Steel 340X-HR (Hot rolled)
Supply condition
ASTM J2340 340X
Choose for thicker gauges (≥2 mm) such as frame rails, brackets and suspension parts where surface finish is not critical.
Values for the HR condition
Other 340X tempers and conditions
340X is listed in 2 conditions; see the grade overview at 340X.
- CR
- HR
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 |
HRThis page 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 |
What is 340X-HR?
340X-HR is 340X supplied in the HR condition — choose for thicker gauges (≥2 mm) such as frame rails, brackets and suspension parts where surface finish is not critical. 340X-HR has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 465 MPa (67.4 ksi) — weaker than 68% of steel grades. Elongation at break is 25% and the elastic modulus is 207 GPa (30 Msi). 340X-HR 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). CR is the default condition FabDigit quotes; HR is available on request or by drawing note.
Advantages
- Readily welded — 87/100, better than 85% of steel grades
- Forms and bends easily — 68/100, better than 83% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
- High electrical conductivity — 9.5 % IACS, better than 75% of steel grades
340X-HR properties
Typical room-temperature values for 340X-HR; 22 are specific to this condition. Other listed values are 340X reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
340X-HR 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-HR has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 465 MPa (67.4 ksi) — weaker than 68% of steel grades. Elongation at break is 25% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
340X-HR 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-HR conducts electricity at 9.5 % IACS, better than 75% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 340X-HR 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-HR's machinability is fair (54/100, better than 54% of steel grades); weldability excellent (87/100); formability good (68/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 340X-HR
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.
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.
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 | — |
340X-HR — frequently asked
What is 340X-HR used for?
340X-HR 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-HR?
340X-HR has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 465 MPa (67.4 ksi) — weaker than 68% of steel grades. Strength varies by condition: see the 2 listed tempers.
Is 340X-HR easy to machine?
Reasonably — machinability is rated fair (54/100, better than 54% 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-HR be welded?
Yes — weldability is rated excellent (87/100). 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-HR?
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-HR 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-HR?
340X-HR 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.