Valley FABRICATOR 251, Руководство по обслуживанию

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August 22, 2008 4-11
SERVICE MANUAL FABRICATOR 251
Contact
Ti
p
Gas
Nozzle
Solid Wire Flux Cored Wire
.023”
(.6mm)
1/4” (6.4mm)
5/16” (7.9mm)
3/8” (9.5mm)
9/16”
(14.3mm)
11/16”
(17.5mm)
.030”
(.8mm)
.035”
(.9mm)
.035”
(.9mm)
.045”
(1.1mm)
Art # A-07186
Wire Diameter
Di s ta n ce: ±1/16”
Figu r e 4-19: Optimum Contact Tip to Wo r k Distances
Electrode Wire Size Selection
The choice of elect r ode wi r e size in conjunction with shielding gas used depends on:
- Thickness of the metal to be welded,
- Type of joint,
- Capacity of the wi r e feed unit and powe r supply,
- The amount of penet r ation r equi r ed,
- The deposition r ate r equi r ed,
- The bead p r ofile desi r ed,
- The position of welding and
- Cost of the elect r ode wi r e.
Weld metal deposition r ate is p r opo r tional to cu rr ent density. Cu rr ent density is defined as the cu rr ent pe r c r oss
sectional a r ea of the elect r ode wi r e and is no r mally exp r essed as amps pe r mm
2
. An example is in Table 4-3 below.
Electrode Wire Size Current (Amps) Current Density(Amps/mm2) Deposition Rate(lbs/hour)
.035”( 0.9mm) 200 314 7.0
.045”(1.2mm) 200 177 6.2
Table 4-3: .035"(0.9mm) , .045"(1.2mm) Wi r e Deposition Rate
Advantages of MIG welding forehand:
- Allows supe r io r visibility of the weld zone
- Flatte r weld bead
- Shallowe r penet r ation
Foreha n d
Vertical
Backha n d
Art # A-07185
Figu r e 4-20: MIG Gun Angle