hot and cold wire TIG

Cold wire TIG is what you're probably used to seeing; wire fed from a spool (or by hand) at ambient temperature to the weld pool. Hot wire TIG has the wire pre-heated before it's introduced to the weld pool. Reduces thermal shock and results in higher deposition and better quality welds.

a secondary current is used in the hot wire applications to preheat the input wire at the front end of the puddle. this process is able to provide a greater volume increase of weld wire into the motlen puddle without as much effects if the wire is cold. if some one is looking at the usage please take note and evaluate the useage carefully. the most important aspect is that some one shows you a workmanship sample of the application and weld joint that this process is intended to be used for. I urge any user to not take a contractors word for the usage unless they can show you prior experience. this is no beginners game and field. only use those with demonstated history of useage etc.

Cold wire feeder:

The wire drive mechanism consists of an electrical motor and a set of gears to power the drive rollers to push the wire. Wire sizes of 0.8 to 2.4 can be fed with constant speed.

Hot wire feeder:

In addition to above mechanism, electrical resistance heated wire is also fed into the weld pool. The heating starts with a AC constant Potential power source and only after wire makes contact with weld pool and completes the electric circuit. The current is so regulated that filler metal reaches is melting point a it approaches the weld. Thus the metal deposition is independent of the arc heat. DC is not recommended for heating purpose as it causes magnetic field effect and wandering arc. The heating current is 60% of arc current and limited to 1.20 mm size max. Otherwise arc swill oscillates widely.

Shielding gas used is generally 75% He & 25% Ar. (or) depending up on the material.

Advantages:

Hot wire technique increases weld deposition rate in TIG process from 3.0 to 5.0 kg / hr compared to 1.5 kg /hr at 4 Kw ( 330A at 12 V) energy in cold wire feeding.

Applications:

Widely used for fabrication of pipe and piping systems for CS, SS, AS, Nickel & Cu alloys in USA and Europe. Since speed of welding is more than 25 cms/min, higher currents and deposit rates can be used thereby increasing production rates by 4 times compared to other method.

Example:

The following are apex. Parameters and may vary depending upon the job req.

1. For 1.6 thk. sheet, 300 A at 90 cms/ min speed is used with HW feeding

For same thk. sheet, 160 A at 60 cms/ min speed is used with CW feeding.

2. For 3.2 thk. sheet, 400 A at 60 cms/ min speed is used with HW feeding

For same thk. sheet, 250 A at 30 cms/ min speed is used with CW feeding

3. For 6.3 thk. sheet, 450 A at 20 cms/ min speed is used with HW feeding

For same thk. sheet, 350 A at 10 cms/ min speed is used with CW feeding

Trust above information is useful to you.

Sridhar .