Steel 1070 · finish state
Steel 1070-BT
Properties of the BT condition, compared with the other 1070 tempers.
Pre-hardened thin strip for clips, retaining rings and flat springs formed directly to shape.
What is 1070-BT?
1070-BT is 1070 supplied in the BT condition — pre-hardened thin strip for clips, retaining rings and flat springs formed directly to shape. 1070-BT has a yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 5% and the elastic modulus is 205 GPa (29.7 Msi). 1070-BT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). HR is the default condition FabDigit quotes; BT is available on request or by drawing note.
Advantages
- High strength — 1,350 MPa (196 ksi), better than 95% of steel grades
- Conducts heat well — 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to weld — 8/100, worse than 100% of steel grades
- Limited ductility — 5%, worse than 98% of steel grades
- Low fracture toughness — 45 MPa·√m (41 ksi·√in), worse than 90% of steel grades
- Limited formability — 15/100, worse than 87% of steel grades
- Limited service temperature — 300°C (572 °F), worse than 77% of steel grades
1070-BT properties
Typical room-temperature values for 1070-BT — 8 properties are specific to this condition; the rest are grade-level values shared by every 1070 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
1070-BT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical15
1070-BT has a yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 5% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
1070-BT is rated for continuous service to 300°C (572 °F). It conducts heat at 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
1070-BT conducts electricity at 9 % IACS, better than 70% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (9/100), worse than 98% of steel grades.
Sustainability4
Producing a kilogram of 1070-BT takes about 25 MJ of energy and emits 2.1 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability6
1070-BT's machinability is fair (45/100, worse than 65% of steel grades); weldability not recommended (8/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 1070 tempers and conditions
1070 is also supplied in 9 other conditions. The full side-by-side table is on the 1070 overview.
- HRDefaultCheapest stock form for parts that will be re-heat-treated or machined then hardened.385 MPa yield · 201 HB
- Q&T 50-55HRCUse for cutting edges, scraper blades and wear plates where hardness matters more than toughness.1,600 MPa yield · 52 HRC
- OTReady-to-coil spring wire supplied at final strength — no post-coiling hardening needed, only stress relief.1,400 MPa yield · 46 HRC
- BTPre-hardened thin strip for clips, retaining rings and flat springs formed directly to shape.1,350 MPa yield · 47 HRC
- Q&THighest strength/elastic limit condition for springs, blades and wear parts; accept low ductility and no welding.1,250 MPa yield · 43 HRC
- CDClose tolerance, higher-yield bar or wire for springs, pins and machined parts without further heat treatment.720 MPa yield · 24 HRC
- SACDSpheroidize-annealed to globular carbides for maximum cold workability, then cold drawn — moderate strength with good ductility and improved machinability for cold heading, upsetting and further wire/bar processing.620 MPa yield · 210 HB
- NormalizedUniform fine pearlite with higher strength than as-rolled; good pre-treatment before machining or hardening.500 MPa yield · 26 HRC
- AnnealedPick when the part must be machined, blanked or cold formed before hardening.350 MPa yield · 183 HB
Working with 1070-BT
Is 1070 easy to machine?
Machine in the annealed or spheroidized state with rigid setups, carbide tooling and moderate speeds; above ~35 HRC use CBN/ceramic or switch to grinding.
Can 1070 be welded?
Poor weldability — high carbon equivalent causes hard, crack-prone HAZ; if unavoidable use 200–350 °C preheat, low-hydrogen consumables and immediate post-weld temper.
Can 1070 be formed, bent or molded?
Cold form only in annealed/soft strip condition with generous bend radii; hot forge 1150–850 °C then slow cool or normalize to avoid quench cracks.
What surface finishes work on 1070?
No inherent corrosion protection: use oil, phosphate, black oxide, zinc or paint; after acid pickling or electroplating of hardened parts bake at 190–210 °C to relieve hydrogen embrittlement. Fine pearlitic or tempered structures take a high mirror polish.
1070 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 |
|---|---|---|
| CGB 70 steel: 0.67–0.75 | 0.65 – 0.75 | 0.7 |
| MnGB/T 699 grade 70: 0.50-0.80 | 0.6 – 0.9 | 0.75 |
| Sinot specified in AISI/SAE bar chemistry; GB 70: 0.17–0.37 | 0.15 – 0.35 | 0.25 |
| Pmax, GB 70: ≤0.035 | ≤ 0.04 | 0.02 |
| Smax, GB 70: ≤0.035 | ≤ 0.05 | 0.03 |
| Crresidual (GB limit) | ≤ 0.25 | — |
| Niresidual (GB limit) | ≤ 0.3 | — |
| Curesidual (GB limit) | ≤ 0.25 | — |
| Fe | balance | — |
1070-BT — frequently asked
What is 1070-BT used for?
1070-BT is typically used for saw blades, cutting knives and springs. In short: spring carbon steel.
What is the yield strength of 1070-BT?
1070-BT has a typical yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 1070-BT easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the annealed or spheroidized state with rigid setups, carbide tooling and moderate speeds; above ~35 HRC use CBN/ceramic or switch to grinding.
Can 1070-BT be welded?
Not readily — weldability is rated not recommended (8/100). Poor weldability — high carbon equivalent causes hard, crack-prone HAZ; if unavoidable use 200–350 °C preheat, low-hydrogen consumables and immediate post-weld temper.
What surface finishes work on 1070-BT?
No inherent corrosion protection: use oil, phosphate, black oxide, zinc or paint; after acid pickling or electroplating of hardened parts bake at 190–210 °C to relieve hydrogen embrittlement. Fine pearlitic or tempered structures take a high mirror polish.
Can 1070-BT be formed, bent or molded?
Cold form only in annealed/soft strip condition with generous bend radii; hot forge 1150–850 °C then slow cool or normalize to avoid quench cracks.
What is the maximum service temperature of 1070-BT?
1070-BT 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 1070-HR and 1070-OT?
HR is the default condition — cheapest stock form for parts that will be re-heat-treated or machined then hardened. OT: ready-to-coil spring wire supplied at final strength — no post-coiling hardening needed, only stress relief. Yield strength is 385 MPa in HR versus 1,400 MPa in OT.
Can FabDigit make parts in 1070-BT?
Yes — 1070-BT is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- SAE J403 / ASTM A29 — Carbon steel bars, grade 1070 — SAE / ASTM (2019)
- ASTM A684 — High-carbon cold-rolled strip — ASTM (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- Machining Data Handbook — Metcut Research Associates (1980)
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.