The 440 MPa rung of the JIS G3113 hot rolled structural ladder — lean C-Mn chemistry, guaranteed yield and elongation, delivered pickled and oiled so frames, arms and rims form and weld without fighting scale.
SAPH440 occupies the middle of the JIS G3113 ladder — above the light-duty SAPH310/370, below the high-strength and microalloyed families that buy their extra yield with alloy additions.
SAPH370 yields at 225 MPa and suits brackets and light mounts; SAPH440 nearly doubles the guaranteed yield (305 MPa) at modest cost. When a cross member keeps cracking at the 370 level, the move to 440 is usually the fix — not a redesign.
Choose 440 when the part carries load or fatigue, not just shape.SAPH310 is a forming-grade hot rolled steel for floor panels and mild stampings. It forms beautifully and carries almost nothing. Using it where the frame needs strength means adding gauge — which usually costs more than stepping up to 440.
Choose 310 for shape, 440 for structure.Microalloyed 420 MPa grades deliver higher yield (420 MPa) and better bendability for the same tensile, but carry alloy cost. SAPH440 is the lean C-Mn route when the print specifies 440 tensile and 305 yield — often the lower landed cost for high volumes.
Choose S420MC when yield or tight-bend formability dominates the design.Values per JIS G3113; silicon is not specified in the standard, typical shown for reference. Actual heats confirmed on the MTC.
| Element | Typical range (%) |
|---|---|
| Carbon (C) | ≤ 0.21 |
| Manganese (Mn) | ≤ 1.20 |
| Phosphorus (P) | ≤ 0.030 |
| Sulfur (S) | ≤ 0.025 |
| Silicon (Si, typ.) | ≤ 0.35 |
Reference: JIS G3113. Final chemistry confirmed with the MTC of the delivered heat.
Elongation varies with gauge per JIS G3113; tensile and yield are guaranteed minima.
| Property | Value | Notes |
|---|---|---|
| Yield strength (min.) | ≥ 305 MPa | JIS G3113 requirement |
| Tensile strength (min.) | ≥ 440 MPa | Typical measured 440 – 580 MPa |
| Elongation, 1.6 – <2.0 mm | ≥ 30% | L₀ = 50 mm, per JIS G3113 by thickness band |
| Elongation, 2.0 – <2.5 mm | ≥ 31% | |
| Elongation, 2.5 – <3.15 mm | ≥ 33% | |
| Elongation, 3.15 – 6.3 mm | ≥ 34% | |
| Bendability (typ.) | 180° / 1t – 2t | Indicative for pickled strip; per JIS G3113 |
Indicative only. Final values depend on gauge, process and the inspection plan agreed at order.
Substitution must be confirmed against your governing standard — chemistry and guaranteed values differ by source.
| Standard | Grade | Notes |
|---|---|---|
| JIS (Japan) | SAPH440 | Base reference — JIS G3113 |
| GB (China) | SAPH440 (approx.) | Direct adoption in GB/T 3273 |
| EN (Europe) | S420MC (approx.) | Confirm against EN 10149-2 |
| China (automotive) | QSTE420TM (approx.) | Confirm against Q/BQB equivalent |
| ASTM (USA) | A1011 SS Grade 55 (approx.) | Confirm against A1011/A1011M |
3.0–4.5 mm pickled strip roll-formed into open or closed-section rails. The 305 MPa yield carries bending loads; pickled surface lets the roll former run without scale scoring the dies.
2.0–3.0 mm blanked and pressed, often spot-welded into the floor module. SAPH440's C-Mn chemistry welds cleanly in mixed-gauge joints with the body sheet.
Rim blanks roll-formed and welded at 2.5–4.0 mm, disc blanks drawn at 2.0–3.5 mm. Fatigue resistance at the weld toe is the design driver — 440 tensile with controlled S gives the margin.
Pressed and welded assemblies taking cyclic load. SAPH440 keeps section thickness down versus 370-grade, cutting part weight without changing the tooling.
Read this before you order, so the rung matches the load.
Use SAPH440 when the part is welded or bolted structure — frame, sub-frame, cross member, suspension arm, wheel rim — and the print calls for a minimum tensile of 440 MPa with clean weldability. It is also the upgrade path when a lighter structural grade is cracking in service and you want to keep the same tooling and section.
Do not use SAPH440 for Class-A painted outer panels (it is hot rolled — surface class is not automotive-exposed quality) or for deep-drawn shells where forming dominates (use SPCE cold rolled deep drawing steel). For structural parts above 440 tensile, step up to 22MnB5+AS press hardening steel if you hot-stamp, or to microalloyed 420–550 MPa grades if you cold-form.
Pair it with SPCE in the same body module — SAPH440 for the skeleton, SPCE for the drawn skins — and with HC180YD+Z bake hardening galvanized where a structural bracket also needs corrosion protection without paint.
Continuous acid pickling strips the hot-rolled scale, then an oil film protects the clean surface until it reaches your press or roll former — the difference between a clean weld and porosity at the joint.
Width tolerance and edge condition managed for roll-forming lines and progressive stamping — burr direction agreed so the forming rolls run clean.
Leveled sheets for blanking and laser cutting, with flatness controlled so blanks sit true in the fixture.
Trimmed edges and a documented inspection report — chemistry, mechanicals and surface — on every delivered coil or bundle.
Stay with SAPH440 while 440 tensile / 305 yield satisfies the FEA and the parts weld and form without issue. Move up to microalloyed 420–550 MPa grades when yield strength or bendability drives section reduction, or to press hardening steel when a structural part needs 1500 MPa and the plant has a hot stamping line. Move down to SAPH370 only for lightly loaded brackets where the cost delta across the volume is real. If the same part is specified on a European print, verify S420MC (EN 10149-2) against your drawing before substitution — chemistry and guaranteed values differ.
Why scale removal changes forming, welding and primer adhesion — and how P&O surface classes are specified.
A side-by-side on chemistry, guaranteed values and cost for chassis-grade hot rolled steel.
Grades matched to frames, suspension and body-in-white parts.
From hot rolled coil to ready-to-form strips and sheets.
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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