1018 1020 1045 12L14 4140 8620 Steel: Properties & Grade Comparison | BELINKER
1018 Steel and Related Grades: Composition, Properties, and CNC Machining
1018 steel is a common low-carbon steel used for machined components, pins, shafts, and fasteners. Its weldability and formability make it a useful starting point when a part does not require the higher strength or hardening response of other grades. Eaton Steel: 1018.
But 1018 is only one option.
A precision turned component may benefit from 1215 or 12L14. A shaft requiring greater hardness may call for 1045. A highly loaded component may justify 4140 or 4340, while a carburized gear may lead the material discussion toward 8620.
This guide explains how these steel grades differ—and what those differences mean when ordering custom CNC-machined parts.
What Does “1018 Steel” Mean?
In the commonly used SAE/AISI designation system, 10xx identifies a plain-carbon steel family. For grades such as 1018 and 1045, the last two digits indicate the approximate nominal carbon content in hundredths of a percent.
1018: approximately 0.18% nominal carbon.
1045: approximately 0.45% nominal carbon.
These are naming conventions, not exact measured compositions. For example, the published carbon range for 1018 is commonly 0.15–0.20%.
Carbon content influences hardening response, but the final properties also depend on processing, section size, and heat treatment. Ryerson: Carbon steel grade numbering, Summit Steel: Chemical composition ranges.
The same numbering shortcut should not be applied mechanically to every designation. In particular, the “L” in 12L14 indicates lead addition, not low carbon as it does in stainless grades such as 316L.
Three Useful Groups for Comparing Machining Steels
Group | Examples | Main reason to evaluate it |
|---|---|---|
Plain-carbon steels | 1010, 1018, 1020, 1045, 1095 | Balance carbon content, fabrication requirements, and heat-treatment response |
Free-machining carbon steels | 1117, 1144, 1215, 12L14 | Improve chip control and machining productivity |
Low-alloy steels | 4130, 4140, 4340, 8620 | Obtain specific hardenability, strength, toughness, or case-hardening performance |
Free-machining steels are a subgroup of carbon steels. The distinction is useful because their sulfur, phosphorus, or lead additions can substantially change machining and fabrication behavior. Chicago Tube & Iron: Carbon steel chemistry, MSCI: Alloy steel families.
Chemical Composition Charts
The following tables show selected chemical composition ranges in weight percent, wt%.
≤ means maximum. A range indicates lower and upper limits. Iron is the balance. A dash means the element is not listed in this comparison, not necessarily that its content is zero.
These are published reference ranges, not a substitute for the applicable purchasing specification. Product form, specification, and grade variants can introduce additional requirements. Verify the material test report against the agreed order requirements.
Plain-carbon steel composition
Grade | Carbon, C | Manganese, Mn | Phosphorus, P | Sulfur, S |
|---|---|---|---|---|
1010 | 0.08–0.13 | 0.30–0.60 | ≤0.040 | ≤0.050 |
1018 | 0.15–0.20 | 0.60–0.90 | ≤0.040 | ≤0.050 |
1020 | 0.18–0.23 | 0.30–0.60 | ≤0.040 | ≤0.050 |
1035 | 0.32–0.38 | 0.60–0.90 | ≤0.040 | ≤0.050 |
1045 | 0.43–0.50 | 0.60–0.90 | ≤0.040 | ≤0.050 |
1050 | 0.48–0.55 | 0.60–0.90 | ≤0.040 | ≤0.050 |
1060 | 0.55–0.65 | 0.60–0.90 | ≤0.040 | ≤0.050 |
1095 | 0.90–1.03 | 0.30–0.50 | ≤0.040 | ≤0.050 |
Silicon and residual-element requirements should be checked separately where specified. Chemistry references: Summit Steel, Capital Steel: 1060 and 1095.
Free-machining steel composition
Grade | Carbon, C | Manganese, Mn | Phosphorus, P | Sulfur, S | Lead, Pb |
|---|---|---|---|---|---|
1117 | 0.14–0.20 | 1.00–1.30 | ≤0.040 | 0.08–0.13 | — |
1144 | 0.40–0.48 | 1.35–1.65 | ≤0.040 | 0.24–0.33 | — |
1215 | ≤0.09 | 0.75–1.05 | 0.04–0.09 | 0.26–0.35 | — |
12L14 | ≤0.15 | 0.85–1.15 | 0.04–0.09 | 0.26–0.35 | 0.15–0.35 |
Chemistry references: Chicago Tube & Iron, Eaton Steel: 1117, 12L14.
Low-alloy steel composition
Grade | Carbon, C | Manganese, Mn | Silicon, Si | Chromium, Cr | Nickel, Ni | Molybdenum, Mo |
|---|---|---|---|---|---|---|
4130 | 0.28–0.33 | 0.40–0.60 | 0.15–0.35 | 0.80–1.10 | — | 0.15–0.25 |
4140 | 0.38–0.43 | 0.75–1.00 | 0.15–0.35 | 0.80–1.10 | — | 0.15–0.25 |
4340 | 0.38–0.43 | 0.60–0.80 | 0.15–0.35 | 0.70–0.90 | 1.65–2.00 | 0.20–0.30 |
8620 | 0.18–0.23 | 0.70–0.90 | 0.15–0.35 | 0.40–0.60 | 0.40–0.70 | 0.15–0.25 |
Phosphorus, sulfur, and residual-element limits are omitted here; they must still be specified and verified. Aircraft-quality and other special procurement requirements may impose tighter limits.
Chemistry references: Coburn-Myers: 4130, Eaton Steel: 4140, Alro: 4340, Eaton Steel: 8620.
1010, 1018, and 1020: Low-Carbon Options
1010 is considered where forming and cold-heading requirements are important.
1018 is a practical option for general-purpose machined parts. Cold-drawn stock offers improved dimensional control and surface condition, which can help when preparing material for machining.
1020 is another common low-carbon grade. Its carbon range overlaps with 1018, but its manganese range differs. The two grades should therefore be evaluated against the actual specification rather than treated as automatically interchangeable. Coburn-Myers: Low-carbon steels, Eaton Steel: Cold-drawn 1018.
For these materials, a useful purchasing question is:
Does the part need general fabrication performance, or a defined final hardness and strength?
If the latter is important, the material condition and heat-treatment requirements deserve as much attention as the grade number.
1035, 1045, 1050, 1060, and 1095: Increasing Carbon Content
Moving toward higher carbon content changes the available hardening response and fabrication tradeoffs.
1035 provides an intermediate option between low-carbon grades and higher-carbon machinery steels.
1045 is widely considered for shafts, axles, studs, and other parts requiring greater strength or hardness than a low-carbon option can provide under comparable conditions. Ryerson: Carbon steel selection guide.
1050 and 1060 extend the carbon range further. 1095 is a high-carbon option whose machining and fabrication requirements differ substantially from 1018.
For these grades, it is important to establish whether the stock will be machined in a softened condition and hardened afterward. Published properties for hot-rolled, spheroidized, cold-drawn, and heat-treated material should not be mixed in one comparison. Capital Steel: Processing-dependent properties of 1060 and 1095.
1018 vs. 1045 steel
Consideration | 1018 | 1045 |
|---|---|---|
Carbon range | 0.15–0.20% | 0.43–0.50% |
Common selection priority | Fabrication and general-purpose parts | Greater hardening response and machinery applications |
Hardening approach | Often considered for carburized surface hardening | Can be directly hardened; results depend on section and process |
Welding | Generally more straightforward | Requires greater attention to material and welding conditions |
Purchasing focus | Stock condition, dimensions, required properties | Heat treatment, hardness, and final properties |
Higher carbon content does not by itself guarantee that a delivered part will be stronger. The comparison must include the material condition. Welding procedures must also account for chemistry, thickness, restraint, and hydrogen control. TWI: Steel welding and cracking prevention.
1117, 1144, 1215, and 12L14: Steels Designed for Machining
These grades become particularly relevant when turning, drilling, threading, and chip control drive manufacturing cost.
1117 combines low carbon with increased manganese and sulfur. It is used for suitable machined parts and can be considered for case-hardening applications. Eaton Steel: 1117, Ryerson selection guide.
1144 contains more carbon and manganese. Be careful with product names: Stressproof® is a specific Niagara LaSalle product made through a controlled drawing and stress-relieving process. Its advertised properties should not be assumed for every bar labeled 1144. Niagara LaSalle: Stressproof.
1215 is a resulfurized and rephosphorized steel used extensively for automatic machining. It offers a free-machining option without the intentional lead addition of 12L14. Eaton Steel: 1215.
12L14 contains lead in addition to sulfur and phosphorus. Its excellent machinability makes it attractive for suitable production parts, but lead content must be acceptable under the customer’s material requirements. Eaton Steel: 12L14.
12L14 vs. 1018 steel
Consider 12L14 when machining productivity is the priority and the application permits its chemistry.
Consider 1018 when welding or forming requirements make a general-purpose low-carbon grade more appropriate.
Free-machining additions involve tradeoffs. A lower machining cost is useful only if the finished part still meets the required mechanical, fabrication, and service conditions.
4130, 4140, and 4340: Low-Alloy Steels for Demanding Components
4130 and 4140 are chromium-molybdenum steels, often called chromoly. 4340 additionally contains a significant nickel addition.
Alloying can improve hardenability: the ability to develop hardness through a section under a given heat-treatment process. Hardenability is different from the hardness measured on an already finished part. Alro: Alloy steel and hardenability.
4130 is used in fabricated and machined applications where its combination of properties is suitable. Welding still requires a procedure appropriate to the actual material and condition. Aircraft Materials: 4130.
4140 is commonly evaluated for shafts, spindles, pins, and other machinery components. Its fatigue and impact performance depend on appropriate heat treatment. Eaton Steel: 4140.
4340 is considered for highly stressed components where deeper hardening and a suitable strength–toughness balance are required. Its grade designation alone does not establish guaranteed mechanical properties. Alro: 4340.
A quotation for annealed 4140 is therefore not directly comparable with one for quenched-and-tempered 4140 unless the remaining processing is included.
8620 Steel: A Common Choice for Carburized Parts
8620 is a low-carbon nickel-chromium-molybdenum steel frequently considered for gears, pinions, shafts, and bushings.
Its low initial carbon content is compatible with carburizing, where carbon is introduced into the surface before subsequent hardening. This can produce a hard, wear-resistant case over a tougher core. Eaton Steel: 8620, Bodycote: Case hardening.
For a carburized part, the drawing should define more than the alloy:
Required surface hardness.
Effective case depth and its measurement criterion.
Core-property requirements where applicable.
Areas that must be protected from carburizing.
Final dimensions and any finishing allowance.
These requirements help connect material selection with the manufacturing sequence.
Why Stock Condition Matters
“1018 steel” or “4140 steel” does not fully describe the material being purchased.
Condition | What the buyer should understand |
|---|---|
Hot rolled | Confirm surface condition, dimensional allowances, and subsequent processing |
Cold drawn | Drawing changes dimensions and mechanical properties |
Annealed | A softened condition used to support subsequent processing |
Quenched and tempered | Specify the required hardness or mechanical properties |
Carburized and hardened | Specify both case requirements and relevant core requirements |
Published strength values are meaningful only when their test conditions and material condition match the application. Alro: Mechanical property reference and limitations.
Do Carbon and Low-Alloy Steels Need Surface Protection?
For many applications, yes. These grades do not provide the corrosion resistance expected from stainless steel.
Finishing should be selected alongside the material. Depending on the environment and drawing requirements, options may include protective oil, black oxide, plating, or paint.
Black oxide is often used when a dark appearance and minimal dimensional change are desirable. Its corrosion protection depends substantially on the accompanying oil or protective treatment; it should not be interpreted as making carbon steel equivalent to stainless steel. Birchwood Technologies: Black oxide finishes.
Specify the finish, relevant coating requirements, masked areas, and final dimensional requirements when requesting a quote.
Frequently Asked Questions
Is 1018 the same as A36?
No. 1018 is a steel chemistry designation, while ASTM A36 is a structural steel specification with requirements that depend on the product. They are not interchangeable simply because both can be described as mild steel. ASTM: Steel specifications.
Can 1018 steel be hardened?
It can be surface-hardened through an appropriate process such as carburizing followed by hardening. Its low carbon content limits conventional direct hardening compared with higher-carbon grades. Ryerson: 1018 and case hardening.
Is 4140 stainless steel?
No. It is a low-alloy chromium-molybdenum steel. Its chromium content does not make it a stainless grade.
Is 12L14 always the cheapest machining option?
No. Machining productivity is only one cost factor. Material availability, quantity, finishing, inspection, and application requirements also affect the finished-part quotation.
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