3.3 Các Phương Pháp Hàn_SAW

7/24/2019 3.3 Cc Phng Php Hn_SAW

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3.3 Cc phng php hn.docx

2. Hn h quang chm (SAW) 1

Hn h quang chm (SAW) l mt phng php hn t ng nng sut cao, thit b, loi hnh rt a

dng ngy cng c p dng ph bin trong sn xut kt cu thp. Hnh 4 l m t s nguyn lca phng php.

Phng php SAW c h s hiu dng nng lng n 100%, t l thuc / dy hn 1:1 , h quang

chy ngm rt t khi v hu nh khng c bc x c hi.

Phng php SAW thng dng sn xut ng , dm thp, bn b p lc, cu kin v thn tu v

boong topsite, sn cng trnh thp.

1 Phng php submerged-arc welding (SAW) - c gi l phng php hn h quang chm hoc hn t ng c cpbng sng ch vo nm 1935. Pht trin nguyn bn c xut bi Jones, Kennedy v Rothermund, qu trnh cthc hin bng cch s dng mt h quang chy gia in cc dy kim loi c hoc c li thuc v b mt vng hn to ra b hn. H quang v kim loi nng chy c che chn bi mt vm hnh thnh t x nng chy t thuc hndng vin cung cp t hp cp. Qu trnh hn khi din ra ngm di lp thuc l hp cht ca vi, nc thytinh, oxyt mangan , calcium fluoride, v cc thnh phn khc. Khi nng chy, thuc hn to nn mt lp dy dn in,

h quang chy trong mi trng nh vy loi tr c cc vng te, ti thiu bc x v khi hn. Hn SAW c phttrin t nguyn l ca phng php SMAW Tuy nhin, c s khc bit r rt v bn cht ca h quang v nng lngnhit . SAW ch yu c thc hin nh cc thit b t ng, mc d thi k u cc phng php bn t ng (semi-automatic) vn c dng. Qu trnh c thc hin ch yu t th phng v gc ngang ; nhng ci tin sau ny chophp thc hin t th hn rnh ngang, thm ch hn t th ng, song i hi cc thay i ph hp v phng thc xl thuc hn v qu trnh ng rn ca b hn. Nng sut p ca hn SAW c th t 45 kg/h (100 lb/h), so snh viMax ~5 kg/h (10 lb/h) ca phng php SNAW r rnh l mt ci tin ngon mc v nng sut. SAW thng c trinkhai vi dng hn ph bin t 300 n 2000 A; cc bin th ca SAW hn nhiu dy (in cc) sau ny c th s dngdng hn n 5000 .Dy in cc s dng trong phng php SAW rt a dng, t mt n (Max) 5 dy, t dng trnn dng dy bng (strip), t dy c, n dy li thuc, thm ch l dy composite (cladding-strip). Ngun hn DC ctnh CV v b cp dy tc khng i thng c a chung s dng dng hn thp, v AC vi b b cp dyiu chnh in p s dng vi dng hn cao.

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https://en.wikipedia.org/wiki/Shielded_metal_arc_weldinghttps://en.wikipedia.org/wiki/Lime_(mineral)https://en.wikipedia.org/wiki/Silicon_dioxidehttps://en.wikipedia.org/wiki/Silicon_dioxidehttps://en.wikipedia.org/wiki/Calcium_fluoridehttps://en.wikipedia.org/wiki/Shielded_metal_arc_welding


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Hnh 5 : S nguyn l phng php SAW.

SAW c th s dng hn hu ht kim loi s dng trong cng nghip. c bit trong cng ngh hn

p 2.

2.1 c im

2.1.1. ng dng a dng

Tnh a dng ca phng php SAW th hin bi nhng c im sau:

Dy (electrode) v thuc hn (Flux) c pht trin c lp vi cc thnh phn khc nhau,khi phi hp thng qua t hp dy - thuc , to ra mi hn c c l tnh phong ph p ngtt mi yu cu ca mi hn.

Phm vi cng dng hn rng , t 300 n 5000A cho php s dng in cc a dng c

v kch thc, hnh dng ln cu to; cho php phng php SAW c nhng ty bin cngngh phong ph.

H quang chy ngm trong vm kh (hoc x nng chy 3) c che chn tt c th to rahai c ch chuyn i nng lng in thnh nhit gip tng hiu sut v cng nng ca qutrnh.

iu chnh cc tham s hn (in p, dng hn, tc , b dy lp x ) c lp gip ti uha qu trnh hng n cc mc tiu (c tnh, nng sut, c im luyn kim) theo yu cuphong ph.

Vn hnh theo c ch t ng, d lp trnh kim sot v duy tr n nh cc tham s ca qutrnh.

Do tnh nng hiu chnh c lp ca cc tham s nn qu trnh ti u ha qui trnh hn tng iphc tp, i hi kin thc v qu trnh v cc c im luyn kim ca t hp dy - thuc. T

mc d gim thiu yu cu k nng ca th hn song li i hi s thnh tho v thu o v qu

trnh.

Do nng sut p cao cn thit b hot ng n nh v tin cy nn ch ph hp khi sn xut hn

khi ln, cng vic n iu, mi hn n gin, ch yu t th phng v gc ngang.

Chi ph u t v qun l cao khng thun tin vi sn xut n l hoc trn cng trng lu ng.

2.1.2. Cc bin thPhng php SAW c nhiu ci tin tng nng sut v tha mn cc yu cu luyn kim ca lp

p. SAW c th s dng dy hn c cu hnh khc nhau hoc thnh phn khc nhau, s dng

chung ngun hn hoc cc ngun hn mc song song. Hnh 6 di y m t cc bin th ca

phng php SAW.

2 Ba phng php p b mt c th p dng SAW bao gm : - Cladding / overlaying : p mt lp kim loi c tnhnng chuyn dng ln b mt tm / cu kin bng thp c c tnh v tnh hn tt. - Hard-facing : p mt lp kim loitng cng ln b mt chi tit.

3 sut nng lng thp (chy trong vm kh hnh thnh t thuc hn) chuyn i nng lng in - nhit thng qua ct

plasma h quang. sut nng lng cao (tc cp dy ln, b dy lp x lng cao) chuyn i nng lng in -nhit thng qua in tr ca lp x, dy hn dm v nng chy trong x lng - burried arc).

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Hi2nh 6 : Cc bin th ca phng php SAW

SAWCore wire

SAWTwin-arc

SAWTandem

SAWTandem-twin

SAWMulti-Wire

S dng dy li thuc,composite trn thit b SAW

S dng hai dy hncng / khc loi trnmt thit b SAW

S dng hai dy hn(khc loi) vi hai thit bSAW khc nhau

S dng hai u hn Twin-arc trong mt qu trnhTandem

S dng phi hp u hn v qutrnh SAW trong mt lt hn

C dy(mm) 1.6 - 5.0 1.2-3.0 3.0-5.0 2.5-3.0 3.0-5.0

Dng hn (A) 200-1000 400-1200 1500-2400 1500-2200 2000-5500

in p (V) 25-38 26-38 28-38 26-38 30-42

Ngun DCEP DCEP DCEP + AC DCEP + AC DCEP + AC + ACNS p (kg/h) >12 >15 >25 >38 >90

Hnh 7 cung cp ton cnh v phm vi dng in v nng sut p. Qua ta thy nng sut p gn nh t l bc nht vi dng hn vi c lng gn

ng : NS0.025Ihn Cng thc ny c th dng lm cn c chn cc tham s qu trnh (mc 2.2).

Hnh 7 quan h nng sut p v dng hn

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2.2. Tham s qu trnh SAW.

2.2.1. Tc ng ca dng hn

on trn, t cc s liu thng k cho thy l dng hn t l bc nht vi nng sut p. V mt

vt l th nng sut p s ph thuc vo hai yu t:

Tc cp dy (WFS) : lngdy hn b t chy trong mt nv thi gian.

H s p (DR) t l kim loic hon nguyn t thuc hn,ty thuc vo lng bt st,qung st c trong thnh phnthuc hn.

Ngoi ra dng hn cng cao th ngu

( su kim loi nn nng chy) cng

cao. Khi lng kim loi nn tham gia

vo b hn c tnh bng % Dilution 4

(% ha tan ca kim loi nn / kim loi

p) vo kim loi mi hn. (hnh 8)

Hnh 8 : Cch c lng % Dilution

Thc t th nh sn xut lun cung cp cho chng ta t hp dy - thuc nhm tha mn yu cu

thnh phn ha hc (Mn, Si) khi hn thp kt cu TMCP ph thuc rt t vo % dilution.

Hnh 9 : m t quan h gia ngu (P) v cng dng hn 5.

4 Chng ta cn kim sot % Dilution do cn phi kim tra hm lng Mn v Si , hai nguyn t nh hng mnh dai

ca mi hn. % Dilution s gip chn t hp dy - thuc ph hp nhm bo m yu cu c tnh.5 c lng : ngu (P) tng gp i khi dng hn tng ln ba ln

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Trn hnh 9 ta cng thy khi tng dng hn th m cao hu nh khng i do vy b rng mi

hn s tng ln.

Cng thc kinh nghim (ESAB) cung cp mt c lng kh ton din 6:

Khi hn vi ngun DCEP : NS (kg /h )= Ihn

50D0.3

Khi hn vi ngun AC : NS (kg /h)= Ihn

40D0.3

Hoc tnh dng hn theo tc cp dy (WFS) nh cng thc :

Trong AMP = dng hn ,DIAM = ng knh dy hn

2.2.2. Tc ng ca in p hn

in p hn khng nh hng n ngu m ch nh hng n b rng mi hn (khi hn khng

vt). i vi mi hn rnh V hoc X , in p cao s to ra mi hn lm d gy kt x, khuyt lm

(UC) , ngc li, in p thp to ra mi hn li d gy thiu chy (IF) hoc chng mp (OL).

Hnh 10 : nh hng ca in p hn n b rng mi hnin p hn cng chu nh hng bi chiu di h quang , do vy nh hng trc tip n b dy

lp x nng chy, v b dy lp x nng chy s tc ng n lng tiu hao thuc hn , nh hng

hm lng Mn, Si cha trong mi hn.

Nhn t khc nh hng n in p hn l dng hn v nh in cc (ESO) (hnh 11)

Hnh 11: in p tng ng dng v ng knh dy hn.

6 Tham s hn chnh xc nht vn l tham s c xc nh khi th nghim qui trnh hn. Cc cng thc tnh hoc kinhnghim ch gip chng ta a ra cc gi tr ni suy t kt qu c trc.

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Theo hnh 11 ng vi ESO tiu chun (38mm) th ta

c quan h gn ng sau 7:

Uhn=Udy+0.04Ihn

Trong : Udy=(21 :27V) ty ng knhdy

2.2.3. nh (ESO - Electrical Stick Out)

nh ESO c nh ngha nh hnh 12. khi hn

ESO thng c iu chnh t 16 n 50 mm khi

khng c on ni ko di m phun, v khng qu

127mm khi s dng on ni ko di (Linc-Fill Nozzle Extension). Hnh 12 : nh ngha ESO

ESO c tc dng nung nng dy hn , do vy, lm tng tc nng chy ca dy. Khi hn dy li

thuc hoc dy composite ESO s nh hng tng i n qu trnh chy n nh ca h quang.

Tt nhin do dng hn SAW kh cao nn tn tht in p trn ESO cng ng k (hnh 13)

Hnh 13 : Tn tht in p h quang do ESO

7 Khi thay i ESO v thuc hn , in p hn cng s c thay i cht t.

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Do vy in p hiu chnh cng cn thay i theo ESO bo m in p h quang hn.

ESO c nh hng mnh n ngu, ESO ngn ngu su v ngc li. ESO thng c ko di

nhm gim ngu v tng b dy

p khi hn p b mt, trongtrng hp ny, nng sut p

c th tng n 50% . Khi hn

thp thng ngu nn mc

2530 mm. ESO s ngn hn

khong 2025 mm khi hn thp

khng g 8.

Hnh 14: nh hng ca ESO n ngu

2.2.4. Tc ng ca tc hn

Tc hn c quan h cht ch vi nng sut p v do vi dng hn. Cng mt dng hn nu

tng tc hn s lm gim c ngu ln b rng kt qu l mi hn hp v m cao d gy thiu

chy v kt x. Ngc li, nu tc hn qu chm so vi mc cn thit qui nh bi cng

dng hn 9, nng lng nhit tng ln to iu kin tng trng c ht v tn tht Mn, Si do to x,

kt qu l tn tht nghim trng v dai.

8 L do rt n gin v thp khng g c in tr sut cao hn.9 Thp hn tc qui nh bi dng hn t 20 n 25 cm/pht.

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2.2.5. Tc ng ca ng knh dy hn

Thc t th chnh mt dng hn (A/mm2) mi l nhn t thc s. Khi tng mt dng hn,

ngu s tng nhanh (hnh 15)

Hnh 15 : nh hng ca ng knh dy (mt dng hn n tit din mi hn.

Nu chng ta nh ngha ch s hnh dng tit din Fhnh dng= Brngmihn

Chiu cao mi hnth khi F < 1 -:-

1.5 nguy c nt dc ca mi hn s rt cao. y chnh l yu t cn cn nhc khi la chn ng

knh dy hn ph hp vi ng dng.

2.2.6. Tc ng ca gc g t 10(gc hn)

Khi hn phng, gc hn (v hng hn) c tc ng mnh n tit din mi hn (hnh 16)

C th l nh hng

ch s hnh dng c nh ngha

pha trn.

Khi hn ng, cch

thc g t v hng

di chuyn khng

ng s to ra mi

hn c bin dng

khng thch hp (do

tc ng tng cng

ca trng lc x v

kim loi nng chy.

Hnh 16: nh hng ca gc g t v hng hn n tit din mi hn

Hnh 17 pha di l cch thc g t khi hn mi hn theo chu vi ng t pha trong v t pha

ngoi.

Hnh 17 : g t in cc v hng hn khi hn mi hn ni ng.

10 Gc g t (in cc) : Electrode manipulation khi nim ch cch thc g t v di chuyn in cc khi hn

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Bng di y a ra cc tc ng ca gc g t v hng hn

Gc g in cc Backhand (hn ko) Thng gc Forehand (hn y)

ngu Cao

Bnh thng

Thp

m cao Mi hn hp, cao Mi hn rng, thp

Kh nng khuyt lm Cao Thp

2.3. Kt lun

Phng php SAW d c pht trin t rt lu song cng c nhiu ci tin nhm tng cht

lng v hiu qu hn. Cc thng s, thit b ca qu trnh c pht trin v hiu chnh c lp,

to ra nhiu kh nng ty bin thch nghi. y chnh l u im, song cng l yu t lm cho

vic thit lp qui trnh hn thm phc tp (c qu nhiu tham s lin quan nhau). Nhng thng tin

trnh by y ch l mt phn nh ch yu lin quan SAW mt dy (rn) hn trn thp kt cu

thng thng. Khi hn trn vt liu khc, bin th khc cn tham kho chi tit hn.

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3.3 Các Phương Pháp Hàn_SAW