CN102639745A - Low-carbon steel sheet and process for producing same - Google Patents
Low-carbon steel sheet and process for producing same Download PDFInfo
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- CN102639745A CN102639745A CN2010800539981A CN201080053998A CN102639745A CN 102639745 A CN102639745 A CN 102639745A CN 2010800539981 A CN2010800539981 A CN 2010800539981A CN 201080053998 A CN201080053998 A CN 201080053998A CN 102639745 A CN102639745 A CN 102639745A
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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- C23C10/06—Solid state diffusion of only metal elements or silicon into metallic material surfaces using gases
- C23C10/08—Solid state diffusion of only metal elements or silicon into metallic material surfaces using gases only one element being diffused
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
- C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
- C21D8/1272—Final recrystallisation annealing
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2251/00—Treating composite or clad material
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Abstract
Disclosed is a low-carbon steel sheet which is a clad steel sheet comprising: a center layer, in terms of sheet thickness, that has a ferrite mixture structure containing at most 1.0 mass% Si and including any one or more of a pearlite phase, a bainite phase, and a martensite phase; and surface layers each comprising a ferrite phase, as the only phase, that contains 3-5 mass% Si. The surface layers have an in-plane tensile stress of 70-160 MPa imposed thereon as an internal stress, and the low-carbon steel sheet therefore has excellent high-frequency characteristics and is inhibited from suffering an increase in iron loss caused by an external stress.
Description
Technical field
The present invention relates to be suitable as the mild steel plate of Power Electronic Technique, relate in particular to the mild steel plate of the reduction of the iron loss deterioration that the raising that can realize high frequency characteristics and external stress cause with the iron core of high-frequency transformer, reactance coil, motor.
Background technology
The iron loss of electro-magnetic steel plate is made up of magnetic hysteresis loss that very relies on precipitate in the steel, crystallization particle diameter, set tissue etc. and the eddy-current loss that very relies on thickness of slab, resistivity, domain structure etc.
General electro-magnetic steel plate is through doing one's utmost to reduce the reductionization that growth property that impurity in the steel improves crystal grain realizes magnetic hysteresis loss.In addition, improve the reductionization that resistivity perhaps realizes the thickness of slab sheet eddy-current loss through the Si that adds 0.5～3.5 quality %.
Wherein, Magnetic hysteresis loss and frequency are proportional, eddy-current loss and frequency square proportional, therefore in commercial frequency (50/60Hz), the magnetic hysteresis loss proportion is big in the iron loss of electro-magnetic steel plate; But when reaching the high frequency more than several kHz, the eddy-current loss proportion becomes big on the contrary.
In recent years, just in the high frequencyization of push-on switch element, the electro-magnetic steel plate that therefore uses for the core material as X-former, reactance coil, motor etc. is also hoped the reduction of high frequency iron loss strongly in electric and electronic technical field.
Need to this, can be below the 0.2mm through the thickness of slab that makes electro-magnetic steel plate, perhaps Si is increased near the 4 quality %, thereby reduce eddy-current loss.But, estimate also can to drive from now on the high frequency that surpasses 10kHz, need to develop unexistent innovative material on the extended line of in the past developing.
In the past, under the excitation condition of such high-frequency region, soft magnetic ferrite, metal crimp powder, material such as noncrystalline had been used.But; They respectively have length; Promptly; Ferrite is because the low and unshakable in one's determination maximization of magneticflux-density, though noncrystalline low iron loss structure coefficient (Building Factor) obviously is worse than electro-magnetic steel plate, MS, the iron loss of metal crimp powder such as sendust powder are all low but expensive in addition and compare saturation magnetic flux density with electro-magnetic steel plate also low etc.Therefore, about the reduction of the high frequency iron loss of electro-magnetic steel plate, also carrying out various researchs recently.
As the method for the high frequency iron loss that reduces electro-magnetic steel plate, put down in writing the Si enriching method of the surface of steel plate that utilizes the siliconising method in the patent documentation 1.
This Si beneficiation technologies for example in the patent documentation 2 put down in writing, be the 3 quality %Si steel plates that make thickness of slab 0.1～0.35mm improve the Si concentration in the steel with the silicon tetrachloride gas reaction in high temperature technology.
In addition, as knowing already, 6.5 quality %Si steel plates have about 2 times intrinsic resistance of 3 quality %Si steel plates; Can effectively reduce eddy-current loss; Therefore favourable with material as high frequency, MS simultaneously is essentially zero, therefore to the excellent effect of the low noise performance of iron core.
Further disclose in the patent documentation 2 in siliconising technology, considered,, also can obtain sufficient magnetic properties through adjustment top layer Si concentration even do not make Si concentration even in the thickness of slab direction from the viewpoint that shortens diffusion time.
In patent documentation 3, about the silicon steel sheet that has the Si concentration gradient in the thickness of slab direction, in order to reduce high frequency iron loss, to the Si concentration difference (maximum-minimum) of thickness of slab direction, stipulate with the difference of the Si concentration at the top layer Si concentration and the surface of steel plate back side.Especially put down in writing the purport that can access minimum iron loss when top layer Si concentration is 6.5 quality %.
And then, in patent documentation 4, put down in writing following electro-magnetic steel plate, that is, electro-magnetic steel plate is carried out siliconising mutually at ferrite handle, processing the top layer is that high Si concentration, thickness of slab central part are the electro-magnetic steel plate of low Si concentration, thereby makes its high frequency characteristics excellent.
In addition; Put down in writing following motor in the patent documentation 5 and used silicon steel sheet; That is, soft steel is carried out in 900～1000 ℃ mutually few humidity province of austenite that siliconising is handled and the steel plate of processing the Si concentration that has improved the top layer, thereby make its processibility good and high frequency characteristics is excellent.
The prior art document
Patent documentation
Patent documentation 1: the special fair 6-45881 communique of Japan
Patent documentation 2: the special fair 5-49744 communique of Japan
Patent documentation 3: TOHKEMY 2005-240185 communique
Patent documentation 4: TOHKEMY 2009-263782 communique
Patent documentation 5: TOHKEMY 2000-328226 communique
Summary of the invention
As stated, can know that iron loss representes that by magnetic hysteresis loss and eddy-current loss sum excitation frequency is high more, eddy-current loss shared ratio in total iron loss increases.The resistivity of material is big more, and eddy current is more difficult to flow, so high frequency uses the big material of resistivity with magnetic core.
Generally, in electro-magnetic steel plate, Si concentration is high more, and resistivity increases more, and the electro-magnetic steel plate that therefore contains the above Si of 3 quality % is suitable as high frequency and uses core material.
On the other hand, it is high more that Si concentration becomes, and steel has the trend that hardening becomes fragile more, the cold rolling difficulty that becomes.In addition, when Si concentration uprises, when being difficult to take place the slab cooling by austenite to ferritic transformation (below be called γ/α change), ferrite directly forms thick tissue, and therefore slab crackle, surface damage take place easily.Thereby in the electro-magnetic steel plate ME of reality, the upper limit of the Si concentration in the steel is 4 quality %.
According to patent documentation 2, permeance is the highest and MS is little is 6.5 quality %Si steel plates in electro-magnetic steel plate.But, unshakable in one's determination for it is used as, need to implement secondary processing such as division processing, stamping-out processing, bending machining.But 6.5 quality %Si steel plates are more crisp than common electro-magnetic steel plate, split easily, so in above-mentioned secondary processing, require the processing technology of height.In addition, the Vickers' hardness Hv of 6.5 quality %Si steel plates is about 390, and compares about the Hv:200 of in the past electro-magnetic steel plate, and is stone.Therefore, the shortcoming that also has the easy short lifeization of press tool.Particularly in the high-frequency applications more than 10kHz, compare with magnetic hysteresis loss, the ratio of eddy-current loss increases, even therefore be widely used magnetic hysteresis loss difference but low (intrinsic resistance is high) of eddy-current loss and cheap other materials such as compressed-core.
In addition, according to patent documentation 2,3 quality %Si steel plates are calendered to final thickness of slab after, be utilized in the siliconising technology that is blown into silicon tetrachloride in the high temperature, can make 6.5 quality %Si steel plates.
But, actual during as magnetic core, need 6.5 quality %Si steel plates after the siliconising be cut apart, punching press or bending machining, at this moment, exist usually crack, damaged problem.
And then; Patent documentation 2 has been put down in writing following example at its Figure 13: when Si concentration was too inhomogeneous, iron loss significantly increased, on the other hand; The ununiformity of Si concentration is suppressed in when following to a certain degree, can obtain no less than the low iron loss of the uniform steel plate of Si concentration.But, when the Si density unevenness is even, the example of comparing lower iron loss with the uniform steel plate of Si concentration is not shown.In addition, for high frequency iron loss, do not put down in writing any concrete numerical value.
In patent documentation 3, put down in writing steel plate in the residual Si of the having concentration gradient of thickness of slab direction as compare the further excellent material of high frequency characteristics with 6.5 quality %Si steel plates.Even the Si concentration on this steel plate top layer is high, the Si concentration of the thickness direction central part of palette is also just about 3 quality %, so be lower than the material of above-mentioned 6.5 quality %Si steel plates from the whole Si concentration of can thinking on average of steel.
But, at this moment,, do not change so γ/α does not take place because the following of Si concentration in the steel is limited to about 3 quality %.Therefore, the steel plate tissue when being cooled to room temperature is made up of the thick ferrite grain that passes through thickness of slab, is cutting apart, still existing during punching press crackle, the damaged problem of being easy to generate.
According to patent documentation 4; For because of being the wide and big such grain-oriented magnetic steel sheet of unusual eddy-current loss of thick secondary recrystallization tissue magnetic domain width originally, also can come effectively minimizing eddy-current loss through the stress distribution of the top layer of this steel plate being given stretchings, give compression to inside.But, because user tropism's electro-magnetic steel plate is as blank, so compare the cost ratio with other high-frequency core material high.In addition; Method as stress distribution is given uses siliconising to handle; But in grain-oriented magnetic steel sheet,, need begin to carry out siliconising and siliconising to average Si concentration from the top layer and reach more than the 4 quality %, top layer Si concentration is increased to more than the 5 quality % in order fully to realize the reduction of eddy-current loss.
In patent documentation 5; The soft steel that will have the austenite phase has carried out the siliconising processing; But handle if carry out siliconising, then crackle takes place, therefore carry out siliconising and handle 900～1000 ℃ of so lower humidity provinces at the interface that γ/α changes in the humidity province that surpasses 1000 ℃.
But, in order to reduce eddy-current loss, preferably handle carrying out siliconising more than 1000 ℃, handle the steel plate materials that also do not crack and the method for manufacture of steel plate even need in above-mentioned interface, implement siliconising more than 1000 ℃.In addition, top layer Si concentration height to the 5～6.5 quality % of the steel of patent documentation 5 record, and have thick secondary recrystallization tissue are so cutting apart, still existing during punching press crackle, damaged problem usually take place.
Use core material as high frequency, also have the dust core of iron powder press-powder moulding, the ferrite core and the based amorphous alloy of Fe of brown iron oxide in addition.To compare resistivity big with 6.5 quality %Si steel plates for they, therefore it is characterized in that eddy-current loss is low.
But ferrite core is because saturation magnetic flux density is low, so the pot life fixes on low output rating and the above high-frequency applications of hundreds of kHz usually.On the other hand, though that dust core, the based amorphous alloy of Fe and electro-magnetic steel plate are compared saturation magnetic flux density is lower slightly, because eddy-current loss is low, so, also likewise use with electro-magnetic steel plate sometimes for the high-frequency applications of high-output power.
But, the problem that iron loss obviously increased when all there was external stress such as real compressed in above-mentioned materials.
As stated, the most poor in processability of high frequency characteristics excellent magnetism material, responsive to outside stress response in addition, when particularly applying stress under compression, iron loss obviously increases mostly.
On the other hand, as the material of excellent in workability, can enumerate as structure material material or shell with the widely used mild steel plate of material.In addition, to outside stress sensitive, even the stress under compression of applying, iron loss can significantly not increase the magnetic of soft steel yet unlike general magneticsubstance that kind.
But the tissue of general mild steel plate is made up of the fine ferrite mixed structure of containing perlite phase, bainite phase and martensitic phase, so its direct current magnetic properties extreme difference.Therefore, be the magnetic core of the commercial frequency of main body for magnetic hysteresis loss, use mild steel plate hardly.
But, if can reduce the eddy-current loss of mild steel plate, can give play to respect to the iron loss of stress under compression few character that rises, then can obtain the core material of the also few excellence of high frequency iron loss is low and external stress causes iron loss deterioration.
The present invention is in view of above-mentioned present situation and the exploitation carried out, and purpose is few mild steel plate and the method for manufacture thereof of iron loss deterioration that provide high frequency characteristics excellence and external stress to cause.
According to patent documentation 3, through in siliconising technology, forming the Si concentration gradient, and the Si concentration difference at the surperficial back side of control steel plate, thereby can realize the reductionization of eddy-current loss in the thickness of slab direction.
Think that this technology is suitable for for soft steel too, can realize the reductionization of eddy-current loss.
But, change because γ/α takes place soft steel, so when pyritous austenite region carries out siliconising and handles, produce and begin the phenomenon that changes mutually to ferrite from the top layer that Si concentration rises.At this moment, there is Si concentration gap between mutually, therefore, becomes discontinuous in the Si at out-phase interface concentration gradient at the ferrite of the austenite of low Si concentration and high Si concentration.If the state with residual this Si concentration gradient cools off; Then as shown in Figure 1; The ferrite of the high Si concentration on top layer does not change mutually; Relative therewith, the austenite of the low Si concentration of thickness of slab central stratum becomes the fine ferrite mixed structure of containing perlite phase, bainite phase and martensitic phase mutually.
That is, soft steel being carried out siliconising handles and gives the situation of Si concentration gradient and differ widely on constituting with the technology that patent documentation 3 records that γ/α changes do not take place.
Below, describe accomplishing experiment of the present invention.The composition of the A～D4 kind soft steel that in this experiment shown in the table 1, uses.
In this table, the steel of symbol (C) expression are implemented following 3 kinds of processing make the sample that is used for this experiment:
In nitrogen, carry out annealed and handle (no siliconising) at 1200 ℃ ... Steel is handled I
1200 ℃ carry out siliconising after, fully make the evenly processing of diffusion of Si (siliconising+long-time diffusion) ... Steel is handled II
1200 ℃ siliconisings+Si is spread the processing of implementing altogether 3 minutes (siliconising+short period of time diffusion) ... Steel is handled III.
[table 1]
(quality %)
| Sample No. | C | Si | Mn | P | S |
| (A) | 0.005 | 0.1 | 0.03 | 0.008 | 0.004 |
| (B) | 0.024 | 0.1 | 0.45 | 0.006 | 0.003 |
| (C) | 0.055 | 0.3 | 1.15 | 0.005 | 0.005 |
| (D) | 0.155 | 0.2 | 1.56 | 0.004 | 0.005 |
Here, the siliconising processing of steel processing II and III is that the sample mean Si concentration after handling is adjusted into 3 quality %Si.Utilize the veneer of 30 * 100mm to measure frame on these samples and magnetize mensuration with exchanging, the iron loss under the condition of magneticflux-density 0.05T, frequency 20kHz is divided into magnetic hysteresis loss and eddy-current loss is measured, the result is compared with direct current.
The result of sample No. (C) is shown in Fig. 2.Should explain, in the drawings, also represent the core loss value of the electro-magnetic steel plate (3 quality %Si steel plates and 6.5 quality %Si steel plates) of identical thickness of slab in the lump.
With respect to the sample of steel processing I, steel is handled the sample of II owing to the resistivity increase that the Si increase causes descends eddy-current loss, in addition; In Si homogenizing process; Thickness of slab carries out γ/α on the whole and changes, and forms thick ferrite tissue, has also reduced magnetic hysteresis loss thus.
In addition, the iron loss of the sample of steel processing II (expression magnetic hysteresis loss+eddy-current loss, also identical for following the present invention) is in a ratio of big value with the iron loss of the electro-magnetic steel plate (3 quality %Si) of identical Si concentration.Its reason is thought: organize each other even the ferrite of identical 3 quality %Si is thick, also because the C amount is less than 50ppm under the situation of electro-magnetic steel plate, relative therewith, the C amount contains more than the 500ppm under the situation of soft steel, so magnetic hysteresis loss increases.
Relative therewith, unusually not only the electro-magnetic steel plate than 3 quality %Si is low for the iron loss of the sample of steel processing III, and also the electro-magnetic steel plate than 6.5 quality %Si is low, especially can see the reductionization of eddy-current loss.
Thereby can be through give the Si concentration gradient in the thickness of slab direction with flux concentrating on the top layer though envisioned; Realize the reductionization of eddy-current loss; But effect and the sample with identical siliconising amount of this moment make the contrast of Si concentration homogenizing, have rested on the degree of the reductionization of inferring 2～3 one-tenth of eddy-current loss realizations.That is, this result of experiment is the reduction effect greater than about 5 one-tenth eddy-current loss, head and shoulders above expection.
Next, in order more to study this phenomenon in great detail, use 4 kinds of materials shown in the table 1, handle at above-mentioned steel and carry out siliconising under the condition of III and wait and make sample.These samples are carried out structure observation in the vertical section, likewise measure iron loss with above-mentioned experiment.Its result is shown in Fig. 3 and 4.
In Fig. 3 (a)～(d), represent section structure photo respectively to the sample after sample No. (A)～(D) the enforcement steel processing III.
Fig. 3 (a) is the monophasic thick grain tissue of ferrite though can see the top layer and the border of thickness of slab central stratum.Relative therewith; Fig. 3 (b) and (c) the thickness of slab central stratum can see soft steel generated austenite annealing temperature mutually after, the ferrite mixed structure of containing bainite structure, pearlitic structure, martensitic stucture that can see when carrying out air cooling, become the visibly different tissue of ferrite single phase structure with the top layer.Among Fig. 3 (d), become the martensitic stucture that contains small amounts of iron oxysome tissue at the thickness of slab central stratum.
Can know not to be in whole steel of having implemented steel processing III, must obtain low iron loss by Fig. 4 above the electro-magnetic steel plate of 6.5 quality %Si.
Therefore; Confirmed the composition of each sample, the result contains the situation more than the 0.3 quality % for situation and the Mn that the C amount contains more than the 200ppm, and the reduction effect of eddy-current loss significantly manifests; Simultaneously, can access the low iron loss of the electro-magnetic steel plate that surpasses 6.5 quality %Si.
In addition, sample D shows low iron loss than common electro-magnetic steel plate (3 quality %Si), but its advantage is compared the trend with reduction with sample B, C.
Then, through chemical grinding observe with sample from the slab warping of a surperficial side when remove at the thickness of slab center.Its result, warpage are that the thickness of slab central side is convex.Hence one can see that, and utilization is ground and before removing, the top layer produced tensile stress, the center produced the stress of compression.
Here; In the present invention; Internal stress is defined as as shown in Figure 5, and original thickness of slab is made as d (mm), when the radius-of-curvature during with above-mentioned slab warping is made as r (mm); Act on tensile stress (face in-draw stress)=the act on stress under compression of thickness of slab central part, face in-draw stress=E * d/ (2r) [MPa] (E representes the modulus in tension of steel plate) on surface.
And then, use the material of the composition of the Sample A become table 1 and sample C, under the condition of above-mentioned steel processing III, Si is carried out various variations diffusion time make sample.For these samples, measure internal stress with aforesaid method, and measure eddy-current loss.Its result is shown in Fig. 6.
According to Fig. 6, containing under C more than the 200ppm, the situation of sample C of Mn more than the 0.3 quality %, the internal stress after above-mentioned siliconising is handled has the trend that becomes big.In addition, be the scope of 70～160MPa at internal stress (face in-draw stress), the reduction of eddy-current loss is remarkable.
The reason of above-mentioned trend is unclear at present, but contriver etc. infer as follows.
For Fe-Si was alloy, in the soft steel level, when the C amount increased in the steel, the γ in the Fe-Si state graph/α boundary line was to the displacement of high Si side, and when implementing the siliconising processing, the part that changes the ferrite phase into increases with the Si concentration gap that keeps austenite part mutually.Think if Si concentration gap increases when high temperature, when then cooling off changing mutually of γ/α taken place and the ferrite of wanting expansible central stratum and the top layer of generation transformation no longer produces internal stress between mutually.
In addition, the effect that Mn adds is: because Mn is the element that makes austenite phase stabilization, so Mn measures when increasing, the phase transition point of γ/α is to the low temperature side displacement.The internal stress that takes place when therefore, thinking cooling further increases.
And then the thickness of slab central stratum is fine mixed structure, and becomes the state that is applied with stress under compression; Therefore be difficult to magnetization, relative therewith, the top layer is thick ferrite crystal grain; And be in the state that is applied with tensile stress, therefore have easy magnetized trend.
Thereby, think that its flux concentrating was on the top layer when direction was magnetized such steel plate in the face of plate, therefore, the result has reduced the eddy-current loss of steel plate.
Should explain, can know that also so long as as above-mentioned sample, have big internal stress, even then apply external stress, core loss value does not rise yet.
That is,,, also can keep the stretched state on top layer even then apply the stress under compression about tens of MPa from the outside so long as externally stress is that zero state produces the internal stress about 70～160MPa down as this sample.Relative therewith, further increase in thickness of slab central part stress under compression, but be exactly to be difficult to magnetized part originally, influence very little.
Its result thinks that the situation that magnetic flux concentrates on the top layer does not easily change, and does not lose the reduction effect of the eddy-current loss of this sample.
In addition; As stated, anneal, relax the Si concentration distribution of steel plate for a long time at high temperature, when perhaps relaxing internal stress; The reduction effect of above-mentioned eddy-current loss and the iron loss deterioration preventing effect of outside stress under compression reduced loses the advantage to the electro-magnetic steel plate with identical Si concentration.
Thereby, can know to comprise the heat treatment period of preferably also considering enforcement till magnetic core is accomplished diffusion time of handling beginning from siliconising.
The present invention is the invention of being based on above-mentioned opinion.
That is, main composition of the present invention is following.
1. a mild steel plate is characterized in that, is the mild steel plate of the cladding type that is made up of thickness of slab central stratum and top layer; The composition of said thickness of slab central stratum be contain below the Si:1.0 quality %, C:0.02～0.16 quality %, Mn:0.3～2.0 quality %, below the P:0.03 quality % and below the S:0.01 quality %; All the other are Fe and unavoidable impurities, and said thickness of slab central stratum is any ferrite mixed structure more than a kind or 2 kinds of containing in perlite phase, bainite phase and the martensitic phase; The composition on said top layer is to contain below Si:3～5 quality %, C:0.02～0.16 quality %, Mn:0.3～2.0 quality %, the P:0.03 quality % and below the S:0.01 quality %, and all the other are Fe and unavoidable impurities, and said top layer is that ferrite is single-phase; This top layer has the face in-draw stress of 70～160MPa as internal stress.
2. according to above-mentioned 1 described mild steel plate, it is characterized in that the total thickness on above-mentioned top layer is 30～60% of total thickness of slab.
3. according to above-mentioned 1 or 2 described mild steel plates, it is characterized in that the thickness of slab of above-mentioned mild steel plate is 0.05～0.35mm.
4. according to each described mild steel plate in above-mentioned 1～3; It is characterized in that the element more than a kind or 2 kinds that is selected among Al:0.002～0.6 quality %, Cr:0.01～1.5 quality %, V:0.0005～0.1 quality %, Ti:0.0005～0.1 quality %, Nb:0.0005～0.1 quality %, Zr:0.0005～0.1 quality %, B:0.0005～0.01 quality % and the N:0.002～0.01 quality % is further contained on the thickness of slab central stratum of above-mentioned mild steel plate and top layer.
5. the method for manufacture of a mild steel plate; It is characterized in that; Through steel plate is heated; In 1050～1250 ℃ austenitic areas and Si is that gas reacts, thereby forms Si content on the top layer of this steel plate: the ferrite phase of 3～5 quality %, in steel, cool off before the Si homogenizing afterwards; Said steel plate contains below the Si:1.0% quality, C:0.02～0.16 quality %, Mn:0.3～2.0 quality %, below the P:0.03 quality % and below the S:0.01 quality %, all the other are Fe and unavoidable impurities.
6. according to the method for manufacture of above-mentioned 5 described mild steel plates, it is characterized in that above-mentioned Si is that gas is the gas more than a kind or 2 kinds that is selected from silicon tetrachloride, trichlorosilane, dichlorosilane, silicomethane, the silicoethane.
7. according to above-mentioned 5 or the method for manufacture of 6 described mild steel plates; It is characterized in that above-mentioned steel plate further contains the element more than a kind or 2 kinds that is selected among Al:0.002～0.6 quality %, Cr:0.01～1.5 quality %, V:0.0005～0.1 quality %, Ti:0.0005～0.1 quality %, Nb:0.0005～0.1 quality %, Zr:0.0005～0.1 quality %, B:0.0005～0.01 quality % and the N:0.002～0.01 quality %.
According to the present invention, can obtain few mild steel plate and the method for manufacture thereof of iron loss deterioration that high frequency characteristics excellence and external stress cause, therefore the core material of excellent in workability can be provided.
Description of drawings
Fig. 1 is the synoptic diagram of expression CRACKING OF LOW CARBON STEELS of the present invention.
Fig. 2 is that the core loss value with the different siliconising treatment processs of soft steel compares and the chart represented.
Fig. 3 be after siliconising that different steel plates become to be grouped into is handled the steel plate cross section organize photo.
Fig. 4 is that the core loss value after the siliconising that different steel plates become to be grouped into is handled compares and the chart represented.
Fig. 5 is the figure of the mensuration main points of the internal stress (face in-draw stress) among expression the present invention.
Fig. 6 is the figure of the relation of expression internal stress (face in-draw stress) and eddy-current loss.
Fig. 7 is the synoptic diagram that is suitable for siliconising stove of the present invention.
Embodiment
Below, specify the present invention.
At first, the structure of steel plate, the qualification reason that becomes to be grouped into etc. are described.Should explain that the % during steel plate becomes to be grouped into is illustrated in expression quality % under the situation that does not have to specify.
As stated, in the present invention importantly to the further additional tensile stress in the top layer of having improved resistivity.
Therefore; Need implement siliconising to the steel plate that becomes austenite phase (below be called the γ phase) at high temperature handles; The Si that increases the top layer measures and improves resistivity, and then only makes the top layer change ferrite phase (below be called the α phase) into, in steel, cools off before the Si homogenizing then.
Through above-mentioned cooling; Thereby form the steel plate of the 3-tier architecture of so-called " cladding type " with 2 layers of top layer of the thickness of slab central stratum and the surface of steel plate back side as shown in Figure 1; Said thickness of slab central stratum is made up of any ferrite mixed structure more than a kind or 2 kinds of containing in perlite phase, bainite phase and the martensitic phase, and said top layer is made up of the high ferrite single phase structure of Si concentration.There is the Si concentration difference between these each top layers and the thickness of slab central stratum, therefore the internal stress that Si concentration gap causes takes place as described above, the top layer additional potential is stretched stress.
Should explain, for the thickness of slab central stratum, under the monophasic situation of ferrite, can not obtain sufficient internal stress, therefore preferably contain above perlite phase, bainite phase and the martensitic phase of 30% (area %) altogether, all the other come down to the ferrite phase.
Here, the Si on top layer amount is 3% when above, and positive big value is got in MS, therefore under the situation that above-mentioned tensile stress plays a role, because magnetoelastic effect and magnetizing easily.Its result when steel plate is magnetized, has promoted magnetic flux to the concentrating of top layer, and eddy current reduces effect and becomes big.
But top layer Si measured greater than 5% o'clock, and MS diminishes on the contrary, and the magnetoelastic effect that tensile stress is brought diminishes, in addition, and surperficial hardening and cause processibility to descend.Thereby the Si amount on top layer is 3～5%.
On the other hand, the MV of the Si of thickness of slab central stratum amount is greater than 1.0% o'clock, diminishes with the Si concentration difference on above-mentioned top layer, and the internal stress of steel plate reduces, so the reduction effect of eddy-current loss dies down.Therefore, the Si concentration of thickness of slab central stratum is below 1.0%.Should explain that the lower value of Si concentration is not special to be limited, but in order when making steel, to remove oxygen in the steel, is preferably about 0.1%.
Should explain, in the present invention, be meant that the Si on the top layer that increases through siliconising infiltrates into inside through sufficient diffusion before the Si homogenizing in the steel, thus the Si concentration of top layer and central stratum become even before.
Thereby, on the top layer part, all have the Si concentration gradient in thickness of slab central stratum part to the thickness of slab degree of depth (center) direction, but this gradient is extremely small, almost can ignore.Thereby top layer Si concentration (amount) among the present invention is meant the average Si concentration (amount) of top layer part.In addition, there is the carbide of point-like or wire in above-mentioned sometimes top layer, but does not also have special problem in this case, and is single-phase better as ferrite in fact.
The tensile stress on above-mentioned top layer need be the face in-draw stress of 70～160MPa.This is because the problem that the tensile stress on top layer during less than 70MPa, exists the reduction effect of eddy-current loss to die down, and on the other hand, during greater than 160MPa, exists magnetic hysteresis loss too to increase and offsets the problem of the reduction effect of eddy-current loss.Thereby, in the present invention, the tensile stress on top layer is defined as 70～160MPa.
In addition, the thickness on above-mentioned top layer is about 30～60% with 2 layers of total thickness that amounts to respect to steel plate preferably.This be because with respect to the total thickness of steel plate less than 30% o'clock, it is big that magnetic hysteresis loss becomes.On the other hand, greater than 60% o'clock, the reduction effect of eddy-current loss died down, and iron loss increases as a result.
Should explain, above-mentioned top layer at thickness, become to be grouped into etc. 2 layers that the aspect need not respectively in top and bottom certain identical, but be preferably same degree.
And then the thickness that is used for steel plate of the present invention is preferably about 0.05～0.35mm.This be because, the thickness of steel plate is during less than 0.05mm, production efficiency descends, manufacturing cost increases.On the other hand, during greater than 0.35mm, eddy-current loss increases, and is not suitable for using core material as high frequency.But even do not satisfy above-mentioned thickness, iron loss of the present invention reduces effect and does not also disappear.
Below, the qualification reason of the composition of the top layer of steel plate and thickness of slab central stratum is described.Should explain, below shown in all the other of steel plate composition be Fe and unavoidable impurities.
In composition, for Si, as stated, need that the top layer is 3～5%, the thickness of slab central stratum is below 1.0%, but for other composition, this is two-layer general for top layer and thickness of slab central stratum.
C：0.02～0.16%、
C is the internal stress that is used to improve steel, obtain sufficient eddy-current loss reduces the necessary element of effect, need contain 0.02% at least.On the other hand, greater than 0.16% o'clock, be easy to generate crackle at the interface of top layer and thickness of slab central stratum.Therefore, C is limited to 0.02～0.16% scope.
Even consider that from the viewpoint that under high frequency, also can access the iron loss lower more preferably C is 0.03～0.10% scope than the electro-magnetic steel plate of 6.5%Si.
Mn：0.3～2.0%
Mn is used to obtain sufficient eddy-current loss to reduce the necessary element of effect, need contain 0.3% at least.On the other hand, greater than 2.0% o'clock, easily after being cooled to room temperature in the also residual γ phase of the thickness of slab central stratum of steel plate, descend with the internal stress on steel plate top layer.Therefore, Mn is limited to 0.3～2.0% scope.
Below the P:0.03%
P is an EMBRITTLEMENT ELEMENTS, owing to be easy to generate crackle on the top layer of steel plate and the interface of thickness of slab central stratum, thus hope to do one's utmost reductionization, but can allow to 0.03%.
Below the S:0.01%
S is the element that becomes hot short reason, because then productivity decline of concentration increase, so hope to do one's utmost reductionization, but can allow to 0.01%.
More than, the basal component of steel plate is illustrated, but in the present invention, in addition, can top layer and thickness of slab central stratum two-layer common contain in the element that is selected from the following stated more than a kind or 2 kinds.
Al：0.002～0.6%
The interpolation of Al can improve intrinsic resistance, therefore is to reducing the eddy-current loss effective elements.Less than down in limited time, lack additive effect, on the other hand, there is the α phase at high temperature before the siliconising in limited time greater than last, so can not make the cladding type steel plate that the present invention proposes.
Cr：0.01～1.5%
The interpolation of Cr can improve intrinsic resistance, therefore is to reducing the eddy-current loss effective elements.Less than down in limited time, lack additive effect, on the other hand, the carbide of separating out on intragranular and grain circle becomes starting point in limited time greater than last, and easy brittle rupture becomes.
V：0.0005～0.1%、Ti：0.0005～0.1%、Nb：0.0005～0.1%、Zr：0.0005～0.1%
The interpolation of V, Ti, Nb and Zr improves the localization effects of magnetic flux to the top layer through reducing permeance at thickness of slab central part formation carbide, nitride, and is therefore effective to reducing eddy-current loss separately.Less than down in limited time, lack additive effect separately, on the other hand, carbide, the nitride of separating out on intragranular and grain circle become starting point in limited time greater than last, and easy brittle rupture becomes.
B：0.0005～0.01%、N：0.002～0.01%
The permeance of this part descends owing to improve the hardenability of thickness of slab central stratum in the process of cooling after siliconising is handled in the interpolation of B and N, owing to improved the localization effects of magnetic flux to the top layer, and therefore effective to reducing eddy-current loss separately.Less than down in limited time, lack additive effect separately, prescribe a time limit greater than last on the other hand, easy embrittlement becomes.
Then, the preferred method of manufacture of mild steel plate of the present invention is described.
Handle the method for manufacture of mild steel plate before for implementing siliconising, not special the qualification can be used known in the past any method well.For example, will become the slab heating that the one-tenth of the thickness of slab central stratum of above-mentioned steel plate is grouped into after, implement hot rolling, carries out cold rolling repeatedly or inserted the cold rolling of the process annealing more than 1 time or 2 times, thereby the steel plate of processing the regulation thickness of slab gets final product.Alternatively, you can implement as needed refining annealing (Shi on げ Annealing).
The steel plate that as above obtains is implemented that siliconising is handled and the Si concentration that increases the top layer forms Si content on the top layer of steel plate: 3～5% ferrite mutually after, in steel, cool off before the Si homogenizing, can make mild steel plate of the present invention thus.
Here, as the method that makes Si infiltration (siliconising), known method all can be used in the past, for example, can enumerate gas phase siliconising method, liquid phase siliconising method, solid phase siliconising method etc.In addition, to be that gas is not special limit the Si that uses this moment, and preferred silane gas for example is selected from the gas more than a kind or 2 kinds in silicon tetrachloride, trichlorosilane, dichlorosilane, silicomethane, the silicoethane.
Below, the method for utilizing gas phase siliconising method infiltration Si is described.
Under the situation of gas phase siliconising method; If fully supply with Si is reactant gases; And the beginning of definite siliconising to end and then the temperature history (residence time of the temperature of each section and steel plate in the stove) till cooling; Then corresponding to thickness of slab and Si addition (siliconising amount), the Si concentration distribution of thickness of slab direction is almost unique to be confirmed.
The siliconising stove that uses among the present invention for example can be enumerated the equipment of structure shown in Figure 7 so long as existing known siliconising stove all can use well.
In the present invention, particularly significantly consider the aspect of the Si concentration distribution of reduction, to Si concentration: when the mild steel plate 1% below is implemented siliconising and handled, preferably under the condition that satisfies following formula 1, implement the siliconising processing from obtaining high frequency iron loss.
Formula 1:1.3 * 10
-4≤(Σ t
k* exp (25000/T
k))/(d
2* [mass%Si]
Add)≤2.2 * 10
-4
Wherein, T
kThe temperature of each section in the stove that steel plate passed through after the expression siliconising was handled and begun, t
kThe expression steel plate is in the residence time of each section, and d representes thickness of slab (mm), [mass%Si]
AddThe expression siliconising is added on the Si amount (increasing amount of the Si mean concns of thickness of slab direction) of steel plate when handling.
Should explain, in the present invention, when temperature changes in the stove, can regard Σ t as
k* exp (25000/T
k) value situation identical, that heat-treat with certain temperature and certain hour.For example, through 5 minutes when 1200 ℃ are cooled to 700 ℃, Σ t
k* exp (25000/T
k) ≈ 1.9 * 10
-6, constant in the time of 1200 ℃, t
kValue be 45 seconds.Thereby it is identical with the heat treated situation that receives 45 seconds at 1200 ℃ that above-mentioned cooling can be regarded as.
In addition, the lower value of the value of above-mentioned formula is less than 1.3 * 10
-4The time, through carry out back operations such as stress relieving than higher temperature, can make the Si concentration distribution suitable.But, less than 1.3 * 10
-4The time, the Si excessive concentration on top layer in fact, the distortion of steel plate takes place in its result when siliconising is handled, perhaps in the man-hour that adds thereafter, crackle, damaged takes place easily in the cut part, therefore preferably satisfies above-mentioned value.
On the other hand, the higher limit of above-mentioned formula is greater than 2.2 * 10
-4The time, internal stress is relaxed, and eddy current reduces effect and descends, and therefore still preferably satisfies above-mentioned value.
Should explain that carry out with tinuous production under the situation of siliconising processing, in the time of below 700 ℃, the Si concentration of steel plate does not change, so the calculating of formula 1 can be arrived till 700 ℃ in the time of reality.
Siliconising treatment temp among the present invention is 1050～1250 ℃.This is because during less than 1050 ℃, can't fully produce internal stress in the time of might cooling off; On the other hand, during greater than 1250 ℃, the high top layer of Si concentration becomes the semi-melting state in siliconising is handled, and steel plate might rupture.
The mild steel plate of having implemented the siliconising processing is behind coating insulation tunicle, through super-dry, sintering circuit.
During through above-mentioned operation, if heat-treating less than 600 ℃, do not cause that then the stress of steel plate relaxes, high frequency iron loss does not rise.But when heat-treating more than 600 ℃, internal stress also relaxes gradually along with change of time, so its high frequency iron loss rises.
Therefore, optimal heat resume when 600～800 ℃ scope is heat-treated have been investigated.Its result has confirmed that so long as satisfy the condition of following formula 2, iron loss just is lower than the homogeneous material of identical thickness of slab, identical Si concentration.Therefore, when 600～800 ℃ scope is heat-treated, preferably satisfy the hot resume of following formula 2.
Formula 2: (Σ t '
k* exp (25000/T '
k))/(d
2* [mass%Si]
Add)≤0.2 * 10
-4
Here, T '
kThe temperature of each heat treatment step that steel plate passed through after the expression siliconising was handled, t '
kThe expression steel plate is in the residence time of each heat treatment step, and d representes thickness of slab (mm), [mass%Si]
AddThe expression siliconising is added on the Si amount (increasing amount of the Si mean concns of thickness of slab direction) in the steel plate when handling.
In addition, same with the situation of above-mentioned formula 1, during temperature variation, can regard Σ t ' as in the stove
k* exp (25000/T '
k) value situation identical, that heat-treat with certain temperature and certain hour.
The mild steel plate of having implemented the siliconising processing is assembled into iron core through various manufacturing procedures such as over-segmentation, shearing, punching press, at this moment, implements stress relieving sometimes.In this case also because the annealing more than 600 ℃ relaxes internal stress, so preferred temperature and time according to the mode regulation stress relieving of satisfying above-mentioned formula 2.
In addition, at drying, the sintering of the tunicle that insulate more than 400 ℃, when stress relieving was implemented in the processing back, preferably heat treatment step and the stress relieving operation with tunicle amounted to, to satisfy the mode design temperature and the time of above-mentioned formula 2.
According to more than, can set creating conditions that the heat treatment period that will till magnetic core is accomplished, implement also takes into account.
Embodiment
< embodiment 1 >
To become the sample that the one-tenth shown in the table 2 is grouped into and roll, form thickness of slab: 0.2mm, heat at 1200 ℃ then, at SiCl
4+ N
2After the siliconising that will be equivalent to 3%Si in the environment is handled and the Si DIFFUSION TREATMENT carries out 3 minutes altogether, be cooled to room temperature with 10 ℃/min.
Utilize Epstein test method(s) (JIS C 2550) to measure the high frequency iron loss of these samples.The result is shown in table 3 with the Si concentration of top layer and thickness of slab central stratum.
[table 2]
| Sample No. | C | Si | Mn | P | S |
| 1 | 0.005 | 0.1 | 0.03 | 0.008 | 0.004 |
| 2 | 0.023 | 0.1 | 0.05 | 0.006 | 0.003 |
| 3 | 0.024 | 0.1 | 0.31 | 0.006 | 0.003 |
| 4 | 0.050 | 0.2 | 0.45 | 0.006 | 0.003 |
| 5 | 0.075 | 0.1 | 1.15 | 0.006 | 0.003 |
| 6 | 0.075 | 0.5 | 1.15 | 0.030 | 0.003 |
| 7 | 0.075 | 0.3 | 1.52 | 0.007 | 0.003 |
| 8 | 0.017 | 0.1 | 0.45 | 0.006 | 0.003 |
(annotate: unit all is %, and all the other are Fe and unavoidable impurities)
[table 3]
Shown in this table, the invention example (No.3～5 and 7) that obtains according to the present invention all can obtain being lower than the iron loss of 3%Si electro-magnetic steel plate.
< embodiment 2 >
To in table 2 with the sample of No.2～5 expression, give abreast with magnetized direction ± stress under compression of 50MPa investigates the variation of iron loss.Utilize Epstein test method(s) (JIS C2550) to measure these high frequency iron loss.
The result who obtains is shown in table 4.
[table 4]
Annotate: 20k=20000
Shown in this table, can know 3%Si electro-magnetic steel plate in the past because external compression stress has shown the significantly iron loss more than 2 times rises, relative therewith, be rising (maximum is also with regard to the iron loss of 14W/kg) slightly according to steel plate of the present invention (sample No.3～5).In addition, even receiving under the situation of outside tensile stress according to steel plate of the present invention, iron loss is also very low, and maximum is 12W/kg just.
Utilizability on the industry
Can obtain the few mild steel plate of iron loss deterioration that high frequency characteristics excellence and then external stress cause in the present invention.Its result can obtain the few high frequency of iron loss with unshakable in one's determination, can make the high X-former of energy efficiency, other electricinstallation thus.
Claims (7)
1. a mild steel plate is characterized in that, is the mild steel plate of the cladding type that is made up of thickness of slab central stratum and top layer,
The composition of said thickness of slab central stratum be contain below the Si:1.0 quality %, C:0.02～0.16 quality %, Mn:0.3～2.0 quality %, below the P:0.03 quality % and below the S:0.01 quality %; All the other are Fe and unavoidable impurities; Said thickness of slab central stratum is any ferrite mixed structure more than a kind or 2 kinds of containing in perlite phase, bainite phase and the martensitic phase
The composition on said top layer is to contain below Si:3～5 quality %, C:0.02～0.16 quality %, Mn:0.3～2.0 quality %, the P:0.03 quality % and below the S:0.01 quality %, and all the other are Fe and unavoidable impurities, and said top layer is that ferrite is single-phase,
This top layer has the face in-draw stress of 70～160MPa as internal stress.
2. mild steel plate according to claim 1 is characterized in that, the total thickness on said top layer is 30～60% of total thickness of slab.
3. mild steel plate according to claim 1 and 2 is characterized in that, the thickness of slab of said mild steel plate is 0.05～0.35mm.
4. according to each described mild steel plate in the claim 1～3; It is characterized in that the element more than a kind or 2 kinds that is selected among Al:0.002～0.6 quality %, Cr:0.01～1.5 quality %, V:0.0005～0.1 quality %, Ti:0.0005～0.1 quality %, Nb:0.0005～0.1 quality %, Zr:0.0005～0.1 quality %, B:0.0005～0.01 quality % and the N:0.002～0.01 quality % is further contained on the thickness of slab central stratum of said mild steel plate and top layer.
5. the method for manufacture of a mild steel plate; It is characterized in that; Through the heating steel plate, in 1050～1250 ℃ austenite region, making itself and Si is that gas reacts, and is the ferrite phase of 3～5 quality % thereby form Si content on the top layer of this steel plate; In steel, cool off before the Si homogenizing afterwards
Said steel plate contains below the Si:1.0% quality, C:0.02～0.16 quality %, Mn:0.3～2.0 quality %, below the P:0.03 quality % and below the S:0.01 quality %, all the other are Fe and unavoidable impurities.
6. the method for manufacture of mild steel plate according to claim 5 is characterized in that, said Si is that gas is the gas more than a kind or 2 kinds that is selected from silicon tetrachloride, trichlorosilane, dichlorosilane, silicomethane, the silicoethane.
7. according to the method for manufacture of claim 5 or 6 described mild steel plates; It is characterized in that said steel plate further contains the element more than a kind or 2 kinds that is selected among Al:0.002～0.6 quality %, Cr:0.01～1.5 quality %, V:0.0005～0.1 quality %, Ti:0.0005～0.1 quality %, Nb:0.0005～0.1 quality %, Zr:0.0005～0.1 quality %, B:0.0005～0.01 quality % and the N:0.002～0.01 quality %.
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| CN102910704A (en) * | 2012-11-09 | 2013-02-06 | 无锡电站辅机厂 | High-speed mixed bed |
| CN102927371A (en) * | 2012-11-09 | 2013-02-13 | 无锡电站辅机厂 | Double-support pipe clamp |
| CN108884535A (en) * | 2016-03-31 | 2018-11-23 | 杰富意钢铁株式会社 | Electromagnetic steel plate and its manufacturing method |
| CN108884535B (en) * | 2016-03-31 | 2020-08-18 | 杰富意钢铁株式会社 | Electromagnetic steel sheet and method for producing same |
Also Published As
| Publication number | Publication date |
|---|---|
| CN102639745B (en) | 2014-08-20 |
| JP5655295B2 (en) | 2015-01-21 |
| JP2011119298A (en) | 2011-06-16 |
| WO2011065023A1 (en) | 2011-06-03 |
| TW201134953A (en) | 2011-10-16 |
| KR20120112435A (en) | 2012-10-11 |
| TWI461544B (en) | 2014-11-21 |
| KR101399995B1 (en) | 2014-05-28 |
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