Steel 340X
ASTM J2340 340X
340X is an SAE J2340 automotive HSLA sheet specification with a 340 MPa minimum yield strength, micro-alloyed and produced to low C, S and P for stamping and welding.
Reference datasheet — 340X is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the CR condition
340X tempers and conditions
340X is supplied in 2 conditions, soft to hard. CR is the default FabDigit quotes; the values on this page are for it.
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
CRDefault Cold rolled | Standard stock condition for stamped body structural panels that are painted or later coated. | 370 | 450 | 26 | 140 HB | 9.5 % IACS |
Hot rolled | Choose for thicker gauges (≥2 mm) such as frame rails, brackets and suspension parts where surface finish is not critical. | 380 | 465 | 25 | 145 HB | 9.5 % IACS |
Supply forms, finishes and certifications
Ways 340X is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
EG | Electrogalvanized | Coating |
GA | Galvannealed | Coating |
HDG | Hot-dip galvanized | Coating |
What is 340X?
340X is an SAE J2340 automotive HSLA sheet specification with a 340 MPa minimum yield strength, micro-alloyed and produced to low C, S and P for stamping and welding. Typical sheet on file shows 370 MPa yield, 450 MPa tensile, 26 % elongation and 140 HB (76 HRB), supplied cold-rolled, hot-rolled, hot-dip galvanized, galvannealed or electrogalvanized. It is chosen for body structural stampings that need more strength than mild steel without losing formability. Corrosion resistance is negligible, so a zinc coating or e-coat is mandatory; step up to 590X where higher yield strength is needed. 340X has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,500°C (2,732 °F). 340X has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 70% of steel grades. Elongation at break is 26% and the elastic modulus is 207 GPa (30 Msi).
What is 340X used for?
- auto body reinforcements
- seat frames
- structural brackets
Advantages
- Readily welded — 89/100, better than 89% of steel grades
- Forms and bends easily — 74/100, better than 89% of steel grades
- Ductile — tolerates forming and impact — 26%, better than 82% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
- High electrical conductivity — 9.5 % IACS, better than 75% of steel grades
340X properties
Typical room-temperature values for 340X-CR; bars are the position among steel grades.
Physical3
340X has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,500°C (2,732 °F).
Mechanical16
340X has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 70% of steel grades. Elongation at break is 26% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
340X is rated for continuous service to 350°C (662 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
340X conducts electricity at 9.5 % IACS, better than 75% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 340X takes about 25 MJ of energy and emits 2.1 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
340X's machinability is good (55/100, better than 62% of steel grades); weldability excellent (89/100); formability very good (74/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. 340X is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 340X
Is 340X easy to machine?
Machines like a medium-carbon-equivalent low-alloy sheet — good chip control but higher tool wear than mild steel; use carbide punches with adequate clearance for blanking and piercing.
Can 340X be welded?
Excellent resistance spot, MIG and laser weldability thanks to low C, S and P; zinc-coated variants need higher weld current and electrode-life management.
Can 340X be formed, bent or molded?
Cold stamps well but springback and edge-crack sensitivity are higher than DDQ steel — allow larger bend radii, control blank-edge quality and compensate die geometry.
340X chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Clow carbon for spot weldability | ≤ 0.13 | 0.07 |
| Mn | ≤ 1.6 | 0.9 |
| Si | ≤ 0.5 | 0.15 |
| P | ≤ 0.03 | 0.02 |
| Slow S for formability/hole expansion | ≤ 0.02 | 0.01 |
| Alkilled/deoxidized | 0.02 – 0.1 | 0.04 |
| Nbmicroalloy, grain refinement | ≤ 0.1 | 0.03 |
| Timicroalloy; Nb+Ti+V total typically ≤ 0.22 | ≤ 0.15 | 0.02 |
| Vmicroalloy | ≤ 0.1 | 0.01 |
| N | ≤ 0.01 | 0.01 |
| Fe | balance |
What surface finishes work on 340X?
No anodizing; use zinc coating (GI/GA/EG), zinc-phosphate plus cathodic e-coat, or powder/paint; bare material must not be left uncoated in service.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 340X in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- J2340 340X
How much does 340X cost?
340X is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
340X — frequently asked
What is 340X used for?
340X is typically used for auto body reinforcements, seat frames and structural brackets. In short: formable 340 MPa HSLA sheet; spot-weldable body steel; available zinc-coated.
What is the yield strength of 340X?
340X has a typical yield strength of 370 MPa (53.7 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 70% of steel grades. Strength varies by condition: see the 2 listed tempers.
Is 340X easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like a medium-carbon-equivalent low-alloy sheet — good chip control but higher tool wear than mild steel; use carbide punches with adequate clearance for blanking and piercing.
Can 340X be welded?
Yes — weldability is rated excellent (89/100). Excellent resistance spot, MIG and laser weldability thanks to low C, S and P; zinc-coated variants need higher weld current and electrode-life management.
What surface finishes work on 340X?
No anodizing; use zinc coating (GI/GA/EG), zinc-phosphate plus cathodic e-coat, or powder/paint; bare material must not be left uncoated in service.
Can 340X be formed, bent or molded?
Cold stamps well but springback and edge-crack sensitivity are higher than DDQ steel — allow larger bend radii, control blank-edge quality and compensate die geometry.
What is the maximum service temperature of 340X?
340X is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 340X-CR and 340X-HR?
CR is the default condition — standard stock condition for stamped body structural panels that are painted or later coated. HR: choose for thicker gauges (≥2 mm) such as frame rails, brackets and suspension parts where surface finish is not critical. Yield strength is 370 MPa in CR versus 380 MPa in HR.
How much does 340X cost?
340X is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- SAE J2340 — Categorization and Properties of Dent Resistant, High Strength, and Ultra High Strength Automotive Sheet Steel — SAE International (2022)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (HSLA sheet steels) — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- GB/T 20564 / HC340LA cold-rolled HSLA sheet (comparable grade) — SAC (China) (2017)
- WorldAutoSteel / worldsteel LCI data for automotive flat-rolled steel — worldsteel (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.