Steel 8MnSi7 +U (Hot rolled)
Finish state
EN 8MnSi7
Cheapest mill condition for wire rod that will be pickled, drawn and annealed by the fastener maker.
Values for the +U condition
Other 8MnSi7 tempers and conditions
8MnSi7 is listed in 6 conditions; see the grade overview at 8MnSi7.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Best cold-heading condition per EN 10263 when severe upsetting or thread rolling follows without intermediate anneal. | 240 | 395 | 32 | 116 HB | 9.3 % IACS |
Annealed | Pick when maximum ductility is needed before heavy multi-station cold heading or deep extrusion. | 255 | 410 | 29 | 122 HB | — |
+UThis page Hot rolled | Cheapest mill condition for wire rod that will be pickled, drawn and annealed by the fastener maker. | 290 | 450 | 23 | 135 HB | — |
Light drawn | Small drafting for surface and size control while keeping most of the annealed ductility for cold heading. | 385 | 490 | 15 | 152 HB | 8 % IACS |
+U+CDefault Cold drawn from untreated hot rolled stock | Standard stocked bar/wire condition: tight tolerance, bright surface and raised yield strength for headers and screw machines. | 490 | 560 | 10 | 175 HB | — |
Carburized and hardened | Final condition for formed parts needing a wear-resistant hard case (0.1–0.5 mm) over a tough, low-carbon core. | 560 | 780 | 11 | 60 HRC | — |
What is 8MnSi7 +U?
8MnSi7 +U is 8MnSi7 supplied in the +U condition — cheapest mill condition for wire rod that will be pickled, drawn and annealed by the fastener maker. 8MnSi7 +U has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 88% of steel grades. Elongation at break is 23% and the elastic modulus is 207 GPa (30 Msi). 8MnSi7 +U has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,490°C (2,714 °F). +U+C is the default condition FabDigit quotes; +U is available on request or by drawing note.
Advantages
- Forms and bends easily — 80/100, better than 93% of steel grades
- Readily welded — 85/100, better than 83% of steel grades
Limitations
- Low strength — 290 MPa (42.1 ksi), worse than 88% of steel grades
8MnSi7 +U properties
Typical room-temperature values for 8MnSi7 +U; 15 are specific to this condition. Other listed values are 8MnSi7 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
8MnSi7 +U has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,490°C (2,714 °F).
Mechanical16
8MnSi7 +U has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 88% of steel grades. Elongation at break is 23% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
8MnSi7 +U is rated for continuous service to 350°C (662 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
8MnSi7 +U conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 8MnSi7 +U takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
8MnSi7 +U's machinability is fair (50/100, worse than 53% of steel grades); weldability excellent (85/100); formability very good (80/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 8MnSi7 +U
Is 8MnSi7 easy to machine?
Gummy in the annealed state — machine in the cold drawn (+C) condition, use sharp positive-rake tools, high speed and flood coolant to avoid built-up edge; expect ~60 % of AISI 1212.
Can 8MnSi7 be welded?
Very good with all arc processes (CE ≈ 0.35–0.40); no preheat needed for thin fastener sections, but avoid welding after case hardening.
Can 8MnSi7 be formed, bent or molded?
Designed for multi-station cold heading, extrusion and thread rolling; supply as +A/+AC with phosphate + soap or polymer lubricant, and use intermediate anneals for reductions above ~70 %.
What surface finishes work on 8MnSi7?
Not anodizable; standard routes are zinc or zinc-nickel electroplating with baking, hot-dip galvanizing, zinc-flake coatings, or phosphate + oil; carburised parts must be plated with H-embrittlement relief bake.
8MnSi7 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 |
|---|---|---|
| Clow carbon for cold formability; per EN 10263-3 cold heading steel | ≤ 0.11 | 0.08 |
| Sisolid-solution strengthening; range varies by producer | 0.2 – 0.6 | 0.4 |
| Mndesignation figure 7 ⇒ ≈1.75 % Mn (Mn ×4 rule) | 1.4 – 1.8 | 1.65 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Altotal Al, grain refinement / N binding | ≥ 0.02 | 0.04 |
| N | ≤ 0.01 | — |
| Fe | balance | — |
8MnSi7 +U — frequently asked
What is 8MnSi7 +U used for?
8MnSi7 +U is typically used for fasteners, cold-formed pins and case-hardened small parts. In short: cold-heading fastener base steel; very good weldability, CE 0.35-0.40; case-hardening chemistry.
What is the yield strength of 8MnSi7 +U?
8MnSi7 +U has a typical yield strength of 290 MPa (42.1 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 88% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 8MnSi7 +U easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Gummy in the annealed state — machine in the cold drawn (+C) condition, use sharp positive-rake tools, high speed and flood coolant to avoid built-up edge; expect ~60 % of AISI 1212.
Can 8MnSi7 +U be welded?
Yes — weldability is rated excellent (85/100). Very good with all arc processes (CE ≈ 0.35–0.40); no preheat needed for thin fastener sections, but avoid welding after case hardening.
What surface finishes work on 8MnSi7 +U?
Not anodizable; standard routes are zinc or zinc-nickel electroplating with baking, hot-dip galvanizing, zinc-flake coatings, or phosphate + oil; carburised parts must be plated with H-embrittlement relief bake.
Can 8MnSi7 +U be formed, bent or molded?
Designed for multi-station cold heading, extrusion and thread rolling; supply as +A/+AC with phosphate + soap or polymer lubricant, and use intermediate anneals for reductions above ~70 %.
What is the maximum service temperature of 8MnSi7 +U?
8MnSi7 +U is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 8MnSi7 +U+C and 8MnSi7-CH?
+U+C is the default condition — standard stocked bar/wire condition: tight tolerance, bright surface and raised yield strength for headers and screw machines. CH: final condition for formed parts needing a wear-resistant hard case (0.1–0.5 mm) over a tough, low-carbon core. Yield strength is 490 MPa in +U+C versus 560 MPa in CH.
Sources
- EN 10263-3 Steel rod, bars and wire for cold heading and cold extrusion — Case hardening steels — CEN (2017)
- EN 10263-1/-2 Cold heading and cold extrusion steels — technical delivery conditions (+U, +A, +AC, +C, +LC) — CEN (2017)
- DIN 1654-3 Cold heading and cold extruding steels — case hardening steels (historical, 8MnSi7) — DIN (1989)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Stahlschlüssel (Key to Steel) — material no. 1.5113 — Verlag Stahlschlüssel Wegst (2019)
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.