1. Why Standards Matter
When a drawing says "C67S" and your supplier quotes "SUP6," are you getting the same material? The answer is: approximately, but not exactly. Spring steel standards define the chemistry, mechanical properties, delivery condition, tolerances and inspection requirements for a given grade. Three standard systems dominate global spring steel strip supply: the European EN system, the German DIN legacy system, and the Japanese JIS system. Each uses different grade names, slightly different chemistry ranges, and different tolerance classifications.
For procurement and engineering teams, misunderstanding these differences can lead to: material that meets one standard but not another, rejected incoming inspections, spring performance variation, and costly re-qualification. This guide provides a structured comparison to help you navigate cross-standard sourcing with confidence.
Important: All standard references in this article are general summaries. Always refer to the latest revision of the governing standard for precise requirements. Chemistry values are indicative ranges from publicly available standard summaries; actual limits are defined in the full standard text.
2. EN 10132-4 — European Standard
EN EN 10132 is a multi-part European standard titled "Cold rolled narrow steel strip for heat treatment." Part 4 specifically covers spring steel strip — steels intended for the manufacture of springs after heat treatment. It is published by CEN (European Committee for Standardization) and is harmonized across all EU member states, meaning that a grade certified to EN 10132-4 is accepted across the European Economic Area.
2.1 Grade System
EN 10132-4 defines both carbon spring steels and alloy spring steels. The grade naming follows the EN steel numbering convention:
- Carbon spring steels: C67S, C75S, C85S — the number indicates approximate carbon content in hundredths of a percent (C67S ≈ 0.67% C), and the "S" suffix denotes spring quality with controlled non-metallic inclusions.
- Alloy spring steels: 51CrV4, 50CrV4 — chromium-vanadium alloyed grades for higher hardenability and elevated-temperature service. The "51" prefix indicates approximately 0.50% carbon, "CrV" indicates chromium-vanadium alloying, and "4" indicates approximately 1% chromium.
The "S" quality designation is important: it imposes stricter requirements for non-metallic inclusion content (evaluated per EN 10247 or similar methods) and surface quality, which directly affect spring fatigue life. General-purpose carbon steel grades (C67E, C75E) without the "S" suffix are not intended for critical spring applications.
2.2 Mechanical Requirements
EN 10132-4 specifies mechanical properties primarily for the hardened and tempered condition, since spring steels are typically heat-treated after forming. The standard defines tensile strength, yield strength and elongation values based on strip thickness and grade. For the as-delivered (soft) condition, hardness ranges are specified rather than tensile properties, because the soft-annealed material's mechanical properties depend on the exact annealing cycle.
Dimensional tolerances in EN 10132-4 are classified into thickness tolerance classes, with specific values depending on thickness range and strip width. The standard also defines edge conditions (sheared, rounded, rolled) and surface quality requirements.
3. DIN 17222 — German Legacy Standard
DIN DIN 17222 was the German national standard for spring steel strip, titled "Strip steel for springs; technical delivery conditions." It was widely used in German automotive and mechanical engineering for decades and defined grades such as CK67, CK75, CK85, and 50CrV4. The "K" in CK67 indicates a killed (fully deoxidized) steel with tighter composition control than non-killed variants.
DIN 17222 has been officially superseded by EN 10132-4 as part of the European standardization program. Under the CEN system, national standards that conflict with European standards must be withdrawn. However, DIN 17222 remains a presence in industry because:
- Many existing drawings and specifications still cite DIN 17222 grade designations, especially in older German automotive programs.
- Some German suppliers and Tier-1 manufacturers continue to reference DIN 17222 in internal specifications out of familiarity.
- The grade names (CK67 vs. C67S) differ, creating apparent complexity even though the underlying materials are broadly similar.
In practice, material supplied to EN 10132-4 C67S is generally accepted as a replacement for DIN 17222 CK67, provided the customer confirms acceptance. The chemistry and property requirements are aligned through the CEN harmonization process. Always confirm with your customer whether EN 10132-4 is acceptable in place of a DIN 17222 citation.
4. JIS G3311 — Japanese Standard
JIS JIS G3311 is the Japanese Industrial Standard titled "Steel strips for springs." It is published by the Japanese Industrial Standards Committee and is the governing standard for spring steel strip in Japan and throughout Japanese OEM supply chains in Southeast Asia, North America and Europe.
4.1 Grade System
JIS G3311 uses the "SUP" prefix (Spring Use Plate/strip) followed by a number. The primary grades include:
- SUP6: Silicon-manganese spring steel, approximately 0.65–0.75% C, higher Si content for improved elastic limit.
- SUP7: Higher carbon spring steel, approximately 0.75–0.90% C, for higher strength springs.
- SUP9 / SUP9A: Chromium-manganese spring steels, approximately 0.50–0.60% C with Cr and Mn, for improved hardenability. SUP9A is a modified composition variant.
- SUP10: Chromium-vanadium spring steel, approximately 0.47–0.57% C with Cr and V, the most widely used alloy spring steel in Japanese automotive applications.
- SUP11A, SUP12, SUP13: Additional alloy variants for specialized applications including silicon-chromium and tungsten-bearing grades.
4.2 SWP Wire Grades
You may also encounter "SWP" grades (SWP-A, SWP-B, SWP-V) in spring steel discussions. These are not defined in JIS G3311 (which covers strip) but in JIS G3560 (piano wire) and related wire standards. SWP-A and SWP-B are high-carbon piano wire grades for cold-drawn spring wire; SWP-V is a chromium-vanadium alloy spring wire. They are mentioned here because buyers sometimes confuse strip and wire standards. If your application uses strip (not wire), JIS G3311 is the correct standard; if it uses wire, refer to the appropriate JIS wire standard.
5. Six-Dimensional Comparison
The table below compares the three standards across six dimensions that matter for procurement and engineering.
| Dimension | EN 10132-4 | DIN 17222 | JIS G3311 |
|---|---|---|---|
| Grade naming | C67S, C75S, 51CrV4 — carbon content + S (spring quality) | CK67, CK75, 50CrV4 — carbon + K (killed) | SUP6, SUP7, SUP10 — SUP + sequence number |
| Chemistry limits | Defined per grade with product analysis tolerances | Similar to EN; superseded but historically aligned | Defined per grade; generally wider Si/Mn ranges than EN |
| Mechanical properties | H&T condition: Rm, Re, A by thickness; soft condition: hardness range | H&T condition properties; historically similar to EN | H&T condition: tensile strength by grade and wire/strip diameter |
| Delivery conditions | Soft annealed, hardened & tempered, cold rolled | Soft annealed, hardened & tempered | Annealed (A), hard rolled, hardened & tempered |
| Tolerance grades | Thickness tolerance classes (A/B); width classes | Historical tolerance classes; superseded by EN | Class 1 / Class 2 thickness and width tolerances |
| Surface & inclusion control | "S" quality = controlled inclusions; surface quality classes | K = killed steel; inclusion requirements per older DIN methods | Surface finish specified; inclusion control per JIS methods |
Table 1: Six-dimensional comparison of spring steel strip standards. Refer to the latest revision of each standard for precise tolerance values and property requirements.
6. Cross-Standard Equivalent Grades
The table below maps commonly used spring steel grades across the three standards, plus AISI/SAE equivalents for reference. These are approximate equivalents — chemistry ranges differ, and substitution should always be confirmed against your governing standard and application requirements.
| Material Family | EN 10132-4 | DIN 17222 | JIS G3311 | AISI/SAE (approx.) |
|---|---|---|---|---|
| Medium-high carbon spring steel | C67S | CK67 | SUP6 | 1065 / 1070 |
| High carbon spring steel | C75S | CK75 | SUP7 | 1075 |
| Very high carbon spring steel | C85S | CK85 | — (not directly mapped) | 1084 / 1095 |
| Cr-Mn spring steel | — (not in standard EN range) | — | SUP9 / SUP9A | 5155 (approx.) |
| Cr-V alloy spring steel | 51CrV4 / 50CrV4 | 50CrV4 | SUP10 | 6150 |
| Si-Cr spring steel | — | — | SUP12 | 9254 (approx.) |
Table 2: Cross-standard approximate equivalent grades. Approximate equivalent, confirm chemistry before substitution. Dashes indicate no direct equivalent in that standard system. AISI/SAE mappings are for reference only and may differ in chemistry and hardenability.
Several important nuances emerge from this mapping. First, JIS G3311 includes grades (SUP9, SUP12) that have no direct EN 10132-4 equivalent, reflecting the Japanese automotive industry's historical preference for chromium-manganese and silicon-chromium alloy systems. Second, the carbon content alignment is approximate — C67S targets ~0.67% C while SUP6 spans 0.65–0.75% C, so a specific heat of SUP6 could fall outside the C67S range. Third, silicon content is consistently higher in JIS grades — SUP6 typically contains 1.50–1.80% Si versus ~0.25% in C67S — which improves elastic limit but can affect decarburization behavior and coating adhesion.
7. Representative Chemistry Comparison
The table below compares the indicative chemical composition ranges for three commonly paired equivalent grades. These ranges are summarized from publicly available standard information; always verify against the latest revision of the full standard text and the specific Mill Test Certificate for the delivered heat.
| Element | C67S (EN 10132-4) | SUP6 (JIS G3311) | 51CrV4 (EN 10132-4) | SUP10 (JIS G3311) |
|---|---|---|---|---|
| Carbon (C) | 0.65 – 0.72 | 0.65 – 0.75 | 0.47 – 0.55 | 0.47 – 0.57 |
| Silicon (Si) | 0.15 – 0.35 | 1.50 – 1.80 | 0.15 – 0.40 | 0.15 – 0.35 |
| Manganese (Mn) | 0.60 – 0.90 | 0.50 – 0.80 | 0.70 – 1.10 | 0.65 – 0.95 |
| Chromium (Cr) | ≤ 0.30 | ≤ 0.35 | 0.90 – 1.20 | 0.80 – 1.10 |
| Vanadium (V) | — | — | 0.10 – 0.25 | 0.10 – 0.20 |
| Phosphorus (P) max | 0.025 | 0.030 | 0.025 | 0.030 |
| Sulfur (S) max | 0.025 | 0.030 | 0.025 | 0.030 |
Table 3: Indicative chemical composition ranges (wt%). Values summarized from public standard information; refer to the latest revision of EN 10132-4 and JIS G3311 for precise limits. "—" indicates element not intentionally added or not specified.
The most striking difference is the silicon content in SUP6. At 1.50–1.80%, SUP6 is essentially a silicon-manganese spring steel, while C67S is a plain carbon spring steel with minimal silicon. This difference is intentional: silicon strengthens ferrite and raises the elastic limit, making SUP6 suitable for springs that must resist permanent set under high stress. However, high silicon also increases the risk of surface decarburization during heat treatment and can make the material more difficult to phosphate or coat. If you are substituting SUP6 with C67S (or vice versa), these behavioral differences must be evaluated in your heat treat and coating processes.
8. Regional Preference & Supply Chain
Standard preference follows regional manufacturing ecosystems:
- Europe: EN 10132-4 is the default. German OEMs may still cite DIN 17222 on legacy programs but generally accept EN 10132-4 as equivalent. French, Italian and Spanish manufacturers use EN exclusively.
- Japan: JIS G3311 is the standard for all domestic spring steel strip. Japanese steel mills (Nippon Steel, JFE, Kobe Steel) produce primarily to JIS, though they can also produce to EN on request for export programs.
- Southeast Asia: Mixed. Japanese-affiliated manufacturers (Toyota, Honda, Suzuki supply chains) use JIS G3311. European-affiliated manufacturers use EN 10132-4. Local manufacturers may accept either, depending on customer requirements.
- North America: AISI/SAE grades (1070, 1075, 6150, 9254) dominate, with ASTM A684 and ASTM 684 as governing standards. However, transplant factories (Japanese and European OEM plants) often use JIS or EN grades to match parent-company specifications.
- China: GB/T standards (e.g., GB/T 1222 for spring steel) are the domestic default, but export-oriented mills produce to EN, JIS and AISI on request. Chinese spring steel strip is commonly supplied with dual certification — e.g., "51CrV4 per EN 10132-4, equivalent to SUP10."
9. How to Choose the Right Standard
The standard selection decision follows a simple hierarchy:
- Customer drawing specification wins. If the drawing says "SUP6 per JIS G3311," you must supply to JIS G3311 unless the customer formally approves a substitution. Do not assume equivalence.
- Destination market drives default. If no standard is specified, use the standard dominant in the destination market: EN for Europe, JIS for Japan/Japanese OEM supply chains, AISI for North America.
- Supply chain availability matters. Some grades are more readily available in certain standards. For example, 51CrV4 per EN 10132-4 is widely stocked by European and Chinese mills; SUP10 per JIS G3311 is more readily available from Japanese mills. If lead time is critical, choose the standard with the best local availability.
- Performance requirements may override. If your spring requires the high elastic limit of silicon-alloyed steel, SUP6 (JIS) may be more suitable than C67S (EN), even if your market is Europe. In this case, specify the JIS grade and confirm your supplier can produce to it.
10. Standard Update Trends
DIN 17222 supersession: The replacement of DIN 17222 by EN 10132-4 is essentially complete at the standards-body level. The remaining presence of DIN 17222 is in legacy drawings and corporate specifications. Over time, as programs are updated and re-qualified, DIN citations will continue to decline. Buyers should proactively request that customers update drawings to cite EN 10132-4.
JIS G3311 revisions: JIS standards are periodically revised by the Japanese Industrial Standards Committee. Revisions typically update chemistry ranges, add new grades, and align with international standards where possible. Always check that you are referencing the latest revision — older revisions may have different tolerance values or grade definitions.
Harmonization trend: There is a gradual global trend toward greater alignment between EN, JIS and ASTM/AISI standards, driven by global supply chains and multinational OEMs. However, full harmonization is unlikely in the near term because each standard system reflects regional material preferences and historical development paths.
11. Procurement Best Practices
- Always cite the full standard designation including revision year (e.g., "C67S per EN 10132-4:2021" not just "spring steel"). This eliminates ambiguity about which revision applies.
- Specify delivery condition explicitly — soft annealed, hardened and tempered, or cold rolled. Different conditions have different property requirements and different prices.
- Request EN 10204 3.1 MTC with every coil, confirming chemistry, mechanical properties, dimensional inspection and standard compliance. See our MTC reading guide for what to check.
- For cross-standard substitution, get written customer approval before shipping. A verbal "it's basically the same" is not sufficient for quality audits or customer rejects.
- Verify tolerance class — both EN and JIS define multiple tolerance classes, and the default class may not meet your precision requirement. Specify the class explicitly.
- For alloy grades (51CrV4 / SUP10), verify hardenability — chemistry within range does not guarantee identical hardenability due to grain size and inclusion differences. For critical springs, request a hardenability test (Jominy) or end-quench data.
- Consider dual certification — many suppliers can certify material to both EN and JIS (or EN and AISI) if the chemistry falls within both ranges. This simplifies inventory management for global programs.
12. Conclusion
EN 10132-4, DIN 17222 and JIS G3311 cover the same fundamental material families — carbon and alloy spring steels — but differ in nomenclature, chemistry ranges, tolerance systems and regional application. The key to successful cross-standard sourcing is: (1) always identify the governing standard on the customer drawing, (2) treat cross-standard equivalents as approximate and verify chemistry before substitution, (3) specify delivery condition, tolerance class and certification type explicitly, and (4) require full MTC documentation for every batch.
For buyers sourcing from China, the good news is that major Chinese mills can produce spring steel strip to all three standard systems, often with dual certification. The cost guide provides indicative pricing for these grades, and our martensitic stainless steel guide covers a related but distinct material family for high-corrosion spring applications.