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