Written by Ed Craig:
Home page of www.weldreality.com.



PIPE / TUBES..ASTM - API Carbon & Low Alloy Steels.
Also a look at the effectiveness of codes and weld procesess.

PIPE Welding Steels and TIG - MIG and Flux Cored Welds.

Every pipe weld application has unique requirements guided by different codes and specifications. The following pipe weld guide is intended as a quick reference to assist with logical welding decisions. The information provided, is certainly incomplete and implies no guarantees.

All pipe and pressure vessel recommendations should be verified by the applicable codes, especially when heat treatment, low hydrogen and low alloy electrodes are required. No pipe weld should be carried out unless that weld is first qualified. If the weld is required to match the properties of the pipe ensure the alloy content of the electrode is matched and verify the preheat or post heat recommendations.

With the introduction of TIP TIG into the USA, pipe shops now have a single, easy to use process that will produce superior weld results than regular TIG, flux cored or any MIG weld trasfer mode.


When welding low and medium carbon steels, the 70XX stick electrodes, E70S-3-6 MIG wires and E7XT-X flux cored electrodes can be used.

When welding low alloy 1.25% Cr - 0.5 Mo or 2.25 Cr - 1% Mo steels with up to 0.05% max carbon, typically 8018-B2L / 9018-B3L (L = low carbon) can be used.

When welding higher strength alloys or when tempering and quenching are required to attain the higher strengths, the higher carbon 8018 B2 and 9018 B3 electrodes are utilized.

For more pipe welding data follow this link

 

COMMON PIPE ELECTRODES

E6010 Minimum Yield 50,000 psi Minimum Tensile 62,000 psi.
E6011 Minimum Yield 50,000 psi Minimum Tensile 62,000 psi.
E7010 Minimum Yield 60,000 psi Minimum Tensile 72,000 psi.
E7018 Minimum Yield 60,000 psi Minimum Tensile 72,000 psi.

E70S-3 and E70X6 MIG Wires.
Minimum Yield 60,000 psi, Minimum Tensile 72,000 psi



Ed providing MIG and FCAW process control training
to Imperial oil pipe welders on 16 inch nat gas pipe

WELD CODES, EFFECTIVENESS AND INADEQUATE INFOMATION.

When it comes to MIG and flux cored welding, rather than providing weld process resolutions, most codes relevant to pipe welding will provide inadequate information or the information they provide simply adds to the global weld process myths and confusion.

Welding decision makers often look codes such as AWS - API and - ASME to provide practical, pipe welding advice and recommendations. Those individuals that that put all their faith in the codes that are governing the specific weld applications they are working on, need to be aware of a little weld reality, The weld information in these codes has too frequently been written and influenced by code committee individuals who lacked MIG / Flux Cored weld process controls & best practices / application expertise.

50 YEARS AFTER THE INTRODUCTION OF THE "MIG PROCESS",
AND 35 YEARS AFTER THE INTRODUCTION OF FLUX CORED ELECTRODES, THE PRIMARY WELD CODES WHEN ADVISING ON THESE PROCESSES STILL CREATE CONFUSION AND TOO MANY QUESTIONS.

API. 5.2.3 Pulsed Gas Metal Arc Welding (GMAW-P. This code states that the pulsed process may be used for any material thickness and whenever the welding system is changed or the settings on existing equipment are "significantly altered" then the fabricator should verify the weld properties. The extent of verification or testing should be as agreed between the purchaser and fabricator.

In a world in which engineering standards should apply, what the hell does significantly altered mean. In contrast to the traditionaL, two control, MIG or flux cored weld process, there are many weld essential variables that can be readily changed when utilizing the pulsed MIG mode. While the API code warns against a "SIGNIFICANT CHANGE" in a pulsed settings", the real world weld decision maker needs to be aware that an insignificant, small parameter change with the highly sensitive, manual pulsed MIG mode, can have a significant influence on the weld fusion attained.

 

While the code bodies in 2013 have very little negative to say about pulsed MIG process, for those of you with grey hair, you may remember that these same codes typically either did not allow regular MIG or the code weld specifications made incorrect recommendations or negative comments on the use of MIG. For example, for five decades, the MIG short circuit process has been treated like a leper, yet the weld reality was and still is in 2013, the Short Circuit mode is the best weld transfer mode for carbon steel, "rotated" pipe, open root welds.

Most of the pipe shops which were embedded with the SMAW and TIG process would typically not consider using the MIG spray transfer mode for rotated pipe welds, yet the reality has been that MIG spray transfer on the rotated pipe applications should provide superior weld fusion and less porosity than any pulsed MIG transfer.

2103: GLOBAL CODES PROVIDE NO INFORMATION ON THE POOR
PULSED MIG WELD MASS TO WELD ENERGY RATIO:

What most weld decision makers and QA personnel are not aware, is that there is on most all position, pulsed MIG pipe weld applications thicker than 6mm, a poor ratio between the moderate pulsed MIG weld energy attained, (influenced by peak to low back ground current changes) and the high weld deposition rates that typically result. The healthy pulsed MIG weld deposition rates push the high weld speeds, (faster weld speeds don't help weld fusion) along with the resulting large weld mass (larger weld mass creates a hinderance to the weld energy produced).

For those of you moving aggressively forward with the manual pulsed MIG process for your all position pipe welds, do not be surprised even when using the highest manual welder skills, when you X-Ray those sluggish stainless or nickel alloys to find lack of fusion.

YOUR LOCAL SALES REP WONT TELL YOU THIS BECAUSE THEY ARE NOT AWARE OF IT. OPTIMUM PULSED MIG WELD FUSION WITH MANUAL WELDS WILL OFTEN BE CONSIDERED MARGINAL, AND MARGINAL WELD FUSION WILL BE MADE WORSE BY THE MANY PROCESS AND HUMAN VARIABLES THAT INFLUENCE THOSE MANUAL PULSED MIG WELDS.



THE CODE RULES SHOULD CHANGE WITH AUTOMATED PULSED MIG WELDS:



I am not aware of any code that discusses the mechanized versus manual pulsed welding differences and the weld quality consequences of those differences. When a code body puts it's stamp of approval on a weld process such as Pulsed MIG, the code is sending the message that this is process that's acceptable for both manual and mechanized pipe welds.

With automated pulsed MIG pipe line welds in which the use of multi-MIG guns is typical, electronic MIG power source features such as volt or current energy spikes can be applied to the weld weave dwell times. These controlled, increased weld energy spikes will improve the 5G pipe side wall weld fusion. Also the controlled pulsed MIG weld speed, the controlled, mechanized weld weaves and the constant wire stick out. are the automated features that will have a lot to do with success of the mechanized pulsed MIG process when used for pipe line welds. Take away these important controls and as it's been for three plus decades the manual pulsed MIG process has proven that the attainment of 100% X-Ray all position pipe weld quality is a challenge. By the way this is a challenge that weld shops in 2013 do not have to face when they can use the far superior TiP TiG manual or automated weld process.



API. 5.2.2 Short Circuiting Gas Metal Arc Welding (GMAW-S). The use of GMAW-S shall be limited to the following conditions:

[] For vertical welding, the root pass and second pass progression for a material of any thickness may be either uphill or downhill.

Ed's response. There is no logic in using MIG short circuit, with the vertical up position on any weld application. Just as there is no logic in this cold process being used for the second pass which from a weld fusion potential is the most sensitive part of any pipe weld..


[] The fill and cap pass for butt or fillet welds may be welded with the short circuit process, provided the thickness of any member does not exceed 3/8 in. (9.5 mm) and vertical welding is performed with uphill progression.

Ed's response. Watch out for lack of weld fusion with the short circuit process welding vert up on any steel parts > 1/8 (> 3 mm0..

Ed testing both the short circuit and STT process
at the difficult 5 to 7 o'clock position

MIG short circuit welding vertical down, while fine for a rotated pipe, open root welds, this process when utilized in the fixed 5G position can cause root problems between 5 to 7 o'clock over head positions. In this location, unmelted wire will occasionally sticks through the open root gap and root weld suck backs may occur.


In 2001, when I wrote this, the most widely used codes made no mention of the use of Spray Transfer, Globular Transfer, STT or metal cored wires, does that mean they can or cannot be used. or does it mean that the people who write the code weld data have nothing to say on the processes that weld the pipes in the industries the codes are utilized?

 

The weld process considerations and confusion
that now surrounds pipe welding.

QUESTION.
2001: Ed when welding pipes we could use SMAW electrodes, flux cored or metal cored electrodes. We use MIG short circuit, globular, spray, pulsed transfer. We also utilize GTAW the Lincoln STT MIG process and sometimes SAW. As much of the welding process information we get is sales driven and the codes are no help, can you shed some light on the subject of logical weld process and electrode selection for code quality welds?


ANSWER.
Obviously with the many process - consumable choices. many factors have to be considered before selecting a weld process or electrode for pipe welding. When it comes to pipe welding the first question that should be addressed is which weld process is the best process for welding pipes. I could readily write a book on this subject or I can simply say this. Visit www.tiptigusa.com and see a pipe weld quality and productivity never attained with with any of the conventional weld processes used throughout the global pipe welding industry...

Ed testing processes - consumables on Nat Gas pipe welds.

What is Yield strength?. The stress that can be applied to a base metal or weld without permanent deformation of the metal.

What is Tensile strength?. The ulltimate tensile strength, is the maximum tensile strength that the metal or weld can with stand before failure occurs.

What is lamellar tearing?. When welding, the weld shrinkage stresses impose tensile strains in the steel plate or on inclusions paralleled to the plate surface. The tensile strains can separate the inclusions causing cracks. Excessive strains can further elongate the cracks. Carbon, manganese and low alloy steels made at the mill with inadequate deoxidization are sensitive to lamellar tearing. The potential for lamellar tearing increases with the amount of inclusions in the plates being welded. Of special concern is when the inclusions are parallel to the plate surface. More data in ASTM A770 / A770M Standard Spec for through thickness tension testing of steel plates.

 

Mechanical Strength of Gas Shielded Flux Cored Electrodes from the ANSI / AWS A5.29. 1198 Specifications for Low Alloy Steel Electrodes for Flux Cored Arc Welding.

What is Hardness? The resistance of a metal or of a weld to penetration. Hardness is related to the strength of the metal. A good way to test a weld after the weld and heat treatment are complete. is to test the hardness of weld and the base metal HAZ surrounding the weld.

What is Ductility? The amount that a metal or weld will deform without breaking. Measured on welds by the % of elongation in 2 inch 51 mm test piece. An E71T-1 flux cored electrode should result in a minimum of 20% elongation. An E70S--6 MIG weld should produce 22%.

 

What is weld Porosity? Weld porosity, a cavity discontinuity that forms from a weld gas reaction. The weld porosity can be trapped inside the weld or at the weld surface. The porosity is typically round in shape but can also be elongated or any shape.


CLUSTER WELD POROSITY. A localized group of pores with random distribution.
Causes. Arc blow, gas flow inconsistency, intermittent material or wire contamination, poor weld parameters or technique.

PIPING WELD POROSITY. The pore length is longer than it's width. Often in fillet welds the pore is seen working its way from the root towards the weld surface. Typical porosity when using argon oxygen mixes on parts >6 mm. Increase weld energy, slow weld speed avoid weaves.

ALIGNED WELD POROSITY. Linear porosity, an array of round pores in a line. Typically caused from contamination in the metal or electrode. Add energy use arc to break up surface ahead of weld.

ELONGATED WELD POROSITY ( wagon tracks). Typically found parallel to weld axis. Classic porosity when moisture is evident in gas shielded flux cored wires. Increasing the flux cored wire stick out and increasing the wire feed rate will help. Baking flux cored wires and storing wires in a dry environment also reduces potential. For MIG welding slow weld speeds, make welds larger, avoid weaves, add energy to decrease weld cooling rate.

SCATTERED WELD POROSITY. Porosity scattered randomly throughout the weld. If the weld surface is gray and looks oxidized it's typically insufficient gas flow. If the weld surface looks as clean as normal the scattered porosity is usually caused by part or electrode contamination, or weld data that causes the weld to freeze too rapidly

LARGE PORE WELD POROSITY. If weld surface is clean and does not look oxidized, the large pore MIG / FCAW porosity is usually a result of excessive gas flow, gas turbulence with gas flow greater than 40 cuft/hr. If weld surface dirty the cause is often a result of insufficient gas less than 20 cuft /hr.

 

PRE HEAT ALSO MEANS MINIMUM INTER-PASS TEMPERATURE

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2010: Question about Flux Cored:
Ed we had the following lunch room discussion. In our pipe shop we recently started to use gas shielded flux cored consumables. We used to use SMAW and we now know that the FCAW will provide superior weld fusion and deposit at least four times as much as SMAW pipe electrodes. I found out that the flux cored wires we are using have been around for more than 25 years. Ed why did it take many in the the pipe / pressure vessel industry so long to accept the FCAW process?

My Answer could be this simple by using one of the most popular sentances found in a pipe weld shop. "Why change the way we have always done it"

The bottom line is If a company management does not have personell with weld process expertise, then this company does not have the resources or confidence necessary to implement a major weld process change.

The bottom line, for decades most of the oil and pipe companies, power companies, chemical plants and pressure vessel shops lacked qualified weld management and engineers that could lead the weld shops when process change was beneficial. So it's understandable that if you walked into a pipe shop in 1960 and then walked into a pipe shop 50 years later in 2010, that when it came to welding pipes little had changed..

As we are all aware, many SMAW and GTAW pipe welders are often die-hard traditionalists who are proud of their manual skills and often less than enthusiastic to make a change to a process which requires process expertise and different best weld practices.

For example, the SMAW welders would try the flux cored wires, and not undersatnding the process requirements they would then play around with the data and MIG equipment controls. Without optimum settings the flux cored consumables would not perform the way they were designed to perform. The stick welders would be disgruntled with the FCAW process and resist the apathetic attempts by the inexperienced weld management to make the cost affective weld process changes.

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STRESS RELIEVING (SR). BASIC GUIDELINES:

STRESS RELIEF - CONTROLLED HEATING & COOLING TO REDUCE STRESS.

STRESS RELIEF MACHINED PARTS FOR DIMENSIONAL STABILITY.

STRESS RELIEF SLOW HEATING AND COOLING REQUIRED

CONFIRM WITH CODE SPECIFICAIONS FOR STRESS RELIEF REQUIREMENTS.

Should a weld professional in a a pipe / pressure vessel shop be able to tell you;

[a] the 0.045 (1.2mm) and 0.035 (1 mm) MIG wire feed position and weld voltage which is the starting point for spray transfer? These are good settings for rotated pipe fill passes.

[b] the 0.045 gas shielded E71T-1 optimum single wire feed setting and voltage for producing a 6 mm, vert up fillet weld on a plate. This is the same setting for welding anny steel pipe vertical up.

If an industry, in which many of it's educators, engineers and managers places little importance in weld process control training, why should we expect welders to focus on the weld process control or best practices details.

 

Why in the welding industry is it difficult to find anyone in management who knows the real cost of a MIG or flux cored weld?

The weld industry management weld cost focus is too often on something easy to understand like the cost of the weld wire or gas mix, rather than on the MIG or flux cored, semi-automatic weld deposition rates attained. When I first bought TiP TiG to North America and discussed with weld shop owners the weld deposition rate differences between TiP TiG and GTAW - FCAW and pulsed MIG, I would too often see the glaze look in the manager's or engineer's eyes. Thats the same look I see in my wifes eyes when i chat to her about welding

When an industry ignores or is not aware of the weld process / application weld deposition rate potential, it's understandable when the real cost of a weld is rarely understood.

What shortage of skilled welders.

The manager states, "how will we ever replace this aging, highly skilled weld workforce"?

TIG - MIG and FCAW Weld Reality:
With all the issues that occur with welding, managers often perceive that the weld processes used in the weld shop must be complex, after all, these processes have been around for decades, yet the weld personel seem to have to play around with the weld controls whenever a new application comes into the weld shop.

THE PIPE SKILLED SHORTAGE WELD REALITY:

It's important to note that for code quality pipe welds, that the TIP TIG process eliminates at least 50% of the GTAW skills required for pipe welds. The majority of weld issues that occur daily in pipe weld shops are a result of an industry and educational system that for decades has placed minimal focus or importance on weld process controls and best weld practice expertise.

WHY THERE SHOULD BE LITTLE CONCERN FOR SKILLED PIPE WELDER SHORTAGES:
While community colleges take many months and sometimes years to train personnel to weld pipe, the following is the weld reality. When training a suitable individual who has never welded, it would take me no more than 5 days to train a TIP TIG welder to weld all position (5G) pipes, and the same 5 days to train that person to weld the pipes with either the MIG / flux cored process. Those trainess would then have the ability to pass any weld qualification test and meet any code requirements.




WELD PERSONNEL WHO ARE PROUD OF THEIR SKILLS SHOULD ALSO TAKE PRIDE IN THEIR WELD PROCESS KNOWLEDGE AND IN THEIR ABILITY TO CNROLL THE WELD PROCESSES AND CONSUMABLES THEY OPERATE.

Consider my CD process control training resources, they are a great training aid for guys who dont want to "play around" with their weld controls..

What is Toughness? The ability of the metal or weld sample at a predetermined temperature to withstand a shock. The test for toughness measures the impact of a pendulum on a notched specimen. You may see that the required impact properties for the metal or weld are 20ft-lbf @ -20 F (27 j @ -29C). Some things that can influence toughness in a weld;

[] lack of fusion.
[] excess weld heat.
[] porosity in welds and laminations in the steels.
[] weld undercut.
[] incorrect weld profiles
[] incorrect weld consumables.

What is Fatigue? The ability of a metal or weld to withstand repeated loads. Fatigue failures occur at stress levels less than the metal or weld yield strength. Some things that can influence fatigue failure:

• Excess weld profiles.
• Welds which cause undercut.
• FCAW or SMAW slag inclusions.
• Lack of weld penetration.
• Excess weld heat, typically from multi-pass welds without inter-pass temp controls.
• Items to a part that adds restraint while welding.
• Items added to a part that can concentrate stresses in a specific location.
• Incorrect selection of filler metal, weld too weak or weld too strong.
  
  

What is Brittleness? The ease at which the weld or metal will break or crack without appreciable deformation. When a metal gets harder it becomes more brittle. Preheat, inter-pass temp controls and post heat all are designed to reduce the potential for brittleness.

What is Malleability? The ability of a metal or weld to be permanently deformed by compression such as in a rolling or forming operation. Ductile metals are malleable.

What is grain size? A good way to demonstrate the effect of the grain size on a metal or weld. Take a full length wooden pencil, then break it in half, now break the two halves in two, try it again. You will note how difficult it is to break the smaller pieces. When we weld, the heat from the weld can make the grains in the base metal elongate, as the weld cools down the grains will get smaller. If we are doing multi-pass welds such as welding in the vee-prep of a pipe, and we don't have inter-pass, or post heat controls the welds may look good, however the high energy from the mult-pass welds may result in grain size greater than that approved by the pipe / steel manufactures. In fatigue situations, elongated grains can influence failure.

HAVE YOU EVER PURCHASED A BOOK ON WELDING?
Most welding books can be boring and few provide practical, cost effective weld data. My books are easy to read and every page will make you a weld process expert.

 

Ed, why can't we use an E71T-1 flux cored wire and weld the pipe root pass and also weld the pipe fill passes vertical down?

You don't want to use the flux cored process for roots or any gaps, as the arc energy is too high, also when welding vertical down with a flux cored wire, you will trap the fast freeze slag.

1990s: Ed Teaching Jessie, age 11,
how to do the pipe MIG root pass

Visit the MIG and flux cored pipe weld data section