Steel SUM43
JIS SUM43
SUM43 sits at the higher-carbon end of the JIS free-cutting range and is comparable to AISI 1141, with about 0.45 % carbon so that manganese sulfide keeps chip control while the matrix responds to quench-and-temper or induction hardening.
Reference datasheet — SUM43 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 CD condition
SUM43 tempers and conditions
SUM43 is supplied in 8 conditions, soft to hard. CD 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 | Pick the spheroidize or full anneal when maximum ductility and allowance for cold forming or heavy cutting matter; 167 HB and 20 % elongation come with the lowest strength of any state. | 345 | 585 | 20 | 167 HB | — |
Hot rolled | Use hot rolled bar for large diameters, heavy roughing allowances or parts to be quenched and tempered later; it is the economical supply form at 670 MPa tensile and 197 HB. | 360 | 670 | 15 | 197 HB | — |
Normalized | Normalize at about 870 °C with air cooling to refine the structure and remove banded segregation from forging or hot rolling, as preparation before quenching and tempering. | 400 | 715 | 15 | 15 HRC | 9.8 % IACS |
CDDefault Cold drawn | Choose the usual stock condition, cold drawn bright bar, for close size tolerance, good surface finish and 620 MPa yield with machinability suited to automatic screw machines. | 620 | 700 | 10 | 212 HB | — |
Induction hardened | Choose when journals, pins and guide faces need a 55 HRC wear surface over a tough cold-drawn core; the 0.45% C self-hardens under induction, but finish machining must precede hardening. | 640 | 760 | 10 | 55 HRC | 8.5 % IACS |
Cold Drawn + Stress Relieved (high-tensile bar) | Specify cold drawing followed by a 500–600 °C stress relief for slender shafts, lead screws and hydraulic rods that distort after machining; yield rises to 690 MPa at 229 HB. | 690 | 790 | 11 | 229 HB | — |
Q&T ~248–302 HB | Use the general-purpose quenched and high-temperature tempered state at 248–302 HB for load-carrying shafts, bolts and pins that need 900 MPa tensile with balanced toughness. | 750 | 900 | 14 | 27 HRC | — |
Q&T 30–34 HRC | Choose quenching with an intermediate temper to 30–34 HRC for drive components needing 1030 MPa tensile and higher wear resistance, trading away toughness and machinability. | 860 | 1,030 | 12 | 32 HRC | — |
What is SUM43?
SUM43 sits at the higher-carbon end of the JIS free-cutting range and is comparable to AISI 1141, with about 0.45 % carbon so that manganese sulfide keeps chip control while the matrix responds to quench-and-temper or induction hardening. It is used for shafts, axles and high-strength fasteners, supplied annealed, hot-rolled, cold-drawn, stress-relieved, normalized, induction-hardened and heat treated to 255 HB or 32 HRC. Typical values are 620 MPa yield, 700 MPa tensile, 10 % elongation, 212 HB, machinability 80 and service to 300 °C. Welding and cold forming are both poor; drop to SUM41 (1137) if forming matters more than strength. SUM43 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). SUM43 has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 78% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi).
What is SUM43 used for?
- Shafts
- Axles
- High-strength fasteners
Advantages
- Easy to machine — 80/100, better than 98% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
- High strength — 620 MPa (89.9 ksi), better than 78% of steel grades
- High electrical conductivity — 9.5 % IACS, better than 75% of steel grades
Limitations
- Limited ductility — 10%, worse than 91% of steel grades
- Low fracture toughness — 50 MPa·√m (45.5 ksi·√in), worse than 86% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
SUM43 properties
Typical room-temperature values for SUM43-CD; bars are the position among steel grades.
Physical3
SUM43 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).
Mechanical15
SUM43 has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 78% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SUM43 is rated for continuous service to 300°C (572 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
SUM43 conducts electricity at 9.5 % IACS, better than 75% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of SUM43 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
SUM43's machinability is very good (80/100, better than 98% of steel grades); weldability poor (20/100); formability poor (25/100).
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. SUM43 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SUM43
Is SUM43 easy to machine?
First choice for automatic lathes: cutting speeds can run 30–50 % above 1045 with good chip breaking and long tool life, but the high sulfur gives low transverse toughness, so watch clamping distortion on deep-hole and thin-wall parts.
Can SUM43 be welded?
Not recommended (high S, 0.45 % C): hot cracking and a hard, brittle HAZ are likely; if welding is unavoidable, preheat 200–300 °C, use low-hydrogen consumables and temper after welding.
Can SUM43 be formed, bent or molded?
Cold forming — bending, knurling and cold heading — is poor because elongated MnS inclusions crack along the rolling direction; form in the annealed or hot condition.
SUM43 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 G 4804 SUM43 | 0.4 – 0.48 | 0.44 |
| Mn | 1.35 – 1.65 | 1.5 |
| Smanganese sulfide inclusions provide free-machining | 0.24 – 0.33 | 0.28 |
| P | ≤ 0.04 | 0.02 |
| Sinot specified by JIS for SUM4x; usually kept low in practice | ≤ 0.35 | 0.15 |
| Curesidual element limit, when specified by purchaser | ≤ 0.3 | |
| Fe | balance |
What surface finishes work on SUM43?
No corrosion resistance, so specify black oxide, phosphate, zinc or hard chrome plating; acid can be retained at sulfide inclusions before plating, and inclusion streaks limit mirror polishing.
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 SUM43 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 1141
How much does SUM43 cost?
SUM43 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.
SUM43 — frequently asked
What is SUM43 used for?
SUM43 is typically used for shafts, axles and high-strength fasteners. In short: strongest SUM free-cutting grade; induction-hardenable and free-cutting; poor cold formability.
What is the yield strength of SUM43?
SUM43 has a typical yield strength of 620 MPa (89.9 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 78% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SUM43 easy to machine?
Yes — machinability is rated very good (80/100, better than 98% of steel grades). First choice for automatic lathes: cutting speeds can run 30–50 % above 1045 with good chip breaking and long tool life, but the high sulfur gives low transverse toughness, so watch clamping distortion on deep-hole and thin-wall parts.
Can SUM43 be welded?
Not readily — weldability is rated poor (20/100). Not recommended (high S, 0.45 % C): hot cracking and a hard, brittle HAZ are likely; if welding is unavoidable, preheat 200–300 °C, use low-hydrogen consumables and temper after welding.
What surface finishes work on SUM43?
No corrosion resistance, so specify black oxide, phosphate, zinc or hard chrome plating; acid can be retained at sulfide inclusions before plating, and inclusion streaks limit mirror polishing.
Can SUM43 be formed, bent or molded?
Cold forming — bending, knurling and cold heading — is poor because elongated MnS inclusions crack along the rolling direction; form in the annealed or hot condition.
What is the maximum service temperature of SUM43?
SUM43 is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SUM43-CD and SUM43-A?
CD is the default condition — choose the usual stock condition, cold drawn bright bar, for close size tolerance, good surface finish and 620 MPa yield with machinability suited to automatic screw machines. A: pick the spheroidize or full anneal when maximum ductility and allowance for cold forming or heavy cutting matter; 167 HB and 20 % elongation come with the lowest strength of any state. Yield strength is 620 MPa in CD versus 345 MPa in A.
How much does SUM43 cost?
SUM43 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 4804 — Sulfur and sulfur-composition free-cutting steels — JISC (2019)
- SAE J403 / ASTM A29 — Carbon and resulfurized carbon steel bars (1141/1144) — SAE / ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.16 — Machining (machinability ratings) — ASM International (1989)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
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.