The sector, ratchet and pawl inside every car seat recliner are fine blanked from spheroidized medium carbon strip — then hardened to carry the load that FMVSS 207 and ECE R17 put on the seat back.
A seat recliner is a loaded mechanism: the sector gear locks the seat back angle, the ratchet holds the pawl, and the pawl transfers the belt-anchor moment into the seat frame. All three are fine blanked steel parts that must shear clean in the die and harden predictably in the furnace. Medium carbon spheroidized strip is the material family that does both.
Low carbon blanks cleanly but cannot reach the 45–52 HRC range a loaded recliner tooth needs after heat treatment — you would rely on case depth alone, and the core stays soft.
Choose medium carbon when the part carries load in the core, not just the case.High carbon hardens harder and cheaper, but the fine-blanked tooth form becomes brittle under shock and the spheroidizing window is narrower. For a fatigue-loaded latch, the toughness of SAE1050 at 48 HRC beats SAE1078 at 55 HRC.
Choose SAE1050-class when impact and fatigue matter more than peak hardness.Plain annealing leaves lamellar pearlite that tears along the shear plane and wears the die. A spheroidized carbide structure shears cleanly at lower force, holds the V-ring impression, and gives a repeatable response to quench and temper.
The metallurgical difference between a torn edge and a 100% burnished shear face.Indicative values drawn from production recliner programs. The final spec is agreed at RFQ against your drawing and governing customer standard.
| Parameter | Typical value | Why it matters |
|---|---|---|
| Strip thickness | 2.0 – 4.0 mm | Sets fine blanking force and tooth strength; thicker strip needs more press tonnage and deeper V-ring |
| Shear surface | 100% burnished (full clean shear) | No fracture zone on the tooth flank; tear = rejected part in the locking flank |
| Rollover (die roll) on tooth tip | Minimized, typically ≤ 8–10% of thickness | Rollover reduces effective tooth height and locking engagement |
| Blanked-part tolerance | ± 0.03 – 0.05 mm (positional per drawing) | Tooth profile and hole pattern must index the recliner assembly |
| Flatness after blanking | 0.05 – 0.15 mm | Stacked parts and assembly alignment; corrected by leveling if tighter |
| Delivery condition | Spheroidized annealed (soft) | Clean shear, die life, and uniform hardenability response |
| Annealed hardness | ~ 120 – 160 HB (indicative) | Low enough to blank without cracking the tooth form |
| Hardness after Q&T | 45 – 52 HRC (typical) or per drawing | Tooth wear resistance and load capacity for seat strength duty |
Regulation reference: seat back strength is verified against the latest revision of the applicable standard (e.g. FMVSS 207 in the US, ECE R17 in Europe, GB 15083 in China) — the material must simply be consistent enough that every production part reproduces the tested one.
All supplied spheroidized with a hardness band and slit to your coil width. The choice between them is mostly about section thickness and how hard the tooth must be after heat treatment.
| Grade | Typical C % | Why it is specified | Typical use in the recliner |
|---|---|---|---|
| SAE1035 | 0.32 – 0.38 | Good blanking + formability, hardens to ~ 40 – 45 HRC; least distortion in Q&T | Thin ratchet plates, stamped links, low-load pawls |
| SAE1050 | 0.48 – 0.55 | Workhorse for loaded teeth; reaches 45 – 52 HRC with good toughness | Sector gear, main ratchet, locking pawl |
| SAE1055 | 0.52 – 0.60 | Higher hardness ceiling than 1050 where wear dominates | High-wear pawl teeth on heavy-duty seats |
| C45E (EN) | 0.42 – 0.50 | European-spec equivalent of SAE1045; familiar to EU Tier-1s | Recliner parts built to EN-based customer standards |
| C55E (EN) | 0.52 – 0.60 | European-spec equivalent of SAE1055 | EU-spec heavy-duty recliner sectors |
Chemistry shown is the typical band for each grade; confirm the delivered heat on the MTC. Equivalent grades from the data sheet: SAE1035 and SAE1050 are stocked; C45E/C55E supplied to the EN equivalent with side-by-side comparison.
Fine blanking is a sheet-metal process, but a recliner part behaves like a precision gear blank. These are the failure modes we see, and the material-side answers.
Die roll rounds the top edge of the tooth and shortens locking engagement. Solution: spheroidized strip with a low, narrow hardness band so the V-ring can clamp the material before the punch moves.
Lamellar carbide or an over-hard anneal makes the shear plane tear instead of burnish. Solution: full spheroidizing cycle + documented hardness, verified on process samples before the coil ships.
After blanking, the part is hardened — and distortion moves the tooth index. Solution: uniform chemistry and hardenability across the coil give repeatable Q&T response; we publish the hardness band so your heat treater holds one cycle.
A hard or inconsistent strip wears the fine blanking die on the tooth flanks. Solution: soft spheroidized condition + consistent gauge keeps die life in the 500k–1M stroke range typical for this part class.
Three HS-FINEB product families cover the recliner bill of materials. Send the drawing and we confirm the match at RFQ.
SAE1035–SAE1050 spheroidized strip for the sector, ratchet and pawl — the core of this page. Fine blanking range →
The recliner return spring that tensions the mechanism — 50CrV4 / 65Mn / SAE1078 hardened-and-tempered strip. SAE1078 strip →
Housing plates and brackets around the mechanism, where strength is secondary to formability. SPCC / DC01 class. Full product matrix →
A typical front-seat recliner sector program, described the way it runs.
The part is a toothed sector, roughly 80 mm across, 3.0 mm thick, with a splined bore on one end and a 12-tooth locking flank on the arc. The drawing calls SAE1050 spheroidized strip, 3.0 × 120 mm coil, and the blanking line runs it through a progressive fine blanking die: V-ring clamp, punch, counter-pressure, one stroke per part at 20–30 strokes per minute. The shear face comes out 100% burnished, rollover held under 0.25 mm on the tooth tip, flatness inside 0.10 mm.
Blanks go to heat treatment — austenitize, oil quench, temper to 46–50 HRC — then the splined bore is broached or shaved. At final assembly the sector indexes against the pawl and the seat back is cycled; the strength sign-off loads the mechanism per the applicable seat strength regulation. Every coil of that 3.0 mm strip came off our line spheroidized, hardness-banded, and slit — which is the only way the heat treater can hold one cycle and the die can hold its edge for the full production run.
If your drawing lands near this envelope — 2.0–4.0 mm medium carbon, spheroidized, Q&T after blanking — the short conversation is: send the drawing, confirm the hardness band and width, and we quote a trial coil.
Related reading: fine blanking vs. conventional stamping — when the shear face has to be clean, and what spheroidizing annealing actually does to carbide structure.
These grade families share material, processing or application territory with the topic on this page.
SAE1078 / 65Mn / SK5 grades for hardened parts, springs and cutting edges.
SAE1045 / C45 grades balancing strength and formability for induction-hardened parts.
65Mn / 50CrV4 / 60Si2Mn grades with high elastic limit and fatigue resistance.
Send the drawing or part number, thickness × width, quantity and destination port. Our engineers reply within one working day with grade match, hardness band and a trial-coil option.