The outer-panel trick: form it soft, let the paint oven make it strong. HC180YD+Z is a 180 MPa yield-class bake hardening steel with a hot-dip zinc coating — stamped easily, then hardened 30–50 MPa in the bake line.
Bake hardening is the quiet member of the advanced high-strength family: it borrows formability from mild steel and gives back stiffness in the paint oven.
DX51D+Z forms and protects, but its strength is fixed — a hood panel in DX51D needs more gauge to resist dents. HC180YD+Z forms almost as easily and gains 30–50 MPa in the bake cycle, so the finished panel is stiffer at the same thickness.
Choose BH when dent resistance and gauge-down are the targets.HC220YD+Z starts 40 MPa higher and suits larger, flatter panels where forming strain is low. HC180YD+Z keeps the formability headroom for deeper draws and complex character lines — the right call when the die, not the stiffness, is the constraint.
Choose 180 class for deep panels, 220 class for flat ones.The bare cold rolled version exists for painted parts where the body shop applies its own anti-corrosion route. The +Z coating adds the sacrificial zinc layer — the standard choice for unibody outer panels exposed to stone chip and salt.
Choose +Z unless your line already coats or the part is interior.Typical values for the bake-hardening base steel — the alloy balance that keeps carbon available for the BH effect. Confirmed on the MTC.
| Element | Typical range (%) |
|---|---|
| Carbon (C) | ≤ 0.008 |
| Manganese (Mn) | ≤ 0.40 |
| Phosphorus (P) | 0.04 – 0.08 |
| Sulfur (S) | ≤ 0.020 |
| Aluminium (Al, total) | ≥ 0.020 |
| Titanium + Niobium (typ.) | 0.02 – 0.08 |
Typical, confirmed on MTC. Interstitial control and microalloy balance determine the bake hardening response.
The second column is the reason this grade exists — yield strength that rises in the paint shop.
| Property | As delivered (skin passed) | After paint bake (typ.) |
|---|---|---|
| Yield strength | 180 – 240 MPa | +30 – 50 MPa (BH₂) |
| Tensile strength | 300 – 380 MPa | 300 – 380 MPa |
| Elongation (typ.) | ≥ 32% | — |
| r₉₀ (plastic strain ratio, typ.) | ≥ 1.6 | — |
| n₉₀ (work hardening, typ.) | ≥ 0.18 | — |
| BH₂ (2% pre-strain, 170 °C × 20 min) | ≥ 30 MPa | measured per order |
Indicative only. Final values depend on gauge and inspection plan; BH₂ can be verified on your gauge when required.
Bake hardening galvanized grades are named differently across standards — confirm the governing print before substitution.
| Standard | Grade | Notes |
|---|---|---|
| GB / China (automotive) | HC180YD+Z | Base reference — bake hardening + hot-dip zinc |
| EN (Europe) | HX180BD+Z (approx.) | Confirm against EN 10346 |
| JIS (Japan) | No direct BH HDG equivalent | Closest: JIS G3313 SECD (electro-galv. drawing) — no BH guarantee |
| ASTM (USA) | No direct BH HDG equivalent | Closest: A653 CS Type B — no BH guarantee |
Approximate, confirm before substitution. The BH response is not guaranteed by the mild-grade standards above.
0.7 mm HC180YD+Z with a character line drawn around the latch area. BH₂ adds the stiffness that keeps the hood from oil-canning under hand pressure — measured after the e-coat bake.
0.7–0.8 mm drawn with the beltline and handle pocket. The +Z coating protects the hem flange where paint coverage is thinnest, and the bake response resists the parking-lot ding.
0.7 mm with deep wheel-arch draw and exposed edges. HC180YD+Z balances the forming freedom the fender needs with the stone-chip dent resistance the wheel arch sees.
0.8 mm large flat panel where dent resistance across a wide surface decides gauge. BH lets the designer keep the section thin and let the oven do the strengthening.
Read this before you order, so the grade matches the body shop.
Use HC180YD+Z when the part is a painted outer panel — hood, door, fender, tailgate — that must resist dents and corrosion, and your line runs a paint bake above roughly 160 °C for 15–30 minutes. That bake is free strength: the die sees a 180 MPa steel and the customer gets a 220+ MPa panel.
Do not use it when there is no paint bake in the process (BH never activates), the part is structural and needs real load capacity (use SAPH440 or 22MnB5+AS), or the draw is so deep that a mild deep-drawing steel like SPCE is needed for the forming itself.
Pair it with SPCE for inner panels that need deep draw freedom, and with the same HC180YD+Z family (e.g. HC220YD+Z) for the flatter, larger panels in the same body program so the body shop runs one coating family.
The +Z coating is applied in-line with the anneal — coating mass (e.g. Z100–Z140) and spangle control agreed so the panel paints evenly.
A controlled final pass sets the as-delivered yield band and surface texture — the process that keeps the 180–240 MPa class honest.
Coil widths for blanking and progressive presses, with edge burr managed so zinc does not build up on the shear line and disturb spot welding.
We can test the bake hardening response on your gauge — 2% pre-strain, 170 °C × 20 min bake — and put the number on the inspection report.
Stay with HC180YD+Z while the part draws comfortably and the paint shop runs a real bake cycle. Move up to HC220YD+Z or a dual-phase grade when flat panels need more stiffness and the forming strain is low. Move across to SPCE + separate corrosion protection when the draw is the bottleneck. If your line bakes below ~150 °C or skips e-coat, the BH never activates — then the honest choice is either a mild galvanized steel at higher gauge or a static high-strength grade, and we will tell you which, rather than sell you a BH effect you cannot use.
The metallurgy behind BH₂, why the paint oven is part of the strength budget, and how to verify the effect.
What the coating suffixes mean and which corrosion protection suits which part.
HS-FINEB steel grades matched to body panels and closures.
From coated coil to ready-to-press blanks.
These grade families share material, processing or application territory with the topic on this page.
DP / TRIP / HSLA grades (HC180YD, HC260LA, DP590) combining strength with formability for lightweighting.
SPHC / Q235 / Q345 scale-free coils with oil coating, cost-effective for structural and tube applications.
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