Why Low-Temperature Impact Testing Matters for A4-80 Stainless Steel Bolts
When a fastener is used in a cold environment — offshore platforms in the North Sea, LNG storage facilities, cryogenic pipelines, or outdoor structural applications in sub-zero climates — tensile strength alone is not enough. A bolt that is strong at room temperature can become brittle and fracture suddenly at low temperatures if it has not been tested and verified for impact toughness.
At FULLERKREG, we subject our DIN933 A4-80 SUS316 stainless steel hex bolts to third-party low-temperature impact testing to verify their performance in demanding cold-service applications. Here is how to read the test report — and why it matters.
The Product: DIN933 A4-80 SUS316 Hex Bolt
| Parameter | Specification |
|---|---|
| Product Type | Hex Bolt (Full Thread) |
| Dimensional Standard | DIN 933 |
| Material | SUS316 (AISI 316 / UNS S31600) |
| Property Class | A4-80 |
| Tensile Strength | ≥800 N/mm² |
| Yield Strength (Rp0.2) | ≥640 N/mm² |
| Elongation | ≥12% |
| Key Alloying Elements | Cr 16–18%, Ni 10–14%, Mo 2–3% |
| Corrosion Resistance | Excellent — seawater, chloride, acid environments |
The molybdenum addition in SUS316 (compared to SUS304) provides significantly improved resistance to pitting and crevice corrosion in chloride-bearing environments, making it the preferred grade for marine, offshore, and chemical process fasteners. The A4-80 property class designation confirms the bolt has been cold-worked to achieve the higher strength level.
The Test: What Is a Charpy Low-Temperature Impact Test?
The Charpy impact test measures the energy absorbed by a material when it fractures under a sudden impact load. A notched specimen is struck by a swinging pendulum hammer, and the energy absorbed (in Joules) is recorded. The higher the absorbed energy, the tougher the material — and the less likely it is to fracture suddenly in service.
For fasteners used in cold environments, the test is performed at a sub-zero temperature (in this case, −20°C) to simulate the actual service condition. Many materials that are ductile at room temperature become brittle at low temperatures — a phenomenon known as ductile-to-brittle transition. Austenitic stainless steels like SUS316 do not exhibit this transition, which is one of the key reasons they are specified for cryogenic and low-temperature applications.
| Test Parameter | Detail |
|---|---|
| Test Method | ISO 898-1:2013 (Charpy V-notch) |
| Notch Type | KV2 (2 mm V-notch) |
| Test Temperature | −20°C |
| Minimum Requirement | ≥27 J (per specimen) |
| Number of Specimens | 3 |
| Testing Laboratory | China Components Test (CCT) — Report No. 2023237771 |
The Test Report: Reading the Results
The third-party test report (Report No. 2023237771, Page 2/2, issued by China Components Test) records the following results for our DIN933 A4-80 SUS316 hex bolts:
| Test Item | Test Method | Requirement | Result (3 specimens) | Conclusion |
|---|---|---|---|---|
| Impact Absorbed Energy KV2 at −20°C (J) | ISO 898-1:2013 | ≥27 J | 235 / 211 / 274 | PASS (符合) |
Note: One specimen absorbed energy exceeding 80% of the testing machine capacity (300 J). This is recorded as a note per standard practice and does not affect the PASS conclusion — it indicates the material’s toughness exceeded the measurable range of the equipment.
What Do These Numbers Mean?
The three specimens absorbed 235 J, 211 J, and 274 J respectively at −20°C — all dramatically exceeding the minimum requirement of 27 J. To put this in perspective:
| Metric | Value |
|---|---|
| Minimum required (per specimen) | 27 J |
| Lowest result recorded | 211 J |
| Highest result recorded | 274 J |
| Average of 3 specimens | 240 J |
| Margin above minimum (lowest specimen) | +184 J (+681%) |
These results confirm that our SUS316 A4-80 bolts retain exceptional toughness at −20°C — absorbing nearly 8× the minimum required energy before fracture. This is characteristic of austenitic stainless steels, which maintain their face-centered cubic (FCC) crystal structure at low temperatures and do not undergo the ductile-to-brittle transition seen in carbon and low-alloy steels.
Why Does This Matter for Your Application?
If your fasteners are used in any of the following environments, low-temperature impact toughness is a critical selection criterion:
- Offshore and subsea structures — North Sea, Arctic, and deep-water installations where ambient temperatures regularly fall below −20°C
- LNG and cryogenic equipment — liquefied natural gas storage tanks, transfer lines, and process equipment operating at −162°C or below
- Cold-climate infrastructure — bridges, pipelines, and structural steelwork in northern Canada, Scandinavia, Russia, and similar regions
- Refrigeration and cold storage — industrial refrigeration plant, cold chain logistics facilities
- Chemical process equipment — reactors and heat exchangers handling cryogenic or sub-zero process streams
In these applications, a fastener that fractures suddenly under impact load — rather than deforming plastically — can cause catastrophic structural failure. Verified impact toughness data from an accredited third-party laboratory is the only reliable way to confirm suitability.
FULLERKREG Quality Assurance
At FULLERKREG, we do not rely solely on material certificates. For critical applications, we commission independent third-party testing through accredited laboratories to verify that our products meet — and exceed — the specified requirements.
- Third-party test reports — available for mechanical properties, chemical composition, and low-temperature impact
- Material Test Certificates (MTC) — EN 10204 3.1 / 3.2 on request
- DIN933 A4-80 SUS316 hex bolts — in stock and available for wholesale supply
- Custom specifications — non-standard dimensions, thread forms, and special alloy grades
Need DIN933 A4-80 SUS316 bolts with verified low-temperature impact data? Contact FULLERKREG — our engineering team will provide full documentation with your order.
FULLERKREG — Precision Fasteners. Global Standards. Reliable Supply.