Welding

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Do you mean MIG Spot? Or ERW Spot? Both are available.

For MIG, Weld Time depends on welding procedure as well as WPS/PQR as per any International Code. Weld Time is dependent on WFS (wire feed speed) and welding speed and skill of the welder.

For Spot, it is 2-3 sec.

Yes. Current should be set according to thickness of metal and welding procedure.

No for your first question. Yes for Back-purging in TIG Process for Stainless Steel welding. You did not mention the welding process used in your job.

This is called Gas Flow rate used in MIG or TIG process.

Yes it varies in any Manual Welding that’s why the range. Quality of welding affects on the Arc Length hence the mechanical properties. Arc Length is one of the four essentials in Arc welding which needs great amount of skill to perform.

Ideal Arc Length is 2-3 mm in MMAW, MIG, and TIG. Hence the Arc Length is more, Bead Width is larger as well as HAZ is more in a given Arc Energy. 

Sheet thickness is important to select the welding process to be able to perform good quality weld.

Arc Length: Arc Length is very important for good quality weld, hence it requires great amount of skill and one of the four “Essential’s” of arc welding shown on the webinar.

Yes, you can. It depends on the skill & knowledge of your supervision. It can be reduced by training. 

Do you mean to improve the weld bead? It depends on lack of skill and knowledge of welders & welding procedure setting (management skill & knowledge). Train them for a shorter period of time (2/3 days).

Strength and weld quality are better in TIG Process.

Generally CO_2, the rate of gas flow should be 14-15 ltr/min in the workshop but in exposed area it should be higher depending of the air-flow to prevent “Porosity” defect. My recommendation is to use Argon-CO₂ of 80% Argon and 20% CO₂ or 82% Argon & 18% CO₂ for good quality weld.

Welding current should be defined as prime welding parameter. It should be set according to the thickness of the job and welding procedure & process.

Do you mean Under-filling? It’s a reason of lack of skill & knowledge in welding. Train your welders to be competitive.

In gas metal arc, the shielding gas can have a major effect on the properties of the base metal. Some of the shielding gases commonly used with GMAW process are pure Argon, Argon-Helium, Argon-Oxygen, Argon-Carbon Dioxide and only Carbon Dioxide. The smoothness of operation, weld bead appearance, weld quality and welding speeds are affected differently with each type of gas mixture.

Leak Proof welding can be done by skilful welder and this can be tested by Dye Penetrant Test (DPT) easily in any metal. Magnetic Particle Inspection can be done only which will have magnetic property.

By fire you mean - “Spatter”. Spatter is a discontinuity but not a “Defect”. It is there in MMAW & MIG Process which you can reduce with good quality electrodes in MMAW and by proper parameter setting in MIG drastically. In TIG or SAW Process, there is no spatter. Why - this depends on the process to be adopted.

Use “Fumes Extractor” available in the market.

This is Butt Joint to be welded in Horizontal position.

Depends on the melting point of the materials to be used. Fusion welding is done above the melting point. For example: Mild Steel melting point = 1530⁰ C, Copper= 1083⁰ C, Aluminium= 660⁰ C.

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IACS: International Association of Classification Societies.

It’s calculated by empirical distortion calculation. But if you want to control the distortion then go as follows:

Control of Distortion can be classified in to the following three things by the welding Engineer:

Reduction of effective shrinkage forces. (Use of back-stepping, welding to be started from the centre, use of planned wandering etc). Making the shrinkage forces itself to work to reduce distortion. (By pre-bending the member or presetting the angle as per your requirement etc). Balancing one shrinkage force with another. (Annealing, Normalizing)

Do you mention Zinc coated sheet? If yes, then follow as under:

We have shown ‘Welding for Galvanized Steel’ in the Webinar. Use Argon-CO₂ for MIG as Shielding Gas – Welding of galvanized steel is done almost exactly the same way as welding of the bare steel of the same composition. The same welding processes, volts, amps, travel speed, etc. can be used with little modification when the switch is made from uncoated steel to galvanized steel unless the zinc coating is unusually thick. 

In any welding, there is a Thermal Cycle to get an Integral Joint so cold metal transfer is not possible. In MIG Process, there are 3 types of metal transfer:

• Dip Transfer
• Globular Transfer.
• Spray Transfer.

High spatter, low mechanical property, poor weld bead etc are the results. Use Argon-CO₂ mixture gas for the same.

Litre/Min is defined in every Flow-Meter. Normally it depends on the type of metal transfer and amperage and location of welding. 15 Ltr/min for MIG in the workshop area is best to use.

Constant Current type power sources are used in MMAW & TIG.

In 1 mm thickness it is difficult to avoid melt-through unless using Pulsed type power source. But it is easier to weld in TIG Process without filler wire (called Autogenous weld) than MIG.

Reduce the Bulging as above though use Support Angle & back-stepping weld and maintain intermittent weld to complete.

In case the joints to be welded in out-of-position TIG is best; if in Flat position MMAW or MIG depending on the thickness of metal also.

Control of Distortion can be classified in to the following three things by the welding Engineer:

• Reduction of effective shrinkage forces. (use of back-stepping, welding to be started from the centre, use of planned wandering etc)
• Making the shrinkage forces itself to work to reduce distortion. (By pre-bending the member or presetting the angle as per your requirement etc)
• Balancing one shrinkage forces by another. (Annealing, Normalizing)

For Dip Transfer = 8 – 12 mm; Globular Transfer = 15 -18 mm; Spray Transfer = 18 – 22 mm, the distance of Stick-Out is from the Contact Tip to the Tip of the filler Wire.

If you mention ERW (because Projection, spot, Seam are used in ERW) this was not our topic though set the current of ERW as H= I²RT.

Re-drying of electrodes can be done in a HOLDING OVEN attached with Thermostat & Portable Oven with Thermostat available in the market (ESAB/Advani). The Procedure of Re-drying should be as follows:

E – 6013 (Rutile electrodes): Bake the same at 80⁰ C for 20-30 min before use.

E – 7018 (Low-Hydrogen electrodes): Bake the same at 250⁰ C minimum for 1 hr before use.

Selecting the diameter of Filler Wire in MIG Process depends on welding position. If you have only Vertical Uphill Butt Joint (3G), go for 0.8 mm diameter (also used for lower thickness) but in case you have different welding position with productivity & quality of welding requirement– go for 1.2 mm which is called Versatile Filler wire in MIG process.

Current is adjusted according to the thickness of the materials to be welded. Current is the prime welding parameter in any welding process.

It is a Butt Joint to be welded in Horizontal position. G stands for Groove.

For Quality checking, follow the ASME Sec IX.

For 1.8 mm thick sheet welding by MIG process should be as follows:

• Train the welder first in Dip Transfer Mode of metal transfer.
• Use Pulsed Power Source, if possible, which will give you best weld in low thick by MIG.
• If IGBT m/c, Amp= 50 – 60, Volt= 16 – 18, Welding Speed = as fast as possible, Penetration= Excess penetration not acceptable as intimated. This should be as per ASME Sec IX. 

IS-7308 (WPS) & IS-7310 (WPQ).

For full penetration single-sided welds without backing, where the measurement of penetration can be made by visual or mechanical means, requalification is required where the base metal thickness differs by 20% from that of the test coupon thickness when the test coupon thickness is 1 in. (25 mm) and under, and 10% when the test coupon thickness is over 1 in. (25 mm). Where the measurement of penetration cannot be made, requalification is required where the base metal thickness differs by 10% from that of the test coupon when the test coupon thickness is 1 in. (25 mm) and under and 5% when the test coupon thickness is over 1 in. (25 mm). For full penetration single-sided welds with backing and partial penetration welds, the minimum base metal thickness qualified shall be equal to that used for the PQR test coupon. The depth of penetration qualified shall be equal to or greater than that measured on the PQR test coupon.