Background technology
The high-magnetic induction, low-iron loss cold rolling non-oriented electrical steel is a non-oriented electrical steel hot of research and development in recent years, and it is adapted in recent years the requirement of high efficiency such as all kinds of motors, electronic transformer iron core, miniaturization is developed.The loss of motor mainly comprises two parts, the one, and iron loss, i.e. core loss, another is a copper loss, i.e. the caused loss of conductor resistance.Concerning cold rolling non-oriented electrical steel, iron loss mainly is made up of magnetic hystersis loss and eddy-current loss.Generally speaking, in order to reduce eddy-current loss, the content of taking to improve the elements such as Si, Al in the steel reaches with measures such as the resistance that increases steel and reduced thickness, but the increase of constituent content such as Si, Al will inevitably reduce the magnetic induction intensity of steel plate, and reduced thickness can be brought problems such as steel mill's cold working difficulty and customer using cost increase to certain degree.Therefore from metallurgy factor control, reduce iron loss and improve often contradiction of magnetic strength.The method that improves magnetic strength, reduction iron loss generally has following several: the content that 1. reduces Si, improve the degree of purity of steel, keep obtaining lower iron loss under the high magnetic strength condition when reaching low silicon content, as Chinese patent application numbers 95105753.7, Japanese patent laid-open 8-3699 etc.; 2. in steel, add the element that improves finished product texture, add Sn, Sb, Cu etc. as using; 3. hot rolled plate being carried out normalizing as Chinese patent handles.This several method uses separately or compound use.First method has proposed very high requirement to smelting, developed utmost point low-sulfur series of high efficiency rate non-oriented electrical steel as Japanese NKK company, the content requirement of S reaches below the 10ppm, reduce hindering the sulfide of grain growth, development product and manufacturing technology have description on document ま て り あ No. 2 (2002) P114~116 of the 41st volume and relevant tens patents.Second method has improved the cost of alloy of steel.Third party's method is very effective to improving magnetic strength, and cost is also very low, to such an extent as to first kind and second kind often also needs to be used in combination with the third method.Purpose to the hot rolled plate normalizing is in order to make hot rolled plate obtain thick grain structure before cold rolling, to obtain high (0kl) texture (The Sumitomo Search No.44December 1990, P120~125) of intensity when making cold-reduced sheet annealing.Hot rolled plate crystal grain is thick more, and the finished product magnetic strength is high more.The normalizing temperature generally is no more than Acl, changes mutually thereby avoid taking place in the normalizing process α → γ → α, and the grain structure refinement improves unfavorable (clear 63-210238, clear 64-55338) to final finished texture on the contrary.Because of the restriction of normalizing temperature,, must increase the normalizing time, as utilize more than the cover annealing 1h, or in continuous annealing furnace, anneal more than the 2min for obtaining thicker grain structure.Nonetheless because the normalizing temperature is lower, and the grain coarsening effect is limited, the effect that magnetic strength improves is limited.T.Kumano etc. studies show that at two-phase section normalizing 30min; cooling velocity is low to moderate 0.2 ℃/s can obtain the thickest hot rolled plate grain structure, magnetic strength best (Journal of Materials Engineering and performance, Vol.4 (4); August 1995, P401~412).Before a kind of mode hot rolled plate soaking zone in annealing furnace handle for a long time, then a kind of mode not only the normalizing time long, and cool time is very long, this dual mode all increases the length of annealing furnace, equipment investment is big, the cost height.
Summary of the invention
In view of existing situation, the object of the present invention is to provide that a kind of non-oriented electrical steel normalizing processing cost is low, the production method of low iron loss high magnetic sensing cold milling orientation less electrical steel strip.
For achieving the above object, the production method of low iron loss high magnetic sensing cold milling orientation less electrical steel strip of the present invention, it comprises the steps:
A. the composition of electrical steel strip is C≤0.0050%, Si 0.1%~2.50%, Al≤1.0%, and Si+2Al≤2.50%, Mn:0.10%~1.50%, P≤0.20%, S≤0.005%, N≤0.0025%, can add among Sn, the Sb one or both, total amount is no more than 0.2%, and all the other are iron and other inevitable impurity, more than are weight percentage;
B. smelting, continuous casting, hot rolling;
C. normalizing is handled, and resulting hot rolled plate is carried out normalizing handle,
Firing rate with 5~15 ℃/s is elevated to Ac
lMore than, 1100 ℃ of following temperature carry out soaking, soaking time: 10s≤t≤90s;
Cooling is adopted the cooling of two stages: at first from the cooling velocity of the condition of high temperature with≤15 ℃/s steel band is cooled to below 650 ℃, then to guarantee that the speed under the template prerequisite is cooled to below 80 ℃;
D. cold rolling, be rolled into cold-reduced sheet with 70~90% reduction ratios;
E. annealing in process is carried out final annealing and coating processing to cold-reduced sheet, to make full craft type cold-rolled non-oriented electrical steel.
Further, after the cold-reduced sheet annealing, or carry out again after the annealing coating 1~10% smooth, to make half craft type cold-rolled non-oriented electrical steel.
The non-oriented electrical steel finished product generally is divided into full technology and two kinds of forms of half technology.Full technology is meant that surface of steel plate has coating, directly is assembled into electric machine iron core after user's punching (electric machine iron core sheet) and uses; Half technology is meant that surface of steel plate does not have coating or coating is arranged, and needs after user's punching (electric machine iron core sheet) lamination is carried out just being assembled into the electric machine iron core use after the further annealing in process.
The hot rolled plate normalizing is handled the back average grain size and is reached more than the 100 μ m.
Principle of the present invention is described below:
The present inventor has furtherd investigate the influence to grain structure and magnetic of normalizing temperature, time and cooling system.With C:0.0030%, Si:0.60%, Mn:0.25%, Al:0.25%, the continuous casting billet of P:0.08%, S:0.0035% and N:0.0021% composition carries out hot rolling, hot rolling thickness of slab 2.60mm.Hot rolled plate is carried out the normalizing of different process system and handle, be cold rolled to 0.50mm then.Cold-reduced sheet is carried out 750 ℃ * 30s annealing, and carry out magnetic detection.The results are shown in accompanying drawing.
The time of different normalizing temperature is 60s among Fig. 1~Fig. 3, and the cooling velocity before 650 ℃ is 5 ℃/s; Annealing temperature is 1050 ℃ among Fig. 4~Fig. 5, and the time is 60s; Annealing temperature is 1050 ℃ among Fig. 6~Fig. 7, and the cooling velocity before 650 ℃ is 5 ℃/s.The Ac1 temperature that the present invention tests steel is 986 ℃.From result of the test as seen, the normalizing temperature surpasses the Acl point, under the situation of high temperature, short time magnetic is not had adverse effect, can further reduce iron loss on the contrary, improves magnetic strength.This mainly is that α and γ two-phase section transformation range are little because under the comparatively pure situation of steel, and the transformation amount is little under situation in short-term, and phase transformation is little to the influence of crystal grain.Adopt lower cooling velocity simultaneously, can further reduce phase transformation the crystal grain and second influence of precipitate mutually.The present invention is as follows to the principle of composition regulation:
Below the C:0.005%.C is the element that hinders grain growth strongly, causes that iron loss increases and magnetic aging, and C is the element that enlarges the γ phase region simultaneously; α and γ two-phase section transformation amount increased when excessive C handled normalizing; reduce the Acl point greatly, crystalline structure is played refining effect, therefore must be controlled at below 0.005%.
Si:0.10%~2.5%。Si increases the resistivity element, is the most important alloying element of electrical sheet, and silicone content surpasses 2.5% and will can not undergo phase transition, and will not have the effect that reduces iron loss and be lower than 0.1%.
Below the Al:1.0%.Al increases the resistivity element, is the most important alloying element of electrical sheet, surpasses 1.0% and will make smelting cast difficulty, and magnetic strength reduces.(Si+2Al) will can not undergo phase transition above 2.5% simultaneously.Therefore stipulate that (Si+2Al) is no more than 2.5% is very necessary.
Mn:0.10%~1.50%。The same resistivity that can increase steel with Si, Al of Mn reduces iron loss, improves the electrical sheet surface state simultaneously, reduces hot-short element, therefore is necessary to add the content more than 0.1%.Because Mn is the element that enlarges the γ phase region,, be necessary its content is limited in 1.5% simultaneously for improving normalizing temperature (Acl point).
Below the P:0.2%.In steel, add the processability that certain phosphorus can improve steel plate, make cold-rolling of steel plate processability deterioration on the contrary but surpass at 0.2% o'clock.
Below the S:0.005%.Surpass 0.005% the Sization thing amount of separating out such as MnS will be increased greatly, hinder grain growth strongly, the iron loss deterioration.
Below the N:0.0025%.Surpass 0.0025% the Nization thing amount of separating out such as AlN will be increased greatly, hinder grain growth strongly, the iron loss deterioration.
Sn, Sb: the surface segregation element, add and can improve finished product texture on a small quantity, improve magnetic strength.One or more total contents surpass 0.2% o'clock DeGrain that improves to performance and improve.
The invention has the advantages that
The present invention has broken through the restriction of normalizing temperature traditionally below the Acl point; by improving the normalizing temperature; shortened the normalizing time greatly, the further alligatoring of crystal grain (more than the 100 μ m), unite simultaneously cooling control reach precipitates such as further making AlN assemble grow up, alligatoring.(0kl) texture is strong in the time of can obtaining the cold-reduced sheet final annealing with this, magnetic strength is high, the high-efficiency non-oriented electrical steel product that crystal grain is easily grown up, iron loss is lower simultaneously.The minimizing of normalizing time simultaneously makes the normalizing unit build investment and operation cost reduces greatly.