Publicidad
Idiomas disponibles
Idiomas disponibles
b) Before starting with any maintenance operation the welding equipment must be disconnect from the power supply.
c) The welding cables and the power supply cable and even the welding machine must be kept in good working conditions. This equipment must
never be used in less proper working conditions.
d) The welding equipment and its accessories must be treated carefully. Keep the machine far from heating sources, ovens or hothouses, from
humid places as water wells, oils or lubricants, from corrosive environments or intemperate weather.
e) Keep the safety systems and the chassis of the machine in proper working conditions.
f) Use the welding equipment only in jobs that are according to the equipment characteristics.
1.6 - Using WELDING or GAS CUTTING equipment.
a) The operator of welding or gas cutting equipments must know the specific characteristics and the correct form of use.
b) The pressures ought to be according to the manufacture recommendations.
c) The welding torches, hoses and reducers must be kept well tightened with no leaks, cleaned and free from oils or lubricant greases.
d) The pressure reducers can not be submitted to sudden changes of pressure and must be used according to the manufacturer specifications.
Do not use an installation without being equipped with proper retention valves.
e) Periodical checks must be made to the installation for detection possible gas leaks or other defects. Qualified personnel must execute the
maintenance operations.
1.7- Handling of Gas Tubes
The user must know and follow the safety instructions for stocking, use and transportation of compressed, liquefied and
dissolved gases under pressure used in welding or cutting operations. Besides the specified norms must follow those that concern the kind of
welding process to be used (Electrode, Tig, Mig, Plasma, Plasma cutting, Laser, etc.), as well as the specific characteristics of the equipment,
the power supply conditions, hygiene norms and safety at work and the machine's safety regulations . The fulfilment of this safety norms, does
not guarantee that the content is enough for all cases or conditions, or invalids the fulfilment of current legal norms.
2 – OPEN ARC WELDING PROCESS
This welding process uses fluxed core wire without shielding gas - OPEN ARC - continuous electrode and is suitable for
reconstruct initial geometrics of pieces submitted to wear, rebuilding, repair or steel construction.
The continuous electrode is composed by a metallic tube containing an internal flux to obtain a shielding gas which promotes:
- The deoxidization of the piece to be welded to avoid porosity.
- A protective layer over the welding piece during solidification.
- The stabilisation of the arc to reduce spatter.
- The addition of metallic elements to increase coating.
Welding parameters which can influence the welding operation:
2.1 – Arc voltage:
a – High voltage (long arc) increases spatter and porosities;
the edges of the seam become irregular.
b – Low voltage (short arc) produces a convex seam with excessive undulation.
Very low voltage reduces voltage and causes extinguishing of arc.
2.2 – Welding current:
a – High current causes slaughtered seams and increases the melting temperature, the deposition rate and the penetration with
an excessive tendency to cause spatters. Increasing current allows welding at high speed and high voltages without causing
porosity.
b - Low current produces narrow seam with high edges and low penetration. It may be advantageous in thin sheet welding
when penetration control is desirable.
2.3 – Welding speed:
a – High welding speed causes low penetration and irregular edges with formation of spatter.
b – Low welding speed causes excessive penetration, slag inclusions in the bath and irregular edge seam.
2.4 - Stick-out
To maintain the best arc stability, the distance between the torch nozzle and the work piece
must be around 50 mm for most part of electrodes. Distance too short causes increase of
current, and spatter formation which can cause damage of the contact tube.
With this method, the welding position becomes more difficult because deposition rates
produce a very fluid bath. The use of positive electrode polarity and low currents is
recommended to improve position welding.
Recommended welding positions:
metal alloy sheath
flux core
shielding gas
slag
weld metal
base metal
Fig.3
OPEN ARC 500A
Fig.1
stick-out
Fig.2
4
Publicidad
