Steel SUM23 · supply condition · default condition
Steel SUM23-HR
Properties of the HR condition, compared with the other SUM23 tempers.
Cheapest mill form for large sections or for re-drawing/forging; loose tolerance and scaled surface.
What is SUM23-HR?
SUM23-HR is SUM23 supplied in the HR condition — cheapest mill form for large sections or for re-drawing/forging; loose tolerance and scaled surface. SUM23-HR has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 415 MPa (60.2 ksi) — weaker than 94% of steel grades. Elongation at break is 22% and the elastic modulus is 200 GPa (29 Msi). SUM23-HR has a density of 7.87 g/cm³ (0.284 lb/in³), heavier than 91% of steel grades. It melts at 1,420°C (2,588 °F).
Advantages
- Easy to machine — 90/100, better than 99% of steel grades
- High electrical conductivity — 10.8 % IACS, better than 94% of steel grades
- Conducts heat well — 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Hard to polish — 40/100, worse than 96% of steel grades
- Low strength — 250 MPa (36.3 ksi), worse than 94% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
SUM23-HR properties
Typical room-temperature values for SUM23-HR — 12 properties are specific to this condition; the rest are grade-level values shared by every SUM23 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
SUM23-HR has a density of 7.87 g/cm³ (0.284 lb/in³), heavier than 91% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical13
SUM23-HR has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 415 MPa (60.2 ksi) — weaker than 94% of steel grades. Elongation at break is 22% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
SUM23-HR is rated for continuous service to 400°C (752 °F). It conducts heat at 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
SUM23-HR conducts electricity at 10.8 % IACS, better than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (8/100), worse than 99% of steel grades.
Sustainability4
Producing a kilogram of SUM23-HR takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 40%.
Manufacturability7
SUM23-HR's machinability is excellent (90/100, better than 99% of steel grades); weldability poor (20/100); formability good (55/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other SUM23 tempers and conditions
SUM23 is also supplied in 4 other conditions. The full side-by-side table is on the SUM23 overview.
- HRDefaultCheapest mill form for large sections or for re-drawing/forging; loose tolerance and scaled surface.250 MPa yield · 121 HB
- CDDefault stock form for screw-machine work: best size tolerance, straightness and chip control.415 MPa yield · 167 HB
- CRFlat product with tight thickness and bright surface for stamped-then-machined parts.380 MPa yield · 152 HB
- AnnealedSoftest condition; chosen when heavy cold heading, deep bending or stress-free machining is required.230 MPa yield · 111 HB
Working with SUM23-HR
Is SUM23 easy to machine?
Benchmark free-cutting steel: run high SFM with light feeds on Swiss/CNC lathes, short broken chips, excellent tool life and finish; avoid grinding-heavy operations where sulfide pull-out hurts Ra.
Can SUM23 be welded?
Not recommended for structural welds — high S and P cause hot cracking and porosity; if unavoidable, use low-hydrogen filler, preheat and expect reduced joint properties.
Can SUM23 be formed, bent or molded?
Cold heading and light bending are possible in the annealed condition, but transverse ductility is poor because of sulfide stringers — bend across the rolling direction with generous radii.
What surface finishes work on SUM23?
No anodizing; protect with zinc or zinc-nickel electroplate, black oxide, phosphate + oil, or nitrocarburizing; case carbonitriding is used for wear surfaces on low-carbon SUM23.
SUM23 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 G4804 SUM23 | ≤ 0.09 | 0.07 |
| Mn | 0.75 – 1.05 | 0.9 |
| Prephosphorized for chip breaking | 0.04 – 0.09 | 0.06 |
| SMnS inclusions give free-cutting behaviour | 0.26 – 0.35 | 0.3 |
| Sinot specified in JIS; kept low (rimmed/capped practice) | ≤ 0.05 | 0.02 |
| Curesidual limit, typical mill practice | ≤ 0.25 | — |
| Fe | balance | — |
SUM23-HR — frequently asked
What is SUM23-HR used for?
SUM23-HR is typically used for screw machine parts, fasteners and threaded studs, bushings and spacers, hydraulic and pneumatic fittings, light-duty shafts and pins and connector bodies. In short: free-machining Japanese bar.
What is the yield strength of SUM23-HR?
SUM23-HR has a typical yield strength of 250 MPa (36.3 ksi) and a tensile strength of 415 MPa (60.2 ksi) — weaker than 94% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is SUM23-HR easy to machine?
Yes — machinability is rated excellent (90/100, better than 99% of steel grades). Benchmark free-cutting steel: run high SFM with light feeds on Swiss/CNC lathes, short broken chips, excellent tool life and finish; avoid grinding-heavy operations where sulfide pull-out hurts Ra.
Can SUM23-HR be welded?
Not readily — weldability is rated poor (20/100). Not recommended for structural welds — high S and P cause hot cracking and porosity; if unavoidable, use low-hydrogen filler, preheat and expect reduced joint properties.
What surface finishes work on SUM23-HR?
No anodizing; protect with zinc or zinc-nickel electroplate, black oxide, phosphate + oil, or nitrocarburizing; case carbonitriding is used for wear surfaces on low-carbon SUM23.
Can SUM23-HR be formed, bent or molded?
Cold heading and light bending are possible in the annealed condition, but transverse ductility is poor because of sulfide stringers — bend across the rolling direction with generous radii.
What is the maximum service temperature of SUM23-HR?
SUM23-HR 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 SUM23-HR and SUM23-CD?
HR is the default condition — cheapest mill form for large sections or for re-drawing/forging; loose tolerance and scaled surface. CD: default stock form for screw-machine work: best size tolerance, straightness and chip control. Yield strength is 250 MPa in HR versus 415 MPa in CD.
Can FabDigit make parts in SUM23-HR?
Yes — SUM23-HR is available for CNC machining with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- JIS G 4804 — Sulfur and sulfur-composite free-cutting steels — JSA (2019)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.