Chuong5 - Vật liệu học

8/14/2019 Chuong5 - Vt liu hc

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Chng 5 thp v gang

5.1.Khi nim chung v thp:

- L vt liu c c tnh tng hp cao nht chu

ti trng phc tp v nng - l vt liu ch yu

ca ch to my

- Dng cung cp: tm, thanh nhiu dng

5.1.1. Khi nim v thp C:

I. Thnh phn ho hc:Ngoi Fe v C (


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l nguyn t quan trng nht quyt nh tchc v c tnh (thp C v HK)

lng C tng cng tng, do dai gim ( quilut bc nht )

VD: C tng 1% HB tng 20-25ak gim 200KJ/m2

tng 40-50 N/mm2( chn 0,8%C) bn bin i khng tuyn theo lng C

c. Cng dng ca thp theo thnh phn C:Thp vi hm lng C thp ( 0,25%) : kt cutrong xy dng

- do dai, bn, cng u thp ( thm)- hiu qu ti v ram khng cao

Thp hm lng C trung bnh ( 0,3-0,5%): chitit my

- do dai, bn, cng kh cao- hiu qu ti v ram tt

Thp hm lng C tng i cao ( 0,5-0,65%)- cng cao, h max chi tit n hi, l so

Thp hm lng C cao ( 0,7%)

- cng, tnh chng mi mn cao dng ct,khun dp2. Man gan:

- do : t qung v kh xy bng fero MnFeO + Mn MnO + Fe

- Ho tan vo F nng cao bn v cng c tnh thp tng


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- Thp cht lng cao : 0,025% S 0,035

%P

- Thp cht lng c bit cao: 0,015% S

0,025 %P+thp C c 3 cht lng u

+thp HK c 3 cht lng sau

2.Theo ph ng php kh xy:

thp si ( kh xy khng trit Fero Mn)

FeO + C Fe+ CO

B mt si to thnh bt kh trong thi

c ( khi cn s ht)khng c lm co

t Si nn do dp su

thp lng : kh xy trit ( Fero Mn +Fero

Si + Al)

khng cn FeO b mt thp phng

lng lm co ln

cng hn thp trn ( Si) v thch hp vi

hn thp na lng: (kh xy bng Fero Mn + Al)

- Thp C thp : c 3 loi trn

- Thp C trung bnh : lng v n lng

- Thp Ccao v HK : lng


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3.Theo cng dng:

- thp cn nng thng dng

- thp kt cu

- thp dng c- thp c cng dng ring

IV. K hiu v cng dng ca cc nhm thp C:

Theo qui tc:

thp thng dng, khng cn nhit luyn khi s

dng k hiu theo c tnh ( trng thi cung cp)

thp phi qua nhiu khu gia cng ch to k

hiu theo thnh phn ho hc

1. Thp cn nng thng dng ( thp C cht l-

ng thng)

Chim 80% lng thp s dng ( trng thi cn

nng)

Theo TCVN 1765-75 : K hiu CT - ko ti thiu

( KG/mm2)

Chia ra lm 3 nhm:Nhm A:

- qui nh v c tnh, khng qui nh v

thnh phn ho hc

CT38 ko= 38 KG/mm2


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- lm cc chi tit khng phi qua gia cng nhit :

bo ton t chc ban u v c tnh theo tiu

chun

Nhm B:- qui nh v thnh phn ho hc, khng qui

nh v c tnh

BCT38: 0,14-0,22%C

- lm cc chi tit phi qua gia cng nng

NhmC:

- qui nh c v c tnh v thnh phn ho hc

CCT38: ko= 38 KG/mm2, 0,14-0,22%C

- lm cc chi tit va phi qua gia cng nng,

va phi bit c tnh ban u

2. Nhm thp kt cu:( thp C cht lng tt)

- qui nh c v c tnh v thnh phn ho hc

- theo TCVN 1766-75, k hiu : C- con s ch

hm lng C trung bnh phn vn

C40 ; C40s; C40n

3.Nhm thp dng c: ( cht lng tt)

- Thnh phn C0,7%

- lm dng c c nng sut thp v TB


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theo TCVN 1822-76: k hiu CD- con s ch hm

lng C trung bnh phn vn

CD70

4.Nhm thp c cng dng ring:- thp l so

- thp dp ngui...

V. u nhc im ca thp C:

u im:

- r tin, d nu luyn- c tnh nht nh, tnh cng ngh tt

nhc im:

- bn trng thi cung cp thp, h=70KG/mm2

( thp), do dai km

- thm ti thp ( 15 mm)

- >3000C bn v cng thp

- chng mi mn km ( so vi thp HK cng %C)

5.1.2. Thp hp kim:

I. Thnh phn v c im ca thp hp

kim:

1. Nguyn t hp kim:

Ngoi Fe,C, tp cht + cc nguyn t vi lng

nht nhthay i


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t chc, tnh cht theo yu cu

Cc nguyn t c coi l hp kim khi: ( nh hn

c coi l tp cht)

Mn0,8-1,0 % Ni0,5-0,8 %Si0,5-0,8 % W0,1-0,5 %

Cr 0,5-0,8 % Mo0,05-0,2 %

Ti,V,Nb,Zr,Cu 0,1 B 0,002

2.Cc c tnh ca thp HK:

C tnh:

- thm ti cao hn thp C cao hn

(sau ti +ram)

Khi s dng cn lu

- bn tng do dai gim- % NTHK cng ln do dai v tnh cng ngh

km

Tnh chu nhit cao: mt s thp khi b

OXHxyt xt cht ( Cr,Si)

Cc tnh cht l ho c bit: khng g,

gin n nhit, t tnh c it

Nhc im: kh nu luyn, t, tnh cng

ngh km


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II. Tc dng ca nguyn t hp kim:

1.Tc dng i vi dung dch rn v gin pha:Thp C+ NTHK Thp HK nh hng ca

NTHK n gin pha Fe-C

Dung dch rn: Phn ln cc NTHK l KL c mng

ging ,

to dung dch rn:

- Mn, Ni l cc nguyn t c kiu mng lptm in

hnh to vi

dung dch rn ho tan v hn m rng vng

(ca gin Fe-C) h thp A1, A3, Amc th tnti T0 thng thp

- Cr l nguyn t c kiu mng lptk to vi dung

dch rn h tan v hn thu hep vng , m rng

nng cao A1, A3, Am

c tn ti T0 cao thp

- y l cc thp khng c chuyn bin pha

- ng SE dch sang tri thp cng tch < 0,8% C ;

thp HK< 2,14 % C c L


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VD: thp 7%W: S 0,2% C

E 0,5%C

Tc dng n c tnh ca F ( trong thp HK

chim 90%):

- % NTHK tng x lch mng tng , cng tng,

do dai

gim

- Nguyn t HKnh hng khc nhau ( Mn,Si, Cr,

Ni):

+ Mn,Sitng mnh bn v cng ca F, gim

mnh do daithp gin 1-2% Si; 2-3%Mn

+ Cr, Ni ho bn F nhng li khng lm gim do dai

>3%Cr xu daiNi ci thin do dai

- Thng hp kim ho ng thi Cr, Ni

2.Tc dng to thnh Ccbt:

a. Ni, Si, Al, Co,Cu khng to cc bt

b. Mn, Cr, Mo, W, V, Zr, Ti, Nb to cc bt :

- Mn, Cr nguyn t to cc bt yu

- Mo, W nguyn t to cc bt trung bnh

- V nguyn t to cc bt mnh


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- Zr, Ti, Nb nguyn t to cc bt rt mnh

c. Cc dng cc bt :

Xmentt hp kim:

Cc bt vi kiu mng phc tp: Mn3C, Cr7C3,Cr23C6

Cc bt kiu Me6C

Cc bt vi kiu mng n gin ( VC, TiC,

WC..)

Tc dng:

-Cc bt HK c cng cao hn Xe

- n nh v ho tan vo kh hn ( Tch cao)

- Tc dng:

Lm tng bn, cng v chng mi mnmnh hn Xe

Kh ho tan vo T0 ti tng, gi nh ht

khi nung

Khi ram tit ra khi M v kt t T0 cao

hn Xe gi c cng cao T0 cao

III. nh hng ca nguyn t hp kim n

qu trnh nht luyn: nh hng ln

1.Chuyn bin khi nung ti:


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ho tan cc bt vo kh T0 ti tng, gi

di hn ( so vi Xe)

VD : Thp 1%C T0 ti = 7800C ( Fe3C)

Thp 1%C, 1,5 %Cr T0 ti = 830- 850 0C( (Fe,Cr)3C

kh ho tan nm bin gii gi cho ht nh

khi nung

mnh nht Ti,Zr, Nb; yu hn: W,V

ring Mn ht pht trin mnh

2. S phn ho ng nhit ca v thm

ti:

S phn ho ng nhit ca qu ngui:

- tt c cc NTHK ( tr Co) khi ha tan vo ng ch "C" dch sang phi gim tc

ti ti hn

- vi cng hm lng NTHK hp kim ho phc tp hiu

qu tt hn hp kim ho n gin

thm ti:

- tt c cc NTHK ( tr Co) u lm tng

thm ti


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C th c cc trng hp :

- Vth< Vli ti thu

- Vkhng kh > Vth ngui trong khng kh nhnc M (t ti)

Hiu qu do ti+ ram:

- nng cao sc chu ti cho chi tit

- tit din ln s dng thp HK c hiu qu

- ngui chm t bin dng, nt (chi tit phc tp)

3.Chuyn bin Mctenxit

Khi ho tan vo , cc NTHK ( tr Co, Al, Si)

h thp Ms sau ti, lng d tng cng c

th gim 1-10 HRC phi GCL hoc ram nhiuln cng tng

4.Chuyn bin khi ram:

nh hng n 3 qu trnh:

- phn ho M

- chuyn bin d M

- kt t Ccbt

u xy ra T0 cao hn ( cc NTHK cn tr s

khuych tn C )


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VD: Tit ra Xe ( t M) 2000C

Xmmtit hp kim 250-3000C

Cc bt Cr 400-450

TiC khng ho tan khi nung, khng kt t khi

ram

Nhn xt:

+ Nng cao tnh chu nhit

+ Cc bt to thnh nh mn, phn tn

cng, tnh chng mi mn tng ho cng

phn tn

IV. Khuyt tt ca thp HK:

1.Thin tch

2.Gin ram:Hin tng ak gim t ngt khi ram 2

khong nhit

Loi I: ( ram 280-3500C)

cha r nguyn nhn - khng khc phc c

(khng thun nghch) Loi II: ( ram 500-6000C v lm ngui chm)

- thng gp thp Cr, Mn, Cr-Ni, Cr-Mn


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- khc phc c (thun nghch) lm ngui

nhanh ( nc hoc du) hoc hp kim ho thm

W hoc Mo

V. Phn loi v k hiu:

1. Phn loi:

a. Theo t chc t vi:

theo t chc cn bng:

thp tct ( P+ F); thp ct (P); thp sct (P+

ccbt);

thp L; thp ; thp F

b. Theo nguyn t hp kim: da vo tn ca

NTHK chnh

thp Cr

tnh cht ca HK do NTHK chnh quyt nh


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c. Theo tng lng cc NTHK:

- thp HK thp : < 2,5%

- thp HK trung bnh: 2,5-10%

- thp HK cao: >10% bit gi tr ca thp

d. Theo cng dng: ( 4 nhm ging thp C)

5. K hiu:

Vit nam: theo h thng ch v s

Ch : theo k hiu cc nguyn t ho hc

S : s u hm lng C (trung bnh phn

vn)

s sau mi nguyn t hm lng nguyn t

(trung bnh phn trm)

nguyn t c hm lng < 1% khng ghi

con s

18CrMnTi , 60Si2

Cc nc khc nhau k hiu khc nhau

160Cr12Mo X12M D2 SKD11STD115.1.3. Thp kt cu:

I. Khi nim:

1. Yu cu:


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thm ti cao, ho b ferit, to cacbit phn tn v

gi ht nh

Theo tc dng v s lng chia thnh 2 nhm:

- nguyn t HK chnh: chim t l chnh trong cc NTHK, thng l

Cr,Mn,Si ( c th Ni)

r, 1-2% ( c bit 6-7%)

vi tng nh nhau th dng nhiu nguyn t hn l

mt nguyt t cc cp thng dng: Cr-Mn; Cr-Ni;

Cr-Mn-Si; Cr-Ni-Mn

- nguyn t hp kim ph:

lng rt t (


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- ng dng cho cc chi tit lm vic trong iu

kin chu mi mn v va p ( bnh rng, cam,

cht...)

- thp phi thm ti + ram1.Thnh phn ho hc:

C: 0,1-0,25 % ( 0,25-0,3 %)

Hp kim: nguyn t c tc dng thc y qu trnh

thm, nng cao bn khng dng thp c Si

(gy thot C), t Mn (ht ln)

Thng dng cc nhm: Cr; Cr- Ni; Cr-Mn-Ti

u im ca thp thm hp kim:

- thm ti cao hn ( thp C)

- t bin dng khi ti lm chi tit ln v phc tp- chng mi mn cao hn ( to cc bt hp kim )

- c kh nng nng cao T0 thm rt ngn thm

2.Cc mc thp v c im:

a. Thp C: C10;C15; C20; C25 v i khi CT38

- sau ti +ram: cng 60-62HRC

- thp ( 500 MPa)

- Tthm9000C ht ln ( sau thm thng phi thng

ho)


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- ti nc chi tit nh, n gin

b. Thp Cr: 15Cr; 20Cr; 15CrV

- cng ging thp C, nhng chng mi mn cao

hn- cao hn ( 700 - 800MPa)

- T0= 900-920 tc thm tng ( do Cr c i lc

vi C)

- nhc im: qu bo ho C

- p dng cho chi tit = 20-40mm

c.Thp Cr-Ni:

d.Thp Cr-Mn-Ti (Mo):

- khc phc cc nhc im ca thp Cr-Ni

- mc thp 18CrMnTi; 25CrMnTi; 30CrMnTi,

25CrMnMo

( 0,1-0,09% Ti)

- T0 thm=950

- u im: r, gia cng d, NL n gin

III. Thp ho tt:

1. c im:

- %C trung bnh: 0,3-0,5 ( thng dng 0,35-0,45)


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- Ch to cc chi tit chu ti trng tnh, b/m b

mi mn mun c c tnh tng hp cao

nhit luyn ho tt

- Hp kim:- cc nhm : Cr, Cr- Mn, Cr- Mn- Si, Cr- Ni, Cr-Ni- Mo

2. Nhit luyn:

- nng cao c tnh tng hp ( chy, ak) Xram

Ti + ram cao

- Xram cn c u im:

cng 220-260 HB gia cng ct tinh tng

bng b/m

t chc F+Xe nh mn ti cm ng tip theo

M ht nhmn c tnh b mt tt

3.Cc mc thp v c im:

a. Thp C: C35, C40, C45, C50- t c cc yu cu ra mc thp

( thm ti 10mm, = 750 MPa, chi tit

n gin, ti nc, r, tnh CN tt)


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- lm trc truyn, khuu trong ng c nh, bnh

rng tc nh

b. Thp Cr: 35Cr, 40Cr, 45Cr, 50Cr , 40CrB ( 1%

Cr)- t cc yu mc cao hn thp C

( thm ti 20mm, = 950 MPa, ti du)

- sau ram ngui nhanh

-40Cr thng lm trc v bnh rng my ct KL

c. Thp Cr-Mn ( Cr-Mn-Si) :

d. Thp Cr-Ni

- do dai cao (Ni/Cr=3 cho dai cao nht)

III. Thp n hi: %C 0,55-0,65

1.iu kin lm vic v yu cu vi l xo, nhp:

Ch ti trng tnh v va p m khng c BD do

gii hn n hi cao ( kh nng chng BD do ln)

cng cao, do dai thp khng c BD d (35-

45HRC)

gii hn mi cao2. Thnh phn ho hc:

mc ch a cc NTHK:


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- nng cao gii hn n hi, cng ( Mn, Si nhiu qu

gy gin)

- nng cao thm ti ng u trn ton tit

din (Cr) nhit luyn: t chc Tram

c bit ch b/m ( cht lng v thot C )

3.Cc mc thp:

a. Thp thng v thp Mn: C65, C70, 65Mn, 70Mn

- c im: h = 800N/mm2

- thm ti thp

- lm bn thnh phm dng dy, bng mng

ti+ramTB to sn phm kh .s

b. Thp Si: 55Si2, 60Si2- h cao, r

- thm ti 20mm

- d thot C khi nung ti

( 5,5mm ti +ramTB trc ch to,

5,5mm ti +ramTB sau ch to)

c. Thp n hi chu nhit: 50CrV, 50CrMnV

-thm ti cao ( hn loi trn)


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- chng ram tt ( 5200C), gi c tnh n hi

3000C

- dng lm l so supp x

V. Thp kt cu c cng dng ring:

1. Thp dp ngui: C5, C8s,

- %C 0,05-0,2; Si 0,07, ht nh v u (cp

6-8)- t chc F ( rt t P)

2. Thp d ct: 12S, 20S, 30S

- %C 0,1-0,4, P 0,08-0,15, S 0,15-0,35, Mn0,8-1

5.2.Thp dng c v c bit:

5.2.1. Thp dng c:

Khi nim: dng vi khi lng t ( 0,1% lng thp

dng)quyt nh s lng v cht lng sn phm.

Ch tiu cht lng quan trng nht cng cao,chng mi mn %C cao, ch NL phc tp

I. Thp v HK lm dao ct:

1.iu kin lm vic ca dao:


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Li ct chu p lc ln khi ph hu KL (to phoi)

Dao b mi st b mn mnh

Cng tch phoi v mi st nhit tp trung v

nung nng phn li dao xu kh nng ct gt

2.Yu cu c tnh ca dao:

cng cao: cao hn cng ca phi

thp,gang thng, thp HK thp (200-220HB)

cng dao

60HRC

thp,gangc bit, thp HK cao(250-300HB)

cng dao

65HRC

Tnh chng mi mn cao:nng cao tui th dao( chnh xc ca chi tit gia cng), ph thuc

vo:

+ cng cao chng mi mn cng tt

cng > 60HRC th c tng thm 1HRC, tui th

dao tng30%

+ hai thp c cng cng thp c nhiu cc bt

phn tn chng mi mn cao hn


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Tnh cng nng: kh gi c cng cao khi

lm vic T0 cao

VD: dao ct vi tc ln yu cu tnh cng nng

cao Ngoi ra cn yu cu:

(un khi tin; xon khi khoan), dai(

trnh m,gy)

3.Thp lm dao ct nng sut thp: ( vct = 5-

10m/pht)

a. Thp cc bon: CD70, CD80 (W1, W2 - M; Y7,

Y8- Nga

c im:

Sau ti + ram thp: 60HRC

CD70; CD80 ti hon ton: T0= 800-820; 780-800

CD90; CD130 ti khng hon ton: T0= 760-780

Nhc im:

- dao nh

- hnh dng n gin- tc ct thp (5m/ph)

b. Thp hp kim thp:

Thnh phn: C 1% ( cao)


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Cr 1%; Si; W; Mn

Chia ra 2 nhm:

c thm ti cao ( hn thp C): 100Cr2;

90CrSi( X, 9XC - Nga)

+ Cr= 1-2 % tng thm ti ti du dao c

hnh dng phc tp v ci thin mt cht tnh cng

nng

+Cr,Si chng ram n 250 0C gi c tnh cng

nngtng tc ct n 10-14 m/ph

+ T0 ti = 830-860; ram 150-2000C 62-64 HRC

c tnh chng mi mn cao: 130Cr0,5;

140CrW5Cr 1%; C 1,5%; W 4 - 5%;

c im:

+ t chc in hnh c lng cc bt ln: 20-30%

cng cao, chng mi mn cao

+NL:

Thp 130Cr0,5 : ti T0= 780-810 , ram 100-1200C

65-66HRC ng dng: dao co r KL, dao co ru

4. thp lm dao ct nng sut cao: ( thp gi )


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a. Khi nim: so vi thp C dng c v thp HK

thp:

Ct gt vi nng sut cao ( 2-4 ln); Vct=

25-35 m/ph Tui th cao gp 8-10 ln

Tnh cng nng 560-6000C

Ti thu tit din bt k

b.Mt s mc thp:

Nhm nng sut thng ( 25m/ph)

80W18Cr4V (P18)

90W9V2 (P9)

Nhm nng sut cao ( 35m/ph)

90W18V2 (P182)

90W18Co5V2 (P18K52)

c.Tc dng ca cc NTHK:

C: 0,7-1,5% kt hp vi cc nguyn t to cc

bt mnh l W, Vchng mi mn cao

Cr: 4% trong mi thp gi tng thm ti

( Cr+W+Mo) >15% t ti

W: 6-18% NTHK quan trng nht to tnh

cng nng:


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Cc bt dng Me6C ch yu khi nung tan vo

ti : M cha nhiu W ram Me6C tit ra

khi M 560-5700C gi c cng n

6000CMo: dng thay th W ( ging kiu mng v dngt)

theo t l 1:1;

V: c t nht 1-2% to VC (mnh) nh mn,

phn tn t ho tan khi nunggi ht nh

v tng tnh chng mi mn

nu %V ln hn tnh mi km v phi tng

thm %C nu khng M mm

e. Nhit luyn:

Ti: 1280-12900

C+Thp hn cha bo ho Wcng nng

km

+ Cao hn chy bin gii ht

nguyn l chn nhit : ho tan nhiu W

nht

kh nhiu Fe3W3C vVC cha tan

T chc t vi sau ti: M+ d (30%)+ ccbt

(15-20%) 62 HRC


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Ram: Kh s. d; d; tng cng 2-3 HRC

To= 550-5700C , 3 ln , 1h/ln

Chuyn bin khi ram:

+ Khi T0 550 Fe3W3C tit ra khi dungdch rn d ngho NTHKM nng cao,

ng sut d nn ln d gim lm ngui khi

ram chuyn bin thnh M cng tng

+ Sau 3 ln ram cn khong 2% d

g.Cng dng:

lm dao ct c hnh dng phc tp + chng

mi mn cao

loi nng sut thng : tnh cng nng 6000C

25m/phloi nng sut cao: 630-6400C 35m/ph

thp gi t li thp gi, thn thp C45

II. Thp lm khun dp ngui:

1. Khi nim : dng bin dng ngui thp

(t,ct,dp..)

2.iu kin lm vic ca khun dp :

chu p lc ln

chu ng sut un


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lc va p v ma st

3.Yu cu i vi thp :

cng cao: 56-62 ( tu theo loi khun v

chiu dy thp dp)(>62 m)

Chng mi mn cao ( tui th khun)

bn, daichu ti trng ln v va p

thm ti v n nh kch thc

4.Cc thp lm khun dp:

a. Thnh phn:

C 1% (cao)

khi chu va p mnh % C gim ( 0,4-0,5%)

khi chu mi mn mnh % C tng ( 1,5-2%)

NTHK:

+tu thuc vo kch thc, hnh dng, tnh

chng mi mn, nng cao tnh thm ti, cc

bt Cr, Mn, Si, W ( 1% mi loi);

c th n 12%Cr ( chng mi mn cao)

Nhit luyn: Ti+ ram thp

b.Thp lm khun dp nh: hnh dng n

gin, chu ti trng nh


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CD100; CD120 ( Y10; Y12) ti nc

mt ngoi ti cng, li do dai ( thm ti

nh)chu va p

c.Thp lm khun trung bnh: 75-100mm (hoc bhnh dng

phc tp, chu ti ln)thp hp kim thp

100Cr; 100CrWMn; 100CrWSiMn (X, XB; XBC)

1%C ; Cr, Mn, Si, W : 1% mi nguyn t ( tng

thm ti)

- c th ti phn cp ( khun nh) hoc ti 2 mi

trng ( khun TB) trnh bin dng

- thin tch cc bt lngy nt kim tra cp cc

bt (ln rn)d.Thp lm khun ln v chng mi mn cao: 200-

300mm

%C cao ( 1,3-2,0%) ; Cr cao (12%)

200Cr12 (X12); 150Cr12Mo ( X12M); 130Cr12V(

X121)

%C cc bt d nhiu (Fe,Cr)7C3chng mi

mn cao

thm ti ln ti du


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c th c nhiu ch NL:(m bo c tnh

v n

nh

kchthc)


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III. Thp lm khun dp nng:

1. Khi nim: dng bin dng nng thp nh rn,chn, p...

2.iu kin lm vic:

Tip xc vi phi nng( 10000C) khun nng(

500-7000C) theo chu k

cng khng cn cao do phi mm

Khun ln, ti trng ln ( vi trm ngn tn)

3.Yu cu vt liu:

bn, dai, cng va phi: 35-45 HRC ( dai

m bo)

Tnh chng mi mn cao Tui th cao

Bn nhit, chng mi nhit T0thay i theo

chu k

4.Thp lm khun dp nng:

a. Thnh phn: % C trung bnh: 0,3-0,5

NTHK: m bo thm ti : Cr ; Ni

chu nhit v chng ram: W


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Nhit luyn: ti +ram T hoc Xram

b. Khun rn:

c im:

kch thc ln, chu ti trng ln, va pT0 nung ( 500-550), thi gian ngn

%C 0,5%; HKH : Cr;Ni

Mc thp: 50CrNiMo; 50CrNiW ( 5XMH; 5XNB)

c.Khun chn, p:

c im;

kch thc nh, p sut cao, va p nh

T0 cao

Thnh phn : tng NTHK10% (cao):

W 5-8%; Mo1%; Cr 2-5%; V 0,5%Mc thp: 30Cr2W8; 30Cr2W8V ( 3X2B8;

3X2B8V)

5.2.2. Thp c bit:

Khi nim:

L thp c tnh cht ho l c bit

Thnh phn C rt cao (>1,2%) hoc rt thp

(13- 20%) vi t chc M, , F


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Khng th thiu c trong CN ho hc ; nhit

cao; in t....

I. Thp khng g:

1. Khi nim : Thp C v HK thng b g trong khng kh

v ho cht

Thp khng g khng trong g trong khng

kh, c tnh chng n

mn cao trong mi trng n mn chia ra 3

cp:

khng g hon ton; khng g; b g

2.S n mn kim loi:

S n mn ph bin l n mn in ho: xy ra

trong dung dch in ly v pht sinh dng in.

Nguyn l n mn: +Khi tip xc vi dung dch

in ly KL to thnh ion chuyn vo dung dch,

li in t tha cho KLto thnh lp in tch

kpin th in cc (tc)+ Nhng 2 KL c tc khc nhau vo cng 1

dung dch v ni vi nhau bng dy dnpin

n mn: KL no c tc m hnb n mn


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3.Nguyn l ca thp khng g:

Trong khng kh trn b mt thp mng nc

ha tan CO2, SO2, H2S dung dch in ly

Thp ( cc bon) thng c 2 pha: F+ Xeto ra pin

n mn( F c tc m hn. Lng Xe cng nhiu

cng nhiu cp pin n mn mnh 2 nguyn l:

+ Lm cho thp c t chc 1 pha F hoc loi tr

pin t vi;

thng l ( ho tan nhiu C) , F t C kh

+ Nng cao Fcc btdng n mn nh

Thp khng g c c im:

Thnh phn C thp t cc bt

Thnh phn Cr v HK cao ( Cr>12,5% v Ni,Mn...)

1 pha

1.Thp khng g 2 pha:

Thnh phn: %C 0,1-0,4; %Cr13

T chc: F ( ho tan Cr cao) + Cc bt Cr

+ khi F ho tan n 12,5% Cr F t gi tr tng

vt 0,2v ( Xe) thp 13% Cr chng n mn


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Mc thp: 12Cr13; 20Cr13; 30Cr13; 40Cr13

( 12X13; 20X13; 30X13; 40X13)

Do tc dng ca Cr cao: im cng tch 0,3% C

Vng (trong khng kh) > Vth thp M

12Cr13; 20Cr13 : thp tct do dai, chu BD, hn

c lm chi tit chu n mn v lm vic T0cao

(tua bin hi)

30Cr13; 40Cr13: thp ct v sct bn, do dai km,

khng BD v hn c chi tit cn n hi: dao

m, l so chu n mn)

2.Thp khng g 1 pha:( )

%Cr= 18%; Ni =9-10% c t chc 1 pha

Cc mc thp: 12Cr18Ni9Ti; 12Cr18Ni9; 17Cr18Ni9

( 12X18H9T; 12X19H9; 17X18H9)

c im:

+ tnh chng n mn cao ( hn 2 pha)

VD: trong mi trng a xt : HNO3 mi nng , mi

nhit

H2SO4 mi nng ,nhit

phng


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+ Ti nhn c t chc 1 pha ( loi tr cc

bt)

+ Do dai, chu BD, hn c trng thi ngui

+ Nhc im : b n mn tinh gii khi lm viclu T0= 400-800

( hoc phn chi tit qua hn hay nung nng

lm vic trong mi trng n mn b n mn)

nguyn nhn:

T0= 400-800 cc bt Cr tit ra bin gii ht

%Cr 8000 C Cr trong ht khuych tn ra kp

bin gii c %Cr > 12,5% lun tn ti mngth ng

khc phc:- gim %C trong thp (0,05-0,08)

trnh to cc bt

- HKH thm nguyn t to cc bt mnh( Ti)

khng to cc bt Cr

II. Thp chng mi mn:

1. c im:


40/47

Dng lm gu xc, bi nghin, xch xe tnglm

vic trong iu kin mi mn v va p

( khng th dng thp C gin v )

T chc c bit c kh nng t bin cnghay t bi trn

2. Thp Man gan ( Hatfind)

Thnh phn: %C=1,3 %Mn=13%

Mc thp: 130Mn13

S dng trng thi c; t chc ; cng thp (

200HB); do cao

Khi chu ma st di p lc ln v va p: b

mt b BD do :

+ Bin cng: mng b x lch nh ht vsiu ht

+ To thnh Mctenxit: di tc dng ca .s cao,

mt phn chuyn bin thnh M ( %C= 1,3%

cao) cng b mt tng (600HB)lp ny

mn lp khc li to thnh

Tnh chng mi mn cao nht khi t chc 1

pha ti ( khi c ngui chm cc bt Mn3C )

Khng gia cng ct gt c, ch sa bng mi


41/47

5.3.Gang:

Khi nim:

- l vt liu ph bin trong CTM

- c tnh km thp nhng tnh c tt- c 4 loi gang ( gang trng gin Fe-C, gang

khchnh dang Grapht)

5.3.1.Gang xm:

- Ph bin nht trong cc loi gang

- T chc t vi: Gr tm + nn ( F+P; P; P+Xe) :

Phn ln C dng t do ( Gr tm)

Phn nh cn li lin kt vi Fe

Xe (hoc khng c) F (GX Ferit)

t Xe F+ P (GX F-P)nhiu XeP (GX P)

I.iu kin to thnh Gr trong gang

xm:

a. Thnh phn ho hc:

Ngoi Fe-C:

- Si l nguyn t thc y s to Gr

- Mn l nguyn t cn tr s to Gr


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Kh nng to Gr c nh gi bng tng

(%C+%Si)

(C+Si) 6% Gr ho mnh ( nn F)

(C+Si) 5-6% Gr ho TB ( nn F+P)

(C+Si) 4-5% Gr ho yu ( nn P)

(C+Si) < 4-4,2% gang trng

b.Tc ngui:

Lm ngui chm to iu kin cho s khuych

tn v tp trung C Gr

c.Gr dng tm l d nht do cu trc ca Gr l cu

trc lp

III. Cc loi gang xm:

1.Thnh phn ho hc:- C%: 2,8-3,5 , nhiu Gr ho cng mnh, T0 chy

thp nhng

c tnh km

- Si: 1,5-3,0% ( gim dn t gang xm FP)

- Mn: 0,5-1,0 ho trng gang, tng bn, cng

- P: 0,1-0,2, tng tnh chy long, chng mi mn,

khng nh hng n Gr

- S: 0,08-0,12%, cn tr Gr ha, xu tnh chy long


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2.C tnh v cc yu t nh h ng:

a.C tnh:

- thp hn so vi thp c cng t chc nn: ( do Gr)

b gang= 1/3-1/5 bthp- c tc dng t bi trn tng tnh chng mi mn

- cng thp: 150-250 HB d ct gt, gin

b.Cc yu t nh hng:

- Gr: s lng, hnh dng, ln v s phn b

- Nn KL: c c tnh cng cao c tnh gang cng

cao tt nht l nn P

c.Cc bin php nng cao c tnh:

- gim lng C gim Gr ( tng T0 chy ca gang)

- bin tnh Gr nh mn v u: hn hp : 65%feroSi + 35%Al

- hp kim ha : tng c tnh nn

- nhit luyn: nn c c tnh theo yu cu ( M, B,

T,X)

3. Cc mc gang xm v cng dng: K hiu : GX- b ko min( KG/mm2)

GX10 ( gang xm F) v np my


44/47

GX15 ( gang xm F-P) v hp gim tc,

mt bch

GX21( gang xm P) cc chi tit chu ti,

thn my quan trng,bnh

GX32 Gr nh mn, chu ti cao v bm

thu lc, bnh rng

GX bin trng: bi nghin , trc nghin

5.3. 2.Gang cu:

- C bn cao nht trong cc loi gang Gr dng

cu

- T chc t vi: Gr dng cu+ nn KL

I.Thnh phn v cch ch to:

a.thnh phn:

- dng GX ch to GC thnh phn ging GX

- (%C+Si)5% m bo Gr ho

- khng c ( hoc c khng ng k cc nguyn t

cn tr cu ho: Ti, Al, Sn, Pb, Zn...- phi c mt lng nh cht bin tnh cu ho

Gr:

0,04-0,08% Mg hoc Ce

- cc nguyn t nng cao c tnh: Ni( 2%), Mn( 1%)


45/47

b. ch to:

- nu chy GX ( T0= 1450) v kh S n 0,01%

- bin tnh: dng Mg nguyn cht hoc hp kim trung

gian ca Mgkhng ch ng lng Mg cn li

Mg< 0,04% GX; Mg>0,08% gang

trng

II.C tnh v cc bin php nng cao c tnh:

1. C tnh : Gr dng cu dng gn v t chia ct

nn nht t lm gim c tnh nn KL

- bgang cu = 79-90% thp cng nn

- bgang cu cao ( 400-1000MPa tng ng thp

CT38,C45)- do cao( =5-15%), dai cao ak= 300-600KJ/m2

- cng va phi ( 200HB)

2. bin php nng cao c tnh:

-bin tnh ht trn, nh, phn b u

- ho bn nn

- NL : ti dng nhit ra B b= 700-1000MPa

3. cc mc gang thng dng:

K hiu: GC- b ko min ( KG/mm2)- %


46/47

GC45-05 ( GC ferit ) dng thay th thp

GC50- 02; GC60-02 ( GC Peclit) bn

trng thi c trc khuu, trc cn

GC70-03, GC100-04 : ti ng nhit ra tchc nn B lm cc chi tit quan trng

Cng dng ni bt: lm trc khuu( hnh dng

phc tp, chu ti ln, va p)

5.3.3.Gang do:

-Gr dng cm bng ( trung gian gia tm v cu) +

nn KL

- Khc vi 2 gang trn : Gr khng to thnh t kt

tinh m to

thnh t gang trng ( trng thi rn)

1. Thnh phn ho hc:

- c bn ging gang trng yu cu kht khe:

trng hon ton

- %C ly thp: 2,2-2,8% t Gr tnh do cao

- lng Si va bin trng hon ton, ng thithc y Gr ha

(%C+Si=3,5)

- vt c mng ngui nhanh( 10-20mm)


47/47

2. Ch to : Phc tp- chu trnh di - tnh kinh t

km ( t)

Tng thi gian 75 h

3. C tnh : trung gian gia GX-GC4. Mc gang v cng dng: GZ- b ko min

( KG/mm2)- %

GZ 30-06 ( GZ ferit)

GZ45-06 (GZ Peclit)

ng dng : ch dng trong trng hp ( 3 yu

cu ng thi)

- hnh dng phc tp, thnh mng, chu va p

- lm trc khuu, guc phanh.

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