Danl Xubap Xả Xe Honda

ieu kien lam viec cua suppap xa trong ong c ot trong cua xe may :

PAGE 13O AN MON HOC CONG NGHE NHIET LUYEN

GVHD : TS.NGUYEN VAN DAN

CHNG I : MOT SO YEU CAU KY VA CHON VAT LIEU CHE TAO SUPAP XA TRONG XE DREAM, WAVE.

I. Muc ch va yeu cau cua mon hoc : Giup sinh vien hieu biet them ve phng phap nghien cu khoa hoc.

Hieu c s bo ve ket cau, ieu kien lam viec, cac yeu cau ky thuat, vat lieu che tao, cac bc gia cong che tao va quy trnh nhiet luyen supap xa.

Nam c cac giai oan nhiet luyen suapap xa e at c c tnh theo yeu cau.

T o chon vat lieu, tnh toan thi gian nung, thi gian gi nhiet, thi gian lam nguoi e che tao supap xa at c cac yeu cau ve c tnh.

Yeu cau : nhiet luyen supap xa trong ong c ot trong cua xe Dream, Wave.

II. Ket cau cua suppap xa :

Gom ba phan chnh : nam suppap ( con goi la tan hoac au ), than suppap va uoi suppap ( hnh 1 ).

Hnh 1. cau tao supap xa

III. ieu kien lam viec cua supap xa trong ong c ot trong cua xe may :

Supap xa co vai tro ong m e thc hien qua trnh thai kh thai trong ong c ot trong.

Do tiep xuc trc tiep vi kh chay nen suppap xa chu ap lc ln va nhiet o cao (600-800(C). Ngoai ra suppap con b an mon hoa hoc do cac kh sinh ra trong qua trnh chay (b oxy hoa).

Khi suppap ong m, nam suppap va ap vi e suppap nen nam de b cong venh va mon ro be mat nam. uoi suppap b mai mon c hoc do co mo ap vao.

Van toc lu ong cua moi chat qua suppap xa rat ln (400-600 m/s) gay mai mon c hoc be mat nam.

nhiet o cao suppap xa co the b giam o cng va giam tnh ben nhiet do to chc mactenxit b phan huy.

Vung chuyen tiep gia than va nam chu nhiet o cao nhat, va gia cac vung nhiet o khong eu nhau.

IV. Cac yeu cau ky thuat oi vi suppap xa :

Do ieu kien lam viec c neu tren, nen suppap xa can cac yeu cau ky thuat sau :

Toan bo suppap phai co c tnh tong hp cao ((b, (0.2, (, (, ak), co tnh on nh nong (tnh ben hoa hoc nhiet o cao) va tnh ben nong (gi c o ben c ly nhiet o cao) v the phai nhiet luyen hoa tot (toi + ram cao). Toi : 1100(C, dau va ram : 700(C, khong kh e at o cng 25-35 HRC.

Ngoai ra, uoi suppap chu mai mon va va ap ln nen can toi bo phan uoi suppap, toi : 1100(C, dau va ram : 550(C, khong kh e at o cng 40-45 HRC.

Chieu sau lp toi 1-1,5 mm.

Nh vay e at c o cng khac nhau bat buoc phai toi va ram hai lan. Lan au toi the tch e at u o cng cho toan bo suppap, sau o toi bo phan phan uoi suppap e at o cng cao hn.

V. Vat lieu che tao suppap xa :

Do suppap xa trong ong c ot trong lam viec trong ieu kien : chu tai trong cao, chu nhiet o cao, b an mon trong moi trng cua san pham kh chay va b mai mon khi va ap nen vat lieu che tao suppap xa la thep hp kim chu nhiet co cac thanh phan Crom, Silic, Mangan

Chon vat lieu lam suppap xa : thep hp kim chu nhiet 40Cr9Si2 (40X9C2 ) Mac thep d phong : 40Cr10Si2Mo (40X10C2M)

Thanh phan hoa hoc va c tnh cua thep 40Cr9Si2Mac thepThanh phan cac nguyen to (%)C tnh

CSiMnCrSPCuTi(b (MPa)(0.2 (MPa)( (%)

40Cr9Si20,35-0,452-3(0,78-100,0250,0300,30,287069025

Anh hng cua cac nguyen to en c, ly, hoa tnh cua thep 40Cr9Si2 lam suppap xa :

Thanh phan Cacbon trung bnh (0,35-0,45%) cua thep am bao o cng va tnh chong mai mon tot sau toi.

Nguyen to Crom, Silic co trong thep tang kha nang chong oxy hoa cho thep nhiet o cao. Cac nguyen to nay khi b oxy hoa tao ra cac oxyt Cr2O3, SiO2 co cau tao st chat, tao ra lp mang bao ve vng chac tren be mat thep nhiet o cao. Lng Silic dung trong gii han 1-2%. Rieng Crom la nguyen to chong oxy hoa quan trong, tnh chong oxy hoa cua thep khong phu thuoc vao to chc cua thep (ferit hoac austenit) ma ch phu thuoc vao ham lng Crom.

Lng Crom cao tang tnh chong mai mon cho thep va tang tnh on nh cua austenit qua nguoi trong thep rat ln.

Crom, Silic con co tac dung lam cham s phan hoa mactenxit, ket tu cacbit (Silic khong tao cacbit), do o o cng va o ben cua thep van cao ngay ca nhiet o cao 600-800(C.

VI. Cac bc che tao suppap xa :

Kiem tra mac thep.

Cat phoi thanh tng oan.

Nung nong phoi va ren trong khuon.

Gia cong c ( tien, bao, phay, xen, khoan, mai, cat, ta).

U kh ng suat (u trong lo buong ien tr)

Toi toan bo suppap (toi the tch trong lo muoi ien cc, lam nguoi trong dau).

Ram cao, lam nguoi ngoai khong kh.

Toi chan suppap (toi bo phan trong lo muoi ien cc, lam nguoi trong dau).

Ram, lam nguoi ngoai khong kh.

Th o cng va c ly tnh.

Gia cong tinh.

San pham, ong goi thanh pham.

CHNG II : CONG NGHE NHIET LUYEN

I. Nung nong va lam nguoi thep va hp kim :

1 Yeu cau :

Nung nong va lam nguoi thep va hp kim la mot nguyen cong quan trong trong cong nghe nhiet luyen. V vay, phai am bao mot so yeu cau :

Nung nong va lam nguoi ung ky thuat : bao gom nhiet o nung, thi gian nung, thi gian gi nhiet, toc o lam nguoi phu hp va phng phap nung phu hp vi tng loai thep, hnh dang, kch thc chi tiet.

Nung nong ong eu gia be mat va trong loi, cung nh cac phan khac nhau cua chi tiet.

Tranh c cac khuyet tat khi nung nh bien dang, cong venh, oxy hoa, thoat cacbon.

2 Cac phng phap nung nong :

oi vi cong nghe u va thng hoa, chi tiet co kch thc va khoi lng ln cho chi tiet vao thiet b nung nhiet o 500_600(C sau o nung chi tiet len en nhiet o quy nh.

oi vi cac chi tiet bang thep cacbon, hp kim thap co hnh dang n gian cho chi tiet vao thiet b nung sau khi a at nhiet o quy nh.

oi vi cac chi tiet co hnh dang phc tap, thep hp kim cao chon cach nung phan cap. Chi tiet c nung va gi nhiet qua mot hoac hai cap trung gian nhng thiet b nung khac trc khi cho vao thiet b nung cuoi cung co nhiet o quy nh.

3 Xac nh thi gian nung va gi nhiet :

3.1. Tnh toan thi gian nung :

Xac nh chi tiet can nung thuoc nhom vat lieu mong hay day dung ch tieu Bio (Bi) :

( _ he so truyen nhiet, (kcal/m.h)

S _ chieu day (ng knh) vat nung, (m)

( _ he so dan nhiet cua kim loai, (kcal/m.h)

neu Bi ( 0,25 : vat mong

neu 0,25 ( Bi ( 0,5 : vat mong va

neu Bi ( 0,5 : vat day

oi vi chi tiet co Bi ( 0,25 :

(nung = (h) (1)

G _ khoi lng me nung (kg)

Cp _ nhiet dung ang ap trong khoang nhiet o nung (kcal/kg.(C)

F _ tong dien tch be mat nung (m2)

( _ he so truyen nhiet tong hp (kcal/m2.h.(C)

( = (bc xa + (oi lu = (bc xa + 10(15

tlo = tcuoi + 50(C

( Neu nung nhieu chi tiet : (nung (thc te) = k.(nung

Thi gian nung theo kinh nghiem :

(nung = a.k.D (2)

a _ he so nung nong (phut/mm)

k _ he so sap xep

D _ kch thc ac trng cua chi tiet (mm)

He so sap xep K tra trong bang

3.2 Thi gian gi nhiet :

(gi = (nung (3)

4. Tac dung cua moi trng nung en chi tiet khi nung :

oi vi thep co hai qua trnh.

a. Qua trnh oxy hoa :

Trong moi trng khong kh hoac muoi nong chay eu cha O2, CO2, H2, hi nc nen khi nung chi tiet se b oxy hoa.

Cac phan ng oxy hoa :

Fe + 1/2O2 = FeO

3FeO + 1/2O2 = Fe3O4

2Fe3O4 + 1/2O2 = 3Fe2O3Fe + CO2 = FeO + CO

3FeO + CO2 = Fe3O4 + CO

2Fe3O4 + CO2 = 3Fe2O3 + CO

Fe + H2O = FeO + H23FeO + H2O = Fe3O4 + H2

2Fe3O4 + H2O = 3Fe2O3 + H2

Neu nhiet o nung Tnung ( 570(C : mang oxyt bao gom Fe2O3 va Fe3O4 mong va xt chat. Khi o s oxy hoa khong lam thay oi kch thc chi tiet, khong bong troc, ch lam giam chat lng be mat chi tiet.

Neu nhiet o nung Tnung > 570(C : mang oxyt bao gom Fe2O3, Fe3O4 va FeO (t le chieu day tng ng = 1 : 10 :100). Do o, mang oxyt chu yeu la FeO rat xop, co nhieu vet nt, de bong troc. V vay, lam thay oi kch thc chi tiet va chat lng be mat rat xau.

b. Qua trnh thoat Cacbon :

Do tng tac cua moi trng oi vi chi tiet khi nung lam thoat cacbon be mat do o cac c ly tnh be mat giam.

Cac phan ng thoat cacbon :

Fe3C + 1/2O2 = 3Fe + CO

Fe((C) + 1/2O2 = Fe + CO

Fe3C + H2O = 3Fe + CO + H2Fe((C) + H2O = Fe + CO + H2Fe3C + CO2 = 3Fe + 2CO

Fe((C) + CO2 = Fe + 2CO

Fe3C + 2H2 = 3Fe + CH4Fe((C) + 2H2 = Fe + CH4

5. Moi trng bao ve khi nung thep va hp kim :

Moi trng kh tr Argon (Ar) : gia thanh cao, ch dung trong phong th nghiem va mot so trng hp ac biet trong san xuat cong nghiep.

Moi trng kh Nit (N2) : la moi trng trung tnh ly tng khong phan ng vi kim loai. Viec che tao kh nit sach rat kho khan nen gia thanh cao. Lu y khi N2 cha mot lng nho oxy cung gay ra oxy hoa.

Moi trng kh Hydro (H2) : hydro ky thuat khong gay oxy hoa nhng lam thoat cacbon, ch dung cho cac kim loai mau, thep cacbon, thep bien the Silic. Kh nay dung e u sang sat v trng hp nay thoat cacbon khong xay ra. Dung hydro lam moi trng bao ve phai chu y loai tr hi nc, neu khong se tr thanh moi trng oxy hoa.

Moi trng chan khong : co o chan khong cao 10-3(10-6 mmHg, am bao cho tiet khong b oxy hoa va thoat cacbon cung nh chat lng be mat chi tiet rat tot.

Moi trng kh bao ve la hon hp kh CO2, CO, H2O, H2, CH4 va N2 vi cac t le thch hp trong o N2 chiem 50-70%. Hon hp kh se co tnh bao ve khong lam cho thep b oxy hoa, thoat hoac tham cacbon.6. Cac moi trng nung nong :

Moi trng khong kh.

Moi trng kim loai nong chay.

Moi trng muoi nong chay.

Thep hp kim cao, thep gio, thep khong g, thep chu nong : 100% BaCl2, oi khi cho them 5-7% axit boric. Nhiet o nong chay cua muoi BaCl2 la 960(C, nhiet o s dung t 1000-1300(C. qua trnh nau chay muoi co s hoa tan oxy nen phai kh oxy bang ferosilic (FeSi).

2BaO + Si ( 2BaO + SiO2

SiO2 lang xuong ay lo nen sau khi kh oxy phai lay het SiO2 ay lo ra roi mi a chi

tiet vao nung.

Thep hp kim thap, trung bnh, thep cacbon : s dung hon hp muoi BaCl2, NaCl va KCl. Nhiet o s dung 750-1000(C, va hon hp muoi c kh oxy bang than cui.

Cong nghe toi phan cap, toi ang nhiet, tham xyanua the long nhiet o thap : thng s dung hon hp muoi NaNO3, NaNO2, KNO3 va KNO2. nhiet o s dung 150-600(C. Do nhiet o lam viec thap nen khi nung nong trong cac hon hp muoi nay khong gay oxy hoa hoac thoat cacbon, v the lo muoi nhiet o thap khong phai kh oxy.

7. Mot so thiet b nung :

hnh 2. lo buong ien tr

hnh 3. lo gieng e toi

hnh 4. lo gieng tham cacbon

hnh 5. lo muoi ien cc

hnh 6. lo muoi ot ngoai

II. U thep :

1 nh ngha va cong dung : nh ngha : U la cong nghe nhiet luyen bao gom nung nong thep len tren nhiet o Ac3 (oi vi thep trc cung tch) hoac Ac1 (oi vi thep cung tch hoac sau cung tch), gi nhiet mot thi gian sau o lam nguoi cham cung lo.

Khi nung va gi nhiet, thep co chuyen bien peclit thanh ostenit, con khi lam nguoi cham cung lo se co chuyen bien ostenit thanh peclit. Tuy nhien, nguoi cung lo ch ung vi thep cacbon va thep hp kim thap, oi vi thep hp kim trung bnh va cao van toc lam nguoi con cham hn na. Cong dung cua u :

Chuan b to chc cho nguyen cong gia cong c hay x ly nhiet tiep theo (toi va ram).

Lam giam o cng thep e de gia cong cat got, tang o deo e de can, keo, dap trang thai nguoi.

Lam ong eu thanh phan hoa hoc tren toan bo tiet dien cua vat uc b thien tch.

Lam giam hoac mat ng suat ben trong cua thep sau cac nguyen cong dap, ren, uc, mai, quan cuon, cat got, han2 Chon cac thong so u :

2.1. Nhiet o nung :

Thep trc cung tch : Tnung = Ac3 + 50(C

Thep cung tch va sau cung tch : Tnung = Ac1 + 50(C

Thi gian nung va gi nhiet : tnh theo cong thc (1), (2), (3).2.2. Lam nguoi :

Thep cacbon, thep hp kim thap lam nguoi cung lo khoang 500(C co the lay chi tiet ra khoi lo.

Thep hp kim trung bnh va thep hp kim cao toc o nguoi phai cham hn toc o nguoi cua lo, khoang 300(C mi lay chi tiet ra khoi lo.

3 Cac phng phap u :

U hoan toan : la phng phap u c tien hanh nhiet o Ac3 + 50(C va c ap dung cho thep trc cung tch (to chc ferit va peclit) vi thanh phan cacbon %C(0,3%. Neu u thap hn nhiet o Ac3 th sau khi lam nguoi to chc hat ostenit se rat tho to.

U khong hoan toan : la phng phap u c tien hanh nhiet o Ac1 + 50(C va c ap dung cho thep cung tch va sau cung tch.

U ang nhiet : do mot so thep hp kim cao co tnh on nh ostenit cao nen khi lam nguoi cung lo thep van con cng, kho gia cong cat got, v vay phai u ang nhiet. Thep sau khi c nung ti nhiet o u, gi nhiet mot thi gian, sau o a vao thiet b khac co nhiet thap hn Ac1 khoang 50_100(C, gi nhiet o nay cho en khi ket thuc chuyen bien ostenit thanh peclit. Thi gian gi ang nhiet theo gian o ch C cua loai thep o.

U cau hoa : la phng phap u c tien hanh nhiet o Ac1 ( 50(C theo quy trnh dao ong nhiet : nung nong len Ac1 + 50(C roi lam nguoi xuong Ac1 - 50(C, lap lai nhieu lan cho ti khi thu c to chc peclit hat. Thng ap dung cho thep sau cung tch va thep dung cu vi o ben, o cng va c tnh cao.

U khuech tan : do mot so vat uc sau khi uc co to chc nhanh cay, nen phai u khuech tan e ong eu hoa thanh phan hoa hoc cua vat uc. U khuech tan c tien hanh nhiet o cao 1100_1500(C, gi nhiet 10_15h.

U thap : do chi tiet sau khi gia cong c kh (ren, dap, tien, bao, phay) ton tai ng suat nen can u thap e kh ng suat. Nhiet o u thap nho hn Ac1 (600_650(C).

U ket tinh lai : kim loai sau khi bien dang deo (can, keo, ren, dap) can u ket tinh lai e tao ra to chc cha t sai lech mang. Nhiet o u bang 0,4_0,5 T(nc cua kim loai o, thi gian gi nhiet phu hp vi tnh chat cua kim loai.

III. Toi thep :

1 nh ngha va muc ch :

1.1. nh ngha : toi la cong nghe nhiet luyen gom nung nong thep len ti nhiet o toi, gi nhiet mot thi gian sau o lam nguoi vi van toc nguoi ln hn van toc nguoi ti han (Vng>Vt.h). Khi toi co chuyen bien ostenit thanh mactenxit, to chc cua thep sau toi la mactenxit toi va ostenit d. V vay sau khi toi bat buoc phai ram thep.

1.2. Muc ch :

Tang o cng, tnh chong mai mon cho chi tiet.

Tang o ben do o lam tang tuoi tho cua chi tiet.2 Chon cac thong so toi thep :2.1. Nhiet o toi :

Thep trc cung tch : T(toi = Ac3 + (30(50(C)

Thep cung tch va sau cung tch : T(toi = Ac1 + (30(50)

Nhiet o toi cua tng loai thep trong cac so tay nhiet luyen thng la mot khoang nhiet o v the chon nhiet o toi phu thoc vao muc ch cua cong nghe.

2.2. Tnh toan thi gian nung va gi nhiet : Xac nh theo cong thc (1), (2), (3).

3 Chon moi trng lam nguoi :

3.1. Moi trng nc :

La moi trng toi pho bien, kinh te vi toc o nguoi cao 400_1200(C/s, nhiet o be nc luon gi nhiet o ( 40(C. Thng ap dung cho cac loai thep cacbon va thep hp kim thap.

Nhc iem cua moi trng toi nc la de gay cong venh va nt do toc o nguoi ln trong chuyen bien mactenxit.

Qua trnh lam nguoi cua chi tiet trong nc xay ra theo 3 giai oan :

Giai oan 1 : nhiet o cao (600_700(C) tao mang hi xung quanh bao boc lay chi tiet, luc nay s thoat nhiet xay ra qua lp mang hi nen toc o nguoi cham.

Giai oan 2 : chat long soi (500_600(C) va tiep xuc vi be mat chi tiet.

Giai oan 3 : mang hi b pha huy kem theo hien tng trao oi nhiet oi lu.

3.2. Moi trng dau :

La moi trng toi thong dung va toc o nguoi cham. Thng ap dung cho thep hp kim. u iem cua moi trng dau la khong gay ng suat. Dau nong 60(C hay c s dung do co o linh ong cao. Nhiet o be dau khong ln hn 200_300(C, do dau se boc chay.

3.3. Moi trng nc + 10% NaOH (NaCl, Na2CO3) :

ay la moi trng toi toc o nguoi manh hn nc trong khoang nhiet o gan ng cong ch C, nhng trong khoang chuyen bien mactenxit lai khong tang la bao. V the thng s dung cho thep cacbon co tiet dien ln. Sau khi toi trong moi trng nay be mat chi tiet b bong troc lp oxit nen sang va phai ra sach be mat (tranh b g).3.4. Moi trng nc + 5% polyvinyl alcol (PVA) :

ay la moi trng co toc o nguoi ln hn dau va nho hn nc. Khi ham lng PVA cang tang toc o nguoi cang cham. Moi trng nay thong dung trong toi tan so cao cua thep hp kim thap.

3.5. Moi trng khong kh nen :

S dung trong mot so thep hp kim cao co van toc nguoi ti han nho, dung khong kh nen t 4_6 at e toi van cng.

3.6. Khuon ep bang kim loai :

Khuon ep bang ong co nc lam nguoi la moi trng toi cho cac la thep mong e tranh cong venh sau khi toi.4 Cac phng phap toi :

4.1. Toi mot moi trng :

Thep sau khi ostenit hoa c toi trong mot trong cac moi trng tren. Thng ng dung cho thep cacbon thap tham cacbon, thep cacbon trung bnh, thep hp kim thap va trung bnh. Cong nghe n gian nhng de gay nt va cong venh.

4.2. Toi trong hai moi trng :

Tien hanh toi thep a ostenit hoa trong moi trng toi th nhat vi Vnguoi > Vth , ti nhiet o gan iem M th mang sang moi trng th hai co Vnguoi cham.

Moi trng th nhat thng la nc, moi trng hai thng la dau. ng dung cho thep cacbon dung cu (cacbon cao) va thep hp kim dung cu. Toi hai moi trng chi tiet t b cong venh va nt nhng chat lng san pham kho on nh va oi hoi cong nhan co trnh o tay nghe cao.

Hnh 7. Cac phng phap toi

a- toi mot moi trng; b- toi hai moi trng

c- toi phan cap; d- toi ang nhiet4.3. Toi phan cap :

Thep sau khi ostenit hoa c lam nguoi trong moi trng toi th nhat vi Vnguoi > Vth thng la moi trng muoi nong chay, ti nhiet o M + 50(C ta gi nhiet mot thi gian sao cho ng ang nhiet cha cat ng bat au chuyen bien. Sau o mang vao moi trng toi th hai thng la dau lam nguoi tiep. Thi gian gi nhiet c xac nh bang ng cong ch C cua thep tng ng. Phng phap nay de thc hien va co tnh khoa hoc cao, nhng oi hoi nhieu thiet b va ch ap dung cho cac chi tiet nho che tao t thep hp kim dung cu co tnh on nh ostenit qua nguoi ln.4.4. Toi ang nhiet :

Giong toi phan cap, ch khac thi gian gi ang nhiet keo dai cho ti khi cat ng ket thuc chuyen bien. To chc sau khi toi ang nhiet la Bainit hoac trustit. Sau khi toi ang nhiet khong can ram lai. Toi ang nhiet thng ap dung cho cac chi tiet nho yeu cau o cng 58_59 HRC che tao t thep gio nh cac loai mui khoan, taro, ban ren

4.5. Toi bo phan :

Co nhieu trng hp chi tiet ch can o cng cao nhng bo phan nao o, trong trng hp nay ta ap dung phng phap toi bo phan.

Nung nong phan can toi en nhiet o toi, sau o lam nguoi nhanh trong moi trng thch hp. Thng toi be mat bang dong ien cam ng tan so cao va toi au mut supap.

Nung toan bo chi tiet en nhiet o toi, sau o lam nguoi nhanh phan can toi trong moi trng thch hp. Thong thng cach nay ket hp vi t ram tiep theo, nen goi la toi t ram (s dung phan nhiet d trong cac phan khong c lam nguoi e ram lai phan a c toi).

Toi t ram thng ap dung cho cac chi tiet dung cu th moc nh uc, trang

4.6. Gia cong lanh :

oi vi nhng loai thep co ham lng cacbon C > 0,6% th iem Mk < 0(C. Cac nguyen to tr Al, Co, Si eu lam ha thap iem Mk. Do o sau khi toi ( moi trng nguoi khoang 40(C) lng Mactenxit toi va ostenit d rat nhieu. V vay can giam ham lng ostenit d bang cach :

Ram e ostenit d chuyen thanh Mactenxit ram.

Ha thap nhiet o gan iem Mk (gia cong lanh) e tang o cng va on nh to chc. Sau gia cong lanh phai ram thap e kh ng suat d (Mtoi chuyen thanh Mram ), tiep theo hoa gia e tang o ben c.

Gia cong lanh c tien hanh sau khi toi bang cach a chi tiet vao moi trng lanh nh tuyet CO2, nit long Nhiet o gia cong lanh tuy thuoc vao iem Mk cua thep. Thi gian gi nhiet e gia cong lanh phu thuoc vao iem Mc.

Neu Mc < T( phong th thi gian chuan b gia cong lanh dai.

Neu Mc > T( phong th phai gia cong lanh ngay sau khi toi.

IV. Ram thep :

1 nh ngha va muc ch :

1.1. nh ngha :

Ram la nguyen cong bat buoc sau khi toi thep bao gom viec nung nong thep a toi len nhiet o thap hn Ac1, gi nhiet mot thi gian sau o lam nguoi ngoai khong kh tnh.

1.2. Muc ch :

Kh ng suat d sau khi toi, ay la ieu bat buoc v thep sau khi toi khong ram ng suat d ket hp vi ng suat c hoc khi lam viec co the dan ti chi tiet b cong venh hoac nt.

Tao ra to chc phu hp vi c tnh phu hp theo yeu cau ky thuat.

2 Cac phng phap ram :

2.1. Ram thap :

Nhiet o ram : 150_200(C

To chc thep a toi sau khi ram thap la Mactenxit ram va ostenit d. Sau khi ram thap o cng cua thep giam 1_2 HRC.

Ram thap c ng dung cho cac chi tiet yeu cau o cng cao, cac chi tiet sau khi tham cacbon cung nh cac chi tiet can tnh chong mai mon cao.

2.2. Ram trung bnh :


To chc cua thep a toi sau khi ram trung bnh la trustit ram, o cng khoang 40_45 HRC va co moun an hoi cao.

Ram trung bnh c ng dung cho cac chi tiet an hoi nh nhp, lo xo2.3. Ram cao :


To chc cua thep a toi sau khi ram cao la xoocbit ram co c tnh tong hp cao ((b, (0,2, (, ak). toi va ram cao con goi la nhiet luyen hoa tot.

Nhiet luyen hoa tot c ap dung cho cac chi tiet che tao bang thep ket cau hoa tot nh tay bien, truc khuyu, truc truyen Chu y khi lam nguoi t nhiet o ram cao cua cac thep hp kim Cr_Ni, Cr_Mn can tien hanh lam nguoi nhanh trong dau.3 Tnh toan thi gian nung va gi nhiet khi ram :

Thi gian nung : Tnh theo cong thc (1).

Thi gian gi nhiet : lay t 1_3 gi.

V. Cac khuyet tat xay ra khi ram va toi thep :

Toi va ram nang cao o ben, o cng do o nang cao tuoi tho cua chi tiet. Tuy nhien khi toi va ram thep cung de gay ra khuyet tat h hong nh nt, cong venh, gion ram.

Nt va cong venh :

Nt va cong venh chi tiet do ng suat khi toi gay ra. ng suat ben trong chi tiet gom ng suat nhiet va ng suat to chc xay ra ca khi nung nong va lam nguoi chi tiet.

ng suat nhiet : ton tai do s chenh lech nhiet o gia be mat va tam chi tiet khi nung nong va lam nguoi. ng suat nhiet gay ra cong venh chi tiet.

ng suat to chc : ton tai trong thep do s sai khac ve the tch rieng gia cac pha (Peclit ostenit, ostenit mactenxit). ng suat to chc chu yeu do ((M va gay ra nt chi tiet khi toi.o cng thap sau khi toi :

Sau khi toi o cng chi tiet khong at co the do :

Nung cha at nhiet o toi, thi gian gi nhiet cha u.

Toc o toi cua moi trng khong u nhanh do nhiet o moi trng tang hoac moi trng b thoai hoa.

Thoat cacbon tren lp be mat khi nung.

Tnh gion cao :

Nhiet o nung khi toi cao qua quy nh lam hat ostenit tr nen tho to, sau khi toi thu c to chc cac kim mactenxit tho to co tnh don cao (nen chon ung thi gian toi va gi nhiet khi nung).

Cac loai thep ket cau hp kim nhom Cr, Mn, Cr_Ni, Cr_Mn khi ram trong khoang nhiet o gion ram loai I va loai II (nen tranh ram nhiet o loai I : 250_350(C, loai II : 500_600(C, sau khi gi nhiet em chi tiet lam nguoi trong dau). CHNG III : QUY TRNH NHIET LUYEN SUPPAP XA

TRONG ONG C XE DREAM, WAVE

I. Cac thong so cua suppap xa :

Hnh 8. Kch thc suppap xa cua ong c ot trong xe gan may Dream, Wave

Vat lieu che tao supap xa : 40Cr9Si2 (40X9C2 )

Khoi lng supap :

G1 = 18,2 g

Dien tch be mat supap :

F1 = 2(*11,75*3 + 2(*2,5*64,5 + (*11,752 + (*2,52 = 1,688.10-3 m2 S o nhiet luyen supap xa :

II. Chon thiet b nhiet luyen :

1 o ga :

c thiet ke theo tng nguyen cong nhiet luyen va phu hp vi thiet b. Vat lieu che tao ga thng dung la thep chu nhiet crom niken dang thanh, tam.

Tren c s thiet o ga, ta tnh c khoi lng ga, so lng chi tiet trong mot ga, so lng ga trong mot me nung.

o ga nhiet luyen supap xa c thiet ke theo tng nguyen cong nhiet luyen phan di.

Vat lieu che tao ga nhiet luyen supap xa : thep chu nhiet X23H18 (( = 7,88 kg/dm3)2 Lo : Lo nhiet luyen supap xa c chon theo nhiet o u, toi, ram cua supap xa.Lo nhiet luyen supap xa

Kieu lo Nhiet olam viec, (CCong suat,kWCong suat khong tai, kW Nang suatlo, kg/hKch thc khoangkhong lam viec, mKch thc ngoai, m

Chieu ronghay ng knh Chieu dai Chieu cao Chieu ronghay ng knh Chieu dai Chieu cao

H30*65700_950184,5500,30,650,20,871,400,79

C2013002010900,22_0,461,1_2,35

C258502515900,33_0,4751,1_2,35

III. Tnh toan he so Bi :

( = 160 kcal/m2.h.(C

S = 23,5.10-3 m

( = 25,1 kcal/m.h.(C

Bi = < 0,25 nen supap xa thuoc nhom vat mong.

IV. U suppap xa :

T(u = 870(C

Lo u : lo buong ien tr H30(65 (CH3_3,0.6,5.2,0/10)

Ga u : dang hop (hnh 9)

So chi tiet trong mot ga : 400 chi tiet

1. Tnh toan thi gian nung :

(nung = K

G = Gga + Gchi tiet = 5,48 + 7,44 = 12,92 kg

Gga = 5,48 kg

Gchi tiet = 400(G1 = 400(18,2.10-3 = 7,44 kg

F = Fga + Fchi tiet = 0,345 + 0,6752 = 1,0202 m2Fga = 0,345 m2 Fchi tiet = 400(F1 = 400(1,688.10-3 = 0,6752 m2 K = 1,7 (Cong nghe nhiet luyen, Pham Th Minh Phng, trang 117)

Cp = 0,216 kcal/kg.(C (Tra cu nhiet luyen, Smucov, trang 14)

( = 50 kcal/m2.(C.h (Tra cu nhiet luyen, Smucov, trang 59)

tau = 30(C

tcuoi = 870(C

tlo = 870 + 50 = 920(C

(nung = phut

2. Thi gian gi nhiet supap :

(gi = (nung = 0,5(16,1 = 8,05 phut

3. Moi trng lam nguoi supap sau khi u : lam nguoi cung lo.

V. Toi toan bo supap xa :

T(toi = 1100(C (nung phan cap : 800(C va nung ket thuc : 1100(C)

Lo toi : lo muoi ien cc C25 (CBC 25/15) nung phan cap 800(C.

C20 (CBC _ 20/10) nung ket thuc 1100(C.

Ga toi : dang ga treo (hnh 10)


Hnh 10. ga toi dang treo1. Khoi lng me nung :

G = Gga + Gchi tiet = 0,94 + 1,274 = 2,214 kg

Gga = 0,94 kg

Gchi tiet = 70(18,2.10-3 = 1,274 kg

2. Tnh toan thi gian nung phan cap (800(C) :

(nung = a.k.D

a = 0,35 phut/mm (Cong nghe nhiet luyen, Nguyen Van Dan, trang 32)

k = 1,7 (Cong nghe nhiet luyen, Pham Th Minh Phng, trang 117)

D = 23,5 mm

(nung = 0,35(1,7(23,5 = 14 phut

3. Thi gian gi nhiet khi nung phan cap :

(gi = (nung = 0,5(14 = 7 phut

4. Tnh toan thi gian nung ket thuc (1100(C) :

(nung = a.k.D



D = 23,5 mm

(nung = 0,2(1,7(23 = 8 phut

5. Thi gian gi nhiet khi nung ket thuc :

(gi = (nung = 0,5(8 = 4 phut

6. Moi trng lam nguoi khi toi toan bo supap : moi trng dau

Thi gian lam nguoi trong dau :

(nguoi = K

k = 1,7

G = 2,214 kg

F = 0,214 m2


= 600 kcal/m2.h.(C (Tra cu nhiet luyen, Smucov, trang 59)

tlo = 40(C

tau = 1100(C

tcuoi = 50(C

(nguoi = 1,7( phut

7. o cng toan bo supap sau khi toi : 54_56 HRC

VI. Ram supap (1) :

T(ram = 700(C

Lo ram : lo buong ien tr H30(65 (CH3_3,0.6,5.2,0/10)

Ga ram : dang hop (hnh 9)


1. Thi gian nung :

(nung = K

k = 1,7

G = 12,92 kg

F = 1,0202 m2



tau = 30(C

tcuoi = 700(C

tlo = 700 + 50 = 750(C

(nung = phut

2. Thi gian gi nhiet :

(gi = 90 phut (Cong nghe nhiet luyen, Nguyen Van Dan, trang 45)

3. Moi trng lam nguoi sau khi ram (1) : lam nguoi ngoai khong kh.

4. o cng toan bo supap sau khi ram (1) : 30_35 HRC

VII. Toi chan supap xa :

T(toi = 1100(C

Lo toi : lo muoi ien cc C20 (CBC _ 20/10)

Ga toi : dang ga treo (hnh 11)


Hnh 11. ga toi dang treo

1. Tnh toan thi gian nung :

(nung = a.k.D



D = 5 mm

(nung = 0,2(1,3(5 = 1,3 phut


(gi = (nung = 0,5(1,3 = 0,65 phut3. Moi trng lam nguoi khi toi chan supap : moi trng dau

Thi gian lam nguoi trong dau 1 phut.

4. o cng chan supap sau khi toi : 54_56 HRCVIII. Ram supap (2) :

T(ram = 550(C

Lo ram (2) : lo buong ien tr H30(65 (CH3_3,0.6,5.2,0/10)

Ga ram : dang hop (hnh 9)

So chi tiet trong mot ga : 400 chi tiet. 1. Thi gian nung :

(nung = K

k = 1,7

G = 12,92 kg

F = 1,0202 m2



tau = 30(C

tcuoi = 550(C

tlo = 550 + 50 = 600(C

(nung = phut


(gi = 60 phut (Cong nghe nhiet luyen, Nguyen Van Dan, trang 45)

3. Moi trng lam nguoi sau khi ram (2) : lam nguoi ngoai khong kh.

4. o cng toan bo supap sau khi ram (2) : 40_45 HRC.

TAI LIEU THAM KHAO

1. Nguyen Van Dan. Cong Nghe Nhiet Luyen Va X Ly Be Mat. Nha Xuat Ban ai Hoc Quoc Gia TP. Ho Ch Minh _ 20022. Pham Th Minh Phng _ Ta Van That. Cong Nghe Nhiet Luyen. Nha Xuat Ban Giao Duc _ 2000.3. A.A.Smucov. Sach Tra Cu Ve Nhiet Luyen Dung Cho Can Bo Ky Thuat. Nha Xuat Ban Khoa Hoc Va Ky Thuat Ha Noi _ 1973.4. ang Vu Ngoan _ Nguyen Ngoc Ha. o An Thiet Ke Cong Nghe Va Thiet B Luyen Kim. Nha Xuat Ban ai Hoc Quoc Gia TP. Ho Ch Minh _ 2003.5. Nguyen Van Tnh. Ky Thuat Che Tao Phu Tung May No Trong May Xay Dng. Nha Xuat Ban Xay Dng Ha Noi _ 1985.6. Pham Minh Tuan. ong C ot Trong7. Nghiem Hung. Nhiet Luyen Phu Tung Oto_May Keo. Nha Xuat Ban Khoa Hoc Va Ky Thuat Ha Noi _ 1985.8. Le Cong Dng. Vat Lieu Hoc. Nha Xuat Ban Khoa Hoc Va Ky Thuat Ha Noi _ 1997.9. X.A.Filinop. So Tay Nhiet Luyen. Nha Xuat Ban Khoa Hoc Va Ky Thuat _ 1978.10. Nghiem Hung. Kim Loai Hoc Va Nhiet Luyen. Nha Xuat Ban giao Duc _ 1993. EMBED AutoCAD.Drawing.15

EMBED Equation.3

EMBED AutoCAD.Drawing.15





EMBED Equation.3

Hnh 9. ga u

dang hop

SVTH : LE CH HAO

_1164205824.unknown

_1164275861.unknown

_1164441469.dwg

_1164524656.unknown

_1164441848.dwg

_1164388617.unknown

_1164276432.dwg

_1164215566.unknown

_1164275650.unknown

_1164206078.unknown

_1164207263.dwg

_1163530236.unknown

_1164129612.dwg

_1164204590.dwg

_1163530250.unknown

_1163530213.unknown

_1163151281.unknown

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