316L stainless steel has good resistance to
chloride erosion, so it is usually used in the marine environment. Stainless
steel pipe with the development of social and economic development, its
application has been more and more widely popularized. For the Qinhuangdao Port
Authority Oil Terminal Pipeline Laying Project using 316L stainless steel pipeline with a total length of 1630m, about 280 welded joints are equal wall
thickness pipe welding, according to the welding properties of the steel to
select the performance of the welding material to match the performance of the
steel. In accordance with the relevant technical requirements of the welding
process test and evaluation, the welding process has been successfully applied
to the construction site.
Base material and welding consumables: the
base material is 316L seamless stainless steel pipe; specifications shall be
quasi 159mm × 5mm. 316L seamless stainless steel pipe chemical composition and
mechanical properties are shown in Table 1,2.
Table.1 316L seamless stainless steel pipe
chemical composition (mass fraction) (%)
Table.2 Mechanical properties of 316L seamless stainless steel pipe
|Yield strength ReL/MPa
|Tensile strength Rm/MPa
|Elongation A (%)
As the thermal conductivity of 316L
stainless steel is small and the coefficient of thermal expansion is large, it
is easy to produce large deformation and welding stress when welding; therefore,
the welding energy should be selected as far as possible to concentrate the
Due to the small thermal conductivity of
austenitic stainless steel, in the same current, it can be compared to low
alloy steel to get a larger depth of fusion. At the same time and because of
its large resistivity, in electrode arc welding, in order to avoid reddening of
the electrode, compared with the same diameter of carbon steel or low alloy
steel electrodes, the welding current is smaller.
Regarding the selection of welding process
parameters, generally smaller welding heat input is used for welding. When
welding rod arc welding, it is appropriate to use small diameter welding rod,
fast multi-pass welding, for the high requirements of the weld, and even the
use of pouring cold water to accelerate the cooling method. Due to the large
sensitivity to thermal cracking, it is more important to strictly control the
welding heat input to prevent serious growth of weld grain and the occurrence
of welding thermal cracking.
In order to improve the weld's thermal
crack resistance and corrosion resistance, welding pays special attention to
the weld zone and prevents harmful elements from penetrating into the weld.
316L stainless steel welding generally does
not require preheating. In order to prevent the weld and heat-affected zone
grain growth and carbide precipitation, to ensure the plasticity, toughness,
and corrosion resistance of welded joints, control the lower inter-channel
temperature, generally not more than 150 ℃.
316L stainless steel seamless steel pipe
using electrode arc welding, tungsten argon arc welding 2 methods, bottoming
filler using argon arc welding, filler, cover surface using electrode arc
welding. Tungsten tungsten arc welding choose H00Cr19Ni12Mo2Cu2 wire,
specifications: quasi 2.0 mm; electrode arc welding choose A022 electrode,
specifications: filler welding quasi 2.0 mm, cover welding quasi 2.5 mm.
H00Cr19Ni12Mo2Cu2 wire features smooth wire feeding, arc combustion
stabilization, weld shaping, and spatter is very little; the mechanical
properties of molten metal are Stable, and there is a high X-ray qualification
rate. Excellent corrosion resistance, ultra-low carbon content, and high Mo
content can prevent intergranular corrosion, no heat treatment after welding,
high-temperature strength, and corrosion-resistant wire. Its chemical
composition is shown in Table 3,4.
Table.3 H00Cr19Ni12Mo2Cu2 wire chemical composition (mass fraction) (%)
Table.4 Chemical composition of A022
welding rod (mass fraction) (%)
A022 electrode features: titanium calcium
flux skin of ultra-low carbon stainless steel electrode, its molten metal w (C)≤ 0.04%, with good heat resistance, corrosion
resistance and anti-cracking, anti-porosity properties, good operating process
performance, good red resistance of the flux skin, good strength, can be AC and
DC dual-use. They are used for welding petroleum pipelines, urea, synthetic
fibers and other equipment and the same type of stainless steel structure.
Welding equipment: tungsten argon arc
welding using a TIG400 type welding machine, electrode arc welding using a WSE-315
type welding machine.
316L stainless steel pipe welding, due to
thermal cracking sensitivity, should strictly control the welding heat input to
prevent the weld grain from serious growth and welding thermal cracking occurring
(using a small welding heat input, as far as possible to use a short arc does
not swing or small swing multi-layer multi-channel welding to reduce the degree
of oxidation). Welding process: small current, fast welding, control inter-pass
temperature is not higher than 80 ℃; the specific welding process parameters are shown in Table 5.
Table.5 Welding process parameters
|Weld bead or weld layer
|Tungsten inert gas arc welding
|Welding rod arc welding
|Welding rod arc welding
Bevel form using a V-shaped bevel, the
blunt edge of the bevel is smaller than the blunt edge of the bevel when
welding carbon steel, about 1.5 mm, the bevel angle is larger than the carbon
steel bevel angle, the form is shown in Figure 1.
Figure 1 Weld bevel form and size
Due to the viscous flow of stainless steel
molten metal, the use of a larger bevel angle of 70 ° to prevent the occurrence
of poor fusion phenomenon while reducing the fusion ratio in welding to ensure
that the welding process parameters are stable to ensure that the stability of
the weld composition; in order to ensure the quality of the root welding weld
channel, the pipe must be filled with argon protection to ensure that the back
of the single-side weld is well formed, and try to send the wire inward when
welding to avoid the occurrence of the root of the inner concave.
Figure.2 316L stainless steel pipe
segmented welding diagram
The welding process must control the
(1) Appearance check for good molding (no
defects such as porosity, slag entrapment, depression, etc.).
(2) The test proves that the mechanical
property index is good. Tensile strength, bending, and hardness test results
are shown in Table 6.
Table.6 Mechanical properties test results
Tensile strength Rm/MPa
Bending test d=4a, 180 °
Heat Affected Zone
(3) Macroscopic metallographic examination,
weld fusion is good, and the depth of fusion meets the requirements (about
1.2 mm). Microscopic metallographic examination, the weld metal is 95% austenite
+5% ferrite organization, intergranular corrosion resistance requirements can
be guaranteed, and the site construction to ensure the quality of welding
(4) In accordance with Q/SYXQ42003
"West-East Gas Pipeline Project Welding Construction and Acceptance
Specification", 100% weld flaw detection testing, fully automatic
ultrasonic testing in line with the Q/SYXQ7-2002 "West-East Gas Pipeline
Project Pipeline Butt Ring Weld Fully Automated Ultrasonic Detection," the
provisions of the one-time test pass rate of 93%, unqualified welds Rework, the
grass-roots level using a grinding wheel to remove defects, weld repair
according to the original test standard inspection, repair should not be more
than 2 times, repair weld testing pass rate of 100%.
According to the 316L stainless steel
material weldability analysis and relevant technical standards, and through the
test demonstration, the development of a realistic welding process, the use of
this process completed the pipeline laying project after nearly a few years of
use of the pipeline did not happen to weld the problem, to solve the problem of
welding, and at the same time also for peers in the encounter of similar
problems to provide a reference.
Author: Wang Yuhong
Tel No：+86-18267732328 / Email:[email protected]
Address：Longwan District, Wenzhou, Zhejiang Province, China.
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