Choosing the Right Stainless Steel Welding Electrode: A Complete Guide

Stainless steel welding rods are mainly used for welding corrosion-resistant or heat-resistant steel with chromium content greater than 10.5% and nickel content less than 50%.

The selection should be based on the stainless steel material and working conditions such as operating temperature, contact medium, etc.

For heat-resistant stainless steel operating under high temperature conditions, it is important to satisfy the thermal crack resistance performance of the weld and the high temperature performance of the welded joint.

For heat-resistant austenitic steels such as 10Cr18Ni9TI and Cr17Ni13, where the ratio of chromium content to nickel content is greater than 1, austenite-ferrite stainless steel welding rods are typically used.

For heat-resistant stabilized austenitic steels such as Cr16Ni25Mo6 and Cr15Ni25W4Ti2, where this ratio is less than 1, while ensuring that the weld metal has a similar chemical composition to the base metal, it is recommended to increase the content of elements such as Mo, W , Mn in the weld metal to increase the crack resistance of the weld.

For corrosion-resistant stainless steel operating in various corrosive media, the selection of stainless steel welding rods should be based on the working medium and temperature.

For operations at temperatures above 300°C in highly corrosive environments, welding rods with stabilized elements such as Ti or Nb or ultra-low carbon stainless steel welding rods are often chosen.

For media containing dilute sulfuric or hydrochloric acid, welding rods with Mo or Mo and Cu are generally preferred.

For equipment operating at normal temperatures with low corrosivity, or simply to avoid rust contamination, it is common to opt for stainless steel rods without Ti or Nb.

For chromium stainless steel, such as 12Cr13 martensitic stainless steel, 10Cr17Ti ferritic stainless steel, etc., to increase the plasticity of the welded joint, chromium-nickel austenitic stainless steel welding rods are often employed.

Stainless Steel Welding Rod Model Number

According to the provisions of GB/T983-2012 “Stainless Steel Welding Rods”, the model number of stainless steel welding rods is divided based on the chemical composition of the deposited metal, coating type, welding position and type of welding current.

The model number compilation method is as follows:

a) The first part is represented by the letter “E” to indicate the welding electrode.

b) The second part is the number that accompanies the letter “E”, indicating the classification of the chemical composition of the deposited metal. The letter “L” indicates a lower carbon content and the letter “H” indicates a higher carbon content. If there are other special requirements for the chemical composition, this is represented by the elementary symbol placed after the number.

c) The third part is the first digit after the hyphen “-“, indicating the welding position, according to Table 2.

Table 2 Welding Position Code

Code	Welding position
-1	PA, PB, PD, PF
-two	PA, PB
-4	PA, PB, PD, PF, PG

The explosive welding position is shown in GB/T16672, where PA = flat welding, PB = flat angle welding, PD = elevation angle welding, PF = vertical upward welding, PG = vertical downward welding

d) The fourth part is the last digit, indicating the type of coating and type of current, according to Table 3.

Table 3 Coating Type Codes

Code	Type of coating	Current type
5	Alkalinity	CC
6	Rutile	AC and DC (a)
7	Type of titanic acid	AC and DC (b)

Template example

Examples of complete electrode models in this standard are as follows:

E 308-1 6

• E – Indicates that the coating type is Rutile, suitable for AC/DC welding
• 308 – Classification code for chemical composition of deposited metal
• 1 – Indication of the welding position
• 6 – Welding indicator rod

Common austenitic, martensitic, and ferritic stainless steel welding rod selections

Here are some specific selections of common austenitic, martensitic, and ferritic stainless steel welding rods:

1. Choosing austenitic stainless steel welding rods (see Table 1)

To ensure that the weld metal of austenitic stainless steel maintains the same corrosion resistance and other properties as the base metal, the carbon content of austenitic stainless steel welding rods should not be higher than that of the base metal.

Table 1 Selection of commonly used austenitic stainless steel welding rods

Steel Grade	Welding Rod Selection
	Note	Model
022Cr19Ni10 06Cr18Ni9	A002 A002 AA001G15	E308L-16 E308L-17 E308L-15
06Cr19Ni9	A101 A102 A102A A107	E308-16 E308-17 E308-15
10Cr18Ni9 10Cr18Ni9Ti	A112 A132 A137	– E347-16
06Cr18Ni10Ti 06Cr18Ni11Nb	A132 A137	E347-16 E347-15
10Cr18Ni12Mo2Ti 06Cr18Ni12Mo2Ti	A202 A201 A207	E316-16 E316-15
06Cr23Ni13 06Cr25Ni13	A302 A301 A307	E309-16 E309-15
10Cr25Ni18 06Cr25Ni20	A402 A407	E310-16 E310-15

2. Choosing martensitic stainless steel welding rods (see Table 2)

There are two types of rods used for welding martensitic stainless steel: chromium-chromium stainless steel welding rods and chromium-nickel austenitic stainless steel welding rods.

Table 2 Selection of common martensitic stainless steel electrodes

Steel Grade	Welding Rod Selection
	Note	Model
12Ch13 20Cr13	G202 G207 G217	E410-16 E410-15
	A102 A107 A302 A307 A402 A407	E308-16 E308-15 E309-16 E309-15 E410-16 E410-15 E410-15
14Cr17Ni2	G302 G307	E430-16 E430-15
	A102 A107 A302 A307 A402 A407	E308-16 E308-15 E309-16 E309-15 E410-16 E410-15 E410-15

3. Choosing ferritic stainless steel welding rods (see Table 3)

Due to the low toughness of metal deposited from ferritic welding materials, combined with the difficulty of effectively transitioning added ferrite-forming elements such as Al and Ti into the weld pool, ferritic welding rods are not widely used.

Table 3 Selection of Ferritic Stainless Steel Welding Rods

Steel Grade	Welding Rod Selection
	Note	Model
022Cr12 06Cr13	G202 G207 G217	E410-16 E410-15
	A302 A307 A402 A407	E309-16 E309-15 E310-16 E310-15
10Cr17 10Cr17Mo 022Cr17Mo 022Cr18Mo2 06Cr17Ti 10Cr17Ti	G302 G307	E430-16 E430-15
	A202 A207 A302 A307 A402 A407	E316-16 E316-15 E309-16 E309-15 E309-15 E310-15 E310-16 E310-15

Stainless Steel Welding Rod Selection Chart

Note	Standard model number (GB)	American Standard Model Number (AWS)	Type of coating	Welding current	Main applications
G202	E410-16	E410-16	Titanium-calcium type	AC/DC	Welding 0Cr13, 1Cr13 surfaces and wear and corrosion resistant surfaces.
G207	E410-15	E410-15	Low hydrogen type	CC	Welding of surface build-ups on 0Cr13, 1Cr13 and wear and corrosion resistant materials.
G217	E410-15	E410-15	Low hydrogen type	CC	Surface coating welding on 0Cr13, 1Cr13 and materials with resistance to wear and corrosion.
G302	E430-16	E430-16	Titanium-calcium type	AC/DC	Cr17 stainless steel welding.
G307	E430-15	E430-15	Low hydrogen type	CC	Cr17 stainless steel welding.
A002	E308L-16	E308L-16	Titanium-calcium type	AC/DC	Welding of ultra-low carbon Cr19Ni11 stainless steel and 0Cr19Ni10 stainless steel structures, such as synthetic fiber, fertilizer, petroleum and other equipment.
A012Si			Titanium-calcium type	AC/DC	Welding ultra-low carbon C2 steel (OOCr17Ni15Si4Nb) used for resistance to concentrated nitric acid.
A022	E316L-16	E316L-16	Titanium-calcium type	AC/DC	Welding of urea and synthetic fiber equipment.
A002N	E316L-16	E316L-16	Titanium-calcium type	AC/DC	Mainly used for welding 316LN stainless steel structures.
A022Si	A		Titanium-calcium type	AC/DC	Used for welding 3RE60 cladding plates or tubes in foundry equipment manufacturing.
A022MO	E317L-16	E317L-16	Titanium-calcium type	AC/DC	Used for welding ultra-low carbon stainless steel 00Cr18Ni12Mo3, as well as for welding chrome stainless steels and composite steels that cannot undergo post-welding heat treatment, as well as different steels.
A032	E317MoCuL-16	E317L-16	Titanium-calcium type	AC/DC	Welding of ultra-low carbon stainless steel structures in equipment used for synthetic fibers and other applications, operating in dilute to medium sulfuric acid environments.
A042	E309MoL-16	E309MOL-16	Titanium-calcium type	AC/DC	Welding of cladding plates and overlay welding in urea synthesis towers, as well as welding of structures of the same type of ultra-low carbon stainless steel.
A052	A	1	Titanium-calcium type	AC/DC	Welding of reactors, separators and other equipment used in sulfuric acid, acetic acid and phosphoric acid environments.
A052Cu	A		Titanium-calcium type	AC/DC	Used for welding reactors, separators and other equipment resistant to sulfuric acid, acetic acid and phosphoric acid environments.
A062	E309L-16	E309L-16	Titanium-calcium type	AC/DC	Welding of structures of the same type of stainless steel, composite steel and dissimilar steels used in synthetic fiber and petrochemical equipment.
A072	A	1	Titanium-calcium type	AC/DC	Used for welding 00Cr25Ni20Nb steel such as nuclear fuel equipment.
A082	A	1	Titanium-calcium type	AC/DC	Used for welding and repair of corrosion-resistant steels, such as 00Cr17Ni15Si4Nb and 00Cr14Ni17Si4, which are resistant to corrosion by concentrated nitric acid.
A102	E308-16	E308-16	Titanium-calcium type	AC/DC	Welding of corrosion-resistant 0Cr19Ni9, 0Cr19Ni11Ti stainless steel structures at working temperatures below 300°C.
A102H	E308H-16	E308H-16	Titanium-calcium type	AC/DC	Welding of corrosion-resistant 0Cr19Ni9 stainless steel structures at working temperatures below 300°C.
A107	E308-15	E308-15	Low hydrogen type	CC	Welding of corrosion-resistant 0Cr18Ni8 stainless steel structures at working temperatures below 300°C.
A132	E347-16	E347-16	Titanium-calcium type	AC/DC	Welding critical 0Cr19Ni11Ti stainless steel stabilized with titanium.
A137	E347-15	E347-15	Low hydrogen type	CC	Welding critical 0Cr19Ni11Ti stainless steel stabilized with titanium.
A157Mn	A		Low hydrogen type	CC	Used for welding high-strength steels and different steels, such as H617 steel.
A146	A	1	Low hydrogen type	CC	Welding of critical 0Cr20Ni10Mn6 stainless steel structures.
A202	E316-16	E316-16	Titanium-calcium type	AC/DC	Welding of 0Cr17Ni12Mo2 stainless steel structures operating in organic and inorganic acidic media.
A207	E316-15	E316-15	Low hydrogen type	CC	Welding of 0Cr17Ni12Mo2 stainless steel structures operating in organic and inorganic acidic media.
A212	E318-16	E318-16	Titanium-calcium type	AC/DC	Welding of 0Cr17Ni12Mo2 stainless steel critical equipment such as urea and synthetic fiber equipment.
A222	E317MuCu-16	1	Titanium-calcium type	AC/DC	Welding of stainless steel structures of the same type and copper content, such as 0Cr18Ni12Mo2Cu2.
A232	E318V-16	1	Titanium-calcium type	AC/DC	Welding general heat and corrosion resistant stainless steel structures such as 0Cr19Ni9 and 0Cr17Ni12Mo2.
A237	E318V-15	1	Low hydrogen type	CC	Welding commonly used heat and corrosion resistant stainless steel structures such as 0Cr19Ni9 and 0Cr17Ni12Mo2.
A242	E317-16	E317-16	Titanium-calcium type	AC/DC	Welding of structures of the same type of stainless steel.
A302	E309-16	E309-16	Titanium-calcium type	AC/DC	Welding structures made of the same type of stainless steel, stainless steel coatings, different steels (such as Cr19Ni9 with low carbon steel), as well as high chromium steel, high manganese steel and so on.
A307	E309-15	E309-15	Low hydrogen type	CC	Welding structures made of the same type of stainless steel, different steels, high chromium steel, high manganese steel and so on.
A312	E309Mo-16	E309Mo-16	Titanium-calcium type	AC/DC	Used for welding stainless steel containers resistant to sulfuric acid corrosion in the medium, as well as for welding stainless steel liners, composite steel plates and different steels.
A312SL	E309Mo-16	E309Mo-16	Titanium-calcium type	AC/DC	Used for welding surface parts of aluminum alloy of Q235, 20g, Cr5Mo and other steel materials, as well as for welding different steel materials.
A316	A	1	Titanium-calcium type	AC/DC	Used for welding stainless steel, composite steel plates and different steels resistant to corrosion in sulfuric acid media.
A317	E309Mo-15	E309Mo-15	Low hydrogen type	CC	Used for welding stainless steel, composite steel plates and different steels resistant to corrosion in sulfuric acid media.
A402	E310-16	E310-16	Titanium-calcium type	AC/DC	Used for welding heat-resistant stainless steel of the same type operating under high temperature conditions, and can also be used for welding hardenable chrome steel and dissimilar steels.
A407	E310-15	E310-15	Low hydrogen type	CC	Used for welding heat-resistant stainless steel of the same type, stainless steel coatings, and can also be used for welding hardenable chrome steel and dissimilar steels.
A412	E310Mo-16	E310Mo-16	Titanium-calcium type	AC/DC	Used for welding heat-resistant stainless steel, stainless steel coatings and different steels operating under high temperature conditions. It also has excellent toughness when welding high-hardenable carbon steel and low-alloy steel.
A422	A	1	Titanium-calcium type	AC/DC	Used for welding and repair of Cr25Ni20Si2 heat-resistant austenitic steel drums in furnace coil rolling mills.
A432	E310H-16	E310H-16	Titanium-calcium type	AC/DC	Specifically used for welding HK40 heat resistant steel.
A462	A	1	Titanium-calcium type	AC/DC	Used for welding furnace tubes (such as HK-40, HP-40, RC-1, RS-1, IN-80, etc.) operating under high temperature conditions.
A502	E16-25MoN-16	1	Titanium-calcium type	AC/DC	Used for welding dissimilar steels, low and medium alloy steels in quenched and tempered states, as well as high resistance structures. It is also suitable for welding quenched and tempered 30CrMnSiA steel, as well as stainless steel, carbon steel, chrome steel and different steels.
A507	E16-25MoN-15	1	Low hydrogen type	CC	Used for welding dissimilar steels, low and medium alloy steels in quenched and tempered states, as well as high resistance structures. It is also suitable for welding quenched and tempered 30CrMnSiA steel as well as stainless steel and carbon steel.
A512	E 16-8-2 -16	1	Titanium-calcium type	AC/DC	Mainly used for welding high temperature and high pressure stainless steel pipelines.
A517	A		Low hydrogen type	CC	Used to weld steel rods with equivalent resistance to sulfuric acid corrosion.
A607	E330MoMnWNb-15	1	Low hydrogen type	CC	Used for welding of stainless steel materials of the same type operating under high temperature conditions of 850°C to 900°C, as well as for welding of collector tubes and expansion tubes in hydrogen conversion furnaces (such as Cr20Ni32 and Cr20Ni37 materials ) .
A707	A	1	Low hydrogen type	CC	Used for welding equipment used in acetic acid, vinyl, urea and other applications.
A717	A	1	Low hydrogen type	CC	Suitable for welding 2Cr15Mn15Ni2N low magnetic stainless steel components in electrophysical devices or for welding dissimilar steels such as 1Cr18Ni11Ti.
A802	A	1	Titanium-calcium type	AC/DC	Welding of pipelines used in the manufacture of synthetic rubber with a sulfuric acid concentration of 50% and specific working temperature and atmospheric pressure, as well as welding of Cr18Ni18Mo2Cu2Ti.
A902	E320-16	E320-16	Titanium-calcium type	AC/DC	Used for welding Carpenter 20Cb nickel alloy in corrosive media such as sulfuric acid, nitric acid, phosphoric acid and oxidizing acids.

Note

AWS

Chemical composition of the deposited metal (%)

Mechanical properties of the deposited metal

Uses

W

Mn

Yes

s

P

Cr

No

Mo

Ass

Others

R m (MPa)

A (%)

E5MoV-15

–

≤0.12 0.074

0.5-0.9 0.68

≤0.50 0.42

≤0.030 0.010

≤0.030 0.019

4.5-6.0 5.3

–

0.40-0.70 0.55

≤0.5 0.052

V: 0.10-0.35 0.25

≥540 625 (750°C×4h)

≥14 20 (750°C×4h)

Used for welding heat-resistant pearlitic steels such as Cr5MoV.

E410-15

E410-15

≤0.12 0.048

≤1.0 0.81

≤0.90 0.44

≤0.030 0.007

≤0.030 0.023

11.0-13.5 13.16

≤0.70 0.51

≤0.75 0.12

≤0.75 0.15

–

≥450 545 (750°C×1h)

≥20 23 (750°C×1h)

Used for surface overlap welding of 0Cr13, 1Cr13 steel and wear-resistant and corrosion-resistant steels.

E410NiMo-15

E410NiMo-15

≤0.06 0.030

≤1.0 0.71

≤0.90 0.26

≤0.030 0.006

≤0.030 0.016

11.0-12.5 12:15

4.0-5.0 4.39

0.40-0.70 0.45

≤0.75 0.17

–

≥760 890 (610°C×1h)

≥15 17 (610°C×1h)

Used for welding 0Cr13 stainless steel.

E308-16

E308-16

≤0.08 0.052

0.5-2.5 1.33

≤0.90 0.71

≤0.030 0.007

≤0.030 0.021

18.0-21.0 19.82

9.0-11.0 9:45 am

≤0.75 0.13

≤0.75 0.20

–

≥550 630

≥35 40

Used for welding 0Cr19Ni9 stainless steel structures with working temperatures below 300°C.

E308-15

E308-15

≤0.08 0.057

0.5-2.5 1.35

≤0.90 0.41

≤0.030 0.007

≤0.030 0.021

18.0-21.0 19.78

9.0-11.0 9.75

≤0.75 0.15

≤0.75 0.20

–

≥550 630

≥35 40

Used for welding 0Cr19Ni9 stainless steel structures with working temperatures below 300°C.

E308H-16

E308H-16

0.04-0.08 0.058

0.5-2.5 1.14

≤0.90 0.62

≤0.030 0.007

≤0.030 0.020

18.0-21.0 7:70 p.m.

9.0-11.0 9.68

≤0.75 0.20

≤0.75 0.10

–

≥550 645

≥35 42

Used for welding 0Cr19Ni9 stainless steel structures with working temperatures below 300°C.

E308L-16

E308L-16

≤0.04 0.028

0.5-2.5 1.15

≤0.90 0.70

≤0.030 0.010

≤0.030 0.019

18.0-21.0 7:25 p.m.

9.0-11.0 9:49 am

≤0.75 0.10

≤0.75 0.13

–

≥520 590

≥35 44

Used for welding ultra-low carbon stainless steel 00Cr19Ni10 or 0Cr18Ni10Ti.

E308L-16W

E308L-16

≤0.04 0.029

0.5-2.5 2.14

≤0.90 0.53

≤0.030 0.010

≤0.030 0.019

18.0-21.0 7:25 p.m.

9.0-11.0 10.2

≤0.75 0.10

≤0.75 0.13

–

≥520 590

≥35 44 -196°C AKV 41(J)

Used for welding ultra-low carbon stainless steel 00Cr19Ni10 or 0Cr18Ni10Ti, which has good toughness at 196°C. It is suitable for welding LNG storage tanks and pipelines.

Welding characteristics and electrode selection of austenitic stainless steel

Austenitic stainless steel is well regarded for its weldability and is widely applied in industries. During welding, no special process measures are generally required. This article analyzes the causes of hot cracking, intergranular corrosion, stress corrosion cracking and weld joint embrittlement (low temperature embrittlement, sigma phase embrittlement and fusion line brittle fracture) that can occur during steel welding. austenitic stainless steel, as well as preventive measures.

Through theoretical and practical analyzes of welding characteristics, the article provides an in-depth insight into the principles and methods of electrode selection when welding different materials under various working conditions. Only through rational process measurements and electrode selection can we achieve perfect welds.

Stainless steel is increasingly used in industries such as aerospace, petroleum, chemicals and nuclear energy. It is divided into chromium stainless steel and chromium-nickel stainless steel according to its chemical composition, and into ferritic stainless steel, martensitic stainless steel, austenitic stainless steel and austenitic-ferritic duplex stainless steel according to its structure.

Among these, austenitic stainless steel (18-8 stainless steel) has superior corrosion resistance to other stainless steels. Although its strength is relatively low, it offers excellent ductility and toughness, as well as good weldability. It is mainly used in chemical containers, equipment and parts, making it the most widely applied stainless steel in industries today.

Despite its many advantages, poor welding techniques or poor welding material selection can introduce many defects into austenitic stainless steel, ultimately affecting its performance.

Features of austenitic stainless steel welding

(I) It is prone to hot cracking

Hot cracking is a defect that can easily occur when welding austenitic stainless steel, including longitudinal and transverse weld cracks, arc cracks, first-pass root cracks, and interlayer cracks in multilayer welding. This is especially true for austenitic stainless steels with high nickel content.

1. Causes of Hot Cracking

(1) Austenitic stainless steel has a large liquid-solid phase gap, resulting in a longer crystallization time and strong crystallographic orientation of single-phase austenite, leading to serious impurity segregation.

(2) It has a small coefficient of thermal conductivity and a large coefficient of linear expansion, resulting in large internal welding stresses (normally tensile stresses in the weld and heat-affected zone).

(3) Elements such as C, S, P, Ni in austenitic stainless steel can form low melting point eutectics in the weld pool. For example, Ni3S2 formed by S and Ni has a melting point of 645°C, while the eutectic Ni-Ni3S2 has a melting point of only 625°C.

2. Preventive measures

(1) Use a duplex frame weld. Strive to make the weld metal austenitic and ferritic duplex structure. Controlling the ferrite content below 3-5% can disrupt the direction of the columnar austenite crystals and refine the grains. Furthermore, ferrite can dissolve more impurities than austenite, reducing the segregation of low-melting eutectics at austenite grain boundaries.

(2) Measurements of the welding process. Quality alkaline coated electrodes should be selected as much as possible, together with small line power, small currents and fast, non-oscillatory welding. When finished, try filling the crater and using argon arc welding on the first run to minimize welding stress and crater cracking.

(3) Control the chemical composition. Strictly limit the content of impurities such as S, P in solder to reduce low melting point eutectics.

(II) Intergranular Corrosion

Intergranular corrosion occurs between grains, causing loss of bond strength between grains, with the strength disappearing almost completely. When subjected to stress, it will fracture along grain boundaries.

1. Causes

According to the chromium depletion theory, when the weld and the heat-affected zone are heated to the sensitization temperature of 450-850°C (dangerous temperature zone), the carbon, which is supersaturated, diffuses to the limits grain size of austenite due to Cr's larger atomic radius and slower diffusion rate. It forms Cr23C6 with the chromium compound at the grain boundary, resulting in chromium-depleted grain boundaries that are insufficient to resist corrosion.

2. Preventive measures

(1) Control carbon content

Use low or ultra-low carbon (W(C) ≤ 0.03%) stainless steel welding materials such as A002.

(2) Add stabilizers

Adding elements such as Ti, Nb to steel and welding materials, which have a stronger affinity for C than Cr, can combine with C to form stable carbides, thus preventing chromium depletion in austenitic grain boundaries. Common stainless steel and welding materials contain Ti, Nb, such as 1Cr18Ni9Ti, 1Cr18Ni12MO2Ti steels, E347-15 electrodes, H0Cr19Ni9Ti welding wire, etc.

(3) Use a duplex structure

By introducing a certain amount of ferrite-forming elements such as Cr, Si, Al, Mo from welding wire or electrodes into the weld, an austenite + ferrite duplex structure is formed in the weld. Because Cr diffuses more rapidly into ferrite than into austenite, Cr diffuses more rapidly toward the ferrite grain boundary, reducing chromium depletion at the austenite grain boundaries. The ferrite content in the weld metal is generally controlled between 5% and 10%. If there is too much ferrite, the weld will be brittle.

(4) Rapid Cooling

Because austenitic stainless steel does not undergo hardening, the cooling rate of the welding joint can be increased during the welding process, for example, by placing a copper pad under the part or cooling it directly with water.

In welding, small currents, high welding speeds, short arcs and multi-pass welding can be used to reduce the residence time of the welded joint in the dangerous temperature zone, preventing the formation of zones with a lack of chromium.

(5) Carry out solution treatment or homogenization heat treatment

After welding, heat the weld joint to 1050-1100 ℃ to dissolve the carbides back into the austenite, and then cool quickly to form a stable single-phase austenitic structure.

Alternatively, carry out a homogenization heat treatment, maintaining the temperature between 850-900°C for 2 hours. At this time, the Cr within the austenite grains diffuses to the grain boundaries, and the Cr content at the grain boundaries again reaches more than 12%, thus preventing intergranular corrosion.

(III) Stress corrosion cracking

Stress corrosion is a form of destructive corrosion that occurs in metals under the combined action of stress and corrosive media. According to examples of stress corrosion cracking failure in stainless steel equipment and components and experimental research, it can be assumed that under the joint action of certain static tensile stresses and specific electrochemical media at certain temperatures, existing stainless steels may exhibit stress corrosion.

One of the main characteristics of stress corrosion cracking is that the combination of corrosive media and materials exhibits selectivity. The media that can cause stress corrosion cracking in austenitic stainless steel mainly include hydrochloric acid and chloride-containing media, as well as sulfuric acid, nitric acid, hydroxides (alkalies), sea water, steam, H2S solution, concentrated NaHCO3+NH3 solution +NaCl and others.

1. Causes

Stress corrosion cracking is the delayed cracking phenomenon that occurs when a welded joint is subjected to tensile stresses in a specific corrosive environment. Stress corrosion cracking in the welded joint of austenitic stainless steel is a severe failure mode, manifesting as brittle failure without plastic deformation.

2. Preventive measures

(1) Rational Processing and Assembly Procedures

Minimize cold deformation as much as possible, avoid forced assembly, and avoid various forms of damage (including assembly and arc burns) during assembly that can act as sources of cracking in the SCC and cause pitting corrosion.

(2) Rational Choice of Welding Material

Ensure a good match between the weld seam and the base material and avoid any adverse structures such as coarse grain and hard, brittle martensite.

(3) Proper welding technique

Make sure the weld seam is well formed and does not produce any stress concentrations or corrosion defects such as undercuts. Adopt a reasonable welding sequence to reduce the welding residual stress level. For example, avoid cross joints, change Y-shaped grooves to X-shaped grooves, appropriately reduce the groove angle, use short welding paths, and utilize low linear energy.

(4) Stress relief treatment

Implement post-weld heat treatment such as full annealing or stress relief annealing. Use post-weld hammering or shot peening when heat treatment is difficult to implement.

(5) Production Management Measures

Control impurities in the medium, such as O2, N2, H2O in liquid ammonia, H2S in liquefied petroleum gas, O2, Fe3+, Cr6+ in chloride solutions, etc. Implement anti-corrosion measures, such as coating, lining or cathodic protection, and adding corrosion inhibitors.

(IV) Welded joint weakening

After heating austenitic stainless steel welds at high temperatures for a certain period, a decrease in impact resistance occurs, known as embrittlement.

1. Weld metal embrittlement at low temperatures (475°C embrittlement)

(1) Causes

The structure of duplex welds containing a large amount of ferrite phase (more than 15%~20%) will experience a significant decrease in plasticity and toughness after heating to 350~500°C. Because the rate of embrittlement is fastest at 475°C, this is called 475°C embrittlement.

For austenitic stainless steel welded joints, corrosion or oxidation resistance is not always the most critical performance. When used at low temperatures, the plasticity and toughness of the weld metal become essential properties.

To meet low temperature toughness requirements, a single austenite structure is typically desired for the weld structure to avoid the presence of δ ferrite. The presence of δ ferrite always worsens toughness at low temperatures, and the more it contains, the more severe the embrittlement.

(2) Preventive Measures

① When ensuring the crack and corrosion resistance of the weld metal, the ferrite phase should be controlled at a lower level, around 5%.

② Welds that suffered embrittlement at 475°C can be eliminated by quenching at 900°C.

2. σ Phase Embrittlement of the Solder Joint

(1) Causes

When austenitic stainless steel welded joints are used for a long period in the temperature range of 375~875°C, an intermetallic FeCr compound known as σ phase is produced. The σ phase is hard and brittle (HRC>68).

Precipitation of the σ phase results in a marked decrease in the impact toughness of the weld, a phenomenon known as σ phase embrittlement. The σ phase generally appears only in duplex structure welds; when the operating temperature exceeds 800 ~ 850°C, the σ phase will also precipitate in single-phase austenite welds.

(2) Preventive Measures

① Limit the ferrite content in the weld metal (less than 15%); use superalloy welding materials, that is, welding materials with high nickel content, and strictly control the content of Cr, Mo, Ti, Nb and other elements.

② Use a small specification to reduce the residence time of weld metal at high temperatures.

③ For the σ phase already precipitated, carry out solution treatment when conditions permit, to dissolve the σ phase in austenite.

④ Heat the solder joint to 1000~1050°C and then cool quickly. The σ phase generally does not occur in 1Cr18Ni9Ti steel.

3. Fragile fracture of the fusion line

(1) Causes

When austenitic stainless steel is used at high temperatures for a prolonged period, brittle fracture may occur along the fusion line.

(2) Preventive Measures

Adding Mo to steel can improve the steel's ability to resist brittle fracture at high temperature.

From the above analysis, it can be seen that the correct choice of welding process measurements or welding materials can prevent the occurrence of the above welding defects. Austenitic stainless steel has excellent weldability, and almost all welding methods can be used to weld austenitic stainless steel.

Among the various welding methods, shielded metal arc welding (SMAW) is widely used due to its adaptability to different positions and different sheet thicknesses. In the following, we will analyze the principles and methods of selecting austenitic stainless steel welding rods for different purposes.

Key Points for Selecting Welding Rods for Austenitic Stainless Steel

Stainless steel is mainly used for corrosion resistance, but it is also used for heat-resistant and low-temperature steels.

Therefore, when welding stainless steel, the performance of the welding rod must match the intended use of the stainless steel. The selection of stainless steel welding rods should be based on the base metal and working conditions, including operating temperature and contact medium.

Table of different stainless steel grades and corresponding welding rod types and numbers.

Steel Grade	Welding Rod Model	Welding rod class	Welding rod nominal composition	Observation
0Cr18Ni11	E308L-16	A002	00Cr19Ni10
0Cr19Ni11
00Cr17Ni14Mo2				Excellent heat resistance, corrosion resistance and crack resistance
00Cr18Ni5Mo3Si2	E316L-16	A022	00Cr18Ni12Mo2
00Cr17Ni13Mo3
00Cr18Ni14Mo2Cu2	E316Cu1-16	A032	00Cr19Ni13Mo2Cu
00Cr22Ni5Mo3N	E309Mo1-16	A042	00Cr23Ni13Mo2
				Corrosion resistance of weld to formic acid, acetic acid and chloride ions
00Cr18Ni24Mo5Cu	E385-16	A052	00Cr18Ni24Mo5
0Cr19Ni9	E308-16	A102	0Cr19Ni10	Titanium-calcium type coating
1Cr18Ni9Ti
1Cr19Ni9	E308-15	A107	0Cr19Ni10	Low hydrogen type coating
0Cr18Ni9
0Cr18Ni9	–	A122	–
				Possessing excellent resistance to intergranular corrosion
0Cr18Ni11Ti	E347-16	A132	0Cr19Ni10Nb
0Cr18Ni11Nb	E347-15	A137	0Cr19Ni10Nb
1Cr18Ni9Ti
0Cr17Ni12Mo2	E316-16	A202	0Cr18Ni12Mo2
00Cr17Ni13Mo2Ti
1Cr18Ni12Mo2Ti				Having better resistance to intergranular corrosion compared to A202
00Cr17Ni13Mo2Ti	E316Nb-16	A212	0Cr18Ni12Mo2Nb
0Cr18Ni12Mo2Cu2	E316Cu-16	A222	0Cr19Ni13Mo2Cu2	Due to the presence of copper, it presents excellent resistance to acids in sulfuric acid media.
0Cr19Ni13Mo3				With a high molybdenum content, it has excellent resistance to non-oxidizing acids and organic acids.
00Cr17Ni13Mo3Ti	E317-16	A242	0Cr19Ni13Mo3
1Cr23Ni13	E309-16	A302	1Cr23Ni13	Different steels, high chromium steels, high manganese steels, etc.
00Cr18Ni5Mo3Si2
00Cr18Ni5Mo3Si2	E309Mo-16	A312	1Cr23Ni13Mo2
				Used for welding high hardenability chrome steel and dissimilar steels.
1Cr25Ni20	E310-16	A402	2Cr26Ni21
1Cr18Ni9Ti	E310-15	A407		Low hydrogen type coating
Cr16Ni25Mo6	E16-25MoN-16	A502
Cr16Ni25Mo6	E16-25MoN-15	A507

(I) Key point one

Generally, the selection of welding rods can refer to the base metal material, choosing welding rods that have the same or similar composition as the base metal. For example, A102 corresponds to 0Cr18Ni9, A137 corresponds to 1Cr18Ni9Ti.

(II) Key point two

Because carbon content has a large impact on the corrosion resistance of stainless steel, it is generally recommended to select stainless steel welding rods where the deposited metal contains a smaller amount of carbon than the base metal. For example, an A022 welding rod should be chosen for 316L.

(III) Key Point Three

The weld metal of austenitic stainless steel must guarantee mechanical properties. This can be verified through an evaluation of the welding process.

(IV) Key Point Four (Heat Resistant Austenitic Steel)

For heat-resistant stainless steel (austenitic heat-resistant steel) used at high temperatures, the selected welding rods must mainly meet the thermal crack resistance of the weld metal and the high-temperature performance of the welded joint.

1. For heat-resistant austenitic steel with Cr/Ni≥1, such as 1Cr18Ni9Ti, austenitic-ferritic stainless steel welding rods are generally adopted, and it is appropriate for the ferrite content in the weld metal to be 2 to 5%. If the ferrite content is too low, the crack resistance of the weld metal is low; if it is too high, it can easily form a brittle sigma phase during prolonged use at high temperatures or heat treatment, causing cracking. For example, A002, A102, A137. In some specific application cases, if a fully austenitic weld metal is required, A402, A407, etc. welding rods can be chosen.
2. For heat-resistant stabilized austenitic steel with Cr/Ni<1, such as Cr16Ni25Mo6, while ensuring that the weld metal is chemically similar to the base metal, the content of Mo, W, Mn and other elements in the weld metal should be increased to maintain thermal resistance and improve crack resistance. For example, using A502, A507.

(V) Key point five (corrosion resistant stainless steel)

For corrosion-resistant stainless steels operating in various corrosive media, welding electrodes should be selected according to the operating medium and temperature, ensuring their corrosion resistance (by carrying out corrosion performance tests on the welded joints).

1. For a medium with strong corrosivity at operating temperatures above 300°C, it is necessary to use stainless steel welding rods with stabilizing elements such as Ti or Nb or ultra-low carbon stainless steel welding rods such as A137 or A002.
2. For media containing dilute sulfuric acid or hydrochloric acid, welding rods with Mo or Mo and Cu are generally selected, such as A032, A052.
3. For work with weak corrosion or equipment exclusively to avoid rust contamination, stainless steel welding rods without Ti or Nb can be used. To ensure the stress corrosion resistance of the weld metal, superalloy welding materials must be used, that is, the content of corrosion-resistant alloy elements (Cr, Ni, etc.) in the weld metal must be greater than than in the base metal. For example, using 00Cr18Ni12Mo2 type welding materials (such as A022) to weld 00Cr19Ni10 parts.

(VI) Key Point Six

For austenitic stainless steel working under low temperature conditions, the low temperature impact toughness at the operating temperature of the welded joint must be guaranteed, therefore pure austenitic welding rods such as A402, A407 are used.

(VII) Key Point Seven

Nickel-based alloy welding rods can also be selected, such as using nickel-based welding material with 9% Mo to weld super-austenitic stainless steel type Mo6.

(VIII) Key Point Eight: Selection of welding rod flux types

1. Since the weld metal of duplex austenitic steel inherently contains a certain amount of ferrite, which provides good plasticity and toughness, the difference between basic flux and titanium-calcium type flux welding rods in terms of crack resistance is not is as significant as with carbon. steel welding rods. Therefore, in practical applications, more attention is paid to the performance of the welding process, mainly using welding rods with flux type codes 17 or 16 (such as A102A, A102, A132, etc.).
2. Only when the rigidity of the structure is high or the crack resistance of the weld metal is low (such as certain chromium martensitic stainless steels, pure austenitic structure chromium-nickel stainless steels, etc.) should it be considered the selection of basic flux stainless steel welding rods with a code of 15 (such as A107, A407, etc.).

Precautions when using stainless steel welding rods

1. Chromium stainless steel exhibits some corrosion resistance (against oxidative acids, organic acids, gaseous corrosion), heat resistance and wear resistance. It is typically used in materials for power plants, chemical plants, and petroleum industries. Chromium stainless steel is relatively difficult to weld; Attention must be paid to the welding process, heat treatment conditions and the selection of appropriate welding rods.
2. Chromium 13 stainless steel exhibits significant hardening after welding and is prone to cracking. If welding is carried out using the same type of chromium stainless steel rods (G202, G207), they must be preheated to above 300°C and slowly cooled to about 700°C after welding. If the part cannot be subjected to post-welding heat treatment, then chrome-nickel stainless steel welding rods (A107, A207) should be selected.
3. For Chromium 17 stainless steel, corrosion resistance and weldability can be improved by appropriately adding stable elements such as Ti, Nb, Mo, etc. It is easier to weld than Chrome 13 stainless steel. If welding with the same type of chrome stainless steel rods (G302, G307), preheating above 200°C and post-weld tempering around 800°C. If post-welding heat treatment is not possible, chrome-nickel stainless steel welding rods (A107, A207) should be chosen.
4. Chrome-nickel stainless steel welding rods have good corrosion resistance and oxidation resistance, widely used in chemical industry, fertilizer industry, petroleum industry and medical equipment manufacturing.
5. During welding of chrome-nickel stainless steel, carbon precipitates due to repeated heating, reducing its corrosion resistance and mechanical properties.
6. Chrome-nickel stainless steel welding rods are titanium-calcium type and low hydrogen type. The titanium-calcium type can be used for both AC and DC, but in AC welding, the fusion penetration is shallow and tends to turn red, therefore, a DC power source is preferably used. Rods with diameters of 4.0 and below can be used for all-position welding, and those of 5.0 and above for flat welding and fillet welding.
7. Welding rods must remain dry during use. The titanium-calcium type should be dried at 150°C for one hour, while the low hydrogen type should be dried at 200-250°C for one hour (repeated drying should be avoided, or the rod coating may crack and peel). The welding rod coating must be kept free of oil and other contaminants to avoid increasing the carbon content in the weld and affecting the weld quality.
8. To avoid intergranular corrosion due to heating, the welding current should not be too high; should be about 20% smaller than that of carbon steel welding rods. The arc length should not be too long, and rapid cooling of the intermediate layer is required. Narrow welding paths are preferred.
9. Welding dissimilar steels requires careful selection of welding rods to avoid thermal cracking or precipitation of the sigma phase that leads to brittleness after high-temperature heat treatment. The selection must follow the standard for choosing welding rods for stainless steels and dissimilar steels, and appropriate welding processes must be adopted.

Conclusion

Welding austenitic stainless steel has unique characteristics, and the selection of welding rods for austenitic stainless steel is particularly important. Through long-term practical experience, it has been proven that using the above measurements can achieve different welding methods for different materials and different welding rods for different materials.

The selection of stainless steel welding rods should be based on the base metal and working conditions, including operating temperature and contact medium. This has great guiding significance for us, as this is the only way to achieve the expected welding quality.