Steel SCM445
JIS SCM445 · AISI/SAE 4145
SCM445 is a 0.45 % carbon chromium-molybdenum through-hardening steel in the JIS SCM family, equivalent to AISI 4145, giving higher hardened strength than SCM440.
Reference datasheet — SCM445 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the QT condition
SCM445 tempers and conditions
SCM445 is supplied in 10 conditions, soft to hard. QT is the default FabDigit quotes; the values on this page are for it.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Pick for maximum machinability and best cold-heading/thread-rolling behaviour before hardening. | 430 | 690 | 23 | 14 HRC | 8.2 % IACS |
Solution annealed | Softest supply condition for heavy machining, deep drilling or cold sizing before final hardening. | 470 | 740 | 20 | 212 HB | 44 W/m·K |
Hot rolled | Mill supply condition for stock to be re-heat-treated; scale and decarburised skin must be machined off. | 560 | 900 | 16 | 26 HRC | 7.8 % IACS |
Normalized | Uniform fine-pearlitic structure for forgings prior to machining or as an economical medium-strength condition. | 670 | 1,030 | 14 | 31 HRC | — |
Cold drawn | Close-tolerance bright bar for shafts machined to size without further heat treatment. | 720 | 860 | 12 | 24 HRC | 7.8 % IACS |
Q&T 28–32 HRC (≈285–311 HB) | Tough general-purpose condition for drill collars, tool joints and shafts where impact matters more than peak strength. | 860 | 1,000 | 17 | 30 HRC | — |
QTDefault Quenched and tempered | Standard commercial supply: oil quenched ~840 °C and tempered ~540–600 °C to the JIS strength class; default for shafts, gears and dies. | 950 | 1,130 | 14 | 35 HRC | — |
Induction hardened | Use when bearing journals or gear teeth need a 55+ HRC wear surface with compressive residual stress on a tough Q&T core. | 950 | 1,130 | 12 | 57 HRC | 7.5 % IACS |
Q&T 40–45 HRC (low-temperature temper) | High-strength condition for dies, punches and heavily loaded pins where wear resistance outranks toughness. | 1,300 | 1,450 | 10 | 43 HRC | — |
Q&T 48–52 HRC (tool condition) | Near-maximum through hardness for wear parts and small tooling; brittle, only for compression-dominated loads. | 1,550 | 1,750 | 7 | 50 HRC | — |
What is SCM445?
SCM445 is a 0.45 % carbon chromium-molybdenum through-hardening steel in the JIS SCM family, equivalent to AISI 4145, giving higher hardened strength than SCM440. It is specified for heavily loaded rotating parts and tooling, and is supplied as bar, tube and forging stock in annealed, spheroidize-annealed, normalized, hot-rolled, cold-drawn, induction-hardened and Q&T conditions from 28-32 up to 48-52 HRC. The default Q&T condition gives 950 MPa yield, 1130 MPa tensile, 14 % elongation at 330 HB / 35 HRC, with service to about 400 °C and machinability of only 40. Weldability is poor (CE ≈ 0.85) and it is bare-corroding, so SCM440 is preferred when welding or easier machining matters more than peak strength. SCM445 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). SCM445 has a yield strength of 950 MPa (138 ksi) and a tensile strength of 1,130 MPa (164 ksi) — stronger than 91% of steel grades. Elongation at break is 14% and the elastic modulus is 207 GPa (30 Msi).
What is SCM445 used for?
- high-strength shafts
- drill collars
- spline shafts
- heavy bolts
Advantages
- High strength — 950 MPa (138 ksi), better than 91% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited formability — 20/100, worse than 80% of steel grades
- Difficult to machine — 40/100, worse than 77% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
- Limited ductility — 14%, worse than 75% of steel grades
SCM445 properties
Typical room-temperature values for SCM445-QT; bars are the position among steel grades.
Physical3
SCM445 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
SCM445 has a yield strength of 950 MPa (138 ksi) and a tensile strength of 1,130 MPa (164 ksi) — stronger than 91% of steel grades. Elongation at break is 14% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
SCM445 is rated for continuous service to 400°C (752 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
SCM445 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SCM445 takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability6
SCM445's machinability is fair (40/100, worse than 77% of steel grades); weldability poor (25/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. SCM445 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SCM445
Is SCM445 easy to machine?
Machine in the annealed/normalised state where possible; at 32–39 HRC use rigid setups, coated carbide, 60–110 m/min and positive rake, and finish-grind after hardening.
Can SCM445 be welded?
Poor weldability (CE ≈ 0.85): preheat 300–350 °C, low-hydrogen consumables, control interpass, and temper/PWHT at 600–650 °C immediately — avoid welding on finished hardened parts.
Can SCM445 be formed, bent or molded?
Hot forge 1100–1200 °C with slow cooling or immediate normalising; cold forming limited to light straightening in the annealed condition.
SCM445 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 0.43 – 0.48 | 0.45 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.3 – 0.6 | 0.45 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Cr | 0.9 – 1.2 | 1.05 |
| Mo | 0.15 – 0.3 | 0.22 |
| Niresidual max | ≤ 0.25 | |
| Curesidual max | ≤ 0.3 | |
| Fe | balance |
What surface finishes work on SCM445?
No corrosion resistance — protect by black oxide, phosphate + oil, hard chrome or QPQ nitrocarburising; bake after plating to avoid hydrogen embrittlement, and cap hardness at 22 HRC for sour service.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel SCM445 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- AISI / SAE
- 4145
How much does SCM445 cost?
SCM445 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
SCM445 — frequently asked
What is SCM445 used for?
SCM445 is typically used for high-strength shafts, drill collars, spline shafts and heavy bolts. In short: highest-strength SCM through-hardener; stronger than SCM440; strength over weldability.
What is the yield strength of SCM445?
SCM445 has a typical yield strength of 950 MPa (138 ksi) and a tensile strength of 1,130 MPa (164 ksi) — stronger than 91% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is SCM445 easy to machine?
Not especially — machinability is rated fair (40/100, worse than 77% of steel grades). Machine in the annealed/normalised state where possible; at 32–39 HRC use rigid setups, coated carbide, 60–110 m/min and positive rake, and finish-grind after hardening.
Can SCM445 be welded?
Not readily — weldability is rated poor (25/100). Poor weldability (CE ≈ 0.85): preheat 300–350 °C, low-hydrogen consumables, control interpass, and temper/PWHT at 600–650 °C immediately — avoid welding on finished hardened parts.
What surface finishes work on SCM445?
No corrosion resistance — protect by black oxide, phosphate + oil, hard chrome or QPQ nitrocarburising; bake after plating to avoid hydrogen embrittlement, and cap hardness at 22 HRC for sour service.
Can SCM445 be formed, bent or molded?
Hot forge 1100–1200 °C with slow cooling or immediate normalising; cold forming limited to light straightening in the annealed condition.
What is the maximum service temperature of SCM445?
SCM445 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SCM445-QT and SCM445-SA?
QT is the default condition — standard commercial supply: oil quenched ~840 °C and tempered ~540–600 °C to the JIS strength class; default for shafts, gears and dies. SA: pick for maximum machinability and best cold-heading/thread-rolling behaviour before hardening. Yield strength is 950 MPa in QT versus 430 MPa in SA.
How much does SCM445 cost?
SCM445 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- JIS G4053 — Low-alloyed structural steels for machine structural use (SCM445) — JSA (2016)
- GB/T 3077 — Alloy structural steels (45CrMo) — SAC (2015)
- SAE J404 / ASTM A29 — Chemical compositions of SAE alloy steels (4145) — SAE / ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- Alloy steel 4145H / 4145H Mod drill-collar bar datasheets — various bar producers (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.