore, the coiling temperature in step (3) of the present invention is 540°C to 570°C.

[0015] Furthermore, the hot-rolled steel coils in step (4) of the present invention are stacked in a pit and cooled to room temperature.

[0016] Furthermore, the mass percentages of Si, Ni and Cr in the steel plate of the present invention are controlled as follows: Si≤0.5%, Ni≤0.01%, Cr≤0.5%.

[0017] Furthermore, the lamellar spacing of the lamellar eutectoid Fe3O4 / α-Fe structure in the surface oxide scale of the hot-rolled steel plate produced by the method of the present invention is 80nm~200nm, the lamellar eutectoid Fe3O4 / α-Fe structure accounts for more than 50% of the total oxide scale, and the total oxide scale thickness is less than 10um.

[0018] The inventive principle of the technical solution of the present invention is:

[0019] Controlling a lower finishing rolling temperature can inhibit the growth of iron oxide scale and keep the total iron oxide scale thickness at a low level; low coiling temperature can inhibit the precipitation of Fe3O4 in the iron oxide scale in the FeO layer; stacking and cooling in a pit after coiling can keep the steel coils warm and slow down the cooling rate, and the pit is oxygen-poor, providing better conditions for eutectoid; Si, Ni, and Cr elements in steel can cause the presence of olivine, making the iron oxide scale easy to break and easy to generate Fe2O3, but not easy to form eutectoid structure, so their content needs to be controlled.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0021] The present invention controls the lamellar spacing of the lamellar eutectoid Fe3O4 / α-Fe structure to be between 80nm and 200nm by controlling the rolling and cooling of the finishing rolling and coiling processes, and controlling parameters such as the finishing rolling inlet temperature, the finishing rolling outlet temperature and the coiling temperature. The lamellar eutectoid Fe3O4 / α-Fe structure accounts for more than 50% of the total iron oxide scale, the FeO content is low, and the total iron oxide scale thickness is less than 10um. The iron oxide scale within this lamellar spacing range and proportion has good toughness and is not easy to fall off when subjected to processing deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the measurement diagram of the lamellar spacing of lamellar eutectoid Fe3O4 / α-Fe in Example 1;

[0023] Figure 2 This is a measurement diagram of the total thickness of the iron oxide scale in Example 1;

[0024] Figure 3 This is the structure diagram of the iron oxide scale in Example 2;

[0025] Figure 4 This is the structure diagram of the iron oxide scale in Example 3;

[0026] Figure 5 This is the structure diagram of the iron oxide scale in comparative example 1. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Example 1

[0028] The weight percentages of the components in the steel billet of this embodiment are: C: 0.439%, Si: 0.2341%, Mn: 0.6773%, S: 0.0011%, P: 0.0133%, Ni: 0.0095%, Cr: 0.0176%, Alt: 0.0356%, and the remainder is iron and residue; the production method thereof comprises:

[0029] (1) The intermediate billet after rough rolling and descaling is subjected to finish rolling, with the finishing rolling inlet temperature of 1015°C and the final rolling temperature of 871°C to obtain the finished rolled plate;

[0030] (2) Cooling the finished rolled plate by front-stage concentrated laminar cooling at a cooling rate of 34.7°C / s to obtain a plate strip;

[0031] (3) coiling the strip at a coiling temperature of 559° C. to obtain a hot-rolled steel coil;

[0032] (4) Stacking the hot-rolled steel coils in a pit and cooling them to room temperature.

[0033] The measurement diagram of the total thickness of the iron oxide scale on the surface of the steel plate in this embodiment is as follows Figure 1 As shown, the average total thickness is 9.049 μm; the iron oxide scale contains Fe3O4 and lamellar eutectoid Fe3O4 / α-Fe structure, and the lamellar spacing measurement diagram of the lamellar eutectoid Fe3O4 / α-Fe structure is shown in Figure 2 As shown, the average value is 173nm, and the lamellar eutectoid Fe3O4 / α-Fe structure accounts for 75% of the total iron scale. This type of iron oxide scale is not easy to fall off during processing and deformation. Example 2

[0034] The weight percentages of the components in the steel billet of this embodiment are: C: 0.415%, Si: 0.3154%, Mn: 0.7059%, S: 0.0010%, P: 0.0159%, Ni: 0.0071%, Cr: 0.0205%, Alt: 0.0213%, and the remainder is iron and residue; the production method thereof comprises:

[0035] (1) The intermediate billet after rough rolling and descaling is subjected to finish rolling, with the finishing rolling inlet temperature being 1030°C and the final rolling temperature being 900°C to obtain the finished rolled plate;

[0036] (2) Cooling the finished rolled plate by front-stage concentrated laminar cooling at a cooling rate of 40.2°C / s to obtain a plate strip;

[0037] (3) coiling the strip at a coiling temperature of 540° C. to obtain a hot-rolled steel coil;

[0038] (4) Stacking the hot-rolled steel coils in a pit and cooling them to room temperature.

[0039] The structure of the iron oxide scale on the surface of the steel plate in this embodiment is shown in the figure below. Figure 3 As shown in the figure, the average total thickness is 5.828μm; the iron oxide scale contains Fe3O4 and lamellar eutectoid Fe3O4 / α-Fe structure, the average interlamellar spacing of the lamellar eutectoid Fe3O4 / α-Fe structure is 185nm, and the lamellar eutectoid Fe3O4 / α-Fe structure accounts for 71.3% of the total iron scale. This type of iron oxide scale is not easy to fall off during processing deformation. Example 3

[0040] The weight percentages of the components in the steel billet of this embodiment are: C: 0.442%, Si: 0.2683%, Mn: 0.6413%, S: 0.0012%, P: 0.0159%, Ni: 0.0056%, Cr: 0.0089%, Alt: 0.0415%, and the remainder is iron and residue; the production method thereof comprises:

[0041] (1) The intermediate billet after rough rolling and descaling is subjected to finish rolling, with the finishing rolling inlet temperature of 1000°C and the final rolling temperature of 850°C to obtain the finished rolled plate;

[0042] (2) Cooling the finished rolled plate by front-stage concentrated laminar cooling at a cooling rate of 31.3°C / s to obtain a plate strip;

[0043] (3) coiling the strip at a coiling temperature of 570° C. to obtain a hot-rolled steel coil;

[0044] (4) Stacking the hot-rolled steel coils in a pit and cooling them to room temperature.

[0045] The structure of the iron oxide scale on the surface of the steel plate in this embodiment is shown in the figure below. Figure 4As shown in the figure, the average total thickness is 9.773μm; the iron oxide scale contains Fe3O4 and lamellar eutectoid Fe3O4 / α-Fe structure, the average interlamellar spacing of the lamellar eutectoid Fe3O4 / α-Fe structure is 192nm, and the lamellar eutectoid Fe3O4 / α-Fe structure accounts for 58.6% of the total iron scale. This type of iron oxide scale is not easy to fall off during processing deformation.

[0046] Comparative Example 1

[0047] The weight percentages of the components in the steel billet of this comparative example are: C: 0.439%, Si: 0.2341%, Mn: 0.6773%, S: 0.0011%, P: 0.0133%, Ni: 0.0095%, Cr: 0.0176%, Alt: 0.0356%, and the remainder is iron and residue; the production method thereof comprises:

[0048] (1) The intermediate billet after rough rolling and descaling is subjected to finish rolling, with the finishing rolling inlet temperature of 1040°C and the final rolling temperature of 910°C to obtain the finished rolled plate;

[0049] (2) Cooling the finished rolled plate by front-stage concentrated laminar cooling at a cooling rate of 35.7°C / s to obtain a plate strip;

[0050] (3) coiling the strip at a coiling temperature of 590° C. to obtain a hot-rolled steel coil;

[0051] (4) directly stacking the hot-rolled steel coils and cooling them to room temperature.

[0052] The structure of the iron oxide scale on the surface of the steel plate in this comparative example is shown in the figure below. Figure 5 As shown, the average total thickness is 11.695μm; the iron oxide scale contains FeO, Fe3O4 and lamellar eutectoid Fe3O4 / α-Fe structure, the average interlamellar spacing of the lamellar eutectoid Fe3O4 / α-Fe structure is 265nm, and the lamellar eutectoid Fe3O4 / α-Fe structure accounts for 16.8% of the total iron scale. Due to the low content of Fe3O4 and lamellar eutectoid Fe3O4 / α-Fe in the iron oxide scale and the large amount of FeO, the iron oxide scale is easy to break and fall off after processing and deformation.

Claims

1. A method for producing a fine lamellar eutectoid iron oxide scale steel plate, characterized in that: The following steps are involved: (1) finishing rolling the intermediate billet after rough rolling and descaling to obtain a finished rolled plate; the inlet temperature of the finishing rolling is ≤1030°C, and the final rolling temperature of the finishing rolling is 850°C to 900°C; (2) Cooling the finished rolled plate to obtain a plate strip; the cooling adopts front-stage concentrated laminar cooling, and the cooling rate is 30°C / s to 50°C / s; (3) Coiling the strip to obtain a hot-rolled steel coil; the coiling temperature is 540° C. to 570° C.; (4) stacking the hot-rolled steel coils in a pit and cooling them to room temperature; The mass percentages of Si, Ni and Cr in the steel plate are controlled as follows: Si≤0.5%, Ni≤0.01%, Cr≤0.5%; The lamellar spacing of the lamellar eutectoid Fe3O4 / α-Fe structure in the surface iron oxide scale of the steel plate produced by the method is 80nm-200nm, the lamellar eutectoid Fe3O4 / α-Fe structure accounts for more than 50% of the total iron oxide scale, and the total iron oxide scale thickness is less than 10um.

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