Metal & Oil & Gas News – Nctv.net
The process of welding stainless steel pipe usually consists of three kinds of soldering, filling and cover welding. The
backing welding is the most important part of the stainless steel tube welding
process, which is related to the quality and progress of the project. It
includes two processes: back filling argon and not argon filling. The backside
argon filling protection is also divided into two kinds: solid core wire plus
TIG process, solid core wire plus TIG and water soluble paper technology, while
the back without argon protection is also divided into two kinds: flux cored
wire backing welding, welding rod bottom welding and TIG welding.
The use of stainless steel backing welding
method is TIG process, according to the actual situation, can have the
following four ways to do the backing welding processing, respectively by using
the method of blocking back sealing plate ventilation protection; the second is
only using soluble paper or combined with the method of blocking protection
ventilation using soluble paper and blocking plate the use of TIG base cored
wire; welding; use of flux cored wire TIG welding backing.
The first is the use of the back blocking
method for sealing plate ventilation protection, in prefabricated stainless
steel pipe, welding need to do rotary welding, are usually easier, this method
is generally used for blocking plate pipe welding on both sides of the mouth to
block the ventilation protection of backing welding at the same time, the outer
side of the adhesive used cloth plugging.
When welding, to use the advance, lag
process gas, lateral adhesive selvage welding edge tear, because the blocking
plate is composed of rubber and tin, is not easy to damage, so that the welding
process can ensure good weld inside filled with argon and ensure its purity, in
order to effectively ensure the weld metal is not inside oxidation, ensure the
quality of weld backing welding.
The second is to use only soluble paper or
the combination of soluble paper and plugged plate for blocking ventilation
protection. Because when stainless steel pipes are fixed and welded, the inside
ventilation is difficult, and some sides are easier to block. In such cases,
water soluble paper and blocking plate can be used for plugging. That is to
say, one side is easy to ventilate and dismantle, and the side is blocked by
blocking plate, and it is not easy to ventilate. It is difficult to remove the
side of the blocking plate and use water soluble paper to do the plugging. And
the outer side is glued with cloth to paste the weld line for plugging.
Stainless steel fixed mouth in welding,
weld on both sides have not ventilation in most cases of the phenomenon, how to
ensure that the inner weld argon protection is a difficult problem, in actual
construction, the use of both sides of the weld of water soluble paper
plugging, pass gas, from the weld center outside the use of adhesive cloth
paste do plugging this method can effectively solve the above problems.
When water soluble paper is used to plug
and ventilate, because it is ventilated from the weld center, in the final
sealing part, we need to quickly insert the vent pipe, and use the remaining
argon inside to protect it, and quickly finish the bottom and seal the mouth.
Using this approach, we should pay
attention to water soluble paper to use double, need is stuck, or will cause
water soluble paper damage loss and the inside of the weld without the
protection of argon, oxidized, cause the weld cut re welding, which can not
guarantee the welding quality, and has seriously affected the period.
Therefore, before welding should strictly check, paste the water soluble paper.
In most construction sites, this welding
method is usually used to make the bottoming. Its quality can be obviously
guaranteed, and at the same time, there is still a certain degree of difficulty
in construction. Therefore, a careful and skilled welder is needed to do this
work.
The third way is not to carry out argon
protection on the back, using flux cored wire plus TIG technology. This method
has been used for many years in China, and the corresponding products have been
used in the field welding, which has achieved relatively good economic
benefits.
Because the back is not filled with argon,
its advantages are also very obvious, the main performance is high efficiency,
convenience, low cost, suitable for installation in the construction site.
However, because of its structural characteristics, the flux cored wire has
high requirements for welders. The wire feeding speed is fast and the accuracy
of wire feeding is also very high. It is difficult to master fully. The welders
should be trained by special training and skilled.
The last one is the back without argon
protection, the use of flux cored wire with TIG process, in the last century in
90s, Japan’s Kobelco and other companies developed grounding wire, and all
these years has been developed and applied in the grounding wire of stainless
steel in the actual construction, obtained very good effect.
The protection mechanism of this process is
to protect the weld metal from molten slag formed by welding wire and
metallurgical reaction of other alloying elements on the back weld. The frontal
weld is protected by argon, slag and alloying elements.
Source: China Stainless Steel Pipes
Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)
