Steel 31CrMoB2-1
EN 31CrMoB2-1
31CrMoB2-1 (1.7272) is a boron-microalloyed low-Cr-Mo quenched-and-tempered steel in the EN 10083 family, where trace boron raises hardenability at lower alloy cost than conventional Cr-Mo grades.
Reference datasheet — 31CrMoB2-1 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
31CrMoB2-1 tempers and conditions
31CrMoB2-1 is supplied in 11 conditions, soft to hard. +QT is the default FabDigit quotes; the values on this page are for it.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Softest condition, chosen for multi-station cold heading/extrusion of bolt and screw blanks before quench & temper. | 370 | 570 | 23 | 170 HB | — |
Annealed | General soft-annealed bar for machining or as a starting stock before quench and temper. | 390 | 600 | 22 | 11 HRC | 8.4 % IACS |
Restricted (core) hardenability band, Jominy-guaranteed | Order this when heat-treat response must sit inside a narrow Jominy band so the core hardness of quenched fasteners/parts is reproducible batch to batch. | 400 | 620 | 20 | 10 HRC | 8.5 % IACS |
Treated to hardness range | Ordered when the mill must certify a delivered hardness window (e.g. ≤207 HB) rather than a specific heat treatment route. | 400 | 610 | 20 | 10 HRC | 8.5 % IACS |
Specified hardenability | Standard hardenability-guaranteed supply condition; pick when parts are hardened in-house and the end-quench curve must be certified. | 410 | 640 | 19 | 14 HRC | 8.2 % IACS |
Hot rolled | Cheapest mill condition; only for parts that will be fully re-heat-treated after forming or forging. | 430 | 680 | 18 | 16 HRC | 8.2 % IACS |
Normalized | Uniform fine-grained structure after hot forming; used to homogenize forgings before final hardening. | 450 | 700 | 18 | 17 HRC | 8.2 % IACS |
Spheroidize annealed and cold drawn | Most common wire/bar supply for cold-heading lines: spheroidized softness plus drawn size tolerance, straightness and clean surface. | 540 | 650 | 12 | 200 HB | — |
Cold drawn | Bright drawn bar for automatic machining where tight tolerance and higher as-supplied strength are wanted without spheroidizing. | 600 | 720 | 10 | 19 HRC | 8 % IACS |
+QTDefault Quenched and tempered | Standard delivered/finished strength condition for bolts, shafts and machine parts needing ~1000 MPa with good toughness. | 850 | 1,000 | 14 | 31 HRC | — |
+QT high strength | High-strength temper for property-class 10.9/12.9 bolts and highly loaded shafts; needs plating bake-out to avoid hydrogen embrittlement. | 1,150 | 1,300 | 10 | 42 HRC | — |
What is 31CrMoB2-1?
31CrMoB2-1 (1.7272) is a boron-microalloyed low-Cr-Mo quenched-and-tempered steel in the EN 10083 family, where trace boron raises hardenability at lower alloy cost than conventional Cr-Mo grades. It is used for fastener- and shaft-grade strength, reaching about 850 MPa yield, 1000 MPa tensile, 14 % elongation and 300 HB (31 HRC) in the +QT condition, with a +QT 40–45 HRC option and service to about 400 °C. Bar and cold-heading wire are the common forms. Weldability is limited (CE ≈ 0.55) and Q&T joints lose local strength; 42CrMo4 is the nearest alternative where higher section strength is needed. 31CrMoB2-1 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). 31CrMoB2-1 has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 88% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi).
What is 31CrMoB2-1 used for?
- high-strength bolts and fasteners
- shafts
- structural pins
- automotive suspension components
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 850 MPa (123 ksi), better than 88% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited ductility — 14%, worse than 75% of steel grades
31CrMoB2-1 properties
Typical room-temperature values for 31CrMoB2-1-+QT; bars are the position among steel grades.
Physical3
31CrMoB2-1 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
31CrMoB2-1 has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 88% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
31CrMoB2-1 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 µm/m·K (6.67 µin/in·°F).
Electrical3
31CrMoB2-1 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 31CrMoB2-1 takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
31CrMoB2-1's machinability is fair (50/100, worse than 53% of steel grades); weldability fair (40/100); formability poor (30/100).
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. 31CrMoB2-1 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 31CrMoB2-1
Is 31CrMoB2-1 easy to machine?
Machine in +AC/+A/+TH (≤210 HB) with carbide inserts; in Q&T above 40 HRC switch to coated carbide or CBN with rigid setups and reduced feeds.
Can 31CrMoB2-1 be welded?
Boron and ~0.31 %C give CE ≈0.55 — preheat 150–250 °C, low-hydrogen consumables and post-weld temper; welded joints in the Q&T state lose local strength.
Can 31CrMoB2-1 be formed, bent or molded?
Cold heading and extrusion only from +AC or +AC+C wire with phosphate+soap or polymer lube; hot forge 1100–1200 °C and re-normalize before hardening.
31CrMoB2-1 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 |
|---|---|---|
| Cgrade-defining carbon level | 0.28 – 0.34 | 0.31 |
| Si | ≤ 0.3 | 0.2 |
| Mn | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.03 | 0.02 |
| Smax; S-resulphurized versions exist for machining | ≤ 0.03 | 0.01 |
| Crdesignation digit 2 = 0.5 % Cr | 0.4 – 0.6 | 0.5 |
| Modesignation digit 1 = 0.1 % Mo | 0.08 – 0.15 | 0.1 |
| Beffective (soluble) boron for hardenability | 8×10⁻⁴ – 0.01 | 0 |
| Tiadded to fix nitrogen and protect boron effect | 0.02 – 0.06 | 0.04 |
| Algrain refining / deoxidation | 0.02 – 0.06 | 0.03 |
| Fe | balance |
What surface finishes work on 31CrMoB2-1?
No anodizing (steel). Protect with zinc, zinc-nickel or zinc-flake coating, phosphate or black oxide; bake at 200 °C within 4 h after electroplating parts 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 31CrMoB2-1 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- EN / DIN / Werkstoff-Nr.
- 1.727210083
- Similar grades
- 30CrMoB
How much does 31CrMoB2-1 cost?
31CrMoB2-1 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
31CrMoB2-1 — frequently asked
What is 31CrMoB2-1 used for?
31CrMoB2-1 is typically used for high-strength bolts and fasteners, shafts, structural pins and automotive suspension components. In short: boron-boosted hardenability; low-cost fastener steel; cold-headable in +AC.
What is the yield strength of 31CrMoB2-1?
31CrMoB2-1 has a typical yield strength of 850 MPa (123 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 88% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is 31CrMoB2-1 easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Machine in +AC/+A/+TH (≤210 HB) with carbide inserts; in Q&T above 40 HRC switch to coated carbide or CBN with rigid setups and reduced feeds.
Can 31CrMoB2-1 be welded?
With care — weldability is rated fair (40/100). Boron and ~0.31 %C give CE ≈0.55 — preheat 150–250 °C, low-hydrogen consumables and post-weld temper; welded joints in the Q&T state lose local strength.
What surface finishes work on 31CrMoB2-1?
No anodizing (steel). Protect with zinc, zinc-nickel or zinc-flake coating, phosphate or black oxide; bake at 200 °C within 4 h after electroplating parts above ~1000 MPa.
Can 31CrMoB2-1 be formed, bent or molded?
Cold heading and extrusion only from +AC or +AC+C wire with phosphate+soap or polymer lube; hot forge 1100–1200 °C and re-normalize before hardening.
What is the maximum service temperature of 31CrMoB2-1?
31CrMoB2-1 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 31CrMoB2-1 cost?
31CrMoB2-1 is a budget-cost steel ($), 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
- EN 10083-3 Steels for quenching and tempering — Alloy steels — CEN (2006)
- EN 10263-4 Steel rod, bars and wire for cold heading and cold extrusion — Steels for quenching and tempering (delivery conditions +A, +AC, +C, +AC+C, +TH) — CEN (2018)
- EN 10084 / EN 10250-3 (hardenability designations +H, +HH, +HL, +CH) — CEN (2008)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A: Steel Heat Treating Fundamentals (boron hardenability) — ASM International (2013)
- GB/T 3077 (comparable 30CrMoB-type boron grades) — SAC (2015)
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.