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

Abstract

An 800 MPa-grade magnetic pole steel for a pumped storage hydroelectric generating unit, comprising the following components in percentage by weight: 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: performing conventional smelting, and then casting into a billet; heating the cast billet; hot rolling for seven passes to a required product thickness; performing laminar cooling; coiling; annealing; and straightening. The e of the present invention does not contain precious alloying elements such as Nb and Mo, the yield strength thereof is greater than or equal to 800 MPa, the elongation A is greater than or equal to 12%, and the magnetic induction property B50 is greater than or equal to 1.60 T, completely meeting and being suitable for the requirements for 800 MPa-grade magnetic pole steel for a pumped storage hydroelectric generator rotor. Moreover, the product thickness thereof does not exceed 2 mm, so that the cost can be reduce by 600-900 yuan / ton of steel compared with the prior art.

Description

800MPa-grade magnetic pole steel for pumped storage hydroelectric generating set and production method TECHNICAL FIELD

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

[0002] Pumped storage power station is the most mature technology, the most optimal economy, the most flexible regulation power source of green low carbon clean of current technology, and wind power, solar power generation, nuclear power, thermal power etc. It is better to cooperate.

[0003] Magnetic pole steel is used in the structure of pumped storage generator and is used in the rotor magnetic pole part, is the main component of the 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, so the demand of yield strength≥800MPa, thickness≤2.0mm extremely thin specification magnetic pole steel is proposed for pumped storage hydroelectric generating set with rated speed up to 600r / min.

[0004] The yield strength of the reported magnetic pole steel is lower, which cannot meet the demand of yield strength≥800MPa of magnetic pole steel under high speed. SUMMARY

[0005] In order to overcome the deficiencies existing in the prior art, the present application provides an 800MPa-grade magnetic pole steel for pumped storage hydroelectric generating set, which has a thickness of≤2.0mm and meets the requirements of yield strength≥800MPa, elongation A≥12%, magnetic induction intensity B 50 ≥1.6T.

[0006] To achieve the above object, the technical scheme of the present application is as follows:

[0007] An 800MPa-grade magnetic pole steel for pumped storage hydroelectric generating set, which comprises the following components and has the following weight percentage contents: 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 unavoidable inclusions.

[0008] Preferably, the weight percentage content of Cr is 0.23-0.27%.

[0009] Preferably, the weight percentage content of Ti is 0.1-0.15%.

[0010] A method for producing 800MPa-grade magnetic pole steel for the pumped storage hydroelectric generating unit, comprising the following steps:

[0011] 1) pouring into a blank after conventional smelting, during which the thickness of the blank is controlled to be between 60-85mm;

[0012] 2) heating the blank, controlling the soaking temperature to be between 1150-1200℃, and controlling the soaking time to be not less than 30min;

[0013] 3) adopting 7-pass hot rolling to the product thickness: controlling the opening rolling temperature to be not less than 1050℃, and the finish rolling temperature to be between 850-900℃;

[0014] 4) carrying out laminar cooling, the cooling speed is 50-70℃ / s, and cooling to the coiling temperature;

[0015] 5) coiling, and controlling the coiling temperature to be between 400-500℃;

[0016] 6) annealing, controlling the annealing heating temperature to be 600-640℃, and the holding time to be 3-6h;

[0017] 7) straightening.

[0018] Preferably: the blank soaking temperature is between 1157-1192℃.

[0019] Preferably: the opening rolling temperature is not less than 1058℃, and the finish rolling temperature is between 868-892℃.

[0020] The role and mechanism of each element and main process in the application are as follows:

[0021] The carbon (C) content of the application is 0.25%-0.30%. Carbon is the most economical strengthening element. However, if the carbon content is between 0.07-0.15%, the steel will occur peritectic reaction during casting, increasing the risk of continuous casting leakage, and too high carbon content will reduce the magnetic performance, so the carbon content is limited to 0.25%-0.30%, which can improve the strength of the steel, ensure the magnetic performance of the steel, and greatly reduce the addition of alloy elements and reduce the cost.

[0022] The manganese (Mn) content of the application is 1.1%-1.5%. 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.

[0023] The chromium (Cr) content of the present application is 0.2%~0.3%. Chromium is a carbide forming element, and has a strong affinity with carbon, which can hinder the diffusion of carbon atoms, Cr is beneficial to refine ferrite grains, improve the strength of the steel plate, and too high is not conducive to the magnetic properties. In the present application, the chromium content is controlled between 0.2%~0.3%, preferably the weight percentage of Cr is between 0.23%~0.27%.

[0024] The titanium (Ti) content of the present application is 0.1%~0.2%. Ti is a strong carbide and nitride forming element, the carbon, nitrogen particles formed can prevent the growth of austenite grains during the reheating and high temperature austenite zone rough rolling process, play a role in refining the grain, improve the toughness of the steel. The fine and dispersed TiC precipitated in the coiling stage can play a significant precipitation strengthening effect, thereby effectively improving the strength of the steel plate. The present application selects Ti content of 0.1%~0.2%, preferably the weight percentage of Ti is 0.10%~0.15%.

[0025] The silicon (Si) content of the present application is 0.10%~0.20%. Si has a solid solution strengthening effect, which can improve the strength of the steel and is beneficial to the magnetic properties. When the content of silicon exceeds a certain range, it will not be conducive to the surface quality, therefore the Si content is controlled to be 0.10%~0.20%.

[0026] 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 is easy to combine 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 on the performance of the steel, control the content of phosphorus and sulfur by deep desulfurization pretreatment of molten iron, and thus reduce the adverse effects.

[0027] The boron (B) content of the present application is 0.0025%~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 and achieving strengthening effect, and B is very cheap, which has a significant effect on cost control. However, too high B content will form low melting point eutectic, concentrated in the grain boundary, causing thermal brittleness. Therefore, the boron content range of the present application is 0.0025%~0.0030%.

[0028] The reason why the present application controls the soaking temperature of the casting blank to be 1150~1200℃ is to ensure complete solid solution of alloying elements and full austenitization, and at the same time improve the uniformity of slab temperature, reduce the deformation resistance and rolling load, which is beneficial to the rolling of thin gauge magnetic pole steel.

[0029] The present application controls the finish rolling temperature to be 850-900 DEG C, the cooling speed to be 50-70 DEG C / s, and the coiling temperature to be 400-500 DEG C, so as to obtain bainite structure by high cooling speed, fully play the effects of structure strengthening and fine grain strengthening, and make TiC particles precipitate by the annealing temperature of 600-640 DEG C, fully play the effect of precipitation strengthening, and improve the strength of the steel plate.

[0030] The magnetic pole steel provided by the present application does not contain precious alloy elements such as Nb and Mo, has a yield strength of ≥800 MPa, an elongation A of ≥12%, a magnetic induction intensity B 50 ≥1.60 T, can fully meet the demand of the 800 MPa grade magnetic pole steel for the pumped storage hydro-generator rotor with a rated rotating speed of 600 r / min, and has a product thickness of not more than 2 mm and a cost of 600-900 yuan / ton of steel, which is lower than that of the prior art. DETAILED DESCRIPTION

[0031] The present application will be described in detail as follows:

[0032] Table 1 is a list of components and weight percentage contents of each embodiment and the comparative example of the present application, and the rest is Fe and inevitable inclusions;

[0033] Table 2 is a list of process parameter values and performance detection of each embodiment and the comparative example of the present application.

[0034] Each embodiment of the present application is produced according to the following steps:

[0035] 1) After conventional smelting, pouring into a blank, during which the thickness of the cast blank is controlled to be 60-85 mm;

[0036] 2) heating the cast blank, controlling the soaking temperature to be 1150-1200 DEG C, and controlling the soaking time to be not less than 30 min;

[0037] 3) adopting 7-pass hot rolling to the product thickness: controlling the opening rolling temperature to be not less than 1050 DEG C, and the finish rolling temperature to be 850-900 DEG C;

[0038] 4) performing laminar cooling, the cooling speed is 50-70 DEG C / s, and cooling to the coiling temperature;

[0039] 5) performing coiling, and controlling the coiling temperature to be 400-500 DEG C;

[0040] 6) performing annealing, controlling the annealing heating temperature to be 600-640 DEG C, and the holding time to be 3-6 h;

[0041] 7) performing straightening.

[0042] The steps of the comparative examples were produced, but the process parameters were set according to Table 2 Comparative Example 1 and Comparative Example 2.

[0043] Table 1 List of chemical components (wt%) of each embodiment of the present application and comparative examples

[0044]

[0045] Table 2 List of main process parameters of each embodiment of the present application and comparative examples

[0046]

[0047] Table 3 List of performance test results of each embodiment of the present application and comparative examples

[0048]

[0049] (Note: In Table 3, the yield strength and elongation were measured according to the national standard GB / T 228, and the magnetic induction intensity was measured according to the national standard GB / T 3655.)

[0050] As can be seen from Table 3, the yield strength of the magnetic pole steel prepared in Examples 1-8 is ≥800 MPa, the elongation A is ≥12%, and the magnetic induction intensity B is ≥1.60 T. 50 Since the rated speed of the pumped storage hydro-generator rotor is high, the strength of the magnetic pole steel is also high to ensure the safety and stability of the unit operation. The performance of the steel plate can meet the requirements of 800 MPa grade magnetic pole steel for pumped storage hydro-generator rotor with a rated speed of up to 600 r / min on the market, and the rolling thickness is not more than 2 mm.

[0051] This specific embodiment is only the best example and is not a limiting implementation of the technical solutions of the present application.

Claims

1. A 800 MPa grade magnetic pole steel for pumped storage hydroelectric generating units, characterized by, The components and weight percentage contents thereof are: 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.

2. A 800 MPa grade pole steel for pumped storage hydroelectric generating units as claimed in claim 1, characterized in that, The weight percentage content of Cr is between 0.23-0.27%.

3. A 800 MPa grade pole steel for pumped storage hydroelectric generating units as claimed in claim 1, characterized in that, The weight percentage content of Ti is between 0.1-0.15%.

4. A method of producing a 800 MPa grade pole steel for pumped storage hydroelectric generating units as claimed in claim 1, characterized in that, The method comprises the following steps: 1) pouring into a blank after conventional smelting, during which the thickness of the cast blank is controlled to be between 60-85mm; 2) heating the cast blank, controlling the soaking temperature to be between 1150-1200℃, and controlling the soaking time to be no less than 30min; 3) adopting 7-pass hot rolling to the product thickness: controlling the opening rolling temperature to be no less than 1050℃, and the final rolling temperature to be between 850-900℃; 4) performing laminar flow cooling, the cooling speed being 50-70℃ / s, and cooling to the coiling temperature; 5) coiling, and controlling the coiling temperature to be between 400-500℃; 6) annealing, controlling the annealing heating temperature to be 600-640℃, and the annealing holding time to be 3-6h; 7) straightening.

5. The method of producing 800 MPa grade pole steel for pumped storage hydroelectric generating units as claimed in claim 4, wherein, Heating the cast blank, controlling the soaking temperature to be between 1157-1192℃.

6. The method of producing 800 MPa grade pole steel for pumped storage hydro generating units as claimed in claim 4 wherein, The opening rolling temperature is no less than 1058℃, and the final rolling temperature is between 868-892℃.

7. The 800 MPa class pole steel for pumped storage hydroelectric generating units produced by the method of claim 4, characterized by, The magnetic pole steel product has a thickness of not more than 2 mm and a yield strength of ≥ 800 MPa, an elongation A of ≥ 12 %, a magnetic induction B 50 ≥ 1.60 T.

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