Steel SNB7-HR (Hot rolled)
Supply condition
Raw bar or forging stock bought for in-house heat treatment of studs and bolts.
Values for the HR condition
Other SNB7 tempers and conditions
SNB7 is listed in 7 conditions; see the grade overview at SNB7.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
soft condition for machining or cold work | Bar supplied soft for deep machining or thread rolling before final quench and temper. | 415 | 655 | 25 | 197 HB | — |
HRThis page Hot rolled | Raw bar or forging stock bought for in-house heat treatment of studs and bolts. | 450 | 750 | 20 | 18 HRC | 7.8 % IACS |
Q&T 100–180 mm dia | Heavy anchor studs and large flange bolting; lowest guaranteed strength class. | 600 | 800 | 22 | 22 HRC | — |
Q&T ≤235 HB | Choose when NACE MR0175 sour-service hardness limits apply; strength is traded for SSC resistance. | 600 | 760 | 20 | 19 HRC | — |
air cooled from austenitizing, pre-machining stock | Uniform-grain intermediate condition for forgings before final Q&T; not a delivery condition for B7 fasteners. | 655 | 1,020 | 18 | 32 HRC | 7.8 % IACS |
Q&T 64–100 mm dia | Larger studs where hardenability limits properties to 655 MPa minimum yield. | 745 | 880 | 21 | 26 HRC | — |
Q&T ≤64mmDefault Q&T ≤64 mm dia | Standard stocked condition for studs, bolts and bar up to 64 mm — 720 MPa minimum yield. | 830 | 950 | 20 | 30 HRC | — |
What is SNB7-HR?
SNB7-HR is SNB7 supplied in the HR condition — raw bar or forging stock bought for in-house heat treatment of studs and bolts. SNB7-HR has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 52% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi). SNB7-HR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F). Q&T ≤64mm is the default condition FabDigit quotes; HR is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 65/100, better than 78% of steel grades
SNB7-HR properties
Typical room-temperature values for SNB7-HR; 23 are specific to this condition. Other listed values are SNB7 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SNB7-HR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F).
Mechanical16
SNB7-HR has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 52% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SNB7-HR is rated for continuous service to 400°C (752 °F). It conducts heat at 42.6 W/m·K (24.6 BTU/hr·ft·°F), worse than 51% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
SNB7-HR conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SNB7-HR takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability6
SNB7-HR's machinability is good (55/100, better than 62% of steel grades); weldability fair (40/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SNB7-HR
Is SNB7 easy to machine?
Machine in annealed condition where possible; at 28–32 HRC use rigid setups, coated carbide, ~80–120 m/min and generous coolant — thread rolling before hardening gives best fatigue life.
Can SNB7 be welded?
Not intended for welding; if unavoidable use low-hydrogen consumables, 250–350 °C preheat and 620–680 °C PWHT to avoid hard HAZ and hydrogen cracking.
Can SNB7 be formed, bent or molded?
Hot forge at 1100–1200 °C then normalize; cold forming only in the annealed state, with re-quench and temper afterwards to restore B7 properties.
What surface finishes work on SNB7?
Bare surfaces rust quickly — zinc plate, hot-dip galvanize (bake to relieve hydrogen), phosphate-and-oil or PTFE coat; keep plating baking cycles per ASTM F1941 to avoid hydrogen embrittlement.
SNB7 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 G4107 SNB7 0.38–0.48 | 0.37 – 0.49 | 0.42 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.65 – 1.1 | 0.88 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Cr | 0.75 – 1.2 | 0.95 |
| Mo | 0.15 – 0.25 | 0.2 |
| Fe | balance | — |
SNB7-HR — frequently asked
What is SNB7-HR used for?
SNB7-HR is typically used for high-temperature bolts, studs and flange fasteners. In short: standard B7 bolting steel; 4140 chemistry, sized tempers; strength to 425 °C.
What is the yield strength of SNB7-HR?
SNB7-HR has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 52% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is SNB7-HR easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machine in annealed condition where possible; at 28–32 HRC use rigid setups, coated carbide, ~80–120 m/min and generous coolant — thread rolling before hardening gives best fatigue life.
Can SNB7-HR be welded?
With care — weldability is rated fair (40/100). Not intended for welding; if unavoidable use low-hydrogen consumables, 250–350 °C preheat and 620–680 °C PWHT to avoid hard HAZ and hydrogen cracking.
What surface finishes work on SNB7-HR?
Bare surfaces rust quickly — zinc plate, hot-dip galvanize (bake to relieve hydrogen), phosphate-and-oil or PTFE coat; keep plating baking cycles per ASTM F1941 to avoid hydrogen embrittlement.
Can SNB7-HR be formed, bent or molded?
Hot forge at 1100–1200 °C then normalize; cold forming only in the annealed state, with re-quench and temper afterwards to restore B7 properties.
What is the maximum service temperature of SNB7-HR?
SNB7-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 SNB7 Q&T ≤64mm and SNB7-HR?
Q&T ≤64mm is the default condition — standard stocked condition for studs, bolts and bar up to 64 mm — 720 MPa minimum yield. HR: raw bar or forging stock bought for in-house heat treatment of studs and bolts. Yield strength is 830 MPa in Q&T ≤64mm versus 450 MPa in HR.
Sources
- JIS G 4107 Alloy steel bolting materials for high temperature service — JSA (2019)
- ASTM A193/A193M Alloy-Steel and Stainless Steel Bolting for High Temperature Service — ASTM (2023)
- ASM Handbook Vol.1 Properties and Selection: Irons, Steels and High-Performance Alloys (4140/4142) — ASM International (1990)
- ASM Handbook Vol.16 Machining — ASM International (1989)
- GB/T 3077 (42CrMo) — SAC (2015)
- NACE MR0175 / ISO 15156 materials for H2S-containing environments — NACE/ISO (2020)
- 42CrMo — Mysteel / 1688 (2026)
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.