cellulose electrodes.

[prashant pansare]

Dear all, What r advantages & dis-advantages of cellulose electrodes. Pl. reply. psp

[Shashank Vagal]

Advantages- cellulose burns to give off gas cloud that protects the weld; deep penetrating arc (difficult to weld areas can be filled) Disadvantages - No baking allowed, so moisture pick up due to poor storage is likely; can not be used on Q&T steels --- On Wed, 14/4/10, prashant pansare <prashan...@yahoo.co.in> wrote:

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[Muzib_ur_Rahuman.]

Dear Mr.Prashant ,I hope thins information be useful about cellulose Electrodes.

 

DH: Downward Welding with High-

Cellulose Electrodes Is Fastest in Root

Pass Welding

In the construction of cross-field pipelines, the highly

efficient spread method is used worldwide, in which a

series of combined operations proceed continuously in a

certain order at a constant speed: leveling the land,

ditching, placing the pipe, machining, welding,

inspecting, coating, and burying the pipe. In this case,

root pass welding efficiency is believed to be a key

factor that determines how fast a pipeline is constructed.

High-cellulose electrodes offer superior welding speeds

as shown in

􀀧􀁊􀁈􀀏􀀁 􀀒. This is the main reason for the

predominant use of high-cellulose electrodes.

However, the weld metal of high-cellulose electrodes

contains higher amounts of diffusible hydrogen than that

of low-hydrogen electrodes.

 

As the content of diffusible hydrogen increases, the

weld metal becomes more susceptible to cold cracking.

In addition, high-cellulose weld metals contain more

oxygen than low-hydrogen weld metals. Because of its

higher oxygen content, the high-cellulose weld metal

exhibits lower impact values compared with the lowhydrogen

weld metal at low temperatures

Therefore, the DH procedure is very useful

particularly in comparatively low-strength, thin-section

pipes for which the impact requirement is not strict and

the crack susceptibility is not high. With this procedure,

stricter controls of preheating and interpass temperatures

are needed to prevent cold cracking than with the

procedures using low-hydrogen electrodes.

 

 

 

 

 

 

 

􀀵􀁂􀁃􀁍􀁆􀀁􀀔􀀏

􀀬􀀰􀀣􀀦􀀭􀀤􀀰􀀁􀁄􀁐􀁗􀁆􀁓􀁆􀁅􀀁􀁆􀁍􀁆􀁄􀁕􀁓􀁐􀁅􀁆􀁔􀀁􀁔􀁖􀁊􀁕􀁂􀁃􀁍􀁆􀀁􀁇􀁐􀁓􀀁􀀢􀀱􀀪􀀁􀁈􀁓􀁂􀁅􀁆􀀁􀁑􀁊􀁑􀁆􀁔􀀁

􀀧

 

--
To post to this group, send email to material...@googlegroups.com
To unsubscribe from this group, send email to materials-weld...@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.

--
K.Muzip ur Rahuman.
QA/QC Coordinator.

BLNG - PROJECTS
Adinin Works Engg.
Brunei

Mob;006737170703

[John Henning]

The primary advantage to cellulose electrodes (EXX10 and EXX11) is that they form a thin slag cover and are what Lincoln electric called "fast freeze".  They produce a deeply penetrating arc but because of the thin slag, solidify rapidily.  Therefore they are very good at bridging gaps and were used for making root passes in piping/pipe lines.

 

The major disadvantage is that the cellulose, a hydrocarbon, breaks down in the heat of the arc and produces copious hydrogen which is absorbed into the molten weld pool.  These electrodes produce the highest weld metal hydrogen of all common practices/processes.  Therefore they may cause hydrogen assisted cracking if the other required factors are present.   

 

A minor disadvantage is that the weld is coarse in appearance due to the high solidification rate and therefore may lack visual appeal.

 

John

---

From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of prashant pansare
Sent: Wednesday, April 14, 2010 8:55 AM
To: mat wel

Subject: [MW:4827] cellulose electrodes.

[Yadav Shiva]

Dear all,

Advantages:

Cellulose electrodes are good for vertical down welding.

- Deep penetrating welding in every position,
- Vertical down welding capability,
- Weld metal with good mechanical properties.

Cellulosic manual electrodes with vertical-down progression has been used for decades. It offers fast travel speeds and can accommodate poor fit-up.

• Pipe strength: While cellulosic electrodes are suitable for low strength pipe, higher strength pipe and weld metal require low hydrogen electrodes to minimize cracking.

• However, past experience has shown that high strength steel pipe can be successfully welded using a cellulosic root and hot pass with proper preheat and filling the remainder of the joint with a low hydrogen electrode.

  
  

disadvantage

However, there main drawbacks:

1) It leaves deep undercut grooves along the edges of the weld face, commonly referred to as wagon tracks; and

 2) it usually is necessary to expose these wagon tracks so they can be consumed by the next weld pass — the “hot” pass. This is done by removing the weld crown by grinding.

3)Thus, using cellulosic electrodes requires extra time after welding the root pass to remove part of the weld and then replace this with new weld metal.

4) Also, cellulosic electrodes produce weld metal with relatively high levels of weld diffusible hydrogen, rendering it crack sensitive when used on higher strength pipe grades.
welding.Its drawbacks 

5) Diffusible hydrogen: Some requirements specify only electrodes that meet a certain maximum weld metal diffusible hydrogen level may be used. In these cases, cellulosic electrodes are usually prohibited.

6)This increase in strength has caused some issues, especially when using cellulosic electrodes which are sensitive to cracking on higher strength steels. It is usually recommended to weld high strength steel with low hydrogen electrode for all passes.

 

Regards,

 

Yadav Shiva Chelliya,
Inspection Engineer,
Doha Qatar,
+974-6166465

[Darcy Morin]

On the consideration of diffusible hydrogen and cellulosic electrodes ie. E6010:

The lower mechanical values do occur in the "as-welded" condition. However, as the product ages (30-60 days), the diffusible hydrogen diffuses from the weld metal and the final "in-service" weld has mechanical properties very similar to the low-hydrogen ie. E7018 weld deposit.

[Yadav Shiva]

Cellulose electrodes are good for vertical down welding.

- Deep penetrating welding in every position,
- Vertical down welding capability,
- Weld metal with good mechanical properties.

Cellulosic manual electrodes with vertical-down progression has been used for decades. It offers fast travel speeds and can accommodate poor fit-up.

• Pipe strength: While cellulosic electrodes are suitable for low strength pipe, higher strength pipe and weld metal require low hydrogen electrodes to minimize cracking.

• However, past experience has shown that high strength steel pipe can be successfully welded using a cellulosic root and hot pass with proper preheat and filling the remainder of the joint with a low hydrogen electrode.

  
  

disadvantage

However, there main drawbacks:

1) It leaves deep undercut grooves along the edges of the weld face, commonly referred to as wagon tracks; and

 2) it usually is necessary to expose these wagon tracks so they can be consumed by the next weld pass — the “hot” pass. This is done by removing the weld crown by grinding.

3)Thus, using cellulosic electrodes requires extra time after welding the root pass to remove part of the weld and then replace this with new weld metal.

4) Also, cellulosic electrodes produce weld metal with relatively high levels of weld diffusible hydrogen, rendering it crack sensitive when used on higher strength pipe grades.
welding.Its drawbacks 

5) Diffusible hydrogen: Some requirements specify only electrodes that meet a certain maximum weld metal diffusible hydrogen level may be used. In these cases, cellulosic electrodes are usually prohibited.

6)This increase in strength has caused some issues, especially when using cellulosic electrodes which are sensitive to cracking on higher strength steels. It is usually recommended to weld high strength steel with low hydrogen electrode for all passes

 

On Wed, Apr 14, 2010 at 7:51 PM, John Henning <jhen...@deltak.com> wrote:

--