NGHIEN Cflu-TRAO BOI
KHAO SAT ANH H U 6 N G CUA M O T SO v i U TO L6N CHAT LUONG GIA C O N G RANH XOAN TRONG L 6 S A U B A N G P H U O N G PHAP DIGN HOA
Nguyen Dflc Minh', Lai Anh TuSnS Nguyen Trpng Doanh^
'Bp Cdng an, 'Hpc vien Ky thudt Quan sfl, 'Trfldng Dai hpc Bdeh khoa Ha Npi
TQM TAT
Gia cong rdnh xoan trong 16 sdu id vdn dephUc tap nhdt trong qud trinh sdn xudt vu khi hien nay.
Gia cong diin hoa la mgt phUdng phdp gia cong dUdc sd dung rgng rdi d cdc cd sd sdn xudt khi phdi gia cdng cdc Id dinh hinh md cdc phUdng phdp gia cong thong thUdng khong the thUc hien dUdc. ChdtlUdng gia cong dien hoa phu thugc vdo khd nhieu yeu to. De dp Ung yeu cdu ky thudt cua nong phdo, ta tap trung vdo khdo sdt ba thong so co dnh hUdng nhieu nhdt den do bong be mat gia cong vd ndng sudt boc tdch kim loai, do la mat do dong, nong do dung dich diin ly vd nhiet do viinggia cong. Tren cd sd do, ta dUa ra che do cong nghe hdp ly deed the ddm bdo ndng suat hoc tdch kim loai phii hdp vdi chdtlUdngbe mat yeu cdu.
ABSTRACT
Cutting spiral drain in deep hole is actually one of the most complex problem in armament manufacturing. Electro-Chemical cutting is one usual method of manufacturing in the mechanical plants for cutting different formed holes which can not realized by others methods. Quality of Electro-chemical cutting depends on many factors. For achieving of technical requirements of artillery, there is a concentration into three factors most influenced to surface quality and productivity of metal eliminating as following: Density of current, density of electro- chemical solution and temperature of cutting zone.
On this knowledge we can determinate optimal cutting parameters for obtaining good productivity with required surface quality.
1 5 1 TAP CHi CO KHi VIET NAM • Sd 4 (Thang 4 nam 2012)
1. CONG NGHE GIA CONG R A N H XOAN BANG DIEN HOA
Gia cdng ranh xoan trong lo sdu la cdng nghe phfle tap nhat trong che tao cac loai ndng sung va ndng phao. Ranh xoan cua ndng phdo thfldng cd hai dang la gdc xodn khdng ddi hoac goc xoan thay doi. Ranh cd gdc xodn khdng ddi thi don gidn hon cho viec che tao, nhflng lam giam tudi thp cua ndng phao. Ranh cd gdc xodn thay ddi lam cho viec gia cdng khd khan hPn, nhflng chat IflOng dfldng dan va tudi thp ndng phao deu dflpc ndng Ien. Mdt trong eac cdng nghe gia cdng ranh xoan hay dflpe sfl dung la cdng nghe gia cdng dien hda. Day la phflpng phdp gia cdng da cd tfl kha lau vd thfldng dflpc sfl dung de gia cdng cdc be mat dinh hinh phflc tap, ddc biet la cae Id, cdc ranh ma cdc phflpng phap thdng thfldng khdng thflc hien dflpc.
Ban chat cua qud trinh dien hda Id la qua trinh bdc tach kim loai nhd hien tflpng phdng dien an mdn A - not trong mdi trfldng dung dich dien phan. Khdi Iflpng kim loai bj hda tan dflpc xac dinh theo cdng thflc sau:
M = k.I. T. rj
(1)Trong dd:
k - dflpng Iflpng dien hda, I - ddng dien, T - thdi gian , q - hieu suat ddng dien.
Cau tao eiia mdy dien hda ranh xoan dflpe the hien tren hinh 1. May nay dflpc dieu khien theo hai true chuyen ddng: tinh tien dau dung cu va quay dau dung cu. Hai chuyen ddng nay cd ti sd truyen khdng ddi trong trfldng hpp gdc xoan khdng ddi va ti sd truyen thay ddi khi gdc xoan thay ddi. Chi tiet gia cdng dflpc dau vdi cflc dflPng vd dung cu dflpe dau vdi cflc am.
Hinh 1: May gia cong ranh xoan di?n hoa Gifla chi tiet va dung dflpc each dien hoan toan. Dien cue dung cu 4 chinh la am ban cua ranh cdt, thfldng dflpc lam tfl kim logi den va phan khong tham gia cat dflpc phu mpt Idp each dien. Dung dich dien ly dfldc bom 15 cap vao dfldi ap suat cao de day litpng kim lo^i dudc boc tach ra khoi vung gia cong. Chat dien ly difpc sfl dung la NaCl hoac NaN03. Trong qua trinh gia cong dien hoa, co rat nhieu yeu to anh hiJdng den chat Ifldng be mat ranh gia cong. Sau day, ta chi tap trung vao mot so thong so co anh hudng chinh den chat lifpng do la : mat dp dong, nong do dung dich dien ly va nhiet do vung gia cdng.
2. ANH HUdNG CUA MAT DO DONG
Mat dp ddng dien ia la thdng sd quan trpng nhat cd nhflng anh hfldng quyet dinh den chat Iflpng ranh xoan trong qud trinh gia cdng.
Chinh vi vay, ta tap trung khdo sdt anh hfldng cua mat dp ddng Ien ndng suat bdc kim loai va dp bdng be mat gia cdng. Can cfl vao cae tai heu va kinh nghiem thflc te khi gia cdng dien hda, ta chpn cae thdng sd cP bdn sau:
- Khe hd gifla eac dien cflc S = 0,5 mm - dp suat dung dich P = 0,6 Mpa - Ndng dp dung dich NaCl = 20%
Cdc mau thi nghiem cd chieu ddi 300mm, Id T'j~I-i' d eac mat dp ddng thay ddi trong khoang tfl: 5 -^ 25 A/cm^ Ket qua thi nghiem thu dflpc nhfl tren bang 1.
TAP C H i CO KHi VIET NAM So 4 (Thang 4 nam 2012)
NGHIEN cflu - TRAO DOI
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Quan h? gifla m?t dp ddng va dp bdng be mat dflpc the hi?n tren hinh 2.
Tr^n dd thj, ta thay, khi ia tang thi toe dp gia cdng ranh xodn tang Ien nhflng khdng phai dfldng tuyen tinh hodn toan nhfl tinh todn. Bdivi, trong cdng thflc tinh theo dinh luat Faraday ehfla tinh d^n cdc van de nhfl hien tflpng bdo hda cua dung dich di^n ly gay nen sfl thu dpng hod be mat sdn pham.
O day, ta thdy, khi ia tdng den hon 20 A/
cm2 vd ndng dp dung djch dien ly 20% thi viec tdch cdc cdc ion kim loai ra khdi vung gia cdng khdng tdt, ddn d^n thu dpng hoa vi v$y khi gia cdng rdnh xodn trong di^u ki?n thflc te nen sfl dyng; i^ = 15 -^ 18 A/cm^
3. ANH HUOtNG CUA NONG DO DUNG DICH D 1 £ N LY
Hinh 2: Do thi anh hudng cua mat dd dong Ien do bong be mat
Anh hfldng cua mat dp ddng Ien tdc dp an mdn kim loai phdi dflpc the hien tren hinh 3.
Trong cdc tdi lieu cung nhfl trong cac thi nghiem thflc te cho thay, ndng dp va thdnh phan dung dich hau nhfl khdng dnh hfldng den toe dp an mdn, tuy nhien, nd cd dnh hfldng den dp bdng be mat. De nghien cflu van de ndy, ta cd dinh cdc tham sd cdng nghe cP ban, chi thay ddi ndng dp dung dich NaCl khi ehfla cd phu gia vd sau khi co phu gia. Ket qua nghien cflu (bang 2) cho thay, khi ndng dp NaCl tang tfl 10% den 20%, dp bong be mat ranh xodn tang. Nhflng neu ndng dp NaCl
>22% thi cd hien tflpng be mat ranh bi thu ddng hod de lai mpt sd ndt san khdng an mdn dflpc.
Hien tflpng ndy xdy ra do luc nay dp set cua dung dich cao, khd nang dd'y cac san pham dien hod ra khdi khu vflc lam viec khdng tot. Cung qua thfl nghiem eho thay, viec bd sung mdt so phu gia nhdm ban che kha nang thu dpng hod la rat quan trpng nhfl: NitPrit Natri NaNO, va axit Boric H^BrO,.
Bang 2
Hinh 3: Anh hfldng cfldng dp dong Ien toe dp an mon
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B ^ TAP CHI CO KHi VIETNAM S6 4(Thang4nam-2012)
Anh NaCl Ien do tren hinh 4.
hfldng cua ndng dp dung dich dien ly tiep dnh hfldng cua nhiet dp dung dich den qud bdng be mat gia cdng dfloc the hien trinh an mdn vd chat lflpng be mat ranh xoan.
Nhdm de tai tien hdnh nghien cflu tren cdc mau ddi 2200mm, kich thflde 161|)37,06, eac thdng sd khdc ed djnh chi thay ddi nhiet dp tiiW C din 40"C. Ket qud cho thay d nhiet dp dung dich nhd hon le^C, viec an mdn rat cham va chat lflpng be mat tdt khi nhiet dp dung djch ldn hon 18"C thi viec an mdn xay ra binh thfldng va tdc dp an mdn tang theo nhiet dp nhfl ket qua d bang 3.
Bdng 3
Hinh 4: Anh hudng cua ndng dp dung dich dien ly Ien dp bong be mat
Qua ket qua tren cho thay nen sfl dung dung dich NaC117 - 20% ed them phu gia de gia cdng rdnh xoan ed the cho dp bdng tdt nhdt.
4. ANH HLTdNG CUA NHIET D p
Cdc nghien cflu tfl tai lieu cua nfldc ngoai da chi ra la: sfl phu thudc eua dp dan dien rieng cua dung dich dien hod vdo nhiet dp dflpc xac dinh thdng qua bieu thflc:
X, ZB [ 1 + ( t d - 1 8 ) ]
d day: Xr ~ ^d dan dien rieng eua dung djch dien hoa d nhiet dp t^, Xi ' ^9 ^^^ ^*^"
rieng cua dung dich dien phan d \ gOQ, /? - he sd nhiet (doi vdi cac dung dich mudi thi ^ = 0,022).
Tuy nhien, doi vdi cdc dung dich dien phdn d cdc nhiet dp khdc nhau cae ket qud tinh todn dp dan dien rieng cd the khdng chinh xac dan den cac ket qua tinh todn cac thdng sd cdng nghe khi gia cdng ranh xoan, vi vay, nhdm de tdi nghien cflu trflc
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5. KET L U A N
Tfl cac ket qua thflc nghiem, ta da thay rd anh hfldng cua cac thdng sd nhfl mat dp ddng, ndng dp dung dich dien ly, nhiet dp Ien dp bdng be mat gia cdng va tdc do an mdn khi gia cdng dien hda. Che dp cdt phu hpp dflpc xdc dinh: i = 14,9 A/cm^ (I = 146 A); U = 20,5 ^ 21,5 V; P = 6 at; T" = 32 ^34''C; dung dich NaCl 17 -^ 20% cd phu gia la NaNO^ va H^BrO^; Tdc dp dich chuyen Catdt 10 -^ ISmm/phut. Chat Iflpng gia cdng ranh xoan tren ndng phdo che tao thfl (37mm) hoan toan dap flng ve dp chinh xdc gia cdng cung nhfl dp bdng be mat. Sau khi thflc hien cdc cdng doan hoan thien nhfl danh bdng, lam sach vd ma, ndng phdo da dflpc dfla di ban thfl nghiem. Dp chinh xdc cua dfldng dan dap flng tflpng dflpng vdi loai phao cung cd cua nfldc ngoai. Ket qud tren ddy cd the flng dung vdo trong sdn xuat dai tra. •
TAP CHI CO KHi V I £ T NAM Sd 4 (Thang 4 nam 2012)
NGHIEN cflu - TRAO DOI
Tai lieu t h a m kliao:
[1]. Nguyen Ngpc Anh, Phan Dinh TliuySn, Nguyin Ngpc ThU. Hi Van Vui (1979), Sd tay cong nghe che tao may. Tap 2, 3, 4, NXB. Khoa hpc v4 Ky thuill. H4 N0i.
[2]. Nguyen DSc Lpc (chu bien). Cpng nghi chl^ tap may, T|p 1, 2. NXB. Khoa hpc vi Ki thuat. Hi Npi.
[3]. Le Hoang Phu , Gia cong lo sau. Trung tam Cong nghe, Bp Qu6c phdng.
[4]. Tran Sy Tuy (chu bien) vi tap the tac gii (1977), Nguyin Ii cit kim Ipai, NXB. Dai hpc vi Trung hpc Chuyen nghiep. Hi Npi.
[5] Todd, H Rpbert; Allen, K. Dell; Alting, Leo (1994). Manufacturing Processes Reference Guide (1st ed.).
Industrial Press Inc.. p. 198-199, ISBN 0-8311-3049-0.
[6] Valenti, Michael. "Making the Cut." Mechanical Engineering. American Society of Mechanical Engineers.
2001.
[7] Ghosh, A., Manufacturing Science, Ellis Horwppd Ltd., Chichester, UK, 1986.
TAP CHi CO KHl VIET NAM • S6 4 (Thang 4 nam 2012)
