What is the difference between SG1, SG2 and SG3 welding wire?

SG1, SG2 and SG3 are names for massive steel welding wire for MIG/MAG welding. The terms are still widely used in workshops and commerce, although modern welding wire is nowadays usually classified according to EN ISO 14341-A.

Globally:

The main difference lies in the chemical composition, in particular the content of manganese and silicon, and the resulting mechanical properties of the weld metal.

What does SG mean?

SG is a historical German designation for solid welding wire for gas-shielded arc welding.

Although modern standards use different codes, the names SG1, SG2 and SG3 have never really disappeared in practice.

As a result, you often hear in workshops:

• Take a roll of SG2.
• This machine is on SG3.
• Do you have 1.0 mm SG2 in stock?

While the modern label can contain for example G3Si1.

What is the modern name for SG1, SG2 and SG3?

The modern European classification uses codes from EN ISO 14341-A.

For example, Böhler Welding lists solid steel wires with classifications 2Si, 3Si1 and 4Si1 within EN ISO 14341-A.

What is SG1 welding wire?

SG1 is the lighter, lower alloy steel welding wire within this traditional range.

The modern agreement is roughly around G2Si1 / 2Si.

This wire contains less silicon and manganese than SG2 and SG3.

SG1 is less common nowadays in general structural fabrication than SG2.

What is SG1 used for?

SG1 can be used for non-alloy and certain low-alloy steels where the required mechanical properties and welding procedure are appropriate.

It is not a wire that you simply choose because it is a lighter. The choice should be tailored to:

• base material
• Material thickness
• Construction standard
• Tensile strength required
• Spherical stroke values
• WPS
• shielding gas

What is SG2 welding wire?

SG2 is by far the best known and most widely used general MIG/MAG-welding wire for structural steel.

The modern agreement is usually G3Si1 / 3Si1.

Böhler Welding carries multiple massive steel wires with EN ISO classification 3Si1, including products for general structural fabrication.

Why is SG2 used so much?

SG2 offers a good balance between:

• Loadability
• Mechanical properties
• arc characteristics
• Availability
• Price
• Applicability to general structural steel

Therefore, SG2 is often the standard choice for steel construction, engineering, repair and general workshop use.

What is SG2 used for?

• Construction steel
• Mechanical engineering
• Repair
• Steel industry
• sheet metal work
• Agricultural machinery
• Vehicle construction
• General MAG applications

For common S235 and S355 applications, a suitable SG2/G3Si1 welding wire is widely used, provided the chosen wire meets the required standard and WPS.

What is SG3 welding wire?

SG3 is a higher alloyed solid steel welding wire within this traditional family.

The modern agreement is usually G4Si1 / 4Si1.

Compared to SG2, SG3 usually contains more manganese and silicon.

What does more manganese and silicon do?

manganese and silicon play different roles in the weld metal.

They influence, among other things:

• Deoxidation
• Strength of weld metal
• Liquid behaviour of the weld pool
• Mechanical properties
• Composition of the final weld metal

However, more Mn and Si does not automatically mean that the wire is better for every application.

Is SG3 stronger than SG2?

In many product ranges, a 4Si1 welding wire is classified in a higher strength class than a similar 3Si1 welding wire.

For example, Böhler mentions 3Si1 products with classifications around G 42 and 4Si1 products around G 46, depending on the specific product and shielding gas.

Therefore, SG3 may be attractive when a higher strength of the weld metal is required.

Always check the exact datasheet for that.

Does G42 or G46 mean the same as tensile strength?

Not directly.

The classification within EN ISO 14341 contains several components and refers, among other things, to strength class, shearing behaviour, shielding gas and chemical composition.

Therefore, read the complete classification and not just one number.

Is SG3 better than SG2?

No.

SG3 is not simply a better SG2.

It is another wire with a different chemical composition and other potential mechanical properties.

If SG2 meets all requirements, SG3 may be unnecessary.

When to choose SG3?

SG3 may be interesting when:

• A higher strength class is required
• The base material required
• An WPS specifically prescribes G4Si1
• Construction standards or customer conditions require this
• The mechanical properties of SG2 are insufficient

The choice must therefore be technically justified.

Is SG3 intended for dirty or rusty steel?

That is sometimes said too simply.

The higher content of silicon and manganese affects the deoxidation of the weld pool, but that does not mean that SG3 is a solution for poorly prepared material.

For good welding, steel surfaces shall still be as free as possible from:

• Oil
• Fat
• Paint
• Fluid
• Heavy rust
• Dirty

Another welding wire does not replace good welding preparation.

What's the difference in chemical composition?

Exact values vary by manufacturer and product.

Globally, the manganese and silicon content rises from SG1 to SG3.

Always use the material certificate or product datasheet of the respective roll for exact percentages.

Why is silicon in steel welding wire?

Silicon works as a deoxidant, among other things.

During welding, oxygen can enter the weld pool. Silicon binds part of it and consequently helps to form a manageable weld metal.

Silicon also influences the flow behaviour of the weld pool.

Why is manganese in steel welding wire?

manganese contributes, among other things, to:

• Deoxidation
• Mechanical properties
• Strength
• Metallurgical control of the weld metal

The exact effect is related to the complete chemical composition and the base material.

Which wire is most commonly used?

For general steel work, SG2 / G3Si1 is usually the most commonly used choice.

This is the wire that you will find on an MIG/MAG machine in many professional workshops by default.

Which wire do you use for S235?

For many normal S235 applications, a suitable SG2/G3Si1 is used.

But when the construction is welded according to a specific standard or WPS, that documentation is leading.

Which wire do you use for S355?

Also for many S355 applications, a suitable G3Si1/SG2-wire is common.

With higher requirements for strength, toughness or specific material combinations, an G4Si1/SG3 or other welding wire can be prescribed.

Can I use SG3 where normal SG2 is used?

Technically that may be possible in some situations, but you should not change filler metal randomly.

In the case of certified work, it shall be verified that:

• The WPS allows
• The strength class fits
• The chemical composition is suitable
• The required stroke value is reached
• The base material is compatible

Can I use SG2 instead of SG3?

That too depends on the requirements.

When a construction or WPS prescribes a higher class, going back to SG2/G3Si1 may mean that the required mechanical properties are no longer guaranteed.

Is SG2 the same as ER70S-6?

Not exactly.

SG2/G3Si1 is a European classification tradition, while ER70S-6 comes from the American AWS system.

There is a lot of overlap in applications and chemical composition, but the systems are not one-on-one the same.

This is also demonstrated by manufacturer data: Böhler mentions both 3Si1 and 4Si1 products under AWS ER70S-6.

Is SG3 the same as ER70S-6?

This cannot be said universally either.

Some G4Si1 products also carry an ER70S-6 classification, while the European EN ISO classification uses a different chemical and mechanical classification.

Therefore, use the full product classification.

Which shielding gas do you use with SG1, SG2 and SG3?

These steel wires are usually used with an argon/CO2 blend gas at MAG welding.

For example, commonly used mixtures are:

• 80/20 Ar/ CO2
• 82/18 Ar/ CO2
• 85/15 Ar/ CO2

Also 100% CO2 may be possible depending on the wire classification and application.

Always check the datasheet, as mechanical classifications may vary per shielding gas.

Does the shielding gas affect the classification?

Yes.

For example, in EN ISO classifications you see indications such as:

• M21
• C1

For certain 3Si1 and 4Si1 welding wire he gives different classifications for mixed gas and for 100% CO2.

Is SG1, SG2 or SG3 suitable for MIG welding?

For steel with an active gas we speak technically of MAG welding, not MIG.

In daily practice it is often simply said to be "MIG-wire" but SG1, SG2 and SG3 are usually used as MAG-wire for steel.

Which diameters are available?

That depends on manufacturer and product line.

Common diameters are:

• 0,6 mm
• 0,8 mm
• 1.0 mm
• 1.2 mm
• 1.6 mm

For general work, 0.8, 1.0 and 1.2 mm are very common.

Which wire size do you choose?

These are global guidelines. Machine power, position, plate thickness and desired deposition rate also play along.

Is copper-coated SG2 different from uncoated wire?

Yes.

The SG or G3Si1 classification does not automatically tell whether the wire is copper coated.

There are both:

• Copper coated solid wire
• Non-copper coated solid wire

For example, he performs several non-coppered ECOspark-wires alongside conventional solid steel wires.

Is non-copper coated wire better?

Not automatically.

It's a different product version. The quality depends on:

• Surface quality
• Wire tolerance
• Contact transfer
• wire feed
• Storage
• Manufacturer

Choose based on process, machine and product quality.

Can I use SG2 from different brands?

For ordinary work, products with the same relevant classification may be comparable, but they are not automatically identical.

Check:

• EN ISO Classification
• Chemical analysis
• Mechanical properties
• Diameter
• Surface treatment
• Certificate
• Approvals

Why can one SG2 weld differently than the other?

Even when two reels are sold both as G3Si1, small differences may exist in:

• Wire area
• Tolerance
• Copper layer
• Chemical composition within standard
• Rinse quality
• wire feed behaviour

Therefore, arc characteristics and spatter may differ slightly in practice.

Which wire should I buy for general steel work?

For general MAG welding of structural steel, SG2 / G3Si1 is usually the logical starting point.

Choose SG3/G4Si1 when required mechanical properties, WPS or application give rise to this.

SG1/G2Si1 is now a less common general choice.

When should you not just choose SG2?

For critical or certified constructions.

Remember:

• High strength steel
• Pressure vessels
• Crane construction
• Bridge construction
• Specific offshore applications
• Certified structural fabrication
• Work with prescribed WPS

There the filler metal must be consciously connected to the base material and the welding procedure.

SG1, SG2 and SG3 in one overview

Is SG3 more expensive than SG2?

That is possible, but the price difference depends on brand, packaging, diameter and supplier.

Price only is not a good reason to choose between SG2 and SG3.

The technical requirements of the welded joint are more important.

From Cjays practice

For the vast majority of normal structural fabrication we come out on SG2 / G3Si1.

That's not because SG3 is worse, but because SG2 does exactly what is needed for many standard steel applications.

SG3 becomes interesting when the application deliberately requires a higher mechanical class or other composition.

We would therefore not recommend:

Oh, yeah, yeah.

The better question is:

Which wire belongs to my base material and the required welding properties?

In normal work you can usually look at:

• base material
• Sheet thickness
• shielding gas
• wire diameter
• Machine power
• Required strength

For certified work, the WPS and material standard are included.

Step plan to choose the right steel welding wire

• Determine which steel you are burdening.
• Check the required mechanical properties.
• Check if an WPS is present.
• Choose the appropriate EN ISO classification.
• Choose the shielding gas.
• Determine the wire diameter.
• Check any labels and certificates.
• Then choose the brand and packaging.

The main conclusion

SG1, SG2 and SG3 are historical names for different classes of massive steel welding wire.

Globally:

• SG1 ≈ G2Si1 / 2Si
• SG2 ≈ G3Si1 / 3Si1
• SG3 ≈ G4Si1 / 4Si1

SG2 is the most commonly used general steel welding wire.

SG3 generally contains more manganese and silicon and can therefore fall into higher mechanical strength classes.

However, SG3 is not automatically better. Choose the wire based on base material, standard, WPS and required mechanical properties.

Further reading

• How do you determine which MIG/MAG welding torch you need?
• What is Pulse MIG/MAG welding and when should you use it?
• What kind of brand is CEWELD / Certilas?

Frequently Asked Questions about SG1, SG2 and SG3

Which one's the most commonly used?

SG2, now commonly referred to as G3Si1, is the most commonly used general steel welding wire.

Is SG2 the same as G3Si1?

In practice, SG2 is usually linked to G3Si1. The exact classification on the datasheet remains guiding.

Is SG3 the same as G4Si1?

Yes, SG3 is now roughly linked to G4Si1.

Is SG3 stronger than SG2?

Many G4Si1 products fall into a higher strength class than similar G3Si1 products, but always check the exact product datasheet.

Can I use SG3 for normal steel?

That can be dependent on application, but it is not automatically necessary or better than SG2.

Which wire do I use for S235?

For many normal applications, SG2/G3Si1 is a common choice.

Which wire do I use for S355?

S355 applications are also used for many G3Si1 applications. With higher requirements, G4Si1 or any other wire may be required.

Is SG2 the same as ER70S-6?

Not exactly. They are classifications from different standard systems and the overlap is not one-to-one.

What gas do you use with SG2?

Usually an argon/CO2 mixture gas such as 82/18 or 80/20. Depending on wire and classification, 100% CO2 may also be possible.

Is SG3 better for rusty steel?

No. More manganese and silicon do not replace good material preparation. Remove heavy rust, paint, oil and dirt before welding.

Choose SG1, SG2 or SG3 welding wire?

For normal steelwork, SG2/G3Si1 is usually the most practical choice. With higher mechanical requirements or prescribed welding procedures, SG3/G4Si1 or any other wire may be necessary.

Cjays Lastechniek can help to choose the right welding wire, wire diameter and the right shielding gas for your MIG/MAG application.