Mechanical applications in the automotive, railway, and machinery industries present engineers with immense durability challenges. When designing advanced moving systems, engineers typically choose carbon spring steel springs to ensure maximum energy storage capacity within restricted installation spaces.
Carbon spring steel springs (most commonly made from patented wire according to EN 10270-1) are high-strength elastic components manufactured from steel with a carbon content ranging from approximately 0.5% to 1.0%.
Through the patenting process—a specialized thermo-mechanical treatment—they achieve a unique, fine-grained pearlitic structure that guarantees the highest elastic limit and tensile strength.
Technological Limitations and the Risk of Hydrogen Embrittlement
Despite their undeniable strength advantages, high-carbon spring steel has two primary limitations: susceptibility to stress relaxation at temperatures above 120°C and a complete lack of natural corrosion resistance. Unprotected carbon wire rapidly coats with iron oxides, which, under cyclic operating conditions, leads to pitting and fatigue micro-cracking.
Another critical hazard is hydrogen embrittlement. It most frequently occurs during improper surface preparation prior to electroplating (e.g., during aggressive acid pickling).
In the automotive sector (in accordance with strict IATF 16949:2016 requirements), eliminating this risk is an absolute prerequisite for approving parts for assembly.
Check also: IATF 16949 Quality in Practice. What Does the Automotive Industry Require from a Spring Manufacturer?
Zinc Flake Coating as a Premium Standard
Combining the hardness of carbon wire with longevity requires advanced surface engineering. Traditional electrogalvanizing carries the aforementioned risk of hydrogen absorption and requires a time-consuming baking (de-embrittlement) process.
At Metalpol, we solved this problem by investing in an automated zinc flake coating line.
Patented Carbon Steel vs. Austenitic Stainless Steel
| Technical Parameter | Patented Carbon Steel (EN 10270-1 SH/DH) | Stainless Steel (EN 10270-3 / AISI 302) |
| Strength (for 2.0 mm wire) | approx. 1950 – 2150 MPa | approx. 1650 – 1850 MPa |
| Shear Modulus ($G$) | 81,500 MPa | 73,000 MPa |
| Natural Corrosion Resistance | None (requires coating) | Very High |
| Stress Relaxation Behavior | Susceptible above 120°C | Resistant up to approx. 250°C |
| Primary Application Sectors | Automotive, railway, heavy machinery | Medical, aerospace, food industry |
Consult Your Project with Our Engineers
Optimizing spring geometry and surface protection at an early stage of R&D can reduce unit costs by up to 25%. Contact us directly to discuss your technical specifications.
- Sales & Logistics Department: +48 (17) 774 5673 / +48 (17) 774 5678
- Technical E-mail: info@mtlpl.eu
FAQ Section
1. Can carbon spring steel springs operate outdoors without a protective coating?
No. High-carbon wire undergoes rapid atmospheric corrosion. Outdoor applications require an anti-corrosion coating (such as zinc flake coating) or switching the material to AISI 302/316 stainless steel.
2. What is the difference between SH and DH class wire in the EN 10270-1 specification?
SH class designates high-strength patented carbon wire intended for static and medium-dynamic applications. DH class features similar tensile strength but adheres to stricter criteria regarding surface defects and property uniformity, making it recommended for extremely high dynamic load applications (e.g., automotive valve springs).
3. Do you fulfill serial production orders directly from 3D CAD files?
Yes. Our engineering department operates using professional CAD/CAM software. We can provide a free quote and a technological feasibility study based on STEP, IGES files, or traditional 2D drawings.
