High silicon steel material with excellent pickling effect and production method

Abstract

The application relates to the technical field of high-silicon steel materials, in particular to a high-silicon steel material with excellent pickling effect and a production method, which comprises the following steps: S1, continuous casting; S2, hot rolling; wherein the hot rolling comprises rough rolling and finish rolling, and after the finish rolling, laminar cooling is carried out, and the laminar cooling adopts front section cooling; S3, normalizing; S4, straightening; S5, pickling; S6, cold rolling; and S7, recrystallization annealing. On the basis of guaranteeing the high-temperature process of the hot rolling and normalizing procedures, the thickness of the iron oxide skin on the steel plate is controlled to be below 8 microns, the content proportion of the compact Fe3O4 in the iron oxide skin is below 70%, and the pickling effect of the steel plate after the normalizing is significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high silicon steel material, and particularly relates to a high silicon steel material with excellent pickling effect and a production method. BACKGROUND

[0002] The high silicon steel material generally refers to an iron-based material with a silicon content of 2% to 4%, and is an important soft magnetic material for manufacturing high-efficiency variable-frequency compressors, new energy automobile driving motors and generator cores. Due to the high silicon content, the hot-rolled plate needs to be subjected to normalizing and then cold-rolled for production. The normalizing treatment can not only make the hot-rolled structure more uniform and coarsen, but also effectively improve the electromagnetic performance. Meanwhile, the proportion of recrystallized grains is increased, which effectively prevents the corrugated defects on the surface of the strip steel. The surface oxide scale of the high silicon steel after normalizing generally consists of four parts, from outside to inside, Fe2O3, Fe3O4, FeO and Fe2SiO4. Among them, Fe2SiO4 is difficult to be pickled due to its compact structure, and Fe2SiO4 is distributed in scales and is tightly connected with the matrix with strong bonding force. In order to improve the electromagnetic performance, the high silicon steel is generally produced by high-temperature finish rolling combined with high-temperature normalizing process. The high-temperature treatment in the hot-rolling and normalizing processes increases the thickness of the surface oxide scale of the steel plate and changes the structure proportion, and the proportion of poor pickling after normalizing is increased. The poor pickling on the surface of the steel plate will lead to the decline of the surface quality of the finished silicon steel plate, the reduction of the core stacking factor and the deterioration of the motor efficiency, which is one of the important factors affecting the quality of the high silicon steel material.

[0003] A Chinese patent application for invention with the application publication number CN111733362A discloses an easy-to-pickling silicon steel plate and a production method thereof. The application overcomes the problem of the large thickness of the surface oxide scale of the silicon steel plate in the conventional technology by means of the appropriate design of the Si, Mn, Al and other element compositions, and the reasonable cooperation of the steelmaking, hot-rolling and cold-rolling processes, and produces the silicon steel plate with thin oxide scale and easy pickling. The application produces the silicon steel plate with thin oxide scale through the composition design and process optimization, but does not describe the structure content of the oxide scale, and ignores the influence of the normalizing process on the thickness and composition of the oxide scale, and cannot fundamentally solve the problem of poor pickling of the silicon steel plate.

[0004] A Chinese patent for invention with the grant announcement number CN109940043B discloses a preparation method of an easy-to-pickling hot-rolled strip steel. The application adopts a heating method of "high-temperature fast burning", combines the reasonable proportion of air and coal gas, and a large reduction in rough rolling, and through the heating, rough descaling, rough rolling, fine descaling, fine rolling and coiling treatment of the cast blank, the hot-rolled strip steel with the surface oxide scale thickness of ≤7μm is obtained, and the problem of the thick surface oxide scale of the strip steel and the difficulty in pickling is effectively solved. The application effectively solves the problem of the thick oxide scale and the difficulty in pickling through the adjustment of the hot-rolling process parameters, but mainly relates to the plain carbon steel, and has little guiding significance for the production of high silicon steel material products. SUMMARY

[0005] The present application aims at the defects of the prior art, and provides a high-silicon steel material with excellent pickling effect and a production method, so as to reduce the proportion of Fe3O4 and Fe2SiO4 components of the iron scale of the steel plate after normalizing, and effectively improve the pickling effect of the high-silicon steel material after normalizing.

[0006] To solve the above technical problems, in a first aspect, the present application provides a high-silicon steel material with excellent pickling effect, comprising the following components by weight percentage: Si: 1.5% to 4.5%, Als: 0.1% to 1.0%, Si+Als≥2.3%, C, S, N, Ti, O are all less than 0.003%.

[0007] Si and Als are alloy elements in the high-silicon steel, and with the increase of the total content, the resistivity of the silicon steel increases, and the iron loss decreases; but with the increase of the Si content, the thermal conductivity of the material decreases, the time of high-temperature processes such as hot rolling and normalizing increases, and the pickling problem is prone to occur.

[0008] C, S, N, O and Ti are all harmful elements in the silicon steel, and the increase of the content leads to the increase of the non-metallic inclusion content of the high-silicon steel and the substantial increase of the iron loss, and in principle, the lower the content of the harmful elements is, the better.

[0009] In a second aspect, the present application provides a production method of a high-silicon steel material with excellent pickling effect, comprising:

[0010] S1, continuous casting;

[0011] S2, hot rolling; wherein the hot rolling comprises rough rolling and finish rolling, and after the finish rolling, laminar cooling is performed, and the laminar cooling adopts front-stage cooling;

[0012] S3, normalizing;

[0013] S4, straightening;

[0014] S5, pickling;

[0015] S6, cold rolling;

[0016] S7, recrystallization annealing.

[0017] Further, the step S1 comprises: continuously casting the molten steel meeting the requirements into a slab with a thickness of 200 to 280 mm.

[0018] Further, the step S2 comprises:

[0019] S21, heating the slab obtained in step S1 to 1000-1180℃, soaking time ≤200min, preferably low temperature heating to reduce the loss of the billet and avoid the solid solution of large size liquid inclusion in the matrix, rough rolling of the slab to obtain an intermediate billet with a thickness of 30-48mm, high pressure water is used to continuously remove the scale on the surface of the slab at the entrance of the rack during the rough rolling process;

[0020] S22, removing the scale on the surface of the intermediate billet by high pressure water, and finishing rolling the intermediate billet to obtain a cold rolling raw material plate with a thickness of 1.5-2.5mm, high pressure water is used to continuously remove the scale on the surface of the intermediate billet during the finishing rolling process;

[0021] S23, laminar cooling the cold rolling raw material plate to reduce the temperature to 580-680℃ for coiling to form a coiled steel plate.

[0022] The pressure of the high pressure water is ≥20MPa.

[0023] Further, in step S22, the finishing rolling temperature is 800-890℃. Low temperature finishing rolling is preferred to reduce the thickness of the third scale on the surface of the hot rolled steel plate, especially to improve the pinning of the Fe2SiO4 bottom layer of the third scale to the matrix.

[0024] Further, in step S23, after forming the coiled steel plate, nitrogen is used for rapid air cooling of the steel plate to below 380℃. Rapid air cooling of the coiled steel plate to below 380℃ can reduce the eutectoid reaction between FeO on the surface of the steel plate and O2 to produce dense Fe3O4 organization, and nitrogen air cooling is preferred to reduce the O2 content in the gas flow.

[0025] Further, step S3 includes: heating the steel plate to 850-950℃ by electromagnetic induction, air cooling to ambient temperature after normalizing treatment for 2-4min, and the whole normalizing process is carried out under nitrogen protection. The thickness of the scale on the surface of the steel plate after normalizing treatment is ≤8μm, and the proportion of Fe3O4 in the scale is ≤70%.

[0026] Further, step S4 includes: using a tension leveler to mechanically remove the scale on the surface of the steel plate, and the elongation of the tension leveler is controlled at 2-4%.

[0027] Further, step S5 includes: pickling the steel plate in 15-20% hydrochloric acid.

[0028] Further, step S6 includes: one cold rolling of the pickled steel plate to a thickness of 0.30-0.60mm.

[0029] Further, step S7 includes: forming a high silicon steel material finished product after recrystallization annealing at 880-980℃.

[0030] The beneficial effects of the present application are:

[0031] 1、The high silicon steel material produced in the present application controls the thickness of the iron oxide scale on the surface of the steel plate to be below 8 microns, and the proportion of Fe3O4 in the iron oxide scale is below 70%, based on the high temperature process of the hot rolling and normalizing processes, and the pickling effect of the steel plate after normalizing is significantly improved.

[0032] 2、The present application immediately cools the cold-rolled raw material plate after finishing rolling by using the front cooling method, which shortens the residence time of the steel plate in the high temperature section, and is beneficial to reduce the thickness of the iron oxide scale of the hot-rolled steel plate.

[0033] 3、The present application uses nitrogen to quickly air cool the coiled steel plate to below 380℃, further reducing the amount of dense Fe3O4 organization generated by the eutectoid reaction of FeO and O2 on the surface of the steel plate.

[0034] 4、The present application uses high-pressure water to remove the iron oxide scale on the surface of the slab before and during rough rolling, before and during finishing rolling, which can effectively control the thickness of the iron oxide scale on the surface of the steel plate. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The present application is a schematic diagram of the thickness of the iron oxide scale on the surface of the high silicon steel material after normalizing. DETAILED DESCRIPTION

[0036] In order to make the technical problems, technical solutions and beneficial effects of the present application more clear and explicit, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0037] Example 1

[0038] The present application provides a production method of high silicon steel material with excellent pickling effect, which comprises:

[0039] 1) The molten steel after vacuum smelting is continuously cast into a slab with a thickness of 230mm, and the chemical composition of the slab is Si: 3.05%; Als: 0.35%; Si+Als: 3.4%; C, S, N, Ti, O are all less than 0.003%, and the rest is Fe and unavoidable impurity elements;

[0040] 2) The slab is heated by a step-by-step heating furnace, the process temperature is 1110℃, the soaking time is 180min, then the surface iron oxide scale is removed by high-pressure water with a pressure of 23MPa, and the intermediate billet is formed by 5 passes of rough rolling to 38mm, and the residual iron oxide scale is removed by high-pressure water at the inlet of the rough rolling stand;

[0041] 3) the intermediate blank is removed from the surface scale by high pressure water with a pressure of 22 MPa, and then is finished by 7 passes to a thickness of 2.15 mm, with a finish rolling temperature of 850°C, and the surface scale is removed by high pressure water at the entrance of the mill during rolling;

[0042] 4) the steel plate after finishing is cooled by laminar flow, and the temperature is reduced to 620°C for coiling, and the laminar flow uses front section cooling, and the coiled steel plate is cooled by nitrogen gas for 30 s to 350°C;

[0043] 5) the hot-rolled steel plate is heated to 900°C by electromagnetic induction, and is air cooled to ambient temperature after normalizing for 2.5 min, and the steel plate is protected by pure nitrogen gas during normalizing;

[0044] 6) the steel plate after normalizing is broken from the scale by a tension leveler, and is pickled in 18% hydrochloric acid, and the tension leveler elongation is 2.4%.

[0045] By the above process, the thickness of the surface scale of the high silicon steel material after normalizing is 7 μm, the proportion of Fe3O4 in the scale is 64%, and the whiteness of the steel plate surface after pickling is 67%.

[0046] Example 2

[0047] The present embodiment provides a production method of high silicon steel material with excellent pickling effect, comprising:

[0048] 1) the molten steel after vacuum smelting is continuously cast into a slab with a thickness of 230 mm, and the chemical composition of the slab is respectively Si: 3.10%; Als: 0.45%; Si+Als: 3.55%; C, S, N, Ti, O are all less than 0.003%, and the rest is Fe and inevitable impurity elements;

[0049] 2) the slab is heated by a walking beam furnace, the process temperature is 1050°C, and the soaking time is 180 min, and then the surface scale is removed by high pressure water with a pressure of 25 MPa, and the billet is roughed by 5 passes to 35 mm, and the residual scale is removed by high pressure water at the entrance of the roughing mill;

[0050] 3) the intermediate blank is removed from the surface scale by high pressure water with a pressure of 22 MPa, and then is finished by 7 passes to a thickness of 2.20 mm, with a finish rolling temperature of 840°C, and the surface scale is removed by high pressure water at the entrance of the mill during rolling;

[0051] 4) the steel plate after finishing is cooled by laminar flow, and the temperature is reduced to 640°C for coiling, and the laminar flow uses front section cooling, and the coiled steel plate is cooled by nitrogen gas for 35 s to 310°C;

[0052] 5) the hot-rolled steel plate is heated to 910°C by electromagnetic induction, and is air cooled to ambient temperature after normalizing for 2.5 min, and the steel plate is protected by pure nitrogen gas during normalizing;

[0053] 6) After the steel sheet is broken down by the stretcher leveler after normalizing, the steel sheet is pickled in 18% hydrochloric acid, and the stretcher leveler elongation is 2.4%.

[0054] After the above process, the thickness of the surface oxide scale of the high silicon steel material after normalizing is 6 μm, the proportion of Fe3O4 in the oxide scale is 61%, and the whiteness of the steel sheet surface after pickling is 68%.

[0055] Example 3

[0056] The present example provides a production method of a high silicon steel material with excellent pickling effect, comprising:

[0057] 1) The molten steel after vacuum smelting is continuously cast into a slab with a thickness of 230 mm, and the chemical composition of the slab is as follows: Si: 3.00%; Als: 0.75%; Si+Als≥3.75%; C, S, N, Ti, O are all less than 0.003%, and the rest is Fe and unavoidable impurity elements;

[0058] 2) The slab is heated by a walking beam furnace, the process temperature is 1150℃, and the soaking time is 200 min. Then the surface oxide scale is removed by high-pressure water with a pressure of 20 MPa. The billet is roughed by 5 passes to 38 mm, and the residual oxide scale is removed by high-pressure water at the inlet of the roughing mill stand;

[0059] 3) The intermediate billet is removed from the surface oxide scale by high-pressure water with a pressure of 25 MPa, and then is finished by 7 passes to a thickness of 2.10 mm, and the final rolling temperature is 860℃. The surface oxide scale is removed by high-pressure water at the inlet of the rolling mill during rolling;

[0060] 4) After finishing, the steel sheet is cooled by laminar flow to 600℃ for coiling, and the laminar flow uses front cooling. The coiled steel sheet is cooled by 50s nitrogen gas to 300℃;

[0061] 5) The hot-rolled steel sheet is heated to 890℃ by electromagnetic induction, and is air-cooled to ambient temperature after normalizing for 2.5 min. The steel sheet is protected by pure nitrogen gas during normalizing;

[0062] 6) After the steel sheet is broken down by the stretcher leveler after normalizing, the steel sheet is pickled in 18% hydrochloric acid, and the stretcher leveler elongation is 2.8%.

[0063] After the above process, the thickness of the surface oxide scale of the high silicon steel material after normalizing is 6.5 μm, the proportion of Fe3O4 in the oxide scale is 63%, and the whiteness of the steel sheet surface after pickling is 65%.

[0064] Comparative Example 1

[0065] The present example provides a production method of a high silicon steel material with excellent pickling effect, comprising:

[0066] 1) The molten steel after vacuum smelting is continuously cast into a slab with a thickness of 230 mm, and the chemical composition of the slab is as follows: Si: 3.00%; Als: 0.50%; Si+Als≥3.5%; C, S, N, Ti, O are all less than 0.003%, and the rest is Fe and inevitable impurity elements;

[0067] 2) The slab is heated in a walking beam furnace, the process temperature is 1180℃, and the soaking time is 180 min, and then the surface scale is removed by high-pressure water with a pressure of 25 MPa, and the billet is roughed by 5 passes to 35 mm, and the residual scale is removed by high-pressure water at the inlet of the roughing mill;

[0068] 3) The intermediate billet is removed from the surface scale by high-pressure water with a pressure of 25 MPa, and then is finished by 7 passes to a thickness of 2.2 mm, and the final rolling temperature is 880℃, and the surface scale is removed by high-pressure water at the inlet of the rolling mill during rolling;

[0069] 4) After finishing rolling, the steel plate is cooled by laminar flow cooling, and the temperature is reduced to 640℃ for coiling, and the laminar flow cooling is used in the later stage;

[0070] 5) The hot-rolled steel plate is heated to 900℃ in an RTF furnace, and is air-cooled to ambient temperature after normalizing for 2.5 min, and the steel plate is protected by pure nitrogen gas during the normalizing soaking process;

[0071] 6) After normalizing, the steel plate is pickled in 18% hydrochloric acid after breaking the scale by a tension leveler, and the tension leveler elongation is 2.5%.

[0072] After the above process, the thickness of the surface scale of the high-silicon steel material after normalizing is 18μm, the proportion of Fe3O4 in the scale is 89%, and the whiteness of the steel plate surface after pickling is 51%.

[0073] As can be seen from Examples 1 to 3 and Comparative Example 1, in Comparative Example 1, the laminar flow cooling after finishing rolling uses the later stage cooling, and there is no nitrogen rapid air cooling after finishing rolling, which leads to poor pickling effect, and the thickness of the surface scale of the high-silicon steel material after normalizing is as high as 18μm, which is much higher than that of Examples 1 to 3, and the proportion of Fe3O4 in the scale is higher, and the whiteness of the steel plate surface after pickling is lower. Therefore, the high-silicon steel material produced by the method of the present application has a surface scale thickness of less than 8μm after hot rolling and normalizing process, and the proportion of compact Fe3O4 in the scale is less than 70%, and the pickling effect of the steel plate after normalizing is significantly improved.

[0074] The above-described embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A high-silicon steel material with excellent pickling effect, characterized by: The components include the following weight percentages: Si: 1.5% to 4.5%, Al: 0.1% to 1.0%, Si+Al ≥ 2.3%; The production method of the high-silicon steel material with excellent pickling effect comprises the following steps: S1, continuous casting; S2, hot rolling; wherein the hot rolling comprises rough rolling and finish rolling, and after the finish rolling, laminar cooling is performed, and the laminar cooling adopts front section cooling; S3, normalizing; S4, straightening; S5, pickling; S6, cold rolling; S7, recrystallization annealing; Step S2 comprises: S21, heating the slab obtained in step S1 to 1000-1180℃ and performing rough rolling to obtain an intermediate slab with a thickness of 30-48mm, and during the rough rolling, high-pressure water is used to continuously remove the oxide scale on the surface of the slab; S22, using high-pressure water to remove the oxide scale on the surface of the intermediate slab, and performing finish rolling on the intermediate slab to obtain a cold rolling raw material plate with a thickness of 1.5mm-2.5mm, and during the finish rolling, high-pressure water is used to continuously remove the oxide scale on the surface of the intermediate slab; S23, laminar cooling the cold rolling raw material plate, and coiling after the temperature is reduced to 580-680℃, to form a coiled steel plate; In step S22, the finish rolling temperature is 800-890℃; In step S23, after the coiled steel plate is formed, nitrogen gas is used to rapidly air cool the steel plate to below 380℃; Step S3 comprises: heating the steel plate to 850-950℃ by electromagnetic induction, air cooling to ambient temperature after 2-4min normalizing treatment, and the entire normalizing process is performed under nitrogen protection; the thickness of the oxide scale on the surface of the steel plate after the normalizing treatment is ≤8μm, and the proportion of Fe3O4 in the oxide scale is ≤70%; Step S4 comprises: mechanically breaking the oxide scale on the surface of the steel plate by using a straightening machine, and the elongation of the straightening machine is controlled to be 2-4%; Step S5 comprises: pickling the steel plate in 15-20% hydrochloric acid; Step S6 comprises: one-time cold rolling the pickled steel plate to a thickness of 0.30-0.60mm; Step S7 comprises: forming a high-silicon steel material finished product after recrystallization annealing at 880-980℃.

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