Can 1045 steel be hardened?

Yes. It through-hardens in thin sections to the low 30s HRC after tempering, and it induction or flame hardens to 55-60 HRC on the surface, which is how most 1045 shafts and gears are made. Large sections cannot be hardened through the middle because plain carbon steel has shallow hardenability; that is when to move to 4140.

With care. Preheat to 150-260 °C (300-500 °F) on anything thicker than about 6 mm, use low-hydrogen consumables such as E7018 or ER70S-6, let it cool slowly and stress relieve loaded joints. Skipping the preheat gives a hard, crack-prone heat-affected zone. Weld before hardening, never after.

What is the difference between 1045 and 4140?

1045 is plain carbon steel; 4140 adds chromium and molybdenum, which lets it harden deep into the section and reach a higher tempered strength, about 1,000 MPa (145 ksi) in the pre-hard 28-32 HRC condition. 1045 is cheaper and easier to weld and is the better choice for induction-hardened shafts in modest sections; 4140 wins for through-hardened, highly loaded or large parts.

Is 1045 good for shafts?

It is the standard shaft steel for general machinery: strong enough, cheap, available as ground shafting, and its journals can be induction hardened for bearings and seals. For high-torque, fatigue-critical or large-diameter shafts, 4140 or 4340 give more strength and deeper hardening.

Carbon steelsUNS G10450

1045 Steel

Also: AISI 1045, SAE 1045, UNS G10450, C1045, 1045 CD, 1045 HR, C45 / 1.0503, C45E / 1.1191, medium carbon steel, S45C (JIS)

1045 is the medium-carbon workhorse for shafts and machine parts: stronger than 1018, induction- or flame-hardenable to 55-60 HRC, still machinable and affordable. Values for cold drawn.

ASTM A108 (cold-finished bar)ASTM A576 (hot-rolled bar)ASTM A29/A29MASTM A830 (plate)SAE J403 (chemistry)

Sourcing 1045 parts or stock?

Attach a drawing (PDF or STEP) or describe the part; a U.S. shop that fits quotes it.

At a glance

1045 Steel typical properties
Density	7.85 g/cm³ (0.284 lb/in³)
Tensile strength	625 MPa (91 ksi) cold drawn; about 565 MPa (82 ksi) hot rolled
Yield strength	530 MPa (77 ksi) cold drawn; about 310 MPa (45 ksi) hot rolled
Hardness	179 HB cold drawn (about 163 HB hot rolled); 55-60 HRC on an induction-hardened surface
Elongation	12% cold drawn; about 16% hot rolled
Modulus of elasticity	200 GPa (29 Msi)
Thermal	Melts at about 1,420-1,490 °C (2,590-2,710 °F); thermal conductivity ~50 W/m·K
Composition	Fe, 0.43-0.50% C, 0.60-0.90% Mn, up to 0.04% P, up to 0.05% S

Typical values, Cold drawn (as stocked); hot-rolled figures noted alongside. Hardness after induction hardening given separately.. Confirm against the mill certificate and the purchase spec.

MachinabilityGood: About 55-60% of the 1212 benchmark. Breaks a better chip and holds a better finish than 1018 because it is harder; carbide tooling is the norm.
WeldabilityFair: Weldable with care: preheat 150-260 °C (300-500 °F) on anything thicker than about 6 mm, low-hydrogen filler (E7018, ER70S-6), slow cool, and post-weld stress relief for loaded joints. Never weld a hardened surface without re-hardening after.
FormabilityFair: Cold forms only gently; bends of hot-rolled flat want a 2x thickness inside radius. Hot forging is easy and common.
Corrosion resistancePoor: Rusts like any plain carbon steel. Hard chrome, zinc plate, black oxide with oil or paint depending on the service.

1045 is a plain carbon steel at about 0.45% carbon, the point where quench hardening starts to pay off. It is stocked as cold-drawn bar for machined parts and as hot-rolled bar and plate for larger sections, and it is the usual answer when 1018 is not strong enough and 4140 is more than the job needs.

Cold-drawn 1045 runs about 625 MPa (91 ksi) tensile and 530 MPa (77 ksi) yield, roughly 40% above cold-drawn 1018, at a machinability rating near 55-60%. Its real advantage is induction hardening: a shaft can be surface hardened to 55-60 HRC on a journal or a spline in seconds while the core stays tough. It also through-hardens in thin sections, to about 25-30 HRC in a tempered part.

The carbon that makes it hardenable makes it fussier to weld: sections above about 6 mm need preheat, low-hydrogen consumables and a slow cool or the heat-affected zone cracks. Hardenability is shallow, so large sections quenched for through-hardness get a hard skin and a soft middle; that is the job for 4140.

Heat treatment

Through harden by austenitizing at 820-850 °C (1,500-1,560 °F), water or brine quench (oil for thin, crack-prone parts) and tempering at 400-650 °C (750-1,200 °F); expect 25-32 HRC after a typical temper and full hardness only in sections under about 12 mm (1/2"). Induction or flame harden to 55-60 HRC on journals, splines, gear teeth and cam lobes with a 1-4 mm case; temper at 150-200 °C (300-400 °F). Normalize at about 870 °C (1,600 °F) for forgings and heavy plate; anneal at 790 °C (1,450 °F) with a furnace cool for maximum machinability.

Tempers and conditions

Cold drawn (as stocked)
Hot rolled
Turned, ground and polished
Normalized
Annealed
Q&T (typically 25-32 HRC)
Induction hardened 55-60 HRC (surface)

Stock forms

Round, square, hex and flat bar (cold drawn)
Hot-rolled round and flat bar
Plate
Precision-ground shafting
Forgings

Relative cost

Tier 1 of 5. About 10-30% over 1018 bar by weight, and roughly two thirds the price of 4140. The cheapest steel that hardens.

Typical applications

Drive shafts, axles and spindles
Hydraulic cylinder rods (hard chrome plated)
Gears, sprockets and racks with induction-hardened teeth
Bolts, studs and pins
Machine bases, rams and heavy weldments in hot-rolled plate
Crankshafts and connecting rods in forgings
Rolls, cams and wear rails

Process compatibility

How 1045 takes each process, and what to specify. Each process links to its own guide and to the shops that do it.

1045 Steel process compatibility
Process	Rating	Notes
CNC Machining	GoodGood	Cleaner chips and finish than 1018; carbide tooling, moderate speeds.
CNC Turning	GoodGood	The standard shaft steel; cold-drawn bar turns true and induction hardens after.
Induction Hardening	ExcellentExcellent	The reference induction steel: 55-60 HRC case on journals and splines with a tough core. Can 1045 steel be induction hardened?
Heat Treating	GoodGood	Through hardens only in thin sections; 25-32 HRC after Q&T in bar under 25 mm, softer in the core beyond that.
CNC Grinding	ExcellentExcellent	Ground after induction hardening to hold shaft journals to a few microns.
Hard Chrome Plating	ExcellentExcellent	The usual finish on hydraulic rods: 25-75 um (0.001-0.003") of chrome over a ground surface.
Welding	FairFair	Preheat 150-260 °C, low-hydrogen consumables, slow cool; stress relieve loaded joints.
Forging	ExcellentExcellent	A standard forging grade for crankshafts, levers and hand tools; normalize after forging.
Black Oxide	GoodGood	Cosmetic finish for hardened pins and shafts; oil it.
Zinc Plating	GoodGood	Fine on soft parts; bake induction-hardened parts within hours of plating to drive out hydrogen.
Laser Cutting	FairFair	Plate cuts cleanly but the edge self-hardens; anneal or machine the edge before forming or tapping.
Nitriding	FairFair	Possible, but without alloying elements the case is thin and only moderately hard; induction hardening is the better fit.
Carburizing	Not recommendedNot recommended	Already at 0.45% carbon; carburizing adds brittleness, not a useful case. Use 1018 or 8620 for carburized parts.

Compare 1045

1045 vs 4140 Steel

Design and sourcing tips

Specify the condition: "1045 cold drawn" for small machined parts, "1045 hot rolled, normalized" for large sections, and the hardness zone and depth for induction-hardened features.
For induction-hardened journals, draw the hardened length with a runout zone and keep it away from shoulders and cross holes, which crack on quenching.
Do not ask for "1045 hardened to 50 HRC through" on anything over about 12 mm: it will not get there. Use 4140 or 4340 when through-hardness matters.
Call out preheat and low-hydrogen procedure on the weld symbol or the notes; many shops treat "carbon steel" as 1018 and skip it.
Hard chrome plated rods: specify the ground finish under the plate (0.4 um Ra or better) and the plate thickness; chrome copies the surface beneath it.

Frequently asked questions

Can 1045 steel be hardened?: Yes. It through-hardens in thin sections to the low 30s HRC after tempering, and it induction or flame hardens to 55-60 HRC on the surface, which is how most 1045 shafts and gears are made. Large sections cannot be hardened through the middle because plain carbon steel has shallow hardenability; that is when to move to 4140.
Can 1045 be welded?: With care. Preheat to 150-260 °C (300-500 °F) on anything thicker than about 6 mm, use low-hydrogen consumables such as E7018 or ER70S-6, let it cool slowly and stress relieve loaded joints. Skipping the preheat gives a hard, crack-prone heat-affected zone. Weld before hardening, never after.
What is the difference between 1045 and 4140?: 1045 is plain carbon steel; 4140 adds chromium and molybdenum, which lets it harden deep into the section and reach a higher tempered strength, about 1,000 MPa (145 ksi) in the pre-hard 28-32 HRC condition. 1045 is cheaper and easier to weld and is the better choice for induction-hardened shafts in modest sections; 4140 wins for through-hardened, highly loaded or large parts.
Is 1045 good for shafts?: It is the standard shaft steel for general machinery: strong enough, cheap, available as ground shafting, and its journals can be induction hardened for bearings and seals. For high-torque, fatigue-critical or large-diameter shafts, 4140 or 4340 give more strength and deeper hardening.

Processes that commonly use it

Related materials

1018 Steel 4140 Steel 1095 Steel A36 Steel 4340 Steel

Where to verify these values

ASTM A108 and ASTM A576 (bar)
ASTM A29/A29M and SAE J403
ASM Handbook Vol. 1 and Vol. 4 (heat treating)
Producer data sheets for 1045 cold-drawn and hot-rolled bar

Carbon steelsUNS G10450

1045 Steel

Also: AISI 1045, SAE 1045, UNS G10450, C1045, 1045 CD, 1045 HR, C45 / 1.0503, C45E / 1.1191, medium carbon steel, S45C (JIS)

1045 is the medium-carbon workhorse for shafts and machine parts: stronger than 1018, induction- or flame-hardenable to 55-60 HRC, still machinable and affordable. Values for cold drawn.

ASTM A108 (cold-finished bar)ASTM A576 (hot-rolled bar)ASTM A29/A29MASTM A830 (plate)SAE J403 (chemistry)

Sourcing 1045 parts or stock?

Attach a drawing (PDF or STEP) or describe the part; a U.S. shop that fits quotes it.

At a glance

1045 Steel typical properties
Density	7.85 g/cm³ (0.284 lb/in³)
Tensile strength	625 MPa (91 ksi) cold drawn; about 565 MPa (82 ksi) hot rolled
Yield strength	530 MPa (77 ksi) cold drawn; about 310 MPa (45 ksi) hot rolled
Hardness	179 HB cold drawn (about 163 HB hot rolled); 55-60 HRC on an induction-hardened surface
Elongation	12% cold drawn; about 16% hot rolled
Modulus of elasticity	200 GPa (29 Msi)
Thermal	Melts at about 1,420-1,490 °C (2,590-2,710 °F); thermal conductivity ~50 W/m·K
Composition	Fe, 0.43-0.50% C, 0.60-0.90% Mn, up to 0.04% P, up to 0.05% S

Typical values, Cold drawn (as stocked); hot-rolled figures noted alongside. Hardness after induction hardening given separately.. Confirm against the mill certificate and the purchase spec.

MachinabilityGood: About 55-60% of the 1212 benchmark. Breaks a better chip and holds a better finish than 1018 because it is harder; carbide tooling is the norm.
WeldabilityFair: Weldable with care: preheat 150-260 °C (300-500 °F) on anything thicker than about 6 mm, low-hydrogen filler (E7018, ER70S-6), slow cool, and post-weld stress relief for loaded joints. Never weld a hardened surface without re-hardening after.
FormabilityFair: Cold forms only gently; bends of hot-rolled flat want a 2x thickness inside radius. Hot forging is easy and common.
Corrosion resistancePoor: Rusts like any plain carbon steel. Hard chrome, zinc plate, black oxide with oil or paint depending on the service.

Heat treatment

Tempers and conditions

Cold drawn (as stocked)
Hot rolled
Turned, ground and polished
Normalized
Annealed
Q&T (typically 25-32 HRC)
Induction hardened 55-60 HRC (surface)

Stock forms

Round, square, hex and flat bar (cold drawn)
Hot-rolled round and flat bar
Plate
Precision-ground shafting
Forgings

Relative cost

Tier 1 of 5. About 10-30% over 1018 bar by weight, and roughly two thirds the price of 4140. The cheapest steel that hardens.

Typical applications

Drive shafts, axles and spindles
Hydraulic cylinder rods (hard chrome plated)
Gears, sprockets and racks with induction-hardened teeth
Bolts, studs and pins
Machine bases, rams and heavy weldments in hot-rolled plate
Crankshafts and connecting rods in forgings
Rolls, cams and wear rails

Process compatibility

How 1045 takes each process, and what to specify. Each process links to its own guide and to the shops that do it.

1045 Steel process compatibility
Process	Rating	Notes
CNC Machining	GoodGood	Cleaner chips and finish than 1018; carbide tooling, moderate speeds.
CNC Turning	GoodGood	The standard shaft steel; cold-drawn bar turns true and induction hardens after.
Induction Hardening	ExcellentExcellent	The reference induction steel: 55-60 HRC case on journals and splines with a tough core. Can 1045 steel be induction hardened?
Heat Treating	GoodGood	Through hardens only in thin sections; 25-32 HRC after Q&T in bar under 25 mm, softer in the core beyond that.
CNC Grinding	ExcellentExcellent	Ground after induction hardening to hold shaft journals to a few microns.
Hard Chrome Plating	ExcellentExcellent	The usual finish on hydraulic rods: 25-75 um (0.001-0.003") of chrome over a ground surface.
Welding	FairFair	Preheat 150-260 °C, low-hydrogen consumables, slow cool; stress relieve loaded joints.
Forging	ExcellentExcellent	A standard forging grade for crankshafts, levers and hand tools; normalize after forging.
Black Oxide	GoodGood	Cosmetic finish for hardened pins and shafts; oil it.
Zinc Plating	GoodGood	Fine on soft parts; bake induction-hardened parts within hours of plating to drive out hydrogen.
Laser Cutting	FairFair	Plate cuts cleanly but the edge self-hardens; anneal or machine the edge before forming or tapping.
Nitriding	FairFair	Possible, but without alloying elements the case is thin and only moderately hard; induction hardening is the better fit.
Carburizing	Not recommendedNot recommended	Already at 0.45% carbon; carburizing adds brittleness, not a useful case. Use 1018 or 8620 for carburized parts.

Compare 1045

1045 vs 4140 Steel

Design and sourcing tips

Specify the condition: "1045 cold drawn" for small machined parts, "1045 hot rolled, normalized" for large sections, and the hardness zone and depth for induction-hardened features.
For induction-hardened journals, draw the hardened length with a runout zone and keep it away from shoulders and cross holes, which crack on quenching.
Do not ask for "1045 hardened to 50 HRC through" on anything over about 12 mm: it will not get there. Use 4140 or 4340 when through-hardness matters.
Call out preheat and low-hydrogen procedure on the weld symbol or the notes; many shops treat "carbon steel" as 1018 and skip it.
Hard chrome plated rods: specify the ground finish under the plate (0.4 um Ra or better) and the plate thickness; chrome copies the surface beneath it.

Frequently asked questions

Can 1045 steel be hardened?: Yes. It through-hardens in thin sections to the low 30s HRC after tempering, and it induction or flame hardens to 55-60 HRC on the surface, which is how most 1045 shafts and gears are made. Large sections cannot be hardened through the middle because plain carbon steel has shallow hardenability; that is when to move to 4140.
Can 1045 be welded?: With care. Preheat to 150-260 °C (300-500 °F) on anything thicker than about 6 mm, use low-hydrogen consumables such as E7018 or ER70S-6, let it cool slowly and stress relieve loaded joints. Skipping the preheat gives a hard, crack-prone heat-affected zone. Weld before hardening, never after.
What is the difference between 1045 and 4140?: 1045 is plain carbon steel; 4140 adds chromium and molybdenum, which lets it harden deep into the section and reach a higher tempered strength, about 1,000 MPa (145 ksi) in the pre-hard 28-32 HRC condition. 1045 is cheaper and easier to weld and is the better choice for induction-hardened shafts in modest sections; 4140 wins for through-hardened, highly loaded or large parts.
Is 1045 good for shafts?: It is the standard shaft steel for general machinery: strong enough, cheap, available as ground shafting, and its journals can be induction hardened for bearings and seals. For high-torque, fatigue-critical or large-diameter shafts, 4140 or 4340 give more strength and deeper hardening.