Luyen Gang

B CNG THNG TRNG CAO NG CNG NGHIP THC PHM TP.H CH MINH Chng 1. Khi nim chung v kim loi v hp kim (2) Chng 2. Hp kim st cacbon (5) Chng 3. Gang (4) Chng 4. Thp (5) Chng 5. Kim loai mu v hp kim mu (2) Chng 6. Nhit luyn (4) Chng 7. Ha bn b mt thp (2) Chng 8. n mn k.loi v phng php chng n mn (2) Chng 9. Vt liu phi kim loi v nhin liu (2) 1 Chng 10. Vt liu compozit (2)

CHNG 3: GANG 3.1. S lc qu trnh luyn gang 3.1.1. Nguyn liu, nhin liu v vt liu 3.1.2. L cao v qu trnh luyn gang 3.2. nh hng ca cacbon v tp cht 3.2.1. Cacbon 3.2.2. Cc tp cht 3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xm 3.3.2. Gang cu 3.3.3. Gang do

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CHNG 3: GANG

MC CH 1. Kin thc: Cung cp cc kin thc + S lc v qu trnh luyn gang. + nh hng ca cacbon v tp cht n gang. + Cc loi gang thng dng v cng dng. 2. K nng: + Kh nng nhn bit v phn tch cc qu trnh luyn gang v nh hng ca cc nguyn t. + T duy logic v vn dng linh hot cc kin thc gii quyt cc vn thc tin.3

CHNG 3: GANG

Sau khi hc xong tit ging ny, sinh vin c kh nng: - Nu s lc c qu trnh luyn gang t l cao. - Phn tch c nh hng ca cc nguyn t n tnh nng ca gang. - Phn loi gang v cng dng ca tng loi - c c k hiu gang theo TCVN4

3.1. S lc qu trnh luyn gang

Gang v thp l vt liu khng th thiu c trong cng nghip. Thp li c ch bin t gang, do vy luyn gang l mt trong nhng cng vic quan trng nht ca ngnh luyn kim. - L cao. - L ng (l ch)5

3.1. S lc qu trnh luyn gang 3.1.1. Nguyn liu, nhin liu v vt liu 1. Qung st Qung st : ch yu l st xyt Fe2-O3 c mu , cha khong 50 60%Fe. Qung st l qung tt nht. Qung st nu: ch yu l st xyt ngm nc (Fe2O3.H2O v 2Fe2O3.3H2O), c mu nu vng n nu thm, cha khong 40 55%Fe.6

3.1. S lc qu trnh luyn gang 3.1.1. Nguyn liu, nhin liu v vt liu 1. Qung st Qung st t: l qung manhtt, tc st t xyt Fe3O4. Qung ny c mu en, cha khong 60 65%Fe, i khi ti 70%Fe. y l qung giu st nht, c t tnh v kh hon nguyn. Qung st cacbnat: l qung xirit FeCO3, cha khong 35 48%Fe.7

3.1. S lc qu trnh luyn gang 3.1.1. Nguyn liu, nhin liu v vt liu 1. Qung st - Nghin nh c kch thc qung ng u. - Lm giu qung kh b cc tp cht v cht bn (i qung theo trng lng hoc dng nam chm). - Nung qung lm cho ht m, axit cacbnic, lu hunh. - Thiu kt qung nh dnh kt li vi nhau, to 8 cho qung c xp.

3.1. S lc qu trnh luyn gang 3.1.1. Nguyn liu, nhin liu v vt liu

2. Nhin liu Than cc c nhit lng cao, bn, c xp cao v cha t lu hunh. 3. Cht tr dung - Cc cht kh chy thng cho thm cht tr dung l CaCO3 to thnh x long. - Cc loi FeSi, FeMn9

3.1. S lc qu trnh luyn gang 3.1.2. L cao v cc qu trnh luyn gang

Hnh: Cu to l cao 1. Mng tho gang; 2. ng dn kh; 3. Thit b cht liu; 4. L gi; 5. Mng tho x

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-Chiu cao 30 35m. -L c 5 phn: + C l. + Bng l. + Ni l + Thn l. + Hng l.11

3.1. S lc qu trnh luyn gang 3.1.2. L cao v cc qu trnh luyn gang1. H thng cp liu Gm mt h thng xe gong dng cp liu. 2. H thng thi v nung gi Mun c 1 tn gang, thng thng cn khong 750 800kg than cc v cn 3000m3 khng kh, khng kh ny c nung nng n 700 8000C. 3. H thng lc kh Kh l cao sau khi i ra khi l phi lc sch trc khi a vo thp nung nng. 12


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Qu trnh to thnh gang Qu trnh to thnh gang l mt qu trnh bin i ha hc phc tp, bao gm ba giai on chnh: 1. Giai on hon nguyn st. 2. Giai on to thnh gang. 3. Giai on to x.15

3.1. S lc qu trnh luyn gang 3.1.2. L cao v cc qu trnh luyn gangQu trnh to thnh gang Hai kh ch yu lm nhim v hon nguyn st l kh cacbon xyt CO v hir H2. C + O2 = CO2 CO2 + C = 2CO (Than cc chy) ( nhit cao) (liu m)16

H2O + C = H2 + CO


Qu trnh to thnh gang Cc kh CO v H2 s hon nguyn st theo cc bc sau: Fe2O3 Fe3O4 FeO Fe Qu trnh din ra theo cc phn ng: 3Fe2O3 + H2 = 2Fe3O4 + H2O Fe3O4 + H2 = 3FeO + H2O FeO + H2 = Fe + H2O17


Qu trnh to thnh gang 1. Giai on hon nguyn st. Ngoi ra, cacbon th rn cng tham gia hon nguyn st theo phn ng: FeO + C = Fe + CO + Q(calo) Phn ng ny hon nguyn ti 50% st xyt ca l cao.18


Qu trnh to thnh gang Sau khi st hon nguyn thn l, li phn ng tip vi cacbon: 3Fe + C = Fe3C Hnh thnh hp cht Fe3C gi l cacbit st hay xmentit. Cacbon ha tan dn vo st n 4%.19


Qu trnh to thnh gang ng thi mt s tp cht cng c hon nguyn nh: silic, mangan, pht pho, lu hunh l cc cht c cha sn trong qung. S hon nguyn ny tin hnh nhit 1000 12000C km theo s thu nhit. MnO + C = Mn + CO Q(calo) SiO2 + C = Si + 2CO Q(calo)20


Nhng sn phm ca l cao Gang: l sn phm chnh ca l cao. X: lng x trong l cao rt ln (khong 60% trng lng gang nu ra). X l cao c dng lm vt liu xy dng, ri ng. Kh l cao: l lng kh kh ln, c nhit dung cao. Kh l cao dng t thp nung, l luyn cc, ng c ga v.v21

3.2. nh hng ca cacbon v tp cht

- Gang l hp kim st v cacbon, c C > 2,14%. - Cc nguyn t tp cht cng nhiu: mangan v silic (0,5 - 2%), pht pho v lu hunh (0,05 - 0,5%). Do c hm lng cacbon cao, nn nhit nng chy ca gang thp hn thp nhiu v v vy nu chy gang d thc hin hn (tnh c tt). Tuy nhin, gang li cng v gin.22

3.2. nh hng ca cacbon v tp cht 3.2.1. Cacbon

Lng cacbon t do cng nhiu th: -Kh nng graphit ha cng mnh. -Nhit chy cng gim. -Gang cng d y khun v t co. Nhng, tng hm lng cacbon s lm gim bn, tng gin. V vy, thng khng dng gang c hm lng C > 4%.23

3.2. nh hng ca cacbon v tp cht 3.2.2. Cc tp chtSilic (Si) (0,5 2%) - L nguyn t lm tng rt mnh kh nng grapht ha ca gang. Khi gang t cacbon v silic th l gang trng. Mangan (Mn) (0,5 2%) - L nguyn t ngn cn s to thnh graphit, nu nhiu s lm ha trng gang. -Kh S: Mn + S MnS (to x v tch ra khi gang lng) -Lm tng bn cho gang.24

3.2. nh hng ca cacbon v tp cht 3.2.2. Cc tp chtPhtpho (P) (0,1 0,2%) - L nguyn t lm gang d chy long. Do , c th y mi ch ca khun, rt cn khi c nhng vt mng. -Tuy nhin, nh hng xu ca pht pho l lm gim c tnh ca gang, lm cho gang tr nn gin. Lu hunh (S) (< 0,1%) - L nguyn t c hi trong gang, n lm gim tnh chy long v cn tr s to thnh graphit.25

3.2. nh hng ca cacbon v tp cht 3.2.2. Cc tp chtPhtpho (P) (0,1 0,2%) - L nguyn t lm gang d chy long. Do , c th y mi ch ca khun, rt cn khi c nhng vt mng. -Tuy nhin, nh hng xu ca pht pho l lm gim c tnh ca gang, lm cho gang tr nn gin. Lu hunh (S) (< 0,1%) - L nguyn t c hi trong gang, n lm gim tnh chy long v cn tr s to thnh graphit.26

3.3 Cc loi gang v cng dng ca chng

T chc t vi, phn gang thnh cc loi: trng, xm, cu v do. -Gang trng l gang trong tt c cacbon nm dng lin kt ha hc Fe3C. -Gang xm, cu, do l cc loi gang m trong phn ln cacbon dng t do (graphit) vi hnh dng khc nhau: tm, cu, cm.27


C tnh - Gang l loi vt liu c bn ko thp, gin cao. Do cha mt lng ln xmentit, gang trng c bn ko rt thp v gin rt cao. - Mt khc trong gang xm, gang do, gang cu t chc graphit do bn bng khng (0) nn c coi nh l cc l hng c sn trong gang, lm mt tnh lin tc ca nn gang, l ni tp trung ng sut ln, lm gang km bn.28


C tnh - Mc tp trung ng sut ph thuc vo hnh dng graphit, ln nht gang xm vi graphit dng tm v b nht gang cu vi graphit dng cu trn. - Ngoi ra, s c mt ca graphit trong gang c nh hng tt n c tnh nh tng kh nng chng mn do ma st, lm tt rung ng v dao ng cng hng.29


Tnh cng ngh - Gang c tnh c tt do nhit nng chy thp. - chy long cao. - Tnh gia cng ct gt tt ( gang xm, cu, do) do graphit trong gang lm phoi d gy vn

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Cng dng - Ni chung, gang c dng ch to cc chi tit chu ti trng tnh v t chu va p nh b my, v, np, cc b phn tnh ti, cc chi tit chu mi mn ma st lm vic trong iu kin kh bi trn. - Ngoi ra, gang cu v gang do do c tnh cao nn c th dng thay th cho thp trong mt s trng hp.31

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xm

Gang xm l loi gang c dng ph bin nht trong ch to c kh v dn dng. - T chc t vi. - K hiu. - Thnh phn ha hc. - C tnh. - Cc mc gang xm thng dng32

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xmT chc t vi -L loi gang m phn ln cacbon ca n nm dng t do (graphit) - Do t chc cha nhiu graphit, mt gang c mu xm, ti (mu ca graphit) nn c tn l gang xm. - Graphit trong gang xm c dng tm cong.33


T chc t vi Ty theo mc to thnh graphit mnh hay yu, gang xm c chia thnh cc loi sau: - Gang xm ferit. - Gang xm ferit - peclit. - Gang xm peclit34

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xmT chc t vi Gang xm ferit - C mc to thnh graphit mnh nht, trong hu nh tt c cacbon dng graphit, khng c xmentit. - Gang ch c hai pha: graphit tm v nn kim loi ferit.35

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xmT chc t vi Gang xm ferit peclit. - C mc to thnh graphit mnh, trong cacbon lin kt khong 0,1 0,6%, to nn nn kim loi ferit peclit (tng ng vi nn thp trc cng tch) - T chc ca gang gm graphit tm v nn kim loi ferit peclit.36

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xmT chc t vi Gang xm peclit - C mc to thnh graphit trung bnh trong lng cacbon lin kt khong 0,6 - 0,8%, to nn nn kim loi peclit (tng ng vi nn thp cng tch) - T chc ca gang gm graphit tm v nn kim loi peclit.37


T chc t vi Nh vy, c th ni t chc t vi ca gang xm ging t chc t vi ca thp trc cng tch v cng tch, tuy nhin do c thm cc tm graphit. Chnh do iu ny m c tnh ca gang khc thp.38

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xmK hiu Tiu chun Vit nam (TCVN 165975) k hiu gang xm bng hai ch "GX" v hai s tip theo + S th nht ch gii hn bn ko (kG/mm2). S th hai ch gii hn bn un (kG/mm2). V d: GX 1532 l gang xm c gii hn bn ko l 15kG/mm2 (150 N/mm2) v gii hn bn un l 32kG/mm2 (320 N/mm2).39

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xmThnh phn ha hc Lng cacbon trong gang xm thng thng khong 2,8 - 3,5%. Cacbon cng nhiu trong gang, kh nng to thnh graphit cng mnh, nhit chy cng thp, cng d c. Tuy nhin khng th dng gang vi cacbon qu cao, v khi s to thnh nhiu graphit lm gim c tnh.40

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xmThnh phn ha hc Lng silic trong gang xm khong 1,5 - 3% Silic l nguyn t thc y mnh s to thnh graphit. Ngoi ra, khi silic ha tan vo ferit ca gang lm tng rt mnh cng v bn pha ny. Thng dng gang xm vi hm lng 0,5 - 1% Mn. Mangan l nguyn t cn tr s to graphit. bo m yu cu to thnh graphit, gia Mn v Si cn phi c t l tng ng: Mn cao th Si cng phi cao.41

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xmThnh phn ha hc Thng dng gang xm cha 0,1 0,2%P Photpho l nguyn t c li do lm tng chy long ca gang lng, lm tng tnh chng mi mn. Tuy nhin nng cao photpho qu mc s lm gang gin. Lu hunh trong gang 0,08 - 0,12%. Lu hunh l nguyn t lm cn tr mnh s to thnh graphit, lm xu tnh c ca gang do lm gim chy long.42


Thnh phn ha hc Cacbon Silic Mangan Photpho Lu hunh 2,8 - 3,5%. 1,5 - 3%. 0,5 - 1%. 0,1 0,2%. 0,08 - 0,12%.43


Thnh phn ha hc Cacbon Silic Mangan Photpho Lu hunh 2,8 - 3,5%. 1,5 - 3%. 0,5 - 1%. 0,1 0,2%. 0,08 - 0,12%.44

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xm C tnh gang xm Graphit l pha c bn rt thp nn trong gang n nh l nhng vt rng, nt c sn, lm mt s lin tc ca nn kim loi, do lm gim mnh bn ko ca gang. Ngoi ra u nhn ca cc tm graphit chnh l ni tp trung ng sut.45

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xmC tnh gang xm Nh vy so vi thp, gang xm c gii hn bn nn khng thua km bao nhiu nhng gii hn bn ko, do, dai li thp hn nhiu. cng ca gang xm trong khong 150 - 250 HB, d gia cng ct. C tnh ca gang ph thuc vo: + nh hng ca graphit. + nh hng nn kim loi.46

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xm+ nh hng ca graphit. - Graphit cng t, c tnh ca gang xm cng cao. Gim lng cacbon tng v nng cao cacbon lin kt. - Graphit tm cng di c tnh ca gang xm cng thp. Lm graphit nh mn. Graphit phn b trn nn kim loi cng u th cng t nh hng xu n c tnh.47

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xm+ nh hng ca nn kim loi Nn kim loi ca gang l yu t quan trng quyt nh c tnh ca gang. Loi gang xm Ferit Ferit - peclit peclit Gii hn bn ko b (N/mm2) 150 150 - 200 210 - 250 cng HB,(kG/mm2) 150 200 220 - 250

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3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xmCc bin php nng cao c tnh ca gang xm - Gim lng cacbon ca gang: nu trong l in, c th gim lng C = 2,22,5%. - Bin tnh: cho cht bin tnh vo, chng s to nn cc xit, nitrit phn tn. - Hp kim ha: a thm nguyn t hp kim - Nhit luyn: ti v ram gang xm, bin nn kim loi thnh t chc xoocbit, trstit, mactenxit ram.49

3.3 Cc loi gang v cng dng ca chng 3.3.1. Gang xmCc mc gang xm v cng dng - Cc mc gang GX00, GX12-28, GX15-32, dng cho cc chi tit khng chu lc nhng li chu va p nhit tt. - Cc mc gang GX21-40, GX24-44, GX32-52, s dng cho cc chi tit chu lc, chu mi mn ... trong ngnh ch to my. - Hai mc GX36-56, GX40-60 dng cho cc chi tit chu mi mn, chu ti trng nng.50

3.3 Cc loi gang v cng dng ca chng 3.3.2. Gang cu

Gang cu l loi gang c c tnh cao, thng c dng thay th cho thp. - T chc t vi. - K hiu. - Thnh phn ha hc v cch ch to. - C tnh. - Cc mc gang cu thng dng51


T chc t vi - Ging nh gang xm, song ch khc l graphit ca n dng thu gn nht: dng qu cu, chnh iu ny lm bn ko ca gang cu rt cao so vi gang xm. - Gang cu ferit, ferit peclit, peclit.52

3.3 Cc loi gang v cng dng ca chng 3.3.2. Gang cuK hiu Tiu chun Vit nam (TCVN 165975) k hiu gang cu bng hai ch "GC" v hai s tip theo + S th nht ch gii hn bn ko (kG/mm2). S th hai ch dn di tng i (%).

V d: GC 455 l gang cu c gii hn bn ko l 45kG/mm2 v dn di tng i l 5%.53

3.3 Cc loi gang v cng dng ca chng 3.3.2. Gang cuCch ch to v thnh phn ha hc Ni chung thnh phn ha hc ca gang cu ging gang xm, song ch khc l gang cu c thm thnh phn cht bin tnh c bit (l Mg, Ce hoc cc nguyn t t him vi hm lng rt nh). Nh cc cht bin tnh cu ha m gang lng tr nn sch cc tp cht nh S v kh, lm tng qu ngui cho gang.54

3.3 Cc loi gang v cng dng ca chng 3.3.2. Gang cu Thnh phn ha hc Cacbon Silic Mangan Photpho Lu hunh Magie 3,0 - 3,6% 2,0 - 3,0% 0,5 - 1,0% 0,15% 0,04 - 0,08% 0,04 - 0,08%55

3.3 Cc loi gang v cng dng ca chng 3.3.2. Gang cu C tnh gang cu- Gang cu c c tnh tng hp tng i cao, gn nh thp cacbon. - C tnh ca gang cu ph thuc ch yu vo t chc ca nn kim loi. Sau khi c, gang cu c nhit luyn p ng cc yu cu c tnh khc nhau. - Graphit cu cng trn, kch thc cng nh v s lng cng t th c tnh ca gang cu cng cao.56


Cc bin php nng cao c tnh ca gang cu - Bin tnh: cho cht bin tnh vo, to graphit cu

cng nh, cng trn cng tt. - Hp kim ha: Nng cao bn ca ferit - Nhit luyn: ti v ram, c bit gang cu rt thch hp ti ng nhit thnh bainit.57

3.3 Cc loi gang v cng dng ca chng 3.3.2. Gang cuCc mc gang cu v cng dng - Gang cu ferit GC 40 - 10 v gang cu peclit GC 60 - 2 v cng 197 269HB. c bit, gang cu sau khi ti ng nhit ra t chc bainit, c th t = 1000 1300 MPa, = 4 8% v cng t 302 369HB. Gang cu c s dng thay cho thp ch to cc chi tit chu lc ln v chu ti trng va p, chu mi mn nh trc khuu t, cam, trc cn, thn tua bin hi...58

3.3 Cc loi gang v cng dng ca chng 3.3.3. Gang do

- T chc t vi. - K hiu. - Thnh phn ha hc. - C tnh. - Cc mc gang do thng dng59


T chc t vi - Ging gang xm v gang cu, song khc hai im: graphit ca n dng cm v graphit cm ny to ra khng phi khi c m do tip theo. - Gang do ferit, ferit-peclit v peclit.60

3.3 Cc loi gang v cng dng ca chng 3.3.3. Gang doK hiu Tiu chun Vit nam (TCVN 165975) k hiu gang do bng hai ch "GZ" v hai s tip theo + S th nht ch gii hn bn ko (kG/mm2). S th hai ch dn di tng i (%).

V d: GZ 33 - 8 l gang do c gii hn bn ko l 33 kG/mm2 v dn di tng i l 8%.61


Cch ch to v thnh phn ha hc Mun c gang do phi nu gang c thnh phn xc nh v c thnh gang trng c t chc trc cng tinh. T gang trng mi c thnh gang do. Theo qui trnh c hai loi gang do: + Gang do tm trng. + Gang do tm en.62

3.3 Cc loi gang v cng dng ca chng 3.3.3. Gang doCch ch to v thnh phn ha hc + Gang do tm trng. Ch to t gang trng c thnh phn cacbon cao 2,6

2,8%, gim lng cacbon t do, cn ra nn peclitv gim bt cacbon bng vic gang do trong mi trng xy ha. Ch nhit khi khi gm gi nhit 980 1060oC trong 60 120 gi, sau lm ngui tng i nhanh to ra t chc peclit - graphit cm.63

3.3 Cc loi gang v cng dng ca chng 3.3.3. Gang doCch ch to v thnh phn ha hc + Gang do tm en. Ch to t gang trng c hm lng cacbon thp 2,2 2,3%. tin hnh trong mi trng trung tnh to nn ferit v graphit cm. Nhit gang do tm en tin hnh 950oC trong 20 gi nhm phn hy xmentit, sau ferit ha nn bng cch lm ngui chm vt c vi tc 3 5oC/gi nhit 760 860oC cho n khi peclit phn ha ht thnh ferit v graphit cm.64

3.3 Cc loi gang v cng dng ca chng 3.3.3. Gang doCch ch to v thnh phn ha hc Hin nay, gim gi thnh gang do, ngi ta thng rt ngn thi gian bng cc bin php: - Tng hm lng Si, gim hm lng C ti mc cho php v bin tnh gang lng bng cc nguyn t chng to graphit tm: B, Bi, Sb ...; - Bin tnh gang lng bng cc nguyn t to mm khi .65

3.3 Cc loi gang v cng dng ca chng 3.3.2. Gang cu Thnh phn ha hc khi c Cacbon Silic Mangan Photpho Lu hunh 2,2 2,8% 0,8 1,4%

1% 0,2% 0,1%66

3.3 Cc loi gang v cng dng ca chng 3.3.3. Gang do C tnh gang do- Do graphit dng tng i tp trung nn gang do c bn ko cao hn gang xm nhng km gang cu. Gii hn bn ko ca gang do trong khong 300 600 N/mm2. - do ca gang do kh cao: = 5 10%, c trng hp vt qu do ca gang cu.67

3.3 Cc loi gang v cng dng ca chng 3.3.3. Gang doCng dng ca gang do - Gang do c c tnh tng i cao, c bit tnh do tt. - Gi thnh ch to cao. Gang do ch c dng cho cc chi tit nh, hnh dng phc tp, thnh mng, chu va p trong cng nghip my ko, t, my dt, my nng nghip ...68

3.3 Cc loi gang v cng dng ca chngGang chu nhit Hp kim ha gang bng cc nguyn t Si, Cr, Al, vi hm lng xc nh to trn b mt mt lp xit bn, st cht, lm cho gang khng b xy ha v trng n.

- Gang hp kim silic cha 4 6% Si. (10000C)- Gang hp kim crm cao cha 12 18%Cr. (9000C) - Gang niken cao cha 14 17% Ni. (6000C) - Gang nhm cao cha 18 25% Al. (9000C)69


Gang chu n mn Gang chu n mn tt phi l gang hp kim cao. Chng c th l gang xm hoc gang cu. Khi hp kim ha gang bng cc nguyn t Cr, Ni, Si vt qu mt gii hn xc nh, chng s lm thay i in th in cc ca cc pha v to ra mt lp mng xit, lm th ng ha qu trnh n mn ca chi tit trong cc mi trng hot tnh.70


Gang chu n mn - Gang silic cao 12 17% Si, c bn km, cng cao, gin, kh gia cng. (HNO3, H2SO4, H3PO4). - Gang crm cao 20 26% Cr, c c tnh kh, nhng cng cao, kh gia cng. (HNO3, H3PO4 v trong dung dch mui) - Gang niken cao 14 30% Ni, c c tnh kh, d gia cng c. (H2SO4, HCl).71

CHNG 3: GANG

CC CU HI1. Nguyn, nhin, vt liu dng luyn gang gm nhng g? Hy k tn tng thnh phn. 2. Trnh by cu to ca l cao v cc thit b ph ca l cao. 3. Cho bit cc phn ng ha hc xy ra trong l cao. 4. Cho bit nh hng ca cacbon v cc nguyn t tp cht n tnh nng ca gang ?72

CHNG 3: GANG

CC CU HI5. V t chc v thnh phn ha hc cc loi gang (trng, xm, do, cu) khc nhau nhng im no? 6. So snh v c tnh ca cc loi gang (xm, do, cu). Nguyn nhn no a n s khc nhau ? 7. Cho bit cng dng ca cc loi gang? 8. Cho bit cng dng ca cc loi gang cu?73

CHNG 3: GANG

CC CU HI9. Cho bit trng hp no nn s dng gang do? 10. Ti sao gi thnh gang do li cao hn so vi gang xm v gang cu? 11. Gii thch cc k hiu sau: GX 1224 ; GZ 306 ; GC 455? 12. Cho bit mt s loi gang chu nhit v chu n mn ?74

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Luyen Gang