Xcel-Arc Razor Weld ARC180 Скачать руководство пользователя

Страница: 25 / 28

Gas Flow Regulators - Sheilding Gases - Gas Flow Rates

Gas Flow Regulators

The job of the gas flow regulator is to reduce the bottle pressure gas down to a lower pressure and deli

ver it at a constant flow. This constant flow of gas is usually fed through the welding machine where it is

controlled by a solenoid valve, operated when the torch trigger is pulled. Once the gas has passed the sole-

noid valve it flows down the torch cable exiting at the gas nozzle to protect the weld pool and surrounding

area. There are two main types of flow regulators commonly used for MIG and TIG welding applications.

Both regulator types perform the same function, but have a different way of setting and measuring the gas

flow. A flow-gauge regulator (Fig.1) has a dial-type pressure gauge to measure the cylinder contents and a

second gauge to measure and deliver the flow rate required.The flow-meter regulator (Fig.2) has a pres

sure gauge to measure the cylinder contents and a flow tube assembly to measure and deliver the flow

rate required. Some flowmeter regulators will have two flow tube assemblies (Fig.3) typically one is used

for supplying gas to the welding machine and the other is used used for purging the welding area with gas

prior to welding, during welding and post welding and at a separate rate of flow from that being supplied to

the welding machine. The amount of gas flow needed to do the job will depend on the welding gas and the

job being done, but a common setting to start with is 10 L/min.

Shielding Gases

Shielding gases are almost always necessary for MIG and TIG welding processes to protect the weld zone

from gases that are contained in the surrounding atmosphere, particularly nitrogen and oxygen. If allowed

into the weld zone these gases will contaminate the weld pool resulting in fusion defects also porosity and

embrittlement of the weld metal. Selecting the right type of shielding gas depends on the welding process

being used and type of material being welded.

The MIG process is typically a mixture of Argon and Co2 (AR90% Co2 10%) or pure Co2 for steel welding

applications, other specialised mixtures of Argon, Co2, and Oxygen are available for stainless steel welding

but with welding aluminium pure Argon is almost always used

The TIG welding process almost always requires 100% Argon for welding of all materials, however in some

specialised applications Helium, or a Helium mix are sometimes used.

Today with the multitude of gas mixes available through a number of different suppliers, it is difficult to list

and recommend which gas mix is better for which job. If you are unsure about what gas or gas mix to use

we recommend you discuss with your application local gas suppliers or your Esseti technical representative.

Gas Flow Rates

For MIG applications the ideal gas flow rate will depend on the type of mig wire, wire feed speed and current

being used and also the type metal transfer mode, i.e. Dip Transfer, Spray. Pulse Mig. Long interconnecting

cables between the power source and wire feeder and also long push pull torch cables may require higher

flow rates to compensate for the distance. As a general rule of thumb;

1. Small weld pools use 10 L/min,

2. Medium weld pools up to 15 L/min

3. Large spray, pulse mig weld pools use up to 25 L/min.
It is important to note that too high gas flow can be just as bad as having too low flow rate. The reason being

that if the gas flow exits the gas nozzle a too high rate it can.
1. create a vortex and draw air into the gas flow and the weld zone causing contamination of the weld.

2. produce turbulence at the weld pool resulting in a poor quality weld.

For TIG applications the ideal gas flow required will depend on the welding job being done, the type of ma

terial being welded and the type of filler wire. As a generalguide start with a flow rate of 6 l/min. If porosity or

contamination appears in the weld then increase the flow rate. Also be aware of the welding environment, if

there is wind or a breeze an increase of flow rate will be required to compensate for this.

Fig.1

Fig.2

Fig.3