1045 Carbon Steel Properties, Uses and Machinability
SAE 1045 is a medium-carbon plain steel that offers more strength and hardening response than low-carbon steel without the alloy cost of 4140. It is widely used for shafts, pins, axles, hydraulic components and surface-hardened parts—but its strength, hardness, ductility and machining behavior depend on product form, diameter, finish and delivery condition.
Common SAE 1045 ranges are approximately 0.43–0.50% carbon and 0.60–0.90% manganese.
Normalized, turned, ground and quenched-and-tempered products are also available, but must be ordered explicitly.
Useful when mild steel is too soft but a deep-hardening alloy grade is unnecessary.
Large sections do not develop the same core response as smaller sections, and welding needs crack-control planning.
Find the answer you need.
1045 describes chemistry—not one guaranteed strength.
1045 carbon steel is an SAE plain-carbon grade identified as SAE 1045 and UNS G10450. The “10” family identifies a plain carbon steel series; “45” indicates a nominal carbon level near 0.45%. That carbon level gives 1045 more attainable hardness and wear resistance than common low-carbon grades while retaining useful machinability in an appropriate supply condition.
The designation does not specify whether a bar is hot rolled, cold drawn, turned and polished, normalized, annealed, quenched and tempered, induction hardened or chrome plated. Each route changes residual stress, surface finish, dimensional tolerance and mechanical properties. A drawing that says only “1045 steel” therefore leaves important engineering decisions unresolved.
The most important purchasing rule
Put the product form, governing specification, delivery condition, dimensional tolerance, required test results and heat-treatment state on the purchase order. Chemistry alone cannot guarantee shaft straightness, core strength, impact performance or surface hardness.
Choose the product form
Bar, plate, forging and finished shafting do not share the same dimensional or testing requirements.
Name the condition
Hot rolled, cold drawn, normalized and Q&T material can behave very differently in machining and service.
Match the section
Diameter controls quench response, core properties, distortion risk and the need for alloy steel.
Qualify the finished part
Test the hardness location, tensile direction, surface condition and geometry that actually carry the load.
1045 carbon steel composition and what the elements do.
The ranges below are common published values for SAE 1045/UNS G10450. The current SAE J403 chemistry table, applicable product specification and permitted product-analysis variation control an actual order.
| Element | Common range, wt% | Engineering effect | What a buyer should verify |
|---|---|---|---|
| Carbon | 0.43–0.50 | Raises attainable martensitic hardness and strength but reduces weldability and increases quench-cracking sensitivity. | Use the heat analysis and product-analysis rules in the governing standard; do not infer carbon from hardness. |
| Manganese | 0.60–0.90 | Supports deoxidation, strength and hardening response and helps control sulfur through manganese sulfides. | Compare the MTR to the ordered SAE or product specification. |
| Phosphorus | Maximum commonly 0.040 | A residual element whose control matters for toughness and forming performance. | C45E and other restricted variants may impose tighter limits. |
| Sulfur | Maximum commonly 0.050 or lower | Inclusion content can affect chip formation, transverse ductility and fatigue behavior. | Do not assume a machinability-treated variant unless it is ordered by its actual designation. |
| Residual alloying elements | Specification-dependent | Chromium, nickel, molybdenum, copper and silicon can influence hardenability and processing even when not intentionally added as an alloy package. | SAE J403 requires additional elements to be reported when heat analysis is requested for conformance. |
Chemical ranges vary by standard, product form and grade variant. C45, C45E, C45R and S45C are comparison starting points, not permission to substitute without a line-by-line standard review.
Mechanical properties of 1045 steel change with size and delivery condition.
There is no single “1045 tensile strength.” The data below show why a defensible specification names both the condition and the dimension represented by the test result.
| Published condition or example | Tensile strength | Yield or proof stress | Elongation | Hardness | Interpretation |
|---|---|---|---|---|---|
| Interlloy hot-rolled benchmark | 570–700 MPa | 300–450 MPa | 14–30% in 50 mm | 170–210 HB | Typical supplier data for hot-rolled 1045 bar, not a universal guaranteed minimum. |
| Interlloy normalized benchmark | About 640 MPa | About 410 MPa | About 22% in 50 mm | About 187 HB | A single typical normalized dataset illustrating a more uniform starting structure. |
| Atlas cold-drawn, ≤16 mm example | 690 MPa minimum | 540 MPa minimum | 8% minimum | 207 HB minimum | Specific AS 1443 product-condition data; cold work raises strength and lowers ductility. |
| Atlas rolled/turned example, ≤260 mm | 600 MPa minimum | 300 MPa minimum | 14% minimum | 179 HB minimum | Specific product-condition data, available with guaranteed properties only when ordered accordingly. |
| Ovako C45 SB1672, <16 mm | 590–740 MPa | 320 MPa minimum | 14% minimum | 165–220 HB | A related C45 producer specification showing dimension-specific minimum yield strength. |
| Ovako C45 Q&T, 20–40 mm | 650–800 MPa | 430 MPa minimum | 16% minimum | 190–240 HB | A quenched-and-tempered related-grade example; larger sizes carry different minimums. |
Why cold-drawn material can move after machining
Cold drawing improves dimensional finish and can raise yield strength through strain hardening, but it also stores residual stress. Deep, asymmetric stock removal may release that stress and bend a long shaft. A normalized, stress-relieved, turned-and-ground or deliberately rough-machine/stress-relieve/finish-machine route may be more stable. The best route depends on stock allowance, length-to-diameter ratio and final tolerance.
Typical physical properties for the C45/1045 family.
Physical-property values are often less sensitive to heat treatment than strength and hardness, but they are still representative data rather than a purchase guarantee. Ovako publishes the following typical values for its C45 family.
| Property | Typical published value | How it is used | Limitation |
|---|---|---|---|
| Density | About 7,800 kg/m³ | Mass, inertia, shipping and fixture calculations. | Use certified density only when the application demands traceable precision. |
| Young’s modulus | About 210 GPa | Elastic deflection and stiffness calculations. | Heat treatment changes strength far more than elastic modulus. |
| Poisson’s ratio | About 0.30 | Elastic stress analysis and simulation inputs. | Confirm model assumptions for temperature and multiaxial loading. |
| Thermal conductivity | About 40–45 W/m·K at ambient temperature | Heating, cooling, welding and thermal-gradient estimates. | Conductivity changes with temperature and exact chemistry. |
| Average CTE, 20–300°C | About 12 µm/m·°C | Thermal growth, fits and furnace allowances. | Use temperature-dependent data for critical thermal systems. |
| Specific heat | About 460–480 J/kg·K near 50–100°C | Heating-energy and process modeling. | Not constant over a full heat-treatment cycle. |
1045 is machinable, but the condition controls chip behavior and stability.
A frequently repeated machinability rating of roughly 55–60% is only a comparative benchmark. It is not a cutting-speed specification. Actual cutting data depend on hardness, microstructure, cold work, scale, interrupted cuts, tool substrate, coating, coolant, machine rigidity and the required finish.
- Hot rolled: economical stock with scale and larger machining allowance; verify decarburization before surface hardening.
- Normalized: often selected for a more uniform ferrite-pearlite structure before machining or induction hardening.
- Cold drawn: better dimensional accuracy and higher as-supplied strength, but potentially higher residual stress.
- Turned, peeled or ground: useful when surface condition, tolerance or defect removal is more important than minimum material cost.
How to set machining parameters without copying an unsafe universal table.
Begin with the cutting-tool manufacturer’s grade-specific starting data for the actual hardness and operation. Then qualify the process using spindle power, chip shape, flank wear, dimensional growth and surface integrity.
Control long, tough chips
Use a chip-breaker and feed range appropriate to medium-carbon steel. Too little feed can rub and create stringers; too much load can accelerate edge failure or deflection. Check the insert maker’s work-material group and hardness band.
Watch heat and evacuation
Deep holes can recut chips and overheat margins. Match point geometry, coolant delivery, peck strategy and tap style to hole depth, condition and machine capability.
Plan stress release
Balance stock removal, support the work, monitor runout between operations and consider rough machining before stress relief. Do not treat cold-drawn straightness as permanent after deep cutting.
Remove decarburized surface
A soft decarburized layer can prevent the target surface response. Confirm machining allowance and inspect the final hardened profile rather than checking only a single surface point.
Sequence heat and finish machining
Leave appropriate grind stock for heat-treatment movement. Critical journals, seal lands and bearing seats normally require a process route designed around final distortion.
Measure the part, not the catalog
Track tool life, burr formation, roughness, straightness, hardness and residual stock. A supplier’s “good machinability” statement cannot qualify the finished component.
How hard can 1045 carbon steel get?
A properly quenched surface can reach the mid-to-high 50s HRC, and some supplier guidance cites approximately 54–60 HRC after flame or induction hardening. That does not mean a large 1045 section becomes 60 HRC through its core.
Low hardenability is the central constraint
1045 lacks the chromium-molybdenum alloy package that helps 4140 harden more deeply. Cooling rate falls toward the center of a section, so martensite fraction and hardness can fall with depth. Geometry, austenite condition, agitation and quench severity determine the profile.
For shafts that need a hard wear surface and a more ductile core, induction or flame hardening is often more useful than attempting to through-harden the entire section. The design should specify effective case depth, surface hardness range, transition profile, core condition, runout after hardening and any grinding allowance.
For quenched-and-tempered parts, tempering is not simply “softening.” It is how the engineer trades maximum hardness for toughness, ductility and dimensional stability. The correct temper is chosen from the required tensile properties, impact behavior and service temperature—not from one generic online recipe.
| Route | Published supplier example | Primary purpose | Qualification requirement |
|---|---|---|---|
| Full anneal | Atlas lists 800–850°C; Interlloy also lists 800–850°C followed by furnace cooling. | Reduce hardness, improve machinability and create a controlled starting structure. | Confirm final hardness, spheroidization if required, decarburization and furnace uniformity. |
| Normalize | Atlas lists 840–880°C; Interlloy lists 870–920°C followed by still-air cooling. | Refine and homogenize the ferrite-pearlite structure after forging or before final processing. | Use the supplier and heat treater’s route for the actual chemistry, section and furnace load. |
| Through harden and temper | Atlas lists 820–860°C followed by water or oil, with tempering around 550–660°C for its Q&T property table. | Develop a strength-and-toughness balance in suitable section sizes. | Map surface-to-core hardness, distortion, cracking and mechanical properties in the represented size. |
| Flame or induction harden | Interlloy lists rapid heating around 820–860°C followed by immediate quenching and cites up to about 54–60 HRC. | Create a wear-resistant surface while retaining the supplied core condition. | Specify case depth, contour coverage, edge effects, residual stress and post-hardening temper. |
| Stress relieve | Atlas lists approximately 550–660°C as a product guidance range. | Reduce machining or welding residual stress. | Confirm that temperature does not destroy previously required strength or surface hardness. |
These temperatures are published supplier starting points, not a universal furnace instruction. Heating rate, hold time, quench medium, agitation and tempering depend on geometry, mass, equipment and the required properties.
1045 can be welded, but it is not a forgiving mild steel.
The combination of approximately 0.45% carbon, rapid weld cooling and restraint can create a hard, low-ductility heat-affected zone. If diffusible hydrogen is also present, delayed cracking becomes possible. The correct procedure depends on actual chemistry, thickness, joint type, hydrogen level, heat input, restraint and service requirement.
A universal rule such as “always preheat to 200°C” is not responsible engineering. Preheat and interpass limits should come from a qualified welding procedure supported by carbon-equivalent calculation and the applicable code. Low-hydrogen consumables and controlled storage are usually part of the strategy, but they do not replace procedure qualification.
Before welding
- Confirm chemistry and current heat-treatment condition.
- Calculate carbon equivalent with the procedure’s accepted formula.
- Assess restraint, section thickness and hydrogen class.
- Remove oil, scale, moisture and surface coatings.
- Decide whether a lower-carbon or alloy alternative is safer.
During and after welding
- Control preheat, interpass temperature and heat input.
- Use a qualified low-hydrogen consumable system.
- Avoid welding directly across a hardened surface without engineering review.
- Apply postheat or stress relief only when the procedure requires it.
- Inspect after the delay period appropriate to hydrogen-cracking risk.
Laser welding does not remove the metallurgy problem.
Laser welding reduces total heat input and heat-affected-zone width, but concentrated energy and rapid cooling can still form hard martensitic regions in 1045. Joint fit-up, beam position, power density, travel speed, filler strategy, preheat and post-weld hardness must be qualified together. A visually narrow weld is not proof of adequate toughness.
Common uses of 1045 carbon steel.
1045 is most persuasive when a mechanical part needs more strength and surface-hardening response than low-carbon steel, while the load and section do not justify a deeper-hardening alloy steel.
- Shafts, spindles, axles, pins and studs.
- Hydraulic rams, piston rods and chrome-plated bar substrates.
- Sprockets, gear racks, rolls, cams and machine components.
- Connecting rods, clutch members and selected automotive or agricultural parts.
- Flame- or induction-hardened wear surfaces with a tougher supporting core.
Choose the condition around the part—not the grade name alone.
Prioritize straightness and stability
Consider turned-and-ground or centerless-ground stock, controlled machining allowance and a stress-management route. Specify runout after every heat-intensive operation.
Separate base strength from coating performance
A hard-chrome surface may provide wear and corrosion resistance while the 1045 substrate carries bending load. Define coating thickness, adhesion, porosity and final surface finish separately.
Use surface hardening deliberately
Specify the effective hardened depth, surface HRC, core property, transition profile and grind stock instead of asking only for “induction hardened 1045.”
Check whether 4140 is safer
As section size, fatigue demand and core-strength requirement rise, a chromium-molybdenum grade may offer a more robust heat-treatment window.
Challenge the material choice
If welding dominates fabrication, a lower-carbon grade may reduce procedure complexity. Do not select 1045 merely because the shaft portion needs strength.
Use 1045 where it earns its cost
When 1018 deforms or wears too quickly and the section remains moderate, 1045 can provide a practical strength-and-machinability balance.
1045 vs 1018, 1060 and 4140 steel.
Comparing one yield-strength number across grades is misleading unless all products share the same condition and size. Use the metallurgy and manufacturing route first.
| Grade | Approximate carbon | Hardenability | Weldability tendency | Typical reason to choose | Primary caution |
|---|---|---|---|---|---|
| 1018 | About 0.15–0.20% | Low; normally case hardened when a hard surface is needed. | Generally better than the higher-carbon options. | Economical machining, forming, welding and carburized components. | Lower through-section strength and wear resistance without added processing. |
| 1045 | About 0.43–0.50% | Low, but enough carbon for through hardening in suitable sections and effective surface hardening. | Procedure-sensitive due to hard HAZ risk. | Shafts, pins, rams and surface-hardened parts needing more strength than mild steel. | Section-sensitive core response, distortion and welding complexity. |
| 1060 | About 0.55–0.65% | Still shallow hardening, with higher attainable hardness. | More crack-sensitive than 1045. | Springs, hand tools and wear/impact edges after controlled heat treatment. | Lower welding margin and greater quench sensitivity. |
| 4140 | About 0.38–0.43% plus Cr-Mo | Substantially deeper than 1045. | Still procedure-sensitive, but selected for Q&T core properties rather than easy welding. | Larger sections, fatigue-loaded shafts, higher core strength and more uniform Q&T response. | Higher material/process cost and its own welding and heat-treatment requirements. |
The comparison is directional. Final selection requires the actual product standard, delivery condition, size, loading mode, environment and inspection plan.
Are C45, S45C and 45 steel equivalent to 1045?
They are common cross-reference starting points, not automatic drop-in replacements. Chemistry limits, cleanliness, grain control, hardenability, test location, delivery condition, dimensional tolerance and inspection rules can differ.
SAE 1045 / UNS G10450
Use SAE J403 for the chemistry framework, then apply the specification governing the actual bar, plate or other product.
C45 / C45E / C45R
C45E typically restricts phosphorus and sulfur more tightly; C45R modifies sulfur control. EN/ISO mechanical properties and dimensions must be reviewed separately.
JIS S45C
A widely used comparison grade. JIS product, heat-treatment and tolerance requirements remain controlling when the drawing names S45C.
GB/T 699 grade 45
Often called “45 steel.” Verify the exact standard edition, quality class, product condition and property requirements rather than translating only the number.
080M40 / 080M46 references
Legacy and supplier cross-references vary. Confirm which standard and revision the drawing intends before approving a substitute.
How to specify 1045 steel correctly.
A good purchase order converts the grade name into measurable requirements. Start with these eight decisions.
1. Product and standard
- Cold-finished bar: ASTM A108 is a common scope.
- Hot-wrought bar: ASTM A29/A29M provides general requirements, while the grade/product specification completes the order.
- Plate to chemistry: ASTM A830/A830M may be relevant when its scope fits.
- Do not apply a bar standard to plate or a plate standard to finished shafting.
2. Delivery condition
- Hot rolled, forged, normalized, annealed or Q&T.
- Cold drawn, turned and polished, peeled or centerless ground.
- Induction-hardened, flame-hardened or chrome-plated only when explicitly required.
- State whether properties are typical or guaranteed.
3. Size and tolerance
- Nominal diameter, length and machining allowance.
- Diameter class, straightness, out-of-round and surface finish.
- Final runout after heat treatment.
- Surface-defect removal and decarburization limits.
4. Mechanical requirements
- Tensile, yield/proof stress and elongation.
- Hardness scale, range and exact test location.
- Impact test temperature, specimen orientation and minimum energy when needed.
- Effective case depth and core hardness for surface-hardened parts.
5. Traceability
- Heat number linked to every cut length or part lot.
- Chemistry and any required product analysis.
- Requested inspection document type, such as EN 10204 3.1 when contractually applicable.
- Heat-treatment lot and furnace records for critical parts.
6. Verification plan
- Incoming positive material identification that can actually measure carbon when carbon confirmation is required.
- Hardness traverse or metallography for hardened profiles.
- NDT after machining, heat treatment or welding as risk requires.
- First-article dimensional and functional testing.
Seven common 1045 specification and processing mistakes.
Using one property row for every condition
Hot-rolled, cold-drawn and Q&T bars are not interchangeable property states. Copying a supplier’s cold-drawn minimum onto an unspecified hot-rolled order invites rejection or failure.
Assuming surface hardness proves core strength
A hard induction-treated surface says little about the core unless depth and core tests are included. This matters for torsional shafts, splines and large pins.
Water quenching by rule of thumb
Severe quenching can raise surface hardness but also distortion and cracking. Quench selection requires geometry, section, agitation, furnace condition and the acceptable hardness gradient.
Welding without hydrogen and hardness control
A clean-looking bead can hide a brittle heat-affected zone or delayed crack. Use a qualified procedure and inspect at the appropriate time.
Deep machining cold-drawn stock without a stress plan
Residual stress can release unevenly and move long parts. Sequence stock removal, stress relief and finish operations around the tolerance.
Treating equivalents as identical
C45E, S45C and grade 45 may be suitable substitutes, but only after standards, conditions, test rules and tolerances are compared.
Choosing 1045 for a critical large-section fatigue part
When deep hardenability, high core strength and impact toughness are mandatory, 4140 or another qualified alloy steel may provide a safer processing window.
Is 1045 the right starting point?
This selector organizes an early engineering conversation. It does not replace a drawing review, heat-treatment trial, welding procedure or material qualification.
1045 is a credible starting point
For a general small-to-moderate mechanical component, 1045 can provide useful strength and machinability when the delivery condition is specified.
- Choose hot rolled, normalized, cold finished or Q&T deliberately.
- Set mechanical properties for the actual section.
- Verify chemistry, straightness and final hardness.
Validate the real material, joint and surface condition.
When 1045 enters a laser cleaning, welding or marking process, send the actual condition, thickness, coating, geometry and required result. Oceanplayer can help plan a representative sample test before equipment selection.
1045 carbon steel answers.
These answers distinguish grade chemistry from condition-specific product performance.
What is 1045 carbon steel?
1045 is a medium-carbon plain steel designated SAE 1045 and UNS G10450. It commonly contains approximately 0.43–0.50% carbon and 0.60–0.90% manganese.
What are the mechanical properties of 1045 steel?
They depend on condition and size. One Interlloy hot-rolled benchmark lists 570–700 MPa tensile strength, 300–450 MPa yield strength, 14–30% elongation and 170–210 HB. Cold-drawn and Q&T products have different values.
What is the hardness of 1045 carbon steel?
There is no single hardness. Hot-rolled or normalized supplier data commonly fall near 165–220 HB. A correctly flame- or induction-hardened surface may reach approximately 54–60 HRC, while the core remains closer to its supplied condition.
Can 1045 steel be through hardened?
Yes, in suitable sections, but 1045 is a low-hardenability plain-carbon grade. Surface-to-core response becomes less uniform as the section grows, so the required hardness profile must be tested.
Is 1045 steel good for shafts?
Yes, for many shafts, pins, axles and hydraulic components. The correct condition depends on straightness, fatigue, section size, surface wear and core-strength requirements. Large critical shafts may justify 4140.
Is 1045 steel easy to machine?
It is generally considered readily machinable in hot-rolled or normalized condition, but cutting data must come from the tool manufacturer for the actual hardness, operation and machine. Cold-drawn stock can carry residual stress that affects long shafts.
Can 1045 carbon steel be welded?
It can be welded with a qualified procedure, but its carbon content creates a hardenable and crack-sensitive heat-affected zone. Preheat, hydrogen control, heat input and post-weld treatment depend on chemistry, thickness and restraint.
Is 1045 steel corrosion resistant?
No. It is plain carbon steel and will rust without protection. Oil, paint, black oxide, plating or another system must be selected for the environment and dimensional requirements.
Is C45 the same as 1045?
C45 is a common comparison grade, but not an automatic equivalent for every order. Compare chemistry, product standard, delivery condition, mechanical requirements, dimensions and testing before substitution.
What is the difference between 1045 and 4140?
1045 is plain carbon steel with low hardenability. 4140 contains chromium and molybdenum, giving deeper and more reliable section hardening for larger or more highly loaded components.
Can handheld XRF confirm 1045 steel?
Conventional handheld XRF does not reliably quantify carbon in steel. Use traceability plus a carbon-capable method such as optical emission spectroscopy or combustion analysis when grade confirmation depends on carbon.
What should a 1045 purchase order include?
Include the product form, standard, delivery condition, size and tolerance, mechanical-property requirements, hardness location, surface condition, traceability, inspection document and any heat-treatment or NDT requirements.
Sources used to condition the guidance.
- SAE J403_202402 — current stabilized SAE standard for carbon-steel chemical compositions and product-analysis context.
- ASTM A108-24 — scope and requirements for cold-finished carbon and alloy steel bars.
- ASTM A29/A29M-23 — general requirements for hot-wrought carbon and alloy steel bars.
- Atlas Steels 1045 Grade Data Sheet — condition-, diameter- and treatment-specific bar properties and application limits.
- Interlloy 1045 Medium Tensile Carbon Steel Bar — typical hot-rolled, normalized and Q&T properties plus heat-treatment and processing guidance.
- Ovako C45 Material Data Sheet — related C45 variants, dimension-dependent properties, physical data and cross-reference context.
- voestalpine AISI 1045 Technical Data — applications, chemistry, surface-hardening and heat-treatment starting points.
- TWI: Hydrogen Cracks in Steels — the interaction of hard microstructure, hydrogen, stress, thickness, heat input and preheat.
Engineering limitation: published property tables describe specific products, specimens and test conditions. Final material selection, heat treatment, welding, machining and acceptance criteria must be qualified for the actual component, governing code and failure risk.