Steel 1018 vs 4140
Steel · grade comparison
Steel 1018 and 4140 are both steel grades. 4140 is the stronger of the two: yield strength 480 MPa (69.6 ksi) against 220 MPa (31.9 ksi) for 1018, about 118% more; tensile strength follows at 690 MPa (100 ksi) vs 400 MPa (58 ksi). In exchange, 1018 is the more ductile: elongation 25% versus 22% for 4140, and 4140 is harder (210 HB vs 116 HB). 1018 conducts heat better (51.9 W/m·K vs 42.6 W/m·K). On the shop floor, 1018 welds better (excellent vs fair) and 1018 sits in a lower cost tier (budget, $) than 4140 (standard, $$).
1018Choose it when the part is bent, formed or impact-loaded, or when it will be welded.
4140Choose it when strength drives the design.
Buyer's decision notes
Choose 1018 for economical low-carbon bar parts that need straightforward forming, welding or case-hardening options. Choose 4140 when the part needs alloy-steel hardenability, wear resistance or a specified quenched-and-tempered property level through its working section.
Compare the same condition
These base-grade routes name chemistry, not delivery condition. Compare hot-rolled, cold-finished, annealed or quenched-and-tempered products separately and match section size; 4140 hardness and strength after heat treatment depend on section and thermal history.
- Core versus case
- 1018 is suited to a ductile low-carbon core and can be case hardened when a hard surface is needed. 4140 is selected when hardenability through more of the section matters. Specify the required case profile or core properties instead of writing only “heat treat.”
- Welding
- 1018 is the more forgiving welded-fabrication choice. A 4140 weld requires engineering review of carbon equivalent, section, preheat, consumable, heat input and post-weld condition; its final properties must be qualified at the joint.
- Machining route
- Both machine differently with delivery condition. Annealed 4140 may be practical before final heat treatment, while prehardened or quenched-and-tempered stock changes tool load and available stress relief. Plan the sequence around distortion and final stock allowance.
- Section effect
- A hardness callout without section size, quench severity, temper and test location is incomplete for 4140. ASTM A400 is a selection guide by section and properties, not a procurement specification; pair it with the applicable material and heat-treatment requirements.
Put this on the RFQ
- State grade, product form, hot- or cold-finished condition, section size, governing material specification and certification.
- Define final core or case properties, test location, heat-treatment sequence, machining allowance and distortion limits.
- Identify welds, fatigue-critical transitions, surface treatment, decarburization limits and whether final inspection occurs after straightening.
Primary references
- Niagara LaSalle — steel grades — Producer guide distinguishing 1018 forming and welding uses from heat-treatable 4140 alloy steel.
- ASTM — A400 — Active steel-bar selection guide organized by section and desired properties; it explicitly is not a procurement specification.
FabDigit resources: 1018 datasheet, 4140 datasheet, CNC design guide and sheet-metal design guide.
1018 vs 4140: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Bulk Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 205 GPa29.7 Msi · Shear Modulus 80 GPa11.6 Msi · Poisson's Ratio 0.29 · Reduction in Area 50% · Fracture Toughness (K_IC) 110 MPa·√m100 ksi·√in
Physical
Density and transition temperatures.
Density
Melting Point (Solidus)
Liquidus Temperature
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Latent Heat of Fusion
Max Service Temperature (continuous)
Min Service Temperature
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.61 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Brazeability / Solderability
Polishability
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Same in both: Typical Recycled Content 30%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
Thermal Diffusivity
Thermal Shock Resistance Index
Strength versus weight
Yield strength against density for every steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | 1018 | 4140 |
|---|---|---|
| Casting & forging | — | Yes |
| Default condition | HR | HR |
| Relative cost | $ Budget | $$ Standard |
| Min. machined wall | 0.8 mm | 0.8 mm |
| Best machined surface | Ra 1.6 µm | Ra 1.6 µm |
Both are offered for CNC machining and Sheet metal. Both take the same 38 finishes: AlCrN, AlTiN, Black Oxide, CVD Al2O3, CVD TiCN, CVD TiN, Cerakote, Chrome Plating, Copper Plating, CrN, DLC, E-Coating and 26 more.
1018 vs 4140 — frequently asked
Is 4140 stronger than 1018?
Yes. 4140 has a typical yield strength of 480 MPa (69.6 ksi) against 220 MPa (31.9 ksi) for 1018 — about 118% more. Tensile strength is 690 MPa (100 ksi) vs 400 MPa (58 ksi).
Which is cheaper, 1018 or 4140?
1018 is the lower-cost material: it sits in the budget tier ($) while 4140 is standard ($$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which welds better, 1018 or 4140?
1018. Its weldability rates excellent (95/100) against fair (40/100) for 4140.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 1018 and 4140 side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.