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Compare 1018 vs 4140 steel strength machinability cost and best uses with our detailed alloy selection guide.

1018 Steel: What It Is and Why It Matters

When engineers compare 1018 vs 4140, 1018 is the go‑to low carbon “workhorse” mild steel: cheap, easy to machine, easy to weld, and predictable.

Chemical Composition of AISI 1018

AISI 1018 steel is a plain, low carbon steel with very limited alloying.

ElementTypical Range (wt%)
Carbon (C)0.15 – 0.20
Manganese (Mn)0.60 – 0.90
Phosphorus (P)≤ 0.04
Sulfur (S)≤ 0.05
Iron (Fe)Balance

Key point: Low carbon = excellent ductility, weldability, and machinability, but limited hardenability compared with 4140 chromoly alloy.

Mechanical Properties of 1018 (Typical, As‑Rolled/Cold Drawn)

Values vary by form and condition, but typical ranges:

PropertycURL Too many subrequests.
Tensile strength~ 440 – 500 MPa (64 – 73 ksi)
Yield strength~ 370 – 415 MPa (54 – 60 ksi)
Elongation~ 15 – 25%
Hardness~ 120 – 170 HB
Modulus of Elasticity~ 205 GPa (29,700 ksi)

Performance profile:

  • Moderate strength vs alloy steels
  • High ductility and good impact toughness
  • Stable and predictable for general fabrication

Workability, Machinability, and Weldability

Compared to 4140 vs 1018 machinability, 1018 is usually easier and more forgiving.

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  • Structural shapes: limited; for pure structural we often move to other structural grades
  • Condition options:
    • Hot rolled
    • Cold finished (better surface and tighter tolerance)
    • Peeled/turned and ground for shafting

We support:

  • Cut‑to‑length
  • Saw cutting, precision cutting
  • Mill certs and full traceability on request

When 1018 Mild Steel Is the Right Choice

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  • Loads are low to moderate and not fatigue‑critical
  • Cost and availability matter more than maximum strength
  • cURL Too many subrequests. easy machining and welding with minimal fuss
  • Parts will be case hardened rather than through‑hardened
  • cURL Too many subrequests. tight dimensional control via cold‑finished bar

Typical 1018 steel applications include:

  • Brackets, plates, base frames
  • Light shafts, pins, bushings (non‑critical)
  • Welded fabrications and structural components
  • Machined fittings, spacers, jigs, and fixtures

If you’re unsure whether 1018 vs 4140 is safer for your load and duty cycle, I usually start with your required yield strength, fatigue life, and budget and size the section from there before recommending the grade.

What Is 4140 Steel?

4140 steel (AISI 4140, “chromoly” steel) is a medium‑carbon chromium‑molybdenum alloy steel. Compared with 1018 mild steel, 4140 gives you much higher strength, hardenability, and fatigue resistance while still being machinable and reasonably weldable when handled correctly.

Chemical Composition & Alloying Elements in 4140

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cURL Too many subrequests. cURL Too many subrequests. cURL Too many subrequests. chromium molybdenum alloy (chromoly) steel.

Mechanical Properties & Strength Profile of 4140

Properties vary a lot with heat treatment. Typical ranges:

ConditionYield Strength (MPa)Tensile Strength (MPa)Hardness (HB)
Annealed415 – 655655 – 895~ 187 – 217
Quenched & Tempered655 – 1030+850 – 1250+~ 248 – 320

Key points:

  • Much stronger than 1018 at the same size
  • Can be tailored from tough/ductile to very high strength with proper tempering
  • Good strength-to-weight for shafts, gears, and high‑load parts

If you care about how strength connects to machining accuracy, it pairs well with tight‑tolerance processes like milled steel machining where precision and stability really matter (see our guide on what milled steel is and how it’s machined).

Hardenability, Toughness & Fatigue Resistance

Why 4140 is a “go‑to” high‑strength alloy:

  • Excellent hardenability
    • Through‑hardens in thicker sections vs simple carbon steels
    • Uniform properties across the cross‑section
  • Good toughness
    • With correct tempering, resists impact and shock loads
    • Lower risk of brittle fracture vs some higher‑carbon alloys
  • Strong fatigue resistance
    • Ideal for rotating shafts, axles, spindles, gears
    • Handles cyclic loads far better than 1018

Available Forms, Conditions & Treatments for 4140

You’ll commonly find 4140 in:

  • Forms
    • Round bar, hex bar, flat bar, plate
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    • Annealed cURL Too many subrequests.
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  • The cost of failure is high (downtime, safety, warranty risk)
  • You want to reduce section size/weight without sacrificing strength

In short:
Use 1018 for low‑stress, general fabrication.
Step up to 4140 when strength, hardenability, and fatigue resistance are critical to your design or your customer’s uptime.

1018 vs 4140: Side‑by‑Side Comparison

Both grades are solid choices, but they solve different problems. Here’s the quick, practical breakdown.

Tensile Strength & Yield Strength: 1018 vs 4140

Typical room‑temperature values (round bar, approximate):

Property1018 (as‑rolled)4140 Annealed4140 Q&T ~28–32 HRC4140 Q&T ~38–42 HRC
Tensile strength (MPa)~440–480~655–745~930–1030~1100–1250
Yield strength (MPa)~320–350~415–450~760–860~900–1050
  • If you’re under 300 MPa working stress, 1018 is usually enough.
  • For high load, shock, or safety‑critical parts, 4140 is the safer bet.

Hardness & Wear Resistance: 1018 vs 4140

Grade / ConditionTypical HardnessWear Performance
1018, as‑rolled~120–170 HBLow
1018, carburized caseSurface up to ~58–62 HRCGood surface wear, soft core
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  • Use 1018 cURL Too many subrequests. cURL Too many subrequests..
  • Use 4140 cURL Too many subrequests. cURL Too many subrequests. cURL Too many subrequests.

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  • 1018:
    • Excellent weldability with MIG, TIG, stick.
    • No preheat for most thicknesses.
  • 4140:
    • Preheat (typically 150–300°C) and controlled cooling required.
    • Higher risk of cracking, needs low‑hydrogen process and proper filler.

If your process is weld‑heavy and shop skills vary, 1018 is lower risk. For cURL Too many subrequests. of hard parts, 4140 works fine if you control tools, speeds, and coolant—similar to what’s needed in precision CNC machining of hard materials as discussed in our ceramic CNC machining guide.

Heat Treatment Response & Hardenability: 1018 vs 4140

  • 1018 steel (AISI 1018):
    • Very low carbon (~0.18% C) = not through‑hardening.
    • Only useful heat treatment: carburizing / case hardening + quench.
  • 4140 chromoly alloy (chromium molybdenum steel 4140):
    • Medium carbon (~0.40% C) + Cr + Mo = high hardenability.
    • Responds extremely well to:
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      • Quench and temper (Q&T)
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    • Can achieve a wide range of strength and hardness profiles.

If you need through‑hardened shafts, gears, or bolts, 4140 wins every time.

Cost, Availability & Sourcing

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Raw material costLowerHigher (alloy additions)
AvailabilityVery commonVery common in bar, less in shapes
Minimum orderLowerSometimes higher for special states
  • 1018 is usually the lowest cost option for mild steel vs alloy steel.
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Weight, Tolerance & Dimensional Stability

Density is almost identical:

Property10184140
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Weight difference is negligible at part level.

Main differences:

  • 1018:
    • More ductile, more forgiving during forming.
    • Less distortion during welding.
  • 4140:
    • More prone to movement during heavy machining and heat treatment.
    • Needs stress‑relieving to maintain tight tolerances on long shafts or thick sections.

For tight tolerance, heat‑treated parts, it’s critical to combine proper heat‑treat control with reliable material testing and traceability—exactly the type of support we bundle with our projects, aligned with the best practices outlined in our comprehensive material testing guide.

In simple terms:

  • 1018 = easy to machine, easy to weld, cheap, for low–medium stress.
  • 4140 = strong, hard, fatigue‑resistant, but needs more process control.

Applications: Where 1018 Shines vs Where 4140 Excels (1018 vs 4140 / 1018 与 4140)

Best applications for 1018 mild steel in general fabrication

AISI 1018 mild steel is my go‑to when you need easy machining, easy welding, and low cost:

  • Brackets, frames, base plates, and fixtures
  • Jigs, simple tooling blocks, alignment plates
  • Pins, bushings, spacers, sleeves with low to moderate loads
  • Welded fabrications, support structures, light machine parts
  • Shafts and couplings where strength demands are modest and failure isn’t critical

If your main goals are good dimensional accuracy, clean machining, and reliable welding, 1018 is usually the smartest and cheapest choice.

Best applications for 4140 alloy steel in high‑stress parts

4140 chromoly alloy (chromium molybdenum steel) comes in when strength, fatigue resistance, and toughness cURL Too many subrequests.

  • High‑load shafts, axles, spindles, and drive components
  • Gears, sprockets, couplings, and high‑torque transmission parts
  • Heavy clamping components, press parts, and high‑strength fasteners
  • Wear parts that benefit from quench‑and‑temper or induction hardening

Anywhere failure would be expensive or dangerous, 4140 is usually a better fit than 1018.

Automotive and transportation: 1018 vs 4140 use cases

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For general structural work and light duty parts, I default to 1018:

  • Welded frames, racks, tables, and guards
  • Bracketry, mounting plates, hinge plates, and tabs
  • Light supports, housings, covers, and non‑pressurized manifolds

It welds clean, distorts less than higher‑carbon steels, and keeps material cost under control.

Hybrid strategies: mixing 1018 and 4140 in the same system

A practical, cost‑driven approach is to mix 1018 and 4140 in one assembly:

  • Use 4140 for high‑stress components (shafts, gears, load‑bearing pins, wear points)
  • Use 1018 for support, alignment, and mounting (frames, brackets, plates, non‑critical spacers)

This way you pay for 4140 only where its strength, wear resistance, and fatigue performance actually matter, while 1018 keeps project budgets and lead times in check.

Fabrication Guide for 1018 vs 4140

Machining 1018: Speeds, Feeds, Tooling

AISI 1018 mild steel is very forgiving to machine. It cuts cleanly, holds size well, and is ideal for CNC prototypes and general production.

Basic tips for machining 1018:

  • Tooling:
    • HSS works for low‑volume; carbide for higher speed and long runs.
    • Use sharp, positive‑rake tools to avoid built‑up edge.
  • Cutting speeds (rough guide):
    • HSS: 25–35 m/min (80–120 SFM)
    • Carbide: 120–180 m/min (400–600 SFM)
  • Feeds & DOC:
    • Roughing: 0.15–0.35 mm/rev feed, 2–4 mm depth of cut
    • Finishing: 0.05–0.15 mm/rev, 0.5–1.5 mm DOC
  • Coolant:
    • Use flood coolant for better tool life and surface finish.
    • Dry cutting is possible but watch heat and built‑up edge.

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  • Avoid chatter: maximize rigidity, minimize tool overhang.

If you’re new to machining 4140 QT, start conservative on speed, then tune for tool life and surface finish.

Welding 1018: Processes and Filler Choices

1018 welding is straightforward and very forgiving.

Best processes:

  • MIG (GMAW): Fast, easy, great for structural and brackets.
  • TIG (GTAW): For cleaner, cosmetic, or precision welds.
  • Stick (SMAW): Good for field work and thicker sections.

Fillers:

  • MIG: ER70S‑6 solid wire
  • TIG: ER70S‑2 / ER70S‑6 rod
  • Stick: E6010/E6011 for root, E7018 for structural work

No preheat needed for typical thicknesses. Just keep:

  • Clean base metal (remove mill scale, oil, rust)
  • Reasonable interpass temperatures to avoid distortion.

Welding 4140: Preheat, Post‑Heat, Cracking Control

4140 alloy steel is not weld‑like‑1018 material. It’s hardenable and prone to cracking if you treat it like mild steel.

Key rules:

  • Preheat:
    • Typical: 150–315°C (300–600°F) depending on thickness and restraint.
    • Thicker and higher strength (QT) needs higher preheat.
  • Interpass temp:
    • Hold between 200–315°C (400–600°F) to manage cooling rate.
  • Post‑weld heat:
    • Slow cool in insulation or an oven.
    • For critical parts, stress‑relieve at 550–650°C (1020–1200°F).

Filler metals:

  • For structural/repair: low hydrogen fillers like E8018‑B2, ER80S‑D2, or 4130/4140‑type rods.
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1018 has low carbon, so through‑hardening is weak – but it excels at case hardening.

Carburizing options:

  • Pack or gas carburizing:
    • 900–950°C (1650–1750°F), carbon‑rich atmosphere.
    • Case depth usually 0.5–1.5 mm, depending on time.
    • Follow with oil quench + temper for a hard shell with a tough core.
  • Carbonitriding (for smaller parts):
    • Adds nitrogen + carbon; useful for wear‑resistant small components.

Use case‑hardened 1018 for pins, bushings, low‑load gears, and wear faces that need a hard skin but not full‑section strength.

Forming, Bending, and Cutting: 1018 vs 4140

Forming & bending:

  • 1018:
    • Excellent formability.
    • Cold bending, rolling, and forming are easy with minimal cracking.
    • Great for brackets, frames, and formed sections.
  • 4140:
    • Annealed: formable, but needs higher force than 1018.
    • QT: limited cold forming; cracking risk. Hot forming is safer.

Cutting:

  • 1018:
    • Saws, laser, plasma, and waterjet cut cleanly.
    • CO₂ lasers work well for standard plate and sheet.
    • Ideal for custom sheet parts and car sheet metal repair components.
  • 4140:
    • Tougher on blades; use quality bandsaw blades and slower speed.
    • For QT 4140, waterjet or high‑power laser is preferred to reduce HAZ hardness.

In practice, I push 1018 for formed and welded structures, and lean on 4140 where machining, heat treatment, and long‑term fatigue performance matter most.

1018 vs 4140: Pros and Cons for Real‑World Projects

When I choose between AISI 1018 steel and 4140 chromoly alloy, I always start from what the part actually needs – not from what looks “strongest” on paper.

Advantages and Disadvantages of 1018 Steel

Pros of 1018 mild steel

  • Excellent machinability – very forgiving, high 1018 machinability rating, ideal for long production runs.
  • Easy welding – minimal preheat, compatible with common filler wires, simple for fab shops.
  • Good for forming – bending, cold forming, and stamping are all easier than with 4140.
  • Low cost & widely available – a go‑to structural steel 1018 cURL Too many subrequests.
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  • High strength – significantly higher mechanical properties of 4140 steel (tensile and yield) than 1018.
  • Great hardenability – responds very well to quenched and tempered 4140 bar and induction hardening.
  • High wear resistance – especially in 4140 normalized vs quenched and tempered conditions.
  • Good fatigue resistance – ideal for alloy steel for gears and shafts, spindles, axles, and tools.
  • Better toughness when treated correctly – strong yet not brittle if heat treated right.

Cons of 4140 steel

  • Harder to machine – especially in higher hardness; needs good tooling and cutting strategy.
  • More demanding to weld – requires preheat, controlled cooling, and often post‑weld heat treatment.
  • Higher material cost – more expensive than 1018, plus added cost for heat treatment.
  • Less forgiving – mistakes in machining, welding, or heat treatment can lead to cracking or distortion.

Use 4140 when your part sees real loads, torque, impact, or long‑term fatigue – for example in automotive, oilfield, and heavy machinery.

Over‑Engineering 4140 vs Under‑Engineering 1018

This is the trap I see most:

  • Over‑engineering with 4140
    • Using 4140 where cURL Too many subrequests. would work fine wastes money on material and heat treatment.
    • Parts can be harder to machine and weld, increasing lead time and scrap risk.
  • Under‑engineering with 1018
    • Using 1018 where you really need 4140 fatigue resistance or higher strength can cause:
      • Premature wear
      • Bending or permanent deformation
      • Cracking or fatigue failure in service

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    • cURL Too many subrequests. 4140 chromoly alloy.
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  • Budget and process capability
    • Tight cost targets, basic shop equipment, simple welds → 1018.
    • Higher budget, access to heat treatment and better machining → 4140.

Quick Decision Checklist: 1018 or 4140?

Use this as a fast filter when deciding 1018 vs 4140（1018 与 4140）:

Choose 1018 if:

  • The part is mainly structural, bracket, fixture, or low‑load.
  • cURL Too many subrequests. easy machining and welding.
  • You’re working to a strict budget and high volume.
  • Little or no heat treatment is planned.

Choose 4140 if:

  • The part is a shaft, gear, spindle, axle, coupler, or high‑stress pin.
  • You need high tensile strength and yield strength, with good fatigue life.
  • You require heat treatable 4140 steel for hardness and wear resistance.
  • Safety, long life, and reliability matter more than lowest cost.

If you’re between the two, I usually start with 1018 for low‑risk parts and step up to 4140 once the design moves into critical, rotating, or high‑load territory.

Frequently Asked Questions About 1018 vs 4140 (1018 与 4140)

Is 4140 stronger than 1018 in typical applications?

Yes. In most real‑world parts, 4140 chromoly alloy is significantly stronger than AISI 1018 mild steel.

  • 1018 (as-rolled): tensile ~440–480 MPa, yield ~250–320 MPa
  • 4140 (quenched & tempered): tensile 850–1100+ MPa, yield 700–900+ MPa

If you’re seeing high load, impact, or fatigue, 4140 is usually the safer choice.

Can 1018 be heat treated like 4140?

No. 1018 is low‑carbon mild steel, so it won’t through‑harden like 4140.

  • 1018: can be case hardened / carburized for a hard skin and soft core
  • 4140: can be through‑hardened by quench & temper to a wide hardness range

Use 1018 when you want an easy‑to‑form base with optional surface hardening, and 4140 when you need true

Why Buy 1018 vs 4140 Steel from a Specialized Supplier (1018 与 4140)

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  • cURL Too many subrequests. round bar, flat bar, plate, block, tube
  • Standard and close‑tolerance sizes for CNC and machining shops

On top of that, we can:

  • Cut‑to‑size for quick production
  • Supply 4140 in annealed, normalized, or quenched and tempered (QT)
  • Arrange heat treatment (quench & temper, stress relief, or case hardening for 1018) so parts go straight to machining

If you’re running a tight machining workflow, you’ll likely benefit from our experience with CNC precision engineering and tolerance control, similar to what’s covered in this practical CNC precision engineering guide with processes and applications.

Technical Support from Metallurgists & Engineers

Choosing between 1018 vs 4140 isn’t just about strength charts. My team can help you:

  • Pick the right grade based on load, fatigue, and budget
  • Decide between 4140 normalized vs quenched and tempered
  • Tune machinability, weldability, and heat treatment to your process
  • Avoid over‑engineering with 4140 or under‑spec’ing with 1018

You get real feedback from people who live in the world of alloy steel for gears and shafts, fixtures, brackets, and high‑stress parts.

How to Request Quotes, Samples & Data Sheets

To move fast on 1018 vs 4140:

  1. Send your material list (grade, size, quantity, condition: as‑rolled, annealed, QT).
  2. Tell us your end use (e.g., shaft, gear, bracket, tooling) so we can sanity‑check the grade.
  3. Ask for:
    • Price quote + lead time
    • Mill certs and data sheets for 1018 and/or 4140
    • Small samples or short bars if you want to test machining or welding first

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For gears, spindle shafts, and drive components, the real battle is 4140 vs other alloy steels like 4130, 4340, or case‑hardening grades.

GradeKey BenefitTypical Part
4140Good mix of strength + toughnessTransmission shafts, couplings
4340Higher toughness, deeper hardeningHeavy‑duty gears, axles
4130Easier to weld, slightly lower strengthRoll cages, frames

If you’re running precision CNC machining on these alloys, a strong process setup like in a dedicated CNC machine operations workflow helps you hold tight tolerances, especially on hardened 4140.

Reference Charts for Steel Tensile and Yield Strength

You should always have quick tensile and yield strength charts available for design checks and customer quotes.

Typical design‑level values (approximate, for quick comparison):

Grade / ConditionYield Strength (MPa)Tensile Strength (MPa)
1018 (cold drawn)~370–420~440–480
1045 (normalized)~380–415~570–625
4140 (QT, ~30–32 HRC)~655–860~850–1030
4140 (QT, ~38–42 HRC)~950–1100+~1100–1300+

Use these as a screening tool only; final design must follow actual mill certs and standards.

Downloadable 1018 vs 4140 Comparison Tools and PDFs

For buyers, engineers, and machinists, I always recommend keeping:

  • 1‑page 1018 vs 4140 comparison sheet
    • Chemical composition
    • Typical mechanical properties
    • Machinability, weldability, heat‑treat response
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