Steel K93050-B (Temper B)
Grade
UNS K93050
Choose for spring elements and thin-wall structural parts needing 500 MPa yield and more stiffness than annealed, while keeping some formability and low expansion.
Values for the B condition
Other K93050 tempers and conditions
K93050 is listed in 3 conditions; see the grade overview at K93050.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Pick this most commonly stocked annealed state when the lowest expansion coefficient, best formability and dimensional stability through later precision machining are required. | 280 | 490 | 40 | 135 HB | 2.1 % IACS |
BThis page Temper B | Choose for spring elements and thin-wall structural parts needing 500 MPa yield and more stiffness than annealed, while keeping some formability and low expansion. | 500 | 620 | 18 | 190 HB | 2.1 % IACS |
Temper D | Use for bar, wire and strip delivered as-drawn or as-rolled for the highest strength and straightness; elongation falls to 8% and precision parts need a later stress-relief. | 670 | 760 | 8 | 25 HRC | 2 % IACS |
What is K93050-B?
K93050-B is K93050 in the B grade — choose for spring elements and thin-wall structural parts needing 500 MPa yield and more stiffness than annealed, while keeping some formability and low expansion. K93050-B has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 63% of steel grades. Elongation at break is 18% and the elastic modulus is 145 GPa (21 Msi). K93050-B has a density of 8.05 g/cm³ (0.291 lb/in³), heavier than 96% of steel grades. It melts at 1,427°C (2,601 °F). A is the default condition FabDigit quotes; B is available on request or by drawing note.
Advantages
- Good corrosion resistance — 27/100, better than 93% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Poor heat conductor — 10.5 W/m·K (6.07 BTU/hr·ft·°F), worse than 100% of steel grades
- Low electrical conductivity — 2.1 % IACS, worse than 99% of steel grades
- Low stiffness — 145 GPa (21 Msi), worse than 98% of steel grades
- High embodied carbon — 5.2 kg CO₂/kg, worse than 96% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
K93050-B properties
Typical room-temperature values for K93050-B; 23 are specific to this condition. Other listed values are K93050 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
K93050-B has a density of 8.05 g/cm³ (0.291 lb/in³), heavier than 96% of steel grades. It melts at 1,427°C (2,601 °F).
Mechanical15
K93050-B has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 63% of steel grades. Elongation at break is 18% and the elastic modulus is 145 GPa (21 Msi).
Thermal6
K93050-B is rated for continuous service to 200°C (392 °F). It conducts heat at 10.5 W/m·K (6.07 BTU/hr·ft·°F), worse than 100% of steel grades. Thermal expansion is 1.6 µm/m·K (0.889 µin/in·°F).
Electrical3
K93050-B conducts electricity at 2.1 % IACS, worse than 99% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (27/100), better than 93% of steel grades.
Sustainability4
Producing a kilogram of K93050-B takes about 66 MJ of energy and emits 5.2 kg of CO₂ — more than 96% of steel grades. Typical recycled content is 30%.
Manufacturability8
K93050-B's machinability is poor (34/100, worse than 86% of steel grades); weldability good (65/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with K93050-B
Is K93050 easy to machine?
Gummy, work-hardens quickly and conducts heat poorly (10.5 W/m·K): use sharp positive-rake tools with a deep cut, light constant feed and generous coolant. Never let the tool dwell or rub, which leaves a hardened skin (machinability 30).
Can K93050 be welded?
Good with GTAW, plasma and electron beam using matching filler, low heat input and clean joint preparation to limit hot cracking from sulfur and phosphorus segregation; stress relieve after welding to restore low-expansion stability.
Can K93050 be formed, bent or molded?
Annealed material deep-draws, bends and spins well (formability 85); half-hard and unannealed stock should be intermediate annealed at about 830–870 °C and cooled rapidly before forming.
What surface finishes work on K93050?
Takes a mirror polish but rusts easily (corrosion score 28) — use electroless nickel, chrome plate or a protective coating. For precision parts, run repeated stress-relief and ageing cycles to stabilize dimensions.
K93050 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 |
|---|---|---|
| Nilow-expansion Invar composition range | 35 – 37 | 36 |
| Clow carbon for F1684-type impurity-controlled grades | ≤ 0.05 | 0.03 |
| Mn | 0.2 – 0.6 | 0.4 |
| Si | ≤ 0.3 | 0.15 |
| P | ≤ 0.02 | 0.01 |
| S | ≤ 0.02 | 0.01 |
| Crresidual | ≤ 0.25 | 0.05 |
| Coresidual | ≤ 0.5 | 0.1 |
| Curesidual | ≤ 0.2 | 0.05 |
| Aldeoxidation residual | ≤ 0.1 | 0.05 |
| Fe | balance | — |
K93050-B — frequently asked
What is K93050-B used for?
K93050-B is typically used for precision instrument frames, optical/laser bench structures and length-standard components. In short: controlled-impurity Invar 36; most formable Invar grade; weldable low-expansion alloy.
What is the yield strength of K93050-B?
K93050-B has a typical yield strength of 500 MPa (72.5 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 63% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is K93050-B easy to machine?
Not especially — machinability is rated poor (34/100, worse than 86% of steel grades). Gummy, work-hardens quickly and conducts heat poorly (10.5 W/m·K): use sharp positive-rake tools with a deep cut, light constant feed and generous coolant. Never let the tool dwell or rub, which leaves a hardened skin (machinability 30).
Can K93050-B be welded?
Yes — weldability is rated good (65/100). Good with GTAW, plasma and electron beam using matching filler, low heat input and clean joint preparation to limit hot cracking from sulfur and phosphorus segregation; stress relieve after welding to restore low-expansion stability.
What surface finishes work on K93050-B?
Takes a mirror polish but rusts easily (corrosion score 28) — use electroless nickel, chrome plate or a protective coating. For precision parts, run repeated stress-relief and ageing cycles to stabilize dimensions.
Can K93050-B be formed, bent or molded?
Annealed material deep-draws, bends and spins well (formability 85); half-hard and unannealed stock should be intermediate annealed at about 830–870 °C and cooled rapidly before forming.
What is the maximum service temperature of K93050-B?
K93050-B is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between K93050-A and K93050-D?
A is the default condition — pick this most commonly stocked annealed state when the lowest expansion coefficient, best formability and dimensional stability through later precision machining are required. D: use for bar, wire and strip delivered as-drawn or as-rolled for the highest strength and straightness; elongation falls to 8% and precision parts need a later stress-relief. Yield strength is 280 MPa in A versus 670 MPa in D.
Sources
- ASTM F1684 — Iron-Nickel and Iron-Nickel-Cobalt Alloys for Low Thermal Expansion Applications — ASTM International (2021)
- ASM Specialty Handbook / ASM Handbook Vol.2 — Low-Expansion Fe-Ni Alloys — ASM International (1990)
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.