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A. GII THIU V LUN N 1. Tnh cp thit ca ti lun n

Trn th gii hin nay, vt liu mi trong k thut ch yu l vt liu trimetal (ba lp); bimetal (hai lp); compozit chu mn; gm kim loi; hp kim cng luyn kim bt lm dng c gia cng c kh; vt liu k thut in v in t; vt liu nan c s dng cho ch to mi cc ph tng mau mn bi tch hp c tnh nng tt ca cc thnh phn c nhiu tnh nng c bit so vi vt liu truyn thng.

Vit Nam hin nay hu ht cc my mc, thit b cng ngh u nhp t nhiu quc gia nh: Anh, M, CHLB c, Nht Bn, Hn Quc, Trung Quc, Lin bang Nga, Ucraina v cc ng u. Sau mt thi gian lm vic chng cn c bo dng v thay th ph tng mau mn chng hng, v d nh cc chi tit dng trc, bc trt, bi, ph tng my ng lc v my cng c vi s lng ln. Hn n l cng ngh tin tin m bo to phi bimetal lm cc chi tit my chu mi mn v c cng cao. V th, ti lun n c ngha khoa hc v thc tin. 2. Mc ch nghin cu

Nghin cu la chn ch hn n thch hp to phi bimetal thp cc bon thp hp kim c dng hnh tr, s dng cho vic ch to cc chi tit my nh: cht bin ca b trc khuu; cht pt tng trong b n ng c t trong; bi tr... 3. i tng nghin cu Nghin cu ng dng cng ngh hn n to phi vt liu bimetal thp C45 thp 15 vi lp thp hp kim hn trn b mt hnh tr c tnh cht n nh v bn bm dnh vi lp thp C45 cao, m bo mc ch s dng c xut. 4. ngha khoa hc v thc tin ca ti

- ngha khoa hc 1. s dng phn mm tin hc chuyn dng x l s liu thc nghim v

nhn c m hnh ton hc m t hm mc tiu bn bm dnh 2 lp (b.d) ph thuc cc thng s hn n (r), (h) v (C) theo quy hoch thc nghim kiu N = 33 c dng a thc cng thc (4.1). T phn tch nh gi mc nh hng ring bit, cng nh nh hng tng hp ca cc tng thng s n n tnh cht c hc v cu trc vt liu bimetal sau hn n. Bng m hnh (4.1) c th iu khin c b thng s cng ngh hn n ch yu chn xc nh c min ti u ca chng, m bo nhn c cht lng lin kt 2 lp bimetal t mc cao;

2. nghin cu thc nghim nh hng ca bin dng do sau hn n phi tr bimetal thp C45 thp X15 bng phng php p chy nng n cht lng lin kt hai lp ca n thng qua hm mc tiu (b.d) ph thuc vo mc bin dng do tng i theo hng knh (). T xc nh quy lut thay i ca (b.d) ph thuc vo () v xc nh bin dng do ti hn nn dng mc = 7,5 15 %;

3. nghin cu kho st v xc nh c c tnh cu trc t vi vt liu ti vng bin gii lin kt hai lp thp C45 thp X15 trng thi sau hn n v bin dng do bng phng php kim tng hc (hin vi quang hc, hin vi in t v phn tch SEM-EDX). Bng cc kt qu thc nghim chng minh c rng: trong vng lin kt 2 lp kim loi bimetal thp C45 thp X15 sau khi hn n c th hnh thnh cc lin kim loi c thnh phn ha hc, c tnh khc nhau. Tuy nhin cc ch

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hn n ti u, s hnh thnh cc tiu vng cu trc c trng c kch thc nh v phn b khng lin tc, nn t nh hng n bn v cht lng phi bimetal.

- ngha thc tin Ln u tin Vit Nam th nghim thnh cng vic ng dng nng lng

n bin dng do tp ng thp hp kim X15 v hn dnh vi li thp cc bon C45 t cht lng cao: bn bm dnh 2 lp vt liu sau hn n t trong khong b.d = 128,7333 258,6667 MPa, c c tnh cu trc t vi vng bin gii lin kt tt. 5. Cc ng gp mi ca lun n

1. h thng ho c s l thuyt cng ngh hn n ng dng cho to phi bimetal dng tm phng, b mt cong t cc ti liu ng ti trong v ngoi nc lm c s khoa hc cho vic gii bi ton bin dng do tp ng v hn n ng thp hp kim X15 vo li thp C45 c dng hnh tr v thc nghim trong iu kin Vit Nam;

2. Bng phng php quy hoch thc nghim kiu ba mc ba yu t (N = qk = 33 = 27) tin hnh th nghim hn n to phi bimetal thp C45 thp X15 dng tr v kho st nh gi nh hng ca 3 thng s cng ngh hn n chnh (r), (h), (C) n bn bm dnh 2 lp (b.d) v c tnh cu trc t vi vng lin kt hai lp trng thi sau hn n. T chn ch hn n ph hp yu cu v cht lng bm dnh gia hai lp kim loi hn n;

3. S dng phng php p chy nng nghin cu nh hng ca mc bin dng do tng i vi khc nhau theo hng knh (V) n (b.d), t cho php xc nh gii hn cn thit ca n chnh kch thc hnh hc dc theo phi n v la chn ch cng ngh hn n phi hp p chy nng thch hp, m bo vt liu phi bimetal t c tnh k thut v c cht lng cao ng dng vo ch to cc chi tit my dng hnh tr. 6. Phng php nghin cu, cch tip cn 6.1. Phng php nghin cu: kt hp nghin cu l thuyt v hn n cc b mt cong v hai tm kim loi vi quy hoch thc nghim xc nh ch hn n m bo nhn c cht lng vt liu bimetal tt nht, 6.2. Cch tip cn ni dung nghin cu

- T nghin cu tng quan cc kt qu ng dng cng ngh hn n trong v ngoi nc xc nh ni dung nghin cu pht trin thm ca lun n;

- Thc nghim xc nh mc bin dng do ti hn theo hng knh ca phi bimetal thp C45 thp X15 sao cho vn m bo bn bm dnh 2 lp v c tnh cu trc vt liu cn thit;

- S dng cc thit b o lng, thit b phn tch kim tng hin i xc nh cc thng s k thut v nh gi c tnh ca vt liu bimetal sau hn n, p chy nng. 7. Cu trc lun n Lun n gm 5 chng vi 136 trang (khng k phn Ph lc): t vn (06 trang); Chng 1: Tng quan v cng ngh hn n v gii hn nghin cu ti lun n (19 trang); Chng 2: C s l thuyt hn n hai tm kim loi (26 trang); Chng 3: Vt liu, thit b th nghim v phng php nghin cu (24 trang); Chng 4: nh hng ca ch n ti bn bm dnh 2 lp v t chc vt liu bimetal thp C45 thp 15ng hnh tr (33 trang); Chng 5: Nghin cu nh hng ca bin dng do n tnh cht vt liu bimetal thp C45 thp 15 sau p

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chy nng (20 trang); Kt lun chung lun n (02 trang); Danh mc cc cng trnh khoa hc cng b (01 trang); Danh mc ti liu tham kho (06 trang); Ngoi ra, phn Ph lc lun n c 20 trang.

B. NI DUNG CHNH CA LUN N Chng 1. TNG QUAN V CNG NGH HN N V GII HN NGHIN CU

TI LUN N 1.1. Khi qut v vt liu kt cu chu mi mn Vt liu chu mn kt cu c cng cao dng lm cc chi tit trong vng bi thng l bng thp hp kim cao, rt kh bin dng do v kh gia cng, cn cc chi tit dng trc nh: cht bin, cht c pit tngc th lm bng thp hp kim thp v thm ti nn cng ngh rt phc tp, chi ph nguyn vt liu v nng lng cao.

T sau nm 1960 cc nc thuc Lin X trc y ti nhiu Vin nghin cu v cc Trng i hc c nhiu nghin cu ng dng cng ngh hn n 1, 2362 ch to vt liu bimetal, trong c bimetal thp thp hp kim chu mn, thp - thp khng g, thp - titan,... V mt l thuyt hn n c s dng hu nh i vi cc cp vt liu khc nhau, c bit l cc cp kim loi v hp kim c c l tnh khc xa nhau v rt kh bm dnh bng cc phng php to phi bimetal khc. Ngoi ra, hn n c th c s dng trong sn xut n chic hoc lot nh cc sn phm vi nng sut cao, m bo to ra cc lin kt kim loi cht lng cao, chi ph u t thit b t tn km, ph hp vi cc nc cha tng c cng nghip luyn kim v my cn mnh nh Vit Nam. Cho n thi im hin nay Vit Nam, cng ngh hn n mi c bt u trin khai nghin cu ng dng dng tm phi bimetal thp cc bon thp hp kim, thp cc bon thp khng r, thp cc bon thp hp kim nhm, thp cc bon hp kim ng, nhng cha c nghin cu su no v vn to phi bimetal dng tr c tnh nng chu mi mn cao.

1.1.1. Vt liu bimetal chu mn ch to chi tit my dng trc, chi tit bi Cc chi tit hnh tr thuc v nhm cht bin, cht c pt tng trong ng c

t, xe my v my ng lc, ca bi trong v ca bi ngoi,... chim phn ln cc ph tng mau mn chng hng cn thay th nh k trong my mc thit b nhiu ngnh kinh t. Hin nay ngoi nc ngi ta sn xut cc loi chi tit bng cc cng ngh to phi tin tin (trong c hn n), tit kim nguyn liu cao, vi lp b mt lm vic c tnh nng c bit, kh nng chu mn cao. Vit Nam hn n l mt trong nhng cng ngh tin tin v ang c nghin cu ng dng trong to phi vt liu bimetal dng trong ch to my, ng tu,...

1.1.2. Mt s chi tit kt cu khc t vt liu bimetal Trong cng nghip ch to cc loi bnh chu p lc cao, vic s dng cng ngh

hn n to ra ng sut d cho trc trong cc lp kim loi thnh bnh cng l mt trong nhng bin php cng ngh tin tin c nhiu nc cng nghip pht trin trn th gii nghin cu p dng thnh cng v cho hiu qu kinh t k thut cao. Trong cng nghip ho cht, ho du vic bc lt pha ngoi cc ng ng dn c th s dng cng ngh hn n. Trong cc cng trnh bin cc kt cu ct hnh tr lm vic trong mi trng n mn x xm thc cao ca nc bin cng c th c hn ch nh bc lt pha ngoi cc chi tit kt cu bng thp khng r. Lp v bc chng xm thc c th c to ra bng phng php phun ph hoc hn n. Tuy

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nhin, nhng tng ch mi c cp n trong mt s patent ca nhiu nh nghin cu trn th gii, nhng kh tip cn c trong iu kin Vit Nam. Do vy, vic nghin cu ng dng hn n to ra lp kim loi b mt c tnh nng k thut cao, lm vic trong iu kin khc nghit c th s l tin khoa hc mi cho nhng nghin cu ng dng tip theo nc ta. 1.2. Nghin cu l thuyt v hn n cc b mt cong dng bn cu ng knh nh

Cc nghin cu l thuyt v thc nghim v kh nng nhn c mi hn khi hn cc b mt cong (hnh 1.1 v 1.2) c cc nh khoa hc Nga xng v a ra cc cng thc tnh ton l thuyt c trch dn trong cng trnh [30].

Theo phng trnh ng cong m t prphin tm hn p, c th xc nh c th tch chim ch ca thuc n, khi lng thuc n v tm kim loi hn p. Gi s chiu dy tm kim loi hn p l (), khe h hn ban u (h) v vic hn n thc hin trn mt na bn cu c bn knh (R), c kch n t tm im. Cc kt qu nghin cu l thuyt nu trn c s dng tnh ton v kim tra bng thc nghim cc thng s va p khi hn n cc t la bng thp c b mt trong l na hnh cu vi bn knh R = 80 mm c hn p mt lp hp kim ng pO6,5- 0,15 c chiu dy 4 mm [1].

Hnh 1.1. S tnh ton phng n hn p b mt hnh cu t pha trong 1

Hnh 1.2. S lan truyn sng n trn b mt hnh tr 1

1.3. Nghin cu l thuyt v hn n cc b mt li hnh tr thnh lp c cng ngh hn n st vi thc tin i vi phi c cnh tuabin

thu lc vi hnh dng prphin khng gian rt phc tp, Lin X trc y nghin cu cc c tnh n ca thuc n dng hnh tr c bn knh (R) th mt phn cch n lun lun b bin dng t mt phng AB thi im ban u (hnh 1.2) thnh ng thn khai CE v a ra cc cng thc tnh ton l thuyt 40. Hiu ng cng c khng nh bng cc nghin cu thc nghim trch dn trong cng trnh 1. 1.4. Nghin cu ng dng nng lng n to phi bimetal, trimetal Vit Nam

1.4.1. Khi qut chung ng dng nng lng n trong hn cc kim loi c thnh phn ha hc v c

tnh khc nhau lm bc trt, cng nh tp ng xy lanh bng thp trong phc hi cm xy lanh gim xc xe t vn ti m c khi xng Vit Nam t nhng nm thp k 80 th k trc [1], [30]. Tuy nhin, cc nghin cu theo hng ny b gin on do c nhiu yu t khch quan ca nn kinh t nc ta giai on ny. Ch sau nm 1995 v cho n nay, nhm nghin cu ng dng hn n ti Vin Nghin cu C kh (B Cng Thng) li tip tc trin khai hng cng ngh ny:

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1. Hn n to phi vt liu bimetal thp cc bon thp cc bon dng c lm dao ct trong my cng c v thp cc bon thp hp kim dng c lm dao bm g [7], [9], [11],[12], [14], [16], [17], [22], [24], [27];

2. Hn n to phi vt liu trimetal thp CT3 nhm AA1050 hp kim nhm ng tu AA5083 s dng trong cng nghip ng tu thu [10], [15], [19], [20], [23], [25], [26];

3. Hn n to phi vt liu trimetal thp 08s nhm AA1050 hp kim nhm chu mn h Al Sn Cu (mc AO9-2) lm bc trt [10], [19], [20], [21], [23], [25], [26];

4. Hn n to phi vt liu bimetal thp 08s ng M1 lm thanh ci dn in in ng lc [13], [18];

5. Mt s ng dng nng lng n khc trong to phi cc chi tit my c kch thc hnh hc ln, kh ch to bng cc cng ngh truyn thng, v d nh bc gi tuc bin thu in, my nghin c ln,ang c trin vng ng dng thc tin.

1.4.2. c im bin dng tp ng kim loi bng nng lng n S n tp ng xy lanh bng thp cho trn hnh 1.3, cn gi thit phn b p

sut nn theo b mt hnh tr ngoi ca ng xy lanh hnh 1.4 [3]. C s l thuyt tnh ton ng dng cho tp ng kim loi bng nng lng n da trn vic gii bi ton sau 7: Chng ta quan st mt ng kim loi hnh tr c bn knh ngoi (R1) v bn knh trong R2, chu p lc p phn b u mt ngoi (xem hnh 3.4 Chng 3). Khi (p) t mt ga tr (p1) no th ng kim loi bt u bin dng do v cc phn t ca ng b dch chuyn vo pha tm mt cch i xng. n gin ha qu trnh tnh ton, chng ti gii hn ng kim loi c chiu dy nh so vi bn knh ca ng. T cho php c th b qua nh hng ca chiu di ng trong php tnh v c th coi nh bi ton phng. Khi , phng trnh cn bng ng sut ti mt phn t nh ca ng khi cha chuyn ng trong ta cc c dng:

0

rdr

d rr (1.14)

Theo iu kin do Misses: Tr 32

(1.15)

trong : r, - ng sut hng tm v ng sut tip tuyn tng ng; T - ng sut chy ca vt liu.

Sau cc php bin i ta c gii hn p sut p1 xy lanh bin dng do di tc dng ca ti trng tnh c xc nh theo biu thc:

2

111 ln3

2RRRrp Tr

(1.19)

y: du biu th p sut nn. Trong trng hp ng thp bin dng di tc dng ca ti trng ng xung cao

tc khi n th T khng th l ng sut chy tnh ca vt liu, m khi ta phi ly

gii hn chy ng td: 2

1ln32

RRp tdtd

(1.20)

Xt trng hp ng b tp co li theo hng knh (vt liu thnh ng chuyn ng hng vo tm) di tc dng ca p lc xung n, nh khoa hc

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ngi Nga eribas A. A. 40 gi thit coi hnh tr b bin dng rt nhanh nh mt cht lng l tng. Khi , nu gi ro l khong cch ca mt phn t nh ca ng i vi tm trc lc bin dng: r(ro, t) l khong cch ca chnh im thi im (t) trong qu trnh dch chuyn khi n.

p lc sinh ra do qu trnh n tc dng ln ng hnh tr c xc nh nh sau:

3

11100 )(/

)(2716)(

dttdR

DHttRRH

Dtp (1.27)

trong : o, D - khi lng ring (g/cm3) v tc n (m/s) ca thuc n tng ng; H - chiu dy lp thuc n (mm).

Kt qu tnh ton v th nghim ng dng phc hi xy lanh thu lc: Vt liu ng bin dng do di tc dng ca nng lng n l xy lanh thu lc bng thp tng ng mc thp C45 trong b phn gim xc ca xe t vn ti m KOMATSU320 (Nht Bn). Vt liu ny c c tnh nh sau: mt 1 = 7,85g/cm3; tr khng chng bin dng Kd = 610,7 MPa; ng c kch thc ban u R10 = 56 mm; R20 = 50 mm. Thuc n c dng l loi amnt 6B c mt ri bng 0 = 0,9 g/cm3 v chiu dy lp thuc n ti thiu bng H = 9 mm. Kt qu th nghim t c rt tt, cc xy lanh thy lc sau phc hi c a vo s dng trn khai trng m Qung Ninh c hiu qu.

1.4.3. xut phng n n tp ng hn vi li thp gia Trong cng trnh [7 tc gi a ra xut hn n to phi bimetal dng ng

trn c s ng dng nng lng n bin dng tp ng phc hi cc xy lanh thu lc ni trn v mt s kt qu thc nghim hn n to phi bimetal dng tr thp C45 thp 15, kho st cu trc t vi vng bin gii lin kt gia hai lp kim loi sau hn n trn mt ct ngang v ct dc theo hng n trn cc phn vng khc nhau theo mt s phng php lun xut cc cng trnh [4], [6], 7, [8], [9]. Bi ton s c hon thnh khi m bo c iu kin sau:

0)(

max

2 HvdttdR (1.33)

Nu dR2/dtmax vH th cn phi tng thm chiu dy lp thuc n v lp li cc th nghim. Cui cng, khi xc nh c (H), ng thi ta s xc nh c (R) ti u bng chng trnh tnh ton theo s khi trn hnh 1.5 chng 1 lun n 7. 1.5. Kt lun chng 1 v gii hn nghin cu ca ti lun n

Kt lun chng 1 1. h thng ho c s l thuyt v kinh nghim thc tin ca nhiu nh

nghin cu trn th gii v hn n to vt liu bimetal nh: c im v s hn n; iu kin hnh thnh lin kt hn n; cc thng s chnh qu trnh hn n 2 tm kim loi; nh hng ca cc thng s n ti tnh cht v cu trc mi hn trong bimetal; c s l thuyt hn n cc b mt cong c ng knh nh; c s l thuyt hn n cc b mt li hnh tr;

2. Hn n to phi bimetal dng thanh, ng hoc dng tm l mt hng cng ngh mi c nghin cu ng dng nhiu nc cng nghip pht trin m bo yu cu v kch thc ln v hiu qu kinh t cao. Vit Nam c th p dng cng ngh ny to phi vt liu bimetal, trimetal dng cho gia cng ch to nhng chi

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tit my c tnh nng c bit (kt hp kh nng chu mi mn cao ca lp hp kim b mt lm vic vi do dai chu va p ca phn kim loi c bn ca thn chi tit) m bng cc cng ngh truyn thng khc kh c th thc hin c, ng thi gii quyt c bi ton chi ph u t thit b cng ngh nh nht;

3. T kt qu nghin cu l thuyt v thc nghim ng dng nng lng n trn th gii v Vit Nam t trc n nay, la chn v a ra min cc gi tr ca lng thuc n cn s dng, khe h hn,cn kho st khi lp quy hoch thc nghim hn n cc loi ng thp vo li thp c bn trong vi mc bin dng co theo hng knh cn thit.

Gii hn nhim v nghin cu ca lun n Vi mc tiu ra ni dung chnh ca lun n ny tp trung vo cc vn sau: 1. Nghin cu l thuyt v hn n to phi bimetal t dng tm, bng n dng

c b mt cong c ng ti trong v ngoi nc la chn phm vi nghin cu thc nghim hn n ng thp hp kim 15 vo mt ngoi i vi chi tit c b mt dng hnh tr lm bng thp C45. iu kin thc nghim hn n y c xc nh trn c s nghin cu trng hp khi ng knh trong ca ng thp hp kim v khe h hn so vi li thp bn trong chn gi tr khng ln. Vi gi thit iu kin bin l nu xt trn mt phn t vt liu ng thp hn dc phi n nh, c th p dng cc thng s n tnh ton ca bi ton hn n tm phng lm d liu u vo cho trng hp hn n b mt cong, s dng phng php iu chnh tng dn ln ti mc to ra c lin kt kim loi gia 2 lp trn phi n dng hnh tr;

2. xut m hnh th nghim v phng php nghin cu thc nghim xc nh cc quy lut c bn khi hn n to phi hnh tr da trn c s l thuyt hn tm, c tnh n bi ton bin dng ng thp 15 hnh tr bc p to lp b mt chu mn pha ngoi li thp c C45 bn trong. Vic xut phng n thc hin th nghim hn n to phi bimetal dng hnh tr vi cc gi thit ban u khi coi s nh hng ca thnh phn bin dng do co ngang theo chu vi xt trn mt ct ngang phi n ti thi im va p ca ng thp bn ngoi vi li thp bn trong s c tnh n trong cc h s n ca m hnh ton hc thc nghim ca lun n l cn thit v kh thi trong iu kin Vit Nam. Cc th nghim hn n trong cng trnh ny ch gii hn trng hp phi n gm ng thp hp kim v li thp cc bon chn trng thi qua x l nhit thng ha c do cao nht;

3. Nghin cu kho st nh hng ca mt s thng s cng ngh hn n chnh n tnh cht lin kt hai lp kim loi bimetal thp C45 thp 15 thng qua th ph hy mu xc nh bn bm dnh hai lp v phn tch t chc t vi vng bin gii 2 lp trn cc mu th nghim dng tr sau hn n bng phng php hin vi quang hc;

4. Nghin cu kho st nh hng ca mc bin dng do tng i theo hng knh phi bimetal thp C45 thp 15 dng hnh tr sau hn n v p chy trng thi nng n bn bm dnh v c tnh cu trc vt liu trn bin gii 2 lp trng thi thng ha bng phng php hin vi quang hc;

5. Phn tch c im cu trc ti cc tiu vng c trng trn vng gn bin gii lin kt 2 lp hn n bng phng php hin vi in t qut v phn tch EDX.

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Chng 2. C S L THUYT HN N HAI TM KIM LOI 2.1. c im ca qu trnh hn n: Hn n l qu trnh nhn c lin kt kim loi v hp kim di tc ng ca nng lng sinh ra khi kch n cc cht n vi s nguyn l cho trn hnh 2.1a d v hnh 2.2.

Hnh 2.1. S n di gc nghing (a),

(b) v n song song (c), (d) 30 Hnh 2.2. S hnh hc tm kim loi hn ti

mt thi im khi hn n 30

Tm kim loi c nh (4) v tm kim loi hn (3) c t di mt gc nghing () khong cch c nh (hO). Trn tm kim loi hn (3) l lp thuc n (2). Ti v tr nh gc nghing l kp n (1). Tt c phi c t trn n (5) bng kim loi, b tng, ct... Khi b kch n, theo ton b lp thuc n s lan truyn sng n vi tc (D) t ti mt vi nghn mt trong mt giy. Di s tc dng ca p sut cao do s n ca kh n, tm kim loi hn t c tc (vO) khong vi trm mt trong mt giy v va p vo vi tm kim loi c nh di mt gc xc nh = + ( - gc va p; - gc un ng; - gc nghing ban u). Kt qu ca qu trnh kch n cc cht n to ra p sut v nhit rt cao, trong vng tip xc hai tm kim loi, to ra tia kim loi cc b to iu kin cho chng lin kt kim loi vi nhau. Tc cao v p sut cao vng va p xy ra s nh sch mng xit trn cc b mt tip xc, lm linh hot ho chng v to ra mi lin kt kim loi gia cc lp vi nhau c dng sng m c trng hoc khng c dng sng 30, 37, 40. 2.2. Nguyn l c bn hnh thnh lin kt kim loi khi hn n

S va p ca cc tm kim loi hn c i km lng bin dng do rt ln, lm xut hin s nung nng ng nhit cc b cc b mt tip xc khi hn n, kt qu qu trnh l hnh thnh c lin kt kim loi 1, 37. Khi , nhn c lin kt bn vng, cn thit phi m bo sao cho thi gian tc dng trong mi hn p lc dng ln hn thi gian kt tinh li ca hn hp cc kim loi hn v kim loi nn nng chy 48.C ch hnh thnh bin gii lin kt kim loi hai lp vt liu dng sng m trong qu trnh hn n cho trn hnh 2.3 2.6 15, 28.

Qu trnh hnh thnh lin kt kim loi gia 2 tm vt liu hn n c m t trn hnh 2.6ac c th phn tch nh sau:

1. V tr ban u ca 2 tm kim loi trc khi hn n theo s song song, t cch nhau vi khe h hn (h), chiu dy lp thuc n (H), chiu dy cc tm kim loi trn v di tng ng l 1 v 2 c cho trn hnh 2.6a. Khi kch n thuc n bng kp n t phn u pakt n, tm kim loi trn di tc dng ca qu trnh n to ra p sut cao (p), nhn c ng nng cao v va p vo tm di, chuyn nng lng vo im va p v to ra trng thi chy lng cc lp b mt 2 tm kim

9

loi hn, ng thi y mng xit ra khi vng c nn cao (vng I hnh 2.6b) hnh thnh lin kt kim loi bn vng;

2. Vng tip xc trong qu trnh chy n chuyn ng t tri sang phi, khi vng II l min c s dch chuyn bin dng do vi cng cao, di p sut cao hn nhiu so vi bn trt l thuyt nn xut hin hng lot cc lch mng trn 2 b mt tip xc hn v chng i su vo pha trong 2 tm kim loi hn n. Ti vng va p gia 2 tm kim loi hn n xut hin tia kim loi cc b nh hiu ng b mt, to iu kin hnh thnh lin kt kim loi gia chng vi nhau trong vng II min tng tc ca cc vt liu cn cha tham gia vo tip xc gia 2 lp (hnh 2.6b);

Hnh 2.3. c im thay i

bn bm dnh theo thi gian hnh thnh tip xc vt l v tng tc ha hc nhanh (a), hn chm (b) trng thi rn khi hn (theo M. X. Shorshor

v Ju.L. Kraculin 28

Hnh 2.4. c im thay i th nng cc nguyn t khi

tch t vt l (f) v tch t ha hc (c) ph thuc vo khong

cch r t nguyn t n b mt vt rn 28

Hnh 2.5. S hnh thnh nh sng m bin dng trong qu trnh va p tc cao 28: 1) Tm kim loi hn; 2) Tm kim loi c nh;

K) im tip xc khi va p

a) b) c) Hnh 2.6. S nguyn l hnh thnh mi hn gia hai tm kim loi trong qu trnh hn n

28: a) S n song song; b) Giai on n cha n nh; c) Giai on n n nh

3. Ton b mi hn cu thnh t cc phn cc b ca kim loi nng chy v ng c nhanh c th t c ch khi di tc dng ca sng n hi d ti (di chuyn ngay sau vng nn p im va p) vi tc sao cho trong vng IV khng xy ra hin tng ph hy mi lin kt kim loi ang hnh thnh gia 2 lp hn n (hnh 2.6c). 2.3. Cc thng s ch yu ca cng ngh hn n: Phn bit cc thng s ch yu c trng cho qu trnh hn n kim loi sau y 1, 30:

1. Nhm thng s ng hc gm c: tc bay ca tm kim loi hn khi va p vo tm kim loi nn (vP), tc im tip xc gia hai tm kim loi (vK), gc va p (), gc un ng ().

2. Nhm thng s vt l gm c: p sut ti im tip xc khi va p (pK), thi gian va p (t) , nhit ti im va p (T).

3. Nhm cc thng s cng ngh: tc n (D) - c trng bi mi loi thuc n; thng s khng n v (r) t l gia khi lng thuc n v khi lng tm kim loi hn; khe h hn (hO) khong cch ban u gia cc tm kim loi hn; nhm b mt tip xc khi hn (RZ); nhit cc tm kim loi hn (T1, T2); kch thc v c tnh ca cc kim loi hn ( bn, cng, dai,).

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4. Nhm cc thng s nng lng gm c: ng nng ring ca tm kim loi hn (W1); ng nng ring ca tm kim loi nn (W2), tnh theo nhm thng s ng hc.

hnh thnh c lin kt kim loi phi m bo iu kin sau: vK CO (2.5)

trong : CO tc sng m trong vt liu cc kim loi hn. i vi s n nghing, tc di chuyn ca im tip xc c xc nh

theo cng thc: vK = D. sin ( ) / sin = D. sin / sin (2.8) Tc hn ch yu c xc nh theo cng thc cho trong cng trnh 30:

vP 1 r 27 / 32 1

1 - r 27 / 32 1 1,2D

; (vi K = 3) (2.13)

Trn thc t, tnh p sut va p khi hn n, tt nht nn s dng cng thc c xut trong cng trnh 37, 43 v c trch dn trong cng trnh 30:

Cc thng s hn n chnh bao gm: 1. Thng s cng ngh 1: c trng cho thuc n s dng, s thay i ca n

ph thuc vo c tnh vt l ca thuc n, th nht l tc n (D): ng knh hoc chiu dy, mt , thnh phn hn hp, kch thc ht, m, v bc c trnh by kh r trong cng trnh 35, 37, 40, 43, 66.

2. Thng s cng ngh 2: (r) t l gia khi lng thuc n s dng v khi lng tm kim loi hn. Nu din tch thuc n c t trn b mt tm kim loi hn bng din tch ca n th thng s ny c xc nh theo cng thc: r = mTN / m1 = O. H / 11 (2.27)

3. Thng s cng ngh 3: l khe h ban u gia hai tm kim loi hn n (hO). Thng s ny c gy nh hng ti cht lng lin kt kim loi gia hai lp bimetal. Cng vi s gia tng ca tng thng s: (D), (r) hoc (hO), s lng cc tp cht nng chy, bc sng v bin sng lin kt u tng t l thun. bn bm dnh hai lp bimetal (b.d) mt s gi tr nht nh ca (D), (r), (hO) s n nh, nu tng chng ln mc qu cao th (b.d) v hiu ng hnh thnh sng lin kt gim. Trn thc t thng cho trc khe h hn hO = (1 2).1 (1 chiu dy tm kim loi hn 30). 2.4. Nghin cu nh hng ca cc thng s hn n n cht lng mi hn

2.4.1. Bin gii ti hn ca vng hn n: Trn hnh 2.8 l th biu din vng

xc nh hn n tt: 2Kb .v (2.30) trong : b bn (tr khng bin dng tc thi) ca kim loi hn.

2.4.2. nh hng ca cc thng s ban u khi hn n n cu trc: c quy lut l thuyt cho trn cc hnh 2.9 2.11.

2.4.3. nh hng ca cng vt liu hn n cht lng mi hn tnh n cng vt liu hn, tc gi cng trnh [1] trch dn xut ca tc

gi cng trnh 34: Re = (1+2) 2Kv / [2(H1+H2)] 10. ngha vt l ca iu kin Re l: p sut ti vng ln cn im tip xc cao

hn nhiu so vi bn ca vt liu va p. S dng iu kin ny hn n i vi thp c cng n 50 HRC v thp cc bon c cng thp cho thy: tc chuyn ng ca im tip xc phi tng ln 1,6 ln.

11

2.4.4. nh hng ca bn b mt n cht lng mi hn Cc mng xit cha b ty sch trn b mt ti xc hn n lm cn tr s hnh

thnh mi lin kt hai lp kim loi hn. Kh nng ph hu v y ra khi khe h hn ca cc mng xit ph thuc vo nhiu yu t nh: bn lin kt gia cc xit vi kim loi, cng xit (so vi cng kim loi nguyn cht), nhit nng chy ca n. c bit c th gy kh khn cho qu trnh hn n l cc cht bn hu c m do s lng ng ca chng trong lp bin gii gia hai lp kim loi s gn cht vi kim loi nn. Cc mng xit t nhin rt mng (chiu dy n 5.10 3 m) khng gy nh hng n cht lng mi hn khi hn n v chiu dy ca n vo khong 2 ln nh hn chiu dy ti thiu kim loi b bc khi b mt tm kim loi nn.

Hnh 2.7. Cc iu kin bin m bo c lin kt kim loi khi hn n: A, B

gii hn di v trn 1

Hnh 2.8. S ph thuc ca chiu dy trung bnh tp cht (2), cc thng s bin dng sng lin kt

(, a) v bn bm dnh (b.d) vo khe h hn (h0)

Hnh 2.9. S ph thuc ca chiu dy trung bnh cc tp cht (2), cc thng s bin dng sng lin kt (, a) v bn bm

dnh hai lp (k.d) vo thng s (r)

Hnh 2.10. S ph thuc ca chiu dy trung bnh cc tp cht (2), cc thng s bin dng sng lin kt (, a) v bn bm

dnh khi ko t (k.d) vo tc n (D) 1

Kt lun chng 2 1. Qua nghin cu h thng ho c s l thuyt v kinh nghim thc tin ca

nhiu nh nghin cu trn th gii v hn n to vt liu bimetal phn ny tc gi lun n la chn phng n th nghim hn n to phi bimetal thp C45 thp hp kim X15 dng hnh tr ph hp vi iu kin Vit Nam vi ba thng s hn n chnh l: T l khi lng thuc n trn khi lng ng thp hp kim hn n (r); T l khe h ban u gia li thp C45 vi ng thp hp kim X15 v chiu dy ng thp hp kim X15 (h); Tc n (D), xc nh bng phng php o trc tip khi hn n i vi mi mt th nghim n c khi lng thuc n khc nhau nh tr gip ca thit b o k thut s hin i m khng p dng phng php tnh ton theo ti liu cng b trc y;

12

2. C s l thuyt trnh by trong chng 2 c kim chng i vi trng hp hn n hai tm kim loi vi nhau v l c s tnh ton ban u thc nghim hn n b mt cong ca lun n. Trong trng hp hn n phi bimetal dng hnh tr th yu t nh hng ca tr khng chng bin dng theo hng co theo chu vi tit din ngang phi n dng hnh tr c gi thit s ch ra trong cc h s n tnh ton ca m hnh ton hc thc nghim s xy dng trong lun n nh gii hn chng 1. Vn ny hin nay khng c nghin cu chuyn su no cng b. Chng 3. VT LIU, THIT B TH NGHIM, PHNG PHP NGHIN CU 3.1. Vt liu s dng cho th nghim

S dng lm mu th nghim l thp C45 lm li trong v ng thp 15 lm v bc theo mt tr bn ngoi c thnh phn ha hc tng ng c tra theo tiu chun ngnh. Li thp C45 c cng mt kch thc hnh hc trong tt c cc th nghim: ng knh d = 54,0 0,05 mm, chiu di L = 300 mm. ng thp hp kim 15 c thay i v chiu dy thnh ng v chn trong khong 1 = (2,0; 2,5; 3,0; 3,5; 4,0) 0,025 mm, c cng mt ng knh trong: d = 55 0,05 mm. Khi ng knh ngoi tng ng s l: D = (59; 60; 61; 62; 63) 0,05 mm.

Trn cc hnh 3.1 3.2 th hin nh chp mt s li thp C.45 v ng thp 15 trc khi ghp thnh pakt hn n.

Hnh 3.1. Li thp C45 hn n Hnh 3.2. ng thp 15 hn n

3.2. Chn trang thit b phc v th nghim 3.2.1. M hnh hn n to phi bimetal dng hnh tr hn n cc phi bimetal dng tr, thanh, trong cng trnh nghin cu ny s

dng m hnh paket hn n (hnh 3.3). Phn b p sut tc dng ln mt tr ng thp khi hn n to phi bimetal thp C45 - thp X15 c biu din trn s hnh 3.4. Thit b o tc n k thut s c s dng th nghim cho trn hnh 3.5.

1

2

3

45

6

7

a) b)

Hnh 3.3. S nguyn l hn n ng kim loi vo li thp c (a)

v m hnh paket trc khi n (b): 1 - Kp n; 2 - Chp nn bng g; 3 - ng kim loi cn tp; 4 - Li thp c nh kch thc ng knh trong; 5 - Thuc n; 6 - ng

bc thuc n bng ba giy; 7 - n

13

Hnh 3.4. S phn b p sut tc dng ln mt tr ng thp khi hn n to phi bimetal thp C45 - thp X15: 1 - ng thp X15; 2 - Li thp C45; 3 -Thuc n; 4 - ng nha

nh hnh thuc n

Hnh 3.6. nh chp thit b o tc n k thut s hin c Vit Nam s dng cho th nghim

3.2.2. Chn thit b th nghim bin dng do phi bimetal sau hn n Sau khi nung nng t nhit 1150 1200OC v gi cho phi ngu nhit,

cc mu bimetal thp C45 thp 15 sau hn n c p nng trn my p thu lc 400 tn (hnh 3.8) vi lng bin dng do tng i t 3 mc quy nh theo quy hoch thc nghim: 1 = 7,5%; 2 = 15% v 3 = 22,5%.

3.2.3. Chn v tr ly mu, thit b th xc nh bn bm dnh hai lp bimetal bn bm dnh hai lp bimetal hn n c xc nh bng cch th ph hu

cc mu dng trong c kch thc tnh ton ph hp vi vt liu lp kim loi hn v kim loi nn. S ct ly phi gia cng cc mu th nghim ko trt xc nh d bn bm dnh 2 lp bimetal trn phi bimetal thp C45 - thp 15 c dng hnh tr nhn c sau hn n cho trn hnh 3.9.

Dc hng n

a)

b)

Hnh 3.8. My p thu lc 400 tn dng th nghim p chy trng thi nng phi

bimetal thp C.45 thp 15 sau hn n ti mt nh my sn xut c kh quc phng Hnh 3.9. S v tr ct ly mu th ph hu xc nh bn bm dnh 2 lp bimetal thp C45 - thp 15 sau hn n hoc sau p chy t phi th nghim dng hnh tr

14

3.2.4. Chn thit b th nghim nghin cu cu trc bin gii hai lp bimetal S dng cc thit b cho trn hnh 3.12.

3.3. Phng php thc hin th nghim 3.3.1. Cch tip cn chung v o c v thng k s liu thc nghim Thc hin theo cc bc xut trong cng trnh 30. 3.3.2. Phng php tin hnh hn n to phi bimetal: Th nghim hn n to phi bimetal thp C45 thp 15 dng hnh tr c

thc hin theo quy hoch thc nghim kiu trc giao N = 33 = 27 30, 31, 32. T cc s liu thc nghim xy dng m hnh ton hc hm mc tiu bn bm dnh hai lp bimetal (b.d) ph thuc vo cc yu t cng ngh hn n chnh trong min kho st chn (r), (h) v (C).

Hnh 3.12. Tht b th nghim ph hu mu

bimetal thp C45 thp 15 c kt ni my tnh xc nh lc ph hu ti mt Trung tm

kim nh vt liu s dng cho lun n

Hnh 3.13a. nh chp knh hin vi quang hc AXIOVERT40 MAT s dng cho th nghim

Hng n

a)

b) Hnh 3.14. Phng php ct ly mu nghin cu xc nh bn bm dnh 2 lp v kho

st cu trc t vi bin gii lin kt gia chng: a) Mu bimetal thp C45 thp 15 dng

hnh tr sau hn n; b) K hiu cc phn vng phi bimetal ct dc theo hng n

Hnh 3.13b. nh chp my phn tch SEM-

EDX JEOL JSM-6490 s dng cho th nghim Vic nh gi tng hp cht lng mi hn n c thc hin trn c s so snh

kt qu th nghim th c tnh ly mu ti nhiu v tr khc nhau theo hng n trn cc mu quy hoch thc nghim vi kt qu nghin cu cu trc bin gii 2 lp bimetal tng ng. V d nh hnh 3.14:

+ Mu c k hiu 4.1 phn vng u phi bimetal theo hng n (1); + Mu c l hiu 4.2 phn vng gia phi bimetal theo hng n (2); + Mu c k hiu 4.3 phn vng cui phi bimetal theo hng n (3).

15

3.3.3. Phng php th nghim p chy phi bimetal: Ch gii hn nghin cu nh hng ca mc bin dng do tng i tng cng () qua 3 ln p chy nng n bn bm dnh 2 lp vt liu bimetal thp C45 thp 15 sau hn n v kho st cu trc t vi vng bin gii 2 lp trng thi thng ha. Phi p chy c nung nng n 1200OC v p chy trong khun kim loi c bi trn bng grapht. Nhit cc mu th nghim sau khi c ly ra khi khun p chy nm trong khong T = 850 900OC, sau khi ly phi ra khi khun p chng c ngui trong khng kh.

3.3.4. Phng php th nghim x l nhit mu bimetal: Mu bimetal thp C45 thp 15 sau hn n v p chy nng c thng ho. 3.3.5. Phng php xc nh bn bm dnh hai lp bimetal

Khi th ph hu mu kp trong g chuyn dng ti trng 12502500 N v tc nn (ko) bng 1,2 1,7 mm/pht. Lc ph hu c xc nh trn s ti nn (ko) ca my th ghi t ng. bn bm dnh hai lp bimetal c tnh theo cng thc sau 30: b.d = K. P/S (3.17) y: b.d bn bm dnh 2 lp bimetal, MPa; P Lc ph hu mu, N; S Din tch b mt tip xc thc t gia 2 lp, mm2; K = 1,58 1,0 (1 = 0,45 1,175 mm).

3.3.6. Phng php nghin cu cu trc kim loi hai lp bimetal Cu trc t vi vt liu trn bin gii 2 lp kim loi hn n c kho st v chp nh

trn knh hin vi quang hc (hnh 3.7), cn thnh phn ha hc ca cc tiu vng c trng gn bin gii 2 lp phn tch SEM-EDX, s dng thit b trn hnh 3.13b.

o cng t vi (HV0,05) hoc (H) vt liu gn bin gii 2 lp thp C45 thp 15: t nh chp cu trc t vi nhng vng cn quan tm vi phng i tnh gi tr trung bnh ca ng cho vt n lm theo din tch ca n theo cng thc sau:

d2 = 2. S / K2T (3.18) trong : d Chiu di ng cho vt n lm, mm; S Din tch vt n lm quy c (1 n v din tch quy c bng 0,3 mm2); K H s tng hnh dng nh chp vt n lm so vi kch thc thc, ph thuc vo h thng lng knh ca my o cng t vi c s dng. cng t vi c tnh theo cng thc:

H = 1,8544. PH / d2 (3.19) trong : PH Ti trng n u chm khi o cng t vi, kG. Kt lun chng 3

1. chn cc phng php thc hin th nghim hn n to phi bimetal thp C45 thp 15; bin dng do bng phng php p chy nng phi sau hn n. Trn c s , la chn mt cch c c s khoa hc vt liu v thit b th nghim ph hp tin hnh nghin cu nh hng ca cc yu t cng ngh chnh khi hn n (r), (h), (C) v mc bin dng do tng cng tng i trong qu trnh p chy phi bimetal thp C45 thp 15 sau hn n () n cht lng ca n ph hp vi iu kin Vit Nam;

2. chn cc phng php nh gi cht lng mi hn theo tiu ch tng hp bn bm dnh v t chc t vi vt liu sau hn n v sau p chy nng ti cc v tr in hnh theo chu vi phi bimetal dng hnh tr trn bin gii 2 lp bng cch s dng trang thit b th nghim hin i. ng thi ng dng phn mm tin hc

16

chuyn dng x l s liu thc nghim bng tnh ton m phng s hm mc tiu bn bm dnh 2 lp bimetal ph thuc vo cc thng s n chnh, a ra phng php nh gi sai s tng i trong php o c trc tip, gin tip ca cc gi tr cn thit trong tnh ton.

Chng 4. NH HNG CA CH HN N TI BN BM DNH HAI LP V T CHC VT LIU BIMETAL THP C45 - THP 15

DNG HNH TR 4.1. nh gi hin trng mu bimetal thp C45 - thp 15 sau hn n

4.1.1. Mu hn n ch thm d cng ngh QHTN 1 Trn hnh 4.1 th hin nh chp mt s mu th nghim hn n ch thm d

cng ngh c chn s b trong khong: r = 1,4 1,8; h = 0,1 0,5 v C = 0,7 1,0. - nh gi hnh thi b mt cc mu bimetal sau hn n theo QHTN 1 cho thy: 1. Hin tng ng thp hp kim 15 ti 03 vng khc nhau ca phi bimetal

sau hn n b bin dng tp vo trong theo chu vi ng knh ca n khng u dc theo hng n, nhng cc mc co ngang khc nhau (3,0 4,5 %).

2. Khi cc thng s (r) v (C) tng, kh nng bm dnh ca ng thp hp kim 15 vi li thp nn C45 c xu hng tng t l thun so vi (r) v (C).

a) 1 2 3 4

b) 5 6 7 8

Hnh 4.1. Mu bimetal thp C45 thp 15 sau khi hn n theo ch n QHTN 1 4.1.2. Mu hn n ch hiu chnh cng ngh QHTN 2 : Khi hn n theo

quy hoch hiu chnh cng ngh (QHTN 2) mu nhn c cho trn hnh 4.3 a,b,c.

02 03 04 05 06 12 14 / 15 / 16 17 24 25 26 27 a) b) c)

Hnh 4.3. Mu bimetal thp C45 thp 15 sau khi hn n theo ch QHTN 2: a) L 1: Mu s 2 6; b) L s 2: Mu s 12, 14 17; c) L s 3: Mu s 24 27

1. Tt c cc mu bimetal thp C45 thp 15 dng hnh tr sau khi hn n u c kh nng bm dnh gia li thp C45 vi ng thp hp kim 15 tt;

2. sai lch tng i gia cc ng knh phi bimetal trung bnh trn 03 phn vng u (1), gia (2) v cui (3) t trong khong 1,5 3,5 % (L th nghim 1); 2,5 3,5 % (L th nghim 2); 3,0 5,5 % (L th nghim 3), trong phn gia phi (2) c hin tng b co vo vi mc ln hn so vi phn u (1) v phn cui (3);

17

3. Khi thng s (h) tng trong khong h = 0,10,3 kh nng bm dnh 2 lp thp 15 v li thp nn C45 c xu hng tng v sau gim trong khong h = 0,30,5. 4.2. Nghin cu nh hng ca ch hn n n bn lin kt hai lp

bimetal thp C45 - thp 15 4.2.1. Xc nh tc n ca thuc n bng phng php o trc tip Thuc n hn hp (AD1 + NH4NO3) vi C = 0,75; 0,875; 1,0 v mt ri 0 =

0,95 0,97 g/cm3. Kt qu o trc tip l: D1 = vk1 = 3430 m/s (l th nghim 1); D2 = vk2 = 3830 m/s (l th nghim 2); D3 = vk3 = 4230 m/s (l th nghim 3).

4.2.2. Kt qu tnh ton xc nh bn bm dnh 2 lp bimetal bn bm dnh 2 lp bimetal thp C45 thp X15 sau hn n trung bnh t

gi tr: (1)b.d = 128,7333 175,6667 MPa (l th nghim 1); (2)b.d = 175,6667 215,6 MPa (l th nghim 2); (3)b.d = 197,3333 258,6667 MPa (l th nghim 3). iu cho thy: b.d cc mu hn n theo QHTN 2 tng t l thun cng chiu tng ca cc thng s (r); (C) v (h = 0,1 0,2), ng thi gim t l nghch theo chiu tng ca (r); (C) v khi (h = 0,2 0,3) (bng 4.5 lun n).

4.2.3. M hnh ton hc hm mc tiu bn bm dnh 2 lp bimetal M hnh ton hc hm mc tiu (b.d) cn tm nhn c nh sau:

600.7542 256.9280 452.8175 446.8207,553162,94,742 207,2851136,650 44,433 22

ChrhCrCrhChr 2bd (4.1)

trong : r T l khi lng thuc n (m0) so vi khi lng ng thp X15 (m1), r = m0/m1; h T l khe h hn h0 so vi chiu dy thnh ng thp X15, h = h0/1; C T l khi lng thuc n amnt (AD1) so vi khi lng hn hp (AD1 + NH4NO3).

a)

b)

c) Hnh 4.7. nh hng ng thi ca 3 thng s r, h v C n bn bm dnh 2 lp

bimetal thp C45 thp X15 sau hn n

18

T cc s liu thc nghim, s dng phn mm tin hc chuyn dng xy dng c th biu din s ph thuc ca hm mc tiu bn bm dnh 2 lp bimetal vo cc thng s hn n chnh (r), (h) v (C) trn hnh 4.7.

T trong m hnh (4.1) v hnh 4.7 cho thy: nh hng ca cc thng s hn n n (b.d) gim dn theo th t nh sau: C h r:

- Thng s (C) c nh hng mnh nht n (b.d) v do h s trc s hng bc 1 (+256,928) v bc 2 (+207,285) ca (C) tuy khng ln, nhng u v mang du dng (+), iu lm tng gi tr cui cng ca (b.d);

- Thng s (h) c nh hng mnh th hai v cc h s trc s hng bc 1 mc d c gi tr ln hn c v mang du dng (+452,8175), nhng h s trc s hng bc 2 li rt ln v mang du m ngc li (1136,65) ca (h);

- Tip sau l thng s (r) v cc h s trc s hng bc 1 (+446,82) v bc 2 (44,433) ca (r) nh hn so vi cc s hn ca (h), ng thi cn k n nh hng tri chiu ca (h) phn vng kho st h = 0,2 0,3 nh nu trn. 4.3. Nghin cu nh hng ca ch hn n n cu trc t vi bin gii hai lp

bimetal thp C45 - thp 15 4.3.1. Cu trc t vi vt liu bimetal thp C45 - thp 15 trn bin gii hai lp

theo mt ct ngang hng n: V d in hnh cho trn cc hnh 4.8e,f (QHTN 1); hnh 4.10c,d &4.11e,f (QHTN 2). Bin gii lin kt 2 lp vt liu bimetal sau hn n mt vi ch QHTN 1 cn c lp cu trc mng mng phn b khng lin tc trn ton b chiu di mu kho st. Nguyn nhn l do chn ch n vi mc thp (r = 1,4) v trung bnh (r = 1,6) v (h = 0,3 0,5) l cha m bo to ra tia kim loi cc b ti vng tip xc va p mnh y ht cc hp cht gia cc thnh phn kim loi thp hn v sn phm n ra khi khe h hn v cha bin dng co tp ng thp 15.

e - Mu s 20 (MS: 012)

f - Mu s 24 (MS: 122)

Hnh 4.8. nh chp cu trc bin gii 2 lp vt liu bimetal thp C45 thp 15 trn mt s mu th nghim theo quy hoch thc nghim nh hng cng ngh (QHTN 1)

c - Mu s 14* (MS: 111)

d - Mu s 15* (MS: 121)

Hnh 4.10. nh chp cu trc bin gii 2 lp vt liu bimetal thp C45 thp 15 trn mt s mu th nghim theo quy hoach thc nghim hiu chnh cng ngh (L s 2-QHTN 2)

19

e - Mu s 25* (MS: 202)

f - Mu s 26* (MS: 212)

Hnh 4.11. nh chp cu trc bin gii 2 lp vt liu bimetal thp C45 thp 15 trn mt s mu th nghim theo quy hoach thc nghim hiu chnh cng ngh (L s 3-QHTN 2)

4.3.2. Cu trc t vi bin gii hai lp bimetal thp C45 thp 15 trn mt ct dc theo hng n: nh chp cu trc vt liu dc hng n in hnh cho trn hnh 4.12e,f. T cho thy: trn b mt bin gii 2 lp vt liu bimetal hn n, lp thp C45 mm hn b bin dng di theo hng n, sng lin kt gia 2 lp gim. Sau iu chnh cc thng s cng ngh hn n, ta c cu trc vt liu trn bin gii 2 lp bimetal c c tnh sau: mi hn nhn c rt tt, khng pht hin thy lp mng mng cu trc hoc lin kim loi cc b trn ton b chiu di mu kho st. Sng lin kt 2 lp thp C45 v thp 15 c tnh cht c trng l bin sng lin kt ln, ng thi bn bm dnh 2 lp c gi tr cao (bng 4.5 lun n).

e - Mu s 6 (MS: 120 )

f - Mu s 6 (MS: 120)

Hnh 4.12. nh chp cu trc bin gii 2 lp bimetal thp C45 thp 15 dc hng n (ae) v vt o cng t vi vng bin gii 2 lp bimetal (e,f)

Ch hn n theo QHTN 2 m bo nhn c phi bimetal thp C45 thp 15 t cht lng tng hp tt, kh dng cho vic ch to chi tit my dng hnh tr c tnh nng c bit v lp vt liu b mt bng thp hp kim chu mn cao. Kt lun chng 4

Bng cc nghin cu thc nghim trong phn ny nhn c cc kt qu sau: 1. Gia i lng (C) vi tc n ca thuc n s dng (D = vk), p sut va p

(pk) v nng lng va p (Wp) theo chiu dy ng thp X15 (1 = 2,0 4,0 mm) c mi quan h sau: Khi hn n vi C = 0,75 xc nh c tc n D1 = vk1 = 3430,0 m/s; tc , p sut v nng lng va p t gi tr tng ng: vp1 = 1029,0 m/s; pk1 = 8,312 GPa; Wp1 = 83,119 166,238 MJ/m2; Khi hn n vi C = 0,875 xc nh c tc n D2 = vk2 = 3830,0 m/s; tc , p sut v nng lng va p t gi tr tng ng: vp2 = 1193,8 m/s; pk2 = 11,1875 GPa; Wp2 = 111,8749 223,75 MJ/m2; Khi hn n vi C = 1,0 xc nh c tc n D3 = vk3 = 4230,0 m/s; tc , p sut v nng lng va p t gi tr tng ng: vp3 = 1365,9 m/s; pk3 = 14,6456 GPa; Wp3 = 146,456 292,912 MJ/m2;

20

2. bn bm dnh 2 lp vt liu bimetal thp C45 thp X15 nhn c cc ch hn n theo QHTN 2 sau hn n (b.d) trn cc mu th nghim lp theo QHTN 2 tng t l thun cng chiu tng ca cc thng s (r), (C) v (h = 0,1 0,2), ng thi gim t l nghch theo chiu tng ca (r), (C) v (h = 0,2 0,3). nh hng ca thng s (C) l mnh nht, sau l thng s (h) v cui cng l thng s (r). bn bm dnh 2 lp bimetal thp C45 thp X15 sau hn n (b.d) trn cc mu th nghim lp QHTN 2 t trong khongb.d = 128,7333 258,6667 MPa;

3. bn bm dnh 2 lp ca vt liu bimetal ln nht b.d = 258,6667 MPa t c ch hn cng cao vi r = 1,7; h = 0,2; C = 1,0 (tng ng vi vp = 1365,9 m/s v pk = 14,6456 GPa) khi sng lin kt gia hai lp thp ln, sch (khng c lp cu trc mng mng), khng b nt v c co tp lp ng thp X15 phn gia phi t 4,5 5,5 % so vi ng knh ban u;

4. Sai lch bin dng co tp ca ng thp X15 theo hng knh trn ton b chiu di phi hnh tr dc hng n sau khi hn n l 1,5 5,5 %. Chng 5. NGHIN CU NH HNG CA BIN DNG DO N TNH CHT VT LIU BIMETAL THP C45 THP X15 SAU P CHY NNG 5.1. nh hng ca bin dng do n bn bm dnh 2 lp vt liu bimetal

Quy lut nh hng ca bin dng do n tnh cht vt liu bimetal thp C45 thp X15 c nh gi thng qua hai tiu ch c bn l bn bm dnh 2 lp (b.d) v c tnh hnh thi cu trc t vi ti vng bin gii gia chng cc trng thi sau hn n, p nng ln 1 vi 1 = 7,5%, ln 2 vi 2 = 15% v ln 3 vi = 22,5%. Mu th nghim sau p chy nng phi bimetal dng hnh tr cho trn hnh 5.1, cn kt qu tnh ton xc nh bn bm dnh 2 lp bimetal cho tyn hnh 5.2.

a) Mu th nghim s 14

b) Mu th nghim s 15

c) Mu th nghim s 16

d) Mu th nghim s 26

Hnh 5.1. nh chp mu th nghim p chy nng t phi bimetal thp C45 thp X15 dng hnh tr qua hn n cc ch c m s: a) (111) ; b (121) ; c) (201) ; d) (212)

170

bn

bm

dn

h,

b.d,

MPa

%0 7,5 15 22,5160

180

190

200

210

220

230

240

250

260

1

2

3

4

Hnh 5.2. th nh hng ca bin dng do n bn bm dnh 2 lp bimetal

thp C45 thp X15 trong qu trnh p chy nng

21

5.2. Xc nh c tnh cc lp vt liu bimetal thp C45 thp 15 sau p chy 1. i vi mu sau p chy nng vi = 15%: cng t vi c xu hng gim

dn theo chiu tng ca khong cch cc vt o i t bin gii lin kt 2 lp bimetal ra c 2 pha kim loi hn (thp X15) v kim loi nn (thp C45). cng lp thp hp kim X15 t HVX15 = 235 260, cn cng lp thp C45 t HVC.45 = 178 199; cng trn bin gii 2 lp bimetal t HVb.g. = 169 175;

2. i vi mu sau p chy nng vi = 22,5%: HVX15 = 311 342, cn cng lp thp C45 t HVC.45 = 240 265. cng trn bin gii 2 lp bimetal t HVb.g. = 264 274. Nguyn nhn v do qua p chy ln 3 vi = 22,5 % lm cho 2 lp vt liu bimetal b bin cng mnh v dn n chng c cng cao hn rt ng k so vi vt liu trn mu sau p chy vi = 15% (bng 4.6 lun n). 5.3. nh hng ca bin dng n hnh thi cu trc t vi mi hn trn bin gii

kin kt 2 lp bimetal V d in hnh trn hnh 5.4 cho thy bin sng lin kt 2 lp bimetal (a)

thay i gim dn theo chiu tng ca mc bin dng do tng i tng cng ()

a - 1 = 7,5 %, mu s 14

b - 2 = 15,0 %, mu s 14

c - 1 = 7,5 %, mu s 15

d - 2 = 7,5 %, mu s 15

Hnh 5.4. nh chp cu trc t vi bin gii 2 lp mu s 14 (a,b) v mu s 15 (c,d): a ,c - Sau p chy nng ln 1; b,d - ln 2

T hnh 5.4 cho thy: bin sng lin kt 2 lp bimetal thay i gim dn theo chiu tng ca bin dng do () v cht lng b mt tip xc tt. 5.4. Nghin cu tnh cht cc tiu vng cu trc c trng vng bin gii lin kt

hai lp vt liu bimetal sau hn n v p chy nng Trn hnh 5.7a l nh t chc t vi in hnh (mu th nghim s No.8-2) sau

hn n v bin dng do vi 2 = 15%, lm ngui sau ngoi khng kh, l mt trong s cc mu c chn phn tch SEM-EDX. T chc t vi lp thp C45 v thp X15 cho hnh 5.8b,c.

tin hnh nghin cu SEM-EDX ti ba phn vng: mp hn n pha lp thp C45; mp pha lp thp X15 v vng bin gii hn n C45 X15 m kt qu cho trn hnh 5.10 v cc bng km theo l v d in hnh.

22

Hnh 5.7a. T chc t vi ca mi hn

bimetal thp C45 thp 15 sau hn n, p chy nng v lm ngui trong

khng kh (x500; 2 =15%)

b) x500

c) x500

Hnh 5.8b,c. nh t chc t vi lp thp C45 (a) v thp X15 (c) sau p chy nng v lm ngui trong khng kh:

a) Peclt + Pherit); b) Peclit mn + Cc bt li

a) Tiu vng 001 v 002, x1000

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

keV

002

0300

600900

120015001800

210024002700

30003300

3600

CKa

SiKa

CrL

a

CrK

a

CrK

b

FeLl

FeLa

FeLs

um

FeKesc

FeKa

FeKb

b) Tiu vng 001 v 002

c) Tiu vng 003 v 004, x3000

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

keV

004

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

CKa

OKa

NaK

a

NaK

sumM

gKaAlK

a

SiKa

KKa

KKbCaK

esc

CaK

a

CaK

b

TiKesc

TiKa

TiKb

CrLa C

rKa

CrK

b

MnL

a

MnK

esc

MnK

a

MnK

b

FeLa

FeLs

um

FeKesc

FeKa

FeKb

d) Tiu vng 003 v 004

e) x3000

a - c: Phn tch theo tiu vng V tr

Kt qu phn tch thnh phn ha hc, % kh.l. C O Na Mg Si K Ca Ti Cr Mn Fe Tng

001 0.27 - - - 0.14 - - - 0.11 - 99.48 100.00 002 0.53 - - - 0.31 - - - 1.74 - 97.42 100.00 003 1.18 - - - 0.56 - - - 1.53 - 96.72 100.00 004 1.51 14.1 1.7 0.02 6.08 0.22 1.13 0.79 12.6 4.2 56.6 100.00

e: Phn tch theo ng mu: , xanh thm, xanh l V tr

Kt qu phn tch thnh phn ha hc EDX theo ng, % kh.l. Khong K.S. C Si Cr Fe Tng

000 0.000 m 2.47 0.64 1.59 95.31 100.00 001 2.763 m 2.03 0.39 1.46 96.12 100.00 002 5.526 m 0.85 0.05 1.50 97.60 100.00 003 8.290 m 1.86 0.95 3.72 93.47 100.00 004 11.053 m 0.62 0.08 1.11 98.19 100.00 005 13.816 m 1.37 0.09 1.09 97.45 100.00 006 16.579 m 1.39 0.01 0.81 97.79 100.00 007 19.343 m 2.22 0.31 0.73 96.74 100.00 008 22.106 m 1.90 0.17 0.48 97.45 100.00 009 24.869 m 2.07 0.12 0.55 97.25 100.00

f) Hnh 5.10. V tr tiu vng kho st mu No.1.3 (1): (a x1000; c x3000); Kt qu phn tch

SEM-EDX tng ng (b; d); V tr v kt qu phn tch SEM-EDX theo ng (e x3000; f)

20 m LG1

Distance0.00 24.87 m

Mas

s%0

4 CSiCr

23

T hnh 5.10 cho thy: t chc phn trn ca nh ng vi thp C45 bao gm peclt v fert; phn di gm peclt mn, cc bt dng li v c fert hp kim. T chc ti mi hn c c trng ca c hai loi thp nu. l kt qu ca s phn b khng u ca cc nguyn t trong thp gy nn.Tng hp t 16 phn tch SEM-EDX tng t xy dng c bng 5.3.

Qua phn tch s liu trong bng 5.3 cho thy: - C s thay i thnh phn ha hc trung bnh t mc thp C45 qua lp hn ti mc thp IIIX15 mt cch tun t m khng c bc nhy t ngt; - Do qu trnh hn n to ra va p rt mnh cng vi qu trnh nng chy cc b, thnh phn cc nguyn t ca thp hai mp mi hn v c bit trong vng hn b thin tch rt mnh s gy nh hng ln ti s hnh thnh t chc v ng sut lp hn;

- Ti cc tiu vng c bit trong lp hn dnh, ngoi cc nguyn t kim loi trong thp cn c xy v cc kim loi khc nh Na, Mg, Al, K, Ca, Ti do bn thn kim loi hn, thuc n v mi trng khng kh trong mi hn khng kp thot ra s hnh thnh cc xt, cc lin kim, c coi l tp cht lm gim cht lng mi hn. cng l nguyn nhn to ra lp mng trong trng hp hn mm. Bng 5.3. S liu tng hp t 16 th nghim SEM-EDX v s phn b thnh phn cc nguyn t trong bimetal thp C45 thp IIIX15 Hm lng ng.t,

% kh.l.

Mp C45 Mp IIIX15 Gia C45 v IIIX15

Tp cht mu phn tch

Danh ngha

Trung bnh

Danh ngha

Trung bnh

Danh ngha

Trung bnh

M1-3

M2-4

M3.2

M3-4

M3.2- 3

C 0,19 0,73 0,48 0,28 1,27 0,43 0,05,2 1,37 3,05 3,00 2,37 1,57 1,59

Si 0,14 0,52 0,26 0,20 0,52 0,26 0,0 0,28 0,27 4,58 12,2 17,6 15,9 6,7

Cr 0,11 0,32 0,24 1,16 1,87 1,76 0,2 1,3 0,85 36,8 3,30 0,38 0,59 3,65

Khc O, Na, Mg, Al, K, Ca, Ti Kt lun chng 5: Qua nghin cu s bin dng do mu sau hn n bng phng php p chy (nng) c th i ti kt lun sau: 1. Trong qu trnh bin dng do phi bimetal thp C45 thp 15, bin sng lin kt gia 2 lp c quy lut gim dn theo chiu tng ca mc bin dng tng i do phi b p co theo hng knh v chy di dc theo hng p. bn bm dnh ca bimetal gim t vi t l 1,85 1,99% ti 5,41 5,55% khi tng mc bin dng t 7,5% ti 22,5%. iu do nhiu nguyn nhn c lin quan ti s lin kt gia hai lp thp nh cng sng ti b mt lin kt, vai tr cu gia cng p nng, s kt tinh li v ng sut to ra, s thay i c tp cht sau bin dng do m cc ng nghip cng tc gi lun n s tip tc nghin cu cng trnh khc; 2. S lin kt gia gia 2 lp vt liu bimetal hn n l do vic to thnh cc t chc mang tnh kim loi. Tuy nhin, do tc va p ln v s nng chy cc b khi hn n m cc nguyn t trong bimetal b thin tch rt mnh, ng thi khng kh v tp cht to thnh trong mi trng hn khng kp thot ht ra ngoi nn vng mi hn ngoi cc t chc pclt

24

mn, cc bt dng li v phert cn tn ti cc xyt v tp cht phi kim. Kt qu lm gim cng v bn bm dnh mi hn v s ph hy ch yu xy ra ti y. iu lm cho bn bm dnh 2 lp bimetal gim dn theo chiu tng ca mc bin dng do ().

KT LUN CHUNG LUN N T kt qu nghin cu trnh by trong lun n, rt ra cc kt lun sau: 1. Hn n bimetal thp C45 - thp X15 dng ng ch to cc chi tit lm

vic trong iu kin chu mi mn l mt cng ngh mi c th thc hin ti Vit nam m khng cn u t nhiu to ra nng lng di p lc cao trong qu trnh va p ca cc lp kim loi hn, nh s hiu qu kinh t trong vic to phi bimetal m bo bn ban u t yu cu k thut cho cc bc gia cng tip theo;

2. Nh mt h thng l thuyt v hn n dng ng v phng php nghin cu hon chnh nh thit b o tc n ca thuc n (D), p sut va p (pk) v nng lng va p (Wp) theo chiu dy ng, t , xy dng c mi quan h gia cc thng s cng ngh nh C, h, r vi bn bm dnh trong bimetal nh thit bi o c th; ng thi dng cc phng php phn tch kim loi hin i, thch hp nh hin vi thng, hin vi in t, SEM, EDX xc nh v gii thch bn cht v nh gi c cht lng ca kt cu hn;

3. Mi quan h gia bn bm dnh 2 lp bimetal hn n (bd) vi cc thng s cng ngh C, r, h c biu din di dng phng trnh hi quy:

600.7542 256.9280 452.8175 446.8207,553162,94,742 207,2851136,650 44,433 22

ChrhCrCrhChr 2bd

Trong , nh hng ca cc thng s gim theo th t nh sau: C h r; 4. bn bm dnh 2 lp ca vt liu bimetal thp C45 thp X15 sau hn

n t gi tr b.d = 128,7333 258,6667 MPa. Gi tr cc i ng vi ch cng ngh hn cng cao: r = 1,7; h = 0,2; C = 1,0 khi sng lin kt gia hai lp thp ln, sch tp cht; 5. Trong qu trnh bin dng do phi bimetal thp C45 thp 15, bin sng lin kt gia 2 lp gim dn theo chiu tng ca mc bin dng tng i do phi b p co theo hng knh v chy di dc theo hng p. bn bm dnh ca bimetal gim t 1,85 1,99% ti 5,41 5,55% khi tng bin dng t 7,5% ti 22,5%. iu do nhiu nguyn nhn c lin quan ti s lin kt gia hai lp thp nh cng sng ti b mt lin kt, vai tr cu gia cng p chy nng, s kt tinh li v ng sut to ra, s thay i cu tp cht sau p chy nng m tc gi lun n s tip tc nghin cu cng trnh nghin cu khoa hc khc; 6. S lin kt gia 2 lp vt liu bimetal l do vic to thnh cc t chc mang tnh kim lai. Tuy nhin, do tc va p ln v s nng chy cc b khi hn n m cc nguyn t trong bimetal b thin tch rt mnh, ng thi khng kh v tp cht to thnh trong mi trng hn khng kp thot ht ra ngoi nn vng mi hn ngoi cc t chc pclt mn, fert v cc bt dng li cn tn ti cc xit v tp cht phi kim. Kt qu lm gim cng v bn bm dnh mi hn v s ph hy ch yu xy ra ti y.