Stainless Steel CB6-SR (Stress relieved)
Heat-treated state
UNS J91804 · ASTM A743 Gr. CB6
Condition of weld-repaired castings after mandatory post-weld temper; properties approach N+T with slightly lower local ductility.
Values for the SR condition
Other CB6 tempers and conditions
CB6 is listed in 6 conditions; see the grade overview at CB6.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition for heavy machining, straightening or welding repair before final hardening. | 400 | 620 | 24 | 180 HB | — |
SRThis page Stress relieved | Condition of weld-repaired castings after mandatory post-weld temper; properties approach N+T with slightly lower local ductility. | 530 | 740 | 14 | 22 HRC | 2.9 % IACS |
N+TDefault Normalized and tempered | Standard supply condition for valve and pump castings: balanced strength, toughness and corrosion resistance. | 550 | 760 | 16 | 21 HRC | — |
As fabricated | Raw casting before heat treatment; hard, brittle untempered martensite — not for service, only for intermediate handling/machining allowance planning. | 650 | 900 | 5 | 36 HRC | 2.7 % IACS |
Hardened and tempered at ~590 °C | Choose when higher yield strength is needed and impact demands are moderate (shafts, stems, wear rings). | 700 | 900 | 13 | 28 HRC | — |
Hardened and low-temperature tempered ~230–280 °C | Maximum hardness/wear resistance condition; accept low toughness and reduced stress-corrosion tolerance. | 900 | 1,150 | 8 | 39 HRC | — |
What is CB6-SR?
CB6-SR is CB6 heat treated to SR — condition of weld-repaired castings after mandatory post-weld temper; properties approach N+T with slightly lower local ductility. CB6-SR has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 740 MPa (107 ksi) — stronger than 81% of stainless steel grades. Elongation at break is 14% and the elastic modulus is 200 GPa (29 Msi). CB6-SR has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,450°C (2,642 °F). N+T is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- Conducts heat well — 25 W/m·K (14.4 BTU/hr·ft·°F), better than 93% of stainless steel grades
- High electrical conductivity — 2.9 % IACS, better than 87% of stainless steel grades
- Low embodied carbon — 3.6 kg CO₂/kg, better than 83% of stainless steel grades
- High strength — 530 MPa (76.9 ksi), better than 81% of stainless steel grades
Limitations
- Limited formability — 11/100, worse than 93% of stainless steel grades
- Limited ductility — 14%, worse than 91% of stainless steel grades
- Low fracture toughness — 62 MPa·√m (56.4 ksi·√in), worse than 86% of stainless steel grades
- Difficult to weld — 38/100, worse than 84% of stainless steel grades
- Needs corrosion protection — 52/100, worse than 76% of stainless steel grades
CB6-SR properties
Typical room-temperature values for CB6-SR; 23 are specific to this condition. Other listed values are CB6 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
CB6-SR has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 83% of stainless steel grades. It melts at 1,450°C (2,642 °F).
Mechanical16
CB6-SR has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 740 MPa (107 ksi) — stronger than 81% of stainless steel grades. Elongation at break is 14% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
CB6-SR is rated for continuous service to 600°C (1,112 °F). It conducts heat at 25 W/m·K (14.4 BTU/hr·ft·°F), better than 93% of stainless steel grades. Thermal expansion is 10.4 µm/m·K (5.78 µin/in·°F).
Electrical3
CB6-SR conducts electricity at 2.9 % IACS, better than 87% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (52/100), worse than 76% of stainless steel grades.
Sustainability4
Producing a kilogram of CB6-SR takes about 53 MJ of energy and emits 3.6 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 75%.
Manufacturability8
CB6-SR's machinability is fair (44/100, better than 81% of stainless steel grades); weldability fair (38/100); formability not recommended (11/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with CB6-SR
Is CB6 easy to machine?
Machine in the annealed or high-tempered condition with rigid setups, sharp positive-rake carbide, low speed/heavy feed to avoid work hardening and glazing; above 30 HRC prefer grinding or CBN.
Can CB6 be welded?
Weldable with matching 410NiMo/E410NiMo or austenitic 309L filler, but requires 200–300 °C preheat, controlled interpass and a mandatory post-weld temper to avoid martensite cracking.
Can CB6 be formed, bent or molded?
Sand or investment cast; needs generous risering (long freezing range, ~2% solidification shrinkage) and slow, protected cooling to limit hot tearing and quench cracks.
What surface finishes work on CB6?
Passivate per ASTM A967 after machining; takes a good mechanical or electropolish; hard chrome or nitriding can be used for wear surfaces — do not anodize.
CB6 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 martensitic; verify limit against current ASTM A743 edition | ≤ 0.06 | 0.04 |
| Mn | ≤ 1 | 0.6 |
| Si | ≤ 1 | 0.7 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.03 | 0.02 |
| Cr16% Cr class — higher than CA-15/CA-40 | 15.5 – 17.5 | 16.5 |
| Nipresent to stabilise austenite/martensite at low carbon | ≤ 2.5 | 1.6 |
| Mooptional/residual | ≤ 0.75 | 0.35 |
| Fe | balance | — |
CB6-SR — frequently asked
What is CB6-SR used for?
CB6-SR is typically used for valve trim, pump components and corrosion-resistant structural castings. In short: more corrosion-resistant than CA15; hardenable cast martensitic; 620 °C service limit.
What is the yield strength of CB6-SR?
CB6-SR has a typical yield strength of 530 MPa (76.9 ksi) and a tensile strength of 740 MPa (107 ksi) — stronger than 81% of stainless steel grades. Strength varies by condition: see the 6 listed tempers.
Is CB6-SR easy to machine?
Not especially — machinability is rated fair (44/100, better than 81% of stainless steel grades). Machine in the annealed or high-tempered condition with rigid setups, sharp positive-rake carbide, low speed/heavy feed to avoid work hardening and glazing; above 30 HRC prefer grinding or CBN.
Can CB6-SR be welded?
With care — weldability is rated fair (38/100). Weldable with matching 410NiMo/E410NiMo or austenitic 309L filler, but requires 200–300 °C preheat, controlled interpass and a mandatory post-weld temper to avoid martensite cracking.
What surface finishes work on CB6-SR?
Passivate per ASTM A967 after machining; takes a good mechanical or electropolish; hard chrome or nitriding can be used for wear surfaces — do not anodize.
Can CB6-SR be formed, bent or molded?
Sand or investment cast; needs generous risering (long freezing range, ~2% solidification shrinkage) and slow, protected cooling to limit hot tearing and quench cracks.
What is the maximum service temperature of CB6-SR?
CB6-SR is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between CB6 N+T and CB6-A?
N+T is the default condition — standard supply condition for valve and pump castings: balanced strength, toughness and corrosion resistance. A: softest condition for heavy machining, straightening or welding repair before final hardening. Yield strength is 550 MPa in N+T versus 400 MPa in A.
Sources
- ASTM A743/A743M — Castings, Iron-Chromium, Iron-Chromium-Nickel, Corrosion Resistant, for General Application — ASTM International (2019)
- ASTM A487/A487M — Steel Castings Suitable for Pressure Service — ASTM International (2020)
- Steel Castings Handbook, 6th ed. — Steel Founders' Society of America / ASM (1995)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
- UNS J91804 alloy record (Metals & Alloys in the Unified Numbering System) — SAE/ASTM (2017)
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.