Control method for eliminating surface line scales of duplex stainless steel hot coil

Abstract

The invention discloses a control method for eliminating line scales on the surface of a duplex stainless steel hot coil. The technical problem of the line scales on the surface of the duplex stainless steel hot coil is solved. The control method comprises the steps that S1, raw materials are subjected to smelting and slab continuous casting, and a casting blank is obtained; s2, the casting blank is subjected to coping treatment through coping equipment; s3, the casting blank is heated through heating equipment; s4, dephosphorization treatment is conducted on the casting blank through high-pressure water dephosphorization equipment; and S5, the casting blank is subjected to hot rolling treatment through a rolling mill. By controlling the casting blank coping parameters, adjusting the hot rolling heating air-fuel ratio and optimizing the high-pressure water descaling process parameters, the line scales on the surface of the duplex stainless steel hot coil are effectively eliminated, and therefore the surface quality of the duplex stainless steel hot coil is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of stainless steel production and processing, and particularly relates to a control method for eliminating surface line scale of hot coil of duplex stainless steel. BACKGROUND

[0002] The duplex stainless steel has the characteristics of austenite and ferrite two-phase structure, is widely applied to the fields of chemical industry, ocean engineering, food processing and the like which have strict requirements on comprehensive performance of materials due to excellent corrosion resistance, strength and processing performance. However, the surface line scale defect has been a key problem restricting the improvement of product quality in the production process of the hot coil.

[0003] The surface line scale defect of the hot coil is generally a heavy grinding mark caused by poor grinding quality of the casting blank, is pressed on the surface of the steel plate after heating and rolling, and is peeled off to form in the subsequent pickling process. The significant feature of the distribution is in the form of intermittent straight lines.

[0004] The surface line scale defect of the hot coil influences the consistency of the surface state of the stainless steel, and the uneven microstructure easily causes the residual and aggregation of corrosive media (such as chloride, acid liquid and the like), accelerates local corrosion (such as pitting corrosion and crevice corrosion), and shortens the service life of the material. Therefore, the elimination of the surface line scale of the hot coil of the duplex stainless steel can realize the fundamental improvement of the surface quality of the hot coil of the duplex stainless steel. SUMMARY

[0005] In order to solve all or part of the above problems, the purpose of the present application is to provide a control method for eliminating the surface line scale of the hot coil of the duplex stainless steel, which effectively eliminates the surface line scale of the hot coil of the duplex stainless steel by controlling the grinding parameters of the casting blank, adjusting the air-fuel ratio of the hot rolling, and optimizing the process parameters of the high-pressure water descaling, so as to improve the surface quality of the hot coil of the duplex stainless steel.

[0006] The present application provides a control method for eliminating the surface line scale of the hot coil of the duplex stainless steel, which comprises the following steps:

[0007] S1, melting and slab continuous casting are performed on raw materials to obtain a casting blank;

[0008] S2, the casting blank is subjected to grinding treatment by a grinding device;

[0009] S3, the casting blank is subjected to heating treatment by a heating device;

[0010] S4, the casting blank is subjected to descaling treatment by a high-pressure water descaling device;

[0011] S5, the casting blank is subjected to hot rolling treatment by a rolling mill;

[0012] In S2, after the billet is coarsely ground with a coarse grinding wheel, it is finely ground with a fine grinding wheel to achieve a surface roughness Rz of 40-60μm.

[0013] Optionally, in S2, the grit size of the coarse grinding wheel is selected to be 16-24#.

[0014] Optionally, in S2, the grit size of the fine grinding wheel is selected to be 40-54#.

[0015] Optionally, in S2, the grinding pressure of the grinding equipment is controlled to be 10-20KN.

[0016] Optionally, in S2, the grinding current of the grinding equipment is controlled to be 15-45A.

[0017] Optionally, in S2, the trolley forward speed of the grinding equipment is controlled to be 20-30 m / min.

[0018] Optionally, in S3, the air-fuel ratio during the billet heating process is controlled to be 3.5-3.9.

[0019] Optionally, in S4, the descaling water impact force of the high-pressure water descaling equipment is controlled to be 1.5-2.5 N / cm. 2 .

[0020] Optionally, in S1, the chemical composition of the billet by mass percentage is: C≤0.030%, Si≤1.00%, Mn≤2.00%, P≤0.035%, S≤0.020%, Cr: 21.0%-23.0%, Ni: 4.50%-6.50%, Mo: 2.5%-3.5%, N: 0.08%-0.20%, with the remainder being Fe and unavoidable impurities.

[0021] As can be seen from the above technical solution, the control method for eliminating surface scale on duplex stainless steel hot-rolled coils provided by the present invention has the following advantages:

[0022] This control method effectively eliminates surface scale on duplex stainless steel hot-rolled coils by controlling the billet grinding parameters, adjusting the hot-rolling heating air-fuel ratio, and optimizing the high-pressure water descaling process parameters, thereby improving the surface quality of duplex stainless steel hot-rolled coils.

[0023] Other features and advantages of the present invention will be set forth in the following description. Attached Figure Description

[0024] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0025] Figure 1This is a flowchart illustrating the control method in an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the surface of the cast billet before the grinding process was improved.

[0027] Figure 3 This is a schematic diagram of the surface of the refurbished casting after the improvement of the refurbishment process;

[0028] Figure 4 A schematic diagram of the surface of a hot-rolled coil produced using existing processes;

[0029] Figure 5 A schematic diagram of the surface of a hot-rolled coil produced to improve the manufacturing process. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be arbitrarily combined with each other.

[0031] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 The illustration shows an embodiment of the present invention, which discloses a method for controlling the elimination of surface scale on duplex stainless steel hot-rolled coils, comprising the following steps:

[0032] S1, the raw materials are smelted and slabs are continuously cast to obtain a cast billet;

[0033] S2, the billet is ground using a grinding equipment;

[0034] S3 involves heating the billet using heating equipment;

[0035] S4, the billet is dephosphorized using a high-pressure water dephosphorization device;

[0036] S5 involves hot rolling the billet using a rolling mill.

[0037] In S1, the chemical composition of the billet by mass percentage is: C≤0.030%, Si≤1.00%, Mn≤2.00%, P≤0.035%, S≤0.020%, Cr: 21.0%-23.0%, Ni: 4.50%-6.50%, Mo: 2.5%-3.5%, N: 0.08%-0.20%, with the remainder being Fe and unavoidable impurities.

[0038] In S2, after the billet is coarsely ground with a coarse grinding wheel, it is finely ground with a fine grinding wheel to make the surface roughness Rz of the billet 40-60μm after grinding, ensuring that there is no iron oxide scale residue on the surface of the billet after grinding.

[0039] In step S2, the coarse grinding wheel grit size is selected as 16-24#, and the fine grinding wheel grit size is selected as 40-54#. In this embodiment, the coarse grinding wheel grit size is 20#, and the fine grinding wheel grit size is 46#. Simultaneously, the grinding pressure of the grinding equipment is controlled at 10-20KN, the grinding current at 15-45A, and the trolley forward speed at 20-30m / min.

[0040] Controlling the air-fuel ratio during the billet heating process is a crucial factor affecting the surface quality of the hot-rolled coil. When the air-fuel ratio increases, the oxide scale formed on the billet surface becomes looser and easier to peel off. Therefore, in S3, the air-fuel ratio (air volume / mixed gas volume) during the billet heating process is adjusted from the traditional 2.5-2.7 to 3.5-3.9. This enhances the surface oxidation of the billet within the heating furnace, creating favorable conditions for the subsequent high-pressure water descaling process.

[0041] Based on increasing the air-fuel ratio for heating, in S4, the descaling water impact force of the high-pressure water descaling equipment is controlled to be 1.5-2.5 N / cm. 2 The high-pressure water descaling technology thoroughly removes the uneven oxide scale from the surface of the billet, effectively avoiding hot-rolled wire scale defects caused by residual oxide scale during the rolling process, thus ensuring the flatness and smoothness of the hot-rolled surface.

[0042] As can be seen from the above process, the control method completely eliminates surface scale defects in duplex stainless steel hot-rolled coils, improves the surface consistency of the hot-rolled coils, reduces the residue and accumulation of corrosive media, lowers the risk of localized corrosion, and enhances the market competitiveness of duplex stainless steel coils.

[0043] To illustrate this application more clearly, the following detailed description is provided in conjunction with comparative examples and specific embodiments:

[0044] Example 1

[0045] S1, the raw materials are smelted and slabs are continuously cast to obtain a billet, and the chemical composition of the billet by mass percentage is: C: 0.015%, Si: 0.45%, Mn: 1.43%, P: 0.025%, S: 0.001%, Cr: 22.36%, Ni: 5.05%, Mo: 3.06%, N: 0.15%, with the remainder being Fe and unavoidable impurities.

[0046] S2, a 200mm thick duplex stainless steel billet is subjected to "coarse grinding with 20# grinding wheel + fine grinding with 46# grinding wheel", while controlling the grinding pressure to 12KN, the grinding current to 25A, and the trolley forward speed to 30m / min, so that the surface roughness Rz of the billet after grinding is 35μm.

[0047] S3, adjust the air-fuel ratio (air volume / mixed gas volume) during the billet heating process to 3.6.

[0048] S4, controlling the descaling water's impact force to 1.5 N / cm. 2 .

[0049] S5, hot rolling of the billet.

[0050] Example 2

[0051] S1, the raw materials are smelted and slabs are continuously cast to obtain a billet, and the chemical composition of the billet by mass percentage is: C: 0.010%, Si: 0.48%, Mn: 1.25%, P: 0.028%, S: 0.001%, Cr: 22.36%, Ni: 5.08%, Mo: 3.12%, N: 0.16%, with the remainder being Fe and unavoidable impurities.

[0052] S2, a 200mm thick duplex stainless steel billet is subjected to "coarse grinding with 20# grinding wheel + fine grinding with 46# grinding wheel", while controlling the grinding pressure at 15KN, the grinding current at 30A, and the trolley forward speed at 25m / min, so that the surface roughness Rz of the billet after grinding is 40μm.

[0053] S3, adjust the air-fuel ratio (air volume / mixed gas volume) during the billet heating process to 3.8.

[0054] S4, controlling the descaling water's impact force to 1.8 N / cm. 2 .

[0055] S5, hot rolling of the billet.

[0056] Example 3

[0057] S1, the raw materials are smelted and slabs are continuously cast to obtain a billet, and the chemical composition of the billet by mass percentage is: C: 0.012%, Si: 0.46%, Mn: 1.33%, P: 0.027%, S: 0.001%, Cr: 22.28%, Ni: 5.06%, Mo: 3.09%, N: 0.15%, with the remainder being Fe and unavoidable impurities.

[0058] S2, a 200mm thick duplex stainless steel billet is subjected to "coarse grinding with 20# grinding wheel + fine grinding with 46# grinding wheel", while controlling the grinding pressure to 19KN, the grinding current to 40A, and the trolley forward speed to 20m / min, so that the surface roughness Rz of the billet after grinding is 50μm.

[0059] S3, adjust the air-fuel ratio (air volume / mixed gas volume) during the billet heating process to 3.9.

[0060] S4, controlling the descaling water's impact force to 2.3 N / cm. 2 .

[0061] S5, hot rolling of the billet.

[0062] Example 4

[0063] S1, the raw materials are smelted and slabs are continuously cast to obtain a billet, and the chemical composition of the billet by mass percentage is: C: 0.015%, Si: 0.45%, Mn: 1.43%, P: 0.025%, S: 0.001%, Cr: 22.36%, Ni: 5.05%, Mo: 3.06%, N: 0.15%, with the remainder being Fe and unavoidable impurities.

[0064] S2, a 200mm thick duplex stainless steel billet is subjected to "rough grinding with a 16# grinding wheel + fine grinding with a 40# grinding wheel", while controlling the grinding pressure at 12KN, the grinding current at 25A, and the trolley forward speed at 30m / min, so that the surface roughness Rz of the billet after grinding is 40μm.

[0065] S3, adjust the air-fuel ratio (air volume / mixed gas volume) during the billet heating process to 3.6.

[0066] S4, controlling the descaling water's impact force to 1.7 N / cm. 2 .

[0067] S5, hot rolling of the billet.

[0068] Example 5

[0069] S1, the raw materials are smelted and slabs are continuously cast to obtain a billet, and the chemical composition of the billet by mass percentage is: C: 0.010%, Si: 0.48%, Mn: 1.25%, P: 0.028%, S: 0.001%, Cr: 22.36%, Ni: 5.08%, Mo: 3.12%, N: 0.16%, with the remainder being Fe and unavoidable impurities.

[0070] S2, a 200mm thick duplex stainless steel billet is subjected to "coarse grinding with 24# grinding wheel + fine grinding with 54# grinding wheel", while controlling the grinding pressure at 15KN, the grinding current at 30A, and the trolley forward speed at 25m / min, so that the surface roughness Rz of the billet after grinding is 35μm.

[0071] S3, adjust the air-fuel ratio (air volume / mixed gas volume) during the billet heating process to 3.8.

[0072] S4, controlling the descaling water's impact force to 1.6 N / cm. 2 .

[0073] S5, hot rolling of the billet.

[0074] Comparative Example

[0075] S1 involves melting raw materials and continuously casting slabs to obtain cast billets.

[0076] S2. A 200mm thick duplex stainless steel billet is rough-ground using a 20# grinding wheel. The grinding pressure is controlled at 20KN, the grinding current at 45A, and the trolley forward speed at 20m / min. After grinding, the surface roughness Rz of the billet is 65μm.

[0077] S3, the air-fuel ratio (air volume / mixed gas volume) during the billet heating process is 2.6.

[0078] S4, controlling the descaling water's impact force to 1.3 N / cm. 2 .

[0079] S5, hot rolling of the billet.

[0080] The surface conditions of the cast billets after grinding and the surface conditions of the rolled plates in Examples 1-5 and the comparative examples were compared, and the comparison results are shown in Table 1.

[0081] Table 1 Comparison of Examples 1-5 with Comparative Examples

[0082] Comparative result Example 1 The surface of the cast slab after grinding had no obvious grinding marks, and the surface of the plate after rolling had no linear defects Example 2 The surface of the cast slab after grinding had no obvious grinding marks, and the surface of the plate after rolling had no linear defects Example 3 The surface of the cast slab after grinding had no obvious grinding marks, and the surface of the plate after rolling had no linear defects Example 4 The surface of the cast slab after grinding had no obvious grinding marks, and the surface of the plate after rolling had no linear defects Example 5 The surface of the cast slab after grinding had no obvious grinding marks, and the surface of the plate after rolling had no linear defects Comparative example The surface of the cast slab after grinding had serious grinding stripes, and the surface of the plate after rolling had linear defects

[0083] like Figures 2-5 As shown, rough grinding will cause heavier grinding marks, while higher grinding pressure and slower grinding speed will cause more severe grinding striations (such as...). Figure 2 As shown). Using a rough grinding followed by fine grinding method can reduce grinding marks (e.g., ...) while removing surface defects from the cast billet. Figure 3 As shown), this is beneficial for removing linear scale from the surface of the rolled sheet. Increasing the air-fuel ratio during billet heating and increasing the descaling water impact force can effectively remove iron scale from the billet surface, preventing it from being pressed in and elongated during rolling to form linear defects (such as...). Figure 4 , Figure 5 (As shown).

[0084] It should be noted that, unless otherwise stated, the technical or scientific terms used in this invention should have the ordinary meaning as understood by one of ordinary skill in the art.

[0085] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention 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 controlling surface scaling of duplex stainless steel hot-rolled coils, characterized in that, Includes the following steps: S1, the raw materials are smelted and slabs are continuously cast to obtain a cast billet; S2, the billet is ground using a grinding equipment; S3 involves heating the billet using heating equipment; S4, the billet is dephosphorized using a high-pressure water dephosphorization device; S5, hot rolling of the billet using a rolling mill; In S2, after the billet is coarsely ground with a coarse grinding wheel, it is finely ground with a fine grinding wheel to achieve a surface roughness Rz of 40-60μm.

2. The control method for eliminating surface scale on duplex stainless steel hot-rolled coils according to claim 1, characterized in that, In S2, the grit size of the coarse grinding wheel is selected as 16-24#.

3. The control method for eliminating surface scale on duplex stainless steel hot-rolled coils according to claim 1, characterized in that, In S2, the grit size of the fine grinding wheel is selected as 40-54#.

4. The control method for eliminating surface scale on duplex stainless steel hot-rolled coils according to claim 1, characterized in that, In S2, the grinding pressure of the grinding equipment is controlled to be 10-20KN.

5. The control method for eliminating surface scale on duplex stainless steel hot-rolled coils according to claim 1, characterized in that, In S2, the grinding current of the grinding equipment is controlled to be 15-45A.

6. The control method for eliminating surface scale on duplex stainless steel hot-rolled coils according to claim 1, characterized in that, In S2, the trolley speed of the grinding equipment is controlled to be 20-30 m / min.

7. The control method for eliminating surface scale on duplex stainless steel hot-rolled coils according to claim 1, characterized in that, In S3, the air-fuel ratio during the billet heating process is controlled to be 3.5-3.

9.

8. The control method for eliminating surface scale on duplex stainless steel hot-rolled coils according to claim 3, characterized in that, In S4, the descaling water impact force of the high-pressure water descaling equipment is controlled at 1.5-2.5 N / cm. 2 .

9. The control method for eliminating surface scale on duplex stainless steel hot-rolled coils according to claim 1, characterized in that, In S1, the chemical composition of the billet by mass percentage is: C≤0.030%, Si≤1.00%, Mn≤2.00%, P≤0.035%, S≤0.020%, Cr: 21.0%-23.0%, Ni: 4.50%-6.50%, Mo: 2.5%-3.5%, N: 0.08%-0.20%, with the remainder being Fe and unavoidable impurities.

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