CN104878292A - Cold-rolled magnetic pole steel with yield strength not less than 400 MPa and production method of cold-rolled magnetic pole steel - Google Patents

Abstract

The invention discloses a cold-rolled magnetic pole steel with yield strength not less than 400 MPa. The cold-rolled magnetic pole steel comprises the following components: 0.07-0.10wt% of C, 0.70-1.00wt% of Mn, 0.15-0.30wt% of Si, P not larger than 0.015wt%, S not larger than 0.010wt%, 0.02-0.07wt% of Als, 0.02-0.10wt% of Ti and 0.02-0.10wt% of Nb. The production method comprises the following steps: smelting, continuous casting to form a billet, and heating; conventional hot rolling; natural cooling and conventional pickling; cold rolling; continuous annealing; cooling, wherein a mixed gas of nitrogen and hydrogen is used for conventional injection, slow cooling and then quick cooling; over-aging treatment; smoothing. According to the invention, main elements comprising C, Si, Mn, Nb and Ti are controlled, and are subjected to heat treatment for 60-180 seconds at 800-850 DEG C in a continuous annealing and soaking zone, so that the microstructure generates ferrite and pearlite stable in performance, and the cold-rolled magnetic pole steel has excellent external force resistance and has the yield strength greater than 400 MPa.

Description

The cold rolled magnetic pole steel of a kind of yield strength >=400MPa and production method

Technical field

The present invention relates to a kind of cold rolled magnetic pole steel and production method, belong to cold rolled magnetic pole steel and the production method of a kind of yield strength >=400MPa particularly, be specifically applicable to hydroelectricity generator group rotor steel.

Background technology

Water power is a kind of environment-friendly type, continuable electrical production method, and recent domestic all greatly developing hydroelectric project to alleviate energy shortage crisis, thus drives the annual production of turbine-generator units constantly to rise.Magnetic pole is the core component of hydraulic generator rotor, is formed by cold rolled magnetic pole steel lamination assembling.The pole plate of electric generating set rotor requires to have the use safety that enough intensity could meet hydrogenerator; Simultaneously for reducing the eddy losses of unit, pole plate must have the magnetic flux more excellent than yoke steel plate; Magnetic pole is made up of the charge-coupled dress of sheet pack, and for ensureing the balance and stability of unit, pole plate requires to have high dimensional precision and surface quality.Three large technological difficulties of high strength, high magnetic flux, high precision magnetic poles steel plate.Along with hydrogenerator is towards unit maximization, type variation and stableization development, more and more higher to the required amount of cold rolled magnetic pole steel plate, demand is also increasing.

Through retrieval:

Chinese patent publication No. is respectively the document of CN100419108C, CN100392133C and CN100392134C, individually discloses 250MPa, 350MPa and 450MPa cold rolled magnetic pole steel and production production method thereof.What the common problem of three all adopted is bell-type annealing mode.There is production efficiency lowly, the deficiency that plate surface quality is not good enough in this kind of annealing way.

Chinese patent notification number is the document of CN101871076B, it discloses a kind of continuous annealing method of 500MPa cold rolled magnetic pole steel.This invention improves magnetic pole steel intensity by adding the alloying element such as Nb, V and Ti, and it is more to add alloying element kind in steel, and each element is requiring that combining changeable meeting in content range causes final finished performance inconsistency large.

China Patent Publication No. is the document of CN103409684A, it discloses a kind of high strength cold-rolled magnetic pole steel and connects and move back production method, its method adopted be underannealing to reach requirement of strength, the bad control of deformed microstructure amount, yield strength less stable.Can find out prior art by above-mentioned patent or be connect that to move back production efficiency low, surface quality is bad, or steel grade alloying element is of a great variety, and continuous annealing is incomplete, and tissue is unstable, and Mechanical Fluctuation is large.The cold rolled magnetic pole steel metallographic structure that the present invention produces is: recrystallize ferrite+perlite.Through inspection, in production in enormous quantities, the yield strength of this steel plate is all greater than 400MPa, and tensile strength is greater than 500MPa, and unit elongation is greater than 20%, and magnetic induction B50 is all greater than 1.63T, and stable mechanical property has excellent magnetic characteristics.

Summary of the invention

The invention provides one and ensureing that tensile strength is greater than 500MPa, unit elongation is greater than 20%, under magnetic induction B50 is all greater than the prerequisite of 1.63T, and the cold rolled magnetic pole steel of yield strength >=400MPa and production method.

Realize the measure of above-mentioned purpose:

The cold rolled magnetic pole steel of a kind of yield strength >=400MPa, its component and weight percent content are: C:0.07 ~ 0.10%, Mn:0.70 ~ 1.00%, Si:0.15 ~ 0.30%, P≤0.015%, S≤0.010%, Als:0.02 ~ 0.07%, Ti:0.02 ~ 0.10%, Nb:0.02 ~ 0.10%, and surplus is Fe and other inevitable impurity; Metallographic structure is recrystallize ferrite+perlite.

Produce the cold rolled magnetic pole steel of a kind of yield strength >=400MPa, its step:

1) become base through smelting, continuous casting and heat, slab heating temperature controls at 1220 ~ 1280 DEG C, and heat-up time is 135 ~ 220s;

2) routine carries out hot rolling;

3), time through naturally cooling to below 70 DEG C, conventional pickling is carried out;

4) carry out cold rolling, control cold rolling total reduction 50 ~ 64%;

5) carry out continuous annealing, control soaking temperature at 800 ~ 850 DEG C, soaking time is at 60s ~ 180s;

6) cool: adopt conventional nitrogen hydrogen mixeding gas to spray slow cooling to 640 ~ 660 DEG C, then be cooled to 420 ~ 440 DEG C under speed of cooling is 30 ~ 60 DEG C/s;

7) carry out Wetted constructures, Wetted constructures temperature is at 360 ~ 410 DEG C, and the Wetted constructures time is 100 ~ 200s, and this operation strip speed is at 140 ~ 180m/min, and steel belt operating speed becomes negative correlativing relation with steel plate thickness;

8) carrying out smooth, is carry out smooth 1.4 ~ 1.8% times in smooth rate.

The effect that of the present invention each element and main technique control:

carbon (C): C 0.07 ~ 0.10%, carbon is the most effective solution strengthening element, therefore along with the increase of carbon content, carbon steel is hardening gradually, and intensity rises, but carbon makes magnetic permeability reduce, and be again the one of the chief elements forming magnetic aging, solid solution carbon and cementite all have larger infringement to magnetic property, therefore under carbon content is less than target, easily occur that yield strength does not reach 400MPa situation in limited time, easily occur that magnetic strength is on the low side when carbon content is greater than range limit;

silicon (Si): Si 0.15 ~ 0.30%, silicon can reduce crystalline anisotropy, and make magnetization easy, magnetic resistance reduces, and significantly improves ratio resistance simultaneously, reduces eddy losses, but steel can be made to become fragile, and hardness rises;

manganese (Mn): Mn 0.70 ~ 1.00%, high Fe content both can improve steel strength, can improve crystalline structure again, optimize magnetic property, but too high Fe content causes inclusion MnS too much to reduce magnetic property on the contrary, Fe content is too high can reduce magnetic property, too lowly easily occurs that yield strength is on the low side;

p, S:for impurity harmful element, in steel, P, S content is more low better, if but control content is too low, and cause production technique cost to increase, setting P :≤0.015%, S≤0.010%.

niobium (Nb), titanium (Ti): Nb0.02 ~ 0.10%, Ti0.02 ~ 0.10%, the form of niobium and the titanium main carbonitride tiny with size in steel exists, play and postpone recrystallize effect, be used for improving the intensity of steel by refined crystalline strengthening and precipitation strength, simultaneously Nb, Ti to the disadvantageous effect of magnetic property than solid solution carbon and cementite little, Nb, Ti content is too low does not have the effect improving steel strength, and too high meeting increases steel product cost greatly.

The present invention compared with prior art, it is by the control to C, Si, Mn, Nb, Ti principal element, add again to connect and move back soaking zone with 800-850 DEG C of thermal treatment 60 ~ 180 seconds, microtexture is made to generate the ferrite+perlite of stable performance, thus there is the premium properties of opposing external force, yield strength is also greater than 400MPa.

Accompanying drawing explanation

Accompanying drawing 1 is metallographic structure figure of the present invention.

Embodiment

Below the present invention is described in detail:

Table 1 is the component value list of various embodiments of the present invention and comparative example;

Table 2 is main technologic parameters and the capabilities list of various embodiments of the present invention and comparative example.

Various embodiments of the present invention are produced according to following steps:

1) become base through smelting, continuous casting and heat, slab heating temperature controls at 1220 ~ 1280 DEG C, and heat-up time is 135 ~ 220s;

2) routine carries out hot rolling;

3), time through naturally cooling to below 70 DEG C, conventional pickling is carried out;

4) carry out cold rolling, control cold rolling total reduction 50 ~ 64%;

5) carry out continuous annealing, control soaking temperature at 800 ~ 850 DEG C, soaking time is at 60s ~ 180s;

6) cool: first adopted by steel plate conventional nitrogen hydrogen mixeding gas to spray slow cooling to 640 ~ 660 DEG C, then be cooled to 420 ~ 440 DEG C under speed of cooling is 30 ~ 60 DEG C/s;

7) carry out Wetted constructures, Wetted constructures temperature is at 360 ~ 410 DEG C, and the Wetted constructures time is 100 ~ 200s, and this operation strip speed is at 140 ~ 180m/min, and steel belt operating speed becomes negative correlativing relation with steel plate thickness;

8) carrying out smooth, is carry out smooth 1.4 ~ 1.8% times in smooth rate.

Table 1 is various embodiments of the present invention and comparative example chemical composition (w%)

Embodiment	C	Si	Mn	P	S	Als	Ti	Nb
									1	0.070	0.15	0.70	0.015	0.008	0.020	0.020	0.020
2	0.098	0.21	0.79	0.011	0.004	0.056	0.029	0.028
									3	0.087	0.20	0.81	0.015	0.004	0.046	0.029	0.029
4	0.081	0.18	0.78	0.014	0.006	0.046	0.030	0.030
									5	0.082	0.17	0.78	0.012	0.004	0.061	0.035	0.040
6	0.10	0.30	1.00	0.015	0.005	0.070	0.040	0.055
									Comparative example 1	0.060	0.10	0.60	0.015	0.008	0.040	0.010	0.010
Comparative example 2	0.11	0.40	1.1	0.015	0.008	0.070	0. 110	0. 110

Table 2 various embodiments of the present invention and comparative example technique significant parameter control list

Table 2 various embodiments of the present invention and comparative example technique significant parameter control list (continued 1)

Table 3 is various embodiments of the present invention and the list of comparative example end properties detected result

As shown in Table 3, the magnetic pole steel produced by the present invention has very high yield strength can reach more than 400MPa, and tensile strength can reach more than 500MPa, and unit elongation is greater than 20%, satisfactory mechanical property.Magnetic induction B50 value is all greater than 1.63T simultaneously, and meet the magnetic property requirements of hydrogenerator to magnetic pole steel completely, can find out that, lower than internal control scope, mechanical property yield strength does not reach requirement by comparative example, higher than internal control scope, magnetic property does not reach requirement.

This embodiment is only the best and exemplifies, the restricted enforcement not to technical solution of the present invention.

Claims (2)

1. the cold rolled magnetic pole steel of yield strength >=400MPa, its component and weight percent content are: C:0.07 ~ 0.10%, Mn:0.70 ~ 1.00%, Si:0.15 ~ 0.30%, P≤0.015%, S≤0.010%, Als:0.02 ~ 0.07%, Ti:0.02 ~ 0.10%, Nb:0.02 ~ 0.10%, and surplus is Fe and other inevitable impurity; Metallographic structure is recrystallize ferrite+perlite.

2. the cold rolled magnetic pole steel of a kind of yield strength >=400MPa described in production claim 1, its step:

1) become base through smelting, continuous casting and heat, slab heating temperature controls at 1220 ~ 1280 DEG C, and heat-up time is 135 ~ 220s;

2) routine carries out hot rolling;

3), time through naturally cooling to below 70 DEG C, conventional pickling is carried out;

4) carry out cold rolling, control cold rolling total reduction 50 ~ 64%;

5) carry out continuous annealing, control soaking temperature at 800 ~ 850 DEG C, soaking time is at 60s ~ 180s;

6) cool: adopt conventional nitrogen hydrogen mixeding gas to spray slow cooling to 640 ~ 660 DEG C, then be cooled to 420 ~ 440 DEG C under speed of cooling is 30 ~ 60 DEG C/s;

7) carry out Wetted constructures, Wetted constructures temperature is at 360 ~ 410 DEG C, and the Wetted constructures time is 100 ~ 200s, and this operation strip speed is at 140 ~ 180m/min, and steel belt operating speed becomes negative correlativing relation with steel plate thickness;

8) carrying out smooth, is carry out smooth 1.4 ~ 1.8% times in smooth rate.