Oct 13, 2026

Why Does My Low-Temperature Weld Pass Tensile Test but Fail Charpy Impact Test?

Why does a low-temperature weld pass tensile test but fail the Charpy impact test? Learn how welding wire selection, weld toughness and temperature affect low-temperature steel welding performance.

Your weld passed the tensile test, but the Charpy impact test failed.

What should you check first?

This problem often appears in:

Low-temperature pressure vessels

LNG and energy equipment

Chemical processing systems

Low-temperature pipelines

Many engineers face the same question:

“If the weld strength is acceptable, why does it fail the impact test?”

The reason is that tensile strength and Charpy impact toughness measure different weld properties.

A weld can withstand static loading but still lack enough toughness to resist brittle fracture at low temperatures.

For low-temperature steel welding, strength is important, but toughness is equally critical.

1. Did You Choose Welding Wire Only Based on Strength?

A common mistake is selecting welding wire only according to tensile strength.

However, a higher-strength welding consumable does not always provide better low-temperature performance.

Tensile testing evaluates:

Ultimate tensile strength

Yield strength

Resistance to pulling force

Charpy impact testing evaluates:

Energy absorption ability

Resistance to brittle fracture

Low-temperature toughness

This means a weld can pass tensile testing but fail Charpy impact testing if the weld metal does not have sufficient toughness at the required temperature.

For low-temperature applications, the key question is not:

“Which welding wire has the highest strength?”

The better question is:

“Which welding wire can maintain toughness under actual service conditions?”

2. Is Your Welding Wire Suitable for Low-Temperature Steel?

Welding consumable selection is one of the most important factors affecting Charpy impact performance.

For low-temperature steel welding, nickel-alloyed welding wires are commonly selected because nickel helps improve weld-metal toughness at reduced temperatures.

Common low-temperature welding consumables include:

GMAW/GTAW Welding Wire

ER80S-Ni1 welding wire

ER80S-Ni2 welding wire

ER80S-Ni3 welding wire

SMAW Welding Electrode

E8018-C3 welding electrode

E8018-Ni1 welding electrode

These AWS classified welding consumables are designed for applications requiring improved low-temperature weld performance.

However, a higher alloy content does not automatically guarantee better Charpy impact results.

Before changing welding wire, check:

Base material grade

Service temperature

Required impact energy

Weld-metal chemistry

Approved welding procedure

For example, ER80S-Ni2 may provide different low-temperature toughness characteristics compared with ER80S-Ni1, but replacement should only be considered after reviewing project requirements.

👉 Internal Link 1: Anchor text: Can ER80S-Ni2 Replace ER80S-Ni1 for Low-Temperature Steel? Link to: Can ER80S-Ni2 Replace ER80S-Ni1 for Low-Temperature Steel?

3. Could the Charpy Test Condition Cause Failure?

Sometimes the welding wire is correct, but the test condition reveals a toughness problem.

A weld that performs well at room temperature may fail when tested at a lower temperature because impact toughness decreases as temperature drops.

Before changing consumables, check:

Check Item	Why It Matters
Impact test temperature	Determines toughness requirement
Required impact energy	Defines acceptance criteria
Test location	Weld metal and HAZ may perform differently
Testing standard	Ensures correct evaluation

For low-temperature service, testing conditions should match the actual operating environment.

4. Can Welding Procedure Reduce Weld Toughness?

Even with the correct welding wire, welding conditions can influence Charpy impact performance.

Important factors include:

Heat Input

Excessive or insufficient heat input may affect weld microstructure and toughness.

Interpass Temperature

Incorrect temperature control during multi-pass welding can change final weld properties.

Cooling Rate

Cooling conditions influence hardness, ductility and impact resistance.

Hydrogen Control

Proper hydrogen control helps maintain weld reliability in critical applications.

The final weld performance depends on the combination of:

Welding consumable

Welding process

Welding parameters

Weld-metal microstructure

5. What Should You Check Before Changing Welding Wire?

If your low-temperature weld passes tensile testing but fails Charpy impact testing, follow these steps:

Step 1: Confirm the Test Requirement

Check:

Required impact temperature

Required impact energy

Testing location

Step 2: Review Welding Consumable Selection

Confirm:

AWS classification

Chemical composition

Application suitability

Step 3: Review Welding Procedure

Check:

Heat input

Preheat temperature

Interpass temperature

Welding parameters

Step 4: Select the Correct Welding Wire

Do not simply choose a stronger welding wire.

The correct filler metal should provide the required balance of:

Strength

Ductility

Impact toughness

For product information:

👉 Internal Link 2: Anchor text: ER80S-Ni1 Welding Wire for Low-Temperature Steel Applications Link to: ER80S-Ni1 Welding Wire for Low-Temperature Steel Applications

FAQ

Can a higher-strength welding wire improve Charpy impact results?

Not always.

Higher tensile strength does not automatically mean better low-temperature toughness. The welding wire must match the required service temperature and impact requirements.

Why are nickel-alloy welding wires used for low-temperature steel?

Nickel can improve weld-metal toughness at reduced temperatures, making nickel-alloy welding wires suitable for many low-temperature applications.

Should I replace ER80S-Ni1 with ER80S-Ni2 if Charpy impact testing fails?

Not necessarily.

The replacement depends on the base material, welding procedure qualification and project requirements.

Conclusion

If your low-temperature weld passes tensile testing but fails the Charpy impact test, do not immediately replace it with a stronger welding wire.

First check:

Is the welding wire suitable for low-temperature steel?

Is the impact test temperature correct?

Does the welding procedure meet requirements?

Does the weld metal provide enough toughness?

For low-temperature steel welding, the best welding wire is not always the strongest one. It is the one that provides reliable impact toughness under the actual service conditions.