800mpa-grade magnetic pole steel for pumped storage hydroelectric generating unit and production method thereof

Abstract

The application discloses a 800MPa-grade magnetic pole steel for pumped storage hydroelectric generating set, which is characterized by the following components and wt%: C: 0.25-0.30%, Si: 0.10-0.20%, Mn: 1.1-1.5%, Cr: 0.2-0.3%, Ti: 0.1-0.2%, B: 0.0025-0.0030%, P: ≤0.015%, S: ≤0.010%, and Als: 0.02-0.10%. The production method comprises the following steps: pouring into a blank after conventional smelting; heating the cast blank; adopting 7-pass hot rolling to the product thickness; carrying out laminar cooling; coiling; annealing; and straightening. The application does not contain valuable alloy elements such as Nb and Mo, and the yield strength of the application is greater than or equal to 800MPa, the elongation A is greater than or equal to 12%, the magnetic induction performance B 50 ≥1.60T, which can fully meet the demand of the 800MPa-grade magnetic pole steel for the pumped storage hydroelectric generator rotor with a rated rotating speed of 600r / min, the product thickness of the application is not more than 2mm, and the cost can be reduced by 600-900 yuan / ton of steel compared with the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of motor steel and production method, exactly belongs to a kind of 800MPa grade magnetic pole steel and production method for pumped storage hydroelectric generating set. BACKGROUND

[0002] Pumped storage power station is the most mature technology, the most optimal economy, the most large-scale development conditions of green low-carbon clean flexible regulating power source of electric power system, and wind power, solar power generation, nuclear power, thermal power etc. Better cooperation.

[0003] Magnetic pole steel is used in the rotor magnetic pole part of pumped storage generator structure, is the main component for generating magnetic field of hydroelectric generator, belongs to rotating component, requires good electromagnetic performance and mechanical property, generally thickness≤2.0mm. With the increase of rated speed of unit, the strength requirement of the required magnetic pole steel plate also increases, thus for the pumped storage hydroelectric generating set with rated speed of 600r / min, the demand of yield strength≥800MPa, thickness≤2.0mm extremely thin gauge magnetic pole steel is proposed.

[0004] Through retrieval:

[0005] The document of Chinese patent application No.CN201210165348.7 discloses "a kind of manufacturing method of high magnetic induction low cost 250MPa grade cold-rolled magnetic pole steel", and its process includes: heating slab to 1200-1260℃, and keeping warm;Hot rolling: final rolling temperature is 850-900℃, coiling temperature is 550-630℃, and cooling mode adopts jet type water cooling mode;Cooling to 60-80℃ for pickling, and cooling mode adopts air cooling mode;Cold rolling: cold rolling reduction is 50-75%;Continuous annealing: soaking temperature is 720-780℃, and soaking time is 60~200s;0.8-1.4% flat extension rate is adopted for flattening, and 250MPa grade cold-rolled magnetic pole steel is prepared. But the yield strength of the produced magnetic pole steel is only 250MPa grade.

[0006] The document with Chinese patent application number CN200910049782.7 discloses a manufacturing method of 500MPa grade cold-rolled magnetic pole steel. The main chemical components of the slab in weight percentage are: C: 0.07-0.10%, Si: 0.18-0.31%, Mn: 1.00-1.50%, P: ≤0.02%, S: ≤0.007%, O ≤0.004%, N ≤0.004%, Nb: 0.046-0.060%, Ti: ≤0.003%, V: 0.050-0.070%, and the balance is Fe and inevitable impurities. It is prepared by the following steps: (1) heating the slab to 1200-1260℃, then rolling the slab into thin steel plate, the final rolling temperature is 830-890℃, and the slab is cooled to 550-600℃ by laminar cooling mode for coiling; (2) cooling by air cooling mode, and pickling; (3) cold rolling; (4) continuous annealing: the temperature of the soaking section of the annealing furnace is controlled at 740-760℃, the speed of the annealing process section is controlled at 120-125m / min, and the soaking section time is controlled at 230-239s; (5) flattening. But the yield strength of the product can only reach 570MPa.

[0007] The document with Chinese patent application number ZL202110575161.3 discloses a tensile strength ≥850MPa magnetic yoke steel with excellent fatigue resistance. The chemical components and weight percentage are: C: 0.03-0.07%, Si: ≤0.15%, Mn: 0.5-1.0%, P: ≤0.015%, S: ≤0.002%, Nb: 0.075-0.095%, V: 0.015-0.025%, Mo: 0.20-0.30%, Als: 0.02-0.10%, N: ≤0.010%, and the balance is Fe and inevitable impurities. Although the yield strength is ≥800MPa, it is close, but it still contains Mo, Nb, V and other precious metals, resulting in high alloy cost. SUMMARY

[0008] The present application aims to overcome the shortcomings of the prior art, and provides an 800MPa grade magnetic pole steel for pumped storage hydroelectric generating set with thickness ≤2.0mm, yield strength ≥800MPa, tensile strength ≥850MPa, elongation A ≥12%, magnetic induction performance B 50 ≥1.6T, and a production method thereof.

[0009] The measures to achieve the above-mentioned purposes are:

[0010] The application discloses a 800MPa-grade magnetic pole steel for a pumped storage hydroelectric generating set, and the components and the weight percentage content of the 800MPa-grade magnetic pole steel are as follows: C: 0.25-0.30%, Si: 0.10-0.20%, Mn: 1.1-1.5%, Cr: 0.2-0.3%, Ti: 0.1-0.2%, B: 0.0025-0.0030%, P: <=0.015%, S: <=0.010%, Als: 0.02-0.10%, and the rest is Fe and inevitable inclusions.

[0011] Preferably, the weight percentage content of Cr is 0.23-0.27%.

[0012] Preferably, the weight percentage content of Ti is 0.1-0.15%.

[0013] The application further discloses a method for producing the 800MPa-grade magnetic pole steel for the pumped storage hydroelectric generating set, and the steps are as follows:

[0014] 1) pouring into a blank after conventional smelting, during which the thickness of the cast blank is controlled to be 60-85mm;

[0015] 2) heating the cast blank, and controlling the soaking temperature to be 1150-1200 DEG C and the soaking time to be not less than 30min;

[0016] 3) adopting 7-pass hot rolling to the product thickness, and controlling the opening rolling temperature to be not less than 1050 DEG C and the final rolling temperature to be 850-900 DEG C;

[0017] 4) laminar cooling is conducted, the cooling speed is 50-70 DEG C / s, and the winding temperature is reached;

[0018] 5) winding is conducted, and the winding temperature is controlled to be 400-500 DEG C.

[0019] 6) annealing is conducted, the annealing heating temperature is controlled to be 600-640 DEG C, and the holding time is 3-6h;

[0020] 7) straightening is conducted.

[0021] Preferably, the soaking temperature of the cast blank is 1157-1192 DEG C.

[0022] Preferably, the opening rolling temperature is not less than 1058 DEG C, and the final rolling temperature is 868-892 DEG C.

[0023] The application further discloses the role and mechanism of each element and the main process.

[0024] The carbon (C) content of the present application is 0.25% to 0.30%, and carbon is the most economical strengthening element. However, if the carbon content is between 0.07-0.15%, the steel will have a peritectic reaction during casting, increasing the risk of continuous casting leakage, and too high carbon content will reduce the magnetic induction performance, so the carbon content is limited to 0.25% to 0.30%, which can improve the strength of the steel, ensure the magnetic induction performance of the steel, and greatly reduce the addition of alloying elements and reduce the cost.

[0025] The manganese (Mn) content of the present application is 1.1% to 1.5%, and manganese can reduce the phase transition temperature of austenite to ferrite, expand the hot working temperature range, and is beneficial to refining the ferrite grain size and improving the yield strength of the steel.

[0026] The chromium (Cr) content of the present application is 0.2% to 0.3%, and chromium is a carbide forming element with strong affinity for carbon, which can hinder the diffusion of carbon atoms, Cr is beneficial to refining the ferrite grain and improving the strength of the steel plate, and too high is not conducive to the magnetic performance. In the present application, the chromium content is controlled to be 0.2% to 0.3%, and preferably: the weight percentage content of Cr is 0.23% to 0.27%.

[0027] The titanium (Ti) content of the present application is 0.1% to 0.2%, Ti is a strong carbide and nitride forming element, and the formed carbon and nitride particles can prevent austenite grain growth during reheating and high temperature austenite region rough rolling, play a role in refining the grain, and improve the toughness of the steel. The fine and dispersed TiC precipitated in the coiling stage can have a significant precipitation strengthening effect, thereby effectively improving the strength of the steel plate. The present application selects Ti content of 0.1% to 0.2%, and preferably: the weight percentage content of Ti is 0.10% to 0.15%.

[0028] The silicon (Si) content of the present application is 0.10% to 0.20%, Si has a solid solution strengthening effect, which can improve the strength of the steel and is beneficial to the magnetic performance, and when the silicon content exceeds a certain range, it will be not conducive to the surface quality, therefore, the Si content is controlled to be 0.10% to 0.20%.

[0029] The phosphorus (P) content of the present application is ≤0.015%, and the sulfur (S) content is ≤0.010%. Phosphorus has adverse effects in steel, such as causing segregation and reducing magnetic induction performance. Sulfur easily combines with manganese to form MnS inclusions, affecting the magnetic induction performance and plasticity of the steel. Therefore, the present application should minimize the adverse effects of phosphorus and sulfur elements on the performance of the steel, control the phosphorus and sulfur content by deep desulfurization pretreatment of the molten iron, and thereby reduce the adverse effects.

[0030] The content of boron (B) in the present application is 0.0025% to 0.0030%, the main role of B is as a surface active element, adsorbed on the austenite grain boundary, delaying the transformation of austenite to ferrite, thereby refining the final structure, achieving strengthening effect, and B is extremely cheap, which has a significant effect on cost control. However, if the content of B is too high, low-melting eutectic will be formed, concentrated in the grain boundary, thereby causing thermal brittleness. Therefore, the content of boron in the present application is in the range of 0.0025% to 0.0030%.

[0031] The reason why the present application controls the soaking temperature of the cast blank to be 1150-1200℃ is to ensure complete solid solution of alloying elements and sufficient austenitizing, while improving the uniformity of slab temperature, reducing the deformation resistance and rolling load, which is beneficial to rolling of thin gauge magnetic yoke steel.

[0032] The purpose of controlling the finish rolling temperature to be 850-900℃, the cooling speed to be 50-70℃ / s, and the coiling temperature to be 400-500℃ in the present application is to obtain bainite structure with high cooling speed, fully play the effects of microstructure strengthening and fine-grain strengthening, and at the same time, through the annealing temperature of 600-640℃, make TiC particles fully precipitate, fully play the effect of precipitation strengthening, and improve the strength of the steel plate.

[0033] The present application does not contain valuable alloying elements such as Nb and Mo, and has a yield strength ≥800MPa, an elongation A ≥12%, and a magnetic induction performance B 50 ≥1.60T, which can fully meet and be applied to the demand of 800MPa grade magnetic pole steel for the pump storage hydro-generator rotor with a rated speed of 600r / min, the thickness of the product is not more than 2mm, and the cost can be reduced by 600-900yuan / ton of steel compared with the prior art. DETAILED DESCRIPTION

[0034] The present application will be described in detail as follows:

[0035] Table 1 is a list of component values of each embodiment and the comparative example of the present application;

[0036] Table 2 is a list of process parameter values and performance detection of each embodiment and the comparative example of the present application.

[0037] Each embodiment of the present application is produced according to the following steps:

[0038] 1) After conventional smelting, cast into a blank, during which the thickness of the cast blank is controlled to be 60-85mm;

[0039] 2) Heat the cast blank, control the soaking temperature to be 1150-1200℃, and control the soaking time to be not less than 30min;

[0040] 3) Hot rolling for 7 passes to the product thickness: control the starting rolling temperature not less than 1050℃, and the final rolling temperature at 850-900℃;

[0041] 4) Perform laminar cooling, the cooling rate is 50-70℃ / s, and cool to the coiling temperature;

[0042] 5) Perform coiling, and control the coiling temperature at 400-500℃.

[0043] 6) Perform annealing, control the annealing heating temperature at 600-640℃, and the holding time is 3-6h; 7) Perform straightening.

[0044] Table 1: Chemical composition list (wt%) of each embodiment of the present application and the comparative examples

[0045]

[0046] Table 2: Main process parameter list of each embodiment of the present application and the comparative examples

[0047]

[0048]

[0049] Table 3: Mechanical property test result list of each embodiment of the present application and the comparative examples

[0050]

[0051] From Table 3, it can be seen that each embodiment of 1-8 meets the market demand with the yield strength ≥800MPa, the elongation A ≥12%, and the magnetic induction performance B 50 ≥1.60T, and the hot rolled plate thickness is rolled to not more than 2mm.

[0052] The specific embodiments are only the best examples, and are not the restrictive implementation of the technical solutions of the present application.

Claims

1. A method for producing 800MPa grade magnetic pole steel for a pumped storage hydroelectric generator set, comprising the following steps: 1) After conventional smelting, the steel is cast into billets, during which the thickness of the billets is controlled at 60-85 mm; 2) Heat the ingot, control the soaking temperature at 1150~1200℃, and control the soaking time to be no less than 30min; 3) Use 7 passes of hot rolling to the product thickness: control the starting rolling temperature to be no less than 1050℃, and the finishing rolling temperature to be between 850℃ and 900℃; 4) Perform laminar cooling at a cooling rate of 50-70°C / s to the coiling temperature; 5) Coil the steel and control the coiling temperature at 400-500°C; 6) Perform annealing, control the annealing heating temperature to 600-640°C, and the holding time to 3-6 hours; 7) Straightening; The 800MPa grade magnetic pole steel used in the pumped storage hydropower unit has the following components and weight percentages: C: 0.25-0.30%, Si: 0.10-0.20%, Mn: 1.45-1.5%, Cr: 0.2-0.3%, Ti: 0.19-0.2%, B: 0.0025-0.0030%, P: ≤0.015%, S: ≤0.010%, Als: 0.02-0.10%, and the remainder is Fe and unavoidable inclusions.

2. The method for producing 800 MPa grade magnetic pole steel for a pumped storage hydroelectric generator set according to claim 1, characterized in that: The uniform heating temperature of the ingot is between 1157 and 1192°C.

3. The method for producing 800 MPa grade magnetic pole steel for a pumped storage hydroelectric generator set according to claim 1, wherein: The starting rolling temperature is not lower than 1058℃, and the final rolling temperature is between 868 and 892℃.

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