S235JR Weldability and Welding Electrode Selection: A Practical Guide for Project Construction

S235JR is one of the most widely used non-alloy structural steels in EN 10025-2. Whether in steel structure construction, pressure pipeline frames, mechanical support manufacturing, or bridge and steel platform assembly, welding is involved in almost every processing stage.
Therefore, understanding S235JR weldability, mastering suitable welding electrodes, and developing a scientific process plan are key to ensuring safety and cost-efficiency in engineering projects.

This guide analyzes S235JR welding from multiple perspectives—including metallurgical principles, welding risks, filler materials, electrode selection, testing standards, and quality control—to offer engineers, contractors, and procurement teams a truly practical S235JR welding implementation solution.

With more than 20 years of steel manufacturing and welding experience, and a complete internal laboratory testing system, LONGMA provides reliable S235JR materials and welding technical support to global customers.

Why Is S235JR Considered to Have Good Weldability?

S235JR belongs to low-carbon, low-alloy structural steel. Its excellent weldability comes from the following metallurgical factors:

1. Low carbon content (generally ≤0.17%)

Low carbon content makes it less likely to form hardened structures during welding, reducing the risk of cold cracking. This is the core reason why S235JR is good weldable.

2. Low alloy element content

Mn, Si, P, and S are strictly controlled at low levels, maintaining good weld metal ductility and crack resistance.

3. Good JR-grade impact toughness

S235JR has an impact value ≥27 J at 20°C, improving resistance to brittle fracture in the weld zone.

4. Suitable for multiple welding processes

Including:

• SMAW (Manual Metal Arc Welding)
• MIG/MAG (Gas Metal Arc Welding)
• TIG Welding
• FCAW (Flux-Cored Welding)
• SAW (Submerged Arc Welding)

Because of these advantages, S235JR weldability is considered “excellent” among structural steels and can meet the welding needs of most engineering applications.

Welding Risk Points of S235JR: Good Weldability ≠ Zero Risk

Although S235JR weldability is good, improper welding may still cause problems:

1. Welding cold cracking (hydrogen-induced cracking)

Main causes:

• Insufficient welding current
• Moist electrodes
• Low-temperature welding
• No post-weld heat retention

This is especially common in thicker S235JR welding components.

2. Welding deformation and residual stress

Particularly in plate welding (≥12 mm thickness).

3. Inconsistent material batches affecting weldability

Low-cost suppliers may provide materials that deviate from EN 10025-2 requirements, leading to poor weldability.

Key to controlling welding risks:
Reliable materials + correct electrodes + reasonable welding procedure.

S235JR Welding Electrode and Filler Wire Selection

Below is the most commonly used electrodes for S235JR material selection guide:

1. SMAW (Manual Welding) Electrode Selection

E7018 is the most common electrode for S235JR, especially for load-bearing components.

2. MIG/MAG Welding Wire Selection

For large-scale S235JR welding, ER70S-6 is the most economical and durable option.

3. TIG (GTAW) Welding Wire

Recommended: ER70S-2 / ER70S-6
Mainly for root passes or thin-wall parts where high weld quality is required.

4. FCAW (Flux-Cored Welding)

Best for outdoor, windy conditions.
Recommended: E71T-1C/M

S235JR Welding Procedure: Before, During, and After Welding

1. Pre-weld Preparation

• Bake electrodes (E7018: 350–400°C for 1 hour)
• Remove oxide scales, oil, rust
• Preheat to 50–80°C if ambient temperature <5°C

2. Welding Process Control

• Adjust current to avoid burn-through or lack of fusion
• Use short-arc welding
• Back-step or intermittent welding to reduce deformation

3. Post-weld Treatment

• Slow cooling or heat retention recommended for thick plates
• Conduct UT/MT inspection for critical welds
• Check weld reinforcement, undercut, porosity

Welding Quality Testing Standards (ASTM / EN)

To verify S235JR welding quality, the following tests and standards are recommended:

These tests ensure S235JR welding performance is reliable, avoiding structural failures.

Procurement Risks and Prevention Suggestions for S235JR Welding

The biggest concern in engineering projects is not welding difficulty, but:

1. Low-cost materials may be fake S235JR

Some markets sell Q235 or lower-grade steel as S235JR, which cracks easily during welding.

2. Incomplete MTC (Material Test Certificate)

Without JR impact values, weldability cannot be confirmed.

3. No weldability verification data

Especially when third-party or internal testing is absent.

Why Choose LONGMA? (Capability Matters More Than Price)

With 20+ years of experience and a full internal laboratory, LONGMA ensures comprehensive quality control.

1. Internal Laboratory: Ensuring Reliable S235JR and Welding Performance

• Spectrometer chemical analysis
• ASTM E8 tensile testing
• ASTM E23 impact testing
• Weld UT inspection
• 3.1 / 3.2 certification available

All S235JR products undergo strict weldability verification, supporting S235JR weldability with reliable data.

2. Professional Electrode Matching Guidance

Recommendations based on plate thickness, welding process, and environmental conditions to offer the best electrodes for S235JR material.

3. Providing WPS/PQR

Ensures traceable and consistent welding parameters during construction.

4. Globally Recognized Stable Quality

LONGMA’s S235JR materials are widely used in:

• Middle Eastern steel structures
• Southeast Asian port projects
• European machinery manufacturing

Quality proven through international engineering applications.

 Summary: How to Ensure Successful S235JR Welding?

To achieve high-quality S235JR welding, remember:

① Choose genuine, compliant S235JR materials
(Avoid counterfeit steel → preserve the natural weldability advantages)

② Use correct electrodes
E7018 / ER70S-6 are the most common and reliable choices.

③ Follow proper welding procedures and testing standards
Comply with ASTM E8 / E23 and ISO NDT requirements.

④ Select a professional supplier with an internal laboratory
Reduce risks caused by unstable welding performance.