Chuong 4- Hoquang

8/9/2019 Chuong 4- Hoquang

1/17

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Chng IV

LUYN THP TRONG L IN H QUANG

4.1. c im v phn loi4.1.1. c im

L in h quang l loi l c dng rt ph bin nc ta. u im ca l

in l:

+ Nu c nhiu loi nguyn vt liu (gang, thp vn ...);

+ Chy hao kim loi t;

+ D dng iu chnh nhit nc thp;

+ Nu c nhiu loi thp, cht lng thp tt;

Hn ch ca l in h quang l in nng t.4.1.2. Phn loi

Da vo cng sut bin p v dung tch cha thp, ngi ta phn ra:

+ L in h quang cng sut thng: 400kVA/tn.

+ L in h quang cng sut cao: 600 800kVA/tn.

+ L in h quang siu cng sut: > 800kVA/tn.

Da vo ngun in, phn ra:

+ L in h quang xoay chiu: dng ngun in xoay chiu, l c ba in cc.+ L in h quang mt chiu: dng ngun in mt chiu, l ch dng mt

in cc.

4.2. Thit b4.2.1. Cu to chung v nguyn l lm vic

Hnh 4.1 trnh by cu to chung ca l in h quang, l gm cc b phn c

bn sau:

+ Bung l;

+ Thit b nghing l;

+ Thit b nng hin cc;

+ Thit bin (my bin th v mng in).


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L in h quang s dng ngun nhit l ngn la h quang sinh ra gia cc

in cc v kim loi nu. Khi nu, in cc c h xung chm vo kim loi gy ra

hin tng ngn mch, sau nng in cc ln cch mt kim loi mt khong cch

nht nh, gia in cc v kim loi pht sinh ngn la h quang. Do h quang gy ra

trc tip gia in cc v kim loi nu nn c gi l h quang trc tip, nhit

ngn la h quang rt cao v nhit tp trung nn nhit truyn cho kim loi rt ln v

Hnh 4.1. Cu to tng th ca l in h quang1) Vi phun oxy 2) in cc grafit 3) ng ht khi bi 4) Np l 5) V l bng thp

6) Ca thao tc 7) Thit b dch chuyn v l 9) B phn dn ng quay l 10) ta bphn dch l 11) Thit b quay np l 13) B phn quay khung l 14) Qut thng kh

15) B phn lm ngui in cc 16) Thit b nng hin cc 17) Dy cp in


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ch yu l truyn nhit bc x. Theo mc nng chy ca kim loi trong bung l,

in cc c iu chnh gi khong cch gia in cc v kim loi n nh, nh

h quang chy n nh.

4.2.2. Bung lBung l gm ba phn: y l, thn l v nc l (hnh 4.2).

y l: lm nhim v cha kim loi v x. Phn trn y l c dng hnh cn,

gc nghing 45o, phn di c dng chm cu. Chiu dy th xy y l thng t

650 700 mm, gm:

+ Lp manhdit thiu kt dy 180 200 mm;

+ Lp gch manhdit dy 295 mm;

+ Lp gch samt dy 130 mm;+ Lp vn samt dy 30 mm;

+ Lp ba aming dy 10 mm.

Ngoi cng l v l bng thp tm dy 20 mm.

Tng l: to khng gian cha liu, ng thi chu lc tc dng ca nc l.

Chiu dy tng l thng t 350 700 mm, gm cc lp:

D2

D1

d

h3

h1

h2

H1

10

0a

b

Hnh 4.2 S cu to bung l in h quang

D3


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+ Lp gch manhdit dy 285 mm.

+ Lp gch samt dy 130 mm.

Nc l: c dng hnh chm cu, xy bng gch crm-manhdit hoc bng gch

dinat, chiu dy khong 300 mm. nc l, khi xy cha ba l trng t ba incc.

Th xy y v tng l in h quang baztrnh by trn hnh 4.3.

.

Cc kch thc cbn ca bung l: thng khi thit k l, s liu cho ban u

l cng sut l (T/h), t c th tnh c khi lng ca m kim loi nu, th tch

ca kim loi v x. Trn cs, xc nh dung tch ni l v cc kch thc cbn

ca bung l.

Da vo hnh 4.2 ta c th tnh nh c th tch ni l:

( )

222

2

1

2

1

rRR3

h.

6

h

8

rh.V +++

+= (4.1)

Trong :2

dr= v

2

DR 1= .

1

2

64

5

3

Hnh 4.3 Th xy tng v y l h quang baz1) Lp manhdit thiu kt 2) Lp gch manhdit 3)Lp gch samt

4) Lp vn samt 5) Lp ba aming 6) V thp


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Cc kch thc ca ni l thng c chn theo chiu cao ni l H:

H5D1= H

2

5

2

DR 1 ==

H.51h1 =

H.5

4hHh

12==

H5

17h2Dd

21==

H7,1d2

1r ==

Thay cc gi tr trn vo cng thc (4.1) ta tnh c:3H6,11V =

Suy ra: 36,11

VH = (4.2)

Cc kch thc khc ca tng l c chn theo chiu cao ni l H nh sau:

200H5200DD 12 +=+= [mm]

( )H2,21,2H1

= [mm]

( ) 200H44,542,5D3 += [mm]

Chiu cao nc l:

33 D8

1

7

1h

= [mm]

Chiu rng ca l:

3D3,0a =

Chiu cao ca l:

a8,0b = .

Dung tch l mi thit k thng nh hn 30 40% so vi sau khi nu, do c

th nu qu t 15 20% (bng 4.1).


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Bng 4.1 Dung tch l h quang luyn thp

Ti trng cht (tn)

L baz

Dung tch

danh ngha

(tn) Nu bnh thng Nu cng bcL axit

0,5 0,7 0,8 0,8 0,9 1,0 1,1

1,5 2,0 2,2 2,3 2,5 2,6 2,8

3,0 3,8 4,2 4,5 5,0 5,2 5,5

5,0 6,0 7,0 7,4 7,8 8,0 8,5

10,0 12,0 13,0 14,0 16,0 -

4.2.3. Thit b nng hin ccTrong qu trnh nu luyn, mc kim loi di in cc thay i, in cc b

mn dn... duy duy tr h quang chy n nh, ba in cc ca l cn phi chuyn

ng ln xung ph hp. Thit b nng hin cc lm nhim viu chnh in cc

trong sut qu trnh nu luyn, m bo khong cch gia in cc v kim loi hoc x

duy tr ng theo yu cu.

Thit b nng hin cc gm:

+ Gi lp in cc;

Hnh 4.4 Thit b nng hin cc1) Gi lp in cc 2) Tr dn hng3) H thng dn ng 4) Kp in cc 5) i trng

5

1

2

4

3


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+ H thng dn ng;

+ Tr dn hng.

Gi lp in cc dng kp in cc, ccu kp c lm ngui bng nc.

Dn ng ccu iu chnh nng hin cc thc hin bng h thng ckh hoc hthng thy lc. Chuyn ng iu chnh c tng ha.

4.2.4. Ccu nghing li vi l in h quang ra thp qua mng ra thp bn hng khi ra thp phi

nghing l. nghing l c th dng ccu ckh hoc thy lc.

4.2.5. Thit binS mng in v bin p ca l in h quang trnh by trn hnh 4.5.

Dng in cao th tng dy (1) qua cu dao khng kh (2), cu dao du

chnh (3), cun cm (7), my bin p (9) ti in cc (12) v sinh ra h quang gia

in cc v kim loi (13). Cu dao khng kh (2) dng ng mthit bin ca l,

n chc ng mkhi cu dao du chnh (3) m. Cu dao du chnh dng ngt

mch in. V y c dng cao th chy qua, nn phi dng cu dao ny m bo

an ton (cu dao u chnh trit tiu c tia la in pht ra khi ngn mch).

m bo an ton cho mch in ca l, ngi ta phi dng h thng ng h

o v rle bo v (6), khi dng in hay in p tng qu t ngt, n c kh nng t

ng ngt mch. Cun cm (7) ca my bin th c kh nng to ra sc in ng cm

ng bin h quang gin on thnh h quang lin tc, do h quang v dng in

n nh, liu s chng chy, nhng khi c cun cm th s tng tiu hao in, khng s

dng ht cng sut ca my bin p, h s cos gim. V vy khi nu chy xong, h

quang v dng in n nh th phi ct cun cm khi mch, thc hin vic

dng cu dao u in cm (8).

Bin p (9) ch yu i dng in h th ph hp vi tng giai on nu

luyn. Yu cu ca bin p l h quang l cch in rt tt, c kh nng qu ti ln

chu c on mch v qu ti thng xuyn.


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1

2

3

4

6

5

7 8

9

10

11

12

13

Hnh 4.5 S thit bin ca l in h quang

1) ng dy cao th 2) Cu dao khng kh 3) Cu dao du chnh 4) B phn odng 5) B phn o p my bin p 6) ng ho v rle bo v 7) Cun cm8) Cu dao du cun cm 9) My bin p 10) Cu dao i in p 11) ng ho,

thit b bo v v tng iu chnh in cc 12) in cc 13) Kim loi


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Ty theo tng giai on nu, ngi ta yu cu nhng cp in p khc nhau. Do

, my bin p cn c nhiu cp in p, thng l su cp in p ty theo cch mc

hnh sao ( ) hay tam gic ().

Th d su cp in p ca my bin p l:

Khi mc tam gic: 260 V - 220 V - 180 V.

Khi mc hnh sao: 150 V - 127 V - 104 V.

Ty theo tng giai on nu, ta s dng in p thch hp, thng thng:

Giai on nu chy: 240 380 V.

Giai on oxy ha: 160 200 V.

Giai on hon nguyn: 140 115 V.

Cng sut my bin p xc nh theo cng thc:

= cos.I.U.3P

Trong :

P - cng sut my bin p;

U, I - in p v cng dng in.

Theo yu cu nu luyn, cng sut gim dn t giai on nu chy sang oxy

ha n hon nguyn (hnh 4.7).

Hnh 4.6 Cc phng php ni cun dy my bin pa) Mc hnh sao b) Mc tam gic

a) b)


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in cc t thiu chuyn dng cho sn xut fer. in cc dng cho luyn thp

thng dng in cc grafit. in cc cacbon hin nay t dng.

Theo cng sut l, in cc grafit c phn ra:

+ in cc grafit thng;+ in cc grafit cng sut cao;

+ in cc grafit siu cng sut.

in cc c ch to dng hnh tr, u cui c phn lp u ni hnh tr hoc

hnh cn c ren (hnh 4.8).

Cc ch tiu ha l ca in cc grafit thng dng trnh by bng 4.3.

Bng 4.3 Cc ch tiu ha l ca in cc grafit thng dng

ng knh in cc (mm)

75 130 150 200 250 350 400 500Ch tiu

cp

cao

cp

1

cp

cao

cp

1

cp

cao

cp

1

cp

cao

cp

1

Thn 8,5 10 9,0 11 9,0 11 9,0 11in trsut

min (.mm2/m) ni 8,5 8,5 8,5 8,5

Thn 7,85 7,85 6,37 6,37Cng b gy

min (Mpa) ni 11,3 11,3 9,81 9,81

Thnh phn tro

max (%)Thn 0,5 0,5 0,5 0,5

Hnh 4.8 Cu to in cc1) Thn in cc 2) u ni

1

2


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Mt thc

min (g/cm3)Thn 2,18 2,.18 2,18 2,18

Thn 19,6 19,6 17,7 17,7 bn nn

min (MPa) ni 29,4 29,4 29,4 29,4

Cng dng in cho php ph thuc ng knh in cc (bng 4.4).

Bng 4.4 Cng dng in cho php

ng knh

in cc

Cng

dng in

cho php (A)

ng knh

in cc

Cng

dng in

cho php (A)

75 1000 1400 300 10000 13000100 1500 2400 350 13000 18000

125 2200 3400 400 18000 23000

150 3500 4200 450 22000 30000

200 5000 6900 500 25000 34000

250 7000 10000

Ch tiu ha l ca in cc grafit siu cng cng sut cho bng (4.5)

Bng 4.5 Ch tiu ha l ca in cc grafit siu cng cng sut

ng knh in cc (mm)

225 400 400 600Ch tiu

Thn u Thn u

Hm lng C (%) 99,3 99,3 99,3 99,3

Tro (%) 0,2 0,2 0,2 0,2

Xp (%) 20 24 20 24 20 23 20 23

Mt (g/cm3) 1,65 1,72 1,74 1,80 1,66 1,73 1,74 1,81

in trsut

(mm2/m)5,0 6,5 4,5 5,5 4,5 5,75 4,0 5,0


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Un (MPa) 9,0 14,0 - 8,5 13,5 -

Nn (MPa) 6,6 10,0 14,0 20,0 6,0 9,5,0 13,0 19,0

M un n hi

(GPa)6,5 11,0 12,5 18,0 6,0 11,0 12,0 17,0

H s dn nhit

(w/m.oC)

175 260 240 260 210 280 250 320

H s gin nnhit

(10-6/oC)0,5 1,0 0,4 0,9 0,3 0,6 0,75 0,6

i vi in cc grafit cn lu :

+ Khi bo qun in cc grafit cn trnh ma gi lm m in cc, trong qutrnh vn chuyn phi ht sc cn thn trnh va p, trc lc s dng cn sy kh

nhit 100oC.

+ Khi ni in cc cn vn cht trnh to khe h, dn n sinh h quang

mi ni khi dng in i qua.

+ Khi np liu trnh liu va p vo in cc.

4.3. Cng ngh nu luyn4.3.1.

Nguyn vt liu

Nguyn vt liu dng luyn thp trong l h quang gm:

+ Nguyn liu kim loi: thp ph, gang, phe-r hp kim, st xp.

+ Liu to x: gm vi, hunh thch ...

+ Liu oxy ha: qung st, kh oxy ...

4.3.2. Cng ngh luyn thp thp trong l in h quang baza) Giai on nng chy

Trong giai on ny liu c nung nng n nhit nng chy v chuyn

sang th lng. y l giai on quan trng trong qu trnh luyn thp, chim ti 60%

thi gian nu luyn.


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u tin cht mt lp thp phm di y l trnh va p gy hng y

l khi cho liu thi ln vo. Tip theo cho gang thi vo khong 50%, sau cht mt

lp thp ph ln trn.

Khi bt u nu luyn, liu cht gn y l, h quang nm gn nc l, ch dngkhong 50% cng sut trnh lm hng nc l. Sau khi liu di in cc nng

chy, kim loi lng tp trung xung y l, xung quanh in cc to thnh h (ta gi

giai on ny l giai on o h), tng cng sut l ln cc i (Wmax) v tip tc iu

chnh in cc i xung duy tr h quang. Khi nc thp tp trung y l dn dn

dng ln v in cc xung gn mt nc thp, iu chnh in cc i ln theo tc

dng ca mt nc thp. Trong qu trnh nu chy, liu st thnh l kh nng chy

v xa h quang, tng qu trnh nng chy ngi ta c th thi kh oxy vo qua cc

vi phun b tr quanh thn l.

Khi liu rn nng chy ch cn cc nh nm trong thp lng, cho thp ph vo

v tip tc nu chy, khng nn cho thp ph vo khi liu nng chy hon ton, v

nh vy d gy bn te kim loi lng gy nguy him.

Trong giai on ny, nhit tiu tn ln, nu chy nhanh cn phi dng cng

sut l ln, kt hp thi thm oxy. Cui giai on nu chy ly mu phn tch thnh

phn ha hc (ch yu l phn tch cacbon v phtpho).

b) Giai on oxy haTrong giai on ny xy ra cc phn ng oxy ha cc nguyn t C, Si, Mn, P, S,

ng thi tin hnh kh kh v tp cht phi kim. Do cc phn ng oxy ha to nhit

nn cng sut l giai on ny khng cn ln (ch cn khong 50% Wmax). Trong giai

on ny Si b khu tin, khi Si ch cn 0,02% th Mn bt u b kh. Trong giai

on nu chy, Mn bt chy khong 50%, sau giai on oxy ha tip tc bt chy

cn li 0,2%.

kh P kim (B) phi cao, hm lng (FeO) cao v nhit (T) thp. Khi

kh S kim phi cao, nhng hm lng FeO trong x cng thp cng tt v nhit

phi cao.


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Trong giai on oxy ho cm m bo [C], [P] v nhit t yu cu. i vi

[S] trong giai on ny t quan tm nhng cui giai on cng phi xc nh [S]

chun b cho giai on x l tip theo.

c) Giai on hon nguynGiai on hon nguyn ch duy nht luyn trong l in h quang mi c cn

trong cc l khc khng c. Mc ch ca giai on ny l kh [S] nu cn, sau kh

[O] v hp kim ho, ng thi nng nhit thp lng.

Kh oxy bng phng php khuch tn: u tin tin hnh co b x oxy ha,

sau tin hnh to x hon nguyn, thnh phn gm vi (CaO) v cht tr dung

(CaF2) v bt than, khi kim ca x tng, hm lng (FeO) gim xung, lng

dng cht to x khong 4 7%.Vi lm tng kim ca x.

Cht trdung CaF2 lm gim nhit nng chy ca CaO.

Bt than: ( ) ( ) { }+=+ COFeCFeO

Lc ny kh [S] rt tt v B tng, (FeO) gim v nhit cao.

Thc t trong giai on ny, hm lng kh [H], [N] vn cn do dng h quang

a vo.

Khi a bt than vo cn trnh ch dng h quang, v khi gp dng h quang:

++ COCaCC2CaO Tcao

++=+ CO(CaO)(Fe)CaCFeO

Cui giai on hon nguyn cho Si v Mn vo t hm lng yu cu ca

mc thp.

[ ]( )MnFeMn%

CCQP 21MnFe

=

Trong :

C1 : hm lng cn c trong thp.

C2: hm lng cn li trong thp lng trc khi cho fer vo.

Sau khi ra thp, ch lng 3 5 pht, ng thi tp cht ni ln v tng s

ng u thnh phn mi tin hnh rt khun.


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i vi quy trnh luyn thp hin i trong l in siu cng sut v c lin

tc, giai on nu luyn thng rt xung di mt gi, l in ch lm hai nhim v

nu chy v oxy ha, cn tinh luyn, kh [O], kh tp cht, kh kh v hp kim ho

tin hnh ngoi l.4.3.3. Tinh luyn ngoi l

Tinh luyn ngoi l c th tin hnh bng phng php chn khng x hoc thi

kh (xo trn). Di y trnh by phng php tinh luyn bng thi kh l phng

php ph bin trong cng ngh luyn thp hin i, l tinh luyn bng l LF (Ladle

Furnace).

S cu to l LF trnh by trn hnh 4.9.

Np l c cu to tng t l in h quang cng sut thng. Tng l gm 4

lp (mt ct A) tnh t ngoi vo gm: v l bng thp, lp aming, lp gch xp cch

Hnh 4.9 S cu to l LF

1) Np l 2) Tng l 3) y l 4) Gch xp 5) L rt6) Tm chn 7) ng dn kh acgng 8) Ca quan st 9) Ca vo liu

2

53

67 4

B

A

C D

BC D

A

1

Gch manhedit Gch xp thu kh Gch ZrO.C

Tm chnchuyn ng

8 9


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nhit v lp gch lm vic. Phn tng l ngang mc cha x (mt ct B), lp lm vic

xy bng gch manhedit. phn y l c b tr cc vin gch xp thu kh (mt ct

C) v l thi kh (mt ct D). Bn di l thi kh t hai tm chn c l cho kh i

qua, mt tm t cnh, mt tm chuyn ng qua li khi lm vic. tinh luyn v kh kh, sau khi cho thp lng vo l, tin hnh to x hon

nguyn, gy h quang chm trong x v thi kh acgng vo l. Khi sc kh acgng vo

l, cc bt kh to ra s xo trn mnh thp lng lm tng qu trnh ni ca cc ht ln

rn, ng thi kh [H], [N] khuch tn vo cc bt kh v b cun ra ngoi. Nhs xo

trn mnh ca thp lng s kh [S] cng tng ng k.

Qu trnh tinh luyn tng t nh giai on hon nguyn trong l in h

quang.

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Chuong 4- Hoquang