Steel SMn438
SMn438 is a manganese alloy steel cross-referenced to AISI 1541, supplied hot-rolled, annealed, normalised, cold-drawn, induction-hardened and quenched-and-tempered to 28–32 or 33–38 HRC.
Reference datasheet — SMn438 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
SMn438 tempers and conditions
SMn438 is supplied in 8 conditions, soft to hard. QT is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — pick it for heavy machining, deep boring or cold forming before hardening. | 340 | 580 | 26 | 170 HB | — |
Hot rolled | Cheapest mill condition for parts that will be heat treated after rough machining. | 380 | 640 | 22 | 190 HB | — |
Normalized | Uniform fine grain and stable machining response for forgings before final Q&T. | 420 | 680 | 22 | 14 HRC | 8.2 % IACS |
Cold drawn | Straight, close-tolerance bright bar for as-supplied shafting where no heat treatment follows. | 640 | 760 | 12 | 20 HRC | — |
QTDefault Quenched and tempered | Standard supply condition for shafts, axles and gear blanks needing ≥785 MPa with good toughness. | 690 | 860 | 20 | 25 HRC | — |
Induction hardened | Choose when journals, splines or gear teeth need a wear-resistant 50–58 HRC skin over a tough core. | 700 | 880 | 16 | 55 HRC | 7.4 % IACS |
Q&T to 28–32 HRC | Higher-strength tempering band for loaded shafts and connecting parts still machinable with carbide. | 790 | 950 | 17 | 30 HRC | — |
Q&T to 33–38 HRC | Maximum useful through-hardness for small sections where wear and strength beat toughness. | 950 | 1,130 | 14 | 35 HRC | — |
What is SMn438?
SMn438 is a manganese alloy steel cross-referenced to AISI 1541, supplied hot-rolled, annealed, normalised, cold-drawn, induction-hardened and quenched-and-tempered to 28–32 or 33–38 HRC. In the default Q&T condition it provides 690 MPa yield, 860 MPa tensile, 20 % elongation and 255 HB (25 HRC) with service to 400 °C, making it a low-cost hardenable bar grade for medium-duty shafts, gears and sprockets. It has no corrosion resistance and CE ≈ 0.7 restricts welding; SCr440 or 4140 are the alternatives when deeper hardening or higher strength is required. SMn438 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). SMn438 has a yield strength of 690 MPa (100 ksi) and a tensile strength of 860 MPa (125 ksi) — stronger than 80% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
What is SMn438 used for?
- shafts
- gears
- sprockets
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 690 MPa (100 ksi), better than 80% of steel grades
SMn438 properties
Typical room-temperature values for SMn438-QT; bars are the position among steel grades.
Physical3
SMn438 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
SMn438 has a yield strength of 690 MPa (100 ksi) and a tensile strength of 860 MPa (125 ksi) — stronger than 80% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SMn438 is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
SMn438 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of SMn438 takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
SMn438's machinability is good (55/100, better than 62% of steel grades); weldability fair (40/100); formability fair (35/100).
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. SMn438 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SMn438
Is SMn438 easy to machine?
Machines like Q&T 1541 at roughly 60 % of 1212; use rigid setups, carbide inserts and 120–180 m/min in the 235–285 HB condition — soften by annealing for heavy stock removal.
Can SMn438 be welded?
CE ≈ 0.7, so preheat 200–300 °C, use low-hydrogen consumables and temper after welding; avoid welding fully hardened parts.
Can SMn438 be formed, bent or molded?
Hot forge 1050–1200 °C then normalize; cold bending is limited — anneal first and keep generous bend radii.
SMn438 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 |
|---|---|---|
| CJIS G4053 SMn438 | 0.35 – 0.41 | 0.38 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 1.35 – 1.65 | 1.5 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Crresidual limit | ≤ 0.35 | |
| Niresidual limit | ≤ 0.25 | |
| Curesidual limit | ≤ 0.3 | |
| Fe | balance |
What surface finishes work on SMn438?
No anodizing (ferrous); protect with oil, phosphate + oil, black oxide or zinc plating, and bake after plating to avoid hydrogen embrittlement above 1000 MPa.
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 SMn438 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 1541
How much does SMn438 cost?
SMn438 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.
SMn438 — frequently asked
What is SMn438 used for?
SMn438 is typically used for shafts, gears and sprockets. In short: low-cost hardenable alloy bar; 1541 manganese-steel equivalent; chromium-free shaft steel.
What is the yield strength of SMn438?
SMn438 has a typical yield strength of 690 MPa (100 ksi) and a tensile strength of 860 MPa (125 ksi) — stronger than 80% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SMn438 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like Q&T 1541 at roughly 60 % of 1212; use rigid setups, carbide inserts and 120–180 m/min in the 235–285 HB condition — soften by annealing for heavy stock removal.
Can SMn438 be welded?
With care — weldability is rated fair (40/100). CE ≈ 0.7, so preheat 200–300 °C, use low-hydrogen consumables and temper after welding; avoid welding fully hardened parts.
What surface finishes work on SMn438?
No anodizing (ferrous); protect with oil, phosphate + oil, black oxide or zinc plating, and bake after plating to avoid hydrogen embrittlement above 1000 MPa.
Can SMn438 be formed, bent or molded?
Hot forge 1050–1200 °C then normalize; cold bending is limited — anneal first and keep generous bend radii.
What is the maximum service temperature of SMn438?
SMn438 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 SMn438-QT and SMn438-A?
QT is the default condition — standard supply condition for shafts, axles and gear blanks needing ≥785 MPa with good toughness. A: softest condition — pick it for heavy machining, deep boring or cold forming before hardening. Yield strength is 690 MPa in QT versus 340 MPa in A.
How much does SMn438 cost?
SMn438 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 G 4053 — Low-alloyed structural steels for machine structural use — JSA (2016)
- SAE J404 / J1268 — Chemical compositions and hardenability of SAE alloy steels (1541/1541H) — SAE International (2021)
- 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)
- GB/T 3077 — Alloy structural steels (comparable 40Mn2) — SAC (2015)
- Mysteel / SMM (2025)
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.