Welding

Welding

Welding Expert

Apurba Kumar Sanyal

Apurba Kumar Sanyal

Diploma in "International Welding Specialist" (IWS-IIW) of International Institute of Welding.

More than 40 years experience in the field of welding:

a. 20 years in production welding.

b. 11 years in welding inspection & QC.

c. 10 years in Welding Training.

Wise experience in Welding & Fabrication consisting of Pressure Vessels & Heat Exchanger, Piping, Shipbuilding & Repairing , Structural , Earth moving Equipment , Panel & Drum(Power Sector), NDT, Welding Electrodes Development & up-gradation (R & D) and Training.

All Questions

41 Questions

1
Answer

What is the SST life (5% rust) of the weld bead of an arc weld & gas weld respectively?

Thank you for your query. To be able to answer your question satisfactorily, the expert has requested additional details - type of steel, why 5%, sensistisation done, welding parameters?  Please provide details and you may upload a picture as well. 

1
Answer

What should be the weld time for MIG welding and spot welding?

Experts answer (NWRTI): There are three possible answrs: 1) GMAW process is used for a Fusion Joint where as Spot Welding is a Non Fusion joint. Hence, time of welding cannot be compared 2) Time depends up on Type and Nature of Joints. Whereas GMAW process is usually applied on plates, Spot Welding is restricted for thin sheets. 3) If GMAW process is applied on thin sheets, in that case, time required shall be more than Spot Welding for a specified length. It also depends on no. of spots to be welded for that particular length. In both the cases,the joints have to be Lap Joint.
Practically, all the data are required and mode of metal transfer in GMAW process is required to be known to calculate the welding time. Thank you for giving us a chance to serve you.

1
Answer

What should be the weld time for MIG welding and spot welding?

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.

1
Answer

Do current settings change with changes in metal thickness?

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

1
Answer

Does gas volume differ for different thicknesses, if yes what could be litre per minute flow?

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.

1
Answer

Does arc length vary with the thickness of substrate or mechanical properties?

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.

1
Answer

What is the relation between arc length and HAZ?

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. 

1
Answer

What is effect of sheet thickness on arc length?

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.

1
Answer

In Stainless Steel welding, how can we reduce the bulging / uneven surface?

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

1
Answer

Is there any method to reduce the MIG weld bead or it is operator skill?

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).

1
Answer

Which strength is more, MIG or TIG welding?

Strength and weld quality are better in TIG Process.

1
Answer

What should be CO2 pressure in MIG welding?

Generally CO2, 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.

1
Answer

How can we define welding current?

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

1
Answer

What is the reason of short filling?

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

1
Answer

Is there any particular reason why Argon is mixed with CO2?

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.

1
Answer

How to do a leak proof welding suitable for MPI test?

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.

1
Answer

Some welding electrodes throw more fire during welding as compared to other, why?

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.

1
Answer

What can we do for the prevention of smoke released during welding?

Use “Fumes Extractor” available in the market.

1
Answer

What is 2G?

This is Butt Joint to be welded in Horizontal position.

1
Answer

What temperature is required for proper fusion?

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.

1
Answer

What is GIZMAG?

Gizmag covers the full spectrum of new and emerging technologies, invention, innovation, and science news.

1
Answer

What is IAC?

IACS: International Association of Classification Societies.

1
Answer

How is distortion calculated?

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)

1
Answer

Blow holes in ZA Sheet during CO2 Mig welding, what is the remedy?

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. 

1
Answer

What is COLD Metal Transfer welding?

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.

1
Answer

If CO2 used in Robotic what will be the effects?

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

1
Answer

How lit/min is calculated or defined?

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.

1
Answer

What is cc type source?

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

1
Answer

How to reduce bulging in SS 1 mm sheet during MIG Welding?

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.

1
Answer

Suggest Best Welding Practice for Stainless Steel Welding?

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.

1
Answer

How to control bulging of Stainless Steel Welding?

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)

1
Answer

What is ideal length of stick-out for 0.8 or 1.2 diameter electrodes?

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.

1
Answer

How to avoid spatter problem in projection nut welding?

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.

1
Answer

How to re-dry electrodes?

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.

1
Answer

How to select Electrode Diameter in MIG welding?

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.

1
Answer

What is the relation between current & thickness of material?

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

1
Answer

What is 2 G?

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

1
Answer

What tests should we do for quality verification of resistance seam welding on 0.5 mm ms sheet?

For Quality checking, follow the ASME Sec IX.

1
Answer

For 1.8 mm MS sheet, MIG Welding we are using current 220A, Voltage 22 - 25 V, Gas Ar & Co2 80:20, penetration observed was 20 to 30%. What to do now for improvement in circular parts of 250 mm Dia.?

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. 

1
Answer

Which Indian standard can be referred for penetration, mechanical strength for 1.8 mm sheet MIG Welding?

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

1
Answer

What should be the minimum penetration for good strength in MIG Welding?

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.