Download - API577 Chapter 5a1
Cc phng php hn
Phn 1 / 3
Ch to & sa cha thit b du kh / ha cht & h thng ng cng ngh
http://www.heatecholdings.com/business_pipingSystem_oil.html
H thng ng ng cng ngh
Thit b & h thng ng cng ngh
Thit b & h thng ng ng cng ngh
Equipments & Piping
Equipments & Piping
Equipments & Piping
TNG QUAN
http://www.substech.com/dokuwiki/doku.php?id=shielded_metal_arc_welding_smaw
Yu cu kin thc ti thiu v cc qu trnh php hn p dng trong cng tc gim st ch to, sa cha thit b ha du v h thng ng ng cng ngh bao gm cc hiu bit c bn v cc qu trnh hn thng dng nh SMAW Shielded Metal Arc Welding, GMAW Gas Metal Arc Welding, FCAW Flux Cored Arc Welding, GTAW Gas Tungsten Arc Welding, SAW Submerged Arc Welding v SW Stud Arc welding.Tt c qu trnh nu trn u p dng ngun nhit hn l h quang hn, song do c s khc bit ln v phng thc duy tr h quang v cung cp kim loi p b sung (filler metal), v mi trng bo v. Kt qu l chng s c u & nhc im ring c xem xt qua cc mc sau:Phm vi p dng
c im cng ngh
Loi hnh v mc hnh thnh cc khim khuyt hn.
HN QUE (H QUANG KIM LOI T BO V - SMAW)
SMAW thng c gi l hn que l mt phng php hn c p dng rng ri nht nh vo tnh tin li, gi thnh r v cht lng mi hn p ng hu ht cc yu cu thit k.SMAW s dng ngun nhit l h quang chy gia u in cc c thuc bc v vng chy (weld pool) t chy in cc bao gm c thuc bc v kim loi c bn (base metal) vng hn. Vng chy c bo v khi s xm hi ca khng kh xung quanh nh kh (CO2) v thuc hn nng chy hnh thnh khi thuc bc b t chy. Mi hn c hnh thnh nh s ng rn vng chy khi h quang di chuyn.Ngun hn (power source) to v duy tr h quang vi in p v dng hn xc lp c th l xoay chiu (AC) hoc mt chiu (DC) vi in cc dng (DCEP) hoc in c m (DCEN).Quan h in p dng hn c c im c nh dng (CC - Constant Current) nh qu trnh hn SMAW c duy tr vi dng hn dao ng bin hp, trong khi in p hn s t l bc nht vi chiu di h quang.
Trong thc t, in p hn qui c (Conventional Voltage) c nh ngha bng cng thcUh = 20 + 0.04 Ih c ngha ng dng st thc tin hn.
Thuc bc que hn
Thuc bc que hn l mt yu t qua trng bo m cht lng mi hn. Thuc bc que hn c th m ng cc vai tr sau:To ra mi trng kh bo v h quang v vng chy khi cc tc ng c hi gy ra bi kh quyn bao quanh h quang hn,
X l tp cht, kh oxt, km hm tc tng trng ht v to x che ph v tinh lc vng chy,
Tng cng c tnh in ca ct plasma h quang nhm duy tr qu trnh chy v phn b nhit n nh,
To lp x nng che ph kim sot nhit, bo v v nh hnh b mt mi hn,
Cung cp cc nguyn t hp kim nhm ci thin c tnh c l ca kim loi mi hn (weld metal).
u im ca phng php SMAW
Phng php SMAW c nhng u im chnh sau:
a.
Trang thit b n gin, r v c ng.
b.
C th tin hnh hn ni cht hp (k c di nc).
c.
Cht lng hn t b tc ng bi gi la.
d.
C th hn tt n rt tt trn hu ht kim loi & hp kim.
Cc hn ch ca phng php SMAW
SMAW c1 nhng hn ch sau:
a.
Nng sut p (Deposition rates) kh thp so vi cc phng php GMAW.
b.
D b ngm x nhng im ni (start / stop) gia cc con (run) / lp hn (layer).
b.
D b ngm x nhng im ni (start / stop) gia cc con (run) / lp hn (layer).
Cht lng, nng sut hn ph thuc nhiu vo tay ngh v kinh nghim, k lut ca th hn.
c.
Shielded metal arc welding
Shielded metal arc welding
SMAW
SMAW
SMAW
SMAW- Underwater Welding
SMAW- Underwater Welding
SMAW- Qualification of Underwater Welders
SMAW- Structural Welding
SMAW- Structural Welding
SMAW-
WPQ Welder Performance Qualification
SMAW- Transmission Pipeline Welding
Equipment is relatively
simple, inexpensive, and
portable.
SMAW- Weld Profile
SMAW- Weld Profile
SMAW- Weld Profile
SMAW- Weld Profile
SMAW- Weld Profile
SMAW- Weld Profile
SMAW- Weld Profile
SMAW- Weld Profile
SMAW- Grinding at Start-Stop
SMAW- Tack Welding
SMAW- Root Pass + Hot Pass
SMAW- Large Tack Weld for Thick Welding
SMAW- Pipeline Tie-in Joint
SMAW- Pipeline Welding
SMAW- WPQ Test Coupon
SMAW- WPQ Test Coupon
SMAW- WPQ Test Coupon
SMAW- AWS Test Positions
SMAW- Smiling Experts at Work
5.3 GAS TUNGSTEN ARC WELDING (GTAW)
GTAW is an arc welding process that uses an arc between a non-
consumable tungsten electrode and the weld pool. The process is used with
shielding gas and without the application of pressure. GTAW can be used
with or without the addition of filler metal.
The CC type power supply can be used with either dc or ac, the choice
depends largely on the metal to be welded. Direct current welding is typically
performed with the electrode negative (DCEN) polarity. DCEN welding offers
the advantages of deeper penetration and faster welding speeds. Alternating
current provides a cathodic cleaning (sputtering) that removes refractory
oxides from the surfaces of the weld joint, which is necessary for welding
aluminum and magnesium. The cleaning action occurs during the portion of
the ac wave, when the electrode is positive with respect to the work piece.
See Figures 3 and 4 for schematics of the GTAW equipment and welding
process.
Hn TIG (Gas tungsten arc welding - GTAW)
Nguyn l phng php GTAW
http://www.substech.com/dokuwiki/doku.php?id=tungsten_inert_gas_arc_welding_tig_gtaw
Gas tungsten arc welding
The cleaning action occurs during the portion of the ac
wave, when the electrode is positive with respect to the
work piece.
GTAW
GTAW
5.3.1 Advantages of GTAW
Some commonly accepted advantages of the GTAW process include:
a.
Produces high purity welds, generally free from defects.
b.
Little post-weld cleaning is required.
c.
Allows for excellent control of root pass weld penetration.
d.
Can be used with or without filler metal, dependent on the application.
5.3.2 Limitations of GTAW
Limitations associated with GTAW process are:
a.
Deposition rates are lower than the rates possible with consumable
electrode arc welding processes.
b.
Has a low tolerance for contaminants on filler or base metals.
c.
Difficult to shield the weld zone properly in drafty environments.
GTAW / TIG Welding
GTAW / TIG Weld
a.
Produces high purity welds, generally free from defects.
TIG weld without
addition of filler
metal- autogenous
weld.
GTAW / TIG Weld
TIG Gas Nozzles
Tungsten
Electrodes
Tungsten
Electrodes
Tungsten
Electrodes
Tungsten
Electrodes
Tungsten- Automation