Thursday, April 15, 2010

Re: [MW:4832] cellulose electrodes.

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.

 

 

 

 

 

 

 

􀀵􀁂􀁃􀁍􀁆􀀁􀀔􀀏

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

􀀧



 
On Wed, Apr 14, 2010 at 9:54 PM, prashant pansare <prashantpan_99@yahoo.co.in> wrote:
Dear all,
What r advantages & dis-advantages of cellulose electrodes.
Pl. reply.
psp

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