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SAE1078 vs C67S vs 65Mn — Spring Steel Strip Compared Six Ways

The three workhorse spring strip grades of the American, European and Chinese standards — same job, different alloying philosophy. This page lines them up so the choice stops being a habit and becomes a decision.

● All three stocked in Shanghai SAE1078 — US high carbon C67S — EN 10132-4 spring strip 65Mn — GB manganese spring steel

At a glanceSAE1078 (AISI high carbon, C 0.72–0.85%), C67S (EN 10132-4 spring strip, C 0.65–0.73%) and 65Mn (GB/T spring steel, C 0.62–0.70% with Mn 0.90–1.20%) are the three spring strip grades that dominate American, European and Asian production respectively. All three harden to the 42–50 HRC class, all three blank cleanly when spheroidized, and all three are available hardened-and-tempered. They differ in hardenability (65Mn's manganese buys deeper hardening in thick sections), cold formability (C67S is the friendliest to stamp), and consistency in thin gauges (lean SAE1078 is the most uniform). The six-dimension comparison below — chemistry, mechanicals, hardenability, fatigue, cost, applications — is the decision map, with equivalents for the adjacent alloy grades.

Chemistry

Chemical composition — the alloying philosophy in three rows

Carbon sets the hardness ceiling; the alloying additions set how deep and how uniformly you reach it. That single difference drives most of the practical decisions below.

Element	SAE1078 (ASTM/AISI)	C67S (EN 10132-4)	65Mn (GB/T)
Carbon (C)	0.72 – 0.85%	0.65 – 0.73%	0.62 – 0.70%
Manganese (Mn)	0.30 – 0.60%	0.60 – 0.90% (typical)	0.90 – 1.20%
Silicon (Si)	residual	0.15 – 0.35% (typical)	0.17 – 0.37% (typical)
Phosphorus (P)	≤ 0.040%	≤ 0.025% (typical)	≤ 0.035% (typical)
Sulfur (S)	≤ 0.050%	≤ 0.025% (typical)	≤ 0.035% (typical)
Alloy character	Lean high carbon, no intentional alloy	Low-alloy spring strip, S-designated	Manganese-alloyed spring steel

Values shown are typical bands for comparison; governing limits follow the latest revision of each standard (ASTM A684/AISI, EN 10132-4, GB/T 1222) and are confirmed on the MTC of the delivered heat.

Mechanicals

Mechanical properties by delivery condition

All three grades are sold either soft for forming or hardened-and-tempered for finished spring properties. The useful comparison is therefore by condition, not by a single number.

Condition	SAE1078	C67S	65Mn
Spheroidized (annealed)	~ 160 – 200 HB; fine blanking / cold forming	+A condition, soft band for forming	Annealed, soft band for blanking
Hardened & tempered (typical band)	1,150 – 1,450 MPa / 38 – 48 HRC	~ 42 – 48 HRC typical (per +QT spec)	~ 42 – 50 HRC typical
Elastic limit after H&T	High at thin gauges	Good; reliable in stamped form	High; deep-hardened core helps thick sections
Formability before hardening	Good when spheroidized	Best of the three — leaner carbon + soft anneal	Good; slightly stiffer due to Mn

Hardness and tensile are indicative and depend on gauge, quench medium and tempering cycle — confirm the agreed band per order.

Hardenability · fatigue · cost

Where the three grades genuinely differ

Chemistry differences are academic until they show up as a soft core, a fatigue crack or a price delta. This is the decision table that matters.

Dimension	SAE1078	C67S	65Mn
Hardenability	Shallow — best in thin strip ≤ ~2.5 mm	Moderate; designed for thin spring strip	Deepest — Mn hardens 3–4 mm+ sections through
Hardness uniformity	Excellent in thin gauges	Good; tight EN process control	Good; Mn reduces sensitivity to quench rate
Fatigue behavior	Good with clean edges + low decarb	Good; cold-formed parts benefit from formability	Good; core support helps heavy-duty cycles
Cost position	Lowest — no alloy	Mid — European spec, controlled limits	Mid-low — Mn is cheap, GB supply chain
Edge case to watch	Soft core in thick sections	Lower max hardness ceiling than 1078	Quench cracking risk if over-tempered tight

Fatigue is a system property — edge quality, decarburization, shot peening and stress level dominate the grade name. All three respond to the same rules.

Applications & selection

Typical applications, and a three-question decision tree

Grade choice usually reduces to three questions: how thick is the section, whose drawing is it, and is the part formed or just blanked?

SAE1078 — the thin-strip generalist

Clutch plates, scraper blades, spring washers, thin clips. Lean chemistry and consistency in 0.3–2.5 mm strip make it the default where the section is thin and the drawing is American.

Pick 1078 for thin gauges and cost-driven programs.

C67S — the European formable spring

Stamped springs, clips and formed spring components in EU production. Lower carbon and EN process control give the best cold formability of the three, at a slightly lower hardness ceiling.

Pick C67S when the part is formed and the drawing is EN.

65Mn — the heavy-section workhorse

Clutch disc springs, heavy washers, spring plates in 3–6 mm sections. Manganese hardens the core where 1078 would run soft; the standard spring steel of Chinese and Asian production.

Pick 65Mn for thick sections needing through-hardening.

How thick is the spring section?≤ 2.5 mm → any of the three works; pick by standard. 3 mm and up → 65Mn (or 50CrV4) to avoid a soft core.
Whose drawing is it?American → SAE1078. European → C67S. Chinese/Asian → 65Mn. This usually decides before any metallurgy discussion.
Is the part formed, or just blanked and hardened?Formed → C67S for formability. Blanked → 1078 or 65Mn per section. Heavily loaded or fatigue-critical → consider 50CrV4-class alloy spring steel.

When fatigue life or load stability is contractual, step up to an alloy spring grade (50CrV4 / 60Si2MnA) rather than pushing any of these three harder — see the related pages below.

A rule of thumb that survives most drawing rooms: if the spring is thinner than about 2.5 mm and the drawing is American, order SAE1078 and stop thinking; if the drawing is European and the part is stamped or formed rather than simply blanked, C67S repays its slightly higher cost in fewer forming rejects; if the section is 3 mm or thicker, or the part runs hot and heavily cycled, 65Mn's manganese is buying real core hardness that 1078 cannot reach at that gauge. Within those lanes all three perform predictably, which is exactly why they have become the default spring strip of three continents. The failure mode to avoid is substitution across lanes — a soft core from 1078 at 4 mm, or a forming crack from 65Mn on a tight bend that C67S would have taken — and that is what the tables above are designed to prevent before the steel is ordered.

Equivalents

Approximate equivalents and adjacent grades

For substitution, confirm chemistry and hardenability against your governing standard — near-equivalents are a starting point, not a guarantee.

SAE1078	C67S	65Mn	Adjacent alloy grades
SAE1078 / AISI 1078	C67S (EN 10132-4)	65Mn (GB/T 1222)	50CrV4 — Cr-V, best fatigue
GB 75 (approx.)	Ck67 (older DIN)	60Si2MnA — Si/Mn higher strength	SUP9 / SUP10 (JIS)
JIS S75C (approx.)	—	—	SAE6150 — US Cr-V equivalent

Equivalents are approximate. We provide a documented side-by-side chemistry and mechanical comparison for any substitution you are considering.

Supply forms & processing

What we deliver for each grade — and what we do in-house before dispatch

All three grades are processed on the same Shanghai lines, so the delivery flexibility is identical; only the metallurgy differs. This table is what an RFQ should pin down.

Delivery option	SAE1078	C67S	65Mn
Spheroidized (soft annealed)	✓ hardness band documented	✓ +A condition	✓ annealed band
Hardened & tempered	✓ 38–48 HRC per spec	✓ +QT, HRC per spec	✓ 42–50 HRC per spec
Slitting to die width	✓ burr-managed	✓ burr-managed	✓ burr-managed
Cut-to-length	✓	✓	✓
Typical strip range	0.3 – 4.0 mm	0.3 – 3.0 mm (spring strip band)	0.5 – 6.0 mm
MTC / inspection doc	✓ per coil	✓ EN 10204-type per coil	✓ per coil

Delivery condition is the single most important line on the RFQ — the same grade can be soft for fine blanking or hardened for finished springs, and the price, process and part all change with it.

Spec questions

Spring steel grade comparison, asked and answered

What is the difference between SAE1078, C67S and 65Mn?

SAE1078 is the American high carbon strip (C 0.72–0.85%), a generalist for springs and blades. C67S is the European EN 10132-4 spring strip (C 0.65–0.73%) with good cold formability. 65Mn is the Chinese manganese spring steel (C 0.62–0.70%, Mn 0.90–1.20%) with better hardenability in heavier sections. The practical difference is section thickness: lean 1078 for thin strip, 65Mn for thicker sections, C67S when the drawing is European.

Can SAE1078, C67S and 65Mn be substituted for each other?

For thin strip they overlap and substitution is common, but hardenability and fatigue behavior differ. 65Mn hardens deeper thanks to manganese; C67S offers better cold formability; SAE1078 is the leanest and most consistent for thin sections. Confirm chemistry and hardenability against your governing standard before substituting.

Which grade is best for fatigue-loaded springs?

For thin strip, SAE1078 with clean edges and controlled decarb performs well; where alloying is allowed, 50CrV4 or 60Si2MnA outperform all three plain grades in fatigue. Among the three, the fatigue result depends more on edge quality, surface decarb and hardness uniformity than on the grade name.

Why does 65Mn contain manganese?

Manganese (0.90–1.20%) is a hardenability enhancer. It lets 65Mn through-harden in heavier 3–4 mm+ sections where a lean SAE1078 of the same thickness would run soft in the core. That is the main reason 65Mn is the standard spring steel of much of Asian production.

What delivery conditions are available for these grades?

All three are available spheroidized (soft annealed) for fine blanking and cold forming, or hardened-and-tempered with a confirmed HRC band for finished spring properties. EN 10132-4 expresses these as +A, +LC, +CR and +QT. State your process at RFQ and we match the condition.

Which of the three should I choose for a 4 mm disc spring?

At 4 mm, hardenability decides: choose 65Mn (or 50CrV4 if fatigue is contractual) rather than SAE1078, which risks a soft core at that section. If the drawing is European and the part is thin, C67S is the natural fit.

Related steel families

Explore related product families

These grade families share material, processing or application territory with the topic on this page.

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